2. By: Maxine Huang and Zoha Momin

3. History Of Johannes Kepler Kepler was a German astronomer and mathematician. He discovered the three laws of planetary motion. His laws described the motions of the planets around the sun.

4. Kepler’s Three Laws 1. Every planet follows and elliptical orbit that is determined by points on either side, called foci. 2. The area swept by an imaginary line connecting the center of the sun to the center of the planet the line sweeps out the same area in the given time. (planets move faster when closer to the sun) 3. The planet’s period is the time it takes to make a revolution. The square of the planet’s period is proportional to the cube of its distance from its average distance from the sun.

5. History of Tycho Brahe Brahe was a Danish astronomer. He was born in 1546 and died in 1601. Tycho made a systematic way to observe the planets and stars. He emphasized the importance of making observations on a regular basis. He attended various universities in Denmark, Germany, and Switzerland because he was nobility.

6. Brahe's Astronomy Brahe’s Observations of planetary motion showed that current tables used to the planets’ positions was incorrect. He spotted a supernova, which helped disprove the common idea that no change could possibly occur beyond the orbit of the moon. Tycho's theory was that the Earth and other planets revolved around the sun. Tycho’s Observations helped the later German Astronomer and Mathematician, Kepler, in his work. Tycho used his naked eyesight, astrolabes, and quadrants to make his observations.

7. Brahe’s Astronomy (contd.) Tycho refused to believe that the earth and the other seven planets revolved around the sun. He thought if the Copernican Theory was true he should have been able to measure it with his instruments but he was unaware that these changes were too small for his instruments to detect.

8. Tycho Brahe Brahe, his apprentices, and instrumentsTycho Brahe posing for a portrait.

9. Johannes Kepler Johannes Kepler posing for a picture in France in the year of 1607.

10. Comparison: Johannes Kepler Tycho Brahe Born in 1571 German Person Mathematician Confirmed The Copernican Theory Born in 1546. Danish Person Refused to accept the Copernican Theory Nobitlty Both: Astronomers From 16 th century

11. Resources White, Raymond E. "Brahe, Tycho." World Book Advanced. 2009. [Place of access.] 15 May 2009. Brahe, Tycho." ClassicLayout. 2009. World Book, Inc.13 May 2009.. “Kepler, Johannes”.(2009). In Compton’s by Britannica. Retrieved May 14, 2009, from Encyclopædia Britannica Online.