Alien City Lights Could Signal E.T. Planets
Astronauts in orbit around the Earth often gaze down on a world lit at night by city lights. Now researchers suggest that scientists could detect alien civilizations from similarly bright lights.
Science fiction has long imagined entire planets covered with cities. Examples include galactic capitols such as Coruscant from the “Star Wars” films and Trantor from sci-fi legend Isaac Asimov’s “Foundation” books.
Assuming that aliens need light to see at night much as we do, theoretical astrophysicist Abraham Loeb at Harvard University and astronomer Edwin Turner at Princeton University reasoned that extraterrestrial civilizations would switch on city lights during the hours of darkness on their world.
“Both Ed and I were attending a conference in Abu Dhabi about novel ways to detect life, and we had a tour guide on a trip to the nearby emirate of Dubai who bragged that it was so bright at night that you could see it easily from space — that’s what gave us the idea,” Loeb told Astrobiology Magazine.
On Earth, artificial illumination comes in two forms — thermal, in the form of incandescent light bulbs, and quantum, in the form of fluorescent lights and LEDs. The spectra or combination of colors from this artificial lighting would likely differ from natural sources of light such as volcanoes, and thus might serve as a lamppost that signals the existence of extraterrestrial technology and intelligent life.
Decline of radio
This new tactic is similar to traditional SETI (search for extraterrestrial life) strategies that hunt for alien radio transmissions. However, given how radio emissions from Earth have declined dramatically in recent decades due to the use of cables, fiber optics and other advances in telecommunications technology, a switch to looking for extraterrestrial light pollution might not be such a far-fetched idea after all, the researchers suggested.
To see how feasible hunting for alien light beacons might be, first Loeb and Turner calculated how well it might work within our solar system. They began with an imaginary alien world in the Kuiper Belt, a region of our solar system beyond the planets that is likely home to a trillion or more comets and extends from 30 to 50 times the distance of Earth to the sun, or 30 to 50 astronomical units.