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ToSeek
2005-Mar-03, 06:58 PM
Einstein Passes New Tests (http://skyandtelescope.com/news/article_1473_1.asp)



Albert Einstein's 90-year-old general theory of relativity has just been put through a series of some of its most stringent tests yet, and it has passed each one with flying colors. Radio observations show that a recently discovered binary pulsar is behaving in lockstep accordance with Einstein's theory of gravity in at least four different ways, including the emission of gravitational waves and bizarre effects that occur when massive objects slow down the passage of time.

01101001
2005-Mar-03, 07:05 PM
Einstein Passes New Tests (http://skyandtelescope.com/news/article_1473_1.asp)
We have to keep taking tests after we die?

I better start studying.

Russ
2005-Mar-03, 07:59 PM
I have a blood test scheduled for next Monday. I guess I better start studying too. :roll: :lol:

PS - Astronomy Magazine has some good articles on Einstein in the Feb. 05' issue.



(edit to add PS)

Tensor
2005-Mar-04, 04:45 AM
Einstein Passes New Tests (http://skyandtelescope.com/news/article_1473_1.asp)



Albert Einstein's 90-year-old general theory of relativity has just been put through a series of some of its most stringent tests yet, and it has passed each one with flying colors. Radio observations show that a recently discovered binary pulsar is behaving in lockstep accordance with Einstein's theory of gravity in at least four different ways, including the emission of gravitational waves and bizarre effects that occur when massive objects slow down the passage of time.

Couldn't have passed the tests. There is no variable G and the binary pulsar doesn't have a misalinged accretion disk.
8)

frogesque
2005-Mar-04, 09:22 AM
Tensor wrote:


Couldn't have passed the tests. There is no variable G and the binary pulsar doesn't have a misalinged accretion disk.

Had to do a double-take there - thought I was on the 'Huygens' thread in ATM =D>

R.A.F.
2005-Mar-04, 12:26 PM
Had to do a double-take there - thought I was on the 'Huygens' thread in ATM =D>

:lol: :lol:

jfribrg
2005-Mar-04, 12:47 PM
Einstein Passes New Tests (http://skyandtelescope.com/news/article_1473_1.asp)



Albert Einstein's 90-year-old general theory of relativity has just been put through a series of some of its most stringent tests yet, and it has passed each one with flying colors. Radio observations show that a recently discovered binary pulsar is behaving in lockstep accordance with Einstein's theory of gravity in at least four different ways, including the emission of gravitational waves and bizarre effects that occur when massive objects slow down the passage of time.

(emphasis mine)

I thought that gravitational waves have never been detected, which Gravity Probe B was supposed to remedy.

Ken Vogt
2005-Mar-04, 01:10 PM
I thought that gravitational waves have never been detected, which Gravity Probe B was supposed to remedy.
From the article (I hope fair use?):

General relativity predicts that two stars orbiting so closely will throw off gravitational waves ripples in the fabric of space-time generated by the motions of massive objects. By doing so, they will lose orbital energy and inch closer together. Radio observations from Australia, Germany, England, and the United States show that the system is doing exactly what Einstein's theory predicts. "The orbit shrinks by 7 millimeters per day, which is in accordance with general relativity," says Michael Kramer (University of Manchester, England), a member of the observing team.

So it's maybe an indirect test, and not actually seeing the wave come by?
Which LIGO would do.

I don't know if the physics relating orbital shrinking to gravity waves leaves no room for alternative explanations, but I can think of one:

A giant cat sits outside the orbit and swats the pulsars with its front paw each time... oops, should take this to ATM. :) :wink:

Argos
2005-Mar-04, 02:13 PM
Einstein Passes New Tests (http://skyandtelescope.com/news/article_1473_1.asp)



Albert Einstein's 90-year-old general theory of relativity has just been put through a series of some of its most stringent tests yet, and it has passed each one with flying colors. Radio observations show that a recently discovered binary pulsar is behaving in lockstep accordance with Einstein's theory of gravity in at least four different ways, including the emission of gravitational waves and bizarre effects that occur when massive objects slow down the passage of time.

(emphasis mine)

I thought that gravitational waves have never been detected, which Gravity Probe B was supposed to remedy.

Yeah, wonder how do they infer that.

Hamlet
2005-Mar-04, 02:22 PM
Einstein Passes New Tests (http://skyandtelescope.com/news/article_1473_1.asp)



Albert Einstein's 90-year-old general theory of relativity has just been put through a series of some of its most stringent tests yet, and it has passed each one with flying colors. Radio observations show that a recently discovered binary pulsar is behaving in lockstep accordance with Einstein's theory of gravity in at least four different ways, including the emission of gravitational waves and bizarre effects that occur when massive objects slow down the passage of time.

(emphasis mine)

I thought that gravitational waves have never been detected, which Gravity Probe B was supposed to remedy.

Yeah, wonder how do they infer that.

I think the GR prediction is that gravitational waves would carry away energy from the binary pulsar thus causing the orbits to shrink. The results from this test showed the orbit is shrinking by 7 millimeters a day in accordance with the GR prediction. This would seem to be evidence that gravitational waves are real and behave as GR predicts.

Tensor
2005-Mar-04, 02:40 PM
I thought that gravitational waves have never been detected, which Gravity Probe B was supposed to remedy.

Gravity Probe B is looking for two effects. First, how much the earth warps space and time and second, the amount of frame dragging the spin of the earth causes.

Eta C
2005-Mar-04, 02:45 PM
Correct. The study of this new binary pulsar is simply a higher precision version of the work the pulsar PSR 1939 + 16 that led to the 1993 Nobel in Physics (http://nobelprize.org/physics/laureates/1993/index.htm). Read Joseph Taylor's Nobel lecture for a description of the comparison of the observed decrease in rotation rate with the theoretical prediction from GR (energy loss through gravitational radiation).

While all of these observations and tests are extremely compelling, they are still not a direct observation of gravitational radiation. There is still a minutely small chance that there is another explanation for the energy loss. That's why detectors like LIGO have been built for final confirmation. Still, most physicists would say the pulsar work demonstrates the existence of gravitational radiation and the validity of GR. It certainly works for me. :)

edit (corrected Taylor's first name, although my initial error is still quoted below. Alas).

Tensor
2005-Mar-04, 02:46 PM
Tensor wrote:


Couldn't have passed the tests. There is no variable G and the binary pulsar doesn't have a misalinged accretion disk.

Had to do a double-take there - thought I was on the 'Huygens' thread in ATM =D>

Sorry about that. I just couldn't help myself. :D

Argos
2005-Mar-04, 02:52 PM
Einstein Passes New Tests (http://skyandtelescope.com/news/article_1473_1.asp)



Albert Einstein's 90-year-old general theory of relativity has just been put through a series of some of its most stringent tests yet, and it has passed each one with flying colors. Radio observations show that a recently discovered binary pulsar is behaving in lockstep accordance with Einstein's theory of gravity in at least four different ways, including the emission of gravitational waves and bizarre effects that occur when massive objects slow down the passage of time.

(emphasis mine)

I thought that gravitational waves have never been detected, which Gravity Probe B was supposed to remedy.

Yeah, wonder how do they infer that.

I think the GR prediction is that gravitational waves would carry away energy from the binary pulsar thus causing the orbits to shrink. The results from this test showed the orbit is shrinking by 7 millimeters a day in accordance with the GR prediction. This would seem to be evidence that gravitational waves are real and behave as GR predicts.

Now I see they explain that in the article. Number one rule: read the linked stuff carefully before posting. :oops:

Thanks anyway.

Kristophe
2005-Mar-04, 03:33 PM
Correct. The study of this new binary pulsar is simply a higher precision version of the work the pulsar PSR 1939 + 16 that led to the 1993 Nobel in Physics (http://nobelprize.org/physics/laureates/1993/index.htm). Read Richard Taylor's Nobel lecture for a description of the comparison of the observed decrease in rotation rate with the theoretical prediction from GR (energy loss through gravitational radiation).

While all of these observations and tests are extremely compelling, they are still not a direct observation of gravitational radiation. There is still a minutely small chance that there is another explanation for the energy loss. That's why detectors like LIGO have been built for final confirmation. Still, most physicists would say the pulsar work demonstrates the existence of gravitational radiation and the validity of GR. It certainly works for me. :)

Strangely enough, I actually have Taylor's paper sitting in front of me for unrelated reasons. To see just how accurate GR's predictions are in the case of PSR 1939 + 16 are astounding.

Tensor
2005-Mar-09, 01:52 AM
Strangely enough, I actually have Taylor's paper sitting in front of me for unrelated reasons. To see just how accurate GR's predictions are in the case of PSR 1939 + 16 are astounding.

Yeah, I was amazed that the graphs of the prediction and the observations are virtually the same. (the first few years are a bit off, but I think they didn't really have good enough data at that point).

Eta C
2005-Mar-09, 02:10 PM
Of course the amazing thing is that the analysis of this new binary pulsar improves what was an already compelling comparison in 1993. I know I've linked to it many times before, but forgive me if I direct people once again to the Particle Data Group's review of Experimental Tests of Gravitational Theory (http://www-pdg.lbl.gov/2004/reviews/gravrpp.pdf). It's intended for physicists and astronomers, so some may find it hard going, but its summary of the current state of tests of GR (complete with references to the original papers) is useful.

Tensor
2005-Mar-09, 02:19 PM
I know I've linked to it many times before, but forgive me if I direct people once again to the Particle Data Group's review of Experimental Tests of Gravitational Theory (http://www-pdg.lbl.gov/2004/reviews/gravrpp.pdf). It's intended for physicists and astronomers, so some may find it hard going, but its summary of the current state of tests of GR (complete with references to the original papers) is useful.

Forgive you????? Thank you. More people should be directed to it. I think I bookmarked that the first time you posted it.