Years ago I visited Freeman Dyson in his office at the Institute For Advanced Study, in Princeton, and we had a long conversation about extraterrestrial intelligence, SETI, Carl Sagan and human destiny (we will use genetic engineering to adapt ourselves to alien environments, so that we can live not only on Mars and the Jovian moons but also on the countless cometary bodies of the Oort Cloud). (Though I’m trying to square that with the realization that I can barely make it out to Home Depot.) At one point in the conversation, Dyson postulated the most likely scenario for discovering an alien civilization: We’ll just see something in a telescope that’s clearly artificial. [I believe all this is somewhere in CBA.] Dyson’s prediction came to mind yesterday when I read about a new paper from scientists who believe that we could, in theory, detect cities on alien worlds. The key is to look for signs of artificially lit worlds — metropolitan areas lit up at night the way our own terrestrial Gothams are.

Abraham Loeb of Harvard and Edwin Turner of Princeton suggest that we could already detect a Tokyo-sized city if it existed on a planetary body at the edge of our solar system (not that anyone thinks Pluto has a whole lot happening at night):

“The search can be extended beyond the Solar System with next generation telescopes on the ground and in space, which would be capable of detecting phase modulation due to very strong artificial illumination on the night-side of planets as they orbit their parent stars.”

There are just a couple of hitches in this plan, and the first one is obvious: We don’t have the technology to do this. We could, in the future, but who’s going to build the alien-city-detecting telescope? The GOP already wants to kill the Webb. Big Science isn’t dead forever, but I think it’s going to be a while before anyone can sell any terrestrial legislature on appropriations for a telescope that could detect a quirky flux in starlight that would suggest that ET is a night owl (possible telescope name: The Owl Finder). (Are the aliens owlians?)

Another hitch: Apparently we could only find these cities if the aliens used a TON of light bulbs. Like, way more than we do. They’d have to be profligate with the illumination. If they’re reading by a lone whale-oil lamp, we’ll never find them.

But getting back to theory, here: The universe, as I said years ago, is full of information that is arriving free of charge here on Earth, and we just need to find a way to discern it. Light is immortal. A single photon can cross the universe. The story of astronomy and cosmology is the story of light, in its various spectral manifestations, speaking to us. In theory there’s no reason why we can’t see evidence of intelligent civilizations out there.

Of course, they may not be there, or (more likely I think), they may be very scattered, with the nearest one so far away that we’d never have a meaningful interaction in any case (because the speed of light is, despite what you may have heard, still the cosmic speed limit and it’s very hard to chat with someone 30,000 light-years away).

And of course there’s the ultimate problem: What would we say about ourselves?

We’d have a LOT of explaining to do.