Helium nuclei play a crucial role in the Big Bang theory as they are one of the first elements to form after the initial explosion. This process, known as nucleosynthesis, is responsible for the creation of all elements in the universe.
During the first few minutes of the Big Bang, the extreme temperatures and pressures allowed for protons and neutrons to combine and form helium nuclei through a process called fusion. This process continued as the universe expanded and cooled, eventually leading to the formation of larger elements.
It is estimated that around 25% of the mass of the universe is made up of helium, with most of it being created during the first few minutes of the Big Bang. This is a significant amount considering that only a small fraction of the universe is made up of elements other than hydrogen and helium.
The presence of helium nuclei in the early universe helped to slow down the expansion of the universe. This is due to the fact that helium is more massive than hydrogen, causing it to have a stronger gravitational pull and therefore slowing the expansion.
While we cannot directly observe the helium nuclei created during the Big Bang, we can study the cosmic microwave background radiation, which is leftover radiation from the initial explosion. This radiation contains small variations in temperature that can tell us about the composition of the early universe, including the presence of helium nuclei.