Johannes Kepler's Accomplishments

Born in December of 1571 in Weil der Stadt of southwest Germany, young Johannes Kepler was a sickly child of poor parents. As a student he was awarded a scholarship to the University of Tubingen, 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 evidence to offer as proof. In 1596, Kepler wrote the first public defense of the Copernican system. This was a dangerous stance, given the Catholic Church deemed such a position heretical in 1615 (they later placed astronomer Galileo Galilei under house arrest for his support of the subject). In search of the most detailed notes about the paths of the planets, and

Astronomers had long struggled to figure out why Mars appeared to walk backwards across the sky. No current model of the solar system — not even Copernicus' — could account for the retrograde motion. Using Brahe's detailed observations, Kepler discovered that the planets traveled in ellipses. The sun didn't sit exactly at the center of their orbit, but instead lay off to the side, at one of the two points known as the foci. Some planets, such as Earth, had an orbit that was very close to a circle, but the orbit of Mars was one of the most widely stretched. The fact that planets travel on elliptical paths is known as Kepler's First Law. Mars appeared to move backward when Earth, on an inner orbit, came from behind the red planet, then caught up and passed

He realized that a planet moved slower farther away from the sun than it did when closer. Once he understood that planets traveled in ellipses, he determined that a line connecting the sun to a planet covered an equal amount of area over the same amount of time. This is Kepler’s Second Law.

Kepler's Third Law was published a decade later, and recognized the relationship between the periods of two planets and their distance from the sun. Specifically, the square of the ratio of the period of two plants is equal to the cube of the ratio of their radius. While his first two laws focus on the specifics of a single planet's movement, his third is a comparison between the orbits of two planets with the same sun.

Though Kepler is best known for his defining laws regarding planetary motion, he made several other contributions to science. He was the first to determine that refraction causes human, and that having two eyes enables depth perception. He created eyeglasses for both near and farsightedness, and explained how a telescope worked. He described images and magnification, and understood the properties of reflection. Kepler claimed that gravity was caused by two bodies, rather than one, and as such, the moon was the cause of the motion of tides on the Earth. Kepler also calculated the birth year of