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Giovanni Cassini studied at the Jesuit college in Genoa and then at the abbey of San Fructuoso.
From 1648 to 1669 Cassini observed at Panzano Observatory and, in 1650, he became professor of astronomy at the University of Bologna.
Cassini observed a comet in 1652-3 and again 1664-5 publishing details of his observations. His interests however were many other than astronomy. He was an expert in hydraulics and engineering and was consulted regarding the flooding of the river Po. He was employed by the Pope to oversee fortifications and worked for the Pope also as an expert on river management.
Cassini was invited to Paris by Louis XIV in 1669. The senate of Bologna and the Pope agreed to the trip which they believed was only to be a short one. However Cassini became director of the Paris Observatory in 1671, becoming a French citizen two years later. He never returned to Italy.
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 (6 books/articles)
References elsewhere in this archive:
Tell me about his part in the longitude problem
Tell me about the Cassinian Ovals
Tell me about the Lemniscate of Bernoulli
Giovanni Cassini was elected to the Royal Society of London in 1672. You can see a history of the Royal Society and a list of the members among the mathematicians in our archive.
There is a Crater Cassini on the moon (named after this mathematician, among others). You can see a list of lunar features named after mathematicians.
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