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Origin or source of gravity?

  1. Oct 5, 2007 #1

    wolram

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    I guess most people know what it does but, AFAIK no one as yet knows the origin (other than the BB) of how gravity came to be or what it (is), why is the origin of gravity so elusive?
     
  2. jcsd
  3. Oct 5, 2007 #2
    Hello Wolram

    To begin with the BB is only a theory and not a fact.

    All info points to an infinite universe with endless time, space and matter. If this is correct than Gravity has no Origin and therfore would seem instant.
     
  4. Oct 6, 2007 #3
    Beacause it's right under our noses.
     
  5. Oct 6, 2007 #4
    I'll have you know that my mustache is not, in fact, the origin of gravity. :wink:
     
  6. Oct 6, 2007 #5

    DaveC426913

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    What is your mustache doing right under my nose?
     
  7. Oct 6, 2007 #6
    What info?
     
  8. Oct 6, 2007 #7

    russ_watters

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    Why should gravity be any different than anything else? We know no more or less about it than we do the other three forces.
     
  9. Oct 6, 2007 #8

    marcus

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    the most accurate theory of gravity, currently, represents it as the way matter affects geometry. I think this remains mysterious. How can matter affect geometry?

    and there is the puzzle about inertia. why should stuff follow geodesics? and why should a thing's inertia ("inertial mass") be the same as the ("gravitational mass") strength with which it bends geometry? this does seem elusive, to use your word.

    I've just been reading a 2001 book by Smolin called *Three Roads to Quantum Gravity* and I'm amazed at how good it is. Didn't expect such clarity and depth in a popular-written book. The last chapter has a prospective on how these very same problems might eventually (over next 10 years say) be addressed and solved. nice thing is that he doesnt just trivialize the problems---he takes a serious look into them. Great book.
     
    Last edited: Oct 6, 2007
  10. Oct 6, 2007 #9

    DaveC426913

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    I would say we know less about gravity than the other forces. For one, we know how the other forces are related.
     
  11. Oct 6, 2007 #10

    marcus

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    For sure! And there's an accurate picture of them within a static geometric framework (Euclidean or Lorentzian). You don't need General Relativity to describe electromagnetism.
     
  12. Oct 6, 2007 #11
    I guess I don't even understand if there is a consensus on whether gravity is a force or not. While apparently GR does not consider it a force, what about QG or string theory? If they postulate a graviton as a carrier, do they consider gravity a force, in opposition to GR?
     
  13. Oct 17, 2007 #12
    It may be that there are certain preconceived notions that have made there way into mainstream physics which hinder our ability to look for gravity. Our "best" "most accurate models are fundimentally flawed. We need to start back at the basics and let go of some of mainstream physics assumptions. The problem is that mainstream physics is about results and not understanding, effect and not cause. We have built pyramids on effect and left cause behind in order to make critical advancements in technology to win wars and stay competative with other countries. Our egos have exceded our understanding and we are too proud to go back and re-trace our steps.
     
  14. Oct 18, 2007 #13

    Chronos

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    I think it is fair to consider gravity as a force. Newton gave this considerable thought.
     
  15. Oct 18, 2007 #14

    pervect

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    The main problem with regarding gravity as "just a force", is that it cannot possibly explain gravitational time dilation.
     
  16. Oct 18, 2007 #15
    Could it be that force that 'pulls' space until it bend / curves
    So that both Einstein and Newton both was right?
    If so we have also achieved a deformation of space / time – right?
    What I mean, - it seems like matter effect space somehow, - for instance black holes of galaxies, but also even the elementary particles 'interacts' with space
    Fx.
    1.) http://en.wikipedia.org/wiki/Frame_dragging
    2.) http://en.wikipedia.org/wiki/Black_hole_electron
     
    Last edited: Oct 18, 2007
  17. Oct 19, 2007 #16

    Chronos

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    This line of reasoning is entirely consistent with GR.
     
  18. Oct 22, 2007 #17
    Hi Bjarne,

    I think it's fair to say that most, but certainly not all, physicists agree that gravity curves the geometry of space. Some say that "gravity acts on space" while others more conservatively say that "gravity acts on matter."

    Since the effects of gravity perfectly mimic a curvature of space, as far as I know there's no (known) way to be sure whether space is actually being curved, or instead whether instead the "force" of gravity just adheres to a geometrically-based algorithm. It's really a fascinating but (so far) quasi-philosophical question.

    There appears at this time to be no justifiable reason to doubt the predictions of GR, but it is very sane to question whether the geometry of space is actually capable of curvature. It's similar to asking whether there really can be more than three spatial dimensions. By definition it's impossible to know, but mathematical formulas are unbounded by physical reality, so we can imagine a higher-dimension spaciality in excrutiating detail. Are advanced theorists modeling reality or just building beautiful sandcastles in the air? Who knows?

    I think that in GR there is no functional distinction between a "force" and "pseudo-force". Einstein appears to personally have favored the notion that gravity is a "real" force, and therefore that, for example, the coriolis effect is also a "real force". But most GR specialists after Einstein seem to believe that both are mere "pseudo-forces."

    In another semantic sense, the definition of "reality" is what's undefinable here. Einstein said that reality is only a category that we choose to put some things into and not others. But we must categorize on a principled basis.

    Jon
     
  19. Oct 22, 2007 #18
    Hi Joinmtkisco
    Yes, - you are right, - what Einstein or Newton said and thought doesn’t take us very far.
    It’s important to keep in mind that space is a ‘connecting link’. It’s no doubt that space must somehow be involved in the ‘phenomena’ - Simply because if we should agree that space is nothing, how can NOTHING arrange exchange of gravity and pull down a stone to earth.

    But exactly how is space involve, - do space really curves, - or just gets ‘thinner’ - or what happens to space between? – Its a pretty good question.
    We know that space expands. Can space also become contracted?
    I think the biggest problem in physic in our time, is that we haven’t understood the connection and nature of space and matter and how these two are connected. This is already clearly emphasized of other related huge understanding problems we have, fx dark matter, dark energy black holes, or think of a simply daily event: the moon, on the one hand it is attracted of the earth, and the (tide) water on earth is attracted of the moon. The earths and the moon are reaching out of each other, we surly can agree. – But what is the role of the space between? - In this case it doesn’t make sense to claim that the ‘contact’ between the moon and the tide is caused of “curvature” of space. How is space ‘linked’ to matter is probably a bit more complex and will certainly be a big question, - in this century? (Sorry for the bad English)
    Bjarne
     
  20. Oct 23, 2007 #19

    Chronos

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    Perspective is a key issue. To any 'fixed' observer, the metric of spacetime appears to be curved. Is that 'reality'? Hard to say. Devising a non-fixed observer is difficult.
     
  21. Oct 23, 2007 #20

    Jorrie

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    Wouldn't a rocket provide a 'real' force on its payload, even in a GR environment? Isn't that different to the 'pseudo-force' of gravity?
     
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