Jan. 16, 2007 — If aliens tens of light-years away have radar and FM radio, we may finally be able to hear them.
A proposal to piggyback detection software onto new radio telescopes designed primarily to observe the early universe could allow astronomers to eavesdrop on everyday sounds from distant, Earth-like civilizations.
"The key is to really identify something that looks suspicious and follow up on it," said Avi Loeb, a professor of astronomy at the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA. Loeb collaborated on the idea with colleague and astrophysicist, Matias Zaldarriaga, also of the Harvard-Smithsonian Center for Astrophysics.
Until now, searches for extraterrestrial life have have relied on conventional observatories, which were built to pick up high-frequency radio waves. Such high-frequency radio waves would probably be emitted from other civilizations only if they were deliberately sent across space as a beacon.
Monitoring these signals has allowed astronomers to record radiation emitting from galaxies, quasars, black holes, stars and other cosmic objects, while at the same, avoiding interference from low-frequency signals generated on Earth by radar, television and FM radio.
But what if aliens have radio and TV like us — could we listen in?
Just as you can't hear AM radio channels on an FM receiver, it's impossible to hear low-frequency signals using high-frequency receivers. It hasn't ever made sense to build a radio observatory able to scan the cosmos for low-frequency signals — until now.
Such facilities, such as the Low Frequency Demonstrator of the Mileura Wide-Field Array in Australia, are now under construction to look back into time and space and map the faint radio glow of cosmic hydrogen left over from the big bang.
"It will tell us about how the universe evolved from being filled with a diffuse cloud of gas to containing discrete objects, [and] allow us to test theories of how that process occurred," said Ed Turner, professor of astrophysical sciences at Princeton University in New Jersey.
It turns out that the radiation from distant cosmic hydrogen has the same frequency as radar, television and FM radio broadcasts on Earth. Loeb and Zaldarriaga propose writing special code into the hydrogen-observing software to also look for artificially generated radiation that could be leaking from an alien civilization.
