3 ms·

The whole shtick is that nothing is really moving FTL in an Alcubierre drive in the way that breaks the censorship principle, not that any not being able to get

The whole shtick is that nothing is really moving FTL in an Alcubierre drive in the way that breaks the censorship principle, not that any not being able to get out is what's helping the concept. There's no underlying reference frame beneath space time itself, so warping space time like this just creates shortcuts. The time element of the vector is still positive for all possible particles, so no closed timelike curves. For an example that can be seen naturally, it's thought that the galaxies on the edge of the observable universe are moving away from us faster than C because of the expansion of the universe and it's warping of space time. The same math works just fine with them moving faster than C towards us if the universe were shrinking.

PaulHoule 5y ago
I think of it as being like one of those trivial "faster-than-light" things like a spot of light. You can easily swing a laser pointer fast enough that the beam would crosses Earth's Moon faster than light. Information is moving outwards, not sideways, so that speed doesn't matter.
- monocasa 5y ago
  That's a different underlying cause. Nobody would say that a rail gun that shoots ball bearings at near C breaks FTL just because you turn it. This is more that space time isn't euclidean. You can see this in how gravitational lensing can create longer straight line paths between two points. Just because you could send light down one pathway and it ends up later than something moving less than C, doesn't mean that you went FTL in a way that breaks causality. An Alcubierre drive is 'just' dynamically modifying the shape of space time to make more useful pathways.
  - PaulHoule 5y ago
    I don't think you can really use the paths.
    - monocasa 5y ago
      Why not? If you can bend space time into the bubble in the first place, why can't you bend it back? The main issue I've heard with 'popping' the bubble isn't that you cut yourself off from the rest of space permanently, it's that there's a collection of everything that would have been along your path time dilated sitting right at the edge of the bubble that flies into the bubble all at once and is pretty nasty for anything in the bubble.

PaulHoule 5y ago

I think of it as being like one of those trivial "faster-than-light" things like a spot of light. You can easily swing a laser pointer fast enough that the beam would crosses Earth's Moon faster than light. Information is moving outwards, not sideways, so that speed doesn't matter.

monocasa 5y ago
That's a different underlying cause. Nobody would say that a rail gun that shoots ball bearings at near C breaks FTL just because you turn it. This is more that space time isn't euclidean. You can see this in how gravitational lensing can create longer straight line paths between two points. Just because you could send light down one pathway and it ends up later than something moving less than C, doesn't mean that you went FTL in a way that breaks causality. An Alcubierre drive is 'just' dynamically modifying the shape of space time to make more useful pathways.
- PaulHoule 5y ago
  I don't think you can really use the paths.
  - monocasa 5y ago
    Why not? If you can bend space time into the bubble in the first place, why can't you bend it back? The main issue I've heard with 'popping' the bubble isn't that you cut yourself off from the rest of space permanently, it's that there's a collection of everything that would have been along your path time dilated sitting right at the edge of the bubble that flies into the bubble all at once and is pretty nasty for anything in the bubble.