We might find aliens through the heat their civilizations give off, astronomers say, but it will take a megatelescope to do the job. Such a telescope, in fact, is planned.
The telescope — called Colossus — would be a massive 250-foot (77 meters) telescope, which is more than double the aperture of any telescope yet constructed.
To keep costs down, the proposed $1 billion telescope would use thin mirror technology and few large aperture mirror segments. The sensitivity of the scope, though, could be enough to spot cities or other signs of aliens for planets as far as 60 to 70 light-years from Earth, its backers said. [Stacking Up the 10 Biggest Telescopes on Earth]
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