On this day in 1977 Jerry Ehman was using Ohio State University's Big Ear radio telescope to hunt for signals emanating from extraterrestrial civilizations. The telescope detected a burst of radio emission that was so intense that Ehman wrote "Wow!" on the paper readout. (The letter U in the six-character sequence corresponds to a strength 30 times that of the background.) What became known as the Wow signal originated from the neighborhood of M55, a globular cluster in Sagittarius. No recurrence of the signal has been detected. Its origin remains a mystery.
