Gian Cassini Biography

Gian Cassini was an important astronomer of the seventeenth and eighteenth centuries, and made many lasting contributions to the development of modern astronomy. Born in 1625 in France, Cassini studied mathematics, engineering, astronomy, and astrology, but worked primarily through his life in astronomy and astrology. Cassini’s interest in these areas was apparent from an early age, as he studied at a Jesuit college in Genoa and an abbey in San Fructuoso. Cassini’s skill and interest in the heavens attracted the patronage of many supporters, who financed his work or taught him valuable skills. Among them were the astronomer and senator Marquis Cornelio Malvasia, who later encouraged the senate of Bologna to commission Cassini to take a year long trip to Paris, France, to help construct the Paris Observatory.  Cassini, however, opted not to return, and stayed in France until his death in 1712. During this time he met and married his wife, Genevieve de Laistre, who granted him an impressive dowry of valuable land, and came to be known as Jean Dominique Cassini. Cassini also made many of his greatest achievements while in France, which surprisingly often had nothing to do with astronomy or astrology. Notably, he conducted negotiations between Bologna and Ferrara over control of the Po River, created memoirs on flooding and avoiding it, and conducted hydraulics experiments.

Cassini’s expertise also led him to make many breakthroughs in engineering and astronomy. He used triangulation to create the first topographic map of France, revealing it to be smaller than previously thought. He made a great number of observations regarding Saturn, including discovering four of Saturn’s moons and their lengths of rotation, discovering Spots and bands on the planet, and finding a new segment of rings, later named the Cassini Division after  him. Cassini devised a series of laws, known as Cassini’s Laws, which describe the motion of the moon. While these laws were not perfectly accurate, they were significant in their time and have since been adjusted to describe other satellites, and even planets. Perhaps most notably, Cassini, along with fellow astronomers, made great strides in mapping the distances of the universe by estimating the Astronomical Unit. This was done by sending a fellow astronomer to French Guyana and taking simultaneous observations of Mars from the two different locations, using this data to determine the distance between Mars and Earth. Although relative distances had already been found, the acquisition of exact values allowed for precise distances to be calculated as never before.

Cassini’s legacy has lived on to the present day, and continues to influence modern astronomy. Starting from a young age, Cassini devoted much of his life to understanding the universe, stopping only when afflicted by blindness before his death. Much of his work was continued by his son and grandson, who themselves became notable astronomers. His name lives on in the Cassini satellite, launched to investigate Saturn.