In our universe if there are two objects that are moving relative to each other then each will see the other's length contracted in the direction of motion and it will see the others clocks running slower than its own clocks.

What if in a parallel universe the effect was reversed so that if there were two objects moving relative to each other they would each see the others length as being expanded in the direction of motion and each would see the others clock as running faster than its own? When two objects are moving at low velocities relative to each other the length expansion and speeding up of time are insignificant but at high velocities the length expansion and speeding up of time becomes significant. An object that is moving in this universe would appear to have less inertia from the reference frame of a stationary observer making it easier to accelerate.

Could this hypothetical universe have complex structures like stars and planets and atoms? Could this hypothetical universe support life?

  • $\begingroup$ you are talking about special relativity that deal with anything which are hasty, for complex structures to form I think you need the other relativity to work! $\endgroup$
    – user6760
    Nov 19, 2015 at 8:22

1 Answer 1


You are speaking about a spacetime geometry where the shortest path between two points will result in longer proper time of the traveller - in other words, unlike our Minkowski geometry, the universe would be governed by Riemannian geometry. Metric signature would be (+,+,+,+) instead of (−,+,+,+), which means there is no distinction between spacelike and timelike trajectories.

The math to calculate the properties of the universe would be rather difficult, but fortunately Greg Egan did it for us in very intricate detail.

There are many differences - no maximum speed, no atoms as we know them, variable speed of light, spontaneous energy generation by matter, possible reversing of the time arrow etc...

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    $\begingroup$ I like that there are already people out there who have considered the implications of this kind of thing. $\endgroup$
    – Joe Bloggs
    Nov 19, 2015 at 10:18
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    $\begingroup$ While I am not a mathematician and could certainly be missing something, I am not seeing that the OP's description matches what you are referring to. He is reversing the effect of relativity, so presumably things like the shortest path would still work close to "normal" at low relative speeds. Or are you saying that reversing relativity requires the other effects described here, giving us the counter-intuitive Riemannian geometry? $\endgroup$ Nov 19, 2015 at 21:25

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