It would be more energy-efficient to send out space probes or inscribed artefacts, "effectively messages in a bottle," suggests Woodruff Sullivan, an astronomer at the University of Washington in Washington state.
Whichever method is used, the quest for ET has many critics.
They say it is rooted in an ancient human reflex -- the dread that we could be all alone in the Universe, and to compensate for this fear we create gods, demons ... and aliens.
"Nothing except statistics supports the idea that life, or at least intelligent life, exists anywhere else but the Earth," the British science fiction writer Brian Aldiss wrote in a bleak commentary in 2001.
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