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Aliens Might Notice Us if We Shot a Giant Laser at Them, Study Says

Two emerging technologies could be combined to produce a powerful infrared signal that could be spotted from distant planets, according to research in The Astrophysical Journal.
Concept art of a megawatt laser blast from Earth. Image: MIT News

Scientists have detected many exoplanets that could host liquid water—the key ingredient for life as we know it. But let’s say our wildest hopes (or worst nightmares) are true, and there are alien lifeforms inhabiting nearby worlds. How would we contact them across distances of several light years?

One way to get the attention of local ETs is to shoot a giant laser at them, according to a study published Monday in The Astrophysical Journal and authored by James Clark, a graduate student at MIT’s department of aeronautics and astronautics, along with MIT professor Kerri Cahoy.


The idea is to amplify an infrared laser signal using a giant telescope. This could produce a signal that would outshine the Sun’s infrared emissions tenfold, an anomaly that would stand out to a smart species observing our solar system from a distant exoplanet.

“This would be a challenging project but not an impossible one,” Clark said in a statement. “The kinds of lasers and telescopes that are being built today can produce a detectable signal, so that an astronomer could take one look at our star and immediately see something unusual about its spectrum. I don’t know if intelligent creatures around the Sun would be their first guess, but it would certainly attract further attention.”

The paper combines two emerging technologies—megawatt lasers and colossal telescopes. Lasers capable of megawatt blasts are in development at the Pentagon, while the 39-meter-wide Extremely Large Telescope (ELT) is currently being constructed in Chile, and is on track to become operational in 2024.

Clark and Cahoy calculated that amplifying a two-megawatt laser through the mirror of a 30-meter telescope could produce an infrared signal that would be detectable on Proxima b, a planet 4.2 light years away. A one-megawatt laser amplified by a 45-meter telescope could be spotted by any observant aliens on the seven Earth-scale worlds of the TRAPPIST-1 system, 40 light years away, according to the paper.

Read More: Here’s Our First View of TRAPPIST-1, the Alien Solar System With Earth-Sized Planets

The authors also pointed out some potential downsides to the idea. Aside from the active debate about whether humans should attempt to contact aliens in the first place, the laser-telescope combo could scramble instruments on board any satellites and aircraft, or lead to vision problems for anyone who looked directly at the beam.

“If you wanted to build this thing on the far side of the moon where no one’s living or orbiting much, then that could be a safer place for it,” Clark said. “In general, this was a feasibility study. Whether or not this is a good idea, that’s a discussion for future work.”

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