The WOW! Signal Reconsidered

Was Evidence of ET Technology Detected in 1977, Dismissed too Hastily?

Do extraterrestrial (ET) intelligent aliens really exist “out there”? The serious Search for Extraterrestrial Intelligence (SETI) has been ongoing for six decades, primarily utilizing radio telescopes (which detect electromagnetic radiation in the radio wave range; optical telescopes use light, another form of electromagnetic radiation). The basic idea is that a technologically sophisticated extraterrestrial civilization will utilize radio waves for communication, perhaps even purposefully sending a message into space to announce their presence. The ETs might be curious to know if they are alone in the universe.

Many skeptics assert that thus far SETI has come up short; no evidence of ETs has been found, they claim. However, this might not be true. Among the community of SETI researchers, as well as the general public, perhaps the most famous possible evidence of technologically advanced ETs “out there” is the so-called Wow! signal detected on 15 August 1977 by the Big Ear radio telescope, at the time operated by Ohio State University as part of the SETI project. The signal received its name when astronomer Jerry R. Ehman, analyzing the data on a computer printout, used a red pen to circle the anomaly and wrote next to it “Wow!”

On the computer printout the Wow! signal consists of a string of numbers and letters reading “6EQUJ5”. This has often been misinterpreted as a message, but in fact the letters used are simply number equivalents above 9, where A = 10 (or actually 10 to just under 11), and so forth. Thus the signal reads “6, 14, 26, 30, 19, 5”. These numbers refer to the intensity of the signal in terms of its strength relative to background noise; therefore, at its “peak” the signal was about 30 to 31 times stronger than the background noise (see J. R. Ehman, 2007/2010, “The Big Ear Wow! Signal (30th Anniversary Report)”). The signal was detected for 72 seconds, but this does not mean it lasted for only 72 seconds, or even that the actual signal got stronger, peaked, and then weakened over 72 seconds. The radio telescope could only be adjusted for height above the horizon; to make measurements of different parts of the sky, it had to wait until a certain portion of the sky came into view as Earth rotates on its axis, and it could only view a certain part of the sky for 72 seconds due to the width of the telescope’s “window.” The increase and decrease in the detected strength of the Wow! signal was probably a function of the target coming into view of the telescope and then going out of view again.

The Wow! signal came from the region of space marked by the constellation Sagittarius, and the actual signal had a frequency that was calculated to be either 1420.356 MHz (megahertz) or 1420.4556 MHz (A. Paris and E. Davies, Winter 2015, Journal of the Washington Academy of Sciences), both of which correspond to a wavelength of just over 21 centimeters. These values are very close to the hydrogen line of 1420.40575177 MHz (a wavelength of approximately 21.106 cm), which is the radiation given off by neutral hydrogen atoms during an electron transition between two levels in the atom. This is a very significant frequency and wavelength for a couple of reasons.

It is common in the known universe, but this “commonness” also makes it “universal.” In a 1959 paper that is widely regarded as launching the SETI radio astronomy efforts, Giuseppe Cocconi and Philip Morrison (both at Cornell University) suggested this range of frequency and wavelength as the optimal signal that an ET might utilize and, therefore, we should focus on (C. Cocconi and P. Morrison, 1959, Nature, vol. 184, no. 4690). And it was this range of frequency and wavelength that astronomer Frank D. Drake focused on for some of the earliest SETI searches in 1960. In this respect, the strong Wow! signal matched the predicted signature of an ET signal. As discussed further below, arguing against the possibility that the Wow! signal originated from Earth (perhaps reflected off of a piece of space debris into the telescope), rather than deep space, is the fact that the 1420 MHz frequency range falls within a spectrum of electromagnetic signals that is reserved for astronomical purposes—terrestrial transmitters are not allowed to operate in this range (and this was the case in 1977 as well as today).

The Wow! signal was never detected again, despite repeated scans of the same region of the sky, including every night for the next 60 days after it was detected. It seems to have been a one-time signal, at least from an Earth perspective (after the initial chance detection, the Wow! source may have stopped broadcasting, or it may have been directed toward another spot in the universe rather than toward Earth). Arguably, a genuine ET signal might be detected only once, whereas many natural phenomena would be expected to last or be continuous for some significant period of time, or be repeated at regular intervals. Thus, the once only detection of the Wow! signal is not necessarily an argument against its artificiality; it may even be considered to support the ET message hypothesis.

Could the Wow! signal have contained a message? That is, could it have been modulated and varying, as is a standard modern radio signal, so as to encode and transmit information? The answer seems to be that this is possible, but we shall never know for certain. The reason we cannot know is due to the equipment being used in 1977. The radio telescope collected data averaged over ten-second intervals, so any modulation that occurred faster than at most about once every five seconds or so would be completely averaged out and go undetected. Think about how many words or notes of music or bits of information can be transmitted over radio waves in five seconds. Over the 72 seconds during which the Wow! signal was detected, a large amount of information may have been transmitted which was lost due to the “averaging” of the equipment.

What are some potential non-ET explanations for the Wow! signal? A number of scenarios have been considered, most of which must be rejected as impossible or extremely unlikely. Planets and asteroids are not known to emit radiation in the range of the Wow! signal, and furthermore none of our solar system’s planets or large known asteroids were at the time in the area from which the Wow! signal originated (the matter of comets is discussed below). Even though there was a ban on transmitting from satellites in the frequency range of the Wow! signal, the orbits of all known satellites were studied and none were near the source of the Wow! signal at the time of detection. Spacecraft and aircraft were (and are) also banned from transmitting in the frequency range of the Wow! signal, and furthermore an aircraft or spacecraft would be moving relative to the stars on the celestial sphere, whereas the Wow! signal source was moving with the stars. The same argument holds for many satellites as well, which from our perspective are moving relative to the stars rather than with the stars.

Might the Wow! signal have originated from Earth, despite the protected status of the frequency range? Yes, if the transmission was directed (either purposefully or by coincidence) toward an object in orbit around Earth (such as a piece of space debris) which reflected the signal back to the radio telescope. But, as already pointed out regarding purposeful satellites (items of space debris in orbit constitute satellites in their own right), the space debris would have to be moving at just the right speed so as to stand still relative to the movement of the background stars; and it would also have to be stable and not spinning or tumbling to any significant degree, which is highly unlikely. All in all, it seems incredibly improbable that the Wow! signal originated from a terrestrial source.

The phenomena of gravitational lensing and interstellar scintillation have both been put forward as potential explanations for the Wow! signal. Dr. Jerry R. Ehman, the discoverer of the Wow! signal on the computer printout, has considered both of these possibilities. Gravitational lensing is a well-known phenomenon wherein electromagnetic radiation, such as radio waves or light, is deflected when passing by a massive object in space (such as a star or a galaxy). This deflection or bending of the electromagnetic waves can act as a lens that focuses and enhances the signal, typically forming rings or intense “bright spots.” If the Wow! signal was due to such gravitational lensing, and the original source was natural, it would generally be expected that the signal would have lasted significantly longer than a few minutes—one would expect to detect it the next day and during subsequent days when the radio telescope again scanned that part of the sky. However, it needs to be made clear that whether or not gravitational lensing was involved, this neither proves nor disproves that the Wow! signal was either natural or artificial. Gravitational lensing could occur with an artificial (ET) signal as well as a natural signal. In fact, an intelligent extraterrestrial civilization might utilize gravitational lensing specifically to enhance the strength of a signal it was purposefully broadcasting.

Scintillation is, simplistically, the concept that as particles of electromagnetic radiation (photons), whether radio waves or light, pass from one point to another, they can be very slightly diverted. This very slight diversion of the light of stars passing through our atmosphere is what makes the stars appear to twinkle. Likewise, light passing through interstellar space (which is not a total vacuum) can give rise to interstellar scintillation. Such scintillation could conceivably enhance the strength of the electromagnetic signal, but for it to be enhanced for a short duration of time at the high level observed in the Wow! signal seems extremely implausible. Furthermore, whether or not such scintillation might enhance a signal has no relevance to whether the signal is natural or artificial—unless, of course, if advanced aliens understand how to utilize scintillation to purposefully enhance a signal.

It has been suggested that the Wow! signal may have been due to a comet and, therefore, is natural (unless there was an alien transmitter or tracking device located on the comet—which is not totally inconceivable). Comets can be surrounded by a cloud of neutral hydrogen (produced when radiation from the Sun splits water associated with the comet into hydrogen and oxygen atoms), and it has been hypothesized that this cometary hydrogen could give off an emission matching the Wow! signal. Were there any comets in the vicinity of the Wow! signal at the time it was detected? In 1977 no such comets were known, but in subsequent decades comets have been discovered that, it has been claimed, were close in the sky to the apparent source of the Wow! signal on 15 August 1977 (A. Paris and E. Davies, 2015). One such comet in particular, known as “266P/Christensen,” has been the focus of heated controversy regarding the Wow! signal.

During the spring/summer of 2017, Antonio Paris published a paper, based on observations purportedly made from late November 2016 to late February 2017, in which he states it was “discovered that comet 266/P Christensen emitted a radio signal at 1420.25 MHz” (A. Paris, vol. 103, no. 2, Summer 2017, Journal of the Washington Academy of Sciences, p. 1 of article). Thus according to Paris, the Wow! signal was the result of a natural phenomenon. Many ET skeptics, as well as the popular press, uncritically accepted these conclusions.

However, many professional radio astronomers have criticized the Paris paper, questioning his observations, data collection, and conclusions. In an open-letter response to Paris (6 June 2017), Robert S. Dixon (Director, Ohio State University SETI Program) noted that comet 266/P Christensen “was nowhere near the position” of the Wow! signal in 1977; thus the Paris observations of comet 266/P Christensen, even if correct, “are irrelevant, because that is not where the comet was in 1977 when the ‘WOW!’ signal was observed.”

Other than possibly by Paris, comets have not been observed emitting radio signals in the frequency, wavelength, and intensity level of the Wow! signal. As Dixon notes, Paris does not cite any references to the work of others in this regard. After contacting experts in cometary and hydrogen phenomena, Dixon found they were “unaware of any hydrogen emission ever having been observed from a comet,” suggesting the observations of Paris may be flawed. Furthermore, according to Dixon and other radio astronomers, the ostensible data presented by Paris are not in standard units or format, and are missing critical information—thus it is not possible to compare his data directly with the Wow! signal. Adding to the doubts, Chris Lintott (an Oxford astrophysicist, quoted in a 12 June 2017 article by Ben Sullivan, Motherboard) stated, “The claimed detection [by Paris from 266/P Christensen]—even if it’s real—is much, much weaker than the Wow signal, and lasts for longer.”

Adding to the argument against a comet source for the Wow! signal, the Big Ear radio telescope utilized two “feed horns” to collect data. These feed horns were slightly offset physically from one another, and thus they sequentially scanned the same area of the sky about five minutes apart. Signals that lasted more than about five minutes were collected by one feed horn and then by the other feed horn. Tellingly, the Wow! signal was picked up by only one of the two feed horns (it is not known if it was detected by the first feed horn or the second feed horn due to the way the electronics and computer programming were set up at the time). By Dr. Jerry R. Ehman’s best estimate, the Wow! signal probably did not last for more than a few minutes, otherwise it would have been detected by both feed horns. If the Wow! signal had been produced naturally by a comet, one would expect it to last (and stay in range of both of the feed horns) for longer than a few minutes, not suddenly “turn on” and/or “turn off” its radio emissions.

Bottom line: The comet theory to explain the Wow! signal has, thus far, failed to stand up to scrutiny.

My strong suspicion, based on the evidence, is that the Wow! signal originated from an intelligent extraterrestrial civilization located many light-years away. Given the estimated 100 to 400 billion stars in the Milky Way Galaxy, which we call home, and the approximately two trillion galaxies in the observable universe (C J. Conselice, A. Wilkinson, K. Duncan, and A. Mortlock, “The Evolution of Galaxy Number Density at Z < 8 and Its Implications”, 11 October 2016), it is inconceivable to me that we are alone; it seems impossible that there are no other technologically sophisticated civilizations in the universe. I believe definitive evidence of ETs will ultimately be recognized—it is just a matter of time.


Robert M. Schoch, Honorary Professor at the Nikola Vaptsarov Naval Academy, Director of the Institute for the Study of the Origins of Civilization at Boston University, and a full-time faculty member at B.U.’s College of General Studies, earned his Ph.D. in geology and geophysics at Yale University. Best known for re-dating the Great Sphinx, he is the author of Forgotten Civilization: The Role of Solar Outbursts in Our Past and Future, and many other books. Website:

By Robert M. Schoch, Ph.D.