Across
- 1. His laws describe planetary orbits
- 5. Planets appear to go backward
- 6. Force that pulls masses together
- 9. Velocity needed to leave orbit
- 10. Oval path of a planet
- 13. Physics of motion and gravity
- 15. Made of massive ancient stones
- 16. Resistance to changing motion
- 19. Greek who backed Earth-centered cosmos
- 20. Native American sky-aligned stone circle
- 21. Uses radio waves to find distances
- 22. Sun-centered
- 25. Study of the universe as a whole
- 26. Space where gravity acts
- 27. Earth-centered with epicycles
- 30. Put the Sun at the center
- 31. – Not held by gravity anymore
- 33. Shift in position from a new viewpoint
- 35. A push or a pull
- 37. Gravity and motion laws guy
- 38. How big something looks in the sky
- 39. Ancient stones that track the Sun
Down
- 2. Small orbit riding a larger orbit
- 3. Long half of an ellipse
- 4. Sun in the middle
- 7. Strength fades with distance squared
- 8. Saw moons of Jupiter through a telescope
- 11. One of two points in an ellipse
- 12. Earth-centered view of cosmos
- 14. Speeding up or slowing down
- 17. Earth-Sun distance measure
- 18. Gold nose charted stars pre-telescope
- 23. Makes the Moon look huge on horizon
- 24. Epicycles master; refined Earth-based model
- 28. Ancient heliocentric thinker
- 29. Shift from Earth to Sun center
- 32. Glowing gas clouds in space
- 34. Orbits a planet or moon
- 36. Large circular paths in old models