Born: December 27, 1571                                                                                                Died: November 15, 1630

    Johannes Kepler was a German mathematician and astronomer. He is sometimes known as the founder of celestial mechanics and the first "natural laws." Kepler is best known for his Three Laws of Planetary Motion and the discovery of elliptical orbits.

Some other important information:

• Kepler was the first to explain how a telescope works.
• He explained that the moon caused tides.
• He hypothesized that the Sun rotates around an axis.

Kepler's First Law: Planets move in ellipses around the Sun. Before Kepler, people thought that planets moved in perfect spherical circles.

Kepler's Second Law: The radius vector describes equal areas in equal times.

Kepler's Third Law: The square of the periodic times are to each other as the cubes of the mean distances. This is thought to be the law that Sir Isaac Newton's Law of Gravity is based upon.

The above picture is used to explain the relative distance of the planets from the Sun in the Corperican System.

References:
http://es.rice.edu/ES/humsoc/Galileo/People/kepler.html
http://www.kepler.arc.nasa.gov/johannes.html
http://csep10.phys.utk.edu/astr161/lect/history/kepler.html