In the very early universe, which of the following types of particles and antiparticles first stopped being spontaneously formed out of photons and why?
A) protons and neutrons, because their formation requires a larger number of photons
B) electrons and positrons, because their formation requires a smaller number of photons
C) protons and antiprotons, because their formation requires higher-energy photons
D) electrons and neutrinos, because their formation requires lower-energy photons
E) Protons, antiprotons, electrons, and neutrinos stopped forming at the same time.

Question

Quizplus · Accepted Answer

Protons and antiprotons require higher-energy photons for their formation, and as the universe expanded and cooled, the energy of photons decreased, preventing their spontaneous formation.

In the Very Early Universe, Which of the Following Types