Kepler

            
             He was a german astronomer and a natural philosopher, noted for formulating and verifying the three laws of planetary motion. These laws are now known as Kepler's Laws.
             Kepler held the chair of Astronomy and Mathematics at Graz University from 1594 until 1600, when he became assistant to the Danish astronomer Tyco Brahe in tn the latter's observatory near Prague. On the death of Tycho in1601, Kepler assumed his position as imperial mathematician and court astronomer to Rudolf II, Holy Roman emperor.
             Kepler was able to derive from the notes of Tycho, a detailed picture of the path of the planet Mars. Whereas all previous investigators had struggled to fit the planetary paths to circles, Kepler, by using Tycho's superb data was able to show that Mars did not move in a circular path, but rather in an elliptical one.
             The shape of an ellipse is described by its long and short dimension called its major and minor axes, respectively. Kepler's discoveries of the nature of planetary motions are expressed in what are known today as Kepler's Three Laws. These laws describe the essential features of planetary motion around the sun. They also describe not only the shape of a planet's path, but also its speed and distance from the sun.
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             *The above drawing is a copy of Kepler's notes on the planetary movement of Mars. The following pages are Kepler's Three laws and the explanation of what an ellipse is and its parts.
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             As for Kepler's Laws, they have an additional significance. Kepler's Laws are the first mathematical formulas to describe the heavens above and change the way man thinks about space and beyond.