A speed beyond light question ^^

The Kopeikin study has been debunked. I'd suggest you read that page on Metarresearch:

http://www.metaresearch.org/cosmology/speed_of_gravity.asp

I mean, you don't need to be Albert Einstein to see how the thing works. Just draw a circle, a point on the circle, a force vector going from the point to the center ( instantaneous gravity like in real life), and then a vector from the point in the same direction as a vector would have had from the point to the center five or ten degrees back on the circle....

gungasnake wrote:

I mean, you don't need to be Albert Einstein to see how the thing works. Just draw a circle, a point on the circle, a force vector going from the point to the center ( instantaneous gravity like in real life), and then a vector from the point in the same direction as a vector would have had from the point to the center five or ten degrees back on the circle....

And how exactly does this high school physics prove that if gravity weren't instantaneous, but only propagated at the speed of light, the solar system would fly apart?

"It is one of the peculiar aspects of the theory of gravitation, that it has both a field interpretation and a geometrical interpretation. ... the fact is that a spin-two field has this geometrical interpretation: this is not something readily explainable -- it is just marvelous. The geometrical interpretation is not really necessary or essential to physics.

Brandon9000 wrote:

gungasnake wrote:

I mean, you don't need to be Albert Einstein to see how the thing works. Just draw a circle, a point on the circle, a force vector going from the point to the center ( instantaneous gravity like in real life), and then a vector from the point in the same direction as a vector would have had from the point to the center five or ten degrees back on the circle....

And how exactly does this high school physics prove that if gravity weren't instantaneous, but only propagated at the speed of light, the solar system would fly apart?

Brandon - Gunga is actually correct in that statement. High-school physics is mostly Newtonian physics, and Newton's gravitational equations unquestionably show the transmission of gravity to be instantaneous.

This was never doubted by anyone since Newton, btw. Subsequent confusion arose because relativity equations for gravity (mathematically speaking, which is the only approach I'm qualified to discuss, being a mathematician and not a physicist) permit both a "geometric" and a "field" interpretation.

I took a seminar with the late, great, Dick Feynman, on mathematical applications of the laws of physics (applications frequently found in apparently completely unrelated fields, like the pricing of options and warrants in financial markets, for which another teacher, Bob Merton, got a Nobel prize, as of course did Feynman) and I posted earlier on this thread a link to his theory of gravity, where he confirms this.

I'll see if I can find the excerpt on the web - BRB. Happy 2009 to y'all, btw!

Gunga - at least Dick Feynman agreed with you, even if Brandon and Edgar don't.

Quote:

"It is one of the peculiar aspects of the theory of gravitation, that it has both a field interpretation and a geometrical interpretation. ... the fact is that a spin-two field has this geometrical interpretation: this is not something readily explainable -- it is just marvelous. The geometrical interpretation is not really necessary or essential to physics.

I typed this text in from a printed book, not available online, but this is the book, available in any university or other scientific library:

R.P. Feynman, Feynman Lectures on Gravitation, Addison-Wesley, New York (1995) p. 113

................
First of all, you're not correct, because Newton's equations make no statement whatsoever about the speed of propagation of gravity. .......

Given two bodies attracting each other, the question then arises as to the speed of propagation of the force itself. Newton demonstrated that unless the force was instantaneous, relative motion would lead to the non-conservation of angular momentum. This he could observe as not being true, in fact the conservation of momentum was one of the observations that led to his theory of gravitation in the first place. He therefore concluded that gravity was instantaneous. In physics the angular momentum of an object with respect to a reference point is a measure for the extent to which, and the direction in which, the object rotates about the reference point. ...

Brandon9000 wrote:

................
First of all, you're not correct, because Newton's equations make no statement whatsoever about the speed of propagation of gravity. .......

LOL Brandon - you don't even know grade school physics if you never heard of Newton's equations; high-school or higher are sadly beyond you, if that's the case, but I rather think your apparent crass ignorance is due to late partying, so here's an easy-to-understand version of Newtonian physics:

Quote:

Given two bodies attracting each other, the question then arises as to the speed of propagation of the force itself. Newton demonstrated that unless the force was instantaneous, relative motion would lead to the non-conservation of angular momentum. This he could observe as not being true, in fact the conservation of momentum was one of the observations that led to his theory of gravitation in the first place. He therefore concluded that gravity was instantaneous. In physics the angular momentum of an object with respect to a reference point is a measure for the extent to which, and the direction in which, the object rotates about the reference point. ...

http://www.nationmaster.com/encyclopedia/Speed-of-gravity

Read the damn book, Brandon, exact reference was posted above. Sober up enough to learn basic Newtonian gravity (infinite GRAVITY propagation speed MUST apply IF angular momentum is to be conserved, and the conservation of angular momentum wasn't doubted by Newton!) first, though.

I really don't see where you add value to this discussion if you can't even grasp complete BASICS. Sorry I'm not going to waste any more time until you start showing at least SOME grasp of basic concepts, never mind relativistic gravity field equations.

The satellite swings low and fast over the southern hemisphere and then slows as it rises toward its apogee in the northern hemisphere, making it appear to "hover" in the sky over northern territories for long periods of time.

Brandon - for reasons unrelated to this discussion, my only work with satellites has centered on Molniya orbits. The speed of satellites in such orbits varies considerably, as I assume you know. As to the field vs geometrical interpretations of gravity, I don't think I can improve on Feynman's analysis.

Some background info for those unfamiliar, though it's a digression from the topic of gravity:

Quote:

The satellite swings low and fast over the southern hemisphere and then slows as it rises toward its apogee in the northern hemisphere, making it appear to "hover" in the sky over northern territories for long periods of time.

http://www.centennialofflight.gov/essay/Dictionary/MOLNIYA/DI166.htm

P.S. to Brandon: it's ironic that you, a physicist, are taking the position usually adopted by mathematicians (geometrical) on gravity, whereas I, trained in mathematics, see the field equations for gravity propagation as blindly obvious! But as Feynman observed, both interpretations are valid - and FYI, neither has been "superseded" yet - check the Lorentz transformations, they're perfectly consistent with relativity, and show the speed of gravity to be as close to infinity as we can measure.