science things

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Across
  1. 3. to collapse inwards
  2. 6. something smaller than an atom
  3. 7. the start of the word is the first letter in the Greek alphabet
  4. 8. shortest day of the year
Down
  1. 1. a form of Electro Magnetic Radiation
  2. 2. the core of an atom
  3. 4. two things combining
  4. 5. the way things travel through the air