Bob McElrath <[EMAIL PROTECTED]> wrote:
To: Henry Spencer <[EMAIL PROTECTED]>True, but macro changes are not instantaneous. They are generally smooth transitions through an existing field (as someone earlier commented on electromagnetic fields).
CC: ERPS <[EMAIL PROTECTED]>
Subject: Re: [ERPS] Perhaps OT: Speed of gravity
Date: Wed, 18 Dec 2002 19:57:54 -0600
Henry Spencer [[EMAIL PROTECTED]] wrote:
> On Wed, 18 Dec 2002 [EMAIL PROTECTED] wrote:
> > Article arguing that the speed of gravity may be infinite...
>
> It has long been understood that orbits would not be stable if gravity
> showed any detectable aberration (change in apparent direction with motion
> of the observer), implying that either gravity's velocity is inordinately
> high or else it does not propagate at all.
>
> Orthodox general relativity says that gravity is a matter of the shape of
> space -- it's not a form of radiation at all. There is no exchange of
> radiation between Earth and Sun to keep Earth in its orbit; Earth is
> moving through space curved by the influence of the Sun, and Earth
> naturally follows a curved path as a result. (I oversimplify a bit.)
>
> Gravity waves, aka gravitational radiation, carry *changes* in the
> curvature of space. Relativity predicts that they move at the speed of
> light, a prediction which has not yet been verified (although there is
> some indirect evidence, like measurement of the energy loss of binary
> pulsars, which agrees quite closely with relativity's predictions here).
>
> If the name "metaresearch.org" hadn't made your bogometer twitch, by the
> way, the name "Tom Van Flandern" at the top should. He's a frequent
> advocate of, to put it politely, far-out theories. It's possible that
> he will eventually be verifiably right about something, but that is not
> the way to bet. Don't sell your relativity textbooks yet.
Kook or no, I think he's right.
I think essentially it boils down to Einstein's equation:
8 pi G = T
where G is the Einstein tensor (geometry) and T is the stress-energy
tensor (matter). General relativity follows from the equality, and is
well tested. Changes in the matter distribution are reflected
*instantaneously* in the geometry. So it should be no surprise that
this is, effectively, an action-at-a-distance theory.
Tony Fredericks "Mind that bus!"
Amateur Rocket Scientist "What Bus?"
E.R.P.S. Member SPLAT!! - Arnold Rimmer
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