Johannes Kepler's Work

When Johannes Kepler was born in the late sixteenth century, scientists believed that planets in the solar system traveled in circular orbits around the Earth. The occasional problem was solved by the addition of miniature circles test — epicycles — to planetary paths. But Kepler not only adamantly defended the idea that planets orbit the sun, he also revealed that their paths were not perfect circles. His descriptions of planetary motions became known as Kepler’s laws.
Born in December of 1571, young Kepler was a sickly child of poor parents. He was awarded a scholarship to the University of Tübingen, where he studied to become a Lutheran minister. While there, he studied the work of Nicolaus Copernicus, who taught that the planets orbited the sun rather than the Earth, though he had no observational evidence to offer as proof.
In 1596, Kepler wrote the first public defense of the Copernican system.
This was a dangerous stance, given that in 1539, Martin Luther, founder of the Lutheran church, derided the theory when he first heard it, while the Catholic church deemed such a position heretical in 1615.
In search of the most detailed notes about the paths of the planets, Kepler contacted astronomer Tycho Brahe. A wealthy Danish nobleman, Brahe built an observatory in Prague where he tracked the motions of the planets and maintained the most accurate observations of the solar system at the time. In 1600, Brahe invited Kepler to come work with him.
Brahe, however, proved to be suspicious and unwilling to share his detailed notes with his assistant. Instead, he assigned Kepler to solve the mystery of Mars, one of the most puzzling problems in astronomy at the time. Ironically, the detailed records of the challenging planet were the tools Kepler needed to understand how the solar system functioned.
When Brahe died in 1601, Kepler managed to acquire Brahe's observations before his family could use them to their financial
benefit.