It has clocked an astonishing 500,000 years in computing time, with another 1,000 years of processing time contributed every day. Using a variety of algorithms, the screensavers have whittled down the 500 million strong signals, or spikes, to about 125 million that look interesting. All of these 125 million signals display a Gaussian, or bell curve, profile. As the Aricebo telescope scans across the sky, the signal becomes progressively stronger and then weaker, just like a bell-shaped curve. But to ensure the signal came from an alien civilization, it must be transmitted from the same part of the sky, at the same frequency, on two or more observations, which would indicate a persistent signal and not just a random burst of energy.
Green dots are signals detected four or more times.
But so far, every signal that merits closer inspection has proven a red herring. Even though 500,000 years of computing time seems like a lot of time to throw at a problem, Werthimer said it's just the beginning. We've got a long way to go. We're searching such a small range of frequencies, it may take another 50 or 100 years. A thorough search for signs of intelligent life would include a much wider swath of the electromagnetic spectrum.