Chapter 8 Crossword puzzle

12345678910111213141516171819202122232425262728293031
Across
  1. 2. years that it took for first surface to form
  2. 4. why stars shine
  3. 7. sun will become a red giant and engulf this
  4. 8. what planets formed through
  5. 9. turns hydrogen into helium
  6. 10. made discovery that universe is still expanding
  7. 14. is just right, keeps water accessible and in one spot
  8. 16. iron sinks to middle and lighter materials form surface
  9. 17. believed heat energy could form complex molecules of life
  10. 20. protects us from uv rays
  11. 23. releases volatile substances and water vapor
  12. 25. Huge rotating aggregations of stars, dust, and gas held together by gravity.
  13. 26. what stars form in
  14. 27. occured 2.5 billion years ago
  15. 28. chemical element that makes up planets, stars, oceans,and organisms
  16. 29. its clear so sun can penetrate
  17. 30. spinning skater that brings their arm in
Down
  1. 1. they are 3.4 -3.5 billion years old and are bacteria-like organisms
  2. 3. oldest rocks on earth
  3. 5. how stars were formed
  4. 6. had an experiment in 1953
  5. 11. included methane, ammonia, co2, and water vapor
  6. 12. star that blows up
  7. 13. provides for gentle tides
  8. 15. early steps of organisms forming organic building blocks
  9. 18. fell for 10 million years
  10. 19. formed in stanley millers experiment
  11. 21. what the sun is
  12. 22. Spiraled galaxy
  13. 24. earth is believed to have formed from these
  14. 31. sun will become this in 6 billion years