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Bright lights, big city - and possibly aliens

An Oct. 9, 2007 file photo shows radio telescopes of the Allen Telescope Array in Hat Creek, Calif. The telescopes were seeking signs of intelligent life in the universe.Ben Margot/AP Photo/File

If alien life is out there, two scientists hope they leave the lights on.

To search for advanced extraterrestrial societies, Avi Loeb of Harvard University and Edwin Turner of Princeton University suggest in a new paper posted online Sunday, astronomers should look for city lights on distant planets. The technology already exists to look for Tokyo-sized cities at the edges of Earth’s own solar system, they said.

“Looking for alien cities would be a long shot, but wouldn’t require extra resources,” Loeb, the director of the Institute for Theory and Computation within the Harvard-Smithsonian Center for Astrophysics in Cambridge, said in a statement released by the center. “And if we succeed, it would change our perception of our place in the universe.”


Loeb, the chairman of the astronomy department at Harvard, said that he and Turner got the idea for this paper when they were visiting Abu Dhabi and a tour guide bragged about how the city is so bright, it can be seen from space. It seemed so obvious, Loeb said, that he was “very surprised that no one suggested this before.”

In the past, scientists have looked for alien civilizations using radio signals and minuscule laser pulses. Like those efforts, Loeb and Turner’s proposal assumes alien cities would have technology similar to that of humans.

“This is reasonable because any intelligent life that evolved in the light from its nearest star is likely to have artificial illumination that switches on during the hours of darkness,” the statement said.

To find these potential cities, Loeb and Turner suggest, astronomers should look at the planet when it is in a night phase; this would help distinguish the artificial light from the light of the sun, they write in their paper, submitted to the scientific journal Astrobiology.

It’s not technically feasible yet to do this for far-off planets. However, Loeb and Turner suggest that scientists can first test the technique on the Kuiper belt -- ring of the solar system that contains Pluto, Eris, and other icy bodies.


“It’s very unlikely that there are alien cities on the edge of our solar system, but the principle of science is to find a method to check,” Turner said in the statement. “Before Galileo, it was conventional wisdom that heavier objects fall faster than light objects, but he tested the belief and found they actually fall at the same rate.”

“The lesson is modesty,” Loeb agreed.

“This is like a venture capital investment,” he later added. “There’s a small chance that it will give you huge dividends.” Besides, Loeb said, the technology already exists and telescope surveys are already planned for the next decade -- why not look for alien life within the solar system?

There could be some problems with this plan, however, as Loeb, who lives in Lexington, found out after he lost power for four days as a result of the past weekend’s freak snowstorm.

“This led me to think, ‘I hope that the alien civilizations don’t use NStar as their electric company,” he said.

Jaime Lutz can be reached at