Big Bang Theory (Douglas's Puzzle)

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Across
  1. 4. SI base unit of thermodynamic temperature
  2. 5. the interaction of electric currents or fields and magnetic fields
  3. 7. the average density of matter required for the Universe to just halt its expansion, but only after an infinite time
  4. 9. a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction
  5. 11. a period of extremely rapid expansion of the universe during its first few moments
  6. 12. a unit of astronomical distance equivalent to the distance that light travels in one year
  7. 14. a form of matter hypothesized to account for 80-85% of the universe's mass
Down
  1. 1. the science of the origin and development of the universe
  2. 2. gravity, the strong force, the weak force and the electromagnetic force
  3. 3. the degree or intensity of heat present in a substance or object
  4. 6. An alternative term for the radiation era in the Big Bang theory
  5. 7. A star that fluctuates in brightness and provides astronomers with a reference they can use to measure great distances in the Universe
  6. 8. light observed from distant stars and galaxies gives evidence that the universe is expanding
  7. 10. a region of space having a gravitational field so intense that no matter or radiation can escape.
  8. 13. began right after the Radiation Era around 3000 years after the big bang began