What is the Big Bang Theory?
The
Big Bang Theory is the leading explanation for how the universe began. It suggests that the universe started from an extremely hot and dense singularity approximately 13.8 billion years ago and has been expanding ever since. This theory forms the cornerstone of
cosmology and provides a comprehensive explanation for the observable universe.
How Do We Know the Universe is Expanding?
One of the primary pieces of evidence for the expansion of the universe is the
redshift of light from distant galaxies, first observed by Edwin Hubble. Hubble discovered that galaxies are moving away from us, and the farther they are, the faster they seem to be receding. This observation led to the formulation of
Hubble's Law, which quantitatively describes this expansion.
How Did Galaxies and Stars Form?
As the universe expanded and cooled further,
gravitational attraction caused matter to coalesce into larger structures. Regions with slightly higher densities attracted more matter, leading to the formation of galaxies and stars. The first
generation of stars, known as Population III stars, were massive and short-lived, contributing to the chemical enrichment of the universe.
What Role Do Dark Matter and Dark Energy Play?
Dark matter and
dark energy are critical components of the universe, comprising about 27% and 68% of its total mass-energy content, respectively. While dark matter exerts gravitational forces that influence the formation of galaxies, dark energy is thought to be responsible for the accelerated expansion of the universe. Understanding these components is a major focus in modern astrophysics.
