The first inhabitants of the world were compelled to accommodate their acts to the daily and annual alternations of light and darkness and of heat and cold. In history there are only a few distinguished men who made such a big contribution to astronomy, one of them was Galileo Galilei and his work with the telescope.

When we look at today's telescopes we mainly are working with either Galileo's telescope or Newton's telescope. These men made such a big impact in astronomy and telescopes, that we still use the same types of telescopes invented by these men!

Galileo or his full name Galileo Galilei was an Italian physicist and astronomer. Galileo was born in Pisa on 15 February 1564 and lived 78 years till 1642 when he passed away. In this time he made such advancement in astronomy, that we still know the name Galileo.

Galileo not only made advancements in astronomy, he is also noted with the invention of the thermometer! Galileo Galilei telescope was the first to make observations of the Moon and its crescents, the Sun, planets and stars.

Most of Galileo's time and energy was in mathematics and that is what he spent most of his time. In fact he became professor of mathematics at the University of Pisa in 1589. What made Galileo change from mathematics and physics to a big interest in astronomy was when he heard about the invention of the telescope in Holland in 1609.

From this date, Galileo immediately focused his attention on building his own telescope. Galileo Galilei telescope was put together and he immediately started viewing the heavens. He published his findings in Sidereus Nuncius . The Starry Messenger one year later in 1610. The book was such a sensation throughout Europe that it made Galileo and his telescope famous.

Galileo Galilei telescope and his findings did not always go so rosy however. At that time the common idea held by the church was that the universe revolved around the Earth! Copernicus had a new theory, the Copernican theory that said that the universe does not revolve around the Earth. Galileo held this belief as well, and it caused major outrage with the church. The church declared the view heretical and Galileo was instructed to abandon the Copernican theory.

In 1632 a book was published called Dialogue Concerning The Two Chief World Systems. In the book the Galileo Galilei telescope was used to make the evidence of how the view adopted by the church was wrong. It resulted to Galileo being sentenced to life imprisonment. The sentence was commuted to house arrest for the rest of his life.

Galileo was a great inventor and has given the world some of the greatest inventions. In a Galileo Galilei telescope, the light enters through a tube starting with a convex objective lens. The light focuses even more with a concave lens in the eyepiece, before meeting the eye with a magnified and upright image.

Galileo Galilei telescope is one which we can never forget. It was an invention which showed at his time a planet (Saturn), one which has ears! Within 2 years of the invention of Galileo's telescope, he gave us fairly accurate information on the orbits of 4 of Jupiter's satellites. Galileo also gave us great information on the Sunspots on the sun.