A pair of noted space thinkers have resigned from an international body in protest at plans to send out powerful radio signals to alien civilisations. The two men feel that the risks of contact with extraterrestrials - who would need to be much more technologically advanced than humanity in order to visit us - have not been adequately considered.
The signalling that lies behind the concern is so-called "active SETI" (SETI meaning the Search for Extra Terrestrial Intelligence). Ordinary SETI efforts typically involve using radio telescope arrays to listen for signals sent out by aliens. With active SETI, however, the idea is to beam out powerful signals from Earth, with the idea of attracting aliens' attention.
More: http://www.theregister.co.uk/2007/12/17/seti_brains_resign_over_active_messages/
Why not just use high powered lasers? Surely it would be more efficient ?
My guess is they're figuring that it's much easier to make a huge radio antenna to receive a very weak signal, perhaps? Then again, given the chances of there being a sufficiently advanced ET being within sane receiving range and looking the right way, why bother at all. ;)
Now where's that alien smiley gone... :cheesy: