Across
- 2. Which one of Kepler's laws states that planets orbit in ellipses?
- 4. Kepler's teacher who provided him with data for his planetary motion laws
- 6. a dead star that has fallen into itself and generated a great gravitational pull
- 8. discovered 3 laws of planetary motion
- 10. satellite that causes tides on Earth
- 11. area around a mass where its gravitational pull can be felt
- 15. this person discovered that gravity is universal
- 17. this occurs when an upward force balances the downward pull of gravity
- 20. force that pulls things towards the center of a mass
- 21. closest path to the Sun when a planet is in orbit
- 22. Newton's theory of gravity confirms this man's theory of the solar system
Down
- 1. speed needed to break the pull of Earth's gravity and begin orbit
- 3. farthest path from Sun when a planet is in orbit
- 5. object that orbits another in space
- 7. Kepler law that says planet orbit speed isn't constant
- 9. time it takes to complete one orbit
- 12. alleged fruit that fell and lead Newton to his theory of gravity
- 13. fixed point on an ellipse
- 14. do the gravity field lines point inward or outward?
- 16. discovered the value for G in Newton's Law of Universal Gravitation
- 18. Kepler law that relates the period of planet orbit to its radius of orbit
- 19. all planets orbit the Sun in this shaped path