What would happen if two spaceships with Alcubierre warp bubbles were colliding? Would the space bubble collapse? Would they reject or push each other? Would they survive it without problems?

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    $\begingroup$ Fear not since both ships already survived the extreme searing blaze within their warp bubbles probably nothing known to science can break them! $\endgroup$
    – user6760
    Dec 4, 2016 at 14:01
  • $\begingroup$ Thanks for your reply! My problem is that black holes also warp space and they are fusing together if close to each other. It seems to me that warped space can eject matter and energy but the interaction of warped spaces is a different question. $\endgroup$
    – Phoenix 40
    Dec 4, 2016 at 16:10
  • $\begingroup$ @Phoenix40: The warping of space that black holes get up to is very different to the warping of space you need for 'ftl' warp bubbles. and in reality we have no idea if black holes actually 'fuse': only that the spatial distortion when two of them get very close is so extreme that we really don't know what is happening. $\endgroup$
    – Joe Bloggs
    Dec 5, 2016 at 17:48

2 Answers 2


This question is well above my metaphorical pay grade, but I would assume they would throw each other MASSIVELY off course if they were approaching each other at a sharp angle.

If they were traveling perpendicular to one another and passed close enough, I assume whichever one hit the expanded space behind the other first would break the speed of light barrier, meaning it would either grow infinitely dense or it would instantly and infinitely break down into pure energy.

If they were traveling parallel to one another, no idea.


I imagine if a 'faster' alcubierre enabled craft (as in their bubble of real-space was being flung across the universe at a faster relative speed) ran into the back of another ships alcubierre 'wake' then the compressed section of time-space from the first craft would collide into the distended section of time-space of the second craft. As the space is compressed and distended at the same time it would end up a sort of zero-sum equation. Once the rear of your alcubierre bubble is collapsed then the forefront would also be unable to hold as far as I understand it. (as a double effect of compressed and distended space-time around a bubble of normal space-time is how you are propelled at FTL speeds)

If however they were to crash on a perpendicular course then the compressed 'front' of your craft may not stay as the most compressed section. If the side of your alcubierre bubble is the most compressed section briefly then your path may be altered, possibly to disastrous effect.

but hey, what does a cat know about theoretical FTL devices?

  • $\begingroup$ It could be that on running into another ship's bubble, the two bubbles merge in the zero sum and the ships actually collide $\endgroup$
    – Separatrix
    Dec 5, 2016 at 9:54
  • $\begingroup$ Separatrix, I guess that would rely on how large the alcubiere bubble around each craft is and haw large the craft themselves are. Two small spacecraft in large bubbles would probably still miss, but tighter bubbles colliding (already probably rare in the vast emptiness of space) would probably result in some kind of awesome zero gravity crash, with shrapnel and crewmembers spiraling off into the void. And nobody can hear their screams $\endgroup$ Dec 7, 2016 at 4:05

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