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Gravity & General Relativity

  1. Apr 13, 2009 #1
    Does Einstein's theory not disprove the idea that Gravity is a force? Perhaps I am completely misunderstanding the theory, but it seems to explicitly say that what we think of as gravity isn't really a force, but is a by-product of the curvature of space-time (the curvature being a symptom of the displacement caused by an object).

    Why, then, is it so important to unify Gravity with the other three forces? Is any work being done to expand them to include the effects of the curvature of space-time, or are there any other explanations being cooked up?

    Disclaimer: I am not a Physics students. I am beginning my studies in Mech. Engineering in the Fall. Currently, I'm learning all of the ideas and concepts of Physics that I possibly can, so tha I'll have the understanding of what the math is telling me by the time the math is given to me.
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  3. Apr 13, 2009 #2


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    Physical theories do not disprove anything. GR just uses a different mathematical concept to model gravity. Newton used a vector field, GR uses geodesics on curved manifolds. A short comparison of the two approaches:
  4. Apr 13, 2009 #3


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    In GR, gravity is the metric field. In quantum field theory, there is the electromagnetic field, and different fields corresponding to electrons, quarks etc. So everything is a field(s). Actually, there isn't a need to unify the gravitational field with the other fields, just to bring it into a consistent quantum theory. However, it is suspected by many that in order to bring it into a consistent theory, the gravitational field and the other fields must be unified, ie. seen as different aspects of a single and hitherto unknown stuff.
  5. Apr 14, 2009 #4
    It's believed that all the "forces" were once combined into a single entity...likely along with mass,time,space,energy etc....At the time of the big bang it's believed all were combined in a very unstable high energy state and rapidly inflated during a phase change towards the lower energy and more stable universe we live in....so understanding how to combine or unify via an overall single mathematical framework is believed to offer new insights..

    Also we know our understanding is incomplete...neither relativity nor quantum mechanics appears to be a final formulation...both a great tools, but have limits at singularities...

    By far the clearest and most intuitive explanation of all this is in Micho Kaku's HYPERSPACE Chapter 6, Einsteins Revenge, where is lays out a simple graphic analogous to an NxN matrix....it's a insightful visual representation on how matter,for example, and the nuclear force and relativity can be seen as part of a single mathematical framework....One part of the matrix includes all of relativity,an adjacent part Maxwell's formulations, and so on...
    The book is worthwhile for just that single representation...and is excellent overall...consider a used paperback from Amazon or other source of your choice....it's sort of like the trampoline analogy for gravity only far more inclusive...

    Relativity offers a more accurate and experimentally verified insight into how gravity behaves than Newton's ....Newton's approach works great in many applications....whether relativity is the best physics will ever be able to do is doubtful ....let's hope so...
    Last edited: Apr 14, 2009
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