2. Copernicus’s Model  Many scientists believed our Earth was the center of the solar system, this theory is called geocentric  Copernicus first proposed our solar system was heliocentric – suncentered

3. Geocentric vs. Heliocentric  Geocentric  Heliocentric

4. Kepler’s Laws 1 st law- Law of Ellipses 2 nd law- Law of Equal Areas 3 rd law- Law of Periods

5. Law of Ellipses- The orbit of every planet is an ellipse (oval shape) with the Sun at one of the two foci.orbit planetellipsefoci

6. Law of Equal Areas- A line joining a planet and the Sun sweeps out equal areas during equal intervals of time.line

7. Law of Periods- The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit. (measures how long on avg. it takes for the planet to make it around the sun).square orbital period proportional cubesemi-major axis

8. Newton’s Applications of Kepler’s Laws  Newton explained why the planets move.  He created his own laws which explained why the planets keep moving around the sun.  He theorized that “gravity” and “inertia” caused the planets to keep moving