
I. Brahe
Background
 a. Copernicus not a great impact right away, but doubts of Ptolemy were growing
 b. Johannes Kepler was next to destroy geocentric idea, but it was not possible without Tycho Brahe’s material

III. Brahe
Possession
 a. Allowed possession of an island near Copenhagen by King Frederick II
 i. On it, he built Uraniborg Castle with a library, observatories, and instruments for astronomy

III. Brahe
20 years
 a. 20 years: he compiled a detailed record of his observations of positions and movements of stars and planets= accurate up to that time
 i. Data led to rejection of AristotelianPtolemaic system
 ii. Also unable to accept Copernicus’ suggestion that earth actually moved

III. Brahe
Last years
 a. Last years in Prague as imperial mathematician to Emperor Rudolf II, who was interested in astronomy, astrology, and the Hermetic tradition
 i. While in Prague, he had Kepler as assistant

I. Kepler
Studies
 a. Destined for career as Lutheran minister
 b. Studied theology and influenced by Michael Mastlin, Germany’s bestknown astronomer, and pursued interests in mathematics and astronomy
 i. Abandoned theology and taught math and astronomy in Graz, Austria
 c. Work shows line between magic and science in early Revolution

I. Kepler
Interests
 a. Interested in Hermetic mathematical magic
 i. In a book written in 1596, he elaborated on his theory that the universe was constructed on basis of geometric figures, like the pyramid and the cube
 Believing that the harmony of the human soul was mirrored in the numerical relations existing between the planets, he focused on discovering “music of the spheres”

I. Kepler
Brilliant mathematician
 a. Brilliant mathematician and astronomer and succeeded Brahe as imperial mathematician to Rudolf II
 i. Gained possession of Brahe’s detailed astronomical data and used them to get three laws of planetary motion
 1. Confirmed his interest in the “music of the spheres” and confirmed Copernicus’ heliocentric theory with some modifications

I. Kepler
Laws
 i. First two laws of planetary motion published in 1609
 1. At Tubingen, he accepted Copernicus’ heliocentric idea, but first law rejected Copernicus by showing that the orbits of the plants were elliptical rather than circular, with sun at one focus of ellipse, not center

I. Kepler
Second Law
 1. Second Law demonstrated that speed of a planet is greater when closer to sun and decreases with distance from sun
 a. Destroyed Aristotle idea that motion of planets was steady and unchanging

I. Kepler
Laws: Third
 i. Ten years later, Third law established that the square of a planet’s period of revolution sis proportional to the cube of its average distance from the sun
 1. Planets with larger orbits revolve at a slower average velocity than those with smaller orbits

I. Kepler
Three Laws
 a. Three laws effectively eliminated the idea of uniform circular motion and idea of crystalline spheres revolving in circular orbits
 i. Basic structure of Ptolemaic system disproved and people free to think in new ways about actual paths of planets revolving around sun in elliptical orbits

I. Kepler
End of life
 a. End of life, Ptolemaic system was losing ground
 i. Questions unanswered: what planets are made of an explanation of universe’s motion

