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 forFurthermore, 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.
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
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)