The Big Bang: Origin of the Universe

The Beginning of Everything

13.8 billion years ago, the universe began. Not in an explosion into space, but as an expansion of space itself. From a state of unimaginable density and temperature, the cosmos we inhabit today unfolded.

The Big Bang isn't just a theory — it's supported by multiple independent lines of evidence and is the foundation of modern cosmology.

What You'll Learn

Evidence for the Big Bang

Scientists didn't guess — they observed:

The Expanding Universe: Galaxies are moving apart. Run the clock backward, and everything converges.

Cosmic Microwave Background: The afterglow of the Big Bang, detected in 1965, exactly as predicted.

Abundance of Light Elements: The ratio of hydrogen to helium matches Big Bang nucleosynthesis predictions.

Large-Scale Structure: The distribution of galaxies matches what we'd expect from early universe density fluctuations.

The First Moments

The early universe was a laboratory for extreme physics:
• Planck epoch (10⁻⁴³ seconds): Known physics breaks down
• Inflation: Faster-than-light expansion in the first fraction of a second
• Particle creation: Quarks, electrons, photons emerge from pure energy
• Nucleosynthesis: The first atomic nuclei form (hydrogen, helium, lithium)
• Recombination: 380,000 years later, atoms form, light is released

From Darkness to Light

For hundreds of millions of years after recombination, the universe was dark. Then the first stars ignited, and cosmic evolution began — stars, galaxies, planets, and eventually life.

What We Still Don't Know

Cosmology answers many questions but raises even bigger ones.