SETI: Search for Extra-Terrestrial Intelligence

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One of the most fundamental questions in science: Does life exist on other worlds?


The 'Wow!' Signal

What is the probability of extra-terrestrial life in the universe?

Where and How should we Look?

How would we communicate with them?

What would be the significance of discovering them?

SETI - Search for Extra-Terrestrial Intelligence

For a very long time we have stared up at the heavens in awe and wondered and asked if we are alone in the universe. These thoughts and questions have played on the minds of many cultures for eons. But we now live in a special time. A time when this age old question might be answered. After all, if intelligent life could evolve here on Earth, then why not elsewhere? Surely we are not the 'best' creation, nature or God has to offer!

The Universe is teeming with stars. We know that for every grain of sand on the entire planet, there are a million stars out there in space. Where we find stars, there are quite often likely to be planets. And where we find planets we may find life. And we know from our own experience on planet Earth that when given the right circumstances and enough time this life may evolve to an intelligent form of life!

So far we have no conclusive evidence to suggest that we are not alone. But the search goes on, and why not? Absence of evidence is not, after all, evidence of absence. We have no reason to believe that we are alone and no justifiable reason to believe that we should be alone in this seemingly infinite universe.

The 85 foot Radio Telescope at Green Bank

SETI is an organisation dedicated to searching the skies for signs of intelligent life, or at least for intelligent technology. But it's an incredibly challenging task. However, post World War II, improvements in radio technology began to emerge. And in the 1950s huge radio telescopes were being built to explore the natural sources of radio waves from deep within the universe. While radio astronomy was in its infancy, it was never-the-less unveiling the dynamics and structure of the universe for the first time.

SETI pioneer, Frank Drake, soon realised this new technology could also be used for other reasons. And in 1960, in Green Bank, West Virginia, he set out on the road to 'first contact' by beginning the first searches on an 85ft radio telescope for evidence of radio signals generated by another civilization's technology, or 'extra-terrestrial' signals.

Drake's Project 'Ozma' was underway. Would they detect a signal from space that would expose the existence of alien life? If so, it had the potential of changing human thinking forever. His first target to point his radio telescope at was Tau Ceti, a star about 12 light years away in the constellation Cetus. This star was chosen because of its sun-like characteristics. Its mass and spectral type are similar to our Suns. And it appears stable with little or no magnetic activity. So it was thought it possibly could harbour an inhabitable planet in its solar system, if it had one.

While no evidence was found from the Tau Ceti observations, even today, it's considered a possible candidate. These days the electromagnetic spectrum is scanned using radio telescopes such as the Arecibo radio telescope in Puerto Rico. Today's computer controlled radio telescopes are more advanced and sensitive and scan the sky running controlled checks against possible natural, terrestrial or extra-terrestrial sources of detected signals.

But the task is enormous since there are vast amounts of both frequencies and space to scan. How do we know what frequencies aliens transmitters would be using and how any messages would be encoded. Other problems would be caused by the cosmic background noise and receiver noise making it very difficult to detect signals over such distances. Also in what direction do we point our telescopes? And how easy is it to distinguish alien signals from natural signals?

Arecibo Radio Telescope - Puerto Rico

SETI collects and analyses deep space radio telescope data from numerous radio telescopes. Due to the enormity of the task your help is needed. And a SETI project, based in the University of California, Berkeley, allows any individual to help analyse this data. Millions of users throughout the world download 'data blocks' onto their computers and using SETI software the computer scans the data for possible signals. If you want your name to be indelibly recorded in the annals of time, this may be your chance!

To date, by far the best contender for an extra-terrestrial signal occurred in August 1977, and is appropriately called the Wow! signal.