Milky Way, a good many of these billions supporting intelligent forms of life.
Two years later, however, Struve was less optimistic, insisting that we must distinguish between the probability of a star pos­sessing planets and the probability that such planets contain in­telligent living organisms. Only a few dozen such stars are closer than twenty light years to us. "But the probability that any of them have intelligent life at the present time is vanish-ingly small. The probability that even if intelligent life now exists outside the solar system, but closer to us than twenty light years away, any artificial radio signals are reaching us now is even smaller. But it is not zero... the attempt to record such signals must be made."6 A. G. W. Cameron, of the National Aeronautics and Space Administration, is similarly inclined to a dimmer view of the uniformity of solar systems.7 The effect of his calculations is to reduce the number of life-bearing planets in the Milky Way from the billions to the millions, most of them quite distant.
The question of the proximity and number of solar systems is thus still not answered to our satisfaction. Indirect methods, such as analyses of stellar motion, have been proposed for such detection. In the not-too-distant future, orbiting telescopes entirely above the atmosphere, or even moon-based instru­ments, may be able to photograph planets in nearby solar systems—if such planets do indeed exist!
Despite the absence of immediately available evidence for such planets and for extraterrestrial intelligent life, most as­tronomers assume their existence in proportions that sound nothing less than fantastic. Shapley proposes a novel theory concerning the existence of life on bodies intermediate in size between that of a star and that of a planet, not having any sun about which to orbit. Myriads of these dark bodies abound in the universe, he maintains, supporting life by lightning and internal radiation. And Cambridge University's cosmologist Fred Hoyle speculates that an interchange of messages between planets of different solar systems is going on, on a vast scale, all the time, and that we are naively unaware of it. "My guess is that there might be a million or more subscribers to the
galactic directory. Our problem is to get our name into that directory."8
The Evolutionary Assumption
All of the above theorizing about extraterrestrial life is based upon one assumption: the natural evolution of life from inert organic chemicals. One hundred years after the seemingly conclusive victory of Louis Pasteur over Felix A. Pouchet, and the abandonment of the theory of the spontaneous generation of life, most scientists maintain that life was indeed generated spontaneously, and that, as Charles Darwin wrote, "The prin­ciple of life . . . [is] a part, or consequence, of some general law."9
Current biochemical research indicates that, given the right conditions, self-duplicating macromolecules will naturally evolve out of previously inert material. Two distinguished biologists, Aaron Novick and Joshua Lederberg, believe that "there is a good, rather than an unlikely, chance for life to develop on a planet like earth," for "spontaneous chemical processes would lead to the formation of many complex mole­cules." Electric discharges on gas mixtures similar in composi­tion to what is presumed to have been the primitive atmos­phere of earth give rise to amino acids, the basic stuff of all life; and further natural synthesis gives rise to nucleic acids, which are self-replicating structures. Such complex compounds, in the absence of any voracious organisms, would continue to breed other molecules identical with themselves out of this "soup," especially in the primitive oceans.10 Indeed, in 1957 Stanley Miller, working under the esteemed chemist Harold C. Urey, mixed water vapor with methane (a com­pound of carbon and hydrogen), hydrogen, and ammonia (a compound of nitrogen and hydrogen), and subjected the mix­ture to a powerful high frequency spark. After a week, he obtained several amino acids and other important organic (carbon-containing) compounds. Miller suggested, and the idea seems to have gained acceptance, that a hydrogen rather than oxygen-dominated atmosphere is the key to the natural synthesis of the organic compounds.11
    E.T. Life Page:   prev <   1   2   3   4   5   6   7     23   24   25   > next       Home