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General Relativity Is At Least 99.95% Right 223

ultracool writes to mention a ScienceDaily piece on compelling proof of general relativity. A team at the University of Manchester have used three years' worth of data on a pair of pulsars as a litmus test, against which they've benchmarked Einstein's theory. From the article: "Though all the independent tests available in the double pulsar system agree with Einstein's theory, the one that gives the most precise result is the time delay, known as the Shapiro Delay, which the signals suffer as they pass through the curved space-time surrounding the two neutron stars. It is close to 90 millionths of a second and the ratio of the observed and predicted values is 1.0001 +/- 0.0005 - a precision of 0.05%. A number of other relativistic effects predicted by Einstein can also be observed. 'We see that, due to its mass, the fabric of space-time around a pulsar is curved. We also see that the pulsar clock runs slower when it is deeper in the gravitational field of its massive companion, an effect known as "time dilation."'"
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General Relativity Is At Least 99.95% Right

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  • by EmbeddedJanitor ( 597831 ) on Saturday September 16, 2006 @06:09AM (#16119544)
    As parent says, a proof is right or wrong.

    However, General Relativity is not a proof, but a model. The various models that give us a way of understannding the world are only that: models, not laws per se.

    When Newton explained gravity, he did not say that he was right. Indeed he said that the model he proposed was the best he could come up with given the limitations of his apparatus. He even predicted that his model would be superceded. And, for most people of today, the physical objects that they interact with can be adequately understood with Newtonian physics.

    Einstein even said "As far as the laws of mathematics refer to reality, they are not certain; as far as they are certain, they do not refer to reality.". Just like Newton's models had limits and fell apart at some point, likely the same will happen to General Relativity when we're one day able to observe things beyond what the model can handle.

  • by Skippy_kangaroo ( 850507 ) on Saturday September 16, 2006 @06:49AM (#16119595)
    Only mathematics has proofs ...And even then they still have axioms. ...And then there is Gödel - "Any theory capable of expressing elementary arithmetic cannot be both consistent and complete." ...Excuse me while I disappear in a funk of existential angst.
  • by ZombieWomble ( 893157 ) on Saturday September 16, 2006 @07:38AM (#16119666)
    You are confusing the concept of mathematical and scientific proof.

    Mathematics is a closed system, for which we know all the rules (because we define them). Thus, things can be proven as being objectively true, false, or unprovable (for as given set of axioms, there are many self-consistent sets).

    Physics and the other sciences, on the other hand, are faced with the dilemma that we can never observe all the behaviour of everything in the universe at once, and thus we are forever working with partial data sets, and fitting our theories to them. As a result, the best we can say is that the theory we have put together fits the observed data to a high degree of precision - but that this may be invalidated at any time by new phenomena. See, for example, the progression from Newtonian mechanics to Relativity, or the long-running debate over the nature of light.

  • Re:time dilation (Score:3, Informative)

    by ChowRiit ( 939581 ) on Saturday September 16, 2006 @07:43AM (#16119678)
    1.21 jigawatts! Learn your basics of time travel!
  • by kfg ( 145172 ) * on Saturday September 16, 2006 @07:44AM (#16119681)
    . . .we really shouldn't pretend his theories are anything more than a bunch of mathematical approximations. . .

    That's what I said. In fact, it's what Newton said as well.

    . . .that reference intuitive concepts. . .

    They reference only observable phenomenon and are valid only within the limits of those observations.

    KFG
  • by TigerTim ( 968445 ) on Saturday September 16, 2006 @09:26AM (#16119896)

    Well you certainly can measure position! What about a single slit experiment? The electron going through the slit has a quite well-defined position, but a less well defined momentum and that is the crux of quantum mechanics. Indeed, as you imply, it is not possible to say the position of the particle is exactly such-and-such because that would violate the uncertainty principle. I would prefer not to mention infinite spreads of position/momenta because this is not helpful; given you mention information propagation, do you not think that this notion might have issues with an infinite wavefunction? The wavefunction in any phase space must be normalizable and this is surely the most important concept. I'll except tunneling as there even the smallest of tails causes the finite barrier to "leak"... eventually.

    An illustration - it is well known that C60 can be made to diffract [univie.ac.at]. What do you mean then that position is meaningless? Do you mean to say that the atoms within the fullerene have no spatial relation to each other? How then do we know the symmetry of the molecule (from the number of absorption lines)? Of course postion is meaningful! Whether it is well defined is quite another matter.

    I would also question your belief that the operators have any more meaning than the objects that the theory puports to describe! And I would certainly not advise trusting the math (although I'm a theoretician) - surely one must actually trust experiment!

    I happen to be a physicist (but I don't particularly think that's relevant). I'm quite sure you grasp QM (the famous quote from Bohr aside), but I'm not sure I agree with the way you have chosen to explain it :-)

    It is very common to say that "position, etc. are meaningless" but that simply isn't a correct statement at all, as I hope I've shown. Sorry for dragging this off topic (and for the profusion of exclamation marks)

  • by tonigonenstein ( 912347 ) on Saturday September 16, 2006 @10:26AM (#16120061)
    This is incorrect. The theorem you are talking about says that you cannot prove the consistency of a complete theory that includes arithmetic in the theory itself. Nothing prevents the theory from being consistent and nothing prevents you from proving the consistency at a higher level (in a meta-theory).
  • by Mark Maughan ( 763986 ) on Sunday September 17, 2006 @01:07AM (#16123293)
    I looked at your paper on your wesite.

    I am afraid to tell you that your theory isn't sensible.

    For instance, in equation (2), if you make the mass density equal to the charge density, then you get nothing. But with opposite charge, you do get something. That's just a simple example.

    Your action, equation (1), contains neither E&M nor linearized gravity. Where is F_mu,nu F^mu,nu? Where is D^2 h_mu,nu D^2 h^mu,nu ?

    I'd suggest that if this is something you are really interested in, you take some courses and learn the fundamentals before you start putting together a theory.

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