In string theory, a pre-Big Bang phase might exist but is still hypothetical.

13.8 Big Bang.
The universe began from an extremely hot, dense state — not a typical "explosion" in space, but an expansion ofspace itself.
Time, space, matter, and energy were all created.

⚛️ First Seconds (10⁻⁴³ to ~1 second) Planck Epoch (t < 10⁻⁴³ sec): Laws of physics as we know them break down. Inflationary Epoch: The universe expanded exponentially fast. Fundamental forces (gravity, electromagnetic, weak, strong) began to separate. Quarks, electrons, neutrinos, and other elementary particles formed.

🔥 First Few Minutes (up to ~20 minutes) Big Bang Nucleosynthesis: Protons and neutrons fused into light elements — mostly hydrogen and helium, with traces of lithium. Universe was still too hot for atoms to form.

🌫️ First 380,000 Years The universe cooled enough for electrons to combine with protons and form neutral atoms — mostly hydrogen. Cosmic Microwave Background Radiation (CMB) was released — we still detect this faint glow today.

13 Small protogalaxies merged through gravity to form larger structures.

13 Some of these early galaxies eventually evolved into massive galaxies like the Milky Way.

13 some had already exploded. Their supernovae seeded the universe with heavier elements (like carbon, oxygen, iron), enabling later generations of stars and planets to form.

13 universe was emerging from the “Dark Ages”, the period after the Big Bang but before stars lit up.

13 Reionization was underway — ultraviolet light from the first stars and galaxies was ionizing hydrogen gas, making the universe transparent to light again.

13 Cosmic web structures — vast filaments of dark matter and gas — were taking shape.