Astronomy crossword puzzle

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Across
  1. 1. Something that pushes or pulls
  2. 3. The tendency of a body at rest to remain at rest and a body in motion to stay in motion
  3. 5. Maker of the geocentric model
  4. 6. The relationship between the distance of planets from the sun and their orbital periods
  5. 8. Proposed the heliocentric model
  6. 10. Places the sun at the center with earth orbiting
  7. 13. A line from the sun to the planet sweeps out equal areas in equal times
  8. 14. The universal force that acts on all objects in the universe
  9. 15. The amount of matter an object contains
Down
  1. 2. Made the theory of relativity
  2. 4. Measured the circumference of the earth
  3. 7. Places the earth at the center of the universe
  4. 9. Nonuniform motion a change in speed either increasing or decreasing
  5. 11. Discovered the law of universal gravitation
  6. 12. Planets move in elliptical orbits with the sun at one focus of the elipse