Probably published late 1970s or early 1980s. A large group of people are organized into a small city that is in a huge contraption that has to keep moving around the earth after some apocalyptic event. They might call the conveyance "Earth City." They have to keep pulling up track behind and placing it in front to proceed.

They are following electromagnetic pulses in the earth's crust that provides motive power for the thing.

The direction in which they are heading is called "up future," whilst the direction from which they have come is called "back past." Any ideas would be much appreciated.

  • Wasn't time slowing down or speeding up if you traveled a distance from the city? And wasn't it a problem that it turned out they were at the location of modern-day Portugal, traveling west, and they would soon reach the ocean? I faintly remember a question and and answer regarding this.
    – vsz
    Jun 25, 2015 at 19:30

1 Answer 1


Is this "Inverted World" by Christopher Priest?

In the novel, an entire city and its people travel across a planet on railway tracks being pursued by a destructive gravitational field. The city's engineers must work to lay fresh track for the city, and pick up the old track as it moves. The ruling faction works to ensure that the people are unaware that the city is even moving. The city enters into crisis as its population decreases, the people grow unruly, and it becomes more and more difficult to stay ahead of the destructive field.

  • possible duplicate
    – user14111
    Jun 25, 2015 at 6:44
  • @user14111 - Yikes. When I get to a real computer I'll de-dupe these
    – Valorum
    Jun 25, 2015 at 7:12
  • @user14111 - In fact, you've got the gold tag now. You can sort it :-)
    – Valorum
    Jun 25, 2015 at 7:14
  • Unlike the diamond (which you volunteered for) the gold badge, being unsolicited, imposes no obligations on the holder. Moreover, I'm not sure I agree with the policy of closing a question as a duplicate just because it happens to have the same answer as another question. Anyway, I was only just interested enough to post these comments; not interested enough to study those questions and answers and figure out which should be closed as duplicates of which.
    – user14111
    Jun 25, 2015 at 7:38
  • 1
    @user14111 - I think the problem is that people see a 'close as duplicate' as a punishment rather than a helpful signpost
    – Valorum
    Jun 25, 2015 at 11:11

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