August 15th, 1977, Jerry R. Ehman was working on a project at the Big Ear radio telescope at Ohio State University when he reviewed print outs from earlier that day. The signal was loud compared to the night sky, and lasted 72 seconds leading Ehman to circle the code 6EQUJ5 and write Wow! in the margin.
Scientists posit the signal is extraterestial in orgin – meaning not originating from earth – but could be the sound of a passing comet, or other action within the universe. The sound has never been recorded since.