Where's the Monolith?
"I Want To Believe"
-- UFO poster on the set of "The X-Files"
(CNN) -- One of the central characters of "2001: A Space Odyssey" is neither a person nor a computer. Instead, it's a giant, black, rectangular slab called the Monolith. It has a knack for showing up just as things start to get really interesting in the history of human evolution. Because of when and where it appears, the Monolith also serves as proof that there's intelligent life beyond our Earth.
Finding a real Monolith hasn't turned out to be so easy.
One person trying to find one is Paul Horowitz, head of the SETI (Search for Extraterrestrial Intelligence) program at Harvard University. Horowitz doesn't really expect to fine an alien artifact buried somewhere on the Earth or moon. He's looking for other signs, such as radio signals or laser beams from other planets.
"The way I look at is the following," Horowitz says. "It's plausible that there are other civilizations. It's entirely plausible that they wish to communicate. After all, we got where we are by being curious and communicating among ourselves. It's hard to imagine turning that off."
Horowitz says space travel is far more difficult and requires much more energy than space communication.
"If you wanted to take a trip to the nearest star with the technology we have now it would take you 50,000 years," he says.
"It may simply be that these advanced civilizations, being composed of reasonably smart folks, have decided they're going to do the efficient thing, and send messages, rather than do the inefficient thing and send objects and do the risky, inefficient thing and send moving creatures over these distances."
Ears to the sky
Horowitz's search for extraterrestrial signals is similar to the work being conducted at the SETI Institute in Mountain View, California. The Institute's best-known program is called Project Phoenix. For about five weeks every year, Project Phoenix uses the world's largest radio telescope in Arecibo, Puerto Rico, to locate alien transmissions.
Another program called, Project SERENDIP, relies on a separate receiver that's attached to the same radio telescope. It's available year round, but most of the time SETI Institute researchers have no control over where it's pointed. The information collected by SERENDIP is used by the wildly popular SETI@home experiment. The data is broken down into packets and sent via the Internet to some 2.6 million personal computers, where it's analyzed. Anyone with a computer and an internet connection can help search for ETs.
SETI@home is sponsored by The Planetary Society, an international organization dedicated to advancing the exploration of the solar system and the search for extraterrestrial life.
Physicist Andrew LePage has written extensively on the various SETI
programs around the world. He believes researchers are doing the best they can with the technology that's available.
"Even with this best technology we couldn't detect 'I Love Lucy' reruns from the next star system over," LePage says. "The signals from very powerful TV transmitters would still be too weak for us to be able to detect.
"We have to search for civilizations much more advanced than ours, ones capable of handling millions, billions, even trillions times more energy than our civilization is capable of manipulating."
LePage says current SETI programs have only looked at a fraction of the frequencies available for interplanetary communication, or have examined only a small number of the nearby stars. He concludes, "There could easily be millions of civilizations just like our own scattered throughout the galaxy and we'd never know it based on our searches to date."
The Fermi Paradox
An artist's rendering of the SETI Institute's planned array of satellite dishes designed to search for extraterrestrial communications
The skeptics believe the reason that we haven't made contact with extraterrestrial beings is that these creatures probably don't exist.
This argument was best expressed by the late Nobel Prize winning nuclear physicist Enrico Fermi. In 1950, Fermi is quoted as asking if extraterrestrials are commonplace, why haven't we made contact with them?
This question became known as the Fermi Paradox.
In the July issue of Scientific American, astronomer Ian Crawford of University College London explains the problem this way. He says that if there were at least one other Earth-like civilization in the Milky Way, it could have easily populated the entire galaxy by now.
Crawford's argument is based on the following scenario. A society with rocket technology colonizes two other planets. Several hundred years later, the two colonies each send out two more colonies of their own. At that rate it would take from 5 million to 50 million years to colonize the entire galaxy. That's a long period of time, but when compared to the age of the Milky Way, it's a mere snap of the fingers.
If advance civilizations are abundant throughout the universe, then Crawford wonders, "Would none of these billions of civilizations, not even a single one, have left any evidence of their existence?"
Horowitz admits it's something he worries about. But he thinks the math works in his favor.
"How can it be," he wonders. "We're talking about odds of advanced life in the galaxy, and we say the odds are so small that there's only a chance of one civilization and guess what? We're it! It only happened here. You know. I think the odds of that being right are something like one in a hundred billion. That's the only number in town."
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