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Jean-Baptiste Chappe d'Auteroche (23 March 1722 – 1 August 1769) was a French
astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...
, best known for his observations of the
transits of Venus frameless, upright=0.5 A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk. During a tran ...
in 1761 and 1769.


Early life

Little is known of Chappe's early life. He was born into a distinguished family holding administrative posts and coming from
Auvergne Auvergne (; ; oc, label= Occitan, Auvèrnhe or ) is a former administrative region in central France, comprising the four departments of Allier, Puy-de-Dôme, Cantal and Haute-Loire. Since 1 January 2016, it has been part of the new region Au ...
, a region of central France. He entered the priesthood, probably as a
Jesuit , image = Ihs-logo.svg , image_size = 175px , caption = ChristogramOfficial seal of the Jesuits , abbreviation = SJ , nickname = Jesuits , formation = , founders ...
, and devoted himself to the study of astronomy. He was appointed assistant astronomer at the Royal Observatory and admitted to the Royal Academy of Sciences on 14 January 1759.


Distance from the Earth to the Sun

In the mid-18th century, the dynamics of the
Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...
were reasonably well understood, but astronomers only had an approximate idea of its scale. If the distance between two planets could be measured, all the other distances would be known from
Kepler's laws of planetary motion In astronomy, Kepler's laws of planetary motion, published by Johannes Kepler between 1609 and 1619, describe the orbits of planets around the Sun. The laws modified the heliocentric theory of Nicolaus Copernicus, replacing its circular orb ...
. The best candidate for an accurate measurement was the distance between the Earth and
Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...
, which could be calculated from observations of
transits of Venus frameless, upright=0.5 A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk. During a tran ...
, when Venus passes directly between the Earth and the Sun, appearing as a small black dot moving across the face of the Sun. However, transits of Venus are very rare. Before 1761, the previous transit had been in 1639; after 1769, the next transit would be in 1874. The importance of the measurement led to an unprecedented international effort to obtain as many observations as possible from different points in the world – points as far apart from one another as possible. Despite the
Seven Years' War The Seven Years' War (1756–1763) was a global conflict that involved most of the European Great Powers, and was fought primarily in Europe, the Americas, and Asia-Pacific. Other concurrent conflicts include the French and Indian War (1754 ...
which was raging throughout most of the world, astronomers were given letters of introduction and safe passage to enable them to reach their observation points and make their observations under the coordination of the various
learned societies A learned society (; also learned academy, scholarly society, or academic association) is an organization that exists to promote an academic discipline, profession, or a group of related disciplines such as the arts and science. Membership may ...
.


Transit of Venus 1761

Chappe was chosen to go to
Tobolsk Tobolsk (russian: Тобо́льск) is a town in Tyumen Oblast, Russia, located at the confluence of the Tobol and Irtysh rivers. Founded in 1590, Tobolsk is the second-oldest Russian settlement east of the Ural Mountains in Asian Russia, ...
in
Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part ...
to observe the
transit of Venus frameless, upright=0.5 A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk. During a tr ...
expected for 6 June 1761. The trip was arduous and Chappe arrived in Tobolsk with little time to spare, although he was able to observe the
lunar eclipse A lunar eclipse occurs when the Moon moves into the Earth's shadow. Such alignment occurs during an eclipse season, approximately every six months, during the full moon phase, when the Moon's orbital plane is closest to the plane of the Ear ...
of 18 May, which enabled him to calculate the
longitude Longitude (, ) is a geographic coordinate that specifies the east– west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek let ...
of Tobolsk. The spring floods of the Tobol and
Irtysh The Irtysh ( otk, 𐰼𐱅𐰾:𐰇𐰏𐰕𐰏, Ertis ügüzüg, mn, Эрчис мөрөн, ''Erchis mörön'', "erchleh", "twirl"; russian: Иртыш; kk, Ертіс, Ertis, ; Chinese: 额尔齐斯河, pinyin: ''É'ěrqísī hé'', Xiao'e ...
rivers had been particularly severe that year, and some of the local peasants blamed the foreigner with his strange equipment who was "messing with the Sun": Chappe had to be protected by a cordon of armed
Cossacks The Cossacks , es, cosaco , et, Kasakad, cazacii , fi, Kasakat, cazacii , french: cosaques , hu, kozákok, cazacii , it, cosacchi , orv, коза́ки, pl, Kozacy , pt, cossacos , ro, cazaci , russian: казаки́ or ...
to make his observations. Fortunately, the weather conditions were excellent, and Chappe was able to observe the entire transit. He published his results from
Saint Petersburg Saint Petersburg ( rus, links=no, Санкт-Петербург, a=Ru-Sankt Peterburg Leningrad Petrograd Piter.ogg, r=Sankt-Peterburg, p=ˈsankt pʲɪtʲɪrˈburk), formerly known as Petrograd (1914–1924) and later Leningrad (1924–1991), i ...
(''Mémoire du passage de Vénus sur le soleil, avec des observations sur l'astronomie et la déclinaison de la boussole faites à Tobolsk, en Sibérie''), and didn't return to France until 1763.. Chappe published an account of his travels through Russia (''Voyage en Sibérie fait en 1761 (avec la description du Kamtschatka, trad. du russe de Khracheninnikow)'') in 1768. The text is hardly a flattering description of the country, and an anonymous pamphlet (''Antidote ou Réfutation du mauvais livre superbement imprimé intitulé : Voyage en Sibérie, etc.'') was soon circulating whose authorship is often attributed to
Catherine the Great , en, Catherine Alexeievna Romanova, link=yes , house = , father = Christian August, Prince of Anhalt-Zerbst , mother = Joanna Elisabeth of Holstein-Gottorp , birth_date = , birth_name = Princess Sophie of Anha ...
herself (although Count Andrey Petrovich Shuvalov is more likely the polemicist).


Longitude measurement

The problem of longitude measurement had been at the heart of astronomical research for a century or more, and
marine chronometer A marine chronometer is a precision timepiece that is carried on a ship and employed in the determination of the ship's position by celestial navigation. It is used to determine longitude by comparing Greenwich Mean Time (GMT), or in the mode ...
s were steadily becoming more accurate. Chappe and physicist
Henri-Louis Duhamel du Monceau Henri-Louis Duhamel du Monceau (20 July 1700, Paris13 August 1782, Paris), was a French physician, naval engineer and botanist. Biography Henri-Louis Duhamel du Monceau was born in Paris in 1700, the son of Alexandre Duhamel, lord of Denai ...
(1700–82) were selected to test one such chronometer, made by
Swiss Swiss may refer to: * the adjectival form of Switzerland *Swiss people Places * Swiss, Missouri *Swiss, North Carolina * Swiss, West Virginia *Swiss, Wisconsin Other uses * Swiss-system tournament, in various games and sports * Swiss Internation ...
watchmaker A watchmaker is an artisan who makes and repairs watches. Since a majority of watches are now factory-made, most modern watchmakers only repair watches. However, originally they were master craftsmen who built watches, including all their part ...
Ferdinand Berthoud Ferdinand Berthoud (born 18 March 1727, in Plancemont-sur-Couvet, Principality of Neuchâtel; died 20 June 1807, in Groslay, Val d'Oise), was a scientist and watchmaker. He became master watchmaker in Paris in 1753. Berthoud, who held the posit ...
(1727–1807) on board the corvette ''L'Hirondelle'' in 1764.


Transit of Venus 1769

For the transit of Venus on 3 June 1769, Chappe's destination was the
Mission Mission (from Latin ''missio'' "the act of sending out") may refer to: Organised activities Religion *Christian mission, an organized effort to spread Christianity *Mission (LDS Church), an administrative area of The Church of Jesus Christ of ...
of
San José del Cabo San José del Cabo (, ''Saint Joseph of the Cape'') is a city located in southern Baja California Sur state, Mexico. It is the seat of Los Cabos Municipality lying at a shallow bay northeast of Cabo San Lucas on the Gulf of California. The city ...
at the tip of the Baja California peninsula in modern-day
Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...
. The journey and observation were uneventful. However, as the expedition was packing to return, an outbreak of fever (possibly
yellow fever Yellow fever is a viral disease of typically short duration. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains – particularly in the back – and headaches. Symptoms typically improve within five days. ...
) hit the area. Chappe stayed to tend the sick, but was infected and died on 1 August. Only one member of the expedition made it back to Paris alive with Chappe's observations and notes. Chappe's account of his journey (''Voyage en Californie, pour l'observation du passage de Vénus sur le disque du soleil'') was published posthumously by his colleague César Cassini de Thury. The manuscript is kept at the Library of
Paris Observatory The Paris Observatory (french: Observatoire de Paris ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centers in the world. Its histo ...
an
available online


Legacy

As well as the contributions his observations of the
transits of Venus frameless, upright=0.5 A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk. During a tran ...
gave to solving the problem of the size of the solar system, his nephew,
Claude Chappe Claude Chappe (; 25 December 1763 – 23 January 1805) was a French inventor who in 1792 demonstrated a practical semaphore system that eventually spanned all of France. His system consisted of a series of towers, each within line of sight of ...
was greatly inspired by reading ''Voyage en Sibérie''. Claude went on, with his brothers, to create the first optical telegraph network using semaphores and telescopes.The Early History of Data Networks
/ref> Asteroid 14961 d'Auteroche, discovered by
Eric Walter Elst Eric Walter Elst (30 November 1936 – 2 January 2022) was a Belgian astronomer at the Royal Observatory of Belgium in Uccle and a prolific discoverer of asteroids. The Minor Planet Center ranks him among the top 10 discoverers of minor planet ...
at
La Silla Observatory La Silla Observatory is an astronomical observatory in Chile with three telescopes built and operated by the European Southern Observatory (ESO). Several other telescopes are located at the site and are partly maintained by ESO. The observatory is ...
in
Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...
in 1996, was named in his honour.


References


External links


How Far to the Sun? The Venus Transits of 1761 & 1769
{{DEFAULTSORT:Chappe D'auteroche, Jean-Baptiste 1722 births 1769 deaths 18th-century French astronomers Members of the French Academy of Sciences 18th-century French Jesuits Jesuit scientists