Bell Labs researchers Arno Penzias and Robert Wilson were studying radio satellite waves with the Holmdel Horn antenna when they came across an inexplicable "hum" that turned out to be residual energy resulting from the Big Bang.

This was the first solid piece of evidence to the theory. 

"That radiation in the expansion of the universe was from the huge explosion, cooled down to the point where it's now in a different part of the spectrum," says Bell Labs President Marcus Weldon. "This radiation left the universe, expanding, caused the radiation to cool, and we detected that cooled radiation which is now in the microwave part of the spectrum."

The Nobel Prize was given to the researchers in 1978 for their work supporting the Big Bang Theory.