How the cosmic microwave background proves the Big Bang
By Ethan Siegel
The journey to understand the universe's origins culminated in the 20th century with the discovery of the cosmic microwave background (CMB), solidifying the Big Bang theory as the cosmic genesis story. Initially, various hypotheses vied for prominence, but the CMB's uniform glow, a relic of the early universe, decisively supports the hot Big Bang model. Through a combination of theoretical insights and observational evidence, including Edwin Hubble's revelation of an expanding universe and the discovery of the CMB's blackbody spectrum, the Big Bang emerged as the most compelling explanation. From the universe's infancy to its present state, the CMB stands as a testament to the universe's evolution and the validity of the Big Bang theory.