Galileo Galilei (1564-1642) was a great Italian mathematician and astronomer.
Galileo was born in Pisa on 15 February 1564, in the same year as William Shakespeare.
The pendulum clock was invented by Galileo after watching a swinging lamp in Pisa Cathedral in 1583.
Galileo’s experiments with balls rolling down slopes laid the basis for our understanding of how gravity affects acceleration (speeding up).
Learning of the telescope’s invention, Galileo made his own to look at the Moon, Venus and Jupiter.
Galileo described his observations of space in a book called The Starry Messenger, published in 1613.
Through his telescope Galileo saw that Jupiter has four moons (see Jupiter’s Galilean moons). He also saw that Venus has phases (as our Moon does).
Jupiter’s moon and Venus’s phases were the first visible evidence of Copernicus’ theory that the Earth moves round the Sun. Galileo also believed this.
Galileo was declared a heretic in 1616 by the Catholic Church, for his support of Copernican theory. Later, threatened with torture, Galileo was forced to deny that the Earth orbits the Sun. Legend has it he muttered `eppur si muove’ (`yet it does move’) afterwards