B Mechanism of Curvature of Space: Does it Happen Instantly?

[Deepak K Kapur]

Hi all,

How does matter curve space (what's the mechanism)?

Does this Curvature happen instantaneously or does it happen at light speed?

Thanks in advance.

 

[Orodruin]

Matter does not curve space. Energy (mass is a form of energy), momentum, and stress act as the source of the curvature of space-time. How this works is described by the Einstein field equations. This is as much "mechanism" anything will get in science. Science makes a model of how things work and then tests its predictions. The model here is that the Universe behaves according to the Einstein field equations.

 

[Ibix]

Slightly contradicting Orodruin, it's possible that a future theory of gravity would provide an explanation, perhaps in terms of some quantum field (or some other structure - I make no predictions). But then you could ask similar questions about the quantum field and Orodruin's answer would be the only one available.Regarding the speed of propagation of curvature, my understanding is that we don't completely know. Localising energy in gravitational fields in order to say how fast it traveled is difficult. We do predict that gravitational waves travel at c and all our current evidence is consistent with this. However, we would be fairly surprised if any influence propagates faster than light - you can usually generate effect-precedes-cause paradoxes if anything does exceed light speed.

 

[Orodruin]

Slightly contradicting Orodruin, it's possible that a future theory of gravity would provide an explanation, perhaps in terms of some quantum field (or some other structure - I make no predictions). But then you could ask similar questions about the quantum field and Orodruin's answer would be the only one available.

I don't see how this contradicts what I said. My comments were about a theory in general. If you alter the underlying assumptions, it might give you the old theory as a result in some limit, but it will be a different theory that rests on its own assumptions for which no "mechanism" is provided.

 

[Ibix]

I don't see how this contradicts what I said.

I read your post as implying that there's no possibility of a more fundamental theory of gravity than general relativity. I know you don't think that, but that's how I read your answer. All I meant was that the OP's specific question may one day have an answer of the sort I suspect the OP wants - "stress-energy emits gravitons", or something like that (I know that's not how quantum gravity theories work). As you say, that theory will rest on its own assumptions that are only justified in a post hoc "because it works" way.

Edit: so I shouldn't have said "contradicting", I should have said "clarifying". I hope contradicting myself clarifies matters.

 

[Deepak K Kapur]

Thanks all of you..