The Big Bang theory is strongly supported by several key pieces of evidence:
- Hubble's Law and the Expansion of the Universe: Edwin Hubble discovered in the 1920s that galaxies are moving away from us, and the farther a galaxy is, the faster it recedes. This redshift-distance relationship indicates that the universe is expanding, implying it was once much smaller and denser
- Cosmic Microwave Background Radiation (CMB): In 1964, scientists detected a faint, uniform radiation filling the universe, known as the cosmic microwave background. This radiation is the afterglow of the Big Bang, providing a snapshot of the universe when it was about 380,000 years old. The CMB’s uniformity and temperature (about 2.725 K) strongly support the theory that the universe began in a hot, dense state
- Abundance of Light Elements: The Big Bang theory predicts the primordial ratios of light elements such as hydrogen, helium, and lithium formed in the early universe. Observations of these elemental abundances in old stars and galaxies closely match the theoretical predictions, reinforcing the model
- Evolution of Galaxies and Large-Scale Structure: The observed changes in galaxy properties over cosmic time and the distribution of large-scale cosmic structures align with the Big Bang model’s predictions of an evolving universe
Together, these observations form the core empirical foundation for the Big Bang theory, making it the most widely accepted explanation for the origin and evolution of the universe
