Once, in 1977, humans intercepted a radio signal that was likely intelligent and extraterrestrial in origin.

In the forty plus years since, it has never been explained, despite thousands of researchers and scientists doing their best to debunk it. That effort is the scientific method in action and, when all other possibilities are exhausted, then our minds can start lingering on the extraordinary.

In August of 1977, astronomers at Ohio State University’s Big Ear Radio Telescope discovered the 72-second burst as they poured over a stack of dot-matrix printings. In that endless series of 0’s,1’s, 2’s, and scattered 3’s, Astronomer Jerry R. Ehman saw six values representing a tremendous increase in signal strength. He circled the now-famous “6EQUJ5” block and scribbled “WOW!” next to it, thus labeling it the WOW! Signal*. To explain the letters simply, the sustained signal was over thirty times stronger than the background radiation and ended only when the Earth’s rotation moved the telescope out of range.

*If you’d like to hear it, follow this YouTube link . Although the Big Ear Radio Telescope did not actually record the background noise, that link offers a representation of what it WOULD HAVE sounded like. Plug in some decent headphones and close your eyes as you listen for the full effect.

You’d think a discovery of this magnitude would be plastered on every newspaper across the country. Some media outlets did run with it, but it remained fairly low-key. Scientists (including the signal’s discoverers) knew many hurdles had to be cleared before endorsing it as a likely sign of intelligent life.

Chief among those hurdles was a repetition of signal from the same location, the globular cluster M55 in the constellation Sagittarius. The radio astronomers listened eagerly for the signal again…and never heard it. Ever again. The signal remains a one-off event, placing it firmly in the realm of scientific mysteries.





In forty years, every proposed, non-extraterrestrial explanation of the signal has been patiently and thoroughly dismissed by the scientific community. Of course there’s debate, but the debate supports intelligent, extraterrestrial origin as the most likely source of the WOW! Signal.

Proposed sources? Magnification of a background signal by atmospheric lensing, a supernova burst in a new frequency, artificial space debris, a comet or a reflection of an Earth-based radio signal. All of these were determined unlikely.

To date, an intelligent, extraterrestrial origin for the WOW! Signal remains the most plausible theory behind the signal.

*Ohio State University’s Radio Observatory was disassembled in 1998. It is now a, uh, golf course.

Want to Know More?

Listen to this a recounting by the signal’s discoverer, Astronomer Jerry R. Ehman, including technical data and his analysis of possible hypotheses.

The most recent hypothesis explaining the WOW! signal (originating from a passing comet) has since been dismissed as unlikely.