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Lesson 43 |
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Are there strangers in space? |
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What does the 'uniquely rational way' for us to communicate with other intelligent beings in space depend on? |
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We must conclude from the work of those who have studied the origin of life, |
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that given a planet only approximately like our own, life is almost certain to start. |
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Of all the planets in our solar system, we are now pretty certain the Earth is the only one on which life can survive. |
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Mars is too dry and poor in oxygen, Venus far too hot, and so is Mercury, |
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and the outer planets have temperatures near absolute zero and hydrogen-dominated atmospheres. |
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But other suns, start as the astronomers call them, are bound to have planets like our own, and as is the number of stars in the universe is so vast, |
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this possibility becomes virtual certainty. |
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There are one hundred thousand million starts in our own Milky Way alone, |
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and then there are three thousand million other milky ways or galaxies, in the universe. |
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so the number of stars that we know exist is now estimated at about 300 million million million. |
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Although perhaps only 1 percent of the life that has started somewhere will develop into highly complex and intelligent patterns, |
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so vast is the number of planets, that intelligent life is bound to be a natural part of the universe. |
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If then we are so certain that other intelligent life exists in the universe, why have we had no visitors from outer space yet? |
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First of all, they may have come to this planet of ours thousands or millions of years ago, |
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and found our then prevailing primitive state completely uninteresting to their own advanced knowledge. |
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Professor Ronald Bracewell, a leading American radio astronomer, |
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argued in Nature that such a superior civilization, on a visit to our own solar system, |
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may have left an automatic messenger behind to await the possible awakening of an advanced civilization. |
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Such a messenger, receiving our radio and television signals, |
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might well re-transmit them back to its home-planet, |
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although what impression any other civilization would thus get from us is best left unsaid. |
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But here we come up against the most difficult of all obstacles to contact with people on other planets |
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-- the astronomical distances which separate us. |
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As a reasonable guess, they might, on an average, be 100 light years away. |
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(A light year is the distance which light travels at 186, 000 miles per second in one year, namely 6 million million miles.) |
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Radio waves also travel at the speed of light, |
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and assuming such an automatic messenger picked up our first broadcasts of the 1920's, |
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the message to its home planet is barely halfway there. |
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Similarly, our own present primitive chemical rockets, |
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though good enough to orbit men, have no chance of transporting us to the nearest other star, |
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four light years away, let alone distances of tens or hundreds of light years. |
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Fortunately, there is a 'uniquely rational way' for us to communicate with other intelligent beings, |
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as Walter Sullivan has put it in his excellent book, |
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We Are not Alone. |
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This depends on the precise radio frequency of the 21-cm wavelength, or 1420 megacycles per second. |
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It is the natural frequency of emission of the hydrogen atoms in space and was discovered by us in 1951; |
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it must be known to any kind of radio astronomer in the universe. |
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Once the existence of this wave-length had been discovered, |
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it was not long before its use as the uniquely recognizable broadcasting frequency for interstellar communication was suggested. |
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Without something of this kind, searching for intelligences on other planets would be like trying to |
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meet a friend in London without a pre-arranged rendezvous and absurdly wandering the streets in the hope of a chance encounter. |