The hunt for alien civilisations may need a rethink. A new paper argues that the signals we're listening for might not be the ones ET would choose.
Historically, SETI – the search for extraterrestrial intelligence – involves scanning the sky for radio signals that another civilization is deliberately sending. The simplest would be a constant blast in all directions, but in a narrow range of frequencies, similar to early radio broadcasts – like a constant hum that would tell a listener it is artificial. From light years away, we would not be able to get any other information – all we would be able to tell from Earth is that a signal was there and where it was coming from, not what it says.
But David Messerschmitt at the University of California, Berkeley points out that such a continuous signal would take a tremendous amount of energy. Assuming aliens have utility bills, he says, they would use a different strategy.
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