Superluminal Time Travel + Time Warp Challenge Answer

What people said

Strong rec cowlinator · 2020-09 · Worldbuilding Stack Exchange · on “Are there any ways to allow some form of FTL travel without allowing time travel?”

PBS Spacetime does an excellent explanation of how FTL relates to time travel, complete with light-cone diagrams and Lorentz transformations. See "Superluminal Time Travel + Time Warp Challenge" at [this video]

Recommends Someone Else 37 · 2017-03 · Worldbuilding Stack Exchange · on “FTL in a relativistic universe: can my scheme be exploited to make a time-machine?”

In short: Yes, as others answerers have shown, a system like that which you describe could be used for potentially-paradox-inducing time travel, if the universe doesn't provide some deep, fundamental way to forbid it. What makes FTL time travel possible is the ability to perform FTL jumps in different frames of reference moving at different speeds relative to each other. This video [this video] , for instance, shows how an FTL ship can go back in time by performing two FTL jumps- one at 2x lightspeed relative to Earth, and one at 2x lightspeed relative to some random reference frame moving at nearly the speed of light away from Earth. In order to prevent time travel, you could find a way to preve

Recommends Lucas Trzesniewski · 2017-03 · Worldbuilding Stack Exchange · on “How does a teleporter logically lead to time travel?”

The Lorentz transformation demands this. Watch this [this video] - you may have to watch some other episodes for this one to make sense, but it's nicely explained there.

Recommends magicalhippo · 2018-08 · Hacker News · on “Alcubierre drive”

Here's a good (IMHO) video showing how this works out, by looking Minkowski diagrams for different observers. [this video]

Recommends Someone Else 37 · 2018-08 · Worldbuilding Stack Exchange · on “Localized manipulation of the speed of light”

The best resource I can point to for FTL time travel is this video by PBS Space Time: [this video] It explains the concept far better than I could in a 600-character StackExchange comment. Also, go watch Space Time's videos on quantum mechanics and general relativity- they're really good, and they'll give you a much better understanding of those theories than you'll get anywhere outside of a high-level college course with a whole lotta math.

Recommends Someone Else 37 · 2019-08 · Worldbuilding Stack Exchange · on “If an Alcubierre Drive is possible, can you communicate FTL without a vessel?”

If Albucierre drives exist, does this imply that communications can travel no faster than the Albucierre driven vessels? Yes. But that doesn't actually mean anything. Because Alcubierre drives can travel through time. If the only technology in your setting not backed by modern hard science is the Alcubierre drive, then there is no other technology in your setting for FTL communication, by definition. You could easily add one, of course, but that's getting off-topic. Any FTL travel technology can send matter and information backward in time if and only if it is capable of making FTL jumps in different directions in different frames of reference moving relative to each other. Alcubierre drives

Recommends Someone Else 37 · 2019-10 · Worldbuilding Stack Exchange · on “Do Alcubierre Drives Mandate Time Travel, or Just Allow it?”

They just allow it. Superluminal time travel requires two FTL jumps in two different reference frames in order to return to your place of origin before you departed. The Alcubierre drive actually makes switching reference frames like this quite easy- all you need is a powerful subluminal rocket engine. Here's how to do it: Fire up your Alcubierre drive to travel some substantial distance away from Earth, then turn it off. Fire up your sublight drive, and accelerate until you're moving away from Earth at a large fraction of the speed of light, then turn that off. Turn around, and fire up your Alcubierre drive again to return to Earth. You'll want to overshoot a bit, since when you drop out of

Recommends Geoff Davids · 2021-11 · Worldbuilding Stack Exchange · on “Time keeping across several star systems”

As some others pointed out, the best way would be to synchronise everything according to a single regular timekeeper, such as a pulsar. This would work fine, since any relativistic effects should be consistent and interactions and exchanges would still abide by the rules too. Everything should work out, causality-wise, allowing everything to be in sync, or have at least consistent time exchange rates. Until you bring in teleportation. This is where the whole system falls apart, since teleportation implies FTL travel. I know you specifically state that your world doesn't have FTL, but unless the time it takes to teleport information / matter is longer than the time light takes to travel the s

Recommends xupybd · 2022-07 · Hacker News · on “Breaking the warp barrier: solitons in Einstein–Maxwell-plasma theory (2021)”

One video with no maths required. [this video] Without the math you can't get a deep understanding or reason about it too much but you can see the issue.

Cites Someone Else 37 · 2018-12 · Worldbuilding Stack Exchange · on “Can this version of the Alderson Drive be used to violate causality?”

The key requirement for FTL time travel is making two separate FTL jumps in two different reference frames . Thus, to prevent paradoxes, you simply need to pick one reference frame (e.g. that of the cosmic microwave background, which the closest thing to a universal stationary reference frame in the universe) and declare it as the only frame in which FTL travel can take place. With your Alderson-based system, this is quite simple: Make all swaps instantaneous in the CMB frame. And you're done. The Alderson points themselves don't have to be stationary relative to anything. If one point is moving rapidly or deep in a gravity well (e.g. orbiting close to a black hole), it will experience time