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Re:The horizon problem for faster than light travel by mannerheim on Thursday January 20, 2022 @10:42PM (#30018875)
In special relativity, faster-than-light travel or communication is equivalent to time travel.
Re:The horizon problem for faster than light travel by drran on Friday January 21, 2022 @03:05AM (#30020565)
But, it doesn't enable time travel. It just makes calculation easier, like «bending» of space-time array.

If you switch from relativity to regular physics with medium instead of pure vacuum (10 years passed since 2012 already, so relativity is busted at this point), then c is the speed of light in medium, so we don't need to bend anything or use negative t to calculate outcomes.

Re:The horizon problem for faster than light travel by mannerheim on Friday January 21, 2022 @12:50PM (#30027137)
> so relativity is busted at this point

Excuse me?

Re:The horizon problem for faster than light travel by xupybd on Thursday January 20, 2022 @10:53PM (#30018934)
Yes but that is only if you are traveling through space faster than light. If you simply skip some of the distance with something like an Alcubierre drive there is no time dilation to deal with.
Re:The horizon problem for faster than light travel by bashinator on Thursday January 20, 2022 @11:57PM (#30019351)
> simply skip some of the distance

My understanding as a lay person of the physics that allow for things like this, is that they require starting conditions that wouldn't produce a universe anything like what we actually live in, or require energy levels around the output of galaxy superclusters to be focused into planck lengths or such. "Technically not impossible" is different for physicists than to normal people ;-)

Re:The horizon problem for faster than light travel by mannerheim on Thursday January 20, 2022 @10:58PM (#30018959)
No, it still results in time travel.

> To answer your question: any FTL drive can be used to create closed time-like loops. With these you can travel back in time, but you get stuck in a loop.

https://physics.stackexchange.com/a/247048

Re:The horizon problem for faster than light travel by xupybd on Thursday January 20, 2022 @11:14PM (#30019070)
Okay, I think there is something I don't understand here. That link references a book I might have to read "Time Travel and Warp Drives".

Thanks!