Robert Wilson and Arno Penzias accidentally discovered the afterglow of the big bang in 1964. Their now-famous horn antenna, built for Bell Labs in New Jersey, was supposed to be picking up the radio waves emitted by galaxy clusters and supernova remnants. But it recorded a temperature that was 3.5 kelvin hotter than it should have been, no matter where they pointed it (see Section 19.2a, p. 511).
We now know this was caused by the first photons to be released after the big bang, which still pervade the cosmos as radio waves. These days, Wilson keeps a sound recording of those waves on his cellphone (see audio link), as New Scientist magazine discovered when they interviewed him at a celebration marking half a century since the discovery.
Robert Wilson is now at the Harvard Smithsonian Center for Astrophysics. In 1978, he and Arno Penzias shared the Nobel prize in physics with Pyotr Kapitsa.