Building the Galilean telescope
The famous Italian scientist Galileo Galilei, born in 1564, is well known all over the world for his telescope.
He built this instrument using a wooden tube and some fundamental accessories such as lenses coming from the Netherlands, where there were famous opticians.
The telescope was hand-made, in fact Galileo curved a convex lens (diameter 5cm) to make it divergent. Then he put a convergent lens in front of the focus to observe space with its parts, which looked 20 times bigger than before. When the telescope was further developed it enlarged the image 30 times.The image is seen reversed and in order to see it correctly you need a prism, despite it reduces light.
His first observations were about the moon, its surface and movements, finally he came to the conclusion that the Sun was at the centre of the Universe and the Earth turned around it in elliptical orbits and around its own axis.
This new revolutionary theory was based on the experimental method and it replaced the Ptolemaic system.