Helium nuclei began permanent formation in the early universe when the temperature dropped to the point where the gamma radiation no longer had enough energy to break nuclei apart as soon as they formed. Did this helium production cease? If so, why?
A) Helium production at the site of the Big Bang has continued, although the rate has decreased.
B) Helium production did not cease until millions of years later when the density of the primordial universe became too low to support nuclear fusion.
C) The production of helium in the early universe ceased after a few minutes, but only because the available energy and particles were being used up in the production of heavier nuclei like carbon, oxygen, and silicon.
D) After a few minutes the early universe cooled to the point where protons no longer had enough energy to overcome the repulsion of the electromagnetic force and come close enough to each other to undergo nuclear fusion.

Question

Quizplus · Accepted Answer

The production of helium in the early universe, a process known as Big Bang nucleosynthesis, ceased after a few minutes because the universe expanded and cooled to a point where the temperatures and densities were no longer sufficient for nuclear fusion to occur. This cooling prevented protons from overcoming their electromagnetic repulsion to fuse into helium nuclei.

Helium Nuclei Began Permanent Formation in the Early Universe When