For almost half a century, many astronomers have been locked in the enduring Search for Extra Terrestrial Intelligence (SETI). Sizable telescopes -- astronomers' eyes and ears -- have been trained to the heavens, looking and listening intently for an otherworldly signal. To date, the search has proved fruitless. Apart from the background noise of space and the occasional astronomical event, SETI astronomers have heard naught but silence.
Except, that is, for a span of 72 seconds in the waning hours of August 15th, 1977, when the Big Ear Radio Observatory of Ohio State University detected a remarkable signal that still, to this day, remains unexplained.
That signal is known as the "Wow! Signal," named after the initial, astonished reaction of astronomer Jerry Ehman, who, upon sifting through the improbable data three days later, penned the following:
To the layperson, this picture may only seem to display an array of dull, random digits. But when you understand what it represents, you'll realize that it's anything but boring.
The numbers indicate the signal intensity detected by Big Ear for certain regions of space, defined as the ratio of signal strength versus the level of background noise. For example, a blank space would denote a signal between zero and one times as loud as the background noise of deep space, "1" would indicate between one and two times as loud, "2" between two and three times as loud, etc. Letters suggest a more intense signal. "A" denotes between ten and eleven times as loud, "B" between eleven and twelve times as loud, etc.
The Wow! signal -- the circled 6EQUJ5 -- meant that Big Ear detected a signal originating from the direction of the constellation Sagittarius that, at its strongest, was thirty times more powerful than the background noise of deep space!
But what's the big whoop? Scientists have discovered signals just as powerful from pulsars, quasars, supernovae and other natural astronomical phenomena. Why is Wow! special? As Robert Gray, author of the book The Elusive Wow: Searching for Extraterrestrial Intelligence
, explained to The Atlantic
With the "Wow!" there wasn't any noise on any of the channels except for
one, and that's just not the way natural radio sources work. Natural
radio sources diffuse static across all frequencies, rather than hitting
at a single frequency... It was a very narrow band, very concentrated,
exactly like a radio station, or a broadcast, from another world would
Furthermore, the signal was detected at a frequency of 1420 Megahertz (1420.4556 MHz to be precise, according to Ehman). This is almost identical to the frequency at which hydrogen, the most common element in the universe, resonates. Years earlier, two Cornell physicists, Philip Morrison and Giuseppe Cocconi, writing in the journal Nature
, postulated that aliens might attempt to make contact using that frequency, since it would likely be meaningful to a society with an understanding of science.
In the wake of the Wow! signal, with all signs improbably pointing to an extraordinary conclusion, Ehman took the data to colleagues John Kraus and Bob Dixon, and the trio set about the task of disproving the finding, as any good scientists would do.Did the signal originate from a planet or an asteroid?
Nope. It didn't fit the type of thermal emission expected from an astral body, and none were in the vicinity at the time of the transmission.
Did the signal come from a satellite or a spacecraft? No. Again, none were in the telescope's beam at the time of the Wow! source.
What about an airplane? Highly unlikely. No planes are allowed to transmit at 1420 MHz and the Wow! signal almost certainly originated from a fixed point with respect to the celestial background (the positions of stars), meaning that it came from light years away.
How about a computer glitch?
Doubtful, as the systems were examined repeatedly afterwards. A ground-based transmission that bounced off space debris? An electromagnetic wave deflected from a star or galaxy? A wave sent from the twinkling of stars? All are plausible explanations, but deemed highly unlikely.
With rigorous analysis performed and all simple explanations pretty much ruled out, the only interpretation remaining was the most improbable one of all: a signal from an alien race. Yet since 1977, astronomers have focused their telescopes at the constellation Sagittarius, pricking up their ears in the direction where Wow! originated. They've heard nothing.
The ultimate rule of science is repeatability, and despite over one hundred follow-up studies on the Wow! signal, it's never once been observed again. "Thus, we have a small sample size of exactly one observation," writes H. Paul Shuch, emeritus executive director of SETI League
makes the signal intriguing, and enigmatic. It is suggestive of, but
not proof of, our cosmic companions."
Years later, astronomical scientists like David Grinspoon
still fantasize about the Wow! signal. Was it perhaps
a snippet of conversation between two alien ships? And we were simply in the right place at the right time to eavesdrop?
But others, like Columbia University astronomer Caleb Scharf approach it with skepticism. It's very hard to exhaust the alternative possibilities when we are constantly learning more and more about the universe, he told NPR
But, he added, "I can't in good conscience say that we will never see something. And I know that if we did, it would be amazing."(Image: The Ohio State University Radio Observatory and the North American AstroPhysical Observatory (NAAPO) via Wikimedia Commons)