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Gravitons or Warped Space-Time?

  1. I believe that gravitation can be quantized and unified with the other fundamental forces.

    50.0%
  2. I do not believe that gravitation can be quantized and I adhere to General Relativity.

    33.3%
  3. I do not agree with either ideology as stated.

    16.7%
  1. Jun 18, 2008 #1
    *Please read the thread before you vote in the poll!

    Disclaimer: I am not advocating a fraudulent theory, I am presenting original evidence and logic (detailing the contradictions in quantized gravity) both of which are certainly open for debate.

    Gravitation

    In classical mechanics, the charge of the gravitational field is equivalent to the translational inertia, such that all objects experience the same acceleration regardless of their mass. This happily corresponds to the notion of non-accelerating motion (straight trajectories in space and time in agreement with the law of inertia) along geodesics (this even applies to massless particles such as photons) in curved space-time that defines the theory of general relativity. However, because general relativity explains the illusion of gravity as well as effects not covered by classical mechanics, such as Einstein rings and anomalous precessions among others, it has effectively replaced the latter as an authoritative construct. With the recent attempts to assimilate gravitation into the quantum mechanical formulation that is used to describe non-gravitational phenomena, gravitons - which represent coherent radiation from gravitational oscillators - are used to impart the force of attraction between masses.

    Fields and Charge

    However, if the carrier particles for gravity were considered to be energetic fluctuations of a simple classical gravitational field, the gravitons would be drawn closer to each other and to the mass of origin because of their own mass-energy equivalence and be selectively absorbed by the greatest masses, preventing gravity for very light objects. Additionally, every graviton would require additional gravitons to convey the influence of its own mass-energy, encouraging a divergent net of recursive bosonic emissions where interactions become sources and mass itself ceases to be conserved. Additionally, black holes (and other heavy objects) would be unable to transmit their own force of attraction because they would necessarily attract all of the gravitational bosons they have emitted.

    Space and Time

    This argument is a particularly strong refutation of the classical gravitational field as transmitted by bosons, so perhaps gravitons are the quantized curving factors of space-time. But space-time warping is a very local effect...rather than affecting each other directly by Newtonian 'action at a distance', masses warp space-time, which then acts on local masses without using intermediate masses: this way the transmission of gravitational potential is not inherently energized or massive and thus prone to an infinite regression of gravitational attractions among carrier particles. On the other hand, if gravitons are not energetic, then they can hardly account for the (yet-to-be-observed) potential radiated by pairs of orbiting neutron stars or colliding quasars. Also, space-time is not a field as it has no direction and no magnitude (it is rather the fields themselves, or the quantum mechanical Hamiltonians, that are defined with and are dependent on the linearly independent variables space and time); it is a spatio-temporal metric that does not exert forces and cannot be excited or transfer a de Broglie momentum because space-time information also does not collide or even interact with matter and matter-field resonances, thus the concept of motion along distorted geodesics seems highly unlikely to be replaced by bosonic momentum transfers made out of space and time. The Schwarzschild radius is derived from the dissipation of kinetic energy by gravitational potential independently of either de Broglie frequency, Lorentz factor, or any other terms that would imply momentum/energy interactions, because it is dependent on curved space-time not inertial scattering and thus is represented by the escape velocity without regard to the momentum because 'gravity' impulses never actually act on it. Gravitons, if they do exist, supposedly must be massless anyway owing to the infinite range of the gravitational interaction, and would rarely couple with matter, making them quite difficult to detect (this is due to the weakness of the force itself which might further implicate a rarity of emissions).

    Possible Tests

    A relatively easy test is one for linear dispersion for particles with different momentums during microlensing; this is useful for tests of starlight because the escape velocity is the same for all colors, and the effects of the interaction would be observable over large distances. If gravity were a force chromatic aberration would occur in gravitational lenses due to the momentum differences in photon color (over a standard interval of time, a field-induced impulse will exert a change in momentum that may cause the trajectory of a lower momentum photon to be affected in compton-like conservation differently than that of a higher momentum photon for equal unmassless photon rest masses acting as gravitational charge). If this does not occur then bent light must be traveling along straight lines in curved space-time. Another test would involve selective absorption on the event horizon of a black hole (or different event horizons for different frequencies of light). If gravity was acting on mass as a gravitational charge, the event horizon of a black hole would cause a gravitational redshift (of light) to beyond the 0 frequency and into the negative range at different radii for different photons, because the force would impart a constant impulse to the (equal) effective photon masses but the displacement into the negative range would occur more quickly for photons with an already low momentum. This should not occur if light is effectively massless and unaffected by bosonic momentum transfer, and so all frequencies would be affected equally at the same radius because they are traveling as null geodesics along distorted space-time intervals (this would also explain why light emitted by electromagnetic processes that are just inside the edge of a black hole don't have enough momentum to escape the black hole from the vicinity of the event horizon).

    Conclusion

    Since gravitons supposedly transmit the 'changes' in space-time caused by fluctuating matter, and because practically every other form of energy is quantized, when gravitons are released after conversion (or when massive particles are converted to pure energy) the transmitted energy that reflects the transition of a quantity of mass is also representing a discretely quantized transformation. But what of Bell's Inequalities? If a nuclear reaction releases an equal and quantized pulse of gravitational energy (and massless light), then this energetic resonance should be subject to the same principle of non-locality (by entanglement) that the other quantized energetic agents that originally contained it are, disputing the axioms that ultimately manifest in the space-time continuum (in fact discrete quantizations of space and time suggest that these metrics would be anything but continuous), right? What I find most interesting is that though the relative spans of space and time are independently dependent on one's relative velocity, this velocity is measured only with respect to space and time, the manipulation of which allow Einstein to preserve the speed of light in vacuo.
     
  2. jcsd
  3. Jun 19, 2008 #2

    Mentz114

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    Shouldn't there be a 'Don't know' category ?

    M
     
  4. Jun 19, 2008 #3

    Garth

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    Or a 'Both' category?
     
  5. Jun 19, 2008 #4

    Haelfix

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    It would help if the OP actually made the discussion underneath the poll accurate.
     
  6. Jun 19, 2008 #5
    The poll is geared towards people who have opinions.

    That is a contradiction.

    What about it is inaccurate?
     
  7. Jun 19, 2008 #6
    Shadowpuppet The problem I see is not so much “inaccuracy” but the poll choices do not jive with two different questions being asked.
    The poll choice is simple “I believe that gravitation can be quantized” Yes or NO

    That does not address the given question “Do you believe in gravitons?”
    Nor does it differentiate a choice between any “ideology”

    Note that GR does not dispute that Mass or Energy can be quantized.
    Therefore the amount of GR warping imposed by a quantized incremental increase of Mass or Energy would be a quantized increase in that warping. Thus it does not follow that adrhereing to GR requires saying NO to quantized gravitation as implied in your second choice.

    Also, the poll implies a choice between ideologies with clearing stating them.
    I would have guessed 1)Classical 2)QM/Non-Local/Standard Model 3) GR Warped Space
    Already one to many for the options and I would have wanted to add 4)LR Local Realism; but that it does not fit within any of the other three is my opinion.

    And the OP rather than help clear up any of that confusion only makes it worse by introduce a different interpretation of what the “ideology” choices addressing gravitons might be. What do you mean by ideology options ? Are they:
    Gravitation
    Fields and Charge
    Space and Time

    I consider myself very fixed in my opinions of how gravity and physics works and feel I understand opinions that differ with mine. But like Haelfix and others I am completely at a loss as to what anyones vote in this poll might really mean.
     
  8. Jun 19, 2008 #7

    JesseM

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    Measurable gravitons would probably only be present when gravitational oscillators produce gravitational waves, in the case of the "force of attraction between masses" one might use "virtual gravitons" in one's calculations, just like virtual photons are used to explain attraction/repulsion between charged particles in quantum electrodynamics, but this could be seen as just a sort of bookkeeping device, with no actual measured force-carrying particles present. The last section of this online FAQ on virtual particles has a helpful discussion:
    Gravitons would be self-interacting which is part of what makes coming up with a quantum theory of gravitation difficult (although my understanding is that string theory has shown that you can actually derive general relativity from a quantum theory of stringy gravitons), but with no quantitative analysis whatsoever, you have no basis for your claim that the self-interaction would have the effect of "preventing gravity for very light objects" or violate conservation of mass/energy.
    Because the force-carrying particles in quantum field theories are only "virtual" rather than real and measurable, it's not wise to generalize one's intuitions about how real particles behave to these virtual particles. See How does the gravity get out of the black hole? from the Usenet Physics FAQ, which says:
    There is no "action at a distance" in quantum field theories like quantum electrodynamics either, at least not of a measurable kind; a measurement of the behavior of a particle at one point in spacetime won't tell you anything about events outside the past light cone of that point.
    Again, this argument about the "infinite regression" somehow leading to predictions which disagree with general relativity is worthless without any quantitative analysis. As I said, I believe in string theory it is possible to reproduce the predictions of general relativity using a theory of self-interacting stringy gravitons; somehow or another, the math works out.
    In physics "field" does not exclusively mean a vector field; GR deals with tensor fields in spacetime, and the fundamental equations of GR are known as the "Einstein field equations".
    This sounds like pure technobabble, and given the handwaveyness of your other comments I doubt you have any well-defined technical definition of what it would mean for "space-time information" to "collide or even interact" with matter of "matter-field resonances".
    Would it? Can you show detailed quantitative calculations that indicate the magnitude of this effect, or point to some other published paper which makes such a calculation?
    Again, calculations?
    The violation of Bell inequalities simply shows that a certain class of hidden-variables theories going by the name "local realism" can be ruled out. It doesn't show that you can ever have a measurably nonlocal effect--in fact it's provably true that you can't according to the accepted rules of quantum field theory, since as I said no information that you obtain via a measurement of a quantum system at one point in spacetime can ever tell you anything about events outside the past light cone of that point.
    What does "measured only with respect to space and time" even mean? In relativity each inertial observer measures the speed of light relative to physical rulers and clocks at rest relative to themselves, spacetime is not an entity with its own rest frame so it's meaningless to talk about measuring the speed of any object relative to spacetime.
     
  9. Jun 19, 2008 #8
    I did address your concern:

    What I am disputing is bosonic momentum transfer in gravitational interactions, which is incompatible with General Relativity. In General Relativity space-time is also not discretely quantized and is not even continuously variable over very small distances (according to Einstein's local equivalence principle; this is the domain of the graviton, unless there is a massive but microscopic black hole, the physics of which I could hardly imagine). The mutual exclusivity of the poll is mainly dependent on this discrepancy, but if you still do not agree with either of the first two choices, then you are free to select the third (I am also not familiar with LR Local Realism; Classical Mechanics fails to account for a lot of gravitational effects, and I consider it to be obsolete for this reason among many others). The headings of my own synopsis describe the introduction (or subject content), the failures of quantifying Classical Mechanics, and the failures of quantifying General Relativity, respectively; they are not meant to accommodate alternate perspectives nor discourage the freedoms of the poll (as I said in the disclaimer, I am biased in favor of option two, and I will vote accordingly if that makes this more comprehensible). Naturally, if you are fixed in your opinions then you will not account for anomalous information, and if you encourage incompatible opinions then you can hardly support your own with authoritative exclusivity. Personally, I am just curious to see if these issues can or have been addressed at all in a unified physics, and my own incentive is derived from the unresolved aspects of a series of comprehensive debates with sincere advocates of quantum gravity.
     
  10. Jun 19, 2008 #9

    Fredrik

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    Just a few thoughts...

    "We believe in gravitons": To me this would mean that we believe that a quantum field theory of gravity makes some sense even though it isn't renormalizable (which considerably limits its predictive power).

    "We believe gravity can be quantized": I would interpret this as meaning "We believe that a theory of gravity can be formulated in the framework of quantum mechanics".

    "We don't believe gravity can be quantized": This is just the negation of the previous statement, so it certainly doesn't mean "I adhere to GR". It could also mean that we don't believe QM is sufficient. (Also, adhering to GR would be really dumb. GR includes a mathematical representation of matter, and matter can't be described by classical mechanics, so there's no way GR can be the final theory of gravitation).

    I think I believe in gravitons. I think gravity can probably be quantized, but I wouldn't be shocked if it can't (i.e if QM needs to be replaced too). I certainly don't adhere to GR.
     
  11. Jun 19, 2008 #10
    I don't know. I believe in Gravity obviously, but to give an explination on what Gravity actually is, that I can't comment on. Do I believe that Gravity exists on the quantum scale? Yes. Do I believe it's a Gravaton? I don't know. Sometimes I picture gravity as actually being the fabric of space it's self and not an actual entity on it's own. But time will tell, I just hope I live long enough...
     
  12. Jun 19, 2008 #11
    Some of the newer quantum gravity theories like CDT do not require carrier particles like gravitons, so Garth is right that there are not enough options in the poll. I would like to vote " I believe gravity can be quantisized but not necessarily require gravitons". :tongue:
     
  13. Jun 19, 2008 #12

    Haelfix

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    Spuppet, most of the discussion in the original post is erroneous. There are so many errors and misunderstandings its hard to even begin to dissect it.

    The quantum field theory of gravitation is completely mathematically isomorphic to general relativity at tree level! There is no sense in which any of the bizarre distinctions you seem to draw are correct in the slightest.

    The answer to the poll question is 'both' classically.
     
  14. Jun 19, 2008 #13
    If no actual force transmitters are present, then presently no actual force is being transmitted. Virtual particles are real, but they only exist for a temporal duration that is dictated by their energy and the Heisenberg Uncertainty relation. It is clear that energy is not being transmitted, because gravitons do not travel through space and time, they are space and time, and as such have no energy to transmit and are thus not prone to mass-energy equivalence and bosonic carrier-interactions. Do you agree that gravitational potential (even when it is radiated) is considered an illusion in the context of space-time geometry? To say that I have no claim for asserting mass-energy equivalence for energetic resonances when this has been demonstrated and the existence of non-interacting (or even interacting) energy-transmitting gravitons has not is scarcely an empirical argument. Also your assertion that virtual particles transmit the non-oscillating component of acceleration is negated in both FAQs you tried to use as proof (both FAQs never answered a single relevant question and other than admitting that quantized gravity is inherently inconsistent, they never made a single definite point concerning the transmission of gravitation and made the entire topic seem much more ambiguous and elusive than it really is).

    You may want to rethink your virtual particle theory.

    Though I did mention this in the context of Newtonian Mechanics, action-at-a-distance may occur between two entangled states (thank you for bringing this up), but that General Relativity does not use intermediate particles to transmit gravitation is still true (which was my point, so I fail to see yours). In String Theory the exact opposite is also probable...there is nothing specific in String Theory that makes empirical reality seem necessarily favored over its rational alternatives more than it seems using a random collection of noises spoken in the English Language. Also, if you are going to defend your theories with math, I prefer equations to sentences. Tensor fields (like the set of Stress-Energy-Momentum Tensors) are mathematical structures used to describe the spatially varying characteristics of real objects while preserving the invariance of these physical quantities across many different frames of reference; they are not real fields and they do not provide a physical mechanism for bosonic emissions.

    If you don't understand what the words 'collision' or 'matter' means, then you will certainly have trouble defending a theory of gravitons.

    You are certainly very thirsty for calculation for someone who offers none of his own; I might do this for someone who already understands what I am talking about but if you do not understand the concepts themselves I doubt that you will follow the math.

    If you cannot describe the entire state of a local system locally, then information does exist which must be transferred to the system. General Relativity is fully described by local quantities and does not allow for non-local interactions and this is not true of quantum mechanics, which is what I said, so what is your point?

    Why are you attacking me? I said that it was interesting, and I mean because the speed of light is not affected by the laws of physics thought thae varibales out of which it is constructed and measured are. In case you never took Calculus I, velocity is the first derivative of length with respect to time. Are you scared to address the real issues or is it just your dislike for me that blinds you from which assertions I am actually making?
     
    Last edited: Jun 19, 2008
  15. Jun 19, 2008 #14
    Here I mean with regard to the theory of gravitation, not the theory of everything.

    I concur. Gravity is one manifestation of the orientation of the fabric of space.

    I apologize for the inconvenience, but I am not familiar with even a single quantum theory that does not rely on discrete carrier particles. Would you care to elaborate?

    I refuse to accept your argument unless you defend even a single assertion that you make...since you haven't dissected it I will assume that you have not understood it...
     
  16. Jun 19, 2008 #15

    DaveC426913

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    I am confident that both theories will usable to describe the same physics. It's kind of like asking if you believe photons are particles or waves.

    So, IMO, the answer to the poll is the one that is not listed: both.
     
  17. Jun 19, 2008 #16
    I was referring to to the Causal Dynamical Triangulations thoery which is being discussed in the Cosmology forum. A introductory paper is here http://arxiv.org/PS_cache/gr-qc/pdf/0607/0607013v1.pdf and a nice introductory article from Scientific American is here http://www.scribd.com/doc/3366486/SelfOrganizing-Quantum-Universe-SCIAM-June-08

    I only posted the links because you asked and because they were already given in the Cosmology forum.
     
  18. Jun 19, 2008 #17
    I would be hesitant to accept that, especially until gravitons are actually discovered...at one point people were certain that the luminiferous æther existed and could describe the same physics as the other models, but this is not so...

    Thanks, I'll look into it.
     
  19. Jun 19, 2008 #18

    Haelfix

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  20. Jun 19, 2008 #19

    JesseM

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    Please define what you mean by "real" and "actual". If you look at section 3 of this theoretical physics FAQ, the author makes the argument that according to at least one reasonable definition of "real", virtual particles should not be considered physically real, but are simply terms in a certain mathematical calculation similar to the individual terms in a Taylor series. In particular, in section 3c he writes:
    This is another handwavey argument based on english-language definitions rather than any technical considerations. In attempts to find quantum theories of gravity involving gravitons, I believe the gravitons are treated as moving in some sort of background spacetime, though I could be missing some subtleties here.
    What are you even talking about? When did I say there is no "mass-energy equivalence for energetic resonances"? Is "energetic resonance" a technical term used in quantum field theory for interactions mediated by virtual force-carrying particles (if so, please provide a reference), or are you just inventing your own technobabble again? I did say that gravitons would be self-interacting (i.e. they themselves would be a source of gravity), if that's what you're trying to get at here. But claims that this would "prevent gravity for very light objects" or "encourage a divergent net of recursive bosonic emissions where interactions become sources and mass itself ceases to be conserved" are nothing but pure fantasy unless you have some actual calculations to back them up (or can refer to some peer-reviewed literature which makes such claims).
    But I'm not trying to make a positive argument for the existence of gravitons, I'm just pointing out that your arguments against them are uninformed and handwavey.
    It's "negated"? Where, exactly? The FAQs are not completely explicit about the fact that real photons are only associated with electromagnetic waves (which only come about due to oscillating charges) while virtual photons are associated with the transmission of the electromagnetic force even in the absence of waves, but this is correct nevertheless, and the virtual particle FAQ does at least strongly imply it in the opening section:
    Where do they say it's "inherently inconsistent"? The sections you quote only say that it is uncertain whether a theory of quantum gravity would include the idea of forces mediated by virtual gravitons or not (although they also point out it's pretty likely that quantum gravity would say the energy levels of gravitational waves are quantized, which suggests that the theory must at least include real gravitons of some kind). I have never claimed that a quantum gravity theory will say the force of gravity is mediated by gravitons--I'm just saying that your arguments which purport to prove there is something inherently impossible about the idea are, again, uniformed and so handwavey as to be "not even wrong".
     
  21. Jun 19, 2008 #20

    JesseM

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    (continued from previous post)

    No, there is absolutely no measurable action-at-a-distance in quantum theory. There are correlations which are incompatible with local realism, but these correlations can never be used to transmit information FTL, and whether one imagines there is some "hidden" nonlocality to explain them depends on your interpretation of QM (the many-worlds interpretation popular among quantum physicists purports to explain these correlations without giving up locality, by getting rid of the 'realism' assumption that each measurement has a unique outcome--see my post #8 on this thread for some references).
    Of course it's true, just as it's true that classical electromagnetism does not use intermediate particles to transmit the electromagnetic force. But since general relativity is manifestly incompatible with quantum physics, it is generally not believed to be the final theory of gravity, and it's thought that its predictions will become significantly wrong at the Planck scale; to find the correct predictions we'll need a theory of quantum gravity, which may or may not include the idea of virtual gravitons mediating the gravitational force.
    Whether string theory turns out to be on the right track or not (and quite a lot of physicists think there's a good chance of that) is irrelevant to my point, which is just that one can construct theories in which the gravitational force is mediated by gravitons, which still manage to reproduce the same predictions as general relativity and don't create the sort of problems that you imagine in your handwavey arguments.
    They aren't my theories, since I am not trying to make any original arguments, just summarize results found by professional physicists who have done the math. If you want references to the literature where the mathematical derivation of general relativity from string theory can be found, I'm sure someone could direct you to them. In contrast, your own arguments about the impossibility of gravitons seem to be original to you rather than just a summary of conclusions stated by professional physicists, so the burden is on you to show that you have some actual rigorous basis for them.
    Tensor fields describe real physical quantities like spacetime curvature at each point in a given coordinate system, so it's unclear why you think they are less "real" than fields describing quantities like electromagnetic force vectors at each point. Again, it would help if you would define the word "real", and then explain rigorously how showing the tensor field of GR is not "real" in whatever sense you choose proves the conclusion that it would be impossible to reproduce GR's predictions using a quantum field in a theory of quantum gravity.
    I wasn't asking what "collision" or "matter" mean in the normal well-understood contexts, I was asking what it would mean for matter to collide with "space-time information", which sounds like gibberish to me. Maybe you were just looking for a technobabblish way of saying that in general relativity, gravity is spacetime curvature which determines how matter moves on geodesics, which is totally different from the quantum picture of forces involving interactions (not really 'collisions' in the classical sense) between real particles and virtual force-carrying particles; I agree they are totally different, but this doesn't rule out the possibility that two such dissimilar theories could lead to the same predictions. It is also true that classical electromagnetism is quite different from quantum electrodynamics, since classical EM involves a continuous field assigning a force vector to every point in space, not particle-particle interactions or "collisions". Nevertheless quantum electrodynamics reproduces classical EM's predictions in the limit, just as it is hoped that a quantum theory of gravity (possibly involving virtual gravitons) would reproduce GR's predictions in the large-scale limit.
    Because, once again, I am not making original arguments but summarizing the views of mainstream physicists. Since you are making original arguments, you should provide calculations proving the impossibility of reproducing GR's predictions in a quantum field theory involving gravitons (such as string theory), which is certainly not a widely-accepted conclusion among physicists. And in any case, if you've read the IMPORTANT! Read before posting thread you'll know that this isn't the correct forum to offer original results which contradict mainstream ideas (for that you should head over to the Independent Research forum).

    Again, although QM rules out local realism, whether this rules out all forms of locality is a matter of interpretation. What's more, if this is meant as a definitive argument against finding a quantum theory which reproduces the predictions of GR, then the same argument could also be used to say that no quantum theory could reproduce the predictions of classical electromagnetism, which is just as local as GR is; and yet we already know it can, because we have the theory of quantum electrodynamics.
    Yes, and in relativity length only has meaning when measured relative to some particular physical ruler, and time only has meaning when measured relative to some particular physical clock. I thought you were saying that we could measure the velocity of light "relative to spacetime" rather than relative to the rulers and clocks of specific inertial observers, which would be wrong; if I misunderstood you here, I apologize.
     
    Last edited: Jun 19, 2008
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