# kb

id: list-of-developers-of-optical-scientific-equipment-20260505-0
file: data/en.wikipedia.org/wiki/List_of_developers_of_optical_scientific_equipment-0.md
category: reference
title: List of developers of optical scientific equipment
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_developers_of_optical_scientific_equipment
date_saved: 2026-05-05T09:36:07.567295+00:00
instance: kb-cron
parent: list-of-developers-of-optical-scientific-equipment-20260505-0
summary:
A developer of optical scientific equipment is an individual who makes and adjusts optical aids for scientific purposes, including telescope optics and microscope lenses. == Telescope developers == James Gilbert Baker Denis Albert Bardou John A. Brashear Laurent Cassegrain Henri Chrétien Alvan Clark John Dollond Charles Wesley Elmer and Richard Scott Perkin Galileo Galilei James Gregory John Hadley Chester Moore Hall Robert Hooke Johannes Kepler Frederick James Hargreaves Christiaan Huygens Hans Lippershey Raymond Augustin Mailhat Dmitri Dmitrievich Maksutov James Henry Marriott Jacob Metius Isaac Newton Georg Simon Plössl Russell W. Porter Jesse Ramsden George Willis Ritchey Christoph Scheiner Bernhard Schmidt James Short See also Timeline of telescope technology and List of astronomical instrument makers == Microscope developers == Ernst Karl Abbe Denis Albert Bardou Christopher Cock Siegfried Czapski Cornelius Drebbel Galileo Galilei Robert Hooke Christiaan Huygens Carl Kellner Anton van Leeuwenhoek Moritz von Rohr See also Timeline of microscope technology == References ==


id: simon-pl-ssl-20260505-0
file: data/en.wikipedia.org/wiki/Simon_Plössl-0.md
category: reference
title: Simon Plössl
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Simon_Plössl
date_saved: 2026-05-05T09:36:08.713363+00:00
instance: kb-cron
parent: simon-pl-ssl-20260505-0
summary:
Simon Plössl (September 19, 1794, Vienna – January 29, 1868, Vienna) was an Austrian optical instrument maker. Initially trained at the Voigtländer company, he set up his own workshop in 1823. His major achievement at the time was the improvement of the achromatic microscope objective. Today he is best known for the eponymous Plössl telescope eyepiece, which follows his 1860 design and has been used extensively by amateur astronomers since the 1980s. == External links == Instruments by Simon Georg Plössl 10 Plössl, Georg Simon A short biography and some instruments from the Hellenic Archives of Scientific Instruments Early large microscope by Simon Plössl, made in 1840 Early travel microscope by Simon Plössl, made in 1845 Plössl Non-inclining Large Microscope, c. 1845


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: 2026-05-05T09:36:09.885912+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: radiguet-et-fils-20260505-0
file: data/en.wikipedia.org/wiki/Radiguet_et_Fils-0.md
category: reference
title: Radiguet et Fils
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Radiguet_et_Fils
date_saved: 2026-05-05T09:36:11.718314+00:00
instance: kb-cron
parent: radiguet-et-fils-20260505-0
summary:
Radiguet et Fils (stylized Radiguet & Fils; English: "Radiguet and Son") was a French manufacturer of precision scientific instruments, established in 1805. According to a history of the firm published in L'Industrie parisienne in 1888, the company was founded in 1805 by a Madame Collot. Ownership then passed to Louis Chevalier (c.1778-1848), younger brother of Vincent Chevalier. In 1830, Chevalier left the company to Honoré-Marie Radiguet (1791-1867), who had once worked as Chevalier's apprentice, and who had made a name for himself in the production of optical equipment, especially parallel mirrors [glaces parallèles] for astronomy and maritime navigation. Under the management of Honoré-Marie's son, Antoine-Honoré Radiguet (1824-1887), the company's purview expanded to include barometers, thermometers, and other scientific equipment. Antoine-Honoré was president of the Trade Association of Precision Instruments [chambre syndicale des instruments de précision]. Antoine-Honoré's financial investment in the application of parallel mirrors to daguerreotype photography lost the company significant sums, as the problem of image reversal which the introduction of his mirrors was supposed to solve was solved by other means. Antoine-Honoré and his son Arthur (1850-1905) marketed their company to a broader public through engineering and photography workshops, as well as through a line of scientific toys


id: horace-b-n-dict-de-saussure-20260505-0
file: data/en.wikipedia.org/wiki/Horace_Bénédict_de_Saussure-0.md
category: reference
title: Horace Bénédict de Saussure
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Horace_Bénédict_de_Saussure
date_saved: 2026-05-05T09:36:12.944546+00:00
instance: kb-cron
parent: horace-b-n-dict-de-saussure-20260505-0
summary:
Horace Bénédict de Saussure (French: [ɔʁas benedikt də sosyʁ]; 17 February 1740 – 22 January 1799) was a Genevan geologist, meteorologist, physicist, mountaineer and Alpine explorer (specifically the Mont Blanc massif), often called the founder of alpinism and modern meteorology, and considered to be the first person to build a successful solar oven. == Early life and education == Horace Bénédict de Saussure was born 17 February 1740, in Conches, near Geneva, in the Republic of Geneva. Saussure's family were Genevan patricians. His father, Nicolas de Saussure, was an agriculturist, agronomist and author. Because his mother was "sickly", Saussure was brought up by his mother's sister and her husband the Genevan naturalist Charles Bonnet, who sparked Horace-Bénédict's early interest in botany. After attending the "Collège" of his hometown, he completed his studies at the Geneva Academy in 1759 with a dissertation on heat (Dissertatio physica de igne). == Career == In 1760, Saussure made the first of numerous trips to Chamonix valley, to collect plant specimens for the noted Swiss anatomist, physiologist and botanist Albrecht von Haller. In 1760, Saussure offered a reward to the first man to reach the summit of Mont Blanc. Inspired by his uncle, Charles Bonnet,


id: horace-b-n-dict-de-saussure-20260505-1
file: data/en.wikipedia.org/wiki/Horace_Bénédict_de_Saussure-1.md
category: reference
title: Horace Bénédict de Saussure
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Horace_Bénédict_de_Saussure
date_saved: 2026-05-05T09:36:12.944546+00:00
instance: kb-cron
parent: horace-b-n-dict-de-saussure-20260505-0
summary:
All of Saussure's observations and experiments from seven Alpine journeys were summed up and published in four quarto volumes, under the general title of Voyages dans les Alpes (1779 – 1796) (There was an octavo issue in eight volumes, issued from 1780 to 1796). The non-scientific portions of the work were first published in 1834, and often since, as Partie pittoresque des ouvrages de M. de Saussure. The Alps were the focus of Saussure's investigations. He saw them as the grand key to the true theory of the earth, and they gave him the opportunity to study geology in a manner never previously attempted. Saussure closely examined the inclination of the strata, the nature of the rocks, the fossils and the minerals. Saussure had a thorough knowledge of the chemistry of the day and applied it to the study of minerals, water and air. His geological observations made him a firm believer in the Neptunian theory: He regarded all rocks and minerals as deposited from aqueous solution or suspension, and attached much importance to the study of meteorological conditions. His work with rocks, erosion, and fossils also led him to believe that the earth was much older than generally thought


id: horace-b-n-dict-de-saussure-20260505-2
file: data/en.wikipedia.org/wiki/Horace_Bénédict_de_Saussure-2.md
category: reference
title: Horace Bénédict de Saussure
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Horace_Bénédict_de_Saussure
date_saved: 2026-05-05T09:36:12.944546+00:00
instance: kb-cron
parent: horace-b-n-dict-de-saussure-20260505-0
summary:
== References == Lives by J Senebier (Geneva, 1801), by Cuvier in the Biographie universelle, and by A. P. de Candolle in Décade philosophique DeCandolle, A.P. (1799). "XVII. Biographical memoirs of M. de Saussure". Philosophical Magazine. Series 1. 4 (13): 96–102. doi:10.1080/14786449908677038. articles by E. Naville in the Bibliothèque universelle (March, April, May 1883) chaps. v.-viii. of Ch. Durier's Le Mont-Blanc (Paris, various editions between 1877 and 1897). This article incorporates text from a publication now in the public domain: Coolidge, William Augustus Brevoort (1911). "Saussure, Horace Bénédict de". In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 24 (11th ed.). Cambridge University Press. p. 238. René Sigrist, Le capteur solaire de Horace-Bénédict de Saussure. Genèse d'une science empirique. Geneva, Passé-Présent / Jullien, 1993. Albert V. Carozzi & Gerda Bouvier, The scientific library of Horace-Bénédict de Saussure (1797): annotated catalog of an 18th-century bibliographic and historic treasure, Geneva, 1994 (Mémoires de la SPHN, t. 46). René Sigrist (ed.), H.-B. de Saussure (1740–1799): un regard sur la terre. Geneva, Georg, 2001. == External links == Pictures and texts of "Les Voyages dans les Alpes" by H. B. de Saussure can be found in the database VIATIMAGES (archived from www3.unil.ch) Horace-Benedict de Saussure and


id: taqi-ad-din-muhammad-ibn-ma-ruf-20260505-0
file: data/en.wikipedia.org/wiki/Taqi_ad-Din_Muhammad_ibn_Ma'ruf-0.md
category: reference
title: Taqi ad-Din Muhammad ibn Ma'ruf
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Taqi_ad-Din_Muhammad_ibn_Ma'ruf
date_saved: 2026-05-05T09:36:14.178868+00:00
instance: kb-cron
parent: taqi-ad-din-muhammad-ibn-ma-ruf-20260505-0
summary:
Taqi ad-Din Muhammad ibn Ma'ruf ash-Shami al-Asadi (Arabic: تقي الدين محمد بن معروف الشامي; Ottoman Turkish: تقي الدين محمد بن معروف الشامي السعدي; Turkish: Takiyüddin‎ 1526–1585) was an Ottoman polymath active in Cairo and Istanbul. He was the author of more than ninety books on a wide variety of subjects, including astronomy, clocks, engineering, mathematics, mechanics, optics, and natural philosophy. In 1574 the Ottoman Sultan Murad III invited Taqi ad-Din to build an observatory in the Ottoman capital, Istanbul. Taqi ad-Din constructed instruments such as an armillary sphere and mechanical clocks that he used to observe the Great Comet of 1577. He also used European celestial and terrestrial globes that were delivered to Istanbul in gift exchanges. His major work from the use of his observatory is titled "The tree of ultimate knowledge [in the end of time or the world] in the Kingdom of the Revolving Spheres: The astronomical tables of the King of Kings [Murad III]" (Sidrat al-muntah al-afkar fi malkūt al-falak al-dawār– al-zij al-Shāhinshāhi). The work was prepared according to the results of the observations carried out in Egypt and Istanbul in order to correct and complete Ulugh Beg's 15th century work, the Zij-i Sultani. The first


id: taqi-ad-din-muhammad-ibn-ma-ruf-20260505-1
file: data/en.wikipedia.org/wiki/Taqi_ad-Din_Muhammad_ibn_Ma'ruf-1.md
category: reference
title: Taqi ad-Din Muhammad ibn Ma'ruf
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Taqi_ad-Din_Muhammad_ibn_Ma'ruf
date_saved: 2026-05-05T09:36:14.178868+00:00
instance: kb-cron
parent: taqi-ad-din-muhammad-ibn-ma-ruf-20260505-0
summary:
The main purpose behind the observatory was to cater to the needs of the astronomers and provide a library and workshop so they could design and produce instruments. This observatory would become one of the largest ones in the Islamic world. It was complete in 1579. It would go on to run until January 22, 1580 which is when it was destroyed. Some say religious arguments was the reason why it was destroyed, but it really came down to political problems. A report by the grand vizier Sinan Pasha to Sultan Murad III goes into how the Sultan and the vizier attempted to keep Taqī Ad-Dīn away from the ulama because it seemed like they wanted to take him to trial for heresy. The vizier informs the sultan that Taqī Ad-Dīn wanted to go to Syria regardless of the sultan's orders. The vizier also warned the sultan that if Taqī Ad-Dīn went there, there is a possibility that he would be noticed by the ulama who would take him to trial. Despite Taqī al-Dīn's originality, his influence seemed to be limited. There are only a small number of surviving copies of his works so they were not able to reach


id: taqi-ad-din-muhammad-ibn-ma-ruf-20260505-2
file: data/en.wikipedia.org/wiki/Taqi_ad-Din_Muhammad_ibn_Ma'ruf-2.md
category: reference
title: Taqi ad-Din Muhammad ibn Ma'ruf
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Taqi_ad-Din_Muhammad_ibn_Ma'ruf
date_saved: 2026-05-05T09:36:14.178868+00:00
instance: kb-cron
parent: taqi-ad-din-muhammad-ibn-ma-ruf-20260505-0
summary:
=== Politics === The rise and fall of Taqī al-Dīn and his observatory depended on political issues that surrounded him. Due to his father's occupation as a professor at the Damascene College of law Taqī al-Dīn spent much of his life in Syria and Egypt. During his trips to Istanbul he was able to make connections with many scholar-jurists. He was also able to use the private library of the Grand Vizier of the time, Semiz Ali Pasha. He then began working under Sultan Murad III's new Grand Vizier's, private mentor Sokollu. Continuing his research on observations of the heavens while in Egypt Taqī al-Dīn used the Galata tower and Sokollu's private residence. Although Murad III was the one who commanded an observatory to be built it was actually Sokollu who brought the idea to him knowing about his interest in science. The Sultan ultimately would provide Taqī al-Dīn with everything he needed from financial assistance for the physical buildings, to intellectual assistance making sure he had easy access to many types of books he would need. When the Sultan decided to create the observatory he saw it as a way to show off the power his monarchy had besides


id: taqi-ad-din-muhammad-ibn-ma-ruf-20260505-3
file: data/en.wikipedia.org/wiki/Taqi_ad-Din_Muhammad_ibn_Ma'ruf-3.md
category: reference
title: Taqi ad-Din Muhammad ibn Ma'ruf
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Taqi_ad-Din_Muhammad_ibn_Ma'ruf
date_saved: 2026-05-05T09:36:14.178868+00:00
instance: kb-cron
parent: taqi-ad-din-muhammad-ibn-ma-ruf-20260505-0
summary:
==== Types of clocks examined ==== Of the clocks in the Grand Vizier's treasury Taqī al-Dīn examined three different types. Those three were weight-driven, spring-driven, and driven by lever escapement. He wrote of these three types of watches but also made comments on pocket watches and astronomical ones. As Chief Astronomer, Taqī al-Dīn created a mechanical astronomical clock. This clock was made to permit more precise measurements at the Constantinople observatory. As stated above the creation of this clock was thought to be one of the most important astronomical discoveries of the sixteenth century. Taqī al-Dīn constructed a mechanical clock with three dials which show the hours, minutes, and seconds, with each minute consisting of five seconds. After this clock it is not known whether Taqī al-Dīn's work in mechanical clocks was ever continued, given that much of the clockmaking after that time in the Ottoman Empire was taken over by Europeans. === Steam === In 1551 Taqī al-Dīn described a self-rotating spit that is important in the history of the steam turbine. In Al-Turuq al-samiyya fi al-alat al-ruhaniyya (The Sublime Methods of Spiritual Machines) al-Dīn describes this machine as well as some practical applications for it. The spit is


id: ulugh-beg-20260505-0
file: data/en.wikipedia.org/wiki/Ulugh_Beg-0.md
category: reference
title: Ulugh Beg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ulugh_Beg
date_saved: 2026-05-05T09:36:15.412895+00:00
instance: kb-cron
parent: ulugh-beg-20260505-0
summary:
Mīrzā Muhammad Tarāghāy bin Shāhrukh (Chagatay: میرزا محمد تراغای بن شاهرخ; Persian: میرزا محمد طارق بن شاهرخ), better known as Ulugh Beg (Persian: الغ‌بیک; 22 March 1394 – 27 October 1449), was a Timurid sultan, as well as an astronomer and mathematician. Ulugh Beg was notable for his work in astronomy-related mathematics, such as trigonometry and spherical geometry, as well as his general interests in the arts and intellectual activities. It is thought that he spoke five languages: Arabic, Persian, Chaghatai Turkic, Mongolian, and a small amount of Chinese. During his rule (first as a governor, then outright) the Timurid Empire achieved the cultural peak of the Timurid Renaissance through his attention and patronage. Samarkand was captured and given to Ulugh Beg by his father Shah Rukh. He built the great Ulugh Beg Observatory in Samarkand between 1424 and 1429. It was considered by scholars to have been one of the finest observatories in the Islamic world at the time and the largest in Central Asia. Ulugh Beg was subsequently recognized as the most important observational astronomer from the 15th century by many scholars. He also built the Ulugh Beg Madrasah (1417–1420) in Samarkand and Bukhara, transforming the cities into


id: ulugh-beg-20260505-1
file: data/en.wikipedia.org/wiki/Ulugh_Beg-1.md
category: reference
title: Ulugh Beg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ulugh_Beg
date_saved: 2026-05-05T09:36:15.412895+00:00
instance: kb-cron
parent: ulugh-beg-20260505-0
summary:
Astronomy piqued Ulugh Beg's interest when he visited the Maragheh Observatory at a young age. This observatory, located in Maragheh, Iran, is where the well-known astronomer Nasir al-Din al-Tusi practised. In 1428, Ulugh Beg built an enormous observatory, similar to Tycho Brahe's later Uraniborg as well as Taqi al-Din's observatory in Constantinople. Lacking telescopes to work with, he increased his accuracy by increasing the length of his sextant; the so-called Fakhri sextant had a radius of about 36 meters (118 feet) and the optical separability of 180" (seconds of arc). The Fakhri sextant was the largest instrument at the observatory in Samarkand (an image of the sextant is on the side of this article). There were many other astronomical instruments located at the observatory, but the Fakhri sextant is the most well-known instrument there. The purpose of the Fakhri sextant was to measure the transit altitudes of the stars. This was a measurement of the maximum altitude above the horizon of the stars. It was only possible to use this device to measure the declination of celestial objects. The image, which can be found in this article, shows the remaining portion of the instrument, which consists of the underground, lower


id: ulugh-beg-20260505-2
file: data/en.wikipedia.org/wiki/Ulugh_Beg-2.md
category: reference
title: Ulugh Beg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ulugh_Beg
date_saved: 2026-05-05T09:36:15.412895+00:00
instance: kb-cron
parent: ulugh-beg-20260505-0
summary:
Ulugh Beg led two major campaigns against his neighbours. This first one took place in 1425 and was directed against Moghulistan and its ruler Shir Muhammad. He was victorious but the impact of the campaign was limited and Shir Muhammad remained in power. A year later, Baraq, Khan of the Golden Horde and former protégé of Ulugh Beg, laid claim to Timurid possessions around the Syr Darya, including the town of Sighnaq. In response to that, in 1427 Ulugh Beg, accompanied by his brother Muhummad Juki, marched against Baraq. In a hill close to Sighnaq the Timurid army was surprised by a smaller enemy force but was soundly defeated. The humiliation suffered at the hands of Baraq was to have a lasting effect on Ulugh Beg. His campaign against the Golden Horde would be the last he would undertake against a neighbouring power. The armies he later sent against them would not win any resounding victories and by the end of his reign his territories would be raided by his northern and easterly foes. In 1439, the Zhengtong emperor ordered an artist to produce a painting of a black horse with white feet and a white forehead that had been


id: ulugh-beg-20260505-3
file: data/en.wikipedia.org/wiki/Ulugh_Beg-3.md
category: reference
title: Ulugh Beg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ulugh_Beg
date_saved: 2026-05-05T09:36:15.412895+00:00
instance: kb-cron
parent: ulugh-beg-20260505-0
summary:
== Bibliography == O'Connor, John J.; Robertson, Edmund F., "Ulugh Beg", MacTutor History of Mathematics Archive, University of St Andrews 1839. L. P. E. A. Sedillot (1808–1875). Tables astronomiques d’Oloug Beg, commentees et publiees avec le texte en regard, Tome I, 1 fascicule, Paris. A very rare work, but referenced in the Bibliographie generale de l’astronomie jusqu’en 1880, by J. 1847. L. P. E. A. Sedillot (1808–1875). Prolegomenes des Tables astronomiques d’Oloug Beg, publiees avec Notes et Variantes, et precedes d’une Introduction. Paris: F. Didot. 1853. L. P. E. A. Sedillot (1808–1875). Prolegomenes des Tables astronomiques d’Oloug Beg, traduction et commentaire. Paris. Le Prince Savant annexe les étoiles, Frédérique Beaupertuis-Bressand, in Samarcande 1400–1500, La cité-oasis de Tamerlan : coeur d'un Empire et d'une Renaissance, book directed by Vincent Fourniau, éditions Autrement, 1995, ISSN 1157-4488. L'âge d'or de l'astronomie ottomane, Antoine Gautier, in L'Astronomie, (Monthly magazine created by Camille Flammarion in 1882), December 2005, volume 119. L'observatoire du prince Ulugh Beg, Antoine Gautier, in L'Astronomie, (Monthly magazine created by Camille Flammarion in 1882), October 2008, volume 122. Le recueil de calendriers du prince timouride Ulug Beg (1394–1449), Antoine Gautier, in Le Bulletin, n° spécial Les calendriers, Institut National des Langues et


id: pierre-vernier-20260505-0
file: data/en.wikipedia.org/wiki/Pierre_Vernier-0.md
category: reference
title: Pierre Vernier
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pierre_Vernier
date_saved: 2026-05-05T09:36:16.630856+00:00
instance: kb-cron
parent: pierre-vernier-20260505-0
summary:
Pierre Vernier (French pronunciation: [pjɛʁ vɛʁnje]; 19 August 1580 at Ornans, Franche-Comté (at that time ruled by the Spanish Habsburgs, now part of France) – 14 September 1637, same location) was a mathematician and instrument inventor. He was the inventor and eponym of the vernier scale used in measuring devices. == Life == He was born in Ornans, France, in 1580. He was taught science by his father. He became captain and castellan of the castle at Ornans, for the King of Spain. He was also later councillor and director general of economy in the County of Burgundy. In Brussels, in the year 1631, Vernier published his treatise La construction, l'usage, et les propriétés du quadrant nouveau de mathématique, and dedicated it to the Infanta. In it, he described the ingenious device which now bears his name, the vernier scale. To a quadrant with a primary scale in half degrees Vernier proposed to attach a movable sector, thirty-one half degrees in length but divided into thirty equal parts (each part therefore consisting of a half-degree plus one minute). In measuring an angle, minutes could be easily reckoned by noticing which division line of the sector coincided with a division line


id: les-william-20260505-0
file: data/en.wikipedia.org/wiki/Les_William-0.md
category: reference
title: Les William
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Les_William
date_saved: 2026-05-05T09:36:17.760881+00:00
instance: kb-cron
parent: les-william-20260505-0
summary:
J. L. (Les) William (18 January 1915 – 4 June 1994) was an Australian builder of scientific instruments. Born in Melbourne, Australia he was known for his beautiful and precision craftsmanship and was known as one of the best scientific instrument makers in Australia. His equipment can be found in Australian laboratories that existed from the 1930s through to the 1980s. He founded a company situated in the Melbourne suburb of Hughesdale called J.L. William Scientific Instruments. William attended Caulfield Technical School and worked at his brother's firm during the Second World War. Soon after he set up his own instrumentation company. He never married and in his later years suffered from motor neurone disease. Les William liked to recall Lord Kelvin's dictum that one did not truly understand a scientific quantity until one could measure it and provide an accurate numerical value. William's career was closely linked to that of his older brother Austin (1913 - 1985). During the Second World War the two brothers worked together producing electrical meters. After the war, Austin continued on in the manufacture of electrical meters while Les established his own company producing high accuracy standard resistors. He died in Melbourne on 4


id: al-zarqali-20260505-0
file: data/en.wikipedia.org/wiki/Al-Zarqali-0.md
category: reference
title: Al-Zarqali
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Al-Zarqali
date_saved: 2026-05-05T09:36:18.928040+00:00
instance: kb-cron
parent: al-zarqali-20260505-0
summary:
Abū Isḥāq Ibrāhīm ibn Yaḥyā al-Naqqāsh al-Zarqālī al-Tujibi (Arabic: إبراهيم بن يحيى الزرقالي); also known as Al-Zarkali or Ibn Zarqala (1029–1100), was an Arab maker of astronomical instruments and an astrologer from the western part of the Islamic world. Although his name is conventionally given as al-Zarqālī, it is probable that the correct form was al-Zarqālluh. In Latin he was referred to as Arzachel or Arsechieles, a modified form of Arzachel, meaning 'the engraver'. He lived in Toledo, Al-Andalus before moving to Córdoba later in his life. His works inspired a generation of Islamic astronomers in Al-Andalus, and later, after being translated, were very influential in Europe. His invention of the Saphaea (a perfected astrolabe) proved very popular and was widely used by navigators until the 16th century. The crater Arzachel on the Moon is named after him. == Life == Al-Zarqālī, of Arab origin, was born in a village near the outskirts of Toledo, the then capital of the newly established Taifa of Toledo. He started work after 1048 under Said al-Andalusi for the Emir Al-Mamun of Toledo and also under Al-Mu'tamid of the Taifa of Seville. Assuming a leading position under Said, Al-Zarqālī conducted solar observations for 25


id: al-zarqali-20260505-1
file: data/en.wikipedia.org/wiki/Al-Zarqali-1.md
category: reference
title: Al-Zarqali
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Al-Zarqali
date_saved: 2026-05-05T09:36:18.928040+00:00
instance: kb-cron
parent: al-zarqali-20260505-0
summary:
=== Tables of Toledo === Al-Zarqālī also contributed to the famous Tables of Toledo, an adaptation of earlier astronomical data by Al-Khwarizmi and Al-Battani, to locate the coordinates of Toledo. His zij and almanac were translated into Latin by Gerard of Cremona in the 12th century, and contributed to the rebirth of a mathematically based astronomy in Christian Europe and were later incorporated into the Tables of Toledo in the 12th century and the Alfonsine tables in the 13th century. Famous as well for his own Book of Tables, of which many had been compiled. Al-Zarqālī's almanac contained tables which allowed one to find the days on which the Coptic, Roman, lunar, and Persian months begin, other tables which give the position of planets at any given time, and still others facilitating the prediction of solar and lunar eclipses. This almanac that he compiled directly provided "the positions of the celestial bodies and need no further computation", it further simplifies longitudes using planetary cycles of each planet. The work provided the true daily positions of the sun for four Julian years from 1088 to 1092, the true positions of the five planets every 5 or 10 days over a period


id: alidade-20260505-0
file: data/en.wikipedia.org/wiki/Alidade-0.md
category: reference
title: Alidade
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Alidade
date_saved: 2026-05-05T09:36:20.541498+00:00
instance: kb-cron
parent: alidade-20260505-0
summary:
An alidade () (archaic forms include alhidade, alhidad, alidad) or a turning board is a device that allows one to sight a distant object and use the line of sight to perform a task. This task can be, for example, to triangulate a scale map on site using a plane table drawing of intersecting lines in the direction of the object from two or more points or to measure the angle and horizontal distance to the object from some reference point's polar measurement. Angles measured can be horizontal, vertical or in any chosen plane. The alidade sighting ruler was originally a part of many types of scientific and astronomical instrument. At one time, some alidades, particularly using circular graduations as on astrolabes, were also called diopters. With modern technology, the name is applied to complete instruments such as the 'plane table alidade'. == Origins == The word in Arabic (الحلقة العضدية, al-ḥilqa al-ʿaḍudiyya, lit. 'the ruler'), signifies the same device. In Greek and Latin, it is respectively called δίοπτρα, "dioptra", and linea fiduciae, "fiducial line". The earliest alidades consisted of a bar, rod or similar component with a vane on each end. Each vane (also called a pinnule or pinule)


id: almucantar-20260505-0
file: data/en.wikipedia.org/wiki/Almucantar-0.md
category: reference
title: Almucantar
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Almucantar
date_saved: 2026-05-05T09:36:21.691077+00:00
instance: kb-cron
parent: almucantar-20260505-0
summary:
An almucantar (also spelled almucantarat or almacantara) is a circle on the celestial sphere parallel to the horizon. Two stars that lie on the same almucantar have the same altitude. The term was introduced into European astronomy by monastic astronomer Hermann Contractus of Reichenau, Latinized from the Arabic word al-muqanṭarah ("the almucantar, sundial", plural: al-muqanṭarāt), derived from qanṭarah ("arch, bridge") == Almucantar staff == An almucantar staff is an instrument chiefly used to determine the time of sunrise and sunset, in order to find the amplitude and consequently the variations of the compass. Usually made of pear tree or boxwood, with an arch of 15° to 30°, it is an example of a backstaff. The sun casts that shadow of a vane (B in the adjacent image) on a horizon vane (A). The horizon vane has a slit or hole to allow the observer to see the horizon in the distance. The observer aligns the horizon and shadow so they show at the same point on the horizon vane and sets the sighting vane (C) to align his line of sight with the horizon. The altitude of the sun is the angle between the shadow vane and the sighting vane


id: armillary-sphere-20260505-0
file: data/en.wikipedia.org/wiki/Armillary_sphere-0.md
category: reference
title: Armillary sphere
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Armillary_sphere
date_saved: 2026-05-05T09:36:22.848952+00:00
instance: kb-cron
parent: armillary-sphere-20260505-0
summary:
An armillary sphere (variations are known as spherical astrolabe, armilla, or armil) is a model of objects in the sky (on the celestial sphere), consisting of a spherical framework of rings, centered on Earth or the Sun, that represent lines of celestial longitude and latitude and other astronomically important features, such as the ecliptic. As such, it differs from a celestial globe, which is a smooth sphere whose principal purpose is to map the constellations. It was invented separately, in ancient China possibly as early as the 4th century BC and ancient Greece during the 3rd century BC, with later uses in the Islamic world and Medieval Europe. With the Earth as center, an armillary sphere is known as Ptolemaic. With the Sun as center, it is known as Copernican. The flag of Portugal features an armillary sphere. The armillary sphere is also featured in Portuguese heraldry, associated with the Portuguese discoveries during the Age of Exploration. Manuel I of Portugal, for example, took it as one of his symbols where it appeared on his standard, and on early Chinese export ceramics made for the Portuguese court. In the flag of the Empire of Brazil, the armillary sphere is also


id: armillary-sphere-20260505-1
file: data/en.wikipedia.org/wiki/Armillary_sphere-1.md
category: reference
title: Armillary sphere
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Armillary_sphere
date_saved: 2026-05-05T09:36:22.848952+00:00
instance: kb-cron
parent: armillary-sphere-20260505-0
summary:
The globe assembly is supported on a pedestal N, and may be elevated or depressed upon the joint O, to any number of degrees from 0 to 90 by means of the arc P, which is fixed in the strong brass arm Q. The globe assembly slides in the upright piece R, in which is a screw at r, to fix it at any proper elevation. In the box T are two wheels (as in Dr Long's sphere) and two pinions, whose axes come out at V and U; either of which may be turned by the small winch W. When the winch is put upon the axis V, and turned backward, the terrestrial globe, with its horizon and celestial meridian, keep at rest; and the whole sphere of circles turns round from east, by south, to west, carrying the sun Y, and moon Z, round the same way, and causing them to rise above and set below the horizon. But when the winch is put upon the axis U, and turned forward, the sphere with the sun and moon keep at rest; and the earth, with its horizon and meridian, turn round from horizon to the sun and moon,


id: armillary-sphere-20260505-2
file: data/en.wikipedia.org/wiki/Armillary_sphere-2.md
category: reference
title: Armillary sphere
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Armillary_sphere
date_saved: 2026-05-05T09:36:22.848952+00:00
instance: kb-cron
parent: armillary-sphere-20260505-0
summary:
Throughout Chinese history, astronomers have created celestial globes (Chinese: 渾象; pinyin: húnxiàng) to assist the observation of the stars. The Chinese also used the armillary sphere in aiding calendrical computations and calculations. According to Joseph Needham, the earliest development of the armillary sphere in China goes back to the astronomers Shi Shen and Gan De in the 4th century BC, as they were equipped with a primitive single-ring armillary instrument. This would have allowed them to measure the north polar distance (declination) a measurement that gave the position in a xiu (right ascension). Needham's 4th century BC dating, however, is rejected by British sinologist Christopher Cullen, who traces the beginnings of these devices to the 1st century BC. During the Western Han dynasty (202 BC – 9 AD) additional developments made by the astronomers Luoxia Hong (落下閎), Xiangyu Wangren, and Geng Shouchang (耿壽昌) advanced the use of the armillary in its early stage of evolution. In 52 BC, it was the astronomer Geng Shouchang who introduced the first permanently fixed equatorial ring of the armillary sphere. In the subsequent Eastern Han dynasty (23–220 AD) period, the astronomers Fu An and Jia Kui added the ecliptic ring by 84 AD. With


id: armillary-sphere-20260505-3
file: data/en.wikipedia.org/wiki/Armillary_sphere-3.md
category: reference
title: Armillary sphere
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Armillary_sphere
date_saved: 2026-05-05T09:36:22.848952+00:00
instance: kb-cron
parent: armillary-sphere-20260505-0
summary:
In its simplest form, consisting of a ring fixed in the plane of the equator, the armilla is one of the most ancient of astronomical instruments. Slightly developed, it was crossed by another ring fixed in the plane of the meridian. The first was an equinoctial, the second a solstitial armilla. Shadows were used as indices of the sun's positions, in combinations with angular divisions. When several rings or circles were combined representing the great circles of the heavens, the instrument became an armillary sphere. Armillary spheres were developed by the Hellenistic Greeks and were used as teaching tools already in the 3rd century BC. In larger and more precise forms they were also used as observational instruments. However, the fully developed armillary sphere with nine circles perhaps did not exist until the mid-2nd century AD, during the Roman Empire. Eratosthenes most probably used a solstitial armilla for measuring the obliquity of the ecliptic. Hipparchus probably used an armillary sphere of four rings. The Greco-Roman geographer and astronomer Ptolemy (c. 100 – c. 170 AD) describes his instrument, the astrolabon, in his Almagest. It consisted of at least three rings, with a graduated circle inside of which another could slide,


id: armillary-sphere-20260505-4
file: data/en.wikipedia.org/wiki/Armillary_sphere-4.md
category: reference
title: Armillary sphere
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Armillary_sphere
date_saved: 2026-05-05T09:36:22.848952+00:00
instance: kb-cron
parent: armillary-sphere-20260505-0
summary:
The armillary sphere is commonly used in heraldry and vexillology, being mainly known as a symbol associated with Portugal, the Portuguese Empire and the Portuguese discoveries. In the end of the 15th century, the armillary sphere became the personal heraldic badge of the future King Manuel I of Portugal, when he was still a Prince. The intense use of this badge in documents, monuments, flags and other supports, during the reign of Manuel I, transformed the armillary sphere from a simple personal symbol to a national one that represented the Kingdom of Portugal and in particular its Overseas Empire. As a national symbol, the armillary sphere continued in use after the death of Manuel I. In the 17th century, it became associated with the Portuguese dominion of Brazil. In 1815, when Brazil gained the status of kingdom united with that of Portugal, its coat of arms was formalized as a golden armillary sphere in a blue field. Representing Brazil, the armillary sphere became also present in the arms and the flag of the United Kingdom of Portugal, Brazil and the Algarves. When Brazil became independent as an empire in 1822, the armillary sphere continued to be present in its national


id: astatic-needles-20260505-0
file: data/en.wikipedia.org/wiki/Astatic_needles-0.md
category: reference
title: Astatic needles
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astatic_needles
date_saved: 2026-05-05T09:36:24.009462+00:00
instance: kb-cron
parent: astatic-needles-20260505-0
summary:
An astatic system comprises two equal and parallel magnetic needles, but with their polarities reversed. This arrangement protects the system from the influence of the terrestrial magnetic field, as the magnetisms of the two needles cancel each other out. Because of this phenomenon, astatic needles were often used in galvanometers. == References == "Museo Galileo - object description". "Static Needles - Joseph Henry Project - Princeton University".


id: astrarium-20260505-0
file: data/en.wikipedia.org/wiki/Astrarium-0.md
category: reference
title: Astrarium
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrarium
date_saved: 2026-05-05T09:36:25.196479+00:00
instance: kb-cron
parent: astrarium-20260505-0
summary:
An astrarium, also called a planetarium, is a medieval astronomical clock made in the 14th century by Italian engineer and astronomer Giovanni Dondi dell'Orologio. The Astrarium was modeled after the Solar System and, in addition to counting time and representing calendar dates and holidays, showed how the planets moved around the celestial sphere in one timepiece. This was its main task, in comparison with the astronomical clock, the main task of which is the actual reading of time. A complex mechanism, it combined the functions of a modern planetarium, clock, and calendar into a singular constructive device. Devices that perform this function were known to have been created prior to the design of Dondi, though relatively little is known about them. It is occasionally erroneously claimed by the details of some sources that the Astrarium was the first mechanical device showing the movements of the planets. == History == === Greek and Roman World === The first astraria were mechanical devices. Archimedes is said to have used a primitive version that could predict the positions of the Sun, the Moon, and the planets. On May 17, 1902, an archaeologist named Valerios Stais discovered that a lump of oxidated material, which


id: astrolabe-20260505-0
file: data/en.wikipedia.org/wiki/Astrolabe-0.md
category: reference
title: Astrolabe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrolabe
date_saved: 2026-05-05T09:36:26.368952+00:00
instance: kb-cron
parent: astrolabe-20260505-0
summary:
An astrolabe (Ancient Greek: ἀστρολάβος, romanized: astrolábos, lit. 'star-taker'; Arabic: ٱلأَسْطُرلاب, romanized: al-Asṭurlāb; Persian: ستاره‌یاب, romanized: Setāreyāb) is an astronomical instrument dating to ancient times. It serves as a star chart and physical model of the visible half-dome of the sky. Its various functions also make it an elaborate inclinometer and an analog calculation device capable of working out several kinds of problems in astronomy. In its simplest form it is a metal disc with a pattern of wires, cutouts, and perforations that allows a user to calculate astronomical positions precisely. It is able to measure the altitude above the horizon of a celestial body, day or night; it can be used to identify stars or planets, to determine local latitude given local time (and vice versa), to survey, or to triangulate. It was used in classical antiquity, the Byzantine Empire, the Islamic Golden Age, the European Middle Ages and the Age of Discovery for all these purposes. The astrolabe, which is a precursor to the sextant, is effective for determining latitude on land or calm seas. Although it is less reliable on the heaving deck of a ship in rough seas, the mariner's astrolabe was developed to solve that


id: astrolabe-20260505-1
file: data/en.wikipedia.org/wiki/Astrolabe-1.md
category: reference
title: Astrolabe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrolabe
date_saved: 2026-05-05T09:36:26.368952+00:00
instance: kb-cron
parent: astrolabe-20260505-0
summary:
The spherical astrolabe was a variation of both the astrolabe and the armillary sphere, invented during the Middle Ages by astronomers and inventors in the Islamic world. The earliest description of the spherical astrolabe dates to Al-Nayrizi (fl. 892–902). In the 12th century, Sharaf al-Dīn al-Tūsī invented the linear astrolabe, sometimes called the "staff of al-Tusi", which was "a simple wooden rod with graduated markings, but without sights. It was furnished with a plumb line and a double chord for making angular measurements and bore a perforated pointer". The geared mechanical astrolabe was invented by Abi Bakr of Isfahan in 1235. The first known metal astrolabe in Western Europe is the Destombes astrolabe made from brass in the eleventh century in Portugal. Metal astrolabes avoided the warping that large wooden ones were prone to, allowing the construction of larger and therefore more accurate instruments. Metal astrolabes were heavier than wooden instruments of the same size, making it difficult to use them in navigation. Herman Contractus of Reichenau Abbey, examined the use of the astrolabe in Mensura Astrolai during the 11th century. Peter of Maricourt wrote a treatise on the construction and use of a universal astrolabe in the last half


id: astrolabe-20260505-2
file: data/en.wikipedia.org/wiki/Astrolabe-2.md
category: reference
title: Astrolabe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrolabe
date_saved: 2026-05-05T09:36:26.368952+00:00
instance: kb-cron
parent: astrolabe-20260505-0
summary:
Mechanical astronomical clocks were initially influenced by the astrolabe; they could be seen in many ways as clockwork astrolabes designed to produce a continual display of the current position of the sun, stars, and planets. For example, Richard of Wallingford's clock (c. 1330) consisted essentially of a star map rotating behind a fixed rete, similar to that of an astrolabe. Many astronomical clocks use an astrolabe-style display, such as the famous clock at Prague, adopting a stereographic projection (see below) of the ecliptic plane. In recent times, astrolabe watches have become popular. For example, Swiss watchmaker Ludwig Oechslin designed and built an astrolabe wristwatch in conjunction with Ulysse Nardin in 1985. Dutch watchmaker Christaan van der Klauuw also manufactures astrolabe watches today. == Construction == An astrolabe consists of a disk with a wide, raised rim, called the mater (mother), which is deep enough to hold one or more flat plates called tympans, or climates. A tympan is made for a specific latitude and is engraved with a stereographic projection of circles denoting azimuth and altitude and representing the portion of the celestial sphere above the local horizon. The rim of the mater is typically graduated into hours of time,


id: astrolabe-20260505-3
file: data/en.wikipedia.org/wiki/Astrolabe-3.md
category: reference
title: Astrolabe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrolabe
date_saved: 2026-05-05T09:36:26.368952+00:00
instance: kb-cron
parent: astrolabe-20260505-0
summary:
The blue sphere represents the celestial sphere. The blue arrow indicates the direction of true north (the North Star). The central blue point represents Earth (the observer's location). The geographic south of the celestial sphere acts as the projection pole. The celestial equatorial plane serves as the projection plane. Three parallel circles represent the projection on the celestial sphere of Earth's main circles of latitude: In orange, the celestial Tropic of Cancer. In purple, the celestial equator. In green, the celestial Tropic of Capricorn. When projecting onto the celestial equatorial plane, three concentric circles correspond to the celestial sphere's three circles of latitude (left side of the image). The largest of these, the projection on the celestial equatorial plane of the celestial Tropic of Capricorn, defines the size of the astrolabe's tympanum. The center of the tympanum (and the center of the three circles) is actually the north-south axis around which Earth rotates, and therefore, the rete of the astrolabe will rotate around this point as the hours of the day pass (due to Earth's rotational motion). The three concentric circles on the tympanum are useful for determining the exact moments of solstices and equinoxes throughout the year: if the


id: astrolabe-20260505-4
file: data/en.wikipedia.org/wiki/Astrolabe-4.md
category: reference
title: Astrolabe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astrolabe
date_saved: 2026-05-05T09:36:26.368952+00:00
instance: kb-cron
parent: astrolabe-20260505-0
summary:
== Bibliography == Evans, James (1998), The History and Practice of Ancient Astronomy, Oxford University Press, ISBN 0-19-509539-1 Stöffler, Johannes (2007) [First published 1513], Stoeffler's Elucidatio – The Construction and Use of the Astrolabe [Elucidatio Fabricae Ususque Astrolabii], translated by Gunella, Alessandro; Lamprey, John, John Lamprey, ISBN 978-1-4243-3502-2 King, D. A. (1981), "The Origin of the Astrolabe According to the Medieval Islamic Sources", Journal for the History of Arabic Science, 5: 43–83 King, Henry (1978), Geared to the Stars: the Evolution of Planetariums, Orreries, and Astronomical Clocks, University of Toronto Press, ISBN 978-0-8020-2312-4 Krebs, Robert E.; Krebs, Carolyn A. (2003), Groundbreaking Scientific Experiments, Inventions, and Discoveries of the Ancient World, Greenwood Press, ISBN 978-0-313-31342-4 Laird, Edgar (1997), Carol Poster and Richard Utz (ed.), "Astrolabes and the Construction of Time in the Late Middle Ages", Constructions of Time in the Late Middle Ages, Evanston, Illinois: Northwestern University Press: 51–69 Laird, Edgar; Fischer, Robert, eds. (1995), "Critical edition of Pélerin de Prusse on the Astrolabe (translation of Practique de Astralabe)", Medieval & Renaissance Texts & Studies, Binghamton, New York, ISBN 0-86698-132-2{{citation}}: CS1 maint: work parameter with ISBN (link) Lewis, M. J. T. (2001), Surveying Instruments of Greece and Rome, Cambridge University Press,


id: astronomical-clock-20260505-0
file: data/en.wikipedia.org/wiki/Astronomical_clock-0.md
category: reference
title: Astronomical clock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astronomical_clock
date_saved: 2026-05-05T09:36:27.581434+00:00
instance: kb-cron
parent: astronomical-clock-20260505-0
summary:
An astronomical clock, horologium, or orloj is a clock with special mechanisms and dials to display astronomical information, such as the relative positions of the Sun, Moon, zodiacal constellations, and major planets. == Definition == The term is loosely used to refer to any clock that shows, in addition to the time of day, astronomical information. This could include the location of the Sun and Moon in the sky, the age and Lunar phases, the position of the Sun on the ecliptic and the current zodiac sign, the sidereal time, and other astronomical data such as the Moon's nodes for indicating eclipses), or a rotating star map. The term should not be confused with an astronomical regulator, a high precision but otherwise ordinary pendulum clock used in observatories. Astronomical clocks usually represent the Solar System using the geocentric model. The center of the dial is often marked with a disc or sphere representing the Earth, located at the center of the Solar System. The Sun is often represented by a golden sphere (as it initially appeared in the Antikythera mechanism, back in the 2nd century BC), shown rotating around the Earth once a day around a 24-hour analog dial. This


id: astronomical-clock-20260505-1
file: data/en.wikipedia.org/wiki/Astronomical_clock-1.md
category: reference
title: Astronomical clock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astronomical_clock
date_saved: 2026-05-05T09:36:27.581434+00:00
instance: kb-cron
parent: astronomical-clock-20260505-0
summary:
Most astronomical clocks have a 24-hour analog dial around the outside edge, numbered from I to XII then from I to XII again. The current time is indicated by a golden ball or a picture of the sun at the end of a pointer. Local noon is usually at the top of the dial, and midnight at the bottom. Minute hands are rarely used. The Sun indicator or hand gives an approximate indication of both the Sun's azimuth and altitude. For azimuth (bearing from the north), the top of the dial indicates South, and the two VI points of the dial East and West. For altitude, the top is the zenith and the two VI and VI points define the horizon. (This is for the astronomical clocks designed for use in the northern hemisphere.) This interpretation is most accurate at the equinoxes, of course. If XII is not at the top of the dial, or if the numbers are Arabic rather than Roman, then the time may be shown in Italian hours (also called Bohemian, or Old Czech, hours). In this system, 1 o'clock occurs at sunset, and counting continues through the night and into the next afternoon, reaching 24


id: astronomical-clock-20260505-2
file: data/en.wikipedia.org/wiki/Astronomical_clock-2.md
category: reference
title: Astronomical clock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astronomical_clock
date_saved: 2026-05-05T09:36:27.581434+00:00
instance: kb-cron
parent: astronomical-clock-20260505-0
summary:
=== "Dragon" hand: eclipse prediction and lunar nodes === The Moon's orbit is not in the same plane as the Earth's orbit around the Sun but crosses it in two places. The Moon crosses the ecliptic plane twice a month, once when it goes up above the plane, and again 15 or so days later when it goes back down below the ecliptic. These two locations are the ascending and descending lunar nodes. Solar and lunar eclipses will occur only when the Moon is positioned near one of these nodes because at other times the Moon is either too high or too low for an eclipse to be seen on the Earth. Some astronomical clocks keep track of the position of the lunar nodes with a long pointer that crosses the dial, with its length extended out to both sides of the dial to pointing at two opposite points on the solar or lunar dial. This so-called "dragon" hand makes one complete rotation around the ecliptic dial every 19 years. It is sometimes decorated with the figure of a serpent or lizard (Greek: drakon) with its snout and tail-tip touching the outer dial, traditionally labelled Latin: "caput draconam" and Latin:


id: astronomical-clock-20260505-3
file: data/en.wikipedia.org/wiki/Astronomical_clock-3.md
category: reference
title: Astronomical clock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astronomical_clock
date_saved: 2026-05-05T09:36:27.581434+00:00
instance: kb-cron
parent: astronomical-clock-20260505-0
summary:
=== Watches === More recently, independent clockmaker Christiaan van der Klaauw created a wristwatch astrolabe, the "Astrolabium" in addition to the "Planetarium 2000", the "Eclipse 2001" and the "Real Moon." Ulysse Nardin also sells several astronomical wristwatches, the "Astrolabium," "Planetarium", and the "Tellurium J. Kepler." === Other examples === Two of Holland America's cruise ships, the MS Rotterdam and the MS Amsterdam, both have large astronomical clocks as their main centerpieces inside the ships' atriums. == Examples by country == === Austria === Innsbruck. The astronomical clock in the gable of 17–19 Maria-Theresien-Strasse is a 20th-century copy of the astronomical clock of the Ulm Rathaus in Germany. Peuerbach. The facade of Peuerbach Town Hall features an astrolabe clock, an enlarged copy of Georg von Peuerbach's original astrolabe of 1457. === Belgium === Lier. The Zimmer tower houses an astronomical clock installed by Louis Zimmer in 1930. On twelve dials surrounding a central clockface, it gives indications including the time around the world, the date, the moon phase, and the equation of time, and includes a tide clock. Senzeilles. The Senzeilles astronomical clock was constructed by self-taught Lucien Charloteaux between 1896 and 1912. A domestic clock housed in a wooden case,


id: astronomical-clock-20260505-4
file: data/en.wikipedia.org/wiki/Astronomical_clock-4.md
category: reference
title: Astronomical clock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astronomical_clock
date_saved: 2026-05-05T09:36:27.581434+00:00
instance: kb-cron
parent: astronomical-clock-20260505-0
summary:
Auxerre. The 15th-century clock in the Tour de l'Horloge has a 24-hour sun hand and a moon hand which completes a revolution in a lunar day of 24 hours 50 minutes, and shows the lunar phase on a rotating moon ball. Beauvais. The Beauvais astronomical clock in Beauvais Cathedral, constructed 1865–1868 by Auguste-Lucien Vérité, has 52 dials that display the times of sunrise, sunset, moonrise, moonset, the phases of the moon, the solstices, the position of the planets, the current time in 18 cities around the world, and the tidal hours. Its 68 automata enact the Last Judgement on the hour. Besançon. The Besançon astronomical clock in Besançon Cathedral (1860) was also constructed by Auguste-Lucien Vérité. Its 70 dials provide 122 indications. Bourges. The Bourges astronomical clock in Bourges Cathedral was installed in 1424. It shows the zodiac, and the moon phase and age. Chartres. The Chartres astronomical clock in Chartres Cathedral is an astrolabe clock, installed in 1528. It was overhauled, its mechanism replaced by an electric mechanism, in 2009. Haguenau. The facade of the Musée alsacien displays an astronomical clock, a modern copy of the clock of the Ulm Rathaus. Lyon. The Lyon astronomical clock in Lyon Cathedral


id: astronomical-clock-20260505-5
file: data/en.wikipedia.org/wiki/Astronomical_clock-5.md
category: reference
title: Astronomical clock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astronomical_clock
date_saved: 2026-05-05T09:36:27.581434+00:00
instance: kb-cron
parent: astronomical-clock-20260505-0
summary:
A group of interior astronomical clocks of the 14th, 15th and 16th centuries in churches of Hanseatic League towns in northern Germany, known as the Hanseatic clocks (the group also includes the clock at Gdańsk, now in Poland). Bad Doberan. At Doberan Minster, an astrolabe clock was installed by Nikolaus Lilienfeld in 1390. Only the dial survives, now positioned above the west door. Lübeck. The astronomical clock of St. Mary's Church, constructed 1561–1566, was destroyed in the bombing of Lübeck in 1942. The present clock is a replacement by Paul Behrens, installed in 1967. Münster. The Münster astronomical clock of 1540 in Münster Cathedral, adorned with hand-painted zodiac symbols, which traces the movement of the planets, plays a glockenspiel tune every noon. Rostock. The Rostock astronomical clock in St. Mary's Church dating from 1472, built by Hans Düringer. Clock with daily time, zodiac, moon phases, and month. With a dedicated electronic database this clock is particularly well documented. Stendal. At St. Mary's Church, an astronomical clock of the 1580s, rebuilt in 1856 (and vandalized by the clockmaker), and restored in 1977. Stralsund. The astronomical clock in St. Nicholas' Church is an astrolabe clock installed by Nikolaus Lilienfeld in 1394. It


id: astronomical-clock-20260505-6
file: data/en.wikipedia.org/wiki/Astronomical_clock-6.md
category: reference
title: Astronomical clock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astronomical_clock
date_saved: 2026-05-05T09:36:27.581434+00:00
instance: kb-cron
parent: astronomical-clock-20260505-0
summary:
=== Malta === Valletta. The clock of the Grandmaster's Palace, installed in 1745, shows the hour, date, month, and lunar phase, and has bells struck by four jacquemarts. Malta has several church clocks that show calendar indications on separate dials, including those of St John's Co-Cathedral, Valletta; St Paul's Cathedral, Mdina; the Rotunda of Mosta; and the Church of St Bartholomew, Għargħur. === Netherlands === Arnemuiden. The 16th-century church clock at Arnemuiden indicates the lunar phase and the time of high tide. Franeker. The Eise Eisinga Planetarium, built 1774–1781, is an orrery and astronomical clock which shows the movements of the solar system. === Norway === Oslo. A 20th-century astronomical clock at Oslo City Hall. === Poland === Gdańsk. In St. Mary's Church there is the Gdańsk astronomical clock dating from 1464 to 1470, and built by Hans Düringer of Toruń. It was reconstructed after 1945. Wrocław. A 16th-century clock showing the moon phase at Wrocław Town Hall. === Slovakia === Stará Bystrica: An astronomical clock in the stylized shape of Our Lady of Sorrows was built in the town square in 2009. The astronomical part of the clock consists of an astrolabe displaying the astrological signs, positions of the


id: list-of-astronomical-instruments-20260505-0
file: data/en.wikipedia.org/wiki/List_of_astronomical_instruments-0.md
category: reference
title: List of astronomical instruments
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_astronomical_instruments
date_saved: 2026-05-05T09:36:28.781458+00:00
instance: kb-cron
parent: list-of-astronomical-instruments-20260505-0
summary:
An astronomical instrument is a device for observing, measuring or recording astronomical data. They are used in the scientific field of astronomy, a natural science that studies celestial objects and the phenomena that occur in the cosmos, with the object of explaining their origin and evolution over time. Many are also used in navigation and surveying. Astronomical instruments include: == See also == Astronomy Outline of astronomy Surveying instrument Measurement instrument == Notes ==


id: astronomical-rings-20260505-0
file: data/en.wikipedia.org/wiki/Astronomical_rings-0.md
category: reference
title: Astronomical rings
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Astronomical_rings
date_saved: 2026-05-05T09:36:29.975083+00:00
instance: kb-cron
parent: astronomical-rings-20260505-0
summary:
Astronomical rings (Latin: annuli astronomici), also known as Gemma's rings, are an early astronomical instrument. The instrument consists of three rings, representing the celestial equator, declination, and the meridian. It can be used as a sun dial to tell time, if the approximate latitude and season is known, or to tell latitude, if the time is known or observed (at solar noon). It may be considered to be a simplified, portable armillary sphere, or a more complex form of astrolabe. == History == Parts of the instrument go back to instruments made and used by ancient Greek astronomers. Gemma Frisius combined several of the instruments into a small, portable, astronomical-ring instrument. He first published the design in 1534, and in Petrus Apianus's Cosmographia in 1539. These ring instruments combined terrestrial and celestial calculations. == Types == === Fixed astronomical rings === Fixed astronomical rings are mounted on a plinth, like armillary spheres, and can be used as sundials. === Traveller's sundial or universal equinoctal ring dial === The dial is suspended from a cord or chain; the suspension point on the vertical meridian ring can be changed to match the local latitude. The time is read off on the equatorial


id: backstaff-20260505-0
file: data/en.wikipedia.org/wiki/Backstaff-0.md
category: reference
title: Backstaff
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Backstaff
date_saved: 2026-05-05T09:36:31.201916+00:00
instance: kb-cron
parent: backstaff-20260505-0
summary:
The backstaff is a navigational instrument that was used to measure the altitude of a celestial body, in particular the Sun or Moon. When observing the Sun, users kept the Sun to their back (hence the name) and observed the shadow cast by the upper vane on a horizon vane. It was invented by the English navigator John Davis, who described it in his book Seaman's Secrets in 1594. == Types of backstaffs == Backstaff is the name given to any instrument that measures the altitude of the sun by the projection of a shadow. It appears that the idea for measuring the sun's altitude using back observations originated with Thomas Harriot. Many types of instruments evolved from the cross-staff that can be classified as backstaffs. Only the Davis quadrant remains dominant in the history of navigation instruments. Indeed, the Davis quadrant is essentially synonymous with backstaff. However, Davis was neither the first nor the last to design such an instrument and others are considered here as well. == Davis quadrant == Captain John Davis invented a version of the backstaff in 1594. Davis was a navigator who was quite familiar with the instruments of the day such as the


id: backstaff-20260505-1
file: data/en.wikipedia.org/wiki/Backstaff-1.md
category: reference
title: Backstaff
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Backstaff
date_saved: 2026-05-05T09:36:31.201916+00:00
instance: kb-cron
parent: backstaff-20260505-0
summary:
=== Usage === In order to use the instrument, the navigator would place the shadow vane at a location anticipating the altitude of the sun. Holding the instrument in front of him, with the sun at his back, he holds the instrument so that the shadow cast by the shadow vane falls on the horizon vane at the side of the slit. He then moves the sight vane so that he observes the horizon in a line from the sight vane through the horizon vane's slit while simultaneously maintaining the position of the shadow. This permits him to measure the angle between the horizon and the sun as the sum of the angle read from the two arcs. Since the shadow's edge represents the limb of the sun, he must correct the value for the semidiameter of the sun. === Instruments that derived from the Davis quadrant === The Elton's quadrant derived from the Davis quadrant. It added an index arm with spirit levels to provide an artificial horizon. == Demi-cross == The demi-cross was an instrument that was contemporary with the Davis quadrant. It was popular outside England. The vertical transom was like a half-transom on a cross-staff, hence


id: backstaff-20260505-2
file: data/en.wikipedia.org/wiki/Backstaff-2.md
category: reference
title: Backstaff
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Backstaff
date_saved: 2026-05-05T09:36:31.201916+00:00
instance: kb-cron
parent: backstaff-20260505-0
summary:
== Benjamin Cole quadrant == A late addition to the collection of backstaves in the navigation world, this device was invented by Benjamin Cole in 1748. The instrument consists of a staff with a pivoting quadrant on one end. The quadrant has a shadow vane, which can optionally take a lens like the Davis quadrant's Flamsteed glass, at the upper end of the graduated scale (A in Figure 7). This casts a shadow or projects an image of the sun on the horizon vane (B). The observer views the horizon through a hole in the sight vane (D) and a slit in the horizon vane to ensure the instrument is level. The quadrant component is rotated until the horizon and the sun's image or shadow are aligned. The altitude can then be read from the quadrant's scale. In order to refine the reading, a circular vernier is mounted on the staff (C). The fact that such an instrument was introduced in the middle of the 18th century shows that the quadrant was still a viable instrument even in the presence of the octant. English scientist George Adams created a very similar backstaff at the same time. Adam's version ensured that


id: ballistic-galvanometer-20260505-0
file: data/en.wikipedia.org/wiki/Ballistic_galvanometer-0.md
category: reference
title: Ballistic galvanometer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ballistic_galvanometer
date_saved: 2026-05-05T09:36:32.373814+00:00
instance: kb-cron
parent: ballistic-galvanometer-20260505-0
summary:
A ballistic galvanometer is a type of sensitive galvanometer; commonly a mirror galvanometer. Unlike a current-measuring galvanometer, the moving part has a large moment of inertia, thus giving it a long oscillation period. It is really an integrator measuring the quantity of charge discharged through it. It can be either of the moving coil or moving magnet type. Before first use the ballistic constant of the galvanometer must be determined. This is usually done by connecting to the galvanometer a known capacitor, charged to a known voltage, and recording the deflection. The constant K is calculated from the capacitance C, the voltage V and the deflection d: K = C V / d {\displaystyle K=CV/d} where K is expressed in coulombs per centimeter. In operation the unknown quantity of charge Q (in coulombs) is simply: Q = k d {\displaystyle Q=kd} . == Grassot Fluxmeter == The Grassot Fluxmeter solves a particular problem encountered with regular galvanometers. For a regular galvanometer, the discharge time must be shorter than the natural period of oscillation of the mechanism. In some applications, particularly those involving inductors, this condition cannot be met. The Grassot fluxmeter resolves this problem, by operating without any restoring force,


id: barcelona-astrolabe-20260505-0
file: data/en.wikipedia.org/wiki/Barcelona_astrolabe-0.md
category: reference
title: Barcelona astrolabe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Barcelona_astrolabe
date_saved: 2026-05-05T09:36:33.541647+00:00
instance: kb-cron
parent: barcelona-astrolabe-20260505-0
summary:
The Barcelona astrolabe is the oldest astrolabe with Carolingian characters that has survived in the Christian Occident. The French researcher Marcel Destombes founded the astrolabe, and left it as legacy to the Institute of the Arab World of Paris in 1983. The Academy of Sciences of Barcelona asked the astrolabe in loan to the Musée of l'Institut du Monde Arabe, to make a replica, today this replica is on display at the Academy of Sciences in the Ramblas. == Description == This astrolabe presents some unusual characteristics. All the engraved characters are in Latin, this fact made the scholars think that the instrument was made in Christian Europe. The pointers of his "spider" indicate eighteen stars: ten boreal stars and eight austral stars (that is to say, situated beneath of the equator). Eleven of them correspond to the date of 980 AD. Still like this, the names of the stars are not engraved on the brass. The words ROMA and FRANCIA are engraved in Latin characters in one of the eardrums. These characters are accompanied by the numbers 41-30 (in Arabic figures). The characters are identical to those used at the end of the 10th century in the Catalan Latin


id: bygrave-slide-rule-20260505-0
file: data/en.wikipedia.org/wiki/Bygrave_slide_rule-0.md
category: reference
title: Bygrave slide rule
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Bygrave_slide_rule
date_saved: 2026-05-05T09:36:34.708068+00:00
instance: kb-cron
parent: bygrave-slide-rule-20260505-0
summary:
The Bygrave slide rule is a slide rule named for its inventor, Captain Leonard Charles Bygrave of the RAF. It was used in celestial navigation, primarily in aviation. Officially, it was called the A. M. L. Position Line Slide Rule (A.M.L. for Air Ministry Laboratories). It was developed in 1920 at the Air Ministry Laboratories at Kensington in London and was produced by Henry Hughes & Son Ltd of London until the mid-1930s. It solved the so-called celestial triangle accurately to about one minute of arc and quickly enough for aerial navigation. The solution of the celestial triangle used the John Napier rules for solution of square-angled spherical triangles. The slide rule was constructed as two coaxial tubes with spiral scales, like the Fuller's cylindrical slide rules, with yet another tube on the outside carrying the cursors. During the Second World War, a closely related version was produced in Germany by Dennert & Pape as the HR1, MHR1 and HR2. == Famous users == Sir Francis Chichester was a renowned aviator and yachtsman. He used a Bygrave Slide Rule as an aid to navigation during flights in the 1930s, one of which was the first solo flight from New Zealand


id: cabinet-of-curiosities-20260505-0
file: data/en.wikipedia.org/wiki/Cabinet_of_curiosities-0.md
category: reference
title: Cabinet of curiosities
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cabinet_of_curiosities
date_saved: 2026-05-05T09:36:35.931697+00:00
instance: kb-cron
parent: cabinet-of-curiosities-20260505-0
summary:
Cabinets of curiosities (German: Kunstkammer [ˈkʊnstˌkamɐ] and Kunstkabinett [ˈkʊnstkabiˌnɛt]), also known as wonder-rooms (German: Wunderkammer [ˈvʊndɐˌkamɐ] ), were encyclopedic collections of objects whose categorical boundaries were, in Renaissance Europe, yet to be defined. Although more rudimentary collections had preceded them, the classic cabinets of curiosities emerged in the sixteenth century. The term cabinet originally described a room rather than a piece of furniture. Modern terminology would categorize the objects included as belonging to natural history (sometimes faked), geology, ethnography, archaeology, religious or historical relics, works of art (including cabinet paintings), and antiquities. In addition to the most famous and best documented cabinets of rulers and aristocrats, members of the merchant class and early practitioners of science in Europe formed collections that were precursors to museums. Cabinets of curiosities served not only as collections to reflect the particular interests of their curators but also as social devices to establish and uphold rank in society. There are said to be two main types of cabinets. As R. J. W. Evans notes, there could be "the princely cabinet, serving a largely representational function, and dominated by aesthetic concerns and a marked predilection for the exotic," or the less grandiose, "the more modest collection


id: cabinet-of-curiosities-20260505-1
file: data/en.wikipedia.org/wiki/Cabinet_of_curiosities-1.md
category: reference
title: Cabinet of curiosities
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cabinet_of_curiosities
date_saved: 2026-05-05T09:36:35.931697+00:00
instance: kb-cron
parent: cabinet-of-curiosities-20260505-0
summary:
Two of the most famously described seventeenth-century cabinets were those of Ole Worm, known as Olaus Wormius (1588–1654) (illustration, above right), and Athanasius Kircher (1602–1680). These seventeenth-century cabinets were filled with preserved animals, horns, tusks, skeletons, minerals, as well as other interesting man-made objects: sculptures wondrously old, wondrously fine or wondrously small; clockwork automata; ethnographic specimens from exotic locations. Often they would contain a mix of fact and fiction, including apparently mythical creatures. Worm's collection contained, for example, what he thought was a Scythian Lamb, a woolly fern thought to be a plant/sheep fabulous creature. However he was also responsible for identifying the narwhal's tusk as coming from a whale rather than a unicorn, as most owners of these believed. The specimens displayed were often collected during exploring expeditions and trading voyages. Cabinets of curiosities would often serve scientific advancement when images of their contents were published. The catalog of Worm's collection, published as the Museum Wormianum (1655), used the collection of artifacts as a starting point for Worm's speculations on philosophy, science, natural history, and more. Cabinets of curiosities were limited to those who could afford to create and maintain them. Many monarchs, in particular, developed large collections. A


id: cabinet-of-curiosities-20260505-2
file: data/en.wikipedia.org/wiki/Cabinet_of_curiosities-2.md
category: reference
title: Cabinet of curiosities
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cabinet_of_curiosities
date_saved: 2026-05-05T09:36:35.931697+00:00
instance: kb-cron
parent: cabinet-of-curiosities-20260505-0
summary:
Sloane meticulously cataloged and created extensive records for most of the specimens and objects in his collection. He also began to acquire other collections by gift or purchase. Herman Boerhaave gave him four volumes of plants from Boerhaave's gardens at Leiden. William Charleton, in a bequest in 1702, gave Sloane numerous books of birds, fish, flowers, and shells and his miscellaneous museum consisting of curiosities, miniatures, insects, medals, animals, minerals, precious stones and curiosities in amber. Sloane purchased Leonard Plukenet's collection in 1710. It consisted of twenty-three volumes with over 8,000 plants from Africa, India, Japan and China. Mary Somerset, Duchess of Beaufort (1630–1715), left him a twelve-volume herbarium from her gardens at Chelsea and Badminton upon her death in 1714. Reverend Adam Buddle gave Sloane thirteen volumes of British plants. In 1716, Sloane purchased Engelbert Kaempfer's volume of Japanese plants and James Petiver's virtual museum of approximately one hundred volumes of plants from Europe, North America, Africa, the Near East, India, and the Orient. Mark Catesby gave him plants from North America and the West Indies from an expedition funded by Sloane. Philip Miller gave him twelve volumes of plants grown from the Chelsea Physic Garden. Sloane acquired approximately


id: cabinet-of-curiosities-20260505-3
file: data/en.wikipedia.org/wiki/Cabinet_of_curiosities-3.md
category: reference
title: Cabinet of curiosities
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cabinet_of_curiosities
date_saved: 2026-05-05T09:36:35.931697+00:00
instance: kb-cron
parent: cabinet-of-curiosities-20260505-0
summary:
=== United States === Thomas Dent Mutter (1811–1859) was an early American pioneer of reconstructive plastic surgery. His specialty was repairing congenital anomalies, cleft lip and palates, and club foot. He also collected medical oddities, tumors, anatomical and pathological specimens, wet and dry preparations, wax models, plaster casts, and illustrations of medical deformities. This collection began as a teaching tool for young physicians. Just prior to Mütter's death in 1859, he donated 1,344 items to the American College of Physicians in Philadelphia, along with a $30,000 endowment for the maintenance and expansion of his museum. Mütter's collection was added to ninety-two pathological specimens collected by Doctor Isaac Parrish between 1849 and 1852. The Mütter Museum began to collect antique medical equipment in 1871, including Benjamin Rush's medical chest and Florence Nightingale's sewing kit. In 1874 the museum acquired one hundred human skulls from Austrian anatomist and phrenologist, Joseph Hyrtl (1810–1894); a nineteenth-century corpse, dubbed the "soap lady"; the conjoined liver and death cast of Chang and Eng Bunker, the Siamese twins; and in 1893, Grover Cleveland's jaw tumor. The Mütter Museum is an excellent example of a nineteenth-century grotesque cabinet of medical curiosities. P. T. Barnum established Barnum's American Museum


id: cabinet-of-curiosities-20260505-4
file: data/en.wikipedia.org/wiki/Cabinet_of_curiosities-4.md
category: reference
title: Cabinet of curiosities
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cabinet_of_curiosities
date_saved: 2026-05-05T09:36:35.931697+00:00
instance: kb-cron
parent: cabinet-of-curiosities-20260505-0
summary:
== Further reading == Under the Sign: John Bargrave as Collector, Traveler, and Witness, Stephen Bann, Michigan, 1995 Beßler, Gabriele, Chambers of Art and Wonders, EGO - European History Online, Mainz: Institute of European History, 2015, retrieved: March 8, 2021 (pdf). The Origins of Museums: The Cabinet of Curiosities in Sixteenth- and Seventeenth-Century Europe, ed. Oliver Impey and Arthur MacGregor, 2001, paperback, 431 pages, ISBN 1-84232-132-3 Cabinets for the curious: looking back at early English museums, Ken Arnold, Ashgate, 2006, ISBN 0-7546-0506-X. Mr. Wilson's Cabinet Of Wonder: Pronged Ants, Horned Humans, Mice on Toast, and Other Marvels of Jurassic Technology, Lawrence Weschler, 1996, trade paperback, 192 pages, ISBN 0-679-76489-5 (see website link above) The Cabinet of Curiosities (novel), Douglas Preston and Lincoln Child, Warner Books, 2003, paperback, ISBN 0-446-61123-9. Helmar Schramm et al. (ed.). Collection, Laboratory, Theater. Scenes of Knowledge in the 17th Century, Berlin/New York 2005, ISBN 978-3-11-017736-7 The Lure of Antiquity and the Cult of the Machine: The Kunstkammer and the Evolution of Nature, Art and Technology Horst Bredekamp (Allison Brown, translator) (Princeton: Marcus Weiner) 1995. Steven Lubar, "Cabinets of Curiosity: What they were, why they disappeared, and why they’re so popular now" == External links == Historic


id: cavallo-s-multiplier-20260505-0
file: data/en.wikipedia.org/wiki/Cavallo's_multiplier-0.md
category: reference
title: Cavallo's multiplier
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cavallo's_multiplier
date_saved: 2026-05-05T09:36:37.078596+00:00
instance: kb-cron
parent: cavallo-s-multiplier-20260505-0
summary:
Cavallo's multiplier was an early electrostatic influence machine, invented in 1795 by the Anglo-Italian natural philosopher Tiberius Cavallo. Its purpose was to multiply, or amplify, a small electric charge to a level where it was detectable by the insensitive electroscopes of the day. Repeated operation of the device could produce voltages high enough to generate sparks. == Description == Cavallo described his machine in his 1795 Treatise on Electricity. He had examined Bennet's charge doubler of 1787 and found it wanting in several regards, notably in its inconsistent operation and tendency to retain the charge from an earlier experiment. Cavallo resolved to build a better device. His machine consisted of four metal plates supported on a wooden board by posts, of which three were insulating and one conducting. The charge to be multiplied was applied to the first of these (plate A), which stood on an insulating post. A moveable insulated metal plate (B) was brought close to A (though not permitted to touch it), and then grounded. The charge on A caused charge separation on B due to electrostatic induction. Plate B was then moved away, breaking its earth connection. Since B was insulated, it acquired and retained a


id: celestial-sphere-woodrow-wilson-memorial-20260505-0
file: data/en.wikipedia.org/wiki/Celestial_Sphere_Woodrow_Wilson_Memorial-0.md
category: reference
title: Celestial Sphere Woodrow Wilson Memorial
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Celestial_Sphere_Woodrow_Wilson_Memorial
date_saved: 2026-05-05T09:36:38.333218+00:00
instance: kb-cron
parent: celestial-sphere-woodrow-wilson-memorial-20260505-0
summary:
The Celestial Sphere (also known as the Woodrow Wilson Memorial Sphere) is an armillary sphere artpiece situated in the Palais des Nations in Geneva, Switzerland, one of the four headquarters of the United Nations. It was donated in 1939 by the Woodrow Wilson Foundation to what was then the League of Nations building. It is today a symbol of Geneva International and of Geneva as the centre of dialogue and peace. The grounds of the Palais des Nations (seat of the United Nations Office at Geneva) contain many fine objects donated by member states of the United Nations, private sponsors and artists. One of them is the huge—over four-meter-diameter—Celestial Sphere is the chef d'oeuvre of the American sculptor Paul Manship (1885–1966) located in the Ariana Park of the Palais des Nations. == History == Contacted in late 1935 by the Board of the Woodrow Wilson Foundation, Manship was asked to provide an idea for a memorial to President of the United States Woodrow Wilson as the founding father of the League of Nations. At that time the Palais des Nations was still under construction. The first idea for Manship's contribution to the new buildings was to have him design two


id: celestial-sphere-woodrow-wilson-memorial-20260505-1
file: data/en.wikipedia.org/wiki/Celestial_Sphere_Woodrow_Wilson_Memorial-1.md
category: reference
title: Celestial Sphere Woodrow Wilson Memorial
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Celestial_Sphere_Woodrow_Wilson_Memorial
date_saved: 2026-05-05T09:36:38.333218+00:00
instance: kb-cron
parent: celestial-sphere-woodrow-wilson-memorial-20260505-0
summary:
=== Dysfunctional rotation system and illumination === Due to the outbreak of the Second World War the rotation motor of the Celestial Sphere was used for several months only. In the files of the Woodrow Wilson Foundation, the following brief description was found: "A complex silence and solitude reigned; the great ceremony of dedication, with the 30th Assembly in session, had become impossible: only an occasional chance visitor and a few especially interested Americans watched the Italians putting the great sphere, representative of universal comity, into its place of high honour." The rotation motor of the Celestial Sphere was not used during 1940–1945 and ceased to function in the early 1960s. === Deteriorating conditions === The sphere began to have significant problems as early as 1942. The alloy used by the Bearzi Atelier contracted so sharply during the winter that a considerable amount of water could and did enter the hollow constellations. The freezing of that water caused the metal to crack. Already several of the constellations had to be repaired in 1942–43 and at least one cover of a meridian had to be replaced after falling off. "Weep holes" were drilled in all the constellations at that time to


id: corbett-s-electrostatic-machine-20260505-0
file: data/en.wikipedia.org/wiki/Corbett's_electrostatic_machine-0.md
category: reference
title: Corbett's electrostatic machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Corbett's_electrostatic_machine
date_saved: 2026-05-05T09:36:40.611013+00:00
instance: kb-cron
parent: corbett-s-electrostatic-machine-20260505-0
summary:
Corbett's electrostatic machine is a static electricity generating device that was made by the Shaker physician Thomas Corbett in 1810. Intended to treat rheumatism, the device built up a static charge and stored it in a Leyden jar, an early type of capacitor. == Description == Corbett was a medical physician for the Shakers, a religious group of colonial America. He was a botanist and preferred herbal medicines to bloodletting. His machine was hand-operated. Rotating a glass cylinder in contact with a silk pad caused a static charge to accumulate on the cylinder. A metal comb collected this charge, which was then stored in a Leyden jar. From the jar, the electrical charge could then be released into the patient, producing a shock akin to "touching a doorknob after walking across carpet in dry weather". == See also == Franklin's electrostatic machine == References ==


id: crookes-tube-20260505-0
file: data/en.wikipedia.org/wiki/Crookes_tube-0.md
category: reference
title: Crookes tube
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Crookes_tube
date_saved: 2026-05-05T09:36:41.769217+00:00
instance: kb-cron
parent: crookes-tube-20260505-0
summary:
A Crookes tube (also Crookes–Hittorf tube) is an early experimental discharge tube with partial vacuum invented by English physicist William Crookes and others around 1869–1875, in which cathode rays, streams of electrons, were discovered. Developed from the earlier Geissler tube, the Crookes tube consists of a partially evacuated glass bulb of various shapes, with two metal electrodes, the cathode and the anode, one at either end. When a high voltage is applied between the electrodes, cathode rays (electrons) are projected in straight lines from the cathode. It was used by Crookes, Johann Hittorf, Julius Plücker, Eugen Goldstein, Heinrich Hertz, Philipp Lenard, Kristian Birkeland and others to discover the properties of cathode rays, culminating in J. J. Thomson's 1897 identification of cathode rays as negatively charged particles, which were later named electrons. Crookes tubes are now used only for demonstrating cathode rays. Wilhelm Röntgen discovered X-rays using the Crookes tube in 1895. The term Crookes tube is also used for the first generation, cold cathode X-ray tubes, which evolved from the experimental Crookes tubes and were used until about 1920. == History == === Invention === Crookes tubes evolved from the earlier Geissler tubes invented by the German physicist and glassblower


id: crookes-tube-20260505-1
file: data/en.wikipedia.org/wiki/Crookes_tube-1.md
category: reference
title: Crookes tube
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Crookes_tube
date_saved: 2026-05-05T09:36:41.769217+00:00
instance: kb-cron
parent: crookes-tube-20260505-0
summary:
=== Discovery of X-rays === When the voltage applied to a Crookes tube is high enough, around 5,000 volts or greater, it can accelerate the electrons to a high enough velocity to create X-rays when they hit the anode or the glass wall of the tube. The fast electrons emit X-rays when their path is bent sharply as they pass near the high electric charge of an atom's nucleus, a process called bremsstrahlung, or they knock an atom's inner electrons into a higher energy level, and these in turn emit X-rays as they return to their former energy level, a process called X-ray fluorescence. Many early Crookes tubes undoubtedly generated X-rays, because early researchers such as Ivan Pulyui had noticed that they could make foggy marks on nearby unexposed photographic plates. On November 8, 1895, Wilhelm Röntgen was operating a Crookes tube covered with black cardboard when he noticed that a nearby fluorescent screen glowed faintly. He realized that some unknown invisible rays from the tube were able to pass through the cardboard and make the screen fluoresce. He found that they could pass through books and papers on his desk. Röntgen began to investigate the rays full-time, and on


id: crookes-tube-20260505-2
file: data/en.wikipedia.org/wiki/Crookes_tube-2.md
category: reference
title: Crookes tube
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Crookes_tube
date_saved: 2026-05-05T09:36:41.769217+00:00
instance: kb-cron
parent: crookes-tube-20260505-0
summary:
=== Cathode rays move in parallel lines === Julius Plücker in 1869 built a tube with an anode shaped like a Maltese Cross facing the cathode. It was hinged, so it could fold down against the floor of the tube. When the tube was turned on, the cathode rays cast a sharp cross-shaped shadow on the fluorescence on the back face of the tube, showing that the rays moved in straight lines. This fluorescence was used as an argument that cathode rays were electromagnetic waves, since the only thing known to cause fluorescence at the time was ultraviolet light. After a while the fluorescence would get 'tired' and the glow would decrease. If the cross was folded down out of the path of the rays, it no longer cast a shadow, and the previously shadowed area would fluoresce more strongly than the area around it. === Perpendicular emission === Eugen Goldstein in 1876 found that cathode rays were always emitted perpendicular to the cathode's surface. If the cathode was a flat plate, the rays were shot out in straight lines perpendicular to the plane of the plate. This was evidence that they were particles, because a luminous object, like a


id: crookes-tube-20260505-3
file: data/en.wikipedia.org/wiki/Crookes_tube-3.md
category: reference
title: Crookes tube
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Crookes_tube
date_saved: 2026-05-05T09:36:41.769217+00:00
instance: kb-cron
parent: crookes-tube-20260505-0
summary:
=== Spectral shift === Eugen Goldstein thought he had figured out a method of measuring the speed of cathode rays. If the glow discharge seen in the gas of Crookes tubes was produced by the moving cathode rays, the light radiated from them in the direction they were moving, down the tube, would be shifted in frequency due to the Doppler effect. This could be detected with a spectroscope because the emission line spectrum would be shifted. He built a tube shaped like an "L", with a spectroscope pointed through the glass of the elbow down one of the arms. He measured the spectrum of the glow when the spectroscope was pointed toward the cathode end, then switched the power supply connections so the cathode became the anode and the electrons were moving in the other direction, and again observed the spectrum looking for a shift. He did not find one, which he calculated meant that the rays were traveling very slowly. It was later recognized that the glow in Crookes tubes is emitted from gas atoms hit by the electrons, not the electrons themselves. Since the atoms are thousands of times more massive than the electrons, they move much


id: cyanometer-20260505-0
file: data/en.wikipedia.org/wiki/Cyanometer-0.md
category: reference
title: Cyanometer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cyanometer
date_saved: 2026-05-05T09:36:45.088006+00:00
instance: kb-cron
parent: cyanometer-20260505-0
summary:
A cyanometer (from cyan and -meter) is an instrument for measuring "blueness", specifically the colour intensity of blue sky. It is attributed to Horace-Bénédict de Saussure and Alexander von Humboldt. It consists of squares of paper dyed in graduated shades of blue and arranged in a color circle or square that can be held up and compared to the color of the sky. == History == Horace-Bénédict de Saussure, a Swiss physicist and mountain climber, is credited with inventing the cyanometer in the 1760s. De Saussure's cyanometer was divided into colored, numbered sections, ranging from white to gradually darker shades of blue, dyed with Prussian blue and arranged in a circle. The cyanometers were manually produced with a predefined recipe of watercolor concentration for each section, and then distributed to friends and fellow naturalists to gather more observations. In an article from 1790, de Saussure presents an illustration of a wheel with 40 stops, though clarifies that it serves merely to give the reader "an idea of its form"; the actual cyanometer had 53 stops (or "degrees"), starting with white as 0 and black as 52. De Saussure believed that the color of the sky was dependent on the amount


id: dioptra-20260505-0
file: data/en.wikipedia.org/wiki/Dioptra-0.md
category: reference
title: Dioptra
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dioptra
date_saved: 2026-05-05T09:36:48.449658+00:00
instance: kb-cron
parent: dioptra-20260505-0
summary:
A dioptra (sometimes also named dioptre or diopter, from Greek: διόπτρα) is a classical astronomical and surveying instrument, dating from the 3rd century BC. The dioptra was a sighting tube or, alternatively, a rod with a sight at both ends, attached to a stand. If fitted with protractors, it could be used to measure angles. == Use == Greek astronomers used the dioptra to measure the positions of stars; both Euclid and Geminus refer to the dioptra in their astronomical works. It continued in use as an effective surveying tool. Adapted to surveying, the dioptra is similar to the theodolite, or surveyor's transit, which dates to the sixteenth century. It is a more accurate version of the groma. There is some speculation that it may have been used to build the Eupalinian aqueduct. Called "one of the greatest engineering achievements of ancient times," it is a tunnel 1,036 metres (3,399 ft) long, excavated through a mountain on the Greek island of Samos during the reign of Polycrates in the sixth century BC. Scholars disagree, however, whether the dioptra was available that early. An entire book about the construction and surveying usage of the dioptra is credited to Hero of Alexandria


id: dividing-engine-20260505-0
file: data/en.wikipedia.org/wiki/Dividing_engine-0.md
category: reference
title: Dividing engine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dividing_engine
date_saved: 2026-05-05T09:36:49.621289+00:00
instance: kb-cron
parent: dividing-engine-20260505-0
summary:
A dividing engine is a device employed to mark graduations on measuring instruments. == History == There has always been a need for accurate measuring instruments. Whether it is a linear device such as a ruler or vernier or a circular device such as a protractor, astrolabe, sextant, theodolite, or setting circles for astronomical telescopes, the desire for ever greater precision has always existed. For every improvement in the measuring instruments, such as better alidades or the introduction of telescopic sights, the need for more exact graduations immediately followed. In early instruments, graduations were typically etched or scribed lines in wood, ivory or brass. Instrument makers devised various devices to perform such tasks. Early Islamic instrument makers must have had techniques for the fine division of their instruments, as this accuracy is reflected in the accuracy of the readings they made. This skill and knowledge seems to have been lost, given that small quadrants and astrolabes in the 15th and 16th centuries did not show fine graduations and were relatively roughly made. In the 16th century, European instrument makers were hampered by the materials available. Brass was in hammered sheets with rough surfaces and iron graving tools were poor quality.


id: eise-eisinga-planetarium-20260505-0
file: data/en.wikipedia.org/wiki/Eise_Eisinga_Planetarium-0.md
category: reference
title: Eise Eisinga Planetarium
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Eise_Eisinga_Planetarium
date_saved: 2026-05-05T09:36:50.802517+00:00
instance: kb-cron
parent: eise-eisinga-planetarium-20260505-0
summary:
The Royal Eise Eisinga Planetarium (Dutch: Koninklijk Eise Eisinga Planetarium) is an 18th-century orrery in Franeker, Friesland, Netherlands. It is currently a museum and open to the public. The orrery has been on the top 100 Dutch heritage sites list since 1990. In September 2023, it received the status of UNESCO World Heritage Site. It is the oldest working orrery in the world. == History == The orrery was built from 1774 to 1781 by Eise Eisinga, a wool carder and amateur astronomer. Eise Eisinga’s mechanical planetarium is built into the timber roof of the living room ceiling of his historic canal house. William I, Prince of Orange and the first King of the Netherlands, was so impressed with the planetarium, he purchased the house and it became a royal planetarium. The museum consists of the planetarium room, a screening room where documentaries are shown, and special exhibits based on modern astronomy. Other parts on permanent display are Eisinga’s former wool combing establishments and a collection of historical astronomical instruments. Those instruments in the collection include Georgian telescopes, 18th century octants and a tellurium, an educational model of the Sun, Earth and Moon. The museum has a Planetarium Café and


id: electric-bath-electrotherapy-20260505-0
file: data/en.wikipedia.org/wiki/Electric_bath_(electrotherapy)-0.md
category: reference
title: Electric bath (electrotherapy)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electric_bath_(electrotherapy)
date_saved: 2026-05-05T09:36:52.142335+00:00
instance: kb-cron
parent: electric-bath-electrotherapy-20260505-0
summary:
An electric bath is a 19th-century medical treatment in which high-voltage electrical apparatus was used for electrifying patients by causing an electric charge to build up on their bodies. In the US this process was known as Franklinization after Benjamin Franklin. The process became widely known after Franklin described it in the mid-18th century, but after that it was mostly practiced by quacks. Golding Bird brought it into the mainstream at Guy's Hospital in the mid-19th century and it fell into disuse in the early 20th century. == Description == The source of electricity for an electric bath was usually a frictional electrical machine. The patient was seated on a wooden stool, and both the patient and the stool insulated from ground by a platform on glass legs or some other insulator. In some arrangements, the patient was lying down rather than seated. The patient was then charged with static electricity either by direct connection to one electrode of the generator (usually the positive), or else through electrostatic induction by holding a large electrode close to the patient's body. The electric tension applied was around 30–50 kV. Treatment could take several hours. Following charging the patient was "bathed" in electricity,


id: electrophorus-20260505-0
file: data/en.wikipedia.org/wiki/Electrophorus-0.md
category: reference
title: Electrophorus
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electrophorus
date_saved: 2026-05-05T09:36:53.319583+00:00
instance: kb-cron
parent: electrophorus-20260505-0
summary:
In electromagnetism, an electrophorus or electrophore is a simple, manual, capacitive, electrostatic generator used to produce charge via the process of electrostatic induction. A first version of it was invented in 1762 by Swedish professor Johan Carl Wilcke. Italian scientist Alessandro Volta improved and popularized the device in 1775, and is sometimes erroneously credited with its invention. The word electrophorus was coined by Volta from the Greek ήλεκτρον, elektron, and φορεύς, phoreus, meaning 'electricity bearer'. == Description and operation == The electrophorus consists of a dielectric plate (originally a 'cake' of resinous material such as pitch or wax, but in modern versions plastic is used) and a metal plate with an insulating handle. The dielectric plate is first charged through the triboelectric effect by rubbing it with fur or cloth. For this discussion, imagine the dielectric gains negative charge by rubbing, as in the illustration below. The metal plate is then placed onto the dielectric plate. The dielectric does not transfer a significant fraction of its surface charge to the metal because the microscopic contact is poor. Instead the electrostatic field of the charged dielectric causes the charges in the metal plate to separate. It develops two regions of charge


id: electroscope-20260505-0
file: data/en.wikipedia.org/wiki/Electroscope-0.md
category: reference
title: Electroscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electroscope
date_saved: 2026-05-05T09:36:54.498121+00:00
instance: kb-cron
parent: electroscope-20260505-0
summary:
The electroscope is an early scientific instrument used to detect the presence of electric charge on a body. It detects this by the movement of a test charge due to the Coulomb electrostatic force on it. The amount of charge on an object is proportional to its voltage. The accumulation of enough charge to detect with an electroscope requires hundreds or thousands of volts, so electroscopes are used with high voltage sources such as static electricity and electrostatic machines. An electroscope can only give a rough indication of the quantity of charge; an instrument that measures electric charge quantitatively is called an electrometer. The electroscope was the first electrical measuring instrument. The first electroscope was a pivoted needle (called the versorium), invented by British physician William Gilbert around 1600. The pith-ball electroscope and the gold-leaf electroscope are two classical types of electroscope that are still used in physics education to demonstrate the principles of electrostatics. A type of electroscope is also used in the quartz fiber radiation dosimeter. Electroscopes were used by the Austrian scientist Victor Hess in the discovery of cosmic rays. == Pith-ball electroscope == In 1731, Stephen Gray used a simple hanging thread, which would be attracted


id: electroscope-20260505-1
file: data/en.wikipedia.org/wiki/Electroscope-1.md
category: reference
title: Electroscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electroscope
date_saved: 2026-05-05T09:36:54.498121+00:00
instance: kb-cron
parent: electroscope-20260505-0
summary:
The gold-leaf electroscope was developed in 1787 by British clergyman and physicist Abraham Bennet, as a more sensitive instrument than pith ball or straw blade electroscopes then in use. It consists of a vertical metal rod, usually brass, from the end of which hang two parallel strips of thin flexible gold leaf. A disk or ball terminal is attached to the top of the rod, where the charge to be tested is applied. To protect the gold leaves from drafts of air they are enclosed in a glass bottle, usually open at the bottom and mounted over a conductive base. Often there are grounded metal plates or foil strips in the bottle flanking the gold leaves on either side. These are a safety measure; if an excessive charge is applied to the delicate gold leaves, they will touch the grounding plates and discharge before tearing. They also capture charge leaking through the air that accumulates on the glass walls, increasing the sensitivity of the instrument. In the precision instruments the inside of the bottle was occasionally evacuated, to prevent the charge on the terminal from leaking off through the ionization of the air. When the metal terminal is touched with


id: electrostatic-generator-20260505-0
file: data/en.wikipedia.org/wiki/Electrostatic_generator-0.md
category: reference
title: Electrostatic generator
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electrostatic_generator
date_saved: 2026-05-05T09:36:55.653201+00:00
instance: kb-cron
parent: electrostatic-generator-20260505-0
summary:
An electrostatic generator, or electrostatic machine, is an electrical generator that produces static electricity, or electricity at high voltage and low continuous current. The knowledge of static electricity dates back to the earliest civilizations, but for millennia it remained merely an interesting and mystifying phenomenon, without a theory to explain its behavior and often confused with magnetism. By the end of the 17th century, researchers had developed practical means of generating electricity by friction, but the development of electrostatic machines did not begin in earnest until the 18th century, when they became fundamental instruments in the studies about the new science of electricity. Electrostatic generators operate by using manual (or other) power to transform mechanical work into electric energy, or using electric currents. Manual electrostatic generators develop electrostatic charges of opposite signs rendered to two conductors, using only electric forces, and work by using moving plates, drums, or belts to carry electric charge to a high potential electrode. == Description == Electrostatic machines are typically used in science classrooms to safely demonstrate electrical forces and high voltage phenomena. The elevated potential differences achieved have also been used for a variety of practical applications, such as operating X-ray tubes, particle accelerators,


id: electrostatic-generator-20260505-1
file: data/en.wikipedia.org/wiki/Electrostatic_generator-1.md
category: reference
title: Electrostatic generator
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electrostatic_generator
date_saved: 2026-05-05T09:36:55.653201+00:00
instance: kb-cron
parent: electrostatic-generator-20260505-0
summary:
==== Friction operation ==== The presence of surface charge imbalance means that the objects will exhibit attractive or repulsive forces. This surface charge imbalance, which leads to static electricity, can be generated by touching two differing surfaces together and then separating them due to the phenomenon of the triboelectric effect. Rubbing two non-conductive objects can generate a great amount of static electricity. This is not the result of friction; two non-conductive surfaces can become charged by just being placed one on top of the other. Since most surfaces have a rough texture, it takes longer to achieve charging through contact than through rubbing. Rubbing objects together increases amount of adhesive contact between the two surfaces. Usually insulators, e.g., substances that do not conduct electricity, are good at both generating, and holding, a surface charge. Some examples of these substances are rubber, plastic, glass, and pith. Conductive objects in contact generate charge imbalance too, but retain the charges only if insulated. The charge that is transferred during contact electrification is stored on the surface of each object. Note that the presence of electric current does not detract from the electrostatic forces nor from the sparking, from the corona discharge, or other


id: electrostatic-generator-20260505-2
file: data/en.wikipedia.org/wiki/Electrostatic_generator-2.md
category: reference
title: Electrostatic generator
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electrostatic_generator
date_saved: 2026-05-05T09:36:55.653201+00:00
instance: kb-cron
parent: electrostatic-generator-20260505-0
summary:
In 1878, the British inventor James Wimshurst started his studies about electrostatic generators, improving the Holtz machine, in a powerful version with multiple disks. The classical Wimshurst machine, that became the most popular form of influence machine, was reported to the scientific community by 1883, although previous machines with very similar structures were previously described by Holtz and Musaeus. In 1885, one of the largest-ever Wimshurst machines was built in England (it is now at the Chicago Museum of Science and Industry). The Wimshurst machine is a considerably simple machine; it works, as all influence machines, with electrostatic induction of charges, which means that it uses even the slightest existing charge to create and accumulate more charges, and repeats this process for as long as the machine is in action. Wimshurst machines are composed of: two insulated disks attached to pulleys of opposite rotation, the disks have small conductive (usually metal) plates on their outward-facing sides; two double-ended brushes that serve as charge stabilizers and are also the place where induction happens, creating the new charges to be collected; two pairs of collecting combs, which are, as the name implies, the collectors of electrical charge produced by the machine; two


id: electrostatic-generator-20260505-3
file: data/en.wikipedia.org/wiki/Electrostatic_generator-3.md
category: reference
title: Electrostatic generator
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electrostatic_generator
date_saved: 2026-05-05T09:36:55.653201+00:00
instance: kb-cron
parent: electrostatic-generator-20260505-0
summary:
The Van de Graaff generator was invented by American physicist Robert J. Van de Graaff in 1929 at MIT as a particle accelerator. The first model was demonstrated in October 1929. In the Van de Graaff machine, an insulating belt transports electric charge to the interior of an insulated hollow metal high voltage terminal, where it is transferred to the terminal by a "comb" of metal points. The advantage of the design was that since there was no electric field in the interior of the terminal, the charge on the belt could continue to be discharged onto the terminal regardless of how high the voltage on the terminal was. Thus the only limit to the voltage on the machine is ionization of the air next to the terminal. This occurs when the electric field at the terminal exceeds the dielectric strength of air, about 30 kV per centimeter. Since the highest electric field is produced at sharp points and edges, the terminal is made in the form of a smooth hollow sphere; the larger the diameter the higher the voltage attained. The first machine used a silk ribbon bought at a five and dime store as the charge transport belt.


id: electrostatic-generator-20260505-4
file: data/en.wikipedia.org/wiki/Electrostatic_generator-4.md
category: reference
title: Electrostatic generator
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electrostatic_generator
date_saved: 2026-05-05T09:36:55.653201+00:00
instance: kb-cron
parent: electrostatic-generator-20260505-0
summary:
== Further reading == Gottlieb Christoph Bohnenberger: Beschreibung unterschiedlicher Elektrizitätsverdoppler von einer neuen Einrichtung nebst einer Anzahl von Versuchen üb. verschiedene Gegenstände d. Elektrizitätslehre [Description of different electricity-doubler of a new device, along with a number of experiments on various subjects of electricity] Tübingen 1798. Holtz, W. (1865). "Ueber eine neue Elektrisirmaschine" [On a new electrical machine]. Annalen der Physik und Chemie (in German). 202 (9). Wiley: 157–171. Bibcode:1865AnP...202..157H. doi:10.1002/andp.18652020911. ISSN 0003-3804. Wilhelm Holtz: the higher charge on insulating surfaces by side pull and the transfer of this principle to the construction of induction machines .. In: Johann Poggendorff, CG Barth (eds): Annals of physics and chemistry. 130, Leipzig 1867, pp. 128–136 Wilhelm Holtz: The influence machine. In: F. Poske (Eds.): Annals of physics and chemistry. Julius Springer, Berlin 1904 (seventeenth year, the fourth issue). O. Lehmann: Dr. J. Frick's physical technique. 2, Friedrich Vieweg und Sohn, Braunschweig 1909, p. 797 (Section 2). F. Poske: New forms of influence machines. In: F. Poske (eds) for the physical and chemical education. journal Julius Springer, Berlin 1893 (seventh year, second issue). C. L. Stong, "Electrostatic motors are powered by electric field of the Earth". October, 1974. (PDF) Oleg D. Jefimenko, "Electrostatic Motors:


id: elton-s-quadrant-20260505-0
file: data/en.wikipedia.org/wiki/Elton's_quadrant-0.md
category: reference
title: Elton's quadrant
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Elton's_quadrant
date_saved: 2026-05-05T09:36:56.867994+00:00
instance: kb-cron
parent: elton-s-quadrant-20260505-0
summary:
An Elton's quadrant is a derivative of the Davis quadrant. It adds an index arm and artificial horizon to the instrument, and was invented by English sea captain John Elton, who patented his design in 1728 and published details of the instrument in the Philosophical Transactions of the Royal Society in 1732. == Construction == This instrument clearly reflects the shape and features of the Davis quadrant. The significant differences are the change in the upper arc to a simple triangular frame and the addition of an index arm. The triangular frame at the top spans 60° as did the arc on the backstaff. The main graduated arc subtends 30° as in the backstaff. The 30° arc is graduated in degrees and sixths of a degree, that is, at ten-minute intervals. The sighting vane of the backstaff is replaced with a sight (called an eye vane) mounted on the end of the index arm. The index arm includes a nonius to allow reading the large scale with ten divisions between the graduations on the scale. This provides the navigator with the ability to read the scale to the nearest minute of arc. The index arm has a spirit level to


id: equatorial-ring-20260505-0
file: data/en.wikipedia.org/wiki/Equatorial_ring-0.md
category: reference
title: Equatorial ring
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equatorial_ring
date_saved: 2026-05-05T09:36:58.041980+00:00
instance: kb-cron
parent: equatorial-ring-20260505-0
summary:
An equatorial ring was an astronomical instrument used in the Hellenistic world to determine the exact moment of the spring and autumn equinoxes. Equatorial rings were placed before the temples in Alexandria, in Rhodes, and perhaps in other places, for calendar purposes. The easiest way to understand the use of an equatorial ring is to imagine a ring placed vertically in the east-west plane at the Earth's equator. At the time of the equinoxes, the Sun will rise precisely in the east, move across the zenith, and set precisely in the west. Throughout the day, the bottom half of the ring will be in the shadow cast by the top half of the ring. On other days of the year, the Sun passes to the north or south of the ring, and will illuminate the bottom half. For latitudes away from the equator, the ring merely needs to be placed at the correct angle to the equatorial plane. At the Earth's poles, the ring would be horizontal. The equatorial ring was about one to two cubits (45cm–90cm) in diameter. Because the Sun is not a point source of light, the width of the shadow on the bottom half of the


id: equatorium-20260505-0
file: data/en.wikipedia.org/wiki/Equatorium-0.md
category: reference
title: Equatorium
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Equatorium
date_saved: 2026-05-05T09:36:59.223473+00:00
instance: kb-cron
parent: equatorium-20260505-0
summary:
An equatorium (plural, equatoria) is an astronomical calculating instrument. It can be used for finding the positions of the Moon, Sun, and planets without arithmetic operations, using a geometrical model to represent the position of a given celestial body. == History == In his comment on Ptolemy's Handy Tables, 4th century mathematician Theon of Alexandria introduced some diagrams to geometrically compute the position of the planets based on Ptolemy's epicyclical theory. The first description of the construction of a solar equatorium (as opposed to planetary) is contained in Proclus's fifth-century work Hypotyposis, where he gives instructions on how to construct one in wood or bronze. The earliest known descriptions of planetary equatoria are in the Latin translation of an early eleventh century text by Ibn al‐Samḥ and a 1080/1081 treatise by al-Zarqālī, contained in the Libros del saber de astronomia (Books of the knowledge of astronomy), a Castilian compilation of astronomical works collected under the patronage of Alfonso X of Castile in the thirteenth century. The Theorica Planetarum (c. 1261–1264) by Campanus of Novara is the earliest extant description of the construction of an equatorium in Latin Europe. Campanus' instrument resembled an astrolabe, with several interchangeable plates within a mater.


id: an-experiment-on-a-bird-in-the-air-pump-20260505-0
file: data/en.wikipedia.org/wiki/An_Experiment_on_a_Bird_in_the_Air_Pump-0.md
category: reference
title: An Experiment on a Bird in the Air Pump
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/An_Experiment_on_a_Bird_in_the_Air_Pump
date_saved: 2026-05-05T09:37:00.402844+00:00
instance: kb-cron
parent: an-experiment-on-a-bird-in-the-air-pump-20260505-0
summary:
An Experiment on a Bird in the Air Pump is a 1768 oil-on-canvas painting by Joseph Wright of Derby, one of a number of candlelit scenes that Wright painted during the 1760s. The painting departed from convention of the time by depicting a scientific subject in the reverential manner formerly reserved for scenes of historical or religious significance. Wright was intimately involved in depicting the Industrial Revolution and the scientific advances of the Enlightenment. While his paintings were recognized as exceptional by his contemporaries, his provincial status and choice of subjects meant the style was never widely imitated. The picture has been owned by the National Gallery in London since 1863 and is regarded as a masterpiece of British art. The painting depicts a natural philosopher, a forerunner of the modern scientist, recreating one of Robert Boyle's air pump experiments, in which a bird is deprived of air before a group of onlookers. The group members exhibit a variety of reactions, such as grief, disbelief and dismay, but for most of the audience scientific curiosity overcomes concern for the bird. The central figure looks out of the picture as if inviting the viewer's participation in the outcome. The painting was


id: an-experiment-on-a-bird-in-the-air-pump-20260505-1
file: data/en.wikipedia.org/wiki/An_Experiment_on_a_Bird_in_the_Air_Pump-1.md
category: reference
title: An Experiment on a Bird in the Air Pump
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/An_Experiment_on_a_Bird_in_the_Air_Pump
date_saved: 2026-05-05T09:37:00.402844+00:00
instance: kb-cron
parent: an-experiment-on-a-bird-in-the-air-pump-20260505-0
summary:
=== Background === During his apprenticeship and early career Wright concentrated on portraiture. By 1762, he was an accomplished portrait artist, and his 1764 group portrait James Shuttleworth, his Wife and Daughter is acknowledged as his first true masterpiece. Benedict Nicolson suggests that Wright was influenced by the work of Thomas Frye; in particular by the 18 bust-length mezzotints which Frye completed just before his death in 1762. It was perhaps Frye's candlelight images that tempted Wright to experiment with subject pieces. Wright's first attempt, A Girl reading a Letter by Candlelight with a Young Man looking over her shoulder from 1762 or 1763, is a trial in the genre, and is fetching though uncomplicated. Wright's, An Experiment on a Bird in the Air Pump forms part of a series of candlelit nocturnes that he produced between 1765 and 1768. There was a long history of painting candlelit scenes in Western art, although as Wright had not at this date traveled abroad, there remains uncertainty as to what paintings he might have seen in the original, as opposed to prints. Nicolson, who made studies of both Wright and other candlelight painters such as the 17th-century Utrecht Caravaggisti, thought their paintings,


id: an-experiment-on-a-bird-in-the-air-pump-20260505-2
file: data/en.wikipedia.org/wiki/An_Experiment_on_a_Bird_in_the_Air_Pump-2.md
category: reference
title: An Experiment on a Bird in the Air Pump
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/An_Experiment_on_a_Bird_in_the_Air_Pump
date_saved: 2026-05-05T09:37:00.402844+00:00
instance: kb-cron
parent: an-experiment-on-a-bird-in-the-air-pump-20260505-0
summary:
An Experiment on a Bird in the Air Pump followed in 1768, the emotionally charged experiment contrasting with the orderly scene from The Orrery. The painting, which measures 72 by 94½ inches (183 by 244 cm), shows a grey cockatiel fluttering in panic as the air is slowly withdrawn from the vessel by the pump. The witnesses display various emotions: one of the girls worriedly watches the fate of the bird, while the other is too upset to observe and is comforted by her father; two gentlemen (one of them dispassionately timing the experiment) and a boy look on with interest, while the young lovers to the left of the painting are absorbed only in each other. The scientist himself looks directly out of the picture, as if challenging the viewer to judge whether the pumping should continue, killing the bird, or whether the air should be replaced and the cockatiel saved. David Solkin suggests that little sympathy is directed toward the bird; the subjects of the painting show the dispassionate detachment of the evolving scientific society. Individuals are concerned for each other: the father for his children, the young man for the girl, but the distress of the cockatiel


id: an-experiment-on-a-bird-in-the-air-pump-20260505-3
file: data/en.wikipedia.org/wiki/An_Experiment_on_a_Bird_in_the_Air_Pump-3.md
category: reference
title: An Experiment on a Bird in the Air Pump
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/An_Experiment_on_a_Bird_in_the_Air_Pump
date_saved: 2026-05-05T09:37:00.402844+00:00
instance: kb-cron
parent: an-experiment-on-a-bird-in-the-air-pump-20260505-0
summary:
The powerful central light source creates a chiaroscuro effect. The light illuminating the scene has been described as "so brilliant it could only be the light of revelation". The single source of light is obscured behind the bowl on the table; some hint of a lamp glass can be seen around the side of the bowl, but David Hockney has suggested that the bowl itself may contain Sulphur, giving a powerful single light source that a candle or oil lamp would not. In the earlier study a candle holder is visible, and the flame is reflected in the bowl. Hockney believes that many of the Old Masters used optical equipment to assist in their painting, and suggests that Wright may have used lenses to transfer the image to paper rather than painting directly from the scene, as he believes the pattern of shadows thrown by the lighting could have been too complicated for Wright to have captured so accurately without assistance. It may be observed, however, that the stand on which the pump is situated casts no shadow on the body of the philosopher, as it could be expected to do. Wright's Air Pump was unusual in that it depicted


id: an-experiment-on-a-bird-in-the-air-pump-20260505-4
file: data/en.wikipedia.org/wiki/An_Experiment_on_a_Bird_in_the_Air_Pump-4.md
category: reference
title: An Experiment on a Bird in the Air Pump
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/An_Experiment_on_a_Bird_in_the_Air_Pump
date_saved: 2026-05-05T09:37:00.402844+00:00
instance: kb-cron
parent: an-experiment-on-a-bird-in-the-air-pump-20260505-0
summary:
Wright exhibited the painting at the Society of Artists Exhibition of 1768 and it was re-exhibited before Christian VII of Denmark in September the same year. Viewers remarked that it was "clever and vigorous", while Gustave Flaubert, who saw it on a visit to England between 1865 and 1866, considered it "charming in naivety and depth". It was popular enough that a mezzotint was engraved from it by Valentine Green which was published by John Boydell on 24 June 1769, and initially sold for 15 shillings. This was reprinted throughout the 18th and 19th centuries, in increasingly weak impressions. Ellis Waterhouse called it "one of the wholly original masterpieces of British art". From Bates, the picture passed to Walter Tyrell; another member of the Tyrell family, Edward, presented it to the National Gallery, London, in 1863, after it had failed to sell at an auction at Christie's in 1854. The painting was transferred to the Tate Gallery in 1929, although it was actually on loan to Derby Museum and Art Gallery between 1912 and 1947. It has been lent out for exhibitions to the National Gallery of Art in Washington, D.C., in 1976, the National Museum of Fine Arts in


id: filar-micrometer-20260505-0
file: data/en.wikipedia.org/wiki/Filar_micrometer-0.md
category: reference
title: Filar micrometer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Filar_micrometer
date_saved: 2026-05-05T09:37:01.632726+00:00
instance: kb-cron
parent: filar-micrometer-20260505-0
summary:
A filar micrometer is a specialized eyepiece used in astronomical telescopes for astrometry measurements, in microscopes for specimen measurements, and in alignment and surveying telescopes for measuring angles and distances on nearby objects. "Filar" derives from the Latin filum ("thread"). It refers to the fine threads or wires used in the device. == Construction and use == A typical filar micrometer consists of a reticle that has two fine parallel wires or threads that can be moved by the observer using a micrometer screw mechanism. The wires are placed in the focal image plane of the eyepiece so they remain sharply superimposed over the object under observation, while the micrometer motion moves the wires across the focal plane. Other designs employ a fixed reticle, against which one wire or a second reticle moves. By rotating the eyepiece assembly in the eyetube, the measurement axis can be aligned to match the orientation of the two points of observation. At one time, it was common to use spider silk as a thread. By placing one wire over one point of interest and moving the other to a second point, the distance between the two wires can be measured with the micrometer portion


id: franklin-bells-20260505-0
file: data/en.wikipedia.org/wiki/Franklin_bells-0.md
category: reference
title: Franklin bells
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Franklin_bells
date_saved: 2026-05-05T09:37:02.808625+00:00
instance: kb-cron
parent: franklin-bells-20260505-0
summary:
Franklin bells (also known as lightning bells) are an early demonstration of electric charge designed to work with a Leyden jar or a lightning rod. Franklin bells are only a qualitative indicator of electric charge and were used for simple demonstrations rather than research. The bells are an adaptation to the first device that converted electrical energy into mechanical energy in the form of continuous mechanical motion: in this case, the moving of a bell clapper back and forth between two oppositely charged bells. == History == Scientific investigation of the phenomena of lightning originates with Benjamin Franklin. He accumulated analogical evidence favoring the supposition that lightning must be an electrical discharge on a large scale. In the mid-18th century, lightning strikes were a serious problem for buildings and structures, causing damage and sometimes even fires. Franklin set out to understand the nature of lightning and to find ways to protect buildings from its destructive effects. He began his investigations by observing how lightning strikes affected various types of buildings. He noticed that some buildings were more vulnerable to lightning strikes than others and that buildings with sharp pointed roofs were more likely to be struck than those with flat


id: franklin-s-electrostatic-machine-20260505-0
file: data/en.wikipedia.org/wiki/Franklin's_electrostatic_machine-0.md
category: reference
title: Franklin's electrostatic machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Franklin's_electrostatic_machine
date_saved: 2026-05-05T09:37:04.008946+00:00
instance: kb-cron
parent: franklin-s-electrostatic-machine-20260505-0
summary:
Franklin's electrostatic machine is a high-voltage static electricity-generating device used by Benjamin Franklin in the mid-18th century for research into electrical phenomena. Its key components are a glass globe which turned on an axis via a crank, a cloth pad in contact with the spinning globe, a set of metal needles to conduct away the charge developed on the globe by its friction with the pad, and a Leyden jar – a high-voltage capacitor – to accumulate the charge. Franklin's experiments with the machine eventually led to new theories about electricity and inventing the lightning rod. == Background == Franklin was not the first to build an electrostatic generator. European scientists developed machines to generate static electricity decades earlier. In 1663, Otto von Guericke generated static electricity with a device that used a sphere of sulfur. Francis Hauksbee developed a more advanced electrostatic generator around 1704 using a glass bulb that had a vacuum. He later replaced the globe with a glass tube of about 2.5 feet (0.76 m) emptied of air. The glass tube was a less effective static generator than the globe, but it became more popular because it was easier to use. Machines that generated static electricity


id: franklin-s-electrostatic-machine-20260505-1
file: data/en.wikipedia.org/wiki/Franklin's_electrostatic_machine-1.md
category: reference
title: Franklin's electrostatic machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Franklin's_electrostatic_machine
date_saved: 2026-05-05T09:37:04.008946+00:00
instance: kb-cron
parent: franklin-s-electrostatic-machine-20260505-0
summary:
== Electrical principles == Franklin's experiments with Leyden jars progressed to connecting several Leyden jars together in a series, with "one hanging on the tail of the other". All of the jars in the series could be charged simultaneously, which multiplied the electrical effect. A similar apparatus had been created earlier by Daniel Gralath. Franklin called this device an "electrical battery", but that term later came to have a different meaning, referring instead to a set of one or more galvanic cells. At that time, the word "battery" was a military term for a group of cannons. Franklin was the first to apply the terms "positive" and "negative" to electricity. Through his research, Franklin was among first to prove the electrical principal of conservation of charge in 1747: a similar discovery was made independently in 1746 by William Watson. Franklin wrote detailed letters and documents about his experiments with the electrostatic machine and Leyden jars. In 1749, Franklin made a list of several ways in which lightning was similar to electricity. He concluded that lightning was essentially nothing more than giant electric sparks, similar to the sparks from the static charges produced by his electrostatic machine. He referred to static


id: franklin-s-electrostatic-machine-20260505-2
file: data/en.wikipedia.org/wiki/Franklin's_electrostatic_machine-2.md
category: reference
title: Franklin's electrostatic machine
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Franklin's_electrostatic_machine
date_saved: 2026-05-05T09:37:04.008946+00:00
instance: kb-cron
parent: franklin-s-electrostatic-machine-20260505-0
summary:
Franklin distributed copies of the electrostatic machine to many of his close associates to encourage them to study electricity. Between 1747 and 1750, Franklin sent many letters to his friend Collinson in London about his experiments with the electrostatic machine and the Leyden jar, including his observations and theories on the principles of electricity. These letters were collected and published in 1751 in a book entitled Experiments and Observations on Electricity. While Joseph Priestley was writing about the history of electricity, Franklin encouraged him to use an electrostatic machine to perform the experiments he was writing about. Priestly designed and used his own variations of Franklin's machine. While replicating the electrical experiments, some unanswered questions prompted Priestly to design additional experiments, leading to additional discoveries. In 1767, he published a 700-page book on his findings called The History and Present State of Electricity. Eighteenth-century scientific laboratories usually contained some form of hand-operated electrostatic machine. Italian scientist Luigi Galvani had an electrostatic generator in his laboratory, where experiments with frog legs led him to conclude that animals generated a vital force, an animal electricity. Another Italian scientist, Alessandro Volta, disagreed with Galvani's claim that the electrical effects were due to something


id: galvanometer-20260505-0
file: data/en.wikipedia.org/wiki/Galvanometer-0.md
category: reference
title: Galvanometer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Galvanometer
date_saved: 2026-05-05T09:37:05.190184+00:00
instance: kb-cron
parent: galvanometer-20260505-0
summary:
A galvanometer is an electromechanical measuring instrument for electric current. Early galvanometers were uncalibrated, but improved versions, called ammeters, were calibrated and could measure the flow of current more precisely. Galvanometers work by deflecting a pointer in response to an electric current flowing through a coil in a constant magnetic field. The mechanism is also used as an actuator in applications such as hard disks. Galvanometers came from the observation, first noted by Hans Christian Ørsted in 1820, that a magnetic compass's needle deflects when near a wire having electric current. They were the first instruments used to detect and measure small amounts of current. André-Marie Ampère, who gave mathematical expression to Ørsted's discovery, named the instrument after the Italian electricity researcher Luigi Galvani, who in 1791 discovered the principle of the frog galvanoscope – that electric current would make the legs of a dead frog jerk. Galvanometers have been essential for the development of science and technology in many fields. For example, in the 1800s they enabled long-range communication through submarine cables, such as the earliest transatlantic telegraph cables, and were essential to discovering the electrical activity of the heart and brain, by their fine measurements of current. Galvanometers


id: galvanometer-20260505-1
file: data/en.wikipedia.org/wiki/Galvanometer-1.md
category: reference
title: Galvanometer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Galvanometer
date_saved: 2026-05-05T09:37:05.190184+00:00
instance: kb-cron
parent: galvanometer-20260505-0
summary:
=== Modern uses === Most modern uses for the galvanometer mechanism are in positioning and control systems. Galvanometer mechanisms are divided into moving magnet and moving coil galvanometers; in addition, they are divided into closed-loop and open-loop - or resonant - types. Mirror galvanometer systems are used as beam positioning or beam steering elements in laser scanning systems. For example, for material processing with high-power lasers, closed loop mirror galvanometer mechanisms are used with servo control systems. These are typically high power galvanometers and the newest galvanometers designed for beam steering applications can have frequency responses over 10 kHz with appropriate servo technology. Closed-loop mirror galvanometers are also used in similar ways in stereolithography, laser sintering, laser engraving, laser beam welding, laser TVs, laser displays and in imaging applications such as retinal scanning with Optical Coherence Tomography (OCT) and Scanning Laser Ophthalmoscopy (SLO). Almost all of these galvanometers are of the moving magnet type. The closed loop is obtained measuring the position of the rotating axis with an infrared emitter and 2 photodiodes. This feedback is an analog signal. Open loop, or resonant mirror galvanometers, are mainly used in some types of laser-based bar-code scanners, printing machines, imaging applications, military


id: galvanometer-20260505-2
file: data/en.wikipedia.org/wiki/Galvanometer-2.md
category: reference
title: Galvanometer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Galvanometer
date_saved: 2026-05-05T09:37:05.190184+00:00
instance: kb-cron
parent: galvanometer-20260505-0
summary:
Edward Weston extensively improved the design of the galvanometer. He substituted the fine wire suspension with a pivot and provided restoring torque and electrical connections through spiral springs rather than through the traditional wristwatch balance wheel hairspring. He developed a method of stabilizing the magnetic field of the permanent magnet, so the instrument would have consistent accuracy over time. He replaced the light beam and mirror with a knife-edge pointer that could be read directly. A mirror under the pointer, in the same plane as the scale, eliminated parallax observation error. To maintain the field strength, Weston's design used a very narrow circumferential slot through which the coil moved, with a minimal air-gap. This improved linearity of pointer deflection with respect to coil current. Finally, the coil was wound on a lightweight form made of conductive metal, which acted as a damper. By 1888, Edward Weston had patented and brought out a commercial form of this instrument, which became a standard electrical equipment component. It was known as a "portable" instrument because it was affected very little by mounting position or by transporting it from place to place. This design is almost universally used in moving-coil meters today. Initially, laboratory


id: galvanometer-20260505-3
file: data/en.wikipedia.org/wiki/Galvanometer-3.md
category: reference
title: Galvanometer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Galvanometer
date_saved: 2026-05-05T09:37:05.190184+00:00
instance: kb-cron
parent: galvanometer-20260505-0
summary:
==== Geomagnetic field measurement ==== A tangent galvanometer can also be used to measure the magnitude of the horizontal component of the geomagnetic field. When used in this way, a low-voltage power source, such as a battery, is connected in series with a rheostat, the galvanometer, and an ammeter. The galvanometer is first aligned so that the coil is parallel to the geomagnetic field, whose direction is indicated by the compass when there is no current through the coils. The battery is then connected and the rheostat is adjusted until the compass needle deflects 45 degrees from the geomagnetic field, indicating that the magnitude of the magnetic field at the center of the coil is the same as that of the horizontal component of the geomagnetic field. This field strength can be calculated from the current as measured by the ammeter, the number of turns of the coil, and the radius of the coils. === Astatic galvanometer === Unlike the tangent galvanometer, the astatic galvanometer does not use the Earth's magnetic field for measurement, so it does not need to be oriented with respect to the Earth's field, making it easier to use. Developed by Leopoldo Nobili in 1825, it


id: globe-of-matelica-20260505-0
file: data/en.wikipedia.org/wiki/Globe_of_Matelica-0.md
category: reference
title: Globe of Matelica
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Globe_of_Matelica
date_saved: 2026-05-05T09:37:06.372345+00:00
instance: kb-cron
parent: globe-of-matelica-20260505-0
summary:
The Globe of Matelica (Globo of Matelica) is an Ancient Greek sundial sculpted on a marble ball. The artifact was found during the 1985 reconstruction of the medieval Palazzo Pretorio, presently Museo Civico Archeologico, of Matelica in the Marches, region of Italy. == Description == The globe measures nearly 29 cm in diameter and appears to be sculpted from a crystalline marble originating near Ephesus in present-day Turkey. It is thought to date from the first two centuries CE. There is one similar item, identified in 1939 by Carl William Blegen in a Museum in Nafplio, Greece. All that remains is the stone component, which is engraved with a variety of inscribed lines and letters. The sphere is bisected by a center line, while on its top are three concentric circles of various diameters, intersected by an arc of a circle and on which words in ancient Greek alphabet are still visible. Additionally it features 13 holes, each marked by a Greek letter. In these holes there were - probably - metallic insertions that delineated the hour. In the lower part there is a large conical depression which ends with a big rectangular hole, likely made to secure the base.


id: groma-surveying-20260505-0
file: data/en.wikipedia.org/wiki/Groma_(surveying)-0.md
category: reference
title: Groma (surveying)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Groma_(surveying)
date_saved: 2026-05-05T09:37:08.672050+00:00
instance: kb-cron
parent: groma-surveying-20260505-0
summary:
The groma (as standardized in the imperial Latin, sometimes croma, or gruma in the literature of the republican times) was a surveying instrument used in the Roman Empire. The groma allowed projecting right angles and straight lines and thus enabling the centuriation (setting up of a rectangular grid). It is the only Roman surveying tool with examples that survive to the present day. == History == The name "groma" came to Latin from the Greek gnoma via the Etruscan language. It is unclear which of the many meanings of the Ancient Greek: γνώμων gnomon (cf. Liddell & Scott, "gnoma" is a form) was used, although in multiple sources the Greek term is used to designate the central point of a camp or town. Dividing the land into rectangular plots was used by the Ancient Greeks, Egyptians and even Mesopotamians. However, the sheer scale of Roman centuriation from the 2nd century BC, when the new colonies were formed mostly to provide for veterans and landless citizens, was unprecedented, so it is not clear to what extent Greek practices influenced the Roman surveyors. The peculiarities of the Roman surveying methods and terminology suggest independence of Roman measurement tradition. The groma may have


id: honcheonsigye-20260505-0
file: data/en.wikipedia.org/wiki/Honcheonsigye-0.md
category: reference
title: Honcheonsigye
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Honcheonsigye
date_saved: 2026-05-05T09:37:09.833489+00:00
instance: kb-cron
parent: honcheonsigye-20260505-0
summary:
The Honcheonsigye (Korean: 혼천시계; Hanja: 渾天時計; lit. 'armillary clock') is an astronomical clock made by Song Yi-Yeong (송이영; 宋以潁), a professor of Gwansanggam (관상감; 觀象監) (one of the scientific institution of Joseon) in 1669. It was designated as South Korean national treasure number 230 in August 9, 1985. The clock used the alarm clock technology created by Christiaan Huygens in 1657. This relic shows that Huygens' technology was spread to East Asia in just 12 years. Also, It demonstrates the astronomy and mechanical engineering technology of the Joseon Dynasty. The clock has an armillary sphere with a diameter of 40 cm. The sphere is activated by a clockwork mechanism, designed to display the position of the heavens at any given time, as well as displaying the hours and marking their passage with a chiming bell. The device is no longer in working order. The clock is owned by Korea University Museum. It is the only remaining astronomical clock from the Joseon period. The clock was purchased from an antiques dealer some time before WWII by Mr Kim Seong-su 김성수 金性洙, the rich businessman and politician who founded Korea University. The historian of science Jeon Sang-Woon 전상운 全相運, who examined the


id: international-coronelli-society-for-the-study-of-globes-20260505-0
file: data/en.wikipedia.org/wiki/International_Coronelli_Society_for_the_Study_of_Globes-0.md
category: reference
title: International Coronelli Society for the Study of Globes
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/International_Coronelli_Society_for_the_Study_of_Globes
date_saved: 2026-05-05T09:37:12.099450+00:00
instance: kb-cron
parent: international-coronelli-society-for-the-study-of-globes-20260505-0
summary:
The International Coronelli Society for the Study of Globes (German: Internationale Coronelli-Gesellschaft für Globenkunde) is a non-profit academic organization devoted to the analysis, restoration and comprehensive study of terrestrial and celestial globes and other cosmographical instruments, such as armillary spheres and planetaria, mainly made before 1850. == History == Founded in Vienna in 1952 by the Austrian engineer and private scholar Robert Haardt (1884–1962), the Society's name is an hommage to Franciscan friar, cosmographer, cartographer, and publisher Vincenzo Coronelli (1650–1718). As of 2023, the Society counts around 300 members from academic institutions around the world. The eponymous Coronelli was not only a renowned producer of large-scale globe pairs, but also the founder of the first geographical society in the world, the Venetian Accademia Cosmografica degli Argonauti. == Activities == Since 1963, it has furthered the study of globe-related topics, including inventorying, restoration and conservation, which have been discussed in dedicated international symposia. The Society awards two international prizes, The International Coronelli-Society Award for Encouragement of Globestudies, and the Fiorini-Haardt Prize for research into pre-1945 globes and their makers. == Publications == Since its foundation in 1952, the society publishes a journal, Der Globusfreund: Wissenschaftliche Zeitschrift für Globenkunde. Since 2002 there


id: jacob-s-staff-20260505-0
file: data/en.wikipedia.org/wiki/Jacob's_staff-0.md
category: reference
title: Jacob's staff
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Jacob's_staff
date_saved: 2026-05-05T09:37:13.264277+00:00
instance: kb-cron
parent: jacob-s-staff-20260505-0
summary:
Jacob's staff is a measuring tool with several variations. It is also known as cross-staff, a ballastella, a fore-staff, a ballestilla, or a balestilha. In its most basic form, a Jacob's staff is a stick or pole with length markings, often with a smaller segment attached perpendicularly. The simplest use of a Jacob's staff is to make qualitative judgements of the height and angle of an object relative to the user of the staff. Most staffs are much more complicated than that, and usually contain a number of measurement and stabilization features. The two most frequent uses are: in astronomy and navigation for a simple device to measure angles, later replaced by the more precise sextants; in surveying (and scientific fields that use surveying techniques, such as geology and ecology) for a vertical rod that penetrates or sits on the ground and supports a compass or other instrument. == Etymology == The origin of the name of the instrument is not certain. Some refer to the Biblical patriarch Jacob, specifically in the Book of Genesis (Gen 32:11). It may also take its name after its resemblance to Orion, referred to by the name of Jacob on some medieval star charts.


id: jacob-s-staff-20260505-1
file: data/en.wikipedia.org/wiki/Jacob's_staff-1.md
category: reference
title: Jacob's staff
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Jacob's_staff
date_saved: 2026-05-05T09:37:13.264277+00:00
instance: kb-cron
parent: jacob-s-staff-20260505-0
summary:
The original version was not reported to be used at sea, until the Age of Discoveries. Its use was reported by João de Lisboa in his Treatise on the Nautical Needle of 1514. Johannes Werner suggested the cross-staff be used at sea in 1514 and improved instruments were introduced for use in navigation. John Dee introduced it to England in the 1550s. In the improved versions, the rod was graduated directly in degrees. This variant of the instrument is not correctly termed a Jacob's staff but is a cross-staff. The cross-staff was difficult to use. In order to get consistent results, the observer had to position the end of the pole precisely against his cheek. He had to observe the horizon and a star in two different directions while not moving the instrument when he shifted his gaze from one to the other. In addition, observations of the sun required the navigator to look directly at the sun. This could be a uncomfortable exercise and made it difficult to obtain an accurate altitude for the sun. Mariners took to mounting smoked-glass to the ends of the transoms to reduce the glare of the sun. As a navigational tool, this instrument


id: large-electrostatic-generator-teylers-20260505-0
file: data/en.wikipedia.org/wiki/Large_electrostatic_generator_(Teylers)-0.md
category: reference
title: Large electrostatic generator (Teylers)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Large_electrostatic_generator_(Teylers)
date_saved: 2026-05-05T09:37:14.441217+00:00
instance: kb-cron
parent: large-electrostatic-generator-teylers-20260505-0
summary:
The large electrostatic generator (Dutch: Van Marum electriseermachine) is a large handcrafted electromechanical instrument designed by Martin van Marum and built by John Cuthbertson in 1784 for the Teylers Museum in Haarlem, where it forms the centerpiece of the instrument room. The concept of an electrostatic generator was new, and the battery (array) of leiden jars was the largest ever built (only one of the 4 sets of leiden jars is on display to conserve space). The two glass disks of the triboelectric generator (friction generator) are 1.65 meters in diameter, and the machine is capable of generating a potential of 330,000 volts. == History == The device is a larger version of a similar model built in Groningen by Gerhard Kuyper in 1774 for physics student Martin van Marum, who used it to make a name for himself in the study of electricity with his lectures and demonstrations. It was Van Marum's dream to create a larger version, and he applied to the Teylers Stichting in 1783 for funding to create such a large instrument in the hope that it would add a valuable contribution to the science of electricity. On April 11 of that year his request was


id: leyden-jar-20260505-0
file: data/en.wikipedia.org/wiki/Leyden_jar-0.md
category: reference
title: Leyden jar
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Leyden_jar
date_saved: 2026-05-05T09:37:15.662578+00:00
instance: kb-cron
parent: leyden-jar-20260505-0
summary:
A Leyden jar (or Leiden jar, or archaically, Kleistian jar) is an electrical component that stores a high-voltage electric charge (from an external source) between electrical conductors on the inside and outside of a glass jar. It typically comprises a glass jar with metal foil cemented to the inside and the outside surfaces, and a metal terminal projecting vertically through the jar lid to make contact with the inner foil. It was the original form of the capacitor (also called a condenser). Its invention was a discovery made independently by German cleric Ewald Georg von Kleist on 11 October 1745 and by Dutch scientist Pieter van Musschenbroek of Leiden (Leyden), Netherlands, in 1745–1746. The Leyden jar was used to conduct many early experiments in electricity, and its discovery was of fundamental importance in the study of electrostatics. It was the first means of accumulating and preserving electric charge in large quantities that could be discharged at the experimenter's will, thus overcoming a significant limit to early research into electrical conduction. Leyden jars are still used in education to demonstrate the principles of electrostatics. == Previous work == The Ancient Greeks already knew that pieces of amber could attract lightweight particles


id: leyden-jar-20260505-1
file: data/en.wikipedia.org/wiki/Leyden_jar-1.md
category: reference
title: Leyden jar
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Leyden_jar
date_saved: 2026-05-05T09:37:15.662578+00:00
instance: kb-cron
parent: leyden-jar-20260505-0
summary:
=== Musschenbroek and Cunaeus === The Leyden jar's invention was long credited to Pieter van Musschenbroek, the physics professor at Leiden University, who also ran a family foundry which cast brass cannonettes, and a small business (De Oosterse Lamp – "The Eastern Lamp") which made scientific and medical instruments for the new university courses in physics and for scientific gentlemen keen to establish their own 'cabinets' of curiosities and instruments. Like von Kleist, Musschenbroek was also interested in, and attempting to repeat, Bose's experiment. During this time, Andreas Cunaeus, a lawyer, learned about this experiment from Musschenbroek, and attempted to duplicate the experiment at home with household items. Unaware of the "Rule of Dufay", that the experimental apparatus should be insulated, Cunaeus held his jar in his hand while charging it, and was thus the first to discover that such an experimental setup could deliver a severe shock. He reported his procedure and experience to Swiss-Dutch natural philosopher Jean-Nicolas-Sebastian Allamand, Musschenbroek's colleague. Allamand and Musschenbroek also received severe shocks. Musschenbroek communicated the experiment in a letter from 20 January 1746 to French entomologist René Antoine Ferchault de Réaumur, who was Musschenbroek's appointed correspondent at the Paris Academy. Abbé Jean-Antoine Nollet


id: leyden-jar-20260505-2
file: data/en.wikipedia.org/wiki/Leyden_jar-2.md
category: reference
title: Leyden jar
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Leyden_jar
date_saved: 2026-05-05T09:37:15.662578+00:00
instance: kb-cron
parent: leyden-jar-20260505-0
summary:
A typical design consists of a glass jar with conducting tin foil coating the inner and outer surfaces. The foil coatings stop short of the mouth of the jar, to prevent the charge from arcing between the foils. A metal rod electrode projects through the nonconductive stopper at the mouth of the jar, electrically connected by some means (usually a hanging chain) to the inner foil, to allow it to be charged. The jar is charged by an electrostatic generator, or other source of electric charge, connected to the inner electrode while the outer foil is grounded. The inner and outer surfaces of the jar store equal but opposite charges. The original form of the device is just a glass bottle partially filled with water, with a metal wire passing through a cork closing it. The role of the outer plate is provided by the hand of the experimenter. Soon John Bevis found (in 1747) that it was possible to coat the exterior of the jar with metal foil, and he also found that he could achieve the same effect by using a plate of glass with metal foil on both sides. These developments inspired William Watson in the same


id: list-of-surveying-instruments-20260505-0
file: data/en.wikipedia.org/wiki/List_of_surveying_instruments-0.md
category: reference
title: List of surveying instruments
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_surveying_instruments
date_saved: 2026-05-05T09:37:16.824358+00:00
instance: kb-cron
parent: list-of-surveying-instruments-20260505-0
summary:
Instruments used in surveying include: Alidade Alidade table Cosmolabe Dioptra Dumpy level Engineer's chain Geodimeter Graphometer Groma (surveying) Laser scanning Level Level staff Measuring tape Plane table Pole (surveying) Prism (surveying) (corner cube retroreflector) Prismatic compass (angle measurement) Ramsden surveying instruments Ranging rod Surveyor's chain Surveyor's compass Tachymeter (surveying) Tape (surveying) Tellurometer Theodolite Half theodolite Plain theodolite Simple theodolite Great theodolite Non-transit theodolite Transit theodolite Seconds theodolite Electronic theodolite Mining theodolite Suspension theodolite Traveling theodolite Pibal theodolite Registering theodolite Gyro-theodolite Construction theodolite Photo-theodolite Robotic theodolite Vernier theodolite Total station Transit (surveying) Tripod (surveying) Universal instrument (surveying) == See also == Astronomical instrument Measurement instrument == Further reading == Lewis, M. J. T. (2001-04-23). Surveying Instruments of Greece and Rome. Cambridge University Press. doi:10.1017/cbo9780511483035. ISBN 978-0-521-79297-4.


id: magdeburg-hemispheres-20260505-0
file: data/en.wikipedia.org/wiki/Magdeburg_hemispheres-0.md
category: reference
title: Magdeburg hemispheres
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Magdeburg_hemispheres
date_saved: 2026-05-05T09:37:18.037607+00:00
instance: kb-cron
parent: magdeburg-hemispheres-20260505-0
summary:
The Magdeburg hemispheres are a pair of large copper hemispheres with mating rims that were used in a famous 1654 experiment to demonstrate the power of atmospheric pressure. When the rims were sealed with grease and the air was pumped out, the sphere contained a vacuum and could not be pulled apart by teams of horses. Once the valve was opened, air rushed in and the hemispheres were easily separated. The Magdeburg hemispheres were invented by German scientist and mayor of Magdeburg, Otto von Guericke, to demonstrate the air pump that he had invented and the concept of atmospheric pressure. Speculation varied about the contents of the sphere. Many thought it was simply empty, while others argued the vacuum contained air or some finer aerial substance. Sound did not transmit through the sphere, indicating that sound needed a medium in order to travel and/or be sensed, while light did not. The first artificial vacuum had been produced a few years earlier by Evangelista Torricelli and inspired Guericke to design the world's first vacuum pump, which consisted of a piston and cylinder with one-way flap valves. The hemispheres became popular in physics lectures as an illustration of the strength of air


id: mariner-s-astrolabe-20260505-0
file: data/en.wikipedia.org/wiki/Mariner's_astrolabe-0.md
category: reference
title: Mariner's astrolabe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mariner's_astrolabe
date_saved: 2026-05-05T09:37:19.216761+00:00
instance: kb-cron
parent: mariner-s-astrolabe-20260505-0
summary:
The mariner's astrolabe, also called sea astrolabe, was an inclinometer used to determine the latitude of a ship at sea by measuring the sun's noon altitude (declination) or the meridian altitude of a star of known declination. Not an astrolabe proper, the mariner's astrolabe was rather a graduated circle with an alidade used to measure vertical angles. They were designed to allow for their use on boats in rough water and/or in heavy winds, which astrolabes are ill-equipped to handle. It's notable for its role during the Age of Exploration where Portuguese and Spanish navigators used it to great success. In the sixteenth century, the instrument was also called a ring. == History == Many dates can be found for the appearance of the first Mariner's astrolabes. The earliest date, 1295, is offered by the Majorcan astronomer Ramon Llull. Later dates center around the late 15th century, with Samuel Purchas claiming that it was adapted for marine navigation by Martin Behaim, a mariner not considered a trustworthy source by some historians. In any event, the instrument was certainly known by the end of the 15th century. Nevertheless, the creation and perfecting of the mariner's astrolabe is attributed to Portuguese navigators


id: maxwell-s-thermodynamic-surface-20260505-0
file: data/en.wikipedia.org/wiki/Maxwell's_thermodynamic_surface-0.md
category: reference
title: Maxwell's thermodynamic surface
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Maxwell's_thermodynamic_surface
date_saved: 2026-05-05T09:37:20.383670+00:00
instance: kb-cron
parent: maxwell-s-thermodynamic-surface-20260505-0
summary:
Maxwell's thermodynamic surface is an 1874 sculpture made by Scottish physicist James Clerk Maxwell (1831–1879). This model provides a three-dimensional space of the various states of a fictitious substance with water-like properties. This plot has coordinates volume (x), entropy (y), and energy (z). It was based on the American scientist Josiah Willard Gibbs’ graphical thermodynamics papers of 1873. In Maxwell's words, the model allowed "the principal features of known substances [to] be represented on a convenient scale." == Construction of the model == Gibbs' papers defined what Gibbs called the "thermodynamic surface," which expressed the relationship between the volume, entropy, and energy of a substance at different temperatures and pressures. However, Gibbs did not include any diagrams of this surface. After receiving reprints of Gibbs' papers, Maxwell recognized the insight afforded by Gibbs' new point of view and set about constructing physical three-dimensional models of the surface. This reflected Maxwell's talent as a strong visual thinker and prefigured modern scientific visualization techniques. Maxwell sculpted the original model in clay and made several plaster casts of the clay model, sending one to Gibbs as a gift, keeping two in his laboratory at Cambridge University. Maxwell's copy is on display at the


id: mural-instrument-20260505-0
file: data/en.wikipedia.org/wiki/Mural_instrument-0.md
category: reference
title: Mural instrument
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mural_instrument
date_saved: 2026-05-05T09:37:21.553584+00:00
instance: kb-cron
parent: mural-instrument-20260505-0
summary:
A mural instrument is an angle measuring instrument mounted on or built into a wall. For astronomical purposes, these walls were oriented so they lie precisely on the meridian. A mural instrument that measured angles from 0 to 90 degrees was called a mural quadrant. They were utilized as astronomical devices in ancient Egypt and ancient Greece. Edmond Halley, due to the lack of an assistant and only one vertical wire in his transit, confined himself to the use of a mural quadrant built by George Graham after its erection in 1725 at the Royal Observatory, Greenwich. Bradley's first observation with that quadrant was made on 15 June 1742. The mural quadrant has been called the "quintessential instrument" of 18th century (i.e. 1700s) observatories. It rose to prominence in the field of positional astronomy at this time. == Construction == Many older mural quadrants have been constructed by marking directly on the wall surfaces. More recent instruments were made with a frame that was constructed with precision and mounted permanently on the wall. The arc is marked with divisions, almost always in degrees and fractions of a degree. In the oldest instruments, an indicator is placed at the centre of


id: neeff-s-wheel-20260505-0
file: data/en.wikipedia.org/wiki/Neeff's_wheel-0.md
category: reference
title: Neeff's wheel
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Neeff's_wheel
date_saved: 2026-05-05T09:37:22.748713+00:00
instance: kb-cron
parent: neeff-s-wheel-20260505-0
summary:
Neeff's wheel, also known as the Blitzrad (German: "lightning wheel" or "spark wheel") is a historical electrical apparatus. It is a kind of contact breaker, designed to interrupt an electrical circuit at periodic intervals, producing visible sparks. It was first presented in the 1830s by the German scientist Christian Ernst Neeff (1782–1849). The arrangement consists of a toothed wheel against which a conductive wire is pressed (by a spring something like that of a mousetrap). Electrical current flows through the wheel into the wire. When the gear wheel is turned, each tooth of the gear causes the wire to ride up and then briefly drop down, losing contact with the wheel and generating a spark. The gear wheel can be driven by a hand crank. Instead of air, the gaps between the teeth of the gear wheel may be filled with a solid electrical insulator such as ebony wood. Neeff credited this innovation to his colleague Johann Philipp Wagner. Neeff's wheel was a forerunner of the modern contact breaker. == References ==


id: nocturnal-instrument-20260505-0
file: data/en.wikipedia.org/wiki/Nocturnal_(instrument)-0.md
category: reference
title: Nocturnal (instrument)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nocturnal_(instrument)
date_saved: 2026-05-05T09:37:23.952358+00:00
instance: kb-cron
parent: nocturnal-instrument-20260505-0
summary:
A nocturnal is an instrument used to determine the local time based on the position of a star in the night sky relative to the pole star. As a result of the Earth's rotation, any fixed star makes a full revolution around the pole star in 23 hours and 56 minutes and therefore can be used as an hour hand. The 4-minute difference between the solar day and sidereal day requires a correction of this giant clock based on the date of observation, and nocturnal helps to apply this correction. Sometimes called a horologium nocturnum (time instrument for night) or nocturlabe (in French and occasionally used by English writers), it is related to the astrolabe and sundial. Knowing the time is important in piloting for calculating tides and some nocturnals incorporate tide charts for important ports. == History == The actual horologium nocturnum, a precursor for the later nocturnal instruments, was invented in the 9th century by Pacificus of Verona. Even if the nightly course of the stars has been known since antiquity, mentions of a dedicated instrument for its measurement are not found before the Middle Ages. The earliest image presenting the use of a nocturnal is in a


id: nonius-device-20260505-0
file: data/en.wikipedia.org/wiki/Nonius_(device)-0.md
category: reference
title: Nonius (device)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nonius_(device)
date_saved: 2026-05-05T09:37:25.100904+00:00
instance: kb-cron
parent: nonius-device-20260505-0
summary:
Nonius is a measuring tool used in navigation and astronomy named in honour of its inventor, Pedro Nunes (Latin: Petrus Nonius), a Portuguese author, mathematician and navigator. The nonius was created in 1542 as a system for taking finer measurements on circular instruments such as the astrolabe. The system was eventually adapted into the Vernier scale in 1631 by the French mathematician Pierre Vernier. == Technical features == The nonius was used to improve the astrolabe's accuracy. This consisted of a number of concentric circles traced on an instrument and dividing each successive one with one fewer divisions than the adjacent outer circle. On a standard scale of 90 degrees, there are an additional 44–45 concentric circles, with each divided into a specific unit size such that a scale unit on position n {\displaystyle n} had an arc of 90 / n {\displaystyle 90/n} degrees. Thus, the outermost quadrant would comprise 90° in 90 equal divisions, the next inner would have 89 divisions, the next 88 and so on. When an angle was measured, the circle and the division on which the alidade fell was noted. A table was then consulted to provide the exact measure. == Applications == The


id: null-detector-20260505-0
file: data/en.wikipedia.org/wiki/Null_detector-0.md
category: reference
title: Null detector
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Null_detector
date_saved: 2026-05-05T09:37:26.301969+00:00
instance: kb-cron
parent: null-detector-20260505-0
summary:
A null detectors is an electrical measurement instrument used to measure minute voltages. High precision null detectors can resolve voltage differences in the nanovolt range. Null detectors are typically designed to have high input impedance to minimize loading the circuit under test. Null detectors have historically used in calibration laboratories in conjunction with Kelvin–Varley dividers and bridge measurement circuits. Because of their sensitivity and specialized operating range, null detectors were more commonly used in laboratory than in routine field measurements. They were used as part of measurement chains that established traceability to national electrical standards, such as those maintained by National Institute of Standards and Technology (NIST). == History of Null Detectors == The development of null detectors is closely tied to the use of balance and comparison methods in electrical measurement, where the detector serves only to indicate the presence of an imbalance rather than to measure an absolute quantity. === Key stages === Galvanometers as null detectors: Early galvanometers, were commonly used as indicators of current or imbalance in circuits. In early balance and comparison arrangements, they were used to detect when two points reached equal potential, without providing calibrated measurements. Bridge circuits: The adoption of bridge circuits,


id: optical-square-20260505-0
file: data/en.wikipedia.org/wiki/Optical_square-0.md
category: reference
title: Optical square
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Optical_square
date_saved: 2026-05-05T09:37:27.471188+00:00
instance: kb-cron
parent: optical-square-20260505-0
summary:
The optical square uses a pentaprism to reflect and refract a beam or sighting 90 degrees, it is used in pairs in surveying and in a singular block in metrology. In optical square A Horizon glass is placed at an angle of 120° with the horizon sight. The Index glass is placed at an angle of 105° with the Index sight. Angle between Index glass and Horizon glass is 45°. == Metrology == Used with an autocollimator or angle dekkor and mirror it can be used for machine tool axis squareness checking and for measuring the squareness of surfaces. It has two mirrors at 45 degree to each other. One is half-silvered, called horizon glass, and other is fully silvered, called index glass. It measures angle by double reflection. Two prisms can be used as an optical square. == Optical square in surveying == In surveying it is used both as a hand held tool for sighting between two poles (often with a plumb bob hung from the handle) and also mounted on a Jacob's staff. == References ==


id: orrery-20260505-0
file: data/en.wikipedia.org/wiki/Orrery-0.md
category: reference
title: Orrery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Orrery
date_saved: 2026-05-05T09:37:28.640506+00:00
instance: kb-cron
parent: orrery-20260505-0
summary:
An orrery ( ) is a mechanical model of the Solar System that illustrates or predicts the relative positions and motions of the planets and moons, usually according to the heliocentric model. It may also represent the relative sizes of these bodies; however, since accurate scaling is often not practical due to the actual large ratio differences, it may use a scaled-down approximation. Mechanical planetary models are known to have existed since the Ancient Greeks, and are known by various names, but the term orrery is derived from a device produced c. 1712 by John Rowley and named for his patron Charles Boyle, 4th Earl of Orrery. Orreries are typically driven by a clockwork mechanism with a globe representing the Sun at the centre, and with a planet at the end of each of a series of arms. == History == === Ancient === Discovered in 1901 in a shipwreck off the Greek island of Antikythera in the Mediterranean Sea, the Antikythera mechanism has been reconstructed as exhibiting the diurnal motions of the Sun, Moon, and the five planets known to the ancient Greeks. The geocentric mechanism has been dated between 205 and 87 BC and is considered one of


id: orrery-20260505-1
file: data/en.wikipedia.org/wiki/Orrery-1.md
category: reference
title: Orrery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Orrery
date_saved: 2026-05-05T09:37:28.640506+00:00
instance: kb-cron
parent: orrery-20260505-0
summary:
That is, 0.4, 0.7, 1.0, 1.6, 2.8, ... The numbers refer to astronomical units, the mean distance between Sun and Earth, which is 1.496 × 108 km (93 × 106 miles). The Derby Orrery does not show mean distance, but demonstrated the relative planetary movements. The Eisinga Planetarium was built from 1774 to 1781 by Eise Eisinga in his home in Franeker, in the Netherlands. It displays the planets across the width of a room's ceiling, and has been in operation almost continually since it was created. This orrery is a planetarium in both senses of the word: a complex machine showing planetary orbits, and a theatre for depicting the planets' movement. Eisinga house was bought by the Dutch Royal family who gave him a pension. In 1764, Benjamin Martin devised a new type of planetary model, in which the planets were carried on brass arms leading from a series of concentric or coaxial tubes. With this construction it was difficult to make the planets revolve, and to get the moons to turn around the planets. Martin suggested that the conventional orrery should consist of three parts: the planetarium where the planets revolved around the Sun, the tellurion (also tellurian


id: orrery-20260505-2
file: data/en.wikipedia.org/wiki/Orrery-2.md
category: reference
title: Orrery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Orrery
date_saved: 2026-05-05T09:37:28.640506+00:00
instance: kb-cron
parent: orrery-20260505-0
summary:
Shoemaker John Fulton of Fenwick, Ayrshire, built three between 1823 and 1833. The last is in Glasgow's Kelvingrove Art Gallery and Museum. The Eisinga Planetarium built by a wool carder named Eise Eisinga in his own living room, in the small city of Franeker in Friesland, is in fact an orrery. It was constructed between 1774 and 1781. The base of the model faces down from the ceiling of the room, with most of the mechanical works in the space above the ceiling. It is driven by a pendulum clock, which has 9 weights or ponds. The planets move around the model in real time. An innovative concept is to have people play the role of the moving planets and other Solar System objects. Such a model, called a human orrery, has been laid out at the Armagh Observatory. In 2024, the LEGO Group commercially produced an orrery of the Sun, Earth, and Moon. The model is assembled exclusively from LEGO elements and reproduces solar and lunar orbits, as well Earth's rotation about a tilted axis. == In popular culture == The construction system Meccano is a popular tool for constructing highly accurate orreries. Model 391, the first Meccano Orrery,


id: passemant-astronomical-clock-20260505-0
file: data/en.wikipedia.org/wiki/Passemant_astronomical_clock-0.md
category: reference
title: Passemant astronomical clock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Passemant_astronomical_clock
date_saved: 2026-05-05T09:37:29.815736+00:00
instance: kb-cron
parent: passemant-astronomical-clock-20260505-0
summary:
The Passemant astronomical clock is an astronomical clock designed by Claude-Simeon Passemant in the eighteenth century. It is displayed in the Salon de la pendule in the petit appartement du roi on the first floor of Versailles, France. The clock set the official time in France for the first time in the kingdom's history. == Description == The clock is an exceptional rococo work over 2 metres (6 ft 7 in) in height, crowned with a moving celestial sphere. It shows the date, time, real time average phases of the moon and Copernican planetary motion. The large astronomical dials mark the rising and setting of the sun and moon every day. Earth is represented by a bronze globe on which all countries are engraved with the main cities. This globe is placed among the rocks and waterfalls, which serve as a universal horizon. The mechanism is designed to be able to display the date until the end of the year 9999. == Creators == The clock mechanism was designed by engineer Claude-Siméon Passemant (1702–1769) and executed by the clockmaker Louis Dauthiau (1730–1809). The rococo-style gilt-bronze box protecting the mechanism was made in 1753 by sculptor Jean-Jacques Caffieri (1735–1792) and bronze-founder


id: a-philosopher-lecturing-on-the-orrery-20260505-0
file: data/en.wikipedia.org/wiki/A_Philosopher_Lecturing_on_the_Orrery-0.md
category: reference
title: A Philosopher Lecturing on the Orrery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/A_Philosopher_Lecturing_on_the_Orrery
date_saved: 2026-05-05T09:37:31.008006+00:00
instance: kb-cron
parent: a-philosopher-lecturing-on-the-orrery-20260505-0
summary:
A Philosopher Lecturing on the Orrery, or the full title, A Philosopher giving that Lecture on the Orrery in which a lamp is put in place of the Sun, is a 1766 painting by Joseph Wright of Derby depicting a lecturer giving a demonstration of an orrery – a mechanical model of the Solar System – to a small audience. It is now in the Derby Museum and Art Gallery The painting preceded his similar An Experiment on a Bird in the Air Pump (National Gallery, London). The first of Wright's candlelit masterpieces, Three Persons Viewing the Gladiator by Candlelight, was painted in 1765, and showed three men studying a small copy of the "Borghese Gladiator". The Gladiator was greatly admired; but his next painting, The Orrery, caused a greater stir, as it replaced the Classical subject at the centre of the scene with one of a scientific nature. Wright's depiction of the awe produced by scientific "miracles" marked a break with previous traditions in which the artistic depiction of such wonder was reserved for religious events, since to Wright the marvels of the technological age were as awe-inspiring as the subjects of the great religious paintings. In both of


id: plane-table-20260505-0
file: data/en.wikipedia.org/wiki/Plane_table-0.md
category: reference
title: Plane table
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Plane_table
date_saved: 2026-05-05T09:37:32.218499+00:00
instance: kb-cron
parent: plane-table-20260505-0
summary:
A plane table (plain table prior to 1830) is a device used in surveying, site mapping, exploration mapping, coastal navigation mapping, and related disciplines to provide a solid and level surface on which to make field drawings, charts and maps. The early use of the name plain table reflected its simplicity and plainness rather than its flatness. "Plane" refers to the table being both flat and levelled (horizontal). == History == The earliest mention of a plane table dates to 1551 in Abel Foullon's "Usage et description de l'holomètre", published in Paris. However, since Foullon's description was of a complete, fully developed instrument, it must have been invented earlier. A brief description was also added to the 1591 edition of Digge's Pantometria. The first mention of the device in English was by Cyprian Lucar in 1590. The Swiss instrument maker Leonhard Zubler published an account of the plane table in Novum instrumentum geometricum, 1607. He used the term Instrumentum Chorographicum crediting its invention to Philipp Eberhard, a fellow Swiss instrument maker based in Zurich. Some have credited Johann Richter, also known as Johannes Praetorius, a Nuremberg mathematician, in 1610 with the first plane table, but this appears to be incorrect.


id: post-office-box-electricity-20260505-0
file: data/en.wikipedia.org/wiki/Post_office_box_(electricity)-0.md
category: reference
title: Post office box (electricity)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Post_office_box_(electricity)
date_saved: 2026-05-05T09:37:34.501965+00:00
instance: kb-cron
parent: post-office-box-electricity-20260505-0
summary:
The post office box was a Wheatstone bridge–style testing device with pegs and spring arms to close electrical circuits and measure properties of the circuit under test. == Resistance measurement == The boxes were used in the United Kingdom by engineers from then General Post Office, who were responsible for UK telecommunications to trace electrical faults, i.e. to determine where a break occurred in a cable which could be several miles in length. It works on the principle of Wheatstone bridge to identify the resistance of wire connected and then by using wire resistivity and cross section calculating length of wire and thus determining where the cable had broken. Post office boxes were common pieces of scientific apparatus in the UK O-Level and A-Level schools public examination physics syllabus in the 1960s. == Construction == A typical post office box is in a wooden box with a hinged lid and a metal or bakelite panel showing circuit connections. Coils of wire are wound non-inductively, mounted in the body of the box, and have a negligible temperature coefficient. Pairs of ratio arms are each 5 10 20 ohms. Resistance arms contains a number of coils from 1 to 5000 ohms with


id: quadrant-instrument-20260505-0
file: data/en.wikipedia.org/wiki/Quadrant_(instrument)-0.md
category: reference
title: Quadrant (instrument)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quadrant_(instrument)
date_saved: 2026-05-05T09:37:35.683233+00:00
instance: kb-cron
parent: quadrant-instrument-20260505-0
summary:
A quadrant is an instrument used to measure angles up to 90°. Different versions of this instrument could be used to calculate various readings, such as longitude, latitude, and time of day. It was first proposed by Ptolemy as a better kind of astrolabe. Several different variations of the instrument were later produced by medieval Muslim astronomers. Mural quadrants were important astronomical instruments in 18th-century European observatories, establishing a use for positional astronomy. == Etymology == The term quadrant, meaning one fourth, refers to the fact that early versions of the instrument were derived from astrolabes. The quadrant condensed the workings of the astrolabe into an area one fourth the size of the astrolabe face; it was essentially a quarter of an astrolabe. == History == During Rigvedic times in ancient India, quadrants called 'Tureeyam's were used to measure the extent of a great solar eclipse. The use of a Tureeyam for observing a solar eclipse by Rishi Atri is described in the fifth mandala of the Rigveda, most likely between c. 1500 and 1000 BC. Early accounts of a quadrant also come from Ptolemy's Almagest around AD 150. He described a "plinth" that could measure the altitude of the


id: quadrant-instrument-20260505-1
file: data/en.wikipedia.org/wiki/Quadrant_(instrument)-1.md
category: reference
title: Quadrant (instrument)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quadrant_(instrument)
date_saved: 2026-05-05T09:37:35.683233+00:00
instance: kb-cron
parent: quadrant-instrument-20260505-0
summary:
Altitude – The plain quadrant with plumb line, used to take the altitude of an object. Gunner's – A type of clinometer used by an artillerist to measure the elevation or depression angle of a gun barrel of a cannon or mortar, both to verify proper firing elevation, and to verify the correct alignment of the weapon-mounted fire control devices. Gunter's – A quadrant used for time determination as well as the length of day, when the sun had risen and set, the date, and the meridian using scales and curves of the quadrant along with related tables. It was invented by Edmund Gunter in 1623. Gunter's quadrant was fairly simple which allowed for its widespread and long-lasting use in the 17th and 18th centuries. Gunter expanded the basic features of other quadrants to create a convenient and comprehensive instrument. Its distinguishable feature included projections of the tropics, equator, ecliptic, and the horizon. Islamic – King identified four types of quadrants that were produced by Muslim astronomers. The sine quadrant (Arabic: Rubul Mujayyab) – also known as the Sinecal Quadrant – was used for solving trigonometric problems and taking astronomical observations. It was developed by al-Khwarizmi in 9th century Baghdad


id: quadrant-instrument-20260505-2
file: data/en.wikipedia.org/wiki/Quadrant_(instrument)-2.md
category: reference
title: Quadrant (instrument)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quadrant_(instrument)
date_saved: 2026-05-05T09:37:35.683233+00:00
instance: kb-cron
parent: quadrant-instrument-20260505-0
summary:
=== Back observation quadrant === In order to perform measurements of the altitude of the sun, a back observation quadrant was developed. With such a quadrant, the observer viewed the horizon from a sight vane (C in the figure on the right) through a slit in the horizon vane (B). This ensured the instrument was level. The observer moved the shadow vane (A) to a position on the graduated scale so as to cause its shadow to appear coincident with the level of the horizon on the horizon vane. This angle was the elevation of the sun. == Framed quadrant == Large-frame quadrants were used for astronomical measurements, notably determining the altitude of celestial objects. They could be permanent installations, such as mural quadrants. Smaller quadrants could be moved. Like the similar astronomical sextants, they could be used in a vertical plane or made adjustable for any plane. When set on a pedestal or other mount, they could be used to measure the angular distance between any two celestial objects. The details on their construction and use are essentially the same as those of the astronomical sextants; refer to that article for details. Navy: Used to gauge elevation on ships


id: radio-latino-20260505-0
file: data/en.wikipedia.org/wiki/Radio_latino-0.md
category: reference
title: Radio latino
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Radio_latino
date_saved: 2026-05-05T09:37:36.860302+00:00
instance: kb-cron
parent: radio-latino-20260505-0
summary:
A radio latino is a measuring instrument used in surveying and military engineering starting in the 16th century. It gets its name from the inventor, Latino Orsini. The radio latino can be considered a kind of geometric square. It was a general purpose instrument that could be used for a variety of angular measurements as well as depth and inside dimension measures. == Usage == The slider (blue in the adjacent diagram) could move along the central rod, causing the deltoid formed by four other rods to change shape symmetrically. The end points of the rods had sights on them, allowing various sight lines to be defined. The central rod was graduated with various scales. These scales allowed the angles between the end rods (represented by the red lines in the diagram) to be determined as well as the angle with its vertex at one end of the main rod and sides (represented by the green lines in the diagram) through the outer joints of the rods. With different graduations, one could determine or lay out: angles between sight lines with a degree scale. internal angles of regular polygons with polygon scales. internal diameters and dimensions (such as the inside


id: ramsden-surveying-instruments-20260505-0
file: data/en.wikipedia.org/wiki/Ramsden_surveying_instruments-0.md
category: reference
title: Ramsden surveying instruments
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ramsden_surveying_instruments
date_saved: 2026-05-05T09:37:38.027690+00:00
instance: kb-cron
parent: ramsden-surveying-instruments-20260505-0
summary:
The Ramsden surveying instruments are those constructed by Jesse Ramsden and used in high precision geodetic surveys carried out in the period 1784 to 1853. This includes the five great theodolites—great in name, great in size and great in accuracy—used in surveys of Britain and other parts of the world. Ramsden also provided the equipment used in the measurement of the many base lines of these surveys and also the zenith telescope used in latitude determinations. == The great theodolites == A total of eight such instruments were manufactured by Ramsden and others for use in Britain, India and Switzerland. Ramsden himself constructed three theodolites and a further two were completed to his design by Mathew Berge, his son-in-law and business successor, after Ramsden's death in 1805. Of the other instruments one was constructed by William Cary and the other two by the firm of Troughton & Simms. === The Royal Society theodolite === In 1783 the Royal Society of London reacted to (unfounded) French criticism of Greenwich Observatory by seeking Royal assent to undertake a high precision geodetic survey, the Anglo-French Survey (1784–1790), between Greenwich and the established French survey stations on the other side of the English Channel.


id: ramsden-surveying-instruments-20260505-1
file: data/en.wikipedia.org/wiki/Ramsden_surveying_instruments-1.md
category: reference
title: Ramsden surveying instruments
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ramsden_surveying_instruments
date_saved: 2026-05-05T09:37:38.027690+00:00
instance: kb-cron
parent: ramsden-surveying-instruments-20260505-0
summary:
=== Great theodolites by other builders === Although the East India Company turned down Ramsden's second theodolite, they commissioned a similar design from another London instrument maker, William Cary. This theodolite was in use in India from 1802 although there was a slight hiatus in 1808 when it was damaged when being hauled to the top of a building. It was repaired and in use for sixty years. A new theodolite to an improved design was made for the Indian Survey by Troughton and Simms in 1830 and the two together saw service until 1874 when the Cary instrument was replaced by another by Troughton and Sims. This last instrument was a monster weighing 1,455 lb (660 kg) when in its travelling cases: it was no surprise that it was deemed too heavy for transport up mountains and it passed to South Africa in 1882. No more great instruments were made after 1874 for continuing advances in precision instruments eclipsed their performance: by the end of the nineteenth century an accuracy of 1 arc second could be obtained with a 12-inch (300 mm) instrument. == Chains and rods == Eighteenth-century surveyors used Gunter's chains which were 22 yards long (one


id: rectangulus-20260505-0
file: data/en.wikipedia.org/wiki/Rectangulus-0.md
category: reference
title: Rectangulus
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rectangulus
date_saved: 2026-05-05T09:37:39.220993+00:00
instance: kb-cron
parent: rectangulus-20260505-0
summary:
The rectangulus was an astronomical instrument made by Richard of Wallingford around 1326. Dissatisfied with the limitations of existing astrolabes, Richard developed the rectangulus as an instrument for spherical trigonometry and to measure the angles between planets and other astronomical bodies. This was one of a number of instruments he created, including the Albion, a form of equatorium, and a famously complicated and expensive horologium (astronomical clock). His Tractus Rectanguli, describing the rectangulus, was an influential text in medieval astronomy and at least thirty copies were known to survive. His Quadripartitum was the first text on spherical trigonometry to be published in Western Europe. The rectangulus was a form of skeleton torquetum. This was a series of nested angular scales, so that measurements in azimuth and elevation could be made directly in polar coordinates, relative to the ecliptic. Conversion from these coordinates though was difficult, involving what was the leading mathematics of the day. The rectangulus was an analogue computing device to simplify this: instead of measuring in angular measurements it could resolve the angles to Cartesian components directly. This then simplified the further calculations. The rectangulus was constructed as a brass pillar with a number of linear scales hinged


id: sextant-astronomy-20260505-0
file: data/en.wikipedia.org/wiki/Sextant_(astronomy)-0.md
category: reference
title: Sextant (astronomy)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sextant_(astronomy)
date_saved: 2026-05-05T09:37:42.520007+00:00
instance: kb-cron
parent: sextant-astronomy-20260505-0
summary:
In astronomy, sextants are devices depicting a sixth of a circle, used primarily for measuring the position of stars. There are two types of astronomical sextants, mural instruments and frame-based instruments. They are of significant historical importance, but have been replaced over time by transit telescopes, other astrometry techniques, and satellites such as Hipparcos. == Mural sextants == The first known mural sextant was constructed in Ray, Iran, by Abu-Mahmud al-Khujandi in 994. To measure the obliquity of the ecliptic, al-Khujandī invented a device that he called al-Fakhri sextant (al-suds al Fakhrī), a reference to his patron, Buwayhid ruler, Fakhr al Dawla (976–997). This instrument was a sixty-degree arc on a wall aligned along a meridian (north–south) line. Al Khujandi's instrument was larger than previous instruments; it had a radius of about twenty meters. The main improvement incorporated in al-Fakhri sextants over earlier instruments was bringing the precision of reading to seconds while older instruments could only be read in degrees and minutes. This was confirmed by al-Birūni, al-Marrākushī and al-Kāshī. Al-Khujandī used his device to measure the sun's angle above the horizon at the summer and winter solstices; these two measurements allow computation of the latitude of the sextant's


id: shadow-square-20260505-0
file: data/en.wikipedia.org/wiki/Shadow_square-0.md
category: reference
title: Shadow square
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Shadow_square
date_saved: 2026-05-05T09:37:43.709972+00:00
instance: kb-cron
parent: shadow-square-20260505-0
summary:
The shadow square, also known as an altitude scale, was an instrument used to determine the linear height of an object, in conjunction with the alidade, for angular observations. An early example was described in an Arabic treatise likely dating to 9th or 10th-century Baghdad. Shadow squares are often found on the backs of astrolabes. == Uses == The main use of a shadow square is to measure the linear height of an object using its shadow. It does so by simulating the ratio between an object, generally a gnomon, and its shadow. If the Sun's ray is between 0 degrees and 45 degrees the umbra versa (Vertical axis) is used, between 45 degrees and 90 degrees the umbra recta (Horizontal axis) is used and when the Sun's ray is at 45 degrees its shadow falls exactly on the umbra media (y=x) It was used during the time of medieval astronomy to determine the height of, and to track the movement of celestial bodies such as the Sun when more advanced measurement methods were not available. These methods can still be used today to determine the altitude, with reference to the horizon, of any visible celestial body. == Gnomon ==


id: slide-rule-20260505-0
file: data/en.wikipedia.org/wiki/Slide_rule-0.md
category: reference
title: Slide rule
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Slide_rule
date_saved: 2026-05-05T09:37:44.876699+00:00
instance: kb-cron
parent: slide-rule-20260505-0
summary:
A slide rule is a hand-operated mechanical calculator consisting of slidable rulers for conducting mathematical operations such as multiplication, division, exponents, roots, logarithms, and trigonometry. It is one of the simplest analog computers. Slide rules exist in a diverse range of styles and generally appear in a linear, circular or cylindrical form. Slide rules manufactured for specialized fields such as aviation or finance typically feature additional scales that aid in specialized calculations particular to those fields. The slide rule is closely related to nomograms used for application-specific computations. Though similar in name and appearance to a standard ruler, the slide rule is not meant to be used for measuring length or drawing straight lines. Maximum accuracy for standard linear slide rules is about three decimal significant digits, while scientific notation is used to keep track of the order of magnitude of results. English mathematician and clergyman Reverend William Oughtred and others developed the slide rule in the 17th century based on the emerging work on logarithms by John Napier. It made calculations faster and less error-prone than evaluating on paper. Before the advent of the scientific pocket calculator, it was the most commonly used calculation tool in science and engineering.


id: slide-rule-20260505-1
file: data/en.wikipedia.org/wiki/Slide_rule-1.md
category: reference
title: Slide rule
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Slide_rule
date_saved: 2026-05-05T09:37:44.876699+00:00
instance: kb-cron
parent: slide-rule-20260505-0
summary:
But since the 7 is above the second set of numbers that number must be multiplied by 10. Thus, even though the answer directly reads 1.4, the correct answer is 1.4×10 = 14. For an example with even larger numbers, to multiply 88×20, the top scale is again positioned to start at the 2 on the bottom scale. Since 2 represents 20, all numbers in that scale are multiplied by 10. Thus, any answer in the second set of numbers is multiplied by 100. Since 8.8 in the top scale represents 88, the answer must additionally be multiplied by 10. The answer directly reads 1.76. Multiply by 100 and then by 10 to get the actual answer: 1,760. In general, the 1 on the top is moved to a factor on the bottom, and the answer is read off the bottom where the other factor is on the top. This works because the distances from the 1 mark are proportional to the logarithms of the marked values. ==== Division ==== The illustration below demonstrates the computation of ⁠5.5/2⁠. The 2 on the top scale is placed over the 5.5 on the bottom scale. The resulting quotient, 2.75, can then be


id: slide-rule-20260505-2
file: data/en.wikipedia.org/wiki/Slide_rule-2.md
category: reference
title: Slide rule
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Slide_rule
date_saved: 2026-05-05T09:37:44.876699+00:00
instance: kb-cron
parent: slide-rule-20260505-0
summary:
==== Future value of money ==== The LLN scales can be used to compute and compare the cost or return on a fixed rate loan or investment. The simplest case is for continuously compounded interest. Example: Taking D as the interest rate in percent, slide the index (the "1" at the right or left end of the scale) of C to the percent on D. The corresponding value on LL2 directly below the index will be the multiplier for 10 cycles of interest (typically years). The value on LL2 below 2 on the C scale will be the multiplier after 20 cycles, and so on. ==== Trigonometry ==== The S, T, and ST scales are used for trig functions and multiples of trig functions, for angles in degrees. For angles from around 5.7 up to 90 degrees, sines are found by comparing the S scale with C (or D) scale. (On many closed-body rules the S scale relates to the A and B scales instead and covers angles from around 0.57 up to 90 degrees; what follows must be adjusted appropriately.) The S scale has a second set of angles (sometimes in a different color), which run in the opposite


id: slide-rule-20260505-3
file: data/en.wikipedia.org/wiki/Slide_rule-3.md
category: reference
title: Slide rule
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Slide_rule
date_saved: 2026-05-05T09:37:44.876699+00:00
instance: kb-cron
parent: slide-rule-20260505-0
summary:
Circular slide rules come in two basic types, one with two cursors, and another with a free dish and one cursor. The dual cursor versions perform multiplication and division by holding a constant angle between the cursors as they are rotated around the dial. The onefold cursor version operates more like the standard slide rule through the appropriate alignment of the scales. The basic advantage of a circular slide rule is that the widest dimension of the tool was reduced by a factor of about 3 (i.e. by π). For example, a 10 cm (3.9 in) circular would have a maximum precision approximately equal to a 31.4 cm (12.4 in) ordinary slide rule. Circular slide rules also eliminate "off-scale" calculations, because the scales were designed to "wrap around"; they never have to be reoriented when results are near 1.0—the rule is always on scale. However, for non-cyclical non-spiral scales such as S, T, and LL's, the scale width is narrowed to make room for end margins. Circular slide rules are mechanically more rugged with smoother motion, but their scale alignment precision is sensitive to the centering of a central pivot; a minute 0.1 mm (0.0039 in) off-centre of the pivot


id: slide-rule-20260505-4
file: data/en.wikipedia.org/wiki/Slide_rule-4.md
category: reference
title: Slide rule
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Slide_rule
date_saved: 2026-05-05T09:37:44.876699+00:00
instance: kb-cron
parent: slide-rule-20260505-0
summary:
The slide rule was invented around 1620–1630, shortly after John Napier's publication of the concept of the logarithm. In 1620 Edmund Gunter of Oxford developed a calculating device with a single logarithmic scale; with additional measuring tools it could be used to multiply and divide. In c. 1622, William Oughtred of Cambridge combined two handheld Gunter rules to make a device that is recognizably the modern slide rule. Oughtred became involved in a vitriolic controversy over priority, with his one-time student Richard Delamain and the prior claims of Edmund Wingate. Oughtred's ideas were only made public in publications of his student William Forster in 1632 and 1653. In 1677, Henry Coggeshall created a two-foot folding rule for timber measure, called the Coggeshall slide rule, expanding the slide rule's use beyond mathematical inquiry. In 1722, Warner introduced the two- and three-decade scales, and in 1755 Everard included an inverted scale; a slide rule containing all of these scales is usually known as a "polyphase" rule. In 1815, Peter Mark Roget invented the log log slide rule, which included a scale displaying the logarithm of the logarithm. This allowed the user to directly perform calculations involving roots and exponents. This was especially


id: slide-rule-20260505-5
file: data/en.wikipedia.org/wiki/Slide_rule-5.md
category: reference
title: Slide rule
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Slide_rule
date_saved: 2026-05-05T09:37:44.876699+00:00
instance: kb-cron
parent: slide-rule-20260505-0
summary:
=== Specialized calculators === Slide rules have often been specialized to varying degrees for their field of use, such as excise, proof calculation, engineering, navigation, etc., and some slide rules are extremely specialized for very narrow applications. For example, the John Rabone & Sons 1892 catalog lists a "Measuring Tape and Cattle Gauge", a device to estimate the weight of a cow from its measurements. There were many specialized slide rules for photographic applications. For example, the actinograph of Hurter and Driffield was a two-slide boxwood, brass, and cardboard device for estimating exposure from time of day, time of year, and latitude. Specialized slide rules were invented for various forms of engineering, business and banking. These often had common calculations directly expressed as special scales, for example loan calculations, optimal purchase quantities, or particular engineering equations. For example, the Fisher Controls company distributed a customized slide rule adapted to solving the equations used for selecting the proper size of industrial flow control valves. Pilot balloon slide rules were used by meteorologists in weather services to determine the upper wind velocities from an ascending hydrogen or helium-filled pilot balloon. The E6-B is a circular slide rule used by pilots and navigators.


id: slide-rule-20260505-6
file: data/en.wikipedia.org/wiki/Slide_rule-6.md
category: reference
title: Slide rule
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Slide_rule
date_saved: 2026-05-05T09:37:44.876699+00:00
instance: kb-cron
parent: slide-rule-20260505-0
summary:
Even during their heyday, slide rules never caught on with the general public. Addition and subtraction are not well-supported operations on slide rules and doing a calculation on a slide rule tends to be slower than on a calculator. This led engineers to use mathematical equations that favored operations that were easy on a slide rule over more accurate but complex functions; these approximations could lead to inaccuracies and mistakes. On the other hand, the spatial, manual operation of slide rules cultivates in the user an intuition for numerical relationships and scale that people who have used only digital calculators often lack. A slide rule will also display all the terms of a calculation along with the result, thus eliminating uncertainty about what calculation was actually performed. It has thus been compared with reverse Polish notation (RPN) implemented in electronic calculators. A slide rule requires the user to separately compute the order of magnitude of the answer to position the decimal point in the results. For example, 1.5 × 30 (which equals 45) will show the same result as 1500000 × 0.03 (which equals 45000). This separate calculation forces the user to keep track of magnitude in short-term memory (which


id: slide-rule-scale-20260505-0
file: data/en.wikipedia.org/wiki/Slide_rule_scale-0.md
category: reference
title: Slide rule scale
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Slide_rule_scale
date_saved: 2026-05-05T09:37:46.082245+00:00
instance: kb-cron
parent: slide-rule-scale-20260505-0
summary:
A slide rule scale is a line with graduated markings inscribed along the length of a slide rule used for mathematical calculations. The earliest such device had a single logarithmic scale for performing multiplication and division, but soon an improved technique was developed which involved two such scales sliding alongside each other. Later, multiple scales were provided with the most basic being logarithmic but with others graduated according to the mathematical function required. Few slide rules have been designed for addition and subtraction, rather the main scales are used for multiplication and division and the other scales are for mathematical calculations involving trigonometric, exponential and, generally, transcendental functions. Before they were superseded by electronic calculators in the 1970s, slide rules were an important type of portable calculating instrument. == Slide rule design == A slide rule consists of a body and a slider that can be slid along within the body and both of these have numerical scales inscribed on them. On duplex rules the body and/or the slider have scales on the back as well as the front. The slider's scales may be visible from the back or the slider may need to be slid right out and replaced


