Galileo Galilei was the first person to observe physical details about the bodies in the solar system and define their relationships to one another. Galileo is credited with vastly improving the design of the telescope, allowing him to make more nuanced observations about the solar system.
Galileo was born in Italy in 1564. In 1589, he was appointed chair of mathematics at the University of Pisa, and it was there that he made many of his important astronomic observations. Most notable among his accomplishments was providing an observable, physical demonstration that the Earth and other planets orbited the sun. This was considered essential to the acceptance of the Copernican model of the solar system that had been introduced in the 16th century.