14 DAY TRIAL // Even though it's not exactly certain at this point that life exists on other worlds, astronomers are already planning to detect advanced civilizations, maybe similar to our own in advancements. There are numerous proposed methods of scanning exoplanets for signs of life, ranging from establishing the chirality, or spin, of molecules to looking for signs of establishments and communities. But a new proposal takes the prize. It says that scanning a planet's atmosphere for signs of light pollution and other types of wastes typically associated with intelligent activity may be our best bet of finding something among the stars, NewScientist reports.
Radio noises have thus far been the best bet, but, taking our own planetary history into account, experts say that finding anything searching for it is doubtful. On the Earth, TV stations have leaked a huge amount of radio signals into the atmosphere, and then in space, but now the technology is being replaced with satellites, which direct the beams straight back at the Earth and cables that lose little to none of the signals. Therefore, if an alien race were to be scouting the skies for us, it would have to capture our signals during a very narrow time-frame, of only a few decades.
The only visible sign of intelligent life that our planet gives off at this point is light pollution. When the Sun moves behind the planet, as seen from a random perspective, the Earth's surface lights up, giving away our position to whoever is watching. “Observed over interstellar distances, they would reveal to the observer the presence of a technology,” a team of French astronomers believes. The group is led by expert Jean Schneider, from the Paris Observatory, in Meudon, France.
Another indicator of our presence here is the amount of chlorofluorocarbon (CFC) gases in the atmosphere, which absorb infrared frequencies at specific wavelengths. These compounds do not form naturally on planets or moons, so detecting them may be a clear indicator of artificial life. Also, even in smaller concentrations, of just several parts per trillion, they are visible if you know what to look for, the scientists add. “CFCs are a very interesting idea to look for advanced civilizations,” Harvard University expert Lisa Kaltenegger concludes.