Great Scientists

Galileo Galilei was born in 1564 at Pisa. Galileo began his studies in medicine at the University of Pisa, but soon dropped out, preferring to study mathematics with Ostilio Ricci. In 1592 he obtained the chair of mathematics at Padua, and began working on the inclined plane and the pendulum. By 1598, Galileo believed in the truth of the Copernican theory, as he wrote to Kepler. Around 1604, he began working on astronomy in order to lecture on the new star that had appeared that year.

In 1609, Galileo heard of the telescope while in Venice, and on his return, constructed one for himself. In 1610, Galileo published his telescopic discoveries in The Starry Messenger, and dedicated the four satellites of Jupiter that he had discovered to Cosimo II, Grand Duke of Tuscany, naming them 'the Medicean stars'.

In The Starry Messenger, in addition to the satellites of Jupiter, Galileo reported that the milky-way was a collection of stars and how the moon in fact had a ragged surface like earth. The Starry Messenger was a sensational success, and Galileo became well known throughout Europe.

At the order of the Pope, Galileo was then summoned (February 1616) by Robert Bellarmino to be cautioned against speaking out on behalf of the Copernican claim. Rumours, however, quickly began to circulate that Galileo had been condemned and prosecuted. In defence, Galileo secured from Bellarmino a letter stating that this was not the case but that he had had been notified of the Papal decision to censor Copernicus' De Revolutionibus because a heliostatic claim was contrary to the literal meaning of Scripture.


Galileo duly kept away from writing on cosmological matters, concentrating instead, on applying his discovery of Jupiter's satellites for determining longitude at sea. In 1623 he wrote the Assayer, published by the Academy of the Lynxes and dedicated to Barberini. There, Galileo famously wrote:
             Philosophy is written in this grand book - the universe - which stands continuously open to our gaze. But the book cannot be understood unless one first learns to comprehend the language and interpret the characters in which it is written. It is written in the language of mathematics, and its characters are triangles, circles, and other geometrical figures, without which it is humanly impossible to understand a single word of it; without these one is wandering about in a dark labyrinth.

In September 1632, Galileo was summoned to Rome, where he arrived in January 1633. First the inquisitors tried to get Galileo to admit that he had earlier been officially banned from teaching Copernicus' theory as true, but Galileo produced Bellarmine's letter to contradict this. By then, both Bellarmine (1621) and Cesi (1630) were dead, and Galileo had few powerful patrons left to defend him. A plea bargain to plead guilty to a lesser charge was scuppered, however, when Urban VIII decided in June that Galileo should be imprisoned for life. Galileo was then interrogated under threat of torture, and made to abjure the 'vehement suspicion of heresy'. He was sentenced to life imprisonment. Galileo spent the rest of his life at his home at Arcetri, under house arrest with the archbishop of Siena. At last he died on 8th, January, 1642 at an age of 77 years.