surepancakes

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Does faster than light travel violate causality? Why/Why not? How?

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...

surepancakes OP ,

Thank you for your answer. When viewed from this perspective it makes more sense.

surepancakes OP ,

From Earth’s frame of reference, time on board the ship is slowed down by a factor of 0.866, while from the ship’s frame of reference, time on Earth is slowed down by the same factor

Why is time on earth slowed down from the ship’s perspective? Shouldn’t it be faster? Like if earth perceives that the time on the ship is passing slower shouldn’t the people on the ship perceive the time on earth as passing faster to compensate?

Also, I have quite a hard time understanding how time exactly slows down. Is it sort of as though we adjusted the time step duration (tickrate, more precisely) of a physics simulation in an area (making everything happen slower/faster there in relation with the rest, where the original timestep is kept)? (Without losing precision and all those problems that occur in a simulation normally) Or is this analogy flawed and that is why I’m not getting it?

surepancakes OP ,

Okay. Thank you! This explanation made it click for me (now I think I get the original example too). Here the real cause of the violation is the instant communication, isn’t it? If the communication was done via radiowaves (which as far as I know also travel at the speed of light) it would not be violated, because of the time it takes for the information to arrive from the Earth to the spaceship and back, is that correct? Is this why (as I have read/heard on several occasions) the upper bound for the speed of information is also the speed of light?

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