# kb

id: sidereal-time-20260505-2
file: data/en.wikipedia.org/wiki/Sidereal_time-2.md
category: reference
title: Sidereal time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sidereal_time
date_saved: 2026-05-05T11:13:28.221801+00:00
instance: kb-cron
parent: sidereal-time-20260505-0
summary:
=== Relationship between solar time and sidereal time intervals === If a certain interval I is measured in both mean solar time (UT1) and sidereal time, the numerical value will be greater in sidereal time than in UT1, because sidereal days are shorter than UT1 days. The ratio is: I m e a n s i d e r e a l I U T 1 = r ′ = 1.002 737 379 093 507 95 + 5.9006 × 10 − 11 t − 5.9 × 10 − 15 t 2 {\displaystyle {\frac {I_{\mathrm {mean\,sidereal} }}{I_{\mathrm {UT1} }}}=r'=1.002\,737\,379\,093\,507\,95+5.9006\times 10^{-11}t-5.9\times 10^{-15}t^{2}} such that t represents the number of Julian centuries elapsed since noon 1 January 2000 Terrestrial Time. == Sidereal days compared to solar days on other planets == Six of the eight solar planets have prograde rotation—that is, they rotate more than once per year in the same direction as they orbit the Sun, so the Sun rises in the east. Venus and Uranus, however, have retrograde rotation. For prograde rotation, the formula relating the lengths of the sidereal and solar days is: or, equivalently: When calculating the formula for a retrograde rotation, the operator of the denominator will be


id: solar-time-20260505-0
file: data/en.wikipedia.org/wiki/Solar_time-0.md
category: reference
title: Solar time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solar_time
date_saved: 2026-05-05T11:13:29.423240+00:00
instance: kb-cron
parent: solar-time-20260505-0
summary:
Solar time is a calculation of the passage of time based on the position of the Sun in the sky. The fundamental unit of solar time is the day, based on the synodic rotation period. Traditionally, there are three types of time reckoning based on astronomical observations: apparent solar time and mean solar time (discussed in this article), and sidereal time, which is based on the apparent motions of stars other than the Sun. == Introduction == A tall pole vertically fixed in the ground casts a shadow on any sunny day. At one moment during the day, the shadow will point exactly north or south (or disappear when and if the Sun moves directly overhead). That instant is called local apparent noon, or 12:00 local apparent time. About 24 hours later the shadow will again point north–south, the Sun seeming to have covered a 360-degree arc around Earth's axis. When the Sun has covered exactly 15 degrees (1/24 of a circle, both angles being measured in a plane perpendicular to Earth's axis), local apparent time is 13:00 exactly; after 15 more degrees it will be 14:00 exactly. The problem is that in September the Sun takes less time (as


id: solar-time-20260505-1
file: data/en.wikipedia.org/wiki/Solar_time-1.md
category: reference
title: Solar time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solar_time
date_saved: 2026-05-05T11:13:29.423240+00:00
instance: kb-cron
parent: solar-time-20260505-0
summary:
The sun has always been visible in the sky, and its position forms the basis of apparent solar time, the timekeeping method used in antiquity. An Egyptian obelisk constructed c. 3500 BC, a gnomon in China dated 2300 BC, and an Egyptian sundial dated 1500 BC are some of the earliest methods for measuring the sun's position. Babylonian astronomers knew that the hours of daylight varied throughout the year. A tablet from 649 BC shows that they used a 2:1 ratio for the longest day to the shortest day, and estimated the variation using a linear zigzag function. It is not clear if they knew of the variation in the length of the solar day and the corresponding equation of time. Ptolemy clearly distinguishes the mean solar day and apparent solar day in his Almagest (2nd century), and he tabulated the equation of time in his Handy Tables. Apparent solar time grew less useful as commerce increased and mechanical clocks improved. Mean solar time was introduced in almanacs in England in 1834 and in France in 1835. Because the sun was difficult to observe directly due to its large size in the sky, mean solar time was determined as a


id: solstice-20260505-0
file: data/en.wikipedia.org/wiki/Solstice-0.md
category: reference
title: Solstice
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solstice
date_saved: 2026-05-05T11:13:30.644057+00:00
instance: kb-cron
parent: solstice-20260505-0
summary:
A solstice is the time when the Sun reaches its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around 20–22 June and 20–22 December. In many countries, the seasons of the year are defined by reference to the solstices and the equinoxes. The term solstice can also be used in a broader sense, as the day when this occurs. For locations not too close to the equator or the poles, the dates with the longest and shortest periods of daylight are the summer and winter solstices, respectively. Terms with no ambiguity as to which hemisphere is the context are "June solstice" and "December solstice", referring to the months in which they take place every year. == Etymology == The word solstice is derived from the Latin sol ('sun') and sistere ('to stand still'), because at the solstices, the Sun's declination appears to "stand still"; that is, the seasonal movement of the Sun's daily path (as seen from Earth) reaches a northern or southern limit before reversing direction. Solstice first entered into English in the Middle English period. An older term in English is its calque sunstead (Old English: sunstede), which


id: solstice-20260505-1
file: data/en.wikipedia.org/wiki/Solstice-1.md
category: reference
title: Solstice
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solstice
date_saved: 2026-05-05T11:13:30.644057+00:00
instance: kb-cron
parent: solstice-20260505-0
summary:
Also during the June solstice, places on the Arctic Circle (latitude 66.56° north) will see the Sun just on the horizon during midnight, and all places north of it will see the Sun above horizon for 24 hours. That is the midnight sun or midsummer-night sun or polar day. On the other hand, places on the Antarctic Circle (latitude 66.56° south) will see the Sun just on the horizon during midday, and all places south of it will not see the Sun above horizon at any time of the day. That is the polar night. During the December Solstice, the effects on both hemispheres are just the opposite. This sees polar sea ice re-grow annually due to lack of sunlight on the air above and surrounding sea. The warmest and coldest periods of the year in temperate regions are offset by about one month from the solstices, delayed by the earth's thermal inertia. == Cultural aspects == === Ancient Greek names and concepts === The concept of the solstices was embedded in ancient Greek celestial navigation. As soon as they discovered that the Earth was spherical they devised the concept of the celestial sphere, an imaginary spherical surface rotating with


id: solstice-20260505-2
file: data/en.wikipedia.org/wiki/Solstice-2.md
category: reference
title: Solstice
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solstice
date_saved: 2026-05-05T11:13:30.644057+00:00
instance: kb-cron
parent: solstice-20260505-0
summary:
The term solstice can also be used in a wider sense, as the date (day) that such a passage happens. The solstices, together with the equinoxes, are connected with the seasons. In some languages they are considered to start or separate the seasons; in others they are considered to be centre points (in England, in the Northern Hemisphere, for example, the period around the northern solstice is known as midsummer). Midsummer's Day, defined as St. Johns Day by the Christian Church, is 24 June, about three days after the solstice itself). Similarly 25 December is the start of the Christmas celebration, and is the day the Sun begins to return to the Northern Hemisphere. The traditional British and Irish main rent and meeting days of the year, "the usual quarter days," were often those of the solstices and equinoxes. Many cultures celebrate various combinations of the winter and summer solstices, the equinoxes, and the midpoints between them, leading to various holidays arising around these events. During the southern or winter solstice, Christmas is the most widespread contemporary holiday, while Yalda, Saturnalia, Karachun, Hanukkah, Kwanzaa, and Yule are also celebrated around this time. In East Asian cultures, the Dongzhi Festival is


id: solstice-20260505-3
file: data/en.wikipedia.org/wiki/Solstice-3.md
category: reference
title: Solstice
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solstice
date_saved: 2026-05-05T11:13:30.644057+00:00
instance: kb-cron
parent: solstice-20260505-0
summary:
=== Solstice determination === Unlike the equinox, the solstice time is not easy to determine. The changes in solar declination become smaller as the Sun gets closer to its maximum/minimum declination. The days before and after the solstice, the declination speed is less than 30 arcseconds per day which is less than 1⁄60 of the angular size of the Sun, or the equivalent to just 2 seconds of right ascension. This difference is hardly detectable with indirect viewing based devices like sextant equipped with a vernier, and impossible with more traditional tools like a gnomon or an astrolabe. It is also hard to detect the changes in sunrise/sunset azimuth due to the atmospheric refraction changes. Those accuracy issues render it impossible to determine the solstice day based on observations made within the 3 (or even 5) days surrounding the solstice without the use of more complex tools. Accounts do not survive but Greek astronomers must have used an approximation method based on interpolation, which is still used by some amateurs. This method consists of recording the declination angle at noon during some days before and after the solstice, trying to find two separate days with the same declination. When those


id: sunrise-equation-20260505-0
file: data/en.wikipedia.org/wiki/Sunrise_equation-0.md
category: reference
title: Sunrise equation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sunrise_equation
date_saved: 2026-05-05T11:13:31.804583+00:00
instance: kb-cron
parent: sunrise-equation-20260505-0
summary:
The sunrise equation or sunset equation can be used to derive the time of sunrise or sunset for any solar declination and latitude in terms of local solar time when sunrise and sunset actually occur. == Geometric equation == The time at which a celestial object crosses the horizon can be calculated by converting its coordinates from the equatorial coordinate system to the horizontal coordinate system, and then solving the equation for an altitude of zero. We then obtain cos ⁡ H 0 = − tan ⁡ ϕ tan ⁡ δ {\displaystyle \cos H_{0}=-\tan \phi \,\tan \delta } where: H 0 {\displaystyle H_{0}} is the solar hour angle at either sunrise (when the negative value is taken) or sunset (when the positive value is taken); ϕ {\displaystyle \phi } is the latitude of the observer on the Earth; δ {\displaystyle \delta } is the Sun's declination. This gives the geometric rise or set time (ignoring refraction) of the center of the Sun. See below for an equation which accounts for these effects. The Earth rotates at an angular velocity of 15°/hour. Therefore, the expression H 0 / 15 ∘ {\displaystyle H_{0}/\mathrm {15} ^{\circ }} , where H 0 {\displaystyle H_{0}}


id: sunrise-equation-20260505-1
file: data/en.wikipedia.org/wiki/Sunrise_equation-1.md
category: reference
title: Sunrise equation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sunrise_equation
date_saved: 2026-05-05T11:13:31.804583+00:00
instance: kb-cron
parent: sunrise-equation-20260505-0
summary:
α 1 {\displaystyle \alpha _{1}} and δ 1 {\displaystyle \delta _{1}} , the right ascension and declination on day D − 1 {\displaystyle D-1} at 0h Universal Time, α 2 {\displaystyle \alpha _{2}} and δ 2 {\displaystyle \delta _{2}} , the right ascension and declination on day D {\displaystyle D} , α 3 {\displaystyle \alpha _{3}} and δ 3 {\displaystyle \delta _{3}} , the right ascension and declination on day D + 1 {\displaystyle D+1} . Calculate the approximate time of the sunset using cos ⁡ H 0 = sin ⁡ h 0 − sin ⁡ ϕ sin ⁡ δ 2 cos ⁡ ϕ cos ⁡ δ 2 . {\displaystyle \cos H_{0}={\dfrac {\sin h_{0}-\sin \phi \,\sin \delta _{2}}{\cos \phi \,\cos \delta _{2}}}.} If the right hand side has an absolute value greater than 1, then the Sun does not go below the horizon on that day and H 0 {\displaystyle H_{0}} does not exist. Calculate the transit, sunrise and sunset time in fractions of a day: m 0 = α 2 + L − θ 0 360 ∘ {\displaystyle m_{0}={\frac {\alpha _{2}+L-\theta _{0}}{360^{\circ }}}} m 1 = m 0 − H 0 360 ∘ {\displaystyle m_{1}=m_{0}-{\frac {H_{0}}{360^{\circ }}}} m 2


id: terrestrial-time-20260505-0
file: data/en.wikipedia.org/wiki/Terrestrial_Time-0.md
category: reference
title: Terrestrial Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Terrestrial_Time
date_saved: 2026-05-05T11:13:32.984785+00:00
instance: kb-cron
parent: terrestrial-time-20260505-0
summary:
Terrestrial Time (TT) is a modern astronomical time standard defined by the International Astronomical Union, primarily for time-measurements of astronomical observations made from the surface of Earth. For example, the Astronomical Almanac uses TT for its tables of positions (ephemerides) of the Sun, Moon and planets as seen from Earth. In this role, TT continues Terrestrial Dynamical Time (TDT or TD), which succeeded ephemeris time (ET). TT shares the original purpose for which ET was designed, to be free of the irregularities in the rotation of Earth. The unit of TT is the SI second, the definition of which is based currently on the caesium atomic clock, but TT is not itself defined by atomic clocks. It is a theoretical ideal, and real clocks can only approximate it. TT is distinct from the time scale often used as a basis for civil purposes, Coordinated Universal Time (UTC). TT is indirectly the basis of UTC, via International Atomic Time (TAI). Because of the historical difference between TAI and ET when TT was introduced, TT is 32.184 s ahead of TAI. == History == A definition of a terrestrial time standard was adopted by the International Astronomical Union (IAU) in 1976 at


id: terrestrial-time-20260505-1
file: data/en.wikipedia.org/wiki/Terrestrial_Time-1.md
category: reference
title: Terrestrial Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Terrestrial_Time
date_saved: 2026-05-05T11:13:32.984785+00:00
instance: kb-cron
parent: terrestrial-time-20260505-0
summary:
The main realization of TT is supplied by TAI. The BIPM TAI service, performed since 1958, estimates TT using measurements from an ensemble of atomic clocks spread over the surface and low orbital space of Earth. TAI is canonically defined retrospectively, in monthly bulletins, in relation to the readings shown by that particular group of atomic clocks at the time. Estimates of TAI are also provided in real time by the institutions that operate the participating clocks. Because of the historical difference between TAI and ET when TT was introduced, the TAI realization of TT is defined thus: T T ( T A I ) = T A I + 32.184 s . {\displaystyle \mathrm {TT(TAI)=TAI+32.184~s} .} The offset 32.184 s arises from history. The atomic time scale A1 (a predecessor of TAI) was set equal to UT2 at its conventional starting date of 1 January 1958, when ΔT (ET − UT) was about 32 seconds. The offset 32.184 seconds was the 1976 estimate of the difference between Ephemeris Time (ET) and TAI, "to provide continuity with the current values and practice in the use of Ephemeris Time". TAI is never revised once published and TT(TAI) has small errors relative


id: tropical-year-20260505-0
file: data/en.wikipedia.org/wiki/Tropical_year-0.md
category: reference
title: Tropical year
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tropical_year
date_saved: 2026-05-05T11:13:34.155727+00:00
instance: kb-cron
parent: tropical-year-20260505-0
summary:
A tropical year, or solar year (or tropical period), is the time that the Sun takes to return to the same position in the sky – as viewed from the Earth or another celestial body of the Solar System – thus completing a full cycle of astronomical seasons. For example, it is the time from vernal equinox to the next vernal equinox, or from summer solstice to the next summer solstice. It is the type of year used by tropical solar calendars. The tropical year is one type of astronomical year and a particular orbital period. Another type is the sidereal year (or sidereal orbital period), which is the time it takes Earth to complete one full orbit around the Sun as measured with respect to the fixed stars, resulting in a duration of 20 minutes and 24.7 seconds longer than the tropical year due to the precession of the equinoxes. Since antiquity, astronomers have progressively refined the definition of the tropical year. The entry for "year, tropical" in the Astronomical Almanac Online Glossary states: the period of time for the ecliptic longitude of the Sun to increase 360 degrees. Since the Sun's ecliptic longitude is measured with respect to


id: tropical-year-20260505-1
file: data/en.wikipedia.org/wiki/Tropical_year-1.md
category: reference
title: Tropical year
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tropical_year
date_saved: 2026-05-05T11:13:34.155727+00:00
instance: kb-cron
parent: tropical-year-20260505-0
summary:
=== 18th and 19th century === From the time of Hipparchus and Ptolemy, the year was based on two equinoxes (or two solstices) some years apart, to average out both observational errors and periodic variations (caused by the gravitational pull of the planets, and the small effect of nutation on the equinox). These effects did not begin to be understood until Newton's time. To model short-term variations of the time between equinoxes (and prevent them from confounding efforts to measure long-term variations) requires precise observations and an elaborate theory of the apparent motion of the Sun. The necessary theories and mathematical tools came together in the 18th century due to the work of Pierre-Simon de Laplace, Joseph Louis Lagrange, and other specialists in celestial mechanics. They were able to compute periodic variations and separate them from the gradual mean motion. They could express the mean longitude of the Sun in a polynomial such as: L0 = A0 + A1T + A2T2 days where T is the time in Julian centuries. The derivative of this formula is an expression of the mean angular velocity, and the inverse of this gives an expression for the length of the tropical year as a


id: tropical-year-20260505-2
file: data/en.wikipedia.org/wiki/Tropical_year-2.md
category: reference
title: Tropical year
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tropical_year
date_saved: 2026-05-05T11:13:34.155727+00:00
instance: kb-cron
parent: tropical-year-20260505-0
summary:
== Time scales and calendar == Apparent solar time is the time indicated by a sundial, and is determined by the apparent motion of the Sun caused by the rotation of the Earth around its axis as well as the revolution of the Earth around the Sun. Mean solar time is corrected for the periodic variations in the apparent velocity of the Sun as the Earth revolves in its orbit. The most important such time scale is Universal Time, which is the mean solar time at 0° longitude (the IERS Reference Meridian). Civil time is based on UT (actually UTC), and civil calendars count mean solar days. However, the rotation of the Earth itself is irregular and is slowing down, with respect to more stable time indicators: specifically, the motion of planets and atomic clocks. Ephemeris time (ET) is the independent variable in the equations of motion of the Solar System, in particular, the equations from Newcomb's work, and this ET was in use from 1960 to 1984. These ephemerides were based on observations made in solar time over a period of several centuries, and as a consequence represent the mean solar second over that period. The SI second, defined


id: tropical-year-20260505-3
file: data/en.wikipedia.org/wiki/Tropical_year-3.md
category: reference
title: Tropical year
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tropical_year
date_saved: 2026-05-05T11:13:34.155727+00:00
instance: kb-cron
parent: tropical-year-20260505-0
summary:
=== Different tropical year definitions === If a different starting longitude for the Sun is chosen than 0° (i.e. ♈︎), then the duration for the Sun to return to the same longitude will be different. This is a second-order effect of the circumstance that the speed of the Earth (and conversely the apparent speed of the Sun) varies in its elliptical orbit: faster in the perihelion, slower in the aphelion. The equinox moves with respect to the perihelion (and both move with respect to the fixed sidereal frame). From one equinox passage to the next, or from one solstice passage to the next, the Sun completes not quite a full elliptic orbit. The time saved depends on where it starts in the orbit. If the starting point is close to the perihelion (such as the December solstice), then the speed is higher than average, and the apparent Sun saves little time for not having to cover a full circle: the "tropical year" is comparatively long. If the starting point is near aphelion, then the speed is lower and the time saved for not having to run the same small arc that the equinox has precessed is longer: that tropical year


id: tzolkinex-20260505-0
file: data/en.wikipedia.org/wiki/Tzolkinex-0.md
category: reference
title: Tzolkinex
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tzolkinex
date_saved: 2026-05-05T11:13:35.358456+00:00
instance: kb-cron
parent: tzolkinex-20260505-0
summary:
The tzolkinex is an eclipse cycle equal to a period of two saros (13,170.636 days) minus one inex (10,571.946 days). As consecutive eclipses in an inex series belongs to the next consecutive saros series, each consecutive tzolkinex belongs to the previous saros series. The tzolkinex is equal to 2598.691 days (about 7 years, 1 month and 12 days). It is related to the tritos in that a period of one tritos plus one tzolkinex is exactly equal to one saros. It is also related to the inex in that a period of one inex plus one tzolkinex is exactly equal to two saros. It corresponds to: 88 synodic months 95.49723 draconic months 7.49723 eclipse years (15 eclipse seasons) 94.31081 anomalistic months. Because of the non-integer number of anomalistic month each eclipse varies in type, i.e. total vs. annular, and greatly varies in length. From remainder of 0.31081, being near 1⁄3, every third tzolkinex comes close to an even number of anomalistic months, but occurs during a different season, and in the opposite hemisphere, thus they may be of the same type (annular vs. total) but otherwise do not have a similar character. == Details == It was first studied by


id: universal-time-20260505-0
file: data/en.wikipedia.org/wiki/Universal_Time-0.md
category: reference
title: Universal Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Universal_Time
date_saved: 2026-05-05T11:13:36.566553+00:00
instance: kb-cron
parent: universal-time-20260505-0
summary:
Universal Time (UT or UT1) is a time standard based on Earth's rotation. While originally it was mean solar time at 0° longitude, precise measurements of the Sun are difficult. Therefore, UT1 is computed from a measure of the Earth's angle with respect to the International Celestial Reference Frame (ICRF), called the Earth Rotation Angle (ERA, which serves as the replacement for Greenwich Mean Sidereal Time). UT1 is the same everywhere on Earth. UT1 is required to follow the relationship where Tu = (Julian UT1 date − 2451545.0). == History == Prior to the introduction of standard time, each municipality throughout the clock-using world set its official clock, if it had one, according to the local position of the Sun (see solar time). This served adequately until the introduction of rail travel in Britain, which made it possible to travel fast enough over sufficiently long distances as to require continuous re-setting of timepieces as a train progressed in its daily run through several towns. Starting in 1847, Britain established Greenwich Mean Time (GMT), the mean solar time at Greenwich, England, to solve this problem: all clocks in Great Britain were set to this time regardless of local solar noon. Using


id: universal-time-20260505-1
file: data/en.wikipedia.org/wiki/Universal_Time-1.md
category: reference
title: Universal Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Universal_Time
date_saved: 2026-05-05T11:13:36.566553+00:00
instance: kb-cron
parent: universal-time-20260505-0
summary:
The rotation of the Earth and UT are monitored by the International Earth Rotation and Reference Systems Service (IERS). The International Astronomical Union also is involved in setting standards, but the final arbiter of broadcast standards is the International Telecommunication Union, or ITU. The rotation of the Earth is somewhat irregular and also is very gradually slowing due to tidal acceleration. Furthermore, the length of the second was determined from observations of the Moon between 1750 and 1890. All of these factors cause the modern mean solar day, on the average, to be slightly longer than the nominal 86,400 SI seconds, the traditional number of seconds per day. As UT is thus slightly irregular in its rate, astronomers introduced Ephemeris Time, which has since been replaced by Terrestrial Time (TT). Because Universal Time is determined by the Earth's rotation, which drifts away from more precise atomic-frequency standards, an adjustment (called a leap second) to this atomic time is needed since (as of 2019) 'broadcast time' remains broadly synchronised with solar time. Thus, the civil broadcast standard for time and frequency usually follows International Atomic Time closely, but occasionally step (or "leap") in order to prevent them from drifting too far


id: astronomical-year-numbering-20260505-0
file: data/en.wikipedia.org/wiki/Astronomical_year_numbering-0.md
category: reference
title: Astronomical year numbering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astronomical_year_numbering
date_saved: 2026-05-05T11:13:37.692854+00:00
instance: kb-cron
parent: astronomical-year-numbering-20260505-0
summary:
Astronomical year numbering is based on AD/CE year numbering, but follows normal decimal integer numbering more strictly. Thus, it has a year 0; the years before that are designated with negative numbers and the years after that are designated with positive numbers. Astronomers use the Julian calendar for years before 1582, including the year 0, and the Gregorian calendar for years after 1582, as exemplified by Jacques Cassini (1740), Simon Newcomb (1898) and Fred Espenak (2007). The prefix AD and the suffixes CE, BC or BCE (Common Era, Before Christ or Before Common Era) are dropped. The year 1 BC/BCE is numbered 0, the year 2 BC is numbered −1, and in general the year n BC/BCE is numbered "−(n − 1)" (a negative number equal to 1 − n). The numbers of AD/CE years are not changed and are written with either no sign or a positive sign; thus in general n AD/CE is simply n or +n. For normal calculation a number zero is often needed, here most notably when calculating the number of years in a period that spans the epoch; the end years need only be subtracted from each other. The system is so named due


id: philosophy-of-space-and-time-20260505-0
file: data/en.wikipedia.org/wiki/Philosophy_of_space_and_time-0.md
category: reference
title: Philosophy of space and time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Philosophy_of_space_and_time
date_saved: 2026-05-05T11:13:39.423280+00:00
instance: kb-cron
parent: philosophy-of-space-and-time-20260505-0
summary:
The philosophy of space and time is a branch of philosophy concerned with ideas about knowledge and understanding within space and time. Such ideas have been central to philosophy from its inception. The philosophy of space and time was both an inspiration for and a central aspect of early analytic philosophy. The subject focuses on a number of basic issues, including whether time and space exist independently of the mind, whether they exist independently of one another, what accounts for time's apparently unidirectional flow, whether times other than the present moment exist, and questions about the nature of identity (particularly the nature of identity over time). == Ancient and medieval views == The earliest recorded philosophy of time was expounded by the ancient Egyptian thinker Ptahhotep (c. 2650–2600 BC), who said: Follow your desire as long as you live, and do not perform more than is ordered, do not lessen the time of the following desire, for the wasting of time is an abomination to the spirit... The Vedas, the earliest texts on Indian philosophy and Hindu philosophy, dating back to the late 2nd millennium BC, describe ancient Hindu cosmology, in which the universe goes through repeated cycles of creation,


id: philosophy-of-space-and-time-20260505-1
file: data/en.wikipedia.org/wiki/Philosophy_of_space_and_time-1.md
category: reference
title: Philosophy of space and time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Philosophy_of_space_and_time
date_saved: 2026-05-05T11:13:39.423280+00:00
instance: kb-cron
parent: philosophy-of-space-and-time-20260505-0
summary:
=== Leibniz and Newton === The great debate between defining notions of space and time as real objects themselves (absolute), or mere orderings upon actual objects (relational), began between physicists Isaac Newton (via his spokesman, Samuel Clarke) and Gottfried Leibniz in the papers of the Leibniz–Clarke correspondence. Arguing against the absolutist position, Leibniz offers a number of thought experiments with the purpose of showing that there is contradiction in assuming the existence of facts such as absolute location and velocity. These arguments trade heavily on two principles central to his philosophy: the principle of sufficient reason and the identity of indiscernibles. The principle of sufficient reason holds that for every fact, there is a reason that is sufficient to explain what and why it is the way it is and not otherwise. The identity of indiscernibles states that if there is no way of telling two entities apart, then they are one and the same thing. The example Leibniz uses involves two proposed universes situated in absolute space. The only discernible difference between them is that the latter is positioned five feet to the left of the first. The example is only possible if such a thing as absolute space


id: philosophy-of-space-and-time-20260505-2
file: data/en.wikipedia.org/wiki/Philosophy_of_space_and_time-2.md
category: reference
title: Philosophy of space and time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Philosophy_of_space_and_time
date_saved: 2026-05-05T11:13:39.423280+00:00
instance: kb-cron
parent: philosophy-of-space-and-time-20260505-0
summary:
=== Einstein === Albert Einstein proposed that the laws of physics should be based on the principle of relativity. This principle holds that the rules of physics must be the same for all observers, regardless of the frame of reference that is used, and that light propagates at the same speed in all reference frames. This theory was motivated by Maxwell's equations, which show that electromagnetic waves propagate in a vacuum at the speed of light. However, Maxwell's equations give no indication of what this speed is relative to. Prior to Einstein, it was thought that this speed was relative to a fixed medium, called the luminiferous ether. In contrast, the theory of special relativity postulates that light propagates at the speed of light in all inertial frames, and examines the implications of this postulate. All attempts to measure any speed relative to this ether failed, which can be seen as a confirmation of Einstein's postulate that light propagates at the same speed in all reference frames. Special relativity is a formalization of the principle of relativity that does not contain a privileged inertial frame of reference, such as the luminiferous ether or absolute space, from which Einstein inferred that


id: philosophy-of-space-and-time-20260505-3
file: data/en.wikipedia.org/wiki/Philosophy_of_space_and_time-3.md
category: reference
title: Philosophy of space and time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Philosophy_of_space_and_time
date_saved: 2026-05-05T11:13:39.423280+00:00
instance: kb-cron
parent: philosophy-of-space-and-time-20260505-0
summary:
=== Relativity of simultaneity === According to special relativity, different inertial observers will call different sets of events simultaneous from one another and they will both be right relative to their inertial frame of reference. That is, for example, while observer A may say that events E1 and E2 are simultaneous, another observer B, that's moving in uniform motion relative to observer A, will say that the two events are not simultaneous. This phenomena, known as relativity of simultaneity, has been used to support the metaphysical view known as eternalism and as an objection against presentism. Eternalists maintain that all events in the present, past, and future are, in a sense, ontologically, on a par. This is to say that present events have no privileged existence as compared to events in the past and future. Presentists, on the other hand, maintain that events in the present have a privileged existence (some even maintain that past and future events don't exist). The relativity of simultaneity has been used in the dialectic against presentists because it's hard to see which observer's present could be the one with privileged existence if special relativity says that all inertial frames of reference are on a


id: philosophy-of-space-and-time-20260505-4
file: data/en.wikipedia.org/wiki/Philosophy_of_space_and_time-4.md
category: reference
title: Philosophy of space and time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Philosophy_of_space_and_time
date_saved: 2026-05-05T11:13:39.423280+00:00
instance: kb-cron
parent: philosophy-of-space-and-time-20260505-0
summary:
=== Thermodynamics solution === The second major family of solutions to this problem, and by far the one that has generated the most literature, finds the existence of the direction of time as relating to the nature of thermodynamics. The answer from classical thermodynamics states that while our basic physical theory is, in fact, time-reversal symmetric, thermodynamics is not. In particular, the second law of thermodynamics states that the net entropy of a closed system never decreases, and this explains why we often see glass breaking, but not coming back together. But in statistical mechanics things become more complicated. On one hand, statistical mechanics is far superior to classical thermodynamics, in that thermodynamic behavior, such as glass breaking, can be explained by the fundamental laws of physics paired with a statistical postulate. But statistical mechanics, unlike classical thermodynamics, is time-reversal symmetric. The second law of thermodynamics, as it arises in statistical mechanics, merely states that it is overwhelmingly likely that net entropy will increase, but it is not an absolute law. Current thermodynamic solutions to the problem of the direction of time aim to find some further fact, or feature of the laws of nature to account for this discrepancy.


id: philosophy-of-space-and-time-20260505-5
file: data/en.wikipedia.org/wiki/Philosophy_of_space_and_time-5.md
category: reference
title: Philosophy of space and time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Philosophy_of_space_and_time
date_saved: 2026-05-05T11:13:39.423280+00:00
instance: kb-cron
parent: philosophy-of-space-and-time-20260505-0
summary:
The positions on the persistence of objects are somewhat similar. An endurantist holds that for an object to persist through time is for it to exist completely at different times (each instance of existence we can regard as somehow separate from previous and future instances, though still numerically identical with them). A perdurantist on the other hand holds that for a thing to exist through time is for it to exist as a continuous reality, and that when we consider the thing as a whole we must consider an aggregate of all its "temporal parts" or instances of existing. Endurantism is seen as the conventional view and flows out of our pre-philosophical ideas (when I talk to somebody I think I am talking to that person as a complete object, and not just a part of a cross-temporal being), but perdurantists such as David Lewis have attacked this position. They argue that perdurantism is the superior view for its ability to take account of change in objects. On the whole, Presentists are also endurantists and Eternalists are also perdurantists (and vice versa), but this is not a necessary relation and it is possible to claim, for instance, that time's passage


id: a-series-and-b-series-20260505-0
file: data/en.wikipedia.org/wiki/A_series_and_B_series-0.md
category: reference
title: A series and B series
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/A_series_and_B_series
date_saved: 2026-05-05T11:13:40.580369+00:00
instance: kb-cron
parent: a-series-and-b-series-20260505-0
summary:
In metaphysics, the A series and the B series are two different descriptions of the temporal ordering relation among events. The two series differ principally in their use of tense to describe the temporal relation between events and the resulting ontological implications regarding time. John McTaggart introduced these terms in 1908, in an argument for the unreality of time. They are now commonly used by contemporary philosophers of time. == History == Metaphysical debate about temporal orderings reaches back to the ancient Greek philosophers Heraclitus and Parmenides. Parmenides thought that reality is timeless and unchanging. Heraclitus, in contrast, believed that the world is a process of ceaseless change, flux and decay. Reality for Heraclitus is dynamic and ephemeral, in a state of constant flux, as in his famous statement that it is impossible to step twice into the same river (since the river is flowing). == McTaggart's series == McTaggart distinguished the ancient conceptions as a set of relations. According to McTaggart, there are two distinct modes in which all events can be ordered in time. === A series === In the first mode, events are ordered as future, present, and past. Futurity and pastness allow of degrees, while the


id: aevum-20260505-0
file: data/en.wikipedia.org/wiki/Aevum-0.md
category: reference
title: Aevum
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Aevum
date_saved: 2026-05-05T11:13:42.925412+00:00
instance: kb-cron
parent: aevum-20260505-0
summary:
In scholastic philosophy, the aevum (also called aeviternity) is the temporal mode of existence experienced by angels and by the saints in heaven. In some ways, it is a state that logically lies between the eternity (timelessness) of God and the temporal experience of material beings. It is sometimes referred to as "improper eternity" or "participated eternity". == Etymology == The word aevum is Latin, originally signifying "age", "aeon", or "everlasting time". It comes from the Greek term "αἰών" meaning eternity in the atemporal sense. Before the 13th century, the term aevum was used synonymously with eternity. The word aeviternity comes from the Medieval Latin neologism aeviternitas. == History == Both Plato and Aristotle recognized two modes of duration: Time and Eternity. Plato said that the soul must be in time while Aristotle said that the soul must be in eternity. The Neoplatonist philosopher Simplicius of Cilicia, said there must be a third mode to describe celestial bodies and souls which are everlasting but still change. In his exegesis of the Book of Genesis, Augustine of Hippo also recognized a mode of duration distinct from time and eternity. In Augustine's view, Heaven and earth, taken to mean formless matter, were


id: atom-time-20260505-0
file: data/en.wikipedia.org/wiki/Atom_(time)-0.md
category: reference
title: Atom (time)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atom_(time)
date_saved: 2026-05-05T11:13:45.286592+00:00
instance: kb-cron
parent: atom-time-20260505-0
summary:
An atom of time is the smallest possible unit of time. == History == One of the earliest occurrences of the word "atom" to mean the smallest possible unit of measuring time is found in the Greek text of the New Testament in Paul's 1 Corinthians 15:52. The text compares the length of time of the "atom" to the time needed for "the twinkling of an eye." The text reads: "ἐν ἀτόμῳ, ἐν ῥιπῇ ὀφθαλμοῦ" – "en atomo, en ripe ophthamou" – the word "atom" is usually translated "a moment" – "In a moment, in the twinkling of an eye". It was later referred to in medieval philosophical writings in this sense as the smallest possible division of time. The earliest known occurrence in English is in Byrhtferth's Enchiridion of 1010–1012, where it was defined as 1/564 of a momentum (1½ minutes), and thus equal to almost 160 milliseconds. It was used in the computus, the calculation used to determine the calendar date of Easter. == See also == Planck time == References ==


id: b-theory-of-time-20260505-0
file: data/en.wikipedia.org/wiki/B-theory_of_time-0.md
category: reference
title: B-theory of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/B-theory_of_time
date_saved: 2026-05-05T11:13:46.457538+00:00
instance: kb-cron
parent: b-theory-of-time-20260505-0
summary:
The B-theory of time, also called the "tenseless theory of time", is one of two positions regarding the temporal ordering of events in the philosophy of time. B-theorists argue that the flow of time is only a subjective illusion of human consciousness, that the past, present, and future are equally real, and that time is tenseless: temporal becoming is not an objective feature of reality. Therefore, there is nothing privileged about the present, ontologically speaking. The B-theory is derived from a distinction drawn by J. M. E. McTaggart between A series and B series. The B-theory is often drawn upon in theoretical physics and is seen in theories such as eternalism. == Origin of terms == The terms A-theory and B-theory, first coined by Richard M. Gale in 1966, derive from Cambridge philosopher J. M. E. McTaggart's analysis of time and change in "The Unreality of Time" (1908), in which events are ordered via a tensed A-series or a tenseless B-series. It is popularly assumed that the A-theory represents time like an A-series, while the B-theory represents time like a B-series. Events (or "times"), McTaggart observed, may be characterized in two distinct but related ways. On the one hand they


id: b-theory-of-time-20260505-1
file: data/en.wikipedia.org/wiki/B-theory_of_time-1.md
category: reference
title: B-theory of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/B-theory_of_time
date_saved: 2026-05-05T11:13:46.457538+00:00
instance: kb-cron
parent: b-theory-of-time-20260505-0
summary:
=== Irreducibility of tense === Earlier B-theorists argued that one could paraphrase tensed sentences (such as "the sun is now shining", uttered on September 28) into tenseless sentences (such as "on September 28, the sun shines") without loss of meaning. Later B-theorists argued that tenseless sentences could give the truth conditions of tensed sentences or their tokens. Quentin Smith argues that "now" cannot be reduced to descriptions of dates and times, because all date and time descriptions, and therefore truth conditionals, are relative to certain events. Tensed sentences, on the other hand, do not have such truth conditionals. The B-theorist could argue that "now" is reducible to a token-reflexive phrase such as "simultaneous with this utterance", yet Smith states that even such an argument fails to eliminate tense. One can think the statement "I am not uttering anything now", and such a statement would be true. The statement "I am not uttering anything simultaneous with this utterance" is self-contradictory, and cannot be true even when one thinks the statement. Finally, while tensed statements can express token-independent truth values, no token-reflexive statement can do so (by definition of the term "token-reflexive"). Smith claims that proponents of the B-theory argue that the


id: craig-callender-20260505-0
file: data/en.wikipedia.org/wiki/Craig_Callender-0.md
category: reference
title: Craig Callender
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Craig_Callender
date_saved: 2026-05-05T11:13:47.702523+00:00
instance: kb-cron
parent: craig-callender-20260505-0
summary:
Craig Callender (born 1968) is a professor of philosophy at the University of California, San Diego. His main areas of research are philosophy of science, philosophy of physics and metaphysics. == Education and career == Callender obtained his PhD in 1997 from Rutgers University with a thesis entitled Time's Arrow under the supervision of Robert Weingard. From 1996-2000, he worked in the Department of Philosophy, Logic & Scientific Method at the London School of Economics. Currently, he is a professor of philosophy at the University of California, San Diego where he is also the co-director of the Institute for Practical Ethics at the University of California, San Diego. Callender serves on the Committee for Freedom and Responsibility of Science of the International Science Council. Callender has written articles for Scientific American on the philosophy of time and participated in the World Science Festival 2013 with Tim Maudlin and Max Tegmark on the same topic. == Selected publications == In reverse chronological order, unless otherwise specified. === Books === Callender, Craig (2017). What Makes Time Special? Oxford University Press, Oxford, ISBN 978-0-19-879730-2 Callender, Craig, ed. (2011). The Oxford handbook of philosophy of time. Oxford Handbooks in Philosophy. Oxford University Press. ISBN


id: centered-world-20260505-0
file: data/en.wikipedia.org/wiki/Centered_world-0.md
category: reference
title: Centered world
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Centered_world
date_saved: 2026-05-05T11:13:48.889143+00:00
instance: kb-cron
parent: centered-world-20260505-0
summary:
A centered world, according to David Kellogg Lewis, consists of (1) a possible world, (2) an agent in that world, and (3) a time in that world. The concept of centered worlds has epistemic as well as metaphysical uses; for the latter, the three components of a centered world have connections to theories such as actualism, solipsism (especially egocentric presentism and perspectival realism), and presentism, respectively. == References ==


id: chronosophy-20260505-0
file: data/en.wikipedia.org/wiki/Chronosophy-0.md
category: reference
title: Chronosophy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chronosophy
date_saved: 2026-05-05T11:13:50.070367+00:00
instance: kb-cron
parent: chronosophy-20260505-0
summary:
Chronosophy is the neologistic designation given by scholar Julius Thomas (J.T.) Fraser to "the interdisciplinary and normative study of time sui generis." == Overview == === Etymology === Fraser derived the term from the Ancient Greek: χρόνος, chronos, "time" and σοφία, sophia, "wisdom". Chronosophia is thus defined as the "specific human skill or knowledge . . . pertaining to time . . . [which] all men seem to possess to some degree . . .". === Purpose === Fraser outlined the purpose of the discipline of chronosophy in five intentions, as follows: to encourage the search for new knowledge related to time; to set up and apply criteria regarding which fields of knowledge contribute to an understanding of time, and what they may contribute; to assist in epistemological studies, especially in those related to the structure of knowledge; to provoke communication between the humanities and the sciences using time as the common theme; and to help us learn more about the nature of time by providing channels for the direct confrontation of a multitude of views. === Assumptions === According to Fraser, any pursuit of chronosophical knowledge necessarily makes two assumptions: When specialists speak of 'time', they speak of various


id: chronosophy-20260505-1
file: data/en.wikipedia.org/wiki/Chronosophy-1.md
category: reference
title: Chronosophy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chronosophy
date_saved: 2026-05-05T11:13:50.070367+00:00
instance: kb-cron
parent: chronosophy-20260505-0
summary:
expansion beyond or abandonment of [traditional areas of] specialization, and the espousal of interdisciplinary or pan-disciplinary methodologies; (1) is a weak criterion, while (2) is a strong one. Neither of the above criteria make reference to time or temporality; for while the ontological possibly of timeless knowledge must always remain, admission of this possibility begs the question (petitio principii): e.g., what form does timeless knowledge take? how would it come to us? how could we ever be separated from such knowledge to begin with? et cetera ad nauseam. The admission is therefore a paradox (akin to Wittgenstein's seventh proposition in Tractatus Logico-Philosophicus: "Whereof one cannot speak, thereof one must be silent."). We must conclude that the proposal of the possibility of timeless knowledge is both necessary and senseless, a conceptual counterpart to the tautologous nature of the concept of time. Should we come to possess knowledge of that which is "beneath" or "behind" time (or, alternatively, conclude we could never have lost possession of it), there would be no discernible need for further chronosophical inquiry—in the face of such eternal truth, it would instead be chronosophy as currently conceived that would appear both necessary and senseless. Hence: all disciplines are


id: coincidence-20260505-0
file: data/en.wikipedia.org/wiki/Coincidence-0.md
category: reference
title: Coincidence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coincidence
date_saved: 2026-05-05T11:13:51.260103+00:00
instance: kb-cron
parent: coincidence-20260505-0
summary:
A coincidence is a remarkable concurrence of events or circumstances that have no apparent causal connection with one another. The perception of remarkable coincidences may lead to supernatural, occult, or paranormal claims, or it may lead to belief in fatalism, which is a doctrine that events will happen in the exact manner of a predetermined plan. In general, the perception of coincidence, for lack of more sophisticated explanations, can serve as a link to folk psychology and philosophy. From a statistical perspective, coincidences are inevitable and often less remarkable than they may appear intuitively. Usually, coincidences are chance events with underestimated probability. An example is the birthday problem, which shows that the probability of two persons having the same birthday already exceeds 50% in a group of only 23 persons. Generalizations of the birthday problem are a key tool used for mathematically modelling coincidences. == Etymology == The first known usage of the word coincidence is from c. 1605 with the meaning "exact correspondence in substance or nature" from the French coincidence, from coincider, from Medieval Latin coincidere. The definition evolved in the 1640s as "occurrence or existence during the same time". The word was introduced to English readers in


id: duration-philosophy-20260505-0
file: data/en.wikipedia.org/wiki/Duration_(philosophy)-0.md
category: reference
title: Duration (philosophy)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Duration_(philosophy)
date_saved: 2026-05-05T11:13:52.453466+00:00
instance: kb-cron
parent: duration-philosophy-20260505-0
summary:
Duration (French: la durée) is a theory of time and consciousness posited by the French philosopher Henri Bergson. Bergson sought to improve upon inadequacies he perceived in the philosophy of Herbert Spencer, due, he believed, to Spencer's lack of comprehension of mechanics, which led Bergson to the conclusion that time eluded mathematics and science. Bergson became aware that the moment one attempted to measure a moment, it would be gone: one measures an immobile, complete line, whereas time is mobile and incomplete. For the individual, time may speed up or slow down, whereas, for science, it would remain the same. Hence Bergson decided to explore the inner life of man, which is a kind of duration, neither a unity nor a quantitative multiplicity. Duration is ineffable and can only be shown indirectly through images that can never reveal a complete picture. It can only be grasped through a simple intuition of the imagination. Bergson first introduced his notion of duration in his essay Time and Free Will: An Essay on the Immediate Data of Consciousness. It is used as a defense of free will in a response to Immanuel Kant, who believed free will was only possible outside time and


id: duration-philosophy-20260505-1
file: data/en.wikipedia.org/wiki/Duration_(philosophy)-1.md
category: reference
title: Duration (philosophy)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Duration_(philosophy)
date_saved: 2026-05-05T11:13:52.453466+00:00
instance: kb-cron
parent: duration-philosophy-20260505-0
summary:
The truth is we change without ceasing...there is no essential difference between passing from one state to another and persisting in the same state. If the state which "remains the same" is more varied than we think, [then] on the other hand the passing of one state to another resembles—more than we imagine—a single state being prolonged: the transition is continuous. Just because we close our eyes to the unceasing variation of every physical state, we are obliged when the change has become so formidable as to force itself on our attention, to speak as if a new state were placed alongside the previous one. Of this new state we assume that it remains unvarying in its turn and so on endlessly. Because a qualitative multiplicity is heterogeneous and yet interpenetrating, it cannot be adequately represented by a symbol; indeed, for Bergson, a qualitative multiplicity is inexpressible. Thus, to grasp duration, one must reverse habitual modes of thought and place oneself within duration by intuition. == Influence on Gilles Deleuze == Gilles Deleuze was profoundly influenced by Bergson's theory of duration, particularly in his work Cinema 1: The Movement Image in which he described cinema as providing people with continuity


id: egocentric-presentism-20260505-0
file: data/en.wikipedia.org/wiki/Egocentric_presentism-0.md
category: reference
title: Egocentric presentism
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Egocentric_presentism
date_saved: 2026-05-05T11:13:53.611819+00:00
instance: kb-cron
parent: egocentric-presentism-20260505-0
summary:
Egocentric presentism is a form of solipsism introduced by Caspar Hare in which other persons can be conscious, but their experiences are simply not present. Similarly, in related work, Hare argues for a theory of perspectival realism in which other perspectives do exist, but the present perspective has a defining intrinsic property. In one example that Hare uses to illustrate his theory (starting on page 354 of the official version of his paper), you learn that you are one of two people, named A and B, who have just been in a train crash; and that A is about to have incredibly painful surgery. You cannot remember your name. According to Hare, naturally, you hope to be B. The point of the example is that you know everything relevant that there is to know about the objective world; all that is missing is your position in it, that is, whose experiences are present, A's or B's. This example is easily handled by egocentric presentism because under this theory, the case where the present experiences are A's is fundamentally different from the case where the present experiences are B's. Hare points out that similar examples can be given to support theories


id: einstein-bergson-debate-20260505-0
file: data/en.wikipedia.org/wiki/Einstein–Bergson_debate-0.md
category: reference
title: Einstein–Bergson debate
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Einstein–Bergson_debate
date_saved: 2026-05-05T11:13:54.954737+00:00
instance: kb-cron
parent: einstein-bergson-debate-20260505-0
summary:
On April 6, 1922, the physicist Albert Einstein and the philosopher Henri Bergson met at the Société française de philosophie and discussed the implications of the theory of relativity on the nature of time. This debate, with the broader discussion it set off, has had wide-ranging implications for Western cosmology and for the prestige of the humanities as compared to science. In 1934, Paul Valéry wrote that the meeting between these two thinkers was the "grande affaire" of the twentieth century. == Context == === Bergson === Henri Bergson was widely viewed as an epoch-defining thinker. For William James, Bergson's Creative Evolution was a work as important for Western philosophy as those of George Berkeley or Immanuel Kant; Jean Wahl concurs, placing Bergson alongside Plato, René Descartes and Kant as one of "the four great philosophers." A cult of personality developed around Bergson following the 1907 publication of Creative Evolution: students would make "mystical pilgrimages" to his summer home in Switzerland; he was referred to as "an enchanter" and "the greatest thinker in the world." His biographer Emily Herring refers to him as being in the early twentieth century "the most famous philosopher in the world." Bergson had a deep


id: einstein-bergson-debate-20260505-1
file: data/en.wikipedia.org/wiki/Einstein–Bergson_debate-1.md
category: reference
title: Einstein–Bergson debate
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Einstein–Bergson_debate
date_saved: 2026-05-05T11:13:54.954737+00:00
instance: kb-cron
parent: einstein-bergson-debate-20260505-0
summary:
Einstein's theory of relativity and his contributions to quantum theory had made him a household name in the scientific community, and by 1919 he even became a public celebrity after the solar eclipse of May 29, 1919, which helped substantiate Einstein's theory of general relativity, with the New York Times proclaiming: “Revolution in Science/New Theory of the Universe/Newtonian Ideas Overthrown.” The new doctrine was widely regarded as necessitating a total overhaul of current understandings of space and time. Einstein's fame had proliferated through his own efforts as well: he had published popular versions of both his treatises, and his Four Lectures on Relativity (delivered in 1921 at Princeton University) had intensified public interest even further. Einstein was invited to France by Paul Langevin, on behalf of the Collège de France, to help “to restore relations between German and French scholars” after World War I, a conflict whose mechanization had enlisted scientists in the service of bloodshed to a previously unprecedented degree. Einstein had opposed the war. On his arrival at the Gare du Nord, Einstein was greeted by crowds of "photographers, reporters, filmmakers, officials and diplomats," and had to slip out a side door to escape the attention. The debate


id: einstein-bergson-debate-20260505-2
file: data/en.wikipedia.org/wiki/Einstein–Bergson_debate-2.md
category: reference
title: Einstein–Bergson debate
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Einstein–Bergson_debate
date_saved: 2026-05-05T11:13:54.954737+00:00
instance: kb-cron
parent: einstein-bergson-debate-20260505-0
summary:
=== Duration and Simultaneity === Later in 1922, Bergson published Duration and Simultaneity, which was explicitly a "confrontation" with Einstein's theory of relativity. It sought to enlist the facts Einstein drew upon in his theories in service of Bergson's vitalist philosophy. He argued that special relativity is rooted in quantifiable clock-time, and that it fails to capture the true essence of time as duration. Distinguishing between "real" time that can be directly experienced and "imaginary" time (i.e. time dilation and relativity of simultaneity) derived form the relativistic formulas, he specifically takes aim at the twin paradox first proposed by Paul Langevin, and calls for the biological aging process to be distinguished from measurable time. In Langevin's example, a traveler makes a round-trip in a rocket for 200 years as measured on Earth, while he himself only experienced 2 years during the flight (see History of the twin paradox). Bergson erroneously rejected this conclusion by claiming that both twins (Peter on Earth and Paul in the rocket) are interchangeable and therefore must be of same age at reunion: p.74: We must now repeat for Paul everything we said about Peter: Since motion is reciprocal, the two people are interchangeable. If, earlier,


id: eternal-return-20260505-0
file: data/en.wikipedia.org/wiki/Eternal_return-0.md
category: reference
title: Eternal return
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eternal_return
date_saved: 2026-05-05T11:13:56.229279+00:00
instance: kb-cron
parent: eternal-return-20260505-0
summary:
Eternal return (or eternal recurrence) is a philosophical concept which states that time repeats itself in an infinite loop, and that exactly the same events will continue to occur in exactly the same way, over and over again, for eternity. In ancient Greece, the concept of eternal return was most prominently associated with Empedocles and with Stoicism, the school of philosophy founded by Zeno of Citium. The Stoics believed that the universe is periodically destroyed and reborn, and that each universe is exactly the same as the one before. This doctrine was fiercely criticised by Christian authors such as Augustine, who saw in it a fundamental denial of free will and of the possibility of salvation. The spread of Christianity therefore diminished classical theories of eternal return. The concept was revived in the 19th century by German philosopher Friedrich Nietzsche. Having briefly presented the idea as a thought experiment in The Gay Science, he explored it more thoroughly in his novel Thus Spoke Zarathustra, in which the protagonist learns to overcome his horror of the thought of eternal return. It is not known whether Nietzsche believed in the literal truth of eternal return, or, if he did not, what he


id: eternal-return-20260505-1
file: data/en.wikipedia.org/wiki/Eternal_return-1.md
category: reference
title: Eternal return
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eternal_return
date_saved: 2026-05-05T11:13:56.229279+00:00
instance: kb-cron
parent: eternal-return-20260505-0
summary:
=== Christian response === Christian authors attacked the doctrine of eternal recurrence on various grounds. Origen argued that the theory was incompatible with free will (although he did allow the possibility of diverse and non-identical cycles). Augustine of Hippo (354–430 AD) objected to the fact that salvation was not possible in the Stoic scheme, arguing that even if a temporary happiness was attained, a soul could not be truly blessed if it was doomed to return again to misery. Augustine also mentions "certain philosophers" who cite Ecclesiastes 1:9–10 as evidence of eternal return: "What is that which hath been? It is that which shall be. And what is that which is done? It is that which shall be done: and there is no new thing under the sun. Who can speak and say, See, this is new? It hath been already of old time, which was before us." Augustine denies that this has reference to the recurrence of specific people, objects, and events, instead interpreting the passage in a more general sense. In support of his argument, he appeals to scriptural passages such as Romans 6:9, which affirms that Christ "being raised from the dead dieth no more". == Friedrich


id: eternal-return-20260505-2
file: data/en.wikipedia.org/wiki/Eternal_return-2.md
category: reference
title: Eternal return
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eternal_return
date_saved: 2026-05-05T11:13:56.229279+00:00
instance: kb-cron
parent: eternal-return-20260505-0
summary:
=== Interpretation === Martin Heidegger points out that Nietzsche's first mention of eternal recurrence in The Gay Science presents this concept as a hypothetical question rather than postulating it as a fact. Many readings argue that Nietzsche was not attempting to make a cosmological or theoretical claim i.e. saying that eternal recurrence is a true statement about how the world works. Instead, the emotional reaction to the thought experiment serves to reveal whether one is living life to the best. According to Heidegger, the significant point is the burden imposed by the question of eternal recurrence, regardless of whether or not such a thing could possibly be true. The idea is similar to Nietzsche's concept of amor fati, which he describes in Ecce Homo: "My formula for greatness in a human being is amor fati: that one wants nothing to be different, not forward, not backward, not in all eternity. Not merely to bear what is necessary, still less conceal it ... but love it." On the other hand, Nietzsche's posthumously published notebooks contain an attempt at a logical proof of eternal return, which is often adduced in support of the claim that Nietzsche believed in the theory as a


id: eternalism-philosophy-of-time-20260505-0
file: data/en.wikipedia.org/wiki/Eternalism_(philosophy_of_time)-0.md
category: reference
title: Eternalism (philosophy of time)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time)
date_saved: 2026-05-05T11:13:57.502214+00:00
instance: kb-cron
parent: eternalism-philosophy-of-time-20260505-0
summary:
In the philosophy of space and time, eternalism is an ontological view according to which all existence in time is equally real, as opposed to presentism or the growing block universe theory of time, in which at least the future is not the same as any other time. Some forms of eternalism give time a similar ontology to that of space, as a dimension, with different times being as real as different places, and future events are "already there" in the same sense other places are already there, and that there is no objective flow of time. It is sometimes referred to as the "block time" or "block universe" theory due to its description of space-time as an unchanging four-dimensional "block", as opposed to the view of the world as a three-dimensional space modulated by the passage of time. == The present == In classical philosophy, time is divided into three distinct regions: the "past", the "present", and the "future". Using that representational model, the past is generally seen as being immutably fixed, and the future as at least partly undefined. As time passes, the moment that was once the present becomes part of the past, and part of the


id: eternalism-philosophy-of-time-20260505-1
file: data/en.wikipedia.org/wiki/Eternalism_(philosophy_of_time)-1.md
category: reference
title: Eternalism (philosophy of time)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time)
date_saved: 2026-05-05T11:13:57.502214+00:00
instance: kb-cron
parent: eternalism-philosophy-of-time-20260505-0
summary:
=== Modern period === One of the most famous arguments about the nature of time in modern philosophy is presented in The Unreality of Time by J. M. E. McTaggart. It argues that time is an illusion. McTaggart argued that the description of events as existing in absolute time is self-contradictory, because the events have to have properties about being in the past and in the future, which are incompatible with each other. McTaggart viewed this as a contradiction in the concept of time itself, and concluded that reality is non-temporal. He called this concept the B-theory of time. Dirck Vorenkamp, a professor of religious studies, argued in his paper "B-Series Temporal Order in Dogen's Theory of Time" that the Zen Buddhist teacher Dōgen presented views on time that contained all the main elements of McTaggart's B-series view of time (which denies any objective present), although he noted that some of Dōgen's reasoning also contained A-Series notions, which Vorenkamp argued may indicate some inconsistency in Dōgen's thinking. Eternalism also encapsulates the theory of world lines, and the concept of linear reality that is - the individual perception of linear time. === Quantum physics === Some philosophers appeal to a specific


id: eternity-20260505-0
file: data/en.wikipedia.org/wiki/Eternity-0.md
category: reference
title: Eternity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eternity
date_saved: 2026-05-05T11:13:58.699406+00:00
instance: kb-cron
parent: eternity-20260505-0
summary:
Eternity, also referred to as sempiternity or forever, is time with no end i.e. infinite. In the context of human life, eternity and death are co-existing realities. == Etymology == Cicero used the word aeternitatis, written at some uncertain time between the years 88 - 81 BC (work: De Inventione 1, 27, 39. : tempus autem est—id quo nunc utimur, nam ipsum quidem generaliter definire difficile est—pars quaedam aeternitatis cum alicuius annui, menstrui, diurni nocturnive spatii certa significatione.) which is an early or the earliest extant written form from which the English word is derived; first shown in history in an approx. 1374 translation by Chaucer. The first usage in French is 1175: eternitez: B. de Ste-Maure, 'Ducs Normandie. == Philosophy == Classical period (8th-7th century BC - 5th-9th century AD) Plato (c. 428–423 BC - 348/347 BC) described time as the moving image of eternity in Timaeus (37 D) using the word: αἰών. Aristotle (384–322 BC) stated οὐρανοῦ was eternal (in Book I of Περὶ οὐρανοῦ) and an eternal world (in Physics). The ancient Greek word for everlastingness was ἀίδιος (aidios) as exists via Plotinus, who also used the word aoin (eternity), in Ennead III.7. The thought of Classical


id: eternity-of-the-world-20260505-0
file: data/en.wikipedia.org/wiki/Eternity_of_the_world-0.md
category: reference
title: Eternity of the world
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eternity_of_the_world
date_saved: 2026-05-05T11:13:59.985243+00:00
instance: kb-cron
parent: eternity-of-the-world-20260505-0
summary:
The eternity of the world is the question, in philosophy, of whether the world has a beginning in time or has existed for eternity. It was a concern for ancient philosophers as well as theologians and philosophers of the 13th century. The problem became a focus of a dispute in the 13th century, when some of the works of Aristotle, who believed in the eternity of the world, were rediscovered in the Latin West. This view conflicted with the view of the Catholic Church that the world had a beginning in time. The Aristotelian view was prohibited in the Condemnations of 1210–1277. == Aristotle == The ancient Greek philosopher Aristotle argued that the world must have existed from eternity in his Physics as follows. In Book I, he argues that everything that comes into existence does so from a substratum. Therefore, if the underlying matter of the universe came into existence, it would come into existence from a substratum. But the nature of matter is precisely to be the substratum from which other things arise. Consequently, the underlying matter of the universe could have come into existence only from an already existing matter exactly like itself; to assume that the


id: eternity-of-the-world-20260505-1
file: data/en.wikipedia.org/wiki/Eternity_of_the_world-1.md
category: reference
title: Eternity of the world
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eternity_of_the_world
date_saved: 2026-05-05T11:13:59.985243+00:00
instance: kb-cron
parent: eternity-of-the-world-20260505-0
summary:
"An actual infinite cannot exist." "An infinite temporal regress of events is an actual infinite." "Thus an infinite temporal regress of events cannot exist." This argument defines event as equal increments of time. Philoponus argues that the second premise is not controversial since the number of events prior to today would be an actual infinite without beginning if the universe is eternal. The first premise is defended by a reductio ad absurdum where Philoponus shows that actual infinites can not exist in the actual world because they would lead to contradictions albeit being a possible mathematical enterprise. Since an actual infinite in reality would create logical contradictions, it can not exist including the actual infinite set of past events. The second argument, the "argument from the impossibility of completing an actual infinite by successive addition", states: "An actual infinite cannot be completed by successive addition." "The temporal series of past events has been completed by successive addition." "Thus the temporal series of past events cannot be an actual infinite." The first statement states, correctly, that a finite (number) cannot be made into an infinite one by the finite addition of more finite numbers. The second skirts around this; the analogous


id: event-philosophy-20260505-0
file: data/en.wikipedia.org/wiki/Event_(philosophy)-0.md
category: reference
title: Event (philosophy)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Event_(philosophy)
date_saved: 2026-05-05T11:14:01.214153+00:00
instance: kb-cron
parent: event-philosophy-20260505-0
summary:
In philosophy, events are objects in time or instantiations of properties in objects. On some views, only changes in the form of acquiring or losing a property can constitute events, like the lawn's becoming dry. According to others, there are also events that involve nothing but the retaining of a property, e.g. the lawn's staying wet. Events are usually defined as particulars that, unlike universals, cannot repeat at different times. Processes are complex events constituted by a sequence of events. But even simple events can be conceived as complex entities involving an object, a time and the property exemplified by the object at this time. Traditionally, metaphysicians tended to emphasize static being over dynamic events. This tendency has been opposed by so-called process philosophy or process ontology, which ascribes ontological primacy to events and processes. == Kim’s property-exemplification == Jaegwon Kim theorized that events are structured. They are composed of three things: object(s) [ x ] {\displaystyle [x]} , a property [ P ] {\displaystyle [P]} and time or a temporal interval [ t ] {\displaystyle [t]} . Events are defined using the operation [ x , P , t ] {\displaystyle [x,P,t]} . A unique event is defined by


id: event-philosophy-20260505-1
file: data/en.wikipedia.org/wiki/Event_(philosophy)-1.md
category: reference
title: Event (philosophy)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Event_(philosophy)
date_saved: 2026-05-05T11:14:01.214153+00:00
instance: kb-cron
parent: event-philosophy-20260505-0
summary:
== Lewis == David Lewis theorized that events are merely spatiotemporal regions and properties (i.e. membership of a class). He defines an event as "e is an event only if it is a class of spatiotemporal regions, both thisworldly (assuming it occurs in the actual world) and otherworldly." The only problem with this definition is it only tells us what an event could be, but does not define a unique event. This theory entails modal realism, which assumes possible worlds exist; worlds are defined as sets containing all objects that exist as a part of that set. However, this theory is controversial. Some philosophers have attempted to remove possible worlds, and reduce them to other entities. They hold that the world we exist in is the only world that actually exists, and that possible worlds are only possibilities. Lewis’ theory is composed of four key points. Firstly, the non-duplication principle; it states that x and y are separate events if and only if there is one member of x that is not a member of y (or vice versa). Secondly, there exist regions that are subsets of possible worlds and thirdly, events are not structured by an essential time. ==


id: an-experiment-with-time-20260505-0
file: data/en.wikipedia.org/wiki/An_Experiment_with_Time-0.md
category: reference
title: An Experiment with Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/An_Experiment_with_Time
date_saved: 2026-05-05T11:14:02.376353+00:00
instance: kb-cron
parent: an-experiment-with-time-20260505-0
summary:
An Experiment with Time is a book by the British soldier, aeronautical engineer and philosopher J. W. Dunne (1875–1949) about his precognitive dreams and a theory of time which he later called "Serialism". First published in March 1927, the book was widely read. Although never accepted by mainstream scientists or philosophers, it has influenced imaginative literature ever since. Dunne published four sequels: The Serial Universe (1934), The New Immortality (1938), Nothing Dies (1940) and Intrusions? (1955). == Description == === Overview === An Experiment with Time discusses two main topics. The first half of the book describes a number of precognitive dreams, most of which Dunne himself had experienced. His key conclusion was that such precognitive visions foresee future personal experiences by the dreamer and not mere general events. The second half develops a theory to try to explain them. Dunne's starting point is the observation that the moment of "now" is not described by science. Contemporary science described physical time as a fourth dimension and Dunne's argument led to an endless sequence of higher dimensions of time to measure our passage through the dimension below. Accompanying each level was a higher level of consciousness. At the end of the


id: an-experiment-with-time-20260505-1
file: data/en.wikipedia.org/wiki/An_Experiment_with_Time-1.md
category: reference
title: An Experiment with Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/An_Experiment_with_Time
date_saved: 2026-05-05T11:14:02.376353+00:00
instance: kb-cron
parent: an-experiment-with-time-20260505-0
summary:
== Publishing history == An Experiment with Time was first published by A & C Black in March 1927. Dunne continued to update it and many new editions and impressions were published over his lifetime. Black brought out a 1929 second edition, prefaced with editorial notes and an extract from a 1928 letter from Arthur Eddington. Dunne then changed publisher to Faber & Faber, with whom he would remain. The third edition incorporated major new material and was published by Faber's in 1932; this and subsequent editions were published in the US by Macmillan. The final version which he had a hand in was published as a "reprint" in 1948. Faber continued printing paperback editions until at least 1973, and others have appeared since. == Reception == === Academic === Initial reactions from the scientific and scientifically-minded community were broadly positive. Nature carried a review by the philosopher and mathematician Hyman Levy. They accepted that Dunne was a sober and rational investigator who was doing his best to take a scientific approach. They acknowledged that if his ideas about time and consciousness were true then his book would be truly revolutionary. However opinions differed over the existence of dream precognition,


id: from-eternity-to-here-20260505-0
file: data/en.wikipedia.org/wiki/From_Eternity_to_Here-0.md
category: reference
title: From Eternity to Here
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/From_Eternity_to_Here
date_saved: 2026-05-05T11:14:03.535877+00:00
instance: kb-cron
parent: from-eternity-to-here-20260505-0
summary:
From Eternity to Here: The Quest for the Ultimate Theory of Time is a nonfiction book by American theoretical physicist Sean M. Carroll, published on January 7, 2010, by Dutton. == Background == In the book, Carroll explores the nature of the arrow of time, that goes forward from the past to the future, and posits that the arrow owes its existence to conditions before the Big Bang. However, reasoning about what was there before the Big Bang has traditionally been dismissed as meaningless, for space and time are considered to be created exactly at the Big Bang. Carroll argues that "understanding the arrow of time is a matter of understanding the origin of the universe" and in his explanations relies on the second law of thermodynamics, which states that all systems in the Universe tend to become more and more disorganized (increase in entropy). His proposed explanation for the arrow of time is based on ideas that go back to Ludwig Boltzmann, an Austrian physicist of the 1870s. == Book organization == The book is divided into four parts and 15 chapters and has an appendix for the relevant math. Part one is entitled, "Time, Experience, and the Universe."


id: further-facts-20260505-0
file: data/en.wikipedia.org/wiki/Further_facts-0.md
category: reference
title: Further facts
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Further_facts
date_saved: 2026-05-05T11:14:04.749751+00:00
instance: kb-cron
parent: further-facts-20260505-0
summary:
In philosophy, further facts are facts that do not logically follow from the physical facts of the world. Reductionists who argue that at bottom there is nothing more than the physical facts thus argue against the existence of further facts. The concept of further facts plays a key role in some of the major works in analytic philosophy of the late 20th century, including in Derek Parfit's Reasons and Persons, and David Chalmers's The Conscious Mind. One context in which the existence of further facts is debated is that of personal identity across time: in what sense is Alice today the same person as Alice yesterday, given that across the two days the state of her brain is different and the atoms that constitute her are different? On the one hand, we may believe that at bottom, there is nothing more than the atoms and their arrangement at different points in time; while we may for practical purposes come up with some notion of sameness of a person, this notion does not reflect anything deeper about reality. Under such a view there would be no further facts. On the other hand, we may believe that there is an additional fact


id: future-20260505-0
file: data/en.wikipedia.org/wiki/Future-0.md
category: reference
title: Future
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Future
date_saved: 2026-05-05T11:14:05.922691+00:00
instance: kb-cron
parent: future-20260505-0
summary:
The future is the time after the past and the present. Its arrival is considered inevitable due to the existence of time and the laws of physics. Due to the apparent nature of the reality and the unavoidability of the future, everything that currently exists and will exist can be categorized as either permanent, meaning that it will exist forever, or temporary, meaning that it will end. In the Occidental view, which uses a linear conception of time, the future is the portion of the projected timeline that is anticipated to occur. In special relativity, the future is considered absolute future, or the future light cone. In the philosophy of time, presentism is the belief that only the present exists and the future and the past are unreal. Religions consider the future when they address issues such as karma, life after death, and eschatologies that study what the end of time and the end of the world will be. Religious figures such as prophets and diviners have claimed to see into the future. Future studies, or futurology, is the science, art, and practice of postulating possible futures. Modern practitioners stress the importance of alternative and plural futures, rather than one


id: future-20260505-1
file: data/en.wikipedia.org/wiki/Future-1.md
category: reference
title: Future
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Future
date_saved: 2026-05-05T11:14:05.922691+00:00
instance: kb-cron
parent: future-20260505-0
summary:
== In psychology == Human behavior is known to encompass anticipation of the future. Anticipatory behavior can be the result of a psychological outlook toward the future, for examples optimism, pessimism, and hope. Optimism is an outlook on life such that one maintains a view of the world as a positive place. People would say that optimism is seeing the glass "half full" of water as opposed to half empty. It is the philosophical opposite of pessimism. Optimists generally believe that people and events are inherently good, so that most situations work out in the end for the best. Hope is a belief in a positive outcome related to events and circumstances in one's life. Hope implies a certain amount of despair, wanting, wishing, suffering or perseverance—i.e., believing that a better or positive outcome is possible even when there is some evidence to the contrary. "Hopefulness" is somewhat different from optimism in that hope is an emotional state, whereas some theories point to optimism as a conclusion reached through a deliberate thought pattern that leads to a positive personal attitudes and by extension is linked to more philanthropic behaviours. Pessimism as stated before is the opposite of optimism. It is


id: future-20260505-2
file: data/en.wikipedia.org/wiki/Future-2.md
category: reference
title: Future
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Future
date_saved: 2026-05-05T11:14:05.922691+00:00
instance: kb-cron
parent: future-20260505-0
summary:
In English grammar, actions are classified according to one of the following twelve verb tenses: past (past, past continuous, past perfect, or past perfect continuous), present (present, present continuous, present perfect, or present perfect continuous), or future (future, future continuous, future perfect, or future perfect continuous). The future tense refers to actions that have not yet happened, but which are due, expected, or may occur in the future. For example, in the sentence, "She will walk home," the verb "will walk" is in the future tense because it refers to an action that is going to, or may, happen at a point in time beyond the present. Verbs in the future continuous tense indicate actions that will happen beyond the present and will continue for a period of time. In the sentence, "She will be walking home," the verb phrase "will be walking" is in the future continuous tense because the action described is not happening now, but will happen sometime afterwards and is expected to continue happening for some time. Verbs in the future perfect tense indicate actions that will be completed at a particular point in the future. For example, the verb phrase, "will have walked," in the


id: future-20260505-3
file: data/en.wikipedia.org/wiki/Future-3.md
category: reference
title: Future
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Future
date_saved: 2026-05-05T11:14:05.922691+00:00
instance: kb-cron
parent: future-20260505-0
summary:
Forecasting is the process of estimating outcomes in uncontrolled situations. Forecasting is applied in many areas, such as weather forecasting, earthquake prediction, transport planning, and labour market planning. Due to the element of the unknown, risk and uncertainty are central to forecasting. Statistically based forecasting employs time series with cross-sectional or longitudinal data. Econometric forecasting methods use the assumption that it is possible to identify the underlying factors that might influence the variable that is being forecast. If the causes are understood, projections of the influencing variables can be made and used in the forecast. Judgmental forecasting methods incorporate intuitive judgments, opinions, and probability estimates, as in the case of the Delphi method, scenario building, and simulations. Prediction is similar to forecasting but is used more generally, for instance, to also include baseless claims on the future. Organized efforts to predict the future began with practices like astrology, haruspicy, and augury. These are all considered to be pseudoscience today, evolving from the human desire to know the future in advance. Modern efforts such as futures studies attempt to predict technological and societal trends, while more ancient practices, such as weather forecasting, have benefited from scientific and causal modelling. Despite the


id: grim-reaper-paradox-20260505-0
file: data/en.wikipedia.org/wiki/Grim_Reaper_paradox-0.md
category: reference
title: Grim Reaper paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Grim_Reaper_paradox
date_saved: 2026-05-05T11:14:07.081424+00:00
instance: kb-cron
parent: grim-reaper-paradox-20260505-0
summary:
In philosophy, the Grim Reaper paradox is a paradox involving an infinite sequence of Grim Reapers, each tasked with killing a person if no reaper has already killed them. The paradox raises questions about the possibility of continuous time and the infinite past (temporal finitism). It is inspired by J. A. Benardete's paradoxes from the 1964 book Infinity: An Essay in Metaphysics. Various formulations of paradoxes involving beginningless sets, whose members perform a function only if no previous member performs it, are all labelled "Benardete Paradoxes". These are examples of supertasks. == Paradox == The paradox supposes there is an infinite sequence of Reapers, each assigned a time to kill a particular person. Each Reaper will only kill this person if no earlier Reaper has already killed them. It is 12pm, and the first Reaper is set to kill the person at 1pm. The second Reaper is set to kill them at 12:30pm, the third at 12:15pm, and so on. As a consequence of these propositions, the person will certainly be killed by a Reaper before 1pm; however, no individual Reaper can kill them, as there is always an earlier Reaper who would do so first. Therefore, it is impossible


id: growing-block-universe-20260505-0
file: data/en.wikipedia.org/wiki/Growing_block_universe-0.md
category: reference
title: Growing block universe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Growing_block_universe
date_saved: 2026-05-05T11:14:08.271158+00:00
instance: kb-cron
parent: growing-block-universe-20260505-0
summary:
The growing block universe, or the growing block view, is a theory of time arguing that the past and present both exist, while the future does not yet exist. The present is the perpetuating factor of time, where new moments are added to the past. By the passage of time more of the world comes into being; therefore, the block universe is said to be growing. The growth of the block is supposed to happen in the present, a very thin slice of spacetime, where more of spacetime is continually coming into being. Growing block theory should not be confused with block universe theory, also known as eternalism. The growing block view is an alternative to both eternalism (according to which past, present, and future all exist) and presentism (according to which only the present exists). It is held to be closer to common-sense intuitions than the alternatives. C. D. Broad was a proponent of the theory (1923). Some modern defenders are Michael Tooley (in 1997) and Peter Forrest (in 2004). Fabrice Correia and Sven Rosenkranz (2015) have developed their own distinctive view of this theory. == Overview == Broad first proposed the theory in 1923. He described the theory


id: hauntology-20260505-0
file: data/en.wikipedia.org/wiki/Hauntology-0.md
category: reference
title: Hauntology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hauntology
date_saved: 2026-05-05T11:14:10.113007+00:00
instance: kb-cron
parent: hauntology-20260505-0
summary:
Hauntology (a portmanteau of haunting and ontology, also spectral studies, spectralities, or the spectral turn) is a range of ideas referring to the return or persistence of elements from the social or cultural past, as if to haunt the present. The term is a neologism first introduced by French philosopher Jacques Derrida in his 1993 book Spectres of Marx. It has since been invoked in fields such as visual arts, philosophy, electronic music, anthropology, criminology, politics, fiction, and literary criticism. While Christine Brooke-Rose had previously punned "dehauntological" (on "deontological") in Amalgamemnon (1984), Derrida initially used "hauntology" for his idea of the atemporal nature of Marxism and its tendency to "haunt Western society from beyond the grave". It describes a situation of temporal and ontological disjunction in which presence, especially socially and culturally, is replaced by a deferred non-origin. The concept is derived from deconstruction, in which any attempt to locate the origin of identity or history must inevitably find itself dependent on an always-already existing set of linguistic conditions. Despite being the central focus of Spectres of Marx, the word hauntology appears only three times in the book, and there is little consistency in how other writers define the term.


id: hauntology-20260505-1
file: data/en.wikipedia.org/wiki/Hauntology-1.md
category: reference
title: Hauntology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hauntology
date_saved: 2026-05-05T11:14:10.113007+00:00
instance: kb-cron
parent: hauntology-20260505-0
summary:
Anthropologists Martha and Bruce Lincoln make a distinction between primary hauntings, in which the haunted recognize the reality and autonomy of metaphysical entities in relatively uncritical, literal manner; and secondary hauntings, which identify "textual residues" history, or as tropes for "collective intrapsychic states" such as trauma and grief. As a case study, they use the example of Ba Chúc's secondary haunting, in which the state-controlled museums display the skulls of the dead and memorabilia, as opposed to traditional Vietnamese burial customs. This is contrasted with the "primary haunting" of Ba Chúc, the paranormal activity said to occur at an execution site marked by a tree. Kit Bauserman notes that for literary and critical theorists, the ghost is "pure metaphor" and "a fictional vessel that co-opts their social agenda", whereas ethnographers and anthropologists "come the closest to engaging ghosts as beings". Some scholars have argued that the "neat distinction quickly breaks down in ethnographic analysis" and that "it is far from clear that the presence of ghosts as metaphysical entities is primary." == See also == Cultural memory Eternal return National memory == Notes == == References == Blanco, María del Pilar; Peeren, Esther (2013). The spectralities reader : ghosts and


id: if-you-find-this-world-bad-you-should-see-some-of-the-others-20260505-0
file: data/en.wikipedia.org/wiki/If_You_Find_This_World_Bad,_You_Should_See_Some_of_the_Others-0.md
category: reference
title: If You Find This World Bad, You Should See Some of the Others
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/If_You_Find_This_World_Bad,_You_Should_See_Some_of_the_Others
date_saved: 2026-05-05T11:14:11.807272+00:00
instance: kb-cron
parent: if-you-find-this-world-bad-you-should-see-some-of-the-others-20260505-0
summary:
"If You Find This World Bad, You Should See Some of the Others", also known as the "Metz speech", is a 1977 speech and essay by science fiction writer Philip K. Dick. He delivered it as the guest of honor on September 24, 1977, at the Second Metz International Science Fiction Festival in Metz, France. Dick prepared his first version of the speech by May of that year, but was asked to deliver a shorter version due to time constraints. The Metz speech, in its shorter form, was recorded on video and was translated to the French audience by an interpreter. Dick's speech lays out his characteristic, yet arcane thoughts on the philosophy of space and time and the concept of alternate universes within a hypothetical multiverse. The speech also discusses Dick's strange and unusual visions from 1974, his interpretation of Christian Gnosticism, and the role of alternate history in his published work. The speech was not well received. Dick spoke in a monotone voice, the interpreter's transcript differed from Dick's speech due to a last minute rewrite, and the audience was left confused and bewildered. At the time, nobody knew exactly what to make of the speech, as it


id: if-you-find-this-world-bad-you-should-see-some-of-the-others-20260505-1
file: data/en.wikipedia.org/wiki/If_You_Find_This_World_Bad,_You_Should_See_Some_of_the_Others-1.md
category: reference
title: If You Find This World Bad, You Should See Some of the Others
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/If_You_Find_This_World_Bad,_You_Should_See_Some_of_the_Others
date_saved: 2026-05-05T11:14:11.807272+00:00
instance: kb-cron
parent: if-you-find-this-world-bad-you-should-see-some-of-the-others-20260505-0
summary:
== Invitation and preparation == The first Metz International Science Fiction Festival (Festival International de la Science-Fiction de Metz) took place from May 24–30, 1976, founded by Philippe Hupp, a book reviewer and French translator of Time out of Joint (1959), as well as a columnist for the French version of Galaxy Science Fiction. Building on the momentum from the success of the first festival, Hupp invited Dick on February 23, 1977, to attend the second festival as the guest of honor. Dick accepted on March 17, and responded to Hupp with a brief description of his planned speech. Even though Dick had accepted the invitation, his reputation for not showing up to conferences was well known. Hupp flew to the United States to make the case to Dick in person. They met for lunch at an Italian restaurant near his apartment in Santa Ana, California. Hupp sold him on the festival, explaining exactly how it would work and how Dick would be taken care of during his time in France. At the meeting, Dick gave Hupp an audio cassette of the speech he had already prepared (dated May 21), and they enjoyed a meal over two bottles of red


id: if-you-find-this-world-bad-you-should-see-some-of-the-others-20260505-2
file: data/en.wikipedia.org/wiki/If_You_Find_This_World_Bad,_You_Should_See_Some_of_the_Others-2.md
category: reference
title: If You Find This World Bad, You Should See Some of the Others
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/If_You_Find_This_World_Bad,_You_Should_See_Some_of_the_Others
date_saved: 2026-05-05T11:14:11.807272+00:00
instance: kb-cron
parent: if-you-find-this-world-bad-you-should-see-some-of-the-others-20260505-0
summary:
== Synopsis == Dick proposes that novelists have a lot of ideas to work with, but most of these are meaningless and of no value. And yet, try as they might, over their entire career, a novelist may only come across a few great ideas. Dick argues that the novelist does not find or create these ideas on their own, rather these ideas are like living entities that seek out the novelist to make themselves manifest to the larger world, to history itself. To support this argument, Dick cites the pre-Socratic philosophers, who proposed the cosmos was a thinking entity, as well as theistic ideas found in works related to Indian Vedanta, Spinoza, and Alfred North Whitehead. Dick points to the existence of a hidden, gnostic, God-like figure, citing the Sufi poet Rumi to make his point: "The workman is invisible within the workshop". From this, Dick places these ideas within a continuum of multiple, parallel universes in a lateral axis of time, independent of linear progression, which he admits is absurd and nonsensical, and undermines his own belief in pantheistic monism. More importantly, Dick asks, what kind of changes would people experience if these realities were to be altered?


id: if-you-find-this-world-bad-you-should-see-some-of-the-others-20260505-3
file: data/en.wikipedia.org/wiki/If_You_Find_This_World_Bad,_You_Should_See_Some_of_the_Others-3.md
category: reference
title: If You Find This World Bad, You Should See Some of the Others
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/If_You_Find_This_World_Bad,_You_Should_See_Some_of_the_Others
date_saved: 2026-05-05T11:14:11.807272+00:00
instance: kb-cron
parent: if-you-find-this-world-bad-you-should-see-some-of-the-others-20260505-0
summary:
== Critical reception == Harlan Ellison did not attend Dick's speech, as they had been estranged since 1975 at the time. Ellison recalled that the people who heard the speech "looked like they had been stunned by a ball peen hammer...they thought [Dick] was either drunk or doped". John Brunner, who originally met Dick in 1964 at a party before Worldcon in Oakland, recalled his own confusion on the matter a decade later: "I...failed to figure out how literally [Dick] intended people to regard his claims", wrote Brunner. "I could not decide whether, after so many years of inner suffering, his reason had been usurped by his own inventions, or whether he had reached the bitter conclusion that the only way to cope with our lunatic world was to treat it as one vast and rather vicious joke, and fight back on the same irrational level." Dick's friend Roger Zelazny, a co-author on the post-apocalyptic science fiction novel Deus Irae (1976), also recalled the confusion of the audience after the speech. At Metz, Zelazny encountered numerous fans engaged in heated arguments over the meaning of the speech. One person told Zelazny that he thought Dick intended to start a new


id: imaginary-time-20260505-0
file: data/en.wikipedia.org/wiki/Imaginary_time-0.md
category: reference
title: Imaginary time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Imaginary_time
date_saved: 2026-05-05T11:14:13.037583+00:00
instance: kb-cron
parent: imaginary-time-20260505-0
summary:
Imaginary time is a mathematical representation of time that appears in some approaches to special relativity and quantum mechanics. It finds uses in certain cosmological theories. Mathematically, imaginary time is real time which has undergone a Wick rotation so that its coordinates are multiplied by the imaginary unit i. Imaginary time is not imaginary in the sense that it is unreal or made-up; it is simply expressed in terms of imaginary numbers. == Origins == In mathematics, the imaginary unit i {\displaystyle i} is − 1 {\displaystyle {\sqrt {-1}}} , such that i 2 {\displaystyle i^{2}} is defined to be − 1 {\displaystyle -1} . A number which is a direct multiple of i {\displaystyle i} is known as an imaginary number. A number that is the sum of an imaginary number and a real number is known as a complex number. In certain physical theories, periods of time are multiplied by i {\displaystyle i} in this way. Mathematically, an imaginary time period τ {\textstyle \tau } may be obtained from real time t {\textstyle t} via a Wick rotation by π / 2 {\textstyle \pi /2} in the complex plane: τ = i t {\textstyle \tau =it} . Stephen


id: immediacy-philosophy-20260505-0
file: data/en.wikipedia.org/wiki/Immediacy_(philosophy)-0.md
category: reference
title: Immediacy (philosophy)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Immediacy_(philosophy)
date_saved: 2026-05-05T11:14:14.226570+00:00
instance: kb-cron
parent: immediacy-philosophy-20260505-0
summary:
Immediacy is a philosophical concept related to time and temporal perspectives, both visual, and cognitive. Considerations of immediacy reflect on how we experience the world and what reality is. It implies a direct experience of an event or object bereft of any intervening medium. An example would be looking at a painting, losing awareness of the medium, and seeing the depiction as real. The medium is an important concept, and somewhat paradoxical, as it is both necessary and yet forgotten. Plato deals with a similar concept in the purity of experience. He tells us that speech is more immediate than writing, because the words emerge more directly from the speaker's mind. Immediacy also possesses characteristics of both of the homophonic heterographs 'immanent' and 'imminent', and what entails to both within ontology. Immediacy also relates to the philosophy of phenomenology, as they are schools of thought which both concern subjective perceptions of objects and time.


id: moving-spotlight-theory-of-time-20260505-0
file: data/en.wikipedia.org/wiki/Moving_spotlight_theory_of_time-0.md
category: reference
title: Moving spotlight theory of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Moving_spotlight_theory_of_time
date_saved: 2026-05-05T11:14:15.388049+00:00
instance: kb-cron
parent: moving-spotlight-theory-of-time-20260505-0
summary:
The moving spotlight theory of time is a theory of time which says that the complete history of the world exists (in much the same sense as the block universe, that is, past, present, and future all exist), but that there is an absolute, objective present moment. On this view, what is present really changes as time passes. This is a "moving spotlight" theory because the objective present "moves" through the block analogous to how a spotlight might traverse (e.g.) a row of houses in a street. This view is suggested, though not endorsed, by C.D. Broad in his Scientific Thought (1923). (Broad endorses the growing block theory of time, though this view can trace it roots further back to Samuel Alexander.) Moving spotlight theory and growing block theory are both taken as intermediary positions between either presentism and eternalism, or the A-theory and B-theory of time. It is common to see the moving spotlight theory described as a "non-presentist A-theory." The moving spotlight theory accepts the dynamic thesis of the A-theory that time really passes, what is objectively present changes, and accepts the static ontology of the B-theory that past, present, and future entities exist: the totality of what


id: non-simultaneity-20260505-0
file: data/en.wikipedia.org/wiki/Non-simultaneity-0.md
category: reference
title: Non-simultaneity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Non-simultaneity
date_saved: 2026-05-05T11:14:16.563486+00:00
instance: kb-cron
parent: non-simultaneity-20260505-0
summary:
Non-simultaneity or nonsynchronism (German: Ungleichzeitigkeit, sometimes also translated as non-synchronicity) is a concept in the writings of Ernst Bloch which denotes the time lag, or uneven temporal development, produced in the social sphere by the processes of capitalist modernization and/or the incomplete nature of those processes. The term, especially in the phrase "the simultaneity of the non-simultaneous", has been used subsequently in predominantly Marxist theories of modernity, world-systems, postmodernity and globalization. == In the work of Ernst Bloch == The phrase "the non-simultaneity of the simultaneous" (die 'Ungleichzeitigkeit' des Gleichzeitigen) was first used by the German art historian Wilhelm Pinder in his 1926 book Das Problem der Generation in der Kunstgeschichte Europas ("The Problem of Generation in European Art History"). Bloch's principal use of the term "non-simultaneity" was in an essay from 1932 which attempted to explain the rise and popularity of Nazism in Germany in the light of the capitalist economic crisis of the Great Depression and which became a chapter of his influential 1935 study Heritage of our Times (Erbschaft dieser Zeit). The essay's central idea is that heterogeneous stages of social and economic development coexist simultaneously in 1930s Germany. Because of uneven modernization, Bloch argues, there remained


id: non-simultaneity-20260505-1
file: data/en.wikipedia.org/wiki/Non-simultaneity-1.md
category: reference
title: Non-simultaneity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Non-simultaneity
date_saved: 2026-05-05T11:14:16.563486+00:00
instance: kb-cron
parent: non-simultaneity-20260505-0
summary:
The more production comes to rest on exchange value, hence on exchange, the more important do the physical conditions of exchange — the means of communication and transport — become for the costs of circulation. Capital by its nature drives beyond every spatial barrier. Thus the creation of the physical conditions of exchange — of the means of communication and transport — the annihilation of space by time — becomes an extraordinary necessity for it. At the same time, Marx showed himself to be acutely aware of the resistances to this overcoming of spatio-temporal barriers, and, more importantly, to the fact that capitalism itself generates its own resistances, or contradictions, to the universalization of its mode of production: But from the fact that capital posits every such limit as a barrier and hence gets ideally beyond it, it does not by any means follow that it has really overcome it, and, since every such barrier contradicts its character, its production moves in contradictions which are constantly overcome but just as constantly posited. Furthermore. The universality towards which it irresistibly strives encounters barriers in its own nature, which will, at a certain stage of its development, allow it to be recognized


id: non-simultaneity-20260505-2
file: data/en.wikipedia.org/wiki/Non-simultaneity-2.md
category: reference
title: Non-simultaneity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Non-simultaneity
date_saved: 2026-05-05T11:14:16.563486+00:00
instance: kb-cron
parent: non-simultaneity-20260505-0
summary:
Modernism must thus be seen as uniquely corresponding to an uneven moment of social development, or to what Ernst Bloch called the "simultaneity of the nonsimultaneous," the "synchronicity of the nonsynchronous" (Gleichzeitigkeit des Ungleichzeitigen): the coexistence of realities from radically different moments of history — handicrafts alongside the great cartels, peasant fields with the Krupp factories or the Ford plant in the distance. Jameson goes on, however, to argue that with the advent of postmodernity and its attendant postmodernisms, the "uneven moment" of modernity has been completely replaced by the mass standardization and homogenization of the third, multinational, phase of capitalist development: the postmodern must be characterized as a situation in which the survival, the residue, the holdover, the archaic, has finally been swept away without a trace. In the postmodern, then, the past itself has disappeared (along with the well-known "sense of the past" or historicity and collective memory). Where its buildings still remain, renovation and restoration allow them to be transferred to the present in their entirety as those other, very different and postmodern things called simulacra. Everything is now organized and planned; nature has been triumphantly blotted out, along with peasants, petit-bourgeois commerce, handicraft, feudal aristocracies and


id: past-20260505-0
file: data/en.wikipedia.org/wiki/Past-0.md
category: reference
title: Past
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Past
date_saved: 2026-05-05T11:14:17.747415+00:00
instance: kb-cron
parent: past-20260505-0
summary:
The past is the set of all events that occurred before a given point in time. The past is contrasted with and defined by the present and the future. The concept of the past is derived from the linear fashion in which human observers experience time, and is accessed through memory and recollection. In addition, humans have recorded the past since the advent of written language. In English, the word past was one of the many variant forms and spellings of passed, the past participle of the Middle English verb passen (whence Modern English pass), among ypassed, ypassyd, i-passed, passyd, passid, pass'd, paste, etc. It developed into an adjective and preposition in the 14th century, and a noun (as in the past or a past, through ellipsis with the adjective past) in the 15th century. == Grammar == In English grammar, actions are classified according to one of the following twelve verb tenses: past (past, uses of English verb forms, past perfect, or past perfect continuous), present (present, present continuous, present perfect, or present perfect continuous), or future (future, future continuous, future perfect, or future perfect continuous). The past tense refers to actions that have already happened. For example, "she


id: past-hypothesis-20260505-0
file: data/en.wikipedia.org/wiki/Past_hypothesis-0.md
category: reference
title: Past hypothesis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Past_hypothesis
date_saved: 2026-05-05T11:14:18.928263+00:00
instance: kb-cron
parent: past-hypothesis-20260505-0
summary:
In cosmology, the past hypothesis is a fundamental law of physics that postulates that the universe started in a low-entropy state, in accordance with the second law of thermodynamics. The second law states that any closed system follows the arrow of time, meaning its entropy never decreases. Applying this idea to the entire universe, the hypothesis argues that the universe must have started from a special event with less entropy than is currently observed, in order to preserve the arrow of time globally. This idea has been discussed since the development of statistical mechanics, but the term "past hypothesis" was coined by philosopher David Albert in 2000. Philosophical and theoretical efforts focus on trying to explain the consistency and the origin of the postulate. The past hypothesis is an exception to the principle of indifference, according to which every possible microstate within a certain macrostate would have an equal probability. The past hypothesis allows only those microstates that are compatible with a much-lower-entropy past, although these states are assigned equal probabilities. If the principle of indifference is applied without taking into account the past hypothesis, a low- or medium-entropy state would have likely evolved both from and toward higher-entropy macrostates,


id: perspectival-realism-20260505-0
file: data/en.wikipedia.org/wiki/Perspectival_realism-0.md
category: reference
title: Perspectival realism
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Perspectival_realism
date_saved: 2026-05-05T11:14:20.083010+00:00
instance: kb-cron
parent: perspectival-realism-20260505-0
summary:
In Caspar Hare's theory of perspectival realism, there is a defining intrinsic property that the things that are in perceptual awareness have. Consider seeing object A but not object B. Of course, we can say that the visual experience of A is present to you, and no visual experience of B is present to you. But, it can be argued, this misses the fact that the visual experience of A is simply present, not relative to anything. This is what Hare's perspectival realism attempts to capture, resulting in a weak version of metaphysical solipsism. As Hare points out, the same type of argument is often used in the philosophy of time to support theories such as presentism. Of course, we can say that A is happening on [insert today's date]. But, it can be argued, this misses the fact that A is simply happening (right now), not relative to anything. Hare's theory of perspectival realism is closely related to his theory of egocentric presentism. Several other philosophers have written reviews of Hare's work on this topic. == See also == Metaphysical subjectivism Centered worlds Benj Hellie's vertiginous question J.J. Valberg's personal horizon == References == == External links == Hare,


id: philosophy-of-time-society-20260505-0
file: data/en.wikipedia.org/wiki/Philosophy_of_Time_Society-0.md
category: reference
title: Philosophy of Time Society
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Philosophy_of_Time_Society
date_saved: 2026-05-05T11:14:21.247470+00:00
instance: kb-cron
parent: philosophy-of-time-society-20260505-0
summary:
The Philosophy of Time Society is an organization which grew out of a National Endowment for the Humanities Summer Seminar on the Philosophy of Time offered by George N. Schlesinger in 1991. The organization itself was formed in 1993. Its stated goal is "to promote the study of the philosophy of time from a broad analytic perspective, and to provide a forum as an affiliated group with the American Philosophical Association, to discuss the issues in and related to the philosophy of time." The current President of the Society is Nina Emery. The Philosophy of Time Society's meetings are held at the division meetings of the American Philosophical Association. In the past, they have included many notable scholars such as Craig Callender, L. A. Paul, Robin Le Poidevin, Ned Markosian, D. H. Mellor, John Perry, Theodore Sider, Michael Tooley, and Dean Zimmerman. Topics of papers have varied widely. == References == == External links == Philosophy of Time Society George Schlesinger Memorial Site


id: physical-cosmology-20260505-0
file: data/en.wikipedia.org/wiki/Physical_cosmology-0.md
category: reference
title: Physical cosmology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Physical_cosmology
date_saved: 2026-05-05T11:14:22.441984+00:00
instance: kb-cron
parent: physical-cosmology-20260505-0
summary:
Physical cosmology is a branch of physics concerned with modeling the universe based on the laws of physics. A cosmological model provides a mathematical description of the largest-scale structures and dynamics of the universe and allows study of fundamental questions about its origin, structure, evolution, and ultimate fate. Cosmology as a science originated with the Copernican principle, which implies that celestial bodies obey identical physical laws to those on Earth, and Newtonian mechanics, which first allowed those physical laws to be understood. Physical cosmology, as it is now understood, began in 1915 with the development of Albert Einstein's general theory of relativity, followed by major observational discoveries in the 1920s: first, Edwin Hubble discovered that the universe contains a huge number of external galaxies beyond the Milky Way; then, work by Vesto Slipher and others showed that the universe is expanding. These advances made it possible to speculate about the origin of the universe, and allowed the establishment of the Big Bang theory, by Georges Lemaître, as the leading cosmological model. A few researchers still advocate a handful of alternative cosmologies; however, most cosmologists agree that the Big Bang theory best explains the observations. Dramatic advances in observational cosmology since


id: physical-cosmology-20260505-1
file: data/en.wikipedia.org/wiki/Physical_cosmology-1.md
category: reference
title: Physical cosmology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Physical_cosmology
date_saved: 2026-05-05T11:14:22.441984+00:00
instance: kb-cron
parent: physical-cosmology-20260505-0
summary:
== Energy of the cosmos == The lightest chemical elements, primarily hydrogen and helium, were created during the Big Bang through the process of nucleosynthesis. In a sequence of stellar nucleosynthesis reactions, smaller atomic nuclei are then combined into larger atomic nuclei, ultimately forming stable iron group elements such as iron and nickel, which have the highest nuclear binding energies. The net process results in a later energy release, meaning subsequent to the Big Bang. Such reactions of nuclear particles can lead to sudden energy releases from cataclysmic variable stars such as novae. Gravitational collapse of matter into black holes also powers the most energetic processes, generally seen in the nuclear regions of galaxies, forming quasars and active galaxies. Cosmologists cannot explain all cosmic phenomena exactly, such as those related to the accelerating expansion of the universe, using conventional forms of energy. Instead, cosmologists propose a new form of energy called dark energy that permeates all space. One hypothesis is that dark energy is just the vacuum energy, a component of empty space that is associated with the virtual particles that exist due to the uncertainty principle. There is no clear way to define the total energy in the universe


id: physical-cosmology-20260505-2
file: data/en.wikipedia.org/wiki/Physical_cosmology-2.md
category: reference
title: Physical cosmology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Physical_cosmology
date_saved: 2026-05-05T11:14:22.441984+00:00
instance: kb-cron
parent: physical-cosmology-20260505-0
summary:
== Areas of study == Below, some of the most active areas of inquiry in cosmology are described, in roughly chronological order. This does not include all of the Big Bang cosmology, which is presented in Timeline of the Big Bang. === Very early universe === The early, hot universe appears to be well explained by the Big Bang from roughly 10−33 seconds onwards, but there are several problems. One is that there is no compelling reason, using current particle physics, for the universe to be flat, homogeneous, and isotropic (see the cosmological principle). Moreover, grand unified theories of particle physics suggest that there should be magnetic monopoles in the universe, which have not been found. These problems are resolved by a brief period of cosmic inflation, which drives the universe to flatness, smooths out anisotropies and inhomogeneities to the observed level, and exponentially dilutes the monopoles. The physical model behind cosmic inflation is extremely simple, but it has not yet been confirmed by particle physics, and there are difficult problems reconciling inflation and quantum field theory. Some cosmologists think that string theory and brane cosmology will provide an alternative to inflation. Another major problem in cosmology is what caused


id: physical-cosmology-20260505-3
file: data/en.wikipedia.org/wiki/Physical_cosmology-3.md
category: reference
title: Physical cosmology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Physical_cosmology
date_saved: 2026-05-05T11:14:22.441984+00:00
instance: kb-cron
parent: physical-cosmology-20260505-0
summary:
Understanding the formation and evolution of the largest and earliest structures (i.e., quasars, galaxies, clusters and superclusters) is one of the largest efforts in cosmology. Cosmologists study a model of hierarchical structure formation in which structures form from the bottom up, with smaller objects forming first, while the largest objects, such as superclusters, are still assembling. One way to study structure in the universe is to survey the visible galaxies, in order to construct a three-dimensional picture of the galaxies in the universe and measure the matter power spectrum. This is the approach of the Sloan Digital Sky Survey and the 2dF Galaxy Redshift Survey. Another tool for understanding structure formation is simulations, which cosmologists use to study the gravitational aggregation of matter in the universe, as it clusters into filaments, superclusters and voids. Most simulations contain only non-baryonic cold dark matter, which should suffice to understand the universe on the largest scales, as there is much more dark matter in the universe than visible, baryonic matter. More advanced simulations are starting to include baryons and study the formation of individual galaxies. Cosmologists study these simulations to see if they agree with the galaxy surveys, and to understand any discrepancy.


id: physical-cosmology-20260505-4
file: data/en.wikipedia.org/wiki/Physical_cosmology-4.md
category: reference
title: Physical cosmology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Physical_cosmology
date_saved: 2026-05-05T11:14:22.441984+00:00
instance: kb-cron
parent: physical-cosmology-20260505-0
summary:
=== Gravitational waves === Gravitational waves are ripples in the curvature of spacetime that propagate as waves at the speed of light, generated in certain gravitational interactions that propagate outward from their source. Gravitational-wave astronomy is an emerging branch of observational astronomy which aims to use gravitational waves to collect observational data about sources of detectable gravitational waves such as binary star systems composed of white dwarfs, neutron stars, and black holes; and events such as supernovae, and the formation of the early universe shortly after the Big Bang. In 2016, the LIGO Scientific Collaboration and Virgo Collaboration teams announced that they had made the first observation of gravitational waves, originating from a pair of merging black holes using the Advanced LIGO detectors. On 15 June 2016, a second detection of gravitational waves from coalescing black holes was announced. Besides LIGO, many other gravitational-wave observatories (detectors) are under construction. === Other areas of inquiry === Cosmologists also study: Whether primordial black holes were formed in our universe, and what happened to them. Detection of cosmic rays with energies above the GZK cutoff, and whether it signals a failure of special relativity at high energies. The equivalence principle, whether or not


id: physics-aristotle-20260505-0
file: data/en.wikipedia.org/wiki/Physics_(Aristotle)-0.md
category: reference
title: Physics (Aristotle)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Physics_(Aristotle)
date_saved: 2026-05-05T11:14:23.733233+00:00
instance: kb-cron
parent: physics-aristotle-20260505-0
summary:
The Physics (Ancient Greek: Φυσικής ἀκρόασις, romanized: Physikḗs akróasis, or: Φυσικής ακροάσεως, Physikḗs akroáseōs; Latin: Physica or Naturales Auscultationes, possibly meaning "Lectures on nature") is a named text, written in ancient Greek, collated from a collection of surviving manuscripts known as the Corpus Aristotelicum, attributed to the 4th-century BC philosopher Aristotle. == The meaning of physics in Aristotle == It is a collection of treatises or lessons that deals with the most general (philosophical) principles of natural or moving things, both living and non-living, rather than physical theories (in the modern sense) or investigations of the particular contents of the universe. The chief purpose of the work is to discover the principles and causes of (and not merely to describe) change, or movement, or motion (κίνησις kinesis), especially that of natural wholes (mostly living things, but also inanimate wholes like the cosmos). In the conventional Andronicean ordering of Aristotle's works, it stands at the head of, as well as being foundational to, the long series of physical, cosmological and biological treatises, whose ancient Greek title, τὰ φυσικά, means "the [writings] on nature" or "natural philosophy". == Description of the content == The Physics is composed of eight books, which are


id: physics-aristotle-20260505-1
file: data/en.wikipedia.org/wiki/Physics_(Aristotle)-1.md
category: reference
title: Physics (Aristotle)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Physics_(Aristotle)
date_saved: 2026-05-05T11:14:23.733233+00:00
instance: kb-cron
parent: physics-aristotle-20260505-0
summary:
The necessary in nature, then, is plainly what we call by the name of matter, and the changes in it. Both causes must be stated by the physicist, but especially the end; for that is the cause of the matter, not vice versa; and the end is 'that for the sake of which', and the beginning starts from the definition or essence… In chapter 3, Aristotle presents his theory of the four causes (material, efficient, formal, and final). Material cause explains what something is made of (for example, the wood of a house), formal cause explains the form which a thing follows to become that thing (the plans of an architect to build a house), efficient cause is the actual source of the change (the physical building of the house), and final cause is the intended purpose of the change (the final product of the house and its purpose as a shelter and home). Of particular importance is the final cause or purpose (telos). It is a common mistake to conceive of the four causes as additive or alternative forces pushing or pulling; in reality, all four are needed to explain (7.198a22-25). What we typically mean by cause in the


id: physics-aristotle-20260505-2
file: data/en.wikipedia.org/wiki/Physics_(Aristotle)-2.md
category: reference
title: Physics (Aristotle)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Physics_(Aristotle)
date_saved: 2026-05-05T11:14:23.733233+00:00
instance: kb-cron
parent: physics-aristotle-20260505-0
summary:
=== Book VII (Η; 241a25–250b7) === Book VII briefly deals with the relationship of the moved to his mover, which Aristotle describes in substantial divergence with Plato's theory of the soul as capable of setting itself in motion (Laws book X, Phaedrus, Phaedo). Everything which moves is moved by another. He then tries to correlate the species of motion and their speeds, with the local change (locomotion, phorà) as the most fundamental to which the others can be reduced. Book VII.1-3 also exist in an alternative version, not included in the Bekker edition. === Book VIII (Θ; 250a14–267b26) === Book VIII (which occupies almost a fourth of the entire Physics, and probably constituted originally an independent course of lessons) discusses two main topics, though with a wide deployment of arguments: the time limits of the universe, and the existence of a Prime Mover — eternal, indivisible, without parts and without magnitude. Isn't the universe eternal, has it had a beginning, will it ever end? Aristotle's response, as a Greek, could hardly be affirmative, never having been told of a creatio ex nihilo, but he also has philosophical reasons for denying that motion had not always existed, on the grounds of


id: physics-aristotle-20260505-3
file: data/en.wikipedia.org/wiki/Physics_(Aristotle)-3.md
category: reference
title: Physics (Aristotle)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Physics_(Aristotle)
date_saved: 2026-05-05T11:14:23.733233+00:00
instance: kb-cron
parent: physics-aristotle-20260505-0
summary:
=== Classical and medieval commentaries on the Physics === A commentary differs from a note in being a distinct work analyzing the language and subsumed concepts of some other work classically notable. A note appears within the annotated work on the same page or in a separate list. Commentaries are typically arranged by lemmas, or quotes from the notable work, followed by an analysis of the author of the commentary. The commentaries on every work of Aristotle are a vast and mainly unpublished topic. They extend continuously from the death of the philosopher, representing the entire history of Graeco-Roman philosophy. There are thousands of commentators and commentaries known wholly or more typically in fragments of manuscripts. The latter especially occupy the vaults of institutions formerly responsible for copying them, such as monasteries. The process of publishing them is slow and ongoing. Below is a brief representative bibliography of published commentaries on Aristotle's Physics available on or through the Internet. Like the topic itself, they are perforce multi-cultural, but English has been favored, as well as the original languages, ancient Greek and Latin. === Some modern commentaries, monographs and articles === == Further reading == Books Die Aristotelische Physik, W. Wieland,


id: present-20260505-0
file: data/en.wikipedia.org/wiki/Present-0.md
category: reference
title: Present
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Present
date_saved: 2026-05-05T11:14:40.578384+00:00
instance: kb-cron
parent: present-20260505-0
summary:
The present is the period of time that is occurring right now. The present is in contrast to the past, the period of time that has already occurred; and the future, the period of time that has yet to occur. It is sometimes represented as a hyperplane in space-time, typically called "now", although modern physics demonstrates that such a hyperplane cannot be defined uniquely for observers in relative motion. The present may also be viewed as a duration. == Historiography == Contemporary history describes the historical timeframe immediately relevant to the present time and is a certain perspective of modern history. == Philosophy and religion == === Philosophy of time === "The present" raises the question: "How is it that all sentient beings experience now at the same time?" There is no logical reason why this should be the case and no easy answer to the question. === In Buddhism === Buddhism and many of its associated paradigms emphasize the importance of living in the present moment—being fully aware of what is happening, and not dwelling on the past or worrying about the future. This does not mean that they encourage hedonism, but merely that constant focus on one's current


id: problem-of-time-20260505-0
file: data/en.wikipedia.org/wiki/Problem_of_time-0.md
category: reference
title: Problem of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Problem_of_time
date_saved: 2026-05-05T11:14:41.783356+00:00
instance: kb-cron
parent: problem-of-time-20260505-0
summary:
In theoretical physics, the problem of time is a conceptual conflict between quantum mechanics and general relativity. Quantum mechanics regards the flow of time as universal and absolute, whereas general relativity regards the flow of time as malleable and relative. This problem raises the question of what time really is in a physical sense and whether it is truly a real, distinct phenomenon. It also involves the related question of why time seems to flow in a single direction, despite the fact that no known physical laws at the microscopic level seem to require a single direction. == Time in quantum mechanics == In classical mechanics, a special status is assigned to time in the sense that it is treated as a classical background parameter, external to the system itself. This special role is seen in the standard Copenhagen interpretation of quantum mechanics: all measurements of observables are made at certain instants of time and probabilities are only assigned to such measurements. Furthermore, the Hilbert space used in quantum theory relies on a complete set of observables which commute at a specific time. == Time in general relativity == In general relativity time is no longer a unique background parameter,


id: problem-of-time-20260505-1
file: data/en.wikipedia.org/wiki/Problem_of_time-1.md
category: reference
title: Problem of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Problem_of_time
date_saved: 2026-05-05T11:14:41.783356+00:00
instance: kb-cron
parent: problem-of-time-20260505-0
summary:
== Proposed solutions to the problem of time == Work started by Don Page and William Wootters suggests that the universe appears to evolve for observers on the inside because of energy entanglement between an evolving system and a clock system, both within the universe. In this way the overall system can remain timeless while parts experience time via entanglement. The issue remains an open question closely related to attempted theories of quantum gravity. In other words, time is an entanglement phenomenon, which places all equal clock readings (of correctly prepared clocks – or any objects usable as clocks) into the same history. In 2013, at the Istituto Nazionale di Ricerca Metrologica (INRIM) in Turin, Italy, Ekaterina Moreva, together with Giorgio Brida, Marco Gramegna, Vittorio Giovannetti, Lorenzo Maccone, and Marco Genovese performed the first experimental test of Page and Wootters' ideas. They confirmed for photons that time is an emergent phenomenon for internal observers of a quantum system but is absent for external observers, which is consistent with the predictions of the Wheeler–DeWitt equation. Consistent discretizations approach developed by Jorge Pullin and Rodolfo Gambini have no constraints. These are lattice approximation techniques for quantum gravity. In the canonical approach, if


id: quantum-logic-clock-20260505-0
file: data/en.wikipedia.org/wiki/Quantum_logic_clock-0.md
category: reference
title: Quantum logic clock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quantum_logic_clock
date_saved: 2026-05-05T11:14:43.041649+00:00
instance: kb-cron
parent: quantum-logic-clock-20260505-0
summary:
A quantum clock is a type of atomic clock with laser cooled single ions confined together in an electromagnetic ion trap. Developed in 2010 by physicists at the U.S. National Institute of Standards and Technology, the clock was 37 times more precise than the then-existing international standard. The quantum logic clock is based on an aluminium spectroscopy ion with a logic atom. Both the aluminum-based quantum clock and the mercury-based optical atomic clock track time by the ion vibration at an optical frequency using a UV laser, that is 100,000 times higher than the microwave frequencies used in NIST-F1 and other similar time standards around the world. Quantum clocks like this are able to be far more precise than microwave standards. == Accuracy == The NIST team are not able to measure clock ticks per second because the definition of a second is based on the standard NIST-F1, which cannot measure a machine more precise than itself. However, the aluminum ion clock's measured frequency to the current standard is 1121015393207857.4(7) Hz. NIST have attributed the clock's accuracy to the fact that it is insensitive to background magnetic and electric fields, and unaffected by temperature. In March 2008, physicists at NIST


id: repetition-kierkegaard-book-20260505-0
file: data/en.wikipedia.org/wiki/Repetition_(Kierkegaard_book)-0.md
category: reference
title: Repetition (Kierkegaard book)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Repetition_(Kierkegaard_book)
date_saved: 2026-05-05T11:14:44.246777+00:00
instance: kb-cron
parent: repetition-kierkegaard-book-20260505-0
summary:
Repetition: A Venture in Experimental Psychology (Danish: Gjentagelsen: Et Forsøg i den eksperimenterende Psychologi) is an 1843 book of philosophical fiction by Søren Kierkegaard that is semi-autobiographical. The book was written under the pseudonym Constantin Constantius to reflect its theme of repetition. The book's narrator explores the question of whether true repetition can exist and includes his experiments with this idea and his interactions with an unnamed melancholic character referred to only as the "Young Man". Kierkegaard published Fear and Trembling, Three Upbuilding Discourses, and Repetition all on the same date, 16 October 1843. While Abraham was the main character in Fear and Trembling, and the Three Upbuilding Discourses were about love, Repetition presents a noticeable contrast between the other two books. == Content == Kierkegaard used the pseudonym Constantin Constantius in this book, reflecting the theme of Repetition. Constantin is currently conducting experiments into whether repetition is possible. The book includes his experiments and his relation to a nameless patient known only as the Young Man. Every patient must have a problem. The Young Man has fallen in love with a girl, proposed marriage, the proposal has been accepted, but now he has changed his mind. Constantin becomes the


id: the-singular-universe-and-the-reality-of-time-20260505-0
file: data/en.wikipedia.org/wiki/The_Singular_Universe_and_the_Reality_of_Time-0.md
category: reference
title: The Singular Universe and the Reality of Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Singular_Universe_and_the_Reality_of_Time
date_saved: 2026-05-05T11:14:45.437869+00:00
instance: kb-cron
parent: the-singular-universe-and-the-reality-of-time-20260505-0
summary:
The Singular Universe and the Reality of Time: A Proposal in Natural Philosophy is a book about cosmology, philosophy of time, metaphysics and scientific naturalism by the American theoretical physicist Lee Smolin and the Brazilian philosopher Roberto Mangabeira Unger. The authors argue that the current crisis in cosmology is a result of physicists making the wrong commitments to universalizing local experiments and to a block universe. They suggest instead that new research projects would be revealed if we took seriously the idea of one, and only one, universe as well as the reality of our experience of time. This new paradigm, they say, would also give rise to the revolutionary notion that the laws of nature might not be immutable. The book was initially published by Cambridge University Press on December 8, 2014. == Synopsis == The book discusses a number of philosophical and physical ideas on the true role of time in the Universe. The text is roughly divided into two halves, the first one written by Unger, and the second by Smolin, both developing the same themes in different ways, with Smolin being more focused on the physics. == Reviews == You might expect a book co-authored by


id: tempora-mutantur-20260505-0
file: data/en.wikipedia.org/wiki/Tempora_mutantur-0.md
category: reference
title: Tempora mutantur
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tempora_mutantur
date_saved: 2026-05-05T11:14:46.612633+00:00
instance: kb-cron
parent: tempora-mutantur-20260505-0
summary:
Tempora mutantur is a Latin adage that refers to the changes brought about by the passage of time. It also appears in various longer hexametric forms, most commonly Tempora mutantur, nos et mutamur in illis, meaning "Times are changed; we also are changed with them". This hexameter is not found in Classical Latin, but is a variant of phrases of Ovid, to whom it is sometimes mis-attributed. In fact, it dates to 16th-century Germany, the time of the Protestant Reformation, and it subsequently was popularised in various forms. == Wording == Tempora mutantur, nos et mutamur in illis can be strictly translated as: "Times are changed; we, too, are changed within them." Like many adages and proverbial maxims drawn from the Latin cultural tradition, this line is in the hexameter verse used in Greek and Latin epic poetry. All other Latin verses cited in this page are hexameters as well. The fact that et follows nos and is accented in the hexameter's rhythm gives an emphasis to it. In this position et, normally meaning "and," can take an emphatic meaning and signify "also, too," or "even". == Grammar == "Tempora," a neuter plural and the subject of the first clause,


id: tempora-mutantur-20260505-1
file: data/en.wikipedia.org/wiki/Tempora_mutantur-1.md
category: reference
title: Tempora mutantur
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tempora_mutantur
date_saved: 2026-05-05T11:14:46.612633+00:00
instance: kb-cron
parent: tempora-mutantur-20260505-0
summary:
== Cultural references == Joseph Haydn gave his Symphony No. 64 the title Tempora mutantur. In James Joyce's novel A Portrait of the Artist as a Young Man, the cronies of the protagonist's (Stephen Dedalus's) father ask him to prove his ability in Latin by asking him "whether it was correct to say: tempora mutantur nos et mutamur or tempora mutantur et nos mutamur in illis." The phrase is meant to be an ironic reference to the decline in fortunes of the Dedalus family at this point in the novel. In Pierson v. Post, dissenting judge and future US Supreme Court Justice Henry Brockholst Livingston argued "If any thing, therefore, in the digests or pandects shall appear to militate against the defendant in error, who, on this occasion, was foxhunter, we have only to say tempora mutantur, and if men themselves change with the times, why should not laws also undergo an alteration?" The English print-maker William Washington (1885-1956) added the adage as an inscription to his 1929 engraving, St Olave's, Southwark, which depicts the demolition of St Olave's Church, Southwark, London, in 1928 to make way for modern development. The adage is inscribed on the Convention Center at Caesars


id: temporal-logic-20260505-0
file: data/en.wikipedia.org/wiki/Temporal_logic-0.md
category: reference
title: Temporal logic
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Temporal_logic
date_saved: 2026-05-05T11:14:47.815934+00:00
instance: kb-cron
parent: temporal-logic-20260505-0
summary:
In logic, temporal logic is any system of rules and symbolism for representing, and reasoning about, propositions qualified in terms of time (for example, "I am always hungry", "I will eventually be hungry", or "I will be hungry until I eat something"). It is sometimes also used to refer to tense logic, a modal logic-based system of temporal logic introduced by Arthur Prior in the late 1950s, with important contributions by Hans Kamp. It has been further developed by computer scientists, notably Amir Pnueli, and logicians. Temporal logic has found an important application in formal verification, where it is used to state requirements of hardware or software systems. For instance, one may wish to say that whenever a request is made, access to a resource is eventually granted, but it is never granted to two requestors simultaneously. Such a statement can conveniently be expressed in a temporal logic. == Motivation == Consider the statement "I am hungry". Though its meaning is constant in time, the statement's truth value can vary in time. Sometimes it is true, and sometimes false, but never simultaneously true and false. In a temporal logic, a statement can have a truth value that varies in time—in


id: temporal-logic-20260505-1
file: data/en.wikipedia.org/wiki/Temporal_logic-1.md
category: reference
title: Temporal logic
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Temporal_logic
date_saved: 2026-05-05T11:14:47.815934+00:00
instance: kb-cron
parent: temporal-logic-20260505-0
summary:
Time has usually been considered by logicians to be what is called 'extralogical' matter. I have never shared this opinion. But I have thought that logic had not yet reached the state of development at which the introduction of temporal modifications of its forms would not result in great confusion; and I am much of that way of thinking yet. The first system of temporal logic was published in 1947 by Polish logician, Jerzy Łoś. In his work Podstawy Analizy Metodologicznej Kanonów Milla (The Foundations of a Methodological Analysis of Mill’s Methods) he presented a formalization of Mill's canons. In Łoś's approach, emphasis was placed on the time factor. Thus, to reach his goal, he had to create a logic that could provide means for formalization of temporal functions. The logic could be seen as a byproduct of Łoś's main aim, albeit it was the first positional logic that, as a framework, was used later for Łoś's inventions in epistemic logic. The logic itself has syntax very different than Prior's tense logic, which uses modal operators. The language of Łoś's logic rather uses a realization operator, specific to positional logic, which binds the expression with the specific context in which


id: temporal-logic-20260505-2
file: data/en.wikipedia.org/wiki/Temporal_logic-2.md
category: reference
title: Temporal logic
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Temporal_logic
date_saved: 2026-05-05T11:14:47.815934+00:00
instance: kb-cron
parent: temporal-logic-20260505-0
summary:
The set of formulas (denoted by For {\displaystyle {\text{For}}} ) is constructed as follows: all first-order logic formulas are in For {\displaystyle {\text{For}}} if τ ∈ S {\displaystyle \tau \in S} and ϕ {\displaystyle \phi } is a propositional variable, then U τ ( ϕ ) ∈ For {\displaystyle U_{\tau }(\phi )\in {\text{For}}} if ϕ ∈ F o r {\displaystyle \phi \in For} , then ¬ ϕ ∈ For {\displaystyle \neg \phi \in {\text{For}}} if ϕ , ψ ∈ For {\displaystyle \phi ,\psi \in {\text{For}}} and ∘ ∈ { ∧ , ∨ , → , ≡ } {\displaystyle \circ \in \{\wedge ,\vee ,\rightarrow ,\equiv \}} , then ϕ ∘ ψ ∈ For {\displaystyle \phi \circ \psi \in {\text{For}}} if ϕ ∈ For {\displaystyle \phi \in {\text{For}}} and Q ∈ { ∀ , ∃ } {\displaystyle Q\in \{\forall ,\exists \}} and υ {\displaystyle \upsilon } is a propositional, moment or interval variable, then Q υ ϕ ∈ For {\displaystyle Q_{\upsilon }\phi \in {\text{For}}} === Original Axiomatic System === U t 1 ¬ p 1 ≡ ¬ U t 1 p 1 {\displaystyle U_{t_{1}}\neg p_{1}\equiv \neg U_{t_{1}}p_{1}} U t 1 ( p 1 → p 2 ) → ( U t 1


id: temporal-logic-20260505-3
file: data/en.wikipedia.org/wiki/Temporal_logic-3.md
category: reference
title: Temporal logic
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Temporal_logic
date_saved: 2026-05-05T11:14:47.815934+00:00
instance: kb-cron
parent: temporal-logic-20260505-0
summary:
Becker's rule: given A→B, deduce TA→TB where T is a tense, any sequence made of G, H, F, and P. Mirroring: given a theorem A, deduce its mirror statement A§, which is obtained by replacing G by H (and so F by P) and vice versa. Duality: given a theorem A, deduce its dual statement A*, which is obtained by interchanging ∧ with ∨, G with F, and H with P. === Translation to predicate logic === Burgess gives a Meredith translation from statements in TL into statements in first-order logic with one free variable x0 (representing the present moment). This translation M is defined recursively as follows: M ( a ) = a ∗ x 0 M ( ¬ ϕ ) = ¬ M ( ϕ ) M ( ϕ ∧ ψ ) = M ( ϕ ) ∧ M ( ψ ) M ( G ϕ ) = ∀ x 1 ( x 0 < x 1 → M ( A + ) ) M ( H ϕ ) = ∀ x 1 ( x 1 < x 0 → M ( A + ) ) {\displaystyle {\begin{aligned}&M(a)&&=a^{*}x_{0}\\&M(\lnot \phi )&&=\lnot M(\phi )\\&M(\phi \land \psi )&&=M(\phi )\land M(\psi )\\&M({\mathsf


id: temporal-parts-20260505-0
file: data/en.wikipedia.org/wiki/Temporal_parts-0.md
category: reference
title: Temporal parts
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Temporal_parts
date_saved: 2026-05-05T11:14:49.008096+00:00
instance: kb-cron
parent: temporal-parts-20260505-0
summary:
In contemporary metaphysics, temporal parts are the parts of an object that exist in time. A temporal part would be something like "the first year of a person's life", or "all of a table from between 10:00 a.m. on June 21, 1994 to 11:00 p.m. on July 23, 1996". The term is used in the debate over the persistence of material objects. Objects typically have parts that exist in space—a human body, for example, has spatial parts like hands, feet, and legs. Some metaphysicians believe objects have temporal parts as well. Originally it was argued that those who believe in temporal parts believe in perdurantism, that persisting objects are wholes composed entirely of temporal parts. This view was contrasted with endurantism, the claim that objects are wholly present at any one time (thus not having different temporal parts at different times). This claim is still commonplace, but philosophers like Ted Sider believe that even endurantists should accept temporal parts. == Definition == Not everyone was happy with the definition by analogy: some philosophers, such as Peter van Inwagen, argued that—even given the definition by analogy—they still had no real idea what a temporal part was meant to be, whilst others


id: temporal-parts-20260505-1
file: data/en.wikipedia.org/wiki/Temporal_parts-1.md
category: reference
title: Temporal parts
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Temporal_parts
date_saved: 2026-05-05T11:14:49.008096+00:00
instance: kb-cron
parent: temporal-parts-20260505-0
summary:
P1: There are intrinsic properties, i.e., properties had by an object independently of anything in the world. P2: If every property had by an object is had to times, then there are no intrinsic properties. C1: Therefore, not every property had by an object is had two times. Objects have some of their properties intrinsically, i.e., simpliciter. P3: But only temporal parts can have their properties simpliciter. C2: Therefore, there are temporal parts. (For this to follow, it is required that there be objects). Premise P1 is an intuitive premise; generally we distinguish between properties and relations. An intrinsic property is just a property that something has independently of anything else; an extrinsic property is had only in relation to something. An example of an extrinsic property is "fatherhood": something is a father only if that something is a male and has a child. An example of an alleged intrinsic property is "shape". According to Lewis, if we know what "shapes" are, we know them to be properties, not relations. However, if properties are had to times, as endurantists say, then no property is intrinsic. Even if a ball is round throughout its existence, the endurantist must say "for all


id: temporality-20260505-0
file: data/en.wikipedia.org/wiki/Temporality-0.md
category: reference
title: Temporality
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Temporality
date_saved: 2026-05-05T11:14:50.165246+00:00
instance: kb-cron
parent: temporality-20260505-0
summary:
In philosophy, temporality refers to the idea of a linear progression of past, present, and future. The term is frequently used, however, in the context of critiques of commonly held ideas of linear time. In social sciences, temporality is studied with respect to the human perception of time and the social organization of time. The perception of time in Western thought underwent significant changes in the three hundred years between the Middle Ages and modernity. Examples in Continental philosophy of philosophers raising questions of temporality include Edmund Husserl's analysis of internal time consciousness, Martin Heidegger's Being and Time, J. M. E. McTaggart's article "The Unreality of Time", George Herbert Mead's Philosophy of the Present, and Jacques Derrida's criticisms of Husserl's analysis. Temporality is "deeply intertwined with the rhetorical act of harnessing and subverting power in the unfolding struggle for justice." Temporalities, particularly in European settler colonialism, have been observed in critical theory as a tool for both subjugation and oppression of Indigenous communities, and Native resistance to that oppression. == Temporal turn == In historiography, questioning periodization, and as a further development after the spatial turn, social sciences have started re-investigating time and its different social understanding. Temporal turn social


id: time-perception-20260505-0
file: data/en.wikipedia.org/wiki/Time_perception-0.md
category: reference
title: Time perception
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_perception
date_saved: 2026-05-05T11:14:51.490071+00:00
instance: kb-cron
parent: time-perception-20260505-0
summary:
In psychology and neuroscience, time perception or chronoception is the subjective experience, or sense, of time, which is measured by someone's own perception of the duration of the indefinite and unfolding of events. The perceived time interval between two successive events is referred to as perceived duration. Though directly experiencing or understanding another person's perception of time is not possible, perception can be objectively studied and inferred through a number of scientific experiments. Some temporal illusions help to expose the underlying neural mechanisms of time perception. The ancient Greeks recognized the difference between chronological time (chronos) and subjective time (kairos). Pioneering work on time perception, emphasizing species-specific differences, was conducted by Karl Ernst von Baer. == Theories == Time perception is typically categorized in five distinct ranges, because different ranges of duration are processed in different areas of the brain: Sub-second timing or millisecond timing Interval timing or seconds-to-minutes timing Circadian timing Astrocyte glutamine clearance delay Mitochondrial hysteresis There are many theories and computational models for time perception mechanisms in the brain. William J. Friedman (1993) contrasted two theories of the sense of time: The strength model of time memory. This posits a memory trace that persists over time, by


id: time-perception-20260505-1
file: data/en.wikipedia.org/wiki/Time_perception-1.md
category: reference
title: Time perception
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_perception
date_saved: 2026-05-05T11:14:51.490071+00:00
instance: kb-cron
parent: time-perception-20260505-0
summary:
if the visual brain wants to get events correct timewise, it may have only one choice: wait for the slowest information to arrive. To accomplish this, it must wait about a tenth of a second. In the early days of television broadcasting, engineers worried about the problem of keeping audio and video signals synchronized. Then they accidentally discovered that they had around a hundred milliseconds of slop: As long as the signals arrived within this window, viewers' brains would automatically resynchronize the signals. He goes on to say, "This brief waiting period allows the visual system to discount the various delays imposed by the early stages; however, it has the disadvantage of pushing perception into the past. There is a distinct survival advantage to operating as close to the present as possible; an animal does not want to live too far in the past. Therefore, the tenth-of-a-second window may be the smallest delay that allows higher areas of the brain to account for the delays created in the first stages of the system while still operating near the border of the present. This window of delay means that awareness is retroactive, incorporating data from a window of time after an


id: time-perception-20260505-2
file: data/en.wikipedia.org/wiki/Time_perception-2.md
category: reference
title: Time perception
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_perception
date_saved: 2026-05-05T11:14:51.490071+00:00
instance: kb-cron
parent: time-perception-20260505-0
summary:
When returning to the hive with nectar, forager honey bees need to know the current ratio of nectar-collecting to nectar-processing rates in the colony. To do so, they estimate the time it takes them to find a food-storer bee, which will unload the forage and store it. The longer it takes them to find one, the busier the food-storer bees are, and therefore the higher the nectar-collecting rate of the colony. Forager bees also assess the quality of nectar by comparing the length of time it takes to unload the forage: a longer unloading time indicates higher quality nectar. They compare their own unloading time to the unloading time of other foragers present in the hive, and adjust their recruiting behavior accordingly. For instance, honey bees reduce the duration of their waggle dance if they judge their own yield to be inferior. Scientists have demonstrated that anesthesia disrupts the circadian clock and impairs the time perception of honey bees, as observed in humans. Experiments revealed that a six-hour-long general anesthesia significantly delayed the start of the foraging behaviour of honeybees if induced during daytime, but not if induced during nighttime. Bumble bees can be successfully trained to respond to a


id: time-perception-20260505-3
file: data/en.wikipedia.org/wiki/Time_perception-3.md
category: reference
title: Time perception
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_perception
date_saved: 2026-05-05T11:14:51.490071+00:00
instance: kb-cron
parent: time-perception-20260505-0
summary:
In an experiment, participants were told to stare at an "x" symbol on a computer screen whereby a moving blue doughnut-like ring repeatedly circled the fixed "x" point. Occasionally, the ring would display a white flash for a split second that physically overlapped the ring's interior. However, when asked what was perceived, participants responded that they saw the white flash lagging behind the center of the moving ring. In other words, despite the reality that the two retinal images were actually spatially aligned, the flashed object was usually observed to trail a continuously moving object in space — a phenomenon referred to as the flash-lag effect. The first proposed explanation, called the "motion extrapolation" hypothesis, is that the visual system extrapolates the position of moving objects but not flashing objects when accounting for neural delays (i.e., the lag time between the retinal image and the observer's perception of the flashing object). The second proposed explanation by David Eagleman and Sejnowski, called the "latency difference" hypothesis, is that the visual system processes moving objects at a faster rate than flashed objects. In the attempt to disprove the first hypothesis, David Eagleman conducted an experiment in which the moving ring suddenly reverses


id: time-perception-20260505-4
file: data/en.wikipedia.org/wiki/Time_perception-4.md
category: reference
title: Time perception
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_perception
date_saved: 2026-05-05T11:14:51.490071+00:00
instance: kb-cron
parent: time-perception-20260505-0
summary:
==== Awe ==== Research has suggested the feeling of awe has the ability to expand one's perceptions of time availability. Awe can be characterized as an experience of immense perceptual vastness that coincides with an increase in focus. Consequently, it is conceivable that one's temporal perception would slow down when experiencing awe. The perception of time can differ as people choose between savoring moments and deferring gratification. ==== Fear ==== Possibly related to the oddball effect, research suggests that time seems to slow down for a person during dangerous events (such as a car accident, a robbery, or when a person perceives a potential predator or mate), or when a person skydives or bungee jumps, where they are capable of complex thoughts in what would normally be the blink of an eye (e.g., a fight-or-flight response). This reported slowing in temporal perception may have been evolutionarily advantageous because it may have enhanced one's ability to intelligibly make quick decisions in moments that were of critical importance to survival. However, even though observers commonly report that time seems to have moved in slow motion during these events, it is unclear whether this is a function of increased time resolution during the


id: time-perception-20260505-5
file: data/en.wikipedia.org/wiki/Time_perception-5.md
category: reference
title: Time perception
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_perception
date_saved: 2026-05-05T11:14:51.490071+00:00
instance: kb-cron
parent: time-perception-20260505-0
summary:
When solved, S 2 − S 1 = K ( log ⁡ R 2 − log ⁡ R 1 ) = K log ⁡ ( R 2 / R 1 ) {\displaystyle S_{2}-S_{1}=K(\log {R_{2}}-\log {R_{1}})=K\log {\left({R_{2}}/{R_{1}}\right)}} . One day would be approximately 1/4,000 of the life of an 11-year-old, but approximately 1/20,000 of the life of a 55-year-old. So a year would be experienced by a 55-year-old as passing approximately five times more quickly than a year experienced by an 11-year-old. If long-term time perception is based solely on the proportionality of a person's age, then the following four periods in life would appear to be quantitatively equal: ages 5–10 (1x), ages 10–20 (2x), ages 20–40 (4x), age 40–80 (8x), as the end age is twice the start age. However, this does not work for ages 0–10, which corresponds to ages 10–∞. ==== Proportional to the subjective time ==== Lemlich posits that the passage of subjective time relative to actual time is inversely proportional to total subjective time, rather than the total real time: d S d R = K S {\displaystyle {\frac {dS}{dR}}={\frac {K}{S}}} When mathematically solved, S 2 = 2 K R + C {\displaystyle S^{2}=2KR+C} It avoids


id: time-perception-20260505-6
file: data/en.wikipedia.org/wiki/Time_perception-6.md
category: reference
title: Time perception
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_perception
date_saved: 2026-05-05T11:14:51.490071+00:00
instance: kb-cron
parent: time-perception-20260505-0
summary:
== Time perception and artificial intelligence == Time perception refers to the ability to represent, estimate, and use temporal information. While it is a fundamental aspect of biological cognition, recent research has increasingly sought to model temporal processing in artificial systems, especially embodied artificial systems. This line of research has been suggested to be crucial for human-robot interaction, where understanding subtle timing cues can improve coordination and collaboration. For example, timing precision also affects user satisfaction, as temporal accuracy in robotic movements often matters more than spatial precision. Computational studies of biological timing mechanisms also help generate testable hypotheses about biological time perception. Consequently, computational and robotic models have been developed to simulate various timing abilities, such as duration estimation, interval reproduction, and temporal prediction, across cognitive and emergent modelling frameworks. Many of these models use neural network dynamics, oscillatory systems, or reinforcement learning to produce clock-like timing without an explicit clock structure. == Applications in urban design == Beyond laboratory settings, time perception has also been studied in relation to the design of urban environments. In this context, Shakibamanesh and Ghorbanian (2017) developed an applied time-based evaluation checklist that enables urban designers to systematically analyze how spatial form, visual


id: time-reborn-20260505-0
file: data/en.wikipedia.org/wiki/Time_Reborn-0.md
category: reference
title: Time Reborn
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_Reborn
date_saved: 2026-05-05T11:14:52.675505+00:00
instance: kb-cron
parent: time-reborn-20260505-0
summary:
Time Reborn: From the Crisis in Physics to the Future of the Universe is a 2013 book by the American theoretical physicist Lee Smolin. Smolin argues for what he calls a revolutionary view that time is real, in contrast to existing scientific orthodoxy which holds that time is merely a "stubbornly persistent illusion" (Einstein's words). Smolin hypothesizes that the very laws of physics are not fixed, but that they actually evolve over time. == Content and concepts == Time Reborn is divided into two parts: Part I describes established physics and its history from the time of Plato and the main established ideas, Newtonian physics (and Leibniz' philosophical views that countered Newton's e.g. on background dependent physics and his religious justification), Albert Einstein's special and general relativity, and quantum mechanics. Part II describes Smolin's views (his "future" for physics, relying on his and ideas of others) on why these all are slightly wrong, that is, the need to reestablish time as fundamental (and probably space as non-fundamental, rather than vice versa, that was Einstein's view) through e.g. one idea, shape dynamics, a duality of Einstein's general relativity, that does that. Smolin argues for what he calls a revolutionary view that


id: time-s-arrow-and-archimedes-point-20260505-0
file: data/en.wikipedia.org/wiki/Time's_Arrow_and_Archimedes'_Point-0.md
category: reference
title: Time's Arrow and Archimedes' Point
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time's_Arrow_and_Archimedes'_Point
date_saved: 2026-05-05T11:14:53.833338+00:00
instance: kb-cron
parent: time-s-arrow-and-archimedes-point-20260505-0
summary:
Time's Arrow and Archimedes Point: New Directions for the Physics of Time is a 1996 book by Huw Price, on the physics and philosophy of the arrow of time. It explores the problem of the direction of time, looking at issues in thermodynamics, cosmology, electromagnetism, and quantum mechanics. Price argues that it is fruitful to think about time from a hypothetical Archimedean point – a viewpoint outside of time. In later chapters, Price argues that retrocausality can resolve many of the philosophical issues facing quantum mechanics and along these lines proposes an interpretation involving what he calls 'advanced action'. == Summary == === Chapter 1 – The View From Nowhen === Price briefly introduces the stock philosophical questions about time, starting with Saint Augustine's observations in Confessions, highlighting the questions 'What is the difference between past and future?', 'Could the future affect the past?' and 'what gives time its direction?'. He then introduces the block universe view where the 'present' is regarded as a subjective notion, which changes from observer to observer, in the same way that the concept of 'here' changes depending on where the observer is. The block universe view rejects the notion that there exists an objective


id: time-s-arrow-and-archimedes-point-20260505-1
file: data/en.wikipedia.org/wiki/Time's_Arrow_and_Archimedes'_Point-1.md
category: reference
title: Time's Arrow and Archimedes' Point
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time's_Arrow_and_Archimedes'_Point
date_saved: 2026-05-05T11:14:53.833338+00:00
instance: kb-cron
parent: time-s-arrow-and-archimedes-point-20260505-0
summary:
=== Chapter 8 – Einstein's Issue: The Puzzle of Contemporary Quantum Theory === This chapter is a self-contained introduction to quantum mechanics. It introduces the EPR paradox and the measurement problem. Bell's theorem and the GHZ experiment are then introduced in the context of hidden-variables interpretations of quantum mechanics. De Broglie–Bohm theory, the many-worlds interpretation, the many-minds interpretation and the quantum decoherence approach are all examined, though Price finds them all ultimately unconvincing. He points out that Bell's theorem relies on the assumption that, when a measurement basis is chosen, this choice is independent of the state of the quantum system being measured. This, he points out, would not necessarily be the case in a world with advanced action. === Chapter 9 – The Case for Advanced Action === Price notes that the independence assumption in Bell's theorem can be relaxed in two ways: the first being that the measurement basis and the state of the quantum system are correlated through a common cause in the past, and the second being what Price calls 'advanced action' – a 'common cause' in the future. He argues against superdeterminism, the idea that a quantum system and measurement apparatus are correlated due to


id: uji-being-time-20260505-0
file: data/en.wikipedia.org/wiki/Uji_(Being-Time)-0.md
category: reference
title: Uji (Being-Time)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Uji_(Being-Time)
date_saved: 2026-05-05T11:14:55.011110+00:00
instance: kb-cron
parent: uji-being-time-20260505-0
summary:
The Japanese Buddhist word uji (有時), usually translated into English as Being-Time, is a key metaphysical idea of the Sōtō Zen founder Dōgen (1200–1253). His 1240 essay titled Uji, which is included as a fascicle in the Shōbōgenzō ("Treasury of the True Dharma Eye") collection, gives several explanations of uji, beginning with, "The so-called "sometimes" (uji) means: time (ji) itself already is none other than being(s) (u) are all none other than time (ji)." Scholars have interpreted uji "being-time" for over seven centuries. Early interpretations traditionally employed Buddhist terms and concepts, such as impermanence (Pali anicca, Japanese mujō 無常). Modern interpretations of uji are more diverse, for example, authors like Steven Heine and Joan Stambaugh compare Dōgen's concepts of temporality with the existentialist Martin Heidegger's 1927 Being and Time. == Terminology == Dōgen's writings can be notoriously difficult to understand and translate, frequently owing to his wordplay with Late Middle Japanese terms. Dōgen's Zen neologism uji (有時, "existence-/being-time") is the uncommon on'yomi Sino-Japanese reading of the Chinese word yǒushí (有時, "sometimes; at times", Wenlin 2016), and plays with the more common kun'yomi native Japanese pronunciation of these two kanji characters as arutoki (或る時, "once; on one occasion; at one point;


id: uji-being-time-20260505-1
file: data/en.wikipedia.org/wiki/Uji_(Being-Time)-1.md
category: reference
title: Uji (Being-Time)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Uji_(Being-Time)
date_saved: 2026-05-05T11:14:55.011110+00:00
instance: kb-cron
parent: uji-being-time-20260505-0
summary:
== Interpretations == Many authors have researched and discussed Dōgen's theories of temporality. In English, there are two books and numerous articles on uji (有時, "being-time; time-being; etc."). According to the traditional interpretation, uji "means time itself is being, and all being is time". Hee-Jin Kim analyzed Dōgen's conception of uji "existence/time" as the way of spiritual freedom, and found that his discourse can be better understood in terms of ascesis rather than vision of Buddha-nature; "vision is not discredited, but penetrated, empowered by ascesis". Steven Heine's 1983 article on the hermeneutics of temporality in the Shōbōgenzō, that is, Dōgen critically reinterpreting and restating, "even at the risk of grammatical distortion," previous views of Buddha-nature in order to reflect the multidimensional unity of uji "being-time". For example, paraphrasing the venerated Nirvana Sutra, "If you wish to know the Buddha-nature's meaning, you should watch temporal conditions. If the time arrives, the Buddha-nature will manifest itself," Dōgen reinterprets the phrase "if the time arrives" (jisetsu nyakushi 時節若至) to mean "the time already arrived" (jisetsu kishi 時節既至) and comments, "There is no time right now that is not a time that has arrived,.. There is no Buddha-nature that is not Buddha-nature fully manifested


id: uji-being-time-20260505-2
file: data/en.wikipedia.org/wiki/Uji_(Being-Time)-2.md
category: reference
title: Uji (Being-Time)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Uji_(Being-Time)
date_saved: 2026-05-05T11:14:55.011110+00:00
instance: kb-cron
parent: uji-being-time-20260505-0
summary:
Being-time has the virtue of seriatim passage; it passes from today to tomorrow, passes from today to yesterday, passes from yesterday to today, passes from today to today, passes from tomorrow to tomorrow. This is because passing seriatim is a virtue of time. Past time and present time do not overlap one another, or pile up in a row. The existential moment has the quality of shifting. It shifts from what we call "today" into "tomorrow," it shifts from "today" into "yesterday," and from "yesterday" into "today" in turn. It shifts from "today" into "today," it shifts from "tomorrow" into "tomorrow." This is because shifting is the quality of the momentary. The moments of the past and the present do not pile on each other nor do they line up side by side. Dainin Katagiri says Dōgen's uji Being-time means the complete oneness of time and space, "dynamically functioning from moment to moment as illumination that is alive in the individual self". When time, being, self, and illumination come together and work dynamically in one's life, time and being are unified. Furthermore, self is time. The "self arrays itself and forms the entire universe." One should perceive each particular thing


id: the-unreality-of-time-20260505-0
file: data/en.wikipedia.org/wiki/The_Unreality_of_Time-0.md
category: reference
title: The Unreality of Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Unreality_of_Time
date_saved: 2026-05-05T11:14:56.211863+00:00
instance: kb-cron
parent: the-unreality-of-time-20260505-0
summary:
"The Unreality of Time" is the best-known philosophical work of University of Cambridge idealist J. M. E. McTaggart (1866–1925). In the argument, first published as a journal article in Mind in 1908, McTaggart argues that time is unreal because our descriptions of time are either contradictory, circular, or insufficient. A slightly different version of the argument appeared in 1927 as one of the chapters in the second volume of McTaggart's most well known book, The Nature of Existence. The argument for the unreality of time is popularly treated as a stand-alone argument that does not depend on any significant metaphysical principles (e.g. as argued by C. D. Broad 1933 and L. O. Mink 1960). R. D. Ingthorsson disputes this, and argues that the argument can only be understood as an attempt to draw out certain consequences of the metaphysical system that McTaggart presents in the first volume of The Nature of Existence. It is helpful to consider the argument as consisting of three parts. In the first part, McTaggart offers a phenomenological analysis of the appearance of time, in terms of the now famous A-series and B-series. In the second part, he argues that a conception of time as only


id: the-unreality-of-time-20260505-1
file: data/en.wikipedia.org/wiki/The_Unreality_of_Time-1.md
category: reference
title: The Unreality of Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Unreality_of_Time
date_saved: 2026-05-05T11:14:56.211863+00:00
instance: kb-cron
parent: the-unreality-of-time-20260505-0
summary:
== The contradiction of the A-series == Attacking the A-series, McTaggart argues that any event in the A-series is past, present, and future, which is contradictory in that each of those properties excludes the other two. McTaggart admits that the contradictory nature of the A-series may not be obvious, because it would appear that events never are simultaneously future, present, and past, but only successively so. However, there is a contradiction, he insists, because any attempt to explain why they are future, present, and past, at different times is (i) circular because we would need to describe the successive order of those "different times" again by invoking the determinations of being future, present or past, and (ii) this in turn will inevitably lead to a vicious infinite regress. The vicious infinite regress arises, because to explain why the second appeal to future, present, and past, doesn't lead again to the same difficulty all over, we need to explain that they in turn apply successively and thus we must again explain that succession by appeal to future, present, and past, and there is no end to such an explanation. It is the validity of the argument in favour of a vicious


id: the-unreality-of-time-20260505-2
file: data/en.wikipedia.org/wiki/The_Unreality_of_Time-2.md
category: reference
title: The Unreality of Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Unreality_of_Time
date_saved: 2026-05-05T11:14:56.211863+00:00
instance: kb-cron
parent: the-unreality-of-time-20260505-0
summary:
== The C-series == Having come to the conclusion that reality can neither form an A- nor a B-series, despite appearances to the contrary, then McTaggart finds it necessary to explain what the world is really like such that it appears to be different from what it appears to be. Here is where the C-series comes into play. McTaggart does not say much about the C-series in the original journal article, but in The Nature of Existence he devotes six whole chapters to discuss it. The C-series is rarely given much attention. When it is mentioned, it is described as "an expression synonymous with 'B-series' when the latter is shorn of its temporal connotations". There is a grain of truth in this, but there is more to the C-series than this. Stripping the temporal features from the B-series only gives what the C-series and B-series have minimally in common, notably the constituents of the series and the formal characteristics of being linear, asymmetric, and transitive. However, the C-series has features that the B-series does not have. The constituents of the C-series are mental states (a consequence of McTaggart's argument in Ch. 34 of The Nature of Existence that reality cannot


id: time-in-physics-20260505-0
file: data/en.wikipedia.org/wiki/Time_in_physics-0.md
category: reference
title: Time in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_in_physics
date_saved: 2026-05-05T11:14:57.752094+00:00
instance: kb-cron
parent: time-in-physics-20260505-0
summary:
In physics, time is defined by its measurement: time is what a clock reads. In classical, non-relativistic physics, it is a scalar quantity (often denoted by the symbol t {\displaystyle t} ) and, like length, mass, and charge, is usually described as a fundamental quantity. Time can be combined mathematically with other physical quantities to derive other concepts such as motion, kinetic energy and time-dependent fields. Timekeeping is a complex of technological and scientific issues, and part of the foundation of recordkeeping. == Markers of time == Before there were clocks, time was measured by those physical processes which were understandable to each epoch of civilization: the first appearance (see: heliacal rising) of Sirius to mark the flooding of the Nile each year the periodic succession of night and day, seemingly eternally the position on the horizon of the first appearance of the sun at dawn the position of the sun in the sky the marking of the moment of noontime during the day the length of the shadow cast by a gnomon Eventually, it became possible to characterize the passage of time with instrumentation, using operational definitions. Simultaneously, our conception of time has evolved, as shown below. == Unit


id: time-in-physics-20260505-1
file: data/en.wikipedia.org/wiki/Time_in_physics-1.md
category: reference
title: Time in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_in_physics
date_saved: 2026-05-05T11:14:57.752094+00:00
instance: kb-cron
parent: time-in-physics-20260505-0
summary:
...a large vessel of water placed in an elevated position; to the bottom of this vessel was soldered a pipe of small diameter giving a thin jet of water, which we collected in a small glass during the time of each descent, whether for the whole length of the channel or for a part of its length; the water thus collected was weighed, after each descent, on a very accurate balance; the differences and ratios of these weights gave us the differences and ratios of the times, and this with such accuracy that although the operation was repeated many, many times, there was no appreciable discrepancy in the results. Galileo's experimental setup to measure the literal flow of time, in order to describe the motion of a ball, preceded Isaac Newton's statement in his Principia, "I do not define time, space, place and motion, as being well known to all." The Galilean transformations assume that time is the same for all reference frames. === Newtonian physics: linear time === In or around 1665, when Isaac Newton (1643–1727) derived the motion of objects falling under gravity, the first clear formulation for mathematical physics of a treatment of time began: linear time,


id: time-in-physics-20260505-2
file: data/en.wikipedia.org/wiki/Time_in_physics-2.md
category: reference
title: Time in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_in_physics
date_saved: 2026-05-05T11:14:57.752094+00:00
instance: kb-cron
parent: time-in-physics-20260505-0
summary:
If at the point A of space there is a clock, an observer at A can determine the time values of events in the immediate proximity of A by finding the positions of the hands which are simultaneous with these events. If there is at the point B of space another clock in all respects resembling the one at A, it is possible for an observer at B to determine the time values of events in the immediate neighbourhood of B. But it is not possible without further assumption to compare, in respect of time, an event at A with an event at B. We have so far defined only an "A time" and a "B time". We have not defined a common "time" for A and B, for the latter cannot be defined at all unless we establish by definition that the "time" required by light to travel from A to B equals the "time" it requires to travel from B to A. Let a ray of light start at the "A time" tA from A towards B, let it at the "B time" tB be reflected at B in the direction of A, and arrive again at A


id: time-in-physics-20260505-3
file: data/en.wikipedia.org/wiki/Time_in_physics-3.md
category: reference
title: Time in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_in_physics
date_saved: 2026-05-05T11:14:57.752094+00:00
instance: kb-cron
parent: time-in-physics-20260505-0
summary:
T = d t ( 1 − 2 G M r c 2 ) d t 2 − 1 c 2 ( 1 − 2 G M r c 2 ) − 1 d r 2 − r 2 c 2 d θ 2 − r 2 c 2 sin 2 ⁡ θ d ϕ 2 {\displaystyle T={\frac {dt}{\sqrt {\left(1-{\frac {2GM}{rc^{2}}}\right)dt^{2}-{\frac {1}{c^{2}}}\left(1-{\frac {2GM}{rc^{2}}}\right)^{-1}dr^{2}-{\frac {r^{2}}{c^{2}}}d\theta ^{2}-{\frac {r^{2}}{c^{2}}}\sin ^{2}\theta \;d\phi ^{2}}}}} where: T {\displaystyle T} is the gravitational time dilation of an object at a distance of r {\displaystyle r} . d t {\displaystyle dt} is the change in coordinate time, or the interval of coordinate time. G {\displaystyle G} is the gravitational constant M {\displaystyle M} is the mass generating the field ( 1 − 2 G M r c 2 ) d t 2 − 1 c 2 ( 1 − 2 G M r c 2 ) − 1 d r 2 − r 2 c 2 d θ 2 − r 2 c 2 sin 2 ⁡ θ d ϕ 2 {\displaystyle {\sqrt {\left(1-{\frac {2GM}{rc^{2}}}\right)dt^{2}-{\frac {1}{c^{2}}}\left(1-{\frac {2GM}{rc^{2}}}\right)^{-1}dr^{2}-{\frac {r^{2}}{c^{2}}}d\theta ^{2}-{\frac {r^{2}}{c^{2}}}\sin ^{2}\theta \;d\phi ^{2}}}} is the change in proper time d τ {\displaystyle d\tau } , or the interval


id: time-in-physics-20260505-4
file: data/en.wikipedia.org/wiki/Time_in_physics-4.md
category: reference
title: Time in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_in_physics
date_saved: 2026-05-05T11:14:57.752094+00:00
instance: kb-cron
parent: time-in-physics-20260505-0
summary:
Khemani, Moessner, and Sondhi define a time crystal as a "stable, conservative, macroscopic clock". == Signalling == Signalling is one application of the electromagnetic waves described above. In general, a signal is part of communication between parties and places. One example might be a yellow ribbon tied to a tree, or the ringing of a church bell. A signal can be part of a conversation, which involves a protocol. Another signal might be the position of the hour hand on a town clock or a railway station. An interested party might wish to view that clock, to learn the time. See: Time ball, an early form of Time signal. We as observers can still signal different parties and places as long as we live within their past light cone. But we cannot receive signals from those parties and places outside our past light cone. Along with the formulation of the equations for the electromagnetic wave, the field of telecommunication could be founded. In 19th century telegraphy, electrical circuits, some spanning continents and oceans, could transmit codes - simple dots, dashes and spaces. From this, a series of technical issues have emerged; see Category:Synchronization. But it is safe to say that


id: time-in-physics-20260505-5
file: data/en.wikipedia.org/wiki/Time_in_physics-5.md
category: reference
title: Time in physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_in_physics
date_saved: 2026-05-05T11:14:57.752094+00:00
instance: kb-cron
parent: time-in-physics-20260505-0
summary:
== Reprise == Ilya Prigogine's reprise is "Time precedes existence". In contrast to the views of Newton, of Einstein, and of quantum physics, which offer a symmetric view of time (as discussed above), Prigogine points out that statistical and thermodynamic physics can explain irreversible phenomena, as well as the arrow of time and the Big Bang. == See also == Relativistic dynamics Category:systems of units Time in astronomy == References == == Further reading == Boorstein, Daniel J., The Discoverers. Vintage. February 12, 1985. ISBN 0-394-72625-1 Dieter Zeh, H., The physical basis of the direction of time. Springer. ISBN 978-3-540-42081-1 Kuhn, Thomas S., The Structure of Scientific Revolutions. ISBN 0-226-45808-3 Mandelbrot, Benoît, Multifractals and 1/f noise. Springer Verlag. February 1999. ISBN 0-387-98539-5 Münster, Gernot (2026). "What is Time? - Thoughts of a Physicist". In Blass, Heribert; Bleger, Leopoldo; Picard, Joëlle (eds.). Time and the Experience of Time. London and New York: Routledge. pp. 41–53. ISBN 978-1-041-11405-5.{{cite book}}: CS1 maint: multiple names: editors list (link) Prigogine, Ilya (1984), Order out of Chaos. ISBN 0-394-54204-5 Serres, Michel, et al., "Conversations on Science, Culture, and Time (Studies in Literature and Science)". March, 1995. ISBN 0-472-06548-3 Stengers, Isabelle, and Ilya Prigogine, Theory Out of


id: absolute-space-and-time-20260505-0
file: data/en.wikipedia.org/wiki/Absolute_space_and_time-0.md
category: reference
title: Absolute space and time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Absolute_space_and_time
date_saved: 2026-05-05T11:14:58.980985+00:00
instance: kb-cron
parent: absolute-space-and-time-20260505-0
summary:
Absolute space and time is a concept in physics and philosophy about the properties of the universe. In physics, absolute space and time may be a preferred frame. == Early concept == A version of the concept of absolute space (in the sense of a preferred frame) can be seen in Aristotelian physics. Robert S. Westman writes that a "whiff" of absolute space can be observed in Copernicus's De revolutionibus orbium coelestium, where Copernicus uses the concept of an immobile sphere of stars. == Newton == Originally introduced by Sir Isaac Newton in Philosophiæ Naturalis Principia Mathematica, the concepts of absolute time and space provided a theoretical foundation that facilitated Newtonian mechanics. According to Newton, absolute time and space respectively are independent aspects of objective reality: Absolute, true and mathematical time, of itself, and from its own nature flows equably without regard to anything external, and by another name is called duration: relative, apparent and common time, is some sensible and external (whether accurate or unequable) measure of duration by the means of motion, which is commonly used instead of true time ... According to Newton, absolute time exists independently of any perceiver and progresses at a consistent pace throughout


id: absolute-space-and-time-20260505-1
file: data/en.wikipedia.org/wiki/Absolute_space_and_time-1.md
category: reference
title: Absolute space and time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Absolute_space_and_time
date_saved: 2026-05-05T11:14:58.980985+00:00
instance: kb-cron
parent: absolute-space-and-time-20260505-0
summary:
== Mathematical definitions == Space, as understood in Newtonian mechanics, is three-dimensional and Euclidean, with a fixed orientation. It is denoted E3. If some point O in E3 is fixed and defined as an origin, the position of any point P in E3 is uniquely determined by its radius vector r = O P → {\displaystyle \mathbf {r} ={\vec {OP}}} (the origin of this vector coincides with the point O and its end coincides with the point P). The three-dimensional linear vector space R3 is a set of all radius vectors. The space R3 is endowed with a scalar product ⟨ , ⟩. Time is a scalar which is the same in all space E3 and is denoted as t. The ordered set { t } is called a time axis. Motion (also path or trajectory) is a function r : Δ → R3 that maps a point in the interval Δ from the time axis to a position (radius vector) in R3. The above four concepts are the "well-known" objects mentioned by Isaac Newton in his Principia: I do not define time, space, place and motion, as being well known to all. == Special relativity == The concepts of


id: arrow-of-time-20260505-0
file: data/en.wikipedia.org/wiki/Arrow_of_time-0.md
category: reference
title: Arrow of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Arrow_of_time
date_saved: 2026-05-05T11:15:00.259019+00:00
instance: kb-cron
parent: arrow-of-time-20260505-0
summary:
The arrow of time, also called time's arrow, is the concept positing the "one-way direction" or "asymmetry" of time. It was developed in 1927 by the British astrophysicist Arthur Eddington, and is an unsolved general physics question. This direction, according to Eddington, could be determined by studying the organization of atoms, molecules, and bodies, and might be drawn upon a four-dimensional relativistic map of the world ("a solid block of paper"). The arrow of time paradox was originally recognized in the 1800s for gases (and other substances) as a discrepancy between microscopic and macroscopic description of thermodynamics / statistical physics. At the microscopic level physical processes are believed to be either entirely or mostly time-symmetric: if the direction of time were to reverse, the theoretical statements that describe them would remain true. Yet at the macroscopic level it often appears that this is not the case: there is an obvious direction (or flow) of time. == Overview == The symmetry of time (T-symmetry) can be understood simply as the following: if time were perfectly symmetrical, a video of real events would seem realistic whether played forwards or backwards. Gravity, for example, is a time-reversible force. A ball that is tossed


id: arrow-of-time-20260505-1
file: data/en.wikipedia.org/wiki/Arrow_of_time-1.md
category: reference
title: Arrow of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Arrow_of_time
date_saved: 2026-05-05T11:15:00.259019+00:00
instance: kb-cron
parent: arrow-of-time-20260505-0
summary:
A related mental arrow arises because one has the sense that one's perception is a continuous movement from the known past to the unknown future. This phenomenon has two aspects: memory (we remember the past but not the future) and volition (we feel we can influence the future but not the past). The two aspects are a consequence of the causal arrow of time: past events (but not future events) are the cause of our present memories, as more and more correlations are formed between the outer world and our brain (see correlations and the arrow of time); and our present volitions and actions are causes of future events. This is because the increase of entropy is thought to be related to increase of both correlations between a system and its surroundings and of the overall complexity, under an appropriate definition; thus all increase together with time. Past and future are also psychologically associated with additional notions. English, along with other languages, tends to associate the past with "behind" and the future with "ahead", with expressions such as "to look forward to welcoming you", "to look back to the good old times", or "to be years ahead". However, this association


id: arrow-of-time-20260505-2
file: data/en.wikipedia.org/wiki/Arrow_of_time-2.md
category: reference
title: Arrow of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Arrow_of_time
date_saved: 2026-05-05T11:15:00.259019+00:00
instance: kb-cron
parent: arrow-of-time-20260505-0
summary:
=== Radiative arrow of time === Waves, from radio waves to sound waves to those on a pond from throwing a stone, expand outward from their source, even though the wave equations accommodate solutions of convergent waves as well as radiative ones. This arrow has been reversed in carefully worked experiments that created convergent waves, so this arrow probably follows from the thermodynamic arrow in that meeting the conditions to produce a convergent wave requires more order than the conditions for a radiative wave. Put differently, the probability for initial conditions that produce a convergent wave is much lower than the probability for initial conditions that produce a radiative wave. In fact, normally a radiative wave increases entropy, while a convergent wave decreases it, making the latter contradictory to the second law of thermodynamics in usual circumstances. === Causal arrow of time === A cause precedes its effect: the causal event occurs before the event it causes or affects. Birth, for example, follows a successful conception and not vice versa. Thus causality is intimately bound up with time's arrow. An epistemological problem with using causality as an arrow of time is that, as David Hume maintained, the causal relation per


id: arrow-of-time-20260505-3
file: data/en.wikipedia.org/wiki/Arrow_of_time-3.md
category: reference
title: Arrow of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Arrow_of_time
date_saved: 2026-05-05T11:15:00.259019+00:00
instance: kb-cron
parent: arrow-of-time-20260505-0
summary:
Certain subatomic interactions involving the weak nuclear force violate the conservation of both parity and charge conjugation, but only very rarely. An example is the kaon decay. According to the CPT theorem, this means they should also be time-irreversible, and so establish an arrow of time. Such processes should be responsible for matter creation in the early universe. That the combination of parity and charge conjugation is broken so rarely means that this arrow only "barely" points in one direction, setting it apart from the other arrows whose direction is much more obvious. This arrow had not been linked to any large-scale temporal behaviour until the work of Joan Vaccaro, who showed that T violation could be responsible for conservation laws and dynamics. == See also == A Brief History of Time Anthropic principle Ilya Prigogine Loschmidt's paradox Maxwell's demon Quantum Zeno effect Royal Institution Christmas Lectures 1999 Samayā Time evolution Time flies like an arrow Time reversal signal processing Wheeler–Feynman absorber theory == References == == Further reading == Lebowitz, Joel L. (2008). "Time's arrow and Boltzmann's entropy". Scholarpedia. 3 (4): 3448. Bibcode:2008SchpJ...3.3448L. doi:10.4249/scholarpedia.3448. Boltzmann, Ludwig (1964). Lectures On Gas Theory. University Of California Press. Translated from the original


id: chronology-protection-conjecture-20260505-0
file: data/en.wikipedia.org/wiki/Chronology_protection_conjecture-0.md
category: reference
title: Chronology protection conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chronology_protection_conjecture
date_saved: 2026-05-05T11:15:01.429196+00:00
instance: kb-cron
parent: chronology-protection-conjecture-20260505-0
summary:
The chronology protection conjecture is a hypothesis first proposed by Stephen Hawking that laws of physics beyond those of standard general relativity prevent time travel⁠‍— even when the latter theory states that it should be possible (such as in scenarios where faster than light travel is allowed). The permissibility of time travel is represented mathematically by the existence of closed timelike curves in some solutions to the field equations of general relativity. The chronology protection conjecture should be distinguished from chronological censorship under which every closed timelike curve passes through an event horizon, which might prevent an observer from detecting the causal violation (also known as chronology violation). == Etymology == In a 1992 paper, Hawking uses the metaphorical device of a "Chronology Protection Agency" as a personification of the aspects of physics that make time travel impossible at macroscopic scales, thus apparently preventing temporal paradoxes. He says: It seems that there is a Chronology Protection Agency which prevents the appearance of closed timelike curves and so makes the universe safe for historians. The idea of the Chronology Protection Agency appears to be drawn playfully from the Time Patrol or Time Police concept, which has been used in many works


id: chronology-protection-conjecture-20260505-1
file: data/en.wikipedia.org/wiki/Chronology_protection_conjecture-1.md
category: reference
title: Chronology protection conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chronology_protection_conjecture
date_saved: 2026-05-05T11:15:01.429196+00:00
instance: kb-cron
parent: chronology-protection-conjecture-20260505-0
summary:
== General relativity and quantum corrections == Many attempts to generate scenarios for closed timelike curves have been suggested, and the theory of general relativity does allow them in certain circumstances. Some theoretical solutions in general relativity that contain closed timelike curves would require an infinite universe with certain features that our universe does not appear to have, such as the universal rotation of the Gödel metric or the rotating cylinder of infinite length known as a Tipler cylinder. However, some solutions allow for the creation of closed timelike curves in a bounded region of spacetime, with the Cauchy horizon being the boundary between the region of spacetime where closed timelike curves can exist and the rest of spacetime where they cannot. One of the first such bounded time travel solutions found was constructed from a traversable wormhole, based on the idea of taking one of the two "mouths" of the wormhole on a round-trip journey at relativistic speed to create a time difference between it and the other mouth (see the discussion at Wormhole#Time travel). General relativity does not include quantum effects on its own, and a full integration of general relativity and quantum mechanics would require a theory


id: curved-spacetime-20260505-0
file: data/en.wikipedia.org/wiki/Curved_spacetime-0.md
category: reference
title: Curved spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Curved_spacetime
date_saved: 2026-05-05T11:15:02.570747+00:00
instance: kb-cron
parent: curved-spacetime-20260505-0
summary:
In physics, curved spacetime is the mathematical model in which, with Einstein's theory of general relativity, gravity naturally arises, as opposed to being described as a fundamental force in Newton's static Euclidean reference frame. Objects move along geodesics—curved paths determined by the local geometry of spacetime—rather than being influenced directly by distant bodies. This framework led to two fundamental principles: coordinate independence, which asserts that the laws of physics are the same regardless of the coordinate system used, and the equivalence principle, which states that the effects of gravity are indistinguishable from those of acceleration in sufficiently small regions of space. These principles laid the groundwork for a deeper understanding of gravity through the geometry of spacetime, as formalized in Einstein's field equations. == Introduction == Newton's theories assumed that motion takes place against the backdrop of a rigid Euclidean reference frame that extends throughout all space and all time. Gravity is mediated by a mysterious force, acting instantaneously across a distance, whose actions are independent of the intervening space. In contrast, Einstein denied that there is any background Euclidean reference frame that extends throughout space. Nor is there any such thing as a force of gravitation, only the structure


id: curved-spacetime-20260505-1
file: data/en.wikipedia.org/wiki/Curved_spacetime-1.md
category: reference
title: Curved spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Curved_spacetime
date_saved: 2026-05-05T11:15:02.570747+00:00
instance: kb-cron
parent: curved-spacetime-20260505-0
summary:
In the discussion of special relativity, forces played no more than a background role. Special relativity assumes the ability to define inertial frames that fill all of spacetime, all of whose clocks run at the same rate as the clock at the origin. Is this really possible? In a nonuniform gravitational field, experiment dictates that the answer is no. Gravitational fields make it impossible to construct a global inertial frame. In small enough regions of spacetime, local inertial frames are still possible. General relativity involves the systematic stitching together of these local frames into a more general picture of spacetime. Years before publication of the general theory in 1916, Einstein used the equivalence principle to predict the existence of gravitational redshift in the following thought experiment: (i) Assume that a tower of height h (Fig. 5-3) has been constructed. (ii) Drop a particle of rest mass m from the top of the tower. It falls freely with acceleration g, reaching the ground with velocity v = (2gh)1/2, so that its total energy E, as measured by an observer on the ground, is ⁠ m + 1 2 m v 2 / c 2 = m + m g h /


id: curved-spacetime-20260505-2
file: data/en.wikipedia.org/wiki/Curved_spacetime-2.md
category: reference
title: Curved spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Curved_spacetime
date_saved: 2026-05-05T11:15:02.570747+00:00
instance: kb-cron
parent: curved-spacetime-20260505-0
summary:
== Distortion of space == The ( 1 − 2 G M / ( c 2 r ) ) {\displaystyle (1-2GM/(c^{2}r))} coefficient in front of ( c Δ t ) 2 {\displaystyle (c\Delta t)^{2}} describes the distortion of time in Newtonian gravitation, and this distortion completely accounts for all Newtonian gravitational effects. As expected, this correction factor is directly proportional to G {\displaystyle G} and M {\displaystyle M} , and because of the r {\displaystyle r} in the denominator, the correction factor increases as one approaches the gravitating body, meaning that time is distorted. But general relativity is a theory of distorted space and distorted time, so if there are terms modifying the spatial components of the spacetime interval presented above, should not their effects be seen on, say, planetary and satellite orbits due to distortion correction factors applied to the spatial terms? The answer is that they are seen, but the effects are tiny. The reason is that planetary velocities are extremely small compared to the speed of light, so that for planets and satellites of the Solar System, the ( c Δ t ) 2 {\displaystyle (c\Delta t)^{2}} term dwarfs the spatial terms. Despite the minuteness of the


id: curved-spacetime-20260505-3
file: data/en.wikipedia.org/wiki/Curved_spacetime-3.md
category: reference
title: Curved spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Curved_spacetime
date_saved: 2026-05-05T11:15:02.570747+00:00
instance: kb-cron
parent: curved-spacetime-20260505-0
summary:
T i j {\displaystyle T^{ij}} are the rates of flow of the i-component of momentum per unit area in the j-direction. Even if there is no bulk motion, random thermal motions of the particles will give rise to momentum flow, so the i = j terms (green) represent isotropic pressure, and the i ≠ j terms (blue) represent shear stresses. One important conclusion to be derived from the equations is that, colloquially speaking, gravity itself creates gravity. Energy has mass. Even in Newtonian gravity, the gravitational field is associated with an energy, ⁠ E = m g h , {\displaystyle E=mgh,} ⁠ called the gravitational potential energy. In general relativity, the energy of the gravitational field feeds back into creation of the gravitational field. This makes the equations nonlinear and hard to solve in anything other than weak field cases. Numerical relativity is a branch of general relativity using numerical methods to solve and analyze problems, often employing supercomputers to study black holes, gravitational waves, neutron stars and other phenomena in the strong field regime. === Energy-momentum === In special relativity, mass-energy is closely connected to momentum. Just as space and time are different aspects of a more comprehensive entity


id: curved-spacetime-20260505-4
file: data/en.wikipedia.org/wiki/Curved_spacetime-4.md
category: reference
title: Curved spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Curved_spacetime
date_saved: 2026-05-05T11:15:02.570747+00:00
instance: kb-cron
parent: curved-spacetime-20260505-0
summary:
m p {\displaystyle m_{p}} is the same as gravitational mass ( m g {\displaystyle m_{g}} ) in the discussion of the equivalence principle. In Newtonian theory, The third law of action and reaction dictates that m a {\displaystyle m_{a}} and m p {\displaystyle m_{p}} must be the same. On the other hand, whether m p {\displaystyle m_{p}} and m i {\displaystyle m_{i}} are equal is an empirical result. In general relativity, The equality of m p {\displaystyle m_{p}} and m i {\displaystyle m_{i}} is dictated by the equivalence principle. There is no "action and reaction" principle dictating any necessary relationship between m a {\displaystyle m_{a}} and m p {\displaystyle m_{p}} . === Pressure as a gravitational source === The classic experiment to measure the strength of a gravitational source (i.e. its active mass) was first conducted in 1797 by Henry Cavendish (Fig. 5-9a). Two small but dense balls are suspended on a fine wire, making a torsion balance. Bringing two large test masses close to the balls introduces a detectable torque. Given the dimensions of the apparatus and the measurable spring constant of the torsion wire, the gravitational constant G can be determined. To study pressure effects by compressing the


id: time-dilation-20260505-0
file: data/en.wikipedia.org/wiki/Time_dilation-0.md
category: reference
title: Time dilation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_dilation
date_saved: 2026-05-05T11:15:03.827371+00:00
instance: kb-cron
parent: time-dilation-20260505-0
summary:
Time dilation is the difference in elapsed time as measured by two clocks, either because of a relative velocity, a consequence of special relativity, or a difference in gravitational potential between their locations due to gravitational time dilation. When unspecified, "time dilation" usually refers to the effect due to velocity. The dilation compares "wristwatch" clock readings between events measured in different inertial frames and is not observed by visual comparison of clocks across moving frames. These predictions of the theory of relativity have been repeatedly confirmed by experiment, and they are of practical concern, for instance in the operation of satellite navigation systems such as GPS and Galileo. == Invisibility == Time dilation is a relationship between clock readings. Visually observed clock readings involve delays due to the propagation speed of light from the clock to the observer. Thus there is no direct way to observe time dilation. As an example of time dilation, two experimenters measuring a passing train traveling at .86 light speed may see a 2 second difference on their clocks while on the train the engineer reports only one second elapsed when the experimenters went by. Observations of a clock on the front of the train


id: time-dilation-20260505-1
file: data/en.wikipedia.org/wiki/Time_dilation-1.md
category: reference
title: Time dilation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_dilation
date_saved: 2026-05-05T11:15:03.827371+00:00
instance: kb-cron
parent: time-dilation-20260505-0
summary:
which expresses the fact that the moving observer's period of the clock Δ t ′ {\displaystyle \Delta t'} is longer than the period Δ t {\displaystyle \Delta t} in the frame of the clock itself. The Lorentz factor gamma (γ) is defined as γ = 1 1 − v 2 c 2 {\displaystyle \gamma ={\frac {1}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}} Because all clocks that have a common period in the resting frame should have a common period when observed from the moving frame, all other clocks—mechanical, electronic, optical (such as an identical horizontal version of the clock in the example)—should exhibit the same velocity-dependent time dilation. === Reciprocity === Given a certain frame of reference, and the "stationary" observer described earlier, if a second observer accompanied the "moving" clock, each of the observers would measure the other's clock as ticking at a slower rate than their own local clock, due to them both measuring the other to be the one that is in motion relative to their own stationary frame of reference. Common sense would dictate that, if the passage of time has slowed for a moving object, said object would observe the external world's time to be correspondingly sped up. Counterintuitively,


id: time-dilation-20260505-2
file: data/en.wikipedia.org/wiki/Time_dilation-2.md
category: reference
title: Time dilation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_dilation
date_saved: 2026-05-05T11:15:03.827371+00:00
instance: kb-cron
parent: time-dilation-20260505-0
summary:
In the Minkowski diagram from the first image on the right, clock C resting in inertial frame S′ meets clock A at d and clock B at f (both resting in S). All three clocks simultaneously start to tick in S. The worldline of A is the ct-axis, the worldline of B intersecting f is parallel to the ct-axis, and the worldline of C is the ct′-axis. All events simultaneous with d in S are on the x-axis, in S′ on the x′-axis. The proper time between two events is indicated by a clock present at both events. It is invariant, i.e., in all inertial frames it is agreed that this time is indicated by that clock. Interval df is, therefore, the proper time of clock C, and is shorter with respect to the coordinate times ef=dg of clocks B and A in S. Conversely, also proper time ef of B is shorter with respect to time if in S′, because event e was measured in S′ already at time i due to relativity of simultaneity, long before C started to tick. From that it can be seen, that the proper time between two events indicated by an unaccelerated clock


id: time-dilation-20260505-3
file: data/en.wikipedia.org/wiki/Time_dilation-3.md
category: reference
title: Time dilation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_dilation
date_saved: 2026-05-05T11:15:03.827371+00:00
instance: kb-cron
parent: time-dilation-20260505-0
summary:
x ( τ ) = c 2 g ( cosh ⁡ g τ c − 1 ) {\displaystyle x(\tau )={\frac {c^{2}}{g}}\left(\cosh {\frac {g\tau }{c}}-1\right)} Velocity: v ( τ ) = c tanh ⁡ g τ c {\displaystyle v(\tau )=c\tanh {\frac {g\tau }{c}}} Coordinate time as function of proper time: t ( τ ) = c g sinh ⁡ g τ c {\displaystyle t(\tau )={\frac {c}{g}}\sinh {\frac {g\tau }{c}}} === Clock hypothesis === The clock hypothesis is the assumption that the rate at which a clock is affected by time dilation does not depend on its acceleration but only on its instantaneous velocity. This is equivalent to stating that a clock moving along a path P {\displaystyle P} measures the proper time, defined by: τ = ∫ P d t 2 − d x 2 / c 2 − d y 2 / c 2 − d z 2 / c 2 {\displaystyle \tau =\int _{P}{\sqrt {dt^{2}-dx^{2}/c^{2}-dy^{2}/c^{2}-dz^{2}/c^{2}}}} The clock hypothesis was implicitly (but not explicitly) included in Einstein's original 1905 formulation of special relativity. Since then, it has become a standard assumption and is usually included in the axioms of special relativity, especially in light of experimental verification up to very


id: time-dilation-20260505-4
file: data/en.wikipedia.org/wiki/Time_dilation-4.md
category: reference
title: Time dilation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_dilation
date_saved: 2026-05-05T11:15:03.827371+00:00
instance: kb-cron
parent: time-dilation-20260505-0
summary:
d t E d t c = 1 + 2 U c 2 − v 2 c 2 + ( c 2 2 U + 1 ) − 1 v ∥ 2 c 2 = 1 − ( β 2 + β e 2 + β ∥ 2 β e 2 1 − β e 2 ) {\displaystyle {\frac {dt_{\text{E}}}{dt_{\text{c}}}}={\sqrt {1+{\frac {2U}{c^{2}}}-{\frac {v^{2}}{c^{2}}}+\left({\frac {c^{2}}{2U}}+1\right)^{-1}{\frac {{v_{\shortparallel }}^{2}}{c^{2}}}}}={\sqrt {1-\left(\beta ^{2}+\beta _{e}^{2}+{\frac {\beta _{\shortparallel }^{2}\beta _{e}^{2}}{1-\beta _{e}^{2}}}\right)}}} where: v ∥ {\displaystyle v_{\shortparallel }} is the radial velocity, v e = 2 G M i r i {\displaystyle v_{e}={\sqrt {\frac {2GM_{i}}{r_{i}}}}} is the escape speed, β = v / c {\displaystyle \beta =v/c} , β e = v e / c {\displaystyle \beta _{e}=v_{e}/c} and β ∥ = v ∥ / c {\displaystyle \beta _{\shortparallel }=v_{\shortparallel }/c} are velocities as a percentage of speed of light c, U = − G M i r i {\displaystyle U={\frac {-GM_{i}}{r_{i}}}} is the Newtonian potential; hence − U {\displaystyle -U} equals half the square of the escape speed. The above equation is exact under the assumptions of the Schwarzschild solution. It reduces to velocity time dilation equation in the presence of motion and absence of gravity, i.e.


id: time-dilation-20260505-5
file: data/en.wikipedia.org/wiki/Time_dilation-5.md
category: reference
title: Time dilation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time_dilation
date_saved: 2026-05-05T11:15:03.827371+00:00
instance: kb-cron
parent: time-dilation-20260505-0
summary:
== In fiction == Velocity and gravitational time dilation have been the subject of science fiction works in a variety of media. Some examples in film are the movies Interstellar and Planet of the Apes. In Interstellar, a key plot point involves a planet, which is close to a rotating black hole and on the surface of which one hour is equivalent to seven years on Earth due to time dilation. Physicist Kip Thorne collaborated in making the film and explained its scientific concepts in the book The Science of Interstellar. The Queen song '39 was written by astrophysicist as well as musician Brian May, and is centred around the time dilation effect on spacefarers searching for a new home for mankind, as we gradually ruin planet Earth. They return successful, only to find that all and everything they knew has long since passed away. Time dilation was used in the Doctor Who episodes "World Enough and Time" and "The Doctor Falls", which take place on a spaceship in the vicinity of a black hole. Due to the immense gravitational pull of the black hole and the ship's length (400 miles), time moves faster at one end than the other.


id: fourth-fifth-and-sixth-derivatives-of-position-20260505-0
file: data/en.wikipedia.org/wiki/Fourth,_fifth,_and_sixth_derivatives_of_position-0.md
category: reference
title: Fourth, fifth, and sixth derivatives of position
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fourth,_fifth,_and_sixth_derivatives_of_position
date_saved: 2026-05-05T11:15:05.034067+00:00
instance: kb-cron
parent: fourth-fifth-and-sixth-derivatives-of-position-20260505-0
summary:
In the physics field of kinematics, the fourth, fifth and sixth derivatives of position are generalizations of velocity and acceleration. They are defined as derivatives of the position vector with respect to time – with the first, second, and third derivatives being velocity, acceleration, and jerk, respectively. These higher-order derivatives are less common than the first three; thus their names are not as standardized, though the concept of a minimum snap trajectory has been used in robotics. The fourth derivative is referred to as snap, leading the fifth and sixth derivatives to be "sometimes somewhat facetiously" called crackle and pop, named after the Rice Krispies mascots of the same name. The fourth derivative is also called jounce. == Applications == Minimizing snap and jerk is useful in mechanical and civil engineering because it reduces vibrations and ensures smoother motion transitions. In civil engineering, railway tracks and roads are designed to limit snap, particularly around bends with varying radii of curvature. When snap is constant, the jerk changes linearly, producing a gradual increase in radial acceleration; when snap is zero, acceleration changes linearly. These profiles are often achieved using mathematical clothoid functions. The same principle is applied by roller coaster designers,


id: fourth-fifth-and-sixth-derivatives-of-position-20260505-1
file: data/en.wikipedia.org/wiki/Fourth,_fifth,_and_sixth_derivatives_of_position-1.md
category: reference
title: Fourth, fifth, and sixth derivatives of position
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fourth,_fifth,_and_sixth_derivatives_of_position
date_saved: 2026-05-05T11:15:05.034067+00:00
instance: kb-cron
parent: fourth-fifth-and-sixth-derivatives-of-position-20260505-0
summary:
p = d c d t = d 2 s d t 2 = d 3 j d t 3 = d 4 a d t 4 = d 5 v d t 5 = d 6 r d t 6 {\displaystyle \mathbf {p} ={\frac {\mathrm {d} \mathbf {c} }{\mathrm {d} t}}={\frac {\mathrm {d} ^{2}\mathbf {s} }{\mathrm {d} t^{2}}}={\frac {\mathrm {d} ^{3}\mathbf {j} }{\mathrm {d} t^{3}}}={\frac {\mathrm {d} ^{4}\mathbf {a} }{\mathrm {d} t^{4}}}={\frac {\mathrm {d} ^{5}\mathbf {v} }{\mathrm {d} t^{5}}}={\frac {\mathrm {d} ^{6}\mathbf {r} }{\mathrm {d} t^{6}}}} The following equations are used for constant pop: c = c 0 + p t s = s 0 + c 0 t + 1 2 p t 2 j = j 0 + s 0 t + 1 2 c 0 t 2 + 1 6 p t 3 a = a 0 + j 0 t + 1 2 s 0 t 2 + 1 6 c 0 t 3 + 1 24 p t 4 v = v 0 + a 0 t + 1 2 j 0 t 2 + 1 6 s 0 t 3 + 1 24 c 0 t 4 + 1 120 p t 5


id: galilean-transformation-20260505-0
file: data/en.wikipedia.org/wiki/Galilean_transformation-0.md
category: reference
title: Galilean transformation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Galilean_transformation
date_saved: 2026-05-05T11:15:06.401340+00:00
instance: kb-cron
parent: galilean-transformation-20260505-0
summary:
In physics, a Galilean transformation is used to transform between the coordinates of two reference frames which differ only by constant relative motion within the constructs of Newtonian physics. These transformations together with spatial rotations and translations in space and time form the inhomogeneous Galilean group (assumed throughout below). Without the translations in space and time the group is the homogeneous Galilean group. The Galilean group is the group of motions of Galilean relativity acting on the four dimensions of space and time, forming the Galilean geometry. This is the passive transformation point of view. In special relativity the homogeneous and inhomogeneous Galilean transformations are, respectively, replaced by the Lorentz transformations and Poincaré transformations; conversely, the group contraction in the classical limit c → ∞ of Poincaré transformations yields Galilean transformations. The equations below are only physically valid in a Newtonian framework, and not applicable to coordinate systems moving relative to each other at speeds approaching the speed of light. Galileo formulated these concepts in his description of uniform motion. The topic was motivated by his description of the motion of a ball rolling down a ramp, by which he measured the numerical value for the acceleration of gravity near


id: galilean-transformation-20260505-1
file: data/en.wikipedia.org/wiki/Galilean_transformation-1.md
category: reference
title: Galilean transformation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Galilean_transformation
date_saved: 2026-05-05T11:15:06.401340+00:00
instance: kb-cron
parent: galilean-transformation-20260505-0
summary:
G 4 = { m : s = 0 , a = 0 , R = I 3 } ≅ ( R 3 , + ) , {\displaystyle G_{4}=\{m:s=0,a=0,R=I_{3}\}\cong \left(\mathbf {R} ^{3},+\right),} uniform frame motions / boosts. The parameters s, v, R, a span ten dimensions. Since the transformations depend continuously on s, v, R, a, Gal(3) is a continuous group, also called a topological group. The structure of Gal(3) can be understood by reconstruction from subgroups. The semidirect product combination ( A ⋊ B {\displaystyle A\rtimes B} ) of groups is required. G 2 ◃ S G a l ( 3 ) {\displaystyle G_{2}\triangleleft \mathrm {SGal} (3)} (G2 is a normal subgroup) S G a l ( 3 ) ≅ G 2 ⋊ G 1 {\displaystyle \mathrm {SGal} (3)\cong G_{2}\rtimes G_{1}} G 4 ⊴ G 1 {\displaystyle G_{4}\trianglelefteq G_{1}} G 1 ≅ G 4 ⋊ G 3 {\displaystyle G_{1}\cong G_{4}\rtimes G_{3}} S G a l ( 3 ) ≅ R 4 ⋊ ( R 3 ⋊ S O ( 3 ) ) . {\displaystyle \mathrm {SGal} (3)\cong \mathbf {R} ^{4}\rtimes (\mathbf {R} ^{3}\rtimes \mathrm {SO} (3)).} == Origin in group contraction == The Lie algebra of the Galilean group


id: galilean-transformation-20260505-2
file: data/en.wikipedia.org/wiki/Galilean_transformation-2.md
category: reference
title: Galilean transformation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Galilean_transformation
date_saved: 2026-05-05T11:15:06.401340+00:00
instance: kb-cron
parent: galilean-transformation-20260505-0
summary:
[ L i j ′ , L k l ′ ] = i [ δ i k L j l ′ − δ i l L j k ′ − δ j k L i l ′ + δ j l L i k ′ ] {\displaystyle [L'_{ij},L'_{kl}]=i[\delta _{ik}L'_{jl}-\delta _{il}L'_{jk}-\delta _{jk}L'_{il}+\delta _{jl}L'_{ik}]\,\!} [ L i j ′ , P k ′ ] = i [ δ i k P j ′ − δ j k P i ′ ] {\displaystyle [L'_{ij},P'_{k}]=i[\delta _{ik}P'_{j}-\delta _{jk}P'_{i}]\,\!} [ L i j ′ , C k ′ ] = i [ δ i k C j ′ − δ j k C i ′ ] {\displaystyle [L'_{ij},C'_{k}]=i[\delta _{ik}C'_{j}-\delta _{jk}C'_{i}]\,\!} [ C i ′ , H ′ ] = i P i ′ {\displaystyle [C'_{i},H']=iP'_{i}\,\!} and finally [ C i ′ , P j ′ ] = i M δ i j . {\displaystyle [C'_{i},P'_{j}]=iM\delta _{ij}~.} where the new parameter M {\displaystyle M} shows up. This extension and projective representations that this enables is determined by its group cohomology. == See also == Galilean invariance Representation theory of the Galilean group Galilei-covariant tensor formulation Poincaré group Lorentz group Lagrangian and Eulerian coordinates == Notes == ==


id: jerk-physics-20260505-0
file: data/en.wikipedia.org/wiki/Jerk_(physics)-0.md
category: reference
title: Jerk (physics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Jerk_(physics)
date_saved: 2026-05-05T11:15:07.559806+00:00
instance: kb-cron
parent: jerk-physics-20260505-0
summary:
Jerk (also known as jolt) is the rate of change of an object's acceleration over time. It is a vector quantity (having both magnitude and direction). Jerk is most commonly denoted by the symbol j and expressed in m/s3 (SI units) or standard gravities per second(g0/s). == Expressions == As a vector, jerk j can be expressed as the first time derivative of acceleration, second time derivative of velocity, and third time derivative of position: j = d a d t = d 2 v d t 2 = d 3 r d t 3 , {\displaystyle \mathbf {j} ={\frac {\mathrm {d} \mathbf {a} }{\mathrm {d} t}}={\frac {\mathrm {d} ^{2}\mathbf {v} }{\mathrm {d} t^{2}}}={\frac {\mathrm {d} ^{3}\mathbf {r} }{\mathrm {d} t^{3}}},} where a is acceleration, v is velocity, r is position, and t is time. Third-order differential equations of the form J ( x . . . , x ¨ , x ˙ , x ) = 0 {\displaystyle J\left({\overset {\mathbf {...} }{x}},{\ddot {x}},{\dot {x}},x\right)=0} are sometimes called jerk equations. When converted to an equivalent system of three ordinary first-order non-linear differential equations, jerk equations are the minimal setting for solutions showing chaotic behaviour. This condition generates mathematical interest in


id: jerk-physics-20260505-1
file: data/en.wikipedia.org/wiki/Jerk_(physics)-1.md
category: reference
title: Jerk (physics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Jerk_(physics)
date_saved: 2026-05-05T11:15:07.559806+00:00
instance: kb-cron
parent: jerk-physics-20260505-0
summary:
== In an idealized setting == Discontinuities in acceleration do not occur in real-world environments because of deformation, quantum mechanics effects, and other causes. However, a jump-discontinuity in acceleration and, accordingly, unbounded jerk are feasible in an idealized setting, such as an idealized point mass moving along a piecewise smooth, whole continuous path. The jump-discontinuity occurs at points where the path is not smooth. Extrapolating from these idealized settings, one can qualitatively describe, explain and predict the effects of jerk in real situations. Jump-discontinuity in acceleration can be modeled using a Dirac delta function in jerk, scaled to the height of the jump. Integrating jerk over time across the Dirac delta yields the jump-discontinuity. For example, consider a path along an arc of radius r, which tangentially connects to a straight line. The whole path is continuous, and its pieces are smooth. Now assume a point particle moves with constant speed along this path, so its tangential acceleration is zero. The centripetal acceleration given by ⁠v2/r⁠ is normal to the arc and inward. When the particle passes the connection of pieces, it experiences a jump-discontinuity in acceleration given by ⁠v2/r⁠, and it undergoes a jerk that can be modeled by


id: jerk-physics-20260505-2
file: data/en.wikipedia.org/wiki/Jerk_(physics)-2.md
category: reference
title: Jerk (physics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Jerk_(physics)
date_saved: 2026-05-05T11:15:07.559806+00:00
instance: kb-cron
parent: jerk-physics-20260505-0
summary:
ζ = d α d t = 1 r 2 ( r × d a d t + d r d t × a ) − 2 r 3 d r d t ( r × a ) + 2 r 2 ( d r d t ) 2 ω − 2 r d 2 r d t 2 ω − 2 r d r d t d ω d t {\displaystyle {\begin{aligned}{\boldsymbol {\zeta }}={\frac {d{\boldsymbol {\alpha }}}{dt}}={\frac {1}{r^{2}}}\left(\mathbf {r} \times {\frac {d\mathbf {a} }{dt}}+{\frac {d\mathbf {r} }{dt}}\times \mathbf {a} \right)-{\frac {2}{r^{3}}}{\frac {dr}{dt}}\left(\mathbf {r} \times \mathbf {a} \right)\\\\+{\frac {2}{r^{2}}}\left({\frac {dr}{dt}}\right)^{2}{\boldsymbol {\omega }}-{\frac {2}{r}}{\frac {d^{2}r}{dt^{2}}}{\boldsymbol {\omega }}-{\frac {2}{r}}{\frac {dr}{dt}}{\frac {d{\boldsymbol {\omega }}}{dt}}\end{aligned}}} replacing d ω d t {\displaystyle {\frac {d{\boldsymbol {\omega }}}{dt}}} we can have the last item as − 2 r d r d t d ω d t = − 2 r d r d t ( r × a r 2 − 2 r d r d t ω ) = − 2 r 3 d r d t ( r × a ) + 4 r 2 ( d r d t ) 2 ω {\displaystyle {\begin{aligned}-{\frac {2}{r}}{\frac {dr}{dt}}{\frac {d{\boldsymbol {\omega }}}{dt}}&=-{\frac {2}{r}}{\frac {dr}{dt}}\left({\frac {\mathbf {r} \times


id: jerk-physics-20260505-3
file: data/en.wikipedia.org/wiki/Jerk_(physics)-3.md
category: reference
title: Jerk (physics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Jerk_(physics)
date_saved: 2026-05-05T11:15:07.559806+00:00
instance: kb-cron
parent: jerk-physics-20260505-0
summary:
To reduce the amplitude of excited stress waves and vibrations, one can limit jerk by shaping motion and making the acceleration continuous with slopes as flat as possible. Due to limitations of abstract models, algorithms for reducing vibrations include higher derivatives, such as jounce, or suggest continuous regimes for both acceleration and jerk. One concept for limiting jerk is to shape acceleration and deceleration sinusoidally with zero acceleration in between (see graphic captioned "Sinusoidal acceleration profile"), making the speed appear sinusoidal with constant maximum speed. The jerk, however, will remain discontinuous at the points where acceleration enters and leaves the zero phases. == In the geometric design of roads and tracks == Roads and tracks are designed to limit the jerk caused by changes in their curvature. Design standards for high-speed rail vary from 0.2 m/s3 to 0.6 m/s3. Track transition curves limit the jerk when transitioning from a straight line to a curve, or vice versa. Recall that in constant-speed motion along an arc, acceleration is zero in the tangential direction and nonzero in the inward normal direction. Transition curves gradually increase the curvature and, consequently, the centripetal acceleration. An Euler spiral, the theoretically optimum transition curve, linearly increases


id: metric-tensor-general-relativity-20260505-0
file: data/en.wikipedia.org/wiki/Metric_tensor_(general_relativity)-0.md
category: reference
title: Metric tensor (general relativity)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Metric_tensor_(general_relativity)
date_saved: 2026-05-05T11:15:08.849054+00:00
instance: kb-cron
parent: metric-tensor-general-relativity-20260505-0
summary:
In general relativity, the metric tensor (in this context often abbreviated to simply the metric) is the fundamental object of study. The metric captures all the geometric and causal structure of spacetime, being used to define notions such as time, distance, volume, curvature, angle, and separation of the future and the past. In general relativity, the metric tensor plays the role of the gravitational potential in the classical theory of gravitation, although the physical content of the associated equations is entirely different. Gutfreund and Renn say "that in general relativity the gravitational potential is represented by the metric tensor." == Notation and conventions == This article works with a metric signature that is mostly positive (− + + +); see sign convention. The gravitation constant G {\displaystyle G} will be kept explicit. This article employs the Einstein summation convention, where repeated indices are automatically summed over. == Definition == Mathematically, spacetime is represented by a four-dimensional differentiable manifold M {\displaystyle M} and the metric tensor is given as a covariant, second-degree, symmetric tensor on M {\displaystyle M} , conventionally denoted by g {\displaystyle g} . Moreover, the metric is required to be nondegenerate with signature (− + + +). A


id: metric-tensor-general-relativity-20260505-1
file: data/en.wikipedia.org/wiki/Metric_tensor_(general_relativity)-1.md
category: reference
title: Metric tensor (general relativity)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Metric_tensor_(general_relativity)
date_saved: 2026-05-05T11:15:08.849054+00:00
instance: kb-cron
parent: metric-tensor-general-relativity-20260505-0
summary:
== Properties == The metric tensor plays a key role in index manipulation. In index notation, the coefficients g μ ν {\displaystyle g_{\mu \nu }} of the metric tensor g {\displaystyle \mathbf {g} } provide a link between covariant and contravariant components of other tensors. Contracting the contravariant index of a tensor with one of a covariant metric tensor coefficient has the effect of lowering the index g μ ν A ν = A μ {\displaystyle g_{\mu \nu }A^{\nu }=A_{\mu }} and similarly a contravariant metric coefficient raises the index g μ ν A ν = A μ . {\displaystyle g^{\mu \nu }A_{\nu }=A^{\mu }.} Applying this property of raising and lowering indices to the metric tensor components themselves leads to the property g μ ν g ν λ = δ μ λ {\displaystyle g_{\mu \nu }g^{\nu \lambda }=\delta _{\mu }^{\lambda }} For a diagonal metric (one for which coefficients g μ ν = 0 , ∀ μ ≠ ν {\displaystyle g_{\mu \nu }=0,\,\forall \mu \neq \nu } ; i.e. the basis vectors are orthogonal to each other), this implies that a given covariant coefficient of the metric tensor is the inverse of the corresponding contravariant coefficient g 00 =


id: metric-tensor-general-relativity-20260505-2
file: data/en.wikipedia.org/wiki/Metric_tensor_(general_relativity)-2.md
category: reference
title: Metric tensor (general relativity)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Metric_tensor_(general_relativity)
date_saved: 2026-05-05T11:15:08.849054+00:00
instance: kb-cron
parent: metric-tensor-general-relativity-20260505-0
summary:
== Curvature == The metric g {\displaystyle g} completely determines the curvature of spacetime. According to the fundamental theorem of Riemannian geometry, there is a unique connection ∇ on any semi-Riemannian manifold that is compatible with the metric and torsion-free. This connection is called the Levi-Civita connection. The Christoffel symbols of this connection are given in terms of partial derivatives of the metric in local coordinates x μ {\displaystyle x^{\mu }} by the formula Γ λ μ ν = 1 2 g λ ρ ( ∂ g ρ μ ∂ x ν + ∂ g ρ ν ∂ x μ − ∂ g μ ν ∂ x ρ ) = 1 2 g λ ρ ( g ρ μ , ν + g ρ ν , μ − g μ ν , ρ ) {\displaystyle \Gamma ^{\lambda }{}_{\mu \nu }={\frac {1}{2}}g^{\lambda \rho }\left({\frac {\partial g_{\rho \mu }}{\partial x^{\nu }}}+{\frac {\partial g_{\rho \nu }}{\partial x^{\mu }}}-{\frac {\partial g_{\mu \nu }}{\partial x^{\rho }}}\right)={\frac {1}{2}}g^{\lambda \rho }\left(g_{\rho \mu ,\nu }+g_{\rho \nu ,\mu }-g_{\mu \nu ,\rho }\right)} (where commas indicate partial derivatives). The curvature of spacetime is then given by the Riemann curvature tensor which is defined in terms of the Levi-Civita connection ∇.


id: proper-time-20260505-0
file: data/en.wikipedia.org/wiki/Proper_time-0.md
category: reference
title: Proper time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Proper_time
date_saved: 2026-05-05T11:15:10.123733+00:00
instance: kb-cron
parent: proper-time-20260505-0
summary:
In relativity, proper time along a timelike world line is defined as the time as measured by a clock following that line. The proper time interval between two events on a world line is the change in proper time, which is independent of coordinates, and is a Lorentz scalar. The interval is the quantity of interest, since proper time itself is fixed only up to an arbitrary additive constant, namely the setting of the clock at some event along the world line. The proper time interval between two events depends not only on the events, but also the world line connecting them, and hence on the motion of the clock between the events. It is expressed as an integral over the world line (analogous to arc length in Euclidean space). An accelerated clock will measure a smaller elapsed time between two events than that measured by a non-accelerated (inertial) clock between the same two events. The twin paradox is an example of this effect. By convention, proper time is usually represented by the Greek letter τ (tau) to distinguish it from coordinate time represented by t. Coordinate time is the time between two events as measured by an observer using


id: proper-time-20260505-1
file: data/en.wikipedia.org/wiki/Proper_time-1.md
category: reference
title: Proper time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Proper_time
date_saved: 2026-05-05T11:15:10.123733+00:00
instance: kb-cron
parent: proper-time-20260505-0
summary:
Δ τ = ∫ ( d t d λ ) 2 − 1 c 2 [ ( d x d λ ) 2 + ( d y d λ ) 2 + ( d z d λ ) 2 ] d λ . {\displaystyle \Delta \tau =\int {\sqrt {\left({\frac {dt}{d\lambda }}\right)^{2}-{\frac {1}{c^{2}}}\left[\left({\frac {dx}{d\lambda }}\right)^{2}+\left({\frac {dy}{d\lambda }}\right)^{2}+\left({\frac {dz}{d\lambda }}\right)^{2}\right]}}\,d\lambda .} If the motion of the particle is constant, the expression simplifies to Δ τ = ( Δ t ) 2 − ( Δ x ) 2 c 2 − ( Δ y ) 2 c 2 − ( Δ z ) 2 c 2 , {\displaystyle \Delta \tau ={\sqrt {\left(\Delta t\right)^{2}-{\frac {\left(\Delta x\right)^{2}}{c^{2}}}-{\frac {\left(\Delta y\right)^{2}}{c^{2}}}-{\frac {\left(\Delta z\right)^{2}}{c^{2}}}}},} where Δ means the change in coordinates between the initial and final events. The definition in special relativity generalizes straightforwardly to general relativity as follows below. === In general relativity === Proper time is defined in general relativity as follows: Given a pseudo-Riemannian manifold with a local coordinates xμ and equipped with a metric tensor gμν, the proper time interval Δτ between two events along a timelike path P is given by the line integral This expression is, as it should be, invariant under


id: proper-time-20260505-2
file: data/en.wikipedia.org/wiki/Proper_time-2.md
category: reference
title: Proper time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Proper_time
date_saved: 2026-05-05T11:15:10.123733+00:00
instance: kb-cron
parent: proper-time-20260505-0
summary:
So for an observer rotating at a constant distance of r from a given point in spacetime at a constant angular rate of ω between coordinate times T 1 {\displaystyle T_{1}} and T 2 {\displaystyle T_{2}} , the proper time experienced will be ∫ T 1 T 2 d τ = ( T 2 − T 1 ) 1 − ( r ω c ) 2 = Δ T 1 − v 2 / c 2 , {\displaystyle \int _{T_{1}}^{T_{2}}d\tau =(T_{2}-T_{1}){\sqrt {1-\left({\frac {r\omega }{c}}\right)^{2}}}=\Delta T{\sqrt {1-v^{2}/c^{2}}},} as v = r ω {\displaystyle v=r\omega } for a rotating observer. This result is the same as for the linear motion example, and shows the general application of the integral form of the proper time formula. == Examples in general relativity == The difference between SR and general relativity (GR) is that in GR one can use any metric which is a solution of the Einstein field equations, not just the Minkowski metric. Because inertial motion in curved spacetimes lacks the simple expression it has in SR, the line integral form of the proper time equation must always be used. === Example 3: The rotating disk (again) === An appropriate coordinate conversion done


id: proper-time-20260505-3
file: data/en.wikipedia.org/wiki/Proper_time-3.md
category: reference
title: Proper time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Proper_time
date_saved: 2026-05-05T11:15:10.123733+00:00
instance: kb-cron
parent: proper-time-20260505-0
summary:
From a non-relativistic point of view this should have been the same as the previous result. This example demonstrates how the proper time equation is used, even though the Earth rotates and hence is not spherically symmetric as assumed by the Schwarzschild solution. To describe the effects of rotation more accurately the Kerr metric may be used. == See also == Lorentz transformation Minkowski space Proper length Proper acceleration Proper mass Proper velocity Clock hypothesis Peres metric == Footnotes == == References == Cook, R. J. (2004). "Physical time and physical space in general relativity". Am. J. Phys. 72 (2): 214–219. Bibcode:2004AmJPh..72..214C. doi:10.1119/1.1607338. ISSN 0002-9505. Foster, J.; Nightingale, J.D. (1978). A short course in general relativity. Essex: Longman Scientific and Technical. ISBN 0-582-44194-3. Kleppner, D.; Kolenkow, R.J. (1978). An introduction to mechanics. McGraw–Hill. ISBN 0-07-035048-5. Kopeikin, Sergei; Efroimsky, Michael; Kaplan, George (2011). Relativistic Celestial Mechanics of the Solar System. John Wiley & Sons. ISBN 978-3-527-40856-6. Landau, L. D.; Lifshitz, E. M. (1975). The classical theory of fields. Course of theoretical physics. Vol. 2 (4th ed.). Oxford: Butterworth–Heinemann. ISBN 0-7506-2768-9. Lawden, Derek F. (2012). An Introduction to Tensor Calculus: Relativity and Cosmology. Courier Corporation. ISBN 978-0-486-13214-3. Lovelock, David; Rund, Hanno (1989),


id: relaxation-physics-20260505-0
file: data/en.wikipedia.org/wiki/Relaxation_(physics)-0.md
category: reference
title: Relaxation (physics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Relaxation_(physics)
date_saved: 2026-05-05T11:15:11.342227+00:00
instance: kb-cron
parent: relaxation-physics-20260505-0
summary:
In the physical sciences, relaxation usually means the return of a perturbed system into equilibrium. Each relaxation process can be categorized by a relaxation time τ. The simplest theoretical description of relaxation as function of time t is an exponential law exp(−t/τ) (exponential decay). == In simple linear systems == === Mechanics: Damped unforced oscillator === Let the homogeneous differential equation: m d 2 y d t 2 + γ d y d t + k y = 0 {\displaystyle m{\frac {d^{2}y}{dt^{2}}}+\gamma {\frac {dy}{dt}}+ky=0} model damped unforced oscillations of a weight on a spring. The displacement will then be of the form y ( t ) = A e − t / T cos ⁡ ( μ t − δ ) {\displaystyle y(t)=Ae^{-t/T}\cos(\mu t-\delta )} . The constant T ( = 2 m / γ {\displaystyle =2m/\gamma } ) is called the relaxation time of the system and the constant μ is the quasi-frequency. === Electronics: RC circuit === In an RC circuit containing a charged capacitor and a resistor, the voltage decays exponentially: V ( t ) = V 0 e − t R C , {\displaystyle V(t)=V_{0}e^{-{\frac {t}{RC}}}\ ,} The constant τ = R C {\displaystyle \tau =RC\


id: relaxation-physics-20260505-1
file: data/en.wikipedia.org/wiki/Relaxation_(physics)-1.md
category: reference
title: Relaxation (physics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Relaxation_(physics)
date_saved: 2026-05-05T11:15:11.342227+00:00
instance: kb-cron
parent: relaxation-physics-20260505-0
summary:
This equation can be solved by substitution to yield [ A ] = k ′ − k e − ( k + k ′ ) t k + k ′ [ A ] 0 {\displaystyle {\ce {[A]}}={k'-ke^{-(k+k')t} \over k+k'}{\ce {[A]}}_{0}} == In atmospheric sciences == === Desaturation of clouds === Consider a supersaturated portion of a cloud. Then shut off the updrafts, entrainment, and any other vapor sources/sinks and things that would induce the growth of the particles (ice or water). Then wait for this supersaturation to reduce and become just saturation (relative humidity = 100%), which is the equilibrium state. The time it takes for the supersaturation to dissipate is called relaxation time. It will happen as ice crystals or liquid water content grow within the cloud and will thus consume the contained moisture. The dynamics of relaxation are very important in cloud physics for accurate mathematical modelling. In water clouds where the concentrations are larger (hundreds per cm3) and the temperatures are warmer (thus allowing for much lower supersaturation rates as compared to ice clouds), the relaxation times will be very low (seconds to minutes). In ice clouds the concentrations are lower (just a few per liter) and


id: spacetime-20260505-0
file: data/en.wikipedia.org/wiki/Spacetime-0.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
In physics, spacetime, also called the space-time continuum, is a mathematical model that fuses the three dimensions of space and the one dimension of time into a single four-dimensional continuum. Spacetime diagrams are useful in visualizing and understanding relativistic effects, such as how different observers perceive where and when events occur. Until the turn of the 20th century, the assumption had been that the three-dimensional geometry of the universe (its description in terms of locations, shapes, distances, and directions) was distinct from time (the measurement of when events occur within the universe). However, space and time took on new meanings with the Lorentz transformation and special theory of relativity. In 1908, Hermann Minkowski presented a geometric interpretation of special relativity that fused time and the three spatial dimensions into a single four-dimensional continuum now known as Minkowski space. This interpretation proved vital to the general theory of relativity, wherein spacetime is curved by mass and energy. == Fundamentals == === Definitions === Non-relativistic classical mechanics treats time as a universal quantity of measurement that is uniform throughout, is separate from space, and is agreed on by all observers. Classical mechanics assumes that time has a constant rate of passage, independent


id: spacetime-20260505-1
file: data/en.wikipedia.org/wiki/Spacetime-1.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
By the mid-1800s, various experiments such as the observation of the Arago spot and differential measurements of the speed of light in air versus water were considered to have proven the wave nature of light as opposed to a corpuscular theory. Propagation of waves was then assumed to require the existence of a waving medium; in the case of light waves, this was considered to be a hypothetical luminiferous aether. The various attempts to establish the properties of this hypothetical medium yielded contradictory results. For example, the Fizeau experiment of 1851, conducted by French physicist Hippolyte Fizeau, demonstrated that the speed of light in flowing water was less than the sum of the speed of light in air plus the speed of the water by an amount dependent on the water's index of refraction. Among other issues, the dependence of the partial aether-dragging implied by this experiment on the index of refraction (which is dependent on wavelength) led to the unpalatable conclusion that aether simultaneously flows at different speeds for different colors of light. The Michelson–Morley experiment of 1887 (Fig. 1-2) showed no differential influence of Earth's motions through the hypothetical aether on the speed of light, and the most


id: spacetime-20260505-2
file: data/en.wikipedia.org/wiki/Spacetime-2.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
On 5 November 1907 (a little more than a year before his death), Minkowski introduced his geometric interpretation of spacetime in a lecture to the Göttingen Mathematical society with the title, The Relativity Principle (Das Relativitätsprinzip). On 21 September 1908, Minkowski presented his talk, Space and Time (Raum und Zeit), to the German Society of Scientists and Physicians. The opening words of Space and Time include Minkowski's statement that "Henceforth, space for itself, and time for itself shall completely reduce to a mere shadow, and only some sort of union of the two shall preserve independence." Space and Time included the first public presentation of spacetime diagrams (Fig. 1-4), and included a remarkable demonstration that the concept of the invariant interval (discussed below), along with the empirical observation that the speed of light is finite, allows derivation of the entirety of special relativity. The spacetime concept and the Lorentz group are closely connected to certain types of sphere, hyperbolic, or conformal geometries and their transformation groups already developed in the 19th century, in which invariant intervals analogous to the spacetime interval are used. Einstein, for his part, was initially dismissive of Minkowski's geometric interpretation of special relativity, regarding it as


id: spacetime-20260505-3
file: data/en.wikipedia.org/wiki/Spacetime-3.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
In a different inertial frame, say with coordinates ( t ′ , x ′ , y ′ , z ′ ) {\displaystyle (t',x',y',z')} , the spacetime interval d s ′ {\displaystyle ds'} can be written in a same form as above. Because of the constancy of speed of light, the light events in all inertial frames belong to zero interval, d s = d s ′ = 0 {\displaystyle ds=ds'=0} . For any other infinitesimal event where d s ≠ 0 {\displaystyle ds\neq 0} , one can prove that d s 2 = d s ′ 2 {\displaystyle ds^{2}=ds'^{2}} which in turn upon integration leads to s = s ′ {\displaystyle s=s'} . The invariance of the spacetime interval between the same events for all inertial frames of reference is one of the fundamental results of special theory of relativity. Although for brevity, one frequently sees interval expressions expressed without deltas, including in most of the following discussion, it should be understood that in general, x {\displaystyle x} means Δ x {\displaystyle \Delta {x}} , etc. We are always concerned with differences of spatial or temporal coordinate values belonging to two events, and since there is no preferred origin, single


id: spacetime-20260505-4
file: data/en.wikipedia.org/wiki/Spacetime-4.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
The x′ axis is also tilted with respect to the x axis. To determine the angle of this tilt, we recall that the slope of the world line of a light pulse is always ±1. Fig. 2-3c presents a spacetime diagram from the viewpoint of observer O′. Event P represents the emission of a light pulse at x′ = 0, ct′ = −a. The pulse is reflected from a mirror situated at distance a from the light source (event Q), and returns to the light source at x′ = 0, ct′ = a (event R). The same events P, Q, R are plotted in Fig. 2-3b in the frame of observer O. The light paths have slopes = 1 and −1, so that △PQR forms a right triangle with PQ and QR both at 45 degrees to the x and ct axes. Since OP = OQ = OR, the angle between x′ and x must also be θ. While the rest frame has space and time axes that meet at right angles, the moving frame is drawn with axes that meet at an acute angle. The frames are actually equivalent. The asymmetry is due to unavoidable distortions in how spacetime


id: spacetime-20260505-5
file: data/en.wikipedia.org/wiki/Spacetime-5.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
All observers will agree that for any given event, an event within the given event's future light cone occurs after the given event. Likewise, for any given event, an event within the given event's past light cone occurs before the given event. The before–after relationship observed for timelike-separated events remains unchanged no matter what the reference frame of the observer, i.e. no matter how the observer may be moving. The situation is quite different for spacelike-separated events. Fig. 2-4 was drawn from the reference frame of an observer moving at v = 0. From this reference frame, event C is observed to occur after event O, and event B is observed to occur before event O. From a different reference frame, the orderings of these non-causally-related events can be reversed. In particular, one notes that if two events are simultaneous in a particular reference frame, they are necessarily separated by a spacelike interval and thus are noncausally related. The observation that simultaneity is not absolute, but depends on the observer's reference frame, is termed the relativity of simultaneity. Fig. 2-6 illustrates the use of spacetime diagrams in the analysis of the relativity of simultaneity. The events in spacetime are invariant,


id: spacetime-20260505-6
file: data/en.wikipedia.org/wiki/Spacetime-6.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
Length contraction, like time dilation, is a manifestation of the relativity of simultaneity. Measurement of length requires measurement of the spacetime interval between two events that are simultaneous in one's frame of reference. But events that are simultaneous in one frame of reference are, in general, not simultaneous in other frames of reference. Fig. 2-9 illustrates the motions of a 1 m rod that is traveling at 0.5 c along the x axis. The edges of the blue band represent the world lines of the rod's two endpoints. The invariant hyperbola illustrates events separated from the origin by a spacelike interval of 1 m. The endpoints O and B measured when t′ = 0 are simultaneous events in the S′ frame. But to an observer in frame S, events O and B are not simultaneous. To measure length, the observer in frame S measures the endpoints of the rod as projected onto the x-axis along their world lines. The projection of the rod's world sheet onto the x axis yields the foreshortened length OC. (not illustrated) Drawing a vertical line through A so that it intersects the x′ axis demonstrates that, even as OB is foreshortened from the point of


id: spacetime-20260505-7
file: data/en.wikipedia.org/wiki/Spacetime-7.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
Fig. 2-10 illustrates the previous discussion of mutual time dilation with Minkowski diagrams. The upper picture reflects the measurements as seen from frame S "at rest" with unprimed, rectangular axes, and frame S′ "moving with v > 0", coordinatized by primed, oblique axes, slanted to the right; the lower picture shows frame S′ "at rest" with primed, rectangular coordinates, and frame S "moving with −v < 0", with unprimed, oblique axes, slanted to the left. Each line drawn parallel to a spatial axis (x, x′) represents a line of simultaneity. All events on such a line have the same time value (ct, ct′). Likewise, each line drawn parallel to a temporal axis (ct, ct′) represents a line of equal spatial coordinate values (x, x′). One may designate in both pictures the origin O (= O′) as the event, where the respective "moving clock" is collocated with the "first clock at rest" in both comparisons. Obviously, for this event the readings on both clocks in both comparisons are zero. As a consequence, the worldlines of the moving clocks are the slanted to the right ct′-axis (upper pictures, clock W′) and the slanted to the left ct-axes (lower pictures, clock W). The


id: spacetime-20260505-8
file: data/en.wikipedia.org/wiki/Spacetime-8.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
These distinctions should result in a difference in the twins' ages. The spacetime diagram of Fig. 2-11 presents the simple case of a twin going straight out along the x axis and immediately turning back. From the standpoint of the stay-at-home twin, there is nothing puzzling about the twin paradox at all. The proper time measured along the traveling twin's world line from O to C, plus the proper time measured from C to B, is less than the stay-at-home twin's proper time measured from O to A to B. More complex trajectories require integrating the proper time between the respective events along the curve (i.e. the path integral) to calculate the total amount of proper time experienced by the traveling twin. Complications arise if the twin paradox is analyzed from the traveling twin's point of view. Weiss's nomenclature, designating the stay-at-home twin as Terence and the traveling twin as Stella, is hereafter used. Stella is not in an inertial frame. Given this fact, it is sometimes incorrectly stated that full resolution of the twin paradox requires general relativity: A pure SR analysis would be as follows: Analyzed in Stella's rest frame, she is motionless for the entire trip. When


id: spacetime-20260505-9
file: data/en.wikipedia.org/wiki/Spacetime-9.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
Fig. 3-1 illustrates that in Newton's theory, time is universal, not the velocity of light. Consider the following thought experiment: The red arrow illustrates a train that is moving at 0.4 c with respect to the platform. Within the train, a passenger shoots a bullet with a speed of 0.4 c in the frame of the train. The blue arrow illustrates that a person standing on the train tracks measures the bullet as traveling at 0.8 c. This is in accordance with our naive expectations. More generally, assuming that frame S′ is moving at velocity v with respect to frame S, then within frame S′, observer O′ measures an object moving with velocity u′. Velocity u with respect to frame S, since x = ut, x′ = x − vt, and t = t′, can be written as x′ = ut − vt = (u − v)t = (u − v)t′. This leads to u′ = x′/t′ and ultimately u ′ = u − v {\displaystyle u'=u-v} or u = u ′ + v , {\displaystyle u=u'+v,} which is the common-sense Galilean law for the addition of velocities. === Relativistic composition of velocities === The composition of velocities is quite


id: spacetime-20260505-10
file: data/en.wikipedia.org/wiki/Spacetime-10.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
The Galilean transformations and their consequent commonsense law of addition of velocities work well in our ordinary low-speed world of planes, cars and balls. Beginning in the mid-1800s, however, sensitive scientific instrumentation began finding anomalies that did not fit well with the ordinary addition of velocities. Lorentz transformations are used to transform the coordinates of an event from one frame to another in special relativity. The Lorentz factor appears in the Lorentz transformations: t ′ = γ ( t − v x c 2 ) x ′ = γ ( x − v t ) y ′ = y z ′ = z {\displaystyle {\begin{aligned}t'&=\gamma \left(t-{\frac {vx}{c^{2}}}\right)\\x'&=\gamma \left(x-vt\right)\\y'&=y\\z'&=z\end{aligned}}} The inverse Lorentz transformations are: t = γ ( t ′ + v x ′ c 2 ) x = γ ( x ′ + v t ′ ) y = y ′ z = z ′ {\displaystyle {\begin{aligned}t&=\gamma \left(t'+{\frac {vx'}{c^{2}}}\right)\\x&=\gamma \left(x'+vt'\right)\\y&=y'\\z&=z'\end{aligned}}} When v ≪ c and x is small enough, the v2/c2 and vx/c2 terms approach zero, and the Lorentz transformations approximate to the Galilean transformations. t ′ = γ ( t − v x / c 2 ) , {\displaystyle t'=\gamma (t-vx/c^{2}),} x ′ = γ ( x − v


id: spacetime-20260505-11
file: data/en.wikipedia.org/wiki/Spacetime-11.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
==== Linearity of the Lorentz transformations ==== The Lorentz transformations have a mathematical property called linearity, since x′ and t′ are obtained as linear combinations of x and t, with no higher powers involved. The linearity of the transformation reflects a fundamental property of spacetime that was tacitly assumed in the derivation, namely, that the properties of inertial frames of reference are independent of location and time. In the absence of gravity, spacetime looks the same everywhere. All inertial observers will agree on what constitutes accelerating and non-accelerating motion. Any one observer can use her own measurements of space and time, but there is nothing absolute about them. Another observer's conventions will do just as well. A result of linearity is that if two Lorentz transformations are applied sequentially, the result is also a Lorentz transformation. Example: Terence observes Stella speeding away from him at 0.500 c, and he can use the Lorentz transformations with β = 0.500 to relate Stella's measurements to his own. Stella, in her frame, observes Ursula traveling away from her at 0.250 c, and she can use the Lorentz transformations with β = 0.250 to relate Ursula's measurements with her own. Because of the linearity


id: spacetime-20260505-12
file: data/en.wikipedia.org/wiki/Spacetime-12.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
=== Energy and momentum === ==== Extending momentum to four dimensions ==== In classical mechanics, the state of motion of a particle is characterized by its mass and its velocity. Linear momentum, the product of a particle's mass and velocity, is a vector quantity, possessing the same direction as the velocity: p = mv. It is a conserved quantity, meaning that if a closed system is not affected by external forces, its total linear momentum cannot change. In relativistic mechanics, the momentum vector is extended to four dimensions. Added to the momentum vector is a time component that allows the spacetime momentum vector to transform like the spacetime position vector ⁠ ( x , t ) {\displaystyle (x,t)} ⁠. In exploring the properties of the spacetime momentum, we start, in Fig. 3-8a, by examining what a particle looks like at rest. In the rest frame, the spatial component of the momentum is zero, i.e. p = 0, but the time component equals mc. We can obtain the transformed components of this vector in the moving frame by using the Lorentz transformations, or we can read it directly from the figure because we know that ⁠ ( m c ) ′


id: spacetime-20260505-13
file: data/en.wikipedia.org/wiki/Spacetime-13.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
==== Four-momentum ==== Because of the close relationship between mass and energy, the four-momentum (also called 4-momentum) is also called the energy–momentum 4-vector. Using an uppercase P to represent the four-momentum and a lowercase p to denote the spatial momentum, the four-momentum may be written as P ≡ ( E / c , p → ) = ( E / c , p x , p y , p z ) {\displaystyle P\equiv (E/c,{\vec {p}})=(E/c,p_{x},p_{y},p_{z})} or alternatively, P ≡ ( E , p → ) = ( E , p x , p y , p z ) {\displaystyle P\equiv (E,{\vec {p}})=(E,p_{x},p_{y},p_{z})} using the convention that c = 1. {\displaystyle c=1.} === Conservation laws === In physics, conservation laws state that certain particular measurable properties of an isolated physical system do not change as the system evolves over time. In 1915, Emmy Noether discovered that underlying each conservation law is a fundamental symmetry of nature. The fact that physical processes do not care where in space they take place (space translation symmetry) yields conservation of momentum, the fact that such processes do not care when they take place (time translation symmetry) yields conservation of energy, and so on. In this


id: spacetime-20260505-14
file: data/en.wikipedia.org/wiki/Spacetime-14.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
==== Energy and momentum conservation ==== In a Newtonian analysis of interacting particles, transformation between frames is simple because all that is necessary is to apply the Galilean transformation to all velocities. Since ⁠ v ′ = v − u {\displaystyle v'=v-u} ⁠, the momentum ⁠ p ′ = p − m u {\displaystyle p'=p-mu} ⁠. If the total momentum of an interacting system of particles is observed to be conserved in one frame, it will likewise be observed to be conserved in any other frame. Conservation of momentum in the COM frame amounts to the requirement that p = 0 both before and after collision. In the Newtonian analysis, conservation of mass dictates that ⁠ m = m 1 + m 2 {\displaystyle m=m_{1}+m_{2}} ⁠. In the simplified, one-dimensional scenarios that we have been considering, only one additional constraint is necessary before the outgoing momenta of the particles can be determined—an energy condition. In the one-dimensional case of a completely elastic collision with no loss of kinetic energy, the outgoing velocities of the rebounding particles in the COM frame will be precisely equal and opposite to their incoming velocities. In the case of a completely inelastic collision with total


id: spacetime-20260505-15
file: data/en.wikipedia.org/wiki/Spacetime-15.md
category: reference
title: Spacetime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spacetime
date_saved: 2026-05-05T11:15:12.625899+00:00
instance: kb-cron
parent: spacetime-20260505-0
summary:
The spacetime symmetry group for Special Relativity is the Poincaré group, which is a ten-dimensional group of three Lorentz boosts, three rotations, and four spacetime translations. It is logical to ask what symmetries if any might apply in General Relativity. A tractable case might be to consider the symmetries of spacetime as seen by observers located far away from all sources of the gravitational field. The naive expectation for asymptotically flat spacetime symmetries might be simply to extend and reproduce the symmetries of flat spacetime of special relativity, viz., the Poincaré group. In 1962 Hermann Bondi, M. G. van der Burg, A. W. Metzner and Rainer K. Sachs addressed this asymptotic symmetry problem in order to investigate the flow of energy at infinity due to propagating gravitational waves. Their first step was to decide on some physically sensible boundary conditions to place on the gravitational field at lightlike infinity to characterize what it means to say a metric is asymptotically flat, making no a priori assumptions about the nature of the asymptotic symmetry group—not even the assumption that such a group exists. Then after designing what they considered to be the most sensible boundary conditions, they investigated the nature of


id: t-symmetry-20260505-0
file: data/en.wikipedia.org/wiki/T-symmetry-0.md
category: reference
title: T-symmetry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/T-symmetry
date_saved: 2026-05-05T11:15:13.998744+00:00
instance: kb-cron
parent: t-symmetry-20260505-0
summary:
T-symmetry or time reversal symmetry is the theoretical symmetry of physical laws under the transformation of time reversal, T : t ↦ − t . {\displaystyle T:t\mapsto -t.} Since the second law of thermodynamics states that entropy increases as time flows toward the future, in general, the macroscopic universe does not show symmetry under time reversal. In other words, time is said to be non-symmetric, or asymmetric, except for special equilibrium states when the second law of thermodynamics predicts the time symmetry to hold. However, quantum noninvasive measurements are predicted to violate time symmetry even in equilibrium, contrary to their classical counterparts, although this has not yet been experimentally confirmed. Time asymmetries (see Arrow of time) generally are caused by one of three categories: intrinsic to the dynamic physical law (e.g., for the weak force) due to the initial conditions of the universe (e.g., for the second law of thermodynamics) due to measurements (e.g., for the noninvasive measurements) == Macroscopic phenomena == === The second law of thermodynamics === Daily experience shows that T-symmetry does not hold for the behavior of bulk materials. Of these macroscopic laws, most notable is the second law of thermodynamics. Many other phenomena, such as


id: t-symmetry-20260505-1
file: data/en.wikipedia.org/wiki/T-symmetry-1.md
category: reference
title: T-symmetry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/T-symmetry
date_saved: 2026-05-05T11:15:13.998744+00:00
instance: kb-cron
parent: t-symmetry-20260505-0
summary:
==== Example: Magnetic Field and Onsager reciprocal relations ==== Let us consider the example of a system of charged particles subject to a constant external magnetic field: in this case the canonical time reversal operation that reverses the velocities and the time t {\displaystyle t} and keeps the coordinates untouched is no more a symmetry for the system. Under this consideration, it seems that only Onsager–Casimir reciprocal relations could hold; these equalities relate two different systems, one subject to B → {\displaystyle {\vec {B}}} and another to − B → {\displaystyle -{\vec {B}}} , and so their utility is limited. However, it was proved that it is possible to find other time reversal operations which preserve the dynamics and so Onsager reciprocal relations; in conclusion, one cannot state that the presence of a magnetic field always breaks T-symmetry. == Microscopic phenomena: time reversal invariance == Most systems are asymmetric under time reversal, but there may be phenomena with symmetry. In classical mechanics, a velocity v reverses under the operation of T, but an acceleration does not. Therefore, one models dissipative phenomena through terms that are odd in v. However, delicate experiments in which known sources of dissipation are removed reveal


id: t-symmetry-20260505-2
file: data/en.wikipedia.org/wiki/T-symmetry-2.md
category: reference
title: T-symmetry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/T-symmetry
date_saved: 2026-05-05T11:15:13.998744+00:00
instance: kb-cron
parent: t-symmetry-20260505-0
summary:
where T {\displaystyle T} is just an ordinary matrix. For complex fields, complex conjugation may be required, for which the mapping K : ( x + i y ) ↦ ( x − i y ) {\displaystyle K:(x+iy)\mapsto (x-iy)} can be thought of as a 2×2 matrix. For a Dirac spinor, T {\displaystyle T} cannot be written as a 4×4 matrix, because, in fact, complex conjugation is indeed required; however, it can be written as an 8×8 matrix, acting on the 8 real components of a Dirac spinor. In the general setting, there is no ab initio value to be given for T {\displaystyle T} ; its actual form depends on the specific equation or equations which are being examined. In general, one simply states that the equations must be time-reversal invariant, and then solves for the explicit value of T {\displaystyle T} that achieves this goal. In some cases, generic arguments can be made. Thus, for example, for spinors in three-dimensional Euclidean space, or four-dimensional Minkowski space, an explicit transformation can be given. It is conventionally given as T = e i π J y K {\displaystyle T=e^{i\pi J_{y}}K} where J y {\displaystyle J_{y}} is the y-component of the


id: t-symmetry-20260505-3
file: data/en.wikipedia.org/wiki/T-symmetry-3.md
category: reference
title: T-symmetry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/T-symmetry
date_saved: 2026-05-05T11:15:13.998744+00:00
instance: kb-cron
parent: t-symmetry-20260505-0
summary:
This means that the entries in Φ are ±1, as a result of which one may have either T2 = ±1. This is specific to the anti-unitarity of T. For a unitary operator, such as the parity, any phase is allowed. Next, take a Hamiltonian invariant under T. Let |a⟩ and T|a⟩ be two quantum states of the same energy. Now, if T2 = −1, then one finds that the states are orthogonal: a result called Kramers' theorem. This implies that if T2 = −1, then there is a twofold degeneracy in the state. This result in non-relativistic quantum mechanics presages the spin statistics theorem of quantum field theory. Quantum states that give unitary representations of time reversal, i.e., have T2 = 1, are characterized by a multiplicative quantum number, sometimes called the T-parity. === Time reversal of the known dynamical laws === Particle physics codified the basic laws of dynamics into the Standard Model. This is formulated as a quantum field theory that has CPT symmetry, i.e., the laws are invariant under simultaneous operation of time reversal, parity and charge conjugation. However, time reversal itself is seen not to be a symmetry (this is usually called CP violation). There


id: time-translation-symmetry-20260505-0
file: data/en.wikipedia.org/wiki/Time-translation_symmetry-0.md
category: reference
title: Time-translation symmetry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time-translation_symmetry
date_saved: 2026-05-05T11:15:15.166138+00:00
instance: kb-cron
parent: time-translation-symmetry-20260505-0
summary:
Time-translation symmetry or temporal translation symmetry (TTS) is a mathematical transformation in physics that moves the times of events through a common interval. Time-translation symmetry is the law that the laws of physics are unchanged (i.e. invariant) under such a transformation. Time-translation symmetry is a rigorous way to formulate the idea that the laws of physics are the same throughout history. Time-translation symmetry is closely connected, via Noether's theorem, to conservation of energy. In mathematics, the set of all time translations on a given system form a Lie group. There are many symmetries in nature besides time translation, such as spatial translation or rotational symmetries. These symmetries can be broken and explain diverse phenomena such as crystals, superconductivity, and the Higgs mechanism. However, it was thought until very recently that time-translation symmetry could not be broken. Time crystals, a state of matter first observed in 2017, break time-translation symmetry. == Overview == Symmetries are of prime importance in physics and are closely related to the hypothesis that certain physical quantities are only relative and unobservable. Symmetries apply to the equations that govern the physical laws (e.g. to a Hamiltonian or Lagrangian) rather than the initial conditions, values or magnitudes of


id: time-variation-of-fundamental-constants-20260505-0
file: data/en.wikipedia.org/wiki/Time-variation_of_fundamental_constants-0.md
category: reference
title: Time-variation of fundamental constants
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time-variation_of_fundamental_constants
date_saved: 2026-05-05T11:15:16.373369+00:00
instance: kb-cron
parent: time-variation-of-fundamental-constants-20260505-0
summary:
The term physical constant expresses the notion of a physical quantity subject to experimental measurement which is independent of the time or location of the experiment. The constancy (immutability) of any "physical constant" is thus subject to experimental verification. Paul Dirac in 1937 speculated that physical constants such as the gravitational constant or the fine-structure constant might be subject to change over time in proportion of the age of the universe. Experiments conducted since then have put upper bounds on their time-dependence. This concerns the fine-structure constant, the gravitational constant and the proton-to-electron mass ratio specifically, for all of which there are ongoing efforts to improve tests on their time-dependence. The immutability of these fundamental constants is an important cornerstone of the laws of physics as currently known; the postulate of the time-independence of physical laws is tied to that of the conservation of energy (Noether's theorem), so that the discovery of any variation would imply the discovery of a previously unknown law of force. In a more philosophical context, the conclusion that these quantities are constant raises the question of why they have the specific value they do in what appears to be a "fine-tuned universe", while their being


id: time-variation-of-fundamental-constants-20260505-1
file: data/en.wikipedia.org/wiki/Time-variation_of_fundamental_constants-1.md
category: reference
title: Time-variation of fundamental constants
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time-variation_of_fundamental_constants
date_saved: 2026-05-05T11:15:16.373369+00:00
instance: kb-cron
parent: time-variation-of-fundamental-constants-20260505-0
summary:
The cosmological constant is a measure of the energy density of the vacuum. It was first measured, and found to have a positive value, in the 1990s. It is currently (as of 2015) estimated at 10−122 in Planck units. Possible variations of the cosmological constant over time or space are not amenable to observation, but it has been noted that, in Planck units, its measured value is suggestively close to the reciprocal of the age of the universe squared, Λ ≈ T−2. Barrow and Shaw proposed a modified theory in which Λ is a field evolving in such a way that its value remains Λ ~ T−2 throughout the history of the universe. == See also == Dirac large numbers hypothesis == References == Marciano, William J. (1984). "Time Variation of the Fundamental "Constants" and Kaluza-Klein Theories". Phys. Rev. Lett. 52 (7): 489–491. Bibcode:1984PhRvL..52..489M. doi:10.1103/physrevlett.52.489. Varshalovich, D. A.; Levshakov, S. A. (1993). "On a time dependence of physical constants". Pis'ma Zh. Eksp. Teor. Fiz. 58 (4): 231–235. Bibcode:1993JETPL..58..237V. Dzuba, V. A.; Flambaum, V. V.; Webb, J. K. (1999). "Space-Time Variation of Physical Constants and Relativistic Corrections in Atoms". Phys. Rev. Lett. 82 (5): 888. arXiv:physics/9802029. Bibcode:1999PhRvL..82..888D. doi:10.1103/physrevlett.82.888. S2CID 18462448. Dzuba,


id: twin-paradox-20260505-0
file: data/en.wikipedia.org/wiki/Twin_paradox-0.md
category: reference
title: Twin paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Twin_paradox
date_saved: 2026-05-05T11:15:17.567728+00:00
instance: kb-cron
parent: twin-paradox-20260505-0
summary:
In physics, the twin paradox is a thought experiment in special relativity involving twins, one of whom takes a space voyage at relativistic speeds and returns home to find that the twin who remained on Earth has aged more. This result appears puzzling because each twin sees the other twin as moving, and so, as a consequence of an incorrect and naive application of time dilation and the principle of relativity, each should paradoxically find the other to have aged less. However, this scenario can be resolved within the standard framework of special relativity: the travelling twin's trajectory involves two different inertial frames, one for the outbound journey and one for the inbound journey. Another way to understand the paradox is to realise the travelling twin is undergoing acceleration, thus becoming a non-inertial observer. In both views there is no symmetry between the spacetime paths of the twins. Therefore, the twin paradox is not actually a paradox in the sense of a logical contradiction. Starting with Paul Langevin in 1911, there have been various explanations of this paradox. These explanations "can be grouped into those that focus on the effect of different standards of simultaneity in different frames, and those


id: twin-paradox-20260505-1
file: data/en.wikipedia.org/wiki/Twin_paradox-1.md
category: reference
title: Twin paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Twin_paradox
date_saved: 2026-05-05T11:15:17.567728+00:00
instance: kb-cron
parent: twin-paradox-20260505-0
summary:
Of all apparently paradox consequences that stem from the time-transformation of the theory of relativity, there is probably none against which the common sense of anyone who is still unfamiliar with the matter is more reluctant, than the one according to which the time indication of a clock shall be dependent on its state of motion. Already in his fundamental paper, Einstein has driven this paradox to the extreme by a thought experiment, recently explained in a very nice way by Langevin in a lecture that is also very readable in other respects. Laue (1911, 1913) went on to elaborate on Langevin's explanation: Using Hermann Minkowski's spacetime formalism, he demonstrated that the world lines of the inertially moving bodies maximise the proper time elapsed between two events, which was also pointed out in the textbooks of Hermann Weyl (1918) or Wolfgang Pauli (1921). Regarding the § Role of acceleration, Laue wrote in 1913 that the asymmetric ageing is completely accounted for by the fact that the astronaut twin travels in two separate frames, while the Earth twin remains in one frame, and the time of acceleration can be made arbitrarily small compared with the time of inertial motion. Even before


id: twin-paradox-20260505-2
file: data/en.wikipedia.org/wiki/Twin_paradox-2.md
category: reference
title: Twin paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Twin_paradox
date_saved: 2026-05-05T11:15:17.567728+00:00
instance: kb-cron
parent: twin-paradox-20260505-0
summary:
No matter what method they use to predict the clock readings, everybody will agree about them. If twins are born on the day the ship leaves, and one goes on the journey while the other stays on Earth, they will meet again when the traveller is 6 years old and the stay-at-home twin is 10 years old. == Resolution of the paradox in special relativity == The paradoxical aspect of the twins' situation arises from the fact that at any given moment the travelling twin's clock is running slow in the earthbound twin's inertial frame, but based on the relativity principle one could equally argue that the earthbound twin's clock is running slow in the travelling twin's inertial frame. One proposed resolution is based on the fact that the earthbound twin is at rest in the same inertial frame throughout the journey, while the travelling twin is not: in the simplest version of the thought-experiment, the travelling twin switches at the midpoint of the trip from being at rest in an inertial frame which moves in one direction (away from the Earth) to being at rest in an inertial frame which moves in the opposite direction (towards the Earth). In


id: twin-paradox-20260505-3
file: data/en.wikipedia.org/wiki/Twin_paradox-3.md
category: reference
title: Twin paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Twin_paradox
date_saved: 2026-05-05T11:15:17.567728+00:00
instance: kb-cron
parent: twin-paradox-20260505-0
summary:
== A non-spacetime approach == As mentioned above, an "out and back" twin paradox adventure may incorporate the transfer of clock reading from an "outgoing" astronaut to an "incoming" astronaut, thus eliminating the effect of acceleration. Also, the physical acceleration of clocks does not contribute to the kinematical effects of special relativity. Rather, in special relativity, the time differential between two reunited clocks is produced purely by uniform inertial motion, as discussed in Einstein's original 1905 relativity paper, as well as in all subsequent kinematical derivations of the Lorentz transformations. Because spacetime diagrams incorporate Einstein's clock synchronisation (with its lattice of clocks methodology), there will be a requisite jump in the reading of the Earth clock time made by a "suddenly returning astronaut" who inherits a "new meaning of simultaneity" in keeping with a new clock synchronisation dictated by the transfer to a different inertial frame. If, instead of incorporating Einstein's clock synchronisation (lattice of clocks), the astronaut (outgoing and incoming) and the Earth-based party regularly update each other on the status of their clocks by way of sending radio signals (which travel at light speed), then all parties will note an incremental buildup of asymmetry in time-keeping, beginning at


id: twin-paradox-20260505-4
file: data/en.wikipedia.org/wiki/Twin_paradox-4.md
category: reference
title: Twin paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Twin_paradox
date_saved: 2026-05-05T11:15:17.567728+00:00
instance: kb-cron
parent: twin-paradox-20260505-0
summary:
This is fobs = 3frest for v/c = 0.8. As for the screen on Earth, it shows that trip back beginning 9 years after launch, and the travelling clock in the screen shows that 3 years have passed on the ship. One year later, the ship is back home and the clock shows 6 years. So, during the trip back, both twins see their sibling's clock going 3 times faster than their own. Factoring out the fact that the light-time-delay is decreasing by 0.8 seconds every second, each twin calculates that the other twin is ageing at 60% their own ageing speed. The x–t (space–time) diagrams at right show the paths of light signals travelling between Earth and ship (1st diagram) and between ship and Earth (2nd diagram). These signals carry the images of each twin and their age-clock to the other twin. The vertical black line is the Earth's path through spacetime and the other two sides of the triangle show the ship's path through spacetime (as in the Minkowski diagram above). As far as the sender is concerned, they transmit these at equal intervals (say, once an hour) according to their own clock; but according to the clock


id: twin-paradox-20260505-5
file: data/en.wikipedia.org/wiki/Twin_paradox-5.md
category: reference
title: Twin paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Twin_paradox
date_saved: 2026-05-05T11:15:17.567728+00:00
instance: kb-cron
parent: twin-paradox-20260505-0
summary:
when the image was emitted. A similar calculation reveals that his twin was ageing at the same reduced rate of εfrest in all low frequency images. === Simultaneity in the Doppler shift calculation === It may be difficult to see where simultaneity came into the Doppler shift calculation, and indeed the calculation is often preferred because one does not have to worry about simultaneity. As seen above, the ship twin can convert the received Doppler-shifted rate to a slower rate of the clock of the distant clock for both red and blue images. When ignoring simultaneity, the ship twin might say the Earth twin was ageing at the reduced rate throughout the journey and therefore should be younger than they are. The ship twin is now back to square one, and has to take into account the change in their notion of simultaneity at the turnaround. The rate they can calculate for the image (corrected for Doppler effect) is the rate of the Earth twin's clock at the moment it was sent, not at the moment it was received. Since they receive an unequal number of red and blue shifted images, they should realise that the red and blue shifted


id: twin-paradox-20260505-6
file: data/en.wikipedia.org/wiki/Twin_paradox-6.md
category: reference
title: Twin paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Twin_paradox
date_saved: 2026-05-05T11:15:17.567728+00:00
instance: kb-cron
parent: twin-paradox-20260505-0
summary:
Phase 1: Rocket (with clock K') embarks with constant proper acceleration a during a time Ta as measured by clock K until it reaches some velocity V. Phase 2: Rocket keeps coasting at velocity V during some time Tc according to clock K. Phase 3: Rocket fires its engines in the opposite direction of K during a time Ta according to clock K until it is at rest with respect to clock K. The constant proper acceleration has the value −a, in other words the rocket is decelerating. Phase 4: Rocket keeps firing its engines in the opposite direction of K, during the same time Ta according to clock K, until K' regains the same speed V with respect to K, but now towards K (with velocity −V). Phase 5: Rocket keeps coasting towards K at speed V during the same time Tc according to clock K. Phase 6: Rocket again fires its engines in the direction of K, so it decelerates with a constant proper acceleration a during a time Ta, still according to clock K, until both clocks reunite. Knowing that the clock K remains inertial (stationary), the total accumulated proper time Δτ of clock K' will be


id: twin-paradox-20260505-7
file: data/en.wikipedia.org/wiki/Twin_paradox-7.md
category: reference
title: Twin paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Twin_paradox
date_saved: 2026-05-05T11:15:17.567728+00:00
instance: kb-cron
parent: twin-paradox-20260505-0
summary:
Using the Dirac delta function to model the infinite acceleration phase in the standard case of the traveller having constant speed v during the outbound and the inbound trip, the formula produces the known result: Δ t = 1 1 − v 2 c 2 Δ τ . {\displaystyle \Delta t={\frac {1}{\sqrt {1-{\tfrac {v^{2}}{c^{2}}}}}}\Delta \tau .\ } In the case where the accelerated observer K' departs from K with zero initial velocity, the general equation reduces to the simpler form: Δ t = ∫ 0 Δ τ e ± ∫ 0 τ ¯ a ( τ ′ ) d τ ′ d τ ¯ , {\displaystyle \Delta t=\int _{0}^{\Delta \tau }e^{\pm \int _{0}^{\bar {\tau }}a(\tau ')d\tau '}\,d{\bar {\tau }},\ } which, in the smooth version of the twin paradox where the traveller has constant proper acceleration phases, successively given by a, −a, −a, a, results in Δ t = 4 a sinh ⁡ ( a 4 Δ τ ) {\displaystyle \Delta t={\tfrac {4}{a}}\sinh({\tfrac {a}{4}}\Delta \tau )\ } where the convention c = 1 is used, in accordance with the above expression with acceleration phases Ta = Δt/4 and inertial (coasting) phases Tc = 0. == A rotational version == Twins


id: list-of-science-and-technology-awards-for-women-20260505-0
file: data/en.wikipedia.org/wiki/List_of_science_and_technology_awards_for_women-0.md
category: reference
title: List of science and technology awards for women
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_science_and_technology_awards_for_women
date_saved: 2026-05-05T11:15:19.164035+00:00
instance: kb-cron
parent: list-of-science-and-technology-awards-for-women-20260505-0
summary:
This list of science and technology awards for women is an index to articles about notable awards made to women for work in science and the STEM (Science, technology, engineering, and mathematics) fields generally. It includes awards for astronomy, space and atmospheric science; biology and medicine; chemistry; engineering; mathematics; neuroscience; physics; technology; and general or multiple fields. == Astronomy, space, atmospheric science == Annie Jump Cannon Award in Astronomy – annual award for outstanding contributions to astronomy by a woman within five years of earning a doctorate degree Peter B. Wagner Memorial Award for Women in Atmospheric Sciences – awarded annually since 1998, based on paper completion, to a woman studying for a Masters or PhD in atmospheric science at a university in the United States == Biology and medicine == Elizabeth Blackwell Medal, given by the American Medical Women's Association to a woman physician "who has made the most outstanding contributions to the cause of women in the field of medicine" Federation of American Societies for Experimental Biology (FASEB) Excellence in Science Award Group on Women in Medicine and Science Leadership Awards, Association of American Medical Colleges Margaret Oakley Dayhoff Award from the Biophysical Society, Rockville, Maryland – given


id: ada-byron-award-20260505-0
file: data/en.wikipedia.org/wiki/Ada_Byron_Award-0.md
category: reference
title: Ada Byron Award
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ada_Byron_Award
date_saved: 2026-05-05T11:15:20.303497+00:00
instance: kb-cron
parent: ada-byron-award-20260505-0
summary:
The Ada Byron Award for Women in Technology (Premio Ada Byron a la Mujer Tecnóloga) is an honor given annually by the University of Deusto to recognize the careers of women in technology. It seeks out women scientists and technologists who have contributed to various scientific disciplines, such as Ada Byron, for whom the award is named. == History == The Ada Byron Award for Women in Technology was established at the University of Deusto in October 2013. Its first edition was presented on 11 April 2014, during the "Women and Technology" session at Forotech 2014, which was held as part of Deusto Engineering and Technology Week. The winner received a cash prize of €3,000. In 2019 it expanded to Mexico, and in 2020 it reached Argentina through the Catholic University of Córdoba and the National Technological University. In 2021 it arrived in Uruguay with the support of the Catholic University of Uruguay, and in Colombia with the Pontificia Universidad Javeriana. Continuing with the internationalization of the award, in 2022, it was expanded to Chile, with the support of the Andrés Bello National University. In 2023, the Ada Byron Award celebrated its tenth edition. To commemorate this milestone, a video


id: african-union-kwame-nkrumah-award-for-scientific-excellence-20260505-0
file: data/en.wikipedia.org/wiki/African_Union_Kwame_Nkrumah_Award_for_Scientific_Excellence-0.md
category: reference
title: African Union Kwame Nkrumah Award for Scientific Excellence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/African_Union_Kwame_Nkrumah_Award_for_Scientific_Excellence
date_saved: 2026-05-05T11:15:21.500559+00:00
instance: kb-cron
parent: african-union-kwame-nkrumah-award-for-scientific-excellence-20260505-0
summary:
The African Union Kwame Nkrumah Award for Scientific Excellence was established by the African Union (AU) to recognize and honor outstanding scientific achievements in Africa. These awards were named after Kwame Nkrumah, the first President of Ghana and a prominent Pan-Africanist, who strongly believed in the importance of science and technology for the development of Africa. It is the highest recognition for science in Africa. The awards aim to recognize and celebrate scientific achievements, promote science and innovation in Africa and inspire the next generation of African scientists. They were established in September 2008. The Kwame Nkrumah Awards are awarded in two categories: Life and Earth Sciences and Basic Science, Technology and Innovation. Nominees are typically selected based on their achievements in advancing scientific knowledge, addressing African challenges, and their contributions to the scientific community at large. The awardees are often recognized during AU summits, where they are presented with both a monetary award and a certificate of recognition. The awards aim to showcase the talent and intellectual contributions of African scientists and play a role in the continent's development by encouraging continued advancements in science and technology. There are 3 types of awards: At the continental level for general


id: anne-bennett-prize-20260505-0
file: data/en.wikipedia.org/wiki/Anne_Bennett_Prize-0.md
category: reference
title: Anne Bennett Prize
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Anne_Bennett_Prize
date_saved: 2026-05-05T11:15:22.666190+00:00
instance: kb-cron
parent: anne-bennett-prize-20260505-0
summary:
The Anne Bennett Prize and Senior Anne Bennett Prize are awards given by the London Mathematical Society. In every third year, the society offers the Senior Anne Bennett prize to a mathematician normally based in the United Kingdom for work in, influence on or service to mathematics, particularly in relation to advancing the careers of women in mathematics. In the two years out of three in which the Senior Anne Bennett Prize is not awarded, the society offers the Anne Bennett Prize to a mathematician within ten years of their doctorate for work in and influence on mathematics, particularly acting as an inspiration for women mathematicians. Both prizes are awarded in memory of Anne Bennett, an administrator for the London Mathematical Society who died in 2012. The prize was established in 2013 and first given in 2014. The Anne Bennett Prizes should be distinguished from the Anne Bennett Memorial Award for Distinguished Service of the Royal Society of Chemistry, for which Anne Bennett also worked. == Anne Bennett Prize Winners == The winners of the Anne Bennett Prize have been: 2015 Apala Majumdar, in recognition of her outstanding contributions to the mathematics of liquid crystals and to the liquid crystal


id: awm-microsoft-research-prize-in-algebra-and-number-theory-20260505-0
file: data/en.wikipedia.org/wiki/AWM–Microsoft_Research_Prize_in_Algebra_and_Number_Theory-0.md
category: reference
title: AWM–Microsoft Research Prize in Algebra and Number Theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/AWM–Microsoft_Research_Prize_in_Algebra_and_Number_Theory
date_saved: 2026-05-05T11:15:23.832907+00:00
instance: kb-cron
parent: awm-microsoft-research-prize-in-algebra-and-number-theory-20260505-0
summary:
The AWM–Microsoft Research Prize in Algebra and Number Theory and is a prize given every other year by the Association for Women in Mathematics to an outstanding young female researcher in algebra or number theory. It was funded in 2012 by Microsoft Research and first issued in 2014. == Winners == Sophie Morel (2014), for her research in number theory, particularly her contributions to the Langlands program, an application of her results on weighted cohomology, and a new proof of Brenti's combinatorial formula for Kazhdan-Lusztig polynomials. Lauren Williams (2016), for her research in algebraic combinatorics, particularly her contributions on the totally nonnegative Grassmannian, her work on cluster algebras, and her proof (with Musiker and Schiffler) of the famous Laurent positivity conjecture. Melanie Wood (2018), for her research in number theory and algebraic geometry, particularly her contributions in arithmetic statistics and tropical geometry, as well as her work with Ravi Vakil on the limiting behavior of natural families of varieties. Melody Chan (2020), in recognition of her advances at the interface between algebraic geometry and combinatorics. Jennifer Balakrishnan (2022), in recognition of her advances in computing rational points on algebraic curves over number fields. Yunqing Tang (2024), for "work in arithmetic


id: awm-siam-sonia-kovalevsky-lecture-20260505-0
file: data/en.wikipedia.org/wiki/AWM-SIAM_Sonia_Kovalevsky_Lecture-0.md
category: reference
title: AWM-SIAM Sonia Kovalevsky Lecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/AWM-SIAM_Sonia_Kovalevsky_Lecture
date_saved: 2026-05-05T11:15:25.025282+00:00
instance: kb-cron
parent: awm-siam-sonia-kovalevsky-lecture-20260505-0
summary:
The AWM-SIAM Sonia Kovalevsky Lecture is an award and lecture series that "highlights significant contributions of women to applied or computational mathematics." The Association for Women in Mathematics (AWM) and the Society for Industrial and Applied Mathematics (SIAM) planned the award and lecture series in 2002 and first awarded it in 2003. The lecture is normally given each year at the SIAM Annual Meeting. Award winners receive a signed certificate from the AWM and SIAM presidents. The lectures are named after Sonia Kovalevsky (1850–1891), a well-known Russian mathematician of the late 19th century. Karl Weierstrass regarded Kovalevsky as his most talented student. In 1874, she received her Doctor of Philosophy degree from the University of Göttingen under the supervision of Weierstrass. She was granted privatdozentin status and taught at the Stockholm University in 1883; she became an ordinary professor (the equivalent of full professor) at this institution in 1889. She was also an editor of the journal Acta Mathematica. Kovalevsky did her important work in the theory of partial differential equations and the rotation of a solid around a fixed point. == Recipients == The Kovalevky Lecturers have been: 2003 Linda R. Petzold, University of California, Santa Barbara, “Towards the


id: joan-joseph-birman-research-prize-in-topology-and-geometry-20260505-0
file: data/en.wikipedia.org/wiki/Joan_&_Joseph_Birman_Research_Prize_in_Topology_and_Geometry-0.md
category: reference
title: Joan & Joseph Birman Research Prize in Topology and Geometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Joan_&_Joseph_Birman_Research_Prize_in_Topology_and_Geometry
date_saved: 2026-05-05T11:15:26.249558+00:00
instance: kb-cron
parent: joan-joseph-birman-research-prize-in-topology-and-geometry-20260505-0
summary:
The Joan & Joseph Birman Research Prize in Topology and Geometry is a prize given every other year by the Association for Women in Mathematics to an outstanding young female researcher in topology or geometry. The prize fund for the award was endowed by a donation in 2013 from Joan Birman and her husband, Joseph Birman, and first awarded in 2015. == Winners == Elisenda Grigsby (2015), for her research in low-dimensional topology, particularly in knot theory and categorified invariants. Emmy Murphy (2017), for her research in symplectic geometry where she developed new techniques for studying symplectic manifolds and contact geometry. Kathryn Mann (2019), for "major breakthroughs in the theory of dynamics of group actions on manifolds". Emily Riehl (2021), for "deep and foundational work in category theory and homotopy theory". Kristen Hendricks (2023), for "highly influential work on equivariant aspects of Floer homology theories". Mona Merling (2025), for "innovative and impactful research in algebraic K-theory, equivariant homotopy theory, and their applications to manifold theory". == See also == List of awards honoring women List of mathematics awards == References == == External links == AWM Birman Research Prize, Association for Women in Mathematics


id: elizabeth-blackwell-medal-20260505-0
file: data/en.wikipedia.org/wiki/Elizabeth_Blackwell_Medal-0.md
category: reference
title: Elizabeth Blackwell Medal
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Elizabeth_Blackwell_Medal
date_saved: 2026-05-05T11:15:27.402908+00:00
instance: kb-cron
parent: elizabeth-blackwell-medal-20260505-0
summary:
The Elizabeth Blackwell Medal is awarded annually by the American Medical Women's Association. The medal is named in honor of Elizabeth Blackwell, the first woman to receive a medical degree in the United States and a pioneer in promoting the education of women in medicine. Established by Elise S. L'Esperance in 1949, 100 years after Blackwell received her medical degree, the medal is granted to a woman physician "who has made the most outstanding contributions to the cause of women in the field of medicine." Before 1993, the medal was only awarded to members of the AMWA. == Recipients == Source: AMWA == See also == List of medicine awards List of prizes, medals, and awards for women in science List of prizes named after people == Notes == == Further reading == "Elizabeth Blackwell medal". Journal of the American Medical Women's Association. 47 (3): 68–69. May–June 1992. PMID 1624663. Vaschak, MR (February 1975). "The Elizabeth Blackwell Annual Award, 1974". Journal of the American Medical Women's Association. 30 (2): 84–85. PMID 163270. Mega, LT; McKinney, PA (Sep–Oct 1990). "Looking back at progress: AMWA award winners". Journal of the American Medical Women's Association. 45 (5): 200–6. PMID 2269768. == External links


id: annie-jump-cannon-award-in-astronomy-20260505-0
file: data/en.wikipedia.org/wiki/Annie_Jump_Cannon_Award_in_Astronomy-0.md
category: reference
title: Annie Jump Cannon Award in Astronomy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Annie_Jump_Cannon_Award_in_Astronomy
date_saved: 2026-05-05T11:15:28.559868+00:00
instance: kb-cron
parent: annie-jump-cannon-award-in-astronomy-20260505-0
summary:
The Annie Jump Cannon Award in Astronomy is awarded annually by the American Astronomical Society (AAS) to a woman resident of North America, who is within five years of receipt of a PhD, for distinguished contributions to astronomy or for similar contributions in related sciences which have immediate application to astronomy. The awardee is invited to give a talk at an AAS meeting and is given a $1,500 honorarium. The award is named in honor of American astronomer Annie Jump Cannon. Margaret Burbidge was due to be given the 1972 award, but she refused it on the grounds of gender discrimination, stating: "It is high time that discrimination in favor of, as well as against, women in professional life be removed". This prompted the AAS to set up its first committee on the status of women in astronomy and they ceased issuing the award directly. From 1973 to 2004 the American Association of University Women issued the awards, on advice from the AAS. The AAS resumed direct issuing of the award in 2005. == List of winners == Source: American Astronomical Society == See also == List of astronomy awards List of women astronomers List of prizes, medals, and awards


id: florence-nightingale-david-award-20260505-0
file: data/en.wikipedia.org/wiki/Florence_Nightingale_David_Award-0.md
category: reference
title: Florence Nightingale David Award
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Florence_Nightingale_David_Award
date_saved: 2026-05-05T11:15:29.777856+00:00
instance: kb-cron
parent: florence-nightingale-david-award-20260505-0
summary:
The Florence Nightingale David Award is an award given every two years (in odd-numbered years) jointly by the Committee of Presidents of Statistical Societies and Caucus for Women in Statistics to a distinguished female statistician. == Description == The award's purpose is to "recognize a female statistician who exemplifies the contributions of Florence Nightingale David" and who "has advanced the discipline and proven herself to be an outstanding role model". Since the founding of the award, it has become a "prestigious hallmark of achievement" among female statisticians. == Winners == The Florence Nightingale David Award was first given in 2001, with David herself being given the award retroactively, dated to 1994. The winners of the award have been: == References ==


id: dorothy-hill-medal-20260505-0
file: data/en.wikipedia.org/wiki/Dorothy_Hill_Medal-0.md
category: reference
title: Dorothy Hill Medal
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dorothy_Hill_Medal
date_saved: 2026-05-05T11:15:31.038014+00:00
instance: kb-cron
parent: dorothy-hill-medal-20260505-0
summary:
The Dorothy Hill Medal is awarded annually and honours the contributions of Dorothy Hill to Australian Earth science and her work in opening up tertiary science education to women. The award supports research in the Earth sciences by female researchers up to 10 years post doctorate for research carried out mainly in Australia. Prior to 2018 the award was known as the Dorothy Hill Award. == Recipients == Source: Australian Academy of Science == See also == List of earth sciences awards == References ==


id: elaine-bennett-research-prize-20260505-0
file: data/en.wikipedia.org/wiki/Elaine_Bennett_Research_Prize-0.md
category: reference
title: Elaine Bennett Research Prize
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Elaine_Bennett_Research_Prize
date_saved: 2026-05-05T11:15:32.194183+00:00
instance: kb-cron
parent: elaine-bennett-research-prize-20260505-0
summary:
The Elaine Bennett Research Prize, awarded every year by the American Economic Association, recognizes and honors outstanding research in any field of economics by a woman not more than ten years beyond her Ph.D. Prior to 2023 the award had been given every other year for a woman not more than seven years beyond her PhD. First awarded in 1998, three of the first six winners of this prize have been the first three female winners of the John Bates Clark Medal. == Past recipients == == See also == List of awards honoring women List of economics awards John Bates Clark Medal == References ==


id: elizabeth-l-scott-award-20260505-0
file: data/en.wikipedia.org/wiki/Elizabeth_L._Scott_Award-0.md
category: reference
title: Elizabeth L. Scott Award
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Elizabeth_L._Scott_Award
date_saved: 2026-05-05T11:15:33.387019+00:00
instance: kb-cron
parent: elizabeth-l-scott-award-20260505-0
summary:
The Elizabeth L. Scott Award is an biennial award given (in even years) by the Committee of Presidents of Statistical Societies and named in honor of Elizabeth Scott, an American statistician. This award recognizes an individual who exemplifies the contributions of Elizabeth L. Scott’s lifelong efforts to further the careers of women in academia. The award is given to an individual who has helped foster opportunities in statistics for women and is presented at the Joint Statistical Meetings. Starting in 2020, the recipient of the award will give a lecture at the Joint Statistical Meetings. == List of Award winners == == See also == List of mathematics awards == References ==


id: faseb-excellence-in-science-award-20260505-0
file: data/en.wikipedia.org/wiki/FASEB_Excellence_in_Science_Award-0.md
category: reference
title: FASEB Excellence in Science Award
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/FASEB_Excellence_in_Science_Award
date_saved: 2026-05-05T11:15:34.596906+00:00
instance: kb-cron
parent: faseb-excellence-in-science-award-20260505-0
summary:
The Excellence in Science Award was established by the Federation of American Societies for Experimental Biology (FASEB) in 1989 to recognize outstanding achievement by women in biological science. All women who are members of one or more of the societies of FASEB are eligible for nomination. Nominations recognize a woman whose career achievements have contributed significantly to further our understanding of a particular discipline by excellence in research. The award includes a $10,000 unrestricted research grant, funded by Eli Lilly and Company. == Award recipients == Source: FASEB Archived 2016-03-04 at the Wayback Machine 1989 Marian Koshland 1990 Elizabeth Hay 1991 Ellen Vitetta 1992 Bettie Sue Masters 1993 Susan Leeman 1994 Lucille Shapiro 1995 Philippa Marrack 1996 Zena Werb 1997 Claude Klee 1998 Eva Neer 1999 Helen Blau 2000 Peng Loh 2001 Laurie Glimcher 2002 Phyllis Wise 2003 Joan A. Steitz 2004 Janet Rossant 2005 Anita Roberts 2006 Marilyn Farquhar and Elaine Fuchs 2007 Frances Arnold 2008 Mina J. Bissell 2009 Susan L. Lindquist 2010 Susan S. Taylor 2011 Gail R. Martin 2012 Susan R. Wessler 2013 Terry Orr-Weaver 2014 Kathryn V. Anderson 2015 Diane Griffin 2016 Bonnie Bassler 2017 Diane Mathis 2018 Lynne E. Maquat 2019 Barbara B. Kahn


id: list-of-female-nominators-for-the-nobel-prize-20260505-0
file: data/en.wikipedia.org/wiki/List_of_female_nominators_for_the_Nobel_Prize-0.md
category: reference
title: List of female nominators for the Nobel Prize
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_female_nominators_for_the_Nobel_Prize
date_saved: 2026-05-05T11:15:35.878491+00:00
instance: kb-cron
parent: list-of-female-nominators-for-the-nobel-prize-20260505-0
summary:
The Nobel Prize (Swedish: Nobelpriset) is a set of five different prizes that, according to its benefactor Alfred Nobel in his 1895 will, must be awarded "to those who, during the preceding year, have conferred the greatest benefit to humankind". The five prizes are awarded in the fields of Physics, Chemistry, Physiology or Medicine, Literature, and Peace. Since 1901, numerous nominators have forwarded their nominations of distinguished individuals or organizations for the prize, and most of these nominators were women. The following is a list of the female nominators for the prestigious Nobel Prize: == Physics == The Nobel Committee for Physics sends confidential forms to persons who are competent and qualified to nominate. According to the nomination process, the individuals are considered the qualified nominators for the physics prize: == Chemistry == For the chemistry prize, the following individuals are considered as qualified nominators: == Physiology or Medicine == For the physiology or medicine prize, the following individuals are entitled to nominate: == Literature == The Nobel Committee of the Swedish Academy sends invitation letters to persons who are qualified to nominate for the Nobel Prize in Literature. The following individuals are eligible forwarding nominations: == Peace == According


id: list-of-female-nominees-for-the-nobel-memorial-prize-in-economic-sciences-20260505-0
category: reference
title: List of female nominees for the Nobel Memorial Prize in Economic Sciences
tags: science, encyclopedia
date_saved: 2026-05-05T11:15:37.126969+00:00
instance: kb-cron
parent: list-of-female-nominees-for-the-nobel-memorial-prize-in-economic-sciences-20260505-0
file:
data/en.wikipedia.org/wiki/List_of_female_nominees_for_the_Nobel_Memorial_Prize_in_Economic_Sciences-0.md

summary:
The Nobel Memorial Prize in Economic Sciences is an annual award established in 1969 by Sweden's central bank, Sveriges Riksbank. Though not one of the original Nobel Prizes, it was founded to celebrate the bank's 300th anniversary and in memory of Alfred Nobel. The laureates are chosen in a manner similar to the Nobel Prizes and receives the recognition during the Nobel ceremonies. As of 2025, 68 Nobel Prizes and the Memorial Prize in Economic Sciences have been awarded to 67 women and since 1901, the year wherein the awarding of the prizes began, hundreds of women have already been nominated and shortlisted carefully in each field. From 1969 to 1972, four women have been nominated for the Nobel Memorial Prize until 2009 when the first female economist was subsequently awarded. In 1969, British economist Joan Robinson became the first ever woman to be nominated for a Nobel Memorial Prize in Economic Sciences. She was nominated multiple times and shortlisted in 1975 and 1976 but remained unrewarded with The New York Times explaining that "[Ms. Robinson] did not win the prize because [the committee] feared that she would either refuse it or, worse, use the Nobel limelight to attack mainstream

source_url:
https://en.wikipedia.org/wiki/List_of_female_nominees_for_the_Nobel_Memorial_Prize_in_Economic_Sciences


id: list-of-female-nominees-for-the-nobel-prize-in-chemistry-20260505-0
file: data/en.wikipedia.org/wiki/List_of_female_nominees_for_the_Nobel_Prize_in_Chemistry-0.md
category: reference
title: List of female nominees for the Nobel Prize in Chemistry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_female_nominees_for_the_Nobel_Prize_in_Chemistry
date_saved: 2026-05-05T11:15:38.377804+00:00
instance: kb-cron
parent: list-of-female-nominees-for-the-nobel-prize-in-chemistry-20260505-0
summary:
The Nobel Prize (Swedish: Nobelpriset) is a set of five different prizes that, according to its benefactor Alfred Nobel, in his 1895 will, must be awarded "to those who, during the preceding year, have conferred the greatest benefit to humankind". The five prizes are awarded in the fields of Physiology or Medicine, Physics, Chemistry, Literature, and Peace. As of 2025, 68 Nobel Prizes and the Memorial Prize in Economic Sciences have been awarded to 67 women and since 1901, the year wherein the awarding of the prizes began, hundreds of women have already been nominated and shortlisted carefully in each field. From 1901 to 1975, 15 women have been nominated for the Nobel Prize in Chemistry and 3 of these nominees were subsequently awarded. In 1911, Polish-French scientist Marie Curie became the first ever women to win a solo Nobel Prize in Chemistry. She became and the only woman to have won two Nobel Prizes: in 1903, she was awarded the Nobel Prize in Physics alongside her husband, Pierre Curie, and Henri Becquerel. Curie's daughter, Irène Joliot-Curie, eventually became the second recipient of the Nobel Prize in Chemistry in 1935, making the two the only mother-daughter pair to have won


id: list-of-female-nominees-for-the-nobel-prize-in-physics-20260505-0
file: data/en.wikipedia.org/wiki/List_of_female_nominees_for_the_Nobel_Prize_in_Physics-0.md
category: reference
title: List of female nominees for the Nobel Prize in Physics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_female_nominees_for_the_Nobel_Prize_in_Physics
date_saved: 2026-05-05T11:15:39.542386+00:00
instance: kb-cron
parent: list-of-female-nominees-for-the-nobel-prize-in-physics-20260505-0
summary:
The Nobel Prize (Swedish: Nobelpriset) is a set of five different prizes that, according to its benefactor Alfred Nobel, in his 1895 will, must be awarded "to those who, during the preceding year, have conferred the greatest benefit to humankind". The five prizes are awarded in the fields of Physiology or Medicine, Physics, Chemistry, Literature, and Peace. As of 2025, 68 Nobel Prizes and the Memorial Prize in Economic Sciences have been awarded to 67 women and since 1901, the year wherein the awarding of the prizes began, hundreds of women have already been nominated and shortlisted carefully in each field. From 1902 to 1975, 13 women have been nominated for the Nobel Prize in Physics and three of the nominees were subsequently awarded. The first woman to win a Nobel Prize was Marie Curie, who won the Nobel Prize in Physics in 1903 with her husband, Pierre Curie, and Henri Becquerel. Curie is also the only woman to have won multiple Nobel Prizes; in 1911, she won the Nobel Prize in Chemistry. Curie's daughter, Irène Joliot-Curie, won the Nobel Prize in Chemistry in 1935, making the two the only mother-daughter pair to have won Nobel Prizes. Of the currently


id: list-of-female-nominees-for-the-nobel-prize-in-physiology-or-medicine-20260505-0
category: reference
title: List of female nominees for the Nobel Prize in Physiology or Medicine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_female_nominees_for_the_Nobel_Prize_in_Physiology_or_Medicine
date_saved: 2026-05-05T11:15:40.767824+00:00
instance: kb-cron
parent: list-of-female-nominees-for-the-nobel-prize-in-physiology-or-medicine-20260505-0
file:
data/en.wikipedia.org/wiki/List_of_female_nominees_for_the_Nobel_Prize_in_Physiology_or_Medicine-0.md

summary:
The Nobel Prize (Swedish: Nobelpriset) is a set of five different prizes that, according to its benefactor Alfred Nobel, in his 1895 will, must be awarded "to those who, during the preceding year, have conferred the greatest benefit to humankind". The five prizes are awarded in the fields of Physiology or Medicine, Physics, Chemistry, Literature, and Peace. As of 2025, 68 Nobel Prizes and the Memorial Prize in Economic Sciences have been awarded to 67 women and since 1901, the year wherein the awarding of the prizes began, hundreds of women have already been nominated and shortlisted carefully in each field. From 1912 to 1956, 19 women have been nominated for the Nobel Prize in Physiology or Medicine wherein one was declared invalid, one was purportedly recommended and one was subsequently awarded. In 1912, Mary Edwards Walker became the first ever woman nominated for prize in physiology or medicine but her nomination was later declared invalid by the Nobel Committee because her nominator was not invited to nominate that year. Hence, Cécile Vogt-Mugnier, nominated first in 1922, became the official first female nominee but never won despite numerous recommendations. She was followed by Maud Slye who was nominated in the


id: rosalind-franklin-award-20260505-0
file: data/en.wikipedia.org/wiki/Rosalind_Franklin_Award-0.md
category: reference
title: Rosalind Franklin Award
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rosalind_Franklin_Award
date_saved: 2026-05-05T11:15:41.962016+00:00
instance: kb-cron
parent: rosalind-franklin-award-20260505-0
summary:
The Royal Society Rosalind Franklin Award was established in 2003 and is awarded annually by the Royal Society to an individual for outstanding work in any field of Science, technology, engineering, and mathematics (STEM) and to support the promotion of women in STEM. It is named in honour of Rosalind Franklin and initially funded by the Department of Trade and Industry (DTI) and subsequently the Department for Innovation, Universities and Skills (DIUS) as part of its efforts to promote women in STEM. Women are a significantly underrepresented group in STEM making up less than 9% of the United Kingdom's full-time and part-time professors in science. The award consists of a medal and a grant of £30,000. The recipient delivers a lecture as part of the Society's public lecture series, some of which are available on YouTube. == Laureates == 2003: Susan Gibson on Make me a molecule. Awarded presented by Patricia Hewitt, serving Minister for Women and Equalities. 2004: Carol V. Robinson on Finding the right balance. 2005: Christine Davies on The quandary of the quark. 2006: Andrea Brand on Constructing a nervous system: stem cells to synapses 2007: Ottoline Leyser on Thinking like a vegetable: how plants decide what


id: garvan-olin-medal-20260505-0
file: data/en.wikipedia.org/wiki/Garvan–Olin_Medal-0.md
category: reference
title: Garvan–Olin Medal
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Garvan–Olin_Medal
date_saved: 2026-05-05T11:15:43.169639+00:00
instance: kb-cron
parent: garvan-olin-medal-20260505-0
summary:
The Francis P. Garvan–John M. Olin Medal, previously called the Francis P. Garvan Medal, is an annual award that recognizes distinguished scientific accomplishment, leadership and service to chemistry by women chemists. The Award is offered by the American Chemical Society (ACS), and consists of a cash prize (US$5,000) and a medal. The medal was designed by Margaret Christian Grigor. == Background == Any individual may nominate a single eligible chemist in one year. Nominees must be a female citizen of the United States. The award was established by Francis Garvan and Mabel Brady Garvan in 1936 in honor of their daughter. It was initially an essay contest, that ran for seven years, as a memorial to their daughter (the American Chemical Society's Prize Essay Contest). It was solely funded by the Francis P. Garvan Medal Endowment from its establishment in 1936 until 1979. W. R. Grace & Co. assumed co-sponsorship of the award from 1979 to 1983. In 1984, Olin Corporation assumed co-sponsorship. Mabel Brady Garvan remained involved with the Award through 1967. The Garvan–Olin Award is the ACS' third-oldest award, and the first award established to honor women chemists. == Award recipients == == See also == List of


id: maria-goeppert-mayer-award-20260505-0
file: data/en.wikipedia.org/wiki/Maria_Goeppert-Mayer_Award-0.md
category: reference
title: Maria Goeppert-Mayer Award
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Maria_Goeppert-Mayer_Award
date_saved: 2026-05-05T11:15:44.372924+00:00
instance: kb-cron
parent: maria-goeppert-mayer-award-20260505-0
summary:
The Maria Goeppert-Mayer Award is an annual prize presented by the American Physical Society in recognition of an outstanding contribution to physics research by a woman. It recognizes and enhances outstanding achievements by women physicists in the early years of their careers. The prize has been awarded since 1986 and is named after Maria Goeppert-Mayer, Nobel laureate in 1963 with J. Hans D. Jensen and Eugene Paul Wigner. Goeppert-Mayer and Jensen were awarded their prize "for their discovery of the nuclear shell structure". Goeppert-Mayer was the second woman to receive a Nobel Prize in Physics after Marie Curie. == Recipients == Source: == See also == List of physics awards == References ==


id: grace-hopper-celebration-of-women-in-computing-20260505-0
file: data/en.wikipedia.org/wiki/Grace_Hopper_Celebration_of_Women_in_Computing-0.md
category: reference
title: Grace Hopper Celebration of Women in Computing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Grace_Hopper_Celebration_of_Women_in_Computing
date_saved: 2026-05-05T11:15:45.565115+00:00
instance: kb-cron
parent: grace-hopper-celebration-of-women-in-computing-20260505-0
summary:
The Grace Hopper Celebration of Women in Computing (GHC) is a series of conferences designed to bring the research and career interests of women in computing to the forefront. It is the world's largest gathering of women and non-binary technologists. The celebration, named after computer scientist Grace Hopper, is organized by the Anita Borg Institute for Women and Technology. GHC 2022 conference was held hybrid in Orlando and virtually at the end of September 2022. == History == In 1994, Anita Borg and Telle Whitney founded the Grace Hopper Celebration of Women in Computing. With the initial idea of creating a conference by and for women computer scientists, Borg and Whitney met over dinner, with a blank sheet of paper, having no idea how to start a conference, and started to plan out their vision. The first Grace Hopper Celebration of Women in Computing was held in Washington, D.C., in June 1994, and brought together 500 technical women. More than a dozen conferences have been held from 1994 to the present; the second was held in 1997 and the conference has been held annually since 2006. The sold-out 2010 conference attracted 2,147 attendees from 29 countries. Beginning in 2011, the


id: grace-hopper-celebration-of-women-in-computing-20260505-1
file: data/en.wikipedia.org/wiki/Grace_Hopper_Celebration_of_Women_in_Computing-1.md
category: reference
title: Grace Hopper Celebration of Women in Computing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Grace_Hopper_Celebration_of_Women_in_Computing
date_saved: 2026-05-05T11:15:45.565115+00:00
instance: kb-cron
parent: grace-hopper-celebration-of-women-in-computing-20260505-0
summary:
=== Childcare and nursing mothers' room === The Grace Hopper Celebration offers free childcare to all attendees, as well as an on-site nursing mothers' room. == Open Source Day == Open Source Day (OSD) is the largest celebration of women in open source. OSD is an all-day hackathon (including workshops) at Grace Hopper Celebration in which participants of all skill levels learn about Open Source while contributing to projects designed to solve real-world problems. OSD is organized in two parts: projects for contributions and hands-on workshops for upskilling. === Open Source Day 2022 === Open Source Day 2022 (OSD22) took place virtually on September 16, 2022 and was open to all GHC22 ticket holders for participation. The Opening Ceremony of OSD22 featured Anne Neuberger, Nithya Ruff and Mishi Choudhary. OSD22 hosted 27 open source projects and 10 workshops. Participants contributed code to 27 open source projects. == Criticisms == The GHC conference has been criticized for a lack of diversity, particularly racial diversity, and financial inaccessibility due to the high cost of attendance. In 2019, the cost of registration, not including hotel, transportation, or other costs, was $450 for students, $600 for academics, and $1,150 for general registration. In 2015,


id: hertha-sponer-prize-20260505-0
file: data/en.wikipedia.org/wiki/Hertha_Sponer_Prize-0.md
category: reference
title: Hertha Sponer Prize
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hertha_Sponer_Prize
date_saved: 2026-05-05T11:15:46.775302+00:00
instance: kb-cron
parent: hertha-sponer-prize-20260505-0
summary:
The Hertha Sponer Prize is a scientific prize of the German Physical Society (German: Deutsche Physikalische Gesellschaft, DPG). It has been awarded annually since 2002 to a female scientist for outstanding scientific work in the field of physics, and was initiated by the Equal Opportunities Working Group of the DPG. The prize is intended to encourage younger female scientists by publicly recognizing them, with the hope that this recognition attracts more women to study physics. The prize consists of a certificate and award of €3,000. Nominations are for recognition of a particular work (journal article or thesis), and self-nominations are permitted. The prize is named after the German physicist Hertha Sponer (1895–1968), who made important contributions to molecular physics and spectroscopy. == Prizewinners == Former prizewinners include: 2002: Karina Morgenstern (Freie Universität Berlin) for dynamic scanning tunneling microscope investigations on nanostructures. 2003: Uta Fritze-von Alvensleben (Göttingen Observatory) for the investigation of galaxy evolution on cosmological time scales, in particular with regard to their interaction. 2004: Myrjam Winning (RWTH Aachen University) for contributions to metallurgy and materials science, in particular X-ray structure investigations of grain boundaries. 2005: Elena Vedmedenko (University of Hamburg) for outstanding work on the magnetism of nanostructures with


id: iota-sigma-pi-20260505-0
file: data/en.wikipedia.org/wiki/Iota_Sigma_Pi-0.md
category: reference
title: Iota Sigma Pi
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Iota_Sigma_Pi
date_saved: 2026-05-05T11:15:48.007677+00:00
instance: kb-cron
parent: iota-sigma-pi-20260505-0
summary:
Iota Sigma Pi (ΙΣΠ) is a national honor society in the United States. It was established in 1900 and specializes in the promotion of women in the sciences, especially chemistry. It also focuses on personal and professional growth for women in these fields. As with all honor societies, they create professional networks along with recognizing achievements of women in chemistry. == History == Iota Sigma Pi was formed during a period when women gained little recognition for their work; therefore, women began to set up their own awards to highlight their abilities on their resumes. It was created by the merger of three chemistry honor societies for women that were established in the early 20th century. Agnes Fay Morgan, department chair of the Department of Household Science and Arts at the University of California, formed Alchemi in 1900. Alchemi spread to the University of Southern California and Stanford University. In 1911, a national chemistry honor society was established at the University of Washington. A third honor society, Iota Sigma Pi, was established at the University of Nebraska in 1912. The latter two societies merged as Iota Sigma Pi in 1913 and were joined by the three chapters of Alchmi in


id: ir-ne-joliot-curie-prize-20260505-0
file: data/en.wikipedia.org/wiki/Irène_Joliot-Curie_Prize-0.md
category: reference
title: Irène Joliot-Curie Prize
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Irène_Joliot-Curie_Prize
date_saved: 2026-05-05T11:15:49.207837+00:00
instance: kb-cron
parent: ir-ne-joliot-curie-prize-20260505-0
summary:
The Irène Joliot-Curie Prize is a French prize for women in science and technology, founded in 2001. It is awarded by the Ministry of Higher Education, Research and Innovation, the Airbus Group corporate foundation, the French Academy of Sciences and the Academy of Technologies, it aims at rewarding women for their work in the fields of science and technology". The prize is named after French scientist Irène Joliot-Curie, a French chemist, physicist and politician who won the Nobel Prize in Chemistry in 1935 for the discovery of artificial radioactivity. (This prize should be distinguished from a different prize with the same name, offered since 1956 by the Société Française de Physique. which rewards work in the field of physics each year.) Each year three awards are given: one for the female scientist of the year, a second to a young female scientist, and a third to a woman in business and technology. In addition, until 2009, of the award a fourth category of awards was given, to an individual or group in recognition of their mentorship of women in science. In 2023, a new category was recognized in a special prize for engagement. Since 2011, the award winners have been


id: krieger-nelson-prize-20260505-0
file: data/en.wikipedia.org/wiki/Krieger–Nelson_Prize-0.md
category: reference
title: Krieger–Nelson Prize
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Krieger–Nelson_Prize
date_saved: 2026-05-05T11:15:50.372357+00:00
instance: kb-cron
parent: krieger-nelson-prize-20260505-0
summary:
The Krieger–Nelson Prize is presented by the Canadian Mathematical Society in recognition of an outstanding woman in mathematics. It was first awarded in 1995. The award is named after Cecilia Krieger and Evelyn Nelson, both known for their contributions to mathematics in Canada. == Recipients == While the award has largely been awarded to a female mathematician working at a Canadian University, it has also been awarded to Canadian-born or -educated women working outside of the country. For example, Cathleen Morawetz, past president of the American Mathematical Society, and a faculty member at the Courant Institute of Mathematical Sciences (a division of New York University) was awarded the Krieger–Nelson Prize in 1997. (Morawetz was educated at the University of Toronto in Toronto, Canada). According to the call for applications, the award winner should be a "member of the Canadian mathematical community". The recipient of the Krieger–Nelson Prize delivers a lecture to the Canadian Mathematical Society, typically during its summer meeting. == See also == List of mathematics awards == References == == External links == Krieger–Nelson Prize, Canadian Mathematical Society.


id: list-of-female-nobel-laureates-20260505-0
file: data/en.wikipedia.org/wiki/List_of_female_Nobel_laureates-0.md
category: reference
title: List of female Nobel laureates
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_female_Nobel_laureates
date_saved: 2026-05-05T11:15:51.507842+00:00
instance: kb-cron
parent: list-of-female-nobel-laureates-20260505-0
summary:
The Nobel Prizes are five separate prizes that, according to Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to Mankind." Additionally, the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel (often referred to as the Nobel Prize in Economics) was established by Sveriges Riksbank in 1968 and is awarded to a "person or persons in the field of economic sciences who have produced work of outstanding importance." As of 2025, according to the Nobel Foundation, 68 Nobel Prizes and the Memorial Prize in Economic Sciences have been awarded to 67 women (Marie Curie has been honoured twice, first in Physics in 1903, then in Chemistry in 1911). Unique Nobel Prize laureates include 894 men, 64 women, and 27 organizations. The approximate distribution of Nobel prizes awarded to women is as follows (regularly updated list from the Nobel Foundation can be found on their website at "Nobel-Prize awarded women" ): twenty women have won the Nobel Peace Prize (16.3% of 110 awarded); eighteen have won the Nobel Prize in Literature (15% of 120 awarded); fourteen have won the Nobel Prize in Physiology or Medicine (5.6% of 230


id: margaret-oakley-dayhoff-award-20260505-0
file: data/en.wikipedia.org/wiki/Margaret_Oakley_Dayhoff_Award-0.md
category: reference
title: Margaret Oakley Dayhoff Award
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Margaret_Oakley_Dayhoff_Award
date_saved: 2026-05-05T11:15:52.712131+00:00
instance: kb-cron
parent: margaret-oakley-dayhoff-award-20260505-0
summary:
The Margaret Oakley Dayhoff Award from the Biophysical Society in Rockville, Maryland, is given to a woman who "holds very high promise or has achieved prominence while developing the early stages of a career in biophysical research". It is "one of the top national honors" in biophysics. The award was established in 1984 in honor of Margaret Dayhoff, a biophysicist associated with the Biophysical Society and the National Biomedical Research Foundation. == Award recipients == Source: Biophysical Society 1984/85: Dagmar Ringe and Bonnie Ann Wallace 1985/86: Barbara A. Lewis 1986/87: Barbara E. Ehrlich 1987/88: Rachel E. Klevit 1988/89: Nancy L. Thompson 1989/90: Anne Walter 1990/91: Jeanne Rudzki Small 1991/92: Hazel M. Holden and Francine R. Smith 1992/93: Carol Vandenberg 1993/94: Jean S. Baum 1994/95: Hillary C. M. Nelson 1995/96: Lynne Regan 1996/97: Susan Marqusee 1997/98: Bonnie Anne Berger 1998/99: Judith R. Mourant 1999: Lydia Gregoret 2000/2001: Millie M. Georgiadis and Ka Yee Christina Lee 2002: Gina MacDonald 2003: Hao Wu 2004: Dorothee Kern 2005: Sarah Keller 2006: Anne Hinderliter 2007: Kalina Hristova 2008: Judith Klein-Seetharaman 2009: Teresa Giraldez, Adrienne L. Fairhall, and Jin Zhang 2010: Crina Nimigean and Maria Spies 2011: Diane Lidke 2012: Lucy R. Forrest 2013: Jennifer L.


id: margaret-w-rossiter-history-of-women-in-science-prize-20260505-0
file: data/en.wikipedia.org/wiki/Margaret_W._Rossiter_History_of_Women_in_Science_Prize-0.md
category: reference
title: Margaret W. Rossiter History of Women in Science Prize
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Margaret_W._Rossiter_History_of_Women_in_Science_Prize
date_saved: 2026-05-05T11:15:53.943095+00:00
instance: kb-cron
parent: margaret-w-rossiter-history-of-women-in-science-prize-20260505-0
summary:
The Margaret W. Rossiter History of Women in Science Prize is awarded by the History of Science Society for an outstanding book (in odd-numbered years) or article (in even-numbered years) on the history of women in science, published at most four years before the year of the award. It was previously called the Women's Prize, but in 2004 the History of Science Society Council voted unanimously at its annual meeting to rename it the Margaret W. Rossiter History of Women in Science Prize. == Recipients == == See also == List of general science and technology awards List of history awards List of science and technology awards for women Women in chemistry Women in science == References ==


id: pearl-meister-greengard-prize-20260505-0
file: data/en.wikipedia.org/wiki/Pearl_Meister_Greengard_Prize-0.md
category: reference
title: Pearl Meister Greengard Prize
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pearl_Meister_Greengard_Prize
date_saved: 2026-05-05T11:15:55.141343+00:00
instance: kb-cron
parent: pearl-meister-greengard-prize-20260505-0
summary:
The Pearl Meister Greengard Prize is an award for women scientists in biology given annually by the Rockefeller University. The Prize was founded by Nobel laureate Paul Greengard and his wife Ursula von Rydingsvard in honor of Greengard's mother, Pearl Meister Greengard, who died giving birth to him. Greengard began funding the award in 1998. Greengard donated the full share of his 2000 Nobel Prize to the fund, and was able to use his new publicity to attract additional funding for the award, which was launched in 2004. The award is meant to shine a spotlight on exceptional female scientists, since, as Greengard observed, "[women] are not yet receiving awards and honors at a level commensurate with their achievements." The award includes a $100,000 honorarium (previously $50,000). Three recipients of the Prize, Carol Greider, Elizabeth Blackburn and Katalin Karikó, have gone on to receive the Nobel Prize in Physiology or Medicine. One recipient, Jennifer Doudna, received the Nobel Prize in Chemistry. == Winners == Source: Rockefeller University Archived August 12, 2017, at the Wayback Machine Nicole Marthe Le Douarin (2004) Philippa Marrack (2005) Mary Frances Lyon (2006) Gail R. Martin, Beatrice Mintz, Elizabeth Robertson (2007) Elizabeth Blackburn, Carol Greider, Vicki


id: lise-meitner-lectures-20260505-0
file: data/en.wikipedia.org/wiki/Lise_Meitner_Lectures-0.md
category: reference
title: Lise Meitner Lectures
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lise_Meitner_Lectures
date_saved: 2026-05-05T11:15:56.346937+00:00
instance: kb-cron
parent: lise-meitner-lectures-20260505-0
summary:
The Lise Meitner Lectures (LML) are a series of public lectures in honour of Lise Meitner. The lectures are organized jointly by the German Physical Society and the Austrian Physical Society, with the intention to showcase outstanding female scientists in physics or related fields. The annual lecture series was launched in 2008, when Lise Meitner's birthday celebrated its 130th anniversary. In October 2008, the Lise Meitner Lecture was held in Vienna and Berlin with an accompanying exhibition. The annual lecture series not only aims at increasing the visibility of successful female researchers, but also at encouraging girls and young women towards careers in physics. == Awardees == 2025: Anne L’Huillier, „Attosecond pulses of light for studying electron dynamics“ 2024: Lisa Kaltenegger, "Alien Earths: Searching for a Second Earth - Challenges, Opportunities and Adventures" 2023: Donna Strickland, "Generating High-Intensity, Ultrashort Optical Pulses" 2022: Viola Priesemann, "Learning in living neuronal networks" (Lernen in lebenden neuronalen Netzwerken) 2021: Claudia Draxl, "Quantum-based Materials Modeling and Artificial Intelligence for Tackling Societal Challenges" 2019: Halina Rubinsztein-Dunlop, "Sculpted light in nano- and microsystems" 2017/18: Nicola Spaldin, "New materials for a new age" (DPG 2018/ÖPG 2017) 2017/18: Johanna Stachel, "Erforschung von Urknallmaterie an der Weltmaschine LHC" (DPG 2017/ÖPG


id: ruth-i-michler-memorial-prize-20260505-0
file: data/en.wikipedia.org/wiki/Ruth_I._Michler_Memorial_Prize-0.md
category: reference
title: Ruth I. Michler Memorial Prize
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ruth_I._Michler_Memorial_Prize
date_saved: 2026-05-05T11:15:57.464640+00:00
instance: kb-cron
parent: ruth-i-michler-memorial-prize-20260505-0
summary:
The Ruth I. Michler Memorial Prize is an annual prize in mathematics, awarded by the Association for Women in Mathematics to honor outstanding research by a female mathematician who has recently earned tenure. The prize funds the winner to spend a semester as a visiting faculty member at Cornell University, working with the faculty there and presenting a distinguished lecture on their research. It is named after Ruth I. Michler (1967–2000), a German-American mathematician born at Cornell, who died in a road accident at the age of 33. The award was first offered in 2007. Its winners and their lectures have included: Rebecca Goldin (2007), "The Geometry of Polygons" Irina Mitrea (2008), "Boundary-Value Problems for Higher-Order Elliptic Operators" Maria Gordina (2009), "Lie's Third Theorem in Infinite Dimensions" Patricia Hersh (2010), "Regular CS Complexes, Total Positivity and Bruhat Order" Anna Mazzucato (2011), "The Analysis of Incompressible Fluids at High Reynolds Numbers" Ling Long (2012), "Atkin and Swinnerton-Dyer Congruences" Megumi Harada (2013), "Newton-Okounkov bodies and integrable systems" Sema Salur (2014), "Manifolds with G2 structure and beyond" Malabika Pramanik (2015), "Needles, Bushes, Hairbrushes, and Polynomials" Pallavi Dani (2016), "Large-scale geometry of right-angled Coxeter groups" Julia Gordon (2017), "Wilkie's theorem and (ineffective) uniform bounds"


id: agnes-fay-morgan-research-award-20260505-0
file: data/en.wikipedia.org/wiki/Agnes_Fay_Morgan_Research_Award-0.md
category: reference
title: Agnes Fay Morgan Research Award
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Agnes_Fay_Morgan_Research_Award
date_saved: 2026-05-05T11:15:58.620407+00:00
instance: kb-cron
parent: agnes-fay-morgan-research-award-20260505-0
summary:
The Agnes Fay Morgan Research Award was established in 1951 by the Iota Sigma Pi honorary society for women in chemistry. The award is given for research achievement in chemistry or biochemistry to a woman not over forty years of age at the time of her nomination. Individual chapters, Iota Sigma Pi members, chemists, and groups of chemists may nominate eligible chemists for the prize. The award was named for Agnes Fay Morgan (1884–1968), biochemist and nutritionist, born in Peoria, Illinois, USA. She studied at the University of Chicago (BS, MS, PhD), and taught at the University of California, Berkeley (1915–54), where she helped organize (1919) what was to become a nationally outstanding home economics department. A founder of the science of nutrition, her research focused on the analysis of nutrients in foods, the stability of vitamins and proteins during food processing, and the physiological effects of vitamin deficiencies. Especially noteworthy was her discovery of the role of pantothenic acid in adrenal function and pigmentation. Her work for government and private agencies included the development of improved methods of dehydrating foods. == Award recipients == Source: Iota Sigma Pi Archived 2019-03-23 at the Wayback Machine == See also == List


id: nancy-millis-medal-for-women-in-science-20260505-0
file: data/en.wikipedia.org/wiki/Nancy_Millis_Medal_for_Women_in_Science-0.md
category: reference
title: Nancy Millis Medal for Women in Science
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nancy_Millis_Medal_for_Women_in_Science
date_saved: 2026-05-05T11:15:59.803463+00:00
instance: kb-cron
parent: nancy-millis-medal-for-women-in-science-20260505-0
summary:
The Nancy Millis Medal for Women in Science, also known as the Nancy Millis Medal, is an annual award conferred by the Australian Academy of Science. It is named in honour of the microbiologist Nancy Millis (1922–2012) and recognises women scientists, with eight to 15 years' experience after completing their PhD, for their outstanding contribution to research and leadership. == Winners == The medal was first awarded in 2014 and annually since: 2014: Emma Johnston 2015: Tamara Davis 2016: Elena Belousova 2017: Kerrie Ann Wilson 2018: Marie-Liesse Asselin-Labat 2019: Jacqueline Batley 2020: Kate Schroder and Nicole Bell 2021: Angela Moles and Cathryn Trott 2022: Vanessa Peterson 2023: Renae Ryan 2024: Anita Ho-Baillie 2025: Natasha Hurley-Walker == References == == External links == Official website


id: noether-lecture-20260505-0
file: data/en.wikipedia.org/wiki/Noether_Lecture-0.md
category: reference
title: Noether Lecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Noether_Lecture
date_saved: 2026-05-05T11:16:00.975014+00:00
instance: kb-cron
parent: noether-lecture-20260505-0
summary:
The Noether Lecture is a distinguished lecture series that honors women "who have made fundamental and sustained contributions to the mathematical sciences". The Association for Women in Mathematics (AWM) established the annual lectures in 1980 as the Emmy Noether Lectures, in honor of one of the leading mathematicians of her time. In 2013 it was renamed the AWM-AMS Noether Lecture and since 2015 is sponsored jointly with the American Mathematical Society (AMS). The recipient delivers the lecture at the yearly American Joint Mathematics Meetings held in January. The ICM Emmy Noether Lecture is an additional lecture series, sponsored by the International Mathematical Union. Beginning in 1994 this lecture was delivered at the International Congress of Mathematicians, held every four years. In 2010 the lecture series was made permanent. The 2021 Noether Lecture was supposed to have been given by Andrea Bertozzi of UCLA, but it was cancelled. The cancellation was made during the George Floyd protests: "This decision comes as many of this nation rise up in protest over racial discrimination and brutality by police". Although she intended to speak on other topics, Bertozzi is known for research on the mathematics of policing, and in a letter to the AMS,


id: owsd-elsevier-foundation-award-20260505-0
file: data/en.wikipedia.org/wiki/OWSD-Elsevier_Foundation_Award-0.md
category: reference
title: OWSD-Elsevier Foundation Award
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/OWSD-Elsevier_Foundation_Award
date_saved: 2026-05-05T11:16:02.233826+00:00
instance: kb-cron
parent: owsd-elsevier-foundation-award-20260505-0
summary:
The OWSD-Elsevier Foundation Awards for Early-Career Women Scientists in the Developing World are awarded annually to early-career women scientists in selected developing countries in four regions: Latin America and the Caribbean, East and Southeast Asia and the Pacific, Central and South Asia, and Sub-Saharan Africa. The Organization for Women in Science for the Developing World (OWSD), the Elsevier Foundation, and The World Academy of Sciences have partnered to recognize achievements of early-career women scientists in developing countries since the award was launched in 2011 as the Elsevier Foundation-OWSD Awards for Young Women Scientists from the Developing World. The award program is open to female scientists who live and work in one of 81 developing countries. Nominations are generally submitted within ten years of the nominee earning a PhD. The maximum number of recipients is currently restricted to five per year: one from each of the four OWSD-recognized regions, plus one additional outstanding candidate, and the awards are granted with a rotating theme annually among three general fields: biological sciences (agriculture, biology and medicine), engineering/innovation & technology, and physical sciences (including chemistry, mathematics and physics). There were six awardees in 2022 as two outstanding candidates were recognised. As of 2014, the


id: rachel-carson-prize-environmentalist-award-20260505-0
file: data/en.wikipedia.org/wiki/Rachel_Carson_Prize_(environmentalist_award)-0.md
category: reference
title: Rachel Carson Prize (environmentalist award)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rachel_Carson_Prize_(environmentalist_award)
date_saved: 2026-05-05T11:16:03.522202+00:00
instance: kb-cron
parent: rachel-carson-prize-environmentalist-award-20260505-0
summary:
The Rachel Carson Prize (Rachel Carson-prisen) is an international environmental award, established in Stavanger, Norway in 1991 to commemorate the achievements of environmentalist Rachel Carson and to award efforts in her spirit. The prize is awarded to a woman who has distinguished herself in outstanding work for the environment in Norway or internationally. The prize was established spontaneously during a 1989 meeting in Stavanger, on the initiative of speaker Berit Ås. The prize consists of money and the sculpture The Cormorant by artist Irma Bruun Hodne. == Awardees == 1991: Sidsel Mørck, Norwegian author and activist 1993: Bergljot Børresen, Norwegian veterinarian 1995: Anne Grieg, Norwegian psychiatrist 1997: Berit Ås, Norwegian feminist and professor in social psychology 1999: Theo Colborn, American zoologist 2001: Renate Künast, German Federal Minister of Consumer Protection, Food and Agriculture 2003: Åshild Dale, Norwegian farmer 2005: Malin Falkenmark, Swedish professor in hydrology 2007: Sheila Watt-Cloutier, Canadian Inuit climate activist 2009: Marie-Monique Robin, French journalist 2011: Marilyn Mehlmann, Swedish environmentalist and writer 2013: Sam Fanshawe, British marine conservationist 2015: Mozhgan Savabieasfahani, Iranian environmental toxicologist 2016: Gabrielle Hecht 2017: Sylvia Earle 2019: Greta Thunberg, Swedish climate activist 2021: Maja Lunde, Norwegian author == See also == Women in science


id: rosalind-franklin-fellowship-20260505-0
file: data/en.wikipedia.org/wiki/Rosalind_Franklin_Fellowship-0.md
category: reference
title: Rosalind Franklin Fellowship
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rosalind_Franklin_Fellowship
date_saved: 2026-05-05T11:16:04.728636+00:00
instance: kb-cron
parent: rosalind-franklin-fellowship-20260505-0
summary:
The Rosalind Franklin Fellowship (RFF) is an initiation of University of Groningen, the Netherlands. It is named in honor of Rosalind Franklin. The purpose of the RFF program is to promote the advancement of talented international researchers at the highest levels of the institution. == History == The program is co-funded by the European Union and primarily directed at female academics, who have a PhD and substantial post-graduation work experience, and who aim for a career towards full professorship at a European top research university. The 5-year fellowship is given to female academics with outstanding track record, including high-quality publications, external funding, and leadership, and provides the fellow with salary and research funds to start a research group and conduct independent research. In 2009, Queen Máxima of the Netherlands joined the Fellowship Ceremony. The RFF program, since its initiation in 2003 and as of 2019, has successfully supported more than 80 female academics, who now constitute more than 10% of the female professors of the university. == Fellows == 2019–2020 Sandy Schmidt, Science and Engineering Hannah Dugdale, Science and Engineering Julia Kamenz, Science and Engineering Inge Holtman, Medical Sciences Hilde Bras, Arts Sumaya Albalooshi, Economics and Business Mònica Colominas Aparicio,


id: ruby-payne-scott-medal-and-lecture-20260505-0
file: data/en.wikipedia.org/wiki/Ruby_Payne-Scott_Medal_and_Lecture-0.md
category: reference
title: Ruby Payne-Scott Medal and Lecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ruby_Payne-Scott_Medal_and_Lecture
date_saved: 2026-05-05T11:16:05.880128+00:00
instance: kb-cron
parent: ruby-payne-scott-medal-and-lecture-20260505-0
summary:
The Ruby Payne-Scott Medal and Lecture for women in science is a distinguished career award that acknowledges outstanding Australian women researchers in the biological sciences or physical science. It is conferred by the Australian Academy of Science and is awarded to researchers who are usually resident in, and conduct their research predominantly in Australia. This award, established in 2021, honours the contributions of Ruby Payne-Scott, particularly in the fields of radiophysics and radio astronomy. == Recipients == == References ==


id: sadosky-prize-20260505-0
file: data/en.wikipedia.org/wiki/Sadosky_Prize-0.md
category: reference
title: Sadosky Prize
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sadosky_Prize
date_saved: 2026-05-05T11:16:07.056560+00:00
instance: kb-cron
parent: sadosky-prize-20260505-0
summary:
The AWM–Sadosky Prize in Analysis is a prize given every other year by the Association for Women in Mathematics to an outstanding young female researcher in mathematical analysis. It was established in 2012, and is named after Cora Sadosky, a mathematician specializing in analysis who became president of the AWM. The winners have included: Svitlana Mayboroda (2014), for her research on "boundary value problems for second and higher order elliptic equations in non-smooth media". Daniela De Silva (2016), for "fundamental contributions to the regularity theory of nonlinear elliptic partial differential equations and non-local integro-differential equations". Lillian Pierce (2018), for research that "spans and connects a broad spectrum of problems ranging from character sums in number theory to singular integral operators in Euclidean spaces". Mihaela Ignatova (2020), "in recognition of her contributions to the analysis of partial differential equations, in particular in fluid mechanics". Yaiza Canzani (2022), "in recognition of outstanding contributions in spectral geometry and microlocal analysis". Robin Neumayer (2024), for "outstanding contributions to calculus of variations, partial differential equations, and geometric analysis". Hong Wang (2026), for "solving central problems in harmonic analysis through the introduction of ground-breaking ideas. In particular, for substantial contributions to the Fourier restriction problem, the


id: saruhashi-prize-20260505-0
file: data/en.wikipedia.org/wiki/Saruhashi_Prize-0.md
category: reference
title: Saruhashi Prize
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Saruhashi_Prize
date_saved: 2026-05-05T11:16:08.225591+00:00
instance: kb-cron
parent: saruhashi-prize-20260505-0
summary:
The Saruhashi Prize (猿橋賞) is an annual prize awarded to a Japanese woman researcher in the natural sciences. The prize recognises accomplishments in research as well as the mentoring of other women scientists. Japanese geochemist Katsuko Saruhashi retired from her position as the director of the Geochemical Research Laboratory in 1980. Her co-workers gifted her ¥5 million and she used the money to establish the Association for the Bright Future of Women Scientists in 1980. The association distributes an annual ¥300,000 prize. It is only available to scientists who are under the age of 50. The book My Life: Twenty Japanese Women Scientists, edited by Yoshihide Kozai, includes essays by twenty of the Saruhashi Prize winners. == Recipients == == See also == List of general science and technology awards == References ==


id: ruth-lyttle-satter-prize-in-mathematics-20260505-0
file: data/en.wikipedia.org/wiki/Ruth_Lyttle_Satter_Prize_in_Mathematics-0.md
category: reference
title: Ruth Lyttle Satter Prize in Mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ruth_Lyttle_Satter_Prize_in_Mathematics
date_saved: 2026-05-05T11:16:09.458770+00:00
instance: kb-cron
parent: ruth-lyttle-satter-prize-in-mathematics-20260505-0
summary:
The Ruth Lyttle Satter Prize in Mathematics, also called the Satter Prize, is one of twenty-one prizes given out by the American Mathematical Society (AMS). It is presented biennially in recognition of an outstanding contribution to mathematics research by a woman in the previous six years. The award was funded in 1990 using a donation from Joan Birman, in memory of her sister, Ruth Lyttle Satter, who worked primarily in biological sciences, and was a proponent for equal opportunities for women in science. First awarded in 1991, the award is intended to "honor [Satter's] commitment to research and to encourage women in science". The winner is selected by the council of the AMS, based on the recommendation of a selection committee. The prize is awarded at the Joint Mathematics Meetings during odd numbered years, and has always carried a modest cash reward. Since 2003, the prize has been $5,000, while from 1997 to 2001, the prize came with $1,200, and $4,000 prior to that. If a joint award is given, the prize money is split between the recipients. Dusa McDuff was the first recipient of the award, for her work on symplectic geometry. A joint award was given for the


id: sharon-keillor-award-for-women-in-engineering-education-20260505-0
file: data/en.wikipedia.org/wiki/Sharon_Keillor_Award_for_Women_in_Engineering_Education-0.md
category: reference
title: Sharon Keillor Award for Women in Engineering Education
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sharon_Keillor_Award_for_Women_in_Engineering_Education
date_saved: 2026-05-05T11:16:10.654193+00:00
instance: kb-cron
parent: sharon-keillor-award-for-women-in-engineering-education-20260505-0
summary:
The Sharon Keillor Award for Women in Engineering Education "recognizes and honors outstanding women engineering educators." Recipients hold an earned doctoral degree in an engineering discipline or related field, have at least five years of teaching experience in an engineering school, and have "an outstanding record in teaching engineering students." The award has been given annually since 2001. == Recipients == == See also == List of engineering awards == References ==


id: suffrage-science-award-20260505-0
file: data/en.wikipedia.org/wiki/Suffrage_Science_award-0.md
category: reference
title: Suffrage Science award
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Suffrage_Science_award
date_saved: 2026-05-05T11:16:11.854355+00:00
instance: kb-cron
parent: suffrage-science-award-20260505-0
summary:
The Suffrage Science award is a prize for women in science, engineering and computing founded in 2011, on the 100th anniversary of International Women's Day by the MRC London Institute of Medical Sciences (LMS). There are three categories of award: life sciences engineering and physical sciences mathematics and computing. The life sciences award was founded in 2011. Every year there are 10 laureates from research backgrounds and one laureate for communication. The engineering and physical sciences award was founded in 2013. Every year there are 12 laureates from areas spanning physics, chemistry and more. The math and computing award was launched on Ada Lovelace Day, 2016. Every year there are five laureates from mathematics, five laureates from computing and one laureate for science communication and the public awareness of science. == Laureates == Laureates have included: === 2026 === Life Sciences Chrystalina Antoniades, University of Oxford Sarah Cooley, Earth Science Data Professionals Organization Cara Croft, Queen Mary University of London Camille Dion, Medical Sciences, London Dima A. Hammoud, NIH Clinical Centre Karoline Kuchenbaecker, University College, London Madeline Lancaster, LMB, Cambridge Liset Menéndez de la Prida, Instituto Cajal CSIC, Spain Arwen Pearson, University of Hamburg Kate Watkins, University of Oxford Dana


id: tagea-brandt-rejselegat-20260505-0
file: data/en.wikipedia.org/wiki/Tagea_Brandt_Rejselegat-0.md
category: reference
title: Tagea Brandt Rejselegat
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tagea_Brandt_Rejselegat
date_saved: 2026-05-05T11:16:13.042805+00:00
instance: kb-cron
parent: tagea-brandt-rejselegat-20260505-0
summary:
The Tagea Brandts Rejselegat (Travel Scholarship) is a Danish award to women who have made a significant contribution in science, literature or art. The grant, which is given without application, was created and endowed by Danish industrialist Vilhelm Brandt (1854–1921) in 1905 in honor of his wife, Tagea Brandt. It is awarded annually on 17 March, her birthday. The charter of 1922 provides that it shall be given to outstanding women in science, art, music, literature and theater arts (particularly in this case to actresses at the Royal Danish Theatre). The intent is for the awardee to both broaden her horizons while promoting Danish society abroad, and to benefit from vacation and rest time. The first scholarships were given in 1924; the first time the amount was DKK 10.000, in 1958 it was increased to DKK 15.000, in 1967 to 25.000, later to 50,000, and currently it is DKK 75.000, which usually is given to 2-3 women annually. == Recipients of the Tagea Brandt Award == == See also == Tagea Brandt Women in Denmark List of awards honoring women List of European art awards == References == == External links == "Tagea Brandts Rejselegat" [Tagea Brandt's Travel Scholarship]. Litterære


id: taiwan-outstanding-women-in-science-awards-20260505-0
file: data/en.wikipedia.org/wiki/Taiwan_Outstanding_Women_in_Science_Awards-0.md
category: reference
title: Taiwan Outstanding Women in Science Awards
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Taiwan_Outstanding_Women_in_Science_Awards
date_saved: 2026-05-05T11:16:14.207961+00:00
instance: kb-cron
parent: taiwan-outstanding-women-in-science-awards-20260505-0
summary:
The Taiwan Outstanding Women in Science Award (TOWIS, Chinese: 台灣傑出女科學家獎; Tongyong Pinyin: Táiwān jiéchū nyǔ kēsyuéjiā jiǎng; Tâi-lô: Tâi-uân kia̍t-tshut lú kho-ha̍k-ka tsióng was jointly established in 2007 by L'Oréal Taiwan and the Chien-Shiung Wu Foundation. It aims to encourage young female students to pursue scientific research as their career by recognizing outstanding female scientists. This award is also known colloquially as the "Taiwan Women's Nobel Prize". The awards include the "Outstanding Award", the "Young Talent Award" and the "Mong Tsui-Chu Scholarship" added in 2012. The scientists participating in the selection are mainly from the three fields of material science, mathematics and information science. The winners are announced annually in March. == Laureates == == See also == List of science and technology awards for women Women in STEM fields Women in engineering Women in science == References == == External links == Taiwan Outstanding Women in Science Awards


id: vinfuture-prize-20260505-0
file: data/en.wikipedia.org/wiki/VinFuture_Prize-0.md
category: reference
title: VinFuture Prize
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/VinFuture_Prize
date_saved: 2026-05-05T11:16:15.406173+00:00
instance: kb-cron
parent: vinfuture-prize-20260505-0
summary:
The VinFuture Prize is an annual international award established in 2020 by the Vietnam-based VinFuture Foundation. The foundation aims to promote research in health, technology, and sustainability. == Founders == The VinFuture Foundation was founded in 2020 by Phạm Nhật Vượng (founder of Vingroup) with his wife, Phạm Thu Hương. The organization operates as an independent nonprofit entity with the stated mission of recognizing research in line with the United Nations’ Sustainable Development Goals (SDGs). == Prize Council == The VinFuture Foundation Prize Council is responsible for setting criteria, evaluating laureates, and selecting winners in recognition of research that "has or will have the potential to bring solutions that can be applied to the everyday life of ordinary people." The Prize Council is chaired by Sir Richard Henry Friend, the Cavendish Professor of Physics at the University of Cambridge, and includes members from international universities and research institutions. === Members === Prof. Pascale Cossart, FRS (Pasteur Institute, Paris, France) Prof. Van-Chi Dang (Ludwig Institute for Cancer Research; Johns Hopkins University, United States) Prof. Martin Andrew Green (University of New South Wales, Australia) Prof. Daniel Kammen (University of California, Berkeley, United States) Prof. Sir Konstantin (Kostya) S. Novoselov, FRS (University of


id: weizmann-women-science-award-20260505-0
file: data/en.wikipedia.org/wiki/Weizmann_Women_&_Science_Award-0.md
category: reference
title: Weizmann Women & Science Award
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Weizmann_Women_&_Science_Award
date_saved: 2026-05-05T11:16:16.698742+00:00
instance: kb-cron
parent: weizmann-women-science-award-20260505-0
summary:
The Weizmann Women & Science Award is a biennial award established in 1994 to honor an outstanding woman scientist in the United States who has made significant contributions to the scientific community. The objective of the award, which includes a $25,000 research grant to the recipient, is to promote women in science, and to provide a strong role model to motivate and encourage the next generation of young women scientists. The award was originally given by the American Committee for the Weizmann Institute of Science (ACWIS) and now it is awarded by the Weizmann Institute and the award ceremony takes place at the Weizmann Institute, located in the city of Rehovoth, Israel. The Weizmann Institute is a center of basic interdisciplinary scientific research and graduate study, addressing crucial problems in technology, medicine and health, energy, agriculture and the environment. == Honorees == 1994 Dr. Joan A. Steitz, a Henry Ford II Professor of Biophysics and Biochemistry at Yale University and an Investigator of the Howard Hughes Medical Institute. 1996 Dr. Vera Rubin, Observational Astronomer, Department of Terrestrial Magnetism, Carnegie Institution 1998 Dr. Jacqueline Barton, Arthur and Marian Hanisch Professor of Chemistry at the California Institute of Technology. 2000 Dr. Carla


id: wicb-junior-and-senior-awards-20260505-0
file: data/en.wikipedia.org/wiki/WICB_Junior_and_Senior_Awards-0.md
category: reference
title: WICB Junior and Senior Awards
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/WICB_Junior_and_Senior_Awards
date_saved: 2026-05-05T11:16:17.900283+00:00
instance: kb-cron
parent: wicb-junior-and-senior-awards-20260505-0
summary:
The Women In Cell Biology Committee of the American Society for Cell Biology (ASCB) recognizes outstanding achievements by women in cell biology by presenting three (previously only two) Career Recognition Awards at the ASCB Annual Meeting. The Junior Award is given to a woman in an early stage of her career (generally seven or eight years in an independent position) who has made exceptional scientific contributions to cell biology and exhibits the potential for continuing a high level of scientific endeavor while fostering the career development of damaged young scientists. The Mid-Career Award (introduced in 2012) is given to a woman at the mid-career level who has made exceptional scientific contributions to cell biology and/or has effectively translated cell biology across disciplines, and who exemplifies a high level of scientific endeavor and leadership. The Senior Award is given to a woman or man in a later career stage (generally full professor or equivalent) whose outstanding scientific achievements are coupled with a long-standing record of support for women in science and by mentorship of both men and women in scientific careers. == Senior awardees == Source: WICB 2020 Erika Holzbaur 2019 Rong Li 2018 Eva Nogales 2017 Harvey Lodish 2016 Susan


id: women-of-discovery-awards-20260505-0
file: data/en.wikipedia.org/wiki/Women_of_Discovery_Awards-0.md
category: reference
title: Women of Discovery Awards
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Women_of_Discovery_Awards
date_saved: 2026-05-05T11:16:19.050132+00:00
instance: kb-cron
parent: women-of-discovery-awards-20260505-0
summary:
The Women of Discovery Awards are given by the non-profit WINGS WorldQuest, in recognition of the achievements of women in science and exploration. The awards were first presented in 2003, the same year that WINGS WorldQuest was formed by Milbry Polk and Leila Hadley Luce. Both the Board of Directors and a Junior Council at the granting organization, WINGS WorldQuest, are involved in selecting the recipients of the Women of Discovery Awards, who are thereafter known as Fellows. The WINGS Women of Discovery Awards and Fellows Program were established to celebrate the ground-breaking work of women explorers and scientists who are actively out in the field today and provide critical, unrestricted funding to support and ensure continued study. Women of Discovery Awards are given in the categories of Lifetime Achievement, Air and Space, Conservation, Courage, Earth, Field Research, Film and Exploration, Humanity, Leadership, and the Sea. In addition, some recipients have been simply designated as "Fellows", without being placed in a category. The awards include an unrestricted financial grant. In addition to its fellowship program, WINGS WorldQuest offers Flag Carrier grants in support of field researchers who are financing explorations. == Fellows == The awards are given every 1-2 years.


id: worms-award-20260505-0
file: data/en.wikipedia.org/wiki/WORMS_Award-0.md
category: reference
title: WORMS Award
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/WORMS_Award
date_saved: 2026-05-05T11:16:20.266642+00:00
instance: kb-cron
parent: worms-award-20260505-0
summary:
The WORMS Award for the Advancement of Women in Operations Research and Management Science is given annually by WORMS, the Forum on Women in OR/MS of the Institute for Operations Research and the Management Sciences, to "a person who has contributed significantly to the advancement and recognition of women in the field of Operations Research and the Management Sciences (OR/MS)". == Recipients == The winners of the WORMS Award have included: == References ==


id: 3rd-stone-20260505-0
file: data/en.wikipedia.org/wiki/3rd_Stone-0.md
category: reference
title: 3rd Stone
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/3rd_Stone
date_saved: 2026-05-05T11:16:32.007406+00:00
instance: kb-cron
parent: 3rd-stone-20260505-0
summary:
3rd Stone is a defunct British magazine devoted to "archaeology, folklore and myth" and dealing with Earth mysteries. == History and profile == The magazine was originally published under the title of Gloucestershire Earth Mysteries (G.E.M.) magazine, founded by Danny Sullivan in the mid-1980s, and the name was changed to 3rd Stone magazine in 1986. The magazine was based in Cheltenham. Neil Mortimer took over as editor in 1995, and edited the magazine until its closure in 2003. 3rd Stone absorbed At the Edge magazine in 1998 before itself ceasing publication in 2003. Aubrey Burl, Ed Krupp, John Michell, Paul Devereux, Jeremy Harte, Rodney Castleden and Stan Beckensall are among the authors who contributed to the magazine. Timothy Darvill, in reviewing The Modern Antiquarian, mentioned that The 3rd Stone followed "much the same path [as that book], and [had] a rapidly increasing subscription base and considerable public following" and that it carried "articles by a wide range of authors and gives each equal weight." 3rd Stone ceased publication with issue 47 published in 2003. == See also == List of magazines of anomalous phenomena == References == == External links == Many issues of 3rd Stone are available for free


id: 4q119-20260505-0
file: data/en.wikipedia.org/wiki/4Q119-0.md
category: reference
title: 4Q119
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/4Q119
date_saved: 2026-05-05T11:16:33.209702+00:00
instance: kb-cron
parent: 4q119-20260505-0
summary:
4Q119 (also 4QLXXLeva; TM 62293; LDAB 3454) designates the remnants of a Greek manuscript of the Book of Leviticus written on parchment. It was found at Qumran cave 4 and is dated to the 1st century BCE or 1st century CE. It got the no. 801 according to the system of Alfred Rahlfs. The manuscript is stored in Rockefeller Museum at Jerusalem (Mus. Inv. Gr. 1004). == Bibliography == Patrick Skehan, Eugene C. Ulrich, Judith E. Sanderson: 119. 4QLXXLeviticusa. Qumran Cave 4.IV (Discoveries in the Judaean Desert 9). Clarendon Press, Oxford 1992. ISBN 0-19-826328-7, pp. 161–165, plate XXXVIII. == External links == "Skehan e.a., Qumran cave 4.4 (Discoveries in the Judaean desert 9)". Trismegistos. Retrieved 2012-12-14.


id: 4q240-20260505-0
file: data/en.wikipedia.org/wiki/4Q240-0.md
category: reference
title: 4Q240
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/4Q240
date_saved: 2026-05-05T11:16:34.401772+00:00
instance: kb-cron
parent: 4q240-20260505-0
summary:
4Q240 ( or 4QCanta) is believed to be a commentary (or pesher) on the Song of Songs, also known as 'Canticles'. Written in Hebrew, it was found in Cave 4 at Qumran in the Judean Desert and comprises part of the Dead Sea Scrolls. From its palaeography (script) it has been identified as being early-Herodian. == Location == Included in Milik's original list, but this fragment has never been located. == See also == List of Hebrew Bible manuscripts Dead Sea Scrolls 4Q106 4Q107 4Q108 4QMMT 6Q6 Tanakh at Qumran == References == == External links == "The Dead Sea Scrolls and Why They Matter" – 4Q240 in Biblical Archaeology Review


id: 1821-in-archaeology-20260505-0
file: data/en.wikipedia.org/wiki/1821_in_archaeology-0.md
category: reference
title: 1821 in archaeology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/1821_in_archaeology
date_saved: 2026-05-05T11:16:35.523905+00:00
instance: kb-cron
parent: 1821-in-archaeology-20260505-0
summary:
The year 1821 in archaeology involved some significant events. == Explorations == October - John Gardner Wilkinson begins a twelve-year stay in Egypt, surveying historical sites. == Finds == 'Gallagh Man', an Iron Age bog body, is found in County Galway, Ireland. == Miscellaneous == "Egyptian Hall" in London displays artifacts from Ancient Egypt brought to the United Kingdom by Giovanni Battista Belzoni. The Philae obelisk is landed in England in December. While not specifically the year 1821, this time period is when one of the most significant categorical discoveries of archaeology was named. Christian Thomsen, a Danish archaeologist, developed the three age system to date objects in museums. These three ages were the "Stone Age," "Bronze Age," and "Iron Age." While not specifically the year 1821, this time period is when one of the most significant findings regarding time and dating archaeological findings was discovered. Boucher de Perthes established a much deeper sense of time than what James Usher had previously established. Perthes determined that the world was significantly older than 4004 BC and thus gave archaeology a deeper, more realistic time frame to work with. == Births == June 21, 1821- The birth of Ephraim George Squier, co-author


id: the-adventure-of-archaeology-20260505-0
file: data/en.wikipedia.org/wiki/The_Adventure_of_Archaeology-0.md
category: reference
title: The Adventure of Archaeology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Adventure_of_Archaeology
date_saved: 2026-05-05T11:16:36.721962+00:00
instance: kb-cron
parent: the-adventure-of-archaeology-20260505-0
summary:
The Adventure of Archaeology (ISBN 978-0-87044-603-0) is a 1985 book written by Dr. Brian M. Fagan, published by the National Geographic press publishing company. The book tells about the development of the history of archeology. It contains stories of treasure hunters and tourists and the development of archeology into a scientific field. == References ==


id: afghan-liturgical-quire-20260505-0
file: data/en.wikipedia.org/wiki/Afghan_Liturgical_Quire-0.md
category: reference
title: Afghan Liturgical Quire
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Afghan_Liturgical_Quire
date_saved: 2026-05-05T11:16:37.902326+00:00
instance: kb-cron
parent: afghan-liturgical-quire-20260505-0
summary:
The Afghan Liturgical Quire (ALQ), also known as the Afghan Siddur, is a quire from the Afghan Geniza in Bamyan, Afghanistan. It is the oldest Hebrew codex ever discovered, and contains Hebrew liturgical texts, including prayers, blessings, and piyyuṭ. The manuscript was written in Hebrew, Aramaic and Judeo-Persian. The book is currently a part of the collection at the Museum of the Bible in Washington, D.C. For an unknown reason, a portion of the Passover haggadah is upside-down in the book. == History == The manuscript was originally believed to have come from the Cairo Geniza in Egypt with an estimated origin from the 900s CE. In 2016, a photograph of the book in Afghanistan from 1997 was discovered, which led to radiometric dating tests on four parts of the manuscript. These parts of the manuscript were dated to c. 780 CE in 2019. The book was found by a Hazara man, who gave it to a local Afghan leader. In 2013, the manuscript was purchased by Steve Green, president of Hobby Lobby and founder of the Museum of the Bible. It was later donated to the museum, which opened in 2017. == See also == Leningrad Codex == References


id: tadahiro-aizawa-20260505-0
file: data/en.wikipedia.org/wiki/Tadahiro_Aizawa-0.md
category: reference
title: Tadahiro Aizawa
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tadahiro_Aizawa
date_saved: 2026-05-05T11:16:39.061290+00:00
instance: kb-cron
parent: tadahiro-aizawa-20260505-0
summary:
Tadahiro Aizawa (相沢 忠洋, Aizawa Tadahiro; June 21, 1926 – May 22, 1989) was a Japanese archaeologist. Aizawa, an amateur stone tool collector who had been peddling nattō, discovered a microlith in Iwajuku, Gunma in 1946, which was recognized in 1949 as a Paleolithic site that had previously been thought not to exist in Japan. == References == Keiji Imamura. Prehistoric Japan: new perspectives on insular East Asia p. 19.


id: al-khawdh-20260505-0
file: data/en.wikipedia.org/wiki/Al-Khawdh-0.md
category: reference
title: Al-Khawdh
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Al-Khawdh
date_saved: 2026-05-05T11:16:40.225824+00:00
instance: kb-cron
parent: al-khawdh-20260505-0
summary:
Al-Khawdh (الخوض) (25°35'N; 58°10'E, altitude 40–50 m) contains several archaeological sites and lies in the Muscat Governorate, Oman, where Early Iron Age and Late Iron Age sites have been under study in recent years. Major finds include a large cemetery of the Early Iron Age i.e. the Lizq-Rumaylah period. and a hoard of over 300 implements made of copper alloy This cemetery lies 2.5 kilometres (1.6 mi) south-east of the hoard site. == See also == Archaeology of Oman Oman Pre-Islamic recent period List of archaeological sites by country == Sources == Paul Yule, Cross-roads – Early and Late Iron Age South-eastern Arabia, Abhandlungen Deutsche Orient-Gesellschaft, vol. 30, Wiesbaden, 2014, ISBN 978-3-447-10127-1; E-Book: ISBN 978-3-447-19287-3. == References ==


id: alfoldean-20260505-0
file: data/en.wikipedia.org/wiki/Alfoldean-0.md
category: reference
title: Alfoldean
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Alfoldean
date_saved: 2026-05-05T11:16:41.414734+00:00
instance: kb-cron
parent: alfoldean-20260505-0
summary:
Alfoldean was a Roman settlement founded in the Roman province of Britannia as a mansio on Stane Street where the road crosses the River Arun. Its remains are now near the village of Slinfold in West Sussex. They have been investigated by archaeologists including Samuel Edward Winbolt and Time Team. == References ==


id: amarna-letter-ea-5-20260505-0
file: data/en.wikipedia.org/wiki/Amarna_letter_EA_5-0.md
category: reference
title: Amarna letter EA 5
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Amarna_letter_EA_5
date_saved: 2026-05-05T11:16:42.606197+00:00
instance: kb-cron
parent: amarna-letter-ea-5-20260505-0
summary:
Amarna Letter EA5, one of the Amarna letters (cited with the abbreviation EA, for "El Amarna"), is a correspondence between Kadašman-Enlil I and Amenhotep III. The letter exists as two artifacts, one at the British Museum (BM29787) and one in the Cairo Museum (C12195). The letter is part of a series of correspondences from Babylonia to Egypt, which run from EA2 to EA4 and EA6 to EA14. EA1 and EA5 are from Egypt to Babylonia. == The letter == === EA 5: Gifts of Egyptian Furniture for the Babylonian Palace === EA 5, letter five of five, Pharaoh to Kadashman-Enlil. (Not a linear, line-by-line translation.) Obverse: (see British Museum) Paragraph 1 (Lines 1-12)--[Thus Nibmuar]ey[a1 Great King, the king of Egypt. Say to] Kadašman-Enlil, the king of Karadunniyaš,2 my brother: For m]e all goes (well). For you may all go well. For you]r [household, your] wives, [your sons, yo]ur [magnates], yo[ur] troops, [yo]ur [horses], your [chariots], and i[n your countries, may all go] well. [For me al]l goes well. For my household, [my] wives, [my sons], my magnates, my ma[ny] troops, my [horses], my chariots, and in [m]y [countries] all goes very, very well. Paragraph 2 (Lines 13-33)--I have [just]3 heard


id: amarna-letter-ea-6-20260505-0
file: data/en.wikipedia.org/wiki/Amarna_letter_EA_6-0.md
category: reference
title: Amarna letter EA 6
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Amarna_letter_EA_6
date_saved: 2026-05-05T11:16:43.764917+00:00
instance: kb-cron
parent: amarna-letter-ea-6-20260505-0
summary:
Amarna Letter EA6 is a correspondence from Burra-Buriyaš to Nimmuwarea(Amenhotep III) the king of Egypt. According to one source, this letter concerns gifts between two kings. The letter is part of a series of correspondences from Babylonia to Egypt, which run from EA2 to EA4 and EA6 to EA14. EA1 and EA5 are from Egypt to Babylonia. The inscription is translated as follows: Say to Nimmuwarea the king of Egypt my brother Thus Burra-Buriyaš the king of Karaduniyaš your brother For me all goes well For you your household your wives your sons your country your magnates your horses your chariots may all go well. Just as previously you and my father were friendly to one another you and I should be friendly to one another Between us anything else what-so-ever is not to be mentioned.Write to me for what you want from my country so that it may be taken to you and I will write to you of what I want from your country so that it may be taken to me...I will trust you...Write to me so that it may be taken to you, And as your greeting gift... and 1 ... I send you == See


id: amarna-letter-ea-11-20260505-0
file: data/en.wikipedia.org/wiki/Amarna_letter_EA_11-0.md
category: reference
title: Amarna letter EA 11
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Amarna_letter_EA_11
date_saved: 2026-05-05T11:16:44.970354+00:00
instance: kb-cron
parent: amarna-letter-ea-11-20260505-0
summary:
Amarna letter EA11 is a letter of correspondence to Akhenaten of Egypt from the king of Babylon, Burna-Buriash II. The tablet onto which letter EA11 is inscribed is badly damaged. The letter content suggests of the place Amarna having experienced an epidemic of some kind of plague. The letter (together with letter EA10) seems to undoubtedly indicate that Akhenaten married his daughters Meritaten and Ankhesenpaaten at a time when they were both 11 or 12 years of age. Meritaten is described as the mistress of the royal house within the text. The letter is part of a series of correspondences from Babylonia to Egypt, which run from EA2 to EA4 and EA6 to EA14. EA1 and EA5 are from Egypt to Babylonia. == See also == Amarna letters: EA 1, EA 2, EA 3, EA 4, EA 5, EA 6, EA 7, EA 8, EA 9, EA 10 == References ==


id: amarna-letter-ea-12-20260505-0
file: data/en.wikipedia.org/wiki/Amarna_letter_EA_12-0.md
category: reference
title: Amarna letter EA 12
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Amarna_letter_EA_12
date_saved: 2026-05-05T11:16:46.166570+00:00
instance: kb-cron
parent: amarna-letter-ea-12-20260505-0
summary:
Amarna letter EA12 is a correspondence written to the King of Egypt by a princess of Babylonia. A scribe named Kidin-Adad is mentioned within the letter. This letter is part of a series of correspondences from Babylonia to Egypt, which run from EA2 to EA4 and EA6 to EA14. EA1 and EA5 are from Egypt to Babylonia. During 1888 the Vorderasiatisches Museum received part of the tablet as part of a group of artifacts given to the museum by J.Simon. A second part of EA12 was given to the museum by Felix von Niemeyer. The letter, translated by W.L. Moran, reads: (1–6) Speak to my lord; thus the princess: To you, your ch[ariot]s, the [m]en and [your house] may it be well. (7–12) May the gods of Burraburiash go with you. Go safely and in peace go forward, see your house. (12–22) In the pre[sence of my lord], thu[s,] I [prostrate myself], saying, “Since G[...] my envoy has brought colored cloth, to your cities and your house, may it be ‹w›ell. Do not murmur in your heart and impose darkness on me.” Your servant, Kidin-Adad, is located with me(?), as the substitute of my lord, I would verily go. ==


id: amarna-letter-ea-27-20260505-0
file: data/en.wikipedia.org/wiki/Amarna_letter_EA_27-0.md
category: reference
title: Amarna letter EA 27
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Amarna_letter_EA_27
date_saved: 2026-05-05T11:16:47.378642+00:00
instance: kb-cron
parent: amarna-letter-ea-27-20260505-0
summary:
Amarna letter EA 27 is a letter addressed to Amenhotep IV and concerns "The Missing Gold Statues Again". The letter is dated to a period within the very beginning of the second regnal year of the pharaoh, and was written by Tushratta, who was living at Washukanni. At the time the pharaoh was located at Thebes. The letter is thought to contain a reference to a royal funeral. == See also == List of Amarna letters by size Amarna letter EA 5, EA 9, EA 15, EA 19, EA 26, EA 27, EA 35, EA 38 EA 153, EA 161, EA 288, EA 364, EA 365, EA 367 == References ==


id: amarna-letter-ea-248-20260505-0
file: data/en.wikipedia.org/wiki/Amarna_letter_EA_248-0.md
category: reference
title: Amarna letter EA 248
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Amarna_letter_EA_248
date_saved: 2026-05-05T11:16:48.539019+00:00
instance: kb-cron
parent: amarna-letter-ea-248-20260505-0
summary:
In Ancient Egypt, the Amarna Period (c. 1350 BC) saw diplomatic correspondence sent to the city of Akhetaten (Amarna), providing valuable insights into the political situations at the time. The Amarna Letter EA 248 (EA 248) is a fragmented letter by Yashdata, a displaced ruler, to the Pharaoh, also mentioning Biridiya of Megiddo. == Translated Text == Say [to] the king, my lord, Sun and god: Message of Ya(shd)ata, the loyal servant of the king and the dirt at the feet of the king. I fall at the feet of the king, my lord, Sun and god, 7 times and 7 times. [9-22] May the king, my lord, know that everything the king, my [l]ord, gave to [his] servant, the men of Than[ak]a [have m]ade off with; they have slaughtered my oxen and driven me away. So I am now with Biridiya. May the King, my lord, take cognizance of his servant. == Akkadian Text == EA 248 248:001 [a-na ]m.LUGAL-ri EN-ia 248:002 u d.UTU u DINGIR.MEß-ia 248:003 qí-bí-ma um-ma m.ya-a[$-d]a-ta 248:004 ÌR ki-it-ti LUGAL-ri 248:005 ù ip-ri GÌR.MEß LUGAL-ri 248:006 a-na GÌR.MEß LUGAL-ri 248:007 EN-ia u d.UTU u DINGIR.MEß-ia 248:008 7-$u u 7-ta-a-an am-qut 248:÷÷÷÷÷ 248:009 li-di-mi LUGAL-ru EN-ia


id: amarna-letter-ea-369-20260505-0
file: data/en.wikipedia.org/wiki/Amarna_letter_EA_369-0.md
category: reference
title: Amarna letter EA 369
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Amarna_letter_EA_369
date_saved: 2026-05-05T11:16:49.750582+00:00
instance: kb-cron
parent: amarna-letter-ea-369-20260505-0
summary:
Amarna letter EA 369 is a letter written on a clay tablet from the pharaoh to Milkilu of Gezer. The tablet is now housed in the Musées Royaux d'Art et d'Histoire, in Brussels. The letter is one of a small number of the Amarna Letters that were written in Egypt, and sent out from the pharaoh to vassals. Other Amarna letters sent to vassals included EA 99, 162, 163, 190, 367, and 370. == The letter == The letter details the king sending female cupbearers, silver, linen garments, carnelian, precious stones, an ebony chair, with a total value of 160 deben. It also states that he is sending forty female cupbearers, which are recorded as 40 silver each. Some linguistic features of the letter indicate that the scribe also may have been of Gezer origin. == Translation == The letter has been translated by Dossin (1934), Rainey (2014) and Moran (1992). Moran's (1992) translation is below: To Milkilu, the ruler of Gazru: Thus the king. He herewith dispatches to you this tablet, saying to you, He herewith sends to you Hanya, the stable <overseer> of the archers, along with everything for the acquisition of beautiful female cupbearers: 9—14 silver, gold,


id: amathus-sarcophagus-20260505-0
file: data/en.wikipedia.org/wiki/Amathus_sarcophagus-0.md
category: reference
title: Amathus sarcophagus
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Amathus_sarcophagus
date_saved: 2026-05-05T11:16:50.931128+00:00
instance: kb-cron
parent: amathus-sarcophagus-20260505-0
summary:
The Amathus sarcophagus is a Cypriot sarcophagus that likely held a king of Amathus. Its sides show procession scenes and typify Cypriot, Greek and Phoenician-Near Eastern styles of the mid-fifth century BCE. The sarcophagus was excavated by Luigi Palma di Cesnola and is currently located at the Metropolitan Museum of Art. == General references == == External links == Media related to Amathus sarcophagus at Wikimedia Commons Amathus sarcophagus in the Metropolitan Museum of Art site


id: ancient-egypt-magazine-20260505-0
file: data/en.wikipedia.org/wiki/Ancient_Egypt_(magazine)-0.md
category: reference
title: Ancient Egypt (magazine)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ancient_Egypt_(magazine)
date_saved: 2026-05-05T11:16:52.094402+00:00
instance: kb-cron
parent: ancient-egypt-magazine-20260505-0
summary:
Ancient Egypt is a magazine that deals with the subject of Egyptology. It is published bi-monthly. Ancient Egypt magazine is pitched somewhere between an academic journal and a travel magazine – bringing the spectacular sights of the ancient world together with the latest archaeological discoveries and theories from the world's leading authorities on the subject, illustrated with numerous photographs. The magazine has been published bi-monthly in the UK since April 2000. The contents concentrate mainly on a wide range of subjects related to ancient Egypt, though it does occasionally include items on Coptic or Islamic Egypt and also items of interest to visitors to Egypt. Edited by Peter Phillips, Ancient Egypt seeks to explain the mysteries of this ancient civilisation in a concise manner. One of the former editors was Robert Bernard Partridge who served in the post from 2004 to 2011. The magazine does not just deal with the past, but has a correspondent in Cairo who provides updates on the latest travel information and assesses the impact Egyptology has on modern Egypt. == References == == External links == Official website


id: ancient-warfare-magazine-20260505-0
file: data/en.wikipedia.org/wiki/Ancient_Warfare_(magazine)-0.md
category: reference
title: Ancient Warfare (magazine)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ancient_Warfare_(magazine)
date_saved: 2026-05-05T11:16:53.275823+00:00
instance: kb-cron
parent: ancient-warfare-magazine-20260505-0
summary:
Ancient Warfare is a glossy Dutch bi-monthly military history magazine. == History and profile == Ancient Warfare was started in 2007. It is published in Rotterdam by the Dutch publishing company Karwansaray. The magazine was founded by Jasper Oorthuys, who now serves as managing director and editor-in-chief. Most of the magazine's feature articles focus on a central theme per issue. These include articles on a specific general, campaign or more abstract phenomenon such as sieges. Each issue usually starts off with a historical introduction to the theme. The introduction is usually followed by an article that delves into relevant sources for the theme, such as a historical narrative or an archaeological source. The theme is then fleshed out by articles on warriors, battles and generals that fit that issue's theme. Among the authors are well-known specialists like Bob Bennett, Duncan B. Campbell, Ross Cowan, Lukas de Blois, Stephen English, Adrian Murdoch, Joseph Pietrykowski, Jona Lendering, and Mike Roberts. The magazine also includes news and letters from readers, as well as reviews of relevant books, games, models, and museums. The illustrations include original artwork, maps and photographs of artifacts. Online free features of the magazine include the editor's blog and a


