How Would We Talk to Aliens?

Allen Telescope Array
The Allen Telescope Array used by the SETI Institute (Search for Extraterrestrial Intelligence) to seek out signals from intelligent aliens.
(Image credit: SETI Institute)

The search for extraterrestrials has gone on long before the SETI Institute was founded in 1984. Sixty years prior, on August 21st, 1924, American officials promoted a national day of radio silence, urging citizens to keep their radios quiet for five minutes on the hour, every hour, so astronomers could use a powerful radio receiver strapped to a dirigible floating two miles up to listen for any potential radio signals coming from Mars. Though the Red Planet was closer to Earth than any other time in the past century, the astronomers heard nothing.

Such silence has been the depressing norm for alien hunters, but hope still abounds. The galaxy is a large place, and on a cosmic scale, we've hardly spent any time looking for extraterrestrials.

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