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Visit Stack Exchange Further thoughts: The metaphor for the expansion of the universe is often described as an inflating balloon, but could it be equally valid to think of expansion as matter falling into its own gravity well, away from infinity minus other matter within its gravity field.
This produces most of the lithium (apart from the BBN Li), beryllium, and boron.
And one more: in a supernova, especially a core collapse supernova, huge quantities of new nuclei are synthesized, very quickly, in the nuclear reactions triggered by the flood of neutrons.
(More details about the physics behind Big Bang Nucleosynthesis can be found in the spotlight text Equilibrium and Change.) As it turns out, Big Bang Nucleosynthesis strongly favours the very light elements like hydrogen and helium - not only standard hydrogen (one proton) and helium-4 (two neutrons and two protons), but also the isotopes deuterium (one proton, one neutron), tritium (one proton, two neutrons) and helium-3 (two protons, one neutron).
By mass, about a quarter of the nuclei in the universe should be helium-4.This ‘r process’, as it is called (actually there’s more than one) produces most of the elements heavier than the iron group (copper to uranium), directly or by radioactive decay of unstable isotopes produced directly. Here are a few links that might interest you: Nucleosynthesis (NASA’s Cosmicopia), Big Bang Nucleosynthesis (Martin White, University of California, Berkeley), and Stellar Nucleosynthesis (Ohio University).Plenty of Universe Today stories on this topic too; for example Stars at Milky Way Core ‘Exhale’ Carbon, Oxygen, Astronomers Simulate the First Stars Formed After the Big Bang, and Neutron Stars Have Crusts of Super-Steel.Most matter was then hydrogen (actually just protons; the electrons were not captured to form atoms until much later), and helium-4 (alpha particles) …with a sprinkling of deuterium, a dash of helium-3, and a trace of lithium-7. The atoms in your body – apart from the hydrogen – were all made in stars … Stars on the main sequence get the energy they shine by from nuclear reactions in their cores; off the main sequence, the energy comes from nuclear reactions in a shell (or more than one shell) around the core.In astronomy – and astrophysics and cosmology – there are two main kinds of nucleosynthesis, Big Bang nucleosynthesis (BBN), and stellar nucleosynthesis.In the amazingly successful set of theories which are popularly called the Big Bang theory, the early universe was very dense, and very hot.The big bang models - the cosmological models based on general relativity - tell us that the early universe was extremely hot and dense.At the earliest stages that can be modelled using current physical theories, the universe was filled with radiation and elementary particles - a hot plasma in which energy was distributed evenly.The effect being that matter radiates space itself as gravity pulls itself away from infinity.Just as heavier elements create a stronger gravity field, heavier elements would accelerate away from infinity minus other matter within its gravity field, at a faster rate.