Giovanni Domenico Cassini - Astronomy and astrology, Engineering, Named after Cassini
Astronomer, born in Perinaldo, NW Italy. In 1650 he became professor of astronomy at Bologna, and in 1669 the first director of the observatory at Paris. He greatly extended knowledge of the Sun's parallax, the periods of Jupiter, Mars, and Venus, and was the first to record observations of zodiacal light. In 1684 he discovered two natural satellites of Saturn, Dione and Tethys. Cassini's division (the gap between two of Saturn's rings) is named after him, and Cassini's laws, describing the rotation of the Moon, were formulated in 1693. He was succeeded as director at Paris by a dynasty of Cassinis.
Astronomy and astrology
Cassini was an astronomer at the Panzano Observatory, from 1648 to 1669.
Along with Robert Hooke, Cassini is given credit for the discovery of the Great Red Spot on Jupiter (ca.
Cassini was the first to make successful measurements of longitude by the method suggested by Galileo, using eclipses of the satellites of Jupiter as a clock.
In 1644 the Marquis Cornelio Malvasia, who was a senator of Bologna with a great interest in astrology, invited Cassini to Bologna and offered him a position in the Panzano Observatory which he was constructing at that time.
In 1669 Cassini moved to France and through a grant from Louis XIV of France helped to set up the Paris Observatory which opened in 1671; While in France Cassini also served as the court astronomer/astrologer of Louis XIV ("The Sun King") for forty-one years, serving the expected dual role yet focusing the overwhelming majority of his time on astronomy rather than the astrology he had studied so much of in his youth.
During this time, Cassini's method of determining longitude was used to measure accurately the size of France for the first time. The country turned out to be considerably smaller than expected, and the king quipped that Cassini had taken more of his kingdom from him than he had won in all his wars.
Engineering
Cassini was employed by Pope Clement IX in regard to fortifications, river management, and flooding of the Po.
The Pope asked Cassini to take Holy Orders to work with him permanently but Cassini turned him down because he wanted to work on astronomy full time.
In the 1670s, Cassini begun work on a project to create a topographic map of France, using Reiner Gemma Frisius's technique of triangulation. The project was continued by his son Jacques Cassini and eventually finished by his grandson Cassini de Thury and published as the Carte de Cassini in 1789 or 1793.
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