By Tim Lambert
Galileo Galilei was born on 15 February 1564 in Pisa, Italy. (He is one of the few famous people known by his first name rather than his surname). Galileo was the first of 6 or, some say, 7 children. His father was a musician and although the family was fairly well off they were by no means rich.
In 1581 Galileo started studying medicine at Pisa University. However he soon ‘fell in love’ with mathematics and he decided to learn to teach mathematics and philosophy. (Much against his father’s wishes!) Galileo left the university in 1585 and began privately teaching mathematics. He soon gained a reputation as a brilliant mathematician and in 1589 he became a lecturer in mathematics at Pisa University.
At that time the ancient Greek philosopher Aristotle was held in very high esteem and many people accepted his ideas without question. However, Galileo did not. Aristotle said that if two objects, a heavy one and a light one both fall from a height the large one will reach the ground first. According to legend, Galileo tested the theory by dropping two different weights from the leaning Tower of Pisa. Both hit the ground at the same time.
However many people now believe this famous experiment is a myth. In any case, other scholars had already concluded that Aristotle was wrong.
However, Galileo’s criticism of Aristotle irritated the other staff at the university and in 1592 his contract was not renewed. Instead from 1592 to 1610 Galileo taught at the University of Padua.
Galileo never married but he did have 3 children, 2 girls, and a boy.
Then in 1609, Galileo heard of a new invention from Holland. A man named Hans Lippershey (c 1570-1619) had invented the telescope. Galileo made his own telescope and soon improved it.
Using a telescope Galileo was able to see several things invisible to the naked eye. Firstly he could see many stars not visible without a telescope. Secondly, the ancient Greeks believed that the Moon was smooth. Looking through a telescope Galileo could see the Moon’s surface is rough, with mountains and craters. He also discovered 4 small ‘moons’ orbiting the planet Jupiter. At the time these were astonishing discoveries. Until then nobody knew that any of the other planets, apart from Earth, had ‘moons’.
Also in 1610, Galileo discovered that Venus has phases like the Moon.
In 1610 Galileo wrote a book called Sidereus Nuncius or The Sidereal Messenger. Also that year he was made mathematician and philosopher of the Grand Duke of Tuscany (at that time Italy was divided into many small states of which Tuscany was one).
At that time astronomers were debating sunspots. A German named Christoph Scheiner claimed that they were satellites of the sun. In 1613 Galileo argued that sunspots are actually on the surface of the Sun.
Meanwhile, in 1543 a theory by the Polish astronomer Nicolaus Copernicus was published Until his time people believed that the Sun, Moon, and planets orbit the Earth. Copernicus argued that the Earth and the other planets orbit the Sun. At first, the church did not have a problem with his theory. However, opinion gradually hardened and in 1616 the Copernican theory was declared heretical.
There is a passage in the Old Testament where a prophet named Joshua commanded the Sun to stand still in the sky (Joshua 10:12-13). Some scholars said this meant the Sun must move. Of course, Joshua knew nothing about Astronomy. To him, the Sun appeared to move across the sky. Naturally, he would command the Sun to stand still and to him, it would have appeared to stand still. The church’s objection to the Copernican theory was based on a misinterpretation of the Bible.
However, Galileo was a resolute supporter of the Copernican theory. In 1632 he published a book called Dialogue Concerning the Two Chief World Systems. As a result, he was summoned to Rome to be examined by the Inquisition. He arrived in January 1633. Galileo was threatened with torture unless he renounced the Copernican theory. Not surprisingly he agreed to do so. Nevertheless, he was put under house arrest for the rest of his life.
In 1634 Galileo published a book about mechanics called Dialogue Concerning Two New Sciences. Then in 1637, he noticed that the Moon moves slightly from side to side. Unfortunately, in 1638 he went blind. Galileo Galilei died on 8 January 1642 aged 77.