Observational evidence supporting the Big Bang theory includes several key phenomena:
- Expansion of the Universe and Redshift of Galaxies: Edwin Hubble's observation that galaxies are moving away from us, with more distant galaxies receding faster, shows the universe is expanding. This redshift of light to longer wavelengths is a fundamental proof of the Big Bang theory
- Cosmic Microwave Background Radiation (CMB): The CMB is the faint, uniform microwave radiation filling the universe, discovered accidentally in 1965 by Penzias and Wilson. It is considered the cooled remnant of the hot, dense state of the early universe shortly after the Big Bang, providing a "snapshot" of the universe about 380,000 years after its origin. The CMB's uniformity and slight anisotropies have been measured by missions like COBE, WMAP, and Planck, confirming predictions of the Big Bang model
- Abundance of Light Elements: The observed proportions of light elements such as hydrogen, helium, and lithium in the universe match the predictions of Big Bang nucleosynthesis, which describes element formation in the first few minutes after the Big Bang when the universe was hot and dense
- Large-Scale Structure of the Universe: The distribution and formation of galaxies and cosmic structures align with models of an expanding universe originating from a hot, dense initial state
These observations collectively form the "four pillars" of Big Bang cosmology: expansion (redshift), cosmic microwave background radiation, light element abundances, and large-scale structure
. While some alternative theories exist, the Big Bang remains the most comprehensive explanation for these observational facts.
