Science of Discworld IV: Judgement Day by Terry Pratchett, Ian Stewart and Jack Cohen

Judgement Day Cover
Wizards fight Priests for control of Roundworld in the latest Science of Discworld book.

The Science of Discworld series is one of the more interesting ideas in popular science writing. The first came out in the late 90s when there was a fad for the Science of the X Files or the Physics of Star Trek books. Between them Pratchett , Stewart and Cohen had a very sensible idea. A Science of Discworld book that explained how the creatures of Discworld could work would be rubbish. You could write about genetics, selection and hunting strategies to explain why a troll under a bridge would wait for a third billy-goat to cross. But the answer is nothing to do with biology, it’s simply how stories work. There wouldn’t be much of story if the first goat kicked the troll over, yelled “Eat dynamite you filthy ore!” and blew the troll up.

Instead the Science of Discworld books have taken another tack. There’s a story that alternates with non-fiction chapters that discuss the science around the story. In the first book a magical accident means that the wizards at Unseen University need to use a lot of magic rapidly before something catastrophic happens. The result is the Roundworld Project, using magic to create a universe with no magic in it. The wizards then observe the formation of galaxies, stars, planets and life.

The second and third books had stronger plots, with baddies from Discworld escaping into Roundworld to cause havoc. In the second book elves change history resulting in Arthur J Nightingale being the world’s greatest writer and not Shakespeare. While changing history back the book discusses the development of Mind in humans. In the third history is altered so that Charles Darwin writes Theology of Species instead of The Origin… and the discussion connects evolution into a wider debate about how science develops.

The fourth is subtitled Judgement Day. A conservative religious sect of the Omnians has found out about the Roundworld project. Despite living on Discworld, the Omnians believe the world is round like ball and that Roundworld is blasphemy. They sue for ownership. The non-fiction is about epistemology, how do we know what we know? It sounds like the book could be a simple science versus religion rant. There’s more to it than that. The first half of the book doesn’t touch much on religion, instead talking about how science works.

A frequent defence of science knowledge is that it is provisional, so it is always open to improvement. It is also a process and Judgement Day does a good job of emphasising this. When the authors talk about superseded ideas they don’t just talk about where other people went wrong. They also point out errors in previous Science of Discworld books, particularly the first.

In the later chapters there are more contrasts between universe-centred and human-centred thinking, which compare scientific and religious attitudes to new knowledge. If you’re determined to take offence then you’ll have the opportunity. Jewish Cathar Scientologists will be particularly annoyed that they’ve been singled out.

The writing is as good as ever. I have skimmed through again looking for a brief section to lift. Sadly the self-contained parts that would make sense, like where problems in the search the Higgs boson are described by comparison to smashing a piano to see what’s inside, are too long to lift sensibly. It a shame because it’s not simply a matter of explaining science, the text also has an enthusiasm for science. So it’s a shame that despite all that it’s only the fourth-best Science of Discworld book. It doesn’t help that Small Gods by Terry Pratchett is a much stronger and three-dimensional exploration of the dark side of faith than the short length of the story Judgement Day allows.

While reading it I had a sense that something was not quite clicking, but I wasn’t sure what. I think the reason is that the previous Science of Discworld stories were largely set on Earth. The wizards could misunderstand Earth in the story and then the misconceptions were discussed in the accompanying chapters. In Science of Discworld IV the story is all set in the Discworld. As a result the non-fiction chapters don’t quite mesh with the story. It is great that Pratchett, Stewart and Cohen are still ambitious and want to create something new instead of treading water, but this time it doesn’t quite gel.

Their willingness to think the premise of the series means that the authors haven’t rested on their laurels. Science of Discworld V should still be worth buying. Another possibility, with their interest in Xenoscience, Evolution or Mind would be Strata II or Dark Side of the Sun II.

If you’ve read and enjoyed the previous books, then this is still worth reading. If you haven’t read any Discworld books, the earlier Science of Discworld books would be better places to start.