What is SETI?

SETI is the Search for Extraterrestrial Intelligence by teams of scientists, computer experts and engineers dedicated to the scientific enquiry into our place in the universe. It is an international effort by a number of independent groups, one of which is SETI Australia.

SETI has mushroomed from the very first experiment run by astronomer Professor Frank Drake in 1960 at the Green Bank radio telescope facility in West Virginia. There have been more than 60 projects since Drake's first effort. Today it is an international effort by a number of independent groups. The three biggest experiments today are Project Phoenix (SETI Institute), SERENDIP (University of California, Berkeley) and Southern SERENDIP (UWS, SETI Australia Centre).

Even as Drake worked on bringing this first experiment together, two physicists, Philip Morrison and Giuseppe Cocconi, noted in a paper in Nature in 1959 that radio waves could be used to detect cosmic company, and that the technology was now available to try to answer one of the most basic and profound questions, "Are we alone?"

A question sometimes asked of SETI researchers is that if we have been looking for this long why haven't we detected anything? No single project has been continuously searching since 1960 and SETI is an enormously difficult experiment to do. It is like trying to find a tiny intelligent needle in a vast cosmic haystack. Another is why we don't hang up the phone on the cosmos after 40 years - the answer is that SETI equipment has improved enormously over that time from being able to scan only one radio channel at a time to many millions of channels. As we get better at it, the chances of success improve. It would be like dialling a number and letting it barely ring once before hanging up.

SETI researchers do face several challenges. It is not just a question of knowing where to look in the sky, but also choosing the most likely point on the radio dial to where ET may be broadcasting, either as a deliberate message or as interstellar communication. And there are literally billions of channels to search.

However, as new a bigger radio telescopes are built there may be a day within the next decade or two when we are able to switch on SETI equipment and see the sky light up with sources of the kind of radio noise we toss out into the cosmos via radio, television and radar signals.

How long before a promising detection is made?

In the meantime, it is a painstaking and exacting search like any other science. If communicating extraterrestrial intelligence exists, then it could be tonight, or next week, in the next decade or perhaps very much longer. SETI equipment is up to a hundred trillion times more sensitive that the one Drake made in 1960 and as one researcher said, "Usually when you improve things by a hundred trillion times, something happens." But it might not. No-one can be certain of success until the day it happens - if it happens. If after a long period of time without result, we may be faced with the possibility that we are alone - or the difficulty of contact is such that to all intents and purposes we *are* alone.

Are we alone?

There are 100 billion suns in our galaxy, and our galaxy is one of a hundred billion other galaxies. And the cosmos is much older than the solar system - meaning life has had a much longer time to get started elsewhere. It suggests that we might not be the only sun with something interesting about it. Of course it may be that we are the first species to rise to intelligence in the galaxy or indeed the universe. Either proposition is quite mindboggling.

What is certain though is that if communicating intelligence exists elsewhere it will be much more advanced than ourselves, perhaps by millions or even billions of years. Statistically, we cannot expect to find a civilisation on our level. If they are less advanced, then we won't hear them because they wouldn't have developed radio telescopes.

Back in our solar system, we know life took hold on Earth almost as soon as it could though the mystery of *how* remains one of our really big questions. One reason for doing SETI is the possibility it may offer an answer.

There are also clues in space that suggest at least low-level life, given the right place, may be quite common in the universe. These include the discovery of the basic building blocks of life in molecular clouds deep in space. Comets and meteorites also carry organic molecules and amino acids.

The Mars rocks examined by NASA and the Open University in the UK suggest microbial life may have formed on the red planet, at least in its distant past. If this bears out then at least two planets in one solar system would have independently evolved life forms, demonstrating the ease with which life gains a foothold.

The possibility exists of finding some kind of microbial life elsewhere in our solar system. NASA's Galileo spacecraft has been surveying possible other sites for life on Jupiter and one of its moons,   Europa, with intriguing results. Titan, a moon of Saturn, is another likely candidate.

Another intriguing piece of the life in the universe puzzle came to light relatively recently - and that is that life is apparently much more robust than previously thought. Bacteria has been discovered several kilometres below the Earth existing on only the minerals in the rocks. Deep in ocean lifeforms have been found feeding on the sulphur spewing from hot, almost boiling vents and at great pressure. It offers hope of finding such life living in the harsh, but not impossible, conditions we see on Mars, Europa and Titan.

Since October 1995 we have known that planets do exist around other stars with about 40 such systems now discovered. NASA is currently working on a project to detect Earth-sized planets around other suns from a space-borne optical telescope. SETI can be viewed as a logical step these efforts.

Given the clues for life elsewhere and the probable existence of Earth-sized planets around other stars, our universe seems to be predisposed towards life. But it is only a hint. There is no conclusive evidence - and that is what science demands.

What SETI doesn't do

SETI doesn't send signals into space; it only listens. It has absolutely nothing to do with UFOs. Although the universe has hundreds of billions of suns that could harbour Earth-like planets, these suns are also so remote from each other that it is hard to imagine.

SETI researchers don't hold out much hope of easy travel between the stars in the way of the fictional Star Trek.   Light travels at 300,000 kilometres per second, and at this rate it would take 4.3 light years just to reach the nearest star system to the sun. To cross our galaxy would take 100,000 years and at vast energy expenditure even if we could reach this speed limit set by Einstein and still unchallenged. If ET is to be found the evidence will be more likely on a stream of electromagnetic waves than in a spaceship.

Other applications for SETI

What is certain is that if SETI is not done, nothing will be found; and if it continues without result, then we still have the gains made in science and technology and offers the opportunity to increase the sum of human knowledge.

For example, very little is known about the universe in the microwave part of the radio spectrum in high resolution. Conventional radio astronomy operates at not less than several hundred hertz, but SETI Australia’s spectrometer can detect signals down to 0.6 of a hertz.

SETI is also being used as an educational tool both in the US and in Australia. The SETI Institute has a suite of books for primary and high school science developed with NASA and National Science Foundation funding and in conjunction with the world-renowned Lawrence Hall of Science. As the result of a collaboration between the SETI Institute and SETI Australia, New South Wales high school students can spend part of the science classes using SETI as a context in which to learn both science and how the sciences are interrelated.

Carol Oliver