Here is your Christmas Gift from Mom and Dad

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Across
  1. 3. forces acting in opposite directions that are equal in newtons
  2. 5. the material through which a wave travels
  3. 6. to move from one geographic region to another
  4. 9. a group of atoms bonded together
  5. 10. object made or used by people in the past
  6. 12. an early city that was like a small, independent country with its own laws and government
  7. 14. a means of supplying land with water
  8. 15. light waves bouncing off a surface
  9. 17. an area in southern Mesopotamia where cities first appeared
Down
  1. 1. the point at which rays parallel to the optical axis meet
  2. 2. in ancient times, the geographic area located between the Tigris and Euphrates rivers
  3. 4. energy an object has due to its motion
  4. 7. the maximum distance that the wave moves from its resting position
  5. 8. an early ancestor of humans
  6. 11. something you can use that people need
  7. 13. the unit to measure frequency
  8. 16. person who doesn't have a permanent home