PDA

View Full Version : This is Getting Boring: General Relativity Passes Yet another Big Test!



Fraser
2010-Mar-18, 05:50 PM
Published in 1915, Einstein's theory of general relativity (GR) passed its first big test just a few years later, when the predicted gravitational deflection of light passing near the Sun was observed during the 1919 solar eclipse.In 1960, GR passed its first big test in a lab, here on Earth; the Pound-Rebka experiment. And over [...]

More... (http://www.universetoday.com/2010/03/18/this-is-getting-boring-general-relativity-passes-yet-another-big-test/)

Buttercup
2010-Mar-18, 06:54 PM
I'm waiting for GR to pass The Slammed Oven Door test.

You know, like with cakes and souffles.

If it does, THEN it'll be legit. :)

Jerry
2010-Mar-20, 10:14 PM
GR has passed every single test except for the tests that have failed, like this one I just mentioned on another thread:

http://xxx.lanl.gov/abs/1002.0525


Comparison with angular size test for ultra-compact radio sources


Compact radio sources have been used by several authors to carry out the angular size test because these sources were thought to be free of evolutionary effects. However, the different results obtained with these sources has raised the suspicion that they may not be such good standard rods. Apparently, these rods are somewhat flexible. For example, Kellermann claimed that the angular size test for these sources fitted Einstein–de Sitter expectations very well, when Einstein–de Sitter was the fashionable model. Jackson & Dodgson claimed the opposite: that it was not compatible with Einstein–de Sitter, and that, given that Omega(m) = 0.2, the best fit for the cosmological constant term was Omega(alpha) = −3.0; flat cosmological models were excluded with > 70% C.L.

Jackson, in the era of the concordance model as the fashionable cosmology, again carried out the analysis of the same data used by Jackson & Dodgson, doing some new corrections due to selection effects and bias, and they get the best fit for Omega(m) = 0.29, Omega(alpha) = 0.37, compatible within 1 sigma with the concordance model. With further data, Jackson & Jannetta get the best fit for Omega(m) = 0.25+0.04 −0.03, Omega(alpha) = 0.97+0.09 −0.13 (68% C.L.).

It seems that the general trend is to obtain the result expected from fashionable cosmologies on the date in which the test is carried out, and when incompatibilities appear, some selections effects, biases, small evolution effects are sought to try to make the results compatible. In my opinion, this is not a very objective way to do science, ...

I can wear sizes 9-11 in men's shoes fairly comfortably, as long as they are fashionable.

TheHalcyonYear
2010-Mar-20, 10:16 PM
GR has passed every single test except for the tests that have failed and have mostly been forgotten.
For those of us who aren't astronomers or astrophysicists, can you present some examples? I hope this isn't seen as hijacking the thread. Since this thread is about General Relativity passing another big test, it would seem that the tests it may (or may not) have failed are also relevant.

KaiYeves
2010-Mar-20, 10:18 PM
It's not boring if things make sense!

TheHalcyonYear
2010-Mar-20, 10:25 PM
It's not boring if things make sense!
I agree. I also know that it was once thought that all that was left for the next generation of physicists was the task of extending the number of significant digits in some of the physical constants. That was just before physics was turned on its ear and a lot of things were opened up for grabs.

I have no doubt that General Relativity, like Newtonian Mechanics, is correct as far as it goes. As to whether is is a subset of something larger, just as Newtonian Mechanics is a subset of General Relativity, I am happy to just wait and see.

KaiYeves
2010-Mar-20, 10:30 PM
I know, I just meant that it's not boring if we get results we actually expect for once.

Jean Tate
2010-Mar-20, 10:31 PM
GR has passed every single test except for the tests that have failed, like this one I just mentioned on another thread:

http://xxx.lanl.gov/abs/1002.0525
I do not see how this preprint can be considered a test of General Relativity.

Can you elaborate please?

Also, what 'other thread' did you mention this in?

TheHalcyonYear
2010-Mar-20, 10:39 PM
I know, I just meant that it's not boring if we get results we actually expect for once.
I agree. Didn't mean to put words into your mouth. I apologize if it sounded that way. :)

Jerry
2010-Mar-20, 10:56 PM
For those of us who aren't astronomers or astrophysicists, can you present some examples? I hope this isn't seen as hijacking the thread. Since this thread is about General Relativity passing another big test, it would seem that the tests it may (or may not) have failed are also relevant.

Check out Martin's paper I edited in above.

http://xxx.lanl.gov/abs/1002.0525

I also have a current thread on this topic in the Against the Mainstream section.

TheHalcyonYear
2010-Mar-21, 12:11 AM
Check out Martin's paper I edited in above.

http://xxx.lanl.gov/abs/1002.0525

I also have a current thread on this topic in the Against the Mainstream section.
uh, this is not a failed test for the General Relativity. Rather it suggests that the Big Bang Theory, as it is currently formulated, does not fit all observations. While I find this interesting, I don't see how this represents a failed test for General Relativity.

TheHalcyonYear
2010-Mar-30, 04:48 AM
Uh, you never got back to this one Jerry. Does this mean that you can't show the relevance of the paper you suggested I read?

Jerry
2010-Mar-30, 05:44 AM
Quite simply, GR predicts that as the universe expands relativistically; the angular scaling factor as a function of the speed of light is 1/z^4 where z is the redshift - distance. In a non-expanding or non-relativistic universe; the angular scale should slide as a function of 1/z^2. Martin points out the the angular size test is consistent with the latter expression, but not the former. While evolution can mitigate this to some degree; there are severe problems with suggesting the angular scale can be accounted for completely by evolution. Relativity makes precise predictions - the proofs to-date are not precise, and sometimes attempt to improve upon them fail.

But the general point is: When a test of relativity fails, that test is downplayed; widely discounted and ignored. That is not boring - that is wrong.

TheHalcyonYear
2010-Mar-31, 07:09 PM
Quite simply, GR predicts that as the universe expands relativistically; the angular scaling factor as a function of the speed of light is 1/z^4 where z is the redshift - distance. In a non-expanding or non-relativistic universe; the angular scale should slide as a function of 1/z^2. Martin points out the the angular size test is consistent with the latter expression, but not the former. While evolution can mitigate this to some degree; there are severe problems with suggesting the angular scale can be accounted for completely by evolution. Relativity makes precise predictions - the proofs to-date are not precise, and sometimes attempt to improve upon them fail.

But the general point is: When a test of relativity fails, that test is downplayed; widely discounted and ignored. That is not boring - that is wrong.
Um, I didn't see all that in the paper. I saw someone attempting to fit the known evidence to a variety of models without endorsing any model over others.

Jean Tate
2010-Apr-01, 08:28 PM
Quite simply, GR predicts that as the universe expands relativistically; the angular scaling factor as a function of the speed of light is 1/z^4 where z is the redshift - distance. In a non-expanding or non-relativistic universe; the angular scale should slide as a function of 1/z^2.
OK, so far.


Martin points out the the angular size test is consistent with the latter expression, but not the former. While evolution can mitigate this to some degree; there are severe problems with suggesting the angular scale can be accounted for completely by evolution.
I think you're reading far more into the preprint than is actually there Jerry, as TheHalcyonYear keeps pointing out.

It reminds me a bit of the Hawkins paper, a few years' ago, on quasar variability and time dilation; until galaxy evolution is well-understood, how can the galaxy angular size-redshift relationship be understood?


Relativity makes precise predictions - the proofs to-date are not precise, and sometimes attempt to improve upon them fail.
Fair enough, but GR does not predict how galaxies evolve, so any test of GR using galaxies can be, at best, only an indirect one.


But the general point is: When a test of relativity fails, that test is downplayed; widely discounted and ignored. That is not boring - that is wrong.
But in this case, it seems you have simply not understood the very paper you are quoting ... it doesn't present a test of GR, nor does it claim to.

tusenfem
2010-Apr-02, 09:02 AM
Quite simply, GR predicts that as the universe expands relativistically; the angular scaling factor as a function of the speed of light is 1/z^4 where z is the redshift - distance. In a non-expanding or non-relativistic universe; the angular scale should slide as a function of 1/z^2. Martin points out the the angular size test is consistent with the latter expression, but not the former. While evolution can mitigate this to some degree; there are severe problems with suggesting the angular scale can be accounted for completely by evolution. Relativity makes precise predictions - the proofs to-date are not precise, and sometimes attempt to improve upon them fail.

But the general point is: When a test of relativity fails, that test is downplayed; widely discounted and ignored. That is not boring - that is wrong.


Jerry, keep your ATM claims and mis/over interpretations of papers on ArXiv to your ATM thread. You know this well enough, i.e. enough to get an infraction.