Are aliens using a quirk of the sun's gravity to transmit information through an interstellar communication network? For the first time ever, astronomers explored this intriguing possibility and scanned for signals coming from hidden nonhuman probes orbiting the sun.
So far, the method hasn't turned up signs of spacefaring aliens, but it represents a promising new avenue of hunting for aliens as part of the search for extraterrestrial intelligence (SETI).
The new search strategy rests on the findings of Albert Einstein, who showed in 1915 that gravity warps the fabric of space-time. This means that massive objects, like stars and galaxies, bend light around them. This effect, known as gravitational lensing, allows scientists to see extremely distant objects whose light has been warped by enormous foreground galaxies and galactic clusters.
"It's a lot like a magnifying glass," Nicholas Tusay, a graduate student at Penn State, told Live Science.
With both gravitational lensing and a magnifying glass, the magnification works best when a person or detector is positioned at a specific place known as the focal point, he said.
The sun's gravitational focal point starts at roughly 550 astronomical units (AU), or 550 times the distance between Earth and the sun, Tusay said. A telescope placed at this spot would have mind-blowing abilities — it could resolve continents and mountains on a planet orbiting another star, he added.
"Light goes both ways," Tusay said. "If you can magnify light coming to you, you can also magnify light going out."
This means gravitational lensing also can be used to efficiently send signals across interstellar distances, so scientists have speculated about tech-savvy aliens placing probes at the focal points of stars, effectively turning them into a gigantic point-to-point communication network.
To test this idea, Tusay and his colleagues used the Green Bank Telescope in West Virginia to conduct six five-minute scans for radio signals coming from the sun's gravitational focal point. And what did they find?
"Nothing," he said. "To state it accurately: In the frequencies we observed, during the time we observed, we found no compelling signals that were extraterrestrial in origin."
The results were published last summer in The Astronomical Journal and were presented last week by Tusay at the 241st meeting of the American Astronomical Society in Seattle.
While the findings aren't yet evidence of ET, Tusay said it's possible that alien probes placed at the sun's gravitational focal point turn on only from time to time. And other stars have properties that make them better nodes in a gigantic space internet, so these could be additional search targets, he added. He sees the method as more of a proof-of-concept that might turn up something interesting if conducted for longer and with more resources.
"We're always talking about new ways to search in the field of SETI," Julia DeMarines, an astrobiologist at the University of California, Berkeley who was not involved in the work, told Live Science. "This is the first time I've seen a dedicated search to this specific possibility of intercepting messages."
When nothing is seen in a SETI search, it could mean several things, she added, including that nobody is out there communicating, or merely that nobody is communicating in these ways. Any new search method is always welcome, DeMarines said. "If you don't look," she added, "then you'll never know."
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Adam Mann is a freelance journalist with over a decade of experience, specializing in astronomy and physics stories. He has a bachelor's degree in astrophysics from UC Berkeley. His work has appeared in the New Yorker, New York Times, National Geographic, Wall Street Journal, Wired, Nature, Science, and many other places. He lives in Oakland, California, where he enjoys riding his bike.
Aren’t radio waves slower than light? If so, why would an advanced alien use radio waves?Reply
"Radio waves are part of the electromagnetic spectrum just like the light waves that we see. Light waves, radio waves, and all of the other electromagnetic waves travel at the speed of light—about 300,000,000 meters per second!"Reply
So, a standard task to be added to future explorations of massive objects: Calculate the object's gravitational lensing focal point, go to that point and look for signals coming in or going out.Reply
I wonder how small an object could be and still have a meaningful or useful lensing effect. Does a less massive object have a weaker lensing (light-bending) effect, implying a focal point that is farther away?
OK.... but why then does the referred to doc read this way:gideonkain said:"Radio waves are part of the electromagnetic spectrum just like the light waves that we see. Light waves, radio waves, and all of the other electromagnetic waves travel at the speed of light—about 300,000,000 meters per second!"
"Learning Goals: Students will be able to...
measure the amount of time it takes for a radio signal to travel to a spacecraft using the speed of light.
demonstrate the delay in radio communication signals to and from a spacecraft.
devise unique solutions to the radio-signal-delay problem."
OK.... speeds are the same so why does the doc refer to a problem?