In physical cosmology, Big Bang nucleosynthesis (also known as primordial nucleosynthesis, and abbreviated as BBN) is the production of nuclei other than those of the lightest isotope of hydrogen (hydrogen-1, 1H, having a single proton as a nucleus) during the early phases of the universe.

Classical mechanics is a branch of physics that deals with the motion of objects, using principles and mathematical equations developed by Isaac Newton and others.

Earth is the third planet from the Sun in our solar system and the only known celestial body to support life.

Helium is a chemical element with the symbol He and atomic number 2.

Helium-3 is a light, non-radioactive isotope of helium, consisting of two protons and one neutron.

Hydrogen is a chemical element with the symbol H and atomic number 1.

An isotope is a variant form of a chemical element that has the same number of protons but a different number of neutrons, giving it a different atomic mass.

Lithium is a chemical element with the symbol Li and atomic number 3.