Does gravity affect a magnetic/electric field?

In summary, the conversation discusses the interaction between gravity and electromagnetic radiation. While in Newtonian gravity, only masses are considered as the source of gravity, in general relativity, the energy-momentum tensor is also taken into account. This means that not only masses, but also momenta of objects can affect the curvature of space-time and therefore, the behavior of electromagnetic fields. This is seen in the bending of light and the red and blue shifts observed in the presence of gravitational fields. However, it is important to note that according to general relativity, gravity does not directly interact with electromagnetic radiation, but rather, it is the curvature of space-time that determines the trajectory of objects and the passing of time.
  • #1
PWiz
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Since light, a form of electromagnetic radiation, gets bent in a gravitational field even though it does not have any rest mass, it is obvious gravity is a force that does much more than just attract two masses towards each other. Since it affects electromagnetic radiation, it has led me to ask: does gravity(or a particularly strong gravitational field) have an affect on an electric/magnetic field or vice versa? There seems to be some connection here.
P.S. I haven't started with GR yet, so please don't expect me to follow a very advanced conceptual understanding of the theory.
 
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  • #2
It is only in Newtonian gravity that the source of gravitation is exclusively masses. Once you go to GR, the source of gravity (really, of space-time curvature) is the energy-momentum tensor - an object that contains both masses and momenta of the contents of the space-time. There is also some feedback, space-time provides the setting for how electromagnetism behaves, so yes, to some extent electromagnetic fields and gravity do interact.
 
  • #3
If you want to work on the effect of gravity on the EM fields then you probably need to start here:
http://en.wikipedia.org/wiki/Maxwell's_equations_in_curved_spacetime
where the difference appears in the ##g_{\mu\nu}## which represents the metric and ##g## which is its determinant.

Sorry that I don't know a gentler answer to the question.
 
  • #4
All forms of electromagnetic radiation (EMR) "seems" to interact with gravitational fields, even radio waves are bended by gravitation. As general relativity (GR) does not include forces in its description, what determine what will happens with the EMR in GR? The space curvature. If a beam is collinear with the "force lines" of the curvature, per example, as when a light ray goes against the gravitational field of a massive body, we will have a red shift. (This is not the cosmological red shift caused by the expanding universe). If the light ray is going to a massive body, then it will be a blue shift. (These are observational results). This is interpreted by Einstein as the effect of gravitation on clocks. And the red shift and blue shift are seeing as a result of time accelerating or reducing its ticks. In other words, those phenomena are seen by relativity as an special case of the general effect of Gravitation on time. In the other hand, when the light rays are not collinear with the gravitational field, then we have the bending of the rays. All these phenomena "look" as if "light" interacts with the gravitational field, however, GR forbid us to think that way. Gravitation curves space, and curved space determine the trajectory of objects and the passing of time inside that space. So PWiz your common sense deduction goes against GR. Personally I have never felt comfortable in this schema.
 
  • #5
@Orodruin Hmmm, I've heard of the term "energy-momentum tensor" a lot in the past few days. The greedy feeling of wanting to grasp the entire concept mathematically is indescribable :H (Getting closer by the day though...!)
@DaleSpam Thanks, I've added Maxwell's equations to my must-learn list :)
@LUIS FONDEUR You've given me a new insight on this. Thanks for adding clarity to my concepts.
 

1. How does gravity affect a magnetic field?

Gravity has no direct effect on a magnetic field. Magnetic fields are created by moving electric charges, while gravity is a force that acts between masses. However, the presence of a large mass, such as a planet or star, can cause distortion in the magnetic field.

2. Can gravity change the strength of an electric field?

No, gravity does not change the strength of an electric field. Electric fields are created by stationary electric charges, while gravity is a force that acts between masses. However, the presence of a large mass may cause a distortion in the electric field.

3. Does gravity affect the direction of a magnetic field?

No, gravity does not affect the direction of a magnetic field. The direction of a magnetic field is determined by the direction of the current or moving charges. Gravity is a force that acts between masses and does not have an influence on the direction of a magnetic field.

4. Can gravity and a magnetic field cancel each other out?

No, gravity and a magnetic field do not cancel each other out. They are two separate forces that act on different types of objects. While gravity is a force that acts between masses, a magnetic field is created by moving electric charges. They do not have opposite effects on each other and cannot cancel each other out.

5. How does gravity affect an electric field?

Gravity has no direct effect on an electric field. Electric fields are created by stationary electric charges, while gravity is a force that acts between masses. However, the presence of a large mass may cause a distortion in the electric field.

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