In episode 31, Liz, Ben and returning guest Joel Martin step sideways into the infinite earths of Terry Pratchett's 2012 collaboration with Stephen Baxter, The Long Earth.

In 2015, plans for a strange but simple box-shaped device called a “Stepper”, powered by a potato, are posted online. Kids all over the world build them and discover that the boxes let them step “East” or “West” into other Earths. There are thousands of such worlds - perhaps millions - all subtly different. But they do have one thing in common: there are no humans on any of them. Fifteen years after “Step Day”, human society is irrevocably altered, and experienced far-stepper Joshua Valienté is offered a new job: to step further from Earth than even he has ever been, and explore the mysteries of the Long Earth in the company of a Tibetan motorcycle repairman reincarnated as a supercomputer...

Based on ideas from Pratchett's 1986 short story “The High Meggas”, written before the popularity of The Colour of Magic led him down a particular leg of the trousers of time, The Long Earth is the first in a series of five novels set in a near future world forever changed by the existence of limitless worlds next door. An epic journey across millions of worlds, Pratchett chose to work with his friend Stephen Baxter, a prolific science fiction author whose work encompasses hard future sci-fi, speculative evolution, alternate history and sequels to classic novels by the likes of H. G. Wells and Arthur C. Clarke. That all seems quite a distance from comic fantasy - but the pairing just works. So - it’s five years since Step Day. Would you visit another Earth? Could you pick which bits were Pratchett, and which Baxter? And what kind of potato is in your stepper box? Use the hashtag #Pratchat31 on social media to join the conversation!

Guest Joel Martin is a writer, editor and podcaster who previously appeared on Pratchat in episode 14, discussing the book that derailed the Long Earth back in 1986, The Colour of Magic. Joel is also the director of the Speculate speculative fiction festival (specfic.com.au). His latest work is the short story “Hunting Time” in Strange Stories Vol. 1, scheduled to be published this month by 42books. Joel's writing podcast, The Morning Bell, is currently on hiatus, but you can find the full back catalogue at themorningbell.com.au. Find out more about him at thepenofjoel.com.

Next month we're stepping back onto the Disc to meet adventurous nine-year-old Tiffany Aching, in 2003's The Wee Free Men! Get your questions in via the hashtag #Pratchat32 by around May 23rd.

You'll find the full notes and errata for this episode on our web site.