radio telescope

Thirty-six years ago today, on August 15, 1977, we (humanity) may have received a signal from an extraterrestrial intelligence. It happened at Perkins Observatory in Delaware, Ohio, and if E.T. was really calling, the man who picked up the line was Jerry Ehman, an astronomer from the University of Michigan. A radio telescope called the Big Ear was scanning the sky looking for radio signals that might not be natural in origin (many natural phenomena, such as quasars, emit radio signals). What the Big Ear heard that day was a strong narrow band radio transmission. It’s rather difficult to describe exactly what happened, so I’ll quote from this report written by Dr. Ehman in 1998:

I began my routine review of the computer printout from the multi-day run that began on August 15th. Several pages into the computer printout I was astonished to see the string of numbers and characters “6EQUJ5” in channel 2 of the printout. I immediately recognized this as the pattern we would expect to see from a narrowband radio source of small angular diameter in the sky. In the red pen I was using I immediately circled those six characters and wrote the notation “Wow!” in the left margin of the computer printout opposite them. After I completed the review of the rest of the printout, I contacted Bob Dixon and Dr. John D. Kraus, the Director of the Big Ear Radio Observatory. They were astonished too. Then we began an analysis of what has been called for 20 years the “Wow! source”. Analyses have continued even through recent years as ideas needed to be tested.

The part of the sky corresponding to the origin of the signal is in the constellation Sagittarius.

So how come we don’t know if it was a signal from intelligent aliens or not? Well, the main thing is that nobody has ever heard it again. Numerous attempts have been made to scan the exact same frequency of the signal, from the early 1980s through the late 1990s. Dr. Ehman himself has said that if it was alien in origin, we should have been able to pick it up again. Why would aliens trying to contact us “blast” us with one 72-second signal, on one night, and then never repeat themselves? Of course we can’t know.


The actual WOW! Signal. This piece of paper is now a historic relic at the Ohio Historical Society.

If it wasn’t aliens, what was it? One possible interpretation is that the signal was a rogue bit of Earth-origin radio traffic that bounced off a piece of space debris orbiting the Earth, like a glint of light flickering off a car’s mirror in the distance. The only problem with that theory is that the frequency of the signal–1420 MHz–is restricted, and theoretically only astronomers can use it (for, among other things, searching for extraterrestrial signals).

Brian Dunning, a well-known skeptic, has done an article on the WOW! signal. You would expect someone known for his rigor in critical thinking to be dismissive of the alien/extraterrestrial possibilities of the event. Actually he is not. Here’s what he has to say:

Wow! has tantalized by evading almost every suggestion put forth to explain it. For one reason, that frequency range is protected; nobody on Earth is allowed to transmit on that frequency. We know the signal did not come from an aircraft or spacecraft passing overhead, because the signal was consistent with a point in the sky that was not moving. No known planets or asteroids were in a position that they could have reflected the signal toward Earth. Any space debris would have had to be absolutely still in space relative to the Big Ear, which is unlikely, and not tumbling, which is also unlikely. Even complicated astronomical effects like gravitational lensing and interstellar scintillation (basically twinkling like that which we observe stars doing visually) have technical reasons that make them very poor candidates to explain Wow!

In conclusion, yes, an alien intelligence is still a candidate explanation for the Wow! signal. But there’s no evidence for this.

In short, it sounds like the chances are actually not so bad that the voice we heard from the sky on August 15, 1977 was actually an alien intelligence. It may not have been directed at us; it may have been some sort of accidental transmission, which would explain why it was not repeated. But it really could be.  Then again, it might not be, but unlike oodles of spurious UFO “sightings” over the years, this is one potential alien contact that we cannot rule out.

We simply don’t have enough information to determine what we heard that night. Perhaps someday we will. If it does turn out to be confirmed, the date August 15, 1977 might well become the most important date in human history–the day we made first contact. *Cue Star Trek theme*!



Radio telescope photo: Hans Linnet, CC license, used with attribution.