We found this article on the NSA website.
We are not alone in the universe. A few years ago, this notion seemed farfetched; today, the existence of extraterrestrial intelligence is taken for granted by most scientists. Sir Bernard Lovell, one of the world's leading radio astronomers, has calculated that, even allowing for a margin of error of 50003, there must be in our own galaxy about 100 million stars which have planets of the right chemistry, dimensions, and temperature to support organic evolution. If we consider that our own galaxy, the Milky Way, is but one of at least a billion other galaxies similar to ours in the observable universe, the number of stars that could support some form of life is, to reach for a word, astronomical. As to advanced (by miserable earth standards) forms of life, Dr. Frank D. Drake of the National Radio Astronomy Observatory at Green Bank, West Virginia, has stated that, putting all our knowledge together, the number of civilizations which could have arisen by now is about one billion. The next question is, "Where is everybody?"
The nearest neighbor to our solar system is Alpha Centauri, only 4.3 light years away; but, according to Dr. Su-Shu Huang of the National Aeronautics and Space Administration, its planetary system is probably too young for the emergence of life. Two other heavenly friends, Epsilon Eridani and Tau Ceti, about 11 light years away, are stronger contenders for harboring life. Nevertheless, if superior civilizations are abundant, the nearest would probably be at least 100 light years away; therefore, it would take 200 years for a reply to be forthcoming, a small matter of seven generations. This should, however, make little difference to us, in view of the enormous potential gain from our contact with a superior civilization. Unless we're terribly conceited (a very unscientific demeanor), we must assume that the "others" are far more advanced than we are.· Even a 50-year gap would be tremendous; a 500-year gap staggers the imagination, and as 1 The substance of this article was presented at a panel discussion of the same title during the 1965 IEEE Conference on Military Electronics held in Washin~on, D. C., on 23 September 196.5. Besides the author as cryptologist, the other members of the panel were Dr. Paul Garvin, linguist; Dr .• John C. Lilly, delphinologist; Dr. William 0. Davis, physicist; and Fr. Francis J. Heyden, S. J., astronomer. The moderator was Dr. Harold Wrioster, Director of Infonnation Services of the Air Force Office of Scit:ntitic Research. ' ' ' '
EXTRATERRESTRIAL INTELLIGENCE for a 5000-year gap . . . (By the way, if they are as much as 50 years behind us, forget it!) It is quite possible that "others" have satellite probes in space, retransmitting to "them" anything that sounds nonrandom to the probe. But they have probably called us several thousand years ago, and are waiting for an answer; or worse yet, they have given up; or, more probably, they have reached such impressive technological advances that they have destroyed themselves. 2 Epsilon Eridani and Tau Ceti were the targets on which Dr. Drake focussed his attention in the spring of 1960 in Project Ozma, an attempt to detect possible intelligent signals from outer space. The frequency selected for listening was 1420.405752 megacycles per second, or a wave length of 21 cm. This particular frequency, postulated independently by two professors on the faculty of Cornell University, Giuseppe Cocconi and Philip Morrison, happens to be the radiation frequency of atomic or free hydrogen which permeates space in great clouds; moreover, this frequency is within the range of radio frequencies able to pass through the earth's atmosphere. Presumably, the significance of this frequency would be known to other intelligent beings in the universe who understand radio theory. We're still talking about radio waves as the communication medium; other possible media might be masers, lasers, or the as yet undiscovered and unnamed "rasers." A technology superior to ours might even have learned how to modulate a beam of neutrinos (weightless, uncharged particles that physicists on earth find it difficult even to detect); if so, "they" may have to wait a century or two before we learn how to build a neutrino receiver. If another civilization were trying to establish communication with us, it would first embark on attention-getting signals of such a nature that we could distinguish them from random cosmic noise; once we receive a recognizable signal, we have a good chance of understanding the message. For example, they could start with trains of signals corresponding to the natural numbers 1, 2, 3, ... , followed perhaps by prime numbers. They might continue with equal-length extended signals consisting of start and stop impulses, with occasional pulses in i In this connection, Professor losif Shklovsky, Russia's greatest radio astronomer, has the following to say in the September 1965 issue of Soviet Life: "Profound crises lie in wait for a developing civilization and one of them may well prove fatal. We are already familiar with several such critical [situations]: (a) Self-destruction as a result of a thermonuclear catastrophe or some other discovery which may have unpredictable and uncontrollable consequences. (b) Genetic danger, (c) Overproduction of infonnation. (d) Restricted capacity of the individual's brain which can lead to excessive specialization, with consequent dangers of degeneration. (e) A crisis precipitated by the creation of artificial intelligent beings." 108 L. D. CALLIMAHOS between; when these signals are aligned flush over one another, they would show a circle, the Pythagorean Theorem, or similar geometric design.