In 1960, a young American astronomer named Frank Drake steered a big radio telescope to a nearby star system eager to listen to an alien world. But so far, even after five decades, the answer is an uncanny silence.
Frank Drake's mission to embark upon the alien hunt has since grown to be a large enterprise beginning its operations in 1985, and is known as SETI (Search for Extraterrestrial Intelligence). The core premise of their search is based on the assumption that our cosmos is teeming with life -- not in its primitive form -- but technologically sophisticated ones, similar or possibly better than ours.
The Drake equation estimates the number of detectable civilizations in the observable universe as something around 10,000, with the most neighboring one at least about 1000 light years away. That itself speaks the major difficulty in the alien search -- literally distances of astronomical proportions.
It is assumed that advanced civilizations are capable of using electromagnetic waves to communicate, or even to get our attention. Consequently, the researchers are looking for "narrow band signals," which would serve as the finger print of the extra terrestrial civilizations.
The natural astronomical objects also produce electromagnetic signals, but those are wide spread and could be distinguished from the artificially produced narrow bands. So far, no confirmed, artificially-produced extraterrestrial signal has ever been found. The SETI@home screen saver software asks the general public to contribute their free computing time to analyze the data SETI receives.
Some experts now caution us about the risk of contacting aliens while others advocate a different approach in seeking aliens.
Recently, the renowned British cosmologist, Stephen Hawking warned that "if aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn't turn out very well for the Native Americans."
As we know, the laws of physics do not allow any travel beyond the speed of light, limiting the possibility of an alien visit. Even if the alien civilizations could accomplish such a high speed travel, that must be at the expense of their enormous resources and time. What on earth would make them to do that? Unless they have mastered laws of physics unknown to us, similar to time travel to breach the space and time, they won't be vacationing on this planet for fun.
In 2008, NASA broadcast the Beatles' song "Across the Universe" aimed at Polaris, the North Star. It would take 431 years for this beam, traveling at the speed of light, to reach the target location. These attempts are more symbolic in nature and reveal the unfathomable nature of space and time that compose our universe.
What if the aliens are so much more advanced than us? Say, their civilization has been around for at least a million years more than ours -- then it's a different game. They might have a completely different mode of communication or transportation. If such aliens want to convey us a message, then broadcasting may not be the best way for them to do that.
They could have genetically engineered us in such a way that we transmit their message in a chemical form called DNA. Our body, which may be nothing more than a carrier of that message, then passes it on to generations that follow. The non-coding DNA, which makes up about 95% of the human genome, is called junk DNA, the functions of which are not completely understood. Some researchers suggest that the evolutionary traits in the junk DNA may help us to identify our alien connection. For now, these suggestions are purely hypothetical in nature. As Carl Sagan noted, "extra ordinary claims require extra ordinary evidences."
Paul Davies, the author of "The Eerie Silence: Renewing Our Search for Alien Intelligence", and director of the Beyond Center for Fundamental Concepts in Science at Arizona State University, has refuted Hawking's arguments in a Wall Street Journal blog. He says that a very advanced civilization may not be aiming for our resources, or even be interested in us, as they might have mastered the know-how of extracting plentiful resources available elsewhere in the universe.
Are we the result of a unique cosmic accident or just one among the many life-infected planets that share a common legacy? There is no guarantee that every intelligent civilization will survive for a long time, as they might destroy themselves or face the inevitable destruction caused by the cataclysmic events that are often unleashed in the cosmos. We don't even know how life began on this planet. How can we be sure that intelligent life exists and flourishes on another planet?
We may never find the alien civilization in our life time, or ever, but I assume we will continue to investigate. There is a fundamental question that arises in the mind of every one of us, "are we alone?" So far, the universe hasn't disclosed all its secrets. As the famous science fiction writer Arthur C. Clarke once said "Either we are alone in the Universe or we are not. Both are equally terrifying."