1. RAP 1. _____sun centered view of the solar system 2._____keeps a tornado going 3. _____discovered sunspots, Venus has phases, 4 moons of Jupiter 4. _____ earth centered view of the solar system 5. _____formed 4.5 billion years ago

2. Key Questions 1. What is gravity? 2. What two things does gravity depend on? 3. What is an ellipse? 4. What is inertia? 5. Why don’t planets fly off into space? 6. Why do planets continue to revolve around the sun? 7. What two factors act together to keep the planets in orbit around the sun?

3. ` 1. Gravity-force that attracts objects to one another 1. Gravity-force that attracts objects to one another 2. distance -closer together more gravitational pull 2. distance -closer together more gravitational pull mass –more mass more gravitational pull mass –more mass more gravitational pull 3. Ellipse-egg shaped path 3. Ellipse-egg shaped path 4. Inertia-tendency of planets to keeping doing what they have been doing 4. Inertia-tendency of planets to keeping doing what they have been doing 5. gravity keeps planets from flying off into space 5. gravity keeps planets from flying off into space 6. inertia keeps planets revolving around the sun 6. inertia keeps planets revolving around the sun 7. gravity and inertia keep planets orbiting the sun 7. gravity and inertia keep planets orbiting the sun