Jean Picard


Jean Picard

Infobox Scientist
name = Jean Picard
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caption = Jean-Felix Picard (1620–1682)
birth_date = July 21, 1620
birth_place = La Flèche
death_date = July 12, 1682
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nationality = French
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field = astronomy
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Jean-Felix Picard (July 21, 1620 – July 12, 1682) was a French astronomer and priest born in La Flèche, where he studied at the Jesuit Collège Royal Henry-Le-Grand. He was the first person to measure the size of the Earth to a reasonable degree of accuracy in a survey conducted 1669-70, for which he is honored with a pyramid at Juvisy-sur-Orge. Guided by Maurolycus's methodology and Snellius's mathematics for doing so, Picard achieved this by measuring one degree of latitude along the Paris Meridian using triangulation along thirteen triangles stretching from Paris to the clocktower of Sourdon, near Amiens. His measurements produced a result of 110.46 km for one degree of latitude, which gives a corresponding terrestrial radius of 6328.9 km. The polar radius has now been measured at just over 6357 km. This was an error only 0.44% less than the modern value. This was another example of advances in astronomy and its tools making possible advances in cartography. Picard was the first to attach a telescope with crosswires (developed by William Gascoigne) to a quadrant, and one of the first to use a micrometer screw on his instruments. The quadrant he used to determine the size of the Earth had a radius of 38 inches and was graduated to quarter-minutes. The sextant he used to find the meridian had a radius of six feet, and was equipped with a micrometer to enable minute adjustments. These equipment improvements made the margin of error only ten seconds, as opposed to Tycho Brahe's four minutes of error. This made his measurements 36 times more accurate. Isaac Newton was to use this value in his theory of universal gravitation.

Picard also travelled to Tycho Brahe's Swedish observatory, Uraniborg, in order to assess its position accurately to compare Tycho's readings to others'.

Picard collaborated and corresponded with many scientists, including Newton, Christian Huygens, Römer, Bartholin, Hudde, and even his main competitor, Giovanni Cassini, although Cassini was often less than willing to return the gesture. These correspondences led to Picard's contributions to areas of science outside the field of geodesy, such as the aberration of light he observed while in Uraniborg, or his discovery of mercurial phosphorecence upon his observance of the faint glowing of a barometer. ["Experience faire à l'Observatoire sur la Barometre simple touchant un nouveau Phenomene qu'on y a découvert", "Le Journal des Sçavans" [later: "Journal des Savants" ] , page 126 (25 May 1676). See also: "Sur la lumière du baromètre" [On the light of the barometer] , "Histoire de l'Académie Royale des sciences de Paris", pages 202-203 (1694). For further information, see: Barometric light.] This discovery led to Newton's studies of spectrometry.

Picard also developed the system of right ascension for measuring positions of celestial objects in relation to the Earth.

His book "Mesure de la Terre" was published in 1671.

There is a lunar crater named after Picard, on the northwest quadrant of Mare Crisium.

The PICARD mission, an orbiting solar observatory, is named after Picard.

Footnotes

External links

*MacTutor Biography|id=Picard_Jean
*CathEncy|wstitle=Jean Picard


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  • Jean Picard —     Jean Picard     † Catholic Encyclopedia ► Jean Picard     Astronomer, b. at La Flêche, 21 July, 1620; d. at Paris, 12 Oct., 1682. He was a priest and prior of Rillé in Anjou. As a pupil of Gassendi he observed with him the solar eclipse of 25 …   Catholic encyclopedia

  • Jean Picard — Jean Felix Picard (1620 1682) Jean Felix Picard (* 21. Juli 1620 in La Flèche; † 12. Juli 1682 in Paris) war Priester und Astronom. Picard bestimmte 1669 als Erster die Länge eines Grades eines Meridianbogens und damit die Größe der Erde mit… …   Deutsch Wikipedia

  • Jean Picard — Jean Picard. Jean Picard (La Fléche el 21 de julio de 1620 París, 12 de julio de 1682) Astrónomo y sacerdote francés. Estudió en el colegio jesuita Henry Le Grand. En 1670 realizó la primera medida de un meridiano de Francia lo que proporcionó… …   Wikipedia Español

  • Jean Picard — (La Fléche el 21 de julio de 1620 París, 12 de julio de 1682) Astrónomo francés. En 1670 realizó la primera medida de un meridiano de Francia lo que proporcionó una medida muy exacta del radio de la Tierra y proporcionó una confirmación de la… …   Enciclopedia Universal

  • Jean Picard — Pour les articles homonymes, voir Picard (homonymie). Jean Felix Picard Portrait anonyme Naissance 21 juillet 1620 La Flèche (France …   Wikipédia en Français

  • Jean Picard — Fransk astronom (1620 1682). Kom til Danmark for nøjagtigt at bestemme Uraniborgs gegrafiske position, da denne var af stor betydning ved udnyttelsen af Tycho Brahes astronomiske obeservationer. Udmålte Hvens længde. Tog Ole Rømer med sig til… …   Danske encyklopædi

  • Jean Picard Le Doux — Jean Picart le Doux Jean Picart le Doux, né à Paris le 31 janvier 1902 et mort en 1982, est un peintre français et peintre cartonnier du renouveau de la tapisserie contemporaine. Il est le fils du peintre Charles Picart le Doux (1881 1959).… …   Wikipédia en Français

  • Picard — steht für: Berger de Picardie, aus der Picardie (Nordfrankreich) stammende Hunderasse Johann Hermann Picard, 1857 gegründeter Werkzeughersteller in Wuppertal MusicBrainz Picard, Programm zum automatisierten Ausfüllen von Metadaten zu Musikdateien …   Deutsch Wikipedia

  • Picard — may refer to* the Picard language, a Langue d oïl and one of the languages of FrancePeople known as PicardPicard, meaning a person from Picardy, a historical region and cultural area of France, is a surname, and may refer to:* Alexandre R. Picard …   Wikipedia

  • Picard (name) — Picard is a surname meaning a person from Picardy, a historical region and cultural area of France.People with the surname Picard* Alexandre R. Picard (1985 ), French Canadian professional ice hockey defenseman * Alexandre Picard (ice hockey)… …   Wikipedia


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