The most famous radio signal in SETI history was detected on the night of August 15, 1977, at the Ohio State University Big Ear Observatory. Big Ear had completed a major wideband mapping of the night sky, and in 1973 had been converted to make a similar map of narrowband sources. Readings, recorded as strings of letters and numbers, cascaded down printout sheets (as in The Matrix). Big Ear volunteer Jerry Ehman, a professor at Franklin University in Columbus, regularly checked these. Reviewing the August 15 data a few days later, Ehman was astonished to find a series of characters that formed 6EQUJ5. He circled the code and added “Wow!” in the margin, after which it became known as the “Wow!” signal. The numbers and letters were not a message as such but indicated the radio signal’s strength. The radio frequency was set at 1420 MHz, the frequency of hydrogen. Since hydrogen is the most abundant element in the universe, it was thought that aliens wanting to attract attention might use this frequency. It is also a frequency which is out of bounds to broadcasters, so would be clear of local noise. The scanning beam registered a reading every six seconds. A number from 1 to 9 denoted each step-up in intensity above the background noise, and the range was extended to 35 by inserting letters of the alphabet. The sequence 6EQUJ5, therefore, denoted a signal that grew in strength to level U and then gradually subsided. This meant that the signal increased from zero to very intense and then decreased again to zero over 37 seconds. Thirty-seven seconds was precisely the time it took the Big Ear scanning beam to cross a point in deep space, so the “Wow!” signal exactly matched the predicted profile for a signal of deep-space origin. The signal was also intermittent. Big Ear had two separate beams that scanned the same area of sky in succession several minutes apart, but the signal appeared on one of the beams and not the other. A strong, focused, intermittent signal coming from the direction of the constellation Sagittarius (and the galactic centre): could it be that Big Ear had detected an alien? For a month following the discovery the Big Ear crew tried to relocate the signal without success. Other SETI searches have also focused on the “Wow!” coordinates, but no more broadcasts from this location have ever been detected. To this day we do not know the source of the strongest and clearest signal ever to come from a SETI search. Since 6EQUJ5 was undoubtedly artificial, and almost certainly of celestial origin, there remains a possibility that it was a true signal from an alien civilisation. But unless the signal is detected again, we will never know for sure. Possible sources of 6EQUJ5 are as follows: Planets—planets emit electromagnetic (EM) radiation, but seldom at narrowband frequencies, and none crossed the “Wow!” coordinates that evening. Asteroids—asteroids have weak magnetic fields making them very weak transmitters. No known asteroids crossed the path of the beam. Satellites/aircraft—no known satellites were in the path of the beam. 1420 MHz is an off-limits band for all transmission. A satellite and especially an aircraft should also show discernable movement against the celestial backdrop. Spacecraft—no known craft in that position. 1420 MHz is an off-limits bandwidth. Reflection from ground-based transmitters—1420 MHz is out of bounds, and harmonics from other bandwidths are too weak for the detected signal strength. Also, this signal’s doppler shift signature rules out local effects. For a signal reflection from space debris, the debris would have to be metallic (likely), so distant as to appear static against the stars (not likely), and not tumbling (highly unlikely). Gravitational lensing—a sustained interstellar effect (subsiding over days, months or years) that should have shown up in the second beam. Interstellar scintillation—causes minimal distortion that still involves a broadcast light years distant, making the source alien in origin. Extraterrestrial intelligence—?
Posted on: Mon, 10 Mar 2014 05:22:43 +0000
Trending Topics
Recently Viewed Topics
© 2015