Lesson 1

Lesson Overview

• Title: The Big Bang Theory and the Formation of Light Elements

• Objective: Provide evidence for and explain the formation of light elements in the Big Bang Theory.

Learning Objectives

• Understand key concepts of cosmology.

• Explain the Big Bang Theory and its significance in the formation of elements.

Cosmology

Definition

• The body of science that studies the origin, evolution, and eventual fate of the universe.

Religious Cosmology

• Explains the universe's origin based on specific religious beliefs.

• Example: Creatio ex nihilo — the concept of God creating the universe as mentioned in Genesis.

Physical Cosmology

• Explains origin based on scientific insights and studies.

• Key Figures:

  • Nicolaus Copernicus: Proposed a heliocentric universe.

  • Albert Einstein: Developed the theory of relativity leading to the understanding of the expanding universe.

  • Big Bang Theory: A major explanation for the universe's expansion.

The Big Bang Theory

Concept

• A cosmological model starting the universe's expansion approximately 13.8 billion years ago.

• Continues to expand.

Initial Conditions

• Began as a singularity containing all space, time, matter, and energy.

• Rapid expansion occurred through a process called inflation.

• Universe cooled as it expanded.

Formation of Light Elements

Initial Particle Formation

• Formation of a 'soup' of matter consisting of subatomic particles.

• Creation of light atom nuclei via nucleosynthesis (nuclear fusion of protons and neutrons).

• Electrons combined with nuclei during recombination to form primordial atoms.

Evidence for the Big Bang Theory

Key Observations

• Vesto Slipher & Carl Wilhelm Wirtz (1910): Measured redshift, indicating that spiral galaxies were moving away from Earth.

• Georges Lemaître (1927): Proposed the expanding universe.

• Edwin Hubble (1929): Calculated galaxy distances based on redshift, confirming the recession of galaxies.

• Robert Wilson & Arno Penzias (1965): Discovered cosmic microwave background radiation (CMBR), a remnant energy from the Big Bang.

• Modern Astronomy: The universe is about 13.8 billion years old, with 5% as ordinary matter.

Big Bang Nucleosynthesis (BBN)

Definition

• The process of producing light elements during the Big Bang expansion.

• Results in stable isotopes of hydrogen, helium, lithium, and beryllium.

Detailed Process

• Deuterium Formation: Proton and neutron fuse to create deuterium (D) and a photon.

• Deuterium Bottleneck: Low binding energy of deuterium leads to its destruction until conditions stabilize.

• Further reactions produce heavier isotopes:

  • Helium-3 and Tritium can be formed from deuterium atoms.

  • Helium-4 can be created from various fusion processes involving protons, deuterium, and tritium.

He-4 and Subsequent Reactions

• Helium-4 formed via a series of fusion reactions has a binding energy of 28 MeV.

• Formation of heavier isotopes and their behavior under high-energy conditions noted as rare.

• Helium-4 can further react to produce Lithium-7 and Beryllium-7.

Cosmic Abundances

Verification of Predictions

• Correlation between predicted and observed cosmic abundances of hydrogen and helium supports the Big Bang Theory.

• Nearly 24% mass of the universe is helium-4; about 74% remains as hydrogen.

Primordial Material Measurement

• Scientists assess primordial materials in regions of the universe devoid of stars and within meteorites (e.g., chondrites) that fall to Earth.

Key Points to Remember

1. The Big Bang Theory describes the universe's initial expansion about 13.8 billion years ago.

2. Big Bang nucleosynthesis produces light elements during the expansion.

3. Observational evidence of hydrogen and helium abundances serves as key proof for the Big Bang Theory.

Questions for Further Exploration

• Nucleosynthesis Diagram Completion: Understanding nuclear reactions during BBN.

• Challenge Question: Why is a neutron released during the fusion of deuterium atoms?

Bibliography

• Clayton, D.D. 1968. Principles of Stellar Evolution and Nucleosynthesis. Chicago, USA: University of Chicago Press.

• National Aeronautics and Space Administration. “The Big Bang.” Accessed December 8, 2016. NASA Website

• Overton, Tina, et al. 2010. Shriver and Atkins' Inorganic Chemistry. 5th ed. London: Oxford University Press.