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Where are the extraterrestrials hiding?

According to Hollywood, the universe beyond Earth is populated by only two types of alien creatures: the good and the bad. The white hats among the extra-terrestrials usually make contact with earthlings reluctantly, as did the Antarean rescue team in Cocoon, or accidentally, as in the unintended abandonment of E.T. But once in touch with the earthlings, these often anthropomorphic aliens help us out by promoting peace, improving our health, or simply amusing our children. When they leave-and the good aliens always leave-we wave them good-by with a thankful tear in the eye.

Although benevolent extra-terrestrials may have the current upper hand at the neighborhood cinemas, it was not long ago that, to paraphrase John Wayne, the only good alien was a dead alien. Inspired by conquest, hunger, or just plain orneriness, the bad guys from space destroyed our cities, devoured our space explorers, took over our bodies, or engaged in endless interstellar battles with our descendants.

Drama depends on antagonism, so it is hardly unexpected that Hollywood has so sharply categorized the denizens of deep space. But surprisingly enough, the temperament of the extra-terrestrials has lately become a matter of scientific interest.

Concern for the true nature of extraterrestrial behavior derives from the continuing failure of a small, back-burner scientific enterprise. For several decades now a limited number of countries, including the superpowers, have expended both scientific manpower and money on the Search for ExtraTerrestrial Intelligence (SETI). Although long a matter for speculation, the question of the existence of alien beings has recently become fashionable for good reason: the development of radio astronomical techniques since World War II has finally provided an effective means for detecting the extra-terrestrials.

The method used is simply to electronically "eavesdrop" on any radio signals that might be deliberately or accidentally beamed our way. Large radio telescopes, which are nothing more than highly directional antennas, are trained on nearby stars regarded as being good candidates for harboring Earth-like planets. Radio signals received by the telescope are then analyzed for any unnatural behavior-a pattern of pulses, for example-that would betray an intelligent broadcaster. There are endless technical nuances to this apparently simple scheme, as scientists try to second-guess extra-terrestrials regarding the likely choice of transmitting frequencies, speed of transmission, and so forth. But the bottom line of two decades of search is a negative result. No convincing sign of life has been heard.

Assessing the Paradox

Given the mammoth technical difficulties involved, it may be premature to attach any significance to this failure, and yet many astronomers are already uncomfortable. Our galaxy alone consists of several hundred billion stars. If only a small fraction harbor life-bearing planets, then the number of intelligent civilizations dispersed throughout the Milky Way could be a million or more. Some of these presumably would have had time to develop the technology of interstellar rocketry.

Now, followers of Von Daniken may believe the aliens have been here, and the UFO crowd thinks they still are, but most scientists are unconvinced by the evidence. Still, not seeing the aliens or their spacecraft causes far less consternation than the apparent lack of radio traffic. If the galaxy is truly filled with life, why do we not hear any communication?

A lot of people are compelled by this collision of expectation and experiment to conclude that there is no life elsewhere; earthlings are the "crown of creation," and the galaxy lies open for our eventual conquest. This is a highly anthropocentric proposition, of course, and therefore suspect. Since the days of Ptolemy and earlier, man has pictured himself at the center of creation, only to be humbled by scientific discovery. Earth is certainly very prosaic from an astronomical standpoint, and it is difficult for many scientists to accept our planet as the only site of intelligent life in the galaxy. Furthermore, in the last two years astronomers have discovered material surrounding a dozen or so nearby stars, suggesting that planets may be quite widespread.

If we choose to acknowledge that life is probably plentiful, then the nagging question remains: Why have we not heard any signs of it? Where are the aliens hiding? Could it be that some aspect of their behavior leads them to conceal their existence? Although it is risky to infer things about the conduct of civilizations that might be millions of years in advance of ours, extraterrestrial sociology has nonetheless become the subject of considerable recent debate.

Nuclear Demise? An obvious question that anyone concerned with these problems might ask is whether an advanced civilization would last very long. Within a few decades of the invention of radios and rockets-the hardware we need to probe the cosmos-earthlings started building nuclear weapons. Perhaps this is a very general phenomenon, and perhaps the outcome we fear most, nuclear self-destruction, is common as wet, In other words, as soon as a civilization any civilization-advances to the point of being able to communicate, it quickly disappears with a radioactive bang.

To avoid this dramatic, but disappointing, fate, normally aggressive civilizations (including ours) may need to become passive and noncompetitive, A cynical reader might wonder if such a reversal of behavior is possible, but one could imagine resorting to genetic engineering to accomplish this if it were seen as necessary to ensure the continued survival of the race. In any case, in this view of evolution, only the societies in which ambition has been curbed will be long-lived. These civilizations will be self-preoccupied; they will not be interested in interstellar contact. We will not hear them, and if we wish to survive as a species, we must become like them.

Although the sociology of subdued passion may rule the galaxy, such passive civilizations would leave the field open for any group that could manage to avoid nuclear crisis and yet still maintain its interest for expansion. The fraction of civilizations that can engineer a less radical solution to the self-destruction problem might be small, but even a tiny number of such societies (indeed, even one) could quickly overrun the galaxy, once more presenting us with the paradox of their apparent silence.

Resource Conservation Consequently, scientists have considered other behavior that could be keeping the aliens from our doorstep. Frank Drake of the University of California, Santa Cruz, suggests that rational beings would never venture far into space, simply because it is too "pensive. He points out that the cost in energy for a colonizing expedition to travel to even nearby stars is comparable to the amount of energy consumed by the United States in a century. No civilization would commit mammoth resources to a project of doubtful benefit when the same resources could invariably be better expended to improve living conditions on the home planet.

While Drake's argument appears rational, it may be, again, too anthropocentric. We Eve in a world where poverty is plentiful and energy is scarce, But should we assume that aliens would reason along the same lines as the present U.S. House Ways and Means Committee? In the next millennium, both energy and space technology will probably become abundant for earthlings, and the relative costs of interstellar exploration will therefore drop. Moreover, even if most extra-terrestrials consider space travel a waste of money, we must assume that they all feel this way if we are to use this argument to explain away the lack of radio signals. Even the most cost-conscious speculator should hesitate to make such an assumption.

But if external factors do not slow the alien advance, perhaps self-imposed restraints might. If life is truly plentiful, then many civilizations can be expected to mature in the time required to colonize the whole galaxy. In that case, it might be reasonable to suppose the galaxy is subdivided into separate regions of influence,"no man's land" between. By agreement or practice, no colonization activities are allowed in these border areas. Proponents of this approach, of course, can then declare that Earth happens to He in such a no man's land, thus explaining our absence of alien company.

The Zoo Hypothesis

John Ball of the M.I.T. Haystack Observatory has elaborated this idea further with hi"zoo hypothesis." In this view, it is not unthinkable that the aliens regard the primitive developments we refer to as civilization as a curiosity, and interesting enough to be left alone. The Earth is merely a zoo in which we, the animals, are unaware of occasional visits by curious extra-terrestrials on the other side of the bars.

Nonetheless, ideas that postulate restraint on the part of our galactic brethren are at odds with human experience at least, and the subtle anthropocentric bias of the "zoo hypothesis" (are we really so interesting?) leaves many researchers uncomfortable. Indeed, perhaps we are being left alone because we are not interesting enough. Remember that the galaxy is roughly 20 billion years old, an age that is ten thousand times longer than the time required for man's evolution from his ancestors. Intelligent beings that develop on separate planets can be expected to differ, on the average, by millions, and perhaps billions, of years in their level of development. When the Spaniards landedin America, the Indian civilization they found was at most a thousand years or so behind the European technical level, and yet that difference proved fatal to the natives. Imagine now some interstellar colonizers finding natives who have a technology lag of millions of years! The first serious galactic colonizers could have proceeded virtually unimpeded, with about as much resistance to their comings as the U.S. Army could expect from the reptiles of the Galapagos Islands. If this scenario is correct, then the galaxy might be presently organized into an empire of the sort that science-fiction writers love to dream up. And a single, dominant civilization just might have the discipline or good sense to ignore or avoid a primitive planet such as Earth.

There are some members of the SETI community who remain unsatisfied with all such sociological explanations. For them, the absence of signals from space is more simply explained: we are, indeed, alone in the galaxy. To substantiate their claim, they point to the tortuous path of evolution on Earth. For example, the earliest microfossils show that life began on our planet 3.5 billion years ago, or only shortly after Earth's crust had cooled from its molten state. But it took a very long time before anything more complex than a one-celled creature could be found on Earth. Repeated catastrophes (including the possible extinction of the dinosaurs due to Earth's collision with a large comet), all of which were a priori improbable, shaped the course of evolution. Finally, 3.5 billion years after life began, intelligent life gained a foothold.

Evolution, in short, is a very uncertain factory for intelligence.

Had the dinosaurs not been wiped out when they were, we would not be here today. If continental drift had not sent Antarctica to the bottom of the world, changing the African climate from a rain forest to a dry savanna, our simian ancestors would not have been forced out of the trees and into a new species. If any of a multitude of circumstances had been a little different, intelligence would never have developed on Earth. There is little to suggest that intelligence has much long-term survival value, From nature's point of view, the most successful survival strategy may be to produce countless varieties of tough, genetically adaptable insects. Making man may have only been an improbable accident.

In the next several millennia, assuming we do not succeed at nuclear hara-kiri, earthlings will Team firsthand what the true situation in space is. Spacecraft will reach the nearby stars, and speculation will yield to observation. Perhaps we will be welcomed, Perhaps we will be fought. But perhaps we will find nothing more advanced than a butterfly.
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Author:Shostak, Seth
Publication:Saturday Evening Post
Date:Sep 1, 1987
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