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 here as atoms and molecules, but almost all of the antiparticles disappeared.
C) The antiparticles annihilated with normal matter particles 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 astronomers see today.

Question

Quizplus · Accepted Answer

The antiparticles created in the early universe annihilated with their particle counterparts, producing photons. This process significantly reduced the number of particles and antiparticles, leaving a slight excess of particles, which went on to form the matter we observe in the universe today.

Within the First Second After the Big Bang, the Universe