Extraterrestrial Civilizations Read Online Free PDF Page A

the development of a practical steam engine, leading on to an Industrial Revolution, which is still in progress. And about 20 years ago we began to dispose of types of energy that could leak out into space in noticeable quantities.
We
became detectable.
    In short, we are not looking merely for extraterrestrial life. We are not even looking merely for extraterrestrial intelligence. We are looking for extraterrestrial civilization that disposes of enough energy of a sufficiently sophisticated kind to be detectable over interstellar distances. After all, if the level of life/intelligence/civilization on some world is such that it is indetectable, we are not going to detect it.
    And now, you see, it is fair to say that on Earth there is exactly one civilization of the kind we are looking for; just one, our own. Asfar as we know, there has never been any other civilization of this kind on Earth, and it was only a few years ago that our own civilization became the kind I’m referring to—a detectable civilization.
    Of course, now that I’ve demonstrated that, in our role of civilization-makers, we are alone on Earth—that is no great tragedy after all. Earth is no longer the only world in the consciousness of human beings. We need only look for civilizations elsewhere, on other worlds, and it may then be discovered that we are not alone after all.
    * Here was an example of another “world” but one that was never visible or in any way sensed in the ordinary way.
    * I do not wish to denigrate the value of inventing fantasy. It is a noble art, requiring great skill. I know. I have been making my living out of it for years. It is one thing, however, to invent an amusing fantasy, and quite another to confuse it with reality.
    † I won’t bother trying to define a “reasonable man.” I suspect that one convenient assumption we can make is that anyone bothering to read this book is a “reasonable man”.
    * Such disputation can be quite nasty and polemical at times, for scientists are quite human, and any given individual among them can be, at times, petty, mean, vindictive—or simply stupid.
    * I make an exception of those inanimate objects, called computers, that have come to exist in the last quarter-century, and that, in some ways, give evidence of properties that can easily be mistaken for intelligence. These are, however, human products, and can fairly be considered as extensions of human intelligence, and not as nonhuman intelligence.
    * There are books that have been written describing how plants seem aware of human speech and react with apparent intelligence to it. As far as biologists can tell, however, there is no scientific merit whatever to such views.

CHAPTER 2
The Moon
PHASES
    If we imagine ourselves looking about at our surroundings with no knowledge concerning them at all, we might be forgiven for thinking the Earth was the only world there was. What, then, made people think there were other worlds?
    It was the Moon. Consider—
    The predominant characteristic of the objects in the sky is their glow. The stars are little bits of sparkling light. The planets are somewhat brighter bits of sparkling light. The Sun is a round circle of blazing light. There is an occasional meteor that produces a brief line of light. There is an even more occasional comet that is an irregular hazy patch of light.
    It is the light that makes the heavenly objects seem altogether different from the Earth, which in itself is dark and gives off no light.
    To be sure, light can be produced on the Earth in the form of fire, but that is altogether different from the heavenly light. Earthly fires have to be fed constantly with fuel or they would flicker and go out, but the heavenly light continues forever without change.
    In fact, the Greek philosopher Aristotle (384–322 B.C .) maintained that all the heavenly objects were composed of a substance called aether, separate and distinct from the elements that made up the Earth. The