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| The transmission raises questions about what we would want aliens to learn about our world |
Nasa started to beam the song towards the North Star, 431 light years from Earth at midnight GMT on Monday, drawing congratulations from former Beatle Sir Paul McCartney and John Lennon's widow, Yoko Ono, who mused that it marked "the beginning of the new age in which we will communicate with billions of planets across the universe."
The transmission raises questions about what we would want aliens to learn about our world
But today's New Scientist asks whether such signals could expose us to the risk of attack from mean spirited aliens.
Scientists considered this question at the "Sound of Silence" meeting at Arizona State University in Tempe this week.
"Before sending out even symbolic messages, we need an open discussion about the potential risks," says Douglas Vakoch of the Seti (Search for ExtraTerrestrial Intelligence) Institute, Mountain View, California.
Humankind has already given away our position in the solar system and information about human biology on the Voyager and Pioneer probes, and in a message sent from the Arecibo observatory in 1974.
"It's very charitable to send out our encyclopaedia, but that may short-change future generations," Vakoch tells New Scientist, calling for caution.
"I have no fear that NASA's latest transmission exposes Earth to any danger from aliens," he tells The Daily Telegraph.
"However, I do believe that even symbolic transmissions from Earth deserve broad-based discussion before hitting "send." "
"Although one-time transmissions to distant stars stand little chance of being intercepted, they do set a precedent for intentionally making ourselves known to other civilizations.
"I think the more important question is what we would want to say about ourselves to other worlds, and that's something deserving of global input," he says.
However, fellow Seti Institute researcher Seth Shostak is not worried and writes off the fears as paranoid, given that "the one thing we know about aliens - if they do exist - is that they are very, very far away."
He adds that we have been announcing our presence for decades. "Military radar signals have already penetrated deep into space, and early broadcasts of Star Trek and I Love Lucy are washing over one star system a day," says Shostak. "If they're listening, they already know we're here."
The meeting - aptly titled "Sound of Silence" - was told that after half a century of combing the skies, the search for extraterrestrial intelligence hasn't heard a peep from any little green men and women, and it may be time for a rethink.
"Have we been looking in the wrong place, at the wrong time, in the wrong way?" asks conference organiser Prof Paul Davies of Arizona State University. "The purpose of this meeting is to brainstorm some radically new thinking on the subject. "
One idea is to focus on the cosmic microwave background, the relic radiation left behind by the Big Bang that contributes to the white noise in a poorly tuned television. Intelligent aliens are likely to be "tuned" to this. Other debates concerned the type of alien signals being sought.
"What other signatures of alien technology might we look for, such as anomalously depleted resources, or debris from waste products?," he tells the Telegraph.
"Could a message be buried in DNA? But we have also heard from sceptics, for example, that it could be a fallacy to suppose that "intelligence" is a biological niche waiting to be filled by evolution. It may be just a quirky trait, like the elephant's trunk."
Efforts to date have not covered much ground in scouring the skies. However last year, the first of the 42 dishes of the Allen Telescope Array began operation, which will be dedicated entirely to SETI. And the proposed Square Kilometre Array telescope will be sensitive enough to pick up signals such as alien TV and radio.
"the one thing we know about aliens - if they do exist - is that they are very, very far away."
That's presumptuous. How do we "know" this?