Science & moon. :)

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Across
  1. 3. something that changes over time
  2. 5. Y & X...
  3. 6. Spins around a bigger object
  4. 7. a pull to the center of something
Down
  1. 1. water rising and falling
  2. 2. the shape of something getting smaller
  3. 4. The shape of something getting bigger
  4. 5. the smallest units of matter