The Origin of the Universe

Big Bang Theory

• The universe began approximately 13.8 billion years ago through an explosive event known as the Big Bang.
• The Planck epoch marks the earliest period in the history of the universe, lasting from T=0 to about 10^-43 seconds after the Big Bang.

Planck Epoch

• No known physical laws describe the conditions during the Planck epoch, making it a limit for current scientific understanding.
• The end of the Planck epoch led to the emergence of fundamental forces and particles.

Key Events Shaping the Universe

• Key events influencing the universe include cosmic inflation, baryogenesis, and nucleosynthesis, which established the framework for cosmic structure.

Radiation Era

• The radiation era immediately following the Big Bang was dominated by high-energy radiation, such as photons, with matter contributing less significantly.

Timeline of the Big Bang

• The Big Bang occurred around 13.8 billion years ago, establishing the timeline for cosmic evolution.

Rapid Expansion

• The universe underwent a rapid expansion during the inflationary epoch, expanding from the size of an atom to the size of a grapefruit in a fraction of a second.

First Chemical Element

• Hydrogen was the first chemical element synthesized in the universe, emerging shortly after the Big Bang during the nucleosynthesis phase.

Cooling Epoch

• The universe cooled sufficiently for quarks to combine and form protons and neutrons during the hadronic epoch.

Nucleosynthesis Epoch

• The nucleosynthesis epoch was characterized by the fusion of protons and neutrons to create light nuclei, including hydrogen and helium.

Atomic Epoch

• The atomic epoch facilitated the creation of hydrogen through recombination, when electrons combined with protons to form neutral hydrogen atoms.

Formation of Stars

• The formation of stars marks a significant stage in the universe’s development when matter began to clump together under gravity, leading to the birth of celestial objects.

Element Production

• Supernova explosions and stellar nucleosynthesis caused vast ripple effects, ultimately contributing to the formation of almost all remaining elements in the universe.