The Wow! signal, a one-off detection at the Ohio State ‘Big Ear’ observatory in 1977, continues to perplex those scientists who refuse to stop investigating it. If the signal were terrestrial in origin, we have to explain how it appeared at 1.42 GHz, while the band from 1.4 to 1.427 GHz is protected internationally – no emissions allowed. Aircraft can be ruled out because they would not remain static in the sky; moreover, the Ohio State observatory had excellent RFI rejection. Jim Benford today discusses an idea he put forward several years ago, that the Wow signal could have originated in power beaming, which would necessarily sweep past us as it moved across the sky and never reappear. And a new candidate has emerged, as Jim explains, involving an entirely natural process. Are we ever going to be able to figure this signal out? Read on for the possibilities. A familiar figure in these pages, Jim is a highly regarded plasma physicist and CEO of Microwave Sciences, as well as being the author of High Power Microwaves, widely considered the gold standard in its field.
by James Benford
The 1977 Wow! signal had the potential of being the first signal from extraterrestrial intelligence. But searches for recurrence of the signal heard nothing. Interest continues, as two lines of thought continue to ponder it.
An Astronomical Maser
A recent paper proposes that the Wow! signal could be the first recorded event of an astronomical maser flare in the hydrogen line [1]. (A maser is a laser-like coherent emission at microwave frequencies. The maser was the precursor to the laser.) The Wow frequency was at the hyperfine transition line of neutral hydrogen, about 1.4 GHz. The suggestion is that the Wow was a sudden brightening from stimulated emission of the hydrogen line in interstellar gas driven by a transient radiation source behind a hydrogen cloud. The group is now going through archival data searching for other examples of abrupt brightening of the hydrogen line.
Maser Wow concept: A transient radiative source behind a cold neutral hydrogen (HI) cloud produced population inversion in the cloud near the hydrogen line, emitting a narrowband burst toward Earth [1].
Image courtesy of Abel Mendez (Planetary Habitability Laboratory, University of Puerto Rico at Arecibo).
Could aliens use the hydrogen clouds as beacons, triggered by their advanced technology? Abel Mendez has pointed out that this was suggested by Bob Dixon in a student’s thesis in 1976 [2]! From that thesis [3]:
“If it is a beacon built by astroengineering, such as an extraterrestrial civilization that is controlling the emission of a natural hydrogen cloud and using it as a beacon, then the only way that it could be ascertained as such, is by some time variation. And we are not set up to study time variation.”
How could such a beacon be built? It would require producing a population inversion in a substantial volume of ionized hydrogen. That might perhaps be done by an array of thermonuclear explosives optimized to produce a narrowband emission into such a volume [4]. Exploded simultaneously, they could produce that inversion, creating the pulse seen on Earth as the Wow.
Why does the Wow! Signal have narrow bandwidth?
In 2021, I published a suggestion that the enigmatic Wow Signal, detected in 1977, might credibly have been leakage from an interstellar power beam, perhaps from launch of an interstellar probe [5]. I used this leakage to explain the observed features of the Wow Signal: the power density received, the Signal’s duration and frequency. The power beaming explanation for the Wow accounted for all four of the Wow parameters, including the fact that the Wow observation has not recurred.
At the 2023 annual Breakthrough Discuss meeting, Mike Garrett of Jodrell Bank inquired “I was thinking about the Wow signal and your suggestion that it might be power beam leakage. But it’s not obvious to me why any technical civilization would limit their power beam to a narrow band of <= 10 kHz. Is there some kind of technical advantage to doing that or some kind of technical limitation that would produce such a narrow-band response?”
After thinking about it, I have concluded that there is ‘some kind of technical advantage’ to narrow bandwidth. In fact, it is required for high-power beaming systems.
Image: The Wow Signal was detected by Jerry Ehman at the Ohio State University Radio Observatory (known as the Big Ear). The signal, strong enough to elicit Ehman’s inscribed comment on the printout, was never repeated.
A Beamer Made of Amplifiers?
High power systems involving multiple sources are usually built using amplifiers not oscillators, for several technical reasons. For example, the Breakthrough Starshot system concept has multiple laser amplifiers driven by a master oscillator, a so-called master oscillator-power amplifier (MOPA) configuration. Amplifiers are themselves characterized by the product of amplifier gain (power out divided by power in) and bandwidth, which is fixed for a given type of device, their ‘gain-bandwidth product’. This product is due to phase and frequency desynchronization between the beam and electromagnetic field outside the frequency bandwidth [6].
Therefore, for wide bandwidth, a lower power per amplifier follows. That means many more amplifiers. Likewise, to go to high power, each amplifier will have a small bandwidth. (Then the number of amplifiers is determined by the power required.) For power beaming applications, to get high power on target is essential: higher power is required, so smaller bandwidth follows.
So why do you get narrow bandwidth? You use very high gain amplifiers to essentially “eat up” the gain-bandwidth product. For example, in a klystron, you have multiple high-Q cavities that result in high gain. The high-gain SLAC-type klystrons had gains of about 100,000. Bandwidths for high power amplifiers on Earth are about one percent of one percent, 0.0001, 10-4. The Wow! bandwidth is 10 kHz/1.41 GHz, about 10-5.
So yes, the physics of amplifiers limits bandwidth in beacons and power beams because both would be built to provide very high power. So, with very high gain in the amplifiers, small bandwidth is the result.
This fact about amplifiers is another reason I think power beaming leakage is the explanation for the Wow. Earth could have accidentally received the beam leakage. Since stars constantly move relative to each other, later launches using the Wow! beam will not be seen from Earth.
Therefore I predicted that each failed additional search for the Wow! to repeat is more evidence for this explanation.
The Wow search goes on
These two very different explanations for the origin of the Wow! have differing future possibilities. I predicted that it wouldn’t be seen again. Each failed additional search for the Wow! to repeat (and there have been many) is more evidence for this explanation. Mendez and coworkers are looking to see if their process has occurred previously. They can prove their explanation by finding such occurrences in existing data. These are two very different possibilities. Only the Mendez concept can be realized soon.
References
1. Abel Mendez,1 Kevin Ortiz, Ceballos, and Jorge I. Zuluaga, “Arecibo Wow! I: An Astrophysical Explanation for the Wow! Signal,” arXiv:2408.08513v2 [astro-ph.HE], 2024.
2. Abel Mendez, private communication.
3. Cole, D. M. (1976). “A Search for Extraterrestrial Radio Beacons at the Hydrogen Line,” Doctoral dissertation, Ohio State University, 1976.
4. Taylor, T., 1986, “Third generation nuclear weapons,” Sci. Am., 256, 4, 1986.
5. James Benford “Was the Wow Signal Due to Power Beaming Leakage?”, JBIS 74 196-200, 2021.
6. James Benford, Edl Schamiloglu, John A. Swegle, Jacob Stephens and Peng Zhang, Ch. 12 in High Power Microwaves, Fourth Edition, Taylor and Francis, Boca Raton, FL, 2024.
You cannot make that inference. Failed searches for a repeat only increase the confidence that this is a rare event, not that the event is caused by power beaming. The same applies to Mendez’ astrophysical explanation.
For example, suppose that some rare event on Earth was “explained” as a supernatural intervention. Would repeated failure to observe that event confirm that the cause was supernatural?
From the Mendez et al paper:
I would want to rule out this natural explanation (and others) before claiming the power beaming was a transient technosignature. What other evidence and inferences can be gathered to support this explanation? For example, does it say anything about the distance to the power beam source, or its input energy?
In one way it is shame that the Wow! signal of 1977 didn’t happen now – going under the assumption here it is an artificial signal from an ETI – because modern technology would have signaled the operators at Big Ear immediately so either they or specialized software could track the signal for those critical details to determine if it were terrestrial or not.
SETI personnel have also said that if the Wow! signal had happened in recent years, it probably would have been dismissed as RFI or some other kind of stray signal from this planet. There are certainly plenty of them and human civilization is only getting noisier in multiple areas.
Yes, astronomical radio telescope facilities have a technology no-use zone, but if you think those zones are not blatantly ignored all the time by the military, teenagers, et al, then I have bridge in Brooklyn for you at a very affordable price.
Even the first modern era SETI program, Project OZMA in 1960, was likely buzzed by a military aircraft that made Frank Drake think finding alien transmissions from the stars was even easier than he imagined.
Remember when the Parkes radio telescope SETI program picked up microwave ovens being used by astronomers at that facility? The media had fun with that because that is the level of technology they are able to grasp, plus making fun of real scientists who make honest mistakes as part of doing real science are the kind of thing they enjoy.
As for professional scientists, it is amusing to note how they tend to bend themselves into pretzels to give a cosmic find a natural, non-intelligent alien reason for something new and mysterious they come across in the heavens, rather than claim it is due to aliens.
Yeah, yeah – I know all about pulsars and LGMs and how they need to be conservative as they follow the scientific process. I agree with that method, but I also think we should stop dismissing the ETI angle since we should be a bit smarter and less socially conservative from the olden days. SETI should no longer be considered fringe, nor should religious bias be used to make us once again the only smart creatures in the Universe, etc.
I am not against this new theory to explain the Wow! signal being detailed here. But recall not too long ago, we had someone claiming it was comets – and they were subsequently found to be lacking in several important details. I am also reminded of all the natural explanations for Oumuamua, even though it did not behave like a regular planetoid or comet, such as accelerating AFTER it entered the Sol system.
I do not want to go to the level of one Dr. Loeb, who started out with the intention of keeping aliens in the science detection game, only to go off the rails by anyone’s reasonable standards. But this is the 21st Century and we need to start acting and thinking with a much wider mindset. The Cosmos is vast and ancient and full of all sorts of possibilities.
The history of such discoveries supports the natural explanation. I don’t see astronomers avoiding the ETI explanation despite the evidence, but rather that they should, rightly, assume a natural explanation first. With ‘Oumuamua. Loeb went out of his way to criticize natural explanations, despite his claims of going where the science leads. He actively avoided natural explanations in favor of artificial ones.
His escapade looking for superdense meteorite debris in the ocean is an example. Suppose, against all odds, he found grains of the meteorite that had atomic masses far in excess of anything we know of on Earth. Does that require manufacture, or a natural process that might create such material? Shouldn’t we explore the possibility of a natural process before accepting one that requires creation by agency?
That doesn’t mean we shouldn’t keep a lookout for ETI artifacts or other evidence, but we should not jump to the “It’s aliens” hypothesis, especially because we have been so wrong in the past. If anything, media from newspapers to movies have hyped the ETI claims. Aren’t the tabloids supposed to be the “real news” source of alien interaction on Earth?
Speaking of which, weren’t we supposed to have a major government release that confirms something astonishing about aliens?
I think it is very important to have the historical background of the Wow! signal discovery so that especially those who grew up in the first quarter of the 21st Century truly grasp just how comparatively primitive the setup for SETI was at the Big Ear radio facility at Ohio State University (OSU).
FYI: Sadly, you can no longer visit Big Ear in Ohio, as the university decided to make a few extra transient dollars by tearing down the radio telescope and turning the land into condos and a golf course. In case you need another reason to wonder why we have detected superior intelligences yet.
But don’t worry, there is a historical marker at the site…
http://www.setileague.org/photos/bigear00.htm
Here are the nitty-gritty technical details:
http://bigear.org/Wow30th/wow30th.htm
Not that Big Ear astronomers weren’t conducting actual radio SETI, but it must be understood that they had a volunteer, Jerry Ehman, checking printouts from the daily sky scans hours and even days after the event. The myth that teams of astronomers are sitting at consoles watching the skies and listening for signals 24/7 is just that, a myth. Especially back in the day. SETI was often a token effort at best.
You should also inquire as to what happened with all the much-touted SETI@Home data – it will make you first shocked, then sad, and then angry. More evidence that astronomy is not taking SETI as seriously as it should.
Here is a newspaper interview with Jerry Ehman from 1994:
http://www.bigear.org/wow.htm
I cannot recommend this 2022 documentary on the Wow! signal enough:
https://www.youtube.com/watch?v=TjQUucV83w4
Here is an interview from 2015 that includes discussions on the Wow! signal. I quote Gerry Harp’s take on it after the link…
https://phys.org/news/2015-07-aliens-day-nowseti-scientists-discuss.html
Harp: “It isn’t at all special or different from signals that we observe every day at the ATA. I hope you’re not disappointed that I’m not so impressed by the “Wow!” signal. I think you will find that many professional scientists in the field do not find the “Wow!” signal very convincing. But that doesn’t mean that SETI isn’t a good thing to do. There is still a 50% chance, by my estimates, that our first discovery of life off of our planet will be a discovery of a transmitting civilization.”
Harp: “The “Wow!” signal was almost certainly radio frequency interference. The signal failed to pass even the simplest tests to exclude interfering signals from that observation campaign. From another perspective, at the Allen Telescope Array (ATA), we see dozens of signals comparable to “Wow!” every day. This is simply because we have much more computational power than they did back when “Wow!” was seen. If the “Wow!” signal were seen today, it would be a yawn. However, there is a silver lining to the “Wow!” signal. “Wow!” has inspired a lot of public interest in SETI. Despite being a not very scientific result, public awareness of “Wow”! has been beneficial to SETI. So I generally think of “Wow!” as being a good thing from that perspective.”
Here is another take on the Wow! signal by Dr. Harp from 2014:
http://cosmicdiary.org/gharp/2014/05/18/seti-your-opinion-doesnt-matter-part-2/
The Very Large Array (VLA) was put into service to look for the Wow! signal in 2001:
http://www.bigear.org/Gray-Marvel.pdf
Here are some earlier blog posts on the Wow! signal from Centauri Dreams:
https://www.centauri-dreams.org/2021/01/22/was-the-wow-signal-due-to-power-beaming-leakage/
https://www.centauri-dreams.org/2023/01/19/an-appreciation-of-setis-robert-gray-1948-2021/
https://www.centauri-dreams.org/2016/01/12/return-to-wow/
https://www.centauri-dreams.org/2007/08/18/the-wow-signal-reexamined/
https://www.centauri-dreams.org/2016/08/27/an-interesting-seti-candidate-in-hercules/
From his question, I gather that Alex Tolley has not read my paper, where such estimates are made.
@Jim,
I would attempt to read your paper (ref 5) in the hope of it not going way over my head, but it is behind the JBIS paywall, and therefore inaccessible to me.
But that isn’t really my point, which is that your assertion of continued non-detection of the signal strengthens your hypothesis, isn’t a valid claim. The lack of further detections only strengthens a claim that the event was rare, insofar as it has been looked for.
[If someone claimed the emission was from a clandestine foreign military, and that lack of further detection was proof of this claim, wouldn’t you expect some positive further hard evidence to support the claim?]
Now let’s turn this around. Let’s say that several very similar events are detected. Does this invalidate your hypothesis and support Mendez’s hypothesis? While I would think this biases the explanation towards a natural one, it does not invalidate the ETI one. One could simply say that there are more beaming events that happen to be detected by our greater number of radio telescopes. Maybe the galaxy is littered with ETI that is polluting the em spectrum by extensive use of power beams that inevitably create these signals in hydrogen clouds.
Is there a copy not behind the JBIS pay wall? If not, please discuss the errors you see in Alex’s arguments.
It is worth comparing this post to one in 2017 where Avi Loeb suggests fast radio bursts may be power beams for ships.
Fast Radio Bursts: Signature of Distant Technology?
We should regard an explanation requiring ETI as an extraordinary claim requiring extraordinary proof. Or as the famous Baker Street private detective once said:
“Impossible” in our case should refer to natural phenomena that cannot explain the observation, leaving” improbable” as the ETI explanation. Unlike Holmes, we cannot eliminate all natural phenomena as we keep discovering new ones, often fitting the explanation we need. This seems to be the path that many such claims follow, whether UFOs (lights and artifacts in the sky), Ancient Alien influence (pyramid construction), or astronomical observations that are initially difficult to explain (Wow! Signal, FRBs, Tabby’s Star, etc.).
A Klystron is used to amplify microwaves and does use a narrow bandwidth, but a maser does not need or use a kylstron since a maser cavity uses the microwave stimulated emission of radiation and population inversion. These are two different types of technology. Radar transmitters use klystrons which spread out much more over long distances than Masers which use coherent microwaves so all the waves are at the same phase, direction and frequency. The wow signal could be either of these. We don’t need a hydrogen cloud to make our own masers, so any ET’s with our level of technological advancement also would not need to use naturally occurring space masers or space lasers from gas clouds. We can build are own.
It could also be space masers or megamasers associated with active galactic nuclei?
The most exasperating aspect of the Wow! signal is its choice of frequency, the 21 cm line, perhaps the most ubiquitous wavelength in nature. Why build a transmitter to operate at that frequency? If someone is trying to attract attention, it makes sense to emit at a frequency where others are bound to be listening. But if that is the case, why such a brief, non-repeatable event?
If they are trying to avoid being detected, then picking a common, natural wavelength makes sense so a potential interception might be dismissed as just cosmic noise, no big deal. But if THAT is the case, why a narrow band brief burst
that shouts out its artificiality? Either way, it just doesn’t make sense.
Is there any reason why a narrow band 21 cm burst would be optimal in some technological sense? Is there some potential application that would require that particular frequency? Perhaps it was chosen so in the event someone detected it they would simply ignore it.
The maser hypothesis solves the issue neatly: its perfectly natural, its not an artifact, and it fits the facts. Its not an explanation by any means, but right now its the best we’ve got.
The only other alternative is that it was a deliberate hoax. Some clever prankster with access to the right equipment and skills, and with some knowledge of what the astronomers were up to at the radio telescope (as well as an understanding of how their equipment works) decided to have some fun at their expense. These conditions are likely to be expected in a university environment.
This is consistent with my hypothesis on virtual Von Neumann machines:
Virtual Von Neumann Probes using Self Amplification and Replication of Electromagnetic Signals through Natural Stellar Processes
https://www.centauri-dreams.org/2017/01/30/virtual-von-neumann-probes-using-self-amplification-and-replication-of-electromagnetic-signals-through-natural-stellar-processes/