“Because of the future-extension, thiotimoline can interact with an event that has not yet taken place. It can, for instance, to use the classic example, dissolve in water approximately one second before the water is added.
“Thiotimoline is, of course, a very simple compound, comparatively. It has, indeed, the simplest molecule capable of displaying endochronic properties-that is, the past-future extension. While this makes possible certain unique devices, the true applications of endochronicity had to await the development of more complicated molecules; polymers that combined endochronicity with firm structure.
“Pellagrini was the first to form endochronic resins and plastics, and, twenty years later, Cudahy demonstrated the technique for binding endochronic plastics to metal. It became possible to make large objects endochronic-entire spaceships, for instance.
“Now let us consider what happens when a large structure is endochronic. I will describe it qualitatively only; it is all that is necessary. The theoreticians have it all worked out mathematically, but I have never known a physics-johnny yet who could pilot a starship. Let them handle the theory, then, and you handle the ship.
“The small thiotimoline molecule is extraordinarily sensitive to the probabilistic states of the future. If you are certain you are going to add the water, it will dissolve before the water is added. If there is even the slightest doubt in your mind as to whether you will add the water, the thiotimoline will not dissolve until you actually add it.
“The larger the molecule possessing endochronicity, the less sensitive it is to the presence of doubt. It will dissolve, swell, change its electrical properties, or in some way interact with water, even if you are almost certain you may not add the water. But then what if you don't, in actual fact, add the water? The answer is simple. The endochronic structure will move into the future in search of water; not finding it, it will continue to move into the future.
“The effect is very much that of the donkey following the carrot fixed to a stick and held two feet in front of the donkey's nose; except that the endochronic structure is not as smart as the donkey, and never gets tired.
“If an entire ship is endochronic-that is, if endochronic groupings are fixed to the hull at frequent intervals-it is easy to set up a device that will deliver water to key spots in the structure, and yet so arrange that device that although it is always apparently on the point of delivering the water, it never actually does.
“In that case, the endochronic groupings move forward in time, carrying all the ship with it and all the objects on board the ship, including its personnel.
“Of course, there are no absolutes. The ship is moving forward in time relative to the universe; and this is precisely the same as saying that the universe is moving backward in time relative to the ship. The rate at which the ship is moving forward, or the universe is moving backward, in time, can be adjusted with great delicacy by the necessary modification of the device for adding water. The proper way of doing this can be taught, after a fashion; but it can be applied perfectly only by inborn talent. That is what we will find out about you all; whether you have that talent.”
Again he paused and appraised them. Then he went on, amid perfect silence:
“But what good is it all? Let's consider starflights and review some of the things you have learned in school.
“Stars are incredibly far apart and to travel from one to another, considering the light-speed limit on velocity, takes years; centuries; millennia. One way of doing it is to set up a huge ship with a closed ecology; a tiny, self-contained universe. A group of people will set out and the tenth generation thereafter reaches a distant star. No one man makes the journey, and even if the ship eventually returns home, many centuries may have passed.
“To take the original crew to the stars in their own lifetime, freezing techniques may keep them in suspended animation for virtually all the trip. But freezing is a very uncertain procedure, and even if the crew survives and returns home, they will find that many centuries have passed on Earth.
“To take the original crew to the stars in their own lifetime, without freezing them, it is only necessary to accelerate to near-light velocities. Subjective time slows, and it will seem to the crew that it will have taken them only months to make the trip. But time travels at the normal rate for the rest of the universe, and when the crew returns they will find that although they, themselves, haveaged and experienced no more than two months of time, perhaps, the Earth itself will have experienced many centuries.
“In every case, star travel involves enormous duration of time on Earth, even if not to the crew. One must return to Earth, if one returns at all, far into the Earth's future, and this means interstellar travel is not psychologically practical.
“But- But, graduates-”
He peered piercingly at them and said in a low, tense voice, “ If we use an endochronic ship, we can match the time-dilatation effect exactly with the endochronic effect. While the ship travels through space at enormous velocity, and experiences a large slowdown in rate of experienced time, the endochronic effect is moving the universe back in time with respect to the ship. Properly handled, when the ship returns to Earth, with the crew having experienced, say, only two months of duration, the entire universe will have likewise experienced only two months' duration. At last, interstellar travel became practical.
“But only if very delicately handled.
“If the endochronic effect lags a little behind the timedilatation effect, the ship will return after two months to find an Earth four months older. This is not much, perhaps; it can be lived with, you might think; but not so. The crew members are out of phase. They feel everything about them to have aged two months with respect to themselves. Worse yet, the general population feels that the crew members are two months younger than they ought to be. It creates hard feelings and discomforts.
“Similarly, if the endochronic effect races a little ahead of the time-dilatation effect, the ship may return after two months to find an Earth that has not experienced any time duration at all. The ship returns, just as it is rising into the sky. The hard feelings and discomforts will still exist.
“No, graduates, no interstellar flight will be considered successful in this star fleet unless the duration to the crew and the duration to Earth match minute for minute. A sixty-second deviation is a sloppy job that will gain you no merit. A hundred-twenty-second deviation will not be tolerated.
“I know, graduates, very well what questions are going through your minds. They went through mine when I graduated. Do we not in the endochronic ship have the equivalent of a time machine? Can we not, by proper adjustment of our endochronic device, deliberately travel a century into the future, make our observations, then travel a century into the past to return to our starting point? Or vice versa, can we not travel a century into the past and then back into the future to the starting point? Or a thousand years, or a billion? Could we not witness the Earth being born, life evolving, the sun dying?
“Graduates, the mathematical-johnnies tell us that this sort of thing creates paradoxes and requires too much energy to be practical. But 1 tell you the hen with paradoxes. We can't do it for a very simple reason. The endochronic properties are unstable. Molecules that are puckered into the time dimension are sensitive indeed. Relatively small effects will cause them to undergo chemical changes that will allow unpuckering. Even if there are no effects at all, random vibrations will produce the changes that will unpucker them.