It is often said that faster than light travel would violate causality.
However, because the universe is expanding, there are actually distant stars that move away from us at a speed greater than the speed of light.
Why is this allowed, even though it could violate causality?
If you only take into account expansion of space, then there is no way to violate causality, because information still cannot travel faster than light. If two galaxies drift apart faster than light, it is not even possible for signals emitted from one galaxy to reach the other. They have crossed each other's Hubble radius.
