This one popped up several weeks ago, when I was too busy to do it justice, so I set it aside for when I had plenty of time to write it up properly, which appears to be now. There are a decent number of details and thus it will take some explaining, so get comfy as we set off on this journey.
There used to be a massive radio telescope at Ohio State University, dubbed the Big Ear, that monitored a portion of the sky each night for any signals within a fairly broad set of wavelengths – this was largely aimed towards intercepting any potential signals of extraterrestrial life, and served as among the first efforts at SETI (Search for Extra-Terrestrial Intelligence.) And on August 15, 1977, the telescope recorded a remarkably strong signal from a relatively barren patch of sky. This wasn’t discovered for a couple of days since the printouts of the recordings had to be examined personally for any anomalies, but when it was, the section that showed peak reception and signal strength was circled and appended, “Wow!” by Jerry R. Ehman, the astronomer evaluating the data. And it was certainly significant, many times stronger than any signal received before and tracing a bell curve of signal strength that helped pinpoint the location in the sky, as well as helping confirm that it was not a stray, fluke signal.
Some background: Radio telescopes aren’t tubes and lenses like optical telescopes, but antennae of different types, and in Big Ear’s case, it was two massive mesh arrays that reflected and bounced the radio waves down to two receivers. The whole affair was fixed and not able to be aimed, but it had a broad focus range and the rotation of the Earth served to track its observation path across the sky. The signal lasted for 72 seconds, which corresponds closely with how long any given point source would be able to be received as the planet rotated.
Mostly, anyway. The way the recording worked, the telescope would take ten seconds of signals received, spending two seconds to average out the signal strength from that period, and record that average as a single digit on the readout. So technically, there were six readings of ten seconds averaged out, allowing for a little slop on the signal strength and start and end periods; this also prevented recording any modulated or patterned signal with short periods. For instance, had a Morse code style signal been received, all of the dots and dashes within that ten seconds would have been simply averaged out to one digit of signal strength, roughly half of the actual signal strength because all of the pauses between dot and dash would be averaged into the final tally as well. However, the curve traced by the rise and fall of signal strength was in accord with a steady, constant signal, getting ‘louder’ and ‘quieter’ as it passed into and out of the focus of the antenna array.
The wavelength of the signal was 1420.4556 Mhz, which is notably close to the wavelength of excited hydrogen electrons, the radio waves emitted when hydrogen is bombarded with energy from an outside source such as a star. The problem was, when the location of the source was plotted, there was nothing within range that should have been able to produce such a signal, and in fact, very little there at all. The signal was also transient: there were two receivers for the telescope, aimed slightly differently, which should have captured the signal three minutes apart – but only one did (and the telescope was not designed to differentiate which one it was.) So at the very least, the signal stopped before the second receiver aimed at the same section of sky, or started after the first did. Moreover, the same section of sky was monitored on subsequent passes – and later on by much more sensitive telescopes. And in the nearly fifty years since, no comparable signal has been detected, from any location. The Wow! signal stands alone as a peculiar anomaly.
In 2017, a potential explanation was put forth, in the form of two comets that converged on that portion of the sky, thus magnifying their own output in the hydrogen wavelength. The popular media ran with this, but it didn’t take long to determine that the comets did not pass through that portion of the sky at the time the signal was received, nor was there any known way for them to emit that strong a signal.
The question that’s been asked repeatedly is, might this actually indicate extraterrestrial intelligence, an attempt to communicate? Arguments have been made that the wavelength could be indicative of this, since it would demonstrate that the transmitting species was aware of the properties and penetrating value of that wavelength. But at the same time, hydrogen is the most abundant element in the universe, and fully to be expected to be received quite often – just, not at that strength. It’s also a restricted frequency for civilian use, so unlikely to be a stray signal or reflection from a terrestrial source (though the military is not so restricted.)
Missing are any factors that would be more convincing of an attempt to communicate (or even just an intercepted transmission not intended for us): patterns, variations, or modulations, any repetition, any further examples, and so on. One long beep, one time only doesn’t exactly say anything, except perhaps an alien driver stalling too long at a cosmic traffic light.
The question that’s been in my mind for years has been, what are the chances this was a simple hoax? Not on the part of the team at Ohio State University, but perhaps by some knowledgeable students? The antenna array probably wasn’t hard to access, nor would it be difficult to build a lightweight radio to transmit on that frequency, perhaps carried in a light plane or even just floated from a balloon. Since the antenna was huge, it could pick up very faint signals, and the wattage of the transmission would not need to be high at all. The signal only being captured in one of the two receivers bolsters this idea slightly. I could easily see this occurring. Except… if you’re going to go through all that trouble, why pick a wavelength so close to hydrogen emissions? Why such a short and simple ‘beep?’ Any elaborations on the idea would probably provoke a better response.
However, a couple of months ago, a paper was released that provided a potential explanation. Examining archive data from the much larger and more sensitive Arecibo radio telescope (which had collapsed a few years earlier,) astronomers found several other signals of the same type, albeit much weaker. These signals were generated simply by clouds of hydrogen excited by external energy sources, and it was hypothesized that the Wow! signal was the same, only produced by a much stronger source exciting a hydrogen cloud to unprecedented levels. The hydrogen cloud has actually been identified, just not the energy source, but given the nature of the signal, the close fit with the frequency, and the presence of many other weaker examples, the evidence is weighing distinctly in favor of this explanation.
Now we get to the critical examination of this all. Without the corroborating detail of the energy source, the explanation isn’t conclusive, though we’d feel more confident if and when it’s even seen again in some other circumstances – just one instance seems unlikely at least. Then again, the nature of the phenomenon is that it’s transient and short-lived, and a radio telescope has to be pointed directly at it when it occurs, so we shouldn’t expect to see it often either.
As for it being a deliberate signal from some extra-terrestrial intelligence? Well, again, it’s just a ‘beep’ in an extremely common natural wavelength, and just like the hoax possibility above, we’d expect to see something more elaborate, or repetition or a pattern or anything. Even singular beeps that went up the spectrum through the wavelengths of hydrogen and helium and oxygen or whatever, something that is highly unlikely to progress by any natural means but would be very indicative of intelligence, would be far better (and we’ve speculated ourselves on doing the exact same thing if we decide to reach out, a message that says, “Hey, this is not random nor probable,” without any language at all.)
Occam’s Razor comes into play. The most recently proposed explanation involves the fewest unknowns and presents examples of weaker versions of the same kind of signal. It has the fewest questions that need to be answered (“What was the energy source?”) and does not require anything that we have no evidence of at all, like extra-terrestrial intelligence. It serves to answer the question for now. Maybe it’ll be overturned in the future – but it’s far more likely that further support for it will appear instead. All we can do is watch for further developments, but that’s how science works.