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."'"

Comments

Re: General Relativity Is At Least 99.95% Right

[QuantumFTL]

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.

But What About the Boomerang Project...?

[S810]

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?

Not good enough for me

[sweetser]

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