Space and force

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Across
  1. 7. the inward force that causes objects to move in a circular path
  2. 8. when a planet is closest to the sun and orbits the fastest
Down
  1. 1. He believed that planets orbit the sun in elliptical paths
  2. 2. the sun and all of the planets and other bodies that travel around it
  3. 3. he observed the phases of Venus
  4. 4. a celestial body that is composed of gas and emits light
  5. 5. the energy of motion
  6. 6. an object in motion stays in motion