Jacques Cassini

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Jacques Cassini

Jacques Cassini , also referred to as Cassini II, (born February 18, 1677 in Paris , † April 16, 1756 in Thury-sous-Clermont ) was a French astronomer and geodesist who dealt with the earth figure and carried out basic preparatory work for the later performed Carte de Cassini .

Live and act

Jacques Cassini was born in Paris on February 18, 1677, the son of Giovanni Domenico Cassini , director of the Paris Observatory . His parents' apartment was in the observatory, so young Jacques had a close connection with astronomy from childhood . He studied at the Collège Mazarin in Paris, which he left at the age of 14 or 15 with a thesis on optics.

In 1694 he was accepted into the Académie Royale des Sciences . Then his father made a trip to Italy with him to make various astronomical observations and localizations and also to repair the Meridiana built by his father in the Basilica of San Petronio in Bologna . In late 1696 Jacques Cassini traveled to England, where he made the acquaintance of Isaac Newton , Edmond Halley , John Flamsteed and others. On March 23, 1698 he was elected a Fellow of the Royal Society of London .

From 1700 he worked together with his father on the degree measurements or triangulations of the extension proposed by Jean Picard from his meridian arc Paris - Amiens to Perpignan in southern France, which had been interrupted by Colbert's death in 1683. After the death of his father and the death of Louis XIV, he continued this work from 1718 in the north as far as Dunkirk . The measurements led him to the assumption that the polar radius of the earth is larger than the equatorial radius, that the earth is therefore egg-shaped. In contrast, English astronomers under the leadership of Isaac Newton in particular took the view that the earth was flattened at the poles because the earth's rotation had to cause a centrifugal force.

From 1709, when his father's eyesight waned, he increasingly took over his duties at the Paris observatory .

In 1733 he undertook the triangulation of the transverse axis from Saint-Malo to Strasbourg , where he was supported by his son César François . Cassini also obtained from these measurement results a confirmation of his view of the egg shape of the earth. The Académie felt compelled to equip two large expeditions to Peru and Lapland to clarify the issue. The measurements by Pierre Bouguer and Charles Marie de La Condamine in Peru in 1735 and by Pierre de Maupertuis in Lapland in 1736 support the thesis of flattening on the poles. Nevertheless, Cassini denied both the flattening of the earth at the poles and Newton's law of gravity throughout his life , but largely withdrew from public discussion.

The Astronomy gave Cassini valuable impulses through his exact tables of sun , moon , planets and the moons of Jupiter and Saturn , as well as by measuring the proper motion of the fixed stars .

In 1746 he became a foreign member of the Royal Academy of Sciences in Berlin.

In addition to his work as an astronomer, Jacques Cassini was Maître des Comptes from 1710 . In dealing with the disputes, he gained a high reputation, so that he was appointed a member of the Chambre de Justice in 1716.

Cassini had acquired the old Château de Fillerval in Thury-sous-Clermont in 1719 and expanded it into his family's summer residence. When he went back there at the age of 79, his carriage overturned. He died on the following day, April 16, 1756, in his castle as a result of this accident.

His successor as director of the observatory was his son César François Cassini de Thury .

Honors

The lunar crater Cassini was named after him and Giovanni Domenico Cassini .

Fonts (selection)

  • Theses mathematicae de optica propugnabuntur a Jacobo Cassini, ... the… 10 August 1691… in Collegio Mazarinaeo . P. Esclassan, Paris 1691, doi : 10.3931 / e-rara-3659 .
  • De la grandeur et de la figure de la terre . In: Academie Royale des Sciences (ed.): Suite des Memoires de l'Academie Royale des Sciences . Imprimerie Royale, Paris 1720, doi : 10.3931 / e-rara-516 (306 pp.).
  • Méthode de déterminer si la Terre est Sphérique ou non, & le rapport de ses degrés entr'eux, tant sur le Méridiens que sur l'Équateur & ses Paralleles . In: Académie Royale des Sciences (ed.): Histoire de l'Académie Royale des Sciences; Memoires de Mathématique et de Physique . Imprimerie Royale, Paris 1738, p. 71 ( full text in Google Book Search). and there:
  • Seconde method de déterminer si la Terre est spherique ou non, indépendamment des observations astronomiques . S. 255 ( full text in Google Book Search).
  • Éléments d'Astronomie . Imprimerie Royale, Paris 1740, doi : 10.3931 / e-rara-19698 (643 pp.).
  • Tables astronomiques du soleil, de la lune, des planetes, des étoiles fixes, et des satellites de jupiter et de Saturne; avec l'explication & l'usage de ces mêmes tables . Imprimerie Royale, Paris 1740, doi : 10.3931 / e-rara-19698 (222 pp.).
  • Jacob Cassini: Mathematical and precise treatise on the figure and size of the earth, whereby the admirable extension of the midday line of the Royal Observatory in Paris through all of France from one end of the same to the other is particularly clearly described and presented . Translated and with a preface by Johann Albrecht Klimmen. Johann Jacob Beumelburg, Arnstadt and Leipzig 1741 (416 pages, full text in the Google book search).
  • Jean-Philippe de Chéseaux, Jacques Cassini: Traité de la Comète qui a paru en décembre 1743 & en janvier, février & mars 1744 . Marc-Michel Bousquet, Lausanne, Geneva 1744 (308 pp., Digitale-sammlungen.de ).
  • César François Cassini de Thury: Addition aux Tables astronomiques de M. Cassini . Durand, Paris 1756 (98 pp., Digitale-sammlungen.de ).
  • Observation of the eclipse of Mars by the moon, made on the Parisian observatory, on January 18th, 1726. In: Wolf Balthasar Adolf von Steinwehr (ed.): Der Königl. Academy of Sciences in Paris. Physical Treatises, seventh part, which contains the years 1723, 1724, 1725 and 1726. Translated from the French by Wolf Balth. Adolph von Steinwehr . Johann Jacob Korn, Breslau 1751, p. 660 ( full text in Google Book Search).

literature

  • Pierre Demours (Red.): List Chronologique des Observations & Mémoires de M. Cassini… depuis l'année 1731 jusqu'à l'année 1740 inclusivement . In: Académie Royale des Sciences (ed.): Table générale des matières contenues dans l 'Histoire ”et dans les“ Mémoires de l'Académie royale des sciences ”. T5 (1731-1740) . tape 5 . Compagnie des Libraires, Paris 1747, p. 73-77 ( digitized on Gallica ).
  • Pierre Demours (Red.): List Chronologique des Observations & Mémoires de M. Cassini… depuis l'année 1741 jusqu'à l'année 1750 inclusivement . In: Académie Royale des Sciences (ed.): Table générale des matières contenues dans l 'Histoire ”et dans les“ Mémoires de l'Académie royale des sciences ”. T6 (1741-1750) . tape 6 . Compagnie des Libraires, Paris 1758, p. 122–123 ( digitized on Gallica ).
  • Agnes Mary Clerke: Cassini . In: Encyclopædia Britannica . 11th edition. tape 5 : Calhoun - Chatelaine . London 1910, section Jacques Cassini (1677–1756) , p. 459 (English, full text [ Wikisource ]).
  • René Taton: Cassini, Jacques (Cassini II) . In: Charles Coulston Gillispie (Ed.): Dictionary of Scientific Biography . tape 3 : Pierre Cabanis - Heinrich von Dechen . Charles Scribner's Sons, New York 1971, p. 104-106 .

Web links

Individual evidence

  1. ^ Jean-Paul Grandjean de Fouchy: Èloge de M. Cassini (obituary) . In: Académie Royale des Sciences (ed.): Histoire de l'Académie Royale des Sciences . Imprimerie Royale, Paris 1756, p. 134 ( digitized on Gallica ).
  2. ↑ Historical academy members on the website of the Berlin-Brandenburg Academy of Sciences
  3. ↑ Antoine-Joseph warm: Mouy et ses environs: Thury-sous-Clermont . D. Père, Beauvais 1873, pp. 429–450, 433 f ( digitized on Gallica )
personal data
SURNAME Cassini, Jacques
ALTERNATIVE NAMES Cassini II
BRIEF DESCRIPTION French astronomer and geographer
DATE OF BIRTH February 18, 1677
PLACE OF BIRTH Paris
DATE OF DEATH April 16, 1756
Place of death Thury-sous-Clermont