"Niven, Larry - The Theory And Practice Of Time Travel" - читать интересную книгу автора (Niven Larry)

"Maybe we can go around you." Svetz hesitated, then plunged in. "Zeera, try this. Send me back to an hour before the earlier Zeera arrives. Ford's automobile won't have disappeared yet. I'll duplicate it, duplicate the duplicate, take the reversed duplicate and the original past you in the big extension cage. That leaves you to destroy the duplicate instead of the original. I reappear after you've gone, leave the original automobile for Ford, and come back here with the reversed duplicate. How's that?"
"It sounded great Would you mind going through it again?"
"Let's see. I go back to-"

This was less of a digression than it seemed. The English language can't handle time travel. We conclude that the ancestors who made our language didn't have minds equipped to handle tithe travel. Naturally we don't either; for our thinking is too dependent on our language.
As far as I know, no language has tenses equipped to handle time travel. No language on Earth. Yet.
But then, no language was ever equipped to handle lasers, television, or spaceflight until lasers, television, and spaceflight were developed. Then the words followed.
If time travel were thrust upon us, would we develop a language to handle it?
We'd need a basic past tense, an altered past tense, a potential past tense (might have been), an altered future tense, an excised future tense (for a future that can no longer happen), a home base present tense, a present-of-the-moment tense, an enclosed present tense (for use while the vehicle is moving through time), a future past tense ("I'll meet you at the bombing of Pearl Harbor in half an hour."), a past future tense ("Just a souvenir I picked up ten million years from now"), and many more. We'd need at least two directions of time flow: sequential personal time, and universal time, with a complete set of tenses for each.
We'd need pronouns to distinguish [you of the past] from [you of the future] and [you of the present]. After all, the three of you might all be sitting around the same table someday.

Meanwhile (if, God willing, the word still has meaning), time travel must be considered fantasy. It violates too many of the laws of physics and reason to be thought otherwise.
But it's a form of fantasy superbly suited to games of logic. The temptation to work out a self-consistent set of laws for time travel must be enormous. So many writers have tried it!
Let's look at some of the more popular possibilities:

DEFENSE OF TIME TRAVEL #1: Assume that (1) One can travel only into the future. (2) The universe is cyclic in time, repeating itself over and over.
This works! All you've got to do is go into the future past the Big Collapse when the universe falls in on itself, through the Big Bang when it explodes again, and keep going until you reach the area of the past you're looking for. Then you murder Hitler in 1920, or use the H-bomb on the damyankees at Appomatox, or whatever your daydream is. There is no Grandfather Paradox.
You merely get a new future.
True, the next version of you will not make the trip. You've eliminated his motive. Thus on the next cycle the damyankees will win the Civil War, Hitler will lead Germany into WWII, and so forth. But you've merely introduced a double cycle. There is no paradox.
Further, your time machine need be nothing more than an EXTREMELY durable time capsule.
OBJECTIONS: Three. First, some people don't believe in cyclic time. (I don't.) Second, locating the proper era is a nontrivial problem when you've got the whole lifetime of the universe to search in. You'd be lucky to find any section of human history. Third, removing your time capsule from the reaction of the Big Bang could change the final configuration of matter, giving an entirely different history.

DEFENSE OF TIME TRAVEL #II: Known as the theory of multiple time tracks.
Let there be a myriad of realities, of universes. For every decision made by any form of life, let it be made both ways; or in all possible wars if there are more then two choices. Let universes be created with every choice.
Then conservation of matter and energy holds only for the universe of universes. One can move time machines from one universe to another.
You've got to admit it's flamboyant!
You still can't visit the past. But you can find a universe where things happened more slowly; where Napoleon is about to fight Waterloo, or Nero is about to ascend the throne. Or, instead of changing the past, you need only seek out the universe where the past you want is the one that happened. The universe you want unquestionably exists. (Though you may search a long, weary time before you find it.)
Ersatz time travel becomes a special case of sidewise-in-time travel, travel between multiple time tracks.
The what-if story has fascinated many writers. Even 0. Henry wrote at least one. From our viewpoint, sidewise-in-time travel solves conservation laws, Grandfather Paradox, everything.
I hate sidewise-in-time travel stories.
Let me show you why.
First, they're too easy to write. You don't need a brain to write alternate-world stories. You need a good history text.
In the second place...did you ever sweat over a decision? Think about one that really gave you trouble, because you knew that what you did would affect you for the rest of your life. Now imagine that for every way you could have jumped, one of you in one universe did jump that way.
Now don't you feel silly? Sweating over something so trivial, when you were going to take all the choices anyway. And if you think that's silly, consider that one of you still can't decide...
In the third place, probability doesn't support the theory of alternate time tracks.
There are six ways a die can fall, right? Which makes thirty-six ways that two dice can fall, including six ways to get a seven. Each way the dice can fall determines one universe. Then the chance of your ending in each of the thirty-six universes is one in thirty-six, right?
Then it doesn't matter if the dice are loaded. One chance in thirty-six, exactly, is the odds for each way the dice can fall. One chance in six, exactly, of getting a seven.
Experience, however, shows that it does matter if the dice are loaded.

DEFENSE OF TIME TRAVEL #III: The idea of reversing the flow of time isn't nearly as silly as it sounds. I quote from an article in the October 1969 issue of Scientific American, "EXPERIMENTS IN TIME REVERSAL," by Oliver E. Overseth.
"All of us vividly recognise the way time flows; we take considerable comfort, for example, in our confidence that the carefully arranged marriage of gin and vermouth is not going to be suddenly annulled in our glass, leaving us with two layers of warm liquid and a lump of ice. It is a curious fact, however, that the laws that provide the basis for our understanding of fundamental physical processes (and presumably biological processes as well) do not favor one direction of time's arrow over another. They would represent the world just as well if time were flowing backward instead of forward and martinis were coming apart rather than being created."
Is the universe really invarient under time reversal? Many physicists think not. Overseth and his partner Roth spent almost two years looking for a case in subatomic physics in which invarience under time reversal is not preserved.
They knew exactly what they were looking for. They were watching (via some very indirect instruments) the decay of a lambda particle into a proton plus a pi meson. The anomaly would have been a nonzero value for the beta component of the spin of the proton.
The point is that they failed to find what they were looking for. There have been many such experiments in recent years, and none have been successful. At the subatomic level, one cannot tell whether time is running backward or forward.
Could a determined man reach the past by reversing himself in time and waiting for last year to happen again?
Present theory says that he would reverse both the spin and the charge of every subatomic particle in his body. The charge reversal converts the whole mass to antimatter. BOOM!
Less dramatically, there is conservation of mass/energy. Reverse the direction of travel in time of a human body, and to any physicist it would look like two people have vanished.
Clearly this is illegal. We can't do it that way.
We might more successfully reverse a man's viewpoint: send his mind backward in time. If there is really no difference between past and future, except in attitude, then it should be possible.
But the traveler risks his memory healing to a tabula rasa, a blank slate. When he reaches his target date he might not remember what to do about it.