gravity's speed

[Matthew B Hoyt]

On Fri, 23 May 1997 09:14:38 +0200 "Paolo Cavallo"
<ton0621 at iperbole.bologna.it> writes:

>Every fundamental interaction in Nature propagates at the speed of 
>light - not
>only gravity. It's required by special relativity.

Well, only sorta kinda.  During BIG gravitation events this changes. 
Allow me
to quote Einstein (and Max Born) from 1913 in a position I believe
continues to be held by
most physicists. [I assume this is a translation, my text is Fron
_Gravitation_ by Misner,
Thorne and Wheeler, 1970]

Max Born: "I should like to put to Herr Einstein a question, namely, how
quickly the action of gravitation 
is propagated in your theory.  That it happens with the speed of light
does not elucidate to me.
There must be a very complicated connection between these ideas.

Einstein: "It is extremely simple to write down the equation for the case
when the perturbation that one
introduces in the field are infinitely small.  Then the g's differ only
infinitesimally from those that would
be present without the perturbation.  The perturbations then travel with
the same velocity as light.

Born: "But for great perturbations things are surely more complicated?"

Einstein:  "Yes, it is a mathematically complicated problem.  It is
especially difficult to find exact 
solutions to the equations, as the equations are nonlinear."

As one with a BA in physics I translate to mean that big gravitational
changes propagate slower
and faster that the speed of light, if for no other reason than that the
gravitational change is manipulating
the spacetime the wave would propagate through.  Though in any case the
overall speed of
progation is near the speed of light (faster or slower), rather than
instanteously (whatever that
could mean in light of special reletivity).

Matt