Both protons and neutrons (and their anti-particles)froze out:
A) after 10⁻⁴³ seconds, at the Planck Era.
B) at 10³² K, at the end of the Inflationary Era.
C) at 10¹³ K, about .0001 seconds after the Big Bang.
D) after about a minute of expansion.
E) about 50,000 years after the Big Bang.

Question

Quizplus · Accepted Answer

Protons and neutrons, along with their anti-particles, froze out at around 10¹³ K, which is about .0001 seconds after the Big Bang. At this time, the temperature had dropped enough for quarks to combine into protons and neutrons. This allowed matter to take shape as neutral atoms began to form. This process is known as recombination, and it marks a significant milestone in the evolution of the universe.

Both Protons and Neutrons (And Their Anti-Particles)froze Out