facts about the world

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Across
  1. 4. hold hands while sleeping so they don't float away
  2. 5. time a trip to mars would take
  3. 7. the sun is this many times bigger than the earth
  4. 11. alyssa dressed as this person yesterday
  5. 13. time it takes the sun's light to reach earth
  6. 15. closest state to russia
  7. 17. location of world's largest known cave system, Mammoth cave
  8. 18. first us president
  9. 19. closet galaxy to ours
Down
  1. 1. only known birds to fly backwards
  2. 2. 186,282 miles per second
  3. 3. fourth longest river in the world
  4. 6. our galaxy
  5. 8. constant acceleration, keeps feet on the ground
  6. 9. discovered special relativity
  7. 10. believed to have killed the dinosaurs
  8. 12. are there more grains of sand or stars in universe?
  9. 14. an object so dense, it collapses in on itself
  10. 16. can sleep for 22 hours a day