GALILEO GALILEI was born in 1564 in Pisa, Italy. He was the eldest of six children and his father was a well known musician. Unfortunately for Galileo, at that time famous musicians were not rich like some are today! Galileo’s father wished for Galileo to be better off than him, so he encouraged Galileo to become a doctor. To the disappointment of his father, Galileo decided to follow his passions and to study mathematics.
Galileo was unlike most other people because he questioned everything that he was taught. Galileo would think whether or not something made any sense to him rather than just believing what his professors and books said. At that time most people just accepted that Aristotle's (a famous philosopher from Ancient Greece) theories were correct. Aristotle said that all objects, no matter how big or heavy they were, fell from a height at the same speed. Galileo decided to put this theory to the test.
It's said that Galileo went to the top of the Leaning Tower of Pisa and dropped two steel balls of different masses. Both hit the ground at the same time! Galileo asked himself: "If Aristotle was wrong about this, then are there other things he may have been wrong about too?"
In 1609 Galileo heard about a new invention that helped people see further. This new invention was known as the "Dutch Spyglass" (because it was invented in Holland) and could make distant objects appear much nearer. The Spyglass consisted of a wooden tube, with two different types of lenses at either side. When used together, the lenses magnified objects to about three times their size! Galileo was very excited at the thought of this new invention.
"Imagine if the planets and stars appeared six, seven or eight times larger. Imagine what new things I might discover!"
Galileo set off to try and improve the magnification of the spyglass. He began to make his own lenses. Eventually Galileo had improved the spyglass so much that he was able to see objects twenty times closer! This was the beginning of an exciting journey for Galileo. Galileo’s telescope allowed him to see objects that were very far away such as planets and moons that no one had ever seen before. Over the weeks, months and years that followed, Galileo made several discoveries that would change people's understanding of the Universe for ever!
Galileo made one of his most important discoveries while observing Jupiter during the winter of 1610. When Galileo looked through his telescope he saw three stars huddled around Jupiter. The following nights he noticed something very strange about the stars; instead of moving with all the other stars in the sky, they moved in the wrong direction! After observing the stars every night for about a week, Galileo also noticed that the stars always appeared to stay close to Jupiter in the sky. This was something that Galileo had never seen before! Stars always moved in the same direction across the sky. After a lot of careful observation Galileo realised that he hadn't been looking at stars through his telescope at all. Galileo had discovered the first moons outside of the Earth's orbit! These worlds were actually in orbit around Jupiter, not the Sun!
Galileo didn't stop there! He continued to observe the night sky with his new telescope. At that time most people thought that the heavenly bodies were perfect and unchanging. Galileo was the first person to discover that the Moon was covered in craters and mountains. He also discovered that the Sun was covered in dark patches, called "Sun spots". Galileo had discovered that the heavens were not so perfect after all!
Another unexpected discovery! He noticed that Venus had phases just like the Earth's moon. Galileo knew that this would only be possible if Venus went around the Sun and not the Earth.
It seemed clear now to Galileo that the Sun was the centre of the Solar System. Galileo realised that the Earth was just another planet going around the Sun.
When the Church heard about Galileo's discoveries they were not happy. Galileo's ideas were a challenge to the authority of the Catholic Church, who taught that the Earth was the centre of the Universe and the Sun went around the Earth. In 1632 Galileo wrote a book called ‘Dialogue Concerning the Two Chief World Systems’. In the book three characters had a conversation on the Geocentric and Heliocentric models of the Universe and which was right. Though Galileo claimed the book was neutral, it was not. Instead the book clearly supported the Heliocentric theory. This angered the Church who had ordered Galileo not to teach the Heliocentric theory. Galileo was sentenced and put under house arrest until his death in 1642. While under house arrest Galileo continued his quest for knowledge and understanding. He even had a couple of books published!
Today Galileo is thought of as one of the great scientists and is recognised for his role in advancing human understanding of the Universe. In 1989 NASA Launched a space probe named in honour of Galileo, which explored Jupiter and its moons. The same moons that Galileo and his amazing telescope had discovered more than 300 years before!