Comment Re:Nothing? (Score 1) 429
OK, sorry, should have said ""X doesn't happen after Y" is an invariant" (there don't exist reference frames such that X happens before Y in one frame and X happens after Y in another frame).
That's only true for timelike separated events. (I.e. events such that a light pulse sent from the earlier event would reach the position of the later event before it occurs.) It is most definitely NOT true for spacelike separated events. This doesn't violate causality though because spacelike separated events cannot possibly influence each other since information can't travel faster than light.