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- from Wikipedia's entry on wormholes.

I have not read this paper. Can anyone explain this to me in a little more detail?

- Thread starter snoopies622
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- #1

- 749

- 15

- from Wikipedia's entry on wormholes.

I have not read this paper. Can anyone explain this to me in a little more detail?

- #2

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- #3

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Actually, it sort of is, if you look at the "maximally extended" Schwarzschild spacetime. The easiest way for me to picture it is to look at the Kruskal chart of Schwarzschild spacetime. There are two horizons on this chart, which appear as 45-degree lines, one going "southeast to northwest" (the "antihorizon") and one going "southwest to northeast" (the "horizon"). They meet in the center, and at that point the two exterior regions, which are the "wedges" to the left and right, touch at that single center point for an instant. This can be viewed as a sort of instantaneous "wormhole" between the two exterior regions. AFAIK that instantaneous wormhole is the Einstein-Rosen bridge.

- #4

PAllen

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The white hole singularity is in the past of any timelike worldline that extends at all into the white hole interior region. Similarly, the black hole singularity is in the future of any time like world line extending at all into the black hole interior.

Kruskal coordinates also show the white hole horizon collapsing at speed c to a point, from whence the black hole horizon grows at c. This last aspect (coordinate speed of c) will look different in other coordinate schemes, but the geometry won't change. This shows how the interior regions are not static at all, while the exterior regions are static.

- #5

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Hey thanks. You've both given me much to think about.

- #6

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This wormhole FAQ might be of interest to you. Here's an excerpt:

Unlike a wormhole, a naturally occurring black hole -- one created through stellar collapse -- is not a bridge between two universes (or distant regions within the same universe). There nevertheless exist certain solutions to the Einstein equations of general relativity in which a bridge between universes – a wormhole -- appears to have a black hole at either end. This is the sense in which certain theoretically possible black holes can be said to be wormholes.

No. The bridge between universes remains open for too short a time for any traveler to cross it.

They do in the sense that people from different universes (or from distant parts of the same universe) can both enter the black hole and meet each other. The meeting will likely be interrupted, however, by the violent deaths of both parties in the black hole’s singularity.

- #7

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Is this the case with all wormholes, or just the Schwarzschild kind? What about something likeThe bridge between universes remains open for too short a time for any traveler to cross it.

[tex]

ds^2 = c^2 dt ^2 - dl^2 - (k^2 + l^2)(d \theta ^2 + sin ^2 \theta d \phi ^2) [/tex]

which is also mentioned in the Wikipedia entry?

- #8

PAllen

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- #9

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- #10

PAllen

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The metric in #7 is traversible. However, it requires enormous negative energy to create this metric (i.e. if you compute the Einstein tensor from it, which equals the stress energy tensor, you would find large negative energy terms).

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