Bright Lights of Broadway: On Another Planet?

"Alien City Lights Could Signal E.T. Planets"
Charles Q. Choi, Astrobiology Magazine, via Space.com (November 4, 2011)

"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...."

This might be worth trying: and requires fewer assumptions than SETI (Search for Extra-Terrestrial Intelligence) techniques that won't work if folks out there aren't:

• Actively trying to contact us
• Use radio waves for communication
• Make the same choices we do, for
  • Frequency
  • Message encoding

The article does point out that the 'city lights' search wouldn't work if ET is nocturnal.

On the other hand, someone said that we may be looking too close to other stars for people:

"...Another possibility involves looking for alien cities far away from the habitable zones of the closest stars, in their equivalents of Kuiper Belts. They would reflect less starlight since they are farther out, so any artificial light we detected from them would be more discernible. In that case, we could detect them with existing satellites if the nighttime lights were as bright as Earth's, Loeb said...."

The Lemming thinks another drawback to a 'city lights' search is what may be an explanation for why we haven't picked up any verifiable radio signals yet. Here in America, and elsewhere, we're starting to try limiting how much energy we waste by lighting up the sky. Downward-facing lights and other energy-saving techniques might cut down the chances that we'd see the bright lights of Broadway - on another planet.

Still, this 'city lights' idea is a step in the right direction - in the Lemming's opinion. What would make the most sense, if folks are serious about finding people elsewhere in the universe, would probably involve looking for what a large civilization couldn't help but produce:

• Sources of heat that don't have an obviously natural source
• Emissions anywhere along the spectrum
  • With narrow frequencies
    • That don't correspond to what elements emit when they're heated

Essentially, we'd be 'listening' for the equivalent of equipment in a factory, rush-hour traffic, or a garage band practicing. Impossible? Not in the Lemming's opinion. Unlikely? That's the 64-dollar question.

Sort-of-related posts:

• "Gliese 581d: Rocky, Close (sort of), and Liquid Water (could be, maybe)"
  (May 18, 2011)
• "Beware Warmonger Imperialist Space Aliens!?"
  (January 11, 2011)
• "Gliese 581g, Space Aliens, and the Canals of Mars"
  (October 12, 2010)
• "Nuclear Weapons, Space Aliens, Conspiracy Theories, and Getting a Grip"
  (September 24, 2010)
• "Earth May Not Be a 'Class M' Planet"
  (December 5, 2009)