4 ms·

In special relativity, faster-than-light travel or communication is equivalent to time travel.

• xupybd 5y ago
  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.
  • mannerheim 5y ago
    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 https://physics.stackexchange.com/a/247048
    • xupybd 5y ago
      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!
  • bashinator 5y ago
    > 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 ;-)
• drran 5y ago
  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.
  • mannerheim 5y ago
    > so relativity is busted at this point Excuse me?