Orazio Grassi was born in Savona in 1583 and died in
Rome in 1654. He was a Jesuit, a mathematician and an architect well known
in history for his strong ideologic battle against
Galileo Galilei about the comets origin. The book in which he disputed his
thesis was Libra Astronomica et
Philosophica published in 1619. The occasion was the
discovery of three comets in 1618, one of which was particularly bright:
these visions brought up in all astronomers the will to formulate original
theories on the comets origin. Galileo had a bright as much as fanciful
idea: according to him a vanishing substance had to evaporate from the
Earth and to be lightened by the Sun to give birth to a comet! Orazio
Grassi was the only one that at first objected harshly to his theory ...and history gave him reason. Grassi had in fact focused the argument
with a theory that unconsciously took again all the points that will be
demonstrated by Newton and Halley two centuries later.A large and lively
correspondence between the two protagonists, where offences and
imprecations are at large, testifies the struggle of the disputation: our
Grassi used the pen-name of Lothario Sarsi, while Galileo published Il
Saggiatore, his most important essay on the subject.
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