Alas for the good old days, when we thought the Earth was the center of the universe. Today we know our sun is only a very average star in a very average galaxy, in a universe where there are 50 billion galaxies, containing half a trillion stars each, around which, based on recent observations, planets appear to be as common as–well, dirt.
That being the case, it would be the height of hubris for us to assume that we are the only form of intelligent life in the universe. But if other intelligent life is out there, where are they?
Those who take their X-Files a little too literally may believe they are already among us, but most scientists think the distances between the stars pretty much preclude the possibility of a visit any time soon For that reason, the search for extraterrestrial intelligence–SETI–has long been focused more on listening for aliens than looking for them.
The father of SETI is radio astronomer Frank Drake. In 1960 he launched Project Ozma at the National Radio Astronomy Observatory in West Virginia. Drake turned his radio telescope on two sun-like stars, Epsilon Eridani and Tau Ceti, listening to them on a specific frequency, 1,420 megahertz, thought to be a likely communication channel because it is the frequency emitted when an electron reverses its spin in an atom of hydrogen, the most abundant element in the universe.
Project Ozma heard nothing, but that didn’t discourage Drake, who is convinced alien civilizations are out there. He’s even come up with an equation to help calculate the likelihood of their existence. You need to know is the rate of star formation, the fraction of stars with planetary systems, the number of planets in each system with conditions favorable to life, the fraction of those planets on which life develops, the fraction of those planets on which life develops intelligence, the fraction of those planets on which intelligent life develops a technical civilization capable of interstellar communication, and the lifetime of such a civilization. We don’t have accurate figures for enough of the equation’s factors to solve it properly, but even conservative guesses, in such an enormous universe, point to huge numbers of extraterrestrial civilizations capable of interstellar communication. That being the case, we should be able to hear them.
In 1992 NASA launched what was supposed to be a decade-long SETI project using the largest available radio telescopes from around the world. But in 1993, Congress shut the project down to save money.
That has left SETI in private hands–such as those of Microsoft co-founder Paul Allen, Intel co-founder Gordon Moore and both co-founders of Hewlett-Packard, who have all put funding into SETI research.
One current effort is Project Phoenix, which is now using the largest radio telescope in the world, the 300-metre-diameter Arecibo Radio Telescope in Puerto Rico (made famous by Goldeneye) to monitor two billion separate frequency channels for several nearby, sun-like stars.
Even more interesting is the SETI@Home project, which will allow anyone with a home computer take part in the search for extraterrestrial intelligence.
SETI@Home is a special kind of screensaver. Like other screensavers, it starts up when you leave your computer unattended, and shuts down when you move the mouse or hit the keyboard again. But rather than simply display interesting or amusing images on your monitor while you’re away, SETI@Home spends its time analyzing radio telescope data it downloads from the Internet. (It will also displays and explain the results.)
SETI@Home, which should be up and running in 1999, is intended to fill in a gap in SETI research. Current SETI projects listen to millions of frequency channels simultaneously for artificial signals. The SETI@Home project will instead listen to a smaller part of the frequency in a much more thorough way. Once just 50,000 PCs are involved, it will rival any other SETI project every carried out.
Of course, even if we don’t hear anybody, that doesn’t mean they’re not there. They could be hiding, using unknown technology, or simply not interested.
Meanwhile, our own radio signals are now reaching thousands of nearby stars. Most TV and radio broadcasts, contrary to popular belief, are too weak to be easily detected–aliens likely aren’t watching Milton Berle–but other signals, such as those produced by certain types of military radar, aren’t.
If aliens are conducting their own version of SETI, they could be shouting “Eureka!” any day down.
