Within the first second after the Big Bang,the universe was filled with high-energy,gamma-ray photons.These photons created huge numbers of elementary particles and their antiparticles through pair production.What happened to these particles?
A) They are still here. They combined to create the first atoms and molecules that compose the physical universe.
B) The particles are still with us as atoms and molecules, but almost all of the antiparticles disappeared.
C) These particle-antiparticle pairs annihilated to produce more photons.
D) This pair production was followed by the era of cosmic inflation during which these particles spread out to produce the matter densities that we see today.

Question

Quizplus · Accepted Answer

The particle and antiparticle pairs produced during the Big Bang annihilated each other to produce more gamma-ray photons. This process continued until the universe had expanded and cooled enough for particles and antiparticles to no longer be produced in large quantities.

Within the First Second After the Big Bang,the Universe Was