All Questions
Tagged with newtonian-gravity general-relativity
227
questions
8
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1
answer
150
views
Can a drop of water be set in rotational motion by rotating mass around it?
We are in empty space and see a spherical drop of water. Around the drop we have placed a massive shell with uniform density. The drop is positioned at the center. Then we set the shell in rotational ...
2
votes
1
answer
185
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How does general relativity resolve the fact that energy is not positive definite in Newtonian gravity?
In Newtonian gravity, the energy of the gravitational field $\vec{g}$ is
$$ U = -\frac{1}{8\pi G}\int |\vec{g}|^{2} d^{3}x $$
(assuming we don't have any point masses that lead to singularities and ...
- 8,640
2
votes
2
answers
790
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Understanding the derivation of the Newtonian limit of GR
I'm having difficulty understanding some of this derivation. The relevant information, as I understand it is:
We've let the lorentzian metric be a perturbation of the minkowski metric:
$$g_{\mu\nu} = \...
- 47
1
vote
2
answers
84
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Flaw when considering gravitation from Newton versus GRT point of view
Stage: Two massive objects are moving slowly with respect to each other and to some galactic background. For example Sun and Earth. We apply Newtonian gravitation concepts and the force felt by the ...
4
votes
3
answers
363
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On an infinite plane, with gravity the same of that of Earth, how far could light at an arbitrary angle travel until bending to hit the plane?
Now, I'm a complete idiot, so bear with me.
I've recently come across the idea that standing an infinite flat Earth would in theory appear the same as standing inside a hollow earth, since light would,...
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0
votes
3
answers
95
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How can weight be equal in the equivalence principle?
According to Einstein, weight will be the same as here in earth in a rocket going at 1G far from gravity fields. If we propulse an object here it will feel two forces, F=mg and F=ma of the thrust, but ...
user189508
-5
votes
1
answer
668
views
How can two objects with the same mass attract each other?
According to Einstein's theory of GR, two objects with the same mass won't atract each other, Why i'm saying this? The atraction according to GR happens because the objects with less curvature of ...
user319766
4
votes
3
answers
370
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What is the physical meaning and origin of the gravitational constant $G$?
Is $G$ just a value to fix the units in the equation? Something like a proportionality constant or a coupling constant?:
$$F=\frac{G m_{1} m_{2}}{r^{2}}$$
Does it have any physical meaning or physical ...
- 4,170
6
votes
1
answer
415
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Why is general relativity in (2+1) dimensions different from cylindrical systems in (3+1) dimensional GR?
The gravitational potential $\Phi$ of an infinite rod in newtonian gravity is $\Phi \sim \ln(r)$. This is the same as the gravitational potential of a point charge in two-dimensional Newtonian gravity ...
- 9,910
-1
votes
1
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148
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Would Newton's law in the solar system be independent from a presumed different fundamental gravitational law? [closed]
A thought experiment:
Let's assume the gravitational field of a black hole without any neighbors would be stronger than the Schwarzschild metric in the Newtonian limit.
Now, we let a solar system (sun ...
- 255
0
votes
1
answer
1k
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How to derive Newton's law of gravitation from general theory relativity [duplicate]
Newton's law of gravitation must be a special case of the general theory of relativity. How can we derive it from field equations of GTR?
If the electric field F/q is equal to E, then does the ...
- 1
0
votes
2
answers
86
views
Does general relativity predict different forces on aircraft than Newtonian mechanics?
When taught how airplanes fly, we are probably always given the Newtonian mechanism: that four forces act on an airplane; lift and weight on the vertical axis, and thrust and drag on the horizontal ...
- 303
0
votes
1
answer
316
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Newtonian limit of geodesic equation and Euler-Lagrange equations
As far as I know the Euler-Lagrange (EL) equations $$\frac{\partial L}{\partial q^m}-\frac{d }{dt}\frac{\partial L}{\partial \dot{q}^m}=0 $$ are covariant time dependent coordinate transformations,
$$...
0
votes
1
answer
151
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Does General Relativity provide a value for $G$? [duplicate]
It only recently was specifically pointed out to me that Einstein was right, and Newton was wrong.
Newton wasn't wholly wrong. He theorized that gravity was a force that acted between bodies, and came ...
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2
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181
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Has the Cavendish Experiment ever been Conducted in Zero Gravity?
Given the shortcomings of applying the gravitational equation to distant astral objects, I am wondering if it has ever been attempted to replicate the Cavendish Experiment in a zero gravity scenario (...
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