> However, faster-than-light communication (which includes travel) breaks something very fundamental about physics, something that is often ignored by sci-fi, and difficult for non-physicists to understand. If you allow faster-than-light (FTL), then you break causality: you are allowing time-travel. One pithy way of saying this is:
>
> Pick two:
>
> Relativity
> Causality
> FTL