A depiction of a section of “The Long Earth” as described in the sci-fi book by the same name by Terry Pratchett and Stephen Baxter, as if viewed through a crystal ball.

The “Long Earth” is a name given to a possibly infinite series of parallel worlds that are similar to Earth, which can be reached by using an inexpensive device called a “Stepper”. The “close” worlds are almost identical to “our” Earth (referred to as “Datum Earth”), while others differ in greater and greater details.

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