Galileo Galilei (1564-1642) was an Italian mathematician, astronomer, and physicist.
He developed the astronomical telescope and was the first to see sunspots, the four main satellites of Jupiter, mountains and craters on the Moon, and the appearance of Venus going through "phases", thus proving it was orbiting the Sun.
In mechanics, Galileo discovered that freely falling bodies, heavy or light, bad the same, constant acceleration (though the story of his dropping cannonballs from the Leaning Tower of Pisa is questionable), and that a body moving on a perfectly smooth horizontal surface would neither speed up nor slow down.
He discovered in 1583 that each oscillation of a pendulum takes the same amount of time despite the difference in amplitude. He i
nvented a hydrostatic balance, and discovered that the path of a projectile was a parabola.
Galileo was born in Pisa, and in 1589 became professor of mathematics at the university there; in 1592 he became a professor at Padua; and in 1610 was appointed chief mathematician to the Grand Duke of Tuscany, Florence.
Galileo's observations and arguments were an unwelcome refutation of the ideas of Aristotle taught at the (Church-run) universities, especially because they made plausible for the first time the heliocentric (Sun-centred) theory of Copernicus.
Galileo's persuasive Dialogues on ike Two Chief Systems of the World in 1632 was banned by the Church authorities at Rome; he was made to recant by the anti-heretical Inquisition and put under house arrest for his last years.
Why is Galileo Galilei famous?
Galileo Galilei was an Italian physicist, mathematician and astronomer who played a major role in the Scientific Revolution.