Extraterrestrial Civilizations (37 page)

In this way, humanity would become no longer a creature of Earth or of the Solar system, but would belong to the whole Universe, drifting outward, ever outward, forming a variety of related species, until such time as the Universe finally came to an enormously slow end and, through one route or another, could no longer support life anywhere within itself.

But what about the extraterrestrial intelligences? Assuming that they do not make use of any dream technologies we cannot even imagine at present, they too may have followed a development that makes the free-worlds a practical way (perhaps the only practical way) of sending living organisms through interstellar space.

Free-worlds may thus arise from thousands of different planetary sources, and some of them may have been moving through space, into and out of the asteroid belts of this star and that, for billions of years.

It may be that if extraterrestrial civilizations have visited us, it has been in the form of free-worlds. And if so, it may be that they have not visited Earth (in which their interest might be limited), but our asteroid belt.

It may be that when our space settlements move out into the asteroid belt we will find ourselves preempted; or perhaps find evidence that free-worlds have been there in the past and have long since gone.
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Or it may be that free-worlds, on principle, avoid Sunlike stars with habitable planets. After all, for free-world purposes almost any star would do. A star might be a short-lived giant, but the free-world can stay far enough away to avoid the radiation and might not need more than, say, a century or two to build new starships out of what planetary material is available at such a distance. Even the least long lived star would last many times that period. Or (much more likely) a star might be pigmyish and cool, but the free-world would not need it for energy, just for the planetary bodies circling it.

If many civilizations adopt that technique, it may well be that some human free-world, dropping down toward some planetary system, will find it already preempted by other free-worlds that are nonhuman.

Surely by that point in history, it will be understood that it is the nature of the mind that makes individuals kin, and that the differences in shape, form, and manner are altogether trivial.

It may be that as the human free-worlds start moving outward, they will find themselves part of a vast brotherhood of intelligence;
part of the complex of innumerable routes by which the Universe has evolved in order to become capable of understanding itself.

And it may be that in combination, humanity and all the extraterrestrial civilizations can advance farther and faster than any one of them could alone. If there is any chance of defeating what we now see as the laws of nature and of bending the entire Universe to the will of the intelligences it has given rise to, then it will be in combined effort that the greatest chance of success will arise.

We have concluded, then, that there may well be over 500,000 civilizations in the Galaxy, but that the only way any of them are likely to emerge from their planetary systems is by interstellar probes or in the form of free-worlds.

There is nothing compelling about either emergence. The vast majority of civilizations, conceivably all of them, may simply remain in their own planetary systems. Any interstellar probes that are sent out may be devices not designed to land on habitable planets but to confine themselves to observations and reports from space. Any free-worlds that may come our way might be more interested in material and energy with which to maintain themselves than in involvement with a sedentary civilization.

In this way, we can rationalize the apparent paradox that while the Galaxy may be rich in civilizations we remain unaware of them.

But what ought we to do in that case?

The simplest answer and the one that involves the least trouble is to do nothing at all. If extraterrestrial civilizations can’t or won’t
reach us, we could just go about our own business. Certainly we have enough troubles of our own to occupy us.

The second possibility is to send out some sort of message in order to make contact. Even if an extraterrestrial civilization can’t reach us, or we them, we can perhaps establish communication across space; even if it is only the message: “We are here. Are you there?”

This is such a normal impulse that back in the nineteenth century, when people were still speculating concerning life on other worlds in the Solar system and almost taking it for granted that there would be civilizations even on the Moon, there were suggestions for methods of communication.

The German mathematician Karl Friedrich Gauss (1777–1855) once suggested that lanes of forest be planted on the steppes of central Asia in the form of a gigantic right triangle with squares on each side. Within the triangle and squares, grain would be planted to darken the shapes with a uniform color. A civilization on the Moon or Mars, for instance, closely studying the surface of the Earth, might see this clear display of the Pythagorean theorem and would conclude at once that there was intelligence on Earth.

The Austrian astronomer Joseph Johann von Littrow (1781–1840) suggested instead that canals be dug, and that kerosene arranged in mathematical forms be floated on the water and set on fire at night. Again, mathematical symbols would be seen from other worlds.

The French inventor Charles Cros (1842–1888) suggested something more flexible—a vast mirror that could be used to reflect light toward Mars. It could then be so manipulated as to send the equivalent of Morse code and actual messages could, in this way, be sent (though they might not necessarily be interpreted, of course).

Interest in establishing communication with extraterrestrial civilizations mounted to the point where, in 1900, a prize of 100,000 francs was offered in Paris to the first person to carry through this task successfully. Communication with Mars was excluded, however. That was thought to be too easy a feat to be worth the money.

All such nineteenth-century suggestions are useless, of course, since there are no intelligent beings on the Moon, Venus, or Mars, and it is doubtful whether the unsophisticated techniques suggested could reach farther (if, indeed, that far).

Besides, in the twentieth century we have, ironically enough, sent out even more spectacular messages with no special effort on our part.

The invention of the electric light and the gradually increasing illumination of our cities and highways has steadily intensified the glitter of Earth’s surface at night, at least over the land areas that are industrialized and urbanized. Astronomers on Mars, puzzling over the light emerging in steadily increasing intensity from Earth’s dark side would be sure to come to the conclusion that a civilization existed on Earth—if there were astronomers on Mars.

The nineteenth-century suggestions made use of light, since that was the most easily manipulable radiation known to cross the vacuum of space at that time. Around the turn of the century, however, radio waves were discovered (like light waves, but a million times longer) and put to use. By 1900, the Yugoslavian-American inventor Nikola Tesla (1856–1943) was already suggesting that radio waves be used to send messages to other worlds.

No deliberate attempt of the kind was made, but it didn’t have to be. With the passing decades radio waves were generated by human beings with ever increasing intensity. Those that could penetrate the upper layers of Earth’s atmosphere did so, and as a result there is a sphere of radio-wave radiation swelling out from Earth in every direction.

Again, astronomers on Mars, if they were aware of this radiation and if they noted that it was growing steadily stronger, would be forced to come to the conclusion that there was a civilization on Earth.

By the second half of the twentieth century, however, it was quite clear that extraterrestrial civilizations did not exist in the Solar system and that if we were to send messages it would have to be to the stars.

This introduced formidable complications. In the Solar system, we at least know where we might aim our messages—at Mars, at Venus, and so on. There is, on the other hand, no way of knowing which star it would be best to aim at.

Furthermore, radiation aimed at the stars would have to be very energetic if it were to maintain sufficient intensity, in view of inevitable dispersion over the light-years, for it to be picked up at even the
distance of the nearest stars.

We are, as I have already said, sending out radio-wave radiation to the stars quite involuntarily. The radio waves that have leaked through the upper layers of our atmosphere have expanded now into a vast ball dozens of light-years in diameter. The outer fringes have passed by many stars already, and although the intensity is excessively minute, it could conceivably be picked up.

However, signals so excessively weak might not seem to the distant astronomers to be incontrovertible proof of a civilization existing somewhere in the neighborhood of our Sun. Even if the astronomers came to the conclusion the civilization existed, the complicated mix of signals would be impossible to sort out and make sense of.

A deliberately emitted beam of radiation could be designed to contain a great deal of information and could be made strong enough to remove all doubt even if its content could not be interpreted.

The trouble is that we do not at the moment want to dispose of the energy to spray messages out into space, especially since we aren’t sure of any specific target, and cannot honestly have much hope of an answer until, at best, many years have passed.

Is there something we can do that will cost less in terms of energy?

We might send a material message, something we can cast arbitrarily into space at little or no cost. To be sure, a material message would be harder to aim than a beam of radiation, and the material message might take many thousands of times longer to get to any specific destination, but at least it would be well within our present capacities.

And the fact is that we
have
sent a message.

On March 3, 1972, the Jupiter probe,
Pioneer 10
, was launched. It passed by Jupiter in December 1973, making its closest approach on December 3, and very successfully sent back photographs and other data that enormously increased our knowledge of that giant planet.

If that were all—if, after having passed Jupiter,
Pioneer 10
had vanished, or exploded, or simply gone dead—it would have proved worthy of the time, effort, and money expended on it. Anything it could do beyond the Jupiter mission was, in a way, an added bonus. Adding a message to it, therefore, would cost virtually nothing.

Pioneer 10
does carry a message, one that was added at the last minute as a matter of sheer bravado.

The message is a gold-anodized aluminum plate, 6 inches by 9 inches, which is attached to the antenna support struts of
Pioneer 10
.