I missed this till now. There'll be a fourth instalment of the Science of Discworld. If you haven't read any of the Science of Discworld books, they're different to the usual Science of… books in that Discworld doesn't run on science so there's not much point explaining how it could work scientifically. Instead it follows an experiment by the wizards of Unseen University to create a world that runs on rules instead of narrativium. Roundworld has no magic so how does a world come together and how does life colonise it?
Science of Discworld II: The Globe was about the development of Mind with the aid of two playwrights and Science of Discworld III: Darwin's Watch looked at how the idea of evolution was invented again and again until Charles Darwin made it stick.
For Science of Discworld IV the Omnians have discovered about the Roundworld project. A world that is actually round but has no gods is a bit of a problem for the Omnians who believe that the disc is a globe, but are very keen on a God.
The current publication date is April 11.http://www.randomhouse.co.uk/editions/the-science-of-discworld-iv-judgement-day/9780091949792
There was also a talk on the science of Discworld in Dublin last year.
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