A high-powered laser and massive telescope could function as a planetary-scale searchlight.
MIT
Astronomers and other researchers have been making a concerted effort to search the cosmos for alien intelligence for decades now. But what about putting on a porch light for any alien astronomers who might be performing the same search from the other side of the galaxy?
A new study out of MIT proposes using a high-powered laser to send a signal into space that could stand out from the massive energy of our sun and basically announce “we’re here!” to anyone who might happen to be looking.
“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,” author James Clark, a graduate student in MIT’s Department of Aeronautics and Astronautics, said in a statement this week. “I don’t know if intelligent creatures around the sun would be their first guess, but it would certainly attract further attention.”
The research came out Monday in The Astrophysical Journal. It suggests that a 1- to 2-megawatt laser could be pointed through the mirrors of a massive telescope — like the controversial Thirty Meter Telescope planned for Hawaii — and shot into space to produce a planetary-scale lighthouse.
If the signal were seen by some form of extraterrestrial intelligence in nearby star systems, like Proxima Centauri of Trappist-1, it could potentially be used as a means of sending brief messages via pulses like Morse code, Clark said.
“If we were to successfully close a handshake and start to communicate, we could flash a message, at a data rate of about a few hundred bits per second, which would get there in just a few years,” Clark said.
Of course several messages intended for potential aliens (and countless not intended for them) have been beamed into space since the advent of broadcasting technology, most of them encoded in radio waves, but none have been sent using super high-powered lasers.
Not everyone agrees that building a laser-powered universal beacon for all of human civilization is a good idea. Famed cosmologist Stephen Hawking famously warned that we should be wary of advanced alien civilizations on habitable exoplanets.
“One day we might receive a signal from a planet like this, but we should be wary of answering back,” Hawking said in the 2016 CuriosityStream series Stephen Hawking’s Favorite Places. “Meeting an advanced civilization could be like Native Americans encountering Columbus. That didn’t turn out so well.”
Such a powerful beam could also present a few safety and technology problems for any biological or digital eyes that happen to look directly at it. Clark says the beam wouldn’t be visible but could still conceivably damage people’s vision inadvertently and could scramble cameras aboard orbiting spacecraft that pass through it.
“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 says. “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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