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Einstein postulated that gravity bends the geometry of space-time then what does magnetism do in to the geometry of space-time, or is there even a correlation between space-time geometry and magnetism?

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    $\begingroup$ I am not sure how exactly to interpret your question, the current two answers assume you ask whether the electromagnetic (EM) field curves space-time. But if your question is more "can the EM field be understood geometrically like gravity"?. Then yes. While gravity is curvature of space-time, electromagnetism turns out to be curvature of a so-called $U(1)$ principle bundle. This provides a analogy to gravity. See en.wikipedia.org/wiki/… $\endgroup$
    – Heidar
    Jun 21, 2012 at 4:43
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    $\begingroup$ @Heidar - You should elaborate that as an answer, it'll be a really interesting one. $\endgroup$
    – Kitchi
    Mar 5, 2013 at 16:22

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That's a very complicated question. Electromagnetic energy does contribute to space-time curvature, just like any other form of energy (e.g. 'mass'), and the curvature of space-time also affects the geometry of fields and their propagation. An example is the trajectory of a photon (a particle of 'light')---which has been observed to be deflected by gravity exactly as general relativity predicts.

Note, however, there is no generally accepted theory which explains both gravity and electromagnetism (i.e. a 'unified theory'), so we don't entirely know how they interact / work-together. Our current framework ('quantum electrodynamics') describes electricity and magnetism as fields on top of a (possibly curved) space-time. I.e. the space-time is treated differently from the electromagnetism.

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    $\begingroup$ there is no generally accepted theory which explains both gravity and electromagnetism Not true. GR explains both. We don't have a theory that explains both and includes quantum mechanics, but there was nothing quantum-mechanical about the question. $\endgroup$
    – user4552
    Oct 28, 2014 at 20:02
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If you want to think about Electromagnetism geometrically then the curvature of the "U(1) bundle" would be the electromagnetic field F. In this way F (the Faraday tensor) plays the role that the Riemann Curvature tensor "R" plays in general relativity. The analog of the Christoffel symbol would be the photon field A. The big difference is the gauge group for EM is U(1) and the "gauge group" for Gravity is the group of diffeomorphisms (essentially coordinate changes) of space-time. But note that U(1) is related to not a real dimension of space but a phase in the wave function (symmetry under phase shifts), this is related to the fact that electric charge isn't literally momentum in a 5th circular dimension (as would be the case if Kaluza-Klein theory were true).

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I want to expand a bit on Heidar's comment as I suspect this may be what you're really asking. Have a look at ALL "forces" as manifestations of properties of space-time as my answer to this covers similar ground.

As Alfred Centauri mentioned in his answer, your comment:

Einstein postulated that gravity bends the geometry of space-time

isn't true. Einstein's theory describes gravity as a curvature in spacetime. Gravity doesn't bend spacetime; we see the curvature as gravity. Describing gravity in this way makes it very different to the other forces, however you can also describe gravity not as curvature in spacetime, but as curvature in a mathematical object called the connection. See http://en.wikipedia.org/wiki/Curvature_form for details of this approach, though I'm afraid that article isn't intended for non-nerds.

The point of describing gravity using a curved connection is that the other forces, strong and weak as well as electromagnetism, can be described in the same way. If you use this approach then magnetism is due to curvature just like gravity is.

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  • $\begingroup$ There is a big difference though between the nature of the connections! A connection on real space should probably be pointed out to not be the same as one on a fibre bundle of space + "internal dimensions". Although what you're saying isn't wrong. $\endgroup$ Jun 21, 2012 at 15:31
  • $\begingroup$ @johnn Rennie, please refer me some references where i can get detailed analyses of curvature of space-time as a electromagnetic , weak and strong forces. $\endgroup$ Feb 18, 2016 at 11:42
  • $\begingroup$ @Rahulkumarwalia: start with the links in my answer to Can all fundamental forces be fictitious forces? $\endgroup$ Feb 18, 2016 at 12:15
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Einstein postulated that gravity bends the geometry of space-time

In the context of GTR, gravity is the curvature of spacetime, not the cause of it. The curvature of spacetime is related to the density and flux of energy and momentum. So, it is said, "matter tells spacetime how to curve, spacetime tells matter how to move".

It's not quite clear what you mean by "magnetism" however it is the case that the classical electromagnetic field transports energy and momentum and thus contributes to the curvature of spacetime.

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    $\begingroup$ Hello. May I ask this: Why do we have to move on the curvature? Why not stand still? Thanks. $\endgroup$ Mar 4, 2016 at 20:02

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