# kb

id: konstantin-tsiolkovsky-20260505-3
file: data/en.wikipedia.org/wiki/Konstantin_Tsiolkovsky-3.md
category: reference
title: Konstantin Tsiolkovsky
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Konstantin_Tsiolkovsky
date_saved: 2026-05-05T10:59:34.323294+00:00
instance: kb-cron
parent: konstantin-tsiolkovsky-20260505-0
summary:
In 1964, The Monument to the Conquerors of Space was erected to celebrate the achievements of the Soviet people in space exploration. Located in Moscow, the monument is 107 meters (350 feet) tall and covered with titanium cladding. The main part of the monument is a giant obelisk topped by a rocket and resembling in shape the exhaust plume of the rocket. A statue of Konstantin Tsiolkovsky, the precursor of astronautics, is located in front of the obelisk. The State Museum of the History of Cosmonautics in Kaluga now bears his name. His residence during the final months of his life (also in Kaluga) was converted into a memorial museum a year after his death. The town Uglegorsk in Amur Oblast was renamed Tsiolkovsky by President of Russia Vladimir Putin in 2015. The crater Tsiolkovskiy, the most prominent crater on the far side of the Moon, was named after him. Asteroid 1590 Tsiolkovskaja was named after his wife. The Soviet Union obtained naming rights by operating Luna 3, the first space device to successfully transmit images of the side of the Moon not seen from Earth. The Tsiolkovsky Memorial Apartment. A museum created in Borovsk where he lived and had


id: franz-abdon-ulinski-20260505-0
file: data/en.wikipedia.org/wiki/Franz_Abdon_Ulinski-0.md
category: reference
title: Franz Abdon Ulinski
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Franz_Abdon_Ulinski
date_saved: 2026-05-05T10:59:35.505970+00:00
instance: kb-cron
parent: franz-abdon-ulinski-20260505-0
summary:
Franz Abdon Ulinski (1890–1974) was an Austrian engineer who was known for his early proposals in spacecraft propulsion. == Biography == Born in Mladějov na Moravě, Moravia (now part of the Czech Republic), Ulinski completed his secondary education in Linz, Austria, in 1910 before joining the Austro-Hungarian Army. Ulinski served in various roles and as a technical officer in the aviation corps during World War I. In 1919, Ulinski proposed a spacecraft design powered by jets of electrons or ions. He published his ideas in a Viennese aeronautical journal in 1920, outlining two potential energy sources: solar panels for energy storage and atomic disintegration for power generation. At the time, his propulsion concepts were not widely adopted, likely due to the energy requirements needed to escape Earth's gravity. Ulinski's work is recognized for anticipating later advancements in ion propulsion technology. Ion thrusters have been utilized in spacecraft such as Deep Space One, which conducted flybys of an asteroid and approached a comet, as well as in the stabilization of satellites in Earth orbit. == References ==


id: wan-hu-20260505-0
file: data/en.wikipedia.org/wiki/Wan_Hu-0.md
category: reference
title: Wan Hu
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wan_Hu
date_saved: 2026-05-05T10:59:36.699508+00:00
instance: kb-cron
parent: wan-hu-20260505-0
summary:
Wan Hu is an alleged Chinese official described in modern sources as possibly the first man to attempt to use a rocket to launch into outer space. Possibly depicted as the "world's first astronaut" and "the first martyr in man's struggle to achieve space flight", NASA named the crater Wan-Hoo on the far side of the Moon after him. According to some Chinese sources, "Wan Hu" was a title granted to him by the imperial court during the early Ming dynasty, and his real name was Tao Chengdao. As a Ming official, he was interested in technological innovation, particularly concerning rockets. He is said to have died in 1390. While the legend is well-known, there is no direct evidence surviving to substantiate it. According to Joseph Needham, the story is dubious and may be invented during or after the Chinoiserie period, considering the lack of firm historical reference. However, Li Chengzhi has argued for the story's plausibility, saying that it may have come from oral transmission by European missionaries who came to China during the late Ming and Qing dynasties, or based on records in an ancient Chinese document that has been subsequently lost. == Legend == === Basic story


id: heinrich-albers-sch-nberg-20260505-0
file: data/en.wikipedia.org/wiki/Heinrich_Albers-Schönberg-0.md
category: reference
title: Heinrich Albers-Schönberg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Heinrich_Albers-Schönberg
date_saved: 2026-05-05T10:59:38.191109+00:00
instance: kb-cron
parent: heinrich-albers-sch-nberg-20260505-0
summary:
Heinrich Ernst Albers-Schönberg (21 January 1865 – 4 June 1921) was a German gynecologist and radiologist. He was a native of Hamburg. He studied medicine at the Universities of Tübingen and Leipzig, where in 1891 he earned his medical doctorate under the guidance of Heinrich Curschmann (1846-1910). From 1892 to 1894 he was an assistant at Hamburg-Eppendorf Hospital, afterwards working as an assistant to gynecologist Paul Zweifel (1848–1927) at the University of Leipzig. Soon afterwards, he settled in Hamburg as a medical practitioner. In 1897, with internist Georg Deycke (1865–1938), he established an X-ray clinic and laboratory in Hamburg. Later, he was appointed head of the radiology department at St Georg Hospital. In 1919 he became a full professor and chair of radiology at the newly established University of Hamburg. Albers-Schönberg is credited with providing a description of osteopetrosis, a condition sometimes referred to as "Albers-Schönberg disease". It is described as a syndrome of excessive bone calcification causing a marble-like appearance with increased radiological density of the skeleton. He was an early specialist in the field of radiological medicine. In 1903 he discovered that exposure to radiation caused damage to the reproductive glands of rabbits. In cooperation with other scientists,


id: samuel-barbour-20260505-0
file: data/en.wikipedia.org/wiki/Samuel_Barbour-0.md
category: reference
title: Samuel Barbour
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Samuel_Barbour
date_saved: 2026-05-05T10:59:39.359709+00:00
instance: kb-cron
parent: samuel-barbour-20260505-0
summary:
Samuel Barbour (1860 – 3 June 1938) was an Australian chemist, photographer and X-ray pioneer in the colony of South Australia. In Australia, the medical men of the day took a slow approach in the adoption of the new science that involved X-rays. Many of the early demonstrations were made by investigators outside the medical field. Upon examination of the initial investigators, several key factors were common. The individuals had already either been experimenting along similar lines to Wilhelm Röntgen with Crookes tubes and such, the physicists or scientists, or were actively associated with electrical work, the electricians, which made them particularly receptive to the technical appeal of the new science of X-rays. Records of the events reveal that among the medical men who witnessed the first images produced as radiographs, a rather small number had any great desire to employ X-rays directly in their own medical practice. After the early investigative work of Thomas Ranken Lyle, William Henry Bragg, Joseph Patrick Slattery, and others, almost all medical men were satisfied with soliciting the services of the external X-ray man when necessity arose for skiagraphs to be produced. As the utilization of X-rays became more acceptable, the involvement of electricians


id: lucien-blake-20260505-0
file: data/en.wikipedia.org/wiki/Lucien_Blake-0.md
category: reference
title: Lucien Blake
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lucien_Blake
date_saved: 2026-05-05T10:59:40.546374+00:00
instance: kb-cron
parent: lucien-blake-20260505-0
summary:
Lucien Ira Blake (September 12, 1853 – May 11, 1916) was an American professor of physics and engineering at the University of Kansas. He pioneered studies in underwater sound transmission, the use of X-rays in medicine and electrochemistry. Blake Hall in the University of Kansas was named after him. == Life and work == Blake was born in Mansfield, Massachusetts, where his father Mortimer Blake (1813-1884) was a Congregationalist minister married to Harriet Louisa Daniels (1817-1906). After graduating from Amherst College in 1877, he went to the University of Berlin where he received a PhD with studies under Heinrich Hertz. He returned to take up a position in 1885 at the Rose Polytechnic Institute in Terre Haute, Indiana. Here he conducted experiments on underwater acoustic communication. He experimented on an underwater communication system off Sandy Hook, New Jersey. He patented several inventions and in 1887 he moved to the University of Kansas. Here he set up a four year course in electrical engineering. From 1892 he managed to set up a new physical and electrical laboratory which came to be called "Blake Hall" in 1898 (it was demolished in 1963). In 1893 he was declared one of the 40 most


id: william-henry-bragg-20260505-0
file: data/en.wikipedia.org/wiki/William_Henry_Bragg-0.md
category: reference
title: William Henry Bragg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Henry_Bragg
date_saved: 2026-05-05T10:59:41.784235+00:00
instance: kb-cron
parent: william-henry-bragg-20260505-0
summary:
Sir William Henry Bragg (2 July 1862 – 12 March 1942) was a British X-ray crystallographer who uniquely shared a Nobel Prize with his son Lawrence Bragg – the 1915 Nobel Prize in Physics "for their services in the analysis of crystal structure by means of X-rays," an important step in the development of X-ray crystallography. == Early life and education == William Henry Bragg was born on 2 July 1862 in Westward, Cumberland, England, the son of Robert John Bragg, a merchant marine officer and farmer, and Mary Wood, a clergyman's daughter. His mother died when he was age 7, and was raised by his uncle (also named William Bragg) at Market Harborough. He was educated at the Grammar School there, at King William's College on the Isle of Man, and—having won an exhibition—at Trinity College, Cambridge. He graduated in 1884 as third Wrangler, and in 1885 earned First Class Honours in the mathematical Tripos. == Career and research == === University of Adelaide === In 1885, Bragg was appointed Elder Professor of Mathematics and Physics at the University of Adelaide in Australia, and started work there in early 1886. Being a skilled mathematician, at that time he had


id: william-henry-bragg-20260505-1
file: data/en.wikipedia.org/wiki/William_Henry_Bragg-1.md
category: reference
title: William Henry Bragg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Henry_Bragg
date_saved: 2026-05-05T10:59:41.784235+00:00
instance: kb-cron
parent: william-henry-bragg-20260505-0
summary:
=== University of Leeds === From 1909 to 1915, Bragg was Cavendish Professor of Physics at the University of Leeds. He continued his work on X-rays with much success. He invented the X-ray spectrometer and with his son, Lawrence, then a research student at Cambridge, founded the new science of X-ray crystallography, the analysis of crystal structure using X-ray diffraction. === World War I === Both of his sons, Lawrence and Robert, were called into the army after the First World War broke out in 1914 . The following year, Bragg was appointed Quain Professor of Physics at University College London. He had to wait for almost a year to contribute to the war effort; in July 1915, he was appointed to the Board of Invention and Research set up by the Admiralty. In September, his younger son Robert died of wounds at Gallipoli. In November, he shared the Nobel Prize in Physics with Lawrence. The Navy was struggling to prevent sinkings by unseen, submerged U-boats. The scientists recommended that the best tactic was to listen for the submarines. The Navy had a hydrophone research establishment at Aberdour, Scotland, staffed with navy men. In November 1915, two young physicists were


id: william-henry-bragg-20260505-2
file: data/en.wikipedia.org/wiki/William_Henry_Bragg-2.md
category: reference
title: William Henry Bragg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Henry_Bragg
date_saved: 2026-05-05T10:59:41.784235+00:00
instance: kb-cron
parent: william-henry-bragg-20260505-0
summary:
== Commemoration == The Electoral district of Bragg in the South Australian House of Assembly was created in 1970, and was named after both William and Lawrence Bragg. The lecture theatre of King William's College (KWC) is named in memory of Bragg; the Sixth-Form invitational literary debating society at KWC, the Bragg Society, is also named in his memory. One of the school "Houses" at Robert Smyth School, Market Harborough, Leicester, is named "Bragg" in memory of him being a student there. Since 1992, the Australian Institute of Physics has awarded the Bragg Gold Medal for excellence in physics for the best Ph.D. thesis by a student at an Australian university. The two sides of the medal contain the images of Sir William Henry and his son Sir Lawrence Bragg. The Experimental Technique Centre at Brunel University is named the Bragg Building. The Sir William Henry Bragg Building at the University of Leeds opened in 2021. In 1962, the Bragg Laboratories were constructed at the University of Adelaide to commemorate 100 years since the birth of Sir William H. Bragg. The Australian Bragg Centre for Proton Therapy and Research also in Adelaide, Australia was completed in late 2023. It is


id: frederick-woodward-branson-20260505-0
file: data/en.wikipedia.org/wiki/Frederick_Woodward_Branson-0.md
category: reference
title: Frederick Woodward Branson
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frederick_Woodward_Branson
date_saved: 2026-05-05T10:59:42.987261+00:00
instance: kb-cron
parent: frederick-woodward-branson-20260505-0
summary:
Frederick Woodward Branson, FIC, FCS (6 March 1851 – 30 November 1933) was a British chemist, glassblower, instrument maker and X-ray pioneer. He worked with Jacob Bell & Co a chemist who reformed the profession, location Oxford Street London. He was a Fellow of the Chemical Society in 1882, and became a Fellow of the Institute of Chemistry in 1888, glassblower, instrument maker and X-ray pioneer. Chairman & managing director of Reynolds & Branson 1898 – 1933. He had many published works 1882–1918. He was given the honorary award of Freeman of the City of London 1908. == Life and times of Frederick W. Branson and his family == Frederick Woodward Branson was born on 6 March 1851 at Hanslope, Newport Pagnell, Buckinghamshire, England. He was the son of Thomas Branson a bricklayer, who later became a farmer. Branson's father inherited the farm via his marriage to Sarah Ann née Woodward, who had inherited it from her father. In 1861, Branson lived with his parents and maternal grandparents, William Woodward an agricultural labourer and farm owner, at Hungate End Farm, Hanslope. The farm consisted of 168 acres (68 ha) and employed six men and six boys. William inherited when he


id: frederick-woodward-branson-20260505-1
file: data/en.wikipedia.org/wiki/Frederick_Woodward_Branson-1.md
category: reference
title: Frederick Woodward Branson
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frederick_Woodward_Branson
date_saved: 2026-05-05T10:59:42.987261+00:00
instance: kb-cron
parent: frederick-woodward-branson-20260505-0
summary:
== The History of Reynolds and Branson Ltd Co 1816–1972 == The original company can be traced back to 1816 (see Grace's Guide which is the leading source of historical information on industry and manufacturing in Britain, The Company was established in 1816) Edward Matterson druggist who was running the firm at 12, Briggate, Leeds in 1822, Matterson was educated at Leeds Grammar School, the company had moved to 13 Briggate, Leeds by 1829 (1822 Baines's Directory and Gazette Edward Matterson is a druggist, and dealer in paint and colours, Location 12, Briggate, Leeds ) (Edward Matterson in Pigot's Directory of 1829 he is still druggist but now located 13 Briggate & 4 Blundel place)(also Noted Baines's Directory 1822 John Cudworth Hop Merchants was located at 13, Briggate Leeds ) (Noted William West is a druggist, located at 14, Briggate in 1822. ) Edward Matterson had been employed by Allen and Hanburys, in 1833 William West F.R.S. took over the company after Matterson went bankrupt (see The bankrupt directory: being a complete register of all the bankrupts, with their residences, trades, and dates when they appeared in the London gazette, from December 1820 to April 1843 ). In 1839 Thomas


id: frederick-woodward-branson-20260505-2
file: data/en.wikipedia.org/wiki/Frederick_Woodward_Branson-2.md
category: reference
title: Frederick Woodward Branson
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frederick_Woodward_Branson
date_saved: 2026-05-05T10:59:42.987261+00:00
instance: kb-cron
parent: frederick-woodward-branson-20260505-0
summary:
Noted that it was a sad end to a company which had been based in Leeds, in some form or another for 156 years.


id: frederick-woodward-branson-20260505-3
file: data/en.wikipedia.org/wiki/Frederick_Woodward_Branson-3.md
category: reference
title: Frederick Woodward Branson
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frederick_Woodward_Branson
date_saved: 2026-05-05T10:59:42.987261+00:00
instance: kb-cron
parent: frederick-woodward-branson-20260505-0
summary:
== Reynolds and Branson chronology == 1822, Edward Matterson druggist, dealer in paint and colours, Location 12, Briggate, Leeds Baines's Directory and Gazette. 1829, Edward Matterson, druggist, located 13 Briggate & 4 Blundel place. Pigot's Directory 1833, William West F.R.S. took over the company after Matterson went bankrupt, see The bankrupt directory London gazette, from December 1820 to April 1843. 1839, Thomas Harvey, chemist and druggist, 5 Commercial Street. Leeds. 1841, Thomas Harvey, chemist and druggist, 13 Briggate. Leeds. 1854, Reynolds returned to Leeds as partner with Harvey in the chemist business and the firm became Harvey & Reynolds. 1856, Harvey & Reynolds, chemist and druggist, 13 Briggate. Leeds. 1861, Harvey, Reynolds & Fowler. Chemist and druggist, 10 Briggate. Leeds. 1864, Haw & Reynolds. Chemist and druggist. Briggate. Leeds. as Thomas Harvey had retired. 1867, Haw, Reynolds, & Co. Chemist and druggist. Briggate. Leeds. 1872, Haw, Reynolds & Co. Chemist. 14 Commercial Street, and 13 Briggate. Leeds. 1886, Reynolds & Branson. Makers of the first short clinical thermometer. 1891, Reynolds & Reynolds, chemist and druggist, 13 Briggate. Leeds 1901, Reynolds & Reynolds, chemist and druggist, 13 Briggate. Leeds 1911, Reynolds & Reynolds, chemist and druggist, 13 Briggate. Leeds == Reynolds


id: frederick-woodward-branson-20260505-4
file: data/en.wikipedia.org/wiki/Frederick_Woodward_Branson-4.md
category: reference
title: Frederick Woodward Branson
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frederick_Woodward_Branson
date_saved: 2026-05-05T10:59:42.987261+00:00
instance: kb-cron
parent: frederick-woodward-branson-20260505-0
summary:
Radium and its Properties. "The Leeds Law Institute was, on the 23rd ult., crowded to the door on the occasion of a lecture by Mr. F. W. Branson, F.I.C., on that mysterious subject known as radium. The Leeds Geological Society and the Leeds Naturalist Club were also represented, and Mr. E. Hawkesworth was in the chair. "The new metal, which Professor Pierre Curie discovered, has, as demonstrated by Mr. Branson, some wonderful properties and a probable great future. "Mr. Branson first showed that radium is an element having the highest atomic weight known, and has a characteristic spectrum, by which it can be easily identified, and that it falls into the group of metals: barium, calcium, and strontium. He then showed the difference between atmospheric (sound) waves and ether waves (heat, light, and electrical), and alluded to the emanations given off by radium as consisting of electrons negatively charged, and also much larger particles of matter termed ions positively charged. The former have very penetrative powers as regards metals and opaque bodies, and are identical with the kathode rays that are given off in an ordinary X-ray tube. "The positively charged particles are not so penetrative; indeed, they are easily


id: frank-styant-browne-20260505-0
file: data/en.wikipedia.org/wiki/Frank_Styant_Browne-0.md
category: reference
title: Frank Styant Browne
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frank_Styant_Browne
date_saved: 2026-05-05T10:59:44.201498+00:00
instance: kb-cron
parent: frank-styant-browne-20260505-0
summary:
Frank Styant Browne (10 July 1854 – 17 April 1938), also known as Styant Browne, was an Australian pharmacist, artist, photographer and X-ray pioneer from Tasmania. In Australia, the medical men of the day took a slow approach in the adoption of the new science that involved X-rays. Many of the early demonstrations were made by investigators outside the medical field. Upon examination of the initial investigators, several key factors were common. The individuals had already either been experimenting along similar lines to Wilhelm Röntgen with Crookes tubes and such, the physicists or scientists, or were actively associated with electrical work, the electricians, which made them particularly receptive to the technical appeal of the new science of X-rays. Records of the events reveal that among the medical men who witnessed the first images produced as radiographs, a rather small number had any great desire to employ X-rays directly in their own medical practice. After the early investigative work of Thomas Ranken Lyle, William Henry Bragg, Joseph Patrick Slattery, and others, almost all medical men were satisfied with soliciting the services of the external X-ray man when necessity arose for skiagraphs to be produced. As the utilization of X-rays became more


id: w-ironside-bruce-20260505-0
file: data/en.wikipedia.org/wiki/W._Ironside_Bruce-0.md
category: reference
title: W. Ironside Bruce
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/W._Ironside_Bruce
date_saved: 2026-05-05T10:59:45.380508+00:00
instance: kb-cron
parent: w-ironside-bruce-20260505-0
summary:
William Ironside Bruce (1876 – 21 March 1921) was a doctor in Europe who conducted early research on the use of X-rays. He headed the X-ray departments at Charing Cross Hospital and at the Hospital for Sick Children. He wrote an early book on X-ray techniques and he was president of the radiology section of the Royal Society of Medicine. In 1921, Bruce was diagnosed with aplastic anaemia, which his physicians attributed to his work with X-rays. He died two months after being diagnosed with the illness. Bruce's death led to the establishment of an X-ray safety committee in Great Britain. == Early life == Bruce was born in Dingwall, the second son of William Bruce, an Aberdeenshire doctor. His uncle was John Mitchell Bruce, a physician who wrote a widely read textbook, Materia Medica and Therapeutics. He was a cousin of Edmund Ironside, 1st Baron Ironside. Many members of the Bruce and Ironside families had come from Keig, a quiet village in Aberdeenshire. Though Bruce was not born there, he received his education in Aberdeen, in the tradition of these relatives. Bruce completed medical school in 1900 at the University of Aberdeen. After medical school he served in the


id: vernon-ellis-cosslett-20260505-0
file: data/en.wikipedia.org/wiki/Vernon_Ellis_Cosslett-0.md
category: reference
title: Vernon Ellis Cosslett
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vernon_Ellis_Cosslett
date_saved: 2026-05-05T10:59:46.532787+00:00
instance: kb-cron
parent: vernon-ellis-cosslett-20260505-0
summary:
Vernon Ellis Cosslett, FRS (16 June 1908 – 21 November 1990) was a British microscopist. The eighth child (of six sons and five daughters) of Edgar William Cosslett (1871–1948), a Welsh cabinet maker and carpenter, clerk of works on the estate of the Earl of Eldon at Stowell Park and latterly a builder, and Anne (née Williams; 1871–1951), he was raised at Cirencester and educated at Cirencester Grammar School, the University of Bristol, the Kaiser-Wilhelm-Institut, Berlin-Dahlem, and University College, London. He was a research fellow at the University of Bristol after completing his PhD there in 1932, having been awarded an H. H. Wills Memorial Fellowship, remaining there until 1935. He then lectured at Faraday House Engineering College, London, until 1939, whilst undertaking part-time research at Birkbeck College, London. Between 1939 and 1941 he was Keddey-Fletcher-Warr Research Fellow of London University, working at the University of Oxford as a temporary lecturer, then lecturing in physics at the University of Oxford Electrical Laboratory from 1941 to 1946. From 1947, as an ICI Research Fellow, Cosslett worked with William Lawrence Bragg at the Cavendish Laboratory, Cambridge University on the electron microscope and founded the Electron Microscopy Department. He also developed improved x-ray


id: friedrich-dessauer-20260505-0
file: data/en.wikipedia.org/wiki/Friedrich_Dessauer-0.md
category: reference
title: Friedrich Dessauer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Friedrich_Dessauer
date_saved: 2026-05-05T10:59:47.719042+00:00
instance: kb-cron
parent: friedrich-dessauer-20260505-0
summary:
Friedrich Dessauer (19 July 1881 – 16 February 1963) was a German physicist, a philosopher, a socially engaged entrepreneur and a journalist. Friedrich Dessauer was born in Aschaffenburg, Kingdom of Bavaria, German Empire. As a young man he was fascinated by new discoveries in the natural sciences. He was particularly interested in the X-rays discovered by Röntgen and their medical applications. After attending the humanistic Gymnasium in Aschaffenburg, he studied electrical engineering and physics at the Technische Universität Darmstadt and the University of Munich. Due to radiation damage during his research on the use of X-rays, his face was badly damaged and he was repeatedly treated with plastic surgery. In connection with this, he was released from military service. Due to the death of his father, he initially interrupted his studies, continued in 1914 at the Goethe University Frankfurt and then completed it in 1917. From 1924 to 1933 he was a Zentrum party member of the Reichstag, the German Parliament. A practicing Catholic with a Jewish grandparent, he was imprisoned by the Nazis when they came to power for his opposition to Hitler. He was released at request of the Turkish government, who invited him to the University of


id: tienne-destot-20260505-0
file: data/en.wikipedia.org/wiki/Étienne_Destot-0.md
category: reference
title: Étienne Destot
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Étienne_Destot
date_saved: 2026-05-05T10:59:48.908017+00:00
instance: kb-cron
parent: tienne-destot-20260505-0
summary:
Étienne Destot (1 March 1864 – 3 December 1918) was a French radiologist and anatomist who was a native of Dijon. He studied medicine in Lyon, and later worked in the hospitals of Hôtel Dieu, Croix-Rousse and Charité in Lyon. In addition to his work in medicine, he was an accomplished sculptor. Destot was a pioneer in the field of radiology. In February 1896, less than two months after Wilhelm Conrad Röntgen (1845–1923) announced his discovery of the X-ray, Destot was making radiographs of patients at the Hôtel-Dieu de Lyon. He made thousands of radiographies, many of which were of patients supplied by surgeon Louis Léopold Ollier (1830–1900). In 1913, due to severe radiation damage to his hands, he was forced to relinquish his position as radiologist. Destot also made contributions in the field of orthopedics, and in 1911 is credited as being the first physician to use the term pilon in orthopedic literature. He was a medical officer during World War I, and died from illness in Châtillon-sur-Seine in 1918. His name is included on the Monument to the X-ray and Radium Martyrs of All Nations erected in Hamburg, Germany in 1936. == Associated eponym == "Destot's space", also


id: francis-john-drake-20260505-0
file: data/en.wikipedia.org/wiki/Francis_John_Drake-0.md
category: reference
title: Francis John Drake
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Francis_John_Drake
date_saved: 2026-05-05T10:59:50.102973+00:00
instance: kb-cron
parent: francis-john-drake-20260505-0
summary:
Francis John Drake, MA MB BS (Melb) (12 December 1860 - 17 December 1929) was resident medical superintendent, Launceston Hospital. In 1860, Drake was born at St. Kilda, Melbourne. On 28 April 1879, he began work as a messenger at the Melbourne Public Library with an annual salary of £50. He attended Scotch College from 1875 to 1880. In 1886, he graduated with a BA degree, and in 1887 received the MA degree from Melbourne. In 1888, Drake completed the MB from the University of Melbourne Medical School. In 1896, the Statistics of the State of Tasmania listed Drake as holding 2 appointments. He was surgeon superintendent at Launceston General Hospital with an annual salary of £400 that included quarters, rations, and fuel. The appointment began on 1 January 1890. Concurrently, Drake held the position as medical officer at the Contagious Diseases Hospital at Launceston. In 1896, Drake and Dr. John Ramsay participated in the first demonstration of X-rays by Frank Styant Browne at Launceston Hospital. The February 1898 issue of the Australasian Medical Gazette listed the resignation of Drake from the Launceston Hospital as surgeon-superintendent. The burial of Drake, who died on 17 December 1929, took place at Box


id: william-duane-physicist-20260505-0
file: data/en.wikipedia.org/wiki/William_Duane_(physicist)-0.md
category: reference
title: William Duane (physicist)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Duane_(physicist)
date_saved: 2026-05-05T10:59:51.295050+00:00
instance: kb-cron
parent: william-duane-physicist-20260505-0
summary:
William Duane (February 17, 1872 – March 7, 1935) was an American physicist who conducted research on radioactivity and X-rays and their usage in the treatment of cancer. He developed the Duane-Hunt Law and Duane's hypothesis. He worked with Pierre and Marie Curie in their University of Paris laboratory for six years and developed a method for generating quantities of radon-222 "seeds" from radium for usage in early forms of brachytherapy. He was a professor at the University of Colorado Boulder, professor-emeritus and chair of biophysics at Harvard University and research fellow of physics at the Harvard Cancer Commission. He received the John Scott Medal and the Comstock Prize in Physics in 1922 and the Leonard Prize of the American Roentgen Ray Society in 1923. == Early life and education == Duane was born in Philadelphia, Pennsylvania, to Charles William and Emma Cushman (Lincoln) Duane. He was a direct descendant of Benjamin Franklin from his father's side. He received an A.B. degree in mathematics from the University of Pennsylvania in 1892 and was valedictorian of his class. He studied at Harvard University and graduated with an A.B. in 1893. He worked as an assistant to John Trowbridge in his research


id: walter-drowley-filmer-20260505-0
file: data/en.wikipedia.org/wiki/Walter_Drowley_Filmer-0.md
category: reference
title: Walter Drowley Filmer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Walter_Drowley_Filmer
date_saved: 2026-05-05T10:59:52.518100+00:00
instance: kb-cron
parent: walter-drowley-filmer-20260505-0
summary:
Walter Drowley Filmer (1 September 1865 – 24 August 1944) was an early pioneer of X-rays in Australia, a wireless engineer, for a time ran the British Royal Train, and a world class entomologist that discovered several new species in his homeland. Filmer was a naturalist and established a private collection at his residence that thousands of people visited. == Life and Times == In 1865, Filmer was born in Maitland, New South Wales, Australia. He was the son of William Filmer (1828–1902) and Amy Filmer née Hatton (1831–1901). He married Mary Anne Eliza née Chessell (1868–1951) in 1890 in Sydney. The couple had 4 children: son, Walter Harold Alexander Filmer (1892–1964), born on 10 February 1892 in Sydney; daughter, Mary Filmer (1895–1895), born in 1895 in Petersham; son, Leroy Drowley Filmer (1902–1976), born on 5 April 1902 in Newcastle; and son, Eric Filmer (1903–1986), born 10 December 1903 in Toronto. In 1944, he died at home at Lake Macquarie. In 1876, at the age of 11, he was apprenticed to a boot maker. In 1884, by the age of 19, Filmer became an assistant telegraph line repairer and operator with the New South Wales Post Office. From 1885 to


id: elizabeth-fleischman-20260505-0
file: data/en.wikipedia.org/wiki/Elizabeth_Fleischman-0.md
category: reference
title: Elizabeth Fleischman
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Elizabeth_Fleischman
date_saved: 2026-05-05T10:59:53.785949+00:00
instance: kb-cron
parent: elizabeth-fleischman-20260505-0
summary:
Elizabeth Fleischman-Aschheim (née Fleischman; March 5, 1867 – August 3, 1905) was an American radiographer who is considered a pioneer of X-ray technology. Fleischman was the first woman to die as a result of X-ray radiation exposure. == Early years == Elizabeth Fleischman was born in El Dorado County, California (possibly in Placerville), on March 5, 1867, the daughter of Jewish immigrants from the Austrian Empire. Her mother, Katherine Lezansky was born in Prague and had several family members who were physicians in what is now the Czech Republic. Her father, Jacob Fleischman, was a baker. Elizabeth was one of five children. By 1876, the family had moved to San Francisco, where Elizabeth's father worked first as a baker and later as a merchant who sold various sundries and cigars. Elizabeth Fleischman attended the Girls' High School and dropped out in her senior year in 1882 to help support her family. She then took courses in bookkeeping and office management, and for a time she worked as a bookkeeper at Friedlander & Mitau, a San Francisco underwear manufacturer. Upon the death of her mother, Fleischman moved in with her sister Estelle, who was married to English physician and surgeon Michael


id: elizabeth-fleischman-20260505-1
file: data/en.wikipedia.org/wiki/Elizabeth_Fleischman-1.md
category: reference
title: Elizabeth Fleischman
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Elizabeth_Fleischman
date_saved: 2026-05-05T10:59:53.785949+00:00
instance: kb-cron
parent: elizabeth-fleischman-20260505-0
summary:
By 1903, the cumulative effects of seven years of unprotected X-ray exposures and twelve-hour workdays began to appear as X-ray dermatitis on her hands. She attributed this irritation to the chemicals used in developing photographic plates. In early 1904, the dermatitis progressed to the point where she sought medical attention. Her doctors found:"The fingers of both hands were found to be badly ulcerated, chiefly the tissues over the middle phalanges and the middle joints....the surfaces presenting both an ulcerated and warty condition, the warts assuming the form of necrogenica-healing alternating with ulceration. All the secreting glands and hair-follicles were destroyed so that the skin was hard and dry and cracked easily. All forms of treatment by ointments and washes were without permanent benefit."She continued to work despite this injury. In 1904, she was responsible for introducing protective measures for the operators of X-ray machines. She commented on the merits of double-plate glass screens, and metals such as lead, aluminium, iron and copper to "resist" X-rays. By late 1904, the dermatitis progressed to cancer. Her doctors attempted to excise a tumor on her right hand, but this failed to halt the progression of the carcinoma. In January 1905 her entire right


id: william-hope-fowler-20260505-0
file: data/en.wikipedia.org/wiki/William_Hope_Fowler-0.md
category: reference
title: William Hope Fowler
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Hope_Fowler
date_saved: 2026-05-05T10:59:54.957712+00:00
instance: kb-cron
parent: william-hope-fowler-20260505-0
summary:
William Hope Fowler CVO FRSE FRCSE (14 March 1876 – 4 October 1933) was a Scottish medical doctor and pioneer of radiology. He was co-founder of the Edinburgh School of Radiology. == Life == He was born in Edinburgh on 14 March 1876, the son of Robert Fowler, an accountant. His early years were spent at 81 Cumberland Street in Edinburgh's New Town. He was educated at Daniel Stewart's College them studied medicine at the University of Edinburgh, graduating with an MB ChB in 1897. He went to work as resident house surgeon at the Edinburgh Royal Infirmary on Lauriston Place. He showed a keen interest in the use of electricity to treat disease and was particularly interested in the newly discovered x-ray process. In 1901 he became the infirmary's Assistant Radiologist under Dawson Turner. In 1907 they were joined by John W. L. Spence. In 1911 he was promoted to Chief Radiologist alongside Archibald McKendrick. In the same year he became Honorary Radiologist to the Admiralty. At this time Fowler was living at 21 Walker Street in Edinburgh's West End. During World War I he was a member of the War Office's X-Ray Commission. In 1933 he was elected


id: wolfram-conrad-fuchs-20260505-0
file: data/en.wikipedia.org/wiki/Wolfram_Conrad_Fuchs-0.md
category: reference
title: Wolfram Conrad Fuchs
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wolfram_Conrad_Fuchs
date_saved: 2026-05-05T10:59:56.130644+00:00
instance: kb-cron
parent: wolfram-conrad-fuchs-20260505-0
summary:
Wolfram Conrad Fuchs (1865–1908) was a German-born electrical engineer who became a pioneer in radiography. He opened the first x-ray laboratory in the United States in Chicago, and had completed over 1400 x-ray examinations by 1896. His work was critical to the history of radiation protection. He was the father of Arthur Wolfram Fuchs (1895 - 1962), the inventor of the fixed kilovoltage technique of radiography. == Early life and education == Fuchs was born in Germany in 1865 to Julius and Wilhelmina Fuchs. The family emigrated to Chicago in 1870. He returned to Germany to study electrical engineering at the University of Berlin and graduated in 1889. He then went on to Paris to study at the Ecole des Beaux Arts. Upon returning to the United States, Fuchs completed his post-graduate work at the Massachusetts Institute of Technology in Boston. == Radiography work == Shortly after Wilhelm Röntgen's discovery of x-rays, Fuchs was traveling in Germany and was interested in the potential implications x-rays could have for electrical engineering. Meanwhile, in Chicago, Dr. Friedrich Cort Hamisch was also becoming interested in x-ray technology and had established a correspondence with Röntgen. He set up an x-ray laboratory but eventually handed


id: frederick-gardiner-radiologist-20260505-0
file: data/en.wikipedia.org/wiki/Frederick_Gardiner_(radiologist)-0.md
category: reference
title: Frederick Gardiner (radiologist)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frederick_Gardiner_(radiologist)
date_saved: 2026-05-05T10:59:57.356572+00:00
instance: kb-cron
parent: frederick-gardiner-radiologist-20260505-0
summary:
Frederick Gardiner FRSE FRCSE FRSM (1874- 8 September 1933) was a Scottish radiologist and dermatologist. == Life == Gardiner was born in Edinburgh in 1874 the son of John Gardiner and his wife Isabella. He studied medicine at the University of Edinburgh graduating MB CM in 1895. He then worked as a Resident first at Stirling Royal Infirmary, then at Dundee Royal Asylum. He returned to Edinburgh for further study, gaining a diploma in Public Health in 1901. He took on a role as Leith Hospital's radiologist in 1901. He gained his doctorate (MD) in 1902 writing his thesis on x-ray use in pulmonary tuberculosis. From 1904 he worked as Assistant Physician at the Edinburgh Royal Infirmary. In 1912 he became a senior Physician and also began lecturing in dermatology at the University of Edinburgh and in extramural classes. He did much to pioneer (in retrospect now seen as a mistake) the use of x-rays in treating of skin diseases. He also worked with Sir Robert Philip on the use of x-rays to diagnose tuberculosis. He lived close to both University and Infirmary, at 9 George Square in Edinburgh (now demolished). During the First World War he worked at Bangour


id: john-hall-edwards-20260505-0
file: data/en.wikipedia.org/wiki/John_Hall-Edwards-0.md
category: reference
title: John Hall-Edwards
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/John_Hall-Edwards
date_saved: 2026-05-05T10:59:58.586277+00:00
instance: kb-cron
parent: john-hall-edwards-20260505-0
summary:
John Francis Hall-Edwards FRSE (19 December 1858 – 15 August 1926) was a British medical doctor and pioneer in the medical use of X-rays in the United Kingdom. == Life == Hall-Edwards was the son of John Edwards, and was born on Moseley Road, Kings Norton near Birmingham. He attended King Edward VI Grammar School in Birmingham. He then studied medicine, apprenticing under Prof Richard Hill Norris at Queens College Medical School. Norris was both a surgeon and keen amateur photographer, being an early user of the dry-plate process, and he familiarised Hall-Edwards with photographic techniques. Hall-Edwards was licensed to practice medicine by the Royal College of Physicians of Edinburgh. From around 1885 he shows a strong interest in photography and was President of the Midland Photographic Club 1891–93. In 1895 he was made an Honorary Member of the Royal Photographic Society following a lecture to the London Camera Club. Initially his work focussed on photography through microscopes. On 11 January 1896 he made the first use of X-rays under clinical conditions when he radiographed the hand of an associate, revealing a sterilised needle beneath the surface. A month later on 14 February he took the first radiograph to direct


id: william-john-hancock-20260505-0
file: data/en.wikipedia.org/wiki/William_John_Hancock-0.md
category: reference
title: William John Hancock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_John_Hancock
date_saved: 2026-05-05T10:59:59.753329+00:00
instance: kb-cron
parent: william-john-hancock-20260505-0
summary:
William John Hancock D.Sc. (Hon), MIEE, MICE, LRCP (2 May 1864 – 26 August 1931) was an Australian of Irish descent, an electrical engineer, telephone pioneer and pioneer in X-rays in the colony of Western Australia. He was honorary radiologist for Perth Hospital and Base Hospital in Fremantle. His list of credentials and accomplishments include M.I.E.E., Member of the Institution of Electrical Engineers, M.I.C.E., Member of the Institution of Civil Engineers, L.R.C.P., Licentiate of the Royal College of Physicians and D.Sc. (Honorary). In the colonies of Australia, the medical men of the day took a slow approach in the adoption of the new science that involved x-rays. Many of the early demonstrations were made by investigators outside the medical field. Upon examination of the initial investigators, several key factors were common. The individuals had already either been experimenting along similar lines to Wilhelm Röntgen with Crookes tubes and such, the physicists or scientists, or were actively associated with electrical work, the electricians, which made them particularly receptive to the technical appeal of the new science of x-rays. Records of the events reveal that among the medical men who witnessed the first images produced as radiographs, a rather small number had


id: william-john-hancock-20260505-1
file: data/en.wikipedia.org/wiki/William_John_Hancock-1.md
category: reference
title: William John Hancock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_John_Hancock
date_saved: 2026-05-05T10:59:59.753329+00:00
instance: kb-cron
parent: william-john-hancock-20260505-0
summary:
Of interest to note, when the Perth Observatory foundation was laid on 29 September 1896, the occasion was attended by Sir John Forrest and other notable dignitaries, and several items of importance were placed in a leaden box (time capsule), sealed and deposited in a cavity beneath the foundation stone. The event was described in the local press and mentioned here since "Röntgen rays tubes, and a description of the process, together with specimen photographs", donated by Hancock were included in the cache. This is the first known instance of a time capsule in Western Australia, and in Australia. In Canberra, on 3 March 1936, at the Australian Institute of Anatomy a face mask was erected in the applied anatomy museum. The bust was unveiled to commemorate Dr. William John Hancock and his service to Australia as a pioneer of X-rays and radiology in Western Australia. Royal Society of Western Australia, Kelvin Gold Medal, inaugural awardee, 1924 University of Western Australia, honorary doctorate of science, 1924 University of Western Australia, Senate, 1915–1927 === Memorial Window at University of Western Australia === In 1934, a stained glass memorial window was placed in the foyer of Winthrop Hall, at the University of


id: guido-holzknecht-20260505-0
file: data/en.wikipedia.org/wiki/Guido_Holzknecht-0.md
category: reference
title: Guido Holzknecht
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Guido_Holzknecht
date_saved: 2026-05-05T11:00:00.948626+00:00
instance: kb-cron
parent: guido-holzknecht-20260505-0
summary:
Guido Holzknecht (3 December 1872 – 30 October 1931) was an Austrian radiologist who was a native of Vienna. He studied in Strasbourg, Königsberg, and Vienna, and became the director of the X-ray laboratory at Vienna General Hospital in 1905 . He later established a central radiology department at the hospital, which became known as the Guido Holzknecht Institute. With radiologist Robert Kienböck (1871–1953), he was a co-founder of the Wiener Röntgengesellschaft (Vienna Radiology Society). The statue of Holzknecht in Arne Carlsson Park was originally made by Josef Josephu. Damaged during the Second World War, it was later restored incorrectly. The family had commissioned Josephu to show missing fingers that Holzknecht had lost due to radiation poisoning. The restored statue shows all of his fingers intact. Additionally, the signature on the restored statue reads JosefHeu, who left Vienna during the War - misspelling the original artist's name. Guido Holzknecht was a pioneer in radiology. In 1902 he devised a color dosimeter (referred to as a "chromoradiometer") for detecting and measuring X-rays. Like a number of other physicians in the early days of radiology, he died from the consequences of radiation poisoning in October 1931 aged 58. He was cremated at


id: william-henry-hosking-20260505-0
file: data/en.wikipedia.org/wiki/William_Henry_Hosking-0.md
category: reference
title: William Henry Hosking
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Henry_Hosking
date_saved: 2026-05-05T11:00:02.127422+00:00
instance: kb-cron
parent: william-henry-hosking-20260505-0
summary:
William Henry Hosking LM, LSA, LRCPI, LRCP, MRCS (26 December 1841–11 March 1917) was a New Zealand medical doctor, hospital superintendent, X-ray and radium pioneer. == Life == Hosking was born in 1841 at Redruth, Cornwall, England, and christened in 1844 at Crowan, Cornwall, England. He was the son of William Hosking, an ironfounder and his wife Elizabeth Phillips. Hosking died of leukemia in 1917 at Masterton. == Education == Hosking was educated at schools in Falmouth and Taunton, then studied and trained at the Charing Cross Hospital Medical School. He achieved several qualifications that included LSA Licentiate of the Society of Apothecaries, London 1863; LRCPI Licentiate of the Royal College of Physicians in Ireland, 1873; LRCP Licentiate of the Royal College of Physicians, London; MRCS Member of the Royal College of Surgeons, England 1873; LM Doctor of Laws, University of Liverpool 1874. He registered under the Medical Practitioners Ordinance of the Province of New Munster in Campbelltown on 19 September 1863. Hosking registered on 23 September 1869 under the Medical Practitioners Act of 1867 at Ross and Masterton. == New Zealand == On 1 May 1863, Hosking departed the United Kingdom bound for the New Munster Province of New


id: richard-lane-joynt-20260505-0
file: data/en.wikipedia.org/wiki/Richard_Lane_Joynt-0.md
category: reference
title: Richard Lane Joynt
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Richard_Lane_Joynt
date_saved: 2026-05-05T11:00:03.514113+00:00
instance: kb-cron
parent: richard-lane-joynt-20260505-0
summary:
Richard Lane Joynt OBE (18 May 1866 - 8 April 1928) was an Irish orthopaedic surgeon, metallurgist, who pioneered the use of x-rays. == Early life and family == Richard Lane Joynt was born at the Grange, Raheny, County Dublin on 18 May 1866. His parents were Jane (née Russell) and William Lane-Joynt, a barrister and mayor of Limerick in 1862 and Dublin in 1867. He had four brothers and a sister. His brother, William Russell, was a barrister and philatelist and Olympic shooter. Lane Joynt spent some of his childhood in Limerick, where his father trained as a solicitor. Through his father, he was a cousin of Augusta, Lady Gregory. Lane Joynt attended the Portora Royal School, Enniskillen, County Fermanagh and entered Trinity College Dublin, graduating with an LM diploma in 1889 and MB, BCh, BAO in 1890. == Career == In 1891 he trained at the Vienna General Hospital, receiving his MD in 1893, and admitted as a fellow of the Royal College of Surgeons in Ireland (RCSI) in 1894 and elected to the County Dublin Infirmary and Meath Hospital. He served as a senior member of the RCSI council. Just two years after the invention of x-rays,


id: thomas-ranken-lyle-20260505-0
file: data/en.wikipedia.org/wiki/Thomas_Ranken_Lyle-0.md
category: reference
title: Thomas Ranken Lyle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thomas_Ranken_Lyle
date_saved: 2026-05-05T11:00:04.726229+00:00
instance: kb-cron
parent: thomas-ranken-lyle-20260505-0
summary:
Sir Thomas Ranken Lyle FRS (26 August 1860 – 31 March 1944) was an Irish-Australian mathematical physicist, radiologist, educator, and rugby player. Lyle was born and educated in Ireland before emigrating to Australia to take up a professorship at the University of Melbourne. There he was a pioneer in the use of X-rays as a medical tool. The Thomas Ranken Lyle Medal is awarded in his name to honour Australian achievements in Physics and Mathematics. In his earlier years in Ireland he was a rugby union forward of some note, who played club rugby for Dublin University and international rugby for Ireland. == Career == Lyle was born in Coleraine, Ireland in 1860, the second son of Hugh Lyle, a well-to-do landowner. He was educated at Trinity College, Dublin, graduating in 1883 with full honours and student medals for his work in mathematics and physics. He received his MA in 1887, and continued his studies in advanced physics and mathematics. By 1889 he had emigrated to Australia, and at the age of 29, took up the position of the chair of natural philosophy at the University of Melbourne. In 1891 a Master of Science was introduced at the university, and


id: cecil-lyster-20260505-0
file: data/en.wikipedia.org/wiki/Cecil_Lyster-0.md
category: reference
title: Cecil Lyster
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cecil_Lyster
date_saved: 2026-05-05T11:00:05.895253+00:00
instance: kb-cron
parent: cecil-lyster-20260505-0
summary:
Cecil Rupert Chaworth Lyster CBE (14 December 1859 – 26 January 1920) was a British physician, electrotherapist and radiologist. Lyster was the son of Alfred Chaworth Lyster and his wife Elizabeth (née Kennett). He began his career as resident medical officer at Charing Cross Hospital in London and then served as resident obstetrical officer from 1881 to 1882. Following travels in the United States and Europe, he was appointed medical superintendent of the Bolingbroke Hospital in 1885. Specialising in electro-therapeutics and radiology, he became medical officer-in-charge of the Electrical Department of Middlesex Hospital in 1902, while still continuing to work as a doctor at the Bolingbroke Hospital. He held these positions until his death. Lyster was appointed Commander of the Order of the British Empire (CBE) in January 1920 for his work in the First World War. He married Edith Thompson (died 1919) in 1903; they had no children. Lyster died from cancer caused by exposure to x-rays during his research, the day before his CBE was gazetted. The gazette was later ante-dated to two days before his death. His name is included on the Monument to the X-ray and Radium Martyrs of All Nations erected in Hamburg, Germany, in


id: monument-to-the-x-ray-and-radium-martyrs-of-all-nations-20260505-0
file: data/en.wikipedia.org/wiki/Monument_to_the_X-ray_and_Radium_Martyrs_of_All_Nations-0.md
category: reference
title: Monument to the X-ray and Radium Martyrs of All Nations
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Monument_to_the_X-ray_and_Radium_Martyrs_of_All_Nations
date_saved: 2026-05-05T11:00:07.063531+00:00
instance: kb-cron
parent: monument-to-the-x-ray-and-radium-martyrs-of-all-nations-20260505-0
summary:
The Monument to the X-ray and Radium Martyrs of All Nations (also known as the X-ray Martyrs' Memorial) is a memorial in Hamburg, Germany, commemorating those who died due to their work with the use of radiation, particularly X-rays, in medicine. It was unveiled on the grounds of St Georg (St George's) Hospital (now the Asklepios Klinik St Georg), on 4 April 1936 by the Deutsche Röntgengesellschaft (the Röntgen Society of Germany). When unveiled, the memorial included 169 names, from fifteen nations, listed alphabetically; by 1959 there were 359, with the additions listed on four separate stone plaques, beside the original columnar stone memorial. == Inscription == The memorial's inscription may be translated as: == Book == An accompanying book, Ehrenbuch der Radiologen aller Nationen (Book of Honour of radiologists of all nations) gives biographies of those commemorated. Three editions have been produced, the most recent in 1992. == Names == The names of those commemorated include: Heinrich Albers-Schönberg (1865–1921) Gustav Baer (1865–1925) Frederick Henry Baetjer (1874–1933) Burton Eugene Baker (1871–1913) Leonhard Baumeister (1874–1953) Eugen Beaujard (1874–1937) Jean Bergonié (1857–1925) Elis Berven (1885–1966) Reginald Blackall (-1925) Barry Blacken Joseph Boine (1883–1935) Percy Brown (?–1950) William Ironside Bruce (1879–1921) Eugene Wilson


id: shoji-nishikawa-20260505-0
file: data/en.wikipedia.org/wiki/Shoji_Nishikawa-0.md
category: reference
title: Shoji Nishikawa
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Shoji_Nishikawa
date_saved: 2026-05-05T11:00:08.235877+00:00
instance: kb-cron
parent: shoji-nishikawa-20260505-0
summary:
Shōji Nishikawa (Japanese: 西川 正治, Nishikawa Shōji, 5 December 1884 – 5 January 1952) was a Japanese physicist and a founding father of crystallography in Japan. == Education and career == Nishikawa was born in 1884 in Hachiōji, Tokyo Prefecture, as the son of an important silk dealer. He grew up in Tokyo and later studied at the Faculty of Science at the Imperial University of Tokyo (now University of Tokyo). His PhD in physics was supervised by Suekichi Kinoshita, with an initial focus on radioactivity. During this time, Nishikawa was inspired by Torahiko Terada to turn his interest turned to crystallography, which was experiencing a worldwide boom with the then new method of X-ray diffraction for structural analysis. The first publications of Nishikawa came out between 1913 and 1915, at a time when the British Nobel Prize winners in physics William Henry Bragg and William Lawrence Bragg were doing groundbreaking pioneering work in this field. Between 1916 and 1919, Nishikawa stayed in the United States and worked at Cornell University, where he was a mentor of the then graduate student Ralph Wyckoff. Before returning to Japan in 1920, Nishikawa also spent six months with William H. Bragg at University


id: george-alexander-pirie-20260505-0
file: data/en.wikipedia.org/wiki/George_Alexander_Pirie-0.md
category: reference
title: George Alexander Pirie
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/George_Alexander_Pirie
date_saved: 2026-05-05T11:00:09.420464+00:00
instance: kb-cron
parent: george-alexander-pirie-20260505-0
summary:
George Alexander Pirie (1863 – 27 October 1929) was a Scottish medical doctor and pioneering researcher in the use of X-rays in clinical medicine. == Early life == George Alexander Pirie was born in Dundee where his father, Dr George Clark Pirie, was a physician at the Dundee Royal Infirmary from 1862 to 1881. The family lived at 43 South Tay Street in Dundee. Pirie graduated with an MA from the University of St. Andrews, and then studied medicine at the University of Edinburgh, graduating with an MB ChM with first-class honours in 1886 and an MD in 1890. == Career == In 1887 he started work at Edinburgh Royal Infirmary as a resident under Scottish physician Sir Thomas Grainger Stewart, before moving to Dundee. Pirie worked at the Dundee Royal Infirmary from 1896 to 1925, and was an early pioneer in the application of X-rays to clinical medicine. He began experimenting with radiology, radiography, and X-rays in 1896, soon after the Wilhelm Röntgen had first demonstrated X-rays and their potential in Germany. Pirie established the first Electrical Department at Dundee Royal Infirmary in 1896. The Tayside Medical History Museum at the University of Dundee holds a number of examples


id: ivan-puluj-20260505-0
file: data/en.wikipedia.org/wiki/Ivan_Puluj-0.md
category: reference
title: Ivan Puluj
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ivan_Puluj
date_saved: 2026-05-05T11:00:10.655208+00:00
instance: kb-cron
parent: ivan-puluj-20260505-0
summary:
Ivan Pavlovych Puluj (Ukrainian: Іван Павлович Пулюй, pronounced [iˈwɑn pʊˈlʲuj]; German: Johann Puluj; 2 February 1845 – 31 January 1918) was a Ukrainian physicist and inventor known for his early research into X-rays. His contributions were largely neglected until the end of the 20th century. == Biography == Puluj was born on 2 February 1845 in Hrymailiv, which was then part of the Kingdom of Galicia and Lodomeria in the Austrian Empire. He was the son of Pavlo Puluj and Xenia née Burshtynska (Ukrainian: син Павла́ Пулю́я i Ксенiї ур. Бурштинської). The family's original surname was Pulguy until 1861. His father, Pavlo, was a landowner who served as burgomaster of Hrymayliv from 1861 to 1865. Ivan grew up in Hrymayliv, and attended primary school in the village. He then attended the gymnasium at Ternopil, where he became a co-founder and active member of the Ukrainian student society Hromada. He graduated with honors from Theological Faculty of the University of Vienna (1869), later also from the Department of Philosophy (1872). During his time there, he was the co-founder and later head of the Sich movement. After graduating, he worked as an assistant to the University of Vienna's experimental physics department. In


id: john-ramsay-surgeon-20260505-0
file: data/en.wikipedia.org/wiki/John_Ramsay_(surgeon)-0.md
category: reference
title: John Ramsay (surgeon)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/John_Ramsay_(surgeon)
date_saved: 2026-05-05T11:00:11.823671+00:00
instance: kb-cron
parent: john-ramsay-surgeon-20260505-0
summary:
Sir John Ramsay CBE FRACS (26 December 1872 – 6 February 1944) was an Australian surgeon, known for his association with the Launceston General Hospital. == Early life and education == Born in Glasgow, Scotland, on 26 December 1872, John Ramsay was the fourth son of the businessman John Ramsay and his wife, Margaret Thomson. The family migrated to Melbourne in 1878, where John Jr Ramsay attended State School No. 2855 at Prahran and Wesley College. He graduated as a Bachelor of Medicine and Surgery (M.B., B.S.) from the University of Melbourne with the Beaney Prize in pathology, in 1893. == Career == After a year's residency at the Royal Melbourne Hospital (1894), Ramsay spent the next year abroad in Auckland as a resident (1895), before being appointed house surgeon at the Launceston General Hospital. In 1896, Ramsay and Dr. Francis John Drake participated in the first demonstration of X-rays by Frank Styant Browne at Launceston General Hospital. In 1898, he became the surgeon-superintendent of the hospital. Graduating with a Master of Surgery degree from the University of Melbourne in 1902, Ramsay published 24 papers, including a discussion of his treatment of hydatid disease, as well as lecturing in Australia


id: henry-jasper-redfern-20260505-0
file: data/en.wikipedia.org/wiki/Henry_Jasper_Redfern-0.md
category: reference
title: Henry Jasper Redfern
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Henry_Jasper_Redfern
date_saved: 2026-05-05T11:00:13.031423+00:00
instance: kb-cron
parent: henry-jasper-redfern-20260505-0
summary:
Henry Jasper Redfern, FSMC, BOA, (1871–1928), or Jasper Redfern was a British optician, photographer, exhibitor, filmmaker, proprietor of photographic and lantern retail business, cinema pioneer and x-ray and radiographic pioneer. The business card of Redfern stated: H. Jasper Redfern, Practical Optician and Scientist, 55 & 57 Surrey Street, Sheffield. == Life and times == In 1871, Redfern was born at Sheffield, Yorkshire (West Riding), England. His parents were Walter Shepherd Redfern, age 31 (born at Sheffield, Yorkshire, England) and Sarah Rosebella Redfern, age 35 (born at Waddingham, Lincolnshire, England). In 1881, he was a resident at 40 Nicholson Road in Heeley, Sheffield, Yorkshire (West Riding), England. Redfern had one sister, Amy Eliza Redfern, age 11 and one brother, John William Redfern, age 7. In 1891, he lived with his parents and brother at 110 Pancras Square in St Pancras, London, England. His occupation was recorded as a photographer's apprentice. In 1894, he resided at 22 Stratford place in the Borough of Saint Pancras, East division, London, England. Redfern lived in a room he rented, the "front room on top floor, unfurnished" with rent of 11 shillings per week, with partial board, and rent paid to Mrs. Redfern at the same


id: henry-jasper-redfern-20260505-1
file: data/en.wikipedia.org/wiki/Henry_Jasper_Redfern-1.md
category: reference
title: Henry Jasper Redfern
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Henry_Jasper_Redfern
date_saved: 2026-05-05T11:00:13.031423+00:00
instance: kb-cron
parent: henry-jasper-redfern-20260505-0
summary:
=== Fred Holmes === In 1894, Redfern teamed with Fred Holmes as manager. Holmes developed skills as photographer, animated picture operator and projectionist. In September 1896, Redfern presented at the YMCA in Sheffield, a double-bill of film and x-ray demonstrations with a Kineopticon, a projector he obtained from Birt Acres. The Kineopticon had recently been patented by Acres on 27 May 1895 and quickly became popular. Redfern was keen to capitalise of this new invention and took advantage of the public's interest and fascination with these new animated or moving pictures. In 1898, Redfern secured an exclusive contract in England for the right to tour the groundbreaking, first feature film of the Corbett-Fitzsimmons boxing match of 1897. Redfern also secured or produced himself, films of local sporting events, and this proved to be a move towards making the headline feature as an event all by itself. He had the foresight to realise that a satisfied audience would return for future events and become loyal customers and customers that would return week after week. Redfern discovered a new market for the new medium of animated or motion pictures. He found new captive audiences and offered an afternoon's or evening's entertainment to


id: henry-jasper-redfern-20260505-2
file: data/en.wikipedia.org/wiki/Henry_Jasper_Redfern-2.md
category: reference
title: Henry Jasper Redfern
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Henry_Jasper_Redfern
date_saved: 2026-05-05T11:00:13.031423+00:00
instance: kb-cron
parent: henry-jasper-redfern-20260505-0
summary:
=== Royal Visits === On 21 May 1897, Redfern recorded events during Queen Victoria's visit, including the decorations on Pinstone Street taken at Sheffield City Centre. The original photograph was a stereo pair. During Queen Victoria's visit, he captured the decorations in Barker's Pool taken at Sheffield City Centre. The original photograph was a stereo pair. On 12 July 1905, Redfern photographed the Royal Visit of King Edward VII and Queen Alexandra, with one picture captured the Royal Couple leaving the Town Hall at Sheffield City Centre. Royal Visit of King Edward VII and Queen Alexandra, Their Majesties arriving at the Town Hall and meeting the Lord Mayor of Sheffield at Sheffield City Centre. On 26 April 1909, Redfern photographed the Royal Visit of the Prince and Princess of Wales, who later became George V and Queen Mary outside the Town Hall at Sheffield City Centre. The Prince and Princess of Wales (later George V) made a Royal Visit at Sheffield to open the Edgar Allen Library at Sheffield University. === Parks and places === In 1897, Redfern took an early photograph of Endcliffe Park taken at Endcliffe in Sheffield. Meersbrook Park at Meersbrook in Sheffield in 1897. In 1897,


id: henry-jasper-redfern-20260505-3
file: data/en.wikipedia.org/wiki/Henry_Jasper_Redfern-3.md
category: reference
title: Henry Jasper Redfern
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Henry_Jasper_Redfern
date_saved: 2026-05-05T11:00:13.031423+00:00
instance: kb-cron
parent: henry-jasper-redfern-20260505-0
summary:
=== 1901 === 7 February 1901, Sheffield Empire Theatre of Varieties; Jasper Redfern's Animated Pictures, and other acts 5 March 1901, Castlefold's Market Employees' Eighth Annual Tea & Concert; H. Jasper Redfern's Animated Pictures, and other acts 19 October 1901, Young Men's Christian Association, Sheffield; Programme of the President's 'At Home' Cinematograph by Mr Jasper Redfern 19 October 1901, Joseph Pickering & Sons, Limited, Sheffield. Employees'; Mr Redfern's, Cinematograph, and other acts 26 November 1901, Sheffield and District Press Club; Programme for Sat 23 November 1901; Arthur Dawes – Vocalist, J. A. Rodgers – Vocalist, J. B. Slack – Vocalist, Harry Heath – Vocalist, Maurice Taylor – cello, Mr Hinchcliffe – violin, Messrs A. Bagshaw, Taylor and Hinchcliffe; Mr H. Jasper Redfern – cinematograph exhibition === 1902 === 18 August 1902, New Palace Theatre, Hull; Programme for Monday, 18 August 1902; Alice Cooke – transformation dancer; The Maisanos – Continental Musical Grotesques; Sybil St. Elmo – Ballad Vocalist; Ross and Grayson – Comedy Act; Edwin Boyde – comedian; Redfern's Pictures, The Coronation of King Edward VII; Millie Hylton, James O'Connor and Charles Brady – Knockabout Comedians; Little Gitana – child vocalist; Sisters Morgan Duettists and Dancers; Glenroy Troupe – Male


id: reynolds-and-branson-20260505-0
file: data/en.wikipedia.org/wiki/Reynolds_and_Branson-0.md
category: reference
title: Reynolds and Branson
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reynolds_and_Branson
date_saved: 2026-05-05T11:00:14.297450+00:00
instance: kb-cron
parent: reynolds-and-branson-20260505-0
summary:
Reynolds & Branson Leeds was a business based at 13 Briggate and 14 Commercial Street in Leeds, England. The business lasted from 1816 (1816) to 1972 (1972). Edward Matterson managed the company in 1822, and William West F.R.S. took over in 1833. The National Archives Records about the company include a day book, sales ledger, and prescription books. The records were created by Reynolds & Branson Ltd. Reynolds & Branson was registered in July 1898 as a limited corporation with a capital of £34,000 in shares of £10 each by Messrs. R. Reynolds, F. W. Branson. No remuneration was given to Mr. R. Reynolds, but a £700 per annum was given to each of the others. In 1890, Richard Reynold's son, Richard Freshfield (Fred) Reynolds was made a partner. The firm was in the business of wholesale and retail for chemists and surgical instrument makers. == Origins == The original company can be traced back to 1816 (see Grace's Guide which is the leading source of historical information on industry and manufacturing in Britain). Edward Matterson was a druggist who ran the firm after being employed by Allen and Hanburys. He was educated at Leeds Grammar School. In 1822 the


id: reynolds-and-branson-20260505-1
file: data/en.wikipedia.org/wiki/Reynolds_and_Branson-1.md
category: reference
title: Reynolds and Branson
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reynolds_and_Branson
date_saved: 2026-05-05T11:00:14.297450+00:00
instance: kb-cron
parent: reynolds-and-branson-20260505-0
summary:
== The war years == During the First World War, he actively pursued efforts to standardize the size and shape of chemical glassware. In 1916, he was elected as an inaugural member of the Society of Glass Technology. He organized research and published works on these topics. Branson sought to secure in Great Britain the manufacturing process for the glass required for the equipment of munition factories.[8][9] Branson contributed a paper on the composition of some types of chemical glassware to the Society of Chemical Industry (J. SOC. Chem. Ind., 1915, 34, 471) in collaboration with his son Frederick Hartridge, a paper to the Transactions of the Society of Glass Technology (1919, 3, 249) "A proposed standard formula for a glass for lamp workers". Branson was chairman until retirement in 1932. His son, Frederick Hartridge, Associate of the Royal Institute of Chemistry AIC, became chairman and managing director of Reynolds & Branson.[5][7] he run the company for 20 years, until his untimely death on 10 February 1952, Frederick Hartridge had appointed his 3 Sons and Daughter as directors of Reynolds & Branson, Frederick Norman the eldest son who attended Ilkley Grammar an all-boys school, Eileen his only daughter, Peter Orchard


id: reynolds-and-branson-20260505-2
file: data/en.wikipedia.org/wiki/Reynolds_and_Branson-2.md
category: reference
title: Reynolds and Branson
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reynolds_and_Branson
date_saved: 2026-05-05T11:00:14.297450+00:00
instance: kb-cron
parent: reynolds-and-branson-20260505-0
summary:
Reynolds and Branson, 1887. Handy Guide to Surgical Instruments and Appliances etc. Reynolds and Branson, 14 Commercial Street, Leeds. Gloucester: John Bellows. 1887. 246p. Reynolds and Branson, 1890. Illustrated Catalogue of Chemical and Physical Apparatus, Pure Chemicals and Reagents. Reynolds and Branson, 14 Commercial Street, Leeds. 1890. 200p. Reynolds and Branson, 1903. Catalogue of Special Preparations. Reynolds and Branson, 14 Commercial Street, Leeds. 1903. 64p. Reynolds and Branson, 1907. Illustrated Catalogue of Optical Lanterns, Slides, Compressed Gases and Accessory Apparatus. Reynolds and Branson, 14 Commercial Street, Leeds. Leeds: McCorquodale & Co. 1907. 204p. Reynolds and Branson, 1908. Illustrated Catalogue of Surgical Instruments and Appliances. Reynolds and Branson, 14 Commercial Street, Leeds. Leeds: Chorley & Pickersgill. 1908. 119p. Reynolds and Branson, 1912. Catalogue of Special Preparations, Surgical Instruments, Trusses etc. Reynolds and Branson, 14 Commercial Street, Leeds. 1912. 84p. Reynolds and Branson, 1912–1920. Catalogue of Laboratory Fittings and Furniture. Reynolds and Branson. 1912–1920. 29p. == Reynolds & Branson Patents == Patents include: #1120 in 1885, #16373 in 1893, #14102 in 1899. Improvements in photographic ‘shutters’ for instantaneous photography. #1650. 1883. Means or apparatus for measuring quantities of highly volatile liquids. No. 3490. 1904. == References == == External links == Reynolds


id: richard-reynolds-chemist-20260505-0
file: data/en.wikipedia.org/wiki/Richard_Reynolds_(chemist)-0.md
category: reference
title: Richard Reynolds (chemist)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Richard_Reynolds_(chemist)
date_saved: 2026-05-05T11:00:15.469000+00:00
instance: kb-cron
parent: richard-reynolds-chemist-20260505-0
summary:
Richard Reynolds, FCS (12 May 1829 – 5 April 1900), was an English pharmaceutical chemist, optician, instrument maker, and X-ray pioneer. == Life and times == Reynolds came from a long line of Quakers, being a descendant of John Gurney. On 12 May 1829, he was born at Banbury, Oxford, England. His father Richard Freshfield Reynolds was an apothecary, known as the druggist of Banbury. His mother was Maria Reynolds, née Bassett. In 1843, Reynolds left school and became apprenticed to James Deane, chemist at Clapham Common. In 1844, he went to Leeds and apprenticed to the chemist Thomas Harvey. During the years 1850 to 1851, he attended the London School of Pharmacy and took first prizes for the examinations held by the Pharmaceutical Society in chemistry, materia medica (medical material/substance) and botany. At this time, T. B. Groves, Henry T. Watts, Dr. William Squire and other notable individuals were at "The Square". The Pharmaceutical Society was located on "The Square". Reynolds returned to Clapham and worked for two years with the chemist James Deane. During the time at Clapham, he took an interest in the analysis of native samples of carbonate of soda. In 1854, Reynolds returned to Leeds


id: wilhelm-r-ntgen-20260505-0
file: data/en.wikipedia.org/wiki/Wilhelm_Röntgen-0.md
category: reference
title: Wilhelm Röntgen
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wilhelm_Röntgen
date_saved: 2026-05-05T11:00:16.715879+00:00
instance: kb-cron
parent: wilhelm-r-ntgen-20260505-0
summary:
Wilhelm Conrad Röntgen (27 March 1845 – 10 February 1923) was a German experimental physicist who produced and detected electromagnetic radiation in a wavelength range known as X-rays (known as "Röntgen rays" in many languages). In 1901, Röntgen became the first recipient of the Nobel Prize in Physics "in recognition of the extraordinary services he has rendered by the discovery of the remarkable rays subsequently named after him." The element roentgenium is named in his honor. == Biography == === Early life and education === Wilhelm Conrad Röntgen was born on 27 March 1845 in Lennep (now part of Remscheid), Prussia, the only child of Friedrich Conrad Röntgen, a merchant and cloth manufacturer, and Charlotte Constanze Frowein. In 1848, he moved with his parents to the Netherlands—where his mother's family lived—rendering him stateless. In 1862, Röntgen enrolled at Utrecht Technical School, where he followed courses for almost two years. In 1865, he was unfairly expelled from the Technical School when he was falsely accused of drawing a caricature of one of the teachers, which was actually drawn by someone else. Without a high school diploma, Röntgen could only attend university in the Netherlands as a visitor. In 1865, he tried


id: wilhelm-r-ntgen-20260505-1
file: data/en.wikipedia.org/wiki/Wilhelm_Röntgen-1.md
category: reference
title: Wilhelm Röntgen
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wilhelm_Röntgen
date_saved: 2026-05-05T11:00:16.715879+00:00
instance: kb-cron
parent: wilhelm-r-ntgen-20260505-0
summary:
In 1895, in his laboratory at the Physical Institute of the University of Würzburg, Röntgen was investigating the external effects of passing an electric discharge through various types of vacuum tube equipment—apparatuses from Heinrich Hertz, Johann Hittorf, William Crookes, Nikola Tesla, and Philipp Lenard. In early November, he was repeating an experiment with one of Lenard's tubes in which a thin aluminium window had been added to permit the cathode rays to exit the tube but a cardboard covering was added to protect the aluminium from damage by the strong electrostatic field that produces the cathode rays. He knew that the cardboard covering prevented light from escaping, yet he observed that the invisible cathode rays caused a fluorescent effect on a small cardboard screen painted with barium platinocyanide when it was placed close to the aluminium window. It occurred to Röntgen that the Crookes–Hittorf tube, which had a much thicker glass wall than the Lenard tube, might also cause this fluorescent effect. In the late afternoon of 8 November 1895, Röntgen was determined to test his idea. He carefully constructed a black cardboard covering similar to the one he had used on the Lenard tube. He covered the Crookes–Hittorf tube


id: wilhelm-r-ntgen-20260505-2
file: data/en.wikipedia.org/wiki/Wilhelm_Röntgen-2.md
category: reference
title: Wilhelm Röntgen
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wilhelm_Röntgen
date_saved: 2026-05-05T11:00:16.715879+00:00
instance: kb-cron
parent: wilhelm-r-ntgen-20260505-0
summary:
In November 2004, the IUPAC named element number 111 roentgenium (Rg) in his honor. The IUPAP adopted the name in November 2011. A collection of Röntgen's papers is held at the National Library of Medicine in Bethesda, Maryland. Today, in Remscheid-Lennep, 40 kilometres east of Röntgen's birthplace in Düsseldorf, is the Deutsches Röntgen-Museum. In Würzburg, where Röntgen discovered X-rays, a non-profit organization maintains his laboratory and provides guided tours to the Röntgen Memorial Site. World Radiography Day is an annual event promoting the role of medical imaging in modern healthcare. It is celebrated on 8 November each year, coinciding with the anniversary of Röntgen's discovery. It was first introduced in 2012 as a joint initiative between the European Society of Radiology, the Radiological Society of North America, and the American College of Radiology. As of 2023, 55 stamps from 40 countries have been issued commemorating Röntgen as the discoverer of X-rays. Röntgen Peak in Antarctica is named after Wilhelm Röntgen. Minor planet 6401 Roentgen is named after him. In 2010, Röntgen's discovery was honored in a Google doodle. == See also == German inventors and discoverers Röntgen Memorial Site Ivan Puluj == Notes == == References == == External links


id: karl-friedrich-schall-20260505-0
file: data/en.wikipedia.org/wiki/Karl_Friedrich_Schall-0.md
category: reference
title: Karl Friedrich Schall
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Karl_Friedrich_Schall
date_saved: 2026-05-05T11:00:17.931644+00:00
instance: kb-cron
parent: karl-friedrich-schall-20260505-0
summary:
Karl Friedrich Schall (16 March 1859 – 19 September 1925) was a German precision engineer and co-founder of the company Reiniger, Gebbert & Schall (RGS) in Erlangen. RGS was a manufacturer and supplier of durable medical equipment and a pioneer in the supply of x-ray equipment worldwide with offices in Berlin, Wien, London, Paris, Rome, Chicago and Sydney. == Life and times == Schall was born in 1859 at Öhringen in the Kingdom of Württemberg as the son of the lawyer William Schall. From 1877 to 1879, he was in Tübingen as a university mechanic and apprenticed as a precision mechanic. During 1880–1881, Schall completed the mandatory one-year volunteer service in the military, and travelled to Paris, London and Switzerland. On 24 January 1887, at Dresden he married Johanna Schmidlin (born 18 October 1859 in Giessbach – died June 1934 in Oberhofen). The couple had three children: Wilhelm, later called William (21 April 1888 – 2 December 1965), Mary Jane (27 May 1889 – October 1927) and Margarete (25 December 1890 – 21 March 1937). In 1893, Schall became a British citizen. == Reiniger, Gebbert and Schall == In 1883, Schall returned to Stuttgart, and opened his own workshop for


id: frank-k-schmidlin-20260505-0
file: data/en.wikipedia.org/wiki/Frank_K._Schmidlin-0.md
category: reference
title: Frank K. Schmidlin
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frank_K._Schmidlin
date_saved: 2026-05-05T11:00:19.091572+00:00
instance: kb-cron
parent: frank-k-schmidlin-20260505-0
summary:
Frank K. Schmidlin (1861-1939) was an Australian X-ray pioneer, that was among the first to utilize the new technology of x-rays for medical applications. In Australia, the medical men of the day took a slow approach in the adoption of the new science that involved x-rays. Many of the early demonstrations were made by investigators outside the medical field. Upon examination of the initial investigators, several key factors were common. The individuals had already either been experimenting along similar lines to Wilhelm Röntgen with Crookes tubes and such, the physicists or scientists, or were actively associated with electrical work, the electricians, which made them particularly receptive to the technical appeal of the new science of x-rays. Records of the events reveal that among the medical men who witnessed the first images produced as radiographs, a rather small number had any great desire to employ X-rays directly in their own medical practice. After the early investigative work of Thomas Ranken Lyle, William Henry Bragg, Joseph Patrick Slattery, and others, almost all medical men were satisfied with soliciting the services of the external X-ray man when necessity arose for skiagraphs to be produced. As the utilization of x-rays became more acceptable, the


id: joseph-patrick-slattery-20260505-0
file: data/en.wikipedia.org/wiki/Joseph_Patrick_Slattery-0.md
category: reference
title: Joseph Patrick Slattery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Joseph_Patrick_Slattery
date_saved: 2026-05-05T11:00:20.272397+00:00
instance: kb-cron
parent: joseph-patrick-slattery-20260505-0
summary:
Joseph Patrick Slattery, CM (21 May 1866 – 31 March 1931) was an Irish-born physicist, radiologist, Catholic priest, pioneer in the field of radiography in Australia and credited with the first use of fluoroscopy in Australia. Born in 1866 in Waterford, Ireland, he traveled to Australia as a deacon in 1888, where he was ordained a priest by Cardinal Moran. As a member of the Vincentian Congregation, he and several of his confreres took over the running of St Stanislaus' at Bathurst from the diocesan clergy. Appointed to the position of professor and taught science, including physics and chemistry. Slattery had a keen interest in the new technology of wireless radio and was the first to install a wireless set west of the Blue Mountains. He was an early pioneer of radio in Australia and found delight in building radio sets. Slattery built an X-ray practice at Bathurst and local doctors benefited greatly from this convenience. He performed mission work for the Vincentian fathers and toured Australia and New Zealand to serve the faithful. Slattery was superior of the Vincentian novitiate at Eastwood. He was appointed vice-rector of St. John's College at the University of Sydney. At Springwood and Manly,


id: john-w-l-spence-20260505-0
file: data/en.wikipedia.org/wiki/John_W._L._Spence-0.md
category: reference
title: John W. L. Spence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/John_W._L._Spence
date_saved: 2026-05-05T11:00:21.436509+00:00
instance: kb-cron
parent: john-w-l-spence-20260505-0
summary:
John Webster Lowson Spence MD LRCP LRCS (11 August 1870 – 15 March 1930) was a Scottish x-ray pioneer and an early victim of radiation poisoning. His name is one of 14 British professionals listed on the Monument to the X-ray and Radium Martyrs of All Nations, which was erected in 1936. In the words of his gravestone: he died that others might live. == Life == He was born in Smyrna in the Ottoman Empire on 11 August 1870 the son of Rev David Brown Spence, a Church of Scotland missionary. He was educated at the Royal High School in Edinburgh. He studied medicine at the University of Edinburgh, and from 1897 studied radiology under, or in correspondence with, Wilhelm Röntgen. He received his doctorate (MD) in 1898. Around 1903 he came to Edinburgh to assist Dawson Turner and William Hope Fowler in their experiments on radiology. In 1907 he became the only radiologist at the Edinburgh Sick Children's Hospital in Sciennes. He was widely respected for his work and kindness. It was common for early radiology pioneers to self-experiment, most commonly on their left arm as the majority of doctors were right-handed. Around 1910 he had several radiation-induced


id: joseph-william-sutton-20260505-0
file: data/en.wikipedia.org/wiki/Joseph_William_Sutton-0.md
category: reference
title: Joseph William Sutton
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Joseph_William_Sutton
date_saved: 2026-05-05T11:00:22.629884+00:00
instance: kb-cron
parent: joseph-william-sutton-20260505-0
summary:
Joseph William Sutton (21 October 1844 – 21 February 1914), identified in the print media as J. W. Sutton, was an Australian engineer, shipbuilder, inventor, pioneer in electric lighting and x-ray pioneer in Queensland. == Life and times == In 1844, Sutton was born in Stepney, London, England. His parents were George Sutton (Shipwright) and Elizabeth Kemmesat. He was christened on 1 December 1844. After Elizabeth's death, the George Sutton with three of his children (Hannah, Henry and Joseph) moved from London and arrived in Sydney 15 October 1852 on board the "Coldstream". (A year later Hannah and Henry were married in the same service 22 December 1853, to Daniel McLauchlan and Jemima Evans respectively at Christ Church St Laurence). Joseph married Mary Hurley (15 September 1847 – 11 July 1926) on 21 October 1869 in Balmain, Sydney. They lived for many years in "Stonehenge" on Bowen Terrace, overlooking the foundry on Kangaroo point. The couple built a home, Hurlton (a name derived from their surnames Hurley and Sutton) in Laurel Avenue, Chelmer in Brisbane. After the death of his widow, Hurlton was purchased in 1928 by William Robert Black, a philanthropist who donated it to the Presbyterian Church for


id: joseph-william-sutton-20260505-1
file: data/en.wikipedia.org/wiki/Joseph_William_Sutton-1.md
category: reference
title: Joseph William Sutton
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Joseph_William_Sutton
date_saved: 2026-05-05T11:00:22.629884+00:00
instance: kb-cron
parent: joseph-william-sutton-20260505-0
summary:
== Kitson Lighting and Heating Company Limited == Joseph William Sutton was a manager and consultant engineer. At the end of 1902 Sutton took an extensive trip to Europe and America for the Kitson Light Co. An article on this trip was written in the Brisbane Courier 17 Jan 1903 entitled "An Australian in England and America" From the Richmond River Express 17 Nov 1903: "On Saturday last Ald. Frost, who has been a consistent advocate for a trial of the Kitson light, for the purposes of, town lighting, was kept busy with the able electrical engineer, Mr. J. Sutton, who was sent from Brisbane by the Kitson Light Co. to instal the lamp at the intersection of Walker and Canterbury streets, in putting up the iron post and fixing the necessary machinery for the production of the light." == Electrical pioneer == On 9 December 1882, at Brisbane Queensland, the public was introduced to electricity by having a demonstration that utilized eight arc lights, erected along Queen Street. The lamps were erected on 20 foot cast iron standards. The power to supply these arc lights was taken from a 10 horsepower Crompton DC generator driven by a Robey steam


id: joseph-william-sutton-20260505-2
file: data/en.wikipedia.org/wiki/Joseph_William_Sutton-2.md
category: reference
title: Joseph William Sutton
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Joseph_William_Sutton
date_saved: 2026-05-05T11:00:22.629884+00:00
instance: kb-cron
parent: joseph-william-sutton-20260505-0
summary:
== Photographic pioneer == Joseph William Sutton was involved in the very beginning of the Queensland Photographic Society: From "The Week" newspaper Brisbane Sat 20 Sept 1884: "PHOTOGRAPHIC SOCIETY.—The newly formed Queensland photographers' society held a meeting on Monday in rooms over Sloss', confectioners, Queen-street. There was a good attendance of members. The following officers were elected for the ensuing year:—President, the Hon A. C. Gregory; vice-presidents, Professor Pepper, and Mr. J. W. Sutton; secretary, Mr. J. R. Hall; committee, Messrs. Rickardo, Lyons, and Service." From the beginning Sutton was often availing his steamers to be used to take members along the Brisbane river for photo shoots, as seen from The Brisbane Courier 17 Feb 1885: "The chairman (Sutton on this occasion) notified his intention of taking the members down the Bay, probably on Saturday next, for the purpose of giving them an opportunity to exhibit their skill in "snapping" pretty glimpses of river scenery." In these early days many of the society meetings were held at the Sutton household: Brisbane Courier 25 Jan 1886. "A MEETING of the Queensland Photographic Society was held on Saturday evening at Mr. J.W. Sutton's house. Mr. Sutton, who is vice-president, took the chair.....


id: joseph-william-sutton-20260505-3
file: data/en.wikipedia.org/wiki/Joseph_William_Sutton-3.md
category: reference
title: Joseph William Sutton
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Joseph_William_Sutton
date_saved: 2026-05-05T11:00:22.629884+00:00
instance: kb-cron
parent: joseph-william-sutton-20260505-0
summary:
== Sugar industry inventor == In 1878, Sutton developed a better method to extract sugar from sugar cane juice."What looks like a decided improvement upon the open air methods hitherto followed to evaporate cane juice has just been patented by Messrs. J. W. Sutton and Co., coppersmiths, Brisbane. Mr. Sutton aims at evaporating juice at a heat of from 120° to 180°. This he does in the open air. He obtains the required temperature by means of a steam coil running around his evaporating pan, which is of the ordinary circular form. This heat will not boil the liquor, of course; that he accomplishes by menus of a perforated pipe or coil coming in at the bottom of the evaporating pan. Through this latter coil, a current of air is forced by a fan blast. The air may either be of atmospheric temperature, or it may be heated, as seems most desirable. In the event of heated air being forced into the liquor, or through it, the air is passed through furnaces in a series of pipes, by which means it becomes highly rarefied, and the temperature is raised at the same time. We have seen the apparatus at work,


id: joseph-william-sutton-20260505-4
file: data/en.wikipedia.org/wiki/Joseph_William_Sutton-4.md
category: reference
title: Joseph William Sutton
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Joseph_William_Sutton
date_saved: 2026-05-05T11:00:22.629884+00:00
instance: kb-cron
parent: joseph-william-sutton-20260505-0
summary:
"Having thus explained the apparatus, Mr. Sutton made several exposures of plates with remarkably good results. One interesting exposure was a collection of various articles, offering various degrees of opacity to the rays. The development of the plates was admirably carried out by Mr. Ferguson under circumstances decidedly unfavourable to such delicate work, with capital results. The exhibition of articles on the fluorescent screen, where the wonderful effects of the X-rays were at once visible, called forth frequent applause. Coins placed in a cigar case were plainly seen, and so were similar articles placed between two-inch thick deal boards, or in the middle of a thick book. Neither the wood nor the paper seemed to offer much resistance to the light. The proceedings were terminated by a hearty vote of thanks to the lecturer and demonstrator." There are many references in the newspapers of the time of Sutton subsequently performing many demonstrations of these invisible rays using himself and other volunteers from his audiences. He later went on to also demonstrate the invisible rays of radium. == Ships built by J. W. Sutton and Company == The following is a partial list of ships built by J. W. Sutton and


id: joseph-william-sutton-20260505-5
file: data/en.wikipedia.org/wiki/Joseph_William_Sutton-5.md
category: reference
title: Joseph William Sutton
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Joseph_William_Sutton
date_saved: 2026-05-05T11:00:22.629884+00:00
instance: kb-cron
parent: joseph-william-sutton-20260505-0
summary:
1880, Essex, iron steamship, 79 gross tons. Length: 91', beam 18'6", draft: 6'3". Built as an unpowered lighter until circa 1888 (engine added) and in 1895 the boiler was added. In April 1903, first registered by William Collin & Sons Ltd, Brisbane. She serviced Maryborough, Queensland. 1882, Iceberg, iron screw steamer, 285 tons and 127 feet long. She was 289 gross registered tons, a refrigerated cargo steamship. 1883, Pearl Steamer for the Sandgate and Woody Point Ferry. See: https://www.flotilla-australia.com/qldothers.htm Archived 2 July 2018 at the Wayback Machine 1883, Mavis, paddle wheel steamer, 47 tons gross measurement, the first steamer to run to Bribie Island. Utilized to convey timber from the Coochin Sawmills to Brisbane, taking back general cargo and supplies for residents in the Bribie district. Built for James Campbell and Sons sawmill. 1883, Redcliffe, Steamer for the Redcliffe and Sandgate Steam Ferry Company. Built June 1883. 1883, Eucalypta, Steamer for Gilbert Burnett, of Cleveland, For carrying timber for his sawmill. Dimensions:— Length, 75 feet; beam, 16 feet and depth of hold, 5 feet. She was propelled by a stern-wheel 11 feet in diameter, driven by a pair of engines of 16 horse-power, fitted with a surface condenser. From "The


id: richard-threlfall-20260505-0
file: data/en.wikipedia.org/wiki/Richard_Threlfall-0.md
category: reference
title: Richard Threlfall
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Richard_Threlfall
date_saved: 2026-05-05T11:00:23.810450+00:00
instance: kb-cron
parent: richard-threlfall-20260505-0
summary:
Sir Richard Threlfall (14 August 1861 – 10 July 1932) was an English chemist and engineer, he established the School of Physics at the University of Sydney and made important contributions to military science during World War I. In 1899, he was elected a fellow of the Royal Society. In 1917, he was created KBE and then GBE in 1927. == Science and consulting career == After the discovery new waves by Heinrich Hertz, Threlfall suggested in a 1890 oral discussion that "Signaling, for instance, might be accomplished secretly by means of a sort of electric ray flasher", thus predicting yet-uninvented radio communications. In July 1915 he invented the 'Threlfallite' hand grenade, consisting of a cylindrical tin containing white phosphorus, paraffin, oil and petrol. Originally designed as an incendiary device to destroy long grass in front of the trenches that gave cover to enemy raiding parties, it also had a useful smoke-producing effect and was used at the Battle of Loos. == Death == Threlfall died on 10 July 1932 and is buried in a family tomb at St Anne's Church, Woodplumpton, Lancashire. He was survived by four sons and two daughters. He was the author of On Laboratory Arts.


id: dawson-turner-radiologist-20260505-0
file: data/en.wikipedia.org/wiki/Dawson_Turner_(radiologist)-0.md
category: reference
title: Dawson Turner (radiologist)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dawson_Turner_(radiologist)
date_saved: 2026-05-05T11:00:24.983568+00:00
instance: kb-cron
parent: dawson-turner-radiologist-20260505-0
summary:
Dawson Fyers Duckworth Turner, FRSE, FRCPE (1857–1928) was a British pioneer of radiology and patron of the arts, who died of radiation related cancer. == Early life == He was born in Liverpool in 1857 the son of Rev Dawson Turner and attended Shrewsbury School in Shropshire. He then studied at Dalhousie University in Nova Scotia, Canada where he graduated BA in 1884. Returning to Britain Turner studied at Edinburgh University where he graduated in medicine (MB CM with honours) in 1888 and attained his MD 1890. He became MRCPE in 1890 and was elected fellow (FRCPE) in 1891. == Early medical career == After serving as resident physician in the Royal Infirmary of Edinburgh under Sir James Affleck he was appointed Lecturer in Physics at the Edinburgh Extramural School of Medicine at Surgeons' Hall, Edinburgh. In addition he acted as clinical tutor in clinical medicine at the Extramural School at Surgeons' Hall. == Radiology career == When X-rays were discovered by Röntgen in 1895 Dawson Turner was one of the first to appreciate their possible application in medicine. He built an early X-ray apparatus in his home at 32 George Square, Edinburgh. On 5 February 1896 he demonstrated X-rays


id: w-watson-and-son-20260505-0
file: data/en.wikipedia.org/wiki/W._Watson_and_Son-0.md
category: reference
title: W. Watson and Son
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/W._Watson_and_Son
date_saved: 2026-05-05T11:00:26.236032+00:00
instance: kb-cron
parent: w-watson-and-son-20260505-0
summary:
W. Watson and Son was an optical instrument maker. In 1837, the William Watson business was established in London for the manufacture of optical instruments. By the 1840s, the company moved into lanterns, slides and associated equipment. In 1868, the name was changed to W. Watson & Son and by this time were located at 313 High Holborn, London. In the 1870s, the company added photographic equipment and became known as a leading manufacturer of the Highest Class Photographic Instruments and Apparatus in England. Into the 1940s, the company remained at 313 High Holborn. == W. Watson and Sons == On 9 January 1881 William Watson died. In 1883, the name of the company was changed to W. Watson & Sons as the son, Charles Henry Watson joined the business. The 1883 Kelly's Business Directory listed both Charles Henry Watson and Henry Watson as associated with the Watson & Sons company located at 23 Walton Street, Aylesbury, England. In 1889, the company participated in the formation of a Photographic Trades Section of the London Chamber of Commerce. In 1894, the company exhibited scientific instruments at the Antwerp Exhibition. In the 1890s, the business continued to grow and advertised in catalogues


id: william-webster-chemical-engineer-20260505-0
file: data/en.wikipedia.org/wiki/William_Webster_(chemical_engineer)-0.md
category: reference
title: William Webster (chemical engineer)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Webster_(chemical_engineer)
date_saved: 2026-05-05T11:00:27.432026+00:00
instance: kb-cron
parent: william-webster-chemical-engineer-20260505-0
summary:
William Webster (1855–1910) was an English chemical engineer credited with developments in gas detection, sewage treatment and medical use of x-rays. A gifted artist and musician, Webster also helped found the Blackheath Concert Halls and the adjacent Conservatoire in Blackheath in south-east London during the 1890s. == Career == Webster was the son of William Webster, a successful building contractor who grew wealthy from constructing major civil engineering and building projects in London. The family lived from 1869 in Wyberton House in Lee Terrace, Blackheath. The younger William Webster trained as a chemical engineer. A fellow of the Chemical Society, he patented a system to detect hydrogenous gases in mines in 1876, and later developed a system for the electrolytic purification of sewage (patent application filed on 22 December 1887; US patent awarded on 19 February 1889), trialled in 1888 at the Crossness Southern Outfall works which had been built by his father's firm in the 1860s. Webster was also a pioneer in x-ray research and a founder member of the Röntgen Society (since 1927 part of the British Institute of Radiology), assisting surgeon Thomas Moore in producing radiographs in 1896, after which Moore set up an x-ray unit at


id: francis-henry-williams-20260505-0
file: data/en.wikipedia.org/wiki/Francis_Henry_Williams-0.md
category: reference
title: Francis Henry Williams
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Francis_Henry_Williams
date_saved: 2026-05-05T11:00:28.558960+00:00
instance: kb-cron
parent: francis-henry-williams-20260505-0
summary:
Francis Henry Williams (15 April 1852–22 June 1936) was an American medical doctor, a pioneer in the field of radiology. == Biography == Williams was born on 15 April 1852, in Uxbridge, Massachusetts. His father was Professor of Ophthalmology at Harvard Medical School. Williams graduated from Massachusetts Institute of Technology in 1873, at the age of twenty-one, then studied medicine at Harvard University, where he obtained his Doctorate in Medicine in 1877. He then spent two years studying in Europe before returning to Boston to practice as a physician. He was awarded the titles of Instructor in Materia Medica and Therapeutics and Assistant Professor of Therapeutics from Harvard Medical School. In 1892, he introduced bacterial examination to Boston City Hospital, and in 1894 was the first physician in the region to neutralize diphtheria with antitoxin. In 1895, Wilhelm Röntgen discovered X-rays ("Röntgen rays"); Williams lost no time in applying this innovation, beginning his use of fluoroscopy in 1896. Williams performed trials of Röntgen's experiments at the MIT laboratories, and conducted research on the diagnostic potential of X-rays for different conditions, including thoracic aneurysm, pericardial effusion, cardiac hypertrophy, pulmonary tuberculosis, and emphysema. He founded what would become the Department of Radiology


id: william-cleaver-woods-20260505-0
file: data/en.wikipedia.org/wiki/William_Cleaver_Woods-0.md
category: reference
title: William Cleaver Woods
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Cleaver_Woods
date_saved: 2026-05-05T11:00:45.169879+00:00
instance: kb-cron
parent: william-cleaver-woods-20260505-0
summary:
William Cleaver Woods, M.B., Ch.M. Edinburgh, M.D. (25 April 1852 – 9 April 1943) was a physician, politician and pioneer of Australian medical science, specialising in X-rays for diagnostic applications and cancer treatments. == Life and times == In 1852, Woods was born in West Derby, Lancashire in England, the son of Richard Woods and Catherine née Cromwell. He was christened on 7 June 1852 in Liverpool, Lancashire, England. At the age of 10, the family moved to Melbourne in Australia and Woods grew up in Ballarat. Woods, a physician from Liverpool, England, married Margaret, née Grieve from New South Wales. The couple travelled to Europe aboard the R.M.S. Oceana for the honeymoon. The Woods had a large family with 9 sons and 2 daughters. The sons included Dr. L.S. Woods from Albury, Dr. John Grieve Woods, also known as the Flying Doctor of Broken Hill, Dr. R.G. Woods from Goulburn, G.C. Woods of Lockhart, and Norman Woods from Sydney. The daughters were Rice from Melbourne and Manning from Albury. Four other sons died prior to his death in 1943. Woods died in 1943 at Sydney, New South Wales, Australia. He was buried at Albury New Cemetery, North Albury, New


id: list-of-unsolved-problems-in-astronomy-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_astronomy-0.md
category: reference
title: List of unsolved problems in astronomy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_astronomy
date_saved: 2026-05-05T11:00:46.788160+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-astronomy-20260505-0
summary:
This article is a list of notable unsolved problems in astronomy. Problems may be theoretical or experimental. Theoretical problems result from inability of current theories to explain observed phenomena or experimental results. Experimental problems result from inability to test or investigate a proposed theory. Other problems involve unique events or occurrences that have not repeated themselves with unclear causes. == Planetary astronomy == === The Solar System === Orbiting bodies and rotation: Are there any non-dwarf planets beyond Neptune? Why do extreme trans-Neptunian objects have elongated orbits? The rotation rate of Saturn: Why does the magnetosphere of Saturn rotate at a rate close to that at which the planet's clouds rotate? What is the rotation rate of Saturn's deep interior? Satellite geomorphology: What is the origin of the chain of high mountains that closely follows the equator of Saturn's moon, Iapetus? Are the mountains the remnant of hot and fast-rotating young Iapetus? Are the mountains the result of material (either from the rings of Saturn or its ring) that over time collected upon the surface? === Extra-solar === How common are Solar System-like planetary systems? (Some observed planetary systems contain Super-Earths and Hot Jupiters that orbit very close to their


id: list-of-unsolved-problems-in-astronomy-20260505-1
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_astronomy-1.md
category: reference
title: List of unsolved problems in astronomy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_astronomy
date_saved: 2026-05-05T11:00:46.788160+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-astronomy-20260505-0
summary:
== Cosmology == Cosmological principle: Is the universe homogeneous and isotropic at sufficiently large scales, as claimed by the cosmological principle and assumed by all models that use the Friedmann–Lemaître–Robertson–Walker (FLRW) metric, including the current version of the ΛCDM model, or is the universe inhomogeneous or anisotropic? Is the CMB dipole purely kinematic, or does it signal anisotropy of the universe, resulting in the breakdown of the FLRW metric and the cosmological principle? Is the Hubble tension evidence that the cosmological principle is false? If the cosmological principle is correct, is the FLRW metric the correct metric describing the universe? Are the observations interpreted as the accelerating expansion of the universe correctly interpreted, or are they instead evidence that the cosmological principle is false? Copernican principle: Are cosmological observations made from Earth representative of observations from the other positions in the universe? Dark matter: What is the identity and composition of dark matter? Is dark matter a particle? If so, is it a WIMP, an axion, the lightest superpartner (LSP), or something else? Do the phenomena attributed to dark matter point to an extension of gravity instead of some other type of matter? Dark energy: What causes the observed accelerating


id: baldwin-effect-astronomy-20260505-0
file: data/en.wikipedia.org/wiki/Baldwin_effect_(astronomy)-0.md
category: reference
title: Baldwin effect (astronomy)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Baldwin_effect_(astronomy)
date_saved: 2026-05-05T11:00:47.961724+00:00
instance: kb-cron
parent: baldwin-effect-astronomy-20260505-0
summary:
The Baldwin effect in astronomy describes a relationship between continuum and emission-line fluxes observed in the electromagnetic spectra of quasars and active galactic nuclei, namely an anticorrelation between the equivalent width, Wλ, of a spectral line and the continuum luminosity, L, in broad UV optical emission lines. This means that the ratio of brightness of the emission line to the brightness of the nearby continuum decreases with increasing luminosity of the continuum. == Discovery and observations == The effect was discovered in observations of high-redshift quasars reported in 1977, and has been commonly named after the discoverer Jack Allen Baldwin, an astronomer at Lick Observatory. It was found that the equivalent width of the broad ultraviolet C IV (λ 1549) emission line, caused by the presence of thrice ionised carbon C3+, decreased with increasing continuum luminosity of the source. For flat-spectrum, radio-loud quasars the relation W λ ∝ L − 2 / 3 {\displaystyle W_{\lambda }\propto L^{-2/3}} was found. The same effect has been observed for other spectral lines such as the Ly-α hydrogen line and the C III] (λ 1909) line of twice ionised carbon. It has also been found for spectral lines in the infrared range, e.g. in


id: blc1-20260505-0
file: data/en.wikipedia.org/wiki/BLC1-0.md
category: reference
title: BLC1
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/BLC1
date_saved: 2026-05-05T11:00:49.157998+00:00
instance: kb-cron
parent: blc1-20260505-0
summary:
BLC1 (Breakthrough Listen Candidate 1) was a candidate SETI radio signal detected and observed during April and May 2019, and first reported on 18 December 2020, spatially coincident with the direction of the Solar System's closest neighboring star, Proxima Centauri. == Signal == The apparent shift in its frequency, consistent with the Doppler effect, was suggested to be inconsistent with what would be caused by the movement of Proxima b, a planet of Proxima Centauri. The Doppler shift in the signal was the opposite of what would be expected from the Earth's spin, in that the signal was observed to increase in frequency rather than decrease. Although the signal was detected by Parkes Radio Telescope during observations of Proxima Centauri, due to the beam angle of Parkes Radio telescope, the signal would be more accurately described as having come from within a circle roughly 16 arcminutes (approximately 1/4 of a degree, half the angular width of Earth's moon) in angular diameter, containing Proxima Centauri, so the signal could have originated elsewhere in the Alpha Centauri system. The signal had a frequency of 982.002 MHz. The radio signal was detected during 30 hours of observations conducted by Breakthrough Listen through the


id: dark-matter-20260505-0
file: data/en.wikipedia.org/wiki/Dark_matter-0.md
category: reference
title: Dark matter
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dark_matter
date_saved: 2026-05-05T11:00:51.613917+00:00
instance: kb-cron
parent: dark-matter-20260505-0
summary:
In astronomy and cosmology, dark matter is an invisible and hypothetical form of matter that does not interact with electromagnetic radiation, including light. Dark matter is implied by gravitational effects that cannot be explained by general relativity unless more matter is present than can be observed. Such effects occur in the context of formation and evolution of galaxies, gravitational lensing, the observable universe's current structure, mass position in galactic collisions, the motion of galaxies within galaxy clusters, and cosmic microwave background anisotropies. Dark matter is thought to serve as gravitational scaffolding for cosmic structures. After the Big Bang, dark matter clumped into blobs along narrow filaments with superclusters of galaxies forming a cosmic web at scales on which entire galaxies appear like tiny particles. In the standard Lambda-CDM model of cosmology, the mass–energy content of the universe is 5% ordinary matter, 26.8% dark matter, and 68.2% a form of energy known as dark energy. Thus, dark matter constitutes 85% of the total mass, while dark energy and dark matter constitute 95% of the total mass–energy content. While the density of dark matter is significant in the halo around a galaxy, its local density in the Solar System is much less


id: dark-matter-20260505-1
file: data/en.wikipedia.org/wiki/Dark_matter-1.md
category: reference
title: Dark matter
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dark_matter
date_saved: 2026-05-05T11:00:51.613917+00:00
instance: kb-cron
parent: dark-matter-20260505-0
summary:
=== 1970s === The hypothesis of dark matter largely took root in the 1970s. Several different observations were synthesized to argue that galaxies should be surrounded by halos of unseen matter. In two papers that appeared in 1974, this conclusion was drawn in tandem by independent groups: in Princeton, New Jersey, by Jeremiah Ostriker, Jim Peebles, and Amos Yahil, and in Tartu, Estonia, by Jaan Einasto, Enn Saar, and Ants Kaasik. One of the observations that served as evidence for the existence of galactic halos of dark matter was the shape of galaxy rotation curves. These observations were done in optical and radio astronomy. In optical astronomy, Vera Rubin and Kent Ford worked with a new spectrograph to measure the velocity curve of edge-on spiral galaxies with greater accuracy. At the same time, radio astronomers were making use of new radio telescopes to map the 21 cm line of atomic hydrogen in nearby galaxies. The radial distribution of interstellar atomic hydrogen (HI) often extends to much greater galactic distances than can be observed as collective starlight, expanding the sampled distances for rotation curves – and thus of the total mass distribution – to a new dynamical regime. Early mapping of


id: dark-matter-20260505-2
file: data/en.wikipedia.org/wiki/Dark_matter-2.md
category: reference
title: Dark matter
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dark_matter
date_saved: 2026-05-05T11:00:51.613917+00:00
instance: kb-cron
parent: dark-matter-20260505-0
summary:
In standard cosmological calculations, "matter" means any constituent of the universe whose energy density scales with the inverse cube of the scale factor, i.e., ρ ∝ a−3 . This is in contrast to "radiation", which scales as the inverse fourth power of the scale factor ρ ∝ a−4 , and a cosmological constant, which does not change with respect to a (ρ ∝ a0). The different scaling factors for matter and radiation are a consequence of radiation redshift. For example, after doubling the diameter of the observable Universe via cosmic expansion, the scale, a, has doubled. The energy of the cosmic microwave background radiation has been halved (because the wavelength of each photon has doubled); the energy of ultra-relativistic particles, such as early-era standard-model neutrinos, is similarly halved. The cosmological constant, as an intrinsic property of space, has a constant energy density regardless of the volume under consideration. In principle, "dark matter" means all components of the universe which are not visible but still obey ρ ∝ a−3 . In practice, the term "dark matter" is often used to mean only the non-baryonic component of dark matter, i.e., excluding "missing baryons". Context will usually indicate which meaning is intended. ==


id: dark-matter-20260505-3
file: data/en.wikipedia.org/wiki/Dark_matter-3.md
category: reference
title: Dark matter
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dark_matter
date_saved: 2026-05-05T11:00:51.613917+00:00
instance: kb-cron
parent: dark-matter-20260505-0
summary:
=== Gravitational lensing === One of the consequences of general relativity is the gravitational lens. Gravitational lensing occurs when massive objects between a source of light and the observer act as a lens to bend light from this source. Lensing does not depend on the properties of the mass; it only requires there to be a mass. The more massive an object, the more lensing is observed. An example is a cluster of galaxies lying between a more distant source such as a quasar and an observer. In this case, the galaxy cluster will lens the quasar. Strong lensing is the observed distortion of background galaxies into arcs when their light passes through such a gravitational lens. It has been observed around many distant clusters including Abell 1689. By measuring the distortion geometry, the mass of the intervening cluster can be obtained. In the weak regime, lensing does not distort background galaxies into arcs, causing minute distortions instead. By examining the apparent shear deformation of the adjacent background galaxies, the mean distribution of dark matter can be characterized. The measured mass-to-light ratios correspond to dark matter densities predicted by other large-scale structure measurements. === Type Ia supernova distance measurements ===


id: dark-matter-20260505-4
file: data/en.wikipedia.org/wiki/Dark_matter-4.md
category: reference
title: Dark matter
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dark_matter
date_saved: 2026-05-05T11:00:51.613917+00:00
instance: kb-cron
parent: dark-matter-20260505-0
summary:
Dark matter can be divided into cold, warm, and hot categories. These categories refer to velocity rather than an actual temperature, and indicate how far corresponding objects moved due to random motions in the early universe, before they slowed due to cosmic expansion. This distance is called the free streaming length. The categories of dark matter are set with respect to the size of the collection of mass prior to structure formation that later collapses to form a dwarf galaxy. This collection of mass is sometimes called a protogalaxy. Dark matter particles are classified as cold, warm, or hot if their free streaming length is much smaller (cold), similar to (warm), or much larger (hot) than the protogalaxy of a dwarf galaxy. Mixtures of the above are also possible: a theory of mixed dark matter was popular in the mid-1990s, but was rejected following the discovery of dark energy. The significance of the free streaming length is that the universe began with some primordial density fluctuations from the Big Bang (in turn arising from quantum fluctuations at the microscale). Particles from overdense regions will naturally spread to underdense regions, but because the universe is expanding quickly, there is a time


id: dark-matter-20260505-5
file: data/en.wikipedia.org/wiki/Dark_matter-5.md
category: reference
title: Dark matter
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dark_matter
date_saved: 2026-05-05T11:00:51.613917+00:00
instance: kb-cron
parent: dark-matter-20260505-0
summary:
There exists no formal definition of a Weakly Interacting Massive Particle (WIMP), but broadly, it is an elementary particle which interacts via gravity and any other force (or forces) which is as weak as or weaker than the weak nuclear force, but also non-vanishing in strength. Many WIMP candidates are expected to have been produced thermally in the early Universe, similarly to the particles of the Standard Model according to Big Bang cosmology, and usually will constitute cold dark matter. Obtaining the correct abundance of dark matter today via thermal production requires a self-annihilation cross section of ⟨ σ v ⟩ {\displaystyle \langle \sigma v\rangle } ≃ 3×10−26 cm3⋅s−1, which is roughly what is expected for a new particle in the 100 GeV/c2 mass range that interacts via the electroweak force. Because supersymmetric extensions of the Standard Model of particle physics readily predict a new particle with these properties, this apparent coincidence has been called the "WIMP miracle", and a stable supersymmetric partner has long been a prime explanation for dark matter. Experimental efforts to detect WIMPs include the search for products of WIMP annihilation, including gamma rays, neutrinos and cosmic rays in nearby galaxies and galaxy clusters; direct detection


id: dark-matter-20260505-6
file: data/en.wikipedia.org/wiki/Dark_matter-6.md
category: reference
title: Dark matter
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dark_matter
date_saved: 2026-05-05T11:00:51.613917+00:00
instance: kb-cron
parent: dark-matter-20260505-0
summary:
Primordial black holes (PBHs) are hypothetical black holes that formed soon after the Big Bang. In the inflationary era and early radiation-dominated universe, extremely dense pockets of subatomic matter may have been tightly packed to the point of gravitational collapse, creating black holes without the supernova compression typically needed to create stellar black holes. The idea was first suggested by Yakov Zeldovich and Igor Dmitriyevich Novikov in 1966, and independently by Stephen Hawking in 1971. Because PBHs would form prior to stellar evolution, they are non-baryonic dark matter candidates and are not limited to the narrow mass range of stellar black holes; they could range from Planck-mass relics to supermassive scales. Interest in PBHs as a primary component of dark matter was revived following the 2015 discovery of gravitational waves by LIGO. Their first detected merger involved black holes of approximately 30 solar masses; such objects are difficult to explain via standard stellar collapse but fit the predicted mass range for PBHs formed during the QCD transition in the early universe. This interest was bolstered in November 2025, when the LIGO/Virgo/KAGRA collaboration reported a candidate gravitational wave signal from a sub-solar mass merger. As no astrophysical process is known to


id: dark-matter-20260505-7
file: data/en.wikipedia.org/wiki/Dark_matter-7.md
category: reference
title: Dark matter
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dark_matter
date_saved: 2026-05-05T11:00:51.613917+00:00
instance: kb-cron
parent: dark-matter-20260505-0
summary:
Direct detection experiments aim to observe interactions between dark matter particles passing through the Earth and ordinary matter detector targets. For Weakly interacting massive particles (WIMPs), the primary signature is a low-energy recoil of nuclei (typically a few keV), which induces energy in the form of scintillation light, ionization, or phonons (heat). For axions, experiments typically search for the conversion of axions into photons within a strong magnetic field (the Primakoff effect). To detect these rare events effectively, it is crucial to maintain an extremely low background, which is why such experiments typically operate deep underground where interference from cosmic rays is minimized. Major underground laboratories hosting these experiments include SNOLAB (Canada), LNGS (Italy), CJPL (China), and the SURF (USA). ==== WIMPs ==== WIMP searches mostly use either cryogenic or noble liquid detector technologies. Cryogenic detectors, operating at temperatures below 100 mK, detect the heat produced when a particle hits an atom in a crystal absorber such as germanium. Experiments using this technology include SuperCDMS and EDELWEISS. Noble liquid detectors detect scintillation and ionization produced by a particle collision in liquid xenon or argon. This technology has led the field in sensitivity for the last decade. Major current experiments include


id: dark-matter-20260505-8
file: data/en.wikipedia.org/wiki/Dark_matter-8.md
category: reference
title: Dark matter
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dark_matter
date_saved: 2026-05-05T11:00:51.613917+00:00
instance: kb-cron
parent: dark-matter-20260505-0
summary:
Stellar heating: If dark matter particles capture inside dense stars like neutron stars or white dwarfs, they can deposit kinetic energy during the capture process or through subsequent annihilation. This mechanism, known as "dark kinetic heating", would maintain the star at a temperature higher than expected for its age, potentially arresting its cooling indefinitely. The observation of old, "cold" neutron stars therefore places stringent limits on the scattering cross-section of dark matter particles with nucleons, as any significant interaction would have kept these stars hotter than observed. Stellar cooling: New light particles, such as axions, could be produced in the hot cores of stars and escape freely, carrying away energy. This additional energy loss channel would alter the evolution of stars, cooling them faster than standard models predict. Comparisons of observed red giant branch tips and white dwarf cooling curves with theoretical models have set some of the strongest constraints on the coupling of axions to electrons and photons. Black hole superradiance: Ultralight bosons, such as axions or dark photons, can extract rotational energy from spinning black holes through a process called superradiance. If the boson's Compton wavelength is comparable to the black hole's event horizon size, the particles form


id: dark-matter-20260505-9
file: data/en.wikipedia.org/wiki/Dark_matter-9.md
category: reference
title: Dark matter
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dark_matter
date_saved: 2026-05-05T11:00:51.613917+00:00
instance: kb-cron
parent: dark-matter-20260505-0
summary:
=== Non-mainstream and less established particle, field, and structure theories === While WIMPs, axions, and primordial black holes remain the primary candidates for dark matter, numerous other theories have been proposed to address specific observational anomalies or theoretical motivations. These alternative models often explore mass ranges and interaction strengths outside the standard parameter space, ranging from ultra-light scalar fields to massive composite states. Some hypotheses posit the existence of complex "dark sectors" with their own fundamental forces, while others suggest that dark matter may be unstable, dynamical, or composed of mirror particles. The following list encompasses these less established but theoretically motivated candidates and frameworks. Chameleon particle – Hypothetical scalar particle that couples to matter more weakly than gravity Dark galaxy – Hypothesized galaxy with no, or very few, stars Dark radiation – Postulated type of radiation that mediates interactions of dark matter Density wave theory – A theory in which waves of compressed gas, which move slower than the galaxy, maintain galaxies' structure Dynamical dark matter Exotic matter – Physics term for multiple concepts Feebly interacting particles Light dark matter – Dark matter weakly interacting massive particles candidates with masses less than 1 GeV Mirror matter – Hypothetical counterpart


id: diffuse-extragalactic-background-radiation-20260505-0
file: data/en.wikipedia.org/wiki/Diffuse_extragalactic_background_radiation-0.md
category: reference
title: Diffuse extragalactic background radiation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Diffuse_extragalactic_background_radiation
date_saved: 2026-05-05T11:00:52.808378+00:00
instance: kb-cron
parent: diffuse-extragalactic-background-radiation-20260505-0
summary:
The diffuse extragalactic background radiation (DEBRA) refers to the photon field of extragalactic origin that fills our Universe. It contains photons whose energies span more than twenty orders of magnitude, from 10−7 eV to more than 100 GeV. This range covers everything from the microwaves emitted by free hydrogen atoms to ultra high-energy gamma rays, which can only be emitted by the most powerful physical processes in the modern universe such as kilonovas and merging black holes. The origin and the physical processes involved are different within every wavelength range. There is plenty of observational evidence that support the existence of the DEBRA. The figure shows a schematic picture, based on many different data sets, of the spectral intensity (also called spectral radiance) multiplied by wavelength of the DEBRA over all the electromagnetic spectrum. This representation is convenient because the area inside the curve is the energy. The nature and history of the universe is coded in this radiation field and any realistic cosmological model must be able to describe it. Understanding the DEBRA is a major challenge of modern cosmology with huge consequences in other fields of astrophysics, therefore extraordinary efforts are being put by theoreticians, observers, and instrumentalists


id: diffuse-interstellar-bands-20260505-0
file: data/en.wikipedia.org/wiki/Diffuse_interstellar_bands-0.md
category: reference
title: Diffuse interstellar bands
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Diffuse_interstellar_bands
date_saved: 2026-05-05T11:00:53.979505+00:00
instance: kb-cron
parent: diffuse-interstellar-bands-20260505-0
summary:
Diffuse interstellar bands (DIBs) are absorption features seen in the spectra of astronomical objects in the Milky Way and other galaxies. They are caused by the absorption of light by the interstellar medium. Circa 500 bands have now been seen, in ultraviolet, visible and infrared wavelengths. The origin of most DIBs remains unknown, with common suggestions being polycyclic aromatic hydrocarbons and other large carbon-bearing molecules. Only one DIB carrier has been identified: ionised buckminsterfullerene (C60+), which is responsible for several DIBs in the near-infrared. The carriers of most DIBs remain unidentified. == Discovery and history == Much astronomical work relies on the study of spectra - the light from astronomical objects dispersed using a prism or, more usually, a diffraction grating. A typical stellar spectrum will consist of a continuum, containing absorption lines, each of which is attributed to a particular atomic energy level transition in the atmosphere of the star. The appearances of all astronomical objects are affected by extinction, the absorption and scattering of photons by the interstellar medium. Relevant to DIBs is interstellar absorption, which predominantly affects the whole spectrum in a continuous way, rather than causing absorption lines. In 1922, though, astronomer Mary Lea Heger first


id: disrupted-planet-20260505-0
file: data/en.wikipedia.org/wiki/Disrupted_planet-0.md
category: reference
title: Disrupted planet
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Disrupted_planet
date_saved: 2026-05-05T11:00:55.190430+00:00
instance: kb-cron
parent: disrupted-planet-20260505-0
summary:
In astronomy, a disrupted planet is a planet or exoplanet or, perhaps on a somewhat smaller scale, a planetary-mass object, planetesimal, moon, exomoon or asteroid that has been disrupted or destroyed by a nearby or passing astronomical body or object such as a star. Necroplanetology is the related study of such a process. The result of such a disruption may be the production of excessive amounts of related gas, dust and debris, which may eventually surround the parent star in the form of a circumstellar disk or debris disk. As a consequence, the orbiting debris field may be an "uneven ring of dust", causing erratic light fluctuations in the apparent luminosity of the parent star, as may have been responsible for the oddly flickering light curves associated with the starlight observed from certain variable stars, such as that from Tabby's Star (KIC 8462852), RZ Piscium and WD 1145+017. Excessive amounts of infrared radiation may be detected from such stars, suggestive evidence in itself that dust and debris may be orbiting the stars. == Examples == === Planets === Examples of planets, or their related remnants, considered to have been a disrupted planet, or part of such a planet, include: ‘Oumuamua


id: epic-204376071-20260505-0
file: data/en.wikipedia.org/wiki/EPIC_204376071-0.md
category: reference
title: EPIC 204376071
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/EPIC_204376071
date_saved: 2026-05-05T11:00:56.346030+00:00
instance: kb-cron
parent: epic-204376071-20260505-0
summary:
EPIC 204376071 is an M-type star in the constellation of Scorpius. Parallax measurements by the Gaia space observatory put the star at a distance of about 440 light-years (130 parsecs) from Earth. It is likely a member of the Upper Sco association, and is young enough that it has not yet become a main-sequence star. Unusual light fluctuations of the star, including up to an 80% dimming in brightness (i.e., "single 80% deep occultation of 1-day duration"), were observed by astronomers. The unusual dimming was not only extremely deep, but also substantially asymmetric, with an egress about twice as long as the ingress. Nonetheless, such an unusual dimming for EPIC 204376071 is much greater than the 22% dimming observed for Tabby's star. Several explanations have been presented to explain the unusual dimming of the EPIC 204376071 star: one, orbiting dust or small particles; or two, a "transient accretion event of dusty material near the corotation radius of the star". The unusual light curve of the star is similar to the light curve of a candidate exoplanet, KIC 10403228 b, which may have been caused by a "tilted ring system" orbiting the planet. In the case of EPIC 204376071, an orbiting


id: faint-young-sun-paradox-20260505-0
file: data/en.wikipedia.org/wiki/Faint_young_Sun_paradox-0.md
category: reference
title: Faint young Sun paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Faint_young_Sun_paradox
date_saved: 2026-05-05T11:00:58.880444+00:00
instance: kb-cron
parent: faint-young-sun-paradox-20260505-0
summary:
The faint young Sun paradox or faint young Sun problem describes the apparent contradiction between observations of liquid water early in Earth's history and the astrophysical expectation that the Sun's output would have been only 70 percent as intense during that epoch as it is during the modern epoch. The paradox is this: with the young Sun's output at only 70 percent of its current output, early Earth would be expected to be completely frozen, but early Earth seems to have had liquid water and supported life. The issue was raised by astronomers Carl Sagan and George Mullen in 1972. Proposed resolutions of this paradox have taken into account greenhouse effects, changes to planetary albedo, astrophysical influences, or combinations of these suggestions. The predominant theory is that the greenhouse gas carbon dioxide contributed most to the warming of the Earth. == Solar evolution == Models of stellar structure, especially the standard solar model predict a brightening of the Sun. The brightening is caused by a decrease in the number of particles per unit mass due to nuclear fusion in the Sun's core, from four protons and electrons each to one helium nucleus and two electrons. Fewer particles would exert less


id: faint-young-sun-paradox-20260505-1
file: data/en.wikipedia.org/wiki/Faint_young_Sun_paradox-1.md
category: reference
title: Faint young Sun paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Faint_young_Sun_paradox
date_saved: 2026-05-05T11:00:58.880444+00:00
instance: kb-cron
parent: faint-young-sun-paradox-20260505-0
summary:
=== Cosmic rays === A minority view propounded by the Israeli-American physicist Nir Shaviv uses climatological influences of solar wind combined with a hypothesis of Danish physicist Henrik Svensmark for a cooling effect of cosmic rays. According to Shaviv, the early Sun had emitted a stronger solar wind that produced a protective effect against cosmic rays. In that early age, a moderate greenhouse effect comparable to today's would have been sufficient to explain a largely ice-free Earth. Evidence for a more active early Sun has been found in meteorites. The temperature minimum around 2.4 Ga goes along with a cosmic ray flux modulation by a variable star formation rate in the Milky Way. The reduced solar impact later results in a stronger impact of cosmic ray flux, which is hypothesized to lead to a relationship with climatological variations. === Mass loss from Sun === It has been proposed several times that mass loss from the faint young Sun in the form of stronger solar winds could have compensated for the low temperatures from greenhouse gas forcing. In this framework, the early Sun underwent an extended period of higher solar wind output. Based on exoplanetary data, this caused a mass loss


id: faint-young-sun-paradox-20260505-2
file: data/en.wikipedia.org/wiki/Faint_young_Sun_paradox-2.md
category: reference
title: Faint young Sun paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Faint_young_Sun_paradox
date_saved: 2026-05-05T11:00:58.880444+00:00
instance: kb-cron
parent: faint-young-sun-paradox-20260505-0
summary:
=== Mars === Mars has its own version of the faint young Sun paradox. Martian terrains show clear signs of past liquid water on the surface, including outflow channels, gullies, modified craters, and valley networks. These geomorphic features suggest Mars had an ocean on its surface and river networks that resemble current Earth's during the late Noachian (4.1–3.7 Ga). It is unclear how Mars's orbital pattern, which places it even further from the Sun, and the faintness of the young Sun could have produced what is thought to have been a very warm and wet climate on Mars. Scientists debate over which geomorphological features can be attributed to shorelines or other water flow markers and which can be ascribed to other mechanisms. Nevertheless, the geologic evidence, including observations of widespread fluvial erosion in the southern highlands, are generally consistent with an early warm and semi-arid climate. Given the orbital and solar conditions of early Mars, a greenhouse effect would have been necessary to increase surface temperatures at least 65 K in order for these surface features to have been carved by flowing water. A much denser, CO2-dominated atmosphere has been proposed as a way to produce such a temperature increase.


id: fast-blue-optical-transient-20260505-0
file: data/en.wikipedia.org/wiki/Fast_blue_optical_transient-0.md
category: reference
title: Fast blue optical transient
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fast_blue_optical_transient
date_saved: 2026-05-05T11:01:00.126530+00:00
instance: kb-cron
parent: fast-blue-optical-transient-20260505-0
summary:
In astronomy, a fast blue optical transient (FBOT), or more specifically, luminous fast blue optical transient (LFBOT), is an explosive transient event similar to supernovae and gamma-ray bursts with high optical luminosity, rapid evolution, and predominantly blue emission. The origins of such explosions are currently unclear, with events occurring at not more than 0.1% of the typical core-collapse supernova rate. This class of transients initially emerged from large sky surveys at cosmological distances, yet in recent years a small number have been discovered in the local Universe, most notably AT 2018cow. The precise definition of what constitutes a 'fast blue optical transient' is currently contentious in the literature, largely defined by the observational properties rather than the underlying mechanisms/objects. Even within the class, growing samples of candidates are beginning to reveal significant variation in properties when the objects are studied in greater detail, potentially indicative of different progenitor channels or explosion mechanisms. == List == == See also == Gamma-ray burst Intermediate luminosity optical transient Supernova == References == == External links == Video (29:36) – Fast optical transients on YouTube (2016; Harvard University)


id: fast-radio-burst-20260505-0
file: data/en.wikipedia.org/wiki/Fast_radio_burst-0.md
category: reference
title: Fast radio burst
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fast_radio_burst
date_saved: 2026-05-05T11:01:01.319119+00:00
instance: kb-cron
parent: fast-radio-burst-20260505-0
summary:
In radio astronomy, a fast radio burst (FRB) is a transient radio wave of duration ranging from a fraction of a millisecond, for an ultra-fast radio burst, to 3 seconds, caused by a high-energy astrophysical process that is not yet understood. Astronomers estimate the average FRB releases as much energy in a millisecond as the Sun puts out in three days. While extremely energetic at their source, the strength of the signal reaching Earth has been described as 1,000 times less than from a mobile phone on the Moon. The first FRB was discovered by Duncan Lorimer and his student David Narkevic in 2007 when they were looking through archival pulsar survey data, and it is therefore commonly referred to as the Lorimer burst. Many FRBs have since been recorded, including several that have been detected repeating in seemingly irregular ways. Only one FRB has been detected to repeat in a regular way: FRB 180916 seems to pulse every 16.35 days. Most FRBs are extragalactic, but the first Milky Way FRB was detected by the CHIME radio telescope in April 2020. In June 2021, astronomers reported over 500 FRBs from outer space detected in one year. When FRBs are polarized,


id: fast-radio-burst-20260505-1
file: data/en.wikipedia.org/wiki/Fast_radio_burst-1.md
category: reference
title: Fast radio burst
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fast_radio_burst
date_saved: 2026-05-05T11:01:01.319119+00:00
instance: kb-cron
parent: fast-radio-burst-20260505-0
summary:
=== Extragalactic origin === The interferometer UTMOST has put a lower limit of 10,000 kilometers for the distance to the FRBs it has detected, supporting the case for an astronomical, rather than terrestrial, origin (because signal sources on Earth are ruled out as being closer than this limit). This limit can be determined from the fact that closer sources would have a curved wave front that could be detected by the multiple antennas of the interferometer. Fast radio bursts have pulse dispersion measurements > 100 pc cm−3, much larger than expected for a source inside the Milky Way galaxy and consistent with propagation through an ionized plasma. Furthermore, their distribution is isotropic (not especially coming from the galactic plane); consequently they are conjectured to be of extragalactic origin. == Origin hypotheses == Because of the isolated nature of the observed phenomenon, the nature of the source remains speculative. As of 2022, there is no generally accepted single explanation, although a magnetar has been identified as a possible source. The sources are thought to be a few hundred kilometers or less in size, as the bursts last for only a few milliseconds. Causation is limited by the speed of light, about


id: fast-radio-burst-20260505-2
file: data/en.wikipedia.org/wiki/Fast_radio_burst-2.md
category: reference
title: Fast radio burst
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fast_radio_burst
date_saved: 2026-05-05T11:01:01.319119+00:00
instance: kb-cron
parent: fast-radio-burst-20260505-0
summary:
=== Hypotheses for repeating FRBs === Repeated bursts of FRB 121102 have initiated multiple origin hypotheses. A coherent emission phenomenon known as superradiance, which involves large-scale entangled quantum mechanical states possibly arising in environments such as active galactic nuclei, has been proposed to explain these and other associated observations with FRBs (e.g. high event rate, repeatability, variable intensity profiles). In July 2019, astronomers reported that non-repeating Fast Radio Bursts may not be one-off events, but actually FRB repeaters with repeat events that have gone undetected and, further, that FRBs may be formed by events that have not yet been seen or considered. Additional possibilities include that FRBs may originate from nearby stellar flares. A FRB with multiple periodic component peaks lasting over 3 seconds was reported in 2022. A neutron star has been proposed as the origin of this FRB. == Bursts observed == === Naming === Fast radio bursts are named by the date the signal was recorded, as "FRB YYMMDD", with a letter appended to distinguish multiple sources first recorded on the same date. The name is of the presumed source rather than the burst of radio waves, so repeated or subsequent bursts from the same apparent location


id: fast-radio-burst-20260505-3
file: data/en.wikipedia.org/wiki/Fast_radio_burst-3.md
category: reference
title: Fast radio burst
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fast_radio_burst
date_saved: 2026-05-05T11:01:01.319119+00:00
instance: kb-cron
parent: fast-radio-burst-20260505-0
summary:
An observation in 2012 of a fast radio burst (FRB 121102) in the direction of Auriga in the northern hemisphere using the Arecibo radio telescope confirmed the extragalactic origin of fast radio pulses by an effect known as plasma dispersion. In November 2015, astronomer Paul Scholz at McGill University in Canada, found ten non-periodically repeated fast radio pulses in archival data gathered in May and June 2015 by the Arecibo radio telescope. The ten bursts have dispersion measures and sky positions consistent with the original burst FRB 121102, detected in 2012. Like the 2012 burst, the 10 bursts have a plasma dispersion measure that is three times larger than possible for a source in the Milky Way Galaxy. The team thinks that this finding rules out self-destructive, cataclysmic events that could occur only once, such as the collision between two neutron stars. According to the scientists, the data support an origin in a young rotating neutron star (pulsar), or in a highly magnetized neutron star (magnetar), or from highly magnetized pulsars travelling through asteroid belts, or from an intermittent Roche lobe overflow in a neutron star-white dwarf binary. On 16 December 2016 six new FRBs were reported in the same


id: fast-radio-burst-20260505-4
file: data/en.wikipedia.org/wiki/Fast_radio_burst-4.md
category: reference
title: Fast radio burst
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fast_radio_burst
date_saved: 2026-05-05T11:01:01.319119+00:00
instance: kb-cron
parent: fast-radio-burst-20260505-0
summary:
=== 2017 === The upgraded Molonglo Observatory Synthesis Telescope (UTMOST), near Canberra (Australia), reported finding three more FRBs. A 180-day three-part survey in 2015 and 2016 found three FRBs at 843 MHz. Each FRB located with a narrow elliptical 'beam'; the relatively narrow band 828–858 MHz gives a less precise dispersion measure (DM). A short survey using part of Australian Square Kilometre Array Pathfinder (ASKAP) found one FRB in 3.4 days. FRB170107 was bright with a fluence of 58±6 Jy ms. According to Anastasia Fialkov and Abraham Loeb, FRB's could be occurring as often as once per second. Earlier research could not identify the occurrence of FRB's to this degree. === 2018 === Three FRBs were reported in March 2018 by Parkes Observatory in Australia. One (FRB 180309) had the highest signal-to-noise ratio yet seen of 411. The unusual CHIME (Canadian Hydrogen Intensity Mapping Experiment) radio telescope, operational from September 2018, can be used to detect "hundreds" of fast radio bursts as a secondary objective to its cosmological observations. FRB 180725A was reported by CHIME as the first detection of a FRB under 700 MHz – as low as 580 MHz. In October 2018, astronomers reported 19 more new non-repeating


id: fast-radio-burst-20260505-5
file: data/en.wikipedia.org/wiki/Fast_radio_burst-5.md
category: reference
title: Fast radio burst
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fast_radio_burst
date_saved: 2026-05-05T11:01:01.319119+00:00
instance: kb-cron
parent: fast-radio-burst-20260505-0
summary:
==== FRB 191228 ==== On 31 December 2019, Australian astronomers, using the Australian Square Kilometre Array Pathfinder (ASKAP), reported the detection of FRB 191228 in the Piscis Austrinus constellation (RA = 22:57(2), DEC = -29:46(40)). === 2020 === ==== FRB 200120E ==== In February & March 2022, astronomers reported that a globular cluster of M81, a grand design spiral galaxy about 12 million light-years away, may be the source of FRB 20200120E, a repeating fast radio burst. ==== FRB 200317 ==== Astronomers reported the discovery of FRB 20200317A (RA 16h22m45s, DEC p+56d44m50s) with FAST (Five-hundred-meter Aperture Spherical radio Telescope) in archival data on 22 September 2023. The detected FRB is "one of the faintest FRB sources detected so far", according to the report. ==== FRB 200428 ==== On 28 April 2020, astronomers at the Canadian Hydrogen Intensity Mapping Experiment (CHIME), reported the detection of a bright radio burst from the direction of the Galactic magnetar SGR 1935+2154 about 30,000 light years away in the Vulpecula constellation. The burst had a DM of 332.8 pc/cc. The STARE2 team independently detected the burst and reported that the burst had a fluence of >1.5 MJy ms, establishing the connection between this burst and


id: fast-radio-burst-20260505-6
file: data/en.wikipedia.org/wiki/Fast_radio_burst-6.md
category: reference
title: Fast radio burst
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fast_radio_burst
date_saved: 2026-05-05T11:01:01.319119+00:00
instance: kb-cron
parent: fast-radio-burst-20260505-0
summary:
==== FRB 220912 ==== On 15 October 2022, astronomers at CHIME/FRB reported the detection of nine bursts in three days of FRB 20220912A. Since later bursts observed between 15 October 2022 and 29 October 2022 by the CHIME/FRB collaboration, astronomers, afterwards, at the Allen Telescope Array (ATA), on 1 November 2022, reported eight more bursts from FRB 20220912A. ATA coordinates were first set to the original settings (23h09m05.49s + 48d42m25.6s) and then later to the newly updated ones (23h09m04.9s +48d42m25.4s). On 13 November 2022, further burst activity of FRB 20220912A was reported by the Tianlai Dish Pathfinder Array in Xinjiang, China and, on 5 December 2022, from several other observatories. On 13 December 2022, over a hundred bursts from FRB 220912A were reported by the Upgraded Giant Metrewave Radio Telescope (uGMRT), operated by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research in India. On 21 December 2022, several more bright bursts of FRB 220912A using the Westerbork-RT1 were reported. Four more bursts were reported on 13 July 2023 by the Medicina Radio Observatory (specifically by the Medicina Northern Cross (MNC) radio telescope) in Bologna, Italy. Based on four bursts, burst rate constraints of FRB 20220912A


id: fermi-paradox-20260505-0
file: data/en.wikipedia.org/wiki/Fermi_paradox-0.md
category: reference
title: Fermi paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fermi_paradox
date_saved: 2026-05-05T11:01:02.535314+00:00
instance: kb-cron
parent: fermi-paradox-20260505-0
summary:
The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence. In simple terms, the Fermi paradox asks why, given the vast number of stars and potentially habitable planets in our observable universe, there is no clear evidence of extraterrestrial civilizations. The paradox is named after physicist Enrico Fermi, who informally posed the question—remembered by Emil Konopinski as "But where is everybody?"—during a 1950 conversation at Los Alamos with colleagues Konopinski, Edward Teller, and Herbert York. The paradox first appeared in print in a 1963 paper by Carl Sagan and the paradox has since been fully characterized by scientists. Early formulations of the paradox have also been identified in writings by Bernard Le Bovier de Fontenelle (1686) and Jules Verne (1865), and by Soviet rocket scientist Konstantin Tsiolkovsky (1933). There have been many attempts to resolve the Fermi paradox, such as suggesting that intelligent extraterrestrial beings are extremely rare, that the lifetime of such civilizations is short, or that they exist but (for various reasons) humans see no evidence. == Chain of reasoning == Some of the facts and hypotheses that together serve to highlight the apparent


id: fermi-paradox-20260505-1
file: data/en.wikipedia.org/wiki/Fermi_paradox-1.md
category: reference
title: Fermi paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fermi_paradox
date_saved: 2026-05-05T11:01:02.535314+00:00
instance: kb-cron
parent: fermi-paradox-20260505-0
summary:
The Fermi question first appeared in print in a footnote of a 1963 paper by Carl Sagan. Two years later, Stephen Dole noted the dilemma at a symposium—"If there are so many advanced forms of life around, where is everybody?"—but did not attribute it to Fermi. A chapter of Intelligent Life in the Universe, co-authored by Sagan and Iosif Shklovsky, was headlined with the Fermi-attributed "Where are they?" The Fermi question also appeared in NASA's 1970 Project Cyclops report, a 1973 book by Sagan, and a 1975 article in JBIS Interstellar Studies by David Viewing that first described it as a paradox. Later that year, Michael Hart published a detailed examination of the paradox in the Quarterly Journal of the Royal Astronomical Society. Hart, who concluded that "we are the first civilization in our Galaxy", proposed four broad categories of solutions to the paradox: those that are physical (a space travel limitation), sociological (aliens choose not to visit Earth), temporal (aliens have not had time to travel to Earth), or that extraterrestrials have already visited. His paper sparked significant interest in the paradox among academics and even politicians, with a discussion held in the House of Lords. A seminal response—"Extraterrestrial


id: fermi-paradox-20260505-2
file: data/en.wikipedia.org/wiki/Fermi_paradox-2.md
category: reference
title: Fermi paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fermi_paradox
date_saved: 2026-05-05T11:01:02.535314+00:00
instance: kb-cron
parent: fermi-paradox-20260505-0
summary:
N = R ∗ ⋅ f p ⋅ n e ⋅ f l ⋅ f i ⋅ f c ⋅ L , {\displaystyle N=R_{*}\cdot f_{\mathrm {p} }\cdot n_{\mathrm {e} }\cdot f_{\mathrm {l} }\cdot f_{\mathrm {i} }\cdot f_{\mathrm {c} }\cdot L,} where N {\displaystyle N} is the number of technologically advanced civilizations in the Milky Way galaxy, and N {\displaystyle N} is asserted to be the product of R ∗ {\displaystyle R_{*}} , the rate of formation of stars in the galaxy; f p {\displaystyle f_{p}} , the fraction of those stars with planetary systems; n e {\displaystyle n_{e}} , the number of planets, per solar system, with an environment suitable for organic life; f l {\displaystyle f_{l}} , the fraction of those suitable planets whereon organic life appears; f i {\displaystyle f_{i}} , the fraction of life-bearing planets whereon intelligent life appears; f c {\displaystyle f_{c}} , the fraction of civilizations that reach the technological level whereby detectable signals may be dispatched; and L {\displaystyle L} , the length of time that those civilizations dispatch their signals. The fundamental problem is that the last four terms ( f l {\displaystyle f_{l}} , f i {\displaystyle f_{i}} , f c {\displaystyle


id: fermi-paradox-20260505-3
file: data/en.wikipedia.org/wiki/Fermi_paradox-3.md
category: reference
title: Fermi paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fermi_paradox
date_saved: 2026-05-05T11:01:02.535314+00:00
instance: kb-cron
parent: fermi-paradox-20260505-0
summary:
=== Anthropics === Anthropic reasoning and the question of why we happen to find ourselves as humans creates a number of potential problems for astrobiology. Walter Barta argues that Hanson's grabby aliens model creates an anthropic dilemma. According to Hanson's model, most observers in our reference class should be grabby aliens themselves. This leads to the question of why we do not find ourselves as grabby aliens, but rather as a species confined to a single planet. == Empirical evidence == There are two parts of the Fermi paradox that rely on empirical evidence—that there are many potentially habitable planets, and that humans see no evidence of life. The first point, that many suitable planets exist, was an assumption in Fermi's time, but is since supported by the discovery that exoplanets are common. Existing models predict billions of habitable worlds in the Milky Way. The second part of the paradox, that humans see no evidence of extraterrestrial life, is also an active field of scientific research. This includes both efforts to find any indication of life, and efforts specifically directed to finding intelligent life. These searches have been made since 1960, and several are ongoing. Although astronomers do not usually


id: fermi-paradox-20260505-4
file: data/en.wikipedia.org/wiki/Fermi_paradox-4.md
category: reference
title: Fermi paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fermi_paradox
date_saved: 2026-05-05T11:01:02.535314+00:00
instance: kb-cron
parent: fermi-paradox-20260505-0
summary:
In 1959, Freeman Dyson observed that every developing human civilization constantly increases its energy consumption, and he conjectured that a civilization might try to harness a large part of the energy produced by a star. He proposed a hypothetical "Dyson sphere" as a means: a shell or cloud of objects enclosing a star to absorb and utilize as much radiant energy as possible. Such a feat of astroengineering would drastically alter the observed spectrum of the star involved, changing it at least partly from the normal emission lines of a natural stellar atmosphere to those of black-body radiation, probably with a peak in the infrared. Dyson speculated that advanced alien civilizations might be detected by examining the spectra of stars and searching for such an altered spectrum. There have been attempts to find evidence of Dyson spheres that would alter the spectra of their core stars. Direct observation of thousands of galaxies has shown no explicit evidence of artificial construction or modifications. In October 2015, there was speculation that a dimming of light from star KIC 8462852, observed by the Kepler space telescope, could have been a result of such a Dyson sphere under construction. However, in 2018, further observations


id: fermi-paradox-20260505-5
file: data/en.wikipedia.org/wiki/Fermi_paradox-5.md
category: reference
title: Fermi paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fermi_paradox
date_saved: 2026-05-05T11:01:02.535314+00:00
instance: kb-cron
parent: fermi-paradox-20260505-0
summary:
New life might commonly die out due to runaway heating or cooling on their fledgling planets. On Earth, there have been numerous major extinction events that destroyed the majority of complex species alive at the time; the extinction of the non-avian dinosaurs is the best known example. These are thought to have been caused by events such as impact from a large asteroid, massive volcanic eruptions, or astronomical events such as gamma-ray bursts. It may be the case that such extinction events are common throughout the universe and periodically destroy intelligent life, or at least its civilizations, before the species is able to develop the technology to communicate with other intelligent species. However, the chances of extinction by natural events may be very low on the scale of a civilization's lifetime. Based on an analysis of impact craters on Earth and the Moon, the average interval between impacts large enough to cause global consequences (like the Chicxulub impact) is estimated to be around 100 million years. === Evolutionary explanations === ==== It is the nature of intelligent life to destroy itself ==== This is the argument that technological civilizations may usually or invariably destroy themselves before or shortly after developing


id: fermi-paradox-20260505-6
file: data/en.wikipedia.org/wiki/Fermi_paradox-6.md
category: reference
title: Fermi paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fermi_paradox
date_saved: 2026-05-05T11:01:02.535314+00:00
instance: kb-cron
parent: fermi-paradox-20260505-0
summary:
Another hypothesis is that an intelligent species beyond a certain point of technological capability will destroy other intelligent species as they appear, perhaps by using self-replicating probes. Science fiction writer Fred Saberhagen has explored this idea in his Berserker series, as has physicist Gregory Benford and also, science fiction writer Greg Bear in his The Forge of God novel, and later Liu Cixin in his The Three-Body Problem series. A species might undertake such extermination out of expansionist motives, greed, paranoia, or aggression. In 1981, cosmologist Edward Harrison argued that such behavior would be an act of prudence: an intelligent species that has overcome its own self-destructive tendencies might view any other species bent on galactic expansion as a threat. It has also been suggested that a successful alien species would be a superpredator, as are humans. Another possibility invokes the "tragedy of the commons" and the anthropic principle: the first lifeform to achieve interstellar travel will necessarily (even if unintentionally) prevent competitors from arising, and humans simply happen to be first. ==== Civilizations only broadcast detectable signals for a brief period of time ==== It may be that alien civilizations are detectable through their radio emissions for only a


id: fermi-paradox-20260505-7
file: data/en.wikipedia.org/wiki/Fermi_paradox-7.md
category: reference
title: Fermi paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fermi_paradox
date_saved: 2026-05-05T11:01:02.535314+00:00
instance: kb-cron
parent: fermi-paradox-20260505-0
summary:
==== Alien species may have only settled part of the galaxy ==== According to a study by Frank et al., advanced civilizations may not colonize everything in the galaxy due to their potential adoption of steady states of expansion. This hypothesis suggests that civilizations might reach a stable pattern of expansion where they neither collapse nor aggressively spread throughout the galaxy. A February 2019 article in Popular Science states, "Sweeping across the Milky Way and establishing a unified galactic empire might be inevitable for a monolithic super-civilization, but most cultures are neither monolithic nor super—at least if our experience is any guide." Astrophysicist Adam Frank, along with co-authors such as astronomer Jason Wright, ran a variety of simulations in which they varied such factors as settlement lifespans, fractions of suitable planets, and recharge times between launches. They found many of their simulations seemingly resulted in a "third category" in which the Milky Way remains partially settled indefinitely. The abstract to their 2019 paper states, "These results break the link between Hart's famous 'Fact A' (no interstellar visitors on Earth now) and the conclusion that humans must, therefore, be the only technological civilization in the galaxy. Explicitly, our solutions admit situations


id: fermi-paradox-20260505-8
file: data/en.wikipedia.org/wiki/Fermi_paradox-8.md
category: reference
title: Fermi paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fermi_paradox
date_saved: 2026-05-05T11:01:02.535314+00:00
instance: kb-cron
parent: fermi-paradox-20260505-0
summary:
==== Information is cheaper to transmit than matter is to transfer ==== If a human-capability machine intelligence is possible, and if it is possible to transfer such constructs over vast distances and rebuild them on a remote machine, then it might not make strong economic sense to travel the galaxy by spaceflight. Louis K. Scheffer calculates the cost of radio transmission of information across space to be cheaper than spaceflight by a factor of 108–1017. For a machine civilization, the costs of interstellar travel are therefore enormous compared to the more efficient option of sending computational signals across space to already established sites. After the first civilization has physically explored or colonized the galaxy, as well as sent such machines for easy exploration, then any subsequent civilizations, after having contacted the first, may find it cheaper, faster, and easier to explore the galaxy through intelligent mind transfers to the machines built by the first civilization. However, since a star system needs only one such remote machine, and the communication is most likely highly directed, transmitted at high-frequencies, and at a minimal power to be economical, such signals would be hard to detect from Earth. By contrast, in economics the counter-intuitive


id: fermi-paradox-20260505-9
file: data/en.wikipedia.org/wiki/Fermi_paradox-9.md
category: reference
title: Fermi paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fermi_paradox
date_saved: 2026-05-05T11:01:02.535314+00:00
instance: kb-cron
parent: fermi-paradox-20260505-0
summary:
===== Radio signals cannot be straightforwardly detected at interstellar distances ===== The greatest challenge is the sheer size of the radio search needed to look for signals (effectively spanning the entire observable universe), the limited amount of resources committed to SETI, and the sensitivity of modern instruments. SETI estimates, for instance, that with a radio telescope as sensitive as the Arecibo Observatory, Earth's television and radio broadcasts would only be detectable at distances up to 0.3 light-years, less than 1/10 the distance to the nearest star. A signal is much easier to detect if it consists of a deliberate, powerful transmission directed at Earth. Such signals could be detected at ranges of hundreds to tens of thousands of light-years distance. However, this means that detectors must be listening to an appropriate range of frequencies, and be in that region of space to which the beam is being sent. Many SETI searches assume that extraterrestrial civilizations will be broadcasting a deliberate signal, like the Arecibo message, in order to be found. Moreover, as human communication technology has advanced, humans have reduced the use of broadband radio transmissions in favor of more efficient and higher-bandwidth methods such as satellite communication and fibre


id: fermi-paradox-20260505-10
file: data/en.wikipedia.org/wiki/Fermi_paradox-10.md
category: reference
title: Fermi paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fermi_paradox
date_saved: 2026-05-05T11:01:02.535314+00:00
instance: kb-cron
parent: fermi-paradox-20260505-0
summary:
==== Intelligent life exists buried below the surfaces of ice planets ==== Planetary scientist Alan Stern put forward the idea that there could be a number of worlds with subsurface oceans (such as Jupiter's Europa or Saturn's Enceladus). The surface would provide a large degree of protection from such things as cometary impacts and nearby supernovae, as well as creating a situation in which a much broader range of orbital configurations are capable of supporting life. Life, and potentially intelligence and civilization, could evolve below the surface of such a planet, but be very hard to detect, insofar as it is generally only possible to observe the surface of planets from space. Stern states, "If they have technology, and let's say they're broadcasting, or they have city lights or whatever—we can't see it in any part of the spectrum, except maybe very-low-frequency [radio]." Moreover, such a civilization may have great difficulty getting to space, insofar as even getting to the surface of their world could present a considerable engineering challenge involving tunneling through many kilometres of ice. This may severely hamper their ability to communicate with us. ==== Advanced civilizations may limit their search for life to technological signatures ====


id: fermi-paradox-20260505-11
file: data/en.wikipedia.org/wiki/Fermi_paradox-11.md
category: reference
title: Fermi paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fermi_paradox
date_saved: 2026-05-05T11:01:02.535314+00:00
instance: kb-cron
parent: fermi-paradox-20260505-0
summary:
The zoo hypothesis states that intelligent extraterrestrial life exists and does not contact life on Earth to allow for its natural evolution and development as a sort of cosmic closed nature reserve. A variation on the zoo hypothesis is the laboratory hypothesis, where humanity has been or is being subject to experiments, with Earth or the Solar System effectively serving as a laboratory. The zoo hypothesis may break down under the uniformity of motive flaw: all it takes is a single culture or civilization (or even a faction or rogue actor within one) to decide to act contrary to the interplanetary consensus, and the probability of such a violation of hegemony increases with the number of civilizations, tending not towards a galactic league with a single policy towards Earth, but towards multiple competing factions. However, if artificial superintelligences are paramount in galactic politics, and such intelligences tend towards consolidation behind a central authority, then this would at least partially address the uniformity of motive flaw by dissuading rogue behavior. Analysis of the inter-arrival times between civilizations in the galaxy based on common astrobiological assumptions suggests that the initial civilization would have a commanding lead over the later arrivals, inasmuch as


id: g-dwarf-problem-20260505-0
file: data/en.wikipedia.org/wiki/G-dwarf_problem-0.md
category: reference
title: G-dwarf problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/G-dwarf_problem
date_saved: 2026-05-05T11:01:04.825572+00:00
instance: kb-cron
parent: g-dwarf-problem-20260505-0
summary:
In astronomy, the G-dwarf problem refers to the apparent discrepancy in the distribution of metallicity levels in stars of different populations as compared to closed box models of galactic chemical evolution. According to closed box models, which represent galaxies without outside non-metallic material inflow, the distribution of metallicity levels in stars should follow a logarithmic curve. This amounts to high and low mass stars having the least metallicity, with G-type stars inbetween. However, these models are inconsistent with Milky Way observations. Other galaxies have been shown to have the same problem. The name comes from G-type stars, which are bright enough to be studied easily, yet are most often found unevolved. This provides an extensive look at relatively young stars. Despite this, the G-dwarf problem has also been observed in K and M dwarfs (the M dwarf problem). == See also == Solar analog List of nearest bright stars List of nearest stars and brown dwarfs Main sequence G-type main-sequence star == References ==


id: galactic-center-gev-excess-20260505-0
file: data/en.wikipedia.org/wiki/Galactic_Center_GeV_excess-0.md
category: reference
title: Galactic Center GeV excess
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Galactic_Center_GeV_excess
date_saved: 2026-05-05T11:01:06.065797+00:00
instance: kb-cron
parent: galactic-center-gev-excess-20260505-0
summary:
The Galactic Center GeV Excess (GCE) is an unexpected surplus of gamma-ray radiation coming from the center of the Milky Way Galaxy. This approximately spherical source of radiation was first detected in 2009 by the Large Area Telescope of the Fermi Gamma-ray Space Telescope and is unexplained by direct observation of possible sources. Two percent of the gamma ray radiation in a 30° radius circle around the Galactic Center is attributed to the GCE. As of 2025, this excessive (and diffused) gamma-ray radiation is not well understood by astronomers. Some astronomers argue that self-annihilating dark matter (which is not otherwise known to radiate) may be the cause of the GCE. This would also explain the excess diffuse microwave glow of the galactic center that had been discovered previously by the WMAP satellite. Other astronomers prefer a population of pulsars (which have not been observed) as the source of the gamma-ray excess. Astronomers have suggested that self-annihilating dark matter may be a dominant contributor to the GCE, based on analysis using non-Poissonian template fitting statistical methods, wavelet methods, and studies by other astronomers may support this idea. More recently, in August 2020, other astronomers have reported that self-annihilating dark matter may


id: gpm-j1839-10-20260505-0
file: data/en.wikipedia.org/wiki/GPM_J1839−10-0.md
category: reference
title: GPM J1839−10
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/GPM_J1839−10
date_saved: 2026-05-05T11:01:07.267702+00:00
instance: kb-cron
parent: gpm-j1839-10-20260505-0
summary:
GPM J1839−10 is a potentially unique ultra-long period magnetar located about 15,000 light-years away from Earth in the Scutum constellation, in the Milky Way. It was discovered by a team of scientists at Curtin University using the Murchison Widefield Array. Its unusual characteristics violate current theory and prompted a search of other radio telescope archives, including the Giant Metrewave Radio Telescope and the Very Large Array, which revealed evidence of the object dating back to 1988. The signature of the object went unnoticed because scientists did not know to look for its unusual behavior. The current understanding of neutron stars is that below a certain rate of rotation, called "the death line", they cease emissions. Uniquely, not only does GPM J1839−10 have an extremely slow rotation of approximately twenty-two minutes, it emits bursts of radio waves lasting up to five minutes, for which there is currently no generally accepted explanation. == See also == GLEAM-X J162759.5−523504.3 GCRT J1745−3009 PSR J0901–4046 == Further reading == P. Beniamini; Z. Wadiasingh; B. D. Metzger (2020). "Periodicity in recurrent fast radio bursts and the origin of ultralong period magnetars". Monthly Notices of the Royal Astronomical Society. 496 (3) (published 23 June 2020): 3390–3401. arXiv:2003.12509.


id: hd-139139-20260505-0
file: data/en.wikipedia.org/wiki/HD_139139-0.md
category: reference
title: HD 139139
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/HD_139139
date_saved: 2026-05-05T11:01:09.708720+00:00
instance: kb-cron
parent: hd-139139-20260505-0
summary:
HD 139139 (also known as EPIC 249706694) is likely part of a bound pair system of main sequence stars about 350 light-years (110 parsecs) away from Earth in the constellation Libra. HD 139139 is a G-type main-sequence star, a little larger and more luminous than the Sun, and at an almost identical temperature. It has an apparent magnitude of 9.8. The companion star is thought to be a K5-K7 red dwarf 3.3″ away from HD 139139. It is about three magnitudes fainter and has a temperature of between 4,100 and 4,300 K. Both stars have a similar proper motion, meaning they may form a gravitationally-bound binary pair. HD 139139 exhibits dips in brightness similar to those caused by transiting Earth-like planets. The Kepler space telescope observed 28 dips in their brightness over an 87-day period (23 August – 20 November 2017). The dips do not appear to be periodic as would be expected if they were due to transiting planets. It is unknown which of the two stars produces the dimming events. Potential explanations that have been investigated include planets transiting a binary star, planets that are perturbing the orbits of each other producing large transit timing variations, a disintegrating


id: iptf14hls-20260505-0
file: data/en.wikipedia.org/wiki/IPTF14hls-0.md
category: reference
title: IPTF14hls
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/IPTF14hls
date_saved: 2026-05-05T11:01:10.902891+00:00
instance: kb-cron
parent: iptf14hls-20260505-0
summary:
iPTF14hls is an unusual supernova star that erupted continuously for about 1,000 days beginning in September 2014 before becoming a remnant nebula. It had previously erupted in 1954. None of the theories nor proposed hypotheses fully explain all the aspects of the object. == Observations == The star iPTF14hls was discovered in September 2014 by the Intermediate Palomar Transient Factory, and it was first made public in November 2014 by the CRTS survey as CSS141118:092034+504148. Based on that information, it was confirmed as an exploding star in January 2015. It was thought then that it was a single supernova event (Type II-P) that would dim in about 100 days, but instead, it continued its eruption for about 1,000 days while fluctuating in brightness at least five times. The brightness varied by as much as 50%, going through five peaks. Also, rather than cooling down with time as expected of a Type II-P supernova, the object maintains a near-constant temperature of about 5000–6000 K. Checks of photographs from the past found one from 1954 showing an explosion in the same location. Since 1954, the star has exploded six times. The principal investigator is Iair Arcavi. His international team used the Low-Resolution


id: iptf14hls-20260505-1
file: data/en.wikipedia.org/wiki/IPTF14hls-1.md
category: reference
title: IPTF14hls
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/IPTF14hls
date_saved: 2026-05-05T11:01:10.902891+00:00
instance: kb-cron
parent: iptf14hls-20260505-0
summary:
=== Shock interaction === Jennifer E Andrews and Nathan Smith hypothesised that the observed light spectrum is a clear signature of shock interaction of ejected material with dense circumstellar material (CSM). They proposed that a typical explosion energy, with "enveloped" or "swallowed" CSM interaction—as seen in some recent supernovae, including SN 1998S, SN 2009ip, and SN 1993J—could "explain the peculiar evolution of iPTF14hls." In December 2017, a team using the Fermi Gamma-ray Space Telescope reported that they may have detected in iPTF14hls, for the first time, high energy gamma-ray emission from a supernova. The gamma-ray source appears ~ 300 days after the explosion of iPTF14hls, and is still observable, but more observations are needed to verify that iPTF14hls is the exact source of the observed gamma-ray emission. If the association between the gamma-ray source and iPTF14hls is real, then there are difficulties with modelling its gamma-ray emission in the framework of particle acceleration in supernova-ejecta-produced shock. The energy conversion efficiency needs to be very high, so it is suggested that a jet (anisotropic emission) from a close companion may be necessary to explain some of the observed data. No X-ray emissions have been detected, which makes the interpretation of the


id: jupiter-mass-binary-object-20260505-0
file: data/en.wikipedia.org/wiki/Jupiter-mass_binary_object-0.md
category: reference
title: Jupiter-mass binary object
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Jupiter-mass_binary_object
date_saved: 2026-05-05T11:01:12.130108+00:00
instance: kb-cron
parent: jupiter-mass-binary-object-20260505-0
summary:
Jupiter-mass Binary Objects or JuMBOs are a hypothetical class of celestial objects, defined as a planetary-mass objects orbiting a common center of mass. Reanalysis of early unpublished claims of their discovery was from observations of the Orion Nebula Cluster by the James Webb Space Telescope identified background sources or brown dwarf stars, but no JuMBO objects. == Observations == JuMBOs were reported using data from the James Webb Space Telescope (JWST) survey of the Orion Nebula in late 2022. Using JWST's Near Infrared Camera (NIRCam), astronomers Samuel Pearson and Mark McCaughrean observed a 1.2 × 0.8 parsec region of the inner nebula and Trapezium Cluster over approximately 35 hours. The survey employed twelve different infrared filters specifically chosen to detect molecular absorption features characteristic of very low-mass objects. The planetary-mass objects were identified by looking for distinctive water and methane absorption patterns in their atmospheres. These molecular signatures appear as dips in brightness at specific wavelengths, allowing researchers to distinguish genuine planetary-mass objects from background stars that might appear similarly faint due to dust extinction. This method proved particularly effective for finding objects with temperatures between 890 and 2520 Kelvin. The survey revealed 540 planetary-mass objects, with 40 binary systems


id: list-of-fast-radio-bursts-20260505-0
file: data/en.wikipedia.org/wiki/List_of_fast_radio_bursts-0.md
category: reference
title: List of fast radio bursts
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_fast_radio_bursts
date_saved: 2026-05-05T11:01:13.433856+00:00
instance: kb-cron
parent: list-of-fast-radio-bursts-20260505-0
summary:
This is a list of fast radio bursts. Items are listed here if information about the fast radio burst has been published. Although there could be thousands of detectable events per day, only detected ones are listed. == Notes == == References ==


id: little-red-dot-astronomical-object-20260505-0
file: data/en.wikipedia.org/wiki/Little_red_dot_(astronomical_object)-0.md
category: reference
title: Little red dot (astronomical object)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Little_red_dot_(astronomical_object)
date_saved: 2026-05-05T11:01:14.629713+00:00
instance: kb-cron
parent: little-red-dot-astronomical-object-20260505-0
summary:
Little red dots (LRDs) are a class of small, red-tinted astronomical objects discovered by the James Webb Space Telescope (JWST). Their discovery was announced in March 2024, and they are poorly understood due to limited data collection. They appear to have existed between 0.6 and 1.6 billion years after the Big Bang (13.2 to 12.2 billion years ago), with a majority found around 600 million years post-Big Bang. As of 2025, 341 LRDs have been identified with JWST. The current leading theory is that the LRDs are a form of primordial galaxy, and the original reports identified LRDs as a type of early active galactic nucleus (AGN) containing a supermassive black hole. However, while this explains their age and appearance, they do not have the same characteristics as known AGNs. For example, they do not appear to emit X-rays, have a flattened rather than steeply rising infrared spectrum, and display very little variability between themselves. In July 2025 it was proposed that LRDs were instead supermassive non-metallic primordial stars—also known as population III stars—of perhaps a million solar masses, seen in the last few thousands of years of their lifetimes. Theoretical modelling of such stars appeared to closely match the


id: little-red-dot-astronomical-object-20260505-1
file: data/en.wikipedia.org/wiki/Little_red_dot_(astronomical_object)-1.md
category: reference
title: Little red dot (astronomical object)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Little_red_dot_(astronomical_object)
date_saved: 2026-05-05T11:01:14.629713+00:00
instance: kb-cron
parent: little-red-dot-astronomical-object-20260505-0
summary:
the Balmer break, emission lines, and Hα absorption line are instead most plausibly explained by a black hole star (BH*) scenario, in which dense gas surrounds a powerful ionising source. In contrast to recently proposed BH* models of dust-reddened AGN, we show that spectral fits in the rest UV to near-infrared favour an intrinsically redder continuum over strong dust reddening. This may point to a super-Eddington accreting massive black hole or, possibly, the presence of (super)massive stars in a nuclear star cluster. The Cliff is the clearest evidence to date that at least some LRDs are not ultra-dense massive galaxies, and are instead powered by a central ionising source embedded in dense, absorbing gas. === CAPERS-LRD-z9 === CAPERS-LRD-z9 is an LRD confirmed to be a broad-line active galactic nucleus (BLAGN) with the red-shift z = 9.288. It is the highest red-shift AGN known. CAPERS-LRD-z9 exhibits a prominent Balmer break and "provides strong evidence in support of the 'dense-gas-enshrouded AGN'" explanation. These unusual Balmer jumps are notable properties of LDRs, causing difficulties in observations and spectroscopic analysis. Some LDRs exhibit a symmetrical density distribution of electron scattering, thus a gaseous envelope absorbing nebular spectra is a credible possibility. === A2744–45924 ===


id: lunar-swirls-20260505-0
file: data/en.wikipedia.org/wiki/Lunar_swirls-0.md
category: reference
title: Lunar swirls
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lunar_swirls
date_saved: 2026-05-05T11:01:15.790463+00:00
instance: kb-cron
parent: lunar-swirls-20260505-0
summary:
Lunar swirls are enigmatic features found across the Moon's surface, which are characterized by having a high albedo, appearing optically immature (i.e. having the optical characteristics of a relatively young regolith), and (often) having a sinuous shape. Their curvilinear shape is often accentuated by low albedo regions that wind between the bright swirls. They appear to overlay the lunar surface, superposed on craters and ejecta deposits, but impart no observable topography. Swirls have been identified on the lunar maria and on highlands - they are not associated with a specific lithologic composition. Swirls on the maria are characterized by strong albedo contrasts and complex, sinuous morphology, whereas those on highland terrain appear less prominent and exhibit simpler shapes, such as single loops or diffuse bright spots. == Association with magnetic anomalies == The lunar swirls are coincident with regions of the magnetic field of the Moon with relatively high strength on a planetary body that lacks, and may never have had, an active core dynamo with which to generate its own magnetic field. Every swirl has an associated magnetic anomaly, but not every magnetic anomaly has an identifiable swirl. Orbital magnetic field mapping by the Apollo 15 and 16 sub-satellites,


id: m-sigma-relation-20260505-0
file: data/en.wikipedia.org/wiki/M–sigma_relation-0.md
category: reference
title: M–sigma relation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/M–sigma_relation
date_saved: 2026-05-05T11:01:16.989418+00:00
instance: kb-cron
parent: m-sigma-relation-20260505-0
summary:
The M–sigma (or M–σ) relation is an empirical correlation between the stellar velocity dispersion σ of a galaxy bulge and the mass M of the supermassive black hole at its center. The M–σ relation was first presented in 1999 during a conference at the Institut d'Astrophysique de Paris in France by David Merritt. Merritt's proposed form of the relation, which he called the "Faber–Jackson law for black holes", was M 10 8 M ⊙ ≈ 3.1 ( σ 200 k m s − 1 ) 4 . {\displaystyle {\frac {M}{10^{8}M_{\odot }}}\approx 3.1\left({\frac {\sigma }{200~{\rm {km}}~{\rm {s}}^{-1}}}\right)^{4}.} where M ⊙ {\displaystyle M_{\odot }} is the solar mass. Publication of the relation in a refereed journal, by two groups, took place the following year. One of many recent studies, based on the growing sample of published black hole masses in nearby galaxies, gives M 10 8 M ⊙ ≈ 1.9 ( σ 200 k m s − 1 ) 5.1 . {\displaystyle {\frac {M}{10^{8}M_{\odot }}}\approx 1.9\left({\frac {\sigma }{200~{\rm {km}}~{\rm {s}}^{-1}}}\right)^{5.1}.} Earlier work demonstrated a relationship between galaxy luminosity and black hole mass, which nowadays has a comparable level of scatter. The M–σ relation is generally interpreted as implying some source of mechanical


id: m-sigma-relation-20260505-1
file: data/en.wikipedia.org/wiki/M–sigma_relation-1.md
category: reference
title: M–sigma relation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/M–sigma_relation
date_saved: 2026-05-05T11:01:16.989418+00:00
instance: kb-cron
parent: m-sigma-relation-20260505-0
summary:
== Importance == Before the M–σ relation was discovered in 2000, a large discrepancy existed between black hole masses derived using three techniques. Direct, or dynamical, measurements based on the motion of stars or gas near the black hole seemed to give masses that averaged ≈1% of the bulge mass (the "Magorrian relation"). Two other techniques—reverberation mapping in active galactic nuclei, and the Sołtan argument, which computes the cosmological density in black holes needed to explain the quasar light—both gave a mean value of M/Mbulge that was a factor ≈10 smaller than implied by the Magorrian relation. The M–σ relation resolved this discrepancy by showing that most of the direct black hole masses published prior to 2000 were significantly in error, presumably because the data on which they were based were of insufficient quality to resolve the black hole's dynamical sphere of influence. The mean ratio of black hole mass to bulge mass in big early-type galaxies is now believed to be approximately 1 : 200, and increasingly smaller as one moves to less massive galaxies. A common use of the M–σ relation is to estimate black hole masses in distant galaxies using the easily measured quantity σ. Black hole


id: o-connell-effect-20260505-0
file: data/en.wikipedia.org/wiki/O'Connell_effect-0.md
category: reference
title: O'Connell effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/O'Connell_effect
date_saved: 2026-05-05T11:01:20.719442+00:00
instance: kb-cron
parent: o-connell-effect-20260505-0
summary:
The O'Connell effect is an asymmetry in the photometric light curve of certain close eclipsing binary stars. It was named after the astronomer Daniel Joseph Kelly O'Connell, SJ of Riverview College in New South Wales who in 1951 studied this phenomenon and distinguished it from the so-called periastron effect described by earlier authors, as it does not necessarily appear near the periastron, when tidal effects and an increase in mutual radiation may cause an increase in luminosity. == The effect == The out-of-eclipse brightness maxima of some binary stars are unequally high. This is contrary to expectations that the observed luminosity of an eclipsing binary should be the same when its components switch positions every half period. The maximum following the primary minimum is nearly always brighter than the preceding one. This is called the positive O'Connell effect, the reverse case is referred to as the negative O'Connell effect. The difference increases with the ellipticity of the stars, and the differences in their sizes and densities. Also, spectral differences have been observed between subsequent maxima. == Attempts at explanation == In some systems where the phenomenon has been observed, such as in CG Cygni, RT Lacertae, XY Ursae Majoris, or


id: odd-radio-circle-20260505-0
file: data/en.wikipedia.org/wiki/Odd_radio_circle-0.md
category: reference
title: Odd radio circle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Odd_radio_circle
date_saved: 2026-05-05T11:01:21.945654+00:00
instance: kb-cron
parent: odd-radio-circle-20260505-0
summary:
In astronomy, an odd radio circle (ORC) is a very large (over 50 times the diameter of our Milky Way ~ 3 million light years) unexplained astronomical object that, at radio wavelengths, is highly circular and brighter along its edges. As of October 2025, there have been 8 such objects (and possibly six more) observed. The observed ORCs are bright at radio wavelengths, but are not visible at visible, infrared or X-ray wavelengths. This is due to the physical process producing this radiation, which is thought to be synchrotron radiation. Three of the ORCs contain optical galaxies in their centers, suggesting that the galaxies might have formed these objects. Only in three cases twin intersecting rings have been seen and they are ORC J2103-6200, ORC J0356-4216 and RAD J131346.9+500320. The last one, RAD J131346.9+500320, discovered by the RAD@home citizen scientists using LOFAR data is currently the farthest and most powerful ORC discovered. == Description == The ORCs were detected in late 2019 after astronomer Anna Kapinska studied a Pilot Survey of the Evolutionary Map of the Universe (EMU), based on the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope array. All of the ORCs are about 1 arcminute in diameter,


id: olbers-paradox-20260505-0
file: data/en.wikipedia.org/wiki/Olbers'_paradox-0.md
category: reference
title: Olbers' paradox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Olbers'_paradox
date_saved: 2026-05-05T11:01:23.117576+00:00
instance: kb-cron
parent: olbers-paradox-20260505-0
summary:
Olbers' paradox, also known as the dark night paradox or Olbers and Cheseaux's paradox, is a historical argument in astrophysics and physical cosmology that says the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe. If the universe were static, homogeneous at a large scale, and populated by an infinite number of stars, any line of sight from Earth must end at the surface of a star and if light from an infinite distance could reach Earth, the night sky should be completely illuminated and very bright. This contradicts the observed darkness and non-uniformity of the night sky. Modern cosmological models do not make all of these assumptions. The darkness of the night sky is one piece of evidence for a dynamic universe, such as the Big Bang model. That model explains the observed darkness by invoking expansion of the universe, which increases the wavelength of visible light originating from the Big Bang to microwave scale via a process known as redshift. The resulting microwave radiation background has wavelengths much longer (millimeters instead of nanometers), which appear dark to the naked eye. Although he was not the first to describe it, the paradox


id: photon-underproduction-crisis-20260505-0
file: data/en.wikipedia.org/wiki/Photon_underproduction_crisis-0.md
category: reference
title: Photon underproduction crisis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photon_underproduction_crisis
date_saved: 2026-05-05T11:01:24.311660+00:00
instance: kb-cron
parent: photon-underproduction-crisis-20260505-0
summary:
The photon underproduction crisis is a cosmological discussion concerning the purported deficit between observed photons and predicted photons. The deficit, or underproduction crisis, is a theoretical problem, arising from comparing observations of ultraviolet light emitted from known populations of galaxies and quasars to theoretical predictions of the amount of ultraviolet light required to simulate the observed distribution of the hydrogen gas in the local universe in a cosmological simulation. The distribution of hydrogen gas was inferred using Lyman-alpha forest observations from Hubble Space Telescope's Cosmic Origins Spectrograph. The amount of light from galaxies and quasars can be estimated from its effect on the distribution of hydrogen and helium in the regions between galaxies. Highly energetic ultraviolet photons can convert electrically neutral hydrogen gas into ionized gas. A team led by Juna Kollmeier reported an unexpected deficit of roughly 400% between ionizing light from known sources and the actual observations of intergalactic hydrogen. Kollmeier and her team wrote in their scientific report, “We examine the statistics of the low-redshift Lyman-alpha forest from smoothed particle hydrodynamic simulations in light of recent improvements in the estimated evolution of the cosmic ultraviolet background (UVB) and recent observations from the Cosmic Origins Spectrograph (COS). We


id: przybylski-s-star-20260505-0
file: data/en.wikipedia.org/wiki/Przybylski's_Star-0.md
category: reference
title: Przybylski's Star
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Przybylski's_Star
date_saved: 2026-05-05T11:01:25.586714+00:00
instance: kb-cron
parent: przybylski-s-star-20260505-0
summary:
Przybylski's Star (pronounced [pʂɨˈbɨlskʲi]), or HD 101065, is a rapidly oscillating Ap star at roughly 356 light-years (109 parsecs) from the Sun in the southern constellation of Centaurus. It is an unusual chemically peculiar star with a unique spectrum showing over-abundances of most rare-earth elements, for example, but under-abundances of more common elements such as iron. == Observation history == This star was first recorded by Benjamin Apthorp Gould on April 29, 1873, and catalogued as the 10th star of Zone 257 with right ascension of 11h 31m 32.89s and declination of −46° 01′ 08″ (at epoch 1875.0) and apparent magnitude of 8.5. In 1961, the Polish-Australian astronomer Antoni Przybylski discovered that this star had a peculiar spectrum that would not fit into the standard framework for stellar classification. Przybylski's observations indicated unusually low amounts of iron and nickel in the star's spectrum, but higher amounts of unusual elements such as strontium, holmium, niobium, scandium, yttrium, caesium, neodymium, praseodymium, thorium, ytterbium, and uranium. In fact, at first Przybylski doubted that iron was present in the spectrum at all. Modern work shows that the iron group elements are somewhat below normal in abundance, but it is clear that the lanthanides, among


id: scp-06f6-20260505-0
file: data/en.wikipedia.org/wiki/SCP_06F6-0.md
category: reference
title: SCP 06F6
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/SCP_06F6
date_saved: 2026-05-05T11:01:26.826949+00:00
instance: kb-cron
parent: scp-06f6-20260505-0
summary:
SCP 06F6 is (or was) an astronomical object of unknown type, discovered on 21 February 2006 in the constellation Boötes during a survey of galaxy cluster CL 1432.5+3332.8 with the Hubble Space Telescope's Advanced Camera for Surveys Wide Field Channel. According to research authored by Kyle Barbary of the Supernova Cosmology Project, the object brightened over a period of roughly 100 days, reaching a peak intensity of magnitude 21; it then faded over a similar period. Barbary and colleagues report that the spectrum of light emitted from the object does not match known supernova types, and is dissimilar to any known phenomenon in the Sloan Digital Sky Survey database. The light in the blue region shows broad line features, while the red region shows continuous emission. The spectrum shows a handful of spectral lines, but when astronomers try to trace any one of them to an element the other lines fail to match up with any other known elements. Because of its uncommon spectrum, the team was not able to determine the distance to the object using standard redshift techniques; it is not even known whether the object is within or outside the Milky Way. Furthermore, no Milky Way star


id: shape-of-the-universe-20260505-0
file: data/en.wikipedia.org/wiki/Shape_of_the_universe-0.md
category: reference
title: Shape of the universe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Shape_of_the_universe
date_saved: 2026-05-05T11:01:27.989865+00:00
instance: kb-cron
parent: shape-of-the-universe-20260505-0
summary:
Determination of the shape of the universe is a problem of physical cosmology. Observational evidence (BOOMERANG Project, MAXIMA, Planck, WMAP) indicates that the observable universe is spatially flat. It is unknown whether the universe is simply connected like euclidean space or multiply connected like a torus. == The observable universe == Human knowledge of the universe is restricted by the fact that any signal information from further than the cosmological horizon within the universe moving towards any position of human perception or telescope is non-available. == Possible shapes of the universe == Einstein stated, by the law of gravitation, heavy masses curve space-time. The curvature of spacetime is the same as the density parameter, represented with Ω (omega). The density parameter is the average density of the universe divided by the critical energy density, that is, the mass energy needed for a universe to be flat. Put another way, If Ω > 1, there is positive curvature. If Ω < 1, there is negative curvature. If Ω = 1, the universe is flat. Scientists could experimentally calculate Ω to determine the curvature two ways. One is to count all the mass–energy in the universe and take its average density, then


id: shape-of-the-universe-20260505-1
file: data/en.wikipedia.org/wiki/Shape_of_the_universe-1.md
category: reference
title: Shape of the universe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Shape_of_the_universe
date_saved: 2026-05-05T11:01:27.989865+00:00
instance: kb-cron
parent: shape-of-the-universe-20260505-0
summary:
=== Curvature === The curvature of the universe places constraints on the topology. If the spatial geometry is spherical, i.e., possess positive curvature, the topology is compact. For a flat (zero curvature) or a hyperbolic (negative curvature) spatial geometry, the topology can be either compact or infinite. Many textbooks erroneously state that a flat or hyperbolic universe implies an infinite universe; however, the correct statement is that a flat universe that is also simply connected implies an infinite universe. The latest research shows that even the most powerful future experiments (like the SKA) will not be able to distinguish between a flat, open and closed universe if the true value of cosmological curvature parameter is smaller than 10−4. If the true value of the cosmological curvature parameter is larger than 10−3 we will be able to distinguish between these three models even now. Final results of the Planck mission, released in 2018, show the cosmological curvature parameter, 1 − Ω = ΩK = −Kc2/a2H2, to be 0.0007±0.0019, consistent with a flat universe. ==== Universe with zero curvature ==== A flat universe can have zero total energy. ==== Universe with positive curvature ==== Poincaré dodecahedral space is a positively curved space,


id: solar-corona-20260505-0
file: data/en.wikipedia.org/wiki/Solar_corona-0.md
category: reference
title: Solar corona
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solar_corona
date_saved: 2026-05-05T11:01:29.364493+00:00
instance: kb-cron
parent: solar-corona-20260505-0
summary:
The solar corona is the outermost layer of the Sun's atmosphere. It is a region filled with relatively hot, tenuous plasma that is structured by the solar magnetic field. The solar corona lies above the photosphere and chromosphere and extends out to the edge of the solar atmosphere where it merges with the solar wind. The chromosphere and corona are separated by a thin, highly dynamic transition region. The outer edge of solar atmosphere where the corona transitions into the solar wind is defined by the Alfvén surface which forms an irregularly shaped boundary around the Sun at heights ranging from about 10 to 20 solar radii (7000000 to 14000000 km) above the photosphere. Coronal light is typically obscured by diffuse sky radiation and glare from the solar disk, but can be easily seen by the naked eye during a total solar eclipse or with a specialized coronagraph. Spectroscopic measurements indicate strong ionization in the corona and a plasma temperature in excess of 1000000 kelvins, much hotter than the surface of the Sun. The solar corona is populated by structures such as prominences, coronal loops, and helmet streamers. == Observational history == In 1724, French-Italian astronomer Giacomo F. Maraldi recognized


id: solar-corona-20260505-1
file: data/en.wikipedia.org/wiki/Solar_corona-1.md
category: reference
title: Solar corona
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solar_corona
date_saved: 2026-05-05T11:01:29.364493+00:00
instance: kb-cron
parent: solar-corona-20260505-0
summary:
The K-corona (K for kontinuierlich, "continuous" in German) is from photospheric light Thomson scattering off free electrons in the corona. Doppler broadening of the scattered photospheric absorption lines spreads them so greatly as to completely obscure them, giving the spectral appearance of a continuum with no absorption lines. The F-corona (F for Fraunhofer) is from photospheric light scattering off dust particles located beyond about one solar radius above the photosphere. These dust particles are much slower than the electrons, so Doppler broadening is negligible. As a result, the Fraunhofer absorption lines observed in the photospheric spectrum are also observed in the F-corona spectrum. The F-corona extends to very high elongation angles from the Sun and merges with the zodiacal light. This white-light component of the coronal radiation is extremely faint relative to the photosphere. The maximum brightness ratio between the photosphere and the corona just above the visible limb is on the order of 10−6 and decreases to 10−9 within a solar diameter from the limb. Furthermore, the sky brightness can be more than three to five orders of magnitude larger than the coronal brightness, rendering the corona unobservable to the naked eye without a total solar eclipses. A small


id: solar-corona-20260505-2
file: data/en.wikipedia.org/wiki/Solar_corona-2.md
category: reference
title: Solar corona
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solar_corona
date_saved: 2026-05-05T11:01:29.364493+00:00
instance: kb-cron
parent: solar-corona-20260505-0
summary:
Active regions involve all the phenomena directly linked to the magnetic field, which occur at different heights above the Sun's surface: sunspots and faculae occur in the photosphere; spicules, Hα filaments and plages in the chromosphere; prominences in the chromosphere and transition region; and flares and coronal mass ejections (CME) happen in the corona and chromosphere. If flares are very violent, they can also perturb the photosphere and generate a Moreton wave. On the contrary, quiescent prominences are large, cool, dense structures which are observed as dark, "snake-like" Hα ribbons (appearing like filaments) on the solar disc. Their temperature is about 5000–8000K, and so they are usually considered as chromospheric features. In 2013, images from the High Resolution Coronal Imager revealed never-before-seen "magnetic braids" of plasma within the outer layers of these active regions. === Helmet streamers === Helmet streamers are large, cap-like coronal structures with long, pointed peaks that usually overlie sunspots and active regions. Coronal streamers are considered to be sources of the slow solar wind. === Bright points === Bright points are small active regions found on the solar disk. X-ray bright points were first detected on April 8, 1969, during a rocket flight. The fraction of


id: solar-corona-20260505-3
file: data/en.wikipedia.org/wiki/Solar_corona-3.md
category: reference
title: Solar corona
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solar_corona
date_saved: 2026-05-05T11:01:29.364493+00:00
instance: kb-cron
parent: solar-corona-20260505-0
summary:
An initial impulsive phase, whose duration is on the order of minutes, strong emissions of energy are often observed even in the microwaves, EUV wavelengths and in the hard X-ray frequencies. A maximum phase A decay phase, which can last several hours. Sometimes also a phase preceding the flare can be observed, usually called as "pre-flare" phase. === Coronal mass ejections === Often accompanying large solar flares and prominences are coronal mass ejections (CME). These are enormous emissions of coronal material and magnetic field that travel outward from the Sun at up to 3000 km/s, containing roughly 10 times the energy of the solar flare or prominence that accompanies them. Some larger CMEs can propel hundreds of millions of tons of material into interplanetary space at 600,000–2,000,000 miles per hour (970,000–3,220,000 km/h). == Physics == === Thermal conduction === In the corona thermal conduction occurs from the external hotter atmosphere towards the inner cooler layers. Responsible for the diffusion process of the heat are the electrons, which are much lighter than ions and move faster. When there is a magnetic field the thermal conductivity of the plasma becomes higher in the direction which is parallel to the field lines rather


id: solar-corona-20260505-4
file: data/en.wikipedia.org/wiki/Solar_corona-4.md
category: reference
title: Solar corona
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solar_corona
date_saved: 2026-05-05T11:01:29.364493+00:00
instance: kb-cron
parent: solar-corona-20260505-0
summary:
The coronal heating problem in solar physics relates to the question of why the temperature of the Sun's corona is millions of kelvins greater than the thousands of kelvins of the surface. Several theories have been proposed to explain this phenomenon, but it is still challenging to determine which is correct. The problem first emerged after the identification of unknown spectral lines in the solar spectrum with highly ionized iron and calcium atoms. The comparison of the coronal and the photospheric temperatures of 6000K, leads to the question of how the 200-times-hotter coronal temperature can be maintained. The problem is primarily concerned with how the energy is transported up into the corona and then converted into heat within a few solar radii. The high temperatures require energy to be carried from the solar interior to the corona by non-thermal processes, because the second law of thermodynamics prevents heat from flowing directly from the solar photosphere (surface), which is at about 5800K, to the much hotter corona at about 1 to 3 MK (parts of the corona can even reach 10MK). Between the photosphere and the corona, the thin region through which the temperature increases is known as the transition region.


id: solar-corona-20260505-5
file: data/en.wikipedia.org/wiki/Solar_corona-5.md
category: reference
title: Solar corona
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solar_corona
date_saved: 2026-05-05T11:01:29.364493+00:00
instance: kb-cron
parent: solar-corona-20260505-0
summary:
=== Wave heating theory === The wave heating theory, proposed in 1949 by Evry Schatzman, proposes that waves carry energy from the solar interior to the solar chromosphere and corona. The Sun is made of plasma rather than ordinary gas, so it supports several types of waves analogous to sound waves in air. The most important types of wave are magneto-acoustic waves and Alfvén waves. Magneto-acoustic waves are sound waves that have been modified by the presence of a magnetic field, and Alfvén waves are similar to ultra low frequency radio waves that have been modified by interaction with matter in the plasma. Both types of waves can be launched by the turbulence of granulation and super granulation at the solar photosphere, and both types of waves can carry energy for some distance through the solar atmosphere before turning into shock waves that dissipate their energy as heat. One problem with wave heating is delivery of the heat to the appropriate place. Magneto-acoustic waves cannot carry sufficient energy upward through the chromosphere to the corona, both because of the low pressure present in the chromosphere and because they tend to be reflected back to the photosphere. Alfvén waves can carry


id: solar-corona-20260505-6
file: data/en.wikipedia.org/wiki/Solar_corona-6.md
category: reference
title: Solar corona
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solar_corona
date_saved: 2026-05-05T11:01:29.364493+00:00
instance: kb-cron
parent: solar-corona-20260505-0
summary:
=== Spicules (type II) === For decades, researchers believed spicules could send heat into the corona. However, following observational research in the 1980s, it was found that spicule plasma did not reach coronal temperatures, and so the theory was discounted. As per studies performed in 2010 at the National Center for Atmospheric Research in Colorado, in collaboration with the Lockheed Martin's Solar and Astrophysics Laboratory (LMSAL) and the Institute of Theoretical Astrophysics of the University of Oslo, a new class of spicules (TYPE II) discovered in 2007, which travel faster (up to 100 km/s) and have shorter lifespans, can account for the problem. These jets insert heated plasma into the Sun's outer atmosphere. The Atmospheric Imaging Assembly on NASA's Solar Dynamics Observatory and NASA's Focal Plane Package for the Solar Optical Telescope on the Japanese Hinode satellite were used to test this hypothesis. The high spatial and temporal resolutions of the newer instruments reveal this coronal mass supply. According to analysis in 2011 by de Pontieu and colleagues, these observations reveal a one-to-one connection between plasma that is heated to millions of degrees and the spicules that insert this plasma into the corona. == See also == == References ==


id: tabby-s-star-20260505-0
file: data/en.wikipedia.org/wiki/Tabby's_Star-0.md
category: reference
title: Tabby's Star
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tabby's_Star
date_saved: 2026-05-05T11:01:31.754034+00:00
instance: kb-cron
parent: tabby-s-star-20260505-0
summary:
Tabby's Star (designated as KIC 8462852 in the Kepler Input Catalog, and also known by the names Boyajian's Star and WTF(Where'sTheFlux?) Star) is a binary star in the constellation Cygnus approximately 1,470 light-years (450 parsecs) from Earth. The system is composed of an F-type main-sequence star and a red dwarf companion. Unusual light fluctuations of Tabby's Star, including up to a 22% dimming in brightness, were discovered by citizen scientists as part of the Planet Hunters project. The discovery was made from data collected by the Kepler space telescope, which observed changes in the brightness of distant stars to detect exoplanets. Several hypotheses have been proposed to explain the star's large irregular changes in brightness, but as of 2024, none of them fully explain all aspects of the resulting light curve. It has been suggested that it is an extraterrestrial megastructure, but evidence tends to discount this suggestion. In September 2019, astronomers reported that the observed dimmings of Tabby's Star may have been produced by fragments resulting from the disruption of an orphaned exomoon. Tabby's Star is not the only star that has large irregular dimmings; other such stars include young stellar objects called YSO dippers, which have different dimming


id: tabby-s-star-20260505-1
file: data/en.wikipedia.org/wiki/Tabby's_Star-1.md
category: reference
title: Tabby's Star
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tabby's_Star
date_saved: 2026-05-05T11:01:31.754034+00:00
instance: kb-cron
parent: tabby-s-star-20260505-0
summary:
On 20 May 2017, Boyajian and her colleagues reported, via The Astronomer's Telegram, on an ongoing dimming event (named "Elsie") which possibly began on 14 May 2017. It was detected by the Las Cumbres Observatory Global Telescope Network, specifically by its telescope in Maui (LCO Maui). This was verified by the Fairborn Observatory (part of the N2K Consortium) in Southern Arizona (and later by LCO Canary Islands). Further optical and infrared spectroscopy and photometry were urgently requested, given the short duration of these events, which may be measured in days or weeks. Observations from multiple observers globally were coordinated, including polarimetry. Furthermore, the independent SETI projects Breakthrough Listen and Near-InfraRed Optical SETI (NIROSETI), both at Lick Observatory, continue to monitor the star. By the end of the three-day dimming event, a dozen observatories had taken spectra, with some astronomers having dropped their own projects to provide telescope time and resources. More generally the astronomical community was described as having gone "mildly bananas" over the opportunity to collect data in real-time on the unique star. The 2% dip event was named "Elsie" (a homophone of "LC", in reference to Las Cumbres and light curve). Initial spectra with FRODOSpec at the two-meter


id: tabby-s-star-20260505-2
file: data/en.wikipedia.org/wiki/Tabby's_Star-2.md
category: reference
title: Tabby's Star
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tabby's_Star
date_saved: 2026-05-05T11:01:31.754034+00:00
instance: kb-cron
parent: tabby-s-star-20260505-0
summary:
== Luminosity == Observations of the luminosity of the star by the Kepler space telescope show small, frequent, non-periodic dips in brightness, along with two large recorded dips in brightness two years apart. The amplitude of the changes in the star's brightness, and the aperiodicity of the changes, mean that this star is of particular interest for astronomers. The star's changes in brightness are consistent with many small masses orbiting the star in "tight formation". The first major dip, on 5 March 2011, reduced the star's brightness by up to 15%, and the next 726 days later (on 28 February 2013) by up to 22%. (A third dimming, around 8%, occurred 48 days later.) In comparison, a planet the size of Jupiter would only obscure a star of this size by 1%, indicating that whatever is blocking light during the star's major dips is not a planet, but rather something covering up to half the width of the star. Due to the failure of two of Kepler's reaction wheels, the star's predicted 750-day dip around February 2015 was not recorded. The light dips do not exhibit an obvious pattern. In addition to the day-long dimmings, a study of a century's


id: tabby-s-star-20260505-3
file: data/en.wikipedia.org/wiki/Tabby's_Star-3.md
category: reference
title: Tabby's Star
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tabby's_Star
date_saved: 2026-05-05T11:01:31.754034+00:00
instance: kb-cron
parent: tabby-s-star-20260505-0
summary:
One proposed explanation for the reduction in light is that it is due to a cloud of disintegrating comets orbiting the star elliptically. This scenario would assume that a planetary system around Tabby's Star has something similar to the Oort cloud and that gravity from a nearby star caused comets from said cloud to fall closer into the system, thereby obstructing the spectra of Tabby's Star. Evidence supporting this hypothesis includes an M-type red dwarf within 132 billion kilometers (885 AU) of Tabby's Star. The notion that disturbed comets from such a cloud could exist in high enough numbers to obscure 22% of the star's observed luminosity has been doubted. The smooth shallow ingress and sharp egress of some dimming events, as well as some symmetric triple dips, are difficult to explain with the comet scenario. Instead, a few asteroid-like bodies embedded in a dust cloud may better explain the star's light curve. Submillimetre-wavelength observations searching for farther-out cold dust in an asteroid belt akin to the Sun's Kuiper Belt suggest that a distant "catastrophic" planetary disruption explanation is unlikely; the possibility of a disrupted asteroid belt scattering comets into the inner system is still to be determined. === Younger


id: tabby-s-star-20260505-4
file: data/en.wikipedia.org/wiki/Tabby's_Star-4.md
category: reference
title: Tabby's Star
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tabby's_Star
date_saved: 2026-05-05T11:01:31.754034+00:00
instance: kb-cron
parent: tabby-s-star-20260505-0
summary:
=== Intrinsic luminosity variations === The reddening observed during the deep dimming events of Tabby's Star is consistent with cooling of its photosphere. It does not require obscuration by dust. Such cooling could be produced by a decreased efficiency of heat transport caused e.g. by decreased effectiveness of convection due to the star's strong differential rotation, or by changes in its modes of heat transport if it is near the transition between radiative and convective heat transport. The "missing" heat flux is stored as a small increase of internal and potential energy. The possible location of this early F star near the boundary between radiative and convective transport seems to be supported by the finding that the star's observed brightness variations appear to fit the "avalanche statistics" known to occur in a system close to a phase-transition. "Avalanche statistics" with a self-similar or power-law spectrum are a universal property of complex dynamical systems operating close to a phase transition or bifurcation point between two different types of dynamical behavior. Such close-to-critical systems are often observed to exhibit behavior that is intermediate between "order" and "chaos". Three other stars in the Kepler Input Catalog likewise exhibit similar "avalanche statistics" in their


id: transient-lunar-phenomenon-20260505-0
file: data/en.wikipedia.org/wiki/Transient_lunar_phenomenon-0.md
category: reference
title: Transient lunar phenomenon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transient_lunar_phenomenon
date_saved: 2026-05-05T11:01:33.015357+00:00
instance: kb-cron
parent: transient-lunar-phenomenon-20260505-0
summary:
A transient lunar phenomenon (TLP) or lunar transient phenomenon (LTP) is a short-lived change in light, color or appearance on the surface of the Moon. The term was created by Patrick Moore in his co-authorship of NASA Technical Report R-277 Chronological Catalog of Reported Lunar Events, published in 1968. Claims of short-lived lunar phenomena go back at least 1,000 years, with some having been observed independently by multiple witnesses or reputable scientists. Nevertheless, the majority of transient lunar phenomenon reports are irreproducible and do not possess adequate control experiments that could be used to distinguish among alternative hypotheses to explain their origins. Most lunar scientists will acknowledge that transient events such as outgassing and impact cratering do occur over geologic time. The controversy lies in the frequency of such events. == Description of events == Reports of transient lunar phenomena range from foggy patches to permanent changes of the lunar landscape. Cameron classifies these as (1) gaseous, involving mists and other forms of obscuration, (2) reddish colorations, (3) green, blue or violet colorations, (4) brightenings, and (5) darkening. Two extensive catalogs of transient lunar phenomena exist, with the most recent tallying 2,254 events going back to the 6th century. Of


id: transient-lunar-phenomenon-20260505-1
file: data/en.wikipedia.org/wiki/Transient_lunar_phenomenon-1.md
category: reference
title: Transient lunar phenomenon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transient_lunar_phenomenon
date_saved: 2026-05-05T11:01:33.015357+00:00
instance: kb-cron
parent: transient-lunar-phenomenon-20260505-0
summary:
=== 1801–1900 === Between 1830 and 1840, the German astronomer Johann Heinrich von Mädler observed a strong reddish tint closely east of crater Lichtenberg in Oceanus Procellarum. See also Barcroft in 1940, Haas at a later date, Baum in 1951, and Hill in 1988. On November 24, 1865, Williams and two others observed for one hour and a half a distinct bright speck like an 8 magnitude star on the dark side near crater Carlini in Mare Imbrium. In 1866, the experienced lunar observer and mapmaker J. F. Julius Schmidt claimed that the Linné crater had changed its appearance. Based on drawings made earlier by J. H. Schröter, as well as personal observations and drawings made between 1841 and 1843, he stated that the crater "at the time of oblique illumination cannot at all be seen" (his emphasis), whereas at high illumination, it was visible as a bright spot. Based on repeat observations, he further stated that "Linné can never be seen under any illumination as a crater of the normal type" and that "a local change has taken place". Today, Linné is visible as a normal young impact crater with a diameter of about 1.5 miles (2.4 km). On


id: transient-lunar-phenomenon-20260505-2
file: data/en.wikipedia.org/wiki/Transient_lunar_phenomenon-2.md
category: reference
title: Transient lunar phenomenon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transient_lunar_phenomenon
date_saved: 2026-05-05T11:01:33.015357+00:00
instance: kb-cron
parent: transient-lunar-phenomenon-20260505-0
summary:
=== 1951–1960 === In 1951, Richard Myer Baum (1930–2017) observed the regions near crater Lichtenberg in Oceanus Procellarum and reported a rose-pink coloration which persisted for a time and then faded. See also J.H.Mädler between 1830 and 1840, Barcroft in 1940, and Hill in 1988. On November 15, 1953, Dr. Leon Stuart photographed a lunar flare at approximately 10 miles southeast of crater Pallas. The duration of the flare was 8 to 10 seconds. According to Bonnie Buratti, the coordinates of the impacted object are 3.88° Latitude / 357.71° Longitude. On May 11, 1954, Peter Cattermole observed the disappearance of the central mountains of crater Eratosthenes, although the surrounding detail remained clearly visible. In 1954, Patrick Moore detected curious ray-like features crossing crater Helmholtz. On June 25, 1955, mountaineer and amateur astronomer Valdemar Axel Firsoff observed a faint mist in crater Theophilus. On July 15, 1955, V.A.Firsoff observed crater Herodotus which had a 'pseudo central peak' casting a shadow. On January 16–17, 1956, Robert Miles of Woodland, Calif., noticed a flash of white or bright blue light east of Mare Crisium. On November 2, 1958, the Russian astronomer Nikolai A. Kozyrev observed an apparent half-hour "eruption" that took place on


id: transient-lunar-phenomenon-20260505-3
file: data/en.wikipedia.org/wiki/Transient_lunar_phenomenon-3.md
category: reference
title: Transient lunar phenomenon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transient_lunar_phenomenon
date_saved: 2026-05-05T11:01:33.015357+00:00
instance: kb-cron
parent: transient-lunar-phenomenon-20260505-0
summary:
=== 1971–1980 === During the Apollo 17 mission in December 1972, Lunar Module Pilot Harrison Schmitt observed a bright flash-like phenomenon north of crater Grimaldi while in orbit around the Moon (First Revolution, 21:11:09 GMT, December 10, 1972). While in orbit, Command Module Pilot Ronald Evans of Apollo 17 noticed a light flash eastward of Mare Orientale (14th Revolution, 22:28:27 GMT, December 11, 1972). In September 1973, the Dutch author of books on mysterious phenomena Hans van Kampen and a friend (Van Cleef) observed near crater Linné a bright point of light which was visible for almost two minutes. === 1981–1990 === On December 27, 1982, British Moon observer Harold Hill noticed the absence of the principal craterlet (Nasmyth A) on the floor of the crater Nasmyth. A similar phenomenon was noticed by P.Wade on December 8, 1981. On January 1, 1983, Harold Hill noticed an unusual bright appearance of craterlet Furnerius A near the pronounced crater Furnerius at the evening terminator. On January 29, 1983, several members of the British Astronomical Association (BAA) observed abnormal brightness and purplish coloration at the bowl shaped crater Torricelli B north-northeast of the pear shaped crater Torricelli in Sinus Asperitatis. On October 29,


id: transient-lunar-phenomenon-20260505-4
file: data/en.wikipedia.org/wiki/Transient_lunar_phenomenon-4.md
category: reference
title: Transient lunar phenomenon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transient_lunar_phenomenon
date_saved: 2026-05-05T11:01:33.015357+00:00
instance: kb-cron
parent: transient-lunar-phenomenon-20260505-0
summary:
Impact events are continually occurring on the lunar surface. The most common events are those associated with micrometeorites, as might be encountered during meteor showers. First witnessed in 1972 on three occasions by the crew of Apollo 17, impact flashes from such events have been detected from multiple and simultaneous Earth-based observations. Tables of impacts recorded by video cameras exist for years since 2005 many of which are associated with meteor showers. Furthermore, impact clouds were detected following the crash of ESA's SMART-1 spacecraft, India's Moon Impact Probe and NASA's LCROSS. Impact events leave a visible scar on the surface, and these could be detected by analyzing before and after photos of sufficiently high resolution. No impact craters formed between the Clementine (global resolution 100 metre, selected areas 7–20 metre) and SMART-1 (resolution 50 metre) missions have been identified. NELIOTA successfully observed a wide range of impacts. The observations took place from 2017 to 2023. During these years, 192 lunar impact flashes were detected, and the size and mass of the asteroids were also measured, as well as the temperature during the collisions and the size of the craters created. As a result, apart from completing its main goal, it


id: ultra-high-energy-cosmic-ray-20260505-0
file: data/en.wikipedia.org/wiki/Ultra-high-energy_cosmic_ray-0.md
category: reference
title: Ultra-high-energy cosmic ray
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ultra-high-energy_cosmic_ray
date_saved: 2026-05-05T11:01:34.246968+00:00
instance: kb-cron
parent: ultra-high-energy-cosmic-ray-20260505-0
summary:
In astroparticle physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray with an energy greater than 1 EeV (1018 electronvolts, approximately 0.16 joules), far beyond both the rest mass and energies typical of other cosmic ray particles. The origin of these highest energy cosmic rays is not known. These particles are extremely rare; between 2004 and 2007, the initial runs of the Pierre Auger Observatory (PAO) detected 27 events with estimated arrival energies above 5.7×1019 eV, that is, about one such event every four weeks in the 3000 km2 (1200 mi2) area surveyed by the observatory. == Observational history == The first observation of a cosmic ray particle with an energy exceeding 1.0×1020 eV (16 J) was made by John Linsley and Livio Scarsi at the Volcano Ranch experiment in New Mexico in 1962. Cosmic ray particles with even higher energies have since been observed. Among them was the Oh-My-God particle observed by the University of Utah's Fly's Eye experiment on the evening of 15 October 1991 over Dugway Proving Ground, Utah. Its observation was shocking to astrophysicists, who estimated its energy at approximately 3.2×1020 eV (50 J)—essentially an atomic nucleus with kinetic energy equal to that of a


id: ultra-high-energy-cosmic-ray-20260505-1
file: data/en.wikipedia.org/wiki/Ultra-high-energy_cosmic_ray-1.md
category: reference
title: Ultra-high-energy cosmic ray
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ultra-high-energy_cosmic_ray
date_saved: 2026-05-05T11:01:34.246968+00:00
instance: kb-cron
parent: ultra-high-energy-cosmic-ray-20260505-0
summary:
=== Neutron stars === One suggested source of UHECR particles is their origination from neutron stars. In young neutron stars with spin periods of under 10 ms, the magnetohydrodynamic (MHD) forces from the quasi-neutral fluid of superconducting protons and electrons existing in a neutron superfluid accelerate iron nuclei to UHECR velocities. The neutron superfluid in rapidly rotating stars creates a magnetic field of 108 to 1011 teslas, at which point the neutron star is classified as a magnetar. This magnetic field is the strongest stable field in the observed universe and creates the relativistic MHD wind believed to accelerate iron nuclei remaining from the supernova to the necessary energy. Another hypothesized source of UHECRs from neutron stars is during neutron star to strange star combustion. This hypothesis relies on the assumption that strange matter is the ground state of matter, but has no experimental or observational data to support it. Due to the immense gravitational pressures from the neutron star, it is believed that small pockets of matter consisting of up, down, and strange quarks in equilibrium acting as a single hadron (as opposed to a number of Σ0 baryons). This will then combust the entire star to strange matter,


id: ultra-high-energy-cosmic-ray-20260505-2
file: data/en.wikipedia.org/wiki/Ultra-high-energy_cosmic_ray-2.md
category: reference
title: Ultra-high-energy cosmic ray
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ultra-high-energy_cosmic_ray
date_saved: 2026-05-05T11:01:34.246968+00:00
instance: kb-cron
parent: ultra-high-energy-cosmic-ray-20260505-0
summary:
== Further reading == Elbert, J. W.; Sommers, P. (1995). "In search of a source for the 320 EeV Fly's Eye cosmic ray". The Astrophysical Journal. 441 (1): 151–161. arXiv:astro-ph/9410069. Bibcode:1995ApJ...441..151E. doi:10.1086/175345. S2CID 15510276. Clay, R.; Dawson, B. (1997). Cosmic Bullets: High Energy Particles in Astrophysics. Perseus Books. ISBN 978-0-7382-0139-9. Seife, C. (2000). "Fly's Eye Spies Highs in Cosmic Rays' Demise". Science. 288 (5469): 1147–1149. doi:10.1126/science.288.5469.1147a. PMID 10841723. S2CID 117341691. The Pierre Auger Collaboration; Abreu; Aglietta; Aguirre; Allard; Allekotte; Allen; Allison; Alvarez; Alvarez-Muniz; Ambrosio; Anchordoqui; Andringa; Anzalone; Aramo; Argiro; Arisaka; Armengaud; Arneodo; Arqueros; Asch; Asorey; Assis; Atulugama; Aublin; Ave; Avila; Backer; Badagnani; et al. (2007). "Correlation of the Highest-Energy Cosmic Rays with Nearby Extragalactic Objects". Science. 318 (5852): 938–943. arXiv:0711.2256. Bibcode:2007Sci...318..938P. doi:10.1126/science.1151124. PMID 17991855. S2CID 118376969. == External links == The Highest Energy Particle Ever Recorded Archived 2009-08-15 at the Wayback Machine The details of the event from the official site of the Fly's Eye detector. John Walker's lively analysis of the 1991 event, published in 1994 Origin of energetic space particles pinpointed, by Mark Peplow for news@nature.com, published January 13, 2005. Saharan, Mohit. "Search for ultra-high energy neutrinos at the Pierre Auger Observatory" (PDF). NNV Annual Meeting 2022, Nikhef.


id: unidentified-infrared-emission-20260505-0
file: data/en.wikipedia.org/wiki/Unidentified_infrared_emission-0.md
category: reference
title: Unidentified infrared emission
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Unidentified_infrared_emission
date_saved: 2026-05-05T11:01:35.430261+00:00
instance: kb-cron
parent: unidentified-infrared-emission-20260505-0
summary:
The unidentified infrared emission (UIR or UIE) bands are infrared discrete emissions from circumstellar regions, interstellar media, star-forming regions and extragalactic objects for which the identity of the emitting materials is unknown. The main infrared features occur around 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 μm, although there are many other weak emission features within the ~ 5–19 μm spectral range. In the 1980s, astronomers discovered that the origin of the UIR emission bands is inherent in compounds made of aromatic C–H and C=C chemical bonds, and some went on to hypothesize that the materials responsible should be free-flying polycyclic aromatic hydrocarbon (PAH) molecules. This assignment was based on the observation that the carrier operates far from thermal equilibrium and should therefore be transiently excited by single-photon absorption, which was taken as indicative of a molecule rather than a bulk solid material. Data recorded with the ESA's Infrared Space Observatory and NASA's Spitzer Space Telescope have suggested that the UIR emission bands arise from compounds that are far more complex in composition and structure than PAH molecules. Moreover, the UIR bands follow a clear evolutionary spectral trend that is linked to the lifespan of the astronomical source; from the time


id: vvv-wit-07-20260505-0
file: data/en.wikipedia.org/wiki/VVV-WIT-07-0.md
category: reference
title: VVV-WIT-07
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/VVV-WIT-07
date_saved: 2026-05-05T11:01:36.622029+00:00
instance: kb-cron
parent: vvv-wit-07-20260505-0
summary:
VVV-WIT-07 is a unique variable star which presents a sequence of recurrent dimmings (Ks~14.35 – 16.164) with a possible deep eclipse in July 2012. The star, located in the Scorpius constellation about 23,000 ly (7,100 pc) away, is not a binary star, which would eliminate such a system from explaining the various observed dimmings. == Overview == The star was found by the "Vista Variables in the Via Lactea" (VVV) project, which is a survey of European Southern Observatory (ESO) variability of the innermost bulge of the Milky Way galaxy. The near-infrared spectra of VVV-WIT-07 appear without features, without prominent emission or absorption lines. The characteristics found in the light curve of VVV-WIT-07 (WIT refers to "What Is This?") are similar to those seen in J1407 (Mamajek's Object), a pre-MS K5 dwarf with a ring system that eclipses the star or, alternatively, to Tabby's star, an F3 IV/V star that shows irregular and aperiodic obscurations in its light curve. From 2010 to 2018, the star dimmed and brightened irregularly (v~14.35 – 16.164), and seemed similar to Tabby's star, except the light from VVV-WIT-07 dimmed by up to 80 percent, while Tabby's star faded by only about 20 percent. Another star,


id: wow-signal-20260505-0
file: data/en.wikipedia.org/wiki/Wow!_signal-0.md
category: reference
title: Wow! signal
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wow!_signal
date_saved: 2026-05-05T11:01:37.835016+00:00
instance: kb-cron
parent: wow-signal-20260505-0
summary:
The Wow! signal was a strong narrowband radio signal detected on August 15, 1977, by Ohio State University's Big Ear radio telescope in the United States, then used to support the search for extraterrestrial intelligence. The signal appeared to come from the direction of the constellation Sagittarius and bore expected hallmarks of extraterrestrial origin. Astronomer Jerry R. Ehman discovered the anomaly a few days later while reviewing the recorded data. On the computer printout, he circled the reading of the signal's intensity, "6EQUJ5", and wrote the comment "Wow!" beside it, leading to the event's widely used name. The entire signal sequence lasted for the full 72-second window during which Big Ear was able to observe it. Despite numerous follow-up searches and hypotheses (including brief consideration of reflections from space debris, interstellar scintillation, and comet hydrogen clouds), the signal has never recurred, and no explanation, terrestrial or otherwise, has been confirmed. While some researchers have suggested it could represent an extraterrestrial transmission, its single occurrence and lack of replication limit the strength of this interpretation. The Wow! signal has inspired targeted searches, scientific discussion about rare astrophysical phenomena, and references in popular culture. == Background == In a 1959 paper, Cornell


id: wow-signal-20260505-1
file: data/en.wikipedia.org/wiki/Wow!_signal-1.md
category: reference
title: Wow! signal
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wow!_signal
date_saved: 2026-05-05T11:01:37.835016+00:00
instance: kb-cron
parent: wow-signal-20260505-0
summary:
=== Time variation === At the time of the observation, the Big Ear radio telescope was only adjustable for altitude (or height above the horizon), and relied on the rotation of the Earth to scan across the sky. Given the speed of Earth's rotation and the spatial width of the telescope's observation window, the Big Ear could observe any given point for just 72 seconds. A continuous extraterrestrial signal, therefore, would be expected to register for exactly 72 seconds, and the recorded intensity of such a signal would display a gradual increase for the first 36 seconds—peaking at the center of the observation window—and then a gradual decrease as the telescope moved away from it. All these characteristics are present in the Wow! signal. == Celestial location == The precise location in the sky where the signal apparently originated is uncertain due to the design of the Big Ear telescope, which featured two feed horns, each receiving a beam from slightly different directions, while following Earth's rotation. The Wow! signal was detected in one beam but not in the other, and the data was processed in such a way that it is impossible to determine which of the two horns


id: wow-signal-20260505-2
file: data/en.wikipedia.org/wiki/Wow!_signal-2.md
category: reference
title: Wow! signal
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wow!_signal
date_saved: 2026-05-05T11:01:37.835016+00:00
instance: kb-cron
parent: wow-signal-20260505-0
summary:
== Searches for recurrence of the signal == Several attempts were made by Ehman and other astronomers to recover and identify the signal. The signal was expected to occur three minutes apart in each of the telescope's feed horns, but that did not happen. Ehman unsuccessfully searched for recurrences using Big Ear in the months after the detection. In 1987 and 1989, Robert H. Gray searched for the event using the META array at Oak Ridge Observatory, but did not detect it. In a July 1995 test of signal detection software to be used in its upcoming Project Argus, SETI League executive director [[H. Paul Shuch made several drift-scan observations of the Wow! signal's coordinates with a 12-meter radio telescope at the National Radio Astronomy Observatory in Green Bank, West Virginia, also achieving a null result. In 1995 and 1996, Gray again searched for the signal using the Very Large Array, which is significantly more sensitive than Big Ear. Gray and Simon Ellingsen later searched for recurrences of the event in 1999 using the 26-meter radio telescope at the University of Tasmania's Mount Pleasant Radio Observatory. Six 14-hour observations were made at positions in the vicinity, but nothing like the


id: avalon-explosion-20260505-0
file: data/en.wikipedia.org/wiki/Avalon_explosion-0.md
category: reference
title: Avalon explosion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Avalon_explosion
date_saved: 2026-05-05T11:01:40.553278+00:00
instance: kb-cron
parent: avalon-explosion-20260505-0
summary:
The Avalon explosion, named from the Precambrian faunal trace fossils discovered on the Avalon Peninsula in Newfoundland, eastern Canada, is a proposed evolutionary radiation of prehistoric animals about 575 million years ago in the Ediacaran period, with the Avalon explosion being one of three eras grouped in this time period. This evolutionary event is believed to have occurred some 33 million years earlier than the Cambrian explosion, which had been long thought to be when complex life started on Earth. Scientists are still unsure of the full extent behind the development of the Avalon explosion, which resulted in a rapid increase in metazoan biodiversity, including the first appearance of some extant infrakingdoms/superphyla such as cnidarians and bilaterians. Many of the Avalon explosion animals are sessile soft-bodied organisms living in deep marine environments, and the first stages of the Avalon explosion were observed through comparatively minimal species. == History == Charles Darwin predicted a time of ecological growth before the Cambrian Period, but there was no evidence to support it until the Avalon explosion was proposed in 2008 by Virginia Tech paleontologists after analysis of the morphological space change in several Ediacaran assemblages. The discovery suggests that the early evolution of


id: cambrian-explosion-20260505-0
file: data/en.wikipedia.org/wiki/Cambrian_explosion-0.md
category: reference
title: Cambrian explosion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cambrian_explosion
date_saved: 2026-05-05T11:01:41.804996+00:00
instance: kb-cron
parent: cambrian-explosion-20260505-0
summary:
The Cambrian explosion (also known as the Cambrian radiation or Cambrian diversification) is an interval of time beginning approximately 538.8 million years ago in the Cambrian period of the early Paleozoic, when a sudden radiation of complex life occurred and practically all major animal phyla started appearing in the fossil record. It lasted for about 13 to 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversification in other groups of organisms as well. Before early Cambrian diversification, most organisms were relatively simple, composed of individual cells or small multicellular organisms, occasionally organized into colonies. As the rate of diversification subsequently accelerated, the variety of life became much more complex and began to resemble that of today. Almost all present-day animal phyla appeared during this period, including the earliest chordates. == History and significance == The seemingly rapid appearance of fossils in the "Primordial Strata" was noted by William Buckland in the 1840s. Charles Darwin in his 1859 book On the Origin of Species discussed the then inexplicable lack of earlier fossils as one of the main difficulties for his theory of descent with slow modification through natural selection. The


id: cambrian-explosion-20260505-1
file: data/en.wikipedia.org/wiki/Cambrian_explosion-1.md
category: reference
title: Cambrian explosion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cambrian_explosion
date_saved: 2026-05-05T11:01:41.804996+00:00
instance: kb-cron
parent: cambrian-explosion-20260505-0
summary:
=== Dating the Cambrian === Radiometric dates for much of the Cambrian, obtained by analysis of radioactive elements contained within rocks, have only recently become available, and for only a few regions. Relative dating (A was before B) is often assumed sufficient for studying processes of evolution, but this, too, has been difficult, because of the problems involved in matching up rocks of the same age across different continents. Therefore, dates or descriptions of sequences of events should be regarded with some caution until better data becomes available. In 2004, the start of the Cambrian was dated to 542 Ma. In 2012, it was revised to 541 Ma then in 2022 it was changed again to 538.8 Ma. Some theory suggest Cambrian explosion occurred during the last stages of Gondwanan assembly, which is formed following Rodinia splitting, overlapped with the opening of the Iapetus Ocean between Laurentia and western Gondwana. The largest Cambrian faunal province is located around Gondwana, which extended from the low northern latitudes to the high southern latitudes, just short of the South Pole. By the middle and later parts of the Cambrian, continued rifting had sent the paleocontinents of Laurentia, Baltica and Siberia on their separate


id: cambrian-explosion-20260505-2
file: data/en.wikipedia.org/wiki/Cambrian_explosion-2.md
category: reference
title: Cambrian explosion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cambrian_explosion
date_saved: 2026-05-05T11:01:41.804996+00:00
instance: kb-cron
parent: cambrian-explosion-20260505-0
summary:
=== Phylogenetic techniques === Cladistics is a technique for working out the "family tree" of a set of organisms. It works by the logic that, if groups B and C have more similarities to each other than either has to group A, then B and C are more closely related to each other than either is to A. Characteristics that are compared may be anatomical, such as the presence of a notochord, or molecular, by comparing sequences of DNA or protein. The result of a successful analysis is a hierarchy of clades—groups whose members are believed to share a common ancestor. The cladistic technique is sometimes problematic, as some features, such as wings or camera eyes, evolved more than once, convergently—this must be taken into account in analyses. From the relationships, it may be possible to constrain the date that lineages first appeared. For instance, if fossils of B or C date to X million years ago and the calculated "family tree" says A was an ancestor of B and C, then A must have evolved more than X million years ago. It is also possible to estimate how long ago two living clades diverged—i.e. about how long ago their


id: cambrian-explosion-20260505-3
file: data/en.wikipedia.org/wiki/Cambrian_explosion-3.md
category: reference
title: Cambrian explosion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cambrian_explosion
date_saved: 2026-05-05T11:01:41.804996+00:00
instance: kb-cron
parent: cambrian-explosion-20260505-0
summary:
Changes in the abundance and diversity of some types of fossil have been interpreted as evidence for "attacks" by animals or other organisms. Stromatolites, stubby pillars built by colonies of microorganisms, are a major constituent of the fossil record from about 2,700 million years ago, but their abundance and diversity declined steeply after about 1,250 million years ago. This decline has been attributed to disruption by grazing and burrowing animals. Precambrian marine diversity was dominated by small fossils known as acritarchs. This term describes almost any small organic-walled fossil—from the egg cases of small metazoans to resting cysts of many different kinds of green algae. After appearing around 2,000 million years ago, acritarchs underwent a boom around 1,000 million years ago, increasing in abundance, diversity, size, complexity of shape, and especially size and number of spines. Their increasingly spiny forms in the last 1 billion years may indicate an increased need for defence against predation. Other groups of small organisms from the Neoproterozoic era also show signs of antipredator defenses. A consideration of taxon longevity appears to support an increase in predation pressure around this time. In general, the fossil record shows a very slow appearance of these lifeforms in


id: cambrian-explosion-20260505-4
file: data/en.wikipedia.org/wiki/Cambrian_explosion-4.md
category: reference
title: Cambrian explosion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cambrian_explosion
date_saved: 2026-05-05T11:01:41.804996+00:00
instance: kb-cron
parent: cambrian-explosion-20260505-0
summary:
Crustaceans, one of the four great modern groups of arthropods, are very rare throughout the Cambrian. Convincing crustaceans were once thought to be common in Burgess Shale-type biotas, but none of these individuals can be shown to fall into the crown group of "true crustaceans". The Cambrian record of crown-group crustaceans comes from microfossils. The Swedish Orsten horizons contain later Cambrian crustaceans, but only organisms smaller than 2 mm are preserved. This restricts the data set to juveniles and miniaturised adults. A more informative data source is the organic microfossils of the Mount Cap formation, Mackenzie Mountains, Canada. This late Early Cambrian assemblage (510 to 515 million years ago) consists of microscopic fragments of arthropods' cuticle, which is left behind when the rock is dissolved with hydrofluoric acid. The diversity of this assemblage is similar to that of modern crustacean faunas. Analysis of fragments of feeding machinery found in the formation shows that it was adapted to feed in a very precise and refined fashion. This contrasts with most other early Cambrian arthropods, which fed messily by shovelling anything they could get their feeding appendages on into their mouths. This sophisticated and specialised feeding machinery belonged to a large (about


id: cambrian-explosion-20260505-5
file: data/en.wikipedia.org/wiki/Cambrian_explosion-5.md
category: reference
title: Cambrian explosion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cambrian_explosion
date_saved: 2026-05-05T11:01:41.804996+00:00
instance: kb-cron
parent: cambrian-explosion-20260505-0
summary:
The Burgess Shale and similar lagerstätten preserve the soft parts of organisms, which provide a wealth of data to aid in the classification of enigmatic fossils. It often preserved complete specimens of organisms only otherwise known from dispersed parts, such as loose scales or isolated mouthparts. Further, the majority of organisms and taxa in these horizons are entirely soft-bodied, hence absent from the rest of the fossil record. Since a large part of the ecosystem is preserved, the ecology of the community can also be tentatively reconstructed. However, the assemblages may represent a "museum": a deep-water ecosystem that is evolutionarily "behind" the rapidly diversifying fauna of shallower waters. Because the lagerstätten provide a mode and quality of preservation that is virtually absent outside of the Cambrian, many organisms appear completely different from anything known from the conventional fossil record. This led early workers in the field to attempt to shoehorn the organisms into extant phyla; the shortcomings of this approach led later workers to erect a multitude of new phyla to accommodate all the oddballs. It has since been realised that most oddballs diverged from lineages before they established the phyla known today—slightly different designs, which were fated to perish


id: cambrian-explosion-20260505-6
file: data/en.wikipedia.org/wiki/Cambrian_explosion-6.md
category: reference
title: Cambrian explosion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cambrian_explosion
date_saved: 2026-05-05T11:01:41.804996+00:00
instance: kb-cron
parent: cambrian-explosion-20260505-0
summary:
== Validity == There is strong evidence for species of Cnidaria and Porifera existing in the Ediacaran and possible members of Porifera even before that during the Cryogenian. Bryozoans, once thought to not appear in the fossil record until after the Cambrian, are now known from strata of Cambrian Age 3 from Australia and South China. The fossil record as Darwin knew it seemed to suggest that the major metazoan groups appeared in a few million years of the early to mid-Cambrian, and even in the 1980s, this still appeared to be the case. However, evidence of Precambrian Metazoa is gradually accumulating. If the Ediacaran Kimberella was a mollusc-like protostome (one of the two main groups of coelomates), the protostome and deuterostome lineages must have split significantly before 550 million years ago (deuterostomes are the other main group of coelomates). Even if it is not a protostome, it is widely accepted as a bilaterian. Since fossils of rather modern-looking cnidarians (jellyfish-like organisms) have been found in the Doushantuo lagerstätte, the cnidarian and bilaterian lineages must have diverged well over 580 million years ago. Trace fossils and predatory borings in Cloudina shells provide further evidence of Ediacaran animals. Some fossils from


id: cambrian-explosion-20260505-7
file: data/en.wikipedia.org/wiki/Cambrian_explosion-7.md
category: reference
title: Cambrian explosion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cambrian_explosion
date_saved: 2026-05-05T11:01:41.804996+00:00
instance: kb-cron
parent: cambrian-explosion-20260505-0
summary:
==== Increase in oxygen levels ==== Earth's earliest atmosphere contained no free oxygen (O2); the oxygen that animals breathe today, both in the air and dissolved in water, is the product of billions of years of photosynthesis. Cyanobacteria were the first organisms to evolve the ability to photosynthesize, introducing a steady supply of oxygen into the environment. Initially, oxygen levels did not increase substantially in the atmosphere. The oxygen quickly reacted with iron and other minerals in the surrounding rock and ocean water. Once a saturation point was reached for the reactions in rock and water, oxygen was able to exist as a gas in its diatomic form. Oxygen levels in the atmosphere increased substantially afterward. As a general trend, the concentration of oxygen in the atmosphere has risen gradually over about the last 2.5 billion years. Oxygen levels seem to have a positive correlation with diversity in eukaryotes well before the Cambrian period. The last common ancestor of all extant eukaryotes is thought to have lived around 1.8 billion years ago. Around 800 million years ago, there was a notable increase in the complexity and number of eukaryotes species in the fossil record. Before the spike in diversity, eukaryotes


id: cambrian-explosion-20260505-8
file: data/en.wikipedia.org/wiki/Cambrian_explosion-8.md
category: reference
title: Cambrian explosion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cambrian_explosion
date_saved: 2026-05-05T11:01:41.804996+00:00
instance: kb-cron
parent: cambrian-explosion-20260505-0
summary:
A range of theories are based on the concept that minor modifications to animals' development as they grow from embryo to adult may have been able to cause very large changes in the final adult form. The Hox genes, for example, control which organs individual regions of an embryo will develop into. For instance, if a certain Hox gene is expressed, a region will develop into a limb; if a different Hox gene is expressed in that region (a minor change), it could develop into an eye instead (a phenotypically major change). Such a system allows a large range of disparity to appear from a limited set of genes, but such theories linking this with the explosion struggle to explain why the origin of such a development system should by itself lead to increased diversity or disparity. Evidence of Precambrian metazoans combines with molecular data to show that much of the genetic architecture that could feasibly have played a role in the explosion was already well established by the Cambrian. This apparent paradox is addressed in a theory that focuses on the physics of development. It is proposed that the emergence of simple multicellular forms provided a changed context and


id: cambrian-explosion-20260505-9
file: data/en.wikipedia.org/wiki/Cambrian_explosion-9.md
category: reference
title: Cambrian explosion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cambrian_explosion
date_saved: 2026-05-05T11:01:41.804996+00:00
instance: kb-cron
parent: cambrian-explosion-20260505-0
summary:
==== Increase in size and diversity of planktonic animals ==== Geochemical evidence strongly indicates that the total mass of plankton has been similar to modern levels since early in the Proterozoic. Before the start of the Cambrian, their corpses and droppings were too small to fall quickly towards the seabed, since their drag was about the same as their weight. This meant they were destroyed by scavengers or by chemical processes before they reached the sea floor. Mesozooplankton are plankton of a larger size. Early Cambrian specimens filtered microscopic plankton from the seawater. These larger organisms would have produced droppings and ultimately corpses large enough to fall fairly quickly. This provided a new supply of energy and nutrients to the mid-levels and bottoms of the seas, which opened up a new range of possible ways of life. If any of these remains sank uneaten to the sea floor they could be buried; this would have taken some carbon out of circulation, resulting in an increase in the concentration of breathable oxygen in the seas (carbon readily combines with oxygen). The initial herbivorous mesozooplankton were probably larvae of benthic (seafloor) animals. A larval stage was probably an evolutionary innovation driven by


id: cambrian-explosion-20260505-10
file: data/en.wikipedia.org/wiki/Cambrian_explosion-10.md
category: reference
title: Cambrian explosion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cambrian_explosion
date_saved: 2026-05-05T11:01:41.804996+00:00
instance: kb-cron
parent: cambrian-explosion-20260505-0
summary:
== Uniqueness of the early Cambrian biodiversification == The "Cambrian explosion" can be viewed as two waves of metazoan expansion into empty niches: first, a coevolutionary rise in diversity as animals explored niches on the Ediacaran sea floor, followed by a second expansion in the early Cambrian as they became established in the water column. The rate of diversification seen in the Cambrian phase of the explosion is unparalleled among marine animals: it affected all metazoan clades of which Cambrian fossils have been found. Later radiations, such as those of fish in the Silurian and Devonian periods, involved fewer taxa, mainly with very similar body plans. Although the recovery from the Permian-Triassic extinction started with about as few animal species as the Cambrian explosion, the recovery produced far fewer significantly new types of animals. Whatever triggered the early Cambrian diversification opened up an exceptionally wide range of previously unavailable ecological niches. When these were all occupied, limited space existed for such wide-ranging diversifications to occur again, because strong competition existed in all niches and incumbents usually had the advantage. If a wide range of empty niches had continued, clades would be able to continue diversifying and become disparate enough for


id: missing-heritability-problem-20260505-0
file: data/en.wikipedia.org/wiki/Missing_heritability_problem-0.md
category: reference
title: Missing heritability problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Missing_heritability_problem
date_saved: 2026-05-05T11:01:44.300327+00:00
instance: kb-cron
parent: missing-heritability-problem-20260505-0
summary:
In genetics, the missing heritability problem refers to a difference between heritability estimates obtained from early genome-wide association studies (GWAS) and heritability estimates from twin and family data across many physical and mental traits, including diseases, behaviors, and other phenotypes. An influential review article in 2008 noted that the amount of phenotypic variance explained by significant loci in GWAS studies up to that point was usually far less than expected based on family studies. This gap was referred to as "missing heritability". Using height as a model trait, a paper in 2010 showed that most of the missing heritability can be explained by the presence of large numbers of low variants whose effect sizes were too small to detect at the sample sizes that were then available. This conclusion has subsequently been confirmed using much larger sample sizes, including a study of 5.4 million individuals that identified around 12,000 independent variants that affect human height. While studies of height have particularly large power due to their very large sample size, other complex traits likely have similar genetic architecture. Thus, the missing heritability problem is largely resolved by the presence of tens of thousands of variants of small effects that could


id: dining-philosophers-problem-20260505-0
file: data/en.wikipedia.org/wiki/Dining_philosophers_problem-0.md
category: reference
title: Dining philosophers problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dining_philosophers_problem
date_saved: 2026-05-05T11:01:47.089416+00:00
instance: kb-cron
parent: dining-philosophers-problem-20260505-0
summary:
In computer science, the dining philosophers problem is an example problem often used in concurrent algorithm design to illustrate synchronization issues and techniques for resolving them. It was originally formulated in 1965 by Edsger Dijkstra as a student exam exercise, presented in terms of computers competing for access to tape drive peripherals. Soon after, Tony Hoare gave the problem its present form. == Problem statement == Five philosophers dine together at the same table. Each philosopher has their own plate at the table. There is a fork between each pair of adjacent plates. The dish served is a kind of spaghetti which has to be eaten with two forks. Each philosopher can only alternately think and eat. Moreover, a philosopher can only eat their spaghetti when they have both a left and a right fork. Thus, two forks will only be available when their two nearest neighbors are thinking, not eating. After an individual philosopher finishes eating, they will put down both forks. The problem is how to design a regimen (a concurrent algorithm) such that any philosopher will not starve; i.e., each can forever continue to alternate between eating and thinking, assuming that no philosopher can know when others


id: dining-philosophers-problem-20260505-1
file: data/en.wikipedia.org/wiki/Dining_philosophers_problem-1.md
category: reference
title: Dining philosophers problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dining_philosophers_problem
date_saved: 2026-05-05T11:01:47.089416+00:00
instance: kb-cron
parent: dining-philosophers-problem-20260505-0
summary:
=== Arbitrator solution === Another approach is to guarantee that a philosopher can only pick up both forks or none by introducing an arbitrator to replace circular waiting, e.g., a waiter. In order to pick up the forks, a philosopher must ask permission of the waiter. The waiter gives permission to only one philosopher at a time until the philosopher has picked up both of his forks. Putting down a fork is always allowed. The waiter can be implemented as a mutex. In addition to introducing a new central entity (the waiter), this approach can result in reduced parallelism: if a philosopher is eating and one of his neighbors is requesting the forks, all other philosophers must wait until this request has been fulfilled, even if forks for them are still available. === Limiting the number of diners in the table === A solution presented by William Stallings is to allow a maximum of n-1 philosophers to sit down at any time. The last philosopher would have to wait (for example, using a semaphore) for someone to finish dining before he "sits down" and requests access to any fork. This negates circular wait, guaranteeing that at least one philosopher may


id: pagh-s-problem-20260505-0
file: data/en.wikipedia.org/wiki/Pagh's_problem-0.md
category: reference
title: Pagh's problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pagh's_problem
date_saved: 2026-05-05T11:01:48.275852+00:00
instance: kb-cron
parent: pagh-s-problem-20260505-0
summary:
Pagh's problem is a data structure problem often used when studying lower bounds in computer science named after Rasmus Pagh. Mihai Pătrașcu was the first to give lower bounds for the problem. In 2021 it was shown that, given popular conjectures, the naive linear time algorithm is optimal. == Definition == We are given as inputs k {\displaystyle k} subsets X 1 , X 2 , … , X k {\displaystyle X_{1},X_{2},\dots ,X_{k}} over a universe U = { 1 , … , k } {\displaystyle U=\{1,\dots ,k\}} . We must accept updates of the following kind: Given a pointer to two subsets X 1 {\displaystyle X_{1}} and X 2 {\displaystyle X_{2}} , create a new subset X 1 ∩ X 2 {\displaystyle X_{1}\cap X_{2}} . After each update, we must output whether the new subset is empty or not. == References ==


id: producer-consumer-problem-20260505-0
file: data/en.wikipedia.org/wiki/Producer–consumer_problem-0.md
category: reference
title: Producer–consumer problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Producer–consumer_problem
date_saved: 2026-05-05T11:01:49.467920+00:00
instance: kb-cron
parent: producer-consumer-problem-20260505-0
summary:
In computing, the producer-consumer problem (also known as the bounded-buffer problem) is a family of problems described by Edsger W. Dijkstra since 1965. Dijkstra found the solution for the producer-consumer problem as he worked as a consultant for the Electrologica X1 and X8 computers: "The first use of producer-consumer was partly software, partly hardware: The component taking care of the information transport between store and peripheral was called 'a channel' ... Synchronization was controlled by two counting semaphores in what we now know as the producer/consumer arrangement: the one semaphore indicating the length of the queue, was incremented (in a V) by the CPU and decremented (in a P) by the channel, the other one, counting the number of unacknowledged completions, was incremented by the channel and decremented by the CPU. [The second semaphore being positive would raise the corresponding interrupt flag.]" Dijkstra wrote about the unbounded buffer case: "We consider two processes, which are called the 'producer' and the 'consumer' respectively. The producer is a cyclic process and each time it goes through its cycle it produces a certain portion of information, that has to be processed by the consumer. The consumer is also a cyclic process and each


id: producer-consumer-problem-20260505-1
file: data/en.wikipedia.org/wiki/Producer–consumer_problem-1.md
category: reference
title: Producer–consumer problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Producer–consumer_problem
date_saved: 2026-05-05T11:01:49.467920+00:00
instance: kb-cron
parent: producer-consumer-problem-20260505-0
summary:
The Go producer-consumer solution uses the main Go routine for consumer and creates a new, unnamed Go routine for the producer. The two Go routines are connected with channel ch. This channel can queue up to three int values. The statement ch := make(chan int, 3) creates the channel, the statement ch <- produceMessage() sends a value into the channel and the statement recvMsg := range ch receives a value from the channel. The allocation of memory resources, the allocation of processing resources, and the synchronization of resources are done by the programming language automatically. == Without semaphores or monitors == Leslie Lamport documented a bounded buffer producer-consumer solution for one producer and one consumer: We assume that the buffer can hold at most b messages, b >= 1. In our solution, we let k be a constant greater than b, and let s and r be integer variables assuming values between 0 and k-1. We assume that initially s=r and the buffer is empty. By choosing k to be a multiple of b, the buffer can be implemented as an array B [0: b - 1]. The producer simply puts each new message into B[s mod b], and the


id: resource-starvation-20260505-0
file: data/en.wikipedia.org/wiki/Resource_starvation-0.md
category: reference
title: Resource starvation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Resource_starvation
date_saved: 2026-05-05T11:01:50.668301+00:00
instance: kb-cron
parent: resource-starvation-20260505-0
summary:
In computer science, resource starvation is a problem encountered in concurrent computing where a process is perpetually denied necessary resources to process its work. Starvation may be caused by errors in a scheduling or mutual exclusion algorithm, but can also be caused by resource leaks, and can be intentionally caused via a denial-of-service attack such as a fork bomb. When starvation is impossible in a concurrent algorithm, the algorithm is called starvation-free, lockout-freed or said to have finite bypass. This property is an instance of liveness, and is one of the two requirements for any mutual exclusion algorithm; the other being correctness. The name "finite bypass" means that any process (concurrent part) of the algorithm is bypassed at most a finite number times before being allowed access to the shared resource. == Scheduling == Starvation is usually caused by an overly simplistic scheduling algorithm. For example, if a (poorly designed) multi-tasking system always switches between the first two tasks while a third never gets to run, then the third task is being starved of CPU time. The scheduling algorithm, which is part of the kernel, is supposed to allocate resources equitably; that is, the algorithm should allocate resources so that


id: sleeping-barber-problem-20260505-0
file: data/en.wikipedia.org/wiki/Sleeping_barber_problem-0.md
category: reference
title: Sleeping barber problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sleeping_barber_problem
date_saved: 2026-05-05T11:01:51.847483+00:00
instance: kb-cron
parent: sleeping-barber-problem-20260505-0
summary:
In computer science, the sleeping barber problem is a classic inter-process communication and synchronization problem that illustrates the complexities that arise when there are multiple operating system processes. The problem was originally proposed in 1965 by computer science pioneer Edsger Dijkstra, who used it to make the point that general semaphores are often superfluous. == Problem statement == Imagine a hypothetical barbershop with one barber, one barber chair, and a waiting room with n chairs (n may be 0) for waiting customers. The following rules apply: If there are no customers, the barber falls asleep in the chair A customer must wake the barber if he is asleep If a customer arrives while the barber is working, the customer leaves if all chairs are occupied and sits in an empty chair if it's available When the barber finishes a haircut, he inspects the waiting room to see if there are any waiting customers and falls asleep if there are none There are two main complications. First, there is a risk that a race condition, where the barber sleeps while a customer waits for the barber to get them for a haircut, arises because all of the actions—checking the waiting room,


id: list-of-unsolved-problems-in-computer-science-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_computer_science-0.md
category: reference
title: List of unsolved problems in computer science
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_computer_science
date_saved: 2026-05-05T11:01:53.389450+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-computer-science-20260505-0
summary:
This article is a list of notable unsolved problems in computer science. A problem in computer science is considered unsolved when no solution is known or when experts in the field disagree about proposed solutions. == Computational complexity == P versus NP problem – The P vs NP problem is a major unsolved question in computer science that asks whether every problem whose solution can be quickly verified by a computer (NP) can also be quickly solved by a computer (P). This question has profound implications for fields such as cryptography, algorithm design, and computational theory. What is the relationship between BQP and NP? NC = P problem NP = co-NP problem P = BPP problem P = PSPACE problem L = NL problem PH = PSPACE problem L = P problem L = RL problem Unique games conjecture Is the exponential time hypothesis true? Is the strong exponential time hypothesis (SETH) true? Do one-way functions exist? Is public-key cryptography possible? Log-rank conjecture Hartmanis–Stearns conjecture == Polynomial versus nondeterministic-polynomial time for specific algorithmic problems == Can integer factorization be done in polynomial time on a classical (non-quantum) computer? Can the discrete logarithm be computed in polynomial time on a classical


id: 3sum-20260505-0
file: data/en.wikipedia.org/wiki/3SUM-0.md
category: reference
title: 3SUM
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/3SUM
date_saved: 2026-05-05T11:01:54.553179+00:00
instance: kb-cron
parent: 3sum-20260505-0
summary:
In computational complexity theory, the 3SUM problem asks if a given set of n {\displaystyle n} real numbers contains three elements that sum to zero. A generalized version, k {\displaystyle k} -SUM, asks the same question on k {\displaystyle k} elements, rather than simply 3. 3SUM can be easily solved in O ( n 2 ) {\displaystyle O(n^{2})} time, and matching Ω ( n ⌈ k / 2 ⌉ ) {\displaystyle \Omega (n^{\lceil k/2\rceil })} lower bounds are known in some specialized models of computation (Erickson 1999). It was conjectured that any deterministic algorithm for the 3SUM requires Ω ( n 2 ) {\displaystyle \Omega (n^{2})} time. In 2014, the original 3SUM conjecture was refuted by Allan Grønlund and Seth Pettie who gave a deterministic algorithm that solves 3SUM in O ( n 2 / ( log ⁡ n / log ⁡ log ⁡ n ) 2 / 3 ) {\displaystyle O(n^{2}/({\log n}/{\log \log n})^{2/3})} time. Additionally, Grønlund and Pettie showed that the 4-linear decision tree complexity of 3SUM is O ( n 3 / 2 log ⁡ n ) {\displaystyle O(n^{3/2}{\sqrt {\log n}})} . These bounds were subsequently improved. The current best known algorithm for 3SUM runs in O


id: 3sum-20260505-1
file: data/en.wikipedia.org/wiki/3SUM-1.md
category: reference
title: 3SUM
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/3SUM
date_saved: 2026-05-05T11:01:54.553179+00:00
instance: kb-cron
parent: 3sum-20260505-0
summary:
=== Three different arrays === Instead of searching for the 3 numbers in a single array, we can search for them in 3 different arrays. I.e., given three arrays X, Y and Z, find three numbers a∈X, b∈Y, c∈Z, such that ⁠ a + b + c = 0 {\displaystyle a+b+c=0} ⁠. Call the 1-array variant 3SUM×1 and the 3-array variant 3SUM×3. Given a solver for 3SUM×1, the 3SUM×3 problem can be solved in the following way (assuming all elements are integers): For every element in X, Y and Z, set: ⁠ X [ i ] ← X [ i ] ∗ 10 + 1 {\displaystyle X[i]\gets X[i]*10+1} ⁠, ⁠ Y [ i ] ← Y [ i ] ∗ 10 + 2 {\displaystyle Y[i]\gets Y[i]*10+2} ⁠, ⁠ Z [ i ] ← Z [ i ] ∗ 10 − 3 {\displaystyle Z[i]\gets Z[i]*10-3} ⁠. Let S be a concatenation of the arrays X, Y and Z. Use the 3SUM×1 oracle to find three elements ⁠ a ′ ∈ S , b ′ ∈ S , c ′ ∈ S {\displaystyle a'\in S,\ b'\in S,\ c'\in S} ⁠ such that ⁠ a ′ + b ′ + c ′ =


id: 3sum-20260505-2
file: data/en.wikipedia.org/wiki/3SUM-2.md
category: reference
title: 3SUM
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/3SUM
date_saved: 2026-05-05T11:01:54.553179+00:00
instance: kb-cron
parent: 3sum-20260505-0
summary:
If there is a solution for 3SUM: z = x + y {\displaystyle z=x+y} , then: T [ h ( z ) ] = T [ h ( x ) ] + T [ h ( y ) ] {\displaystyle T[h(z)]=T[h(x)]+T[h(y)]} and h ( z ) = h ( x ) + h ( y ) {\displaystyle h(z)=h(x)+h(y)} , so this solution will be found by the Conv3SUM solver on T. Conversely, if a Conv3SUM is found on T, then obviously it corresponds to a 3SUM solution on S since T is just a permutation of S. This idealized solution doesn't work, because any hash function might map several distinct elements of S to the same cell of T. The trick is to create an array ⁠ T ∗ {\displaystyle T^{*}} ⁠ by selecting a single random element from each cell of T, and run Conv3SUM on ⁠ T ∗ {\displaystyle T^{*}} ⁠. If a solution is found, then it is a correct solution for 3SUM on S. If no solution is found, then create a different random ⁠ T ∗ {\displaystyle T^{*}} ⁠ and try again. Suppose there are at most R elements in each cell of T. Then


id: aanderaa-karp-rosenberg-conjecture-20260505-0
file: data/en.wikipedia.org/wiki/Aanderaa–Karp–Rosenberg_conjecture-0.md
category: reference
title: Aanderaa–Karp–Rosenberg conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Aanderaa–Karp–Rosenberg_conjecture
date_saved: 2026-05-05T11:01:55.807273+00:00
instance: kb-cron
parent: aanderaa-karp-rosenberg-conjecture-20260505-0
summary:
In theoretical computer science, the Aanderaa–Karp–Rosenberg conjecture (also known as the Aanderaa–Rosenberg conjecture or the evasiveness conjecture) is a group of related conjectures about the number of questions of the form "Is there an edge between vertex u {\displaystyle u} and vertex v {\displaystyle v} ?" that have to be answered to determine whether or not an undirected graph has a particular property such as planarity or bipartiteness. They are named after Stål Aanderaa, Richard M. Karp, and Arnold L. Rosenberg. According to the conjecture, for a wide class of properties, no algorithm can guarantee that it will be able to skip any questions: any algorithm for determining whether the graph has the property, no matter how clever, might need to examine every pair of vertices before it can give its answer. A property satisfying this conjecture is called evasive. More precisely, the Aanderaa–Rosenberg conjecture states that any deterministic algorithm must test at least a constant fraction of all possible pairs of vertices, in the worst case, to determine any non-trivial monotone graph property. In this context, a property is monotone if it remains true when edges are added; for example, planarity is not monotone, but non-planarity is monotone. A


id: aanderaa-karp-rosenberg-conjecture-20260505-1
file: data/en.wikipedia.org/wiki/Aanderaa–Karp–Rosenberg_conjecture-1.md
category: reference
title: Aanderaa–Karp–Rosenberg conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Aanderaa–Karp–Rosenberg_conjecture
date_saved: 2026-05-05T11:01:55.807273+00:00
instance: kb-cron
parent: aanderaa-karp-rosenberg-conjecture-20260505-0
summary:
== Definitions == In the context of this article, all graphs will be simple and undirected, unless stated otherwise. This means that the edges of the graph form a set (and not a multiset) and each edge is a pair of distinct vertices. Graphs are assumed to have an implicit representation in which each vertex has a unique identifier or label and in which it is possible to test the adjacency of any two vertices, but for which adjacency testing is the only allowed primitive operation. Informally, a graph property is a property of a graph that is independent of labeling. More formally, a graph property is a mapping from the class of all graphs to { 0 , 1 } {\displaystyle \{0,1\}} such that isomorphic graphs are mapped to the same value. For example, the property of containing at least one vertex of degree two is a graph property, but the property that the first vertex has degree two is not, because it depends on the labeling of the graph (in particular, it depends on which vertex is the "first" vertex). A graph property is called non-trivial if it does not assign the same value to all graphs. For


id: aanderaa-karp-rosenberg-conjecture-20260505-2
file: data/en.wikipedia.org/wiki/Aanderaa–Karp–Rosenberg_conjecture-2.md
category: reference
title: Aanderaa–Karp–Rosenberg conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Aanderaa–Karp–Rosenberg_conjecture
date_saved: 2026-05-05T11:01:55.807273+00:00
instance: kb-cron
parent: aanderaa-karp-rosenberg-conjecture-20260505-0
summary:
== Deterministic query complexity == For deterministic algorithms, Rosenberg (1973) originally conjectured that for all nontrivial graph properties on n {\displaystyle n} vertices, deciding whether a graph possesses this property requires Ω ( n 2 ) {\displaystyle \Omega (n^{2})} The non-triviality condition is clearly required because there are trivial properties like "is this a graph?" which can be answered with no queries at all. The conjecture was disproved by Aanderaa, who exhibited a directed graph property (the property of containing a "sink") which required only O ( n ) {\displaystyle O(n)} queries to test. A sink, in a directed graph, is a vertex of indegree n − 1 {\displaystyle n-1} and outdegree zero. The existence of a sink can be tested with less than 3 n {\displaystyle 3n} queries. An undirected graph property which can also be tested with O ( n ) {\displaystyle O(n)} queries is the property of being a scorpion graph, first described in Best, van Emde Boas & Lenstra (1974). A scorpion graph is a graph containing a three-vertex path, such that one endpoint of the path is connected to all remaining vertices, while the other two path vertices have no incident edges other than the


id: aanderaa-karp-rosenberg-conjecture-20260505-3
file: data/en.wikipedia.org/wiki/Aanderaa–Karp–Rosenberg_conjecture-3.md
category: reference
title: Aanderaa–Karp–Rosenberg conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Aanderaa–Karp–Rosenberg_conjecture
date_saved: 2026-05-05T11:01:55.807273+00:00
instance: kb-cron
parent: aanderaa-karp-rosenberg-conjecture-20260505-0
summary:
== Quantum query complexity == For bounded-error quantum query complexity, the best known lower bound is Ω ( n 2 / 3 ( log ⁡ n ) 1 / 6 ) {\displaystyle \Omega {\bigl (}n^{2/3}(\log n)^{1/6}{\bigr )}} as observed by Andrew Yao. It is obtained by combining the randomized lower bound with the quantum adversary method. The best possible lower bound one could hope to achieve is Ω ( n ) {\displaystyle \Omega (n)} , unlike the classical case, due to Grover's algorithm which gives an O ( n ) {\displaystyle O(n)} -query algorithm for testing the monotone property of non-emptiness. Similar to the deterministic and randomized case, there are some properties which are known to have an Ω ( n ) {\displaystyle \Omega (n)} lower bound, for example non-emptiness (which follows from the optimality of Grover's algorithm) and the property of containing a triangle. There are some graph properties which are known to have an Ω ( n 3 / 2 ) {\displaystyle \Omega (n^{3/2})} lower bound, and even some properties with an Ω ( n 2 ) {\displaystyle \Omega (n^{2})} lower bound. For example, the monotone property of nonplanarity requires Θ ( n 3 / 2 ) {\displaystyle


id: artificial-general-intelligence-20260505-0
file: data/en.wikipedia.org/wiki/Artificial_general_intelligence-0.md
category: reference
title: Artificial general intelligence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Artificial_general_intelligence
date_saved: 2026-05-05T11:01:56.982213+00:00
instance: kb-cron
parent: artificial-general-intelligence-20260505-0
summary:
Artificial general intelligence (AGI) is a hypothetical type of artificial intelligence that matches or surpasses human capabilities across virtually all cognitive tasks. Beyond AGI, artificial superintelligence (ASI) would outperform the best human abilities across every domain by a wide margin. Unlike artificial narrow intelligence (ANI), whose competence is confined to well‑defined tasks, an AGI system can generalise knowledge, transfer skills between domains, and solve novel problems without task‑specific reprogramming. Creating AGI is a stated goal of technology companies such as OpenAI, Google, xAI, and Meta. A 2020 survey identified 72 active AGI research and development projects across 37 countries. AGI is a common topic in science fiction and futures studies. Contention exists over whether AGI represents an existential risk. Some AI experts and industry figures have stated that mitigating the risk of human extinction posed by AGI should be a global priority. Others find the development of AGI to be in too remote a stage to present such a risk. == Terminology == AGI is also known as strong AI, full AI, human-level AI, human-level intelligent AI, or general intelligent action. The term "artificial general intelligence" was used in 1997 by Mark Gubrud in a discussion of the implications of


id: artificial-general-intelligence-20260505-1
file: data/en.wikipedia.org/wiki/Artificial_general_intelligence-1.md
category: reference
title: Artificial general intelligence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Artificial_general_intelligence
date_saved: 2026-05-05T11:01:56.982213+00:00
instance: kb-cron
parent: artificial-general-intelligence-20260505-0
summary:
==== Ikea test ==== The "Ikea test", also known as the Flat Pack Furniture Test, involves an AI controls a robot which attempts to assemble a Ikea flat-pack furniture product after having been shown the parts and instructions. As early as 2013, MIT's IkeaBot demonstrated fully autonomous multi-robot assembly of an IKEA Lack table in ten minutes, with no human intervention and no pre-programmed assembly instructions. The robots inferred the assembly sequence from the geometry of the parts alone. In December 2025, MIT researchers demonstrated a "speech-to-reality" system combining large language models with vision-language models and robotic assembly: a user says "I want a simple stool" and a robotic arm constructs the furniture from modular components within five minutes, using generative AI to reason about geometry, function, and assembly sequence from natural language alone. The FurnitureBench benchmark, published in the International Journal of Robotics Research in 2025, now provides a standardised real-world furniture assembly benchmark with over 200 hours of demonstration data for training and evaluating autonomous assembly systems. ==== Coffee test ==== Steve Wozniak proposed a test where a machine is required to enter an average American home and figure out how to make coffee. It must find the


id: artificial-general-intelligence-20260505-2
file: data/en.wikipedia.org/wiki/Artificial_general_intelligence-2.md
category: reference
title: Artificial general intelligence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Artificial_general_intelligence
date_saved: 2026-05-05T11:01:56.982213+00:00
instance: kb-cron
parent: artificial-general-intelligence-20260505-0
summary:
At the turn of the century, many mainstream AI researchers hoped that strong AI could be developed by combining programs that solve various sub-problems. Hans Moravec wrote in 1988: I am confident that this bottom-up route to artificial intelligence will one day meet the traditional top-down route more than halfway, ready to provide the real-world competence and the commonsense knowledge that has been so frustratingly elusive in reasoning programs. Fully intelligent machines will result when the metaphorical golden spike is driven, uniting the two efforts. However, even at the time, this was disputed. For example, Stevan Harnad of Princeton University concluded his 1990 paper on the symbol grounding hypothesis by stating: The expectation has often been voiced that "top-down" (symbolic) approaches to modeling cognition will somehow meet "bottom-up" (sensory) approaches somewhere in between. If the grounding considerations in this paper are valid, then this expectation is hopelessly modular and there is really only one viable route from sense to symbols: from the ground up. A free-floating symbolic level like the software level of a computer will never be reached by this route (or vice versa) – nor is it clear why we should even try to reach such a level,


id: artificial-general-intelligence-20260505-3
file: data/en.wikipedia.org/wiki/Artificial_general_intelligence-3.md
category: reference
title: Artificial general intelligence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Artificial_general_intelligence
date_saved: 2026-05-05T11:01:56.982213+00:00
instance: kb-cron
parent: artificial-general-intelligence-20260505-0
summary:
Progress in artificial intelligence has historically gone through periods of rapid progress separated by periods when progress appeared to stop. Ending each hiatus were fundamental advances in hardware, software or both to create space for further progress. For example, the computer hardware available in the twentieth century was not sufficient to implement deep learning, which requires large numbers of GPU-enabled CPUs. In the introduction to his 2006 book, Goertzel says that estimates of the time needed before a truly flexible AGI is built vary from 10 years to over a century. As of 2007, the consensus in the AGI research community seemed to be that the timeline discussed by Ray Kurzweil in 2005 in The Singularity is Near (i.e. between 2015 and 2045) was plausible. Mainstream AI researchers have given a wide range of opinions on whether progress will be this rapid. A 2012 meta-analysis of 95 such opinions found a bias towards predicting that the onset of AGI would occur within 16–26 years for modern and historical predictions alike. That paper has been criticized for how it categorized opinions as expert or non-expert. In 2012, Alex Krizhevsky, Ilya Sutskever, and Geoffrey Hinton developed a neural network called AlexNet, which


id: artificial-general-intelligence-20260505-4
file: data/en.wikipedia.org/wiki/Artificial_general_intelligence-4.md
category: reference
title: Artificial general intelligence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Artificial_general_intelligence
date_saved: 2026-05-05T11:01:56.982213+00:00
instance: kb-cron
parent: artificial-general-intelligence-20260505-0
summary:
=== Early estimates === For low-level brain simulation, a very powerful cluster of computers or GPUs would be required, given the enormous quantity of synapses within the human brain. Each of the 1011 (one hundred billion) neurons has on average 7,000 synaptic connections (synapses) to other neurons. The brain of a three-year-old child has about 1015 synapses (1 quadrillion). This number declines with age, stabilizing by adulthood. Estimates vary for an adult, ranging from 1014 to 5×1014 synapses (100 to 500 trillion). An estimate of the brain's processing power, based on a simple switch model for neuron activity, is around 1014 (100 trillion) synaptic updates per second (SUPS). In 1997, Kurzweil looked at various estimates for the hardware required to equal the human brain and adopted a figure of 1016 computations per second. (For comparison, if a "computation" was equivalent to one "floating-point operation" – a measure used to rate current supercomputers – then 1016 "computations" would be equivalent to 10 petaFLOPS, achieved in 2011, while 1018 was achieved in 2022.) He used this figure to predict that the necessary hardware would be available sometime between 2015 and 2025, if the exponential growth in computer power at the time of


id: artificial-general-intelligence-20260505-5
file: data/en.wikipedia.org/wiki/Artificial_general_intelligence-5.md
category: reference
title: Artificial general intelligence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Artificial_general_intelligence
date_saved: 2026-05-05T11:01:56.982213+00:00
instance: kb-cron
parent: artificial-general-intelligence-20260505-0
summary:
Sentience (or "phenomenal consciousness"): The ability to "feel" perceptions or emotions subjectively, as opposed to the ability to reason about perceptions. Some philosophers, such as David Chalmers, use the term "consciousness" to refer exclusively to phenomenal consciousness, which is roughly equivalent to sentience. Determining why and how subjective experience arises is known as the hard problem of consciousness. Thomas Nagel explained in 1974 that it "feels like" something to be conscious. If we are not conscious, then it doesn't feel like anything. Nagel uses the example of a bat: we can sensibly ask "what does it feel like to be a bat?" However, we are unlikely to ask "what does it feel like to be a toaster?" Nagel concludes that a bat appears to be conscious (i.e., has consciousness) but a toaster does not. In 2022, a Google engineer claimed that the company's AI chatbot, LaMDA, had achieved sentience, though this claim was widely disputed by other experts. Self-awareness: To have conscious awareness of oneself as a separate individual, especially to be consciously aware of one's own thoughts. This is opposed to simply being the "subject of one's thought"—an operating system or debugger can be "aware of itself" (that is,


id: artificial-general-intelligence-20260505-6
file: data/en.wikipedia.org/wiki/Artificial_general_intelligence-6.md
category: reference
title: Artificial general intelligence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Artificial_general_intelligence
date_saved: 2026-05-05T11:01:56.982213+00:00
instance: kb-cron
parent: artificial-general-intelligence-20260505-0
summary:
=== Revitalising environmental conservation and biodiversity === AGI could significantly contribute to preserving the natural environment and protecting endangered species. By analyzing satellite imagery, climate data, and wildlife patterns, AGI systems could identify environmental threats earlier and recommend targeted conservation strategies. AGI could help optimize land use, monitor illegal activities like poaching or deforestation in real-time, and support global efforts to restore ecosystems. Advanced predictive models developed by AGI could also assist in reversing biodiversity loss, ensuring the survival of critical species and maintaining ecological balance. === Enhancing space exploration and colonization === AGI could revolutionize humanity's ability to explore and settle beyond Earth. With its advanced problem-solving skills, AGI could autonomously manage complex space missions, including navigation, resource management, and emergency response. It could accelerate the design of life support systems, habitats, and spacecraft optimized for extraterrestrial environments. Furthermore, AGI could support efforts to colonize planets like Mars by simulating survival scenarios and helping humans adapt to new worlds, expanding the possibilities for interplanetary civilization. == Risks == === Existential risks === AGI may represent multiple types of existential risk, which are risks that threaten "the premature extinction of Earth-originating intelligent life or the permanent and drastic destruction of


id: artificial-general-intelligence-20260505-7
file: data/en.wikipedia.org/wiki/Artificial_general_intelligence-7.md
category: reference
title: Artificial general intelligence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Artificial_general_intelligence
date_saved: 2026-05-05T11:01:56.982213+00:00
instance: kb-cron
parent: artificial-general-intelligence-20260505-0
summary:
=== Mass unemployment === Researchers from OpenAI estimated in 2023 that "80% of the U.S. workforce could have at least 10% of their work tasks affected by the introduction of LLMs, while around 19% of workers may see at least 50% of their tasks impacted". They consider office workers to be the most exposed, for example mathematicians, accountants or web designers. AGI could have a better autonomy, ability to make decisions, to interface with other computer tools, but also to control robotized bodies. A common belief among top AI company insiders is that most workers will face technological unemployment from AGI, starting with white-collar jobs and, as robotics improves, extending to blue-collar jobs. Critics of the idea argue that AGI will complement rather than replace humans, and that automation displaces work in the short term but not in the long term. According to Stephen Hawking, the outcome of automation on the quality of life will depend on how the wealth will be redistributed: Everyone can enjoy a life of luxurious leisure if the machine-produced wealth is shared, or most people can end up miserably poor if the machine-owners successfully lobby against wealth redistribution. So far, the trend seems to be


id: artificial-intelligence-content-detection-20260505-0
file: data/en.wikipedia.org/wiki/Artificial_intelligence_content_detection-0.md
category: reference
title: Artificial intelligence content detection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Artificial_intelligence_content_detection
date_saved: 2026-05-05T11:01:58.213819+00:00
instance: kb-cron
parent: artificial-intelligence-content-detection-20260505-0
summary:
Artificial intelligence detection software aims to determine whether some content (text, image, video or audio) was generated using artificial intelligence (AI). This software is often unreliable. == Accuracy issues == Many AI detection tools have been shown to be unreliable in detecting AI-generated text. In a 2023 study conducted by Weber-Wulff et al., researchers evaluated 14 detection tools including Turnitin and GPTZero and found that "all scored below 80% of accuracy and only 5 over 70%." They also found that these tools tend to have a bias for classifying texts more as human than as AI, and that accuracy of these tools worsens upon paraphrasing. === False positives === In AI content detection, a false positive is when human-written work is incorrectly flagged as AI-written. Many AI detection platforms claim to have a minimal level of false positives, with Turnitin claiming a less than 1% false positive rate. However, later research by The Washington Post produced much higher rates of 50%, though they used a smaller sample size. False positives in an academic setting frequently lead to accusations of academic misconduct, which can have serious consequences for a student's academic record. Additionally, studies have shown evidence that many AI detection


id: artificial-intelligence-content-detection-20260505-1
file: data/en.wikipedia.org/wiki/Artificial_intelligence_content_detection-1.md
category: reference
title: Artificial intelligence content detection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Artificial_intelligence_content_detection
date_saved: 2026-05-05T11:01:58.213819+00:00
instance: kb-cron
parent: artificial-intelligence-content-detection-20260505-0
summary:
== Anti text detection == There is software available designed to bypass AI text detection. In practice, evasion may not require specialized bypass tools. Paraphrasing, style editing, and removal of repeated discourse markers can substantially reduce the effectiveness of detectors that rely on recognizable surface patterns. A study published in August 2023 analyzed 20 abstracts from papers published in the Eye Journal, which were then paraphrased using GPT-4.0. The AI-paraphrased abstracts were examined for plagiarism using QueText and for AI-generated content using Originality.AI. The texts were then re-processed through an adversarial software called Undetectable.ai in order to reduce the AI-detection scores. The study found that the AI detection tool, Originality.AI, identified text generated by GPT-4 with a mean accuracy of 91.3%. However, after reprocessing by Undetectable.ai, the detection accuracy of Originality.ai dropped to a mean accuracy of 27.8%. Some experts also believe that techniques like digital watermarking are ineffective because they can be removed or added to trigger false positives. "A Watermark for Large Language Models" paper by Kirchenbauer et al. (2023) also addresses potential vulnerabilities of watermarking techniques. The authors outline a range of adversarial tactics, including text insertion, deletion, and substitution attacks, that could be used to bypass


id: artificial-wisdom-20260505-0
file: data/en.wikipedia.org/wiki/Artificial_wisdom-0.md
category: reference
title: Artificial wisdom
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Artificial_wisdom
date_saved: 2026-05-05T11:01:59.482721+00:00
instance: kb-cron
parent: artificial-wisdom-20260505-0
summary:
Artificial wisdom (AW) is an artificial intelligence (AI) system which is able to display the human traits of wisdom and morals while being able to contemplate its own “endpoint”. Artificial wisdom can be described as artificial intelligence reaching the top-level of decision-making when confronted with the most complex challenging situations. The term artificial wisdom is used when the "intelligence" is based on more than by chance collecting and interpreting data, but by design enriched with smart and conscience strategies that wise people would use. == Overview == The goal of artificial wisdom is to create artificial intelligence that can successfully replicate the “uniquely human trait[s]” of having wisdom and morals as closely as possible. Thus, artificial wisdom, must “incorporate [the] ethical and moral considerations” of the data it uses. There are also many significant ethical and legal implications of AW which are compounded by the rapid advances in AI and related technologies alongside the lack of the development of ethics, guidelines, and regulations without the oversight of any kind of overarching advisory board. Additionally, there are challenges in how to develop, test, and implement AW in real world scenarios. Existing tests do not test the internal thought process by which


id: berman-hartmanis-conjecture-20260505-0
file: data/en.wikipedia.org/wiki/Berman–Hartmanis_conjecture-0.md
category: reference
title: Berman–Hartmanis conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Berman–Hartmanis_conjecture
date_saved: 2026-05-05T11:02:01.730158+00:00
instance: kb-cron
parent: berman-hartmanis-conjecture-20260505-0
summary:
In structural complexity theory, the Berman–Hartmanis conjecture is an unsolved conjecture named after Leonard C. Berman and Juris Hartmanis. Informally, it states that all NP-complete languages look alike, in the sense that they can be related to each other by polynomial time isomorphisms. == Statements == === Statement using p-isomorphism === An isomorphism between formal languages L1 and L2 is a bijective map f from strings in the alphabet of L1 to strings in the alphabet of L2, with the property that a string x belongs to L1 if and only if f(x) belongs to L2. A polynomial-time isomorphism, or p-isomorphism for short, is an isomorphism f where both f and its inverse function can be computed in an amount of time polynomial in the lengths of their arguments. Berman and Hartmanis conjectured that all NP-complete languages are p-isomorphic to each other. === Statement using paddable languages === A formal language L is paddable if there is a polynomial time function f(x,y), with a polynomial time inverse, such that for every x and every y, the string x belongs to L if and only if f(x,y) belongs to L. That is, it is possible to pad the input x with


id: computational-complexity-of-mathematical-operations-20260505-0
file: data/en.wikipedia.org/wiki/Computational_complexity_of_mathematical_operations-0.md
category: reference
title: Computational complexity of mathematical operations
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Computational_complexity_of_mathematical_operations
date_saved: 2026-05-05T11:02:05.185210+00:00
instance: kb-cron
parent: computational-complexity-of-mathematical-operations-20260505-0
summary:
The following tables list the computational complexity of various algorithms for common mathematical operations. Here, complexity refers to the time complexity of performing computations on a multitape Turing machine. See big O notation for an explanation of the notation used. Note: Due to the variety of multiplication algorithms, M ( n ) {\displaystyle M(n)} below stands in for the complexity of the chosen multiplication algorithm. == Arithmetic functions == This table lists the complexity of mathematical operations on integers. On stronger computational models, specifically a pointer machine and consequently also a unit-cost random-access machine it is possible to multiply two n-bit numbers in time O(n). == Algebraic functions == Here we consider operations over polynomials and n denotes their degree; for the coefficients we use a unit-cost model, ignoring the number of bits in a number. In practice this means that we assume them to be machine integers. For this section M ( n ) {\displaystyle M(n)} indicates the time needed for multiplying two polynomials of degree at most n {\displaystyle n} . == Special functions == Many of the methods in this section are given in Borwein & Borwein. === Elementary functions === The elementary functions are constructed by


id: computational-complexity-of-matrix-multiplication-20260505-0
file: data/en.wikipedia.org/wiki/Computational_complexity_of_matrix_multiplication-0.md
category: reference
title: Computational complexity of matrix multiplication
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Computational_complexity_of_matrix_multiplication
date_saved: 2026-05-05T11:02:06.334401+00:00
instance: kb-cron
parent: computational-complexity-of-matrix-multiplication-20260505-0
summary:
In theoretical computer science, the computational complexity of matrix multiplication dictates how quickly the operation of matrix multiplication can be performed. Matrix multiplication algorithms are a central subroutine in theoretical and numerical algorithms for numerical linear algebra and optimization, so finding the fastest algorithm for matrix multiplication is of major practical relevance. Directly applying the mathematical definition of matrix multiplication gives an algorithm that requires n3 field operations to multiply two n × n matrices over that field (Θ(n3) in big O notation). Surprisingly, algorithms exist that provide better running times than this straightforward "schoolbook algorithm". The first to be discovered was Strassen's algorithm, devised by Volker Strassen in 1969 and often referred to as "fast matrix multiplication". The optimal number of field operations needed to multiply two square n × n matrices up to constant factors is still unknown. This is a major open question in theoretical computer science. As of January 2024, the best bound on the asymptotic complexity of a matrix multiplication algorithm is O(n2.371339). However, this and similar improvements to Strassen are not used in practice, because they are galactic algorithms: the constant coefficient hidden by the big O notation is so large that they are


id: computational-complexity-of-matrix-multiplication-20260505-1
file: data/en.wikipedia.org/wiki/Computational_complexity_of_matrix_multiplication-1.md
category: reference
title: Computational complexity of matrix multiplication
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Computational_complexity_of_matrix_multiplication
date_saved: 2026-05-05T11:02:06.334401+00:00
instance: kb-cron
parent: computational-complexity-of-matrix-multiplication-20260505-0
summary:
=== Group theory reformulation of matrix multiplication algorithms === Henry Cohn, Robert Kleinberg, Balázs Szegedy and Chris Umans put methods such as the Strassen and Coppersmith–Winograd algorithms in an entirely different group-theoretic context, by utilising triples of subsets of finite groups which satisfy a disjointness property called the triple product property (TPP). They also give conjectures that, if true, would imply that there are matrix multiplication algorithms with essentially quadratic complexity. This implies that the optimal exponent of matrix multiplication is 2, which most researchers believe is indeed the case. One such conjecture is that families of wreath products of Abelian groups with symmetric groups realise families of subset triples with a simultaneous version of the TPP. Several of their conjectures have since been disproven by Blasiak, Cohn, Church, Grochow, Naslund, Sawin, and Umans using the Slice Rank method. Further, Alon, Shpilka and Chris Umans have recently shown that some of these conjectures implying fast matrix multiplication are incompatible with another plausible conjecture, the sunflower conjecture, which in turn is related to the cap set problem. === Lower bounds for ω === There is a trivial lower bound of ⁠ ω ≥ 2 {\displaystyle \omega \geq 2} ⁠. Since any


id: computational-complexity-of-matrix-multiplication-20260505-2
file: data/en.wikipedia.org/wiki/Computational_complexity_of_matrix_multiplication-2.md
category: reference
title: Computational complexity of matrix multiplication
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Computational_complexity_of_matrix_multiplication
date_saved: 2026-05-05T11:02:06.334401+00:00
instance: kb-cron
parent: computational-complexity-of-matrix-multiplication-20260505-0
summary:
provided that A and D − C A − 1 B {\displaystyle {D}-{CA}^{-1}{B}} are invertible. Thus, the inverse of a 2n×2n matrix may be computed with two inversions, six multiplications and four additions or additive inverses of n×n matrices. It follows that, denoting respectively by I(n), M(n) and A(n) = n2 the number of operations needed for inverting, multiplying and adding n×n matrices, one has I ( 2 n ) ≤ 2 I ( n ) + 6 M ( n ) + 4 A ( n ) . {\displaystyle I(2n)\leq 2I(n)+6M(n)+4A(n).} If n = 2 k , {\displaystyle n=2^{k},} one may apply this formula recursively: I ( 2 k ) ≤ 2 I ( 2 k − 1 ) + 6 M ( 2 k − 1 ) + 4 A ( 2 k − 1 ) ≤ 2 2 I ( 2 k − 2 ) + 6 ( M ( 2 k − 1 ) + 2 M ( 2 k − 2 ) ) + 4 ( A ( 2 k − 1 ) + 2 A ( 2 k − 2 ) ) ⋮ {\displaystyle {\begin{aligned}I(2^{k})&\leq 2I(2^{k-1})+6M(2^{k-1})+4A(2^{k-1})\\&\leq 2^{2}I(2^{k-2})+6(M(2^{k-1})+2M(2^{k-2}))+4(A(2^{k-1})+2A(2^{k-2}))\\&\,\,\,\vdots \end{aligned}}} If M ( n ) ≤


id: discrete-logarithm-20260505-0
file: data/en.wikipedia.org/wiki/Discrete_logarithm-0.md
category: reference
title: Discrete logarithm
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Discrete_logarithm
date_saved: 2026-05-05T11:02:07.615506+00:00
instance: kb-cron
parent: discrete-logarithm-20260505-0
summary:
In mathematics, for given real numbers a {\displaystyle a} and b {\displaystyle b} , the logarithm log b ⁡ ( a ) {\displaystyle \log _{b}(a)} is a number x {\displaystyle x} such that b x = a {\displaystyle b^{x}=a} . The discrete logarithm generalizes this concept to a cyclic group. A simple example is the group of integers modulo a prime number (such as 5) under modular multiplication of nonzero elements. For instance, take b = 2 {\displaystyle b=2} in the multiplicative group modulo 5, whose elements are 1 , 2 , 3 , 4 {\displaystyle {1,2,3,4}} . Then: 2 1 = 2 , 2 2 = 4 , 2 3 = 8 ≡ 3 ( mod 5 ) , 2 4 = 16 ≡ 1 ( mod 5 ) . {\displaystyle 2^{1}=2,\quad 2^{2}=4,\quad 2^{3}=8\equiv 3{\pmod {5}},\quad 2^{4}=16\equiv 1{\pmod {5}}.} The powers of 2 modulo 5 cycle through all nonzero elements, so discrete logarithms exist and are given by: log 2 ⁡ 1 = 4 , log 2 ⁡ 2 = 1 , log 2 ⁡ 3 = 3 , log 2 ⁡ 4 = 2. {\displaystyle \log _{2}1=4,\quad \log _{2}2=1,\quad \log _{2}3=3,\quad \log _{2}4=2.} More generally, in any group


id: discrete-logarithm-20260505-1
file: data/en.wikipedia.org/wiki/Discrete_logarithm-1.md
category: reference
title: Discrete logarithm
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Discrete_logarithm
date_saved: 2026-05-05T11:02:07.615506+00:00
instance: kb-cron
parent: discrete-logarithm-20260505-0
summary:
=== Modular arithmetic === One of the simplest settings for discrete logarithms is the group Zp×. This is the group of multiplication modulo the prime p {\displaystyle p} . Its elements are non-zero congruence classes modulo p {\displaystyle p} , and the group product of two elements may be obtained by ordinary integer multiplication of the elements followed by reduction modulo p {\displaystyle p} . The k {\displaystyle k} th power of one of the numbers in this group may be computed by finding its ' k {\displaystyle k} th power as an integer and then finding the remainder after division by p {\displaystyle p} . When the numbers involved are large, it is more efficient to reduce modulo p {\displaystyle p} multiple times during the computation. Regardless of the specific algorithm used, this operation is called modular exponentiation. For example, consider Z17×. To compute 3 4 {\displaystyle 3^{4}} in this group, compute 3 4 = 81 {\displaystyle 3^{4}=81} , and then divide 81 {\displaystyle 81} by 17 {\displaystyle 17} , obtaining a remainder of 13 {\displaystyle 13} . Thus 3 4 = 13 {\displaystyle 3^{4}=13} in the group Z17×. The discrete logarithm is just the inverse operation. For example,


id: discrete-logarithm-20260505-2
file: data/en.wikipedia.org/wiki/Discrete_logarithm-2.md
category: reference
title: Discrete logarithm
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Discrete_logarithm
date_saved: 2026-05-05T11:02:07.615506+00:00
instance: kb-cron
parent: discrete-logarithm-20260505-0
summary:
Baby-step giant-step Function field sieve Index calculus algorithm Number field sieve Pohlig–Hellman algorithm Pollard's rho algorithm for logarithms Pollard's kangaroo algorithm (aka Pollard's lambda algorithm) There is an efficient quantum algorithm due to Peter Shor. Efficient classical algorithms also exist in certain special cases. For example, in the group of the integers modulo p {\displaystyle p} under addition, the power b k {\displaystyle b^{k}} becomes a product b ⋅ k {\displaystyle b\cdot k} , and equality means congruence modulo p {\displaystyle p} in the integers. The extended Euclidean algorithm finds k {\displaystyle k} quickly. With Diffie–Hellman, a cyclic group modulo a prime p {\displaystyle p} is used, allowing an efficient computation of the discrete logarithm with Pohlig–Hellman if the order of the group (being p − 1 {\displaystyle p-1} ) is sufficiently smooth, i.e. has no large prime factors. == Comparison with integer factorization == While computing discrete logarithms and integer factorization are distinct problems, they share some properties: both are special cases of the hidden subgroup problem for finite abelian groups, both problems seem to be difficult (no efficient algorithms are known for non-quantum computers), for both problems efficient algorithms on quantum computers are known, algorithms from one problem


id: expression-problem-20260505-0
file: data/en.wikipedia.org/wiki/Expression_problem-0.md
category: reference
title: Expression problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Expression_problem
date_saved: 2026-05-05T11:02:10.988150+00:00
instance: kb-cron
parent: expression-problem-20260505-0
summary:
The expression problem is a problem in programming languages that concerns the extensibility and modularity of statically typed data abstractions. The goal is to define a data abstraction that is extensible both in its representations and its behaviors, where one can add new representations and new behaviors to the data abstraction, without recompiling existing code, and while retaining static type safety (e.g., no casts). The statement of the problem exposes deficiencies in programming paradigms and programming languages. Philip Wadler, one of the co-authors of Haskell, has originated the term. == History == Philip Wadler formulated the challenge and named it "The Expression Problem" in response to a discussion with Rice University's Programming Languages Team (PLT). He also cited three sources that defined the context for his challenge: The problem was first observed by John Reynolds in 1975. Reynolds discussed two forms of Data Abstraction: User-defined Types, which are now known as Abstract Data Types (ADTs) (not to be confused with Algebraic Data Types), and Procedural Data Structures, which are now understood as a primitive form of Objects with only one method. He argued that they are complementary, in that User-defined Types could be extended with new behaviors, and Procedural Data


id: generalized-star-height-problem-20260505-0
file: data/en.wikipedia.org/wiki/Generalized_star-height_problem-0.md
category: reference
title: Generalized star-height problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Generalized_star-height_problem
date_saved: 2026-05-05T11:02:12.169658+00:00
instance: kb-cron
parent: generalized-star-height-problem-20260505-0
summary:
The generalized star-height problem in formal language theory is the open question whether all regular languages can be expressed using generalized regular expressions with a limited nesting depth of Kleene stars. Here, generalized regular expressions are defined like regular expressions, but they have a built-in complement operator. For a regular language, its generalized star height is defined as the minimum nesting depth of Kleene stars needed in order to describe the language by means of a generalized regular expression, hence the name of the problem. More specifically, it is an open question whether a nesting depth of more than 1 is required, and if so, whether there is an algorithm to determine the minimum required star height. Regular languages of generalized star-height 0 are also known as star-free languages. The theorem of Schützenberger provides an algebraic characterization of star-free languages by means of aperiodic syntactic monoids. In particular star-free languages are a proper decidable subclass of regular languages. == See also == Eggan's theorem and Generalized star height sections of the Star height article Star height problem == References == Janusz A. Brzozowski (1980). "Open problems about regular languages". In Ronald V. Book (ed.). Formal Language Theory: Perspectives and Open


id: gilbert-pollak-conjecture-20260505-0
file: data/en.wikipedia.org/wiki/Gilbert–Pollak_conjecture-0.md
category: reference
title: Gilbert–Pollak conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Gilbert–Pollak_conjecture
date_saved: 2026-05-05T11:02:13.415449+00:00
instance: kb-cron
parent: gilbert-pollak-conjecture-20260505-0
summary:
In mathematics, the Gilbert–Pollak conjecture is an unproven conjecture on the ratio of lengths of Steiner trees and Euclidean minimum spanning trees for the same point sets in the Euclidean plane. It was proposed by Edgar Gilbert and Henry O. Pollak in 1968. Specifically, the conjecture states that for every finite set of points in the Euclidean plane, the Euclidean minimum spanning tree is no longer than 2 / 3 {\displaystyle 2/{\sqrt {3}}} times the length of the Steiner minimum tree. == Statement == For a set of points in the plane, the shortest network of line segments that connects the points, having only the given points as endpoints, is the Euclidean minimum spanning tree of the set. It may be possible to construct a shorter network by using additional endpoints, not present in the given point set. These additional points are called Steiner points and the shortest network that can be constructed using them is called a Steiner minimum tree. The Steiner ratio is the supremum, over all point sets, of the ratio of lengths of the Euclidean minimum spanning tree to the Steiner minimum tree. Because the Steiner minimum tree is shorter, this ratio is always greater than


id: graph-isomorphism-problem-20260505-0
file: data/en.wikipedia.org/wiki/Graph_isomorphism_problem-0.md
category: reference
title: Graph isomorphism problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Graph_isomorphism_problem
date_saved: 2026-05-05T11:02:14.671887+00:00
instance: kb-cron
parent: graph-isomorphism-problem-20260505-0
summary:
The graph isomorphism problem is the computational problem of determining whether two finite graphs are isomorphic. The problem is not known to be solvable in polynomial time nor to be NP-complete, and therefore may be in the computational complexity class NP-intermediate. It is known that the graph isomorphism problem is in the low hierarchy of class NP, which implies that it is not NP-complete unless the polynomial time hierarchy collapses to its second level. At the same time, isomorphism for many special classes of graphs can be solved in polynomial time, and in practice graph isomorphism can often be solved efficiently. This problem is a special case of the subgraph isomorphism problem, which asks whether a given graph G contains a subgraph that is isomorphic to another given graph H; this problem is known to be NP-complete. It is also known to be a special case of the non-abelian hidden subgroup problem over the symmetric group. In the area of image recognition it is known as the exact graph matching problem. == State of the art == In November 2015, László Babai announced a quasi-polynomial time algorithm for all graphs, that is, one with running time 2 O ( (


id: graph-isomorphism-problem-20260505-1
file: data/en.wikipedia.org/wiki/Graph_isomorphism_problem-1.md
category: reference
title: Graph isomorphism problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Graph_isomorphism_problem
date_saved: 2026-05-05T11:02:14.671887+00:00
instance: kb-cron
parent: graph-isomorphism-problem-20260505-0
summary:
digraphs labelled graphs, with the proviso that an isomorphism is not required to preserve the labels, but only the equivalence relation consisting of pairs of vertices with the same label "polarized graphs" (made of a complete graph Km and an empty graph Kn plus some edges connecting the two; their isomorphism must preserve the partition) 2-colored graphs explicitly given finite structures multigraphs hypergraphs finite automata Markov Decision Processes commutative class 3 nilpotent (i.e., xyz = 0 for every elements x, y, z) semigroups finite rank associative algebras over a fixed algebraically closed field with zero squared radical and commutative factor over the radical. context-free grammars normal-form games balanced incomplete block designs Recognizing combinatorial isomorphism of convex polytopes represented by vertex-facet incidences. ==== GI-complete classes of graphs ==== A class of graphs is called GI-complete if recognition of isomorphism for graphs from this subclass is a GI-complete problem. The following classes are GI-complete: connected graphs graphs of diameter 2 and radius 1 directed acyclic graphs regular graphs bipartite graphs without non-trivial strongly regular subgraphs bipartite Eulerian graphs bipartite regular graphs line graphs split graphs chordal graphs regular self-complementary graphs polytopal graphs of general, simple, and simplicial convex polytopes in arbitrary dimensions.


id: integer-factorization-20260505-0
file: data/en.wikipedia.org/wiki/Integer_factorization-0.md
category: reference
title: Integer factorization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Integer_factorization
date_saved: 2026-05-05T11:02:17.162295+00:00
instance: kb-cron
parent: integer-factorization-20260505-0
summary:
In mathematics, integer factorization is the decomposition of a positive integer into a product of integers. Every positive integer greater than 1 is either the product of two or more integer factors greater than 1, in which case it is a composite number, or it is not, in which case it is a prime number. For example, 15 is a composite number because 15 = 3 · 5, but 7 is a prime number because it cannot be decomposed in this way. If one of the factors is composite, it can in turn be written as a product of smaller factors, for example 60 = 3 · 20 = 3 · (5 · 4). Continuing this process until every factor is prime is called prime factorization; the result is always unique up to the order of the factors by the prime factorization theorem. To factorize a small integer n using mental or pen-and-paper arithmetic, the simplest method is trial division: checking if the number is divisible by prime numbers 2, 3, 5, and so on, up to the square root of n. For larger numbers, especially when using a computer, various more sophisticated factorization algorithms are more efficient. A prime


id: integer-factorization-20260505-1
file: data/en.wikipedia.org/wiki/Integer_factorization-1.md
category: reference
title: Integer factorization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Integer_factorization
date_saved: 2026-05-05T11:02:17.162295+00:00
instance: kb-cron
parent: integer-factorization-20260505-0
summary:
For current computers, GNFS is the best published algorithm for large n (more than about 400 bits). For a quantum computer, however, Peter Shor discovered an algorithm in 1994 that solves it in polynomial time. Shor's algorithm takes only O(b3) time and O(b) space on b-bit number inputs. In 2001, Shor's algorithm was implemented for the first time, by using NMR techniques on molecules that provide seven qubits. In order to talk about complexity classes such as P, NP, and co-NP, the problem has to be stated as a decision problem. It is known to be in both NP and co-NP, meaning that both "yes" and "no" answers can be verified in polynomial time. An answer of "yes" can be certified by exhibiting a factorization n = d(⁠n/d⁠) with d ≤ k. An answer of "no" can be certified by exhibiting the factorization of n into distinct primes, all larger than k; one can verify their primality using the AKS primality test, and then multiply them to obtain n. The fundamental theorem of arithmetic guarantees that there is only one possible string of increasing primes that will be accepted, which shows that the problem is in both UP and co-UP.


id: integer-factorization-20260505-2
file: data/en.wikipedia.org/wiki/Integer_factorization-2.md
category: reference
title: Integer factorization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Integer_factorization
date_saved: 2026-05-05T11:02:17.162295+00:00
instance: kb-cron
parent: integer-factorization-20260505-0
summary:
To obtain an algorithm for factoring any positive integer, it is necessary to add a few steps to this algorithm such as trial division, and the Jacobi sum test. === Expected running time === The algorithm as stated is a probabilistic algorithm as it makes random choices. Its expected running time is at most Ln[⁠1/2⁠, 1+o(1)]. == See also == Aurifeuillean factorization Bach's algorithm – For generation of random factorized numbers Canonical representation of a positive integer Factorization Multiplicative partition – Way to write a number as a product of other numbers p-adic valuation Integer partition – Decomposition of an integer as a sum of positive integers == Notes == == References == Richard Crandall and Carl Pomerance (2001). Prime Numbers: A Computational Perspective. Springer. ISBN 0-387-94777-9. Chapter 5: Exponential Factoring Algorithms, pp. 191–226. Chapter 6: Subexponential Factoring Algorithms, pp. 227–284. Section 7.4: Elliptic curve method, pp. 301–313. Donald Knuth. The Art of Computer Programming, Volume 2: Seminumerical Algorithms, Third Edition. Addison-Wesley, 1997. ISBN 0-201-89684-2. Section 4.5.4: Factoring into Primes, pp. 379–417. Samuel S. Wagstaff Jr. (2013). The Joy of Factoring. Providence, RI: American Mathematical Society. ISBN 978-1-4704-1048-3.. Warren, Henry S. Jr. (2013). Hacker's Delight (2 ed.). Addison Wesley -


id: k-server-problem-20260505-0
file: data/en.wikipedia.org/wiki/K-server_problem-0.md
category: reference
title: K-server problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/K-server_problem
date_saved: 2026-05-05T11:02:18.322111+00:00
instance: kb-cron
parent: k-server-problem-20260505-0
summary:
The k-server problem is a problem of theoretical computer science in the category of online algorithms, one of two abstract problems on metric spaces that are central to the theory of competitive analysis (the other being metrical task systems). In this problem, an online algorithm must control the movement of a set of k servers, represented as points in a metric space, and handle requests that are also in the form of points in the space. As each request arrives, the algorithm must determine which server to move to the requested point. The goal of the algorithm is to keep the total distance all servers move small, relative to the total distance the servers could have moved by an optimal adversary who knows in advance the entire sequence of requests. The problem was first posed by Mark Manasse, Lyle A. McGeoch and Daniel Sleator (1988). The most prominent open question concerning the k-server problem is the so-called k-server conjecture, also posed by Manasse et al. This conjecture states that there is an algorithm for solving the k-server problem in an arbitrary metric space and for any number k of servers that has competitive ratio exactly k. Manasse et al. were


id: log-rank-conjecture-20260505-0
file: data/en.wikipedia.org/wiki/Log-rank_conjecture-0.md
category: reference
title: Log-rank conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Log-rank_conjecture
date_saved: 2026-05-05T11:02:19.507086+00:00
instance: kb-cron
parent: log-rank-conjecture-20260505-0
summary:
In theoretical computer science, the log-rank conjecture states that the deterministic communication complexity of a two-party Boolean function is polynomially related to the logarithm of the rank of its input matrix. Let D ( f ) {\displaystyle D(f)} denote the deterministic communication complexity of a function, and let rank ⁡ ( f ) {\displaystyle \operatorname {rank} (f)} denote the rank of its input matrix M f {\displaystyle M_{f}} (over the reals). Since every protocol using up to c {\displaystyle c} bits partitions M f {\displaystyle M_{f}} into at most 2 c {\displaystyle 2^{c}} monochromatic rectangles, and each of these has rank at most 1, D ( f ) ≥ log 2 ⁡ rank ⁡ ( f ) . {\displaystyle D(f)\geq \log _{2}\operatorname {rank} (f).} The log-rank conjecture states that D ( f ) {\displaystyle D(f)} is also upper-bounded by a polynomial in the log-rank: for some constant C {\displaystyle C} , D ( f ) = O ( ( log ⁡ rank ⁡ ( f ) ) C ) . {\displaystyle D(f)=O((\log \operatorname {rank} (f))^{C}).} Lovett proved the upper bound D ( f ) = O ( rank ⁡ ( f ) log ⁡ rank ⁡ ( f ) )


id: one-way-function-20260505-0
file: data/en.wikipedia.org/wiki/One-way_function-0.md
category: reference
title: One-way function
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/One-way_function
date_saved: 2026-05-05T11:02:24.099877+00:00
instance: kb-cron
parent: one-way-function-20260505-0
summary:
In computer science, a one-way function is a function that is easy to compute on every input, but hard to invert given the image of a random input. Here, "easy" and "hard" are to be understood in the sense of computational complexity theory, specifically the theory of polynomial time problems. This has nothing to do with whether the function is one-to-one; finding any one input with the desired image is considered a successful inversion. (See § Theoretical definition, below.) The existence of such one-way functions is still an open conjecture. Their existence would prove that the complexity classes P and NP are not equal, thus resolving the foremost unsolved question of theoretical computer science. The converse is not known to be true, i.e. the existence of a proof that P ≠ NP would not directly imply the existence of one-way functions. In applied contexts, the terms "easy" and "hard" are usually interpreted relative to some specific computing entity; typically "cheap enough for the legitimate users" and "prohibitively expensive for any malicious agents". One-way functions, in this sense, are fundamental tools for cryptography, personal identification, authentication, and other data security applications. While the existence of one-way functions in this sense is


id: one-way-function-20260505-1
file: data/en.wikipedia.org/wiki/One-way_function-1.md
category: reference
title: One-way function
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/One-way_function
date_saved: 2026-05-05T11:02:24.099877+00:00
instance: kb-cron
parent: one-way-function-20260505-0
summary:
=== Multiplication and factoring === The function f takes as inputs two prime numbers p and q in binary notation and returns their product. This function can be "easily" computed in O(b2) time, where b is the total number of bits of the inputs. Inverting this function requires finding the factors of a given integer N. The best factoring algorithms known run in O ( exp ⁡ 64 9 b ( log ⁡ b ) 2 3 ) {\displaystyle O\left(\exp {\sqrt[{3}]{{\frac {64}{9}}b(\log b)^{2}}}\right)} time, where b is the number of bits needed to represent N. This function can be generalized by allowing p and q to range over a suitable set of semiprimes. Note that f is not one-way for randomly selected integers p, q > 1, since the product will have 2 as a factor with probability 3/4 (because the probability that an arbitrary p is odd is 1/2, and likewise for q, so if they're chosen independently, the probability that both are odd is therefore 1/4; hence the probability that p or q is even, is 1 − 1/4 = 3/4). === The Rabin function (modular squaring) === The Rabin function, or squaring modulo N = p q


id: online-matrix-vector-multiplication-problem-20260505-0
file: data/en.wikipedia.org/wiki/Online_matrix-vector_multiplication_problem-0.md
category: reference
title: Online matrix-vector multiplication problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Online_matrix-vector_multiplication_problem
date_saved: 2026-05-05T11:02:25.285814+00:00
instance: kb-cron
parent: online-matrix-vector-multiplication-problem-20260505-0
summary:
In computational complexity theory, the online matrix-vector multiplication problem (OMv) asks an online algorithm to return, at each round, the product of an n × n {\displaystyle n\times n} matrix and a newly-arrived n {\displaystyle n} -dimensional vector. OMv is conjectured to require roughly cubic time. This conjectured hardness implies lower bounds on the time needed to solve various dynamic problems and is of particular interest in fine-grained complexity. == Definition == In OMv, an algorithm is given an integer n {\displaystyle n} and an n × n {\displaystyle n\times n} Boolean matrix M {\displaystyle M} . The algorithm then runs for n {\displaystyle n} rounds, and at each round i {\displaystyle i} receives an n {\displaystyle n} -dimensional Boolean vector v i {\displaystyle v_{i}} and must return the product M v i {\displaystyle Mv_{i}} (before continuing to round i + 1 {\displaystyle i+1} ). An algorithm is said to solve OMv if, with probability at least 2 / 3 {\displaystyle 2/3} over the randomness of the algorithm, it returns the product M v i {\displaystyle Mv_{i}} at every round i {\displaystyle i} . === Variants of OMv === The online vector-matrix-vector problem (OuMv) is a variant of OMv where


id: separating-words-problem-20260505-0
file: data/en.wikipedia.org/wiki/Separating_words_problem-0.md
category: reference
title: Separating words problem
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Separating_words_problem
date_saved: 2026-05-05T11:02:29.955919+00:00
instance: kb-cron
parent: separating-words-problem-20260505-0
summary:
In theoretical computer science, the separating words problem is the problem of finding the smallest deterministic finite automaton that behaves differently on two given strings, meaning that it accepts one of the two strings and rejects the other string. It is an open problem how large such an automaton must be, in the worst case, as a function of the length of the input strings. == Example == The two strings 0010 and 1000 may be distinguished from each other by a three-state automaton in which the transitions from the start state go to two different states, both of which are terminal in the sense that subsequent transitions from these two states always return to the same state. The state of this automaton records the first symbol of the input string. If one of the two terminal states is accepting and the other is rejecting, then the automaton will accept only one of the strings 0010 and 1000. However, these two strings cannot be distinguished by any automaton with fewer than three states. == Simplifying assumptions == For proving bounds on this problem, it may be assumed without loss of generality that the inputs are strings over a two-letter alphabet.


id: solving-chess-20260505-0
file: data/en.wikipedia.org/wiki/Solving_chess-0.md
category: reference
title: Solving chess
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solving_chess
date_saved: 2026-05-05T11:02:31.151898+00:00
instance: kb-cron
parent: solving-chess-20260505-0
summary:
Solving chess consists of finding an optimal strategy for the game of chess; that is, one by which one of the players (White or Black) can always force either a victory or a draw (see solved game). It is also related to more generally solving chess-like games (i.e. combinatorial games of perfect information) such as Capablanca chess and infinite chess. In a weaker sense, solving chess may refer to proving which one of the three possible outcomes (White wins; Black wins; draw) is the result of two perfect players, without necessarily revealing the optimal strategy itself (see indirect proof). No complete solution for chess in either of the two senses is known, nor is it expected that chess will be solved in the near future (if ever). Progress to date is extremely limited; there are tablebases of perfect endgame play with a small number of pieces (up to seven), and some chess variants have been solved at least weakly. Calculated estimates of game-tree complexity and state-space complexity of chess exist which provide a bird's eye view of the computational effort that might be required to solve the game. == Partial results == === Endgame tablebases === Endgame tablebases are computerized


id: solving-chess-20260505-1
file: data/en.wikipedia.org/wiki/Solving_chess-1.md
category: reference
title: Solving chess
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solving_chess
date_saved: 2026-05-05T11:02:31.151898+00:00
instance: kb-cron
parent: solving-chess-20260505-0
summary:
== Predictions on when or if chess will be solved == In 1950, Shannon calculated, based on a game tree complexity of 10120 and a computer operating at one megahertz (a big stretch at that time: the UNIVAC 1 introduced in 1951 could perform ~2000 operations per second or 2 kilohertz) that could evaluate a terminal node in 1 microsecond would take 1090 years to make its first move. Even allowing for technological advances, solving chess within a practical time frame would therefore seem beyond any conceivable technology. Hans-Joachim Bremermann, a professor of mathematics and biophysics at the University of California at Berkeley, further argued in a 1965 paper that the "speed, memory, and processing capacity of any possible future computer equipment are limited by specific physical barriers: the light barrier, the quantum barrier, and the thermodynamical barrier. These limitations imply, for example, that no computer, however constructed, will ever be able to examine the entire tree of possible move sequences of the game of chess." Nonetheless, Bremermann did not foreclose the possibility that a computer would someday be able to solve chess. He wrote, "In order to have a computer play a perfect or nearly perfect game, it will


id: superintelligence-ban-20260505-0
file: data/en.wikipedia.org/wiki/Superintelligence_ban-0.md
category: reference
title: Superintelligence ban
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Superintelligence_ban
date_saved: 2026-05-05T11:02:32.351937+00:00
instance: kb-cron
parent: superintelligence-ban-20260505-0
summary:
Superintelligence ban refers to proposed legal, ethical, or policy measures intended to restrict or prohibit the development of artificial superintelligence, AI systems that would surpass human cognitive abilities in nearly all domains. The idea arises from concerns that such systems could become uncontrollable, potentially posing existential threats to humanity or causing severe social and economic disruption. == Background == The concept of limiting or banning superintelligence research has roots in early 21st-century debates on artificial general intelligence (AGI) safety. Thinkers such as Nick Bostrom and Eliezer Yudkowsky warned that self-improving AI could rapidly exceed human oversight. As advanced models like large-scale language models and autonomous agents began demonstrating complex reasoning abilities, policymakers and ethicists increasingly discussed the need for legal constraints on the creation of systems capable of recursive self-improvement. In October 2025, the Future of Life Institute published a statement calling for "a prohibition on the development of superintelligence, not lifted before there is broad scientific consensus that it will be done safely and controllably, and strong public buy-in." This statement was signed by various public personalities, such as Richard Branson and Steve Wozniak, and AI experts, such as Yoshua Bengio and Geoffrey Hinton. == Rationale == Supporters of


id: synchronizing-word-20260505-0
file: data/en.wikipedia.org/wiki/Synchronizing_word-0.md
category: reference
title: Synchronizing word
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Synchronizing_word
date_saved: 2026-05-05T11:02:33.627503+00:00
instance: kb-cron
parent: synchronizing-word-20260505-0
summary:
In computer science, more precisely, in the theory of deterministic finite automata (DFA), a synchronizing word or reset sequence is a word in the input alphabet of the DFA that sends any state of the DFA to one and the same state. That is, if an ensemble of copies of the DFA are each started in different states, and all of the copies process the synchronizing word, they will all end up in the same state. Not every DFA has a synchronizing word; for instance, a DFA with two states, one for words of even length and one for words of odd length, can never be synchronized. == Existence == Given a DFA, the problem of determining if it has a synchronizing word can be solved in polynomial time using a theorem due to Ján Černý. A simple approach considers the power set of states of the DFA, and builds a directed graph where nodes belong to the power set, and a directed edge describes the action of the transition function. A path from the node of all states to a singleton state shows the existence of a synchronizing word. This algorithm is exponential in the number of states. A


id: unique-games-conjecture-20260505-0
file: data/en.wikipedia.org/wiki/Unique_games_conjecture-0.md
category: reference
title: Unique games conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Unique_games_conjecture
date_saved: 2026-05-05T11:02:34.810219+00:00
instance: kb-cron
parent: unique-games-conjecture-20260505-0
summary:
In computational complexity theory, the unique games conjecture (often referred to as UGC) is a conjecture made by Subhash Khot in 2002. The conjecture postulates that the problem of determining the approximate value of a certain type of game, known as a unique game, has NP-hard computational complexity. It has broad applications in the theory of hardness of approximation. If the unique games conjecture is true and P ≠ NP, then for many important problems it is not only impossible to get an exact solution in polynomial time (as postulated by the P versus NP problem), but also impossible to get a good polynomial-time approximation. The problems for which such an inapproximability result would hold include constraint satisfaction problems, which crop up in a wide variety of disciplines. The conjecture is unusual in that the academic world seems about evenly divided on whether it is true or not. == Formulations == The unique games conjecture can be stated in a number of equivalent ways. === Unique label cover === The following formulation of the unique games conjecture is often used in hardness of approximation. The conjecture postulates the NP-hardness of the following promise problem known as label cover with unique


id: unique-games-conjecture-20260505-1
file: data/en.wikipedia.org/wiki/Unique_games_conjecture-1.md
category: reference
title: Unique games conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Unique_games_conjecture
date_saved: 2026-05-05T11:02:34.810219+00:00
instance: kb-cron
parent: unique-games-conjecture-20260505-0
summary:
=== Two-prover proof systems === A unique game is a special case of a two-prover one-round (2P1R) game. A two-prover one-round game has two players (also known as provers) and a referee. The referee sends each player a question drawn from a known probability distribution, and the players each have to send an answer. The answers come from a set of fixed size. The game is specified by a predicate that depends on the questions sent to the players and the answers provided by them. The players may decide on a strategy beforehand, although they cannot communicate with each other during the game. The players win if the predicate is satisfied by their questions and their answers. A two-prover one-round game is called a unique game if for every question and every answer by the first player, there is exactly one answer by the second player that results in a win for the players, and vice versa. The value of a game is the maximum winning probability for the players over all strategies. The unique games conjecture states that for every sufficiently small pair of constants ε, δ > 0, there exists a constant k such that the following promise


id: unique-games-conjecture-20260505-2
file: data/en.wikipedia.org/wiki/Unique_games_conjecture-2.md
category: reference
title: Unique games conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Unique_games_conjecture
date_saved: 2026-05-05T11:02:34.810219+00:00
instance: kb-cron
parent: unique-games-conjecture-20260505-0
summary:
== Results == Marek Karpinski and Warren Schudy have constructed linear time approximation schemes for dense instances of unique games problem. In 2008, Prasad Raghavendra has shown that if the unique games conjecture is true, then for every constraint satisfaction problem the best approximation ratio is given by a certain simple semidefinite programming instance, which is in particular polynomial. In 2010, Prasad Raghavendra and David Steurer defined the gap-small-set expansion problem, and conjectured that it is NP-hard. The resulting small set expansion hypothesis implies the unique games conjecture. It has also been used to prove strong hardness of approximation results for finding complete bipartite subgraphs. In 2010, Sanjeev Arora, Boaz Barak and David Steurer found a subexponential time approximation algorithm for the unique games problem. A key ingredient in their result was the spectral algorithm of Alexandra Kolla (see also the earlier manuscript of A. Kolla and Madhur Tulsiani). The latter also re-proved that unique games on expander graphs could be solved in polynomial time, and was one of (if not the) first graph algorithms to take advantage of the full spectrum of a graph rather than just its first two eigenvalues. In 2012, it was shown that distinguishing instances


id: x-y-sorting-20260505-0
file: data/en.wikipedia.org/wiki/X_+_Y_sorting-0.md
category: reference
title: X + Y sorting
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/X_+_Y_sorting
date_saved: 2026-05-05T11:02:36.037820+00:00
instance: kb-cron
parent: x-y-sorting-20260505-0
summary:
In computer science, X + Y sorting is the problem of sorting pairs of numbers by their sums. Applications of the problem include transit fare minimisation, VLSI design, and sparse polynomial multiplication. As with comparison sorting and integer sorting more generally, algorithms for this problem can be based only on comparisons of these sums, or on other operations that work only when the inputs are small integers. It is unknown whether this problem has a comparison-based solution whose running time is asymptotically faster than sorting an unstructured list of equally many items. Therefore, research on the problem has focused on two approaches to settle the question of whether such an improvement is possible: the development of algorithms that improve on unstructured sorting in their number of comparisons rather than in their total running time, and lower bounds for the number of comparisons based on counting cells in subdivisions of high-dimensional spaces. Both approaches are historically tied together, in that the first algorithms that used few comparisons were based on the weakness of the cell-counting lower bounds. == Problem statement and history == The input to the X + Y {\displaystyle X+Y} sorting problem consists of two finite collections of numbers


id: x-y-sorting-20260505-1
file: data/en.wikipedia.org/wiki/X_+_Y_sorting-1.md
category: reference
title: X + Y sorting
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/X_+_Y_sorting
date_saved: 2026-05-05T11:02:36.037820+00:00
instance: kb-cron
parent: x-y-sorting-20260505-0
summary:
( x + x 2 + x 9 ) ( 1 + x 4 + x 9 ) = x + x 2 + x 5 + x 6 + x 9 + x 10 + x 11 + x 13 + x 18 . {\displaystyle {\begin{aligned}(&x+x^{2}+x^{9})(1+x^{4}+x^{9})\\&=x+x^{2}+x^{5}+x^{6}+x^{9}+x^{10}+x^{11}+x^{13}+x^{18}.\\\end{aligned}}} The degrees are always integers, so integer-based algorithms for X + Y {\displaystyle X+Y} sorting may be applied. However, for polynomials whose number of terms is comparable to their degree, FFT-based polynomial multiplication algorithms may be significantly more efficient than term-by-term multiplication. == Number of orderings == A well-known lower bound for unstructured sorting, in the decision tree model, is based on the factorial number of sorted orders that an unstructured list may have. Because each comparison can at best reduce the number of possible orderings by a factor of two, sorting requires a number of comparisons at least equal to the binary logarithm of the factorial, which is n log 2 ⁡ n − O ( n ) {\displaystyle n\log _{2}n-O(n)} . Early work on X + Y {\displaystyle X+Y} sorting followed a similar approach by asking how many different sorted orderings are possible for this problem, and proving that this number


id: x-y-sorting-20260505-2
file: data/en.wikipedia.org/wiki/X_+_Y_sorting-2.md
category: reference
title: X + Y sorting
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/X_+_Y_sorting
date_saved: 2026-05-05T11:02:36.037820+00:00
instance: kb-cron
parent: x-y-sorting-20260505-0
summary:
== Number of comparisons == For the classical comparison sorting problem, the time to sort and the number of comparisons needed to sort are within constant factors of each other. But for X + Y {\displaystyle X+Y} sorting, the number of comparisons is smaller than the best time bound known: Michael Fredman showed in 1976 that X + Y {\displaystyle X+Y} sorting can be done using only O ( n 2 ) {\displaystyle O(n^{2})} comparisons. More generally, he showed that any set of N {\displaystyle N} elements, whose sorted ordering has already been restricted to a family Γ {\displaystyle \Gamma } of orderings, can be sorted using log 2 ⁡ | Γ | + O ( N ) {\displaystyle \log _{2}|\Gamma |+O(N)} comparisons, by a form of binary insertion sort. For the X + Y {\displaystyle X+Y} sorting problem, N = n 2 {\displaystyle N=n^{2}} , and | Γ | = O ( n 8 n ) {\displaystyle |\Gamma |=O(n^{8n})} , so log 2 ⁡ | Γ | = O ( n log ⁡ n ) {\displaystyle \log _{2}|\Gamma |=O(n\log n)} and Fredman's bound implies that only O ( n 2 ) {\displaystyle O(n^{2})} comparisons are needed. However, in Fredman's


id: list-of-unsolved-problems-in-mathematics-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-0.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Many mathematical problems have been stated but not yet solved. These problems come from many areas of mathematics, such as theoretical physics, computer science, algebra, analysis, combinatorics, algebraic, differential, discrete and Euclidean geometries, graph theory, group theory, mathematical logic, number theory, set theory, Ramsey theory, dynamical systems, and partial differential equations. Some problems belong to more than one discipline and are studied using techniques from different areas. Prizes are often awarded for the solution to a long-standing problem, and some lists of unsolved problems, such as the Millennium Prize Problems, receive considerable attention. This list is a composite of notable unsolved problems mentioned in previously published lists, including but not limited to lists considered authoritative, and the problems listed here vary widely in both difficulty and importance. == Notable lists == Various mathematicians and organizations have published and promoted lists of unsolved mathematical problems. In some cases, the lists have been associated with prizes for the discoverers of solutions. === Millennium Prize Problems === Of the original seven Millennium Prize Problems listed by the Clay Mathematics Institute in 2000, six remain unsolved to date: Birch and Swinnerton-Dyer conjecture Hodge conjecture Navier–Stokes existence and smoothness P versus NP Riemann hypothesis Yang–Mills


id: list-of-unsolved-problems-in-mathematics-20260505-1
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-1.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Birch–Tate conjecture on the relation between the order of the center of the Steinberg group of the ring of integers of a number field to the field's Dedekind zeta function. Casas-Alvero conjecture: if a polynomial of degree d {\displaystyle d} defined over a field K {\displaystyle K} of characteristic 0 {\displaystyle 0} has a factor in common with its first through d − 1 {\displaystyle d-1} -th derivative, then must f {\displaystyle f} be the d {\displaystyle d} -th power of a linear polynomial? Connes embedding problem in Von Neumann algebra theory Crouzeix's conjecture: the matrix norm of a complex function f {\displaystyle f} applied to a complex matrix A {\displaystyle A} is at most twice the supremum of | f ( z ) | {\displaystyle |f(z)|} over the field of values of A {\displaystyle A} . Determinantal conjecture on the determinant of the sum of two normal matrices. Eilenberg–Ganea conjecture: a group with cohomological dimension 2 also has a 2-dimensional Eilenberg–MacLane space K ( G , 1 ) {\displaystyle K(G,1)} . Farrell–Jones conjecture on whether certain assembly maps are isomorphisms. Bost conjecture: a specific case of the Farrell–Jones conjecture Finite lattice representation problem: is every finite lattice isomorphic to


id: list-of-unsolved-problems-in-mathematics-20260505-2
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-2.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
The Brennan conjecture: estimating the integral powers of the moduli of the derivative of conformal maps into the open unit disk, on certain subsets of C {\displaystyle \mathbb {C} } Fuglede's conjecture on whether nonconvex sets in R {\displaystyle \mathbb {R} } and R 2 {\displaystyle \mathbb {R} ^{2}} are spectral if and only if they tile by translation. Goodman's conjecture on the coefficients of multivalued functions Invariant subspace problem – does every bounded operator on a complex Banach space send some non-trivial closed subspace to itself? Kung–Traub conjecture on the optimal order of a multipoint iteration without memory Lehmer's conjecture on the Mahler measure of non-cyclotomic polynomials The mean value problem: given a complex polynomial f {\displaystyle f} of degree d ≥ 2 {\displaystyle d\geq 2} and a complex number z {\displaystyle z} , is there a critical point c {\displaystyle c} of f {\displaystyle f} such that | f ( z ) − f ( c ) | ≤ | f ′ ( z ) | | z − c | {\displaystyle |f(z)-f(c)|\leq |f'(z)||z-c|} ? The Pompeiu problem on the topology of domains for which some nonzero function has integrals that vanish over every congruent copy Sendov's conjecture:


id: list-of-unsolved-problems-in-mathematics-20260505-3
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-3.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Sudoku: How many puzzles have exactly one solution? How many puzzles with exactly one solution are minimal? What is the maximum number of givens for a minimal puzzle? Tic-tac-toe variants: Given the width of a tic-tac-toe board, what is the smallest dimension such that X is guaranteed to have a winning strategy? (See also Hales–Jewett theorem and nd game) Chess: What is the outcome of a perfectly played game of chess? (See also first-move advantage in chess) Go: What is the perfect value of Komi? Set: What is the largest possible cap set, as a function of n {\displaystyle n} in the n {\displaystyle n} -dimensional affine space over the three-element field? Are the nim-sequences of all finite octal games eventually periodic? Is the nim-sequence of Grundy's game eventually periodic? ==== Games with imperfect information ==== Rendezvous problem === Geometry === ==== Algebraic geometry ==== Abundance conjecture: if the canonical bundle of a projective variety with Kawamata log terminal singularities is nef, then it is semiample. Bass conjecture on the finite generation of certain algebraic K-groups. Bass–Quillen conjecture relating vector bundles over a regular Noetherian ring and over the polynomial ring A [ t 1 , … , t n


id: list-of-unsolved-problems-in-mathematics-20260505-4
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-4.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
The spherical Bernstein's problem, a generalization of Bernstein's problem Carathéodory conjecture: any convex, closed, and twice-differentiable surface in three-dimensional Euclidean space admits at least two umbilical points. Cartan–Hadamard conjecture: can the classical isoperimetric inequality for subsets of Euclidean space be extended to spaces of nonpositive curvature, known as Cartan–Hadamard manifolds? Chern's conjecture (affine geometry) that the Euler characteristic of a compact affine manifold vanishes. Chern's conjecture for hypersurfaces in spheres, a number of closely related conjectures. Closed curve problem: find (explicit) necessary and sufficient conditions that determine when, given two periodic functions with the same period, the integral curve is closed. The filling area conjecture, that a hemisphere has the minimum area among shortcut-free surfaces in Euclidean space whose boundary forms a closed curve of given length The Hopf conjectures relating the curvature and Euler characteristic of higher-dimensional Riemannian manifolds Osserman conjecture: that every Osserman manifold is either flat or locally isometric to a rank-one symmetric space Yau's conjecture on the first eigenvalue that the first eigenvalue for the Laplace–Beltrami operator on an embedded minimal hypersurface of S n + 1 {\displaystyle S^{n+1}} is n {\displaystyle n} . ==== Discrete geometry ==== The big-line-big-clique conjecture on the existence of either


id: list-of-unsolved-problems-in-mathematics-20260505-5
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-5.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Falconer's conjecture: sets of Hausdorff dimension greater than d / 2 {\displaystyle d/2} in R d {\displaystyle \mathbb {R} ^{d}} must have a distance set of nonzero Lebesgue measure The values of the Hermite constants for dimensions other than 1–8 and 24 What is the lowest number of faces possible for a holyhedron? Inscribed square problem, also known as Toeplitz' conjecture and the square peg problem – does every Jordan curve have an inscribed square? The Kakeya conjecture – do n {\displaystyle n} -dimensional sets that contain a unit line segment in every direction necessarily have Hausdorff dimension and Minkowski dimension equal to n {\displaystyle n} ? The Kelvin problem on minimum-surface-area partitions of space into equal-volume cells, and the optimality of the Weaire–Phelan structure as a solution to the Kelvin problem Lebesgue's universal covering problem on the minimum-area convex shape in the plane that can cover any shape of diameter one Mahler's conjecture on the product of the volumes of a centrally symmetric convex body and its polar. In Meissner body): Are the two Meissner tetrahedra the minimum-volume three-dimensional shapes of constant width? Moser's worm problem – what is the smallest area of a shape that can cover every


id: list-of-unsolved-problems-in-mathematics-20260505-6
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-6.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
==== Graph drawing and embedding ==== The Albertson conjecture: the crossing number can be lower-bounded by the crossing number of a complete graph with the same chromatic number Conway's thrackle conjecture that thrackles cannot have more edges than vertices The GNRS conjecture on whether minor-closed graph families have ℓ 1 {\displaystyle \ell _{1}} embeddings with bounded distortion Harborth's conjecture: every planar graph can be drawn with integer edge lengths Negami's conjecture on projective-plane embeddings of graphs with planar covers The strong Papadimitriou–Ratajczak conjecture: every polyhedral graph has a convex greedy embedding Turán's brick factory problem – Is there a drawing of any complete bipartite graph with fewer crossings than the number given by Zarankiewicz? Guy's conjecture on the crossing number for complete graphs – Is there a drawing of any complete graph with fewer crossings than the number given by his upper bound? Universal point sets of subquadratic size for planar graphs ==== Restriction of graph parameters ==== Does there exist a conference graph for every number of vertices v > 1 {\displaystyle v>1} where v ≡ 1 mod 4 {\displaystyle v\equiv 1{\bmod {4}}} and v {\displaystyle v} is an odd sum of two squares? Conway's 99-graph problem: does there


id: list-of-unsolved-problems-in-mathematics-20260505-7
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-7.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
==== Miscellaneous graph theory ==== Delta-conjecture (1978): consider a complete graph ( V ; E 1 , … , E d ) {\displaystyle (V;E_{1},\dots ,E_{d})} each edge of which is colored by one of d {\displaystyle d} colors such that there exists a triangle Δ {\displaystyle \Delta } colored in three pairwise distinct colors. Then, in each chromatic component ( V , E i ) , i = 1 , … , d {\displaystyle (V,E_{i}),i=1,\dots ,d} , one can choose a maximal independent vertex-set such that the intersection of the obtained d {\displaystyle d} sets is empty. The imbalance conjecture: If the imbalance for each edge of a graph is at least 1, is the multiset of all edge imbalances always graphic? The implicit graph conjecture on the existence of implicit representations for slowly-growing hereditary families of graphs Ryser's conjecture relating the maximum matching size and minimum transversal size in hypergraphs The second neighborhood problem: does every oriented graph contain a vertex for which there are at least as many other vertices at distance two as at distance one? Sidorenko's conjecture on homomorphism densities of graphs in graphons Teschner's bondage number conjecture: is the bondage number of a graph always


id: list-of-unsolved-problems-in-mathematics-20260505-8
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-8.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Büchi's problem on sufficiently large sequences of square numbers with constant second difference. Carmichael's totient function conjecture: do all values of Euler's totient function have multiplicity greater than 1 {\displaystyle 1} ? Catalan–Dickson conjecture on aliquot sequences: no aliquot sequences are infinite but non-repeating. Exponent pair conjecture: for all ε > 0 {\displaystyle \varepsilon >0} , is the pair ( ε , 1 / 2 + ε ) {\displaystyle (\varepsilon ,1/2+\varepsilon )} an exponent pair? The Gauss circle problem: how far can the number of integer points in a circle centered at the origin be from the area of the circle? Grimm's conjecture: each element of a set of consecutive composite numbers can be assigned a distinct prime number that divides it. Hall's conjecture: for any ε > 0 {\displaystyle \varepsilon >0} , there is some constant c ( ε ) {\displaystyle c(\varepsilon )} such that either y 2 = x 3 {\displaystyle y^{2}=x^{3}} or | y 2 − x 3 | > c ( ε ) x 1 / 2 − ε {\displaystyle |y^{2}-x^{3}|>c(\varepsilon )x^{1/2-\varepsilon }} . Lehmer's totient problem: if ϕ ( n ) {\displaystyle \phi (n)} divides n − 1 {\displaystyle n-1} , must n {\displaystyle n}


id: list-of-unsolved-problems-in-mathematics-20260505-9
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-9.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Leopoldt's conjecture: a p-adic analogue of the regulator of an algebraic number field does not vanish. Stark conjectures (including Brumer–Stark conjecture) Characterize all algebraic number fields that have some power basis. ==== Analytic number theory ==== Beilinson's conjectures about special values of L-functions. Do Siegel zeros exist? Find the value of the De Bruijn–Newman constant. Is Selberg class of Dirichlet series equal to class of automorphic L-functions? Hardy–Littlewood zeta function conjectures Keating–Snaith conjecture concerning the asymptotics of an integral involving the Riemann zeta function Hilbert–Pólya conjecture: the nontrivial zeros of the Riemann zeta function correspond to eigenvalues of a self-adjoint operator. Lindelöf hypothesis that for all ε > 0 {\displaystyle \varepsilon >0} , ζ ( 1 / 2 + i t ) = o ( t ε ) {\displaystyle \zeta (1/2+it)=o(t^{\varepsilon })} The density hypothesis for zeroes of the Riemann zeta function. Location of nontrivial zeros of L-functions, especially conjectures concerning their critical lines: Grand Riemann hypothesis: do the nontrivial zeros of all automorphic L-functions lie on the critical line 1 / 2 + i t {\displaystyle 1/2+it} with real t {\displaystyle t} ? Generalized Riemann hypothesis for Selberg class: do the nontrivial zeros of all functions in Selberg class


id: list-of-unsolved-problems-in-mathematics-20260505-10
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-10.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Littlewood conjecture: for any two real numbers α , β {\displaystyle \alpha ,\beta } , lim inf n → ∞ n ‖ n α ‖ ‖ n β ‖ = 0 {\displaystyle \liminf _{n\rightarrow \infty }n\,\Vert n\alpha \Vert \,\Vert n\beta \Vert =0} , where ‖ x ‖ {\displaystyle \Vert x\Vert } is the distance from x {\displaystyle x} to the nearest integer. Schanuel's conjecture on the transcendence degree of certain field extensions of the rational numbers. In particular: Are π {\displaystyle \pi } and e {\displaystyle e} algebraically independent? Which nontrivial combinations of transcendental numbers (such as e + π , e π , π e , π π , e e {\displaystyle e+\pi ,e\pi ,\pi ^{e},\pi ^{\pi },e^{e}} ) are themselves transcendental? The four exponentials conjecture: the transcendence of at least one of four exponentials of combinations of irrationals Are Euler's constant γ {\displaystyle \gamma } and Catalan's constant G {\displaystyle G} irrational? Are they transcendental? Is Apéry's constant ζ ( 3 ) {\displaystyle \zeta (3)} transcendental? Which transcendental numbers are (exponential) periods? How well can non-quadratic irrational numbers be approximated? What is the irrationality measure of specific (suspected) transcendental numbers such as π {\displaystyle \pi } and γ


id: list-of-unsolved-problems-in-mathematics-20260505-11
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-11.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Fortune's conjecture that no Fortunate number is composite. The Gaussian moat problem: is it possible to find an infinite sequence of distinct Gaussian prime numbers such that the difference between consecutive numbers in the sequence is bounded? Gillies' conjecture on the distribution of prime divisors of Mersenne numbers. Landau's problems Goldbach conjecture: all even natural numbers greater than 2 {\displaystyle 2} are the sum of two prime numbers. Legendre's conjecture: for every positive integer n {\displaystyle n} , there is a prime between n 2 {\displaystyle n^{2}} and ( n + 1 ) 2 {\displaystyle (n+1)^{2}} . Twin prime conjecture: there are infinitely many twin primes. Are there infinitely many primes of the form n 2 + 1 {\displaystyle n^{2}+1} ? Problems associated to Linnik's theorem New Mersenne conjecture: for any odd natural number p {\displaystyle p} , if any two of the three conditions p = 2 k ± 1 {\displaystyle p=2^{k}\pm 1} or p = 4 k ± 3 {\displaystyle p=4^{k}\pm 3} , 2 p − 1 {\displaystyle 2^{p}-1} is prime, and ( 2 p + 1 ) / 3 {\displaystyle (2^{p}+1)/3} is prime are true, then the third condition is also true. Polignac's conjecture: for all positive


id: list-of-unsolved-problems-in-mathematics-20260505-12
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-12.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
Does the partition principle (PP) imply the axiom of choice (AC)? (Woodin) Does the generalized continuum hypothesis below a strongly compact cardinal imply the generalized continuum hypothesis everywhere? Does the generalized continuum hypothesis entail ♢ ( E cf ⁡ ( λ ) λ + ) {\displaystyle {\diamondsuit (E_{\operatorname {cf} (\lambda )}^{\lambda ^{+}}})} for every singular cardinal λ {\displaystyle \lambda } ? Does the generalized continuum hypothesis imply the existence of an ℵ2-Suslin tree? If ℵω is a strong limit cardinal, is 2 ℵ ω < ℵ ω 1 {\displaystyle 2^{\aleph _{\omega }}<\aleph _{\omega _{1}}} (see Singular cardinals hypothesis)? The best bound, ℵω4, was obtained by Shelah using his PCF theory. The problem of finding the ultimate core model, one that contains all large cardinals. Woodin's Ω-conjecture: if there is a proper class of Woodin cardinals, then Ω-logic satisfies an analogue of Gödel's completeness theorem. Does the consistency of the existence of a strongly compact cardinal imply the consistent existence of a supercompact cardinal? Does there exist a Jónsson algebra on ℵω? Is OCA (the open coloring axiom) consistent with 2 ℵ 0 > ℵ 2 {\displaystyle 2^{\aleph _{0}}>\aleph _{2}} ? Reinhardt cardinals: Without assuming the axiom of choice, can a


id: list-of-unsolved-problems-in-mathematics-20260505-13
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-13.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
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parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
=== Graph theory === Kahn–Kalai conjecture (Jinyoung Park and Huy Tuan Pham, 2022) Blankenship–Oporowski conjecture on the book thickness of subdivisions (Vida Dujmović, David Eppstein, Robert Hickingbotham, Pat Morin, and David Wood, 2021) Ringel's conjecture that the complete graph K 2 n + 1 {\displaystyle K_{2n+1}} can be decomposed into 2 n + 1 {\displaystyle 2n+1} copies of any tree with n {\displaystyle n} edges (Richard Montgomery, Benny Sudakov, Alexey Pokrovskiy, 2020) Disproof of Hedetniemi's conjecture on the chromatic number of tensor products of graphs (Yaroslav Shitov, 2019) Kelmans–Seymour conjecture (Dawei He, Yan Wang, and Xingxing Yu, 2020) Goldberg–Seymour conjecture (Guantao Chen, Guangming Jing, and Wenan Zang, 2019) Babai's problem (Alireza Abdollahi, Maysam Zallaghi, 2015) Alspach's conjecture (Darryn Bryant, Daniel Horsley, William Pettersson, 2014) Alon–Saks–Seymour conjecture (Hao Huang, Benny Sudakov, 2012) Read–Hoggar conjecture (June Huh, 2009) Scheinerman's conjecture (Jeremie Chalopin and Daniel Gonçalves, 2009) Erdős–Menger conjecture (Ron Aharoni, Eli Berger 2007) Road coloring conjecture (Avraham Trahtman, 2007) Robertson–Seymour theorem (Neil Robertson, Paul Seymour, 2004) Strong perfect graph conjecture (Maria Chudnovsky, Neil Robertson, Paul Seymour and Robin Thomas, 2002) Toida's conjecture (Mikhail Muzychuk, Mikhail Klin, and Reinhard Pöschel, 2001) Harary's conjecture on the integral sum number of complete graphs (Zhibo Chen,


id: list-of-unsolved-problems-in-mathematics-20260505-14
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics-14.md
category: reference
title: List of unsolved problems in mathematics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_mathematics
date_saved: 2026-05-05T11:02:37.770898+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-mathematics-20260505-0
summary:
=== Books discussing unsolved problems === Chung, Fan; Graham, Ron (1999). Erdös on Graphs: His Legacy of Unsolved Problems. AK Peters. ISBN 978-1-56881-111-6. Croft, Hallard T.; Falconer, Kenneth J.; Guy, Richard K. (1994). Unsolved Problems in Geometry. Springer. ISBN 978-0-387-97506-1. Guy, Richard K. (2004). Unsolved Problems in Number Theory. Springer. ISBN 978-0-387-20860-2. Klee, Victor; Wagon, Stan (1996). Old and New Unsolved Problems in Plane Geometry and Number Theory. The Mathematical Association of America. ISBN 978-0-88385-315-3. du Sautoy, Marcus (2003). The Music of the Primes: Searching to Solve the Greatest Mystery in Mathematics. Harper Collins. ISBN 978-0-06-093558-0. Derbyshire, John (2003). Prime Obsession: Bernhard Riemann and the Greatest Unsolved Problem in Mathematics. Joseph Henry Press. ISBN 978-0-309-08549-6. Devlin, Keith (2006). The Millennium Problems – The Seven Greatest Unsolved* Mathematical Puzzles Of Our Time. Barnes & Noble. ISBN 978-0-7607-8659-8. Blondel, Vincent D.; Megrestski, Alexandre (2004). Unsolved problems in mathematical systems and control theory. Princeton University Press. ISBN 978-0-691-11748-5. Ji, Lizhen; Poon, Yat-Sun; Yau, Shing-Tung (2013). Open Problems and Surveys of Contemporary Mathematics (volume 6 in the Surveys in Modern Mathematics series) (Surveys of Modern Mathematics). International Press of Boston. ISBN 978-1-57146-278-7. Waldschmidt, Michel (2004). "Open Diophantine Problems" (PDF). Moscow Mathematical Journal. 4 (1):


id: list-of-problems-in-loop-theory-and-quasigroup-theory-20260505-0
file: data/en.wikipedia.org/wiki/List_of_problems_in_loop_theory_and_quasigroup_theory-0.md
category: reference
title: List of problems in loop theory and quasigroup theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_problems_in_loop_theory_and_quasigroup_theory
date_saved: 2026-05-05T11:02:39.093380+00:00
instance: kb-cron
parent: list-of-problems-in-loop-theory-and-quasigroup-theory-20260505-0
summary:
In mathematics, especially abstract algebra, loop theory and quasigroup theory are active research areas with many open problems. As in other areas of mathematics, such problems are often made public at professional conferences and meetings. Many of the problems posed here first appeared in the Loops (Prague) conferences and the Mile High (Denver) conferences. == Open problems (Moufang loops) == === Abelian by cyclic groups resulting in Moufang loops === Let L be a Moufang loop with normal abelian subgroup (associative subloop) M of odd order such that L/M is a cyclic group of order bigger than 3. (i) Is L a group? (ii) If the orders of M and L/M are relatively prime, is L a group? Proposed: by Michael Kinyon, based on (Chein and Rajah, 2000) Comments: The assumption that L/M has order bigger than 3 is important, as there is a (commutative) Moufang loop L of order 81 with normal commutative subgroup of order 27. === Embedding CMLs of period 3 into alternative algebras === Conjecture: Any finite commutative Moufang loop of period 3 can be embedded into a commutative alternative algebra. Proposed: by Alexander Grishkov at Loops '03, Prague 2003 === Frattini subloop for Moufang loops


id: list-of-problems-in-loop-theory-and-quasigroup-theory-20260505-1
file: data/en.wikipedia.org/wiki/List_of_problems_in_loop_theory_and_quasigroup_theory-1.md
category: reference
title: List of problems in loop theory and quasigroup theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_problems_in_loop_theory_and_quasigroup_theory
date_saved: 2026-05-05T11:02:39.093380+00:00
instance: kb-cron
parent: list-of-problems-in-loop-theory-and-quasigroup-theory-20260505-0
summary:
Let ( Q , ∗ ) {\displaystyle (Q,*)} , ( Q , + ) {\displaystyle (Q,+)} be two quasigroups defined on the same underlying set Q {\displaystyle Q} . The distance d ( ∗ , + ) {\displaystyle d(*,+)} is the number of pairs ( a , b ) {\displaystyle (a,b)} in Q × Q {\displaystyle Q\times Q} such that a ∗ b ≠ a + b {\displaystyle a*b\neq a+b} . Call a class of finite quasigroups quadratic if there is a positive real number α {\displaystyle \alpha } such that any two quasigroups ( Q , ∗ ) {\displaystyle (Q,*)} , ( Q , + ) {\displaystyle (Q,+)} of order n {\displaystyle n} from the class satisfying d ( ∗ , + ) < α n 2 {\displaystyle d(*,+)<\alpha \,n^{2}} are isomorphic. Are Moufang loops quadratic? Are Bol loops quadratic? Proposed: by Aleš Drápal at Loops '99, Prague 1999 Comments: Drápal proved in (Drápal, 1992) that groups are quadratic with α = 1 / 9 {\displaystyle \alpha =1/9} , and in (Drápal, 2000) that 2-groups are quadratic with α = 1 / 4 {\displaystyle \alpha =1/4} . === Campbell–Hausdorff series for analytic Bol loops === Determine the Campbell–Hausdorff series


id: list-of-problems-in-loop-theory-and-quasigroup-theory-20260505-2
file: data/en.wikipedia.org/wiki/List_of_problems_in_loop_theory_and_quasigroup_theory-2.md
category: reference
title: List of problems in loop theory and quasigroup theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_problems_in_loop_theory_and_quasigroup_theory
date_saved: 2026-05-05T11:02:39.093380+00:00
instance: kb-cron
parent: list-of-problems-in-loop-theory-and-quasigroup-theory-20260505-0
summary:
For a loop Q, let Mlt(Q) denote the multiplication group of Q, that is, the group generated by all left and right translations. Is |Mlt(Q)| < f(|Q|) for some variety of loops and for some polynomial f? Proposed: at the Milehigh conference on quasigroups, loops, and nonassociative systems, Denver 2005 === Does every finite alternative loop have 2-sided inverses? === Does every finite alternative loop, that is, every loop satisfying x(xy) = (xx)y and x(yy) = (xy)y, have 2-sided inverses? Proposed: by Warren D. Smith Comments: There are infinite alternative loops without 2-sided inverses, cf. (Ormes and Vojtěchovský, 2007) === Finite simple nonassociative automorphic loop === Find a nonassociative finite simple automorphic loop, if such a loop exists. Proposed: by Michael Kinyon at Loops '03, Prague 2003 Comments: It is known that such a loop cannot be commutative (Grishkov, Kinyon and Nagý, 2013) nor have odd order (Kinyon, Kunen, Phillips and Vojtěchovský, 2013). === Moufang theorem in non-Moufang loops === We say that a variety V of loops satisfies the Moufang theorem if for every loop Q in V the following implication holds: for every x, y, z in Q, if x(yz) = (xy)z then the subloop generated by x,


id: list-of-problems-in-loop-theory-and-quasigroup-theory-20260505-3
file: data/en.wikipedia.org/wiki/List_of_problems_in_loop_theory_and_quasigroup_theory-3.md
category: reference
title: List of problems in loop theory and quasigroup theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_problems_in_loop_theory_and_quasigroup_theory
date_saved: 2026-05-05T11:02:39.093380+00:00
instance: kb-cron
parent: list-of-problems-in-loop-theory-and-quasigroup-theory-20260505-0
summary:
Proposed: by Jonathan D. H. Smith and Alena Vanžurová at Loops '03, Prague 2003 Solved by: Alena Vanžurová, 2004. Solution: No, the class of cores of Bol loops is not closed under subalgebras. Furthermore, the class of cores of groups is not closed under subalgebras. Here is an outline of the proof: Cores of abelian groups are medial, by (Romanowska and Smith, 1985), (Rozskowska-Lech, 1999). The smallest nonabelian group S 3 {\displaystyle S_{3}} has core containing a submagma G {\displaystyle G} of order 4 that is not medial. If G {\displaystyle G} is a core of a Bol loop, it is a core of a Bol loop of order 4, hence a core of an abelian group, a contradiction. === Parity of the number of quasigroups up to isomorphism === Let I(n) be the number of isomorphism classes of quasigroups of order n. Is I(n) odd for every n? Proposed: by Douglas S. Stones at 2nd Mile High Conference on Nonassociative Mathematics, Denver 2009 Solved by: Douglas S. Stones, 2010. Solution: I(12) is even. In fact, I(n) is odd for all n ≤ 17 except 12. (Stones 2010) === Classification of finite simple paramedial quasigroups === Classify the finite simple


id: list-of-unsolved-problems-in-statistics-20260505-0
file: data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_statistics-0.md
category: reference
title: List of unsolved problems in statistics
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_statistics
date_saved: 2026-05-05T11:02:40.300576+00:00
instance: kb-cron
parent: list-of-unsolved-problems-in-statistics-20260505-0
summary:
There are many longstanding unsolved problems in mathematics for which a solution has still not yet been found. The notable unsolved problems in statistics are generally of a different flavor; according to John Tukey, "difficulties in identifying problems have delayed statistics far more than difficulties in solving problems." A list of "one or two open problems" (in fact 22 of them) was given by David Cox. == Inference and testing == How to detect and correct for systematic errors, especially in sciences where random errors are large (a situation Tukey termed uncomfortable science). The Graybill–Deal estimator is often used to estimate the common mean of two normal populations with unknown and possibly unequal variances. Though this estimator is generally unbiased, its admissibility remains to be shown. Meta-analysis: Though independent p-values can be combined using Fisher's method, techniques are still being developed to handle the case of dependent p-values. Behrens–Fisher problem: Yuri Linnik showed in 1966 that there is no uniformly most powerful test for the difference of two means when the variances are unknown and possibly unequal. That is, there is no exact test (meaning that, if the means are in fact equal, one that rejects the null hypothesis with


id: 1-3-2-3-conjecture-20260505-0
file: data/en.wikipedia.org/wiki/1/3–2/3_conjecture-0.md
category: reference
title: 1/3–2/3 conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/1/3–2/3_conjecture
date_saved: 2026-05-05T11:02:41.499495+00:00
instance: kb-cron
parent: 1-3-2-3-conjecture-20260505-0
summary:
In order theory, a branch of mathematics, the 1/3–2/3 conjecture states that, if one is comparison sorting a set of items then, no matter what comparisons may have already been performed, it is always possible to choose the next comparison in such a way that it will reduce the number of possible sorted orders by a factor of 2/3 or better. Equivalently, in every finite partially ordered set that is not totally ordered, there exists a pair of elements x and y with the property that at least 1/3 and at most 2/3 of the linear extensions of the partial order place x earlier than y. == Example == The partial order formed by three elements a, b, and c with a single comparability relationship, a ≤ b, has three linear extensions, a ≤ b ≤ c, a ≤ c ≤ b, and c ≤ a ≤ b. In all three of these extensions, a is earlier than b. However, a is earlier than c in only two of them, and later than c in the third. Therefore, the pair of a and c have the desired property, showing that this partial order obeys the 1/3–2/3 conjecture. This example shows


id: 1-3-2-3-conjecture-20260505-1
file: data/en.wikipedia.org/wiki/1/3–2/3_conjecture-1.md
category: reference
title: 1/3–2/3 conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/1/3–2/3_conjecture
date_saved: 2026-05-05T11:02:41.499495+00:00
instance: kb-cron
parent: 1-3-2-3-conjecture-20260505-0
summary:
== Applications == In 1984 Jeff Kahn and Saks proposed the following application for the problem: suppose one wishes to comparison sort a totally ordered set X, for which some partial order information is already known in the form of a partial order on X. In the worst case, each additional comparison between a pair x and y of elements may yield as little information as possible, by resolving the comparison in a way that leaves as many linear extensions as possible compatible with the comparison result. The 1/3–2/3 conjecture states that, at each step, one may choose a comparison to perform that reduces the remaining number of linear extensions by a factor of 2/3; therefore, if there are E linear extensions of the partial order given by the initial information, the sorting problem can be completed in at most log 3 / 2 ⁡ E {\displaystyle \log _{3/2}E} additional comparisons. However, this analysis neglects the complexity of selecting the optimal pair x and y to compare. Additionally, it may be possible to sort a partial order using a number of comparisons that is better than this analysis would suggest, because it may not be possible for this worst-case behavior


id: 1-3-2-3-conjecture-20260505-2
file: data/en.wikipedia.org/wiki/1/3–2/3_conjecture-2.md
category: reference
title: 1/3–2/3 conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/1/3–2/3_conjecture
date_saved: 2026-05-05T11:02:41.499495+00:00
instance: kb-cron
parent: 1-3-2-3-conjecture-20260505-0
summary:
== References == Aigner, Martin (1985), "A note on merging", Order, 2 (3): 257–264, doi:10.1007/BF00333131, S2CID 118877843. Brightwell, Graham R. (1989), "Semiorders and the 1/3–2/3 conjecture", Order, 5 (4): 369–380, doi:10.1007/BF00353656, S2CID 86860160. Brightwell, Graham R. (1999), "Balanced pairs in partial orders", Discrete Mathematics, 201 (1–3): 25–52, doi:10.1016/S0012-365X(98)00311-2. Brightwell, Graham R.; Felsner, Stefan; Trotter, William T. (1995), "Balancing pairs and the cross product conjecture", Order, 12 (4): 327–349, CiteSeerX 10.1.1.38.7841, doi:10.1007/BF01110378, MR 1368815, S2CID 14793475. Brightwell, Graham R.; Winkler, Peter (1991), "Counting linear extensions", Order, 8 (3): 225–242, doi:10.1007/BF00383444, S2CID 119697949. Felsner, Stefan; Trotter, William T. (1993), "Balancing pairs in partially ordered sets", Combinatorics, Paul Erdős is eighty, Bolyai Society Mathematical Studies, vol. 1, Budapest: János Bolyai Mathematical Society, pp. 145–157, MR 1249709. Fredman, M. L. (1976), "How good is the information theory bound in sorting?", Theoretical Computer Science, 1 (4): 355–361, doi:10.1016/0304-3975(76)90078-5 Kahn, Jeff; Linial, Nati (1991), "Balancing extensions via Brunn-Minkowski", Combinatorica, 11 (4): 363–368, doi:10.1007/BF01275670, S2CID 206793172. Kahn, Jeff; Saks, Michael (1984), "Balancing poset extensions", Order, 1 (2): 113–126, doi:10.1007/BF00565647, S2CID 123370506. Khachiyan, Leonid (1989), "Optimal algorithms in convex programming decomposition and sorting", in Jaravlev, J. (ed.), Computers and Decision Problems (in Russian), Moscow: Nauka, pp. 161–205. As


id: andrews-curtis-conjecture-20260505-0
file: data/en.wikipedia.org/wiki/Andrews–Curtis_conjecture-0.md
category: reference
title: Andrews–Curtis conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Andrews–Curtis_conjecture
date_saved: 2026-05-05T11:02:42.701762+00:00
instance: kb-cron
parent: andrews-curtis-conjecture-20260505-0
summary:
In mathematics, the Andrews–Curtis conjecture states that every balanced presentation (i.e. a presentation with the same number of generators and relations) of the trivial group can be transformed into a trivial presentation by a sequence of Nielsen transformations on the relators together with conjugations of relators, named after James J. Andrews and Morton L. Curtis who proposed it in 1965. It is difficult to verify whether the conjecture holds for a given balanced presentation or not. It is widely believed that the Andrews–Curtis conjecture is false. While there are no counterexamples known, there are numerous potential counterexamples. It is known that the Zeeman conjecture on collapsibility implies the Andrews–Curtis conjecture. == Further reading == Andrews, J. J.; Curtis, M. L. (1965), "Free groups and handlebodies", Proceedings of the American Mathematical Society, 16 (2), American Mathematical Society: 192–195, doi:10.2307/2033843, JSTOR 2033843, MR 0173241 "Low-dimensional topology, problems in", Encyclopedia of Mathematics, EMS Press, 2001 [1994] == References ==


id: arnold-conjecture-20260505-0
file: data/en.wikipedia.org/wiki/Arnold_conjecture-0.md
category: reference
title: Arnold conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Arnold_conjecture
date_saved: 2026-05-05T11:02:43.869021+00:00
instance: kb-cron
parent: arnold-conjecture-20260505-0
summary:
The Arnold conjecture, named after mathematician Vladimir Arnold, is a mathematical conjecture in the field of symplectic geometry, a branch of differential geometry. == Strong Arnold conjecture == Let ( M , ω ) {\displaystyle (M,\omega )} be a closed (compact without boundary) symplectic manifold. For any smooth function H : M → R {\displaystyle H:M\to {\mathbb {R} }} , the symplectic form ω {\displaystyle \omega } induces a Hamiltonian vector field X H {\displaystyle X_{H}} on M {\displaystyle M} defined by the formula ω ( X H , ⋅ ) = d H . {\displaystyle \omega (X_{H},\cdot )=dH.} The function H {\displaystyle H} is called a Hamiltonian function. Suppose there is a smooth 1-parameter family of Hamiltonian functions H t ∈ C ∞ ( M ) {\displaystyle H_{t}\in C^{\infty }(M)} , t ∈ [ 0 , 1 ] {\displaystyle t\in [0,1]} . This family induces a 1-parameter family of Hamiltonian vector fields X H t {\displaystyle X_{H_{t}}} on M {\displaystyle M} . The family of vector fields integrates to a 1-parameter family of diffeomorphisms φ t : M → M {\displaystyle \varphi _{t}:M\to M} . Each individual φ t {\displaystyle \varphi _{t}} is a called a Hamiltonian diffeomorphism of


id: baum-connes-conjecture-20260505-0
file: data/en.wikipedia.org/wiki/Baum–Connes_conjecture-0.md
category: reference
title: Baum–Connes conjecture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Baum–Connes_conjecture
date_saved: 2026-05-05T11:02:45.104924+00:00
instance: kb-cron
parent: baum-connes-conjecture-20260505-0
summary:
In mathematics, specifically in operator K-theory, the Baum–Connes conjecture suggests a link between the K-theory of the reduced C*-algebra of a group and the K-homology of the classifying space of proper actions of that group. The conjecture sets up a correspondence between different areas of mathematics, with the K-homology of the classifying space being related to geometry, differential operator theory, and homotopy theory, while the K-theory of the group's reduced C*-algebra is a purely analytical object. The conjecture, if true, would have some older famous conjectures as consequences. For instance, the surjectivity part implies the Kadison–Kaplansky conjecture for discrete torsion-free groups, and the injectivity is closely related to the Novikov conjecture. The conjecture is also closely related to index theory, as the assembly map μ {\displaystyle \mu } is a sort of index, and it plays a major role in Alain Connes' noncommutative geometry program. The origins of the conjecture go back to Fredholm theory, the Atiyah–Singer index theorem and the interplay of geometry with operator K-theory as expressed in the works of Brown, Douglas and Fillmore, among many other motivating subjects. == Formulation == Let Γ be a second countable locally compact group (for instance a countable discrete group).


