Universe

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Across
  1. 3. the smallest unit of matter
  2. 5. an object in space that has a strong pull
  3. 6. the distance light travels
  4. 7. how much matter is in an object
Down
  1. 1. theory of how the universe formed
  2. 2. hydrogen atoms bond to form helium and generate heat
  3. 4. unit composed of 2 or more atoms