Extraterrestrial intelligence

(¦ek·strə·tə′res·trē·əl in′tel·ə·jəns)

(astronomy) The potential existence beyond the earth of other advanced civilizations with a technology at least as developed as that on earth.

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The potential existence beyond the Earth of other advanced civilizations with a technology at least as developed as that on Earth. The idea that life, especially life with intelligence, might exist in other parts of the universe is a very old one. Early ideas were based on an intuitive belief in the enormity of the universe and in what is now called the mediocrity principle, namely that there is nothing special about the Sun, the Earth, and the human race.

Present ideas are also based on the mediocrity principle supported by the universality of the laws of physics and chemistry, and by the enormity of the universe. The Sun is one of 2 × 10¹¹ stars of the Galaxy (the Milky Way), and there are about 10¹¹ galaxies in the visible universe. The chemical evolution, that is, the natural formation of complex organic compounds, that led to the origin of life on Earth is quite common in the universe. Life on Earth started at least 3.5 × 10⁹ years ago, that is, soon after the formation of the oceans, indicating a rather straightforward natural process. Through mutations and Darwinian selection, evolution advanced slowly from primitive unicellular microorganisms to advanced multicellular organisms with intelligence. Intelligence, which is favored by evolution because it has a high survival value, evolved into a technological society.

The search for extraterrestrial intelligence was initiated only after the development of radio astronomy and large radio telescopes, because radio waves seem to be the most efficient means of communication over interstellar distances. At least 60 radio searches have been carried out, and three radio observatories search continuously for radio signals. The results continue to be negative, but selecting the proper frequency, bandwidth, polarization, target, and so forth, is an extremely complex problem. See also Radio astronomy; Radio telescope.

In the early 1960s, F. Drake developed an equation to estimate the number N of advanced technological civilizations currently active in the Galaxy. The Drake equation, N = R × P × L, gives N in terms of the rate R at which new stars are born in the Galaxy, the probability P (actually a product of probability factors) that any one of these stars will possess the necessary conditions (luminosity, planets at the appropriate distances, and so forth) for life to originate and to slowly evolve to a technological civilization, and the average longevity L of such civilizations. The values advocated by the proponents of the Drake equation yield a value of N of approximately 200,000 stellar civilizations. However, the uncertainties in P and L are very large and some scientists think that the human race is probably the only advanced civilization in the Galaxy; that is, N equals 1.

In the mid-1970s, the possibility of large human colonies in space began to be seriously considered, and the idea that such self-sustained habitats could undertake multigeneration trips of several centuries to other stars began to gain acceptance. Many scientists think that galactic colonization is not only possible but an almost inevitable consequence of the evolution of intelligence and technology. This concept, however, leads to two extreme alternatives: either the Galaxy has already been colonized, in which case N must be very large; or it has not been colonized, because no one was there to do so, in which case N must be very small. Both alternatives are contrary to the results of the Drake equation, which negates galactic colonization and predicts an intermediate value of N. All three alternatives, however, contain serious contradictions which are not easy to reconcile.

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It was once believed that the earth lay in the centre of the universe, with the entire sky revolving round it. We know better today. The earth is an ordinary planet, the sun is an ordinary star, and our galaxy, with its hundred thousand million stars, is an ordinary galaxy. It has been found that many stars are attended by planets, and it is therefore logical to assume that 'other earths' must be common; it follows that life is likely to be widespread. This view is not accepted by all authorities, however, and at the moment we have no proof that life exists anywhere except on the earth. If it does exist, does this indicate that there may well be intelligent civilizations — and, if so, will they resemble our own?The solar system. In the solar system, only the earth is suitable for advanced life of the kind we can understand. It is just possible that primitive organisms may exist on Mars or the large satellites of Jupiter, but certainly there can be nothing more. We cannot rule out the possibility that life appeared on Mars, only to die out when conditions there became hostile, but again there is no proof, and we will not find out one way or the other until we can obtain samples from the planet and analyse them in our laboratories. It has been said that if the earth were not suitable for us, we would not be here — we would be somewhere else.

However, if we consider an earthlike planet orbiting a solar-type star — and there must be many of these — it is not unreasonable to suggest that life may have appeared and evolved just as it has done on our own world. Our civilization is only a few thousand years old; a civilization that is older than this may well be far more advanced than ours. On the other hand, there is always the possibility that a civilization may have destroyed itself by warfare, as we have been in danger of doing: in fact the threat is still with us at the present time.Alien life? All the evidence indicates that life, wherever it appears, must be carbon based. If this is wrong, then much of our modern science is also wrong, which is hard to believe. Extraterrestrial intelligence may therefore not be wildly different from ours, though there will certainly be important variations — particularly with civilizations on planets which are markedly more massive or less massive than the earth, or which have more extreme climates. But when we consider totally alien life forms, we are entering the realm of science fiction, so that speculations are not only endless but also pointless. We can at once discount all claims of 'alien contact' and UFOs. If there are many advanced civilizations in the galaxy it is not impossible that they could visit earth, but there is not the slightest evidence that they have done so as yet.Possibilities of contact. There is no prospect of achieving interstellar travel by any methods available to us at the moment. Even if we could travel at 99.9 per cent of the speed of light, a journey would last for years; the nearest stars which are of solar type, and which may well be planetary centres, are more than ten light years away. Exotic methods of travel, such as space warps, time warps, wormholes, and thought travel, may become practicable in the future, but again there is no point in speculating. We need a fundamental 'breakthrough', which may come this year, next year, in 100 years, 1,000 years — or never. Remember, however, that science fiction does often turn into science fact, and television would have been regarded as sheer science fiction not so very long ago.SETI. By now SETI, the Search for Extra-Terrestrial Intelligence, is being taken very seriously indeed. The only hope lies in picking up a radio message from afar. Obviously any message would have to be based upon mathematics (and after all, we did not invent mathematics; we merely discovered it). The procedure is to 'listen out' at various selected wavelengths which will be familiar to any other civilizations in the galaxy. As long ago as 1991 the International Astronomical Union laid down the official procedures to be followed by any researcher who does manage to establish contact, and at least it is reasonable to assume that a civilization of our type will be able to interpret a mathematical message.Dangers of contact. It has been claimed that attempts to contact extraterrestrial civilizations are unwise, because of the fear that we might attract unwelcome attention from hostile beings. Yet this seems unreasonable, for two reasons. First, our presence will be known already. If we agree that full-scale broadcasting began around 1920, we are 'radio noisy' to any civilizations within about 80 light years of us (the various spacecraft now on their way out of the solar system will not be within range of any other star for an immensely long period, and moreover the chances of their being identified are vanishingly small). Secondly, any civilization capable of achieving interstellar travel will be far more rational than we are. As was said by the American astronomer Percival Lowell almost a century ago, 'War is the survival among us from savage times, and affects now the boyish and unthinking element of the nation. It is something a people outgrow'.Effects on ourselves. If we could contact an extraterrestrial civilization, the effects upon our thinking would indeed be profound; we would have to adjust to different characteristics, different philosophies, and different religions. One day it may happen, and all in all it would be strange if we were unable to recognize any form of extraterrestrial intelligence that we might encounter.

(Published 2004)

— Patrick Moore

Bibliography
• Boss, A. (1998). Looking for Earths.
• Crosswell, K. (1997). Planet Quest.
• Drake, F., and Sobel, D. (1993). Is Anyone Out There?
• McDonough, T. (1987). The Search for Extraterrestrial Intelligence.
• Moore, P. (2000). The Data Book of Astronomy.
• Swift, D. (ed.) (1990). SETI Pioneers.

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