# kb

id: perpetual-motion-20260505-2
file: data/en.wikipedia.org/wiki/Perpetual_motion-2.md
category: reference
title: Perpetual motion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Perpetual_motion
date_saved: 2026-05-05T11:10:47.264034+00:00
instance: kb-cron
parent: perpetual-motion-20260505-0
summary:
Another theoretical machine involves a frictionless environment for motion. This involves the use of diamagnetic or electromagnetic levitation to float an object. This is done in a vacuum to eliminate air friction and friction from an axle. The levitated object is then free to rotate around its center of gravity without interference. However, this machine has no practical purpose because the rotated object cannot do any work as work requires the levitated object to cause motion in other objects, bringing friction into the problem. Furthermore, a perfect vacuum is an unattainable goal since both the container and the object itself would slowly vaporize, thereby degrading the vacuum. To extract work from heat, thus producing a perpetual motion machine of the second kind, the most common approach (dating back at least to Maxwell's demon) is unidirectionality. Only molecules moving fast enough and in the right direction are allowed through the demon's trap door. In a Brownian ratchet, forces tending to turn the ratchet one way are able to do so while forces in the other direction are not. A diode in a heat bath allows through currents in one direction and not the other. These schemes typically fail in two ways:


id: perpetual-motion-20260505-3
file: data/en.wikipedia.org/wiki/Perpetual_motion-3.md
category: reference
title: Perpetual motion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Perpetual_motion
date_saved: 2026-05-05T11:10:47.264034+00:00
instance: kb-cron
parent: perpetual-motion-20260505-0
summary:
The drinking bird toy functions using small ambient temperature gradients and evaporation. It runs until all water is evaporated. A capillary action-based water pump functions using small ambient temperature gradients and vapour pressure differences. With the "capillary bowl", it was thought that the capillary action would keep the water flowing in the tube, but since the cohesion force that draws the liquid up the tube in the first place holds the droplet from releasing into the bowl, the flow is not perpetual. A Crookes radiometer consists of a partial vacuum glass container with a lightweight propeller moved by (light-induced) temperature gradients. Any device picking up minimal amounts of energy from the natural electromagnetic radiation around it, such as a solar-powered motor. Any device powered by changes in air pressure, such as some clocks (Cox's timepiece, Beverly Clock). The motion leeches energy from moving air which in turn gained its energy from being acted on. A heat pump, due to it having a COP above 1: the energy it consumes as work is less than the energy it moves as heat. The Atmos clock uses changes in the vapor pressure of ethyl chloride with temperature to wind the clock spring. A


id: history-of-perpetual-motion-machines-20260505-0
file: data/en.wikipedia.org/wiki/History_of_perpetual_motion_machines-0.md
category: reference
title: History of perpetual motion machines
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/History_of_perpetual_motion_machines
date_saved: 2026-05-05T11:10:48.521981+00:00
instance: kb-cron
parent: history-of-perpetual-motion-machines-20260505-0
summary:
The history of perpetual motion machines dates at least back to the Middle Ages. For millennia, it was not clear whether perpetual motion devices were possible or not, but modern theories of thermodynamics have shown that they are impossible. Despite this, many attempts have been made to construct such machines, continuing into modern times. Modern designers and proponents sometimes use other terms, such as "overunity", to describe their inventions. == History == === Pre-19th century === There are some unsourced claims that a perpetual motion machine called the "magic wheel" (a wheel spinning on its axle powered by lodestones) appeared in 8th-century Bavaria. This historical claim appears to be unsubstantiated though often repeated. Early designs of perpetual motion machines were done by Indian mathematician–astronomer Bhaskara II, who described a wheel (Bhāskara's wheel) that he claimed would run forever. A drawing of a perpetual motion machine appeared in the sketchbook of Villard de Honnecourt, a 13th-century French master mason and architect. The sketchbook was concerned with mechanics and architecture. Following the example of Villard, Peter of Maricourt designed a magnetic globe which, if it were mounted without friction parallel to the celestial axis, would rotate once a day. It was intended


id: history-of-perpetual-motion-machines-20260505-1
file: data/en.wikipedia.org/wiki/History_of_perpetual_motion_machines-1.md
category: reference
title: History of perpetual motion machines
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/History_of_perpetual_motion_machines
date_saved: 2026-05-05T11:10:48.521981+00:00
instance: kb-cron
parent: history-of-perpetual-motion-machines-20260505-0
summary:
==== 1900 to 1950 ==== In 1900, Nikola Tesla claimed to have discovered an abstract principle on which to base a perpetual motion machine of the second kind. No prototype was produced. He wrote:A departure from known methods – possibility of a "self-acting" engine or machine, inanimate, yet capable, like a living being, of deriving energy from the medium – the ideal way of obtaining motive power. David Unaipon, Australian inventor, had a lifelong fascination with perpetual motion. One of his studies on Newtonian mechanics led him to create a shearing machine in 1910 that converted curvilineal motion into straight line movement. The device is the basis of modern mechanical shears. In the 1910s and 1920s, Harry Perrigo of Kansas City, Missouri, a graduate of MIT, claimed development of a free energy device. Perrigo claimed the energy source was "from thin air" or from aether waves. He demonstrated the device before the Congress of the United States on December 15, 1917. Perrigo had a pending application for the "Improvement in Method and Apparatus for Accumulating and Transforming Ether Electric Energy". Investigators report that his device contained a hidden motor battery. Popular Science, in the October 1920 issue, published an article


id: history-of-perpetual-motion-machines-20260505-2
file: data/en.wikipedia.org/wiki/History_of_perpetual_motion_machines-2.md
category: reference
title: History of perpetual motion machines
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/History_of_perpetual_motion_machines
date_saved: 2026-05-05T11:10:48.521981+00:00
instance: kb-cron
parent: history-of-perpetual-motion-machines-20260505-0
summary:
The motionless electromagnetic generator (MEG) was built by Tom Bearden. Allegedly, the device can eventually sustain its operation in addition to powering a load without application of external electrical power. Bearden claimed that it didn't violate the first law of thermodynamics because it extracted vacuum energy from the immediate environment. Critics dismiss this theory and instead identify it as a perpetual motion machine with an unscientific rationalization. Science writer Martin Gardner said that Bearden's physics theories, compiled in the self-published book Energy from the Vacuum, are considered "howlers" by physicists, and that his doctorate title was obtained from a diploma mill. Bearden then founded and directed the Alpha Foundation's Institute for Advanced Study (AIAS) to further propagate his theories. This group has published papers in established physics journals and in books published by leading publishing houses, but one analysis lamented these publications because the texts were "full of misconceptions and misunderstandings concerning the theory of the electromagnetic field." When Bearden was awarded U.S. patent 6,362,718 in 2002, the American Physical Society issued a statement against the granting. The United States Patent and Trademark Office said that it would reexamine the patent and change the way it recruits examiners, and re-certify


id: johann-bessler-20260505-0
file: data/en.wikipedia.org/wiki/Johann_Bessler-0.md
category: reference
title: Johann Bessler
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Johann_Bessler
date_saved: 2026-05-05T11:10:49.735647+00:00
instance: kb-cron
parent: johann-bessler-20260505-0
summary:
Johann Ernst Elias Bessler (ca. 1680 – 30 November 1745), known as Orffyreus or Orffyré, was a German entrepreneur who claimed to have built several perpetual motion machines. Those claims generated considerable interest and controversy among some of the leading natural philosophers of the day, including Gottfried Wilhelm Leibniz, Johann Bernoulli, John Theophilus Desaguliers, and Willem 's Gravesande. The modern scientific consensus is that Bessler perpetrated a deliberate fraud, although the details of this have not been satisfactorily explained. == Life and career == Bessler was born to a peasant family in Upper Lusatia, in the German Electorate of Saxony, circa 1680. He went to school in Zittau, where (according to his own account) he excelled in his studies and became a favorite of Christian Weise, the rector of the local Gymnasium. After he left school he began to travel widely, seeking his fortune. Having saved an alchemist from drowning in a well, he was rewarded with instruction on the fabrication of elixirs. After that Bessler earned his living as a healer and an unlicensed physician. He was also an apprentice watchmaker, until his fortunes improved when he married the wealthy daughter of the physician and mayor of Annaberg, Dr.


id: johann-bessler-20260505-1
file: data/en.wikipedia.org/wiki/Johann_Bessler-1.md
category: reference
title: Johann Bessler
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Johann_Bessler
date_saved: 2026-05-05T11:10:49.735647+00:00
instance: kb-cron
parent: johann-bessler-20260505-0
summary:
== Mechanism of Orffyreus's Wheel == Bessler's devices were all hollow wheels, with canvas covering the internal mechanism, that turned on a horizontal axis supported by vertical wooden beams on either side of the wheel. Christian Wolff, who viewed the wheel in 1715, wrote that Bessler freely revealed that the device utilized weights of about 1.8 kg (4 pounds). Fischer von Erlach, who viewed the wheel in 1721, reported: "At every turn of the wheel can be heard the sound of about eight weights, which fall gently on the side toward which the wheel turns." In a letter to Sir Isaac Newton, 's Gravesande reported that, when pushed, the wheel took two or three revolutions to reach a maximum speed of about 25 revolutions per minute. The wheels at Merseburg and Kassel were attached to three-bobbed pendula, one on either side, which presumably acted as regulators, limiting the maximum speed of revolution. Bessler never revealed the mechanism that kept his wheel in motion and, according to surviving sources, the Landgrave of Hesse-Kassel was the only person whom he ever allowed to examine the inside of the wheel. In 1719 Bessler published a pamphlet in German and Latin, entitled The Triumphant


id: bh-skara-s-wheel-20260505-0
file: data/en.wikipedia.org/wiki/Bhāskara's_wheel-0.md
category: reference
title: Bhāskara's wheel
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Bhāskara's_wheel
date_saved: 2026-05-05T11:10:50.902672+00:00
instance: kb-cron
parent: bh-skara-s-wheel-20260505-0
summary:
Bhāskara's wheel was a hypothetical perpetual-motion machine design created around 1150 CE by the Indian mathematician Bhāskara II. The wheel consisted of curved or tilted spokes partially filled with mercury. Once in motion, the mercury would flow from one side of the spoke to another, thus forcing the wheel to continue motion, in constant dynamic equilibrium. Like all perpetual-motion machines, Bhaskara's wheel is a long-discredited mechanism. To truly overbalance the wheel (so that torque in one direction is greater than the other) and cause motion, the radius of the spokes would have to be altered throughout the course of the wheel's motion. This would have to be done actively, thus consuming energy in the process — and so the machine would cease to be a perpetual-motion engine. It's also important to consider the wheel as it moves, as it can be placed into an overbalanced position so that the math makes it appear that there is an overall torque. It is perfectly possible for the wheel to exert a motion if it is placed off balance (much in the same way a pendulum will swing if moved out of a perfectly vertical position), but that motion does not continue indefinitely


id: brownian-ratchet-20260505-0
file: data/en.wikipedia.org/wiki/Brownian_ratchet-0.md
category: reference
title: Brownian ratchet
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Brownian_ratchet
date_saved: 2026-05-05T11:10:52.112794+00:00
instance: kb-cron
parent: brownian-ratchet-20260505-0
summary:
In the philosophy of thermal and statistical physics, the Brownian ratchet or Feynman–Smoluchowski ratchet is an apparent perpetual motion machine of the second kind (converting thermal energy into mechanical work), first analysed in 1912 as a thought experiment by Polish physicist Marian Smoluchowski. It was popularised by American Nobel laureate physicist Richard Feynman in a physics lecture at the California Institute of Technology on May 11, 1962, during his Messenger Lectures series The Character of Physical Law in Cornell University in 1964 and in his text The Feynman Lectures on Physics as an illustration of the laws of thermodynamics. The simple machine, consisting of a tiny paddle wheel and a ratchet, appears to be an example of a Maxwell's demon, able to extract mechanical work from random fluctuations (heat) in a system at thermal equilibrium, in violation of the second law of thermodynamics. Detailed analysis by Feynman and others showed why it cannot actually do this. == The machine == The device consists of a gear known as a ratchet that rotates freely in one direction but is prevented from rotating in the opposite direction by a pawl. The ratchet is connected by an axle to a paddle wheel that


id: brownian-ratchet-20260505-1
file: data/en.wikipedia.org/wiki/Brownian_ratchet-1.md
category: reference
title: Brownian ratchet
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Brownian_ratchet
date_saved: 2026-05-05T11:10:52.112794+00:00
instance: kb-cron
parent: brownian-ratchet-20260505-0
summary:
== History == The ratchet and pawl was first discussed as a second law-violating device by Gabriel Lippmann in 1900. In 1912, Polish physicist Marian Smoluchowski gave the first correct qualitative explanation of why the device fails; thermal motion of the pawl allows the ratchet's teeth to slip backwards. Feynman did the first quantitative analysis of the device in 1962 using the Maxwell–Boltzmann distribution, showing that if the temperature of the paddle T1 was greater than the temperature of the ratchet T2, it would function as a heat engine, but if T1 = T2 there would be no net motion of the paddle. In 1996, J. M. R. Parrondo and Pep Español used a variation of the above device in which no ratchet is present, only two paddles, to show that the axle connecting the paddles and ratchet conducts heat between reservoirs; they argued that although Feynman's conclusion was correct, his analysis was flawed because of his erroneous use of the quasistatic approximation, resulting in incorrect equations for efficiency. Marcelo Osvaldo Magnasco and Gustavo Stolovitzky (1998) extended this analysis to consider the full ratchet device, and showed that the power output of the device is far smaller than the Carnot


id: cox-s-timepiece-20260505-0
file: data/en.wikipedia.org/wiki/Cox's_timepiece-0.md
category: reference
title: Cox's timepiece
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cox's_timepiece
date_saved: 2026-05-05T11:10:53.302768+00:00
instance: kb-cron
parent: cox-s-timepiece-20260505-0
summary:
Cox's timepiece is a clock developed in the 1760s by James Cox. It was developed in collaboration with John Joseph Merlin (with whom Cox also worked on developing automata). Cox claimed that his design was a true perpetual motion machine, but as the device is powered from changes in atmospheric pressure via a mercury barometer, this is not the case. The clock still exists, but was deactivated at the time of its relocation to the Victoria and Albert Museum in London. == Design and history == The clock is similar to other mechanical clocks, except that it does not need winding. The change of pressure in the Earth's atmosphere acts as an external energy source and causes sufficient movement of the winding mechanism. This keeps the mainspring coiled inside the barrel. The clock is designed to enable the timepiece to run indefinitely and overwinding is prevented by a safety mechanism. The prime mover, encased in a finely detailed clock body, is a Fortin mercury barometer. The barometer contained 68 kilograms (150 pounds) of mercury (approximately 5 litres). == Similar clocks == A similar design is Cornelis Drebbel's circa 1610 device that told the time, date, and season. The gold machine


id: garabed-t-k-giragossian-20260505-0
file: data/en.wikipedia.org/wiki/Garabed_T._K._Giragossian-0.md
category: reference
title: Garabed T. K. Giragossian
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Garabed_T._K._Giragossian
date_saved: 2026-05-05T11:10:54.499920+00:00
instance: kb-cron
parent: garabed-t-k-giragossian-20260505-0
summary:
Garabed T. K. Giragossian was an Armenian living in Boston who is remembered for developing a perpetual motion device shortly after the turn of the 20th century. He immigrated to America in 1891. In 1917, Giragossian claimed, reportedly fraudulently, to have developed a "free energy machine". The assignment of the patent to the United States government was conditionally accepted in Pub. Res. 65-21, 40 Stat. 435, enacted on February 8, 1918, and authorized the Secretary of the Interior to form a scientific committee to investigate the machine. The committee issued a report on July 1, 1918 finding that the principles were not sound. According to an editorial in the Scientific American in 1918, Giragossian claimed that the machine, named Garabed, took energy out of the cosmos and turned it into mechanical motion. Editors of the Journal of the American Medical Association compared him and his methods with quacks in the medical world; they pointed out that he could not answer the question what qualifications he had to undertake his work, and that he repeatedly only replied, he was an honest man and that he could prove it with signatures of friends and sponsors. They deplored the waste of time of


id: incredible-utility-20260505-0
file: data/en.wikipedia.org/wiki/Incredible_utility-0.md
category: reference
title: Incredible utility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Incredible_utility
date_saved: 2026-05-05T11:10:55.660767+00:00
instance: kb-cron
parent: incredible-utility-20260505-0
summary:
In United States patent law, incredible utility is a concept according to which, in order for an invention to be patentable, it must have some credible useful function. If it does not have a credible useful function despite the assertions of the inventor, then the application for patent can be rejected as having "incredible utility". The invention does not have to work the way the inventor thinks it works, but it must do something useful. Patents that have been held invalid for incredible utility include: an invention asserted to change the taste of food using a magnetic field (Fregeau v. Mossinghoff, 776 F.2d 1034, 227 USPQ 848 (Fed. Cir. 1985)), a perpetual motion machine (Newman v. Quigg, 877 F.2d 1575, 11 USPQ2d 1340 (Fed. Cir. 1989)), a flying machine operating on "flapping or flutter function" (In re Houghton, 433 F.2d 820, 167 USPQ 687 (CCPA 1970)), a cold fusion process for producing energy (In re Swartz, 232 F.3d 862, 56 USPQ2d 1703, (Fed. Cir. 2000)), a method for increasing the energy output of fossil fuels upon combustion through exposure to a magnetic field (In re Ruskin, 354 F.2d 395, 148 USPQ 221 (CCPA 1966)), uncharacterized compositions for curing a wide


id: infinite-energy-magazine-20260505-0
file: data/en.wikipedia.org/wiki/Infinite_Energy_(magazine)-0.md
category: reference
title: Infinite Energy (magazine)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Infinite_Energy_(magazine)
date_saved: 2026-05-05T11:10:56.880702+00:00
instance: kb-cron
parent: infinite-energy-magazine-20260505-0
summary:
Infinite Energy: The Magazine of New Energy Technology, more commonly referred to simply as Infinite Energy, is a bi-monthly magazine published in New Hampshire that details theories and experiments concerning alternative energy, new science and new physics. The phrase "new energy" in the subtitle is a euphemism for perpetual motion. The magazine was founded by Eugene Mallove, who was its editor-in-chief, and is owned by the non-profit New Energy Foundation. It was established in 1994 as Cold Fusion magazine and changed its name in March 1995. Topics of interest include "new hydrogen physics," also called cold fusion; vacuum energy, or zero point energy; and so-called "environmental energy" which they define as the attempt to violate the Second Law of Thermodynamics, for example with a perpetual motion machine Archived March 6, 2009, at the Wayback Machine. This is done in pursuit of the founder's commitment to "unearthing new sources of energy and new paradigms in science." The magazine has also published articles and book reviews that are critical of the Big Bang theory that describes the origin of the universe. The magazine had a print run of 3,000, and is available on U.S. newsstands. The issues ranged in size from 48


id: magnet-motor-20260505-0
file: data/en.wikipedia.org/wiki/Magnet_motor-0.md
category: reference
title: Magnet motor
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Magnet_motor
date_saved: 2026-05-05T11:10:58.157864+00:00
instance: kb-cron
parent: magnet-motor-20260505-0
summary:
A magnet motor or magnetic motor is a type of perpetual motion machine, which is intended to generate a rotation by means of permanent magnets in stator and rotor without external energy supply. Such a motor is theoretically as well as practically not realizable. The idea of functioning magnetic motors has been promoted by various hobbyists. It can be regarded as pseudoscience. There are frequent references to free energy and sometimes even links to esotericism. Magnet motors are not to be confused with the commonly used permanent magnet motors, which are powered from an external electrical energy supply. == Working principle == A hypothetical magnet motor works with permanent magnets in stator and rotor. By a special arrangement of the attracting and repelling poles, a rotational movement of the rotor is supposedly permanently maintained. Practical implementations fail because there is no substantial energy in magnets that could be employed for propulsion or to compensate for energy losses. The force between permanent magnets is conservative as the magnetic field follows a potential, so that there is no work done over a closed cycle. After a short amount of time, such a motor will stop moving and assume an equilibrium position. Rationalizations


id: stefan-marinov-20260505-0
file: data/en.wikipedia.org/wiki/Stefan_Marinov-0.md
category: reference
title: Stefan Marinov
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Stefan_Marinov
date_saved: 2026-05-05T11:10:59.391675+00:00
instance: kb-cron
parent: stefan-marinov-20260505-0
summary:
Stefan Marinov (Bulgarian: Стефан Маринов) (1 February 1931 – 15 July 1997) was a Bulgarian physicist, researcher, writer, and lecturer who promoted anti-relativistic theoretical viewpoints and later in his life defended the ideas of perpetual motion and free energy. In 1997, he self-published experimental results that confirmed classical electromagnetism and disproved that a machine he had constructed could be a source of perpetual motion. == Life and education == Marinov was born on 1 February 1931 in Sofia to a family of intellectual communists. In 1948, Marinov finished Soviet College in Prague, then studied physics at the Czech Technical University in Prague and Sofia University. Marinov was an Assistant Professor of Physics from 1960 to 1974 at Sofia University. In 1966–67, 1974, and 1977, Marinov was subject to compulsory psychiatric treatment in Sofia because of his political dissent. In September 1977, Marinov received a passport and successfully emigrated out of the country, moving to Brussels. In 1978, Marinov moved to Washington, D.C. Later he lived in Italy and Austria. In his later years, Marinov earned a living as a horse groom. == Work == One of Marinov's interests was the quest for free energy sources via the construction of toy


id: mathematicall-magick-20260505-0
file: data/en.wikipedia.org/wiki/Mathematicall_Magick-0.md
category: reference
title: Mathematicall Magick
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mathematicall_Magick
date_saved: 2026-05-05T11:11:00.618332+00:00
instance: kb-cron
parent: mathematicall-magick-20260505-0
summary:
Mathematicall Magick. Or, The Wonders that may be Performed by Mechanicall Geometry is a treatise by the English clergyman, natural philosopher, polymath and author John Wilkins (1614–1672). It was first published in 1648 in London; another edition was printed in 1680 and further editions were published in 1691 and 1707. The work is dedicated to Charles I Louis, the Elector Palatine. The first book describes traditional mechanical devices, speed, siege engines and the modern guns of Wilkins' era. The second book covers Wilkins' theories and observations on land yachts, submarines, flying machines, and perpetual motion. Wilkins thought that human aviation is feasible, if only sufficient exercise, research and development is directed towards it. He envisioned flying machines that would be large enough to carry several people. The book repeats tales about early attempts at human flight, including Busbequius' 16th-century reports about Turkish flight experiments in Constantinople. Wilkins also mentions Anglo-Saxon flight experiments during the reign of Edward the Confessor. The researcher called "Elmerus" in the text is probably Eilmer of Malmesbury, who experimented with gliding flight in the 11th century. == Abstract == Wilkins dedicated his work to His Highness the Prince Elector Palatine (Charles I Louis) who was in


id: maxwell-s-demon-20260505-0
file: data/en.wikipedia.org/wiki/Maxwell's_demon-0.md
category: reference
title: Maxwell's demon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Maxwell's_demon
date_saved: 2026-05-05T11:11:01.829049+00:00
instance: kb-cron
parent: maxwell-s-demon-20260505-0
summary:
Maxwell's demon is a thought experiment that appears to disprove the second law of thermodynamics. It was proposed by the physicist James Clerk Maxwell in 1867. In his first letter, Maxwell referred to the entity as a "finite being" or a "being who can play a game of skill with the molecules". Lord Kelvin would later call it a "demon". In the thought experiment, a demon controls a door between two chambers containing gas. As individual gas molecules (or atoms) approach the door, the demon quickly opens and closes the door to allow only fast-moving molecules to pass through in one direction, and only slow-moving molecules to pass through in the other. Because the kinetic temperature of a gas depends on the velocities of its constituent molecules, the demon's actions cause one chamber to warm up and the other to cool down. This would decrease the total entropy of the system, seemingly without applying any work, thereby violating the second law of thermodynamics. The concept of Maxwell's demon has provoked substantial debate in the philosophy of science and theoretical physics, which continues to the present day. It stimulated work on the relationship between thermodynamics and information theory. Most scientists argue


id: maxwell-s-demon-20260505-1
file: data/en.wikipedia.org/wiki/Maxwell's_demon-1.md
category: reference
title: Maxwell's demon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Maxwell's_demon
date_saved: 2026-05-05T11:11:01.829049+00:00
instance: kb-cron
parent: maxwell-s-demon-20260505-0
summary:
== Criticism and development == Several physicists have calculated that the second law of thermodynamics is not actually violated under a more complete analysis of the whole system, including the demon. The essence of the physical argument is to show, by calculation, that any demon must "generate" more entropy segregating the molecules than it could ever eliminate by the method described. That is, it would take more thermodynamic work to gauge the speed of the molecules and selectively allow them to pass through the opening between A and B than the amount of energy gained by the difference of temperature caused by doing so. One of the most famous responses to this question was suggested in 1929 by Leó Szilárd, and later by Léon Brillouin. Szilárd pointed out that a real-life Maxwell's demon would need to have some means of measuring molecular speed, and that the act of acquiring information would require an expenditure of energy. Since the demon and the gas are interacting, the total entropy of the gas and the demon combined must be considered. The expenditure of energy by the demon causes an increase in the entropy of the demon that is larger than the lowering of


id: maxwell-s-demon-20260505-2
file: data/en.wikipedia.org/wiki/Maxwell's_demon-2.md
category: reference
title: Maxwell's demon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Maxwell's_demon
date_saved: 2026-05-05T11:11:01.829049+00:00
instance: kb-cron
parent: maxwell-s-demon-20260505-0
summary:
== Experimental work == In 2007, David Leigh announced the creation of a nano-device based on the Brownian ratchet popularized by Richard Feynman. Leigh's device is able to drive a chemical system out of equilibrium, but it must be powered by an external source (light in this case) and therefore does not violate thermodynamics. Previously, researchers including Nobel Prize winner Fraser Stoddart had created ring-shaped molecules called rotaxanes, which could be placed on an axle connecting two sites, A and B. Particles from either site would bump into the ring and move it from end to end. If a large collection of these devices were placed in a system, half of the devices had the ring at site A and half at B, at any given moment in time. Leigh made a minor change to the axle so that if a light is shone on the device, the center of the axle thickens, restricting the motion of the ring. It keeps the ring from moving, however, only if it is at A. Over time, therefore, the rings are bumped from B to A and get stuck there, creating an imbalance in the system. In his experiments, Leigh was able to


id: maxwell-s-demon-20260505-3
file: data/en.wikipedia.org/wiki/Maxwell's_demon-3.md
category: reference
title: Maxwell's demon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Maxwell's_demon
date_saved: 2026-05-05T11:11:01.829049+00:00
instance: kb-cron
parent: maxwell-s-demon-20260505-0
summary:
How Maxwell's Demon Continues to Startle Scientists Bennett, C. H. (1987) "Demons, Engines and the Second Law", Scientific American, November, pp108-116 Binder, P.-M. (2008). "Reflections on a Wall of Light". Science. 322 (5906): 1334–1335. doi:10.1126/science.1166681. PMID 19039125. S2CID 42821883. Earman, J. & Norton, J. (1998). "Exorcist XIV: The Wrath of Maxwell's Demon. Part I. From Maxwell to Szilard" (PDF). Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics. 29 (4): 435–471. Bibcode:1998SHPMP..29..435E. doi:10.1016/S1355-2198(98)00023-9. Earman, J. & Norton, J. (1999). "Exorcist XIV: The Wrath of Maxwell's Demon. Part II. From Szilard to Landauer and Beyond" (PDF). Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics. 30 (1): 1–40. Bibcode:1999SHPMP..30....1E. doi:10.1016/s1355-2198(98)00026-4. Feynman, R. P.; et al. (1996). Feynman Lectures on Computation. Addison-Wesley. pp. 148–150. ISBN 978-0-14-028451-5. Jordy, W. H. (1952). Henry Adams: Scientific Historian. New Haven. ISBN 978-0-685-26683-0. {{cite book}}: ISBN / Date incompatibility (help) Khan, Salman. "Maxwell's Demon". Archived from the original on 2010-03-17. Maroney, O. J. E. (2009) ""Information Processing and Thermodynamic Entropy" The Stanford Encyclopedia of Philosophy (Autumn 2009 Edition) Maxwell, J. C. (1871). Theory of Heat. London, New York [etc.] Longmans, Green.,


id: methernitha-20260505-0
file: data/en.wikipedia.org/wiki/Methernitha-0.md
category: reference
title: Methernitha
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Methernitha
date_saved: 2026-05-05T11:11:03.031957+00:00
instance: kb-cron
parent: methernitha-20260505-0
summary:
Methernitha refers to two related entities, both founded by Paul Baumann — Methernitha Christian Alliance and Methernitha Cooperative. One is a religious group, and the other is a community in Linden, Switzerland, based on the group's principles. == Organizations == === The religious group === The Methernitha Christian Alliance exists as a loose association of members who subscribe to the teachings of the Holy Scriptures. Members do not have organized meetings, nor do they necessarily live in the same area. Current members are distributed throughout Switzerland and other countries. The Alliance was founded in the 1950s by a small group of Christian oriented people whose goal was to live according to the teachings of the Bible. Eventually the group founded a commune in Linden in the canton of Bern. === The community === Originally based on the principles of the Methernitha Christian Alliance, the Methernitha Cooperative is now more philosophically inclusive and in 1960 was registered with the Swiss Commercial Register as a legal entity. The organisation was laid down in Articles of Association and adheres to the Rules of the Swiss Federation. The Cooperative is a residential joint venture work group operated on a democratic basis. Administration staff are


id: joseph-westley-newman-20260505-0
file: data/en.wikipedia.org/wiki/Joseph_Westley_Newman-0.md
category: reference
title: Joseph Westley Newman
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Joseph_Westley_Newman
date_saved: 2026-05-05T11:11:04.160020+00:00
instance: kb-cron
parent: joseph-westley-newman-20260505-0
summary:
Joseph Westley Newman (July 2, 1936 – March 6, 2015) was an American inventor and author who developed an "energy machine" which he attempted to patent, but was rejected by the US Patent and Trademark Office on grounds of being a perpetual motion machine. He described this device in a book, The Energy Machine of Joseph Newman. Newman alleged that he had a mechanical explanation for Albert Einstein's unified field theory of physics. After applying for patents on the perpetual motion motor, he battled for over seven years against what he claimed was a government conspiracy to suppress his supposed discoveries, garnering national attention as a result. Further testing revealed that the machine did not operate at 100% efficiency, nor did it output more energy than was input, as Newman claimed. == Early life == After Newman graduated from Baker High School in Mobile, Alabama, he joined the U.S. Air Force in 1955 to serve as an expediter, and was stationed at Ramey Air Force Base in Puerto Rico where he witnessed Hurricane Betsy devastate the island in 1956. The aftermath of the hurricane prompted Newman to make a pledge to God that he would devote the rest of his


id: newman-s-energy-machine-20260505-0
file: data/en.wikipedia.org/wiki/Newman's_energy_machine-0.md
category: reference
title: Newman's energy machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Newman's_energy_machine
date_saved: 2026-05-05T11:11:05.406275+00:00
instance: kb-cron
parent: newman-s-energy-machine-20260505-0
summary:
Newman's Energy Machine was a DC motor which the inventor, Joseph Newman, claimed to produce mechanical power exceeding the electrical power being supplied to it. In 1979, Newman attempted to patent the device, but it was rejected by the United States Patent Office as being a perpetual motion machine. When the rejection was later appealed, the United States district court requested that Newman's machine be tested by the National Bureau of Standards (NBS). The NBS concluded in June 1986 that output power was not greater than the input. Thus, the patent was again denied. The scientific community has rejected Newman's ideas about electricity and magnetism as pseudoscientific and his claims as false. == Claims by the inventor == By adding rolls to the armature of a motor, a larger and larger counter-electromotive force is generated on the motor. Newman outlined his claims about there being a fundamental electromagnetic interaction in all matter ultimately derived from only one type of force particle propagating at the speed of light. Newman claims that the motor derives its power by converting some of the mass of the copper in the coils into usable energy, in application of Einstein's mass–energy equivalence. According to proponents of


id: perepiteia-20260505-0
file: data/en.wikipedia.org/wiki/Perepiteia-0.md
category: reference
title: Perepiteia
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Perepiteia
date_saved: 2026-05-05T11:11:06.645018+00:00
instance: kb-cron
parent: perepiteia-20260505-0
summary:
Perepiteia is claimed to be a new generator developed by the Canadian inventor Thane Heins. The device is named after the Greek word for peripety, a dramatic reversal of circumstances or turning point in a story. The device was quickly attributed the term "perpetual motion machine" by several media outlets. Due to the long history of hoaxes and failures of perpetual motion machines and the incompatibility of such a device with accepted principles of physics, Heins' claims about Perepiteia have been treated with considerable skepticism. In 2003, Heins filed a patent application in Canada but no patent was granted. Heins also founded Potential Difference Inc, the website of which contains a series of videos of the inventor demonstrating the machine. US patent #9,230,730 issued in 2016 pertaining to another of Thane's inventions, a bi-toroidal topology transformer. Heins has recently stated that he is unsure whether or not the machine really produces energy, but in communications with science writer David Bradley of ScienceBase, Heins made claims of up to 7000% efficiency for the bi-toroidal transformer. Heins, who reportedly works 8–12 hours a day on the Perepiteia, insists that it is viable and that "This technology should be mainstream." == Theory ==


id: reactionless-drive-20260505-0
file: data/en.wikipedia.org/wiki/Reactionless_drive-0.md
category: reference
title: Reactionless drive
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reactionless_drive
date_saved: 2026-05-05T11:11:07.898688+00:00
instance: kb-cron
parent: reactionless-drive-20260505-0
summary:
Reactionless drive refers to hypothetical and unproven forms of spacecraft propulsion that would generate thrust without expelling propellant or other reaction mass. A propellantless drive is not necessarily reactionless if it functions as an open system interacting with external fields, but a reactionless drive is generally conceived as a self-contained or closed-system device, which is why such claims are commonly treated as conflicting with Newton's third law and the conservation of momentum. Reactionless-drive claims are therefore often compared to perpetual motion machines or other impossible-energy schemes if their reported performance is taken at face value. The expression has been in English-language newspaper use since at least 1963 and later became a recurring public label for alleged no-propellant engines. Concepts described this way have included the Dean drive, electrogravitics and lifters, gyroscopic and oscillation devices, microwave-cavity thrusters such as the EmDrive and Cannae drive, the helical engine, Mach-effect or MEGA drives, quantum drive claims, and the quantum vacuum thruster. No reactionless drive has become an accepted propulsion technology, and reported effects from devices such as a thrusting antenna and the EmDrive have later been described as null results, below photon-thrust limits, or experimental artifacts rather than evidence of new physics. Speculative


id: reactionless-drive-20260505-1
file: data/en.wikipedia.org/wiki/Reactionless_drive-1.md
category: reference
title: Reactionless drive
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reactionless_drive
date_saved: 2026-05-05T11:11:07.898688+00:00
instance: kb-cron
parent: reactionless-drive-20260505-0
summary:
== History and terminology == In English-language popular writing, a reactionless drive is generally described as a hypothetical propulsion concept that would generate thrust without expelling propellant or reaction mass. These explanations usually define the term by contrast with ordinary rockets, which move by throwing exhaust out the back, whereas a reactionless drive would supposedly produce forward motion without that reaction mass exchange. The term has often been used for electrically powered or internally driven concepts said to convert stored energy directly into thrust, including microwave-cavity devices, inertial schemes, and other self-contained engine proposals. In this usage, the core claim is not merely low-propellant propulsion but propulsion without expelled mass, which is why these articles repeatedly tie the idea to Newton's third law and the conservation of momentum. Several of these sources also describe reactionless-drive claims as bordering on perpetual-motion or free-energy arguments if the reported thrust and power figures were accepted at face value. Some writers have treated reactionless drives as a long-running science fiction trope as much as a technical claim, tying their appeal to the rocket equation and to the desire for a space engine that avoids the mass penalties of conventional rocketry. Winchell Chung, creator of


id: reactionless-drive-20260505-2
file: data/en.wikipedia.org/wiki/Reactionless_drive-2.md
category: reference
title: Reactionless drive
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reactionless_drive
date_saved: 2026-05-05T11:11:07.898688+00:00
instance: kb-cron
parent: reactionless-drive-20260505-0
summary:
The Dean drive was a claimed reactionless device built by Norman L. Dean, who said that his working models functioned as a "reactionless thruster". The Dean drive received extensive promotion from John W. Campbell in Astounding Science Fiction beginning in 1960. Dean held several private demonstrations but never revealed the exact design of the models nor allowed independent analysis of them. Campbell published photographs of the device operating on a bathroom scale, and the June 1960 cover of Astounding featured a painting of a United States submarine near Mars supposedly propelled by a Dean drive. In 1984, physicist Amit Goswami wrote that the Dean drive had become so embedded in genre consciousness that "it is now customary in SF (science fiction) circles to refer to a reactionless drive as a Dean drive". The Visual Encyclopedia of Science Fiction catalogued the Dean drive as a distinct propulsion concept for space travel in the genre. Dean's claims of reactionless thrust generation were later argued to be mistaken, with the apparent "thrust" likely caused by friction between the device and the surface on which it rested rather than any effect that would operate in free space. === Electrogravitics and lifters === Electrogravitics began


id: reactionless-drive-20260505-3
file: data/en.wikipedia.org/wiki/Reactionless_drive-3.md
category: reference
title: Reactionless drive
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reactionless_drive
date_saved: 2026-05-05T11:11:07.898688+00:00
instance: kb-cron
parent: reactionless-drive-20260505-0
summary:
James F. Woodward's Mach-effect propulsion program grew out of his long interest in using Mach's principle to pursue propellantless propulsion. By 1995, according to a later Wired profile, Woodward's ideas about Mach effects had coalesced into a full theory, and he turned to building a thruster based on stacks of piezoelectric disks that he believed could exploit tiny transient mass fluctuations. Earlier conference literature framed the work in propellantless-propulsion terms: Thomas L. Mahood's 1999 AIP conference paper was titled Propellantless propulsion: Recent experimental results exploiting transient mass modification, while a 2006 AIP paper by Paul March and Andrew Palfreyman described the Woodward effect as a transient mass fluctuation in energy-storing ions and reported experimental verification efforts at 2 to 4 MHz. By 2020, the device was being referred to publicly as the Mach Effect Gravitational Assist, or MEGA, drive. Wired reported that Woodward and Hal Fearn secured NIAC funding in 2017 and used it to develop improved thrusters and the conceptual SSI Lambda interstellar probe. The same report described the device as an electricity-powered propulsion system designed to operate without propellant, while also noting mixed test results, the small scale of the reported forces, and the need for independent replication


id: reactionless-drive-20260505-4
file: data/en.wikipedia.org/wiki/Reactionless_drive-4.md
category: reference
title: Reactionless drive
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reactionless_drive
date_saved: 2026-05-05T11:11:07.898688+00:00
instance: kb-cron
parent: reactionless-drive-20260505-0
summary:
=== Quantum vacuum thruster === The Q-thruster, or Quantum Vacuum Plasma Thruster, was a proposed propulsion concept associated with Harold G. White's Eagleworks Laboratories program (also called the Advanced Propulsion Physics Laboratory) at NASA's Johnson Space Center. In a 2011 Eagleworks presentation, White and his coauthors said the laboratory would commission its torsion pendulum with an existing Quantum Vacuum Plasma Thruster and described earlier QVPT work as suggesting very high specific impulse and specific force, with speculative applications ranging from human Mars missions to one-year Neptune transits at higher power levels. In a 2013 NASA brief, White described Q-thrusters as a low-TRL form of electric propulsion that would "push off of the quantum vacuum" using magnetohydrodynamics, treating the vacuum as a sea of virtual particles, and argued that recent model development and test data suggested performance competitive for in-space propulsion. NASA project summaries in 2014 for the Q-Thruster Breadboard Campaign said three FY13 test campaigns had produced measurable thrust, raising the concept from TRL 2 to early TRL 3, and described the technology as a mission-enabling form of electric propulsion with about seven times the thrust-to-power ratio of Hall thrusters and a target of 0.4 N/kW at maturity. B. Kent


id: charles-redheffer-20260505-0
file: data/en.wikipedia.org/wiki/Charles_Redheffer-0.md
category: reference
title: Charles Redheffer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Charles_Redheffer
date_saved: 2026-05-05T11:11:09.124357+00:00
instance: kb-cron
parent: charles-redheffer-20260505-0
summary:
Charles Redheffer was an American inventor who claimed to have invented a perpetual motion machine. First appearing in Philadelphia, Redheffer exhibited his machine to the public, charging high prices for viewing. When he applied to the government for more money, a group of inspectors were sent to examine the machine. It was discovered the machine was actually powered by a device Redheffer claimed was powered by the machine. Redheffer moved to New York City and set up a similar scam after rebuilding his machine. However, an engineer detected that it was a fake by listening to its unsteady motions at an exhibition. He discovered that the machine was operated by a man using a crank in a room on the floor above. Redheffer returned to Philadelphia. He later claimed to have created another machine, but refused to demonstrate it to anyone. He managed to get a patent for his machine in 1820, but after this his fate is unknown. == Personal life == Little has been recorded about Redheffer's life, other than his connection to the hoax. According to one source, he was from Germantown in Philadelphia, but most sources simply state that he appeared in Philadelphia with his machine.


id: simple-magnetic-overunity-toy-20260505-0
file: data/en.wikipedia.org/wiki/Simple_Magnetic_Overunity_Toy-0.md
category: reference
title: Simple Magnetic Overunity Toy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Simple_Magnetic_Overunity_Toy
date_saved: 2026-05-05T11:11:10.347412+00:00
instance: kb-cron
parent: simple-magnetic-overunity-toy-20260505-0
summary:
The Simple Magnetic Overunity Toy (SMOT) is a 1985 invention by Greg Watson from Australia that claims to show "over-unity" energy — that is, it supposedly produces more energy than it consumes, a perpetual motion machine. It is a type of magnet motor. == Overview == In the theoretical SMOT design, a steel ball is pulled up a ramp by an array of permanent magnets. At the top of the ramp it falls, converting magnetic attraction into kinetic energy. A SMOT-like structure is shown in Emil T. Hartman's patent. Watson claims that a mechanism called regauging happens that allows the cycle to be repeated without the application of outside energy. Perpetual motion ("over-unity") has not been achieved with a SMOT. The ball can be cycled from the starting point of one SMOT to the starting point of a second SMOT (and third and fourth), and by arranging multiple SMOT's in a circle the ball can be circulated along the SMOT's thus giving the illusion of overunity, but the ball can never return to its starting place without adding energy to compensate for frictional losses or for any other energy dissipated by the system. == Construction == The SMOT consists of


id: steorn-20260505-0
file: data/en.wikipedia.org/wiki/Steorn-0.md
category: reference
title: Steorn
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Steorn
date_saved: 2026-05-05T11:11:12.120259+00:00
instance: kb-cron
parent: steorn-20260505-0
summary:
Steorn Ltd () was a small, private technology development company based in Dublin, Ireland. In August 2006, it announced that it had developed a technology to provide "free, clean, and constant energy" via an apparent perpetual motion machine, something which is contrary to the law of conservation of energy, a fundamental principle of physics. Steorn challenged the scientific community to investigate its claim and, in December 2006, said that it had chosen a jury of scientists to do so. In June 2009 the jury gave its unanimous verdict that Steorn had not demonstrated the production of energy. Steorn gave two public demonstrations of its technology. In the first demonstration, in July 2007 at the Kinetica Museum in London, the device failed to work. The second demonstration, which ran from December 2009 to February 2010 at the Waterways Visitor Centre in Dublin, involved a motor powered by a battery and provided no independent evidence that excess energy was being generated. It was dismissed by the press as an attempt to build a perpetual motion machine, and a publicity stunt. In November 2016, the company laid off its staff, closed its facility, and prepared for liquidation. It was finally liquidated in May


id: steorn-20260505-1
file: data/en.wikipedia.org/wiki/Steorn-1.md
category: reference
title: Steorn
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Steorn
date_saved: 2026-05-05T11:11:12.120259+00:00
instance: kb-cron
parent: steorn-20260505-0
summary:
=== Jury process === In its advertisement in The Economist, Steorn challenged scientists to form an independent jury to test its technology and publish the results. Within 36 hours of the advertisement being published, 420 scientists contacted Steorn and, on 1 December 2006, Steorn announced it had selected a jury. It was headed by Ian MacDonald, emeritus professor of electrical engineering at the University of Alberta, and the process began in February 2007. In June 2009 the jury announced its unanimous verdict that "Steorn's attempts to demonstrate the claim have not shown the production of energy. The jury is therefore ceasing work". Dick Ahlstrom, writing in the Irish Times, concluded from this that Steorn's technology did not work. Steorn responded by saying that because of difficulties in implementing the technology the focus of the process had been on providing the jury with test data on magnetic effects for study. Steorn also said that these difficulties had been resolved and disputed its jury's findings. === Demonstrations === On 4 July 2007, the technology was to be displayed at the Kinetica Museum, Spitalfields Market, London. A unit constructed of clear plastic was prepared so that the arrangement of magnets could be seen


id: zero-point-energy-20260505-0
file: data/en.wikipedia.org/wiki/Zero-point_energy-0.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
Zero-point energy (ZPE) is the lowest possible energy that a quantum mechanical system may have. Unlike in classical mechanics, quantum systems constantly fluctuate in their lowest energy state as described by the Heisenberg uncertainty principle. Therefore, even at absolute zero, atoms and molecules retain some vibrational motion. Apart from atoms and molecules, the empty space of a vacuum also has these properties. According to quantum field theory, the universe can be thought of not as isolated particles but continuous fluctuating fields: matter fields, whose quanta are fermions (in other words, leptons and quarks), and force fields, whose quanta are bosons (such as photons and gluons). All these fields have zero-point energy. These fluctuating zero-point fields lead to a kind of reintroduction of an aether in physics since some systems can detect the existence of this energy. However, this aether cannot be thought of as a physical medium if it is to be Lorentz invariant such that there is no contradiction with Albert Einstein's theory of special relativity. The notion of a zero-point energy is also important for cosmology, and physics currently lacks a full theoretical model for understanding zero-point energy in this context; in particular, the discrepancy between theorized and


id: zero-point-energy-20260505-1
file: data/en.wikipedia.org/wiki/Zero-point_energy-1.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
The uncertainty principle states that no object can ever have precise values of position and velocity simultaneously. The total energy of a quantum mechanical object (potential and kinetic) is described by its Hamiltonian which also describes the system as a harmonic oscillator, or wave function, that fluctuates between various energy states (see wave-particle duality). All quantum mechanical systems undergo fluctuations even in their ground state, a consequence of their wave-like nature. The uncertainty principle requires every quantum mechanical system to have a fluctuating zero-point energy greater than the minimum of its classical potential well. This results in motion even at absolute zero. For example, liquid helium does not freeze under atmospheric pressure regardless of temperature due to its zero-point energy. Given the equivalence of mass and energy expressed by Albert Einstein's E = mc2, any point in space that contains energy can be thought of as having mass to create particles. Modern physics has developed quantum field theory (QFT) to understand the fundamental interactions between matter and forces; it treats every single point of space as a quantum harmonic oscillator. According to QFT the universe is made up of matter fields, whose quanta are fermions (i.e. leptons and quarks), and


id: zero-point-energy-20260505-2
file: data/en.wikipedia.org/wiki/Zero-point_energy-2.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
To those who maintained the existence of a plenum as a philosophical principle, nature's abhorrence of a vacuum was a sufficient reason for imagining an all-surrounding aether ... Aethers were invented for the planets to swim in, to constitute electric atmospheres and magnetic effluvia, to convey sensations from one part of our bodies to another, and so on, till a space had been filled three or four times with aethers. Moreover, the results of the Michelson–Morley experiment in 1887 were the first strong evidence that the then-prevalent aether theories were seriously flawed, explicitly confirming the invariance of the speed of light predicted by Maxwell's equations, as later axiomatized in special relativity that ruled out the idea of a stationary aether altogether. To scientists of the period, it seemed that a true vacuum in space might be created by cooling and thus eliminating all radiation or energy. From this idea evolved the second concept of achieving a real vacuum: cool a region of space down to absolute zero temperature after evacuation. Absolute zero was technically impossible to achieve in the 19th century, so the debate remained unsolved. === Second quantum theory === In 1900, Max Planck derived the average energy ε


id: zero-point-energy-20260505-3
file: data/en.wikipedia.org/wiki/Zero-point_energy-3.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
Kurt Bennewitz and Francis Simon (1923), who worked at Walther Nernst's laboratory in Berlin, studied the melting process of chemicals at low temperatures. Their calculations of the melting points of hydrogen, argon and mercury led them to conclude that the results provided evidence for a zero-point energy. Moreover, they suggested correctly, as was later verified by Simon (1934), that this quantity was responsible for the difficulty in solidifying helium even at absolute zero. In 1924 Robert Mulliken provided direct evidence for the zero-point energy of molecular vibrations by comparing the band spectrum of 10BO and 11BO: the isotopic difference in the transition frequencies between the ground vibrational states of two different electronic levels would vanish if there were no zero-point energy, in contrast to the observed spectra. Then just a year later in 1925, with the development of matrix mechanics in Werner Heisenberg's article "Quantum theoretical re-interpretation of kinematic and mechanical relations" the zero-point energy was derived from quantum mechanics. In 1913 Niels Bohr had proposed what is now called the Bohr model of the atom, but despite this it remained a mystery as to why electrons do not fall into their nuclei. According to classical ideas, the fact that


id: zero-point-energy-20260505-4
file: data/en.wikipedia.org/wiki/Zero-point_energy-4.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
From quantum theory there follows the existence of so called zero-point oscillations; for example each oscillator in its lowest state is not completely at rest but always is moving about its equilibrium position. Therefore electromagnetic oscillations also can never cease completely. Thus the quantum nature of the electromagnetic field has as its consequence zero point oscillations of the field strength in the lowest energy state, in which there are no light quanta in space ... The zero point oscillations act on an electron in the same way as ordinary electrical oscillations do. They can change the eigenstate of the electron, but only in a transition to a state with the lowest energy, since empty space can only take away energy, and not give it up. In this way spontaneous radiation arises as a consequence of the existence of these unique field strengths corresponding to zero point oscillations. Thus spontaneous radiation is induced radiation of light quanta produced by zero point oscillations of empty space This view was also later supported by Theodore Welton (1948), who argued that spontaneous emission "can be thought of as forced emission taking place under the action of the fluctuating field". This new theory, which Dirac


id: zero-point-energy-20260505-5
file: data/en.wikipedia.org/wiki/Zero-point_energy-5.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
In 1948 Hendrik Casimir showed that one consequence of the zero-point field is an attractive force between two uncharged, perfectly conducting parallel plates, the so-called Casimir effect. At the time, Casimir was studying the properties of colloidal solutions. These are viscous materials, such as paint and mayonnaise, that contain micron-sized particles in a liquid matrix. The properties of such solutions are determined by Van der Waals forces – short-range, attractive forces that exist between neutral atoms and molecules. One of Casimir's colleagues, Theo Overbeek, realized that the theory that was used at the time to explain Van der Waals forces, which had been developed by Fritz London in 1930, did not properly explain the experimental measurements on colloids. Overbeek therefore asked Casimir to investigate the problem. Working with Dirk Polder, Casimir discovered that the interaction between two neutral molecules could be correctly described only if the fact that light travels at a finite speed was taken into account. Soon afterwards after a conversation with Bohr about zero-point energy, Casimir noticed that this result could be interpreted in terms of vacuum fluctuations. He then asked himself what would happen if there were two mirrors – rather than two molecules – facing


id: zero-point-energy-20260505-6
file: data/en.wikipedia.org/wiki/Zero-point_energy-6.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
where ω = √k/m is the angular frequency at which the system oscillates. A more thorough treatment, showing that the energy of the ground state actually saturates this bound and is exactly E0 = V0 + ⁠ħω/2⁠, requires solving for the ground state of the system. == Atomic physics == The idea of a quantum harmonic oscillator and its associated energy can apply to either an atom or a subatomic particle. In ordinary atomic physics, the zero-point energy is the energy associated with the ground state of the system. The professional physics literature tends to measure frequency, as denoted by ν above, using angular frequency, denoted with ω and defined by ω = 2πν. This leads to a convention of writing the Planck constant h with a bar through its top (ħ) to denote the quantity ⁠h/2π⁠. In these terms, an example of zero-point energy is the above E = ⁠ħω/2⁠ associated with the ground state of the quantum harmonic oscillator. In quantum mechanical terms, the zero-point energy is the expectation value of the Hamiltonian of the system in the ground state. If more than one ground state exists, they are said to be degenerate. Many systems have degenerate ground


id: zero-point-energy-20260505-7
file: data/en.wikipedia.org/wiki/Zero-point_energy-7.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
implies that quantum theory does not allow states of the radiation field for which the photon number and a field amplitude can be precisely defined, i.e., we cannot have simultaneous eigenstates for a†a and a. The reconciliation of wave and particle attributes of the field is accomplished via the association of a probability amplitude with a classical mode pattern. The calculation of field modes is entirely classical problem, while the quantum properties of the field are carried by the mode "amplitudes" a† and a associated with these classical modes. The zero-point energy of the field arises formally from the non-commutativity of a and a†. This is true for any harmonic oscillator: the zero-point energy ⁠ħω/2⁠ appears when we write the Hamiltonian: H c l = p 2 2 m + 1 2 m ω 2 q 2 = 1 2 ℏ ω ( a a † + a † a ) = ℏ ω ( a † a + 1 2 ) {\displaystyle {\begin{aligned}H_{cl}&={\frac {p^{2}}{2m}}+{\tfrac {1}{2}}m\omega ^{2}{q}^{2}\\&={\tfrac {1}{2}}\hbar \omega \left(aa^{\dagger }+a^{\dagger }a\right)\\&=\hbar \omega \left(a^{\dagger }a+{\tfrac {1}{2}}\right)\end{aligned}}} It is often argued that the entire universe is completely bathed in the zero-point electromagnetic field, and as such it can add only some


id: zero-point-energy-20260505-8
file: data/en.wikipedia.org/wiki/Zero-point_energy-8.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
A k ( r ) = 1 V e k e i k ⋅ r {\displaystyle \mathbf {A} _{\mathbf {k} }(\mathbf {r} )={\frac {1}{\sqrt {V}}}e_{\mathbf {k} }e^{i\mathbf {k} \cdot \mathbf {r} }} which satisfies the Helmholtz equation, transversality, and the "box normalization": ∫ V d 3 r | A k ( r ) | 2 = 1 {\displaystyle \int _{V}d^{3}r\left|\mathbf {A} _{\mathbf {k} }(\mathbf {r} )\right|^{2}=1} where ek is chosen to be a unit vector which specifies the polarization of the field mode. The condition k · ek = 0 means that there are two independent choices of ek, which we call ek1 and ek2 where ek1 · ek2 = 0 and e2k1 = e2k2 = 1. Thus we define the mode functions: A k λ ( r ) = 1 V e k λ e i k ⋅ r , λ = { 1 2 {\displaystyle \mathbf {A} _{\mathbf {k} \lambda }(\mathbf {r} )={\frac {1}{\sqrt {V}}}e_{\mathbf {k} \lambda }e^{i\mathbf {k} \cdot \mathbf {r} }\,,\quad \lambda ={\begin{cases}1\\2\end{cases}}} in terms of which the vector potential becomes: A k λ ( r , t ) = 2 π ℏ c 2 ω k V [ a k λ ( 0 ) e


id: zero-point-energy-20260505-9
file: data/en.wikipedia.org/wiki/Zero-point_energy-9.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
for high values of v. It diverges proportional to v4 for large v. There are two separate questions to consider. First, is the divergence a real one such that the zero-point energy really is infinite? If we consider the volume V is contained by perfectly conducting walls, very high frequencies can only be contained by taking more and more perfect conduction. No actual method of containing the high frequencies is possible. Such modes will not be stationary in our box and thus not countable in the stationary energy content. So from this physical point of view the above sum should only extend to those frequencies which are countable; a cut-off energy is thus eminently reasonable. However, on the scale of a "universe" questions of general relativity must be included. Suppose even the boxes could be reproduced, fit together and closed nicely by curving spacetime. Then exact conditions for running waves may be possible. However the very high frequency quanta will still not be contained. As per John Wheeler's "geons" these will leak out of the system. So again a cut-off is permissible, almost necessary. The question here becomes one of consistency since the very high energy quanta will act as


id: zero-point-energy-20260505-10
file: data/en.wikipedia.org/wiki/Zero-point_energy-10.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
x ˙ = ( i ℏ ) − 1 [ x . H ] = 1 m ( p − e c A ) p ˙ = ( i ℏ ) − 1 [ p . H ] = 1 2 ∇ ( p − e c A ) 2 − m ω 0 2 x ˙ = − 1 m [ ( p − e c A ) ⋅ ∇ ] [ − e c A ] − 1 m ( p − e c A ) × ∇ × [ − e c A ] − m ω 0 2 x ˙ = e c ( x ˙ ⋅ ∇ ) A + e c x ˙ × B − m ω 0 2 x ˙ {\displaystyle {\begin{aligned}\mathbf {\dot {x}} &=(i\hbar )^{-1}[\mathbf {x} .H]={\frac {1}{m}}\left(\mathbf {p} -{\frac {e}{c}}\mathbf {A} \right)\\\mathbf {\dot {p}} &=(i\hbar )^{-1}[\mathbf {p} .H]{\begin{aligned}&={\tfrac {1}{2}}\nabla \left(\mathbf {p} -{\frac {e}{c}}\mathbf {A} \right)^{2}-m\omega _{0}^{2}\mathbf {\dot {x}} \\&=-{\frac {1}{m}}\left[\left(\mathbf {p} -{\frac {e}{c}}\mathbf {A} \right)\cdot \nabla \right]\left[-{\frac {e}{c}}\mathbf {A} \right]-{\frac {1}{m}}\left(\mathbf {p} -{\frac {e}{c}}\mathbf {A} \right)\times \nabla \times \left[-{\frac {e}{c}}\mathbf {A} \right]-m\omega _{0}^{2}\mathbf {\dot {x}} \\&={\frac {e}{c}}(\mathbf {\dot {x}} \cdot \nabla )\mathbf {A} +{\frac {e}{c}}\mathbf {\dot {x}} \times \mathbf {B}


id: zero-point-energy-20260505-11
file: data/en.wikipedia.org/wiki/Zero-point_energy-11.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
The total field acting on the dipole has two parts, E0(t) and ERR(t). E0(t) is the free or zero-point field acting on the dipole. It is the homogeneous solution of the Maxwell equation for the field acting on the dipole, i.e., the solution, at the position of the dipole, of the wave equation [ ∇ 2 − 1 c 2 ∂ 2 ∂ t 2 ] E = 0 {\displaystyle \left[\nabla ^{2}-{\frac {1}{c^{2}}}{\frac {\partial ^{2}}{\partial t^{2}}}\right]\mathbf {E} =0} satisfied by the field in the (source free) vacuum. For this reason E0(t) is often referred to as the "vacuum field", although it is of course a Heisenberg-picture operator acting on whatever state of the field happens to be appropriate at t = 0. ERR(t) is the source field, the field generated by the dipole and acting on the dipole. Using the above equation for ERR(t) we obtain an equation for the Heisenberg-picture operator x ( t ) {\displaystyle \mathbf {x} (t)} that is formally the same as the classical equation for a linear dipole oscillator: x ¨ + ω 0 2 x − τ x . . . = e m E 0 ( t ) {\displaystyle \mathbf {\ddot {x}} +\omega


id: zero-point-energy-20260505-12
file: data/en.wikipedia.org/wiki/Zero-point_energy-12.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
= [ z ( t ) , m z ˙ ( t ) ] + [ z ( t ) , e c A z ( t ) ] = [ z ( t ) , m z ˙ ( t ) ] = ( i ℏ e 2 2 π 2 m c 3 ) ( 8 π 3 ) ∫ 0 ∞ d ω ω 4 ( ω 2 − ω 0 2 ) 2 + τ 2 ω 6 {\displaystyle {\begin{aligned}[z(t),p_{z}(t)]&=\left[z(t),m{\dot {z}}(t)\right]+\left[z(t),{\frac {e}{c}}A_{z}(t)\right]\\&=\left[z(t),m{\dot {z}}(t)\right]\\&=\left({\frac {i\hbar e^{2}}{2\pi ^{2}mc^{3}}}\right)\left({\frac {8\pi }{3}}\right)\int _{0}^{\infty }{\frac {d\omega \,\omega ^{4}}{\left(\omega ^{2}-\omega _{0}^{2}\right)^{2}+\tau ^{2}\omega ^{6}}}\end{aligned}}} For the dipole oscillator under consideration it can be assumed that the radiative damping rate is small compared with the natural oscillation frequency, i.e., τω0 ≪ 1. Then the integrand above is sharply peaked at ω = ω0 and: [ z ( t ) , p z ( t ) ] ≈ 2 i ℏ e 2 3 π m c 3 ω 0 3 ∫ − ∞ ∞ d x x 2 + τ 2 ω 0 6 = ( 2 i ℏ e 2 ω 0 3 3 π m c 3 ) ( π τ ω


id: zero-point-energy-20260505-13
file: data/en.wikipedia.org/wiki/Zero-point_energy-13.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
The Standard Model hypothesises a field called the Higgs field (symbol: ϕ), which has the unusual property of a non-zero amplitude in its ground state (zero-point) energy after renormalization; i.e., a non-zero vacuum expectation value. It can have this effect because of its unusual "Mexican hat" shaped potential whose lowest "point" is not at its "centre". Below a certain extremely high energy level the existence of this non-zero vacuum expectation spontaneously breaks electroweak gauge symmetry which in turn gives rise to the Higgs mechanism and triggers the acquisition of mass by those particles interacting with the field. The Higgs mechanism occurs whenever a charged field has a vacuum expectation value. This effect occurs because scalar field components of the Higgs field are "absorbed" by the massive bosons as degrees of freedom, and couple to the fermions via Yukawa coupling, thereby producing the expected mass terms. The expectation value of ϕ0 in the ground state (the vacuum expectation value or VEV) is then ⟨ϕ0⟩ = ⁠v/√2⁠, where v = ⁠|μ|/√λ⁠. The measured value of this parameter is approximately 246 GeV/c2. It has units of mass, and is the only free parameter of the Standard Model that is not a dimensionless number.


id: zero-point-energy-20260505-14
file: data/en.wikipedia.org/wiki/Zero-point_energy-14.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
The fine-structure constant is the coupling constant of quantum electrodynamics (QED) determining the strength of the interaction between electrons and photons. It turns out that the fine-structure constant is not really a constant at all owing to the zero-point energy fluctuations of the electron-positron field. The quantum fluctuations caused by zero-point energy have the effect of screening electric charges: owing to (virtual) electron-positron pair production, the charge of the particle measured far from the particle is far smaller than the charge measured when close to it. The Heisenberg inequality where ħ = ⁠h/2π⁠, and Δx, Δp are the standard deviations of position and momentum states that: Δ x Δ p ≥ 1 2 ℏ {\displaystyle \Delta _{x}\Delta _{p}\geq {\frac {1}{2}}\hbar } It means that a short distance implies large momentum and therefore high energy i.e. particles of high energy must be used to explore short distances. QED concludes that the fine-structure constant is an increasing function of energy. It has been shown that at energies of the order of the Z0 boson rest energy, mzc2 ≈ 90 GeV, that: α ≈ 1 129 {\displaystyle \alpha \approx {\frac {1}{129}}} rather than the low-energy α ≈ ⁠1/137⁠. The renormalization procedure of eliminating


id: zero-point-energy-20260505-15
file: data/en.wikipedia.org/wiki/Zero-point_energy-15.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
In the late 1990s it was discovered that very distant supernovae were dimmer than expected suggesting that the universe's expansion was accelerating rather than slowing down. This revived discussion that Einstein's cosmological constant, long disregarded by physicists as being equal to zero, was in fact some small positive value. This would indicate empty space exerted some form of negative pressure or energy. There is no natural candidate for what might cause what has been called dark energy but the current best guess is that it is the zero-point energy of the vacuum, but this guess is known to be off by 120 orders of magnitude. The European Space Agency's Euclid telescope, launched on 1 July 2023, will map galaxies up to 10 billion light years away. By seeing how dark energy influences their arrangement and shape, the mission will allow scientists to see if the strength of dark energy has changed. If dark energy is found to vary throughout time it would indicate it is due to quintessence, where observed acceleration is due to the energy of a scalar field, rather than the cosmological constant. No evidence of quintessence is yet available, but it has not been ruled out either.


id: zero-point-energy-20260505-16
file: data/en.wikipedia.org/wiki/Zero-point_energy-16.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
=== Casimir batteries and engines === A common assumption is that the Casimir force is of little practical use; the argument is made that the only way to actually gain energy from the two plates is to allow them to come together (getting them apart again would then require more energy), and therefore it is a one-use-only tiny force in nature. In 1984 Robert Forward published work showing how a "vacuum-fluctuation battery" could be constructed; the battery can be recharged by making the electrical forces slightly stronger than the Casimir force to reexpand the plates. In 1999, Pinto, a former scientist at NASA's Jet Propulsion Laboratory at Caltech in Pasadena, published in Physical Review his thought experiment (Gedankenexperiment) for a "Casimir engine". The paper showed that continuous positive net exchange of energy from the Casimir effect was possible, even stating in the abstract "In the event of no other alternative explanations, one should conclude that major technological advances in the area of endless, by-product free-energy production could be achieved." Garret Moddel at University of Colorado has highlighted that he believes such devices hinge on the assumption that the Casimir force is a nonconservative force. He argues that there is sufficient


id: zero-point-energy-20260505-17
file: data/en.wikipedia.org/wiki/Zero-point_energy-17.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
=== Space travel and gravitational shielding === The use of zero-point energy for space travel is speculative and does not form part of the mainstream scientific consensus. A complete quantum theory of gravitation (that would deal with the role of quantum phenomena like zero-point energy) does not yet exist. Speculative papers explaining a relationship between zero-point energy and gravitational shielding effects have been proposed, but the interaction (if any) is not yet fully understood. According to the general theory of relativity, rotating matter can generate a new force of nature, known as the gravitomagnetic interaction, whose intensity is proportional to the rate of spin. In certain conditions the gravitomagnetic field can be repulsive. In neutron stars for example, it can produce a gravitational analogue of the Meissner effect, but the force produced in such an example is theorized to be exceedingly weak. In 1963 Robert Forward, a physicist and aerospace engineer at Hughes Research Laboratories, published a paper showing how within the framework of general relativity "anti-gravitational" effects might be achieved. Since all atoms have spin, gravitational permeability may be able to differ from material to material. A strong toroidal gravitational field that acts against the force of gravity could


id: zero-point-energy-20260505-18
file: data/en.wikipedia.org/wiki/Zero-point_energy-18.md
category: reference
title: Zero-point energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zero-point_energy
date_saved: 2026-05-05T11:11:13.426148+00:00
instance: kb-cron
parent: zero-point-energy-20260505-0
summary:
Similarly to a dumbbell put in a suitable rotational state, but with nuclear mass density, dineutrons are nearly ideal sources of gravitational waves at X-ray and gamma-ray frequencies. The dynamical interplay, mediated by nuclear forces, between the electrically neutral dineutrons and the electrically charged core nucleus is the fundamental mechanism by which nuclear vibrations can be converted to a rotational state of dineutrons with emission of gravitational waves. Gravity and gravitational waves are well described by General Relativity, that is not a quantum theory, this implies that there is no Zero-point energy for gravity in this theory, therefore dineutrons will emit gravitational waves like any other known source of gravitational waves. In Fontana and Binder paper, nuclear species with dynamical instabilities, related to the Zero-point energy of the electromagnetic field and nuclear forces, and possessing dineutrons, will emit gravitational waves. In experimental physics this approach is still unexplored. In 2014 NASA's Eagleworks Laboratories announced that they had successfully validated the use of a Quantum Vacuum Plasma Thruster which makes use of the Casimir effect for propulsion. In 2016 a scientific paper by the team of NASA scientists passed peer review for the first time. The paper suggests that the zero-point


id: speculative-evolution-20260505-0
file: data/en.wikipedia.org/wiki/Speculative_evolution-0.md
category: reference
title: Speculative evolution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speculative_evolution
date_saved: 2026-05-05T11:11:15.055975+00:00
instance: kb-cron
parent: speculative-evolution-20260505-0
summary:
Speculative evolution is a subgenre of science fiction and an artistic movement focused on hypothetical scenarios in the evolution of life, and a significant form of fictional biology. It is also known as speculative biology and it is referred to as speculative zoology in regards to hypothetical animals. Works incorporating speculative evolution may have entirely conceptual species that evolve on a planet other than Earth, or they may be an alternate history focused on an alternate evolution of terrestrial life. Speculative evolution is often considered hard science fiction because of its strong connection to and basis in science, particularly biology. Speculative evolution is a long-standing trope within science fiction, often recognized as beginning as such with H. G. Wells's 1895 novel The Time Machine, which featured several imaginary future creatures. Although small-scale speculative faunas were a hallmark of science fiction throughout the 20th century, ideas were only rarely well-developed, with some exceptions such as Stanley Weinbaum's Planetary series, Edgar Rice Burroughs's Barsoom, a fictional rendition of Mars and its ecosystem published through novels from 1912 to 1948, and Amtor, a fictional rendition of Venus and its ecosystem published through novels from 1934 to 1964, and Gerolf Steiner's Rhinogradentia, a fictional


id: speculative-evolution-20260505-1
file: data/en.wikipedia.org/wiki/Speculative_evolution-1.md
category: reference
title: Speculative evolution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speculative_evolution
date_saved: 2026-05-05T11:11:15.055975+00:00
instance: kb-cron
parent: speculative-evolution-20260505-0
summary:
Edgar Rice Burroughs, who wrote in the early 20th century, can like Wells be considered an early speculative evolution author. Although his fictional ecosystems were still relatively small in scope, they were the settings of many of his novels and as such quite well-developed. In particular, Burroughs's Barsoom, a fictional version of the planet Mars which appeared in ten novels published from 1912 to 1948, featured a Martian ecosystem with a variety of alien creatures and several distinct Martian cultures and ethnic groups, as well as Amtor, a fictional version of the planet Venus which appeared in five novels published from 1934 to 1964, also featured a Venusian ecosystem with a variety of alien creatures and several distinct Venusian cultures and ethnic groups. Stanley Weinbaum's Planetary series also includes significantly conceptualized and developed alien life. Frederik Pohl wrote that before Weinbaum, science fiction's aliens "might be catmen, lizard-men, antmen, plantmen or rockmen; but they were, always and incurably, men. Weinbaum changed that. ... it was the difference in orientation – in drives, goals and thought processes – that made the Weinbaum-type alien so fresh and rewarding in science fiction in the mid-thirties." In 1930, Olaf Stapledon published a "future history",


id: speculative-evolution-20260505-2
file: data/en.wikipedia.org/wiki/Speculative_evolution-2.md
category: reference
title: Speculative evolution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speculative_evolution
date_saved: 2026-05-05T11:11:15.055975+00:00
instance: kb-cron
parent: speculative-evolution-20260505-0
summary:
== As an educational and scientific tool == Although primarily characterized as entertainment, speculative evolution can be used as educational tool to explain and illustrate real natural processes through using fictional and imaginary examples. The worlds created are often built on ecological and biological principles inferred from the real evolutionary history of life on Earth and readers can learn from them as such. For example, all of Dixon's speculative works are aimed at exploring real processes, with After Man exploring evolution, The New Dinosaurs zoogeography and both Man After Man and Greenworld (2010) exploring climate change, offering an environmental message. In some cases, speculative evolution artists have successfully predicted the existence of organisms that were later discovered to resemble something real. Many of the animals featured in Dixon's After Man are still considered plausible ideas, with some of them (such as specialized rodents and semi-aquatic primates) being reinforced with recent biology studies. A creature dubbed "Ceticaris", conceived by artist John Meszaros as a filter-feeding radiodont, was published in the 2013 book All Your Yesterdays, and in 2014, the actual Cambrian radiodont Tamisiocaris was discovered to have been a filter-feeder. In honor of Meszaros's prediction, Tamisiocaris was included in a new


id: speculative-evolution-20260505-3
file: data/en.wikipedia.org/wiki/Speculative_evolution-3.md
category: reference
title: Speculative evolution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speculative_evolution
date_saved: 2026-05-05T11:11:15.055975+00:00
instance: kb-cron
parent: speculative-evolution-20260505-0
summary:
Perhaps the most famous speculative work on a hypothetical alien ecosystem is Wayne Barlowe's 1990 book Expedition, which explores the fictional exoplanet Darwin IV. Expedition was written as a report of a 24th-century expedition that had been led to the planet by a team composed of both humans and intelligent aliens and used paintings and descriptive texts to create and describe a fully realized extraterrestrial ecosystem. Barlowe later served as an executive producer of a TV adaptation of the book, Alien Planet (2005) where exploration of Darwin IV is instead carried out by robotic probes and the segments detailing the ecosystems of the planet are intercut with interviews with scientists, such as Michio Kaku, Jack Horner and James B. Garvin. Other examples of speculative evolution focused on extraterrestrial life include Dougal Dixon's 2010 book Greenworld, TV programmes such as 1997 the BBC2/Discovery Channel special Natural History of an Alien and the 2005 Channel 4/National Geographic programme Extraterrestrial as well as a variety of personal web-based artistic projects, such as C. M. Kosemen's "Snaiad" and Gert van Dijk's "Furaha", and collaborative web-based projects like "Sagan 4", envisioning the biosphere of entire alien worlds. Through science fiction, the speculative biology of extraterrestrial


id: speculative-evolution-20260505-4
file: data/en.wikipedia.org/wiki/Speculative_evolution-4.md
category: reference
title: Speculative evolution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speculative_evolution
date_saved: 2026-05-05T11:11:15.055975+00:00
instance: kb-cron
parent: speculative-evolution-20260505-0
summary:
=== Future evolution === The evolution of organisms in the Earth's future is a popular subset of speculative evolution. A relatively common theme in future evolution is civilizational collapse and/or humans becoming extinct due to an anthropogenic extinction event caused by environmental degradation. After such a mass extinction event, the remaining fauna and flora evolve into a variety of new forms. Although the foundations of this subset were laid by Wells's The Time Machine already in 1895, it is generally agreed that it was definitively established by Dixon's After Man in 1981, which explored a fully realized future ecosystem set 50 million years from the present. Dixon's third work on speculative evolution, Man After Man (1990) is also an example of future evolution, this time exploring an imagined future evolutionary path of humanity. Peter Ward's Future Evolution (2001) makes a scientifically accurate approach to the prediction of patterns of evolution in the future. Ward compares his predictions with those of Dixon and Wells. He tries to understand the mechanism of mass extinctions and the principles of recovery of ecosystems. A key point is that "champion supertaxa" who diversify and speciate at a greater rate, will inherit the world after mass


id: after-man-20260505-0
file: data/en.wikipedia.org/wiki/After_Man-0.md
category: reference
title: After Man
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/After_Man
date_saved: 2026-05-05T11:11:16.243451+00:00
instance: kb-cron
parent: after-man-20260505-0
summary:
After Man: A Zoology of the Future is a 1981 speculative evolution book written by Scottish geologist and paleontologist Dougal Dixon and illustrated by several illustrators including Diz Wallis, John Butler, Brian McIntyre, Philip Hood, Roy Woodard and Gary Marsh. The book features a foreword by Desmond Morris. After Man explores a hypothetical future set 50 million years after extinction of humanity, a time period Dixon dubs the "Posthomic", which is inhabited by animals that have evolved from survivors of a mass extinction succeeding our own time. After Man used a fictional setting and hypothetical animals to explain the natural processes behind evolution and natural selection. In total, over a hundred different invented animal species are featured in the book, described as part of fleshed-out fictional future ecosystems. Reviews for After Man were highly positive and its success spawned two follow-up speculative evolution books which used new fictional settings and creatures to explain other natural processes: The New Dinosaurs (1988) and Man After Man (1990). After Man and Dixon's following books inspired the speculative evolution artistic movement which focuses on speculative scenarios in the evolution of life, often possible future scenarios (such as After Man) or alternative paths in the


id: after-man-20260505-1
file: data/en.wikipedia.org/wiki/After_Man-1.md
category: reference
title: After Man
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/After_Man
date_saved: 2026-05-05T11:11:16.243451+00:00
instance: kb-cron
parent: after-man-20260505-0
summary:
=== Later editions === In March 2018, Breakdown Press published a new edition of the book, updated to reflect modern science relating to evolution. The updated version also features new artwork for some of the animals, created by Dixon himself. The release of the new edition was celebrated with an event hosted at Conway Hall in London on 11 September that same year, which included a joint talk with Dixon and British paleontologist and science writer Darren Naish. The event also included showcases of original sketches and models and a showing of the Japanese stop-motion adaptation of After Man. A 40th Anniversary Edition of After Man was published by Breakdown Press in February 2022, featuring 18 additional pages of production material and previously unpublished sketches as well as a new afterword written by Dixon. == Reception == The first review of After Man was one made by Professor Barry Cox of King's College London in a science-based radio programme. Cox's review was extremely negative, but subsequent reviews were highly positive. Peter Stoler's review in Time called the animals in the book "variously amusing or appalling" but "perfectly logical". Dan Brothwell, writing for the British Book News stated that the world


id: after-man-20260505-2
file: data/en.wikipedia.org/wiki/After_Man-2.md
category: reference
title: After Man
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/After_Man
date_saved: 2026-05-05T11:11:16.243451+00:00
instance: kb-cron
parent: after-man-20260505-0
summary:
=== Exhibitions === In 1987, an exhibition based on the book and organized by a Japanese exhibition company, featuring a number of "life"-size models of the animals featured therein, was displayed at the Denver Museum of Natural History, from 6 February to 3 May, and then at the California Academy of Sciences from 5 June to 7 September. The exhibition began with a "time tunnel", which visitors passed through before being met by several dioramas featuring the speculative future animals, including two full-size animatronic figures produced by Dinamation. According to spokespeople from both museums, the exhibition garnered positive reactions from visitors. The exhibition also included illustrations Dixon had previously made of a possible future evolutionary path of humanity, previously published under the title Visions of Man Evolved in Omni in 1982. Prior to this, a limited version of the exhibition (featuring 8 models rather than the 19 dioramas featured in the 1987 version) had been at the Newquay Zoo in Cornwall in 1983, in Japan in 1984 and in various locations within the United States from 1985 to 1986. The exhibition was later featured at the Orlando Science Center in 1989 and the Science Museum of Western Virginia in 1992.


id: alien-planet-20260505-0
file: data/en.wikipedia.org/wiki/Alien_Planet-0.md
category: reference
title: Alien Planet
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Alien_Planet
date_saved: 2026-05-05T11:11:17.440077+00:00
instance: kb-cron
parent: alien-planet-20260505-0
summary:
Alien Planet is a 2005 docufiction TV special created for the Discovery Channel. Based on the 1990 book Expedition by the artist and writer Wayne Barlowe, Alien Planet explores the imagined extraterrestrial life of the fictional planet Darwin IV in the style of a nature documentary. Although closely following Barlowe's depiction of Darwin IV, Alien Planet features a team of scientists and science fiction figures discussing Darwin IV as if it had actually been discovered. Among the people featured are Michio Kaku, Stephen Hawking, Jack Horner, James B. Garvin and George Lucas. Alien Planet garnered positive reviews as a thought-provoking programme, though some criticism was raised concerning the strange creatures featured, which some reviewers saw as bordering on implausible. == Plot == Alien Planet starts out with an unmanned interstellar spacecraft named Von Braun, leaving Earth's orbit. Traveling at 20% the speed of light (37,000 miles/s), it reaches Darwin IV, a planet 6.5 light-years away, in 42 years. Upon reaching orbit, it deploys the Darwin Reconnaissance Orbiter, which looks for potential landing sites for the probes. The first probe, Balboa, explodes along with its lifting body transport during entry, because one of its wings failed to unfold. Two backup probes,


id: alien-planet-20260505-1
file: data/en.wikipedia.org/wiki/Alien_Planet-1.md
category: reference
title: Alien Planet
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Alien_Planet
date_saved: 2026-05-05T11:11:17.440077+00:00
instance: kb-cron
parent: alien-planet-20260505-0
summary:
== Production == Alien Planet is based on Expedition (1990) by the American artist and writer Wayne Barlowe, a heavily illustrated book which aimed to explore and describe a fictional extraterrestrial ecosystem as if it was as real as that of Earth. Barlowe served as one of the executive producers of the adaptation. For the TV version, a broad team of scientists, and other figures, were assembled to comment on the life on Darwin IV, or to make general statements on life on Earth or out in the universe. Some of the people featured include physicists Michio Kaku and Stephen Hawking, paleontologist Jack Horner, NASA chief scientist James B. Garvin and director, screenwriter and producer George Lucas. Though the documentary gives the appearance of the featured scientists having designed Darwin IV and its animals, most of what is shown of the actual planet and its life follows what is described in Expedition. Though much of Darwin IV and its creatures is identical to what was presented in the book, Alien Planet diverges from Expedition in several ways. Unlike Expedition, which is set in the mid-24th century, Alien Planet is set at an unspecified point in the near future, and unlike


id: alien-worlds-2020-tv-series-20260505-0
file: data/en.wikipedia.org/wiki/Alien_Worlds_(2020_TV_series)-0.md
category: reference
title: Alien Worlds (2020 TV series)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Alien_Worlds_(2020_TV_series)
date_saved: 2026-05-05T11:11:18.665571+00:00
instance: kb-cron
parent: alien-worlds-2020-tv-series-20260505-0
summary:
Alien Worlds is a British sci-fi nature docufiction narrated by Sophie Okonedo. The 4-part miniseries, depicted by using CGI techniques, blends fact with science fiction and conceptualizes what alien life might be like by applying the laws of life on Earth to imagined exoplanets. The series was released on Netflix on 2 December 2020. == Episodes == == Reception == The weekend after the series' release, it was one of Netflix's top 10 shows in the UK. Sheena Scott of Forbes called the series "entertaining and very informative science fiction" and said that the most interesting part of the series was the non-fiction sections about planet Earth, which show "the breadth of knowledge scientists have accumulated about our planet". Likewise, Emma Stefansky of Thrillist said the alien creatures were fun, but "it's the Earth-bound science that ends up being the most interesting part". == See also == Alien Planet, a 2005 Discovery Channel TV film with a similar premise Natural History of an Alien, a 1998 TV film, also by the Discovery Channel Extraterrestrial (Alien Worlds in the UK) a 2005 National Geographic documentary series == References == == External links == Alien Worlds at IMDb Alien Worlds on Netflix


id: all-tomorrows-20260505-0
file: data/en.wikipedia.org/wiki/All_Tomorrows-0.md
category: reference
title: All Tomorrows
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/All_Tomorrows
date_saved: 2026-05-05T11:11:19.874175+00:00
instance: kb-cron
parent: all-tomorrows-20260505-0
summary:
All Tomorrows: A Billion Year Chronicle of the Myriad Species and Mixed Fortunes of Man is a 2006 work of science fiction and speculative evolution written and illustrated by the Turkish artist C. M. Kösemen under the pen name Nemo Ramjet. It explores a hypothetical future path of human evolution set from the near future to a billion years from the present. Several future human species evolve through natural means and through genetic engineering, conducted by both humans themselves and by a mysterious and superior alien race called the Qu. Inspired by the science fiction works of Olaf Stapledon and Edward Gibbon's The History of the Decline and Fall of the Roman Empire, Kösemen worked on All Tomorrows from 2003 to the publication of the book as a free PDF file online in 2006. Kösemen has announced the first English-language print edition of All Tomorrows in physical form, with new text, updated illustrations, and grammatical fixes. The first English print edition was published in November 2025. == Summary == Sometime during the Cretaceous period, The Qu visit Earth and abduct presumably thousands of dinosaurs from Earth and begin genetically-engineering them for life on other planets. Then, the Qu begin seeding


id: all-tomorrows-20260505-1
file: data/en.wikipedia.org/wiki/All_Tomorrows-1.md
category: reference
title: All Tomorrows
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/All_Tomorrows
date_saved: 2026-05-05T11:11:19.874175+00:00
instance: kb-cron
parent: all-tomorrows-20260505-0
summary:
== Development == Kösemen worked on All Tomorrows from 2003–2006. The work of Olaf Stapledon, particularly Last and First Men (1930) and Star Maker (1937), served as the main inspiration for the work, alongside Edward Gibbon's The History of the Decline and Fall of the Roman Empire. All Tomorrows is written in the style of a historical work, narrated by an alien creature recounting the history of humanity. According to Kösemen, the: "tone of voice is a high school student fanboying on the Decline and Fall of the Roman Empire by Edward Gibbon". The artwork is also reflective of this "archaeological" approach, with faded and textured visual effects applied to the paintings. The original reason for adding the faded tint to the paintings was Kösemen wanting to avoid the paintings looking like "horrible racist caricatures". The book was released for free online as a PDF on 4 October 2006 and has since then, per Kösemen himself, "had a life of its own as a PDF floating around the backwaters of the internet like a ghost ship". One of the common links which All Tomorrows has been shared through is a wiki site dedicated to speedrunning. The first licensed physical edition


id: all-yesterdays-20260505-0
file: data/en.wikipedia.org/wiki/All_Yesterdays-0.md
category: reference
title: All Yesterdays
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/All_Yesterdays
date_saved: 2026-05-05T11:11:21.026630+00:00
instance: kb-cron
parent: all-yesterdays-20260505-0
summary:
All Yesterdays: Unique and Speculative Views of Dinosaurs and Other Prehistoric Animals is a 2012 art book on the palaeoartistic reconstruction of dinosaurs and other extinct animals by John Conway, C. M. Kosemen and Darren Naish. A central tenet of the book concerns the fact that many dinosaur reconstructions are outdated, overly conservative, and inconsistent with the variation observed in modern animals. This focus is communicated through an exploration of views of dinosaurs and related animals that are unusual and sometimes even confusing to viewers, but which are well within the bounds of behaviour, anatomy and soft tissue that we see in living animals. == Overview == The book first recounts the history of changing perceptions of dinosaurs as expressed in artwork. It begins with the sluggish and slow dinosaurs seen in the works of Charles R. Knight, and then continues into analyzing reconstructions after the dinosaur renaissance. It points out that these reconstructions do not take the often bizarre integumentary coverings of living animals into account, and that dinosaurs should be portrayed as natural animals that aren't 'shrink-wrapped' with many of the individual bones visible. The remainder of the book consists of pictures with accompanying explanatory texts. Each picture


id: astrobiology-20260505-0
file: data/en.wikipedia.org/wiki/Astrobiology-0.md
category: reference
title: Astrobiology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrobiology
date_saved: 2026-05-05T11:11:22.445611+00:00
instance: kb-cron
parent: astrobiology-20260505-0
summary:
Astrobiology (also xenology or exobiology) is a scientific field within the life and environmental sciences that studies the origins, early evolution, distribution, and future of life in the universe by investigating its deterministic conditions and contingent events. As a discipline, astrobiology is founded on the premise that life may exist beyond Earth. Research in astrobiology comprises three main areas: the study of habitable environments in the Solar System and beyond, the search for planetary biosignatures of past or present extraterrestrial life, and the study of the origin and early evolution of life on Earth. The field of astrobiology has its origins in the 20th century with the advent of space exploration and the discovery of exoplanets. Early astrobiology research focused on the search for extraterrestrial life and the study of the potential for life to exist on other planets. In the 1960s and 1970s, NASA began its astrobiology pursuits within the Viking program, which was the first US mission to land on Mars and search for signs of life. This mission, along with other early space exploration missions, laid the foundation for the development of astrobiology as a discipline. Regarding habitable environments, astrobiology investigates potential locations beyond Earth that could


id: astrobiology-20260505-1
file: data/en.wikipedia.org/wiki/Astrobiology-1.md
category: reference
title: Astrobiology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrobiology
date_saved: 2026-05-05T11:11:22.445611+00:00
instance: kb-cron
parent: astrobiology-20260505-0
summary:
Astrobiological research makes a number of simplifying assumptions when studying the necessary components for planetary habitability. Carbon and Organic Compounds: Carbon is the fourth most abundant element in the universe and the energy required to make or break a bond is at just the appropriate level for building molecules that are not only stable, but also reactive. The fact that carbon atoms bond readily to other carbon atoms allows for the building of extremely long and complex molecules. As such, astrobiological research presumes that the vast majority of life forms in the Milky Way galaxy are based on carbon chemistries, as are all life forms on Earth. However, theoretical astrobiology entertains the potential for other organic molecular bases for life, thus astrobiological research often focuses on identifying environments that have the potential to support life based on the presence of organic compounds. Liquid water: Liquid water is a common molecule that provides an excellent environment for the formation of complicated carbon-based molecules, and is generally considered necessary for life as we know it to exist. Thus, astrobiological research presumes that extraterrestrial life similarly depends upon access to liquid water, and often focuses on identifying environments that have the potential to


id: astrobiology-20260505-2
file: data/en.wikipedia.org/wiki/Astrobiology-2.md
category: reference
title: Astrobiology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrobiology
date_saved: 2026-05-05T11:11:22.445611+00:00
instance: kb-cron
parent: astrobiology-20260505-0
summary:
The study of microbial life in the subsurface of Mars: Scientists are using data from Mars rover missions to study the composition of the subsurface of Mars, searching for biosignatures of past or present microbial life. The study of liquid bodies on icy moons: Discoveries of surface and subsurface bodies of liquid on moons such as Europa, Titan and Enceladus showed possible habitability zones, making them viable targets for the search for extraterrestrial life. As of September 2024, missions like Europa Clipper and Dragonfly are planned to search for biosignatures within these environments. The study of the atmospheres of planets: Scientists are studying the potential for life to exist in the atmospheres of planets, with a focus on the study of the physical and chemical conditions necessary for such life to exist, namely the detection of organic molecules and biosignature gases; for example, the study of the possibility of life in the atmospheres of exoplanets that orbit red dwarfs and the study of the potential for microbial life in the upper atmosphere of Venus. Telescopes and remote sensing of exoplanets: The discovery of thousands of exoplanets has opened up new opportunities for the search for biosignatures. Scientists are using telescopes


id: astrobiology-20260505-3
file: data/en.wikipedia.org/wiki/Astrobiology-3.md
category: reference
title: Astrobiology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrobiology
date_saved: 2026-05-05T11:11:22.445611+00:00
instance: kb-cron
parent: astrobiology-20260505-0
summary:
Yamato 000593, the second largest meteorite from Mars, was found on Earth in 2000. At a microscopic level, spheres are found in the meteorite that are rich in carbon compared to surrounding areas that lack such spheres. The carbon-rich spheres may have been formed by biotic activity according to some NASA scientists. On 5 March 2011, Richard B. Hoover, a scientist with the Marshall Space Flight Center, speculated on the finding of alleged microfossils similar to cyanobacteria in CI1 carbonaceous meteorites in the fringe Journal of Cosmology, a story widely reported on by mainstream media. However, NASA formally distanced itself from Hoover's claim. According to American astrophysicist Neil deGrasse Tyson: "At the moment, life on Earth is the only known life in the universe, but there are compelling arguments to suggest we are not alone." === Elements of astrobiology === ==== Astronomy ==== Most astronomy-related astrobiology research falls into the category of extrasolar planet (exoplanet) detection, the hypothesis being that if life arose on Earth, then it could also arise on other planets with similar characteristics. To that end, a number of instruments designed to detect Earth-sized exoplanets have been considered, most notably NASA's Terrestrial Planet Finder (TPF) and ESA's


id: astrobiology-20260505-4
file: data/en.wikipedia.org/wiki/Astrobiology-4.md
category: reference
title: Astrobiology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrobiology
date_saved: 2026-05-05T11:11:22.445611+00:00
instance: kb-cron
parent: astrobiology-20260505-0
summary:
Biology cannot state that a process or phenomenon, by being mathematically possible, has to exist forcibly in an extraterrestrial body. Biologists specify what is speculative and what is not. The discovery of extremophiles, organisms able to survive in extreme environments, became a core research element for astrobiologists, as they are important to understand four areas in the limits of life in planetary context: the potential for panspermia, forward contamination due to human exploration ventures, planetary colonization by humans, and the exploration of extinct and extant extraterrestrial life. Until the 1970s, life was thought to be entirely dependent on energy from the Sun. Plants on Earth's surface capture energy from sunlight to photosynthesize sugars from carbon dioxide and water, releasing oxygen in the process that is then consumed by oxygen-respiring organisms, passing their energy up the food chain. Even life in the ocean depths, where sunlight cannot reach, was thought to obtain its nourishment either from consuming organic detritus rained down from the surface waters or from eating animals that did. The world's ability to support life was thought to depend on its access to sunlight. However, in 1977, during an exploratory dive to the Galapagos Rift in the deep-sea exploration


id: astrobiology-20260505-5
file: data/en.wikipedia.org/wiki/Astrobiology-5.md
category: reference
title: Astrobiology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrobiology
date_saved: 2026-05-05T11:11:22.445611+00:00
instance: kb-cron
parent: astrobiology-20260505-0
summary:
== Philosophy == David Grinspoon called astrobiology a field of natural philosophy. Astrobiology intersects with philosophy by raising questions about the nature and existence of life beyond Earth. Philosophical implications include the definition of life itself, issues in the philosophy of mind and cognitive science in case intelligent life is found, epistemological questions about the nature of proof, ethical considerations of space exploration, along with the broader impact of discovering extraterrestrial life on human thought and society. Dunér has emphasized philosophy of astrobiology as an ongoing existential exercise in individual and collective self-understanding, whose major task is constructing and debating concepts such as the concept of life. Key issues, for Dunér, are questions of resource money and monetary planning, epistemological questions regarding astrobiological knowledge, linguistics issues about interstellar communication, cognitive issues such as the definition of intelligence, along with the possibility of interplanetary contamination. Persson also emphasized key philosophical questions in astrobiology. They include ethical justification of resources, the question of life in general, the epistemological issues and knowledge about being alone in the universe, ethics towards extraterrestrial life, the question of politics and governing uninhabited worlds, along with questions of ecology. For von Hegner, the question of astrobiology and


id: astrobiology-20260505-6
file: data/en.wikipedia.org/wiki/Astrobiology-6.md
category: reference
title: Astrobiology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrobiology
date_saved: 2026-05-05T11:11:22.445611+00:00
instance: kb-cron
parent: astrobiology-20260505-0
summary:
Mars Science Laboratory The Mars Science Laboratory (MSL) mission landed the Curiosity rover that is currently in operation on Mars. It was launched 26 November 2011, and landed at Gale Crater on 6 August 2012. Mission objectives are to help assess Mars' habitability and in doing so, determine whether Mars is or has ever been able to support life, collect data for a future human mission, study Martian geology, its climate, and further assess the role that water, an essential ingredient for life as we know it, played in forming minerals on Mars. Tanpopo The Tanpopo mission is an orbital astrobiology experiment investigating the potential interplanetary transfer of life, organic compounds, and possible terrestrial particles in the low Earth orbit. The purpose is to assess the panspermia hypothesis and the possibility of natural interplanetary transport of microbial life as well as prebiotic organic compounds. Early mission results show evidence that some clumps of microorganism can survive for at least one year in space. This may support the idea that clumps greater than 0.5 millimeters of microorganisms could be one way for life to spread from planet to planet. ExoMars rover ExoMars is a robotic mission to Mars to search for


id: astrobiology-20260505-7
file: data/en.wikipedia.org/wiki/Astrobiology-7.md
category: reference
title: Astrobiology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrobiology
date_saved: 2026-05-05T11:11:22.445611+00:00
instance: kb-cron
parent: astrobiology-20260505-0
summary:
Catling, David C. (2013). Astrobiology: A Very Short Introduction. Oxford: Oxford University Press. ISBN 978-0-19-958645-5. Chyba, C. F.; Hand, K. P. (2005). "Astrobiology: The Study of the Living Universe". Annual Review of Astronomy and Astrophysics. 43 (1): 31–74. Bibcode:2005ARA&A..43...31C. doi:10.1146/annurev.astro.43.051804.102202. S2CID 2084246. Cockell, Charles S. (2015). Astrobiology: Understanding Life in the Universe. NJ: Wiley-Blackwell. ISBN 978-1-118-91332-1. Dick, Steven J.; James Strick (2005). The Living Universe: NASA and the Development of Astrobiology. Piscataway, NJ: Rutgers University Press. ISBN 978-0-8135-3733-7. Gilmour, Iain; Mark A. Sephton (2004). An introduction to astrobiology. Cambridge: Cambridge Univ. Press. ISBN 978-0-521-83736-1. Grinspoon, David (2004) [2003]. Lonely planets: The natural philosophy of alien life. New York: ECCO. ISBN 978-0-06-018540-4. Jakosky, Bruce M. (2006). Science, Society, and the Search for Life in the Universe. Tucson: University of Arizona Press. ISBN 978-0-8165-2613-0. Kolb, Vera M., ed. (2015). Astrobiology: An Evolutionary Approach. Boca Raton: CRC Press. ISBN 978-1-4665-8461-7. Kolb, Vera M., ed. (2019). Handbook of Astrobiology. Boca Raton: CRC Press. ISBN 978-1-138-06512-3. Loeb, Avi (2021). Extraterrestrial: The First Sign of Intelligent Life Beyond Earth. Houghton Mifflin Harcourt. ISBN 978-0358278146 Astrobiology, published by Mary Ann Liebert, Inc., is a peer-reviewed journal that explores the origins of life, evolution, distribution, and destiny in


id: dinosauroid-20260505-0
file: data/en.wikipedia.org/wiki/Dinosauroid-0.md
category: reference
title: Dinosauroid
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dinosauroid
date_saved: 2026-05-05T11:11:23.678272+00:00
instance: kb-cron
parent: dinosauroid-20260505-0
summary:
The dinosauroid is a hypothetical species created by Dale A. Russell in 1982. Russell theorized that if a dinosaur such as Stenonychosaurus had not perished in the Cretaceous–Paleogene extinction event, its descendants might have evolved to fill the same ecological niche as humans. While the theory has been met with criticism from other scientists, the dinosauroid has been featured widely in books and documentaries since the theory's inception. == Theory == In 1982, Dale A. Russell, then curator of vertebrate fossils at the Canadian Museum of Nature in Ottawa, conjectured a possible evolutionary path for Stenonychosaurus, if it had not perished in the Cretaceous–Paleogene extinction event, suggesting that it could have evolved into intelligent beings similar in body plan to humans. Over geologic time, Russell noted that there had been a steady increase in the encephalization quotient or EQ (the relative brain weight when compared to other species with the same body weight) among the dinosaurs. Russell had discovered the first Troodontid skull, and noted that, while its EQ was low compared to humans, it was six times higher than that of other dinosaurs. Russell suggested that if the trend in Stenonychosaurus evolution had continued to the present, its brain


id: dragon-s-egg-20260505-0
file: data/en.wikipedia.org/wiki/Dragon's_Egg-0.md
category: reference
title: Dragon's Egg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dragon's_Egg
date_saved: 2026-05-05T11:11:24.889940+00:00
instance: kb-cron
parent: dragon-s-egg-20260505-0
summary:
Dragon's Egg is a 1980 hard science fiction novel by American writer Robert L. Forward. In the story, Dragon's Egg is a neutron star with a surface gravity 67 billion times that of Earth, and inhabited by cheela, intelligent creatures the size of sesame seeds who evolve, live, and think a million times faster than humans. Most of the novel, from May to June 2050, chronicles the cheela civilization beginning with its discovery of agriculture to advanced technology and its first face-to-face contact with humans, who are observing the hyper-rapid evolution of the cheela civilization from orbit around Dragon's Egg. Dragon's Egg attempts to communicate unfamiliar ideas and imaginative scenes while giving adequate attention to the known scientific principles involved. == Plot summary == === The neutron star === Half a million years ago and 50 light-years from Earth, a star in the constellation Draco turns supernova, and the star's remnant becomes a neutron star. The radiation from the explosion causes mutations in many Earth organisms, including a group of hominina that become the ancestors of Homo sapiens. The star's short-lived plasma jets are lop-sided because of anomalies in its magnetic field, and set it on a course passing within


id: dragon-s-egg-20260505-1
file: data/en.wikipedia.org/wiki/Dragon's_Egg-1.md
category: reference
title: Dragon's Egg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dragon's_Egg
date_saved: 2026-05-05T11:11:24.889940+00:00
instance: kb-cron
parent: dragon-s-egg-20260505-0
summary:
In 2032, a cheela develops the race's first weapon and tactics while overcoming a dangerous predator. In November 2049 a human expedition to Dragon's Egg starts building orbital facilities. The rest of the story, including almost the whole history of cheela civilization, spans from 22 May 2050 to 21 June 2050. By humans' standards, a "day" on Dragon's Egg is about 0.2 seconds, and a typical cheela's lifetime is about 40 minutes. One clan organizes the first cheela agriculture, which brings predictable food supply but provokes grumbling about the repetitive work. Shortly after, a volcano emerges in the area, and the clan invents the first sledge to carry food from more distant sources. However, within a few generations the volcano pollutes the soil. One clan leads its population on a long, arduous journey to new territory that is fertile and uninhabited. Although one genius invents mathematics to calculate and measure the band's food supply, the situation is desperate and the clan's survival depends on the self-sacrifice of the oldest members. Over the course of generations, the cheela come to worship the humans' spacecraft as a god, and their records of its satellites' movements cause them to develop writing. Several generations


id: dragon-s-egg-20260505-2
file: data/en.wikipedia.org/wiki/Dragon's_Egg-2.md
category: reference
title: Dragon's Egg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dragon's_Egg
date_saved: 2026-05-05T11:11:24.889940+00:00
instance: kb-cron
parent: dragon-s-egg-20260505-0
summary:
Science fiction critic John Clute wrote that the novel "generates a sense of wonder that is positively joyous", saying it was "a romance of science". Chris Aylott described it as "a minor classic of science fiction – one that shows off both the best and worst elements of hard SF. ... the ideas definitely come first." He found the writing of the human cast dull, but appreciated Forward's ability to share his fascination with the cheela and to create communications between races that lived at vastly different speeds. Greg Costikyan reviewed Dragon's Egg in Ares Magazine #8 and commented that "Dragon's Egg is interesting because it is the epitome of what "hard" science fiction is all about – extrapolation of the most interesting facets of scientific knowledge and speculation." Lambourne, Shallis, and Shortland consider that the research and detailed construction of the scenario make Dragon's Egg an excellent example of hard science fiction. Scientist Seth Shostak described the book's science as "fanciful but impossible to dismiss". John Pierce also regarded Dragon's Egg as hard science fiction at its best, while Forward's later novel Martian Rainbow (1991) was the genre at its worst. Both novels have cardboard human characters, but this


id: evolution-baxter-novel-20260505-0
file: data/en.wikipedia.org/wiki/Evolution_(Baxter_novel)-0.md
category: reference
title: Evolution (Baxter novel)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Evolution_(Baxter_novel)
date_saved: 2026-05-05T11:11:26.065398+00:00
instance: kb-cron
parent: evolution-baxter-novel-20260505-0
summary:
Evolution is a collection of short stories that work together to form an episodic science fiction novel by author Stephen Baxter. It follows 565 million years of human evolution, from shrewlike mammals 65 million years in the past to the ultimate fate of humanity and its descendants, both biological and non-biological, 500 million years in the future. == Plot ==


id: evolution-baxter-novel-20260505-1
file: data/en.wikipedia.org/wiki/Evolution_(Baxter_novel)-1.md
category: reference
title: Evolution (Baxter novel)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Evolution_(Baxter_novel)
date_saved: 2026-05-05T11:11:26.065398+00:00
instance: kb-cron
parent: evolution-baxter-novel-20260505-0
summary:
=== Protagonists in the Purga–human line === Characters listed below descend from Purga and are either ancestral to or descended from humans. Purga (65 Mya, Montana). A female Purgatorius. Despite being a shrew-like insectivore and barely self-aware, she is ancestral to all primates. After losing two mates and their litters to a Troodon attack and cannibalism, she manages to bear two pups. They witness the Chicxulub impact, although one of the pups is cooked alive and her mate succumbs to hypothermia. Purga and her surviving pup eventually arrive at a shore, where other Purgatorius are feeding on a dying Ankylosaurus. Her pup joins them but Purga, now elderly and satisfied that her offspring will survive, retreats and dies in her burrow. Her fossilized tooth is discovered by Joan Useb in 2010. Plesi (63 Mya, North America). A female plesiadapid. Although Earth is lush again, her species still looks very similar to Purgatorius. She has two pups and one of them is killed by an Oxyclaenus. Noth (51 Mya, Ellesmere Island). A 2-year-old Notharctus male living with its herd in the Arctic forests. His species is lemur-looking, matriarchal and far more social, but still lacks a theory of mind. Noth wanders


id: evolution-baxter-novel-20260505-2
file: data/en.wikipedia.org/wiki/Evolution_(Baxter_novel)-2.md
category: reference
title: Evolution (Baxter novel)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Evolution_(Baxter_novel)
date_saved: 2026-05-05T11:11:26.065398+00:00
instance: kb-cron
parent: evolution-baxter-novel-20260505-0
summary:
In 2031, she is pregnant and flying to a conference in Rabaul on global warming, where she meets primatologist Alyce Sigurdardottir and Bex Scott, the genetically enhanced daughter of celebrity scientist Alison Scott. As protesters from the "Fourth World" disrupt the conference, the Rabaul caldera erupts, setting the sequence of events that collapse civilization. In the epilogue, set in 2049, a 52-year-old Joan and her 18-year-old daughter Lucy rescue feral children left behind in the Galápagos Islands due to the ensuing wars and toxic rain. Reflecting on humanity's bleak future, Lucy asks Joan whether she has been happy and she responds affirmatively, based on the fact that unlike their ancestors, they have a glimpse into the past and can be certain that some form of life will survive into the far future. Robert Wayne "Snowy" Snow (millennia in the future, United Kingdom). A 31-year-old male military officer, genetically modified to facilitate cryogenic sleep. During the post-Rabaul wars, the United Nations deploys military officers in suspended animation worldwide to deter international invasions. Centuries later, officers Snowy, Ahmed, Sidewise, Bonner and Moon awaken and soon realize that human civilization has long collapsed. Ahmed, the leader, attempts to rebuild civilization, but with Moon


id: evolution-baxter-novel-20260505-3
file: data/en.wikipedia.org/wiki/Evolution_(Baxter_novel)-3.md
category: reference
title: Evolution (Baxter novel)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Evolution_(Baxter_novel)
date_saved: 2026-05-05T11:11:26.065398+00:00
instance: kb-cron
parent: evolution-baxter-novel-20260505-0
summary:
=== Protagonists outside the Purga–human line === Characters listed below are not ancestral to or descend from humans, although some are primates and thus descend from Purga. Listener (145 Mya, Pangaea). A female Ornitholestes living with Stego, her mate. Unlike most animals in the book, they are fully sapient, with complex language, leather belts, whips, and a culture that revolves around Diplodocus hunting. Stego is killed by an Allosaurus during a hunt, and Listener swears to kill the Diplodocus matriarch that indirectly caused his death. Ten years later, she and her three sons manage to hunt the matriarch, which dooms the herd as well as the Ornitholestes settlement. They become extinct and humans never discover that another sapient species preceded them. Roamer (32 Mya, North Africa). A female of a capuchin-like primate species unknown to paleontology. After a flood destroys her home, she finds herself and other members of her species on a haphazard raft on the Atlantic. Starvation and thirst nearly kill them, but Roamer and two other survivors eventually land on the rainforests of Yucatán and their descendants give rise to a new line of monkeys. Dig (10 Mya, Antarctica). A female of a lemming-like primate species. The


id: expedition-book-20260505-0
file: data/en.wikipedia.org/wiki/Expedition_(book)-0.md
category: reference
title: Expedition (book)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Expedition_(book)
date_saved: 2026-05-05T11:11:27.264761+00:00
instance: kb-cron
parent: expedition-book-20260505-0
summary:
Expedition: Being an Account in Words and Artwork of the 2358 A.D. Voyage to Darwin IV is a 1990 speculative evolution and science fiction book written and illustrated by the American artist and writer Wayne Barlowe. Written as a first-person account of a 24th-century crewed expedition to the fictional exoplanet of Darwin IV, Expedition describes and discusses an imaginary extraterrestrial ecosystem as if it were real. The extraterrestrial or alien organisms of Darwin IV were designed to be "truly alien", with Barlowe having grown dissatisfied with the common science fiction trope of alien life being similar to life on Earth, especially the notion of intelligent alien humanoids. None of Darwin IV's wildlife have eyes, external ears, hair, or jaws, and they bear little resemblance to terrestrial organisms. Various sources of inspiration were used for the creature designs, including dinosaurs, modern beasts and different types of vehicles. Expedition garnered very favorable reviews, being praised particularly for its many illustrations and for the level of detail in the text, which serves to maintain the illusion of realism. Several reviewers also criticized the life forms, finding some of them to be implausible or doubting that Darwin IV could actually function as an ecosystem.


id: expedition-book-20260505-1
file: data/en.wikipedia.org/wiki/Expedition_(book)-1.md
category: reference
title: Expedition (book)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Expedition_(book)
date_saved: 2026-05-05T11:11:27.264761+00:00
instance: kb-cron
parent: expedition-book-20260505-0
summary:
== Reception == A review in Publishers Weekly stated that the book had an "abundance of lavish full-color illustrations and detailed black-and-white sketches" and that the many details mentioned in the book, such as information on the planet of Darwin IV itself, and the intricate details on the behavior of the various creatures, "help maintain the illusion of realism and immediacy such a first person narrative demands". In his 2005 review in The Space Review of Alien Planet, a 2005 TV special based on Expedition, space historian Dwayne A. Day described Expedition as "highly regarded". The book was nominated for the 1991 Chesley Award for Artistic Achievement. Also in 1991, Expedition was named the 'Best Book for Teenagers' by the New York Public Library. A portion of the book, "Sea Strider Skull and Littoralope" was reprinted by the American Littoral Society in 1996. A review in The Vindicator described Expedition as a "lavish science-fiction bestiary", but stated that the "weird creatures lack the necessary aura of plausibility". This review was not the only one that found some of the creatures implausible. In his 2005 review of Alien Planet, which featured the same lifeforms, Dwayne A. Day stated that "the animals


id: extraterrestrial-tv-program-20260505-0
file: data/en.wikipedia.org/wiki/Extraterrestrial_(TV_program)-0.md
category: reference
title: Extraterrestrial (TV program)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Extraterrestrial_(TV_program)
date_saved: 2026-05-05T11:11:28.488734+00:00
instance: kb-cron
parent: extraterrestrial-tv-program-20260505-0
summary:
Extraterrestrial, also known in the UK as Alien Worlds, is a British-American two-part television documentary miniseries, aired in 2005 in the UK by Channel 4, by the National Geographic Channel in the US on Monday, May 30, 2005 and produced by Big Wave Productions Ltd. The program focuses on the hypothetical and scientifically feasible evolution of alien life on extrasolar planets, providing model examples of two different fictional worlds, one in each of the series's two episodes. The documentary is based on speculative collaboration of a group of American and British scientists, who were collectively commissioned by National Geographic. For the purposes of the documentary, the team of scientists divides two hypothetical examples of realistic worlds on which extraterrestrial life could evolve: A tidally locked planet (dubbed "Aurelia") orbiting a red dwarf star and a large moon (dubbed "Blue Moon") orbiting a gas giant in a binary star system. The scientific team of the series used a combination of accretion theory, climatology, and xenobiology to imagine the most likely locations for extraterrestrial life and most probable evolutionary path such life would take. The "Aurelia" and "Blue Moon" concepts seen in the series were also featured in the touring exhibition The


id: extraterrestrial-tv-program-20260505-1
file: data/en.wikipedia.org/wiki/Extraterrestrial_(TV_program)-1.md
category: reference
title: Extraterrestrial (TV program)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Extraterrestrial_(TV_program)
date_saved: 2026-05-05T11:11:28.488734+00:00
instance: kb-cron
parent: extraterrestrial-tv-program-20260505-0
summary:
==== Traditional assumptions tested ==== Nonetheless, the scientists employed by the programme decided to test the traditional assumptions for such a planet and start a model out for it from a protoplanetary disk through to its eventual death. Their estimations suggested such a planet could indeed hold on to its atmosphere, although with freakishly unusual results by Earth standards. Aurelia would be gravitationally locked. Due to this, Aurelia would not have seasons or a day/night cycle, as half would be in perpetual darkness, a permanent ice age. The other half would contain a giant, unending hurricane with permanent torrential rain at the point directly opposite the local star. Between these two zones, it would be suitable for life. The giant hurricane might generate enormous waves in the ocean, which would migrate outwards. They would be wind-driven and would not reach the top of an ocean to the bottom, as a tsunami does. Nonetheless, waves as big and as devastating as those humans call freak waves might be regular. Simple bacterial and algal life would not be threatened. === Lifeforms of Aurelia === In continued speculation, and assuming that there was land in this habitable zone, it would be likely to


id: extraterrestrial-tv-program-20260505-2
file: data/en.wikipedia.org/wiki/Extraterrestrial_(TV_program)-2.md
category: reference
title: Extraterrestrial (TV program)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Extraterrestrial_(TV_program)
date_saved: 2026-05-05T11:11:28.488734+00:00
instance: kb-cron
parent: extraterrestrial-tv-program-20260505-0
summary:
=== Lifeforms of the Blue Moon === Skywhales are prey to the insect-like caped Stalkers, colony-living predators that have several different tasks. Scouts find skywhales and mark them with a special scent, then return to the nest to spread the word. Workers then swarm out in huge numbers, detecting the whale and working together to bring them down from the sky and kill them. Finally, there is a queen, who stays in the nest and constantly lays eggs that become new stalkers. This lifestyle is based on earth's hornets. The Stalkers are also prey, for the Pagoda branches are draped with the lethal webs of the plant-like ghost traps. Once a Stalker is caught in a ghost trap web, the carnivore uses its tentacles to lift its catch up into its mouth, to be digested by the acid in a primitive stomach. As well as Skywhales, giant Kites also fly above the forest canopy. These parasol-like grazers can grow up to 5 m (16 ft) in diameter and still stay airborne. Their tethers help control their floating, while their jellyfish-like tentacles snatch Helibug larvæ from the water-filled sky pond. Helibugs have a trilaterally symmetrical body plan, with three eyes, three


id: the-first-men-in-the-moon-20260505-0
file: data/en.wikipedia.org/wiki/The_First_Men_in_the_Moon-0.md
category: reference
title: The First Men in the Moon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_First_Men_in_the_Moon
date_saved: 2026-05-05T11:11:29.677986+00:00
instance: kb-cron
parent: the-first-men-in-the-moon-20260505-0
summary:
The First Men in the Moon by the English author H. G. Wells is a scientific romance about a journey to the Moon by two Englishmen who discover that a sophisticated extraterrestrial civilisation of insect-like creatures ("Selenites") inhabits the lunar interior. The first-person narrator Mr. Bedford, a businessman, recounts his adventure with an eccentric scientist (Mr. Cavor), who has invented a gravity-blocking substance (cavorite) that the pair then use to construct a spherical spacecraft to reach the Moon, hoping to find valuable minerals. The work was originally serialised in The Strand Magazine (UK) and The Cosmopolitan (USA) from November 1900 to June 1901 and was published in hardcover book form in 1901. Wells called it one of his "fantastic stories". The novel is a major work in the long history of the Moon in science fiction, which dates back to classical antiquity and includes earlier encounters with lunar beings and civilisations, often satirical in nature. The scientific inspiration in large part would come from Jules Verne and his book From the Earth to the Moon in 1865, which used a cannon shot to launch a spacecraft with a human crew, and the sequel Around the Moon in 1869 about the


id: the-first-men-in-the-moon-20260505-1
file: data/en.wikipedia.org/wiki/The_First_Men_in_the_Moon-1.md
category: reference
title: The First Men in the Moon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_First_Men_in_the_Moon
date_saved: 2026-05-05T11:11:29.677986+00:00
instance: kb-cron
parent: the-first-men-in-the-moon-20260505-0
summary:
On the surface of the Moon the two men discover a desolate landscape, but as the Sun rises, the thin, frozen atmosphere vaporises and strange plants begin to grow with extraordinary rapidity. Bedford and Cavor leave the capsule, but in romping about in the much lower gravity get lost in the rapidly growing jungle. They hear for the first time a mysterious booming coming from beneath their feet. They encounter "great beasts", "monsters of mere fatness", that they dub "mooncalves", and five-foot-high "Selenites" tending them. At first they hide and crawl about, but growing hungry partake of some "monstrous coralline growths" of fungus that inebriate them. They wander drunkenly until they encounter a party of six extraterrestrials, who capture them. The insectoid lunar natives (referred to as "Selenites", after Selene, the Greek moon goddess) are part of a complex and technologically sophisticated society that lives underground, but this is revealed only in radio communications received from Cavor after Bedford's return to Earth. Bedford and Cavor break out of captivity beneath the surface of the Moon and flee, with Bedford killing several Selenites. In their flight they discover that gold is common on the Moon. In their attempt to find their


id: the-first-men-in-the-moon-20260505-2
file: data/en.wikipedia.org/wiki/The_First_Men_in_the_Moon-2.md
category: reference
title: The First Men in the Moon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_First_Men_in_the_Moon
date_saved: 2026-05-05T11:11:29.677986+00:00
instance: kb-cron
parent: the-first-men-in-the-moon-20260505-0
summary:
Cavor's account explains that Selenites exist in hundreds of forms, many with a particular exaggerated physical feature suited to a single function, such as an enlarged arm or tentacle, or a highly developed smelling organ. Without a confining rigid bony skull, Selenite brains are able to grow continuously, and intellectual functionaries have greatly enlarged brains but reduced physical bodies. They are aided by special attendants whose only role is to support them and help them move about. A Selenite finds fulfilment in carrying out the specific social function or task for which each has been brought up or modified. Specialisation is the essence of Selenite society: "And so it is with all sorts and conditions of Selenites—each is a perfect unit in a world machine..." Cavor learns that when members of society who perform a particular function are not needed, they are drugged and deposited on the ground in a dormant state in a huge area where giant fungus is grown for food. These superfluous members of society will be revived when it is determined that they are needed again. He reflects that: "To drug the worker one does not want and toss him aside is surely far better than


id: the-first-men-in-the-moon-20260505-3
file: data/en.wikipedia.org/wiki/The_First_Men_in_the_Moon-3.md
category: reference
title: The First Men in the Moon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_First_Men_in_the_Moon
date_saved: 2026-05-05T11:11:29.677986+00:00
instance: kb-cron
parent: the-first-men-in-the-moon-20260505-0
summary:
The character Jet Morgan takes a copy of the book along with him in the Journey into Space story, Journey to the Moon from 1953 and its 1958 re-recording, Operation Luna. Cavorite was featured as a major plot device in the 1999 first volume of The League of Extraordinary Gentlemen, and Cavor (given the first name of Selwyn) also appears in the volume and is mentioned in The League of Extraordinary Gentlemen: Black Dossier. In The League of Extraordinary Gentlemen, Volume III: Century, the Selenites are featured as enemies of the nude lunar Amazons. Cavorite also is used as a minor plot device in Warehouse 13, with its gravity blocking properties used by Wells to make a trap. Cavorite and Cavor also play a major role in the end of Scarlet Traces: The Great Game, with the Selenites also briefly depicted. The video game Voyage: Inspired by Jules Verne was based both on Wells's The First Men in the Moon, along with Jules Verne's From the Earth to the Moon and Around the Moon. Cavorite, Cavor, and the Selenites are a large factor in The Martian War, where Cavor's ship takes Wells, his wife, and T.H. Huxley first to the


id: flanimals-20260505-0
file: data/en.wikipedia.org/wiki/Flanimals-0.md
category: reference
title: Flanimals
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Flanimals
date_saved: 2026-05-05T11:11:30.875413+00:00
instance: kb-cron
parent: flanimals-20260505-0
summary:
Flanimals is a book series written by comedian Ricky Gervais and illustrated by Rob Steen. It depicts an assortment of seemingly useless or inadequate fictional animals and their behaviour. The cover Flanimal is the Grundit. The book is published by Faber and Faber, which has also published the sequels More Flanimals, Flanimals of the Deep and Flanimals: The Day of the Bletchling. Flanimals: Pop Up was published October 2009 by Walker Books in the UK and in March 2010 by Candlewick Press in the US. == List of Flanimals == Coddleflop: A green mush puddle that absorbs substances and flips over to protect its soft top. However, since its bottom is equally soft, this strategy is never successful. Plamglotis: A purple ape-like Flanimal with no legs so it swallows its hands to walk around to find food, which it cannot eat because its mouth is full. Mernimbler: A fluffy, pink, round Flanimal that feeds on honey water and soft cloud bits. It transforms into an aggressive, ogre-like adult stage when someone comments on its cuteness. They devour everything and die of chronic indigestion. Grundit: A heavily built blue Flanimal with a bump on its head from falling off Puddloflaj. Their


id: the-flight-of-dragons-book-20260505-0
file: data/en.wikipedia.org/wiki/The_Flight_of_Dragons_(book)-0.md
category: reference
title: The Flight of Dragons (book)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Flight_of_Dragons_(book)
date_saved: 2026-05-05T11:11:32.051729+00:00
instance: kb-cron
parent: the-flight-of-dragons-book-20260505-0
summary:
The Flight of Dragons is a 1979 speculative evolution book written by Peter Dickinson and illustrated by Wayne Anderson. == Thesis == According to Dickinson's hypothesis, the chief obstacle to admitting the past existence of dragons is the difficulty of powered flight by such a large organism. To resolve this, he introduces a dirigible-like structure in which hydrochloric acid would dissolve large amounts of rapidly growing bone, releasing massive amounts of hydrogen that, once aloft, would support the body above the ground. The dragon's wings are traced to "modifications of the ribcage" (an anatomical evolutionary path shared by the genus Draco), and the expulsion of fire from the throat, as a means of removal of excess gas. The absence of fossil evidence is traced again to the internal acids, which (in Dickinson's view) would dissolve the bones soon after death. Dickinson states he got the idea for his "pseudo-scientific monograph" after looking at one of Ursula K. Le Guin's Earthsea books: This one had a bulky body and rather stubby wings, which obviously would never get it airborne, let alone with the two people it was carrying on its back, and all its own weight of muscle and bone. Obviously


id: fragment-novel-20260505-0
file: data/en.wikipedia.org/wiki/Fragment_(novel)-0.md
category: reference
title: Fragment (novel)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fragment_(novel)
date_saved: 2026-05-05T11:11:33.197529+00:00
instance: kb-cron
parent: fragment-novel-20260505-0
summary:
Fragment (2009) is a science-based thriller by author and screenwriter Warren Fahy. The novel focuses on a crew of young scientists from a reality TV show who must try to survive when their research vessel, the Trident, lands on Henders Island, where predatory creatures have been living and evolving for over half a billion years. Producer Lloyd Levin optioned Fahy's screenplay adaptation of Fragment for a major motion picture. Pandemonium, Fahy's sequel to Fragment, was published in March 2013. == Plot summary == In 1791, Captain Ambrose Henders and his crew stop at a tiny island in search of fresh water in the South Pacific. After one man, Henry Frears, is sent to obtain water, Captain Henders is forced to retreat to prevent more loss of life when Frears is eaten by unknown creatures. He writes of the account in his journal. In the present day, an exploratory research vessel "The Trident" sails across the same stretch of the Pacific filming for a documentary series called "Sea life". When Captain Sol picks up an EPIRB distress beacon, The crew decides to investigate. They set ashore to scope out the shipwrecked "Balboa Bilbo", from which the distress beacon emanated. After arriving


id: future-evolution-20260505-0
file: data/en.wikipedia.org/wiki/Future_Evolution-0.md
category: reference
title: Future Evolution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Future_Evolution
date_saved: 2026-05-05T11:11:34.363353+00:00
instance: kb-cron
parent: future-evolution-20260505-0
summary:
Future Evolution is a book written by paleontologist Peter Ward and illustrated by Alexis Rockman. He addresses his own opinion of future evolution and compares it with Dougal Dixon's After Man: A Zoology of the Future and H. G. Wells's The Time Machine. == History of book == According to Ward, humanity may exist for a long time. Nevertheless, we are impacting our planet. He splits his book in different chronologies, starting with the near future (the next 1,000 years). Humanity would be struggling to support a massive population of 11 billion. Global warming raises sea levels. The ozone layer weakens. Most of the available land is devoted to agriculture due to the demand for food. Despite all this, the oceanic wildlife remains untethered by most of these impacts, specifically the commercial farmed fish. This is, according to Ward, an era of extinction that would last about 10 million years (note that many human-caused extinctions have already occurred). After that, Earth gets stranger. Ward labels the species that have the potential to survive in a human-infested world. These include dandelions, raccoons, owls, pigs, cattle, rats, snakes, and crows to name but a few. In the human-infested ecosystem, those preadapted to


id: the-future-is-wild-20260505-0
file: data/en.wikipedia.org/wiki/The_Future_Is_Wild-0.md
category: reference
title: The Future Is Wild
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Future_Is_Wild
date_saved: 2026-05-05T11:11:35.613543+00:00
instance: kb-cron
parent: the-future-is-wild-20260505-0
summary:
The Future Is Wild (also referred to by the acronym FIW) is a 2002 speculative evolution docufiction miniseries and an accompanying multimedia entertainment franchise. The Future Is Wild explores the ecosystems and wildlife of three future time periods: 5 million, 100 million, and 200 million years in the future, in the format of a nature documentary. Though the settings and animals are fictional, the series has an educational purpose, serving as an informative and entertaining way to explore concepts such as evolution and climate change. The Future Is Wild was first conceived by independent producer Joanna Adams in 1996 and developed together with various scientists, including Dougal Dixon, best known as the author of the 1981 book After Man, which also explored future wildlife. The 2002 series was an international co-production, involving the Franco-German channel Arte, the German ZDF, the Austrian ORF, the Italian MFE - MediaForEurope (via their Mediaset division), and the American Animal Planet and Discovery Channel. Wildly successful, The Future Is Wild continues to be broadcast to this day and has been shown on TV in more than 60 countries. The success of The Future Is Wild spawned a large multimedia franchise, including books, children's entertainment, exhibitions,


id: the-future-is-wild-20260505-1
file: data/en.wikipedia.org/wiki/The_Future_Is_Wild-1.md
category: reference
title: The Future Is Wild
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Future_Is_Wild
date_saved: 2026-05-05T11:11:35.613543+00:00
instance: kb-cron
parent: the-future-is-wild-20260505-0
summary:
== Development and production == The idea for The Future Is Wild was first conceived in 1996 by Joanna Adams, a British entrepreneur who has previously produced documentaries on modern and extinct animals. As an independent producer, Adams wanted to create a documentary series different from anything that had come before, and something that could not be copied by larger production companies. The series was envisioned as an entertaining, informative and inspirational way to explain planetary change and evolution, suitable for the popular market worldwide. In 1996, the concept of the series, and ideas for an accompanying multimedia franchise, was first unveiled at the Frankfurt Book Fair and the MIPTV Media Market. The Future Is Wild was influenced by Scottish geologist and paleontologist Dougal Dixon's 1981 book After Man, which imagines wildlife and ecosystems 50 million years in the future. Dixon was brought in as a consultant early on in the development of the series and designed many of the creatures featured. The series was not able to use any of Dixon's creatures from After Man, given that the rights to adapting After Man were at this time owned by DreamWorks SKG. Nevertheless, several creatures were similar to Dixon's earlier


id: the-future-is-wild-20260505-2
file: data/en.wikipedia.org/wiki/The_Future_Is_Wild-2.md
category: reference
title: The Future Is Wild
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Future_Is_Wild
date_saved: 2026-05-05T11:11:35.613543+00:00
instance: kb-cron
parent: the-future-is-wild-20260505-0
summary:
In 2007, a 3D animated children's series (targeted at children aged six to twelve) based on The Future Is Wild premiered on Discovery Kids. Consisting of 26 episodes, each 22 minutes in length, the series was also simply called The Future Is Wild, and followed the four children C.G., Ethan, Emily and Luis, and their pet Squibbon, as they travelled through time and explored the settings and animals seen in the original series. According to Joanna Adams, the animated series, just like the original series, encourages viewers to think about the future of the planet, but "this time it is devoted particularly to kids and our future science is woven into some really fun stories about a group of time travelling kids." Portions of the original The Future Is Wild team worked on the series, and it was jointly produced by the Singaporean company iVL Animation and the Canadian company Nelvana. It was the first co-produced Singaporean 3D-animated TV programme to be broadcast in the United States and Germany. === Exhibitions === The Future Is Wild has been adapted into exhibition form, both for use as a temporary exhibition or short-term events, and for long-term high-profile attractions. There have been


id: the-future-is-wild-20260505-3
file: data/en.wikipedia.org/wiki/The_Future_Is_Wild-3.md
category: reference
title: The Future Is Wild
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Future_Is_Wild
date_saved: 2026-05-05T11:11:35.613543+00:00
instance: kb-cron
parent: the-future-is-wild-20260505-0
summary:
=== Cancelled projects === Following the success of The Future Is Wild, plans were made to adapt the series into a feature film with Warner Bros., but those plans fell through after the release of the film Avatar (2009), when Warner Bros. felt that the bar for such a film had been raised too high. Joanna Adams and the team at one point also worked on developing a sequel documentary series to the original The Future Is Wild series, dubbed The Future Is Wild 2, and had raised the necessary funding, but the project collapsed when Discovery Channel announced that they would no longer be making documentaries. In 2015, the virtual reality and augmented reality developer Cornel Hillmann, and his studio, STUDIO CGARTIST, began developing The Future Is Wild for virtual reality, initially focusing on small-scale preview projects. The first completed project was a small preview programme for Google Cardboard, which met with positive response at the 2016 Frankfurt Book Fair. A The Future Is Wild virtual reality game, The Future Is Wild VR, was in development in 2016. According to Hillmann, the game was intended to be a first-person exploration game with survival elements, with players able to travel


id: future-predator-20260505-0
file: data/en.wikipedia.org/wiki/Future_predator-0.md
category: reference
title: Future predator
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Future_predator
date_saved: 2026-05-05T11:11:36.813727+00:00
instance: kb-cron
parent: future-predator-20260505-0
summary:
The future predator is a fictional future apex predator in the British science fiction television programme Primeval. The future predator was conceived by producers Tim Haines and Adrian Hodges and was designed by Daren Horley. Giant and flightless future descendants of bats, the predators are ruthless creatures that appear several times throughout the series. They were positively received and have been termed by some commentators as the "Daleks of Primeval" owing to their repeated appearances and how difficult they are to stop. == Description and design == The central story of Primeval revolves around time portals (called "anomalies") opening up and letting through various prehistoric creatures into the present. While making the programme, the producers concluded that anomalies should logically be able to connect the present to the future as well. The future predators are flightless macropredatory future descendants of bats about the size of lions. They walk on their knuckles and are quadrupedal, though are also able to run and rear up bipedally at times. With their elongated arms, evolved from the wings of their ancestors, they are also able to leap and climb. Since the predators rely on advanced echolocation to hunt, their eyes have atrophied away. The


id: gal-pagos-novel-20260505-0
file: data/en.wikipedia.org/wiki/Galápagos_(novel)-0.md
category: reference
title: Galápagos (novel)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Galápagos_(novel)
date_saved: 2026-05-05T11:11:37.964524+00:00
instance: kb-cron
parent: gal-pagos-novel-20260505-0
summary:
Galápagos is a 1985 novel by the American author Kurt Vonnegut, his eleventh published novel. Set in the Galápagos Islands after a global financial disaster, the novel questions the merit of the human brain from an evolutionary perspective. The title is both a reference to the islands on which part of the story plays out, and a tribute to Charles Darwin, on whose theory Vonnegut relies to reach his own conclusions. It was published by Delacorte Press. == Plot summary == Galápagos is the story of a small band of mismatched humans who are shipwrecked on the fictional island of Santa Rosalia in the Galápagos Islands after a global financial crisis cripples the world's economy. Shortly thereafter, a disease renders all humans on Earth infertile, with the exception of the people on Santa Rosalia, making them the last specimens of humankind. Over the next million years, their descendants, the only fertile humans left on the planet, eventually evolve into a furry species resembling sea lions: though possibly still able to walk upright (it is not explicitly mentioned, but it is stated that they occasionally catch land animals), they have a snout with teeth adapted for catching fish, a streamlined skull


id: greenworld-20260505-0
file: data/en.wikipedia.org/wiki/Greenworld-0.md
category: reference
title: Greenworld
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Greenworld
date_saved: 2026-05-05T11:11:39.128105+00:00
instance: kb-cron
parent: greenworld-20260505-0
summary:
Greenworld (Japanese: グリーンワールド Hepburn: Gurīn wārudo) is a 2010 speculative evolution and science fiction book written by Scottish geologist and paleontologist Dougal Dixon and primarily illustrated by Dixon himself, alongside a few images by other artists. Greenworld features a fictional alien planet of the same name and a diverse biosphere of alien organisms. Greenworld has so far only been published in Japan, where it was released in two volumes. The premise of Greenworld follows human colonisation of the alien planet over the course of a thousand years, chronicling mankind's disastrous impact on Greenworld's ecosystems, similar to how humans today are impacting Earth and its life. Greenworld and its creatures were originally designed by Dixon as a design exercise for his local science fiction group and the planet and its organisms first appeared in a 1992 episode of the Channel 4 series Equinox, followed by appearances in various other media, including the 1997 programme Natural History of an Alien. Greenworld's premise is similar to, and repurposed from, Dixon's original idea for his book Man After Man (1990), which would have involved humans time-travelling 50 million years into the future to colonize biosphere of the future he had developed for After Man


id: last-and-first-men-20260505-0
file: data/en.wikipedia.org/wiki/Last_and_First_Men-0.md
category: reference
title: Last and First Men
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Last_and_First_Men
date_saved: 2026-05-05T11:11:40.393257+00:00
instance: kb-cron
parent: last-and-first-men-20260505-0
summary:
Last and First Men: A Story of the Near and Far Future is a "future history" science fiction novel written in 1930 by the British author Olaf Stapledon. A work of unprecedented scale in the genre, it describes the history of humanity from the present onwards across two billion years and eighteen distinct human species, of which our own is the first. The book employs a narrative conceit that, under subtle inspiration, the novelist has unknowingly been dictated a channelled text from the last human species. Stapledon's conception of history follows a repetitive cycle with many varied civilisations rising from and descending back into savagery over millions of years, as the later civilisations rise to far greater heights than the first. The book anticipates the science of genetic engineering, and is an early example of the fictional supermind: a consciousness comprising many telepathically linked individuals. In the novel, a series of devastating European wars in the 21st century result in the United States and China being the last remaining superpowers on planet Earth. This eventually leads to a Sino-American war which ends with the creation of a first World State. In the 26th century, individual religions go extinct. All human


id: last-and-first-men-20260505-1
file: data/en.wikipedia.org/wiki/Last_and_First_Men-1.md
category: reference
title: Last and First Men
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Last_and_First_Men
date_saved: 2026-05-05T11:11:40.393257+00:00
instance: kb-cron
parent: last-and-first-men-20260505-0
summary:
== Species of humans == First Men. (Chapters 1–6) The First Men are our own species. Beginning in the early twenty-first century, several increasingly devastating wars take place in Europe, which result in the United States and China becoming the two dominant superpowers on Earth. In the twenty-fourth century, the US and China go to war, and the war concludes with the formation of the First World State. In the twenty-sixth century, all religions and secular science consolidate into a religion based on the worship of motion whose god is Gordelpus, the Prime Mover. Four millennia after the formation of the First World State, humans deplete Earth's supply of fossil fuels, resulting in the total collapse of civilization. 100,000 years later, the Patagonian Civilization emerges. One feature of the Patagonian civilization was a cult of youth. One day, a riot occurs at a mine, and the rioters inadvertently cause a colossal subterranean explosion, rendering most of the Earth's surface uninhabitable for millions of years save for the poles and the northern coast of Siberia. The only survivors of the disaster are thirty-five humans stationed at the North Pole, whose descendants eventually split up into two separate species, the Second Men


id: last-and-first-men-20260505-2
file: data/en.wikipedia.org/wiki/Last_and_First_Men-2.md
category: reference
title: Last and First Men
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Last_and_First_Men
date_saved: 2026-05-05T11:11:40.393257+00:00
instance: kb-cron
parent: last-and-first-men-20260505-0
summary:
Eighteenth Men. (Chapters 15–16) The most advanced humans of all, essentially a perfected version of the 17th species. A race of philosophers and artists with a very liberal sexual morality. "Superficially we seem to be not one species but many." (One interesting aspect of the Eighteenth Men is that they have a number of different "sub-genders", variants on the basic male and female pattern, with distinctive temperaments. The Eighteenth Men's equivalent of the family unit includes one of each of these sub-genders and is the basis of their society. The units have the ability to act as a group mind, which eventually leads to the establishment of a single group mind uniting the entire species.) This species no longer dies naturally, but only by accident, suicide, or being killed. Despite their hyper-advanced civilisation, they practice ritual cannibalism. They are eventually extinguished on Neptune after a supernova consumes the remains of the Solar System, faster than any means of escape they can devise for their corporeal forms. This last species of man devises a method of panspermia, a virus to broadcast life to other worlds and ultimately cause the evolution of new sentient species throughout the galaxy.


id: last-and-first-men-20260505-3
file: data/en.wikipedia.org/wiki/Last_and_First_Men-3.md
category: reference
title: Last and First Men
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Last_and_First_Men
date_saved: 2026-05-05T11:11:40.393257+00:00
instance: kb-cron
parent: last-and-first-men-20260505-0
summary:
=== Sub-humans === Baboon-like Submen. (Chapter 7) "Bent so that as often as not they used their arms as aids to locomotion, flat-headed and curiously long-snouted, these creatures were by now more baboon-like than human". Seal-like Submen. (Chapter 13) "The whole body was moulded to stream-lines. The lung capacity was greatly developed. The spine had elongated, and increased in flexibility. The legs were shrunken, grown together, and flattened into a horizontal rudder. The arms also were diminutive and fin-like, though they still retained the manipulative forefinger and thumb. The head had shrunk into the body and looked forward in the direction of swimming. Strong carnivorous teeth, emphatic gregariousness, and a new, almost human, cunning in the chase, combined to make these seal-men lords of the ocean". Period of Eclipse. (Chapter 14) "Man's consciousness was narrowed and coarsened into brute-consciousness. By good luck the brute precariously survived." Nature succeeds in colonising Neptune where sapient life fails. Human-derived mammals of all shapes come to dominate Neptune's ecosystem before adapting well enough for the vestiges of opposable thumbs and intelligence to become assets again. == Reception == Wendy Graham reviewed Last and First Men for Adventurer magazine and stated that "I found the


id: last-and-first-men-20260505-4
file: data/en.wikipedia.org/wiki/Last_and_First_Men-4.md
category: reference
title: Last and First Men
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Last_and_First_Men
date_saved: 2026-05-05T11:11:40.393257+00:00
instance: kb-cron
parent: last-and-first-men-20260505-0
summary:
== Influences on other writers == Brian Aldiss, in his preface to the 1962 edition, acknowledges the deep impression on him—and considerable influence on his own later writing—of Stapledon's book, which he encountered in 1943 while a British soldier fighting the Japanese in Burma, "An appropriately unusual period of life at which to encounter a vision so far outside ordinary experience." Aldiss also mentions James Blish as another writer deeply influenced by Stapledon. C. S. Lewis, in his own preface to That Hideous Strength, notes: "I believe that one of the central ideas of this tale came into my head from conversations I had with a scientific colleague, some time before I met a rather similar suggestion in the works of Mr. Olaf Stapledon. If I am mistaken in this, Mr. Stapledon is so rich in invention that he can afford to lend, and I admire his invention (though not his philosophy) so much that I should feel no shame to borrow." The reference to objecting to Stapledon's philosophy was no accident. In particular, Lewis objected to Stapledon's idea, as expressed in the present book, that mankind could escape from an outworn planet and establish itself on another one; this


id: the-last-dragon-2004-film-20260505-0
file: data/en.wikipedia.org/wiki/The_Last_Dragon_(2004_film)-0.md
category: reference
title: The Last Dragon (2004 film)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Last_Dragon_(2004_film)
date_saved: 2026-05-05T11:11:41.572330+00:00
instance: kb-cron
parent: the-last-dragon-2004-film-20260505-0
summary:
The Last Dragon, known as Dragons: A Fantasy Made Real in the United States, and also known as Dragon's World in other countries, is a 2004 British docufiction made by Darlow Smithson Productions for Channel Four and broadcast on both Channel Four and Animal Planet. It posits a speculative evolution of dragons from the Cretaceous period up to the 15th century, and suppositions about what dragon life and behaviour might have been like if they had existed and evolved. It uses the premise that the ubiquity of dragons in world mythology suggests that dragons could have existed. They are depicted as a scientifically feasible species of reptile that could have evolved, somewhat similar to the depiction of dragons in the Dragonology series of books. The dragons featured in the show were designed by John Sibbick. The programme switches between two stories. The first uses CGI to show the dragons in their natural habitat throughout history. The second shows the story of a modern-day scientist at a museum, Dr. Jack Tanner, who believes in dragons. When the frozen remains of an unknown creature are discovered in the Carpathian Mountains, Tanner and two colleagues from the museum undertake the task of examining


id: living-fossil-short-story-20260505-0
file: data/en.wikipedia.org/wiki/Living_Fossil_(short_story)-0.md
category: reference
title: Living Fossil (short story)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Living_Fossil_(short_story)
date_saved: 2026-05-05T11:11:42.719946+00:00
instance: kb-cron
parent: living-fossil-short-story-20260505-0
summary:
"Living Fossil" is a science fiction story by American writer L. Sprague de Camp, on the concepts of human extinction and future evolution. It was first published in the magazine Astounding Science-Fiction for February 1939. It first appeared in book form in the anthology A Treasury of Science Fiction (Crown Publishers, 1948); it later appeared in the anthologies Gates to Tomorrow (Atheneum, 1973), and The SFWA Grand Masters, Volume 1 (Tor Books, 1999). The story has been translated into Danish, Swedish and Italian. It is perhaps the earliest work of fiction dealing with the afterwards popular theme of humanity being replaced by other intelligent primates in the future, later epitomized by Pierre Boulle's Planet of the Apes. == Plot summary == In the far future (perhaps five to ten million years from now), humans and much of the world's fauna have gone extinct, and new creatures have evolved from the remaining species to take their places. Jmu, intelligent primates evolved from capuchin monkeys, now fill the niche left by humans, giant agoutis that of horses, giant tapirs that of elephants. There are also giant rabbits. Other animals, like bears, lions, deer, geese, ducks, snakes, dragonflies, grasshoppers, fleas and mayflies, continue


id: man-after-man-20260505-0
file: data/en.wikipedia.org/wiki/Man_After_Man-0.md
category: reference
title: Man After Man
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Man_After_Man
date_saved: 2026-05-05T11:11:43.925085+00:00
instance: kb-cron
parent: man-after-man-20260505-0
summary:
Man After Man: An Anthropology of the Future is a 1990 speculative evolution and science fiction book written by Scottish geologist and palaeontologist Dougal Dixon and illustrated by Philip Hood. The book also features a foreword by Brian Aldiss. Man After Man explores a hypothetical future path of human evolution set from 200 years in the future to 5 million years in the future, with several future human species evolving through genetic engineering and natural means through the course of the book. Man After Man is Dixon's third work on speculative evolution, following After Man (1981) and The New Dinosaurs (1988). Unlike the previous two books, which were written much like field guides, the focus of Man After Man lies much on the individual perspectives of future human individuals of various species. Man After Man, like its predecessors, uses its fictional setting to explore and explain real natural processes, in this case climate change through the eyes of the various human descendants in the book, who have been engineered specifically to adapt to it. Reviews of Man After Man were generally positive, but more mixed than the previous books and criticised its scientific basis to a greater extent than that


id: man-after-man-20260505-1
file: data/en.wikipedia.org/wiki/Man_After_Man-1.md
category: reference
title: Man After Man
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Man_After_Man
date_saved: 2026-05-05T11:11:43.925085+00:00
instance: kb-cron
parent: man-after-man-20260505-0
summary:
== Reception == Like its predecessors After Man and The New Dinosaurs, Man After Man received generally positive reviews, though the science of the book was criticised in a greater extent than that featured in the preceding works. Writing for the Los Angeles Times, reviewer John Wilkes likened the future explored within Man After Man to the world of the film Blade Runner (1982) in its grim depictions of "technological progress decaying into human viciousness". Wilkes praised the introductionary chapters of the book, particularly the "easy-to-grasp and clearly illustrated" chapter on genetics. The various future human species were referred to by Wilkes as "truly wondrous" but "miserable". Wilkes also praised the "striking" illustrations by Philip Hood, particularly that of the "vacuumorph", though noted that some of his artwork was somewhat anatomically questionable and that some aspects of the book's science and technology "raised questions too involved to introduce here". He concluded that the greatest strength of the work was its ability to "compel empathy with such strange creatures". Writing for the magazine The Skeptic, British critic and author David Langford stated that the book was a "superior coffee-table production", but found it "illuminating and fun" rather than realistic. In particular,


id: mermaids-the-body-found-20260505-0
file: data/en.wikipedia.org/wiki/Mermaids:_The_Body_Found-0.md
category: reference
title: Mermaids: The Body Found
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mermaids:_The_Body_Found
date_saved: 2026-05-05T11:11:46.144511+00:00
instance: kb-cron
parent: mermaids-the-body-found-20260505-0
summary:
Mermaids: The Body Found is a pseudo-documentary television program originally aired on American TV channels Animal Planet (May 27, 2012) and Discovery Channel (June 17, 2012). It tells a story of a scientific team's investigative efforts to uncover the source behind mysterious underwater recordings of an unidentified marine body. The show presents the controversial aquatic ape hypothesis as evidence that mermaids exist, along with a digitally manufactured video. A sequel broadcast called Mermaids: The New Evidence aired May 26, 2013. Mermaids: The Body Found and its sequel Mermaids: The New Evidence are examples of what is known as docufiction, in which documentary style and programming elements are combined with fictional – or sometimes, less egregiously, speculative – science and fiction. This type of programming receives particular criticism when, as in the original broadcast of Mermaids: The Body Found, there are only a few, easily missed disclaimers to indicate the speculative nature of the programming. On the contrary, the serious tone of the majority of the presentation implied that it was a factual documentary. The first airings of the two Mermaids programs apparently gathered the attention of millions of people and also drew some of Animal Planet's largest audiences ever. ==


id: mystery-flesh-pit-national-park-20260505-0
file: data/en.wikipedia.org/wiki/Mystery_Flesh_Pit_National_Park-0.md
category: reference
title: Mystery Flesh Pit National Park
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mystery_Flesh_Pit_National_Park
date_saved: 2026-05-05T11:11:47.300568+00:00
instance: kb-cron
parent: mystery-flesh-pit-national-park-20260505-0
summary:
The Mystery Flesh Pit National Park is an ongoing science fiction/horror project by artist Trevor Roberts that blends multimedia illustrations, writings and immersive world building. The story revolves around the fictional Mystery Flesh Pit, a colossal, ancient superorganism discovered beneath the town of Gumption, Texas, during an oil excavation. The pit was then transformed into a tourism destination and harvested for raw materials, until a catastrophic disaster in 2007 forced its closure. The project is a satire of corporate greed: the disaster which closed the park occurred due to cost-cutting on vital safety features, and ultimately the bigger hubris was building a theme park inside the superorganism in the first place even though it was never fully explored or understood. == Development == Trevor Roberts is an architect, a career which developed his taste in art. In 2019, while in the break room of an architecture firm, the idea for the project began when he photographed a rotting cantaloupe. After editing this into a photo of an open mine in South Africa, the result reminded him of a Works Progress Administration (WPA) National Park poster. Roberts posted his work to a subreddit, where it was well received, and he began


id: natural-history-of-an-alien-20260505-0
file: data/en.wikipedia.org/wiki/Natural_History_of_an_Alien-0.md
category: reference
title: Natural History of an Alien
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Natural_History_of_an_Alien
date_saved: 2026-05-05T11:11:48.508040+00:00
instance: kb-cron
parent: natural-history-of-an-alien-20260505-0
summary:
Natural History of an Alien, also known as Anatomy of an Alien in the US, is an early Discovery Channel pseudo-documentary similar to Alien Planet, aired in 1998. This pseudo-documentary featured various alien ecosystem projects, from the Epona Project to Ringworld. It also featured many notable scientists and science fiction authors such as Dr. Jack Cohen, Derek Briggs, Christopher McKay, David Wynn-Williams, Emily Holton, Peter Cattermole, Brian Aldiss, Sil Read, Wolf Read, Edward K. Smallwood, Adega Zuidema, Steve Hanly, Kevin Warwick and Dougal Dixon. == Plot == The viewer is in an intergalactic spaceship named the S.S. Attenborough, run by a small green alien. They visit a series of locations and discuss them as if in a documentary. It starts with Earth during the Cambrian, and Mars. They then visit asteroids and talk about the possibility of panspermia seeding solar system with life. They continue their journey to Europa, but with a number of speculative organisms. From there the journey takes them to a series of fictional planets full of alien organisms. === Europa === ==== Featured organisms ==== Europa Cone Bacteria: Orange-gray bacteria that grow in towers that rise many miles above the ocean floor. Inside these vents warm


id: natural-history-of-an-alien-20260505-1
file: data/en.wikipedia.org/wiki/Natural_History_of_an_Alien-1.md
category: reference
title: Natural History of an Alien
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Natural_History_of_an_Alien
date_saved: 2026-05-05T11:11:48.508040+00:00
instance: kb-cron
parent: natural-history-of-an-alien-20260505-0
summary:
==== Featured organisms ==== Epona Pagoda Tree: A thin-trunked, green, sessile photosynthetic animal that appears like a tree surrounded by large, disk-shaped "leaves" which are evolved limbs. The "leaves" grow very large to get as much carbon dioxide as possible. While sessile, the trees are capable of a remarkable range of movement, a trait inherited from their mobile ancestors. If a "herbivore" comes to nibble on them, they are able to fold back their branches. Spring Croc: A green, hopping, one-legged, predatory, Venus flytrap-like creature, and the major predator on Epona. It lies in wait for its prey, usually while partially submerged. Uther: A brownish-gray flying creature resembling a cross between a Sharovipteryx and a pterosaur. They are descended from flying fish-like ancestors. They began their avian-like lifestyle hunting Salacopods (small, amphibian-like creatures), and later adapted to feeding on larger carcasses. They then became predators themselves. In order to fly, they use a combination of hydrogen peroxide and ethanol to hyper-oxygenate their blood, which allows them incredible stamina. === Greenworld === Greenworld is a fictional world created by Dougal Dixon. It is an Earth-like planet filled with lush rainforests. ==== Featured organisms ==== Curlywhorl: An arboreal, purple-red, centipede/iguana-like creature evolved


id: the-new-dinosaurs-20260505-0
file: data/en.wikipedia.org/wiki/The_New_Dinosaurs-0.md
category: reference
title: The New Dinosaurs
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_New_Dinosaurs
date_saved: 2026-05-05T11:11:49.697233+00:00
instance: kb-cron
parent: the-new-dinosaurs-20260505-0
summary:
The New Dinosaurs: An Alternative Evolution is a 1988 speculative evolution book written by Scottish geologist and palaeontologist Dougal Dixon and illustrated by several illustrators including Amanda Barlow, Peter Barrett, John Butler, Jeane Colville, Anthony Duke, Andy Farmer, Lee Gibbons, Steve Holden, Philip Hood, Martin Knowelden, Sean Milne, Denys Ovenden and Joyce Tuhill. The book also features a foreword by Desmond Morris. The New Dinosaurs explores a hypothetical alternate Earth, complete with animals and ecosystems, where the Cretaceous-Paleogene extinction event never occurred, leaving non-avian dinosaurs and other Mesozoic animals an additional 65 million years to evolve and adapt over the course of the Cenozoic to the present day. The New Dinosaurs is Dixon's second work on speculative evolution, following After Man (1981). Like After Man, The New Dinosaurs uses its own fictional setting and hypothetical wildlife to explain natural processes with fictitious examples, in this case the concept of zoogeography and biogeographic realms. It was followed by another speculative evolution work by Dixon in 1990, Man After Man. Although criticised by some palaeontologists upon its release, several of Dixon's hypothetical dinosaurs bear a coincidental resemblance in both appearance and behaviour to dinosaurs that were discovered after the book's publication. As


id: the-new-dinosaurs-20260505-1
file: data/en.wikipedia.org/wiki/The_New_Dinosaurs-1.md
category: reference
title: The New Dinosaurs
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_New_Dinosaurs
date_saved: 2026-05-05T11:11:49.697233+00:00
instance: kb-cron
parent: the-new-dinosaurs-20260505-0
summary:
=== Later editions === According to Dixon's own website, "Dinosaur science has moved on since first publication in 1988, and the original introduction of the book has aged considerably." In the 2010s, Dixon worked to revise and update this information for more recent international editions of The New Dinosaurs. In August 2025, Breakdown Press published a new edition of The New Dinosaurs. The new edition features heavily revised introductory sections on evolution and Mesozoic life in order to reflect advancements in science since 1988. The cladistic placement and ancestry of several of the animals were also altered to fit with a more modern understanding of dinosaur relationships, behavior, and evolution. As an example, the new edition assigns several animals identified merely as "coelurosaurs" in the original book to specific groups and families. Another example is that the 2025 The New Dinosaurs has tyrannosaurs go completely extinct in the mid-Cenozoic, and presents the scavenging "gourmand" in South America as an abelisaur rather than a tyrannosaur. == Reception == The New Dinosaurs became a bestseller upon its release and like its predecessor After Man, The New Dinosaurs garnered positive reviews from critics. William F. Allman, writing for the U.S. News & World


id: orion-s-arm-20260505-0
file: data/en.wikipedia.org/wiki/Orion's_Arm-0.md
category: reference
title: Orion's Arm
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Orion's_Arm
date_saved: 2026-05-05T11:11:51.307445+00:00
instance: kb-cron
parent: orion-s-arm-20260505-0
summary:
The Orion's Arm Universe Project (OA) is a multi-authored online hard science fiction world-building project, first established in 2000 by M. Alan Kazlev, Donna Malcolm Hirsekorn, Bernd Helfert and Anders Sandberg and further co-authored by many people since. Anyone can contribute articles, stories, artwork, or music to the website. The first published Orion's Arm book, a collection of five novellas set within the OA universe, called Against a Diamond Sky, was released in September 2009. == Canon == The fictional setting of Orion's Arm takes place about 10,000 years in the future, where an interstellar civilization spread across thousands of light-years, with inhabited planets and space habitats. Its inhabitants range from humans to extensively modified human beings, including superhumans with advanced augmentations and internal AI systems, while most people exist as softwares. Engineered wormholes are used for interstellar travel and transport, although not for time travel. The setting also includes several alien civilizations and evidence of more advanced alien societies in the past. At its highest levels, directed human evolution has produced vast godlike beings linked across interstellar distances, capable of understanding and creating technologies beyond ordinary minds. == Reception == Orion's Arm has been reviewed in the role-playing magazine


id: the-planiverse-20260505-0
file: data/en.wikipedia.org/wiki/The_Planiverse-0.md
category: reference
title: The Planiverse
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Planiverse
date_saved: 2026-05-05T11:11:52.520481+00:00
instance: kb-cron
parent: the-planiverse-20260505-0
summary:
The Planiverse is a novel by A. K. Dewdney, written in 1984 about a two-dimensional world. == Plot == In the spirit of Edwin Abbott Abbott's Flatland, Dewdney and his computer science students simulate a two-dimensional world with a complex ecosystem. To their surprise, they find their artificial 2D universe has somehow accidentally become a means of communication with an actual 2D world: Arde. They make a sort of "telepathic" contact with "YNDRD", referred to by the students as Yendred, a highly philosophical Ardean, as he begins a journey across the western half, Punizla, of the single continent Ajem Kollosh to learn more about the spiritual beliefs of the people of the East, Vanizla. Yendred mistakes Dewdney's class for "spirits" and takes great interest in communicating with them. The students and narrator communicate with Yendred by typing on the keyboard; Yendred's answers appear on the computer's printout. The name Yendred (or "Yendwed", as pronounced by one of the students, who has a speech impediment) is simply "Dewdney" reversed. Written as a travelogue, Yendred's journey through the West takes him through several cities. He visits the Punizlan Institute for Technology and Science, where Arde's technology is explored in great detail. For


id: pseudo-panspermia-20260505-0
file: data/en.wikipedia.org/wiki/Pseudo-panspermia-0.md
category: reference
title: Pseudo-panspermia
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pseudo-panspermia
date_saved: 2026-05-05T11:11:53.722526+00:00
instance: kb-cron
parent: pseudo-panspermia-20260505-0
summary:
Pseudo-panspermia (sometimes called soft panspermia, molecular panspermia or quasi-panspermia) is a well-supported hypothesis for a stage in the origin of life. The theory first asserts that many of the small organic molecules used for life originated in space (for example, being incorporated in the solar nebula, from which the planets condensed). It continues that these organic molecules were distributed to planetary surfaces, where life then emerged on Earth and perhaps on other planets. Pseudo-panspermia differs from the fringe theory of panspermia, which asserts that life arrived on Earth from distant planets. == Background == Theories of the origin of life have been recorded since the 5th century BC, when the Greek philosopher Anaxagoras proposed an initial version of panspermia: life arrived on earth from the heavens. In modern times, full panspermia has little support amongst mainstream scientists. Pseudo-panspermia, in which molecules are formed and transported through space is, however, well-supported. == Extraterrestrial creation of organic molecules == Interstellar molecules are formed by chemical reactions within very sparse interstellar or circumstellar clouds of dust and gas. Usually this occurs when a molecule becomes ionised, often as the result of an interaction with cosmic rays. This positively charged molecule then draws in


id: quintaglio-ascension-trilogy-20260505-0
file: data/en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy-0.md
category: reference
title: Quintaglio Ascension Trilogy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy
date_saved: 2026-05-05T11:11:54.877432+00:00
instance: kb-cron
parent: quintaglio-ascension-trilogy-20260505-0
summary:
The Quintaglio Ascension Trilogy is a series of novels written by Canadian science fiction author Robert J. Sawyer. The books depict an Earth-like world on a moon which orbits a gas giant, inhabited by a species of highly evolved, sentient Tyrannosaurs, among various other creatures from the late Cretaceous period, imported to this moon by aliens 65 million years prior to the story. The series consists of three books: Far-Seer, Fossil Hunter, and Foreigner. == The trilogy == == The Quintaglios == The Quintaglio are a fictional species of sapient theropods which first appeared in Robert J. Sawyer's short story "Uphill Climb", and later on starred in his Quintaglio Ascension Trilogy. Descended from earth's dinosaurs, (specifically, Tyrannosaurs), they live on a moon orbiting a gas giant that they refer to as "The Face of God". === Evolution === As stated above, Quintaglios are Tyrannosaurs. It is stated in Fossil Hunter that they're directly descended from Nanotyrannus (although debate among paleontologists since the series' initial creation suggests Nanotyrannus might simply be a juvenile form of Tyrannosaurus rex; if so, that species would be the Quintaglio's true direct ancestor). Isolation on the Quintaglio Moon (along with some genetic modifications to their Tyrannosaur


id: quintaglio-ascension-trilogy-20260505-1
file: data/en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy-1.md
category: reference
title: Quintaglio Ascension Trilogy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy
date_saved: 2026-05-05T11:11:54.877432+00:00
instance: kb-cron
parent: quintaglio-ascension-trilogy-20260505-0
summary:
=== Religion and tradition === Quintaglios are a very religious people. Their original creation myth tells of a goddess who laid the "Eight Eggs of Creation". From the first egg came all the water, and from the second came the land. From the third came all the air, and from the fourth came the sun. From the fifth came the stars, planets and moons, and from the sixth came all the plants. Finally, from the seventh came all the herbivores (Ceratopsians, Ankylosaurs, Sauropods and Hadrosaurs, among others), and from the eighth and final egg came the carnivores which preyed upon them, (Tyrannosaurs, Ornithomimids and Dromaeosaurids, among others.) God created the five original female hunters by biting off her left arm, each of her fingers becoming a Quintaglio. They wished to create as God did, so she bit off her right arm and these became the first males, the mates of the original hunters. Quintaglio tradition states that a Quintaglio must go on at least one proper hunt in their life in order to go through the rites of passage. After a successful hunt, the Quintaglio gets a hunting tattoo which symbolises their passage into adulthood. Adults with no hunting tattoo


id: quintaglio-ascension-trilogy-20260505-2
file: data/en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy-2.md
category: reference
title: Quintaglio Ascension Trilogy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy
date_saved: 2026-05-05T11:11:54.877432+00:00
instance: kb-cron
parent: quintaglio-ascension-trilogy-20260505-0
summary:
=== Technology === Quintaglios have a level of technology comparable to our own Renaissance. They have sailing ships, and electricity hasn't been discovered yet, nor have fossil fuels or solar power. The telescope and the microscope are recent inventions and modern-style medicine is in its infancy. Aviation is also in its infancy, and haven't gotten more advanced than gliders yet. Thanks to Afsan and Toroca, Quintaglios are also aware of the solar system and evolution. Buildings are made out of stone or mud, and not much attention is given to them; due to frequent earthquakes, structures rarely stand for very long. Quintaglios have no firearms, and due to their laws and customs pertaining to using weapons to kill food it is highly unlikely that they ever will. In the epilogue at the end of Foreigner, the Quintaglio's technological prowess has increased dramatically due to new technology recovered from the ancient alien spaceship. The Quintaglios have apparently achieved spaceflight, built computers and set up temporary colonies on nearby moons. They are on their way to colonising new worlds, and it is implied that they are on their way to Earth. === Reproduction and family structures === The estrous cycle of female


id: quintaglio-ascension-trilogy-20260505-3
file: data/en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy-3.md
category: reference
title: Quintaglio Ascension Trilogy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy
date_saved: 2026-05-05T11:11:54.877432+00:00
instance: kb-cron
parent: quintaglio-ascension-trilogy-20260505-0
summary:
=== Main characters === Sal-Afsan: The main character of the series. He was the apprentice astrologer to the court astrologer, Tak Saleed. Afsan is described as being thin for a Quintaglio; ironically, the name Afsan means "Meaty thighbone". Afsan is a mathematical Genius- as a child; he never had any problem solving puzzles set forth by his teaching master. Afsan is open minded, inquisitive, and rational; the necessary qualities for a good scientist. On his pilgrimage, Afsan discovers that the Face of God is just a planet, and also discovers that their world is a moon that orbits it; furthermore, the Quintaglio moon is too close to the planet, and that it causes stresses that will one day reduce it to a ring of rubble surrounding the planet. When he declares his findings, he is met with opposition from the Master of the Faith, Det Yenalb, and is blinded as punishment for his "heresy". Afsan's ability to keep a level headed, strategic perspective has also made him an expert hunter. His kills were few, but memorable and dramatic- on his first hunt, he killed the biggest Sauropod ever seen, slew the water serpent Kal-Ta-Goot during his pilgrimage, and single-handedly killed


id: quintaglio-ascension-trilogy-20260505-4
file: data/en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy-4.md
category: reference
title: Quintaglio Ascension Trilogy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy
date_saved: 2026-05-05T11:11:54.877432+00:00
instance: kb-cron
parent: quintaglio-ascension-trilogy-20260505-0
summary:
Tak-Saleed: Afsan's mentor and the former court astrologer under Empress Len-Lends. He is a gruff, crotchety, ancient Quintaglio, and creche-mate of Var-Keenir. He went through six apprentice astrologers before he took on Afsan. He actually found the truth of celestial bodies before Afsan, and was glad to know Afsan discovered more before his death. Dy-Dybo: Former prince, now the Emperor of all of Land, and Afsan's close friend. Despite not being the fastest or the strongest of Lends' egglings - actually the weakest and the easiest one to be manipulated, he nevertheless became the greatest ruler the Quintaglio race has ever seen. He has a good sense of humour, and a legendary appetite. In Fossil Hunter, a political scandal concerning his legitimacy as Emperor is one of the main plot threads. Wab-Novato: Inventor of the Far Seer and the first astronaut. She led the important project of great escape, and discovered many valuable ancient remains. She and Afsan mated and laid eight eggs together, one of them died in infancy, and other 3 died for sibling rivalry in adolescence. She also have a daughter later with another male friend, but the daughter was indifferent to her and later died in


id: quintaglio-ascension-trilogy-20260505-5
file: data/en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy-5.md
category: reference
title: Quintaglio Ascension Trilogy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy
date_saved: 2026-05-05T11:11:54.877432+00:00
instance: kb-cron
parent: quintaglio-ascension-trilogy-20260505-0
summary:
Shovelmouth (Hadrosaurs): Large, duckbilled dinosaurs, they are hunted as food by Quintaglios and occasionally used as beasts-of-burden. Despite having stringy meat, they form the staple of the Quintaglio diet. Corythosaurus, Parasaurolophus and Lambeosaurus are seen (although the latter is apparently extinct) as well as completely new varieties of shovelmouth/hadrosaur, including one with a three-pointed crest and a breed from Arj'Toolar that is orange with blue stripes, and reportedly the tastiest kind of all. Armourback (Ankylosaurs): A few Armourbacks are seen and mentioned in passing. They are noted as being extremely difficult to kill. The Lubalites and Palace staff use a few Armourbacks as riding mounts during the final battle in Far-Seer, and the Quintaglio version of the Turtles all the way down story substitutes turtles with armourbacks. Mekt, one of the Original Five and the first bloodpriest, apparently killed an Armourback. Hornface (Ceratopsians): Hunted as food and occasionally domesticated by Quintaglios. Three species are confirmed to exist. The most commonly seen variety are "Triple Hornface" (Triceratops), but "Spikefrills" (Styracosaurus) and "Boss-Nosed Hornface" (Pachyrhinosaurus) are also depicted. Einiosaurus is also mentioned but like the Lambeosaurus is apparently extinct. A Triple Hornface apparently killed Lubal, one of the Original Five. Det-Yenalb rides


id: quintaglio-ascension-trilogy-20260505-6
file: data/en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy-6.md
category: reference
title: Quintaglio Ascension Trilogy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quintaglio_Ascension_Trilogy
date_saved: 2026-05-05T11:11:54.877432+00:00
instance: kb-cron
parent: quintaglio-ascension-trilogy-20260505-0
summary:
== Themes and allegory == The Quintaglio Ascension Trilogy is intended to be an allegory to the human races' Age of Enlightenment. Each book features a Quintaglio equivalent to a prominent human thinker. Sal-Afsan is a Quintaglio version of Galileo, his son Toroca is the Quintaglio equivalent to Charles Darwin, and Mokleb is a Quintaglio Sigmund Freud. The Quintaglio Ascension Trilogy has an underlying theme of standing up for the truth in the face of overwhelming opposition, of dedication to a cause no matter what. It champions new, innovative ideas overcoming fundamentalist dogma, of rationality overcoming mysticism. These themes are explored in other books by Robert J. Sawyer. == Reception == The Quintaglio Ascension Trilogy has generally been very well received; the Toronto Star called Far-Seer "One of the year's outstanding SF books"", Far-Seer, Fossil Hunter and Foreigner consistently receive four- to five-star ratings in user reviews on amazon.com, and both Far-Seer and Fossil Hunter received Homer awards for "Best Novel" during their initial release dates. The books have been praised for their creativity, endearing characters, and social relevance. Sawyer has remarked in his short story anthology Iterations that the Quintaglio Ascension has generated the most fan-mail for anything he


id: rhinogradentia-20260505-0
file: data/en.wikipedia.org/wiki/Rhinogradentia-0.md
category: reference
title: Rhinogradentia
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rhinogradentia
date_saved: 2026-05-05T11:11:56.103765+00:00
instance: kb-cron
parent: rhinogradentia-20260505-0
summary:
Rhinogradentia is a fictitious order of extinct shrew-like mammals invented by German zoologist Gerolf Steiner. Members of the order, known as rhinogrades or snouters, are characterized by a nose-like feature called a "nasorium", which evolved to fulfill a wide variety of functions in different species. Steiner also created a fictional persona, naturalist Harald Stümpke, who is credited as author of the 1961 book Bau und Leben der Rhinogradentia (translated into English in 1967 as The Snouters: Form and Life of the Rhinogrades). According to Steiner, it is the only remaining record of the animals, which were wiped out, along with all the world's Rhinogradentia researchers, when the small Pacific archipelago they inhabited sank into the ocean due to nearby atomic bomb testing. Successfully mimicking a genuine scientific work, Rhinogradentia has appeared in several publications without any note of its fictitious nature, sometimes in connection with April Fools' Day. == Background == Rhinogradentia, their island home of Hy-yi-yi, zoologist Harald Stümpke, and a host of other people, places, and documents are fictional creations of Gerolf Steiner (1908–2009), a German zoologist. Steiner is best known for his fictional work as Stümpke, but he was an accomplished zoologist in his own right. He


id: rhinogradentia-20260505-1
file: data/en.wikipedia.org/wiki/Rhinogradentia-1.md
category: reference
title: Rhinogradentia
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rhinogradentia
date_saved: 2026-05-05T11:11:56.103765+00:00
instance: kb-cron
parent: rhinogradentia-20260505-0
summary:
== Publication history == Steiner's books as Stümpke have been translated into other languages, sometimes crediting other names based on the country of publication. "Harald Stümpke", "Massimo Pandolfi", "Hararuto Shutyunpuke", and "Karl D. S. Geeste" are pseudonyms. Translator names are real. Stümpke, Harald (1957). Bau und Leben der Rhinogradentia. Stuttgart: Gustav Fischer Verlag. ISBN 3-437-30083-0. OCLC 65616734. Stümpke, Harald (1962). Anatomie et Biologie des Rhinogrades — Un Nouvel Ordre de Mammifères (Trans. Robert Weill). Paris: Masson. ISBN 978-2-10-005449-7. OCLC 46829688. Stümpke, Harald (1967). The Snouters: Form and Life of the Rhinogrades (Trans. Leigh Chadwick). Garden City, NY: The Natural History Press. OCLC 436148. Pandolfi, Massimo (1992). I Rinogradi di Harald Stümpke e la zoologia fantastica (Trans. Achaz von Hardenberg). Padua: Franco Muzzio. ISBN 88-7021-485-0. OCLC 875787215. Shutyunpuke, Hararuto (1997). Bikōri: atarashiku-hakken-sareta-honyūrui-no-kōzō-to-seikatsu. Tokyo: Hakuhinsha. ISBN 4-938706-19-9. OCLC 76500640. Geeste, Karl D. S. (1988). Stümpke's Rhinogradentia: Versuch einer Analyse. Stuttgart: Gustav Fischer Verlag. ISBN 3-437-30597-2. OCLC 28345723. == Legacy == Rhinogradentia is considered one of the best known biological hoaxes and scientific jokes and Steiner's pseudonymous works on the subject continue to be reprinted and translated. The first edition did not explicitly state that it was a hoax. Following the publication of


id: rolling-and-wheeled-creatures-in-fiction-and-legend-20260505-0
file: data/en.wikipedia.org/wiki/Rolling_and_wheeled_creatures_in_fiction_and_legend-0.md
category: reference
title: Rolling and wheeled creatures in fiction and legend
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rolling_and_wheeled_creatures_in_fiction_and_legend
date_saved: 2026-05-05T11:11:57.374988+00:00
instance: kb-cron
parent: rolling-and-wheeled-creatures-in-fiction-and-legend-20260505-0
summary:
Legends and speculative fiction reveal a longstanding human fascination with rolling and wheeled creatures. Such creatures appear in mythologies from Europe, Japan, pre-Columbian Mexico, the United States, and Australia, and in numerous modern works. == Rolling creatures == The triskelion is a motif with central symmetry used since ancient times. A variant with three human legs appears in the medieval flag of the Isle of Man. A variant with the head of Medusa in the union of the legs is associated with Sicily. It is not known the meaning it had in antiquity or its original Greek name. The hoop snake, a creature of legend in the United States and Australia, is said to grasp its tail in its mouth and roll like a wheel towards its prey. Japanese culture includes a similar mythical creature, the Tsuchinoko. Buer, a demon mentioned in the 16th-century grimoire Pseudomonarchia Daemonum, was described in Collin de Plancy's 1825 edition of Dictionnaire Infernal as having "the shape of a star or wheel". The 1863 edition of this book featured an illustration by Louis Le Breton, depicting a creature with five legs radially arranged. Neil R. Jones' 1937 story "On the Planet Fragment" features aliens dubbed


id: rolling-and-wheeled-creatures-in-fiction-and-legend-20260505-1
file: data/en.wikipedia.org/wiki/Rolling_and_wheeled_creatures_in_fiction_and_legend-1.md
category: reference
title: Rolling and wheeled creatures in fiction and legend
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rolling_and_wheeled_creatures_in_fiction_and_legend
date_saved: 2026-05-05T11:11:57.374988+00:00
instance: kb-cron
parent: rolling-and-wheeled-creatures-in-fiction-and-legend-20260505-0
summary:
L. Frank Baum's 1907 children's novel Ozma of Oz features humanoid creatures with wheels instead of hands and feet, called Wheelers. Their wheels are composed of keratin, which has been suggested by biologists as a means of avoiding nutrient and waste transfer problems with living wheels. Despite moving quickly on open terrain, the Wheelers are stymied by obstacles in their path that do not hinder creatures with limbs. They also appear in the 1985 film Return to Oz. The surrealist artist Remedios Varo (1908–1963) painted images of fantastical creatures with wheels as their bases, such as Homo rodans (1959), Fantastic animal (1959), and The Ladies at Bonhuer. Keith Laumer's 1965 science fiction novel Retief's War is set on a planet where the native aliens have metallic and mechanical aspects. They are divided into physically disparate tribes, most of which have wheels, while a few fly with rotors and there are aquatic creatures (possibly non-sentient) with propellers. The 1966 novella The Last Castle by Jack Vance describes "power-wagons" as creatures with a mix of biological and mechanical elements, including wheels. The 1968 novel The Goblin Reservation by Clifford D. Simak features an intelligent alien race that uses biological wheels. Kurt Vonnegut's


id: rotating-locomotion-in-living-systems-20260505-0
file: data/en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems-0.md
category: reference
title: Rotating locomotion in living systems
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems
date_saved: 2026-05-05T11:11:58.609567+00:00
instance: kb-cron
parent: rotating-locomotion-in-living-systems-20260505-0
summary:
Several organisms are capable of rolling locomotion. However, true wheels and propellers—despite their utility in human vehicles—do not play a significant role in the movement of living things (with the exception of the corkscrew-like flagella of many prokaryotes). Biologists have offered several explanations for the apparent absence of biological wheels, and wheeled creatures have appeared often in speculative fiction. Given the ubiquity of wheels in human technology, and the existence of biological analogues of many other technologies (such as wings and lenses), the lack of wheels in nature has seemed, to many scientists, to demand explanation—and the phenomenon is broadly explained by two factors: first, there are several developmental and evolutionary obstacles to the advent of a wheel by natural selection, and secondly, wheels have several drawbacks relative to other means of propulsion (such as walking, running, or slithering) in natural environments, which would tend to preclude their evolution. This environment-specific disadvantage has also led humans in certain regions to abandon wheels at least once in history. == Known instances of rotation in biology == There exist two distinct modes of locomotion using rotation: first, simple rolling; and second, the use of wheels or propellers, which spin on an axle


id: rotating-locomotion-in-living-systems-20260505-1
file: data/en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems-1.md
category: reference
title: Rotating locomotion in living systems
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems
date_saved: 2026-05-05T11:11:58.609567+00:00
instance: kb-cron
parent: rotating-locomotion-in-living-systems-20260505-0
summary:
The only known example of a biological "wheel" or "propeller"—a system capable of providing continuous propulsive torque about a fixed body—is the flagellum, a corkscrew-like tail used by single-celled prokaryotes for propulsion. The bacterial flagellum is the best known example. About half of all known bacteria have at least one flagellum; thus, given the ubiquity of bacteria, rotation may in fact be the most common form of locomotion used by living systems—though its use is restricted to the microscopic environment. At the base of the bacterial flagellum, where it enters the cell membrane, a motor protein acts as a rotary engine. The engine is powered by proton motive force, i.e. by the flow of protons (hydrogen ions) across the bacterial cell membrane due to a concentration gradient set up by the cell's metabolism. (In species of the genus Vibrio, there are two kinds of flagella, lateral and polar, and some are driven by a sodium ion pump rather than a proton pump.) Flagella are quite efficient, allowing bacteria to move at speeds of up to 60 cell lengths per second. The rotary motor at the base of the flagellum is similar in structure to ATP synthase. Spirillum bacteria have helical


id: rotating-locomotion-in-living-systems-20260505-2
file: data/en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems-2.md
category: reference
title: Rotating locomotion in living systems
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems
date_saved: 2026-05-05T11:11:58.609567+00:00
instance: kb-cron
parent: rotating-locomotion-in-living-systems-20260505-0
summary:
In the case of a driven wheel, a torque must be applied to generate the locomotive force. In human technology, this torque is generally provided by a motor, of which there are many types, including electric, piston-driven, turbine-driven, pneumatic, and hydraulic (torque may also be provided by human power, as in the case of a bicycle). In animals, motion is typically achieved by the use of skeletal muscles, which derive their energy from the metabolism of nutrients from food. Because these muscles are attached to both of the components that must move relative to each other, they are not capable of directly driving a wheel, and can only do so through a linkage. In addition, large animals cannot produce high accelerations, as inertia increases rapidly with body size. ==== Friction ==== Reducing friction is vital for minimizing wear on mechanical components and preventing overheating. As the relative speed of the components rises, and as the contact force between them increases, the importance of friction mitigation increases. Various types of bearing and/or lubricant may be used to reduce friction at the interface between two components. In biological joints such as the human knee, friction is reduced by means of cartilage with


id: rotating-locomotion-in-living-systems-20260505-3
file: data/en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems-3.md
category: reference
title: Rotating locomotion in living systems
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems
date_saved: 2026-05-05T11:11:58.609567+00:00
instance: kb-cron
parent: rotating-locomotion-in-living-systems-20260505-0
summary:
Work by vehicle engineer Mieczysław G. Bekker implies that the distribution of irregularities in natural terrains is log-normal; that is, small obstacles are far more common than larger ones. Thus, obstacle navigation is a challenge for locomotion in natural terrains at all size scales. The primary means of obstacle navigation are to go around obstacles and to go over them; each has its attendant challenges. ==== Going around ==== Anatomist Michael LaBarbera of the University of Chicago illustrates the poor maneuverability of wheels by comparing the turning radii of walking and wheelchair-using humans. As Jared Diamond points out, most biological examples of rolling are found in wide open, hard-packed terrain, including the use of rolling by dung beetles and tumbleweeds. ==== Going over ==== Wheels are poor at dealing with vertical obstacles, especially obstacles on the same scale as the wheel itself, and may be unable to climb vertical obstacles taller than about 40% of the wheel height. Because of this limitation, wheels intended for rough terrain require a larger diameter. In addition, without articulation, a wheeled vehicle can become stuck on top of an obstacle, with the obstacle between the wheels, preventing them from contacting the ground. Limbs, in


id: snaiad-20260505-0
file: data/en.wikipedia.org/wiki/Snaiad-0.md
category: reference
title: Snaiad
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Snaiad
date_saved: 2026-05-05T11:11:59.802654+00:00
instance: kb-cron
parent: snaiad-20260505-0
summary:
Snaiad is a speculative evolution, science fiction, and artistic worldbuilding project by Turkish artist C. M. Kösemen, focused on a fictional exoplanet of the same name. Begun in the early 2000s and inspired by earlier works such as Wayne Barlowe's 1990 book Expedition, Kösemen has produced hundreds of paintings and sketches of creatures of Snaiad, with detailed ecological roles and taxonomic relationships to each other. The sheer number of invented creatures and lineages makes Snaiad one of the most biologically diverse fictional worlds. Since Snaiad artwork was first published by Kösemen online, the project has garnered a following and international attention, especially online. Fans of Snaiad have produced fan art, not only of Kösemen's own creatures but also of their own imagined Snaiadi creatures, consistent with the biological principles followed by the rest of the project's lifeforms. Kösemen hopes to eventually publish the project in book form. == Premise == Snaiad is an exoplanet slightly larger than Earth located outside of the Milky Way. The planet is home to a large variety of fauna, which Kösemen has designed and meticulously documented, along with creating maps and a geopolitical story of Snaiad as it undergoes the process of human colonization about


id: son-of-man-novel-20260505-0
file: data/en.wikipedia.org/wiki/Son_of_Man_(novel)-0.md
category: reference
title: Son of Man (novel)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Son_of_Man_(novel)
date_saved: 2026-05-05T11:12:01.024514+00:00
instance: kb-cron
parent: son-of-man-novel-20260505-0
summary:
Son of Man is a science fiction novel by American writer Robert Silverberg, published in 1971. The book is about Clay, a 20th-century man, who travels billions of years into the future and meets humanity in its future forms. Some of the issues discussed in the book are sexuality, telepathic communication between people, physical prowess or frailty, division of humans by caste or ability, and the preservation of ancient wisdom, among other things. == Plot == == Reception == Norman Spinrad has described it as "brilliant". Matt Hughes considers it "an artifact of its period, a remarkable, heady, head-trippy plunge into a new way of writing sf, and into a new way of thinking", but notes that because Silverberg is addressing "the timeless questions -- what are we? where do we come from? where are we going?", the book has not become "stale and musty". == References == == External links == Silverberg, Robert (May 22, 2006). "Son of Man by Robert Silverberg". majipoor.com (Quasi-Official Site for Robert Silverberg's works). Archived from the original on May 23, 2006. Retrieved April 19, 2026. Son of Man title listing at the Internet Speculative Fiction Database Son of Man at Worlds Without End


id: thermobiology-20260505-0
file: data/en.wikipedia.org/wiki/Thermobiology-0.md
category: reference
title: Thermobiology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermobiology
date_saved: 2026-05-05T11:12:02.252150+00:00
instance: kb-cron
parent: thermobiology-20260505-0
summary:
Thermobiology is the scientific study of how temperature impacts biology and how organisms have adapted to the temperature of their environments. Examples include the natural selection for adaptations such as thermoregulation in macro-organisms including fur growth in mammals and seasonal shedding of leaves in deciduous plants, but also the reliance of thermophilic bacteria on heat-resistant DNA polymerase and the use of sub-zero cryopreservation of biological tissue in research and medicine. A major branch of thermobiology is the molecular mechanisms of those biological adaptions, such as those observed in selective activation of enzymes and variable membrane permeability. == Thermoregulation in macro-organisms == == Molecular mechanisms == === Enzyme kinetics === Enzymes allow biochemical processes to occur in lower temperature ranges, and can become inactivated at higher temperatures. === Freezing point depression === ==== Protein-mediated ==== ==== Prevention of crystal formation ==== === RNA Thermometers === === Membrane porosity === === Mutations === == Artificial applications == === Food preservation === Mankind has long taken advantage of the natural thermobiological properties of bacterial and mold in food preservation. Techniques that have existed for hundreds of years or even thousands of years, long before humans understood the underlying mechanisms, include boiling, bog butter,


id: the-time-machine-20260505-0
file: data/en.wikipedia.org/wiki/The_Time_Machine-0.md
category: reference
title: The Time Machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Time_Machine
date_saved: 2026-05-05T11:12:21.252983+00:00
instance: kb-cron
parent: the-time-machine-20260505-0
summary:
The Time Machine is an 1895 dystopian, post-apocalyptic, science fiction novella by H. G. Wells about a Victorian scientist known as the Time Traveller who travels to the year 802,701. The work is generally credited with the popularization of the concept of time travel by using a vehicle or device to travel purposely and selectively forward or backward through time. The term "time machine", coined by Wells, is now almost universally used to refer to such a vehicle or device. Utilizing a frame story set in then-present Victorian England, Wells's text focuses on a recount of the otherwise anonymous Time Traveller's journey into the far future. A work of future history and speculative evolution, The Time Machine is interpreted in modern times as a commentary on the increasing inequality and class divisions of Wells's era, which he projects as giving rise to two separate human species: the fair, childlike Eloi; and the savage, simian Morlocks, distant descendants of the contemporary upper and lower classes respectively. It is believed that Wells's depiction of the Eloi as a race living in plenitude and abandon was inspired by the utopic romance novel News from Nowhere (1890), though Wells's universe in the novel is


id: the-time-machine-20260505-1
file: data/en.wikipedia.org/wiki/The_Time_Machine-1.md
category: reference
title: The Time Machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Time_Machine
date_saved: 2026-05-05T11:12:21.252983+00:00
instance: kb-cron
parent: the-time-machine-20260505-0
summary:
== History == Wells had considered the notion of time travel before, in a short story titled "The Chronic Argonauts" (1888). This work, published in his college newspaper, was the foundation for The Time Machine. He frequently stated that he had thought of using some of this material in a series of articles in the Pall Mall Gazette, but in response to a request by W. E. Henley, the editor of National Observer, he rewrote "The Chronic Argonauts" into a series of seven loosely connected and fictionalized essays which were anonymously published in the newspaper from 17 March to 23 June 1894. The series was never completed as Henley stepped down from his role as editor in National Observer. With his encouragement, Wells continued to work on the story, and at the end of the year, when Henley was given the position as editor of Heinemann's periodical The New Review, he arranged for the story to be published there in serialized form in the January to May 1895 editions instead, for which Wells was paid £100 (equal to about £11,000 today). Henry Holt and Company published the first book edition (possibly prepared from a different manuscript) on 7 May 1895;


id: the-time-machine-20260505-2
file: data/en.wikipedia.org/wiki/The_Time_Machine-2.md
category: reference
title: The Time Machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Time_Machine
date_saved: 2026-05-05T11:12:21.252983+00:00
instance: kb-cron
parent: the-time-machine-20260505-0
summary:
In the new narrative, the Time Traveller goes into the future, observing things moving in quick motion around him. He sees his house disappear and turn into a lush garden. The Traveller stops in A.D. 802,701, and meets the Eloi, a society of small, childlike humanoids. They live in small communities within large and futuristic yet deteriorating buildings and adhere to a fruit-based diet. His efforts to communicate with them are hampered by their lack of curiosity or discipline. The Eloi appear happy and carefree but fear the dark, particularly moonless nights. They give no response to nocturnal disappearances, possibly because they are so afraid of them. After exploring the area around the Eloi's residences, the Traveller reaches the top of a hill and sees the ruins of a former metropolis. He concludes that the entire planet has reverted to a natural state, with little trace of human society or engineering from the hundreds of thousands of years prior, and that communism has at last been achieved. He also theorizes that intelligence springs from necessity; with no real challenges facing the Eloi, they have devolved into weak and naïve creatures with no understanding of the world around them. Returning to


id: the-time-machine-20260505-3
file: data/en.wikipedia.org/wiki/The_Time_Machine-3.md
category: reference
title: The Time Machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Time_Machine
date_saved: 2026-05-05T11:12:21.252983+00:00
instance: kb-cron
parent: the-time-machine-20260505-0
summary:
== Scholarship == Significant scholarly commentary on The Time Machine began from the early 1960s, initially contained in various broad studies of Wells's early novels (such as Bernard Bergonzi's The Early H.G. Wells: A Study of the Scientific Romances) and studies of utopias/dystopias in science fiction (such as Mark R. Hillegas's The Future as Nightmare: H.G. Wells and the Anti-Utopians). Much critical and textual work was done in the 1970s, including the tracing of the very complex publication history of the text, its drafts, and unpublished fragments. === Academic publications === A further resurgence in scholarship came around the time of the novella's centenary in 1995, and a major outcome of this was the 1995 conference and substantial anthology of academic papers, which was collected in print as H.G. Wells's Perennial Time Machine. This publication then allowed the development of a guide-book for academic study at Master's and Ph.D. level: H.G. Wells's The Time Machine: A Reference Guide. The scholarly journal The Wellsian has published around twenty articles on The Time Machine, and a U.S. academic journal The Undying Fire, devoted to H.G. Wells studies, has published three articles since its inception in 2002. === Subtext of the names Eloi


id: the-time-machine-20260505-4
file: data/en.wikipedia.org/wiki/The_Time_Machine-4.md
category: reference
title: The Time Machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Time_Machine
date_saved: 2026-05-05T11:12:21.252983+00:00
instance: kb-cron
parent: the-time-machine-20260505-0
summary:
==== 1949 BBC teleplay ==== The first visual adaptation of the book was a live teleplay broadcast from Alexandra Palace on 25 January 1949 by the BBC, which starred Russell Napier as the Time Traveller and Mary Donn as Weena. No recording of this live broadcast was made; the only record of the production is the script and a few black and white still photographs. A reading of the script, however, suggests that this teleplay remained fairly faithful to the book. ==== 1960 film ==== In 1960, the novella was made into a US science fiction film, also known promotionally as H.G. Wells's The Time Machine. The film starred Rod Taylor, Alan Young, and Yvette Mimieux. The film was produced and directed by George Pal, who also filmed a 1953 version of Wells's The War of the Worlds. The film won an Academy Award for time-lapse photographic effects showing the world changing rapidly. In 1993, Rod Taylor hosted Time Machine: The Journey Back reuniting him with Alan Young and Whit Bissell, featuring the only sequel to Mr. Pal's classic film, written by the original screenwriter, David Duncan. In the special were Academy Award-winners special effect artists Wah Chang and Gene


id: the-time-machine-20260505-5
file: data/en.wikipedia.org/wiki/The_Time_Machine-5.md
category: reference
title: The Time Machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Time_Machine
date_saved: 2026-05-05T11:12:21.252983+00:00
instance: kb-cron
parent: the-time-machine-20260505-0
summary:
=== Comics === Classics Illustrated was the first to adapt The Time Machine into a comic book format, issuing an American edition in July 1956. The Classics Illustrated version was published in French by Classiques Illustres in Dec 1957, and Classics Illustrated Strato Publications (Australian) in 1957, and Kuvitettuja Klassikkoja (a Finnish edition) in November 1957. There were also Classics Illustrated Greek editions in 1976, Swedish in 1987, German in 1992 and 2001, and a Canadian reprint of the English edition in 2008. In 1976, Marvel Comics published a new version of The Time Machine, as #2 in their Marvel Classics Comics series, with art by Alex Niño. (This adaptation was originally published in 1973 by Pendulum Press as part of their Pendulum Now Age Classics series; it was colourised and reprinted by Marvel in 1976.) In 1977, Polish painter Waldemar Andrzejewski adapted the novel as a 22-page comic book, written in Polish by Antoni Wolski. From April 1990, Eternity Comics published a three-issue miniseries adaptation of The Time Machine, written by Bill Spangler and illustrated by John Ross — this was collected as a trade paperback graphic novel in 1991. In 2018, US imprint Insight Comics published an adaptation


id: the-time-machine-20260505-6
file: data/en.wikipedia.org/wiki/The_Time_Machine-6.md
category: reference
title: The Time Machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Time_Machine
date_saved: 2026-05-05T11:12:21.252983+00:00
instance: kb-cron
parent: the-time-machine-20260505-0
summary:
La Belle Valence by Théo Varlet and André Blandin (1923) in which a squadron of World War I soldiers find the Time Machine and are transported back to the Spanish town of Valencia in the 14th century. Die Rückkehr der Zeitmaschine (1946) by Egon Friedell was the first direct sequel. It dwells heavily on the technical details of the machine and the time-paradoxes it might cause when the time machine was used to visit the past. After visiting a futuristic 1995 where London floats in the sky and the weather is created by companies, as well as the year 2123 where he meets two Egyptians who study history using "intuition" instead of science, the time traveller, who is given the name James MacMorton, travels to the past and ends up weeks before the time machine was built, causing it to disappear. He is forced to use the miniature version of his time machine, which already existed at that time, to send telegraphic messages through time to a friend (the author), instructing him to send him things that will allow him to build a new machine. After returning to the present, he tells his friend what happened. The 24,000-word German original


id: the-time-machine-20260505-7
file: data/en.wikipedia.org/wiki/The_Time_Machine-7.md
category: reference
title: The Time Machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Time_Machine
date_saved: 2026-05-05T11:12:21.252983+00:00
instance: kb-cron
parent: the-time-machine-20260505-0
summary:
Sawyer begins with this quote from the Wells original: "I have suspected since that the Morlocks had even partially taken it [the time machine] to pieces while trying in their dim way to grasp its purpose." In the Sawyer story, the Morlocks develop a fleet of time machines and use them to conquer the same far future Wells depicted at the end of the original, by which time, because the sun has grown red and dim and thus no longer blinds them, they can reclaim the surface of the world. The Time Traveller and his machine appear in the story Allan and the Sundered Veil by Alan Moore and Kevin O'Neill, which acts as a prequel to The League of Extraordinary Gentlemen, Volume One. The Time Traveller shares an adventure with fellow literary icons Allan Quatermain, John Carter, and Randolph Carter. David Haden's novelette The Time Machine: A Sequel (2010) is a direct sequel, picking up where the original finished. The Time Traveller goes back to rescue Weena but finds the Eloi less simple than he first imagined, and time travel far more complicated. Simon Baxter's novel The British Empire: Psychic Battalions Against the Morlocks (2010) imagines a steampunk/cyberpunk future


id: the-time-machine-20260505-8
file: data/en.wikipedia.org/wiki/The_Time_Machine-8.md
category: reference
title: The Time Machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_Time_Machine
date_saved: 2026-05-05T11:12:21.252983+00:00
instance: kb-cron
parent: the-time-machine-20260505-0
summary:
== The Time Traveller == Although the Time Traveller's real name is never given in the original novella, other sources have named him: The 1960 film named him H. George Wells, although he was only called George in dialogue. In the 1978 telefilm version of the story, the Time Traveller (this time a modern-day American) is named Dr. Neil Perry. H. G. Wells's great-grandson, Simon Wells, directed a 2002 remake where the Time Traveller's name is Alexander Hartdegen. In The Time Ships, Stephen Baxter's sequel to The Time Machine, the Time Traveller encounters his younger self via time travel. His younger self reacts with embarrassment to his older self's knowledge of his real names: "I held up my hand; I had an inspiration. "No. I will use—if you will permit—Moses." He took a deep pull on his brandy, and gazed at me with genuine anger in his grey eyes. "How do you know about that?" Moses—my hated first name, for which I had been endlessly tormented at school—and which I had kept a secret since leaving home!" This is a reference to H. G. Wells's story "The Chronic Argonauts", the story which grew into The Time Machine, in which the


id: the-world-of-kong-20260505-0
file: data/en.wikipedia.org/wiki/The_World_of_Kong-0.md
category: reference
title: The World of Kong
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/The_World_of_Kong
date_saved: 2026-05-05T11:12:22.457057+00:00
instance: kb-cron
parent: the-world-of-kong-20260505-0
summary:
The World of Kong: A Natural History of Skull Island is a 2005 art book released as a tie-in to the film King Kong (2005). The book is written in the form of a field guide and natural history of the version of Skull Island and its creatures as presented in the film. == Summary == The World of Kong features a fictional natural history of the island of Skull Island, upon which much of the film King Kong (2005) takes place. The narrative in the book's introductory chapter presents the book as the result of Project Legacy, a series of seven zoological expeditions led by Carl Denham (played by Jack Black in the film) to the island between 1935 (two years after the film takes place) and 1948, when the island sank into the sea due to volcanic and geological activity. The book features extensive artwork and descriptions of the different animals catalogued during these expeditions, descendants of various prehistoric animals that at different times in the past migrated to the island. The version of Skull Island presented in The World of Kong is the richest version of the island in terms of the sheer number of animals, featuring


id: anti-sidereal-time-20260505-0
file: data/en.wikipedia.org/wiki/Anti-sidereal_time-0.md
category: reference
title: Anti-sidereal time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Anti-sidereal_time
date_saved: 2026-05-05T11:12:23.999275+00:00
instance: kb-cron
parent: anti-sidereal-time-20260505-0
summary:
Anti-sidereal time and extended-sidereal time are artificial time standards used to analyze the daily variation in the number of cosmic rays received on Earth. Anti-sidereal time has about 364.25 days per year, one day less than the number of days in a year of solar time, 365.25. Thus each anti-sidereal day is longer than a solar day (24 hr) by about four minutes or 24 hr 4 min. Extended-sidereal time has about 367.25 days per year, one day more than the number of days in a year of sidereal time, 366.25. Thus each extended-sidereal day is shorter than a sidereal day (23 hr 56 min) by about four minutes or 23 hr 52 min. All years mentioned have the same length. == Amplitude modulation sidebands == Cosmic rays received on Earth exhibit daily variations in amplitude in solar time due to the distribution of cosmic rays in the inner heliosphere and to the Compton-Getting effect caused by Earth's orbital velocity around the Sun. Other daily variations in amplitude in sidereal time are caused by the anisotropy in the direction from which cosmic rays are received relative to the plane of our galaxy, the Milky Way. Both are contaminated by an


id: astronomical-chronology-20260505-0
file: data/en.wikipedia.org/wiki/Astronomical_chronology-0.md
category: reference
title: Astronomical chronology
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astronomical_chronology
date_saved: 2026-05-05T11:12:25.187127+00:00
instance: kb-cron
parent: astronomical-chronology-20260505-0
summary:
Astronomical chronology, or astronomical dating, is a technical method of dating events or artifacts that are associated with astronomical phenomena. Written records of historical events that include descriptions of astronomical phenomena have done much to clarify the chronology of the Ancient Near East; works of art which depict the configuration of the stars and planets and buildings which are oriented to the rising and setting of celestial bodies at a particular time have all been dated through astronomical calculations. == Dating historical events == The use of descriptions of astronomical phenomena to date historical events began in the 16th century, a time of a renewed humanistic interest in history and of increasingly precise astronomical tables. Eclipses in particular are relatively infrequent events and can be dated precisely. When the circumstances are not exact and descriptions leave ambiguities, one can often use other details such as the month of the eclipse or the position of other stars and planets to identify the specific eclipse. Astronomical dating, like other forms of historical interpretation, requires care in interpreting the surviving written records. John Steele has proposed three questions that must be asked when dating an event: Does the record refer to an actual


id: astronomical-time-20260505-0
file: data/en.wikipedia.org/wiki/Astronomical_time-0.md
category: reference
title: Astronomical time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astronomical_time
date_saved: 2026-05-05T11:12:26.357228+00:00
instance: kb-cron
parent: astronomical-time-20260505-0
summary:
Astronomical time is a time based on cyclic astronomical events. Simple examples are the recurring cycle of day and night, a consequence of Earth's rotation, and the recurring cycle of the year as the Earth circles the Sun. Requirements for high precision time scales in astronomy have led to continue refinements in the definition of time. Some of the time standard scales are sidereal time, solar time, and universal time. == Rotational time == To use Earth's rotation as a basis for timekeeping requires precise measurement of the rotation rate. Observations of star motion as the Earth rotates gives Sidereal time. This form of time is vital for astronomy but inconvenient for normal uses because it ignores the position of the Sun. Thus the Sun could be overhead at sidereal midnight. Solar time, measuring Earth's rotation with respect to the Sun, was the historical basis for civil time. Precise measurements must account for the elliptical orbit of the Earth around the Sun. Mean solar time accounts for this effect. Basing time on the Earth's rotation assumes that the rotation speed is constant. However astronomical observations have shown three variations in speed. Secular variation is a linear increase the length of


id: barycentric-coordinate-time-20260505-0
file: data/en.wikipedia.org/wiki/Barycentric_Coordinate_Time-0.md
category: reference
title: Barycentric Coordinate Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Barycentric_Coordinate_Time
date_saved: 2026-05-05T11:12:27.561234+00:00
instance: kb-cron
parent: barycentric-coordinate-time-20260505-0
summary:
Barycentric Coordinate Time (TCB, from the French Temps-coordonnée barycentrique) is a coordinate time standard intended to be used as the independent variable of time for all calculations pertaining to orbits of planets, asteroids, comets, and interplanetary spacecraft in the Solar System. It is equivalent to the proper time experienced by a clock at rest in a coordinate frame co-moving with the barycenter (center of mass) of the Solar System : that is, a clock that performs exactly the same movements as the Solar System but is outside the system's gravity well. It is therefore not influenced by the gravitational time dilation caused by the Sun and the rest of the system. TCB is the time coordinate for the Barycentric Celestial Reference System (BCRS). TCB was defined in 1991 by the International Astronomical Union, in Recommendation III of the XXIst General Assembly. It was intended as one of the replacements for the problematic 1976 definition of Barycentric Dynamical Time (TDB). Unlike former astronomical time scales, TCB is defined in the context of the general theory of relativity. The relationships between TCB and other relativistic time scales are defined with fully general relativistic metrics. The transformation between TCB and Geocentric Coordinate Time


id: barycentric-julian-date-20260505-0
file: data/en.wikipedia.org/wiki/Barycentric_Julian_Date-0.md
category: reference
title: Barycentric Julian Date
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Barycentric_Julian_Date
date_saved: 2026-05-05T11:12:28.709634+00:00
instance: kb-cron
parent: barycentric-julian-date-20260505-0
summary:
The Barycentric Julian Date (BJD) is the Julian Date (JD) corrected for differences in the Earth's position with respect to the barycentre of the Solar System. Due to the finite speed of light, the time an astronomical event is observed depends on the changing position of the observer in the Solar System. Before multiple observations can be combined, they must be reduced to a common, fixed, reference location. This correction also depends on the direction to the object or event being timed. In 1991, the BJD replaced the Heliocentric Julian Date (HJD), which reduced times to the centre of the Sun, which itself orbits the barycentre. The difference between HJD and BJD is up to ±4 s. == Magnitude of the correction == The correction is small for objects at the poles of the ecliptic. Elsewhere, it is approximately an annual sine curve, and the highest amplitude occurs on the ecliptic. The maximum correction corresponds to the time in which light travels the distance from the barycentre to the Earth, i.e. ±8.3 min (500 s, 0.0058 days). == Time Standard == JD and BJD are defined independent of the time standard. JD can be expressed as e.g. UTC, TT, TAI,


id: cosmic-calendar-20260505-0
file: data/en.wikipedia.org/wiki/Cosmic_Calendar-0.md
category: reference
title: Cosmic Calendar
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cosmic_Calendar
date_saved: 2026-05-05T11:12:29.949426+00:00
instance: kb-cron
parent: cosmic-calendar-20260505-0
summary:
The Cosmic Calendar is a method to visualize the chronology of the universe, scaling its currently understood age of 13.787 billion years to a single year in order to help intuit it for pedagogical purposes in science education or popular science. A similar analogy used to visualize the geologic time scale and the history of life on Earth is the Geologic Calendar. In this visualization, the Big Bang took place at the beginning of January 1 at midnight, and the current moment maps onto the end of December 31 just before midnight. At this scale, there are 438 years per cosmic second, 1.58 million years per cosmic hour, and 37.8 million years per cosmic day. The Solar System materialized in Cosmic September. The Phanerozoic corresponds only to the latter half of December, with the Cenozoic only happening on the penultimate day on the Calendar. The Quaternary only applies to the last four hours on the final Cosmic Day, with the Holocene only applying to the final 23 Cosmic Seconds. On the other hand, relic radiation is dated at the first fifteen minutes of the very first Cosmic Day; even if we stretch the Cosmic Calendar to 100 years, the relic


id: daytime-20260505-0
file: data/en.wikipedia.org/wiki/Daytime-0.md
category: reference
title: Daytime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Daytime
date_saved: 2026-05-05T11:12:31.170231+00:00
instance: kb-cron
parent: daytime-20260505-0
summary:
Daytime is the period of the day in which the Sun is above the local horizon in a given location. It is sometimes just called "day". During the daytime an area is illuminated by daylight, a combination of direct sunlight and indirect light from the sky. At any given time, about half of the Earth is facing the Sun and experiencing daytime. The length of daytime varies with latitude and changes over the course of the year, as the Earth moves around the Sun. Other planets and natural satellites that rotate relative to a luminous primary body such as a local star also experience daytime, but this article primarily discusses daytime on Earth. == Characteristics == Approximately half of Earth is illuminated at any time by the Sun, but because of atmospheric and other effects that extend the reach of indirect illumination, the area of the planet covered by either direct or indirect illumination amounts to slightly more than half the surface. The almost-hemispherical part of Earth experiencing daytime at any given instant changes continuously as the planet rotates on its own axis. The axis of the Earth's rotation is not perpendicular to the plane of its orbit around the


id: daytime-20260505-1
file: data/en.wikipedia.org/wiki/Daytime-1.md
category: reference
title: Daytime
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Daytime
date_saved: 2026-05-05T11:12:31.170231+00:00
instance: kb-cron
parent: daytime-20260505-0
summary:
=== In the tropics === The tropics occupy a zone of Earth's surface between 23.44° north and 23.44° south of the Equator. Within this zone, the Sun will pass almost directly overhead (or culminate) on at least one day per year. The line of 23.44° north latitude is called the Tropic of Cancer, because when it was named, the Sun passed overhead at this location at the time of year when it was near the constellation of Cancer. The equivalent line of south latitude is called the Tropic of Capricorn, for similar reasons. The sun enters and leaves each zodiacal constellation slightly later each year at the rate of about 1 day every 72 years. For more information, see precession of the equinoxes. On the Tropical Circles, the Sun is directly overhead only once per year, on the corresponding solstice. At latitudes closer to the Equator and on the Equator itself, it will be overhead twice per year (on the equinoxes in the case of the Equator), leading to the Lahaina Noon or zero shadow day phenomenon. Outside the tropics, the Sun never passes directly overhead. === Around the poles === Around the poles, which coincide with the rotational axis


id: decimal-time-20260505-0
file: data/en.wikipedia.org/wiki/Decimal_time-0.md
category: reference
title: Decimal time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decimal_time
date_saved: 2026-05-05T11:12:32.390542+00:00
instance: kb-cron
parent: decimal-time-20260505-0
summary:
Decimal time is the representation of the time of day using units which are decimally related. This term is often used specifically to refer to the French Republican calendar time system used from 1794 to 1800, during the French Revolution, which divided the day into 10 decimal hours, each decimal hour into 100 decimal minutes and each decimal minute into 100 decimal seconds (100,000 decimal seconds per day), as opposed to the more familiar standard time, which divides the day into 24 hours, each hour into 60 minutes and each minute into 60 seconds (86,400 SI seconds per day). The main advantage of a decimal time system is that, since the base used to divide the time is the same as the one used to represent it, the representation of hours, minutes and seconds can be handled as a unified value. Therefore, it becomes simpler to interpret a timestamp and to perform conversions. For instance, 1h23m45s is 1 decimal hour, 23 decimal minutes, and 45 decimal seconds, or 1.2345 decimal hours, or 123.45 decimal minutes or 12345 decimal seconds; 3 hours is 300 minutes or 30,000 seconds. This property also makes it straightforward to represent a timestamp as a fractional


id: decimal-time-20260505-1
file: data/en.wikipedia.org/wiki/Decimal_time-1.md
category: reference
title: Decimal time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decimal_time
date_saved: 2026-05-05T11:12:32.390542+00:00
instance: kb-cron
parent: decimal-time-20260505-0
summary:
VIII. Each month is divided into three equal parts, of ten days each, which are called décades... XI. The day, from midnight to midnight, is divided into ten parts or hours, each part into ten others, so on until the smallest measurable portion of the duration. The hundredth part of the hour is called decimal minute; the hundredth part of the minute is called decimal second. This article will not be required for the public records, until from the 1st of Vendémiaire, the year three of the Republic. (September 22, 1794) (emphasis in original) Thus, midnight was called dix heures ("ten hours"), noon was called cinq heures ("five hours"), etc. ==== Representation ==== The colon (:) was not yet in use as a unit separator for standard times, and is used for non-decimal bases. The French decimal separator is the comma (,), while the period (.), or "point", is used in English. Units were either written out in full, or abbreviated. Thus, five hours eighty three minutes decimal might be written as 5 h. 83 m. Even today, "h" is commonly used in France to separate hours and minutes of 24-hour time, instead of a colon, such as 14h00. Midnight


id: decimal-time-20260505-2
file: data/en.wikipedia.org/wiki/Decimal_time-2.md
category: reference
title: Decimal time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decimal_time
date_saved: 2026-05-05T11:12:32.390542+00:00
instance: kb-cron
parent: decimal-time-20260505-0
summary:
==== Metric system ==== In designing the new metric system, the intent was to replace all the various units of different bases with a small number of standard decimal units. This was to include units for length, weight, area, liquid capacity, volume, and money. Initially the traditional second of time equal to 1/86400 day was proposed as the base of the metric system, but this was changed in 1791 to base the meter on a decimal division of a measurement of the Earth, instead. Early drafts of the metric system published in 1793 included the new decimal divisions of the day included with the Republican calendar, and some of the same individuals were involved with both projects. On March 28, 1794, Joseph-Louis Lagrange proposed to the Commission for Republican Weights and Measures on dividing the day into 10 decidays and 100 centidays, which would be expressed together as two digits, counting periods of 14 minutes and 24 seconds since midnight, nearly a quarter hour. This would be displayed by one hand on watches. Another hand would display 100 divisions of a centiday, which is 1/10,000 day, or 8.64 seconds. A third hand on a smaller dial would further divide these


id: decimal-time-20260505-3
file: data/en.wikipedia.org/wiki/Decimal_time-3.md
category: reference
title: Decimal time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decimal_time
date_saved: 2026-05-05T11:12:32.390542+00:00
instance: kb-cron
parent: decimal-time-20260505-0
summary:
On 23 October 1998, the Swiss watch company Swatch introduced a decimal time called Internet Time for its line of digital watches, which divided the day into 1,000 ".beats", (each 86.4 seconds in standard time) counted from 000–999, with @000 being midnight and @500 being noon standard time in Switzerland, which is Central European Time (one hour ahead of Universal Time). Although Swatch did not specify units smaller than one .beat, third party implementations extended the standard by adding "centibeats" or "sub-beats", for extended precision: @248.00. Each "centibeat" was a hundredth of a .beat and was therefore equal to one French decimal second (0.864 seconds). When using .beats and centibeats, Swatch Internet Time divided the day into 1,000 French decimal minutes and each decimal minute into 100 decimal seconds. So 9pm was 21:00:00 in standard time and @875.00 in extended Swatch Internet Time. Swatch no longer markets digital watches with Internet Time. == Conversions == There are exactly 86,400 standard seconds (see SI for the current definition of the standard second) in a standard day, but in the French decimal time system there were 100,000 decimal seconds in the day; thus, the decimal second was 13.6% shorter than its standard


id: decimal-time-20260505-4
file: data/en.wikipedia.org/wiki/Decimal_time-4.md
category: reference
title: Decimal time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decimal_time
date_saved: 2026-05-05T11:12:32.390542+00:00
instance: kb-cron
parent: decimal-time-20260505-0
summary:
== Scientific decimal time == Scientists often record time as decimal. For example, decimal days divide the day into 10 equal parts, and decimal years divide the year into 10 equal parts. Decimals are easier to plot than both (a) minutes and seconds, which uses the sexagesimal numbering system, (b) hours, months and days, which has irregular month lengths. In astronomy, the so-called Julian day uses decimal days centered on Greenwich noon. Seconds in a decimal minute Since there are 60 seconds in a minute, a tenth part represents ⁠60/10⁠ = 6 seconds. Minutes in a decimal hour Since there are 60 minutes in an hour, a tenth part represents ⁠60/10⁠ = 6 minutes. Hours in a decimal day Since there are 24 hours in a day, a tenth part represents ⁠24/10⁠ = 2.4 hours (2 hours and 24 minutes). Length of a decimal year Since there are about 365 days in a year, there are about ⁠365/10⁠ = 36.5 days in a tenth of a year. Hence the year 2020.5 represents the day 2 July 2020. More exactly, a "Julian year" is approximately 365.25 days long, so a tenth of the year is 36.525 days (36 days, 12 hours,


id: dynamical-time-scale-20260505-0
file: data/en.wikipedia.org/wiki/Dynamical_time_scale-0.md
category: reference
title: Dynamical time scale
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dynamical_time_scale
date_saved: 2026-05-05T11:12:33.622656+00:00
instance: kb-cron
parent: dynamical-time-scale-20260505-0
summary:
In time standards, dynamical time is the independent variable of the equations of celestial mechanics. This is in contrast to time scales such as mean solar time which are based on how far the earth has turned. Since Earth's rotation is not constant, using a time scale based on it for calculating the positions of heavenly objects gives errors. Dynamical time can be inferred from the observed position of an astronomical object via a theory of its motion. A first application of this concept of dynamical time was the definition of the ephemeris time scale (ET). In the late 19th century it was suspected, and in the early 20th century it was established, that the rotation of the Earth (i.e. the length of the day) was both irregular on short time scales, and was slowing down on longer time scales. The suggestion was made, that observation of the position of the Moon, Sun and planets and comparison of the observations with their gravitational ephemerides would be a better way to determine a uniform time scale. A detailed proposal of this kind was published in 1948 and adopted by the IAU in 1952 (see Ephemeris time - history). Using data from


id: eclipse-cycle-20260505-0
file: data/en.wikipedia.org/wiki/Eclipse_cycle-0.md
category: reference
title: Eclipse cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eclipse_cycle
date_saved: 2026-05-05T11:12:34.827205+00:00
instance: kb-cron
parent: eclipse-cycle-20260505-0
summary:
Eclipses may occur repeatedly, separated by certain intervals of time: these intervals are called eclipse cycles. The series of eclipses separated by a repeat of one of these intervals is called an eclipse series. == Eclipse conditions == Eclipses may occur when Earth and the Moon are aligned with the Sun, and the shadow of one body projected by the Sun falls on the other. So at new moon, when the Moon is in conjunction with the Sun, the Moon may pass in front of the Sun as viewed from a narrow region on the surface of Earth and cause a solar eclipse. At full moon, when the Moon is in opposition to the Sun, the Moon may pass through the shadow of Earth, and a lunar eclipse is visible from the night half of Earth. The conjunction and opposition of the Moon together have a special name: syzygy (Greek for "junction"), because of the importance of these lunar phases. An eclipse does not occur at every new or full moon, because the plane of the Moon's orbit around Earth is tilted with respect to the plane of Earth's orbit around the Sun (the ecliptic): so as viewed from Earth,


id: eclipse-cycle-20260505-1
file: data/en.wikipedia.org/wiki/Eclipse_cycle-1.md
category: reference
title: Eclipse cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eclipse_cycle
date_saved: 2026-05-05T11:12:34.827205+00:00
instance: kb-cron
parent: eclipse-cycle-20260505-0
summary:
The Moon must be in new phase. The longitude of perigee or apogee of the Moon must be the same. The longitude of the ascending node or descending node must be the same. The Earth will be nearly the same distance from the Sun, and tilted to it in nearly the same orientation. These conditions are related to the three periods of the Moon's orbital motion, viz. the synodic month, anomalistic month and draconic month, and to the anomalistic year. In other words, a particular eclipse will be repeated only if the Moon will complete roughly an integer number of synodic, draconic, and anomalistic periods and the Earth-Sun-Moon geometry will be nearly identical. The Moon will be at the same node and the same distance from the Earth. This happens after the period called the saros. Gamma (how far the Moon is north or south of the ecliptic during an eclipse) changes monotonically throughout any single saros series. The change in gamma is larger when Earth is near its aphelion (June to July) than when it is near perihelion (December to January). When the Earth is near its average distance (March to April or September to October), the change in


id: eclipse-cycle-20260505-2
file: data/en.wikipedia.org/wiki/Eclipse_cycle-2.md
category: reference
title: Eclipse cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eclipse_cycle
date_saved: 2026-05-05T11:12:34.827205+00:00
instance: kb-cron
parent: eclipse-cycle-20260505-0
summary:
SM = 29.530588853 days (Synodic month) DM = 27.212220817 days (Draconic month) AM = 27.55454988 days (Anomalistic month) EY = 346.620076 days (Eclipse year) Note that there are three main moving points: the Sun, the Moon, and the (ascending) node; and that there are three main periods, when each of the three possible pairs of moving points meet one another: the synodic month when the Moon returns to the Sun, the draconic month when the Moon returns to the node, and the eclipse year when the Sun returns to the node. These three 2-way relations are not independent (i.e. both the synodic month and eclipse year are dependent on the apparent motion of the Sun, both the draconic month and eclipse year are dependent on the motion of the nodes), and indeed the eclipse year can be described as the beat period of the synodic and draconic months (i.e. the period of the difference between the synodic and draconic months); in formula: EY = SM × DM SM − DM {\displaystyle {\mbox{EY}}={\frac {{\mbox{SM}}\times {\mbox{DM}}}{{\mbox{SM}}-{\mbox{DM}}}}} as can be checked by filling in the numerical values listed above. Eclipse cycles have a period in which a certain number of synodic months closely


id: eclipse-cycle-20260505-3
file: data/en.wikipedia.org/wiki/Eclipse_cycle-3.md
category: reference
title: Eclipse cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eclipse_cycle
date_saved: 2026-05-05T11:12:34.827205+00:00
instance: kb-cron
parent: eclipse-cycle-20260505-0
summary:
=== Notes === Fortnight Half a synodic month (29.53 days). When there is an eclipse, there is a fair chance that at the next syzygy there will be another eclipse: the Sun and Moon will have moved about 15° with respect to the nodes (the Moon being opposite to where it was the previous time), but the luminaries may still be within bounds to make an eclipse. For example, the penumbral lunar eclipse of May 26, 2002 is followed by the annular solar eclipse of June 10, 2002 and penumbral lunar eclipse of June 24, 2002. The shortest lunar fortnight between a new moon and a full moon lasts only about 13 days and 21.5 hours, while the longest such lunar fortnight lasts about 15 days and 14.5 hours. (Due to evection, these values are different going from quarter moon to quarter moon. The shortest lunar fortnight between first and last quarter moons lasts only about 13 days and 12 hours, while the longest lasts about 16 days and 2 hours.) For more information see eclipse season. Synodic month Similarly, two events one synodic month apart have the Sun and Moon at two positions on either side of the node,


id: eclipse-cycle-20260505-4
file: data/en.wikipedia.org/wiki/Eclipse_cycle-4.md
category: reference
title: Eclipse cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eclipse_cycle
date_saved: 2026-05-05T11:12:34.827205+00:00
instance: kb-cron
parent: eclipse-cycle-20260505-0
summary:
Metonic cycle or enneadecaeteris Nearly 6940 days, but as an eclipse cycle can be taken as 235 synodic months. This is just an hour and a half less than 19 years of 365+1⁄4 days. It is also 5 "octon" periods and close to 20 eclipse years, so it yields a short series of four or five eclipses on the same calendar date or on two calendar dates. It is equivalent to 110 "hollow months" of 29 days and 125 "full months" of 30 days. Twenty four Metonic cycles of 235 months makes an eclipse cycle of 456 years, equivalent to 17 inex periods minus two saros periods. Semanex Equal to a whole number of weeks plus a hundredth of a day, so consecutive eclipses of the cycle are usually on the same day of the week. Each eclipse in this period is a member of a preceding saros series, always occurring on alternating nodes. Thix This eclipse cycle, which seems to have been known in Maya astronomy, is about one day more than 36 260-day tzolk'ins (the basis of the Maya calendar). The name was suggested by Charles H. Smiley in 1973 from the fact that it is around thirty


id: eclipse-cycle-20260505-5
file: data/en.wikipedia.org/wiki/Eclipse_cycle-5.md
category: reference
title: Eclipse cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eclipse_cycle
date_saved: 2026-05-05T11:12:34.827205+00:00
instance: kb-cron
parent: eclipse-cycle-20260505-0
summary:
Macdonald cycle An eclipse cycle equal to 299 years and about ten and a half months, always occurring on the same node. Peter Macdonald found that a series of eclipses of especially long duration visible from Britain occurs with this interval in the period AD 1 to 3000. A Macdonald series has around ten eclipses and lasts about 3000 years. All or most are on the same day of the week, since the interval is only about an hour less than a whole number of weeks and the length is fairly constant becauses the anomaly of the moon is almost constant. Utting cycle The seventh convergent in the continued fractions development between the ratio of the eclipse year and synodic month, if this ratio is approximated as between 2.17039173 and 2.17039179. Discussed by James Utting in 1827. Selebit An eclipse cycle where the number of eclipse years (354.5) closely matches (by chance) the number of days in a lunar year (354.371). It equals approximately 336 years 5 months 6 days or 4161 lunations. It is a convergent in the continued fractions development of the ratio between the eclipse year and the synodic month, giving a series of eclipses one selebit


id: eclipse-cycle-20260505-6
file: data/en.wikipedia.org/wiki/Eclipse_cycle-6.md
category: reference
title: Eclipse cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eclipse_cycle
date_saved: 2026-05-05T11:12:34.827205+00:00
instance: kb-cron
parent: eclipse-cycle-20260505-0
summary:
Tetradia Sometimes 4 total lunar eclipses occur in a row with intervals of 6 lunations (one semester) between them, and this is called a tetrad. Giovanni Schiaparelli noticed that there are eras when such tetrads occur comparatively frequently, interrupted by eras when they are rare. This variation takes about 6 centuries. Antonie Pannekoek (1951) offered an explanation for this phenomenon and found a period of 591 years. Van den Bergh (1954) from Theodor von Oppolzer's Canon der Finsternisse found a period of 586 years. This happens to be an eclipse cycle; see Meeus [I] (1997). The phenomenon is related to the elliptical orbit of the Earth, as explained below. Recently Tudor Hughes explained that secular changes in the eccentricity of the Earth's orbit cause the period for occurrence of tetrads to be variable, and it is currently about 565 years; see Meeus III (2004) for a detailed discussion. The Tetradia period also shows up in the distance between eras in which there are pairs of (non-consecutive) eclipses seven months apart, or eras in which there are more pairs of eclipses one month apart, or eras in which there are saros series in which gamma is fairly constant for many decades,


id: eclipse-cycle-20260505-7
file: data/en.wikipedia.org/wiki/Eclipse_cycle-7.md
category: reference
title: Eclipse cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eclipse_cycle
date_saved: 2026-05-05T11:12:34.827205+00:00
instance: kb-cron
parent: eclipse-cycle-20260505-0
summary:
year = 28.945 × number of the saros series + 18.030 × number of the inex series − 2882.55 When this is greater than 1, the integer part gives the year AD, but when it is negative the year BC is obtained by taking the integer part and adding 2. For instance, the eclipse in saros series 0 and inex series 0 was in the middle of 2884 BC. A "panorama" of solar eclipses arranged by saros and inex has been produced by Luca Quaglia and John Tilley showing 61775 solar eclipses from 11001 BC to AD 15000 (see below). Each column of the graph is a complete Saros series which progresses smoothly from partial eclipses into total or annular eclipses and back into partials. Each graph row represents an inex series. Since a saros, of 223 synodic months, is slightly less than a whole number of draconic months, the early eclipses in a saros series (in the upper part of the diagram) occur after the Moon goes through its node (the beginning and end of a draconic month), while the later eclipses (in the lower part) occur before the Moon goes through its node. Every 18 years, the eclipse


id: eclipse-cycle-20260505-8
file: data/en.wikipedia.org/wiki/Eclipse_cycle-8.md
category: reference
title: Eclipse cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eclipse_cycle
date_saved: 2026-05-05T11:12:34.827205+00:00
instance: kb-cron
parent: eclipse-cycle-20260505-0
summary:
D, the mean elongation (angle between the Sun and Moon longitudes) F, the mean argument of latitude (the angle between the Moon and the ascending node) l, the mean anomaly of the Moon (how far the Moon is from perigee) l', the mean anomaly of the Sun (or of the Earth) These four arguments are basically linear functions of time but with slowly varying higher-order terms. A diagram of inex and saros indices such as the "Panorama" shown above is like a map, and we can consider the values of the Delaunay arguments on it. The mean elongation, D, goes through 360° 223 times when the inex value goes up by 1, and 358 times when the saros value goes up by 1. It is thus equivalent to 0°, by definition, at each combination of solar saros index and inex index, because solar eclipses occur when the elongation is zero. From D one can find the actual elapsed time from some reference time such as J2000, which is like a linear function of inex and saros but with a deviation that grows quadratically with distance from the reference time, amounting to about 19 minutes at a distance of 1000 years.


id: eclipse-cycle-20260505-9
file: data/en.wikipedia.org/wiki/Eclipse_cycle-9.md
category: reference
title: Eclipse cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eclipse_cycle
date_saved: 2026-05-05T11:12:34.827205+00:00
instance: kb-cron
parent: eclipse-cycle-20260505-0
summary:
The upshot is that the properties vary slowly over the diagram in any of the three sets of saros series. The accompanying graph shows just the saros series that have saros index modulo 3 equal to zero. The blue areas are where the mean anomaly of the Moon is near 0°, meaning that the Moon is near perigee at the time of the eclipse, and therefore relatively large, favoring total eclipses. In the red area, the Moon is generally further from the Earth, and the eclipses are annular. We can also see the effect of the Sun's anomaly. Eclipses in July, when the Sun is further from the Earth, are more likely to be total, so the blue area extends over a greater range of inex index than for eclipses in January. The waviness seen in the graph is also due to the Sun's anomaly. In April the Sun is further east than if its longitude progressed evenly, and in October it is further west, and this means that in April the Moon catches up with the Sun relatively late, and in October relatively early. This in turn means that the argument of latitude at the actual time of the


id: eclipse-cycle-20260505-10
file: data/en.wikipedia.org/wiki/Eclipse_cycle-10.md
category: reference
title: Eclipse cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eclipse_cycle
date_saved: 2026-05-05T11:12:34.827205+00:00
instance: kb-cron
parent: eclipse-cycle-20260505-0
summary:
== Eclipse periods == In addition to the eclipse cycles, there are periods in eclipse behavior that do not correspond to an eclipse cycle. As mentioned previously, there is the period of around 565 years in which central eclipses move around the anomalistic year (near to the Tetradia cycles). This is the period of the alternation between times when central eclipses do not move much in date (for example in the 20th century they were in July and are now moving into June) and times when central eclipses move rapidly in date. There is also the period of around 1640 years between times when central eclipses are at perigee (or agogee). In the figure above showing inex versus time of year, this is the time between the successive blue patches when total eclipses are more common than annular ones. The central eclipe at perigee of 1781 (and similar ones around then) will recurr only after this much time, around AD 3420. There are short periodicities in the sizes of the Sun and Moon at the times of eclipses. Both the angular size of the Moon in the sky at eclipses at the ascending node and the size of the Sun


id: eclipse-cycle-20260505-11
file: data/en.wikipedia.org/wiki/Eclipse_cycle-11.md
category: reference
title: Eclipse cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eclipse_cycle
date_saved: 2026-05-05T11:12:34.827205+00:00
instance: kb-cron
parent: eclipse-cycle-20260505-0
summary:
40940.998 synodic months, 44429.006 draconic months, 43876.990 anomalistic months, 3310.007 anomalistic years, resp. Note that in this example, in terms of anomaly (position with respect to perigee) the Moon returns to within 1% of an orbit (about 3.4°), rather than 3.2% as predicted using today's values of month lengths. The fact that the day is getting longer means there are more revolutions of the Earth since some point in the past than what one might calculate from the time and date, and fewer from now to some future time. This effect means eclipses occur earlier in the day or calendar, going in the opposite direction relative to the effect of the lengthening synodic month already mentioned. This effect is known as ΔT. It cannot be calculated exactly but amounts to around 50 minutes per millennium squared. In our example above, this means that although the eclipse in 1688 BC was centered on March 16 at 00:15:31 in Dynamic time, it actually occurred before midnight and therefore on March 15 (using time based on the location of present-day Greenwich, and using the proleptic Julian calendar). The fact that the argument of latitude is decreased explains why one sees a curvature in


id: eclipse-season-20260505-0
file: data/en.wikipedia.org/wiki/Eclipse_season-0.md
category: reference
title: Eclipse season
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eclipse_season
date_saved: 2026-05-05T11:12:36.129663+00:00
instance: kb-cron
parent: eclipse-season-20260505-0
summary:
An eclipse season is a period of roughly 1 month, occurring roughly every six months, when the orbits of the Earth, Sun, and Moon align such that solar and lunar eclipses occur. Eclipse seasons are the result of the axial parallelism of the Moon's orbital plane (tilted five degrees to the Earth's orbital plane), just as Earth's weather seasons are the result of the axial parallelism of Earth's tilted axis as it orbits around the Sun. During the season, the "lunar nodes" – the line where the Moon's orbital plane intersects with the Earth's orbital plane – align with the Sun and Earth, such that a solar eclipse is formed during the new moon phase and a lunar eclipse is formed during the full moon phase. Only two (or occasionally three) eclipse seasons occur during each year, and each season lasts about 35 days and repeats just short of six months (173 days) later, thus two full eclipse seasons always occur each year. Either two or three eclipses happen each eclipse season. During the eclipse season, the Moon is at a low ecliptic latitude (less than around 1.5° north or south), hence the Sun, Moon, and Earth become aligned straightly


id: ephemeride-lunaire-parisienne-20260505-0
file: data/en.wikipedia.org/wiki/Ephemeride_Lunaire_Parisienne-0.md
category: reference
title: Ephemeride Lunaire Parisienne
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ephemeride_Lunaire_Parisienne
date_saved: 2026-05-05T11:12:37.291641+00:00
instance: kb-cron
parent: ephemeride-lunaire-parisienne-20260505-0
summary:
Éphéméride Lunaire Parisienne is a lunar theory developed by Jean Chapront, Michelle Chapront-Touzé, and others at the Bureau des Longitudes in the 1970s to 1990s. == Method == ELP gives a series expansion of the orbital elements and the coordinates of the Moon. The authors refer to it as a "semi-analytical" theory because they developed their expressions not purely symbolically, but introduced numerical values for orbital constants from the outset; but they also constructed partial derivatives of all terms with respect to these constants, so they could make corrections afterwards to reach the final solution. ELP has been fitted not directly to observations, but to the numerical integrations known as the Jet Propulsion Laboratory Development Ephemeris (which includes the Lunar Ephemerides), that in their turn have been fitted to actual astronomical observations. ELP was fitted initially to the DE200, but improved parameters have been published up to DE405. Even though ELP contains more than 20,000 periodic terms, it is not sufficiently accurate to predict the Moon's position to the centimeter accuracy with which it can be measured by LLR. An attempt was made to improve the planetary terms with the ELP/MPP02 lunar theory, but heuristic corrections remained necessary. == Advantages


id: ephemeris-time-20260505-0
file: data/en.wikipedia.org/wiki/Ephemeris_time-0.md
category: reference
title: Ephemeris time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ephemeris_time
date_saved: 2026-05-05T11:12:38.449522+00:00
instance: kb-cron
parent: ephemeris-time-20260505-0
summary:
In metrology, ephemeris time (ET) is time in association with any ephemeris (itinerary of the trajectory of an astronomical object). In practice it has been used more specifically to refer to: a former standard astronomical time scale adopted in 1952 by the IAU, and superseded during the 1970s. This time scale was proposed in 1948, to overcome the disadvantages of irregularly fluctuating mean solar time. The intent was to define a uniform time (as far as was then feasible) based on Newtonian theory (see below: Definition of ephemeris time (1952)). Ephemeris time was a first application of the concept of a dynamical time scale, in which the time and time scale are defined implicitly, inferred from the observed position of an astronomical object via the dynamical theory of its motion. a modern relativistic coordinate time scale, implemented by the JPL ephemeris time argument Teph, in a series of numerically integrated Development Ephemerides. Among them is the DE405 ephemeris in widespread current use. The time scale represented by Teph is closely related to, but distinct (by an offset and constant rate) from, the TCB time scale currently adopted as a standard by the IAU (see below: JPL ephemeris time argument Teph).


id: ephemeris-time-20260505-1
file: data/en.wikipedia.org/wiki/Ephemeris_time-1.md
category: reference
title: Ephemeris time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ephemeris_time
date_saved: 2026-05-05T11:12:38.449522+00:00
instance: kb-cron
parent: ephemeris-time-20260505-0
summary:
== History (1952 standard) == Ephemeris time (ET), adopted as standard in 1952, was originally designed as an approach to a uniform time scale, to be freed from the effects of irregularity in the rotation of the Earth, "for the convenience of astronomers and other scientists", for example for use in ephemerides of the Sun (as observed from the Earth), the Moon, and the planets. It was proposed in 1948 by the American astronomer G M Clemence. From the time of John Flamsteed (1646–1719) it had been believed that the Earth's daily rotation was uniform. But in the later nineteenth and early twentieth centuries, with increasing precision of astronomical measurements, it began to be suspected, and was eventually established, that the rotation of the Earth (i.e. the length of the day) showed irregularities on short time scales, and was slowing down on longer time scales. The evidence was compiled by the Dutch astronomer Willem de Sitter, who wrote "If we accept this hypothesis, then the 'astronomical time', given by the Earth's rotation, and used in all practical astronomical computations, differs from the 'uniform' or 'Newtonian' time, which is defined as the independent variable of the equations of celestial mechanics". De


id: ephemeris-time-20260505-2
file: data/en.wikipedia.org/wiki/Ephemeris_time-2.md
category: reference
title: Ephemeris time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ephemeris_time
date_saved: 2026-05-05T11:12:38.449522+00:00
instance: kb-cron
parent: ephemeris-time-20260505-0
summary:
Ls = 279° 41' 49".04 + 129,602,771".10T +2".32T2 +0.0748B . . . . . (2) Clemence's 1948 proposal, however, did not adopt such a correction of mean solar time. Instead, the same numbers were used as in Newcomb's original uncorrected formula (1), but now applied somewhat prescriptively, to define a new time and time scale implicitly, based on the real position of the Sun: Ls = 279° 41' 48".04 + 129,602,768".13E +1".089E2 . . . . . (3) With this reapplication, the time variable, now given as E, represents time in ephemeris centuries of 36525 ephemeris days of 86400 ephemeris seconds each. The 1961 official reference summarized the concept as such: "The origin and rate of ephemeris time are defined to make the Sun's mean longitude agree with Newcomb's expression" From the comparison of formulae (2) and (3), both of which express the same real solar motion in the same real time but defined on separate time scales, Clemence arrived at an explicit expression, estimating the difference in seconds of time between ephemeris time and mean solar time, in the sense (ET-UT): δ t = + 24 s .349 + 72 s .3165 T + 29 s .949 T 2


id: ephemeris-time-20260505-3
file: data/en.wikipedia.org/wiki/Ephemeris_time-3.md
category: reference
title: Ephemeris time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ephemeris_time
date_saved: 2026-05-05T11:12:38.449522+00:00
instance: kb-cron
parent: ephemeris-time-20260505-0
summary:
== JPL ephemeris time argument Teph == High-precision ephemerides of sun, moon and planets were developed and calculated at the Jet Propulsion Laboratory (JPL) over a long period, and the latest available were adopted for the ephemerides in the Astronomical Almanac starting in 1984. Although not an IAU standard, the ephemeris time argument Teph has been in use at that institution since the 1960s. The time scale represented by Teph has been characterized as a relativistic coordinate time that differs from Terrestrial Time only by small periodic terms with an amplitude not exceeding 2 milliseconds of time: it is linearly related to, but distinct (by an offset and constant rate which is of the order of 0.5 s/a) from the TCB time scale adopted in 1991 as a standard by the IAU. Thus for clocks on or near the geoid, Teph (within 2 milliseconds), but not so closely TCB, can be used as approximations to Terrestrial Time, and via the standard ephemerides Teph is in widespread use. Partly in acknowledgement of the widespread use of Teph via the JPL ephemerides, IAU resolution 3 of 2006 (re-)defined Barycentric Dynamical Time (TDB) as a current standard. As re-defined in 2006, TDB is


id: ephemeris-time-20260505-4
file: data/en.wikipedia.org/wiki/Ephemeris_time-4.md
category: reference
title: Ephemeris time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ephemeris_time
date_saved: 2026-05-05T11:12:38.449522+00:00
instance: kb-cron
parent: ephemeris-time-20260505-0
summary:
== Bibliography == G M Clemence, "On the System of Astronomical Constants", Astronomical Journal, vol. 53(6) (1948), issue #1170, pp. 169–179. G M Clemence (1971), "The Concept of Ephemeris Time", Journal for the History of Astronomy, vol. 2 (1971), pp. 73–79. B Guinot and P K Seidelmann (1988), "Time scales – Their history, definition and interpretation", Astronomy and Astrophysics, vol. 194 (nos. 1–2) (April 1988), pp. 304–308. 'ESAA (1992)': P K Seidelmann (ed.), "Explanatory Supplement to the Astronomical Almanac", University Science Books, CA, 1992; ISBN 0-935702-68-7. 'ESAE 1961': "Explanatory Supplement to the Astronomical Ephemeris and the American Ephemeris and Nautical Almanac" ('prepared jointly by the Nautical Almanac Offices of the United Kingdom and the United States of America', HMSO, London, 1961). IAU resolutions (1976): Resolutions adopted by the IAU in 1976 at Grenoble. "Improved Lunar Ephemeris", US Government Printing Office, 1954. W Markowitz, R G Hall, S Edelson (1955), "Ephemeris time from photographic positions of the moon", Astronomical Journal, vol. 60 (1955), p. 171. W Markowitz, R G Hall, L Essen, J V L Parry (1958), "Frequency of cesium in terms of ephemeris time", Physical Review Letters, vol. 1 (1958), 105–107. W Markowitz (1959), "Variations in the Rotation of the


id: equation-of-time-20260505-0
file: data/en.wikipedia.org/wiki/Equation_of_time-0.md
category: reference
title: Equation of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equation_of_time
date_saved: 2026-05-05T11:12:39.793727+00:00
instance: kb-cron
parent: equation-of-time-20260505-0
summary:
The equation of time describes the discrepancy between two kinds of solar time. The two times that differ are the apparent solar time, which directly tracks the diurnal motion of the Sun, and mean solar time, which tracks a theoretical mean Sun with uniform motion along the celestial equator. Apparent solar time can be obtained by measurement of the current position (hour angle) of the Sun, as indicated (with limited accuracy) by a sundial. Mean solar time, for the same place, would be the time indicated by a steady clock set so that over the year its differences from apparent solar time would have a mean of zero. The equation of time is the east or west component of the analemma, a curve representing the angular offset of the Sun from its mean position on the celestial sphere as viewed from Earth. The equation of time values for each day of the year, compiled by astronomical observatories, were widely listed in almanacs and ephemerides. The equation of time can be approximated by a sum of two sine waves: Δ t e y = − 7.659 sin ⁡ ( D ) + 9.863 sin ⁡ ( 2 D + 3.5932 )


id: equation-of-time-20260505-1
file: data/en.wikipedia.org/wiki/Equation_of_time-1.md
category: reference
title: Equation of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equation_of_time
date_saved: 2026-05-05T11:12:39.793727+00:00
instance: kb-cron
parent: equation-of-time-20260505-0
summary:
=== Early astronomy === The irregular daily movement of the Sun was known to the Babylonians. Book III of Ptolemy's Almagest (2nd century) is primarily concerned with the Sun's anomaly, and he tabulated the equation of time in his Handy Tables. Ptolemy discusses the correction needed to convert the meridian crossing of the Sun to mean solar time and takes into consideration the nonuniform motion of the Sun along the ecliptic and the meridian correction for the Sun's ecliptic longitude. He states the maximum correction is 8+1⁄3 time-degrees or 5⁄9 of an hour (Book III, chapter 9). However he did not consider the effect to be relevant for most calculations since it was negligible for the slow-moving luminaries and only applied it for the fastest-moving luminary, the Moon. Based on Ptolemy's discussion in the Almagest, values for the equation of time (Arabic taʿdīl al-ayyām bi layālayhā) were standard for the tables (zij) in the works of medieval Islamic astronomy. === Early modern period === A description of apparent and mean time was given by Nevil Maskelyne in the Nautical Almanac for 1767: "Apparent Time is that deduced immediately from the Sun, whether from the Observation of his passing the Meridian,


id: equation-of-time-20260505-2
file: data/en.wikipedia.org/wiki/Equation_of_time-2.md
category: reference
title: Equation of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equation_of_time
date_saved: 2026-05-05T11:12:39.793727+00:00
instance: kb-cron
parent: equation-of-time-20260505-0
summary:
From 1767 to 1833, the British Nautical Almanac and Astronomical Ephemeris tabulated the equation of time in the sense 'add or subtract (as directed) the number of minutes and seconds stated to or from the apparent time to obtain the mean time'. Times in the Almanac were in apparent solar time, because time aboard ship was most often determined by observing the Sun. This operation would be performed in the unusual case that the mean solar time of an observation was needed. In the issues since 1834, all times have been in mean solar time, because by then the time aboard ship was increasingly often determined by marine chronometers. The instructions were consequently to add or subtract (as directed) the number of minutes stated to or from the mean time to obtain the apparent time. So now addition corresponded to the equation being positive and subtraction corresponded to it being negative. As the apparent daily movement of the Sun is one revolution per day, that is 360° every 24 hours, and the Sun itself appears as a disc of about 0.5° in the sky, simple sundials can be read to a maximum accuracy of about one minute. Since the equation


id: equation-of-time-20260505-3
file: data/en.wikipedia.org/wiki/Equation_of_time-3.md
category: reference
title: Equation of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equation_of_time
date_saved: 2026-05-05T11:12:39.793727+00:00
instance: kb-cron
parent: equation-of-time-20260505-0
summary:
== Secular effects == (Note: the word “secular” in this context means “pertaining to the passage of time over long periods”, not “lacking religion”. See, for example, “secular trend”, which also uses the word in this sense.) The two above mentioned factors have different wavelengths, amplitudes and phases, so their combined contribution is an irregular wave. At epoch 2000 these are the values (in minutes and seconds with UT dates): On shorter timescales (thousands of years) the shifts in the dates of equinox and perihelion will be more important. The former is caused by precession, and shifts the equinox backwards compared to the stars. But it can be ignored in the current discussion as our Gregorian calendar is constructed in such a way as to keep the vernal equinox date at 20 March (at least at sufficient accuracy for our aim here). The shift of the perihelion is forwards, about 1.7 days every century. In 1246 the perihelion occurred on 22 December, the day of the solstice, so the two contributing waves had common zero points and the equation of time curve was symmetrical: in Astronomical Algorithms Meeus gives February and November extrema of 15 m 39 s and May


id: equation-of-time-20260505-4
file: data/en.wikipedia.org/wiki/Equation_of_time-4.md
category: reference
title: Equation of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equation_of_time
date_saved: 2026-05-05T11:12:39.793727+00:00
instance: kb-cron
parent: equation-of-time-20260505-0
summary:
EOT, the time difference between apparent solar time and mean solar time; GHA, the Greenwich Hour Angle of the apparent (actual) Sun; GMHA = Universal Time − Offset, the Greenwich Mean Hour Angle of the mean (fictitious) Sun. Here time and angle are quantities that are related by factors such as: 2π radians = 360° = 1 day = 24 hours. The difference, EOT, is measurable since GHA is an angle that can be measured and Universal Time, UT, is a scale for the measurement of time. The offset by π = 180° = 12 hours from UT is needed because UT is zero at mean midnight while GMHA = 0 at mean noon. Universal Time is discontinuous at mean midnight so another quantity day number N, an integer, is required in order to form the continuous quantity time t: t = N + ⁠UT/24 hr⁠ days. Both GHA and GMHA, like all physical angles, have a mathematical, but not a physical discontinuity at their respective (apparent and mean) noon. Despite the mathematical discontinuities of its components, EOT is defined as a continuous function by adding (or subtracting) 24 hours in the small time interval between the discontinuities in GHA


id: equation-of-time-20260505-5
file: data/en.wikipedia.org/wiki/Equation_of_time-5.md
category: reference
title: Equation of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equation_of_time
date_saved: 2026-05-05T11:12:39.793727+00:00
instance: kb-cron
parent: equation-of-time-20260505-0
summary:
E, the Sun's eccentric anomaly (note that this is different from M); ν, the Sun's true anomaly; λ = ν + λp, the Sun's true longitude on the ecliptic. All these angles are shown in the figure on the right, which shows the celestial sphere and the Sun's elliptical orbit seen from the Earth (the same as the Earth's orbit seen from the Sun). In this figure ε is the obliquity, while e = √1 − (b/a)2 is the eccentricity of the ellipse. Now given a value of 0 ≤ M ≤ 2π, one can calculate α(M) by means of the following well-known procedure: First, given M, calculate E from Kepler's equation: M = E − e sin ⁡ E {\displaystyle M=E-e\sin {E}} Although this equation cannot be solved exactly in closed form, values of E(M) can be obtained from infinite (power or trigonometric) series, graphical, or numerical methods. Alternatively, note that for e = 0, E = M, and by iteration: E ≈ M + e sin ⁡ M {\displaystyle E\approx M+e\sin {M}} This approximation can be improved, for small e, by iterating again: E ≈ M + e sin ⁡ M + 1 2 e 2 sin ⁡


id: equation-of-time-20260505-6
file: data/en.wikipedia.org/wiki/Equation_of_time-6.md
category: reference
title: Equation of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equation_of_time
date_saved: 2026-05-05T11:12:39.793727+00:00
instance: kb-cron
parent: equation-of-time-20260505-0
summary:
1) Δ t e y = − 2 e sin ⁡ M + y sin ⁡ ( 2 M + 2 λ p ) = − 7.659 sin ⁡ M + 9.863 sin ⁡ ( 2 M + 3.5932 ) {\displaystyle \Delta t_{ey}=-2e\sin {M}+y\sin \left(2M+2\lambda _{p}\right)=-7.659\sin {M}+9.863\sin \left(2M+3.5932\right)} minutes This equation was first derived by Milne, who wrote it in terms of λ = M + λp. The numerical values written here result from using the orbital parameter values, e = 0.016709, ε = 23.4393° = 0.409093 radians, and λp = 282.9381° = 4.938201 radians that correspond to the epoch 1 January 2000 at 12 noon UT1. When evaluating the numerical expression for Δtey as given above, a calculator must be in radian mode to obtain correct values because the value of 2λp − 2π in the argument of the second term is written there in radians. Higher order approximations can also be written, but they necessarily have more terms. For example, the second order approximation in both e and y consists of five terms 2) Δ t e 2 y 2 = Δ t e y − 5 4 e 2 sin ⁡ 2 M + 4 e y


id: equation-of-time-20260505-7
file: data/en.wikipedia.org/wiki/Equation_of_time-7.md
category: reference
title: Equation of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equation_of_time
date_saved: 2026-05-05T11:12:39.793727+00:00
instance: kb-cron
parent: equation-of-time-20260505-0
summary:
arctan η ⁡ x = arctan ⁡ x + π round ⁡ ( η − arctan ⁡ x π ) {\displaystyle \arctan _{\eta }x=\arctan x+\pi \operatorname {round} {\left({\frac {\eta -\arctan x}{\pi }}\right)}} . It produces a value that is as close to η as possible. The function round rounds to the nearest integer. Applying this yields: Δ t ( M ) = M + λ p − arctan M + λ p ⁡ ( cos ⁡ ε tan ⁡ λ ) {\displaystyle \Delta t(M)=M+\lambda _{p}-\arctan _{M+\lambda _{p}}\left(\cos {\varepsilon }\tan {\lambda }\right)} . The parameter M + λp arranges here to set Δt to the zero nearest value which is the desired one. === Secular change === The difference between the MICA and Δt results was checked every 5 years over the range from 1960 to 2040. In every instance the maximum absolute error was less than 3 s; the largest difference, 2.91 s, occurred on 22 May 1965 (day 141). However, in order to achieve this level of accuracy over this range of years it is necessary to account for the secular change in the orbital parameters with time. The equations that describe this variation are: e = 1.6709 ×


id: equation-of-time-20260505-8
file: data/en.wikipedia.org/wiki/Equation_of_time-8.md
category: reference
title: Equation of time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equation_of_time
date_saved: 2026-05-05T11:12:39.793727+00:00
instance: kb-cron
parent: equation-of-time-20260505-0
summary:
The value of B in the above calculation is an accurate value for the Sun's ecliptic longitude (shifted by 90°), so the solar declination δ becomes readily available: δ = − arcsin ⁡ ( sin ⁡ 23.44 ∘ ⋅ cos ⁡ B ) {\displaystyle \delta =-\arcsin \left(\sin 23.44^{\circ }\cdot \cos B\right)} which is accurate to within a fraction of a degree. == See also == Azimuth – Horizontal angle from north or other reference cardinal direction Milankovitch cycles – Global climate cycles == Notes == == References == == External links == NOAA Solar Calculator "USNO data services". Archived from the original on 29 May 2014. (include rise/set/transit times of the Sun and other celestial objects) The equation of time described on the Royal Greenwich Observatory web site The Equation of Time and the Analemma, by Kieron Taylor An article by Brian Tung containing a link to a C program using a more accurate formula than most (particularly at high inclinations and eccentricities). The program can calculate solar declination, Equation of Time, or Analemma Doing calculations using Ptolemy's geocentric planetary models with a discussion of his E.T. graph Equation of Time Longcase Clock by John Topping C.1720 The equation of


id: equinox-20260505-0
file: data/en.wikipedia.org/wiki/Equinox-0.md
category: reference
title: Equinox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equinox
date_saved: 2026-05-05T11:12:40.992576+00:00
instance: kb-cron
parent: equinox-20260505-0
summary:
A solar equinox is a moment in time when the Sun appears directly above the equator, rather than to its north or south. On the day of the equinox, the Sun appears to rise directly east and set directly west. This occurs twice each year, around 20 March and 23 September. An equinox is equivalently defined as the time when the plane of Earth's equator passes through the geometric center of the Sun's disk. This is also the moment when Earth's rotation axis is directly perpendicular to the Sun-Earth line, tilting neither toward nor away from the Sun. In modern times, since the Moon and (to a lesser extent) the planets cause Earth's orbit to vary slightly from a perfect ellipse, the equinox is officially defined by the Sun's more regular ecliptic longitude rather than by its declination. The instants of the equinoxes are currently defined to be when the apparent geocentric longitude of the Sun is 0° and 180°. The word is derived from the Latin aequinoctium, from aequa (equal) and nox (night). On the day of an equinox, daytime and nighttime are of approximately equal duration all over the planet. Contrary to popular belief, they are not exactly


id: equinox-20260505-1
file: data/en.wikipedia.org/wiki/Equinox-1.md
category: reference
title: Equinox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equinox
date_saved: 2026-05-05T11:12:40.992576+00:00
instance: kb-cron
parent: equinox-20260505-0
summary:
==== Modern dates ==== The dates of the equinoxes change progressively during the leap-year cycle, because the Gregorian calendar year is not commensurate with the period of the Earth's revolution about the Sun. It is only after a complete Gregorian leap-year cycle of 400 years that the seasons commence at approximately the same time. In the 21st century the earliest March equinox will be 19 March 2096, while the latest was 21 March 2003. The earliest September equinox will be 21 September 2096 while the latest was 23 September 2003 (Universal Time). === Names === Vernal equinox and autumnal equinox: these classical names are direct derivatives of Latin (ver = spring, and autumnus = autumn). These are the historically universal and still most widely used terms for the equinoxes, but are potentially confusing because in the southern hemisphere the vernal equinox does not occur in spring and the autumnal equinox does not occur in autumn. The equivalent common language English terms spring equinox and autumn (or fall) equinox are even more ambiguous. It has become increasingly common for people to refer to the September equinox in the southern hemisphere as the Vernal equinox. March equinox and September equinox: names referring


id: equinox-20260505-2
file: data/en.wikipedia.org/wiki/Equinox-2.md
category: reference
title: Equinox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equinox
date_saved: 2026-05-05T11:12:40.992576+00:00
instance: kb-cron
parent: equinox-20260505-0
summary:
=== Unequal intervals between equinoxes === Because the movement of the Earth on its orbit obeys Kepler's laws of planetary motion, the interval from March equinox to September equinox is about 186 days, while the interval from September equinox to March equinox is about 179 days, which makes the polar day at the North Pole about 7 days longer than that at the South Pole. === Auroras === Mirror-image conjugate auroras have been observed during the equinoxes. === Cultural aspects === The equinoxes are sometimes regarded as the start of spring and autumn. A number of traditional harvest festivals are celebrated on the date of the equinoxes. People in a large part of the former Persian Empire, in Iran, Afghanistan, Tajikistan and most of the Central Asia, celebrate the Persian new year, Nowruz, which is spring equinox in northern hemisphere. This day marks the new year in Solar Hijri calendar. Religious architecture is often determined by the equinox; the Angkor Wat Equinox during which the sun rises in a perfect alignment over Angkor Wat in Cambodia is one such example. Catholic churches, since the recommendations of Charles Borromeo, have often chosen the equinox as their reference point for the orientation


id: establishment-of-a-port-20260505-0
file: data/en.wikipedia.org/wiki/Establishment_of_a_port-0.md
category: reference
title: Establishment of a port
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Establishment_of_a_port
date_saved: 2026-05-05T11:12:42.120534+00:00
instance: kb-cron
parent: establishment-of-a-port-20260505-0
summary:
Establishment of a port is the technical expression for the time that elapses between the moon's transit across the local meridian at new or full moon at a given place and the time of the next high water at that place. As an example in the UK, the interval (constant at any one place) may vary from 6 minutes (Harwich) to 11 hours 45 minutes (North Foreland) meaning that the time difference of high water between those two places is 21 minutes. At London Bridge it is 1 hour 58 minutes. The term establishment of the port is identical to the obsolescent term High Water Full and Change (HWF&C) Full referring to the full moon and change referring to the new moon. Before the creation of modern tide tables, it was a quick way of predicting the time of local high water. The moon’s passage at the local meridian is about 50 minutes later each day. If it is HWF&C 1 hour 30 minutes and we are three days after the full moon, then the morning high water is 1h 30 + 150 minutes = 0400. == References ==


id: exeligmos-20260505-0
file: data/en.wikipedia.org/wiki/Exeligmos-0.md
category: reference
title: Exeligmos
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Exeligmos
date_saved: 2026-05-05T11:12:43.310591+00:00
instance: kb-cron
parent: exeligmos-20260505-0
summary:
An exeligmos (Ancient Greek: ἐξελιγμός, lit. 'turning of the wheel') is a period of 54 years, 33 days that can be used to predict successive eclipses with similar properties and location. For a solar eclipse, after every exeligmos a solar eclipse of similar characteristics will occur in a location close to the eclipse before it. For a lunar eclipse the same part of the earth will view an eclipse that is very similar to the one that occurred one exeligmos before it (see main text for visual examples). The exeligmos is an eclipse cycle that is a triple saros, three saroses (or saroi) long, with the advantage that it has nearly an integer number of days so the next eclipse will be visible at locations and times near the eclipse that occurred one exeligmos earlier. In contrast, each saros, an eclipse occurs about eight hours later in the day or about 120° to the west of the eclipse that occurred one saros earlier. It corresponds to: 3 saroses 669 synodic months 725.996 draconic months 56.996 eclipse years (114 eclipse seasons) 716.976 anomalistic months The 57 eclipse years means that if there is a solar eclipse (or lunar eclipse), then after


id: first-point-of-aries-20260505-0
file: data/en.wikipedia.org/wiki/First_point_of_Aries-0.md
category: reference
title: First point of Aries
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/First_point_of_Aries
date_saved: 2026-05-05T11:12:44.495909+00:00
instance: kb-cron
parent: first-point-of-aries-20260505-0
summary:
The first point of Aries, also known as the cusp of Aries or the vernal point, is the location of the March equinox (the vernal equinox in the northern hemisphere, and the autumnal equinox in the southern), used as a reference point in celestial coordinate systems. In diagrams using such coordinate systems, it is often indicated with the symbol ♈︎. Named for the constellation of Aries, it is one of the two points on the celestial sphere at which the celestial equator crosses the ecliptic, the other being the first point of Libra, located exactly 180° from it. Due to precession of the equinoxes since the positions were originally named in antiquity, the position of the Sun when at the March equinox is now in Pisces; when it is at the September equinox, it is in Virgo (as of J2000). Along its yearly path through the zodiac, the Sun meets the celestial equator as it travels from south to north at the first point of Aries, and from north to south at the first point of Libra. The first point of Aries is considered to be the celestial "prime meridian" from which right ascension is calculated. == History == The


id: geocentric-coordinate-time-20260505-0
file: data/en.wikipedia.org/wiki/Geocentric_Coordinate_Time-0.md
category: reference
title: Geocentric Coordinate Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Geocentric_Coordinate_Time
date_saved: 2026-05-05T11:12:45.635159+00:00
instance: kb-cron
parent: geocentric-coordinate-time-20260505-0
summary:
Geocentric Coordinate Time (TCG - Temps-coordonnée géocentrique) is a coordinate time standard intended to be used as the independent variable of time for all calculations pertaining to precession, nutation, the Moon, and artificial satellites of the Earth. It is equivalent to the proper time experienced by a clock at rest in a coordinate frame co-moving with the center of the Earth : that is, a clock that performs exactly the same movements as the Earth but is outside the Earth's gravity well. It is therefore not influenced by the gravitational time dilation caused by the Earth. The TCG is the time coordinate for the Geocentric Celestial Reference System (GCRS). TCG was defined in 1991 by the International Astronomical Union. Unlike former astronomical time scales, TCG is defined in the context of the general theory of relativity. The relationships between TCG and other relativistic time scales are defined with fully general relativistic metrics. Because the reference frame for TCG is not rotating with the surface of the Earth and not in the gravitational potential of the Earth, TCG ticks faster than clocks on the surface of the Earth by a factor of about 7.0 × 10−10 (about 22 milliseconds per year).


id: geologic-calendar-20260505-0
file: data/en.wikipedia.org/wiki/Geologic_Calendar-0.md
category: reference
title: Geologic Calendar
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Geologic_Calendar
date_saved: 2026-05-05T11:12:46.802754+00:00
instance: kb-cron
parent: geologic-calendar-20260505-0
summary:
The Geologic Calendar is a scale in which the geological timespan of the Earth is mapped onto a calendrical year; that is to say, the day one of the Earth took place on a geologic January 1 at precisely midnight, and today's date and time is December 31 at midnight. On this calendar, the inferred appearance of the first living single-celled organisms, prokaryotes, occurred on a geologic February 25 around 12:30 pm to 1:07 pm, dinosaurs first appeared on December 13, the first flower plants on December 22 and the first primates on December 28 at about 9:43 pm. The first anatomically modern humans did not arrive until around 11:48 p.m. on New Year's Eve, and all of human history since the end of the last ice-age occurred in the last 82.2 seconds before midnight of the new year. A variation of this analogy instead compresses Earth's 4.6 billion year-old history into a single day: While the Earth still forms at midnight, and the present day is also represented by midnight, the first life on Earth would appear at 4:00 am, dinosaurs would appear at 10:00 pm, the first flowers 10:30 pm, the first primates 11:30 pm, and modern humans


id: golden-number-time-20260505-0
file: data/en.wikipedia.org/wiki/Golden_number_(time)-0.md
category: reference
title: Golden number (time)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Golden_number_(time)
date_saved: 2026-05-05T11:12:48.005113+00:00
instance: kb-cron
parent: golden-number-time-20260505-0
summary:
A golden number (sometimes capitalized) is a number assigned to each year in sequence which is used to indicate the dates of all the calendric new moons for each year in a 19-year Metonic cycle. They are used in computus (the calculation of the date of Easter) and also in Runic calendars. The golden number of any Julian or Gregorian calendar year can be calculated by dividing the year by nineteen, taking the remainder and adding one. (In mathematics this can be expressed as ((year number modulo 19) + 1). For example, 2026 divided by 19 gives 106, remainder 12, which after adding 1 gives the golden number 13. The golden number, as it was later called, first appears in a calendar composed by Abbo of Fleury around the year 1000. Around 1162 a certain Master William referred to this number as the golden number "because it is more precious than the other numbers." The name refers to the practice of printing golden numbers in gold. The term became widely known and used, in part through the computistic poem Massa Compoti written by Alexander de Villa Dei around 1200. == See also == Dominical letter Date of Easter Paschal Full


id: heliacal-rising-20260505-0
file: data/en.wikipedia.org/wiki/Heliacal_rising-0.md
category: reference
title: Heliacal rising
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Heliacal_rising
date_saved: 2026-05-05T11:12:49.181530+00:00
instance: kb-cron
parent: heliacal-rising-20260505-0
summary:
The heliacal rising ( hih-LY-ə-kəl) of a star or a planet occurs annually, when it becomes visible above the eastern horizon at dawn in the brief moment just before sunrise (thus becoming "the morning star"). A heliacal rising marks the time when a star or planet becomes visible for the first time again in the night sky after having set with the Sun at the western horizon in a previous sunset (its heliacal setting), having since been in the sky only during daytime, obscured by sunlight. Historically, the most important such rising is that of Sirius, which was an important feature of the Egyptian calendar and astronomical development. The rising of the Pleiades heralded the start of the Ancient Greek sailing season, using celestial navigation, as well as the farming season (attested by Hesiod in his Works and Days). Heliacal rising is only one of several types of alignment for stars' risings and settings; mostly the risings and settings of celestial objects are organized into lists of morning and evening risings and settings. Culmination in the evening and the culmination in the morning are separated by half a year, while on the other hand risings and settings in the evenings


id: heliacal-rising-20260505-1
file: data/en.wikipedia.org/wiki/Heliacal_rising-1.md
category: reference
title: Heliacal rising
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Heliacal_rising
date_saved: 2026-05-05T11:12:49.181530+00:00
instance: kb-cron
parent: heliacal-rising-20260505-0
summary:
== History == Constellations containing stars that rise and set were incorporated into early calendars or zodiacs. The Sumerians, Babylonians, Egyptians, and Greeks all used the heliacal risings of various stars for the timing of agricultural activities. Because of its position about 40° off the ecliptic, the heliacal risings of the bright star Sirius in Ancient Egypt occurred not over a period of exactly one sidereal year but over a period called the "Sothic year" (from "Sothis", the name for the star Sirius). The Sothic year was about a minute longer than a Julian year of 365.25 days. Since the development of civilization, this has occurred at Cairo approximately on July 19 on the Julian calendar. Its returns also roughly corresponded to the onset of the annual flooding of the Nile, although the flooding is based on the tropical year and so would occur about three quarters of a day earlier per century in the Julian or Sothic year. (July 19, 1000 BC in the Julian Calendar is July 10 in the proleptic Gregorian Calendar. At that time, the sun would be somewhere near Regulus in Leo, where it is around August 21 in the 2020s.) The ancient Egyptians appear


id: heliocentric-julian-day-20260505-0
file: data/en.wikipedia.org/wiki/Heliocentric_Julian_Day-0.md
category: reference
title: Heliocentric Julian Day
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Heliocentric_Julian_Day
date_saved: 2026-05-05T11:12:50.338245+00:00
instance: kb-cron
parent: heliocentric-julian-day-20260505-0
summary:
The Heliocentric Julian Date (HJD) is the Julian Date (JD) corrected for differences in the Earth's position with respect to the Sun. When timing events that occur beyond the Solar System, due to the finite speed of light, the time the event is observed depends on the changing position of the observer in the Solar System. Before multiple observations can be combined, they must be reduced to a common, fixed, reference location. This correction also depends on the direction to the object or event being timed. == Magnitude and limitations == The correction is zero (HJD = JD) for objects at the poles of the ecliptic. Elsewhere, it is approximately an annual sine curve, and the highest amplitude occurs on the ecliptic. The maximum correction corresponds to the time in which light travels the distance from the Sun to the Earth, i.e. ±8.3 min (500 s, 0.0058 days). JD and HJD are defined independent of the time standard. Rather, JD can be expressed as e.g. UTC, UT1, TT or TAI. The differences between these time standards are of the order of a minute, so that for minute accuracy of timings the standard used has to be stated. The HJD correction


id: hipparchic-cycle-20260505-0
file: data/en.wikipedia.org/wiki/Hipparchic_cycle-0.md
category: reference
title: Hipparchic cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hipparchic_cycle
date_saved: 2026-05-05T11:12:51.525496+00:00
instance: kb-cron
parent: hipparchic-cycle-20260505-0
summary:
The Greek astronomer Hipparchus introduced three cycles that have been named after him in later literature. == Calendar cycle == Hipparchus proposed a correction to the 76-year-long Callippic cycle, which itself was proposed as a correction to the 19-year-long Metonic cycle. He may have published it in the book "On the Length of the Year" (Περὶ ἐνιαυσίου μεγέθους), which has since been lost. From solstice observations, Hipparchus found that the tropical year is about 1⁄300 of a day shorter than the 365+1⁄4 days that Calippus used (see Almagest III.1). So he proposed to make a 1-day correction after 4 Calippic cycles, i.e. 304 years = 3,760 lunations = 111,035 days. === Error implicit in the cycle === This is a very close approximation for an integer number of lunations in an integer number of days (with an error of only 0.014 days). However, it is in fact 1.37 days longer than 304 tropical years. The mean tropical year is actually about 1⁄128 day (11 minutes 15 seconds) shorter than the Julian calendar year of 365+1⁄4 days. These differences cannot be corrected with any cycle that is a multiple of the 19-year cycle of 235 lunations; it is an accumulation of


id: hipparchic-cycle-20260505-1
file: data/en.wikipedia.org/wiki/Hipparchic_cycle-1.md
category: reference
title: Hipparchic cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hipparchic_cycle
date_saved: 2026-05-05T11:12:51.525496+00:00
instance: kb-cron
parent: hipparchic-cycle-20260505-0
summary:
4,267 synodic months 4,612 minus ⁠1/48⁠ sidereal months 4,630.531 draconic months 4,573.002 anomalistic months 727 eclipse seasons There are other eclipse intervals that also have the properties desired by Hipparchus, for example an interval of 81.2 years (four of the 251-month cycles, or 19 inex minus 26 saros) which is even closer to a whole number of anomalistic months (1076.00056), and almost equally close to a half-integer number of draconic months (1089.5366). The "tritrix" eclipse cycle, consisting of 1743 synodic months, 1891.496 draconic months, or 1867.9970 anomalistic months (140.925 years, equivalent to 3 inex plus 3 saros) is about as accurate as the interval of Hipparchus in terms of anomalistic months, but repeats many more times, around 20. An exceptionally accurate eclipse cycle from this point of view is one of 1154.5 years (43 inex minus 5 saros), which is much closer to a whole number of anomalistic months (15303.00005) than the interval of Hipparchus. At the solar eclipse of October 17, 1781, the moon had an anomaly of 0°, and similar eclipses have occurred every 1054.5 years for more than 4000 years and will continue at least 13,000 more years. The period of Hipparchus is also accurate in the


id: jens-olsen-s-world-clock-20260505-0
file: data/en.wikipedia.org/wiki/Jens_Olsen's_World_Clock-0.md
category: reference
title: Jens Olsen's World Clock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Jens_Olsen's_World_Clock
date_saved: 2026-05-05T11:12:52.768969+00:00
instance: kb-cron
parent: jens-olsen-s-world-clock-20260505-0
summary:
Jens Olsen's World Clock or Verdensur is an advanced astronomical clock which is displayed in Copenhagen City Hall. The clock consists of 12 movements which together have 15,448 parts. The clock is mechanical and must be wound once a week. Displays include lunar and solar eclipses, positions of the stellar bodies, and a perpetual calendar, in addition to the time. The fastest gear completes a revolution every ten seconds and the slowest every 25,753 years. == History == The clock was designed and calculated by Jens Olsen (1872–1945), who was a skilled locksmith, and later learned the trade of clockmaking. He also took part in the beginning of the clock's construction, and died in 1945, 10 years before the clock was completed. The calculations for the clock were made up until 1928, after which they were supervised by the astronomer Elis Strömgren. The drawings for the clock were made between 1934 and 1936, and the actual production of the clock took place from 1943 until 1955. The clock was started on 15 December 1955 by King Frederik IX and Jens Olsen's youngest grandchild Birgit. Deviations in expected readings identified in 1991 were caused by increased friction from oil in the


id: jens-olsen-s-world-clock-20260505-1
file: data/en.wikipedia.org/wiki/Jens_Olsen's_World_Clock-1.md
category: reference
title: Jens Olsen's World Clock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Jens_Olsen's_World_Clock
date_saved: 2026-05-05T11:12:52.768969+00:00
instance: kb-cron
parent: jens-olsen-s-world-clock-20260505-0
summary:
==== Sunrise/Sunset ==== The Sunrise/Sunset movement is the rightmost movement of the left section, and includes a part of shutters that move throughout the year to indicate the time of sunrise and sunset. These can be read from an inner stationary 24-hour solar time dial or an outer 24-hour mean time dial (compensating for the EoT). ==== Gregorian Calendar ==== The Gregorian Calendar is located at the bottom of the left section. It displays the year, month, day of month, and day of week. These are changed discontinuously at mean midnight, and are otherwise not moving. ==== Stellar Heavens ==== The Stellar Heavens movement is the top dial of the right section, and shows the current overhead celestial sphere. This is displayed using a stereoscopic projection (similar to an astrolabe), with fixed threads showing reference lines for meridian and zenith in the local frame and tropics, equator, and circumpolar circle in the celestial frame. The polar precession circle is also marked, which is notably the slowest motion in the clock. ==== Heliocentric Revolution ==== The Heliocentric Revolution movement is located on the right side of the right section and is functionally an orrery, showing the 8 planets rotating about a


id: jens-olsen-s-world-clock-20260505-2
file: data/en.wikipedia.org/wiki/Jens_Olsen's_World_Clock-2.md
category: reference
title: Jens Olsen's World Clock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Jens_Olsen's_World_Clock
date_saved: 2026-05-05T11:12:52.768969+00:00
instance: kb-cron
parent: jens-olsen-s-world-clock-20260505-0
summary:
Rotational information is transmitted via sets of bevels gears at both the source and destination module, with a shaft between them. These are continuously rotating (unbounded), although not always constant speeds. The gearing at both modules is always configured such that the shaft rotates at a meaningful rate (such as 1 rotation per mean day). Note that this is not the simplest design but helps observers understand more readily, likely by intent. Linear translations are transmitted via steel ribbons. These are analog signals of limited range (bounded), such as the current value of the Equation of Time or various solar and lunar anomalies. The ribbons generally go upwards to the top of the case, where there is a bell-crank system to transfer them horizontally to above the relevant destination movement, from which they can descend. Impulses are transferred via rods. These are discretely occurring signals that trigger discontinuous events, such as midnight causing the date to change. These also use the bell-crank system in the top of the case == See also == Clock of the Long Now Rasmus Sørnes == Further reading == Otto Mortensen Jens Olsen's Clock: A Technical Description Technological Institute, Copenhagen, 1957. == References == ==


id: julian-day-20260505-0
file: data/en.wikipedia.org/wiki/Julian_day-0.md
category: reference
title: Julian day
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Julian_day
date_saved: 2026-05-05T11:12:53.938677+00:00
instance: kb-cron
parent: julian-day-20260505-0
summary:
The Julian day is a continuous count of days from the beginning of the Julian period; it is used primarily by astronomers, and in software for easily calculating elapsed days between two events (e.g., food production date and expiration date). The Julian period is a chronological interval of 7980 years, derived from three multi-year cycles: the Indiction, Solar, and Lunar cycles. The last year that was simultaneously the beginning of all three cycles was 4713 BC (−4712), so that is year 1 of the current Julian period, making AD 2026 year 6739 of that Period. The next Julian Period begins in the year AD 3268. Historians used the period to identify Julian calendar years within which an event occurred when no such year was given in the historical record, or when the year given by previous historians was incorrect. The Julian day number (JDN) has the same epoch as the Julian period, but counts the number of days since the epoch rather than the number of years since then. Specifically, Julian day number 0 is assigned to the day starting at noon Universal Time on Monday, January 1, 4713 BC, proleptic Julian calendar (November 24, 4714 BC, in the proleptic


id: julian-day-20260505-1
file: data/en.wikipedia.org/wiki/Julian_day-1.md
category: reference
title: Julian day
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Julian_day
date_saved: 2026-05-05T11:12:53.938677+00:00
instance: kb-cron
parent: julian-day-20260505-0
summary:
The Modified Julian Date (MJD) was introduced by the Smithsonian Astrophysical Observatory in 1957 to record the orbit of Sputnik via an IBM 704 (36-bit machine) and using only 18 bits until August 7, 2576. MJD is the epoch of VAX/VMS and its successor OpenVMS, using 63-bit date/time, which allows times to be stored up to July 31, 31086, 02:48:05.47. The MJD has a starting point of midnight on November 17, 1858, and is computed by MJD = JD − 2400000.5 The Truncated Julian Day (TJD) was introduced by NASA/Goddard in 1979 as part of a parallel grouped binary time code (PB-5) "designed specifically, although not exclusively, for spacecraft applications". TJD was a 4-digit day count from MJD 40000, which was May 24, 1968, represented as a 14-bit binary number. Since this code was limited to four digits, TJD recycled to zero on MJD 50000, or October 10, 1995, "which gives a long ambiguity period of 27.4 years". (NASA codes PB-1–PB-4 used a 3-digit day-of-year count.) Only whole days are represented. Time of day is expressed by a count of seconds of a day, plus optional milliseconds, microseconds and nanoseconds in separate fields. Later PB-5J was introduced which increased the


id: julian-day-20260505-2
file: data/en.wikipedia.org/wiki/Julian_day-2.md
category: reference
title: Julian day
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Julian_day
date_saved: 2026-05-05T11:12:53.938677+00:00
instance: kb-cron
parent: julian-day-20260505-0
summary:
where a is the year of the indiction cycle, b of the lunar cycle, and c of the solar cycle. John Collins described the details of how these three numbers were calculated in 1666, using many trials. A summary of Collin's description is in a footnote. Reese, Everett and Craun reduced the dividends in the Try column from 285, 420, 532 to 5, 2, 7 and changed remainder to modulo, but apparently still required many trials. The specific cycles used by Scaliger to form his tricyclic Julian Period were, first, the indiction cycle with a first year of 313. Then he chose the dominant 19-year Alexandrian lunar cycle with a first year of 285, the Era of Martyrs and the Diocletian Era epoch, or a first year of 532 according to Dionysius Exiguus. Finally, Scaliger chose the post-Bedan solar cycle with a first year of 776, when its first quadrennium of concurrents, 1 2 3 4, began in sequence. Although not their intended use, the equations of de Billy or Gauss can be used to determined the first year of any 15-, 19-, and 28-year tricyclic period given any first years of their cycles. For those of the Julian Period,


id: julian-day-20260505-3
file: data/en.wikipedia.org/wiki/Julian_day-3.md
category: reference
title: Julian day
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Julian_day
date_saved: 2026-05-05T11:12:53.938677+00:00
instance: kb-cron
parent: julian-day-20260505-0
summary:
The period thus arising of 7980 Julian years, is called the Julian period, and it has been found so useful, that the most competent authorities have not hesitated to declare that, through its employment, light and order were first introduced into chronology. We owe its invention or revival to Joseph Scaliger, who is said to have received it from the Greeks of Constantinople. The first year of the current Julian period, or that of which the number in each of the three subordinate cycles is 1, was the year 4713 BC, and the noon of January 1 of that year, for the meridian of Alexandria, is the chronological epoch, to which all historical eras are most readily and intelligibly referred, by computing the number of integer days intervening between that epoch and the noon (for Alexandria) of the day, which is reckoned to be the first of the particular era in question. The meridian of Alexandria is chosen as that to which Ptolemy refers the commencement of the era of Nabonassar, the basis of all his calculations. At least one mathematical astronomer adopted Herschel's "days of the Julian period" immediately. Benjamin Peirce of Harvard University used over 2,800 Julian days


id: julian-day-20260505-4
file: data/en.wikipedia.org/wiki/Julian_day-4.md
category: reference
title: Julian day
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Julian_day
date_saved: 2026-05-05T11:12:53.938677+00:00
instance: kb-cron
parent: julian-day-20260505-0
summary:
== Julian day number calculation == The Julian day number can be calculated using the following formulas (integer division rounding towards zero is used exclusively, that is, positive values are rounded down and negative values are rounded up): The months January to December are numbered 1 to 12. For the year, astronomical year numbering is used, thus 1 BC is 0, 2 BC is −1, and 4713 BC is −4712. JDN is the Julian Day Number. Use the previous day of the month if trying to find the JDN of an instant before midday UT. === Converting Gregorian calendar date to Julian day number === The algorithm is valid for all (possibly proleptic) Gregorian calendar dates after November 23, −4713. Divisions are integer divisions towards zero; fractional parts are ignored. JDN = 1461 ⋅ ( Y + 4800 + M − 14 12 ) 4 + 367 ⋅ ( M − 2 − 12 ⋅ M − 14 12 ) 12 − 3 ⋅ Y + 4900 + M − 14 12 100 4 + D − 32075 {\displaystyle {\text{JDN}}={\frac {1461\cdot \left({\text{Y}}+4800+{\frac {{\text{M}}-14}{12}}\right)}{4}}+{\frac {367\cdot \left({\text{M}}-2-12\cdot {\frac {{\text{M}}-14}{12}}\right)}{12}}-{\frac {3\cdot {\frac {{\text{Y}}+4900+{\frac {{\text{M}}-14}{12}}}{100}}}{4}}+{\text{D}}-32075} === Converting Julian calendar date to Julian day number


id: julian-year-astronomy-20260505-0
file: data/en.wikipedia.org/wiki/Julian_year_(astronomy)-0.md
category: reference
title: Julian year (astronomy)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Julian_year_(astronomy)
date_saved: 2026-05-05T11:12:55.113997+00:00
instance: kb-cron
parent: julian-year-astronomy-20260505-0
summary:
In astronomy, a Julian year (symbol: a or aj) is a unit of measurement of time defined as exactly 365.25 days of 86400 SI seconds each. The length of the Julian year is the average length of the year in the Julian calendar that was used in Western societies until the adoption of the Gregorian Calendar, and from which the unit is named. Nevertheless, because astronomical Julian years are measuring duration rather than designating dates, this Julian year does not correspond to years in the Julian calendar or any other calendar, nor does it correspond to the many other ways of defining a year. == Usage == The Julian year is not a unit of measurement in the International System of Units (SI), but it is recognized by the International Astronomical Union (IAU) as a non-SI unit for use in astronomy. Before 1984, both the Julian year and the mean tropical year were used by astronomers. In 1898, Simon Newcomb used both in his Tables of the Sun in the form of the Julian century (36 525 days) and the "solar century" (36524.22 days), a rounded form of 100 mean tropical years of 365.24219879 days each according to Newcomb. However,


id: local-mean-time-20260505-0
file: data/en.wikipedia.org/wiki/Local_mean_time-0.md
category: reference
title: Local mean time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Local_mean_time
date_saved: 2026-05-05T11:12:56.287689+00:00
instance: kb-cron
parent: local-mean-time-20260505-0
summary:
Local mean time (LMT) is a form of solar time that corrects the variations of local apparent time, forming a uniform time scale at a specific longitude. This measurement of time was used for everyday use during the 19th century before time zones were introduced beginning in the late 19th century; it still has some uses in astronomy and navigation. The difference between local mean time and local apparent time is the equation of time. == Past use == Local solar time or sundial time was used until the early 19th century when accurate mechanical clocks became commonplace. Local mean time continued in use until various countries adopted a national standard time. Each town or city kept its own meridian, so locations one degree of longitude apart had times four minutes apart. This became a problem in the mid 19th century when railways needed clocks for railway time that were synchronized between stations, while local people needed to match their clock (or the church clock) to the time tables. Standard time means that the same time is used throughout some regional time zone—usually, it is at an offset from Greenwich Mean Time or the local mean time of the capital


id: lunar-theory-20260505-0
file: data/en.wikipedia.org/wiki/Lunar_theory-0.md
category: reference
title: Lunar theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lunar_theory
date_saved: 2026-05-05T11:12:57.491453+00:00
instance: kb-cron
parent: lunar-theory-20260505-0
summary:
Lunar theory attempts to account for the motions of the Moon. There are many small variations (or perturbations) in the Moon's motion, and many attempts have been made to account for them. After centuries of being problematic, lunar motion can now be modeled to a very high degree of accuracy (see section Modern developments). Lunar theory includes: the background of general theory; including mathematical techniques used to analyze the Moon's motion and to generate formulae and algorithms for predicting its movements; and also quantitative formulae, algorithms, and geometrical diagrams that may be used to compute the Moon's position for a given time; often by the help of tables based on the algorithms. Lunar theory has a history of over 2000 years of investigation. Its more modern developments have been used over the last three centuries for fundamental scientific and technological purposes, and are still being used in that way. == Applications == Applications of lunar theory have included the following: In the eighteenth century, comparison between lunar theory and observation was used to test Newton's law of universal gravitation by the motion of the lunar apogee. In the eighteenth and nineteenth centuries, navigational tables based on lunar theory, initially in


id: lunar-theory-20260505-1
file: data/en.wikipedia.org/wiki/Lunar_theory-1.md
category: reference
title: Lunar theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lunar_theory
date_saved: 2026-05-05T11:12:57.491453+00:00
instance: kb-cron
parent: lunar-theory-20260505-0
summary:
The synodic month, i.e. the mean period for the phases of the Moon. Now called "System B", it reckons the synodic month as 29 days and (sexagesimally) 3,11;0,50 "time degrees", where each time degree is one degree of the apparent motion of the stars, or 4 minutes of time, and the sexagesimal values after the semicolon are fractions of a time degree. This converts to 29.530594 days = 29d 12h 44m 3.33s, to compare with a modern value (as at 1900 Jan 0) of 29.530589 days, or 29d 12h 44m 2.9s. This same value was used by Hipparchos and Ptolemy, was used throughout the Middle Ages, and still forms the basis of the Hebrew calendar. The mean lunar velocity relative to the stars they estimated at 13° 10′ 35″ per day, giving a corresponding month of 27.321598 days, to compare with modern values of 13° 10′ 35.0275″ and 27.321582 days. The anomalistic month, i.e. the mean period for the Moon's approximately monthly accelerations and decelerations in its rate of movement against the stars, had a Babylonian estimate of 27.5545833 days, to compare with a modern value 27.554551 days. The draconitic month, i.e. the mean period with which the path of


id: lunar-theory-20260505-2
file: data/en.wikipedia.org/wiki/Lunar_theory-2.md
category: reference
title: Lunar theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lunar_theory
date_saved: 2026-05-05T11:12:57.491453+00:00
instance: kb-cron
parent: lunar-theory-20260505-0
summary:
The nodes and the inclination of the lunar orbital plane both appear to librate, with a monthly (according to Tycho) or semi-annual period (according to Kepler). The lunar longitude has a twice-monthly Variation, by which the Moon moves faster than expected at new and full moon, and slower than expected at the quarters. There is also an annual effect, by which the lunar motion slows down a little in January and speeds up a little in July: the annual equation. The refinements of Brahe and Kepler were recognized by their immediate successors as improvements, but their seventeenth-century successors tried numerous alternative geometrical configurations for the lunar motions to improve matters further. A notable success was achieved by Jeremiah Horrocks, who proposed a scheme involving an approximate 6 monthly libration in the position of the lunar apogee and also in the size of the elliptical eccentricity. This scheme had the great merit of giving a more realistic description of the changes in distance, diameter and parallax of the Moon. === Newton === A first gravitational period for lunar theory started with the work of Newton. He was the first to define the problem of the perturbed motion of the Moon in


id: lunar-theory-20260505-3
file: data/en.wikipedia.org/wiki/Lunar_theory-3.md
category: reference
title: Lunar theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lunar_theory
date_saved: 2026-05-05T11:12:57.491453+00:00
instance: kb-cron
parent: lunar-theory-20260505-0
summary:
Newton's diagrammatic scheme, since his time, has been represented in other and perhaps visually clearer ways. Shown here is a vector presentation indicating, for two different positions, P1 and P2, of the Moon in its orbit around the Earth, the respective vectors LS1 and LS2 for the perturbing acceleration due to the Sun. The Moon's position at P1 is fairly close to what it was at P in Newton's diagram; corresponding perturbation LS1 is like Newton's LS in size and direction. At another position P2, the Moon is farther away from the Sun than the Earth is, the Sun's attraction LQ2 on the Moon is weaker than the Sun's attraction SQ=SQ2 on the Earth, and then the resulting perturbation LS2 points obliquely away from the Sun. Constructions like those in Newton's diagram can be repeated for many different positions of the Moon in its orbit. For each position, the result is a perturbation vector like LS1 or LS2 in the second diagram. Shown here is an often-presented form of the diagram that summarises sizes and directions of the perturbation vectors for many different positions of the Moon in its orbit. Each small arrow is a perturbation vector like LS, applicable


id: lunar-theory-20260505-4
file: data/en.wikipedia.org/wiki/Lunar_theory-4.md
category: reference
title: Lunar theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lunar_theory
date_saved: 2026-05-05T11:12:57.491453+00:00
instance: kb-cron
parent: lunar-theory-20260505-0
summary:
the mean motions or positions of the Moon and the Sun, together with three coefficients and three angular positions, which together define the shape and location of their apparent orbits: the two eccentricities ( e {\displaystyle e} , about 0.0549, and e ′ {\displaystyle e'} , about 0.01675) of the ellipses that approximate to the apparent orbits of the Moon and the Sun; the angular direction of the perigees ( Γ {\displaystyle \Gamma } and Γ ′ {\displaystyle \Gamma '} ) (or their opposite points the apogees) of the two orbits; and the angle of inclination ( i {\displaystyle i} , mean value about 18523") between the planes of the two orbits, together with the direction ( Ω {\displaystyle \Omega } ) of the line of nodes in which those two planes intersect. The ascending node ( Ω {\displaystyle \Omega } ) is the node passed by the Moon when it is tending northwards relative to the ecliptic. From these basic parameters, just four basic differential angular arguments are enough to express, in their different combinations, nearly all of the most significant perturbations of the lunar motions. They are given here with their conventional symbols due to Delaunay; they are


id: lunar-theory-20260505-5
file: data/en.wikipedia.org/wiki/Lunar_theory-5.md
category: reference
title: Lunar theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lunar_theory
date_saved: 2026-05-05T11:12:57.491453+00:00
instance: kb-cron
parent: lunar-theory-20260505-0
summary:
==== Reduction to the ecliptic ==== The reduction to the ecliptic represents the geometric effect of expressing the Moon's motion in terms of a longitude in the plane of the ecliptic, although its motion is really taking place in a plane that is inclined by about 5 degrees. Its principal term is − 412 ″ sin ⁡ ( 2 F ) {\displaystyle -412''\sin(2F)} . The analysts of the mid-18th century expressed the perturbations of the Moon's position in longitude using about 25-30 trigonometrical terms. However, work in the nineteenth and twentieth century led to very different formulations of the theory so these terms are no longer current. The number of terms needed to express the Moon's position with the accuracy sought at the beginning of the twentieth century was over 1400; and the number of terms needed to emulate the accuracy of modern numerical integrations based on laser-ranging observations is in the tens of thousands: there is no limit to the increase in number of terms needed as requirements of accuracy increase. == Modern developments == === Digital computers and lunar laser ranging === Since the Second World War and especially since the 1960s, lunar theory has been further developed


id: lunar-theory-20260505-6
file: data/en.wikipedia.org/wiki/Lunar_theory-6.md
category: reference
title: Lunar theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lunar_theory
date_saved: 2026-05-05T11:12:57.491453+00:00
instance: kb-cron
parent: lunar-theory-20260505-0
summary:
== Bibliography == 'AE 1871': "Nautical Almanac & Astronomical Ephemeris" for 1871, (London, 1867). E W Brown (1896). An Introductory Treatise on the Lunar Theory, Cambridge University Press. E W Brown. "Theory of the Motion of the Moon", Memoirs of the Royal Astronomical Society, 53 (1897), 39–116. E W Brown. "Theory of the Motion of the Moon", Memoirs of the Royal Astronomical Society, 53 (1899), 163–202. E W Brown. "Theory of the Motion of the Moon", Memoirs of the Royal Astronomical Society, 54 (1900), 1–63. E W Brown. "On the verification of the Newtonian law", Monthly Notes of the Royal Astronomical Society 63 (1903), 396–397. E W Brown. "Theory of the Motion of the Moon", Memoirs of the Royal Astronomical Society, 57 (1905), 51–145. E W Brown. "Theory of the Motion of the Moon", Memoirs of the Royal Astronomical Society, 59 (1908), 1–103. E W Brown (1919). Tables of the Motion of the Moon, New Haven. M Chapront-Touzé & J Chapront. "The lunar ephemeris ELP-2000", Astronomy & Astrophysics 124 (1983), 50–62. M Chapront-Touzé & J Chapront: "ELP2000-85: a semi-analytical lunar ephemeris adequate for historical times", Astronomy & Astrophysics 190 (1988), 342–352. M Chapront-Touzé & J Chapront, Analytical Ephemerides of the


id: metonic-cycle-20260505-0
file: data/en.wikipedia.org/wiki/Metonic_cycle-0.md
category: reference
title: Metonic cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Metonic_cycle
date_saved: 2026-05-05T11:12:58.748160+00:00
instance: kb-cron
parent: metonic-cycle-20260505-0
summary:
The Metonic cycle or enneadecaeteris (from Ancient Greek: ἐννεακαιδεκαετηρίς, from ἐννεακαίδεκα, "nineteen") is a period of almost exactly 19 years after which the lunar phases recur at the same time of the year. The recurrence is not perfect, and by precise observation the Metonic cycle defined as 235 synodic months is just 2 hours, 4 minutes and 58 seconds longer than 19 tropical years. Meton of Athens, in the 5th century BC, judged the cycle to be a whole number of days, 6,940. Using these whole numbers facilitates the construction of a lunisolar calendar. A tropical year (about 365.24 days) is longer than 12 lunar months (about 354.36 days) and shorter than 13 of them (about 383.90 days). In a Metonic calendar (a type of lunisolar calendar), there are twelve years of 12 lunar months and seven years of 13 lunar months. == Application in traditional calendars == In the Babylonian and Hebrew lunisolar calendars, the years 3, 6, 8, 11, 14, 17, and 19 are the long (13-month) years of the Metonic cycle. This cycle forms the basis of the Greek and Hebrew calendars. A 19-year cycle is used for the computation of the date of Easter each year.


id: morning-20260505-0
file: data/en.wikipedia.org/wiki/Morning-0.md
category: reference
title: Morning
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Morning
date_saved: 2026-05-05T11:12:59.945120+00:00
instance: kb-cron
parent: morning-20260505-0
summary:
Morning is either the period from sunrise to noon, or the period from midnight to noon. In the first definition it is preceded by the twilight period of dawn, and there are no exact times for when morning begins (also true of evening and night) because it can vary according to one's latitude, and the hours of daytime at each time of year. However, morning strictly ends at noon, when afternoon starts. Morning precedes afternoon, evening, and night in the sequence of a day. Originally, the term referred to sunrise. == Etymology == The Late Modern English words morning and tomorrow began in Early Middle English as morwening, developing into morwen, then morwe, and eventually morrow. English, unlike some other languages, has separate terms for morning and tomorrow, despite their common root. Other languages, like Dutch, Scots and German, may use a single word – morgen – to signify both morning and tomorrow. == Significance == === Cultural implications === Morning prayer is a common practice in several religions. The morning period includes specific phases of the Liturgy of the Hours of Christianity. Some languages that use the time of day in greeting have a special greeting for morning, such


id: night-20260505-0
file: data/en.wikipedia.org/wiki/Night-0.md
category: reference
title: Night
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Night
date_saved: 2026-05-05T11:13:01.139082+00:00
instance: kb-cron
parent: night-20260505-0
summary:
Night, or nighttime, is the period of darkness when the Sun is below the horizon. Daylight illuminates one side of the Earth, leaving the other in darkness. The opposite of nighttime is daytime. Earth's rotation causes the appearance of sunrise and sunset. Moonlight, airglow, starlight, and light pollution dimly illuminate night. The duration of day, night, and twilight varies depending on the time of year and the latitude. Night on other celestial bodies is affected by their rotation and orbital periods. The planets Mercury and Venus have much longer nights than Earth. On Venus, night lasts about 58 Earth days. The Moon's rotation is tidally locked, rotating so that one of the sides of the Moon always faces Earth. Nightfall across portions of the near side of the Moon results in lunar phases visible from Earth. Organisms respond to the changes brought by nightfall: darkness, increased humidity, and lower temperatures. Their responses include direct reactions and adjustments to circadian rhythms governed by an internal biological clock. These circadian rhythms, regulated by exposure to light and darkness, affect an organism's behavior and physiology. Animals more active at night are called nocturnal and have adaptations for low light, including different forms of


id: night-20260505-1
file: data/en.wikipedia.org/wiki/Night-1.md
category: reference
title: Night
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Night
date_saved: 2026-05-05T11:13:01.139082+00:00
instance: kb-cron
parent: night-20260505-0
summary:
The length of night on Earth varies depending on the time of year. Longer nights occur in winter, with the winter solstice being the longest. Nights are shorter in the summer, with the summer solstice being the shortest. Earth orbits the Sun on an axis tilted 23.44 degrees. Nights are longer when a hemisphere is tilted away from the Sun and shorter when a hemisphere is tilted toward the Sun. As a result, the longest night of the year for the Northern Hemisphere will be the shortest night of the year for the Southern Hemisphere. Night's duration varies least near the equator. The difference between the shortest and longest night increases approaching the poles. At the equator, night lasts roughly 12 hours throughout the year. The tropics have little difference in the length of day and night. At the 45th parallel, the longest winter night is roughly twice as long as the shortest summer night. Within the polar circles, night will last the full 24 hours of the winter solstice. The length of this polar night increases closer to the poles. Utqiagvik, Alaska, the northernmost point in the United States, experiences 65 days of polar night. At the pole itself,


id: night-20260505-2
file: data/en.wikipedia.org/wiki/Night-2.md
category: reference
title: Night
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Night
date_saved: 2026-05-05T11:13:01.139082+00:00
instance: kb-cron
parent: night-20260505-0
summary:
Living organisms react directly to the darkness of night. Light and darkness also affect circadian rhythms, the physical and mental changes that occur in a 24-hour cycle. This daily cycle is regulated by an internal "biological clock" that is adjusted by exposure to light. The length and timing of nighttime depend on location and time of year. Organisms that are more active at night possess adaptations to the night's dimmer light, increased humidity, and lower temperatures. === Animals === Animals that are active primarily at night are called nocturnal and usually possess adaptations for night vision. In vertebrates' eyes, two types of photoreceptor cells sense light. Cone cells sense color but are ineffective in low light; rod cells sense only brightness but remain effective in very dim light. The eyes of nocturnal animals have a greater percentage of rod cells. In most mammals, rod cells contain densely packed DNA near the edge of the nucleus. For nocturnal mammals, this is reversed with the densely packed DNA in the center of the nucleus, which reduces the scattering of light. Some nocturnal animals have a mirror, the tapetum lucidum, behind the retina. This doubles the amount of light their eyes can process.


id: night-20260505-3
file: data/en.wikipedia.org/wiki/Night-3.md
category: reference
title: Night
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Night
date_saved: 2026-05-05T11:13:01.139082+00:00
instance: kb-cron
parent: night-20260505-0
summary:
During the day, plants engage in photosynthesis and release oxygen. By night, plants engage in respiration, consuming oxygen and releasing carbon dioxide. Plants can draw up more water after sunset, which facilitates new leaf growth. As plants cannot create energy through photosynthesis after sunset, they use energy stored in the plant, typically as starch granules. Plants use this stored energy at a steady rate, depleting their reserves almost right at dawn. Plants will adjust their rate of consumption to match the expected time until sunrise. This avoids prematurely running out of starch reserves, and it allows the plant to adjust for longer nights in the winter. If a plant is subjected to artificially early darkness, it will ration its energy consumption to last until dawn. Succulent plants, including cacti, have adapted to the limited water availability in arid environments like deserts. The stomata of cacti do not open until night. When the temperature drops, the pores open to allow the cacti to store carbon dioxide for photosynthesis the next day, a process known as crassulacean acid metabolism (CAM). Cacti and night-blooming plants use CAM to store up to 99% of the carbon dioxide they use in daily photosynthesis. Ceroid cacti


id: night-20260505-4
file: data/en.wikipedia.org/wiki/Night-4.md
category: reference
title: Night
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Night
date_saved: 2026-05-05T11:13:01.139082+00:00
instance: kb-cron
parent: night-20260505-0
summary:
Artificial lighting expanded the scope of acceptable work and leisure after dark. In the 1600s, the major European cities introduced streetlights. These were lit by lamplighters each evening outside of the summer months. Early streetlights were metal and glass enclosures housing candles or oil lamps. They were suspended above streets or mounted on posts. The use of artificial lighting led to an increase in acceptable nightlife. In more rural areas, night remained a period of rest and nocturnal labor. Young adults, the urban poor, prostitutes, and thieves benefited from the anonymity of darkness and frequently smashed the new lanterns. Gas lighting was invented in the 1800s. A gas mantle was over ten times brighter than an oil lamp. Gas lighting was associated with the creation of regular police forces. In England, police departments were tasked with maintaining the gas lights, which became known as "police lamps". Daytime routines were further pushed back into the night by the electric light bulb—invented in the late 19th century—and the widespread usage of newer timekeeping devices like watches. Electric lights created night shifts for traditionally daytime fields, like India's cotton industry, and created opportunities for working adults to attend night school. === Fear of


id: night-20260505-5
file: data/en.wikipedia.org/wiki/Night-5.md
category: reference
title: Night
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Night
date_saved: 2026-05-05T11:13:01.139082+00:00
instance: kb-cron
parent: night-20260505-0
summary:
Many times in the night season, there have been certain spirits heard softly going or spitting or groaning, who being asked what they were have made answer that they were the souls of this or that man and that they now endure extreme torments. In folklore, nocturnal preternatural beings like goblins, fairies, werewolves, pucks, brownies, banshees, and boggarts have overlapping but non-synonymous definitions. The werewolf—and its francophone variations, the loup-garou and rougarou—were believed to be people who transformed into beasts at night. In West Africa and among the African diaspora, there is a widespread tradition of a type of vampire who removes their human skin at night and travels as a blood-sucking ball of light. Variation includes the feu-follet, the Surinamese asema, the Caribbean sukuyan, the Ashanti obayifo, and the Ghanaian asanbosam. The medieval fear of night-flying European witches was influenced by the Roman strix. The Romans described the strix as capable of changing between a beautiful woman and an owl-shaped monster. Common themes among these mythical nocturnal entities include hypersexuality, predation, shapeshifting, deception, mischief, and malice. === Nightlife === Nightlife, sometimes referred to as "the night-time economy", is a range of entertainment available and generally more popular from the


id: night-20260505-6
file: data/en.wikipedia.org/wiki/Night-6.md
category: reference
title: Night
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Night
date_saved: 2026-05-05T11:13:01.139082+00:00
instance: kb-cron
parent: night-20260505-0
summary:
Night photography can capture the natural colors of night by increasing the exposure time, or length of time captured in the photography. Longer exposures open the possibility for photographers to use light painting to selectively illuminate a scene. Digital photography can also make use of high-ISO settings, which increase the sensitivity to light, to take shorter exposure shots. This makes it possible to capture moving subjects without turning their movements into a blur. === Painting === Dating back to prehistoric cave paintings, artists have used a range of symbols to denote and depict the night sky. The first widely accepted portrayal of the night sky is the Nebra sky disc created c. 1600 BC. In medieval art, astrological signs gave meaning to paintings of night scenes. Adam Elsheimer's paintings on copper plates were some of the earliest realistic depictions of the night sky. Baroque paintings typically used a darker color scheme than previous painting styles in Europe. From the 17th century, darkness took up larger areas of paintings on average. Changes in the chemical composition of the paint itself and the development of new techniques for representing light led to the tenebrism style of painting. Tenebrism used stark, realistic depictions


id: noon-20260505-0
file: data/en.wikipedia.org/wiki/Noon-0.md
category: reference
title: Noon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Noon
date_saved: 2026-05-05T11:13:02.309491+00:00
instance: kb-cron
parent: noon-20260505-0
summary:
Noon (also known as noontime or midday) is 12 o'clock in the daytime. Solar noon is the time when the Sun appears to contact the local celestial meridian. This is when the Sun reaches its apparent highest point in the sky, at 12 noon apparent solar time and can be observed using a sundial. The local or clock time of solar noon depends on the date, longitude, and time zone, with Daylight Saving Time tending to place solar noon closer to 1:00pm. == Etymology == The word noon is derived from Latin nona hora, the ninth canonical hour of the day, in reference to the Western Christian liturgical term Nones, (number nine), one of the seven fixed prayer times in traditional Christian denominations. The Roman and Western European medieval monastic day began at 6:00 a.m. (06:00) at the equinox by modern timekeeping, so the ninth hour ended at what is now 3:00 p.m. (15:00) at the equinox. In English, the meaning of the word shifted to midday and the time gradually moved back to 12:00 local time – that is, not taking into account the modern invention of time zones. The change began in the 12th century and was fixed


id: octaeteris-20260505-0
file: data/en.wikipedia.org/wiki/Octaeteris-0.md
category: reference
title: Octaeteris
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Octaeteris
date_saved: 2026-05-05T11:13:03.509120+00:00
instance: kb-cron
parent: octaeteris-20260505-0
summary:
In astronomy, an octaeteris (Greek: ὀκταετηρίς, plural: octaeterides) is the period of eight solar years after which the moon phase occurs on the same day of the year plus one or two days. This period is also in a very good synchronicity with five Venusian visibility cycles (the Venusian synodic period) and thirteen Venusian revolutions around the Sun (Venusian sidereal period). This means, that if Venus is visible beside the Moon, after eight years the two will be again close together near the same date of the calendar. The octaeteris, also known as oktaeteris, was noted by Cleostratus in ancient Greece as a ⁠2 923+ 1 /2⁠ day cycle. The octaeteris is the calendar used for the Olympic games; if one Olympiad was 50 months long, the next would be 49 lunar months long. This octaeteris calendar is used for the Olympic dial of the Antikythera mechanism, to determine the time of the Olympic games and other Greek festivities. == See also == Metonic cycle Eclipse cycle == References == Meeus, Jean (1997). Mathematical Astronomy Morsels. Willmann-Bell. Chapter 9, p. 51, Table 9.A "Some eclipse Periodicities".


id: orbital-period-20260505-0
file: data/en.wikipedia.org/wiki/Orbital_period-0.md
category: reference
title: Orbital period
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Orbital_period
date_saved: 2026-05-05T11:13:04.738684+00:00
instance: kb-cron
parent: orbital-period-20260505-0
summary:
The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets, exoplanets orbiting other stars, or binary stars. It may also refer to the time it takes a satellite orbiting a planet or moon to complete one orbit. For celestial objects in general, the orbital period is determined by a 360° revolution of one body around its primary, e.g. Earth around the Sun. Periods in astronomy are expressed in units of time, usually hours, days, or years. Its reciprocal is the orbital frequency, a kind of revolution frequency, in units of hertz. == Small body orbiting a central body == According to Kepler's Third Law, the orbital period T of two point masses orbiting each other in a circular or elliptic orbit is: T = 2 π a 3 G M {\displaystyle T=2\pi {\sqrt {\frac {a^{3}}{GM}}}} where: a is the orbit's semi-major axis G is the gravitational constant, M is the mass of the more massive body. For all ellipses with a given semi-major axis the orbital period is the same, regardless of


id: orbital-period-20260505-1
file: data/en.wikipedia.org/wiki/Orbital_period-1.md
category: reference
title: Orbital period
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Orbital_period
date_saved: 2026-05-05T11:13:04.738684+00:00
instance: kb-cron
parent: orbital-period-20260505-0
summary:
For celestial objects in general, the orbital period typically refers to the sidereal period, determined by a 360° revolution of one body around its primary relative to the fixed stars projected in the sky. For the case of the Earth orbiting around the Sun, this period is referred to as the sidereal year. This is the orbital period in an inertial (non-rotating) frame of reference. Orbital periods can be defined in several ways. The tropical period is more particularly about the position of the parent star. It is the basis for the solar year, and respectively the calendar year. The synodic period refers not to the orbital relation to the parent star, but to other celestial objects, making it not a merely different approach to the orbit of an object around its parent, but a period of orbital relations with other objects, normally Earth, and their orbits around the Sun. It applies to the elapsed time where planets return to the same kind of phenomenon or location, such as when any planet returns between its consecutive observed conjunctions with or oppositions to the Sun. For example, Jupiter has a synodic period of 398.8 days from Earth; thus, Jupiter's opposition occurs


id: ramesside-star-clocks-20260505-0
file: data/en.wikipedia.org/wiki/Ramesside_star_clocks-0.md
category: reference
title: Ramesside star clocks
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ramesside_star_clocks
date_saved: 2026-05-05T11:13:05.928376+00:00
instance: kb-cron
parent: ramesside-star-clocks-20260505-0
summary:
The Ramesside star clocks are ancient Egyptian star clocks appearing on the ceilings of several royal tombs of the Ramesside period. Two sets of star clocks appear on the tomb Ramesses VII and Ramesses IX. Although all of the sets are corrupt to some degree, a prototype clock can be reconstructed from them. == References ==


id: relative-hour-20260505-0
file: data/en.wikipedia.org/wiki/Relative_hour-0.md
category: reference
title: Relative hour
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Relative_hour
date_saved: 2026-05-05T11:13:07.167936+00:00
instance: kb-cron
parent: relative-hour-20260505-0
summary:
Relative hour (Hebrew singular: shaʿah zǝmanit / שעה זמנית; plural: shaʿot - zǝmaniyot / שעות זמניות), sometimes called halachic hour, temporal hour, seasonal hour and variable hour, is a term used in rabbinic Jewish law that assigns 12 hours to each day and 12 hours to each night, all throughout the year. A relative hour has no fixed length in absolute time, but changes with the length of daylight each day - depending on summer (when the days are long and the nights are short), and in winter (when the days are short and the nights are long). Even so, in all seasons a day is always divided into 12 hours, and a night is always divided into 12 hours, which invariably makes for a longer hour or a shorter hour. At Mediterranean latitude, one hour can be about 45 minutes at the winter solstice, and 75 minutes at summer solstice. All of the hours mentioned by the Sages in either the Mishnah or Talmud, or in other rabbinic writings, refer strictly to relative hours. Another feature of this ancient practice is that, unlike the standard modern 12-hour clock that assigns 12 o'clock pm for noon time, in the ancient


id: relative-hour-20260505-1
file: data/en.wikipedia.org/wiki/Relative_hour-1.md
category: reference
title: Relative hour
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Relative_hour
date_saved: 2026-05-05T11:13:07.167936+00:00
instance: kb-cron
parent: relative-hour-20260505-0
summary:
=== Disputations === In old times, the hour was detected by observation of the position of the sun, or when the first three stars appeared in the night sky. During the first six hours of the day, the sun is seen in the eastern sky. At the sixth hour, the sun is always at its zenith in the sky, meaning, it is either directly overhead, or parallel (depending on the hemisphere). Those persons living in the Northern Hemisphere, the sun at noon time will appear overhead slightly towards the south, whereas for those living in the Southern Hemisphere, the sun at noon time will appear overhead slightly towards the north (an exception being in the tropics, the sun can sometimes be directly overhead). From the 6th and a half hour to the 12th hour, the sun inclines towards the west, until it sets. The conclusion of a day at the end of twilight may slightly vary in minutes from place to place, depending on the elevation and the terrain. Typically, nightfall ushers in more quickly in the low-lying valleys, than it does on a high mountaintop. There are two major opinions how to calculate these times: The Magen Avraham (Shulhan


id: relative-hour-20260505-2
file: data/en.wikipedia.org/wiki/Relative_hour-2.md
category: reference
title: Relative hour
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Relative_hour
date_saved: 2026-05-05T11:13:07.167936+00:00
instance: kb-cron
parent: relative-hour-20260505-0
summary:
== Practical bearing == In Jewish Halacha, the practical bearing of this teaching is reflected in many halachic practices. For example, according to Jewish law, the morning recitation of Kriyat Shema must be made between slightly before sunrise and the end of the third hour of the day, a time that actually fluctuates on the standard 12-hour clock, depending on the time of year. Its application is also used in determining the time of the Morning Prayer, which must be recited between sunrise until the end of the fourth hour, but post facto can be said until noon time, and which times will vary if one were to rely solely on the dials of the standard 12-hour clock, depending on the seasons. On the eve of Passover, chametz can only be eaten until the end of the fourth-hour of the day, and must be disposed of by the end of the fifth hour. In Jewish tradition, prayers were usually offered at the time of the daily whole-burnt offerings. The historian, Josephus, writing about the daily whole-burnt offering, says that it was offered twice each day, in the morning and about the ninth hour. The Mishnah, a compendium of Jewish oral


id: rotation-period-astronomy-20260505-0
file: data/en.wikipedia.org/wiki/Rotation_period_(astronomy)-0.md
category: reference
title: Rotation period (astronomy)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rotation_period_(astronomy)
date_saved: 2026-05-05T11:13:25.739752+00:00
instance: kb-cron
parent: rotation-period-astronomy-20260505-0
summary:
In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the sidereal rotation period (or sidereal day), i.e., the time that the object takes to complete a full rotation around its axis relative to the background stars (inertial space). The other type of commonly used "rotation period" is the object's synodic rotation period (or solar day), which may differ, by a fraction of a rotation or more than one rotation, to accommodate the portion of the object's orbital period around a star or another body during one day. == Measuring rotation == For solid objects, such as rocky planets and asteroids, the rotation period is a single value. For gaseous or fluid bodies, such as stars and giant planets, the period of rotation varies from the object's equator to its pole due to a phenomenon called differential rotation. Typically, the stated rotation period for a giant planet (such as Jupiter, Saturn, Uranus, Neptune) is its internal rotation period, as determined from the rotation of the planet's magnetic field. For objects that are not spherically symmetrical, the rotation period is, in general, not fixed, even in


id: saros-astronomy-20260505-0
file: data/en.wikipedia.org/wiki/Saros_(astronomy)-0.md
category: reference
title: Saros (astronomy)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Saros_(astronomy)
date_saved: 2026-05-05T11:13:27.065142+00:00
instance: kb-cron
parent: saros-astronomy-20260505-0
summary:
In astronomy, the saros ( ) is a length of time covering exactly 223 synodic months (18 years 11 days and 8 hours), 242 draconic months and 239 anomalistic months. Arising naturally due to synchronization between lunar phase, nodal precession, and apsidal precession, it can be used to predict eclipses of the Sun and Moon. One saros period after an eclipse, the Sun, Earth, and Moon return to approximately the same relative geometry, a near straight line, and a nearly identical eclipse will occur, in what is referred to as an eclipse cycle. Every eclipse has an associated saros series and all succeeding or preceding eclipses have a different saros series associated with them - as the eclipse of the same series occurs or occurred with a gap of one saros only. Solar and lunar eclipses have different saros series. A series of eclipses that are separated by one saros is called a saros series. It corresponds to: 6,585.321347 solar days 18.029 years 223 synodic months 241.999 draconic months 18.999 eclipse years (38 eclipse seasons of 173.31 days) 238.992 anomalistic months 241.029 sidereal months The 19 eclipse years means that if there is a solar eclipse (or lunar eclipse), then


id: saros-astronomy-20260505-1
file: data/en.wikipedia.org/wiki/Saros_(astronomy)-1.md
category: reference
title: Saros (astronomy)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Saros_(astronomy)
date_saved: 2026-05-05T11:13:27.065142+00:00
instance: kb-cron
parent: saros-astronomy-20260505-0
summary:
After one saros, the Moon will have completed roughly an integer number of synodic, draconic, and anomalistic periods (223, 242, and 239) and the Earth-Sun-Moon geometry will be nearly identical: the Moon will have the same phase and be at the same node and the same distance from the Earth. In addition, because the saros is close to 18 years in length (about 11 days longer), the Earth will be nearly the same distance from the Sun, and tilted to it in nearly the same orientation (same season). Given the date of an eclipse, one saros later a nearly identical eclipse can be predicted. During this 18-year period, about 40 other solar and lunar eclipses take place, but with a somewhat different geometry. One saros equaling 18.03 years is not equal to a perfect integer number of lunar orbits (Earth revolutions with respect to the fixed stars of 27.32166 days sidereal month), therefore, even though the relative geometry of the Earth–Sun–Moon system will be nearly identical after a saros, the Moon will be in a slightly different position with respect to the stars for each eclipse in a saros series. The axis of rotation of the Earth–Moon system exhibits a


id: saros-astronomy-20260505-2
file: data/en.wikipedia.org/wiki/Saros_(astronomy)-2.md
category: reference
title: Saros (astronomy)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Saros_(astronomy)
date_saved: 2026-05-05T11:13:27.065142+00:00
instance: kb-cron
parent: saros-astronomy-20260505-0
summary:
As an example of a single saros series, this table gives the dates of some of the 72 lunar eclipses for saros series 131. This eclipse series began in AD 1427 with a partial eclipse at the southern edge of the Earth's shadow when the Moon was close to its descending node. In each successive saros, the Moon's orbital path is shifted northward with respect to the Earth's shadow, with the first total eclipse occurring in 1950. For the following 252 years, total eclipses occur, with the central eclipse in 2078. The first partial eclipse after this will occur in the year 2220, and the final partial eclipse of the series will occur in 2707. The total lifetime of lunar saros series 131 is 1280 years. Solar saros 138 interleaves with this lunar saros with an event occurring every 9 years 5 days alternating between each saros series. Because of the +1⁄3 fraction of days in a saros, the visibility of each eclipse will differ for an observer at a given locale. For the lunar saros series 131, the first total eclipse of 1950 had its best visibility for viewers in Eastern Europe and the Middle East because mid-eclipse was


id: sidereal-time-20260505-0
file: data/en.wikipedia.org/wiki/Sidereal_time-0.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:
Sidereal time ("sidereal" pronounced sy-DEER-ee-əl, sə-) is a system of timekeeping used especially by astronomers. Using sidereal time and the celestial coordinate system, it is easy to locate the positions of celestial objects in the night sky. Sidereal time is a "time scale that is based on Earth's rate of rotation measured relative to the fixed stars". A sidereal day (also known as the sidereal rotation period) represents the time for one rotation about the planet axis relative to the stars. Viewed from the same location, a star seen at one position in the sky will be seen at the same position on another night at the same time of day (or night), if the day is defined as a sidereal day. This is similar to how the time kept by a sundial (Solar time) can be used to find the location of the Sun. Just as the Sun and Moon appear to rise in the east and set in the west due to the rotation of Earth, so do the stars. Both solar time and sidereal time make use of the regularity of Earth's rotation about its polar axis: solar time is reckoned according to the position of the


id: sidereal-time-20260505-1
file: data/en.wikipedia.org/wiki/Sidereal_time-1.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:
== Effects of precession == Earth's rotation is not a simple rotation around an axis that remains always parallel to itself. Earth's rotational axis itself rotates about a second axis, orthogonal to the plane of Earth's orbit, taking about 25,800 years to perform a complete rotation. This phenomenon is termed the precession of the equinoxes. Because of this precession, the stars appear to move around Earth in a manner more complicated than a simple constant rotation. For this reason, to simplify the description of Earth's orientation in astronomy and geodesy, it was conventional to chart the positions of the stars in the sky according to right ascension and declination, which are based on a frame of reference that follows Earth's precession, and to keep track of Earth's rotation, through sidereal time, relative to this frame as well. (The conventional reference frame, for purposes of star catalogues, was replaced in 1998 with the International Celestial Reference Frame, which is fixed with respect to extra-galactic radio sources. Because of the great distances, these sources have no appreciable proper motion.) In this frame of reference, Earth's rotation is close to constant, but the stars appear to rotate slowly with a period of about


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


