# Black Hole Information Paradox and Alcubierre Warp Drives

#### O10infinity

Suppose Alcubierre warp drives or some alternative form of warp drive is possible. Then surely a warp drive could enter the event horizon of a black hole, observe the interior, and exit the horizon, returning with information from within the black hole. What about black holes never visited by a civilization with warp drives? Perhaps in quantum gravity there exist ‘Alcubierre particles’ which travel faster than light. These differ from tachyons in that they would have real rest mass. If they are stable they could be used by astronomers to observe black holes interiors and parts of the universe to distant to be observed by light. If they are unstable they could still survive long enough to exit an event horizon carrying information. Where does this leave the black hole information paradox?

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#### Dale

Mentor
Suppose Alcubierre warp drives or some alternative form of warp drive is possible. Then surely a warp drive could enter the event horizon of a black hole, observe the interior, and exit the horizon, returning with information from within the black hole.
Hi O10infinity, welcome to PF!

That is an interesting question. I think that it is far from "surely" the case that it could enter the event horizon observe and exit, but I suppose it could be possible. I can see some arguments for it, but I would tend to think in terms of a pair of wormholes rather than an Alcubierre drive.

I don't know of any papers on the subject, and we really need the discussion to be in keeping with the professional literature. Perhaps some of the other members know of one.

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#### O10infinity

What could prevent a warp drive from entering and exiting an event horizon? Remember that in GR the region near an event horizon doesn't have particularly strong curvature. The tidal forces near a supermassive black hole will be small, so the spacetime around the warp drive will be nearly flat when it crosses the event horizon. For it not to work, we need something special about the event horizon which will destroy the warp drive or create a barrier to escaping the black hole.

Is there anything which favors wormholes over warp drives for horizon crossing?

Hi O10infinity, welcome to PF!

That is an interesting question. I think that it is far from "surely" the case that it could enter the event horizon observe and exit, but I suppose it could be possible. I can see some arguments for it, but I would tend to think in terms of a pair of wormholes rather than an Alcubierre drive.

I don't know of any papers on the subject, and we really need the discussion to be in keeping with the professional literature. Perhaps some of the other members know of one.

#### PAllen

What could prevent a warp drive from entering and exiting an event horizon? Remember that in GR the region near an event horizon doesn't have particularly strong curvature. The tidal forces near a supermassive black hole will be small, so the spacetime around the warp drive will be nearly flat when it crosses the event horizon. For it not to work, we need something special about the event horizon which will destroy the warp drive or create a barrier to escaping the black hole.

Is there anything which favors wormholes over warp drives for horizon crossing?
My intuition agrees with yours (that a warp drive could enter and leave the horizon), but intuition in GR is very unreliable. It needs to be calculated. Like Dalespam, I have not come across a paper on this, but I also never looked very hard. So I wouldn't say I know the answer. At most I have a hunch that is the same as yours.

A few points: you speak of warp drives as if they exist. It is not known that they exist, it is not known if they could exist in our universe (because of the negative mass requirement to build one). This leaves them as not being very relevant to the information paradox (especially that it is not known if they could exist, even in principle). I, and I believe many (but far from all) physicists would bet that they cannot exist at all in our universe.

The reason wormholes are a better candidate is that at least unstable worm holes are believed to follow from initial conditions that we know could be set up, in principle. Further, their possible connection to the information paradox is an area of current research. There was a recent paper on just this topic by Juan Maldacena and Leonard Susskind.

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