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February 4, 2000
The Rediff Interview/ Dr Paul Shuch
'What do you say to a bacterium?'
Dr Paul Shuch, executive director, SETI League, came to India recently and addressed a series of lectures about the search for extraterrestrial intelligent life forms. In an interview with Priya Ganapati, the searcher for ETs discusses the difficulties of finding life in outer space, leave alone the intelligent variety,
Do you believe that there is intelligent life out there?
I strongly believe that life is abundant. Intelligence may be much more rare. But certainly life will permeate the cosmos.
I can more easily imagine a proton without an electron orbiting it than I can imagine planets without life. Life would be a natural consequence of the same physical processes that cause stars, galaxies, planets.
Intelligence may be more rare but the evolutionary biologists suggest that nature should select for intelligence, it does have survival value. So given enough planets... and we certainly have enough planets...
Given enough time --and we certainly have enough time -- at least in some places life will evolve to the intelligent level.
Is this based on your personal belief or do we have proof to substantiate it?
My personal beliefs... I hope, as a scientist, my personal beliefs are based on some scientific facts. It is a scientific fact that planets around certain classes of stars are very common. We know this now. We have observed 30 or so different planetary systems....
Can you give us some examples...
The very first example I can give you.... Just about 4-5 years ago. Mitchell Myor, my colleague at the Geneva observatory detected the very first planet around another sunlight star. This is the 51 Pegasi B planet, about 42 light years from earth. This is a star that is almost exactly like our sun. It is 0.98 the radius of our sun, has about 96 per cent the mass of our sun. It is the same solar class, same temperature approximately. It is a little bit older -- eight billion years. Our sun is five billion... But almost a twin to our sun.
Here is a star almost exactly like our sun and it was the first star around which a planet was detected. Since then, in these last five years, we have detected around similar stars about 30 other planetary systems. We now know that a certain kind of star will almost always produce planets. It's just a part of its natural history.
Given that planets are common is the first step in the process. Now how about the properties necessary for life. The chemicals necessary for the formation of life are common throughout the cosmos. Radio astronomy tells us this. We have measured in interstellar space with radio telescopes natural emission lines from complex organic molecules.
The very stuff of which we are made exists in space. If it exists in space it also exists in planetary atmospheres.
But does water exist there?
In interstellar space we have abundant hydrogen and we have abundant hydroxyl, the OH radical. Those are the dissociation products of water.
Water itself cannot form in space. But where there is hydrogen and where there is hydroxyl under the right conditions of temperature and pressure water will form. Of these 30 planetary systems that we have detected so far, I think there are two that we have confirmed have the proper temperature for liquid water.
Which are these two planets?
One of them is in the Apslona Andromedi system and the other was 70 Virginus. Both are 50 light years away or so. That seems to be about the average distance for the interesting planets... About 40-50 light years away. So our neighbours are not going to be very close but they won't be too remote either.
Okay, so planets no problem. The chemistry, hydrocarbon chemistry, no problem. Liquid water no problem. So how about the spark that creates life? We know what happened here. We have high level of certainty that it happened on Mars because of the microbial evidence in meteors. So, we imagine that process happened everywhere. So let's assume a universe teeming with microbes. The problem is, as a communication engineer, I don't know how to communicate with a microbe.
What do you say to a bacterium? How does it answer you? So my kind of science demands that the microbe must colonise into more complex organisms. We have seen evidence of that only on our planet right now. But there is nothing exotic about that process. Everywhere on earth that you have introduced microbes they have developed higher life forms, in every imaginable environment. From the frozen waste of the Antarctic to the hottest temperature, under sea thermal events microbes and higher organisms have flourished. Life is incredibly persistent. It is like a good reporter (smiles).
The entire SETI project is looking not for microbes but for intelligent life out there...
This is what is the greatest challenge for SETI. Whereas microbial life will be very common and complex primitive life will also be very common, intelligent life will be so much rare. We believe technological civilisations will be much more scarce.
Why are we searching for technological civilisations then? Because we can learn something from them. I am a student. All scientists are students. Always. There is not much that I can learn from a bacterium. But there is a great deal I can learn from an intelligent organism. Obviously I seek my professor wherever possible.
If, there is intelligent life out there what are the chances that we can find it?
The one thing I emphasise to the critics of SETI is that there is only one probability that we know for certain. And that is the probability of finding intelligent life if we do not search. And that is zero.
Beyond that we can only speculate as to probabilities. I know that, if based upon what we know of engineering today, if there is intelligent life that has technology equal to the technology of earth right now and if they are today within, let's say within a thousand light years, we have the technology today to detect them.
So it all depends on how far away they are and if they exist at this moment in time at this level of technology. But we use ourselves as an example because we invoke what I call the assumption of mediocrity. We are not highly intelligent so others should have at least our level of technology.
Why is SETI so important to you personally?
My personal background as a communications engineer. The challenge has always been receiving ever weaker signals from ever more distant locations. This is the ultimate distance communications challenge for me as an engineer. If I can design a receiver that will detect this signal, that will be the culmination of my professional training.
As for society at large, we have asked this question since the beginning of time: Are we alone? We have through modern science, just recently, been able to answer most of the ancient questions. But this question still eludes us. Humankind is a curious species. We want to know for the sake of knowing. If I don't search somebody else will. Because all humankind wants to know.
How is the search for extra terrestrial intelligence done?
The first question we have to ask ourselves is on what frequencies might signals be transmitted by other civilisations. There is a lot of debate in the SETI community about what are the best places in the radio spectrum to look.
If you look at your FM radio dial, you can receive signals anywhere from 88-108 Mhz. Within that region, we have a couple of different hundred possible communications channels.
The cosmic radio dial is ever so much broader. It is almost infinite in scope. There are not just a couple of hundred possible channels but many billions of possible channels. Tuning a radio dial suggests that you receive at any given moment one station. But if we receive one station at a time, we will be spending time in a search which exceeds the life of the universe. So this is not a practical solution.
The first thing that we have done is to develop instruments called multichannel spectrum analysers. Think of a MCSA as a radio receiver that can receive thousands or millions, or maybe even billions, of radio channels at one time. So, a lot of our time goes in developing such instruments.
You can think of them as having a huge number of radio receivers all working in parallel. Once you have the instrumentation that can monitor all these frequencies at once, then the question is that how can you actually listen to them? I can't listen to a billion radio stations at once. But my computer can. The signals that we are seeking will not be evident to any of the human senses. We will not be able to hear any of the audio or see television pictures from the stars.
What we will do is receive energies in which some intelligent pattern may be very deeply buried, very far below the threshold of human perception. The key is that the computer -- although an incredibly stupid machine -- is a very fast machine. And when you are that fast you can afford to be pretty stupid.
The computer very systematically sorts through all the possible channels incredibly rapidly and has the time to listen to each one. Many computers are able to listen to millions of channels simultaneously in real time because they are so fast. And if anything is there with some sort of a pattern that suggests it is non-random, that is to say artificial, the computer will detect it far before the human mind could.
So the search is actually conducted by computers. All that the human does is maintain the computers and feed it.
How would you know if a signal that you have detected is an intelligent extraterrestrial signal?
There are about half a dozen different characteristics that we call the hallmarks of artificiality that we are looking for. Those characteristics might be present in some combination in some non-intelligent signals also because of the random processes of the universe. What we are look for is these characteristics in combination.
And more of those individual characteristics that we see simultaneously the higher is our confidence that we have discovered something...
What are these non-intelligent signals?
The best example is star noise. You look at a star and it sends out electromagnetic waves. You call that star light because your eyes can see them. But stars also send out electromagnetic waves that your eyes cannot see, like microwave and gamma rays and cosmic waves and x-rays.
Stars emit energy in many different portions of the spectrum. Radio astronomy specifically looks at radio waves coming from stars and from galaxies and from interstellar molecules and from pulsars, quasars and all the other astrophysical objects. Radio astronomy is concerned with the natural emissions from astrophysical objects. SETI is a specialised subset of radio astronomy. We look at the same types of signals. But within those signals we are looking for something that was not produced by nature but, rather, by intelligent species.
What are some of the characteristics that you look for to identify an intelligent signal?
We look for temporal coherence. That is to say a time pattern that indicates an intelligence. I will give you an example. We live on a rotating planet. If I turn on a radio transmitter here on earth and if you step back a few hundred light years and point a radio telescope at earth and if you wait for a few hundred years for the signal to reach you, you'll notice something peculiar. You will notice that my radio signal is there and then its gone. And then it is back 24 hours later and then its gone again. And then, 24 hours later, it is back again. From this you conclude that the planet that is sending this signal is rotating once every 24 hours. A pattern like this -- a temporal pattern -- is a very convincing piece of evidence. It is not conclusive but it is one clue...
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