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  4. How is the spacetime curvature approximated?
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How is the spacetime curvature approximated?

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Offline saspinski (OP)

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How is the spacetime curvature approximated?
« on: 06/06/2017 01:10:57 »
The classical gravitation law can, at the surface of a spherical homogeneous body, be written as:
a = G*(4/3*π*r³)*μ / r² =  4/3*π*G*μ*r; and the divergence of the acceleration in spherical coordinates is: div a = 4*π*G*μ.
where μ is the body density and G the gravitational constant.
That divergence has units of 1/T². When comparing to the Gaussian expression for the curvature of the surface of the sphere: 1/R²,  there is a similarity. Is it only a coincidence or the GR measure of spacetime curvature for that geometry can be approximated, for small velocities and mass densities, by that expression?

« Last Edit: 06/06/2017 20:02:14 by chris »
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Offline PmbPhy

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Re: How is the spacetime curvature approximated?
« Reply #1 on: 16/06/2017 01:54:58 »
Quote from: saspinski on 06/06/2017 01:10:57
The classical gravitation law can, at the surface of a spherical homogeneous body, be written as:
a = G*(4/3*π*r³)*μ / r² =  4/3*π*G*μ*r; and the divergence of the acceleration in spherical coordinates is: div a = 4*π*G*μ.
where μ is the body density and G the gravitational constant.
That divergence has units of 1/T². When comparing to the Gaussian expression for the curvature of the surface of the sphere: 1/R²,  there is a similarity. Is it only a coincidence or the GR measure of spacetime curvature for that geometry can be approximated, for small velocities and mass densities, by that expression?


A coincidence. Spacetime cannot be specified by a single number. It's specified by a 4x4 tensor.
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Offline jeffreyH

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Re: How is the spacetime curvature approximated?
« Reply #2 on: 16/06/2017 12:54:00 »
Well I have some observations that I do not have time to post at the moment.
« Last Edit: 16/06/2017 16:34:47 by jeffreyH »
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