chapter 7 and 8

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Across
  1. 4. our galaxy is know as
  2. 8. connects the polar ocean waters
  3. 11. layer that protects us from UV
  4. 16. estimated number of galaxies
  5. 17. ocean used as a trade route between africa and asia
  6. 18. why stars shine
  7. 19. clumping smaller particles into larger masses
  8. 20. continent of south pole
  9. 22. discovered red shift
  10. 23. Early steps of organisms forming from organic building blocks
  11. 25. oldest rocks found in austalia
  12. 29. the largest ocean
  13. 31. are aggregations of gas and dust which may be several hundred kilometers in diameter
  14. 33. percentage that the Atlantic covers earth
Down
  1. 1. huge rotating aggregations of stars, dust, and gas held together by gravity
  2. 2. a theory on beginning of univerese
  3. 3. years the accretion period lasts
  4. 5. how old are the oldest fossils
  5. 6. the star that gives earth heat
  6. 7. includes all the countries south of panama
  7. 9. percent of ice that covers earth
  8. 10. a super nova explosion is also known as
  9. 12. the sun is what kind of star
  10. 13. smallest continent
  11. 14. release of volatile substances and water vapor
  12. 15. theory on how stars and planets were formed
  13. 21. Star’s core will eventually collapse in an explosion
  14. 24. person who experimented in 1953
  15. 26. suggested that heat energy from thermal vents in the sea could have formed into complex molecules of life
  16. 27. amount of years it took for rain to eventually form oceans
  17. 28. the first surface formed how many years ago
  18. 30. the smallest ocean
  19. 32. massive spheres of incandescent gas