4. THE WOW! SIGNAL
Then one night in 1977, a radio telescope in the US picked up a remarkable signal from direction of the constellation Sagittarius…A few days later, a volunteer researcher for Ohio State University’s now-defunct Big Ear radio observatory, named Jerry Ehman, was flipping through the computer printouts generated by the telescope’s scan of the skies on August 15. During those days, such information was run through an IBM 1130 mainframe computer and printed on perforated paper, and then painstakingly examined manually. Ehman spotted a vertical column with the alphanumerical sequence “6EQUJ5,” which had occurred at 10:16 PM EST. Clearly astounded, he wrote the words “Wow!” on the original printout of the signal (Figure 4-1).
The Wow! Signal, as it came to be known, was loud and clear and lasted for 72 seconds. It was defined by a string of letters—6EQUJ5—superimposed in a long sequence of low numbers—ones, twos, threes and fours—the low numbers representing background hum of an ordinary signal. Each digit on the printout represented the intensity of a radio signal, from zero to 35, with intensities over 9 being represented by letters. Thus “U” represented a signal thirty times higher than the background noise level. As the telescope swept across the sky, something extraordinary caused the signal to surge and the computer started outputting letters instead of numbers. What perhaps is most interesting was, the frequency of the Wow Signal resonated at 1420 MHz, right on the fabled hydrogen line, which precisely is the frequency band that Cocconi and Morrison thought could be used by an alien civilization for interstellar signaling.
It could be possible that the Wow! Signal had terrestrial origin. But careful analysis by scientists eliminated that possibility.
The signal intensity had the expected shape of a typical narrowly focused bell curve—the intensity of the signal grew as Big Ear approached the signal, and decreased as Big Ear moved away from the signal (see Figure 4-2). This meant that the signal could have originated from a single point in space. Could the signal be produced by a moving object such as a satellite? That possibility was also eliminated because of two reasons. Firstly, only astronomical research is allowed to be conducted at the 1420 MHz frequency (“protected spectrum”), which is why it is extremely unlikely that the Wow! Signal was man made. Secondly, to duplicate the signal, the satellite would have to be located just at the right place, and moving precisely in line with Big Ear, which was highly unlikely as well.
The most significant fact was the signal’s frequency, being so close to the hydrogen line. This, combined with the signal’s intensity distribution over the 72 seconds for which it was recorded, supported the conclusion that the signal originated somewhere near the Chi Sagittarii star group. Interestingly, if the signal indeed came from an alien civilization, it would have required a 2.2 gigawatt transmitter, vastly more powerful than any of the existing terrestrial radio stations.
A search was immediately conducted for a repeat of the Wow! Signal. Scientists scanned the sky in the direction of the constellation Sagittarius, where the signal had originated. More and more sensitive telescopes were used, along with improved software that was designed to find signals among the background noise.
But despite of searching for several decades, the signal has never been found again. The “Wow!” signal remains the only reliably recorded signal apparently received from deep space that has the quality of an intentional signal. Where the signal came from is still a mystery.
We may never know if the Wow! Signal was a message from an alien species, or a radio burst from a natural source that coincidentally hit the hydrogen line.