Sir Terry Pratchett and Transworld Publishers have announced a contest for new writers: The Terry Pratchett Anywhere But Here, Anywhen But Now Prize.

Writers are invited to submit novels set on “some version of the past, present or future of a planet Earth” — alternate histories, parallel universes, etc., but all set on Earth and adhering to the actual laws of science.

Entrants must be over 18, live in the UK, Ireland, or the Commonwealth, and must have no previously published full-length works of fiction. The deadline for submissions is December 31, 2010, with a shortlist of six to be announced March 31, 2011, and the winner revealed by the end of May 2011. The winning author will be offered a publishing contract by Transworld with a £20,000 advance.

Further details, and complete terms and conditions, are available at Pratchett’s website.