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staedtler staedtler
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7 years ago
Why did the formation of particle-antiparticle pairs (such as protons and antiprotons) from gamma rays come to an end within the first second after start of the Big Bang?
A)   Expansion of the universe carried the gamma rays too far apart for them to collide and form particle-antiparticle pairs.
B)   The gamma-ray energy decreased as the universe expanded.
C)   The universe became transparent to radiation, so gamma rays and particles no longer interacted.
D)   The formation of particle-antiparticle pairs exhausted the supply of gamma rays, preventing further formation of particle-antiparticle pairs.
Textbook 
Discovering the Universe

Discovering the Universe


Edition: 7th
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hyponoticahyponotica
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