“If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans,” said the world’s most famous theoretical physicist, Stephen Hawking, late last month. He warned scientists not to try to communicate with extraterrestrials, pointing out that “We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet.”
Hawking’s concern is shared by others in the field. They don’t object to passive SETI: it can’t do any harm to ‘Search for Extra-Terrestrial Intelligence’ by listening with radio telescopes for the radio emissions of civilizations around other stars. However, they think that active SETI—sending out messages saying “Here we are”—is just asking for trouble.
“Active SETI…is a deliberate attempt to provoke a response by an alien civilization whose capabilities, intentions, and distance are not known to us,” wrote Michael Michaud, former Deputy Director of the Office of International Security Policy in the U.S. State Department, in 2005. The recent discovery of at least 400 planets orbiting nearby stars makes the issue more urgent, for we now know that planets are very common in our galaxy.
There have already been attempts at active SETI. In 1974 Frank Drake, the astronomer who founded the SETI project, used the Arecibo radio telescope to beam a message towards the globular star cluster M13, which has over a million stars in it. But M13 is 25,000 light-years away, so we have at least 25,000 years to prepare for any response to the message.
In 2008, however, a high-powered message was sent to the Gliese 581 system, a five-planet system that is only 20 light-years away and has two planets in the “habitable zone” for life. The message will get there in 2029.
Several messages have been beamed to other nearby planetary systems since then, in the blithe assumption that anybody there will be friendly. Scientist and author Jared Diamond has said that “those astronomers now preparing again to beam radio signals out to hoped-for extraterrestrials are naive, even dangerous”.