The Big Bang theory is the cosmological model that describes the origin and evolution of the universe. The theory is supported by several observational evidences
, including the observed redshift of galaxies, the cosmic microwave background radiation, and the abundance of light elements in the universe.
One of the key pieces of evidence supporting the Big Bang theory is the observed redshift of distant galaxies. This redshift is a result of the expansion of the universe, which causes the light emitted by galaxies to be stretched to longer wavelengths. The greater the redshift, the greater the distance of the galaxy from us. This observation supports the idea that the universe is expanding and suggests that at some point in the past, all matter and energy must have been concentrated in a single point, which is the initial singularity of the Big Bang.
Another important piece of evidence is the cosmic microwave background radiation (CMBR). This radiation is a faint glow of radiation that permeates the entire universe and is thought to be leftover radiation from the early stages of the universe. The CMBR was discovered in 1965 and has since been studied extensively. Its existence and properties are consistent with the predictions of the Big Bang theory, providing strong support for the idea that the universe began in a hot, dense state and has been expanding ever since.
The abundance of light elements, such as hydrogen and helium, in the universe is also consistent with the predictions of the Big Bang theory. According to the theory, during the early stages of the universe, when it was extremely hot and dense, nuclear reactions occurred that produced these light elements. The ratios of these elements predicted by the Big Bang theory match up with the observed abundances in the universe, further supporting the idea that the universe began with a hot, dense state and has been expanding and evolving since then.
In addition to these observational evidences, the Big Bang theory is also supported by theoretical considerations, such as the general theory of relativity, which describes the behavior of gravity on cosmological scales. The theory also provides explanations for other observations, such as the large-scale structure of the universe and the distribution of galaxies.
Overall, the Big Bang theory is a well-supported cosmological model that explains the origin and evolution of the universe. Its observational and theoretical evidences provide a compelling picture of how the universe began and has been changing over billions of years.