Lesson 3: Astronomy after Copernicus
Tycho Brahe
The most important astronomer of the generation after Copernicus was the Danish nobleman, Tycho Brahe. Unlike the modest Copernicus, Brahe was a man who did things in a big way. His home and observatory on the island of Hven, Uraniborg, "the fortress of Urania" (Urania was the Muse of Astronomy) was funded by the Danish crown and has claimed to be Europe’s first scientific research institute.
One of the duties of Tycho for the King was making astronomical forecasts. Oster’s document 3.3 is a defense of astrology by Tycho. At Uraniborg, Tycho and his many followers made the best and most systematic observations ever made with the naked eye, using improved instruments, many of which he designed himself and had built in the instrument shop that was part of the Uraniborg complex.
Uraniborg also included alchemical laboratories and a printing press that printed Tycho’s works. He eventually acquired his own paper mill. Tycho’s observations provided astronomers with the best data to date on the position of the celestial bodies, and Uraniborg itself became famous, an attraction for visitors to Denmark, including royalty. Tycho’s ambition was not merely to accumulate accurate astronomical observations, but to use them as the basis of a new astronomical theory. He knew Copernicus’s theory, but was not impressed by it, as he saw no reason to accept the radically counter-intuitive idea of a moving earth. The "Tychonic" model of the solar system was based on a stationary earth with the moon and sun orbiting it, and the other planets orbiting the sun.
Although the Tychonic system was mathematically equivalent to the Copernican and incorporated some of the advantages of Copernicanism in terms of simplicity, it was not produced all at once by simply inverting Copernicanism. Tycho worked it out over a period of years before he published it in his Of More Recent Phenomena of the Ethereal World (1588).
Tycho’s theory appealed to many astronomers who liked combining the elegance of Copernicanism with the traditional physics based on the stationary earth. The system eventually became the chief rival to Copernicanism in the seventeenth century.
Tycho’s picture of the sun and planets had one important revolutionary effect that Copernicanism, at least as Copernicus had conceived it, did not. It ended the doctrine of the celestial spheres–the intersecting orbits that Tycho’s system required were incompatible with planets carried on solid spheres.
As for Tycho himself, Uraniborg’s downfall was at the hands of the same Danish monarchy that had sustained it. When King Christian IV took power in 1596 at the age of nineteen, he was determined to retrench Danish finances and challenge the power of the great noble families like the Brahes. After a brief struggle, Tycho left Uraniborg and Denmark forever in the summer of 1597. He went to the capital of the Holy Roman Empire, Prague, where the Holy Roman Emperor, Rudolf II, was assembling scientists and magicians at his court.
Tycho was appointed Imperial Mathematician, with a young German astronomer named Johannes Kepler as his assistant and eventual successor. Kepler obtained Tycho’s log of observations after the Dane’s death, and they were the data on which he built his astronomical theories.
