I didn’t know either, but this article [0] has some thorough explanations.
I think the basic idea is that when two people are experiencing time dilation, FTL communication makes it possible (according to relativity equations) for a recipient to receive a message, reply to it, and have the original sender receive the reply before the point in time (in the original sender’s point of reference) the original sender sent the initial message, which clearly violates causality.
I think your scenario would not break causality because you are assuming both A and B are experiencing time at the same pace, so there would be no way to take advantage of time dilation.
Comments
I didn’t know either, but this article [0] has some thorough explanations.
I think the basic idea is that when two people are experiencing time dilation, FTL communication makes it possible (according to relativity equations) for a recipient to receive a message, reply to it, and have the original sender receive the reply before the point in time (in the original sender’s point of reference) the original sender sent the initial message, which clearly violates causality.
I think your scenario would not break causality because you are assuming both A and B are experiencing time at the same pace, so there would be no way to take advantage of time dilation.
[0] https://en.m.wikipedia.org/wiki/Tachyonic_antitelephone