Astronomy #1

2. The time it takes the Earth to revolve is a __.
4. Figured out that gravity holds the planets in orbits.
7. One light year is about 6 __ miles.
8. A huge number of stars orbiting together.
9. The Earth is a sphere orbiting a star. a.k.a. a ________
10. Said the heavens must be perfect circles because they were made by the gods.
14. The plane of the solar system.
15. A bunch of galaxies.
16. A bunch of local groups.
20. All of the super clusters together.
22. One galactic year is about 230 __ Earth years.
23. Apollonius came up with a solution for retrograde motion. __ within circles.

1. The time it takes the Earth to rotate is a __.
3. The average distance from the Earth to the Sun.
5. Reinvented a model of the universe with the Sun in the center.
6. Made an observatory to collect as much data on the visible universe as possible.
8. Used the telescope to definitively show the Earth is NOT the center of the universe.
11. Discovered that the planets orbit in ellipses, not circles.
12. The North Star.
13. The distance light can travel in a year.
17. Used math to show the Earth is likely a sphere.
18. A star with planets around it.
19. First to discover that there are other galaxies.
21. Created the complete Earth-centered model of the universe.