Sixty years ago, space aliens were the preserve of lunatics and eccentrics, thanks to decades of sci-fi schlock, flying-saucer nonsense and Lowellian fantasies of Martian canals. Then, in 1950, came Enrico Fermi and his paradox - "Where the hell is everyone?" - and, 10 years later, the first attempts to put the search for ET on a scientific footing, courtesy of Frank Drake, who pointed a radio telescope at Tau Ceti and heard... silence.
Since then, a modestly funded programme to detect alien radio transmissions has stepped up a gear, and we have made significant astronomical discoveries pertinent to the question of alien life. Despite this, Fermi's paradox has deepened, as the sheer size and antiquity of the universe has become increasingly apparent.
Today it is rare to meet an astronomer who doesn't believe that the universe is teeming with life. There is a feeling in the air that light will soon be shed on some of science's most fundamental questions: is Earth's biosphere unique? Do other minds ponder the universe?