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Does Gravity bend Gravity?

  1. Oct 1, 2012 #1
    As the experiment proving Einstein's Relativity where the light waves from a star bend from the gravity of the Sun when viewed from a solar eclipse.

    Does Gravity do the same?

    Is Gravity an electromagnetic effect?

    The Gravity of the Earth has a tail from the Solar Wind that is bent due to the Earth's Gravity.

    Does the Gravity of the Earth bend the Gravitational effects of the Sun, Moon and the Planets Gravity collectively?
    Last edited: Oct 1, 2012
  2. jcsd
  3. Oct 1, 2012 #2


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    Gravity is not an electromagnetic phenomenon, it would otherwise be adequately explained by Maxwell's equations.
  4. Oct 1, 2012 #3
    Yes, gravity is not a Electromagnetic Phenomenon but does it yield to the pull of another Gravitational source?
  5. Oct 1, 2012 #4


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    Er, no, there is no observational evidence of this.
  6. Oct 2, 2012 #5
    Why have you came to this conclusion ? As chronos says, where is the evidence ?
  7. Oct 2, 2012 #6


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    The Earth does not have a tail of gravity. The Earth's magnetic field disrupts the solar wind, which being composed of charged particles produce their own magnetic field. This interaction causes the magnetic field of the Earth to develop a tail as the particles bump up against the Earth's field on the near side and get pushed outwards, leaving a "void" of solar wind behind the Earth. (At least I think that's what happens)
    Gravity does not behave similar to the EM force in this manner.
  8. Oct 2, 2012 #7
    So you are saying gravity is a linear since it does not form a tail.

    Does Gravity act like a wave or a particle?

    It must be a particle in reverse.
  9. Oct 2, 2012 #8


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    I think you have a misunderstanding of what gravity is. This ties in to the other fundamental forces of nature as well. Let me see if I can explain.

    Science has come up with 4 ways to explain how two objects can "interact". Interact meaning that one object can cause a change in another object, or that one object can spontaneously change. That's the underlying theme of an interaction, change. It could be a change in position, velocity, a decay of a particle into other particles, absorption of a photon, and other things. Remember, an interaction is NOT a physical object! It is not a particle! As such none of the forces can be assigned things like spin, velocity, or even a position. These things can only be assigned to objects. (I'm going to abstain from attempting to describe QFT, where things are a little less clear cut)

    Each of the 4 fundamental forces, or interactions, has specific rules that we have observed them to follow. For example, the electromagnetic force only works between two electrically charged particles. This means that a neutral particle such as a neutrino does not partake in this kind of interaction. Gravity on the other hand is believed to affect ALL particles. It so happens that our primary theory describing gravity, General Relativity, explains gravity as bending and curving of space, much like the surface of the Earth is riddled with mountains and valleys and such. (Only an analogy, don't read too far into it)

    The tail in the Earths magnetic field is NOT a result of the EM force itself being stretched out, for that cannot happen. Remember, the force isn't an object! It is actually a result of charged particles having their paths changed, and the resulting interactions between those particles and the magnetic field of the Earth. The field, which is a way of describing how particles will interact with each other through a force, is determined by what particles we already have present and how they are acting. Without particles we could not have any concept of the field, as we wouldn't even be able to observe it!

    Does that make sense?

    Here's a link or two:

    (It's kind of advanced, so if you can't make heads or tails of it don't worry about it.)
  10. Oct 2, 2012 #9
    In a sense it does. Einstein's field equations are highly nonlinear and the solution for the metric tensor depends upon its self.

    There is an energy density associated with a gravitational field, and this energy density acts as a source of gravity in it's own right. So if your question is does gravity gravitate, then I believe so.
  11. Oct 2, 2012 #10


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    Hmm. Do you have a reference that could explain this? (Or can you explain it in a little more detail?) I haven't heard of this before.
  12. Oct 2, 2012 #11


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    Two sentences from “Einstein, Albert, in “The Principle of Relativity”, Dover Publications, 1952” seem to agree with dipole’s statements:

    “The energy of the gravitational field itself contributes to the space-time curvature.” and

    “The total gravitating action created by the galaxy or cluster depends on its total energy, that is, the total ponderable energy plus the gravitational energy.”

  13. Oct 2, 2012 #12

    That's a complicated question, but the short answer is yes, which is why it's been so difficult to get a theory of quantum gravity.
  14. Oct 2, 2012 #13


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    There you have it Philo. It doesn't work quite the way you imagine it to, but yes, gravity does in fact affect itself.
  15. Oct 2, 2012 #14
    Here is a non-technical explanation


    I'm looking for something that goes into the more gory details.
  16. Oct 2, 2012 #15
    I heard that space itself is the gravity that pushes us down,

    heavy mass such as the sun warped space, and planets orbit the sun
  17. Oct 3, 2012 #16
    Does anyone know the resullts about the twin Grail (Gravity Recovery and Interior Laboratory)spacecrafts that went around the Moon measuring the gravity in 2011 & 2012?
  18. Oct 3, 2012 #17


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    Awesome, that explains things pretty well for me. Thanks Twofish.

    Gravity is the result of the curvature of spacetime, which is caused by mass and energy being present.
  19. Oct 4, 2012 #18
    There are some close analogies between gravity and electromagnetic fields though when dealing with rotating masses which is probably where the OP is getting confused.


    Very fascinating stuff.
  20. Oct 5, 2012 #19
    Also, it's an interesting fact that if you write Einstein's equations in five dimensions, you get Maxwell's equations


    This is a deep and profound fact although people aren't sure exactly what it means.
  21. Oct 5, 2012 #20
    That's extremely interesting, it's as if the rotating mass somehow "brings out" whatever characteristics this fifth dimension has to produce the same results.

    I'd love to do research in GR if I didn't care about ever finding a job. :)
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