My current understanding of Big Bang Theory is very surface level - enough to make me think that such an event never occurred. Probably understanding it on much deeper level will give me more confidence.
Regardless I find the picture we have painted till now to be very fascinating - actually its more of a puzzle that has revealed a picture. Hence this is my effort to contextualise the most popular cosmological theory.
Sequence of events post Big Bang
➡️ 13.8 billion years ago Big Bang occurred - it was not an explosion but expansion of space itself. The big bang theory is rooted on the observation that galaxies are moving away from us across all directions.
Immediately post big bang, following events take place,
➡️ Planck Epoch (0 to 10^-43 seconds): All four fundamental forces (gravity, strong, weak, and electromagnetic) were unified. Conditions were so extreme that conventional particles did not exist.
➡️ Grand Unification Epoch (10^-43 to 10^-36 seconds): Gravity separated from the other forces. The universe expanded rapidly (inflation) around 10^-37 seconds, causing huge cooling, allowing forces to differentiate further.
➡️ Quark Epoch (10^-12 to 10^-6 seconds): The universe was a hot quark-gluon plasma. Quarks and gluons existed freely but could not yet bind to form hadrons. At approximately 10^-6 seconds, quarks combined into protons and neutrons (baryogenesis), with a slight excess of matter over antimatter.
➡️ Lepton Epoch (~1 second): Electrons, positrons, neutrinos dominated. Many electron-positron pairs annihilated leaving a small residue of electrons.
➡️ Nucleosynthesis (2 to 20 minutes): Protons and neutrons fused to form light nuclei—mainly deuterium, helium-3, helium-4, and trace amounts of lithium—while temperature dropped to about a billion kelvin.
➡️ Recombination (about 370,000 years): Electrons combined with nuclei to form neutral atoms. This made the universe transparent to photons, releasing the cosmic microwave background radiation visible today.
➡️ Universal Goldilocks Zone (10 and 17 million years after the Big Bang): CMB 273 and 373 K
➡️ First Star - 30 million years post Big Bang
➡️ Water Molecule Synthesis - 100 to 200 million years post Big Bang, when first stars went supernovae to create heavy elements like Oxygen.
➡️ First Planets - billion years post Big Bang
Now for context let’s go through the history of our solar system
➡️ 4.6 billion years ago Solar System began forming
➡️ 4.55 billion years ago Sun was born
➡️ 4.54 billion years ago Earth, Moon and Planets were formed
➡️ 3.5 to 3.8 billion years ago single celled life began evolving
➡️ 600 million years ago multicellular life began evolving
➡️ 530 million years ago, during the early Cambrian period, first amphibians evolved
➡️ 540 million years ago Cambrian Explosion led to sudden variety in life across Earth
➡️ 245 to 230 million years ago during late Triassic, first bipedal dinosaurs started living along side other fauna
➡️ 66 to 68 million years ago during late Cretaceous, Deccan Traps began forming due to lava floods
➡️ 50 million years ago Indian plate starts colliding with Eurasian plate starting the formation of Himalayas
➡️ 2 to 3 million years ago the homo family branches out from the evolutionary tree
➡️ 300,000 years ago, homo sapiens branch out of homo family
➡️ 11,700 years ago, age of agriculture begins
➡️ 250 years ago, industrialisation begins