Has ET evolved to be discreet? An evolutionary tendency for inconspicuous aliens would solve a nagging paradox – and also suggest that we Earthlings should think twice before advertising our own existence.
As physicist Enrico Fermi argued in 1950, unless the evolution of life is unique to Earth, there must be many intelligent species out there. So why have they neither phoned home nor been detected by us?
"It's a real paradox," says Adrian Kent of the Perimeter Institute in Waterloo, Ontario, Canada.
In order to explain the Fermi paradox, Kent turns to natural selection – and suggests that it may favour quiet aliens.
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