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 be 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.
“Let's go back to our river,' Steiger said. 'Remember that
I said the current of the river is the timestream and that the river itself represents history, the timeline? If a person travels back in time and does something relatively insignificant my picking up the pillow, for example-then that would be like tossing a very small pebble into a swiftly flowing stream. It wouldn't even make a ripple. A more significant form of interference-the killing of our hypothetically childless thief, for example-might be compared to tossing a rather large rock into the river.
It would make a splash, but unless the interference was significant enough to alter the flow of events, the ripples would be dissipated by the force of the current. Still with me?'
''Yes, I think so,' Gulliver said, paying very close attention.
“Now,' said Steiger, 'an act of interference that was significant enough to actually alter the flow of events and cause a severe temporal disruption-something like my killing my great grandfather, in other words could be compared to our throwing a gigantic boulder into the river, something huge, big enough to make the river overflow its banks on both sides and flow around it. And that is what we call a timestream split. For a short period of time, you would have two rivers, one flowing around each side of the giant boulder. One fork of the river would represent the past as it had happened before the act of disruption. The other would represent the creation of a second past, a parallel timeline, in which the act of disruption had been taken into account. A live grandfather in one, a dead grandfather in the other. And the person causing the disruption which created the split would wind up in that second timeline, because there would have to be an original timeline in which his past, up to the moment he disrupted it, was preserved intact. And at some point, unless the disruption was of sufficient magnitude to keep both timelines apart indefinitely, those two separate timelines must rejoin and the results could be disastrous.'
Gulliver gaped at him, slack jawed.
'And that's only the simplified explanation,' Steiger said.
'It can get a great deal more complicated than that. Even if it wasn't against all regulations for me to attempt to save my brother's life-and I've never been all that religious about following regulations to begin with-there would still be no guarantee that I could do it. And even if I could, there would still have to be a past in which my brother died, because it's already happened, do you see? If I tried to change it, I'd risk creating a timestream split. Or at the very least, I would bring about what's known as a 'ripple' in the timestream, sort of a miniature timestream split of short duration, one that would also have completely unforeseeable results. '
'The place is clean,' Delaney said, coming back into the bedroom. 'Well, did he explain it to you, Doctor?'
Gulliver looked up at him and the bewildered expression on his face said it an.
'Yep, I guess he did,' Delaney said.
Then Andre screamed.
Delaney and Steiger both drew their weapons and ran into the sitting room.
'Don't shoot, it's only me,' said Lucas Priest.
Chapter 5
''It can't be,' said Andre, after a moment of stunned silence.
Delaney had his plasma pistol aimed directly at Priest's chest. 'I don't know who you are, mister,' he said, 'but don't you move a muscle. '
Lucas stood motionless with his hands raised. 'Come on, Finn, it's me, for chrissake. Lucas. Your old partner, remember?'
'Try again. I buried my old partner.'
'Yeah, I know,' said Lucas, with a grimace. He kept his hands raised and carefully avoided making any sudden moves. 'I figured this wasn't going to be easy. Look, I can explain. I realise this is going to be bit hard to believe, but-'
'It's gotta be his twin,'' said Steiger, interrupting him.
'From the congruent universe…
Delaney shook his head. 'No. he's dead, too. I ought to know, I killed him.'
'Maybe in the congruent universe, Lucas Priest had a twin brother,' Steiger said, keeping his gun trained on Lucas.
'Yeah, and maybe I was triplets,' said Lucas, wryly, 'but I'm not. Finn, remember that time we took some R amp; R and went down to that Mexican border town and got in-'
'That was all in the arrest report the Federales filed,' said Delaney. 'You could have seen that when the S.O.G. swiped data from the
Archives Section. '
'Oh, Right. I forgot about that. Okay, wait a minute, what about that time we got drunk and you told me that when you were fourteen, that sexy young high school
English teacher you had made you stay after school one day and-'
'I've been drunk lots of time, ' Delaney said, hastily, with a quick glance at the others. He swallowed nervously and moistened his lips. 'It's entirely possible I might've told that story to somebody else.'
