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Electro-Gravity ideas, Dark Energy

  1. Oct 6, 2011 #1
    Hello all,

    I know that there has been much work on the unification of gravity and electromagnetism, but I was wondering if they could be united the same way that electricity and magnetism were united- a changing gravitational field creates an electromagnetic field, and a changing electromagnetic field creates a gravitational field.
    Is there anything that prevents this? Or maybe is this already the accepted concept and what we are still waiting for is the evidence.

    Thanks for any replies!
  2. jcsd
  3. Oct 6, 2011 #2
    Aaaaand I'm a fruitloop and forgot to add the second part of my question. If, indeed, this is the way that Electrogravity [for lack of a better term] works, is it possible that it could account for the expansion of the universe [dark energy]?
    My reasoning is this [coming from the point of veiw of m-theory and branes]:
    If we are living on a 3-dimensional brane in a higher dimensional universe, there would be a boundry point between this brane and the higher dimensional bulk. What if, instead of being on the edge of our space, every point on our brane is in contact with the boundry? Similar to a two dimensional being living on a plane brane, becuase it only has two dimensions and cannot "travel" in the third to reach the boundry at the edge of it's space, it must be in contact with the boundry at every point. If this is the case, it might be possible that electomagnetic fields coming from changing gravitational fields [because of the difference in strength of EM to gravity, these changing fields would most likley be on the scale of entire galaxies, not just individual planetary bodies or stars] could be causeing the expansion of space between the galaxies via radiation pressure on the fabric of spacetime?

    If i'm completly incorrect on everything, please tell me why, with equations if possible. I really want to understand this and progress, not just find out if i'm right.

  4. Oct 6, 2011 #3
    I really have no mathematical backing to this, so I can't speak definitely. But an obvious fundamental relationship between gravity and electromagnetism such as the one you named would most likely be easily noticed. Throwing a baseball does not cause electromagnetic fields to fluctuate around it (assume it is electrically neutral).

    It should also be noted that the electromagnetic force has been mathematically linked with the weak nuclear force (the so-called 'electroweak force') and there are good theories supporting a link between the electroweak force and the strong nuclear force so if gravity was directly linked with electromagnetism it would also have to be linked with those.
  5. Oct 6, 2011 #4
    Thats interesting about the elecroweak force i didnt account for that at all. What i was thinking, however, was that possibly the effects of the relation between gravity and electomagnetism/electroweak force might be so subtle that we could never measure it on somthing so small as a baseball, or even a star, but entire galexies perhaps. Its so facinating how all the forces seem to be coming together with the em weak and strong forces. I hadnt heard about the weak and strong unifying before.
  6. Oct 6, 2011 #5
    It's an interesting idea, and really I can't comment because I don't have anywhere close to the mathematical skill required.
    If you're interested in Unification of the Forces, Wikipedia has a good page explaining some of the theories.


    Be warned, the more detail you want to know about stuff like this, the more and more math you'll need.
  7. Oct 10, 2011 #6
    Let's see.....

    Put a huge wire with a changing electromagnetic field, look for changes in gravity. None detected.

    Move a non-charged object back and forth. Look for electromagnetic fields. None detected.

    So, the answer is, no it can't because, we don't detect gravity changes near changing electromagnetic fields and vice versa.

    We don't observe it.
  8. Oct 10, 2011 #7
    No. One reason for this is that if changing gravity were interacting with electromagnetic waves, we would see it, and any "dark" matter or energy that comes from it, wouldn't be dark.

    Except that we know how EM works, and the expansion of the universe works nothing like EM.

    No equations necessary. I have a wire with a changing electromagnetic field. I see no changes in gravity. I move some mass around, no changes in EM.
  9. Oct 10, 2011 #8
    OK, take two galaxies in front of each other. If there was some strong coupling between EM and gravity then one galaxy ought to wildly change the image of the galaxy behind it.

    Also, you can do some rough numbers. We can measure small effects very, very accurately in the laboratory. So if you end up with *zero* effects in the laboratory, then that's going to limit the amount of the force at galaxy levels.

    The other thing is that for these sorts of things it helps, not to guess too early what might be going on. You start with observations and you are able to say that whatever is causing the interaction of galaxies has properties X, Y, and Z, and then figure out what the limits on observation are.

    Grand unification theories.
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