Tycho Brahe, Johannes Kepler and Planetary Motion(2/2)

The first book he wrote was Astronomia Nova, or New Astronomy, in which he developed a concept of planetary movement that had nothing to do with the ideas of the Church. Planets, he thought, were no longer moved by angels, but by a force emanating from the sun. But what this force was, he couldn't say. Kepler's book aroused little attention. Even the famous Italian astronomer Galileo Galilei kept his silence. Kepler was very much a loner with his ideas, but he worked on tirelessly. Then in 1618 everything changed. A bitter internal conflict between Protestants and Catholics in Bohemia quickly escalated into the Thirty Years' War. A year later, Kepler published his Harmonices Mundi, or Harmony of the World, whose title summarizes its content. He detected a harmony in the universe. In it, he added a third law to his other two. This third law was perhaps the most remarkable. It describes a characteristic constant which can be calculated from the orbital period of a planet and the semi-major axis of its elliptical orbit. Kepler's third law is valid for all heavenly bodies orbiting a common central body. The moon shares the same constant, for example, with artificial satellites in Earth orbit. The same is true with a different constant of all the planets, asteroids and comets orbiting the sun. Kepler was now certain he was beginning to understand God's plan of creation, but he did not fall prey to the illusion that his Harmony of the World would be immediately understood. In his preface he wrote, My book may have to wait a hundred years for a reader, for God himself had to wait six thousand years for someone who could penetrate his Word. In fact, it took about fifty years before this reader was found. The English scientist Isaac Newton. Kepler's third law forms the basis of the law of gravity, that Newton published in 1687 in his monumental work, the Principia Mathematica. In it, Newton describes a universal force of attraction which is a property of any body possessing mass. This force explains the movements of the stars, the planets and their moons. Newton was a legend in his lifetime and received a knighthood for his scientific achievements. Kepler, by contrast, was denied fame and social success. Worse still, as a Protestant, he was forced to leave what was now Catholic Prague. But where could he go? The Thirty Years' War was raging throughout Central Europe. The general of the imperial Catholic forces, Wallenstein, offered Kepler a post in the relative security of Sargon in Silesia. But Wallenstein had no interest in astronomy. All he wanted to know was whether the stars were favorable for his military plans. Once again, Kepler was forced to earn his living from horoscopes. But Wallenstein didn't even pay on time, so Kepler got into serious difficulties. He went to Regensburg in the hope of calling in some old debts of his own. There, he fell ill and died on the 15th of November, 1630. He was buried in the Protestant cemetery outside the city. Three years later, the site was laid waste in the confusion of the war. Kepler's work made the Copernican worldview unassailable. Working entirely alone, he succeeded in using Tuchel Brahe's observational data to correctly interpret the movements of the planets. His achievement went unrecognized in his lifetime, but our modern view of the universe is still based on his insights.