Gravity's mechanism

Discussion in 'Physics & Math' started by quantum_wave, Feb 4, 2013.

  1. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Cavendish Experiment
    http://images.google.com/search?hl=...c&biw=1024&bih=594&sei=QsMPUdS6KuPA0AG7_YDgDg

    Gravity is measured and quantified experimentally, and I don't know for sure that current theory explains the mechanics that are going on to cause the observable effect.

    I'm not making any statement about an explanation that is not generally excepted science, I am asking if those of you who are well informed in physics and math say that there is known mechanics explaining the effect or is that what the big issue is, i.e. the search for quantum gravity that has not yet given us a generally accepted answer? Is it true that we don't have the answer yet?
     
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  3. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    We have the math and the geometry that describes the effects of whatever causes gravity. The EFEs, if I have interpreted the popular media version that a layman can read properly, quantifies gravity enough to make highly accurate predictions about the motion of planets, moons, stars, etc. and makes predictions that there is a curvature of space that would have to be caused by the presence of matter and energy density. What I think is not yet agreed upon is the "how" matter and energy density warp space. Have I worded that right?

    And since I haven't gotten an answer to the question in the OP, and I have concluded that we don't have an answer yet, or at least one that can be called a consensus, what we have is generally accepted theory. In fact I think we have General Relativity Theory and we have Quantum Mechanics where the quantum gravity research and theoretical physics is going on. The goal of science would logically be to reconcile GR and QM. It might just be that the solution lies in the quantum gravity research, and we can be pretty certain that however it gets resolved at the quantum level, the EFEs will still be the best macro quantification, except for some possible tweaks based on the quantum solution.

    I really have researched a lot of different theories in the quantum realm and though I'm certainly not conversant in any of them, and I don't want to sound like I know more than I do by dropping buzz words from them, no one will dispute that there are many avenues of research going on. But would someone post what specific research looks promising at this point in time and maybe a link to a scholarly page or paper that I could read. Of course I don't expect to magically understand any real physics, but I do like to read to myself in the privacy of my room, since they have made the Internet available everywhere and to everyone these days.
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  5. AlphaNumeric Fully ionized Moderator

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    Title change to something more appropriate to the thread
     
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  7. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Who, besides me, thinks that the promising research is in the area of quantum gravity?

    I wouldn't want to sound like I think I understand the problematic issues of quantum gravity, but would anyone agree or disagree with my conclusions that we don't know of a mechanism that curves or warps space? And would anyone agree that though the EFEs have pretty well quantified the effect of gravity, the mechanics may not be some mechanism that curves or warps space but instead may be some other way of achieving action at a distance?
     
  8. Mazulu Banned Banned

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    Nobody knows for sure what the mechanism is. But there are some guesses.



    _____
    The theme for The Closer Season 7 dvd is love and loss.This season is also the final season of the series.[/QUOTE]
     
  9. Q-reeus Valued Senior Member

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    With so much reading you no doubt have come across gravity-as-a-field-theory approaches, like that of Yuri Baryshev (try Googling arXiv:0809.2323) for instance?
     
  10. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Yes
    I Googled it (here is the link: http://arxiv.org/abs/1209.1609) and will have to look at the PDF later, but thanks, I was looking for just that kind of a recommendation. Do you have an opinion on it, or any discussion? Is the "mechanism" going to be the gravitational field defined by a set of equations without any physical explanation except that "its the field" that causes gravity, and does it support the standard particle model and the search for the particle or boson that employs the field to achieve gravity? Is there experimentation or practicle experiments to test it?
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  11. Q-reeus Valued Senior Member

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    Good to hear.
    Yes but only as a layman. Best if you read through the intro and at least skim the contents to get a feel for where he's at before serious discussion, yes?
    He claims, with some justification imo, it offers a better hope for unifying gravity and QM owing to gravity being cast as a 'normal' field theory from the outset.
    Well not for now - his theory like a number of GR rivals reproduces the usual tests. As black holes do not exist in his approach, certain crucial tests along those lines would be decisive imo. NASA has hyped 'direct evidence' for BH's on various occasions for decades but if pressed will admit there is still no such direct evidence. Maddeningly it seems always to be 'a few years off'. Remotely confirming differences between an actual BH and an extremely dark grey object is a big ask. Anyway like I said, read the paper and you will be in a better position to make further comment.
     
  12. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    I've been putting off my response because my layman view is unimportant when it comes to the physics and math, and given that it is approriate for moderators in the hard science forums to try to fucus discussions here on hard science. I'll just say that the link is interesting, and I think it is extending soulutions to the EFEs to new territory closer to the quantum realm, but not getting there. The quantum gravity solution to the reconciliation of GR and QM still missing, and I think (I know the universe does not care what I think, it is just a normal thing to do) it will take a quantum solution.
     
  13. Q-reeus Valued Senior Member

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    2,605
    That approach actually rejects the EFE's which are a purely geometric based expression of how gravity works. Baryshev concentrates on the classical predictions of his theory but you will find he claims it is QM at heart. As a one man band tilting at an incumbent with legions of followers, he will probably die of old age having made little impact - right or wrong.
    Right well as an example of a purely quantum based approach, maybe you have already looked at the superfluid vacuum one as per Wikipedia article here:
    http://en.wikipedia.org/wiki/Superfluid_vacuum_theory
    I don't understand anywhere near enough of even the basic principles to sensibly comment about pros and cons. Just how many other currently viable theories are out there who knows. Good luck with continued studies!
     
  14. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Please do me a favor and post a link to Baryshev's paper. He did not author the paper I was looking at :shrug:. I must have screwed up when I Googled it after your earlier suggestion.
    I know that I am not going to be able to do justice by any comments on superfluid vacuum theory either except that in principle, as a layman, it looks like the presence of a background superfluid corresponds to what I refer to as an aether. In the sub forums where my aether ideas are tolerated, one might see some correlation to the layman descriptions of the superfluid, but I don't claim to be doing science and certainly wouldn't discuss my hobby of researching and forming opinions on "aether think" here.
     
  15. Q-reeus Valued Senior Member

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    Just checked your #7 and yeah, that link was not the right one! One you want is here: http://arxiv.org/abs/0809.2323
    It is so termed there in a number of places and by some authors linked to at bottom of that article.
    Quite some years ago I came across someone pushing the idea of a superfluid vacuum but it was definitely not the somewhat mainstreamish one in the Wiki article! Must go.:sleep:
     
  16. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Lol, so if we can say that the superfluid theory is somewhat "mainstreamish" we are saying a lot! I don't think that science enthusiasts, layman or professional, have any intention of revisiting the old aether theory of our granddaddy's day. There is no luminiferous aether that was associated with absloute space. I seems to me that any superfluid, if we can even refer to it as aether, would NOT be some kind of fixed extra fine particulate substance that physical objects like particles and planets push their way through. If there is a superfluid wouldn't it have to have certain characteristics that are consistent with what science says is possible, as opposed to the luminiferous ether theory that was superceded by spacetime?

    Is the Superfluid Vacuum Theory the quantum level competitor of spacetime, or is it a quantum realm extension of the EFE's?
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  17. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Be envious, I am heading out to the Florida State Fair, perfect weather, lol. But before I do, I wanted to add this excerpt from the 1600's to 1800's that states the concept of the fixed ether in absolute space for comparison:


    http://www.gutenberg.org/files/14725/14725-h/14725-h.htm

    TREATISE ON LIGHT

    By

    CHRISTIAAN HUYGENS

    Rendered into English

    By

    SILVANUS P. THOMPSON

    Flip on down to page #14 for a description of the luminiferous ether in Huygens' words:

    "Now in applying this kind of movement to that which produces Light there is nothing to hinder us from estimating the particles of the ether to be of a substance as nearly approaching to perfect hardness and possessing a springiness as prompt as we choose. It is not necessary to examine here the causes of this hardness, or of that springiness, the consideration of which would lead us too far from our subject. I will say, however, in passing that we may conceive that the particles of the ether, notwithstanding their smallness, are in turn composed of other parts and that their springiness consists in the very rapid movement of a subtle matter which penetrates them from every side and constrains their structure to assume such a disposition as to give to this fluid matter the most overt and easy passage possible."
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  18. Q-reeus Valued Senior Member

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    Agreed. But I am partial to a modified LET for reasons relating to presumed existence of gravitational waves.
    Sure but one prediction of SVT is failure of Lorentz invariance at very small scales and that implies afaik a kind of preferred frame.
    Not quite sure how to answer that. Best I can tell though the guiding thought in developing SVT is to make sure it matches GR at 'low energies' - meaning anything considerably below Planck energy scale. That implies fapp perfect match with all conceivable astrophysical data. Might be wrong on that.

    By contrast, Baryshev outright contends GR is foundationally flawed as a classical theory in the classical regime (e.g. gravity does or does not gravitate) and thence predicts departures that should be observable in the hopefully near future - as mentioned in earlier post. Layman's commentary here!
     
  19. arfa brane call me arf Valued Senior Member

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    --http://relativity.livingreviews.org/open?pubNo=lrr-2005-1&page=articlesu8.html
     
  20. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    The link in your post didn't work, but I think I have corrected it when I remove the two dashes before http.

    The quote in your post is a bit too technical for me but it is a good time for me to start getting a grip,

    Please Register or Log in to view the hidden image!

    . I hope someone will respond and shed some more light on the issues referred to.
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  21. arfa brane call me arf Valued Senior Member

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    One of the problems is that quantum mechanics assumes the existence of space and time; time is Newtonian and absolute in QM, or rather, QM is a theory that assumes a fixed background.
    Relativity says that space and time emerge from a four-dimensional structure, in which each dimension is equivalent (a symmetry), and the geometry is dynamical rather than fixed.

    That is, the emergence of time 'locally', so it appears to be one of the four equivalent 'real' dimensions, leaves three other dimensions which look spatial. We live in a universe which has a broken symmetry.
     
  22. Lakon Valued Senior Member

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    Hi all.

    This question isn't relevant to the recent posts here, but it certainly is to the thread title - Gravity's mechanism.

    Simply put, what is it ? If gravity is defined by spacetime curvature, what impels an object at rest to move along that curvature ? Newtons first law of motion says (I think) that an object at rest will remain at rest unless some other force acts on it. What force acts on an object to make it move along said curvature ? Thanks. And keep it simple please.
     
  23. Q-reeus Valued Senior Member

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    In geometric theory like GR an object moves along a 'straight line' in curved spacetime unless acted on by a (necessarily non-gravitational) force. Believe it or not, when standing perfectly still on terra firma, the ground you are standing on is accelerating you upwards at a constant acceleration of g - in GR-speak. It's in a flat spacetime theory like Newtonian gravity that the inverse is true - you are subject to a constant downward force of gravity and the ground furnishes an equal and opposite force; thus no net acceleration. Here's a nice YouTube vid that graphically illustrates the differing viewpoints:
    http://www.youtube.com/watch?annota...&feature=iv&src_vid=izKLw1V7YJ8&v=DdC0QN6f3G4

    If you want to know why matter curves spacetime in a GR type theory, sorry can't help you.
     

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