Summary
Highlights
This video will teach about the formation of light elements in the early universe, known as Big Bang Nucleosynthesis.
The Big Bang theory explains the primordial creation and expansion of space, stating that the universe originated from an infinitely dense and hot point. A fraction of a second after the explosion, quarks formed protons and neutrons, which then combined to create light elements.
Nucleosynthesis is the process of creating new atomic nuclei from pre-existing nuclei, primarily protons and neutrons. The early universe was too hot for particles to combine, but as it expanded and cooled, protons and neutrons began to form elements. This process started with the formation of deuterium (an isotope of hydrogen) from one proton and one neutron.
An atom's identity is determined by the number of protons. Hydrogen has one proton. When deuterium combines with a neutron, tritium is formed, which is still hydrogen. Hydrogen has three isotopes: protium (one proton), deuterium (one proton, one neutron), and tritium (one proton, two neutrons).
Two deuterium particles can combine to produce helium, which has two protons and two neutrons. Helium can also be formed when tritium is bombarded with a proton. When a helium ion is bombarded with a triton, lithium (three protons, four neutrons) is formed. When two helium ions combine, beryllium (four protons, four neutrons) is formed. Lithium and beryllium require more energy to form, so they are less abundant than hydrogen and helium.
The universe is estimated to contain 75% hydrogen and 25% helium. As the universe continued to expand and cool, minutes after the Big Bang, the temperature dropped too low for particles to combine and form more elements, leading to the current elemental composition.
This explains how light elements were formed in the early universe through Big Bang Nucleosynthesis. The next lesson will cover the formation of heavier elements through stellar nucleosynthesis during stellar evolution.