Dec. 27, 2013, marks the 442nd birthday of the German astronomer Johannes Kepler. His three laws of planetary motion contributed to our understanding of how the planets move around the sun. But more importantly, they helped lay the groundwork for the English scientist Sir Isaac Newton to develop his theory of gravitation. Kepler also contributed to optics (the study of light) and the study of crystals. He was also one of the earliest writers of science fiction.
Kepler was born in Weil (near Stuttgart), Germany. In college, he learned of the ideas of the Polish astronomer Nicolaus Copernicus. Most scholars at the time believed in geocentrism, the idea that Earth was the center of the universe and that all other objects revolved around it. Copernicus had proposed rather that Earth and all the other planets revolved around the sun, an idea called heliocentrism. After college, Kepler began a lifelong search to work out the underlying principles of planetary motion. He began to exchange letters with the great Danish astronomer Tycho Brahe. Kepler joined as an assistant at Tycho’s observatory in Prague, in what is now the Czech Republic. Kepler was thus able to use the massive library of observations gathered by Tycho to formulate his laws.
Kepler’s discoveries provide a clear example of how scientific breakthroughs often rely on a foundation of earlier work. Kepler was introduced to the teachings of Copernicus. He gained access to the tremendous body of observations made by Brahe. Kepler also heard of discoveries made by the Italian scientist Galileo, made using a new instrument called the telescope. In turn, Kepler’s work went on to influence Newton’s thinking on gravitation. Newton went on to influence a wide variety of scientific fields. As Newton himself once said, “If I have seen further than others, it is because I have stood on the shoulders of giants.”