In the 'fantasy' universe of the phenomenally best-selling Discworld series, events in fact mostly follow the dictates of common sense. Everyone in Discworld knows that the world is flat and that million-to-one chances crop up nine times out of ten. In our own world, science tells us that our more 'logical' universe does not obey common sense at all. The appeal of Discworld lies in the fact that much of it does make sense in a way that particle physics does not. The aim of 'The Science of Discworld' is to use the comfortable but curious science of Discworld to illuminate the less comfortable science of our own world. The vehicle for this is the 'Roundworld Project', set up within Discworld by various wizards at the Unseen University, who set out to construct a carefully tailored magical exclusion zone, inside which magic is reduced to nill and only rigid 'scientific' rules apply. Roundworld, it turns out' is in fact our own universe. With us inside it. Terry Pratchett presents here a brilliant new Discworld story, and Ian Stewart and Jack Cohen weave around it a hugely entertaining discussion of scientific issues in our own universe.