The Universe: Origins, Structure, and Key Facts

Cosmic Overview

The universe is incomprehensibly vast, and our understanding of its origin continues to evolve. The leading scientific theory is the Big Bang.

Big Bang Theory

• Origin: ~13.8 billion years ago from an extremely hot, dense state.
• Expansion: Rapid inflation followed by ongoing expansion; rate ~70 km/s/megaparsec (Hubble constant).
• Cooling: Allowed formation of subatomic particles, atoms, stars, galaxies.

Large-Scale Structure

• Superclusters: Vast assemblies of galaxy clusters (e.g., Laniakea, our home supercluster).
• Filaments & Walls: Thread-like structures connecting superclusters.
• Voids: Immense near-empty regions, hundreds of millions of light-years across.

Contents

• ~2 trillion galaxies
• ~10²⁴ stars
• Planets, black holes, neutron stars, dark matter (27%), dark energy (68%), ordinary matter (5%)

Key Numbers

• Age: 13.8 billion years
• Observable diameter: 93 billion light-years
• Expansion: accelerating (dark energy)

Cosmology remains an active frontier—questions about dark matter, dark energy, inflation, and the universe's ultimate fate drive cutting-edge research.