Cosmic Microwave Background Radiation

The Cosmic Microwave Background radiation is the most powerful evidence for the Big Bang. Detected accidentally in 1964 by Arno Penzias and Robert Wilson, this faint glow is the afterglow of the universe's birth 13.8 billion years ago, with a nearly uniform temperature of 2.725 K across the sky, a precision unmatched by any other cosmic relic. It outperforms #2 Expansion of the Universe in direct temporal evidence, as the CMB locks in the exact moment recombination occurred, while Hubble's observations only describe subsequent motion. Furthermore, the CMB's blackbody spectrum matches theoretical predictions to within 50 parts per million, a degree of accuracy that surpasses the typical cosmological benchmark.