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Across
  1. 5. SPIRAL GALAXY CONTAINING OUR SOLAR SYSTEM, COMPOSED OF APPROXIMATELY A TRILLION STARS.
  2. 7. LARGE SYSTEM OF STARS HELD TOGETHER BY A MUTUAL GRAVITATION AND ISOLATED FROM SIMILAR SYSTEMS BY VAST REGIONS OF SPACE.
  3. 9. ENERGY TRANSMITTED BY ELECTROMAGNETIC WAVES.
  4. 12. ATTRACTS NUCLEONS TO ONE ANOTHER WITHIN THE NUCLEUS.
  5. 14. THE VELOCITY OF RECESSION OF DISTANT GALAXIES FROM OUR OWN IS PROPORTIONAL TO THEIR DISTANCE FROM US.
  6. 17. CONTAINS ELECTRIC AND MAGNETIC FEILDS AND IS RESPONSIBLE FOR ATOMIC STRUCTURE AND CHEMICAL REACTIONS.
  7. 19. UNIVERSE THAT HAS LIMITED DENISITY AND APPEARS FLAT.
  8. 20. CATACLYSMIC BIRTH OF THE UNIVERSE FROM THE OBSERVED EXPANSION OF THE UNIVERSE.
  9. 22. HYPOTHETICAL FORM OF ENERGY THAT PERMCATES SPACE AND EXERTS A NEGATIVE PRESSURE.
Down
  1. 1. NATURAL FORCE OF ATTRACTION EXERTED BY A CELESTIAL BODY.
  2. 2. HYPOTHETICAL FORM OF MATTER INVISIBLE TO ELECTROMAGNETIC RADIATION.
  3. 3. BRANCH OF ASTROMONY THAT DEALS WITH THE GENERAL STRUCTURE AND EVOLUTION OF THE UNIVERSE.
  4. 4. SUFFICENT MATTER AND SUFFICIENT GRAVITATION THAT HALTS EXPANSION.
  5. 6. ELEMENTS WITH A POSITIVE ENERGY.
  6. 8. INSUFFICENT MATTER AND INSUFFICENT GRAVITATION TO HALT EXPANSION.
  7. 10. A DECREASE IN THE MEASURED FREQUENCY OF LIGHT FROM A RECEDING SOURCE.
  8. 11. RESPONSIBLE FOR NUCLEAR DECAY.
  9. 13. ELECTROMAGNETIC RADIATION COMING FROM EVERY DIRECTION IN THE UNIVERSE.
  10. 15. SCIENCE THAT DEALS WITH THE MATERIAL UNIVERSE BEYOND THE EARTHS ATMOSPHERE.
  11. 16. SMALLEST PARTICLES OF AN ELEMENT.
  12. 18. THE TOTALITY OF A KNOWN OR SUPPOSED OBJECTS AND PHENOMENA THROUGHOUT SPACE.
  13. 21. A CLOUD OF INTERSTELLAR GAS AND DUST.