1. Ch. 29 Sec. 1 Overview of Solar System

2. Early Ideas  Humans have watched the sky for thousands of years  Planets change position relative to the stars Easy to recognize the differenceEasy to recognize the difference  Believed to be Geocentric: earth centered  Copernicus in 1543 noticed a difference in movement of planets Heliocentric: Sun centeredHeliocentric: Sun centered

3. Planet Motion  Normal direction of planets is to the east  Occasionally a planet will move in opposite direction Retrograde MotionRetrograde Motion

4. Kepler’s 1 st Law  Kepler used his mentors data on planetary motion Demonstrated that planets move in an ellipseDemonstrated that planets move in an ellipse Kepler’s 1 st LawKepler’s 1 st Law

5. Kepler’s 1 st Law  Eccentricity A planets distance isn’t always the same from sunA planets distance isn’t always the same from sun Perihelion: Closest to sunPerihelion: Closest to sun Aphelion: Furthest from sunAphelion: Furthest from sun Measured from 0 – 1: 0 – circle / 1 - parabolaMeasured from 0 – 1: 0 – circle / 1 - parabola

6. Kepler’s 2 nd Law  An imaginary line sweeps out from sun to planet of equal area in equal amounts of time 2 nd Law2 nd Law2 nd Law2 nd Law

7. Other Discoveries  Galelio Use 1 st telescopesUse 1 st telescopes Discovered 4 moons around JupiterDiscovered 4 moons around Jupiter  Newton Gravity: observed the orbits of planets and moonGravity: observed the orbits of planets and moon Force is directly proportional to massForce is directly proportional to mass

8. Gravity  Force of gravity grows stronger with an increase in mass  Force of gravity grows smaller with increasing distance  Center of mass will be closer to the heavier object