History of Astronomy

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Across
  1. 3. the flatness of an ellipse
  2. 4. geocentric dude from long ag
  3. 5. its launch started Space Race
  4. 6. Ancient Greek dude who thought Sun was center of Universe
  5. 9. the shape of orbits
  6. 16. heliocentric dude who thought orbits were circles
  7. 17. a calendar based on the sun
  8. 19. figured out positions of 777 stars
  9. 21. Earth-centered Universe
Down
  1. 1. dude who figured out the size of Earth
  2. 2. a calendar based on the moon
  3. 7. sun-centered universe
  4. 8. galaxy and redshift dude
  5. 10. P^2 = a^3
  6. 11. US vs USSR name
  7. 12. measured by Newton's version of Kepler's 3rd law
  8. 13. telescope dude who found the moons of Jupiter and phases of Venus
  9. 14. discovered that orbits are ellipses
  10. 15. Ancient Greek dude who thought the Earth was the center of Universe
  11. 18. two of these are in an ellipse
  12. 20. Where a star is positioned on an ellipse
  13. 22. gravity dude