Existing Laser Technology Could Be Fashioned Into Earth's 'Porch Light' To Attract Alien Astronomers, Study Finds (mit.edu)

If extraterrestrial intelligence exists somewhere in our galaxy, a new MIT study proposes that laser technology on Earth could, in principle, be fashioned into something of a planetary porch light -- a beacon strong enough to attract attention from as far as 20,000 light years away. From a report: The research, which author James Clark calls a "feasibility study," appears today in The Astrophysical Journal. The findings suggest that if a high-powered 1- to 2-megawatt laser were focused through a massive 30- to 45-meter telescope and aimed out into space, the combination would produce a beam of infrared radiation strong enough to stand out from the sun's energy. Such a signal could be detectable by alien astronomers performing a cursory survey of our section of the Milky Way -- especially if those astronomers live in nearby systems, such as around Proxima Centauri, the nearest star to Earth, or TRAPPIST-1, a star about 40 light-years away that hosts seven exoplanets, three of which are potentially habitable. If the signal is spotted from either of these nearby systems, the study finds, the same megawatt laser could be used to send a brief message in the form of pulses similar to Morse code.

Comments

The 3 Body Problem

[Anonymous Coward]

If you want a awesome book series about this exact type of thing, I recommend `The Three Body Problem`. It's a great book to get into (translated) Chinese scifi literature

Re:How much RF energy do we broadcast?

[Geoffrey.landis]

That's indistinguishable from background noise a few light years out. Hence the entire point of this study on how to purposefully send a signal that is distinguishable at a distance.

No. Check your facts.

He's correct: our RF broadcasts are indistinguishable from background noise at even a few parsecs distance. The stars turn out to be a very very long way away.

There are two exceptions: the Arecibo planetary radar, and ballistic missile warning radars.

But the Arecibo dish is very rarely used as radar, and if it did by coincidence happen to illuminate a star with inhabited planets behind the planet it was looking at... it's likely that it would never point that direction again, ever. The aliens would see one bright blip--if they were looking with an Arecibo sized radio telescope at the right frequency at exactly the right time--but if they look again, nothing.

Ballistic missile warning radar would be more repeatable, but it sweeps small parts of near-polar sky with a repeat time of 24 hours. So, if they see the blip as the radar passes over their star, unless they look again exactly 24 hours later, again, they won't see anything.

And, at a hundred parsecs, even those signals are too faint to detect-- they're swamped by the background. The galaxy is 100 thousand parsecs across. So, no: most of the galaxy couldn't hear us even if they had Arecibo-sized telescopes listening.

Re:Yeah, just what we need

[dunnomattic]

"If they take the ship, they'll rape us to death, eat our flesh, and sew our skins into their clothing. And, if we're very, very lucky, they'll do it in that order."
-Zoe, Firefly (2002)