(CNN) - of a valley in Northern California, Jill Tarter is listening to the universe.
Jill Tarter at the Allen Telescope Array in California, which monitors the signals of the signs of extraterrestrial life.
Its ears are 42 telescopes radio large and sophisticated, spread over several hectares, which analyses the cosmos for signals of extraterrestrial origin. If intelligent life forms exist on other planets, and they try to contact us, Tarter will be among the first to know.
We, citizens of the only Earth in the universe? It is a question that has long fascinated astronomers, science fiction authors, children with backyard telescopes and frameworks Hollywood meets churn shows abroad. Surveys have found that most Americans believe there is a form of life beyond our planet.
"It's a fundamental question," said Tarter, inspiration from real life for the character of Jodie Foster in the film of 1997 "Contact". "And it is a matter that the person in the street can understand." It is not as a... super-collisionneur or some search for neutrino buried in ice. This is the case, ' we are alone? How we could find some? That means that we tell about ourselves and our place in the universe? »
"We try to understand how the universe began, the form galaxies and structures to large scale, and hence the origins of life we take place?" Said Tarter.
"It is of valid questions to ask of the universe." And a valid question is whether if the same thing happened here [on Earth] happened elsewhere. "" 
See an overview of the series of "In Search of foreign" CNN ".
With advances in technology, scientists hope to get an answer sooner than later. Rovers recovered photographs of the surface of Mars showing forms resembling fossils. NASA hopes to launch in a decade a Terrestrial Planet Finder, an Observatory in orbit detecting planets around nearby stars and determine if they could support life.
These developments are catnip to scientists like Geoffrey Marcy, a Professor of astronomy at the University of California-Berkeley, who discovered extrasolar planets more than anyone.
"It was not more than 13 years ago that we had not found planets around stars, and most people thought that us would never have." Behold, therefore we are not only after finding planets, we are looking for habitable planets, signs of biology on planets, "Marcy said CNN." "" It is an extraordinary explosion of a field of science that is not only a few years ago. »
Then there is Tarter, whose quest for signs of extraterrestrial life he kept on the margins of the dominant science for decades. While pursuing his Ph.d. at the University of Berkeley, Tarter fell on a technical report which floated the idea of use of radio telescopes to listen to emissions by beings exotic.
He became a professional life. In 1984, Tarter founded research, Institute for Extraterrestrial Intelligence (SETI) in California. Using telescopes in Australia, West Virginia and Puerto Rico, she led a dozen scouring of approximately 750 stellar systems near extraterrestrial radio signals.
None were found, although Tarter had a few false alarms. In 1998, she intercepted a mysterious signal that lasted for hours. Tarter is so excited that she misconstrued his own results to computer: a vessel of Observatory of NASA in orbit around the Sun came from the signal.
Today, Tarter listening heaven with the Allen Telescope Array, a collection of 20 feet of large telescopes approximately 300 miles north of San Francisco. Scopes-like flat are a joint effort by SETI and radio astronomy Lab of UC-Berkeley and has been funded largely by the co-founder of Microsoft Paul Allen, who has donated more $ 25 million to the project.
Unlike existing radio telescopes, which scans the sky for a limited period, the Allen Telescope Array Probes the 24 universe.
Each of the 42 bodies aims to another region of the sky, collecting the data volumes that are continuously studied by computers for unusual. Then, auditors must filter out the noise from aircraft and satellites.
"We are going to listen to something that we do not believe can be produced by Mother Nature", said Tarter. "We use the radio frequency, other people are using optical telescopes... and in both cases we are looking for an artificial nature of a signal."
"In the case of radio, we are looking for a lot of power be overwritten in a single channel on the radio dial." In optics, they look very bright flashes that last a nanosecond... or less step slow the heartbeat sorts of things. To date, that we never found a natural source that can be done. »
Alien signals may be transmission for their own use would be difficult to detect, said Tarter. Astronomers are more likely to discover an intentionally broadcast radio transmission to Earth, she said.
SETI astronomers, however, is sending not a signal in space to attempt to communicate with aliens.
Professor of the University of California Marcy is skeptical about the existence of intelligent extraterrestrial life and believes that the vast distances in our galaxy would make communication between the Earth and human beings humans on other planets almost impossible.
"Nearest neighbour could be at halfway across our Galaxy, 50 000 light years away." Communicate with them will be one hundred thousand years for a signal return, "says.
Tarter remains unwavering. The Allen Telescope Array has already done, in 10 minutes, which takes after its scientists 10 days. When the project is completed, it will have 350 telescopes which, combined, can survey of tens of thousands of stellar systems.
"We look in more places and more faster frequencies that we never could." And who will just get better with time. We do something now, we could not do when we started, we could not do five years ago, "she said."
"Consider as a cosmic haystack." There is a needle somewhere. If you remove a few straws, are you going to get disappointed because you have not found the needle again? No.. We have not really begun to explore. »
Correspondent for CNN Miles O'Brien contributed to this story. All About Astronomy • UFOs and alien abductions • SETI Institute