Anniversary of the Wow! Signal


On August 15, 1977 the Wow! Signal was received by Ohio State University’s Big Ear Radio Telescope. The narrowband radio signal had the characteristics of what scientists expect of an extraterrestrial signal.

Astronomer Jerry R. Ehman was working at Big Ear as a volunteer.  His job involved analysing large amounts of data processed by an IBM 1130 mini computer and printed on perforated paper. On August 15 at 22:16 (02:16 UTC), Ehman spotted a series of values of signal intensity and frequency that rocked the astronomy world.

The telescope’s observation window could observe any given point for just 72 seconds. A continuous extraterrestrial signal, scientists agree, would be expected to register for exactly 72 seconds, and the recorded intensity of such signal would display a gradual increase for the first 36 seconds – peaking at the center of the observation window – and then a gradual decrease. All these characteristics are present in the Wow! signal.

Nearly 20 years previously, in a 1959 paper, Cornell physicists Philip Morrison and Giuseppe Cocconi speculated that any extraterrestrial attempting to communicate via radio signals might choose to do so using a frequency of 1420 megahertz, which is naturally emitted by hydrogen, the most common element in the universe and therefore likely familiar to all technologically advanced civilizations.

Two different values for the signal’s frequency have been given: 1420.36 mega hertz (J. D. Kraus) and 1420.46 megahertz (J. R. Ehman), both very close to the value of 1420.4 megahertz of hydrogen. The two values are in fact the same distance apart from the hydrogen line – the first 0.04975 below and the second 0.04985.

Through a complicated system of “signal to noise ratio ,“ the Wow! Signal had a reading of 6EQUJ5 which translates to approximately 30 times normal background noise.

Despite many attempts, a replication of the signal has never been recorded, and Ehman himself resists “drawing vast conclusions from half-vast data.” There have been many hypotheses about the origin including natural and man-made sources, but none of them adequately explain all aspects of the signal. Ehman and others think that the most likely explanation is that it is from an extraterrestrial civilization.


This image is a scan of a color copy of the original computer printout, taken several years after the 1977 arrival of the Wow! Signal.  It is not available for copyright as it consists solely of factual information that connot be conveyed in any other manner.


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