Forgot your password?
typodupeerror

General Relativity Is At Least 99.95% Right 223

Posted by Zonk
from the happy-hair dept.
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."'"
This discussion has been archived. No new comments can be posted.

General Relativity Is At Least 99.95% Right

Comments Filter:
  • by Anonymous Coward on Saturday September 16, 2006 @05:32AM (#16119480)
    Observations that support a theory are nice, but they are not a proof.
    • by smash (1351) on Saturday September 16, 2006 @05:42AM (#16119494) Homepage Journal
      You can never *prove* a theory, you can merely disprove it by finding evidence which does not support it.
      • by snarkh (118018)
        Actually, you can neither prove nor disprove a theory with observations.
        You observations are just making a theory more or less likely to hold.

        What does it mean to disprove a theory, in any case? Does special general relativity disprove Newton's theory?
        • Re: (Score:2, Insightful)

          by jawtheshark (198669) *

          Does special general relativity disprove Newton's theory?

          Yes, it does. Newtonian physics are bound to certain limits, at those limits strange things happen that Newtonian physics do not predict. Relativity explains both the experimental results of Newtonian physics and those where they go bonkers. So, relativity proves that Newton was wrong in certain conditions. This does not mean that Newtonian physics are unusable and that's why they are still taught in high school.

          Compare it to something we

    • by kfg (145172) * on Saturday September 16, 2006 @05:43AM (#16119496)
      . . .they are not a proof.

      Only mathematics has proofs, but observations that support a theory demonstrate that the model has predictive value. Observations that do not support a theory demonstrate that the model is, at best, incomplete.

      Ignoring the predictive value of a model, whether it is complete or not, demonstrates that you are an idiot. Within its limits of significance Newton's theory of gravitation is still just as "correct" as Relativity.

      Facts are not proofs, but they are facts.

      KFG
      • by QuantumFTL (197300) * <justin.wickNO@SPAMgmail.com> on Saturday September 16, 2006 @06:42AM (#16119581)
        Within its limits of significance Newton's theory of gravitation is still just as "correct" as Relativity.

        That's like saying "for whatever region of the hypothesis space a given theory gives usably correct predictions, it's useful." Of course that's true, however part of using a theory correctly is knowing how far it goes. Quantum theory has demonstrated that the fundamental concepts in newtonian physics (position, momentum, energy, time, etc) are not really meaningful when you boil things down to the lowest levels we can observe.

        I mean, you can tell someone that a VCR works because there's a little man in there that knows when you said you wanted something taped and writes all the TV programs down on tape. I mean, I don't think people actually believe this, but their black-box model of a VCR is essentially equivilent to this. The reality of how a VCR works, of course, is much more complex in many ways, and involves failure modes that non-electronic type people will likely fail to predict because of their incomplete view of the situation.

        Newtonian physics is not merely an appoximation error, the fundamental set of concepts and intuitions are just completely unhelpful at any scale but mezoscale (that on which we exist, somewhere between atom and star).
        • Re: (Score:2, Insightful)

          by kfg (145172) *
          Newtonian physics is not merely an appoximation error. . .

          It's errors are completely quantifiable.

          . . .the fundamental set of concepts and intuitions are just completely unhelpful at any scale but mezoscale. . .

          Newton himself noted that there were observable limits to his model and that whatever fundamental concepts it provided were also extremely limited, giving no greater understanding of mechanism. They are purely empirical observation.

          You will, however, find that if you wish to predict the path of a sim
          • by QuantumFTL (197300) * <justin.wickNO@SPAMgmail.com> on Saturday September 16, 2006 @07:27AM (#16119645)
            It's errors are completely quantifiable.

            Newton's formulas are not merely missing a few parameters... they involve concepts that simply stop making any logical sense once you get down to very small scales. The idea of a "particle" even existing in a single position, as far as we can tell with modern QM, is completely absurd and meaningless. The concept of an exact momentum is equally so. The "clockwork universe" which contains action at a distance (causal nonlocality) and non-discrete space, time, energy etc (rather than discrete geometry and quanta) is simply so far from the "truth" that our experiments reveal - namely that particles act as if they are in infinite numbers of places at once (or nearly so, given plank limits on spaceitme).

            You will, however, find that if you wish to predict the path of a simple artillary shell or design an automobile they are "correct," they have predictive value, specifically because the phenomenon exist within the limits of the model's significance. Taking Relativity into account does nothing but complicate the math to provide a bogus level of significance and Quantum Theory is completely irrelevant.

            Back at university, I used these "wrong" theories all the time, as they are useful (if erroneous) abstractions. The problem is that theories are not merely useful for their ability to predict things within the realm of known experience, but also new and different things beyond the current frontiers. Newton's theories, as elegant and beautiful as they are, were long ago surpassed and are now almost useless when it comes to generating new predictions about unobserved phenomena in the universe. The mark of a truly good theory is not that it can compress the set of known expimental results well, but that it can predict entirely new ones, outside the original domain in which it was devised.

            Newton was a far smarter man than anyone posting here on slashdot, but like Einstein, he got so very much fundamental very wrong. I think if he lived here today, he'd get new and exciting things wrong (like modern theorists) and that that's a very valuable part of science, but we really shouldn't pretend his theories are anything more than a bunch of mathematical approximations that reference intuitive concepts that have almost no meaning at very small (and possible very large) scales.
            • 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
            • Re: (Score:3, Insightful)

              by mrpeebles (853978)
              I don't think you are giving classical mechanics enough credit. Sure, it is wrong on several accounts. But it some ways, it seems to have gotten things fundamentally right, in a way that I personally think almost seems to transcend the mathematics. For example, the idea of conservation of energy and momentum seems to be preserved in some form over and over again. And remember that QM is still in the language of classical mechanics. We of course talk about, for example, quantum mechanical Hamiltonians and La
              • I don't think you are giving classical mechanics enough credit. Sure, it is wrong on several accounts. But it some ways, it seems to have gotten things fundamentally right, in a way that I personally think almost seems to transcend the mathematics.

                The reason it seems so right is that it accurately describes the physics approximation that's hard wired into your brain. Do remember that instinct formed some science too.
          • by ThatsNotFunny (775189) on Saturday September 16, 2006 @10:03AM (#16119995)
            It's errors are completely quantifiable.
            I point out your mistake not to be a grammar nazi, but because of the incredible irony.
            • Re: (Score:3, Insightful)

              by stonecypher (118140)
              As long as we're in language Nazi mode, please learn what Irony means [tri-bit.com]. Rebuttal references to bargain-basement dictionaries whose sales are set by their word count, or to user-written collections of mass misimpression like Princeton Word-Net and Wikipedia will be met with derision and mockery. Oh, and by the by, grandparent's error isn't in grammar, it's in conjugational syntax. Believe it or not, not every single rule in language is a grammar rule. A real language Nazi would know that.

              Please don't enga
        • Within its limits of significance Newton's theory of gravitation is still just as "correct" as Relativity.

          That's like saying "for whatever region of the hypothesis space a given theory gives usably correct predictions, it's useful."


          No, it isn't. What he said compares the utility of accuracy to the demands of daily use, and thereby displays the lack of contrast in daily life between two progressive states of the understanding of physics. What you said is a tautological observation that a usably accurate p
      • 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.
        • Re: (Score:2, Informative)

          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).
        • Re: (Score:3, Insightful)

          by Anonymous Coward
          Godel's Incompleteness Theorem is really rather less interesting than most people seem to make it out to be. What it amounts to is taking a system X and looking at the statement "This statement is unprovable in X". If it is provable in X then X is inconsistent. If it isn't provable then there is a true statement (namely, "This statement is unprovable in X") that is unprovable in X, so it is incomplete.

          It really shouldn't be surprising that when a system is powerful enough to talk about itself we can end up
      • Only mathematics has proofs

        And logic, semantics, many subfields of philosophy, tactics, game theory, economics, and other purely theoretical rigorous fields. But, your point remains valid.

        Ignoring the predictive value of a model, whether it is complete or not, demonstrates that you are an idiot.

        Well, either that, or that he's trying really hard to be academically proper, and doesn't know how. Cut the kid some slack.
    • 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.

      • I don't recall Newton explaining gravity. I recall him describing its effects. Not the same thing. As far as I can ascertain, we still don't have a friggin' clue as to what gravity is, only how it behaves.
        • by doshell (757915)

          One could argue that the objective of science is to provide models that accurately describe our Universe and allow us to make predictions about its evolution. That's finding out "how". The question of "why" is of a different nature -- it can't be answered using the tools of science -- and falls into the problem domains of philosophy and theology. So don't really expect science to answer all possible questions, but keep in mind it does answer quite a few of them as it stands. :)

        • OK, Newton explained how gravity behaves and was able to attach it to a mathematical model. Pre-Newton shit just fell on the floor.
      • Re: (Score:3, Interesting)

        by gsn (989808)

        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.

        Absolutely, and with General Relativity despite its stunning success we know that it must fail at some scale because as a classical theory it simply does not match what we know about space at the very small scale.

        The vacuum is a much more active place and while at the long scale it can be described my a nice smooth m

        • and the univese is asymptotically deSitter space

          Er, I thought it was an anti-deSitter space? The two are fairly different.
    • Why would anyone mod insightful what is clearly a deep misunderstanding of science?
  • by physicsphairy (720718) on Saturday September 16, 2006 @05:34AM (#16119482) Homepage
    I think what they mean to say is that "Reality is at least 99.95% right."

    Let's not go attempting to invalidate any theories I've spent hundreds of hours trying to understand, ok?
  • by Anonymous Coward on Saturday September 16, 2006 @05:36AM (#16119487)

    all we need are 20 pounds of trash and 1.2 jigawatts from the town square clock at midnight!
  • by A Brand of Fire (640320) on Saturday September 16, 2006 @05:44AM (#16119500) Homepage

    I think 99.95% is about as close to dead-on-balls-accurate as it gets with our current knowledge of the universe; I mean, there's always a margin for error in absolutely everything, it's just one of the facts of the chaotic universe in which we live. Still, it just goes to show how far ahead of the game (and of the times) Einstein was.

    Einstein's still my hero. He's the Samuel L. Jackson of science.

    • Re: (Score:3, Insightful)

      by Antony-Kyre (807195)
      If Einstein is the Samuel L. Jackson of science, what would Tesla be comparable to?
    • Re: (Score:2, Insightful)

      by hajus (990255)
      Yet, Einstein was dead wrong when it came to god playing dice :)
    • Re: (Score:3, Interesting)

      by tkittel (619119)
      I agree - Einstein is the man.

      But regarding your "I think 99.95% is about as close to dead-on-balls-accurate as it gets with our current knowledge of the universe", allow me to take this opportunity to point out that Quantum Electrodynamics (the extension of electromagnitism and quantum mechanics into a quantum field theory) surely is the most accurate theory we have today.

      In some circumstances its predictions have been verified to an astounding 14-15 decimal places! (Thats something crazy like 99.999999999
    • by nametaken (610866)
      Aww, now I have to say it...

      Get these mother-f'n Newtonian physicists out of my mother-f'n audience!

      Do they speak English in when they give you the Nobel Prize? English mother-f'r! Do, they, speak, it?

      God, I'm sorry.
      • General and Special Relativity. When you absolutely, positively, have to limit the speed of every last mother-f'er in the room, accept no substitutes!
    • 99.95% correct still leaves tremendous room for unknowns. It's that last 0.05% where all the interest lies - where we fail to predict accurately because we are wrong about whatever is occuring.
  • Sooo.... (Score:5, Funny)

    by hyfe (641811) on Saturday September 16, 2006 @06:13AM (#16119550)
    So, The General Relativity Theory is relativly correct?

    (sorry)

  • hey (Score:2, Funny)

    by maynard (3337)
    in this shop we shoot for five nines!
  • by MarsDude (74832) on Saturday September 16, 2006 @09:58AM (#16119982) Homepage
    Isn't that (at most) 0.05% the most interesting part?
    • No. It's the tolerance of error for this particular measurement. The measurement taken is closer than 0.05% to the predicted value. 0.05% comes from to what precision we believe the experiment is valid.
  • by S810 (168676) on Saturday September 16, 2006 @10:23AM (#16120052) Homepage
    I thought that the Boomerang Project from 1998 and 2003 proved that beacuse the background radiation in space was spread out the way it is, that this disproved that Space-Time was curved? Check out http://cmb.phys.cwru.edu/boomerang/ [cwru.edu]. Not that I wanted this to be true, but what I watched on NASA TV in 2003 said that it was the facts. So if his General Theory is 99.95% accurate, is this the .05% variance?
    • No. The ±0.05% error is tolerance for experimental inaccuracy. It's not a measurement of how wrong the theory is according to data. It's a measurement of how close the correct data is to our recorded data.
  • by sweetser (148397) <sweetser@alum.mit.edu> on Saturday September 16, 2006 @12:01PM (#16120396) Homepage
    Hello:

    The measurement is still in the range of first order parametrized post-Newtonian accuracy. What the Donkey Kong that means is that these are the coefficients to the metric that are being tested:

            dtaU^2 = (1 - 2 GM/c^2 R + 2 (GM/c^2 R)^2) dt^2
                          - (1 + 2 GM/c^2 R) dR^2/c^2
                          - R^2/c^2 dtheta^2
                          - R^2/c^2 sin^2 theta dphi^2

    It is the 5 integers there (1, -2, +2, -1, -2) that are confirmed by this experiment. That is NOT NEWS, because it is not new. Shapiro got the same results. What would be news is if the experiment got to second order parameterized post Newtonian accuracy. I asked Prof. Clifford Will an expert on experimental tests of GR when where the data hunters going to gather that data. He said he knew of no one even discussing it. The reason is that the data must for 2nd order PPN effects must be a million fold more accurate, so we need data that is 99.99995% accurate.

    I care a lot about 2nd order PPN tests, since that is were my proposal to unify gravity and EM using a 4D wave equation differs. GR says the metric should go here:

            GR:
            dtaU^2 = (1 - 2 GM/c^2 R + 2 (GM/c^2 R)^2 -3/2 (GM/c^2 R)^3) dt^2
                          - (1 + 2 GM/c^2 R + 3/2 (GM/c^2 R)^2) dR^2/c^2
                          - R^2/c^2 dtheta^2
                          - R^2/c^2 sin^2 theta dphi^2

            GEM (gravity and EM):
            dtaU^2 = (1 - 2 GM/c^2 R + 2 (GM/c^2 R)^2 -4/3 (GM/c^2 R)^3) dt^2
                          - (1 + 2 GM/c^2 R + 2 (GM/c^2 R)^2) dR^2/c^2
                          - R^2/c^2 dtheta^2
                          - R^2/c^2 sin^2 theta dphi^2

    At first order PPN accuracy, the coefficients (1, -2, 2, -1, -2) are the same. At second order, they are different. That's the data I need. I'll probably be dead before it shows up.

    doug
  • Isn't Einstein's relativity just a much smaller magnitude extra term on Newton's mechanics? Negligible at human scales. Einstein's correction to Newton was much less than 0.05%. If relativity is really as much as 0.05% off, that leaves a vast amount of unexplained phenomena in our big Universe.
    • by doshell (757915)

      Isn't Einstein's relativity just a much smaller magnitude extra term on Newton's mechanics? Negligible at human scales.

      That's a rather vague way to put it. Relativistic effects on a body moving at 1 m/s are negligible to the point that Newtonian mechanics can be considered 100% correct for all practical purposes. Take another body moving at a speed close to the speed of light (we deal with those every day in modern Physics) and it's a very different story -- I can assure you the effects are very much not

    • by Shihar (153932)
      Newton's rules work well most of the time, but you really need relativity and quantum mechanics in this day and age. For astronomical work, Newton is roughly close, but using just his rules alone you will find inaccuracies and dramatically limit what you can learn from astronomy. If you want to plot a course to the moon, you can probably do it with just Newtonian rules. If you want to understand how old the universe is estimate sizes and distances of celestial objects, you really need more then what Newt
      • by Doc Ruby (173196)
        I know all that. What I'm saying is that if Einstein is off by 0.05%, that's pretty big. Einstein's extra terms on Newton's equations are a much smaller improvement on Newton, and an improvement on Einstein to cover that 0.05% would be a much bigger improvement on Einstein.

        It's all relative (pun intended), and the news that Einstein is off by so much is not so flattering to Einstein.
    • Isn't Einstein's relativity just a much smaller magnitude extra term on Newton's mechanics?

      God, no. Einstein's relativity is a complete inversion of physics, that recasts all fundamental processes as related to time and the speed of light. Relativity and Newtonian Mechanics are as similar as a paintbrush and spraypaint, in that they achieve generally the same results, but through a fundamentally completely different approach.

      [[0.05%]] Negligible at human scales.

      0.05% of a six foot tall man's height is
  • There's no such thing as proof of a scientific theory, so talking about how a theory is "almost proven" is just plain wrong.

    And trying to quantify the "provenness" of a theory with a figure also shows a deep misunderstanding of how science works. There are any number of quantifiable tests that have matched general relativity's predictions, and each of these have different error bars. So picking one at random and using it as the measure of how "proven" general relativity is doesn't make any sense at all.

    • There's no such thing as proof of a scientific theory, so talking about how a theory is "almost proven" is just plain wrong.

      The word "almost" does not occur in either the article or the Slashdot summary. You might as well lambast them that claiming iron is made from honeybees and old shoes is just plain wrong.

      And trying to quantify the "provenness" of a theory with a figure also shows a deep misunderstanding of how science works.

      This is probably why nobody attempted to do so.

      There are any number of qu
  • Since when is 99.95% a big number when we're dealing with astronomy? I think Newton's laws are precise within 99.95%.

    99.95% of what?

    • I think Newton's laws are precise within 99.95%.

      Well, they are (up to about 0.6 c, at least,) but that's not the point. Indeed, the disparity between expected and measured data is less than 0.01%, which is also specifically mentioned in both the writeup (phrased as the measurement ratio and posited as 1:1.001) and in the article.

      99.95% of what?

      The ±0.05% refers to the accuracy of the measurement used to glean the data, and has nothing to do with the theory or the difference between the expected

You've been Berkeley'ed!

Working...