There was silence for a while. Ascar smoked noisily and shuffled his feet, staring at the ceiling. He seemed to have become unaware of Heshke’s presence.
“Has any attempt been made to contact people in the past?” Heshke asked then. “Probably they could answer a good many of our questions.”
“Huh?” Ascar’s attention jerked back into the room. He stared at Heshke with glazed eyes. “Oh. Oh, you don’t know about that, do you?”
“Don’t know about what?” asked Heshke in some exasperation.
“About what it’s like in the past. You can’t talk to the people there because they don’t hear you. They don’t see you, either. What’s more you can knock them down and they don’t react in any way at all, just lie there squirming and eventually get up again. It’s as if they were robots going through motions which time has already ordained.”
Heshke stared at him.
“Oh, I know it sounds weird,” Ascar said with a wave of his hand, “but that’s how it is.”
“Do you mean they have no consciousness?”
“They act like they have no consciousness. Like robots, predetermined mechanisms,” Ascar repeated.
“That sounds… sort of dream-like. Are you sure the Titans couldn’t be right?”
“Oh no, it accords with my theory of how the time traveller works very well. You’ve probably read fictional stories about time travel and got your ideas of time from them. They always make the past or the future sound no different in essence from present time; but we know now that they’re very different indeed.”
The physicist finished his tobacco roll and threw away the end, groping in his pocket for another. Heshke gave him one and helped him light it. “How?”
“I’ll explain. Think of the universe as a four-dimensional continuum – three dimensions of space, as is our ordinary experience, and an additional dimension which we call time, extending into the infinite past and the infinite future. If we take the moving ‘now’ out of the picture we, could just as easily call it a universe of four dimensions of space. So now we have a static four-dimensional matrix. That’s basically what the universe consists of, but there’s one other factor: the fleeting present moment, sweeping through the fourth dimension like a travelling wave.”
Heshke was no physicist but he had read widely and to some extent was already familiar with what Ascar was saying. He nodded, picturing it to himself. “The ‘now’ that we seem to be trapped in, being moved on from one moment to the next.”
“That’s right. What is this ‘now’? Does anything exist outside it? For centuries the philosophical question has been whether the past and the future have any existence, or whether only the present that we experience has existence. Well, we’ve found out the answer to that question all right: the past and the future do exist, but they have no ‘now’. In effect, they have no time. No differentiation between before and after. They’re both dead, as it were.”
“So that’s why the people in the past act like robots?”
Ascar nodded. “The travelling ‘now-wave’ has passed them by. Consciousness can only exist in the ‘now’ – somehow or other it appears to be a function of it.”
“This time-wave – what does it consist of?”
“We’re not really sure. Some form of energy that travels through the four-dimensional continuum like a shock wave. We know its velocity: it travels with the speed of light. And as it goes it has the power to make events happen and to organise matter into living forms. You know in olden times they used to talk about the ‘life force’? This is the life force.”
A thought occurred to Heshke. “You say there’s no time in the past. But what if you went back in time and changed something? What happens to the past as it was before you changed it? There’d have to be a kind of time there because there’d be a before you changed it and an after you changed it.…” He broke off in confusion.
The physicist grinned. “What you’re talking about used to be called the Regression Problem, and it exercised us too when we first realised time travel was possible. Actually, in a slightly different form, it’s an ancient philosophical riddle: how can time pass without having another ‘time’ to pass in? One instant ‘now’ is at one point and the next instant it’s at the adjacent point, passed on to the next event, and so you seem to have a ‘before’ and an ‘after’ associated with the same moment – one where ‘now’ was there and one where it wasn’t.”
“Yes, I think that’s what I mean,” Heshke said slowly.
Ascar nodded. “These paradoxes have largely disappeared now that we’re able to make on-the-spot observations. Theorists used to posit an additional fifth dimension to accommodate these changes, but we know better than that now. The universe is indifferent to all artificially imposed changes, as well as to where ‘now’ is situated. It doesn’t distinguish between one configuration and another: therefore any changes you make don’t alter anything.”
Heshke didn’t understand him. “But there’s still the old riddle, what if I went back and murdered my father before I was born…?”
“It would probably turn out that your father was somebody else,” Ascar said acidly. “Joking apart, if you did succeed in ‘killing’ your father, you’d find that he was still alive… later. Cause and effect, as we understand it, only takes place in the travelling now-wave – what we call the Absolute Present. We’ve established that experimentally. Elsewhere the universe behaves indifferently, and if you do force changes on the past, then the consequences die away instead of accumulating.”
“You’re beginning to lose me,” Heshke said slowly. “I find it hard to grasp… that even when tomorrow comes I shall still be here today, smoking this roll… only I won’t be aware of it.”
Ascar rubbed his jaw and yawned tiredly. “That’s it: you’ve got it exactly. Now we are here; shortly the Absolute Present will have moved a few minutes further on, taking our consciousness with it. But the past doesn’t vanish, it’s merely that you can’t see it – just as you can’t see the future yet, even though it exists up there ahead of us. The time traveller acts like a lever, detaching a fragment of the present and moving it about independently. If that fragment has your consciousness attached to it you can then see the past, or the future.”
“How far have you been into the future?” asked Heshke suddenly.
Again Ascar looked sour. “Only about a hundred years, no further. There’s no point.”
“Oh? Why not?”
“Because do you know what you find in the future? Just an empty desolation! There are no living forms – no people, no animals, no grass, no birds or trees or anything. Not a virus or a microbe. Just one second futureward of where we’re sitting the world is void of all life, and these chairs we’re sitting on are empty.”
Horrified, Heshke blinked at him. Ascar smiled crookedly. “It’s logical, if you think about it. There’s life in the past, even if it does behave like clockwork, because the now-wave has already swept over it and the now-wave creates life. But it hasn’t reached the future yet. Everything we’ve constructed out of inorganic matter – our buildings, our machines, and so on – are there, but without the hand of man to maintain them they fall into a state of decay. And as for the substance of our own bodies, that’s dust, just dust.”
And Heshke sat contemplating that vast, dead emptiness.
4
The Titan time traveller was considerably larger than its alien prototype. Instead of the latter’s cylindrical form it had a cagelike structure, being square at both ends and ribbed with louvres. One end contained the cabin for the crew and passengers, the other the bulky drive machinery. It did, however, borrow some features from the alien design: the windows were of a thick nearly-opaque material possessing the quality of image-control, capable of being adjusted so as to admit or block light, and the control system copied the alien concept in its entirety.