Cosmology Na23EA

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Across
  1. 2. Leftover heat signal from the early universe, abbrev. (3)
  2. 4. Proposed the heliocentric model in 1543 (10)
  3. 6. Most abundant material in the universe
  4. 7. Invisible medium scientists once thought light travelled through (5)
  5. 8. Cause of galaxies moving apart (9)
Down
  1. 1. Calculated initial space temperature in Kelvin (4 digits)
  2. 2. Einstein added this "constant" to keep the universe still (13)
  3. 3. Came up with the primeveal atom model (8)
  4. 5. Galaxies shift toward this colour as they move away (3)