Brahe, Tycho

(1546-1601)

   Danish astronomer, known primarily for his fresh and highly accurate observations of the orbits of the planets. After study at Copenhagen and several German universities, he settled in an isolated castle belonging to his family and devoted himself to scientific work. His earliest major achievement was his careful tracking of a "new star" (a supernova) never previously observed. This object caused great excitement among astronomers; it was bright enough to be seen even by day and remained clearly visible for more than a year. His observations clearly established that it was beyond the moon, thus challenging the prevailing belief that the superlunary universe was perfect and unchanging. His book (1573) reporting these observations caught the attention of astronomers throughout Europe. Other observations by Brahe also challenged traditional astronomy, including his demonstration that the comet of 1577 did not follow the circular orbit required by current theory and cut across several planetary orbits. Brahe's observations also noted many discrepancies between the actual location of planets and their locations as predicted in current planetary tables.

   Although these discoveries confirmed the widespread uneasiness of 16th-century astronomers about traditional astronomy, Brahe found the heliocentric theory of Nicolaus Copernicus too radical and devised an alternative theory (the "Tychonic system") that tried to account for his discoveries without removing the earth from the center of the universe. According to this theory, the other planets revolve about the sun rather than the earth, but the sun and planets still revolve about the earth. Brahe was the last major astronomer to reject the Copernican system, and also the last to function without the assistance of the telescope. Brahe also had elaborate apparatus for alchemical experiments, but little is known about this work. He was a painstaking mathematician, carrying out intricate calculations by lengthy arithmetical procedures since his generation still lacked the mathematical discoveries (logarithms, for example) made in the following century. Because he was compiling fresh experimental data unmatched by any contemporary, the brilliant German mathematician Johannes Kepler accepted his invitation to join him in Denmark and entered his service again when Brahe moved to the court of the Emperor Rudolf II in Prague. Although Kepler disagreed with Brahe's rejection of Copernican astronomy, Brahe bequeathed all of his papers to him when he died in 1601, thus putting into the younger man's hands the vast body of fresh experimental data that became one of the foundations of his books supporting the Copernican hypothesis.