“You think I wouldn’t save my own brother if I could?” said Steiger, grimly.
“Why can’t you?”
“It’s difficult to explain, Doctor, but the fact is it would be too dangerous. What’s done is done. There’s nothing we can do about it.”
“Can you not tell me why?” said Gulliver.
“Go ahead,” Delaney said. “We’ll check out the sitting room.”
Steiger sighed and sat down on the bed. “Very well, Doctor. I’ll see if I can explain it in a way that you can understand. Think of time as a river. A very swiftly flowing river. The current of that river is the timestream, specifically, the inertial flow of the timeline.”
Furrows appeared in Gulliver’s forehead as he frowned, trying to follow it. Steiger grunted and shook his head.
“Look, just imagine that the current of our river of time is the force that impels events, all right? And the length of the river itself is all of history, the timeline. Got that?”
Gulliver nodded. “Yes, I think I understand.”
“Good,” said Steiger. “Now, when someone from the future, someone like myself, goes back into the past, he risks doing something that would somehow interfere with the flow of events. Actually, everything I do back here constitutes a form of interference. Even my presence in this room is a form of interference, because after all, there was a point in time at which, in this particular moment, I was never in this room at this particular moment, do you understand?”
Gulliver was frowning once again.
Steiger grimaced. “Hell, I told you it was complicated. Look, as we sit here right now, this very moment, I won’t even be born for about another thousand years. And yet, here I am, sitting here and talking to you, a man who lived almost a thousand years before my time. That’s an example of what we call temporal interference.” He picked up a pillow. “Even an action as insignificant as my picking up this pillow is an example of temporal interference, because there was a point in time, before we came back here, when this moment passed and I was not here to pick up this pillow and the action of this pillow being picked up didn’t happen, see?”
“I … I believe I do see, yes,” said guava. “You were right, it is rather complicated, isn’t it? Much like these circular arguments philosophers are always having. “
“Yes, very much like that, in a way,” said Steiger. “Now, take the fact that I’ve picked up this pillow.” He dropped it back down onto the bed. “It’s an insignificant action. It doesn’t really change anything, does it? In fact, it’s so insignificant that it doesn’t have any effect upon our river of time at all. The fact that I have picked up a pillow in this room has had no discernible effect upon events in this time period, even though it was an event that did not originally take place. You follow?”
Gulliver nodded once again, though he looked a bit uncertain.
“Good. Now imagine that you and I go out tonight and have a few drinks. On the way back, as we’re passing a dark alley, a thief confronts us at knifepoint and demands all of our money. He lunges at me with the knife and in the struggle, I manage to get the knife away from him and kill him. Now, that act is obviously much more significant than merely picking up a pillow, and I don’t mean merely for its
moral implications. Suppose the man I’ve killed had a wife or children. Perhaps he never would have had a wife and children. It’s possible that he would have lived out the remainder of his life alone, in insignificance, doing nothing of any importance whatsoever. And it’s also possible that if I hadn’t been there, you would have been the one to struggle with him, get the knife away and kill him. In that case, his death, in and of itself, has not significantly altered events in this time period. My temporal interference in causing his death is negligible in terms of the grand scheme of things. You with me so far?”
“Yes, I think so,” said Gulliver, listening intently.
“All right,” said Steiger, “now let’s examine another possibility in that same hypothetical situation. Suppose that if it wasn’t for my interference, that thief would have attacked somebody else. After all, it was my idea that we go out for a drink; if I hadn’t come back here and interfered, you would have stayed home and the thief would have attacked another victim. And in that event, he would not have died. He would have’ killed his victim, prospered from his ill-gotten gains, married and had children. Except, now that I have gone back into the past and killed him, obviously those children will never be born. And that victim will not die, at least not at that particular time. So by my interference, I have altered history. I have changed the past. I have disrupted the flow of events. Now let’s take it a bit further. What if that thief had been my ancestor, my great, great grandfather about a dozen times removed?”
“Good lord!” said Gulliver. “Then by killing him, you’ve prevented the birth of his children, which means that … that you could never have been born!”
“Precisely,” Steiger said.
“But… but if you could never have been born,” said Gulliver, frowning, “then ... then how… how is it possible that you could have . . .” his voice trailed off and he stared at Steiger with an expression of utter confusion.
“That, my friend, is what’s known as a temporal paradox,” said Steiger. “If you went back into the past and killed your grandfather before your father had been born, then you wouldn’t have been born, so how could you have gone back and killed your grandfather in the first place?”
“It makes no sense,” said Gulliver. “How is it possible?”
“Well, for years, scientists believed it wasn’t possible,” Steiger replied. “They believed that the past was an immutable absolute. It had already happened, therefore it could not be changed. According to their thinking, if I went back into the past and tried to kill my grandfather, something would have prevented me from doing it, otherwise I couldn’t have gone back to try it in the first place because the very fact that I was alive to do it meant that my grandfather had survived my attempt on his life. You see?”
Gulliver knitted his brows as he ran through it once more in his mind and nodded slowly. “Yes, I think I understand. It all seems very logical now that you’ve explained it.”
“Except it doesn’t work that way,” said Steiger.
“Oh, dear,” said Gulliver. “And I thought I was beginning to understand it.”
“Don’t worry,” Steiger said. “All the scientists were wrong as well and they had the advantage of having a lot more knowledge than you do. Or perhaps I should say they will have that advantage … in about another 950 years or so.”
“What is the answer, then?” Gulliver said, anxiously.