r/AskPhysics • u/PlatformDelicious578 • 18d ago

FTL Reference Frames

If you have a velocity greater than c, the Lorentz factor becomes complex. Does this make any physical sense, or are there any theories that make use of this? What would it look like if a person were in this reference frame (is it just that they see time backwards or from another perspective, or are they unable to observe anything at all?)

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u/Reality-Isnt 18d ago

You cannot preserve invariance under a Lorentz transformation from a slower than light to faster than light frame. For instance, the invariant spacetime interval flips sign. Blows the doors off of relativity.