Galileo (1564-1642) was an astronomer, philosopher, mathematician and physicist, one of the fathers of the scientific revolution. After publishing studies in geometry, mechanics, mathematics, inventing a water pump, the first thermometer, and discovering the law of uniformly accelerated motion (physics), he learned that a lens had been invented in the Netherlands that made it possible to see distant objects. Then he began experimenting with tube lenses. Thus, he managed to make a much better telescope than the Dutch one, since it had six magnifications and not three.
Galileo manufactured 60 telescopes, of different qualities and magnifications. In addition, the telescope was used for maritime and war applications (it allowed us to see approaching ships or armies in the distance, which is why Venice appointed him a professor for life with a good salary). Galileo with him searched the sky, and thus he was the first human being to observe that the moon has valleys and mountains; that Venus has satellites; that the Milky Way is not a cloud but is made up of millions of stars.