The Wow! Signal

On Aug. 15, 1977, a telescope at Ohio State University detected a strong narrowband radio signal in the constellation Sagittarius — one so unusual that astronomer Jerry Ehman marked the printout with an exclamation.

The signal’s intensity rose and then fell as the beam swept past its position in the sky. That’s consistent with an extraterrestrial origin … but in 30 years and more than 100 searches, no one has been able to relocate it.

Without a recurrence, there’s no way to know what Ehman’s telescope heard that night — it’s just a frustrating splash in a large, silent sea.