All Questions
Tagged with newtonian-gravity general-relativity
227
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When is it appropriate to say Newtonian gravity is a force? When is it not appropiate? [closed]
Please help me understand the notion of force when it is applied to Newtonian gravity. From my understanding forces in physics involve interactions with at least 2 objects and can cause an ...
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Is there a deeper relationship between symmetry and gravitational potential comparing Newton's and Einstein's gravity?
In this question, see Why is general relativity in (2+1) dimensions different from cylindrical systems in (3+1) dimensional GR?, it is mentioned
"The gravitational potential Φ of an infinite rod ...
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EM 4-potential vs gravity 4-potential?
In classical field theory, the electrostatic and gravitational fields have very similar differential forms:
$$\vec \nabla\cdot \vec{E}=\frac{\rho}{\varepsilon_0}$$
$$\vec \nabla\cdot \vec{g}=-4\pi G\...
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Quantised Newtonian potential as an operator in non-relativistic QM [closed]
Suppose we have two slowly moving (effectively static) masses $m_1,m_2$, interacting through gravity, that are not occupying a definite state of position i.e. that matter is being treated quantum ...
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Einstein's equation of gravitation field [duplicate]
I'm looking for the reason why there is the number eight $8$ at the r.h.s. of EI:
$$R_{\mu\nu}-\frac{1}{2}Rg_{\mu\nu}=\frac{8\pi G}{c^2}T_{\mu\nu}.$$
My attempt was to take the limit of this equation ...
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How does gravity act and propagate in a 2+1D universe?—Newtonian versus general relativity
In a hypothetical 2+1D universe:
if we apply the Newtonian concept of gravity, we might expect that the gravitational force between two mass points with a distance of $r$ would diminish linearly with ...
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References on Newton-Cartan Gravity
I'm interested in learning a bit about Newton-Cartan gravity, and I would like some references on the topic. I am already familiar with differential geometry and general relativity, so those could be ...
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When does Newtonian physics fail?
When does Newtonian physics fail?
The answer by Zo the Relativist to the question How accurate is Newtonian Gravity? includes the statement:
The key point is that Newtonian physics fails when, ...
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Physical relevance of the $ij$ components of the Einstein field equations in the Newtonian limit
In the weak field limit of general relativity (with matter described by a perfect fluid consisting only of dust), we have the following correspondences:
$00$-component of the Einstein field equations ...
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Why can Newtonian gravity provide the correct value of the Schwarzschild radius? [duplicate]
By using Newtonian gravity, we can equate the kinetic and potential energy of a test mass in order to obtain the escape velocity of an object from a large mass $M$:
$$\frac{1}{2} m v^2 = \frac{GMm}{r}$...
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What's the Newtonian potential in 2+1 gravity?
I understand that there are no propagating degrees of freedom (i.e. gravitational waves) in 2+1 dimensions. There are a couple of arguments to show this. One is to count degrees of freedom of general ...
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Gravitational effects on a celestial body and the difference between a pendulum and a regular clock
Imagine a planet with the same properties as Earth, this time moving in an elliptical orbit around a heavy star of a large number of solar masses. Also imagine that the surface of this planet is as ...
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Derivative of Ricci tensor and Euler-Lagrange equations ambiguity
I'm currently working in a problem about formulating a Lagrangian for Newton-Cartan theory and i'm currently proving if it works.
In order to do this i'm required to compute the derivative of the ...
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Does General Relativity imply greater accelerations than Newtonian gravity in strong gravitational fields? [duplicate]
Does General Relativity imply greater accelerations than Newtonian gravity in strong gravitational fields, such as at 2 m/s^2?
Do the general relativistic corrections add up to more "gravity"...
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How close was Maxwell to general relativity? [closed]
In a recent paper by Accolierastro's recent video, she goes back to Maxwells seminal paper on electromagnetism, and the section on gravity. In Maxwells paper, he notes the similarity between the lines ...
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Negative Energy and Gravity
Why do many science communicators say that negative masses fall upwards? Is it the same in the physics literature that they say that negative masses fall upwards?
In general relativity, things don't ...
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How does a curvature in time equate to Newtonian gravity? [duplicate]
I often read that a curvature in time (the rate at which clocks tick) near a massive object, is considered to be the source of Newtonian gravity.
This got me wondering, does General Relativity use the ...
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Newtonian approximation for the tidal forces at the event horizon of a black hole
I'm currently working on a problem where I have to calculate the tidal forces a person experiences if their feet touches the Schwartzschild radius and their head is $1.8m$ elevated above the ...
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Can the gravitational singularities of black holes be solved by potential or self-energy?
In Newtonian Mechanics, the energy density of gravitational field is negative in comparison with the positive energy density assigned to mass density, meaning that that the total positive energy of ...
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Does gravity actually have a ‘reaction force’? [duplicate]
By (my limited knowledge of) Einstein’s theory of General Relativity, as gravity is not a force but rather the effect of an object’s inertial path following a geodesic through curved spacetime due to ...
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Equivalence Principle in Newtonian Physics vs GR: A Thought Experiment
I have a question regarding the equivalence principle as it applies in Newtonian Physics and General Relativity. Consider a thought experiment involving a free-falling elevator.
Inside the elevator, ...
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Contradiction in negative mass interactions according to GR
I quote Sabine Hossenfelder:
Gravitation is a spin-2 interaction. It is straightforward to see that this means that like charges attract and unlike charges repel. The charge of gravity is the mass. ...
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What is the difference between GPE and gravitational self energy in GR?
What is the difference between gravitational potential energy and gravitational self energy in General Relativity? Are they both the same in Newtonian gravity?
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Interpretation of gravitational waves
A wave has peaks and valleys. I can think of a sine wave as a wave with peaks and valleys.
Now, if gravity is a wave, can we say that gravity would have peaks and valleys, with the valley becoming ...
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How is when an object moves gravity not effect it ? As Einstein sais?
Experiment:
*a water bottle with a hole . Water is falling from the hole when the bottle is in rest . When the bottle is released and falls , water stops falling as gravity is not doing effect on it . ...
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Is there an equation that is quick to use that calculates gravity around black holes?
Is there an equation the can calculate gravity around black holes but is less time consuming than EFE? I want to find an equation that is simpler/faster than Einstein's Field Equations but can still ...
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Since when did inertial mass and gravitional mass became equal?
If we think about inertial mass and gravitational mass as independent concepts and develop physics then we would know after a while they are only propotional (by precision we have by now). but it seem ...
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How does Einstein's theory of relativity prove Newton's laws of gravitation (or is it incorrect)?
I have heard that at the speed of light the Newton's laws of gravitation stop working. Why does that happen or does that even happen? Is there any proof to it? From what I have heard It's related to ...
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How was the $n$-body problem solved before computers?
Explaining the anomalous progression of Mercurys orbit was one of the first successes of general relativity. Given that a $n$-body problem is not solvable analytically even in the Newtonian picture (I'...
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General relativity when can we approximate to Newtonian gravity?
Lets consider this scenario in deep void of space where other curvatures of large objects are negligible in this case and we bring 2 objects lets say $A$ and $B$.
We give it a force slightly lower ...
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