Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Unification of Gravity versus General Relativity - The Ubiquity of Contradiction

  1. Jun 30, 2009 #1
    Unification of Gravity versus General Relativity -- The Ubiquity of Contradiction

    Is it just me or is something smelling rotten about unifying gravity with the fundamental forces? Didn't science unanimously agree that Einstein's "Theory of Relativity" correctly explained gravity as not a force but curvature of space-time? In fact, I thought that GR was promoted from a theory a law of nature.

    In consideration of GR I think it is strange to persist about the existence of gravitons and attempt to unify a pseudo-force like gravity with anything. My humble opinion is that it is bad science to contradict existing LAWS Nature like GR and then construct billion dollar machines to understand why the contradiction doesn't unify nicely with others.

    What if the graviton appears at LHC, will GR be demoted from a law of Nature back to a theory? And at what point does science advance forward and stop stumbling backward over gravity? Finally, experiment did not grant GR acceptance as a law of nature, apparently this requires faith, should GR be added to the Holy Bible as a deified grace of God?
     
    Last edited: Jun 30, 2009
  2. jcsd
  3. Jun 30, 2009 #2

    George Jones

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    1) The LHC is not going to used to look for gravitons.

    2) I not sure what the difference between a law and a theory is.

    3) No scientific theory is ever proved.

    It is true that we have no experimental evidence that contradicts GR in any accepted way, but this does not mean that theoretical phyiscs should grind to a halt.
     
  4. Jun 30, 2009 #3
    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    Good thing you were humble or we could make fun of such a statement.

    Name me one theory that has been right from the start: not Ptolmy, Not Copernicus, not Alchemy, not Newton, Einstein is closest, but quantum mechanics begs to differ, etc,etc...don't be fooled into thinking we understand much of anything....
     
  5. Jun 30, 2009 #4
    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    True it is not builit specifically to look for them but there are experiments designed to detect them should they occur.

    In science, I understood it to mean set assumptions or principles that try to explain a natural phenonmena, like gravity of which one attempts to validate with proof. A law is like the rule book for nature and hard ever violated by nature.

    Then why is GR used everyday in GPS and it can be shown that curved space refracts light?

    I agree but why was GR accepted if no one wants to live by it?
     
  6. Jun 30, 2009 #5
    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    Ok, if GR is untrue the gravity is not result of curved space-time although no one can deny it curves space-time. Before disregarding a theory, or law like GR, I thought, one must have verifiable proof or a more correct alternate. I thought this is how scientific process worked.

    It get's confusing to me at times because there are too many schools of thought. And a few I notice beleive in both GR and graviton.

    Einstein, unlike Ptolmy; Copernicus; Alchemy; Newton, was able to verify his findings down to decimal points of with verified and quantified predictions. None of the others did that. Although newton explained almost all the known orbits of planets, he did not accurately predict an unknown and unseen phenomena like bending of light by gravity.

    [A sidebar about the Newton and Einstein]
    Although great men of science, I think both newton and einstein are given too much credit. Their accomplishments did required leaps of faith, arcane insight (especially Einstein) and prodigious amount of effort, but essentially all they did was connect the dotted lines. The true genius, and hero to science, is Max Planck and his work on black body radiation.
     
    Last edited: Jun 30, 2009
  7. Jun 30, 2009 #6

    Dale

    Staff: Mentor

    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    Hi earamsey,

    George is correct, this is a general point about science. Theories are not proven, they are verified or falsified. If an experimental result agrees with a theory's prediction then the experiment is said to verify the theory, and it gives evidence that the theory is good. However, it does not prove the theory for the simple fact that there can be more than one theory that predict the same result for any given experiment and the experiment cannot distinguish between two such theories.

    Gravitational time dilation and gravitational lensing are experimentally verified predictions that any correct theory of gravity will have to make, but that does not constitute a proof of any theory that makes those predictions. Do you see the difference?
     
  8. Jun 30, 2009 #7

    Mentz114

    User Avatar
    Gold Member

    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    I disagree completely and even find this offensive. Connect the dots ? You are are arrogant and ignorant, sir. I find your opinions worthless.
     
  9. Jun 30, 2009 #8

    DaveC426913

    User Avatar
    Gold Member

    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    A theory attempts to model behaviour, giving some insight. A law simply describes it.

    Newton's Law of Gravity simply states the observed relationship between mass, distance and the forces experienced: F = G* (m1*m2/r^2).

    Einstein's theory attempts to model how this relationship works.
     
  10. Jun 30, 2009 #9
    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    GR and gravitons are no more incompatible than Maxwell's equations and photons. Just as photons are what you get when you quantize propagating wave modes of the EM field, gravitons are what you get when you quantize propagating wave modes of spacetime.
     
  11. Jul 1, 2009 #10

    Fredrik

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    It wouldn't smell bad at all if you knew anything about these theories, or at least what a theory is.

    No. Scientists agree that it makes much better predictions about the results of experiments than previous theories, but that's it.

    There's no such thing as a promotion from a theory to a law.

    I disagree with DaveC's answer. A law is just a small part of a theory that can be expressed succinctly in the form of a sentence or an equation. For example, Newton's law of gravity is a small part of Newton's theory of gravity.

    This is misleading in my opinion. There are no experiments that contradict GR's predictions about gravity, but there are of course many thousands of experiments that prove that matter doesn't behave the way that GR says it behaves.

    Earamsey, this is why GR needs to be "unified" with QM. We know that the way that GR describes matter isn't just wrong, but extremely wrong. The reason why the predictions of GR can still agree with experiments to a ridiculous degree of accuracy is that the effect of the microscopic details on anything we can measure (in an experiment where GR is distinguishable from Newtonian gravity) is many orders of magnitude smaller than the measurement's margin of error.

    This doesn't prove GR correct. It only proves that GR makes better predictions than Newton's theory about the results of these specific experiments.

    You can never prove a theory to be correct. Experiments can only tell us how accurate the theory's predictions are. Even if the predictions are within the margin of error, we still don't know if the prediction would pass the test of a better measurement, or even if it would pass the same test tomorrow.

    There's a theory involving gravitons that makes essentially the same predictions as GR.
     
  12. Jul 1, 2009 #11

    DaveC426913

    User Avatar
    Gold Member

    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    But that only defines a law in terms of a theory. In fact, a law stands alone, i.e. the law can exist whether or not there is any theory to model it.
     
  13. Jul 1, 2009 #12

    Fredrik

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    Take Newton's law of gravity for example. It doesn't "stand alone" in any way. It just tells us what the force is, and this is useless information without the rest of the theory. In particular we need the relationship between force and acceleration. And even that relationship doesn't make sense without the assumption that space can be mathematically represented by [itex]\mathbb R^3[/itex] and time by [itex]\mathbb R[/itex]. All of these assumptions are part of the theory.
     
  14. Jul 1, 2009 #13
    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    do the gravitons cause the warping of space by moving between our visible dimensions and the extra dimensions? - sort of like gravitons dragging the extra dimensions into and out of our visible dimensions?
     
    Last edited: Jul 1, 2009
  15. Jul 1, 2009 #14

    Fredrik

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    I don't know what that even means, but since it's possible to describe gravity in terms of gravitons without introducing any extra dimensions, I have to say that the answer is "no".
     
  16. Jul 2, 2009 #15
    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    suppose the extra dimensions exist and can decompact and then enter the visible dimensions as result of graviton movement causing a warping of the visible dimensions?
     
  17. Jul 2, 2009 #16

    Fredrik

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    That's a lot of supposing, and I don't know what it would mean for one dimension to enter another.
     
  18. Jul 2, 2009 #17

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    This sounds a lot like word salad.

    From reading your posts, I think there are two things that you are probably unaware of. One is that PF is not a place to develop personal theories (except for the IR section), and the other is that theoretical physics is not about somehow putting a list of scientific-sounding words in the right order. It's about making a testable mathematical description of nature.

    That's the direction you need to be going in.
     
  19. Jul 2, 2009 #18

    Haelfix

    User Avatar
    Science Advisor

    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    The distinction between a law and a theory is semantics, some people think of a law as an axiom, but the two are interchangeable in physics (from a different set of axioms you can derive a theory statement that is in fact the original law or axiom under consideration). The only thing that we care about is whether such and such a thing is empirically testable, and at that level the distinction drops out as its simply circular.

    Amusingly, the lingo kind of stayed in the parlance, even when said laws were demonstrated to be incorrect (for instance Newtons law of gravitation is quite incorrect when applied to certain physical regimes, and GR in a sense is more fundamental).
     
  20. Jul 2, 2009 #19

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    I side with George, theories are either affirmed or unsupported - never proven [and rarely disproven]. It is perfectly acceptable to adjust theory to fit new observational evidence. That is commonly referred to as science.
     
  21. Jul 2, 2009 #20

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    Re: Unification of Gravity versus General Relativity -- The Ubiquity of Contradictio

    Not at the LHC. (And if you come back with a statement about "KK gravitons", I would retort with the fact that these are very different objects to ordinary gravitons.

    I don't think that's very nice, although I too would have preferred if earamsey got his facts straight before accusing people of doing it all wrong.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Unification of Gravity versus General Relativity - The Ubiquity of Contradiction
Loading...