I don't think that helps - I can stick all of ABCD on planets of their own which are moving in the desired fashion. All ansible communication happens between pairs which are at rest relative to each other, and every ansible is at rest relative to the local lump of mass. (We can't get out of this one by saying the local centre of mass moves as C passes B, because they can easily talk at lightspeed over a moderately long distance such that B's planet's gravity doesn't do much at C and vice versa).
If all ansibles only work in _one_ frame, they all must be at rest relative to each other, we've already thrown out relativity because we have a preferred frame of reference - something's special about being stationary relative to the other ansibles.
The thing about causality violation is that not only do we have no evidence it's happened, but it doesn't even have to have happened yet. I'm content enough to say that something is impossible based on our current understanding and observations, because outside of pure maths that's always what "impossible" means.
If one of relativity and causality is going to give way, my money would be on relativity, which at least looks a little shaky around the edges with all this spooky dark matter floating about when we can't see or touch it.
no subject
Date: 2018-07-25 09:34 pm (UTC)If all ansibles only work in _one_ frame, they all must be at rest relative to each other, we've already thrown out relativity because we have a preferred frame of reference - something's special about being stationary relative to the other ansibles.
The thing about causality violation is that not only do we have no evidence it's happened, but it doesn't even have to have happened yet. I'm content enough to say that something is impossible based on our current understanding and observations, because outside of pure maths that's always what "impossible" means.
If one of relativity and causality is going to give way, my money would be on relativity, which at least looks a little shaky around the edges with all this spooky dark matter floating about when we can't see or touch it.