Poisson's equation for gravitational field

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Discussion Overview

The discussion revolves around proving Poisson's equation for a gravitational field, specifically focusing on the independence of Gauss's Law from the choice of closed surface surrounding a point mass. The scope includes theoretical aspects and mathematical reasoning related to gravitational fields.

Discussion Character

  • Technical explanation, Mathematical reasoning, Debate/contested

Main Points Raised

  • One participant questions how to prove that Gauss's Law is independent of the choice of closed surface surrounding a point mass.
  • Another participant suggests using the divergence theorem as a potential approach.
  • A participant expresses difficulty in proving that the integral does not depend on the closed surface.
  • There is a suggestion that proving the law for a sphere could extend to any closed surface.
  • One participant provides a mathematical expression involving integrals over a closed surface and its corresponding volume, seeking validation of its correctness.
  • A later reply indicates that the use of the divergence theorem is now clear to the original poster after some clarification.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the proof method, as there are multiple approaches suggested, including the divergence theorem and working with infinitesimal masses. The discussion remains unresolved regarding the specific proof of independence from the closed surface.

Contextual Notes

Limitations include the lack of detailed steps in the proof and the dependence on the definitions of the mathematical concepts involved, such as the divergence theorem and the nature of closed surfaces.

Who May Find This Useful

Readers interested in gravitational fields, mathematical proofs in physics, and the application of Gauss's Law may find this discussion relevant.

Sphinx
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Hello everyone!
I have a question concerning the proof of Poisson's equation for a gravitational field.
My question is how can i prove that Gauss's Law is independent of the choice of the closed surface surrounding the point mass?
Thanks in advance
 
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Did you try using the divergence theorem?
 
Yes, but this is the last step of the proof , my difficulty resides in proving that the integral doesn't depend on the closed surface
 
It would easier to help you if you actually showed what you did.
 
You can either use the divergence theorem (the thing is that if you can prove it for a sphere you can prove it for any closed surface), or become hardcore (for no reason) and work with infinitesimal masses.
 
Last edited:
∫ƒ.ds over a closed surface =∫div(f) dΩ over the corresponding volume =∫div(f) dΩ over a sphere enclosing the volume =∫ƒ.ds over the surface of the sphere
is that correct??
 
Yes, so what is your question?
 
I didn't see how to use the div theo, but know it's clear.
Thank u very much Orodruin & ChrisVer
 

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