BIG BANG THEORY & BIG BANG NUCLEOSYNTHESIS (BBN)

Big Bang Theory Overview

• The most widely accepted explanation for the origin of the universe.

• Suggests the universe began from a singularity-an extremely hot, dense point.

• Space itself expanded, causing the universe to cool over time.

Early Universe Conditions

• At the very beginning: temperature and density were extremely high.

• As expansion happened, particles formed:Quarks → combined to form protons and neutrons
  Eventually → atoms and later galaxies

Big Bang Nucleosynthesis (BBN)

• Occurred within 3-20 minutes after the Big Bang.

• Protons and neutrons fused to create the first atomic nuclei.

• Only light clements were formed:

• Ilydrogen (H). Deuterium (H)

• Helium (He and "Hc)
  Small amounts of Lithium (Li) and
  Beryllium

• Heavier elements (carbon, oxygen, silicon, iron, etc.) did NOT form during BBN.

Formation of Hydrogen Isotopes

Proton (H) - hydrogen with no neutrons

• Deuteron (H) → 1 proton + 1 neutron

Triton (H) 1 proton + 2 neutrons

* Isotopes differ in neutron number.

Helium & Light Element Formation

• Helium-4 (*He) forms from combinations of deuterons and Helium-3.

• Lithium and Beryllium require higher energies, so they reman rare.

Composition of the Universe

• Approximately 75% Hydrogen, 25%
  Helium (by mass).

• This ratio is evidence supporting the Big
  Bang Theory