The Cosmos through the Telescope of Galileo Galeili

He published his findings in Istoria e Dimostrazioni Inround Alle Macchie Solari e Loro Accidenti Rome.

One of his main discoveries is that of the rotation of the Sun, also in contradiction with Aristotle’s principles of perfection and immutability of celestial objects.

He also discovered that Venus has phases, like the Moon. In addition to the phases, an enormous decrease in size and brightness is observed (as indicated in the figure), the only explanation for which is the variation in the Earth-Venus distance, much greater than that derived from the Ptolemaic model.

He also observed that the way in which the phases appeared could only be explained from the Copernicus model, since if the Earth was considered in the center (figure 8) the corresponding phases were completely different from those observed.

With the contributions of Kepler and Galileo, the new model of the universe is established: A heliocentric system with elliptical orbits that follow Kepler’s first two laws, and at the correct distances from the Sun set by the third law that relates them to the periods of revolution ( spin) around the Sun.