Here's why:
* The Big Bang theory predicted the existence of the CMB: The theory states that the universe began in a hot, dense state and has been expanding and cooling ever since. This cooling process should have left behind a faint afterglow of radiation, which is exactly what the CMB is.
* The CMB's properties match the Big Bang model: The CMB has a near-perfect blackbody spectrum at a temperature of about 2.7 Kelvin, which aligns with the predictions of the Big Bang theory.
* The CMB is nearly uniform across the sky, but with tiny fluctuations: These fluctuations provide evidence for the initial seeds of structure formation in the early universe, as predicted by the Big Bang model.
The discovery of the CMB provided strong observational evidence for the Big Bang theory and solidified its standing as the dominant cosmological model.
