Friday, February 24, 2012

The 'Wow!' Signal


At 11:16 p.m. Eastern Daylight Time on the evening of August 15, 1977, astronomers working on the Search for Extraterrestrial Intelligence (SETI) project at the 'Big Ear' radio telescope at the Perkins Observatory of Ohio State University detected a very unusual signal from space. The intensity of the signal relative to the expected background noise of deep space was so extreme that the reaction of Dr. Jerry R. Ehman, the first person to examine the printout of the recorded data, was to draw a circle around the relevant portion on the sheet and add a single word note indicating his reaction: "Wow!" For this reason, the signal has become known as the 'Wow!' Signal. Despite numerous attempts to find the source again over the ensuing three plus decades, the signal has never been duplicated. Nor has it ever been explained.

The original 'Wow!' Signal printout including Dr. Ehman's handwritten reaction. (1)

Although a few letters and numbers on a sheet of printout hardly seem worthy of such a dramatic response, an explanation of this data ("6EQUJ5") and some background may suffice to explain Ehman's amazement. The radio telescope would continually scan the skies and record the intensity of signals received at various frequencies. The countless sources of radio wave emissions in the observable universe produce a complex pattern, but one which tends in general towards a relatively uninteresting background pattern of "noise." The printout above shows a very small segment of the data that the telescope received on that evening, with the blank spaces between the alphanumeric characters indicating an intensity between 0 and 1 in terms of signal-to-noise ratio. The 1's indicate an intensity between 1 and 2, and so on for the numeric characters, beyond which the alphabet indicates intensities beyond 10-to-1. So the pertinent portion, "6EQUJ5" means that the signal to noise ratio peaked at more than 30-to-1, as indicated by the letter "U." What is significant about this intensity is not simply that it suggested a powerful source of electromagnetic emissions from the position in the night sky at which the telescope was then pointed, but that the frequency was almost precisely 1420 MHz, what is known as the "hydrogen line." Because hydrogen is the most common element in the universe, it had previously been hypothesized that an extraterrestrial civilization "broadcasting" its presence into space would choose the frequency at which hydrogen resonates (the hydrogen line) because this would allow for the best propagation of a signal:

Eighteen years earlier, two Cornell physicists, Philip Morrison and Giuseppe Cocconi, had tried to imagine how an intelligent alien civilization might try to signal Earth. We should look, they said, for a radio transmission. Radio waves are cheap to produce, don't require much energy and travel vast distances across space. Cocconi and Morrison guessed that the aliens would choose a frequency that would mean something to creatures who know math and chemistry. Hydrogen is the most common element in the universe. Zap a hydrogen atom and it will resonate at a particular rate: 1420 megahertz (MHz). So look, they said, for a signal coming in at 1420 MHz. And look for something loud, something that would catch our attention. And on Aug. 15, in it came, exactly as predicted. (2)

 Because the Perkins Observatory telescope utilized two feed horns to capture data, with no method of determining which had received a particular signal, the SETI team's effort to localize the source was made more difficult. However, it was possible to narrow the location down to two "small" portions of the heavens, in the constellation Sagittarius, viewable here:  'Wow!' Signal Location (3)


The question is obvious: what is the source and significance of the 'Wow!' Signal? As numerous attempts have been made over the years to find the signal again and all have met with failure (4), this question remains intriguing, but fails a crucial test of scientific methodology in that there is no indication that it is replicable. Dr. Ehman himself has gone on the record as doubting that the signal had intelligent extraterrestrial origins: "Even if it were intelligent beings sending a signal, they'd do it far more than once. We should have seen it again when we looked for it 50 times. Something suggests it was an Earth-bound signal that simply got reflected off a piece of space debris." (5) However, he later changed his opinion on this hypothesis, and has all but ruled out the possibility of reflection off of space debris, as indicated in the 30th anniversary report on the signal:

[S]ince all of the possibilities of a terrestrial origin have been either ruled out or seem improbable, and since the possibility of an extraterrestrial origin has not been able to be ruled out, I must conclude that an ETI (ExtraTerrestrial Intelligence) might have sent the signal that we received as the Wow! source. The fact that we saw the signal in only one beam could be due to an ETI sending a beacon signal in our direction and then sending it in another direction that we couldn't detect. Of course, being a scientist, I await the reception of additional signals like the Wow! source that are able to be received and analyzed by many observatories. Thus, I must state that the origin of the Wow! signal is still an open question for me. (6)

The pertinent information related to the point of view from which the anomalous data represented by the 'Wow!' Signal must be considered includes the fact that to date there is no credible evidence of life existing elsewhere in our universe beyond our own planet. Although some scientists have conjectured that the almost unimaginable vastness of the cosmos, with its billions of galaxies and trillions of stars, suggests statistically that it is exceedingly improbable that we are alone, as yet we have no evidence to the contrary. This extraordinary situation is known as the "Fermi Paradox". We should also remember the fact that the observations recorded at the Big Ear observatory were part of the Search for Extraterrestrial Intelligence. This may have led to the information being interpreted in a way that would not have been the case in other circumstances, such as more mainstream astronomical investigations. Our own individual interpretations may also vary according to the point of view from which we approach such phenomena as the 'Wow!' Signal. Certainly, many people are quite prepared to accept the existence of extraterrestrial life almost as a given, while others demand a much higher level of proof than is generally accepted as having been provided to date.

The information related to this case is, of course, the data recorded by the telescope on the night of August 15, 1977. This is without doubt the element of the 'Wow!' Signal event that has lent it its mystery. Rather than being just another routine UFO sighting case, the 'Wow!' Signal is a puzzle based on hard scientific evidence. Of course, many questions regarding the data remain unanswered, and the possibility of a commonplace, earth-bound explanation exists, but nevertheless, for nearly thirty-five years, no one has been able to conclusively determine the source of the signal. Thus, the original data printout, with Dr. Ehman's legendary handwritten reaction, is currently preserved by the Ohio Historical Society. (7)

Of course, the implications of the 'Wow!' Signal are astounding to consider. As already mentioned, there is a sizable segment of society that believes that alien encounters are quite common. This is certainly not the case in the scientific community, however. While many feel that the statistical possibility of Earth being the universe's sole occupied planet are vanishingly small, it is generally accepted that no evidence of extraterrestrial life has yet been found. Were the 'Wow!' Signal to be confirmed as such evidence, our understanding of our place and role in the universe would be forever altered. This theme has been depicted in countless films, works of fiction, and so forth, because it is one of the most remarkable possibilities that we Earthlings can imagine. Thousands of years of speculative philosophy and religion have placed humanity at the center of reality as we understand it. The 'Wow!' Signal, if confirmed as originating from another intelligent occupant of the universe, would change everything...

Maggie Starbard/NPR An illustration of detail from the "Wow!" document.


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