In 1965, Arno Penzias and Robert Wilson, two radio astronomers at Bell Telephone Laboratories, stumbled upon a mysterious and persistent background noise that pervaded their radio telescope. After much investigation and the elimination of potential terrestrial and instrumental sources, they concluded that this noise was cosmic in origin. Their findings, published on May 20, 1965, identified this radiation as the Cosmic Microwave Background (CMB) — the afterglow of the Big Bang, providing critical empirical support for the Big Bang theory of the universe’s origin. This discovery, serendipitous as it was, marked a monumental advancement in cosmology, transforming our understanding of the universe’s earliest moments.