Alien-hunters are calling for messages to be broadcast directly into space to tell ET that we are here. But others are urging caution, saying it could be dangerous to reveal our existence to other civilisations.

Presumably they fear that despite the incredible distances between the stars, aliens who tune in could send an invasion fleet!

The bid to send messages to the stars is led by scientists frustrated at our failure to discover signals from extra-terrestrials.

They are calling for an overhaul of the tactics employed by SETI – the Search for Extra-Terrestrial Intelligence – which simply listens to the heavens.

Five million home computer users around the world have signed up to run their Seti@home screensaver to help analyse radio signals from space.

These are overwhelmingly produced naturally by galaxies and other exotic objects in deep space. But scientists are seeking signs of an intelligent message – a task akin to looking for a very small needle in a very large haystack.

New Scientist reports this week that some in the SETI team are now calling for a radical change by beaming messages into space – just as Nasa did in a stunt on Monday when they broadcast the Beatles hit Across The Universe towards the Pole Star.

Astronomer Richard Gott, of Princeton University, New Jersey, says that if aliens took the same attitude as Earthlings, we would never hear from each other. He said: “We’ll all be sitting round listening, but nobody’s doing any talking.”

But Douglas Vakoch, of the SETI Institute, said: “Before sending out even symbolic messages, we need an open discussion about the potential risks. We have 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.”

Some believe such discussions are academic because humans have been sending signals into space since the dawn of radio and TV.

Professor Ian Morison, of the Jodrell Bank radio observatory, in Cheshire, has told Skymania: “Humans have been leaking signals into space for years, beaming out at the speed of light.

“If any aliens have powerful enough technology, they could be tuning in to our old broadcasts.” As he has also pointed out, powerful new radio telescopes being built on Earth might be able to detect alien broadcasts too!

Picture: The giant Lovell radio dish at Jodrell Bank, in the UK.

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