Extraterrestrial Civilizations - Isaac Asimov [122]
We might, therefore, send stellar probes outward. The expense would still be enormous, but it would be far less than that involved in sending human beings. We can indulge in greater acceleration, eliminate life-support systems for either living or frozen astronauts, and feel no concern for the psychological welfare of astronauts. Nor need we fear future shock, since there would be no particular reason for an automatic probe to return—and even if it did, it would not matter to it that generations had passed.
We can imagine advanced civilizations sending out very advanced probes, but surely there must come a point of diminishing returns. The more elaborate the probe, the more difficult and uncertain its maintenance would have to be. Over thousands or even millions of years, it is hard to suppose that anything really elaborate would keep working faultlessly. (Surely even the most advanced civilization could not alter the second law of thermodynamics or the uncertainty principle.)
If we go to an extreme, we might imagine a crew of advanced robots as intelligent as human beings, for instance, exploring the Universe as human beings themselves could not. And yet if robots are that intelligent, might they not also find themselves vulnerable to the diseases of intelligence—boredom, depression, rage, murder, and suicide?
It might well be necessary, then, to strike some middle ground, and send out probes containing devices elaborate enough to send back as much useful and interesting information as possible, but simple enough to endure through the ages. It seems obvious, though, that this middle ground will result in ships being piloted by devices far less intelligent than human beings.
This, too, may be the answer to the puzzle of why we have not been visited by other civilizations. Perhaps we have been; but not by living organisms. Perhaps probes have passed through our Solar system and have sent messages back on the nature and properties of the Sun and its planets, and, specifically, on the fact that a habitable planet exists in the system. If one has passed recently enough, it might have reported a burgeoning civilization.
Of course, we can’t say how often a probe may have passed through, or when the last probe passed, or whether all the probes have belonged to some one particular civilization.*
WORLDS ADRIFT
A conservative view of the possibilities of interstellar travel has made it seem that there is no practical way of sending intelligent organisms from star to star and that the best way would be the use of automatic probes.
So far, however, we have made the assumption that a crew of astronauts must complete a round-trip voyage to the stars in the space of a human lifetime—either by going faster than light, by experiencing time dilatations, by possessing extended lifetimes, or by the use of deep freezing. Every such device seems impractical.
But then, what if we abandon the assumption and do not require a round-trip in a single lifetime?
Suppose we design a ship that will coast to Alpha Centauri and take centuries to make the trip. Suppose we do not expect the astronauts to be immortal or frozen, but to live normal lifetimes in the normal manner.
Naturally, they will die long before the voyage is completed. However, astronauts of both sexes are on board, and children are born to them, and these carry on—and their children do the same— and their children—for many generations until the destination is reached *An elaborate life-support system is still needed, but the problem of keeping the astronauts occupied and unbored may be solved. Having children helps pass the time. Deaths and births will bring about a steady change in personnel and remove the boredom implicit in a long, long period of the same old faces. Then, too, youngsters born on the ship will know no other existence (at least firsthand) and presumably will not be bored.
On the other hand,