Re: Einstein's GR passes extreme test

Ken S. Tucker wrote:
On Jul 17, 10:53 am, "Ken S. Tucker" <dynam...@xxxxxxxxxxxx> wrote:
On Jul 17, 10:04 am, Martin Brown <|||newspam...@xxxxxxxxxxxxxxxxxx>
wrote:

On Jul 17, 4:37 pm, "Ken S. Tucker" <dynam...@xxxxxxxxxxxx> wrote:

The tidal forces are very brutal for a pair of pulsars in tightly
bound slowly decaying orbit. The first work on the double pulsar
entailed determining the rate of energy loss as a result of
gravitational radiation. It matched theory.
The great thing about this system is you have extremely accurate
clocks in a tightly bound orbit (star quakes excepted they are almost
as good as our best atomic clocks). When the first binary pulsar was
discovered the measurements revealed a systematic error in
observational timing that was eventually traced to an error in the
computer algebra program that was used to compute the GR path
corrections in our solar system.
A paper on the oldest known one with 30 years of data summarised is
online free access at:
http://arxiv.org/abs/astro-ph/0407149
There is a rather nice summary of gravity through the ages at:http://einstein.stanford.edu/SPACETIME/spacetime3.html

(Binary Pulsar is toward the end)
I pretty much agree.
The neutron star pair is separated by ~ 2 x Earth to Moon, so the
tidal
"forces" would be rather extreme compared to the Earth Moon system.
Given the unknowns within the structure of n-stars, I could fudge any
parameters to agree with nearly any theory.
There are enough observables in the new system to tightly constrain
theoreticians.
I doubt that, the Earth day loses .0018 secs / century and the
moon recedes 3.5 cm/year due to tides. Need the original
paper to see what the authors really said.

I can't point you at the paper free access but their poster on the eclipse study itself is online at:

http://www.mpe.mpg.de/IAU_JD02/poster/JD02-33.pdf

The original article is in Science magazine for July PPV
http://www.sciencemag.org/cgi/content/abstract/321/5885/104

That said, by setting the parameters to agree with GR, provides
insight into the structure. But then 3rd body contamination may be
present. It would be quite surprising if this could really be called a
"confirmation of GR", but it doesn't disprove it.

It would have to be a special sort of third body to hang around in
that neighbourhood. And if it was there and close enough to make a
real difference it would prevent the orbital parameters from matching
the GR expected values.

As I wrote, I think I could still get GR by adjusting the masses by
fiddling,

You might. I would be more worried about the interactions of their extremely strong magnetospheres at such close quarters, but they seem to have it under control. The fact that one eclispes the other and both are observable high precision clocks in mutual orbit does make things rather well constrained. The only real uncertainty is how much they are spinning with a component along our line of sight.

They have even used the evolution of the orbital parameters to map out the beam profile of the pulsar beam (on one of the others).

and then placing in orbiting objects away from the pair, and btw I'm a
GRist, and glad there's a few in this group.

Hi Ken, once long ago I was a radio astronomer.

Hi Martin and fella's, here's a sample of the parameter
complexities I was referring to,
http://relativity.livingreviews.org/open?pubNo=lrr-2006-3&page=articlesu17.html
Ken

It is mentioned in the pulsar zoo page of this J0737-3039a,b. The discovery paper of B is online free access at:

http://arxiv.org/abs/astro-ph/0401086

Double pulsars are thought to be rare.

Regards,
Martin Brown
** Posted from http://www.teranews.com **
.

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