The space telescope Kepler has identified more than 1,200 Earthlike planets to date. Some of them might support intelligent life.
Avi Loeb of the Harvard-Smithsonian Center for Astrophysics and Edwin Turner of Princeton University believe the best way to find that life would be a systematic search for the glow of cities on the night side of exoplanets.
In a paper—"Detection Technique for Artificially-Illuminated Objects in the Outer Solar System and Beyond"—published on Cornell University's website and in Astrobiology, the two scientists outline an intriguing plan to detect signs of artificial illumination as a means of finding intelligent extra-terrestrials.
Search for city lights may best SETI Institute effort
The novel idea—to seek out intelligence in the galaxy visually—may be a better approach than the decades long Search for Extra-terrestrial Intelligence (SETI) that was first formally implemented by NASA with astronomer Frank Drake, Bernard Oliver of Hewlett-Packard Corporation, and other scientists. Those early efforts searched for radio waves.
It was an idea first suggested in 1896 by the genius Nikola Tesla. He suggested that intelligent life on other planets might be detected by intercepting their radio transmissions.
The SETI project, initially funded by the US government, has sought private donations to stay alive in recent years. With the contraction of the economy, the visionary quest has fallen on hard times.
When SETI was born the technology to actually see planets around other stars didn't exist. Now that it does and more than a thousand planets have been located, the switch to detecting artificial light sources makes sense.
According to a Harvard press release about the idea, the two scientists "calculate that today's best telescopes ought to be able to see the light generated by a Tokyo-sized metropolis at the distance of the Kuiper Belt—the region occupied by Pluto, Eris, and thousands of smaller icy bodies. So if there are any cities out there, we ought to be able to see them now."
The method the two propose that astronomers employ to find planets with city lights relies upon the fact that all celestial bodies orbiting a star go through phases like Earth's moon. Just as astronauts can see and photograph the cities lit up on the nighttime part of the world, so too can astronomers find the darkened sides of planets with regions illuminated by artificial light.
Although the technique may not be successful until the next generation of space telescopes are deployed, the approach can be refined by experimenting with it using orbiting objects at the farthest reaches of the solar system.
"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 aid in the press release. "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."
Co-author of the study, Loeb, also admits that even with better observing technology discovering intelligent alien life will not be easy. And that assumes it's out there, although most astronomers now believe extraterrestrial intelligence may be throughout the galaxy and the universe.
Loeb argues that although the chances of discovery by the proposed method may be slim, no real additional cost or exotic resources would be necessary. He thinks it's worth the effort to add such a check to the list of observational protocols.
Besides, he mentioned, someone else may have discovered us already using the same technique.