Do you remember the first weeks of class?

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Across
  1. 2. the closest natural satellite to the earth, 240,000 miles away
  2. 4. the antimatter that is the counter part of electrons
  3. 5. "nuclear glue"
  4. 8. these type of glasses are needed to treat nearsightedness
  5. 10. this reaction will take place with a new element when the sun runs out of hydrogen
  6. 14. a phenomena that is seen when a wave encounters an obstacle
  7. 16. the largest planet in our solar system
  8. 18. atom particle with no charge
  9. 19. once things goes in this hole, nothing comes out
  10. 20. our is named the Milky Way
  11. 21. we're lucky this substance expands when it is in a solid state
  12. 22. responsible for color vision in the eyes
  13. 23. no color vision, used in dim light, to see out of corners of the eye
Down
  1. 1. was once considered the furthest planet in our solar system
  2. 2. the planet that has the most properties that are similar to earth
  3. 3. an area in the sky named after a collection of stars
  4. 6. this tissue is responsible for creating sharp central vision
  5. 7. this nerve transmits visual information to the brain
  6. 9. this reflects light back for a second chance if it misses the rods in the eyes
  7. 11. the closest planet to the sun
  8. 12. interstellar cloud of dust, hydrogen, and helium
  9. 13. the big bang and the steady state are both an example of a ______?
  10. 15. the light sensitive tissue in the back of the inner eye
  11. 17. when a suns gravity is so great it is able to crush atoms
  12. 20. Jupiter, Saturn, Uranus and Neptune are examples of gas _____?