THE CODEBREAKERS

by DAVID KAHN

  At the same time, other scientists were working out the so-called “code of life” of the nucleic acids, DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). These giant molecules are composed of a few simple chemical compounds, including amino acids like those synthesized by Miller, only repeated hundreds of thousands of times in a complicated pattern. Their structure resembles a twisted ladder whose sidepieces form a double spiral; the molecule unzips down the rungs to form two separate semimolecules, each of which attaches to itself compounds floating in the environment—thereby twice re-creating the ladder and reproducing the original molecule. The pattern with which the compounds of these nucleic acids fit together—a pattern that differs from one animal species to another—carries the instructions of heredity. Thus DNA and RNA are responsible for the essential characteristic of life: its ability to persist, its continuity. They themselves lie at the border between the animate and the inanimate. These biological experiments tended to show that life could arise spontaneously from ordinary, nonliving chemical compounds present on the primitive Earth. And if it could happen on that typical planet, Earth, it could happen on others.

  Thus astronomy and biology converged upon the likelihood that life exists elsewhere in the universe. Man is just now reaching that conclusion. But the galactic time-scale reduces to the blink of a gnat’s eye man’s existence on Earth. Consequently, it is unlikely that other forms of life elsewhere have evolved to precisely the same point of cosmic consciousness. Chance alone would predict that on half the other planets life might be still in the unicellular state or in their equivalent of Neanderthal man. But on the other half civilization might have soared far beyond Earth’s still primitive efforts.

  In 1959, as all these avenues of investigation were reaching the crossroads that meant life exists elsewhere, a question asserted itself to several minds at almost the same time. Might these superior civilizations be trying to contact us? Frank Drake was beginning the thinking that culminated in Project Ozma. And two physicists from Cornell, who had long been interested in the general question of life in outer space, finally spent a few days to see whether communication was feasible between different solar systems. Their calculations showed that it was, and they sent the report of their investigations to Nature, the prestigious British scientific weekly. Its publication of their paper on September 19, 1961, made discussion of this science-fiction question “respectable,” brought it out into the open, and stimulated a vigorous colloquy among scientists that is still continuing.

  The article, by Philip Morrison and Giuseppe Cocconi, was entitled “Searching for Interstellar Communications.” After briefly recapitulating the likelihood that long-lived civilizations might arise in-other solar systems, they said:

  It follows, then, that near some star rather like the Sun there are civilizations with scientific interests and with technical possibilities much greater than those now available to us.

  To the beings of such a society, our Sun must appear as a likely site for the evolution of a new society. It is highly probable that for a long time they will have been expecting the development of science near the Sun. We shall assume that long ago they established a channel of communication that would one day become known to us, and that they look forward patiently to the answering signals from the Sun which would make known to them that a new society has entered the community of intelligence. What sort of channel would it be?

  Communication may be effected in two ways: in person, which is to say by direct face-to-face contact, and not in person, which is by writing, radio, telegraph, telephone, flashing lights, or other similar long-distance means. Communication in person is far easier than not in person, for it has access to many more resources.

  Probably the first problem of a spaceman on another planet would be to decide whether the three-headed monster that meets him is trying to signal “Welcome, earthling” or “Scram, one-head!” If this question is settled amicably, both sides could proceed to the setting up of a more extended communication. As a preliminary step, the spaceman would obviously have to determine which of his five senses could be used to “talk” to a creature that may have only some of them.

  Smell seems useless. Roy Bedichek, in The Sense of Smell, tells why:

  It may be worth a pause here to consider the problem of producing a language—that is, a give and take of important information—by means of odors alone. There is first the chemical difficulty of creating a countless number of distinctive odors. Only perfumers, perhaps, can appreciate the unreasonableness of this demand. Solve it, however, and you have made hardly a beginning. Each species must have a broadcasting equipment competent on the instant to generate the odor molecules carrying the particular message the animal at the moment wishes to communicate. After this seemingly impossible task has been accomplished, there remains the technology of devising a receiving set of high selectivity to receive the broadcast, decodify it and pass it on to the power with authority to prescribe and enforce appropriate action.

  The other chemical sense, taste, suffers from these defects and more: taste organs can respond only to substances that they contact and that are dissolved in water.

  Touch, however, has served humans as a relatively useful means of expression. Perhaps the most dramatic example is Helen Keller. Blind and deaf since the age of nineteen months, she learned by matching the vibrations of her teacher’s vocal cords to objects she felt with her hands. Eventually she managed to comprehend, speak, and write. Though this system depends upon the peculiar accessibility of the human larynx, its remarkable success in the face of severe obstacles suggests that the basic method may be adapted to conversations with Martians—meaning here the inhabitants of any other planet. Perhaps the spaceman could give an object to the Martian and let him first feel it with his antennae, then run those antennae over the Braille word for the object. Or, while the Martian is handling the object, the spaceman might send him the signal for the object in “vibratese,” an experimental system of tactile communication by buzzes of different intensity and length applied to various parts of the body. But touch itself is hampered by its relative grossness and its need to physically contact the communicator. These serious limitations will probably relegate it to a subordinate role in man-to-Martian communication, just as on Earth.

  Sight and hearing, then, are left as the most workable senses for conversations involving humans. With these two, communication would probably begin with a simple show-and-tell process, like that used in many schools to teach reading. The spaceman could pick up a rock and say “rock,” could run a short distance and say “run,” and so forth. Eventually communication might be established. But if the Martians—or any life forms on nearby planets, if such exist—are a subhuman species, communication, in the sense of a two-way exchange with men, would probably not be possible. These lower forms would not have the intelligence for it. Men might, however, observe their communications among themselves. This usually amounts to an instinctual behavior highly restricted in the information that it conveys. Such, for example, is the “language” of the bees. The German zoologist Dr. Karl von Frisch found that when a bee arrived at her hive laden with nectar, she would perform a sort of “dance” with great vigor. Suddenly one of the other bees would fly out of the hive. Others would follow. Within minutes some of these bees would appear at the source of the nectar, which was often some distance away and not visible from the hive. Through repeated experiments, von Frisch found that the rate at which the bee turned during her dance indicated the distance of the food source from the hive. When the food was only 100 yards away, the bee turned between nine and ten times in 15 seconds. At 200 yards, she turned seven times, and at about a mile, only twice. Her dance then pinpointed the food source by giving its direction from the hive. When she danced at an angle of, say, fifty degrees to the left of vertical on the hive wall, the food source was located fifty degrees to the left of a line between the hive and the sun. So precise is the apian system of communication, von Frisch fo
und, that it steers bees directly even to food hidden behind the ridge of a mountain. But this study, while valuable in learning about the creatures that man might find on other planets, has little relevance to communicating with them.

  In any event, communication by direct contact occupies but a small part of the problem of messages from outer space. It is highly questionable whether intelligent life even exists on Venus or Mars, and the frozen black voids of interstellar space are so inconceivably vast that many scientists feel that man will never attempt to cross them in spaceships. Relativity limits any vehicle to the speed of light, and in a galaxy 60,000 light-years across it would take eons even at that speed—which no human conveyance shows any sign of even approaching—to penetrate even part way into the more populous neighborhoods of the galaxy.

  Some scientists think, nevertheless, that some sort of tangible object might be sent on such a flight by one advanced civilization seeking to contact another. Leslie C. Edie wondered whether one might not fill a maintenance-free package with a great deal of information and set it adrift in the gravitational currents of space, rather like a message in a bottle intended for a distant shore. Perhaps the messages might be graven microscopically on ultrathin metal plates, or perhaps even organized into the structure of the molecules to convey information—surely as compact a message as is possible. Edie suggested looking again at meteorites to see whether anything like this has already been done with the carbonaceous material sometimes found therein.

  A rather similar technique was envisioned in 1962 by Dr. Ronald N. Bracewell, a leading radio astronomer. Bracewell has suggested that the traveling package might consist of a radio with tape-recorded messages, or perhaps directed by a microminiaturized computer with the size and memory-capacity of a human brain. The advanced society would aim this to swing silently among the planets of the target star, scanning all radio frequencies. When it heard a signal, it would mimic back that signal on the same frequency. If the planet then repeated this message once again, indicating that it was ready to accept the information, the probe would automatically pour out its information. Presumably it would carry an encyclopedic store of knowledge. “Such a probe may be here now, in our solar system, trying to make its presence known,” Bracewell wrote. As evidence, he offered several unexplained radio “echoes” heard in 1927, 1928, and 1934 by several careful scientists. These “echoes,” Bracewell thought, were in reality the probe’s repeating back to Earth the signals that it had heard to alert Earth to its presence. His idea has been criticized on several grounds, among them that while it might not cost too much for a civilization to spray such probes into the surrounding space, it seems exceedingly difficult to armor them against the erosion of space for hundreds of millions of years. In any event, the theory has not received widespread acceptance.

  Perhaps the object to be sent might consist of the lightest “things” in the universe—electrons. An electron gun could shoot beams of these charged particles through space. They would be received by a scintillation detector, which gives off flashes of light whenever an electron hits it. The system can carry a great deal of information with high efficiency, but its range seems limited to about 100,000 miles—far under the trillions needed for interstellar communication. The same general idea has been proposed for another subatomic particle, the neutrino. It would be ideal for long-distance communication, since it weighs nothing and carries no electric charge, and hence would not be distracted from its course by the magnetic fields of space. There is a little problem in that scientists on Earth are hard put to detect their presence at all—neutrinos pass all the way through Earth without leaving any evidence of their passage—and observing a modulated beam of them seems definitely beyond present terrestrial capacities. Other civilizations, however, may have solved these problems.

  The fastest and cheapest means of interstellar communication appears to be, not by object, but by electromagnetic waves. These are the waves of radio, heat, light, ultraviolet, X rays, and gamma radiation. All, of course, travel at the speed of light. And it is clearly easier to push a radio signal out into space than to launch a probe. “Interstellar communication across the galactic plasma without dispersion in direction and flight time is practical, so far as we know, only with electromagnetic waves,” wrote Cocconi and Morrison.

  The question at once arises, Which waves? Natural considerations quickly limit the possibilities. Signals by X rays cannot be focused. Gamma rays are given off by radioactive materials; perhaps these unwanted by-products of a nuclear reactor might find useful employment in space communication. Unfortunately, they do not carry beyond 100,000 miles, and, so, like electrons, have insufficient range.

  Morrison has made the imaginative suggestion that a civilization fling an opaque screen, perhaps consisting of many individual morsels of matter, into space on a line between the parent sun and the target star. The civilization would move the screen, perhaps by magnetism, into and out of that line, thereby causing the whole parent sun to appear to blink. The pattern of the blinks would, of course, form the signal. An effort of this magnitude might not be too difficult for an advanced society. A subtle refinement of this, suggested by Drake, uses a cloud of material that would absorb, not all the light, but only certain wavelengths of it. These missing wavelengths, which would leave a black line in a spectrogram of the star’s light, would indicate the existence of an artificial element and consequently of a civilization. Though Drake seemed to propose this more as an indicator than as a signal device, it might be possible to shift this cloud, or renew it in the face of its dispersion by the outflow of gas from the star, and so transmit messages. Another possible light-wave system uses the natural absorption by elements in a star’s atmosphere of certain wavelengths of the light emitted by its incandescent body. This absorption likewise leaves a black line in the otherwise bright and rainbowlike spectrogram of its light. Dr. Charles Townes, who won a Nobel Prize for fathering the maser and its optical cousin, the laser, suggested, with a colleague, Robert N. Schwartz, that laser light, which can be very finely tuned, might be focused into the narrow slot of the black absorption line, like fitting a key into a keyhole, and turned on and off to send messages. Astronomers on distant planets, seeing the fine inner line of light where nature would not have it, would recognize it as artificial.

  While all these methods may be feasible despite their great technical difficulties, the most practical method of all appears to be radio. Man today has a sophisticated understanding of radio’s superiority. But in an almost instinctive fashion, man recognized radio as a natural choice for interplanetary communication soon after it was invented. Nikola Tesla, who was a pioneer in the field and who, though an eccentric, made solid contributions, observed at his radio laboratory in Colorado in 1899 periodic “electrical actions” with “a clear suggestion of number and order that were not traceable to any cause then known to me.” “The feeling is constantly growing on me,” he wrote, “that I had been the first to hear the greeting of one planet to another.” Twenty-one years later, the inventor of radio, Guglielmo Marconi, was reported as saying that some inexplicable radio signals heard by his company on both sides of the Atlantic might be signals from another planet. They are now thought to be the phenomenon known as “whistlers,” caused by lightning, heard by Marconi years before others had noticed them.

  With the close approach of Mars to Earth in 1924, the question of Mars-Earth communication erupted into excited discussion. Lieutenant Commander Fitzhugh Green asked, “Could We Decode Messages From Mars?” in Popular Science Monthly, and went on to note that “Twenty-one different methods have been suggested to communicate with Mars this summer”—none of them particularly acute. David Todd, former head of the astronomy department at Amherst College, sought to have all radio stations on Earth shut down during the passage and listen for signals from Mars. The Army and Navy actually ordered their stations to avoid unnecessary transmissions and to listen for unusual signals. The executive officer of the Signal Corps
announced that the chief of its code section, one William F. Friedman, was standing by to decipher any messages received. At Camp Alfred Vail, the Army’s major Signal Corps center, now Fort Monmouth, three radio stations did listen. Others may have searched the radio bands too. This was, despite its haphazard, transient, and superficial nature, man’s first known attempt to listen for messages from other worlds. On the night of August 24 recorded dashes followed by a voice pronouncing words were heard. Nothing was done about it, as it seemed to be just a human radio test. In addition, a Washington man named Jenkins, an early television pioneer, heard some mysterious signals that he recorded on moving photographic strips from 1 p.m. August 22 to 5 p.m. August 23, 1924. Accepting the Signal Corps’ implied invitation, he brought the strips to Friedman’s office. Recalled Friedman: “I thought him a sort of visionary and didn’t try to do anything with his record. I was probably wrong!”

  Since that time, the development of radio astronomy and general advances in radio technique have made it possible to eliminate large portions of the radio spectrum as likely channels for any messages from outer space. For a number of technical reasons—attenuation in space, power required, facility of reception—“The wide radio band from, say 1 Me [megacycle] to 104 Me, remains as the rational choice,” Cocconi and Morrison wrote. But where precisely in this still enormous range should man listen? The question is that which faces the driver of a car who is in a part of the country where he does not know the radio stations but wants to pick up the broadcast of a particular major-league ball game. He has to tune his radio across the entire dial, listening at each station, until he finds what he wants. With interstellar broadcasts, not only is the dial immensely broader, but also the signal would be far weaker and far less recognizable than the voice of a familiar announcer.