Across
- 4. a circular path that planets follow to demonstrate retrograde motion in Ptolemy's geocentric model
- 5. discovered galaxies outside the milky way and expansion of the universe
- 9. the concept that the earth is the center of the universe
- 11. the planet in our solar system that is moving the fastest
- 12. credited with three laws that explain the orbits of planets
- 14. closest point of approach to the sun in a planet's orbit
- 17. the apparent "backwards" movement of a planet with respect to background stars
Down
- 1. philospher who's work Almagest catalogued the constellations known to ancient greeks and proposed a mathematical model of geocentrism that was accepted for nearly 1500 years
- 2. farthest point of approach to the sun in a planets orbit
- 3. a man known for using his telescope to make many discovered about our solar system
- 5. the concept that the sun is the center of the solar system and planets, including Earth, revolve around the Sun
- 6. discovered a nova or "new star" by carefully recording positions of objects including planets from his island tower observatory
- 7. the attractive force that holds the universe together
- 8. the planet moving the slowest (hint- kepler's 3rd law)
- 10. the shape of planetary orbits proposed in Kepler's first law of motion
- 13. the man given credit for proposing the heliocentric model to "western" culture
- 15. credited with the Three Laws of Motion and Universal Gravitation providing understanding of how planets orbit the sun
- 16. the path a planet takes around the sun