Tycho Brahe (1546–1601)

Tycho Brahe

Tycho Brahe was a Danish astronomer who was well known for his accurate measurements of the heavens. He saw the benefits of both the Copernicus model and Ptolemy's model. He proposed a model that was a combination of the two. He assumed that the earth was stationary and was located at the center of the universe. The sun and the moon revolved around the earth. The other five planets revolved around the sun. Figure 9 shows his model (without epicycles).

Figure 9: Planetary model of Tycho Brahe.

It is not obvious, but it can be shown that Tycho Brahe's model is mathematically equivalent to the Copernicus model. Therefore, they have the same accuracy. The model of Tycho Brahe had the advantage of being consistent with Ptolemy's intuitive arguments for a stationary earth. Thus, at this point in history, belief in an earth-centered universe was still a very rational position.