How exactly does FTL travel cause reverse time travel?

[georgir]

It doesn't matter if you talk about travel, information transfer or any kind of causal relation.
Observers can not agree on the chronological order of space-like separated events, so a common sense interpretation is that they can not be causally related.
If you allow some space-like separated events to be causally related, you must by extension allow all of them to be causally related, in either direction, because there's nothing special about any pair of space-like separated events.
If you allow all space-like separated events to be causally related, you must allow time-like separated events to be causally related in reverse chronological order, by means of a third proxy event which is space-like separated from both.

 

[.Scott]

It doesn't matter if you talk about travel, information transfer or any kind of causal relation.
Observers can not agree on the chronological order of space-like separated events, so a common sense interpretation is that they can not be causally related.
If you allow some space-like separated events to be causally related, you must by extension allow all of them to be causally related, in either direction, because there's nothing special about any pair of space-like separated events.
If you allow all space-like separated events to be causally related, you must allow time-like separated events to be causally related in reverse chronological order, by means of a third proxy event which is space-like separated from both.

It doesn't matter if you talk about travel, information transfer or any kind of causal relation.

That was part of my point - and the reason I was free to substitute information transfer for actual material travel.

Observers can not agree on the chronological order of space-like separated events, so a common sense interpretation is that they can not be causally related.

But for the purpose of the exercise, I presumed that one caused the other. To be specific what we are calling "cause" is the original source of the information. Since we are addressing a "what if" question, I wasn't going to challenge whether the experiment was actually possible.

If you allow some space-like separated events to be causally related, you must by extension allow all of them to be causally related, in either direction, because there's nothing special about any pair of space-like separated events.

Okay, but for this exercise we are presuming that certain ones have been created by our FTL transmitter - so they are special.

 

[georgir]

But for the purpose of the exercise...

My post was just answering the OP, don't take it personal ;) I completely don't mind and don't care what exercises you do in your own head...

I do see an interesting point in your reply, inadvertent or not... A single "special" pair of causally connected space-like events, or even a whole class of such pairs matching certain restrictions does not lead to reversely-connected time-like separated events.

The exact restrictions are interesting... the pairs will have to be parallel, or one-directional, or something else that does not allow them to form a "proxy".