THE BIG BANG

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Across
  1. 3. Big groups of stars connected by gravity.
  2. 5. After a few minutes, protons and neutrons joined to form _______________ of hydrogen and helium.
  3. 6. What did atoms that formed gases and then became very hot and liberated energy and light become?
  4. 8. The balloon experiment shows how the universe is still__________________.
  5. 12. Atoms formed around 300_______________years after the big bang.
  6. 13. The science of the origin and development of the universe.
  7. 14. A well-thought out explanation for what has been observed in the world.
  8. 15. The universe came into existence some 13.8________________ years ago.
Down
  1. 1. What formed when a solar nebula collapsed about 10 billion years ago?
  2. 2. The first elements formed: Hydrogen and ______.
  3. 4. Atoms released extra energy in the form of photons also known as___________.
  4. 7. After a second the universe started to expand, stretch and cool.What is this phase called?
  5. 9. How big was the point that started the universe?
  6. 10. The most widely accepted theory about the origin and evolution of the universe.
  7. 11. A system was formed about 10 billion years after the big bang.