Speed of Gravity Results 'Incorrect,' Physicist Says

Space.Com ^ | 16 January 2003 | Robert Roy Britt

[NukeMan]

Aren't many mathematical principles (theorems and such) assumptions which lead to seemingly valid conclusions?

Yes, but theorems are different than physics. Mathematicians are epistemological zealots, and aren't supposed to use 'observations' to prove or disprove a theorem, but only the axioms and logical, non-contradictory application of identities afterwards. Unless, of course, you are Luitzen Brouwer and others like him, who don't accept the law of the excluded middle!

[Paradox]

I'm a little perplexed at the controversy, as this experimental methodology has been "on the table" for some time. You'd think these objections would have been raised from serious quarters sooner.

I read their results in "New Scientist" magazine. Perhaps the establishment is a bit miffed that they went ahead and "published" in a non-technical weekly such as that one?

I also wonder how much this has to do with the work by Kopeikin. To quote New Scientist:

"He reworked the equations of general relativity to express 
the gravitational field of a moving body in terms of its mass, 
velocity and the speed of gravity. If you could measure the 
gravitational field of Jupiter, while knowing its mass and 
velocity, you could work out the speed of gravity". 

Is Kopeikins work generally regarded as valid? I admit I dont keep up on physics.

[Grampa Dave]

It would be nice if they addressed the phoney science advanced by the global warming Watermelon Jihadists.

[atlaw]

I just dropped a flashlight on the kitchen floor. It broke, but as far as I could tell, the light and the flashlight got there at the same time.

[LiteKeeper]

read later

[RightWhale]

Kopeikin said he has found a mistake hidden deep in Will's calculations, and that other mathematicians concur. "He does not agree," Kopeikin said of Will today. "But mathematics is against him."

---

Be on the lookout for the specific math that is in question.

[Free the USA]

http://www.freerepublic.com/perl/bump-list

[Mad Dawgg]

"Thursday on a report from last week that claimed the speed of gravity had been determined by observation and was equal to the speed of light.

OK, so if the speed of gravity equals the speed of light and according to Albert E. to attain the speed of light you would go back in time. Then when I fall down I should get younger ...

Correct?

[Roscoe]

Peter van Nieuwenhuizen, a physicist at Stony Brook University in New York, called the interpretation of the results by Fomalont and Kopeikin "compete nonsense,"

Ouch. Bump.

[AdA$tra]

Gravity is working my my body fast enough.

[XLurk]

I always thought that the speed of gravity varied relative to the cost of the carpet (or something like that...).

[Paradox]

The speed of Gravity varies in proportion to the age of the woman, and the size of her breasts.

[Fiddlstix]

Bump

[txhurl]

So it terminal velocity still 120mph, or is it 115 now?

[Mind-numbed Robot]

Thankyou for the response concerning theorems and such and mathematicians and observation, but it doesn't satisfy my ignorant but curious mind. Isn't much, perhaps most, of physics, especially the quantum kind, mathematics. Perhaps later observation is necessary to verify postulations in accordance with the "scientific method" but the guts of it all is mathematics, right? Isn't the issue in question with this article not so much the observation but the math behind it?

If my questions seem like a kid constantly asking why, then I understand if you want to ignore them.

[William Tell]

Physicist said: ' I'm a little perplexed at the controversy, as this experimental methodology has been "on the table" for some time. '

Physicist, I haven't had time to read up on this and I can't handle any General Relativity content. However, I have a perhaps simplistic view of what might be observable here.

Einstein's prediction that light would be affected by gravity predicts that light from a distant star will not follow a straight line when passing close to our sun but will be slightly bent toward the sun. Thus, the apparent position of a star which appears near the sun during an eclipse can be different than it would be without the effect of the sun's gravity.

I am imagining that Jupiter's gravity would have the same effect on the light from a distant star ( or galaxy ), and thus the light coming from the star would bend toward Jupiter if it passed through the stronger gravity near its surface.

Since the measurement of time has become so accurate with cesium beam clocks and such, it would be possible to chart the apparent position of the star versus time.

If gravity was instantaneous, then the symmetry of Jupiter's shape would result in equal bending of light on either side as Jupiter passes in front of the star. For the sake of my description, imagine that Jupiter is passing from right to left.

As Jupiter nears the path of light from the star, the light is bent such that the star would seem to shift toward our left as Jupiter nears it. The light would be travelling on a more and more curved path which would pass closer and closer to Jupiter's surface, until it would finally have to pass through Jupiter to get to us. At that instant, the star would disappear behind Jupiter.

As Jupiter moves further to the left, the star will appear on the right of Jupiter. Its position will be shifted to the right from where it would be without the presence of Jupiter. As Jupiter continues to pass to our left, the apparent position of the star will move to the left until it once again occupies the position in the sky expected in the absence of Jupiter.

Since the travel times to earth are virtually the same for all of these light rays, and assuming that gravity is instantaneous, I would predict that the apparent movements of the position of the distant star would be symmetrical with respect to both time and position of Jupiter. Or, in other words, if a movie of this event were filmed and run backwards, the events would be just as if we were viewing the original event in a mirror.

Now, finally, for my question. Is the experiment alluded to here one of measuring asymmetry in the apparent shifting of the position of the star? I can imagine that this event might have an asymmetrical appearance in both time and space if the gravitational field being generated by Jupiter was slight lower in the direction in which Jupiter is advancing because of a finite propogation speed for "gravity waves" or "gravitons" or whatever is interacting with the photons from the distant star.

Is this roughly what is happening? I am trying to save myself the disappointment of looking up the source materials and finding that I can't follow it.

Thanks for any tutoring.