# Suppose relative v in S <> -v in S'

1. Aug 26, 2009

### jason12345

If S' moves with velocity v in S, then SRT requires S to move with velocity -v in S'. What happens if this isn't true? the limiting velocity c would no longer be an invariant is an obvious consequence, what else?

Thanks.

2. Aug 27, 2009

### CompuChip

Well, it would mean that physics would become observer-dependent. If we were both in spaceships in empty space, for example, we would be able to devise an experiment which told us who of us was in S, and who was in S'. In other words, who is in absolute motion.

If you even think about particle physics (for example accelerating particles in a laboratory, or particles crashing towards the earth at high velocities) you would hopefully see why this is highly undesirable.

3. Aug 27, 2009

### jason12345

The limiting velocity of particles would be frame dependent, meaning even the physics of mechanics was frame dependent. Even though extremely unlikely, I can't think of any experiment which rules this out unambiguously.