Science of Discworld III

blinking in the light of common day.
    Panting slightly, Ponder hurried over to Ridcully.
    ‘You said you wanted a map, sir,’ he said.
    ‘Yes, Stibbons. Can’t plan a campaign without a map!’
    ‘Then look up now, sir! Here it comes!’
    The air wavered for a moment, and then the mated rainbows gave birth. Frozen streamers of light looped through the hazy air of the hall. They twisted and tangled and curved in ways that suggested more than the everyday four dimensions were involved.
    ‘Looks very pretty,’ said the Archchancellor, blinking. ‘Er …’
    ‘I thought it would help us sort out further nodalities,’ said Ponder.
    ‘Ah yes, good idea,’ said Ridcully. ‘No one wants unsorted nodalities.’ The other senior wizards nodded sagely.
    ‘ By which I mean ,’ Ponder added, ‘it will show us those points where our intervention will have been going to be was essential, if I can put it that way.’
    ‘Oh,’ said the Archchancellor. ‘Er … what does the coloured line mean, exactly?’
    ‘Which one, sir?’
    ‘All of them, man!’
    ‘Well, the points of intervention that require a human show up as red circles. Those that can be left to Hex are white. The blue lines represent the author of, ahem, The Ology , the yellow lines is the optimum path for the author of The Origin , and the green line represent slippage between futures. Known thaumic occlusions are purple, but I expect you worked that out already.’
    ‘What’s that one?’ said the Dean, pointing to a red circle with his staff.
    ‘We must make certain he doesn’t get off the boat at an island called Tenerife,’ said Ponder. ‘Seasickness again, you see. Quite a few Darwins got off there.’
    The tip of the staff moved. ‘And that one?’
    ‘He must get off the boat at the island of St Jago. He has valuable insights there.’
    ‘Sees things evolvin’, that kind of thing?’ said Ridcully.
    ‘No, sir. You can’t see things evolving, even when they’re doing it.’
    ‘We saw them on Mono Island,’ said the Lecturer in Recent Runes. ‘You could practically hear them!’
    ‘Yes, sir. But we have a god of evolution. Gods aren’t patient. On Roundworld, evolution takes time. Lots of time. Darwin was raised in the belief that the Roundworld universe was created in six days –’
    ‘Which is correct, as I have pointed out,’ said the Dean proudly.
    ‘Yes,’ said Ponder, ‘but I have also pointed out that on the inside it took billions of years. It is vital that Darwin realises that evolution has got lots of time to work in.’
    Before the Dean could protest, Ponder turned back to the shining, twisting tangle of light.
    ‘ There is where the mast falls on his head in the port of Buenos Aires,’ he said, pointing. ‘The Beagle was shot at. It was meant to be a blank, fired from a cannon, but for some reason it had been loaded. The British were very upset about it, and issued a stern diplomatic protest by sending a warship to bombard the port torubble. This one is where Darwin bludgeons himself into unconsciousness with his own bolas in Argentina. This one is where he’s severely injured putting down an insurrection—’
    ‘He got about a bit for a man who collected flowers and things,’ said Ridcully, with a touch of admiration.
    ‘Look, I’ve been thinking about all this,’ said the Dean. ‘This “science” is all about the search for truth, yes? Why don’t we just tell them the truth?’
    ‘You mean tell them that their universe was accidentally started by you, Dean, sticking your hand into some raw firmament created to use up spare power from the thaumic reactor?’ said Ridcully.
    ‘Put like that it seems a bit unlikely, I admit, but—’
    ‘No direct contact, Dean, we agreed about that,’ said Ridcully. ‘We just clear his way. What’s that nodality, Stibbons? It’s flashing.’
    Ponder looked at where the Archchancellor’s staff was pointing.
    ‘That’s a tricky one, sir. We will have to ensure that Edward Lawson, a British official in the Galápagos Islands, isn’t struck by a meteorite. It’s a new malignity, Hex says. In a number of histories, it happens a few days before he meets Darwin. Remember, sir? I mentioned it in my yellow folder that was delivered to your office this morning.’ Ponder sighed. ‘He draws Darwin’s attention to some interesting facts.’
    ‘Ah, I read that one,’ said Ridcully, his happy tone indicating that this was a lucky coincidence. ‘Darwin seemed to