I really do not see the signal.
Nelson, at the Battle of Copenhagen
There is a more subtle argument relating to the previous section. Suppose advanced ETCs do indeed create "different" mathematics, or — which is easier to accept and may amount to the same thing — suppose their mathematics was millions of years in advance of ours. If they were transmitting to us right now, would we even recognize that their transmissions were artificial?
Much of the present SETI effort concentrates on the waterhole region and on simple multiples of the hydrogen line frequency (2, 3, n times the frequency, and so on). Perhaps ETCs using a different mathematics see nothing special about such frequencies; the "obvious" frequencies for them might be something quite different. But that is a minor point; let us suppose they broadcast in the waterhole region. The hope of communicating with
ETCs is predicated on finding signals containing simple mathematical patterns and developing from this a shared language. In other words, we hope to receive signals encoded in some math-based language like Freudenthal's LINCOS.147 Is this hope reasonable?
There are two aspects to this question, which we should keep separate. First, could we recognize a signal as artificial? Second, if we recognize a signal, could we decode its meaning?
The efforts of SETI scientists are doomed if they cannot distinguish between an artificial transmission and a natural emission. However, physicists have shown that if a message is sent electromagnetically and has been encoded for optimal efficiency, then an observer who is ignorant of the coding scheme will find the message indistinguishable from black-body radiation.148 Now, black-body radiation is simply the radiation an object emits because it is hot; astronomers detect black-body radiation all the time, and of course they apply the simplest explanation to their observations. But they could be observing messages that have been encoded for optimal efficiency! If ETCs do not care whether we know about them, and if they encode their communications to each other with optimal efficiency, then we could intercept their messages and remain unaware of their existence. It is yet another difficulty that SETI scientists must face.
If advanced ETCs want us to find them, then they could easily encode messages we would recognize as artificial. A signal containing pulses distributed according to some obvious pattern — the first few prime numbers, say — would leave no doubt in our minds about its origin. We have to hope, then, that ETCs want to be noticed. But even if we detect a message, could we decode the contents? Consider the Voynich Manuscript.149 In 1912, Wilfred Voynich, a collector, bought this 234-page book from the Jesuit College at the Villa Mondragone, Frascati, in Italy. It presently resides in the Rare Book Room and Library of Yale University, where it is cataloged by the less romantic name of MS 408. The book was probably written some time between the 13th century and 1608. And this is almost everything we know about the manuscript: it was written in a language or code that no one has yet deciphered. It seems to contain information about herbalism and astrology, among other things, but no one is sure; it could, for example, be a medieval hoax.
Whatever information the Voynich Manuscript contains, we know it was written by a human being in the not too distant past. So the author had the same sensory inputs as the rest of us; a cultural background that is recognizable, if not identical to our own; human emotions that drove him in exactly the same way that they drive us. And yet he wrote a book we cannot decipher. If such a situation can occur with a member of our own species, what chance do we have of understanding a message from an ETC?
figure 38 Folio 78rfrom the Voynich Manuscript. Note the strange text characters. At first glance they seem to be from a foreign language that you cannot quite place; but detailed researches have shown that the characters belong to no known language. Are they characters in some private code? Is the whole thing simply a hoax? No one is figure 38 Folio 78rfrom the Voynich Manuscript. Note the strange text characters. At first glance they seem to be from a foreign language that you cannot quite place; but detailed researches have shown that the characters belong to no known language. Are they characters in some private code? Is the whole thing simply a hoax? No one is
If aliens exist, then they will possess different sense organs, different emotions, different philosophies and, perhaps, even different mathematics. I suspect if astronomers ever detect a message from intelligent extraterrestrials, the dominant emotion mankind would feel — after an initial period of excitement and euphoria — would be frustration. We might struggle for millennia without ever deciphering the meaning of the message.
But does any of this have relevance to the Fermi paradox? Well, one scenario people have offered is that ETCs long ago realized interstellar travel was impossible, made contact with each other through EM signals and, over the aeons, agreed to communicate with each other with signals encoded for optimal efficiency. They then lost interest in contacting younger civilizations like our own, so we find the Galaxy filled with black-body radiation. That may have happened, but it is another example of a "just-so" story; it offers no testable prediction.
On the other hand, if we detected a signal that was clearly artificial in origin, then, even if we could not decipher it, we could infer the existence of intelligent extraterrestrial beings. So whether we can understand aliens is a quite separate question from whether they exist and has no real bearing on the Fermi paradox.
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