Ch. 8 Crossword

3. what happens when a star's core collapses
4. what specific kind of water do scientists look at in the ocean and in comets to see if the proportions match
8. our galaxy
10. based o scientific research, 6 billion years from now, the Sun will ___ from engulfing other planets
11. material scientists look at to determine the age of Earth's crust
13. during the time when the Earth was mostly molten, what type of element sank to the center of Earth
14. responsible for the formation of Earth's gravitational field
15. Earth formed ___ billion years ago
16. a miniature planet
17. discovered that distant galaxies and stars are receding from the Earth in all directions
18. where was life believed to have started
20. mixed the early atmosphere gases in a closed container with a spark
22. what caused the first clouds to form
24. oldest fossils are ___ billion years old of bacteria-like organisms

1. what planet is believed to have had a magnetic field that disappeared when its core cooled
2. suggested that heat energy from thermal vents in the sea could have formed into complex molecules of life
4. these elements where the most abundant after the Big Bang
5. theory of how the universe was created
6. the first organisms on Earth were similar to ___
7. early steps of organisms forming from organic building blocks
9. how our planet solidified
12. the Earth and ocean are an indirect result of a solar ___
19. the sun with theoretically turn into a ___ in 6 billion years
21. after the primordial clouds cooled, they formed water droplets and it rained for ___ million years
23. there were at least islands of continental crust on Earth ___ billion years ago