Spacetime Fabric Shear Strength

[stglyde]

Inside a black hole singularily, the center is pulling spacetime to it, but because the spacetime fabric inside and outside the event horizon are connected... it doesn't shear or break. But during a Big Crunch, the entire spacetime of the universe would be sucked back into the singularity and there would be no spacetime outside the singularity. My question is. What must be the mass of black holes before it can shred the spacetime fabric at the event horizon and sucking the spacetime inside the event horizon into the singularity? How do you calculate for it?

 

[phinds]

Inside a black hole singularily, the center is pulling spacetime to it, but because the spacetime fabric inside and outside the event horizon are connected... it doesn't shear or break. But during a Big Crunch, the entire spacetime of the universe would be sucked back into the singularity and there would be no spacetime outside the singularity. My question is. What must be the mass of black holes before it can shred the spacetime fabric at the event horizon and sucking the spacetime inside the event horizon into the singularity? How do you calculate for it?

I doubt if this question makes any sense, but I can't say that for sure.

"Fabric" is a very unfortunate choice of words that derives from a comment Einstein made and think of space like it was clothe won't get you anywhere.

 

[Drakkith]

As Phinds said, spacetime is not, as far as we know, a fabric like the popular description says.

 

[e.bar.goum]

As above. Analogies can be taken too far.

 

[yoron]

I never liked words as the 'fabric' myself. It makes it sound as a classical 'space' has to be something we can collect, to then build on as some sort of puzzle. A 'space' is to me classically defined as that place where nothing exists.

That's also what makes it meaningless to define it in distance. You need matter separated to define that 'space'. Not having any matter to hang your definitions of it on that 'perfect space' won't exist, even though it might be 'there' in some theoretical manner, as defined by 'energy' possibly.

The Big Bang was 'something' of a enormous energy density, inflating the 'space' faster than light. But 'space' as such don't have a 'speed'.

 

[stglyde]

I never liked words as the 'fabric' myself. It makes it sound as a classical 'space' has to be something we can collect, to then build on as some sort of puzzle. A 'space' is to me classically defined as that place where nothing exists.

That's also what makes it meaningless to define it in distance. You need matter separated to define that 'space'. Not having any matter to hang your definitions of it on that 'perfect space' won't exist, even though it might be 'there' in some theoretical manner, as defined by 'energy' possibly.

The Big Bang was 'something' of a enormous energy density, inflating the 'space' faster than light. But 'space' as such don't have a 'speed'.

But how come in the Planck scale, space is said to be in fluctuations and tearing such that microscopic wormholes and quantum foam were created.. tearing can occur in a fabric...

 

[phinds]

But how come in the Planck scale, space is said to be in fluctuations and tearing such that microscopic wormholes and quantum foam were created.. tearing can occur in a fabric...

Do you ever eat bananas? Monkeys eat bananas. Does that make you a monkey?

As e.bar.goum said, analogies can be carried too far. Get over it.

 

[Drakkith]

But how come in the Planck scale, space is said to be in fluctuations and tearing such that microscopic wormholes and quantum foam were created.. tearing can occur in a fabric...

I don't know much about wormholes, but Quantum Foam has nothing to do with tearing spacetime.

 

[stglyde]

I don't know much about wormholes, but Quantum Foam has nothing to do with tearing spacetime.

What do you make of this wikipedia entry?:

"Physicists have not found any natural process which would be predicted to form a wormhole naturally in the context of general relativity, although the quantum foam hypothesis is sometimes used to suggest that tiny wormholes might appear and disappear spontaneously at the Planck scale,[6][7] and stable versions of such wormholes have been suggested as dark matter candidates.[8][9] It has also been proposed that if a tiny wormhole held open by a negative-mass cosmic string had appeared around the time of the Big Bang, it could have been inflated to macroscopic size by cosmic inflation.[10]"

Ref 6 refers to: Thorne, Kip S. (1994). Black Holes and Time Warps.
Ref 7 refers to: http://arxiv.org/abs/gr-qc/9309017 "Quantum Dynamics of Lorentzian Spacetime Foam"

 

[Drakkith]

Wormholes are a product of GR and Quantum Foam from QM or a related field. The two theories have never been successfully merged so I don't see any relation between the two. If someone else knows otherwise please step forward.

 

[Markus Hanke]

Wormholes are a product of GR and Quantum Foam from QM or a related field. The two theories have never been successfully merged so I don't see any relation between the two. If someone else knows otherwise please step forward.

You are right, purely from a mathematical standpoint a "wormhole metric" is a valid solution to the Einstein Field Equations. This does not mean, however, that the energy configurations need to create such a metric are physically possible. That question will need to be considered under the rules of the yet-to-be-established quantum gravity.

 

[Dale]

Spacetime is not a fabric in GR, one of the chief differences being that fabric has a unique rest frame and spacetime does not.

Spacetime is a (pseudo Lorentzian) manifold in GR, which means that if you zoom into a small piece it "looks like" R4 in the sense that it can be smoothly mapped to R4.

The quantum foam problem is simply that at small enough length scales this mapping may no longer be smooth due to the presence of massive, short-lived virtual particles.

 

[stglyde]

You are right, purely from a mathematical standpoint a "wormhole metric" is a valid solution to the Einstein Field Equations. This does not mean, however, that the energy configurations need to create such a metric are physically possible. That question will need to be considered under the rules of the yet-to-be-established quantum gravity.

To create a wormhole between Earth and pluto may take the energy of an entire galaxy or more to bend spacetime. But is it possible that with the yet to be established quantum gravity.. one simply need some reconfiguration of the metric to reorient and establish a rosen-einstein bridge without needing incredible amount of energy much like a 2 year old kid taking a lifetime a bend a plastic chair with his hands when he could simply pour gasoline to the chair and a lighter is enough to melt the chair to a blob?

 

[jtbell]

Reminder: speculation about the properties and predictions of theories that don't even exist yet is outside the scope of this forum. If there are indeed current theories of quantum gravity that can do what you want, they are probably best discussed in the "Beyond the Standard Model" forum.

 

[HarryRool]

Wormholes are a product of GR and Quantum Foam from QM or a related field. The two theories have never been successfully merged so I don't see any relation between the two. If someone else knows otherwise please step forward.

Early attempts to quantize gravity produced and equation that, although far too difficult to actually solve in any realistic case, is nevertheless conceptually enlightening.

This equation, the Wheeler-DeWitt equation, is analogous to the Schroedinger equation of quantum mechanics. A solution to the Schroedinger equation describes a particle whose position could be anything possible. A solution to the Wheeler-DeWitt equation describes a universe whose geometry could be anything possible. Just as quantum particles have a fuzzy position, quantum universes have fuzzy geometry. This fuzziness in the case of universes is call the "quantum foam" and it is presumed to include wormhole geometries.

That's what I got from recently reading a wormhole book aimed at a lay audience.

 

[Drakkith]

Early attempts to quantize gravity produced and equation that, although far too difficult to actually solve in any realistic case, is nevertheless conceptually enlightening.

This equation, the Wheeler-DeWitt equation, is analogous to the Schroedinger equation of quantum mechanics. A solution to the Schroedinger equation describes a particle whose position could be anything possible. A solution to the Wheeler-DeWitt equation describes a universe whose geometry could be anything possible. Just as quantum particles have a fuzzy position, quantum universes have fuzzy geometry. This fuzziness in the case of universes is call the "quantum foam" and it is presumed to include wormhole geometries.

That's what I got from recently reading a wormhole book aimed at a lay audience.

I see. That is pretty interesting!