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TheTuringTester
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Given that we know experimentally that time slows and space bends in the presence of matter, what is the actual physical mechanism that enables matter to bend space and slow time?
There is no mechanism. The Einstein Field Equations which relate the spacetime curvature tensor to the stress-energy tensor is an axiom of GR.TheTuringTester said:Given that we know experimentally that time slows and space bends in the presence of matter, what is the actual physical mechanism that enables matter to bend space and slow time?
I disagree. There is a mechanism and the EFE is the description of that mechanism. That it is an axiom in GR just means that we cannot express this mechanism in terms of anything else.PeroK said:There is no mechanism. The Einstein Field Equations which relate the spacetime curvature tensor to the stress-energy tensor is an axiom of GR.
Just so you are clear, time does NOT slow for the person experiencing it. That is, if I am very low in a gravity well and you are very high in the same well, you will see my clock tick more slowly than yours and I will see yours tick more rapidly than mine, BUT ... locally, we each will see our time ticking away at one second per second.TheTuringTester said:Given that we know experimentally that time slows and space bends in the presence of matter,
PeroK said:There is no mechanism.
Perhaps splitting the difference here, general relativity doesn't explain how mass and energy curve spacetime, but it describes the curvature that is generated. Whether the Einstein field equations (which do the describing of curvature) count as a "mechanism" or not is kind of up to you. For a host of reasons, though, most physicists believe there's a more fundamental theory to be found here which would hopefully say how it works.Dale said:I disagree.
I think the root cause of my question is that I am trying to understand is if gravity is not a force, it's just the result of curved spacetime - do we have a name for the force that bends space and slows time and it is the same force acting equally - does time slow in exact proportion to space bending - and if not, is that force pulling on space and time through the same mechanism? I know I am struggling to put a classical visualization on something that might not have a classical definition, but I think there is value in that struggle to help light the path ahead to a more accurate visualization in baby steps from the concrete to the abstract.PeroK said:There is no mechanism. The Einstein Field Equations which relate the spacetime curvature tensor to the stress-energy tensor is an axiom of GR.
We don't know the mechanism. I would be very surprised if it is anything like a force, though. I suspect you are thinking of the rubber sheet curved by a weight on it, which is a deeply evocative and almost entirely wrong picture you see in a lot of popsci.TheTuringTester said:do we have a name for the force that bends space and slows time and it is the same force acting equally
Space and time are fairly arbitrary distinctions we put on spacetime, which is the thing that's curved. And there isn't a single number to describe the curvature of space even when you've defined it, so there isn't really a sensible answer to this question.TheTuringTester said:does time slow in exact proportion to space bending
There is no accurate visualisation of a curved 4d pseudo-Riemannian manifold. I gather one can prove that you can't draw a representation of one in any finite dimensional Euclidean space. There are visualisations of limited parts of one - forum member A.T.'s animation is a good one:TheTuringTester said:I think there is value in that struggle to help light the path ahead to a more accurate visualization in baby steps from the concrete to the abstract.
You should forget forces as they don't generalise beyond Newtonian mechanics. Spacetime is a geometric model.TheTuringTester said:I think the root cause of my question is that I am trying to understand is if gravity is not a force, it's just the result of curved spacetime - do we have a name for the force that bends space and slows time and it is the same force acting equally - does time slow in exact proportion to space bending - and if not, is that force pulling on space and time through the same mechanism? I know I am struggling to put a classical visualization on something that might not have a classical definition, but I think there is value in that struggle to help light the path ahead to a more accurate visualization in baby steps from the concrete to the abstract.
That is a good point. So let me explain how I think of "mechanisms".Ibix said:Whether the Einstein field equations (which do the describing of curvature) count as a "mechanism" or not is kind of up to you.
Yes, we call them the Christoffel symbols. In a non-inertial frame the Christoffel symbols give the fictitious forces, and in curved spacetime they give the equivalent of the Newtonian gravitational field.TheTuringTester said:do we have a name for the force that bends space and slows time and it is the same force acting equally -
Matter bends space through its mass and energy. According to Einstein's theory of general relativity, mass and energy create a gravitational field that warps the fabric of space, causing objects to follow curved paths.
Yes, any type of matter with mass and energy can bend space. However, the amount of bending depends on the mass and energy of the object. Objects with larger masses and higher energies will have a stronger gravitational pull and thus, a greater effect on bending space.
According to Einstein's theory of relativity, time and space are interconnected. As matter bends space, it also affects time. The closer an object is to a massive body, the slower time passes for that object. This is known as gravitational time dilation.
There is no limit to how much matter can bend space. As long as an object has mass and energy, it will have a gravitational field that can bend space. However, the amount of bending decreases with distance from the object.
The bending of space affects the movement of objects by altering their trajectory. Objects will follow the curved path created by the warped space, rather than a straight line. This is why planets orbit around the sun and why objects fall towards the center of the Earth.