The Origin of the Light Elements

The Origin of the Light Elements

Big Bang Theory

• The emergence of the universe brought about the formation of elements, and consequently of matter.

• One of the most popular attempts to describe the universe is the big bang theory.

• It was first proposed, though not named, by Belgian astrophysicist and priest Abbe Georges Edouard Lemaitre (1894 -1966).

Big Bang Theory

• postulates that the universe emerged from a state of enormous density and energy.

• Fred Hoyle coined the name “big bang” that was made in response to Einstein’s work.

• Albert Einstein proposed that the universe is spatially bound (finite) and has a uniform distribution of matter when averaged on very large scales.

• Lemaitre argued that Einstein’s model was not physically realistic since slight variations in inhomogeneity would result in a loss in equilibrium, and thus expansion or contraction.

3 key observational pieces of evidence that support the big bang model

• a. Hubble or cosmic expansion

• b. Cosmic Microwave Background (CMB)

• c. Primordial or Big bang Nucleosynthesis (BBN)

Hubble or cosmic expansion

• Hubble’s law (Edwin Hubble) also known as Hubble expansion, states that other galaxies are moving away relative to the Milky Way at a rate proportional to distance and was the first observational evidence of Lemaitre’s big bang model.

Cosmic Microwave Background (CMB)

• In the 1940s, theoretical physicist and cosmologist George Gamow, together with Robert Herman and Ralph Alpher, predicted that if the early stage of the universe was hot and dense, then an afterglow of radiation must fill-up the universe because of the cooling process.

• This afterglow is detected today as cosmic microwave radiation, also known as the cosmic microwave background (CMB).

Primordial or big bang nucleosynthesis

• Primordial or big bang nucleosynthesis produced the light elements shortly after the big bang. The light elements include hydrogen (11H) and its isotope deuterium (21 H), helium-3 (32He) and helium-4 (42He), and lithium-7 (73Li).