August, 15 1977: a pulse of radio waves at 1,420MHz radiates down from space to be received by the Big Ear radio telescope in Ohio for 72 seconds. Then: nothing. Sporadic searches of the area since have failed to find this interstellar radio chorus. It's origins remain a mystery.
We are of course talking about the fabled 'Wow!' signal, the SETI detection that never was. Critics argued that because it switched off after a short time, never to heard from again, it could not be a real alien signal. There was no message contained within it, no structure, no signature of intelligent design.
© Ohio State University Radio Observatory/NAAPO. The computer print out that shows the โWow!โ signal detected in 1977.
Now there is a new explanation that raises the credibility of the 'Wow' signal's extraterrestrial hypothesis, an idea we'll call 'Benford Beacons'. Developed by the Benford family of scientists - James, Dominic and the science fiction author Gregory - it is a powerful argument against the expectation of a continuous, omnidirectional transmitter built by altruistic aliens that has held SETI in its sway for much of the last fifty years. The basic point of the Benford Beacons is that ET will not be omnipotent, but will face a cost for any actions they decide to take. "A beacon is limited by its power budget," writes Louis K Scheffer of Caltech in the SETI 2020 review. Therefore, ET civilisations will want to optimise their costs, limit waste, and make their signalling apparatus more efficient. They won't be blasting out signals in all directions continuously, but will 'ping' world after world, over and over again, with short bursts to try and grab our attention. It would be more akin to Twitter than 'Encyclopaedia Galactica'.