The Science of Discworld, by Terry Pratchett, mathematician Ian Stewart, and biologist Jack Cohen, is one half Discworld novel, in which the wizards accidentally create a universe without magic and are fascinated by the way it develops its own rules in the absence of Narrative Causality, and one half popular science text, as Stewart and Cohen explain how the Roundworld Project (i.e., our universe) actually works.It was followed by three sequels: The Science of Discworld II: The Globe, in which the wizards must stop The Fair Folk preying on the superstitious folk of Elizabethan Roundworld, while Stewart and Cohen talk about the nature of storytelling and belief, and The Science of Discworld III: Darwin's Watch, in which the wizards stop the God of Evolution from seriously confusing Charles Darwin, while Stewart and Cohen discuss his theory in more detail than they had to spare in the first book.The Science of Discworld IV: Judgement Day was announced at the 2012 Discworld Convention, and released 11 April 2013. In this one, a sect of Omnian extremists start claiming Roundworld is evidence they were right all along, and therefore it belongs to them, while a sceptical Roundworld librarian ends up on the Disc.
The Science of Discworld series contains examples of:
As You Know: Zigzagged in the fiction portions, in which Ponder uses this phrase out of politeness when he suspects Ridcully doesn't know something about physics; this gives him the chance to contrast Discworld physics (which the readers don't necessarily know) with Roundworld rules (which readers might know, but Ridcully doesn't).
Different World, Different Movies: When they write that intelligence appears to be useful enough that it would probably still have arisen is some form if we hadn't appeared (the fiction parts show a number of civilisations getting a foothold on Roundworld in much earlier epochs, only to be wiped out by cataclysmic disasters) they speculate that if sentient crabs had evolved on the Earth in humans' place, three of them might be writing The Science of Dishworld, about a bowl-shaped world that's carried on the backs of gigantic marine invertebrates.
In-universe, the third book is about the wizards' attempts to ensure that Charles Darwin writes On The Origin Of Species, not Theology Of Species.
Exact Words: What are the chances of Ponder's thaum-splitting magical reactor "just blowin' up and destroyin' the entire university?" None at all. If it goes up, it won't just blow up the university - it'll destroy the entire Discworld.
Expy: Ratonasticthenes for Eratosthenes, and Antigonus for Archimedes.
For Want of a Nail: The numerous events that prevent Shakespeare or Darwin from producing their works in alternate Roundworld timelines.
Hex also mentions how, in 1734, a German shoemaker named Joshua Goddelson left his house by the back door, setting in motion a chain of events that (somehow) leads to commercial fusion power in 2017.
The Fundamentalist: The Omnian fundamentalists in the fourth book are so close-minded that they remain convinced only they know the True Word of Om even when the god in question manifests specifically to tell them to stop being idiots.
In Spite of a Nail: Apparently, if Darwin had become a believer in what we'd now call "intelligent design", Richard Dawkins would have been the author of The Origin Of Species, sadly too late to make a difference. Which suggests that there's a historical imperative that Dawkins must be a Darwinist, even if Darwin isn't.
The data is there to be found, Darwin or no Darwin, but in this scenario Richard Dawkins is the only person bloody-minded enough to go against an established authority and mine out the inconsistencies of the widely accepted model. It's unlikely that Darwin's theory had anything in itself to do with Dawkins becoming an atheist in the first place.
Interrupted Suicide: Rincewind repeatedly puts a fish back into the water, not realizing it's adapting to life on land rather than trying to kill itself.
It Will Never Catch On: The wizards do this a lot, first claiming that planets are no place for life, that the sea is only place for a intelligent creature, that the primates will never amount to anything, and so on.
Also, that the "terribly dull lizards" would never catch anyone's interest, such that any accounts of Roundworld prehistory will most likely skip over their era.
Lies to Children: The Trope Namer. In the fiction sections, Ponder describes his thaumic reactor to the other faculty using Lies-To-Wizards, and Hex's reports mainly consist of Lies-To-People.
No Name Given: Reaches its climax here, with the wizards even naming elements things like "Runium" and "Wranglium" after their titles rather than their actual (unknown) names.
Noodle Implements: While preparing for Shakespeare to write A Midsummer Night's Dream, the Wizards run into various problems that Ridcully solves via a set of noodle implements. Most of the time the reader can easily figure out what he is going to do with them (The sole exception being related to a folk remedy that is explained in one of the science chapters).
Retcon: The first book uses 'splitting the thaum' as a magical equivalent of 'splitting the atom'. In previous books, thaums were just an arbitrary measurement of magic (and with the competing Prime system) rather than the smallest possible unit of magic.
Running Gag: In the second and third volumes, the Wizards find history has been meddled with and someone surnamed Nightingale has been inserted into a place someone else (William Shakespeare and Charles Darwin, respectively) should have been in.
Science Marches On: Chapter 10 of Book Four illustrates the nature of science by devoting some space to the theories the first book favoured about the formation of the moon and the origins of life, and explaining why they're probably wrong after all.
Space Elevator: One appears in Book One. In the later books, the wizards' goal is the continued existence of a timeline that contains it.
What Could Have Been: The programme for the 2006 Discworld Convention reveals the synopsis of a completely different Science of Discworld III, in which the wizards visit assorted fictional Marses, culminating in the Discworld-universe's own version of Barsoom: a flat square planet, on the back of four thoats on the back of a giant zitidar, while Ankh-Morpork was invaded by the Martian tripods.
Year Inside, Hour Outside: Early in the Project, millions of years pass in Roundworld for every Discworld day. Later, Hex takes control of time's passage within the artificial universe, and can subvert, avert, invert or play this trope straight at will.
Zany Scheme: The wizards' interventions. Particularly the Noodle Implements-heavy one in volume 2, where they invoke various folk remedies to ensure William Shakespeare is born a boy.