Galileo Galilei was born on 15 February 1564 in Pisa, Italy. From childhood, he showed a keen interest in mathematics and natural philosophy, though his father, Vincenzo Galilei, wanted him to become a medical doctor. Accordingly, Galileo enrolled for a medical degree at the University of Pisa in 1581, but he never completed it because of his stronger interest in mathematics.
In 1586, Galileo wrote his first scientific book, The Little Balance (La Balancitta), in which he described Archimedes’ method of finding the relative densities (specific gravities) of substances using a balance. In 1589, in his series of essays titled De Motu, he presented his theories on falling objects, using an inclined plane to slow down the rate of descent.
In 1592, Galileo was appointed Professor of Mathematics at the University of Padua in the Republic of Venice. There, he continued his studies on the theory of motion and, through experiments with inclined planes and the pendulum, formulated the law of uniformly accelerated motion, stating that the distance travelled by an object is proportional to the square of the time taken.
Galileo was also a remarkable craftsman. He developed a series of telescopes with optical performance far superior to those available at the time. Around 1640, he designed the first pendulum clock. In his book Starry Messenger, he described his astronomical discoveries, claiming to have observed mountains on the Moon, the Milky Way composed of tiny stars, and four small bodies orbiting Jupiter. In his works Discourse on Floating Bodies and Letters on the Sunspots, he recorded his observations of sunspots.
Using his own telescopes and observations of Saturn and Venus, Galileo argued that all planets orbit the Sun and not the Earth, contrary to the beliefs of that period.