Discrete space or time would cause some problems for the equivalence principle - that the laws of physics should look the same to all observers, irrespective of

Discrete space or time would cause some problems for the equivalence principle - that the laws of physics should look the same to all observers, irrespective of their relative velocities. It's hard to imagine how physics could look the same to all observers if spacetime is a discrete entity that can be contracted by different factors along different axes for different observers.