Since the beginning of intellectual civilization, people have gazed at the silent stars and wondered whether mankind is unique or if there exists other intelligent beings, who contemplate and think like us, in the cosmos. In a Universe whose vastness and age are both beyond ordinary human understanding, our Earth seems to be a tiny speck and we ponder over the ultimate significance of the tiny but exquisite blue planet.

Are we alone in the Universe? Or are we just an instance of the general rule of the Universe? These questions led to the search for extraterrestrial intelligence. In the late 20th century, scientists came upon the idea of scanning the sky and “listening “ for non-random patterns of electromagnetic emissions. SETI or Search for Extra Terrestrial Intelligence is the brainchild of that endeavor.

The idea of SETI began in 1959 with the publication of a paper in the British journal ‘Nature’ by Guiseppe Cocconi and Phillip Morrison. It discussed the probability of existence of alien civilization and the probable methods of detecting them. Around the same time a young astronomer, Frank Drake organized the first serious attempt to listen to possible radio signals from other civilizations. This programme, known as Project Ozma, was set up at the National Radio Astronomy Observatory in Green Bank, West Virginia. Drake and two student assistants launched Project Ozma by pointing their new 85-feet wide radio telescope at the star Tau Ceti, 12 light years away, and loud pulsing signals burst from the loudspeakers. They performed a simple test, moving the telescope away from Epsilon Eridani. But when they pointed the telescope back at the star, it was quiet.

About a week and half later, the loud pulsing noise returned, but they soon figured out that the signal was coming from a passing plane. After 200 hours spent listening to Tau Ceti and Epsilon Eridani, Project Ozma was over.

Since Project Ozma, there have been six or seven other such programmes, none yielding any encouraging results, but there have been intriguing signals. The so-called “Wow!” signal was a powerful burst of narrow frequency sound that came from the constellation Sagittarius. On Aug 15,1977, at the Big Ear Observatory near Columbia, Ohio, Jerry Ehman, a Franklin University astronomy professor and SETI volunteer, while monitoring extra terrestrial noise spotted something peculiar in the computer printout and wrote “Wow” in the margin. The Wow! Signal, as it’s been called ever since, was 30 times stronger than surrounding background noise.

It covered only a very small range of frequencies much smaller than any natural emission, and it appeared to have been turned on and off as the telescope was observing it. Despite searching that section of the sky, in the constellation Sagittarius nothing like it has been heard again. Wow! May indeed have been a Hi! from an alien but if so, the alien hasn’t bothered to try again.

Some scientists have attempted to estimate the number of advanced technical civilizations in the Milky Way galaxy, after considering factors like the number and the age of stars, the abundance of planetary systems and the possibility of origin of life within them. And what they came up with is around a million technical civilizations possible in our Galaxy alone. Of which, till date we have only been able to listen to about a thousand stars.

So are we really alone? Is the Earth unique, not only in the solar system but also in the Universe? How prevalent is life in the universe? Is it the result of independent stars or are planets “seeded”. Is evolution highly divergent or convergent? What is our destiny? Do cultures survive the death of their primary stars and of a collapsing universe?

Failure to discover extra terrestrial life could never possibly answer these questions in the affirmative, but the discovery of one such civilization would provide the needed counter- example and provide at least partial answers. And the day this happens, will herald the birth of anew science.

In the 45 years since the initial Project Ozma, many others have been carried out with more sensitive equipment, over much larger time frames – observing thousands of other stars. So far no conclusive alien signals have been detected, but we have only begun to scratch the surface. There is a long way to go. There are thousands of billions of stars in the universe. To complicate matters further there are millions of frequencies that a signal could be received on. It is possible that we just haven’t looked in the right place in the right time yet.