The thrill of time travel

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Across
  1. 2. something that marks the edge or limit.
  2. 6. the act or process of thinking, wondering, or guessing about something.
  3. 8. a problem that is a mystery or not easily understood
  4. 9. not known and not able to be explained.
  5. 11. a statement in arithmetic that uses an equal sign to show the equality of two quantities.
  6. 12. the area that contains the entire universe beyond the earth.
  7. 13. to know through direct sight or experience of
  8. 15. size as measured in length, width, or depth.
  9. 16. the force by which all objects in the universe are attracted to each other.
  10. 17. in physics, a theory that time and space are relative, not absolute
Down
  1. 1. the act of moving or changing places.
  2. 3. to change or adjust to one's own advantage.
  3. 4. having or showing an ability to conceive of things that do not exist; creative.
  4. 5. sickness or disease.
  5. 7. a scientist who works in physics.
  6. 10. important in history.
  7. 14. to wind or weave something around something else.