August 15 will mark 40 years since the now famous “Wow!” signal, the first definitive — and as yet unexplained — detected transmission from outer space, was received by a SETI (Search for Extraterrestrial Intelligence) listening post. And after those 40 years, not only can it not be explained, but the “Wow!” signal also cannot be ruled out as being transmitted by an alien civilization.
As Forbes reported this week, the “Wow!” signal was received at Ohio State University’s Big Ear Radio Observatory (now defunct) in August 1977. It became known as the “Wow!” signal because of the three-letter designation applied in the margins of the data sheet (by astronomer Jerry Ehman) when it was detected. Unfortunately, however, in the nearly 40 years since the data rolled out, the signal has not been repeated.
Bob Dixon, Ohio State University’s Search for Extraterrestrial Intelligence program director in 1977, at one time told Forbes contributor Bruce Dorminey that the signal at least originated at a distance farther than the Moon.
Several indicators gave astronomers hope that the signal came from far beyond the Moon. The direction of the signal came from the star cluster M55 in the constellation of Sagittarius. It also closely matched the narrow emission line of hydrogen at 1420 megahertz, known as a radio-quiet spot by scientists with the potential for being an interstellar transmission frequency for alien civilizations. And at the time the “Wow!” signal was received, it was the strongest SETI candidate signal ever recorded.
Now there are, of course, the much stronger FRBs (Fast Radio Bursts), the first of which was detected in 2007. These milliseconds-long broadband pulses of radio energy are also of unknown origin. But in contrast to the “Wow!” signal, there is a set of repeating FRBs.
But as romantic as it is to press for the idea that the “Wow!” signal is of extraterrestrial origin, there are those who argue that it is unlikely. Dan Werthimer, chief scientist at the University of California at Berkeley’s SETI program, acknowledged that the term “Wow!” was appropriately used, but he also says that the find would have been more impressive had the signal been replicated, because that would have indicated that the signal was an artificial radio broadcast from an interstellar source.
Werthimer believes that, with 99 percent confidence, the signal received at the Big Ear Radio Observatory was produced not by aliens, but by radio frequency interference (RFI).
And there are other hypotheses as to what produced the “Wow!” signal. A 2015 paper published by the Washington Academy of Sciences posited that two comets transited the Sagittarius constellation and produced a hydrogen cloud around the comets’ nuclei. (Dorminey argues that, if this were the case, a signal along the hydrogen emission line would likely have been picked up within the last five decades. This, as noted, has not happened.)
Dorminey believes the signal emanates from a “very distant or unusual and/or poorly-understood astrophysical phenomenon.”
From Forbes: “Werthimer, however, says either the ‘Wow!’ signal’s rise and fall in strength was actually intrinsic to the signal, in which case he says it would have to be RFI. Or if the signal were from a distant source, he says, then it would be constant in power and its rise and fall in strength would be due to Earth’s rotation.”
That state of ambiguity is what sets up the possibility that the signal is alien in origin, something that Werthimer acknowledges.
“We can’t rule out E.T.”
Nor can it be ruled out that an alien civilization had nothing to do with the signal. In a 2012 podcast, skeptic Brian Dunning noted (per Skeptoid) that the 1977 radio detection was “apparently, a signal from outer space.” However, he added, “In conclusion, yes, an alien intelligence is still a candidate explanation for the Wow! signal. But there’s no evidence for this. A stronger candidate is the significantly more vague explanation of an interstellar radio source of unknown origin.”
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