Earth 'noise' could attract alien invaders

The Arecibo telescope in Puerto Rico bounces radio waves off of asteroids (Image:

No matter how quiet we try to be now it's too late to prevent alien invaders. So says Alexander Zaitsev of the Institute of Radio Engineering and Electronics in Moscow, Russia, who points the finger at astronomers.

For 40 years, astronomers have fired microwaves off objects to chart near-Earth space and track the movement of close asteroids - and these signals are traceable back to us.

By comparison, Zaitsev says, dedicated transmissions - often described as "shouting into an unknown jungle" - are a mere whisper. He calculates the astronomy signals have filled an area of the sky 2000 times greater than dedicated broadcasts have managed to date (www.arxiv.org/0804.2754).

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