The Big Bang Theory UPSC

I. Origin of the Universe

📌 The theory posits that the universe began approximately 13.8 billion years ago from an infinitely dense and hot singularity. This singularity expanded rapidly in a process called cosmic inflation, leading to the formation of matter, energy, space, and time.

II. Key Phases of Evolution

📌 Planck Epoch (0–10⁻⁴³ seconds): Quantum gravity dominated.

📌 Inflationary Epoch (10⁻³⁶–10⁻³² seconds): Rapid expansion smoothed the universe.

📌 Nucleosynthesis (3–20 minutes): Formation of light elements (hydrogen, helium).

📌 Recombination (380,000 years): Electrons combined with nuclei, releasing photons (observed as Cosmic Microwave Background Radiation).

📌 Formation of Structures (1 million years–present): Gravity caused gas clouds to coalesce into stars, galaxies, and planets.