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General Relativity Is At Least 99.95% Right
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."'"
Observations that support a theory are nice, but they are not a proof.
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?
When things get complex, multiply by the complex conjugate.
all we need are 20 pounds of trash and 1.2 jigawatts from the town square clock at midnight!
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.
[End of Line]
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 He even predicted that his model would be superceded.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.
Engineering is the art of compromise.
(sorry)
"" How about taking the safety labels off everything, and let the stupidity-problem solve itself? """
How can they say anything is 99.95% right, have they never heard of the Cartesian method of doubt. . .
.05%. They are perfectly aware of the lack of knowledge that could be hiding in that .05%, but that .05% defines the limit of our lack of knowledge.
.so all in all I'd say about 1-5% doubt - but you can never know
Yes, that's why they said what they said, i.e. that they have only shown the predictive accuracy of Relativity to a margin of error of
. .
And this makes no sense whatsover, because you are just pulling numbers out of your ass. Yes, it's true that you can never "know," but you can measure and increase the degree of your surity.
KFG
in this shop we shoot for five nines!
You can't measure position in quantum physics [...] As far as we known, the "particle" *NEVER* has an exact position or momentum, but rather is at an infinite set of locations.
At least in principle, you can measure position in quantum physics. The particle is temporarily put in a position eigenstate with an exact position eigenvalue associated with it (the momentum is completely indeterminate, however). This only lasts for an instant, however, before the state evolves into a superposition of position eigenstates.
Remember, it is an axiom of quantum mechanics that measuring observables puts the system in an eigenstate of that observable; the eigenvalue corresponds to an exact measurement of that observable. (You will not be in an eigenstate of any observable that commutes with it, and therefore those quantities will not be known exactly — the Heisenberg uncertainty principle.) Of course, you could quibble about our practical ability to put a particle into an exact position eigenstate, as opposed to an eigenstate of an observable merely very similar to the position operator.
there is no such thing as "fabric of space-time". It's a convenient buzzword but it doesn't mean anything
Of course it means something: it is a summary of the distance and time measurements we make, and can be described in terms of geometrical curvature. If it didn't mean anything, then it wouldn't have any observable consequences.
Things work as if Einstein was right, but there is no evidence that he was right.
You're splitting hairs that don't exist. "Working as if Einstein was right" is "evidence that he was right". It's the only kind of evidence possible.
If you pass a current through a wire it generates a magnetic field. If that field crosses another wire it generates a current in that wire.
That's not necessarily true. A static magnetic field doesn't induce a current in a wire. You might be talking about alternating current, which produces a time-varying magnetic field.
It's exactly as if the magnetic field moved from one wire across the other.
I don't know what you mean by a magnetic field "moving", but certainly the magnetic field of one wire can intersect the position of another wire.
The flaw is that if you wrap both wires through an iron donut all the field is inside the iron - absolutely NO field is detected anywhere around either wire.
Perhaps I'm visualizing the geometry wrong, but your statement appears to be false.
The theory is false, but it is "exactly as if" it were true.
What theory? That the (time-varying) magnetic field produced by one current can induce a current in another wire? That theory is always true. (Of course, you have to take into account induction from other objects which may cancel that current.)
Likewise, Einstein's theory may give correct answers even though nobody actually knows why.
It is not possible to know "why" a theory is true, at least if that theory regards some fundamental phenomenon. It's possible to explain "why" some approximate theory is true by deriving it from a more fundamental one, assuming the more fundamental theory is true.
For one thing, plasma physicists can easily explain a lot of effects in electrical terms, relying on laboratory observations instead of imagined theories.
Nonsense. Plasma physicists use theories just like any other physicist does. Those theories of course are electromagnetic in nature.
Astronomers ignore plasma physics because nobody ever taught it to them.
More nonsense. Plenty of astronomers use plasma physics. What are you, an Alfven plasma cosmology crackpot?
Isn't that (at most) 0.05% the most interesting part?
Obviously, you never had any education about electrodynamics, or you would recognise your example as bullshit.
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
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/. 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?
"I think you know what I'm talkin' about, Mr. President; We're gonna kill us a mummy!" - Bruce Campbell as Elvis Presley
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
Working on new views of old physics at http://VisualPhysics.org