'Not this fast!' said the Dean. The dishevelled wizards looked up at the rapidly crowding night. Discworld constellations changed frequently as the world moved through the void, which meant that astrology was cutting-edge research rather than, as elsewhere, a clever way of avoiding a proper job. It was amazing how human traits and affairs could so reliably and continuously be guided by a succession of big balls of plasma billions of miles away, most of whom have never even heard of humanity. 'We're marooned on some other world!' moaned the Senior Wrangler.
'Er . . . I don't think so,' said Ponder. 'You've got a better suggestion, I suppose?'
'Er . . . you see that big patch of stars over there?' The wizards looked at the large cluster twinkling near the horizon. 'Very pretty,' said Ridcully. 'Well?'
'I think it's what we call the Small Boring Group of Faint Stars. It's about the right shape,' said Ponder. 'And I know what you're going to say, sir, you're going to say, “But they're just a blob in the sky, not a patch on the blobs we used to get,” sir, but, you see, that's what they might have looked like when Great A'Tuin was much closer to them, thousands of years ago. In other words, sir,' Ponder drew a deep breath, in dread of everything that was to come, 'I think we've travelled backwards in time. For thousands of years.' And that was the other side of the odd thing about wizards. While they were quite capable of spending half an hour arguing that it could not possibly be Tuesday, they'd take the outrageous in their pointy-shoed stride. The Senior Wrangler even looked relieved. 'Oh, is that it?' he said. 'Bound to happen eventually,' said the Dean. 'It's not written down anywhere that these holes connect to the same time, after all.'
'Going to make gettin' back a bit tricky,' said Ridcully. 'Er . . .' Ponder began. 'It might not be so simple as that, Archchancellor.'
'You mean as simple as finding a way to move through time and space?'
'I mean there might not be any there to go back to,' said Ponder. He shut his eyes. This was going to be difficult, he knew it. 'Of course there is,' said Ridcully. 'We were there only this morn— Only yesterday. That is to say, yesterday thousands of years in the future, naturally.'
'But if we're not careful we might alter the future, you see,' said Ponder. The mere presence of us in the past might alter the future. We might already have altered history. It's vital that I tell you this.'
'He's got a point, Ridcully,' said the Dean. 'Was there any of that rum left, by the way?'
'Well, there isn't any history happening here,' said Ridcully. 'It's just an odd little island.'
'I'm afraid tiny actions anywhere in the world may have huge ramifications, sir,' said Ponder. 'We certainly don't want any ramifications. Well, what's your point? What do you advise?'
It had been going so well. They almost seemed up to speed. This may have been what caused Ponder to act like the man who, having so far fallen a hundred feet without any harm, believes that the last few inches to the ground will be a mere formality. 'To use the classic metaphor, the important thing is not to kill your own grandfather,' he said, and smacked into the bedrock. 'What the hell would I want to do that for?' said Ridcully. 'I quite liked the old boy.'
'No, of course, I mean accidentally,' said Ponder. 'But in any case—'
'Really? Well, as you know, I accidentally kill people every day,' said Ridcully. 'Anyway, I don't see him around—'
'It's just an illustration, sir. The problem is cause and effect, and the point is—' The point, Mister Stibbons, is that you suddenly seem to think everyone comes over all fratricidal when they go back in time. Now, if I'd met my grandfather I'd buy him a drink and tell him not to assume that snakes won't bite if you shout at them in a loud voice, information which he might come to thank me for in later life.'
'Why?' said Ponder. 'Because he would have some later life,' said Ridcully. 'No, sir, no! That'd be worse than shooting him!'
'It would?'
'Yes, sir!'
'I think there may be one or two steps in your logic that I have failed to grasp, Mister Stibbons,' said the Archchancellor coldly. 'I suppose you're not intending to shoot your own grandfather, by any chance?'
'Of course not!' snapped Ponder. 'I don't even know what he looked like. He died before I was born.'
'Ah-hah!'
'I didn't mean—'
'Look, we're a lot further back in time than that,' said the Dean. 'Thousands of years, he says. No one's grandfather is alive.'
'That's a lucky escape for Mister Stibbons senior, then,' said Ridcully. 'No, sir,' said Ponder. 'Please! What I was trying to get across, sir, is that anything you do in the past changes the future. The tiniest little actions can have huge consequences. You might . . . tread on an ant now and it might entirely prevent someone from being born in the future!'
'Really?' said Ridcully. 'Yes, sir!' Ridcully brightened up. That's not a bad wheeze. There's one or two people history could do without. Any idea how we can find the right ants?'
'No, sir!' Ponder struggled to find a crack in his Archchancellor's brain into which could be inserted the crowbar of understanding, and for a few vain seconds thought he had found one. 'Because . . . the ant you tread on might be your own, sir!'
'You mean . . . I might tread on an ant and this'd affect history and I wouldn't be born?'
'Yes! Yes! That's it! That's right, sir!'
'How?' Ridcully looked puzzled. 'I'm not descended from ants.'
'Because . . .' Ponder felt the sea of mutual incomprehension rising around him, but he refused to drown. 'Well . . . er . . . well, supposing it . . . bit a man's horse, and he fell off, and he was carrying a very important message, and because he didn't get there in time there was a terrible battle, and one of your ancestors got killed – no, sorry, I mean didn't get killed—'