I have heard this mentioned several times with this exact wording, that faster than light travel would break/violate causality and I do not exactly understand why and how it would do that. Could someone more well-versed in physics explain to me why that would be the case? Or is it not the case? (Yes, I am fully aware, that faster than light speeds are impossible in real life, but I am more curios about how it would hypothetically affect physics, were it possible). I am somewhat familiar with physics and more so with mathematics (engineering student), if that helps anyone to explain it at an appropriate level.
Exactly.
When I say the parties observe each other slowing down, or observe the simultaneous point in the other’s timeline jumping around, they don’t observe this in real time unless they’re using faster-than-light communication. Using conventional means, it’s only after receiving the signals and compensating for the redshift or blueshift that they can reconstruct the other’s past timeline relative to their own.