Elasticity of Spacetime: Does Spacetime Stiffen?

sqljunkey · Nov 15, 2019

Does spacetime have elasticity ? I was reading this and they are talking about the stiffness of spacetime.

phinds · Nov 15, 2019

sqljunkey said:

Does spacetime have elasticity ? I was reading this and they are talking about the stiffness of spacetime.

Spacetime is not a "thing" that can be bent or stretched, or have stiffness or elasticity, it is just geometry. We use the term "bent" regarding the path of objects through space-time but that is only by applying Euclidean Geometry, which actually does not apply. Objects, in the absence of other force, travel in straight lines in space-time, but these "straight lines" are more correctly called "geodesics" and are straight lines in Riemann Geometry (but bent in Euclidean Geometry) which is the correct math to describe space-time.

EDIT: I should also note to be completely correct that I have been told by people who understand this thing way better than I do that it is actually "pseudo" Riemann Geometry that describes space time.

dsaun777 · Nov 15, 2019

sqljunkey said:

Does spacetime have elasticity ? I was reading this and they are talking about the stiffness of spacetime.

Spacetime is stiff upon first derivatives then gets stretchy at 2nd derivatives.

Vanadium 50 · Nov 15, 2019

dsaun777 said:

Spacetime is stiff upon first derivatives then gets stretchy at 2nd derivatives.

What do you mean by that?

PeterDonis · Nov 15, 2019

sqljunkey said:

I was reading this and they are talking about the stiffness of spacetime.

What they are talking about is a speculative model in which what we call "spacetime" is treated as if it were an elastic medium in order to investigate the implications of such a model. It is not something that can really be discussed at the "B" level and it is certainly not something that needs to be considered at all in order to understand the standard model of spacetime in General Relativity.

sqljunkey · Nov 16, 2019

yeah I'm sorry it's confusing to me to figure out which discussion level to use here. Does this speculative model have a name?

PeterDonis · Nov 16, 2019

sqljunkey said:

Does this speculative model have a name?

Not that I know of.

Vanadium 50 · Nov 16, 2019

I think it's just Kirk playing with numbers.

Elasticity of Spacetime: Does Spacetime Stiffen?

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