Cassini

Giovanni Domenico Cassini

Born: 8 June 1625 in Perinaldo, Republic of Genoa (now Italy)
Died: 14 Sept 1712 in Paris, France

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Giovanni Cassini was invited to Paris by Louis XIV in 1669 and became director of the observatory there in 1671 becoming a French citizen 2 years later. Cassini was the first to observe Saturn's 4 moons (1671 - 1672 - 1684 - 1684) and he discovered the gap in the ring system of Saturn now known as the Cassini division in 1675.

In 1680 he studied the Cassinian curve which is the locus of a point the product of whose distances from two fixed foci is constant. He worked on this as part of a study of the relative motions of the Earth and the Sun. The lemniscate of Jacob Bernoulli is a member of the Cassinian curves but this was not realised for 100 years.

Cassini also made a measurement of an arc of longitude in 1712 but obtained a result which wrongly suggested that the Earth was elongated at the poles. Twenty four years later Maupertuis obtained the correct result verifying Newton's predictions.

References elsewhere in this archive:

Tell me about the Cassinian Ovals

Tell me about the Lemniscate of Bernoulli

Other Web sites:

Florence, Italy

References:

  1. Dictionary of Scientific Biography
  2. Biography in Encyclopaedia Britannica
  3. B Fontenelle, Éloge de J D Cassini, Histoire de l'Académie royale des Sciences 1712 (Paris, 1714).
  4. T J Herczeg, On Cassini's early 'observations' of Beta Lyrae, Astronomical Society of the Pacific 99 (1987), 186-190. 
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JOC/EFR February 1996