🚀 go-pugleaf

In article <1992Sep29.065640.18839@CSD-NewsHost.Stanford.EDU> pratt@Sunburn.Stanford.EDU (Vaughan R. Pratt) writes:

   If we had chosen our parents more carefully so as to be born in a solar
   system with a binary star, we might find it easier to determine the
   velocity of gravity experimentally than with good old Sol.  In a binary
   system the gravity from each component should arrive at the other
   component delayed by several seconds, whence it should appear to be
   coming not from the center of the "transmitting" star, but where that
   center was a few seconds earlier.  While this isn't much of a
   displacement, it might be just enough to be measurable with enough
   technology, care, and time.

Figured I might as well interject at this point.
Tom? You lurking there waiting to pounce??? ;-)
The "gravity" from each component in a binary star does
not arrive delayed, see for example LPPT 12.4 and MTW 18.4 and 39.9,
especially eqn 39.64

Essentially, in GR, bodies moving geodesically act as if the
classical force is coming from a body at the geodesically projected
position of the body - to the first 2.5 orders at least, the higher
order effect shows up as gravitational radiation. What happens
if one of the bodies is moved by a "external force" is not clear,
as the boundary conditions of the problem have never been well
defined as applications of "force" require some rearrangement
of the local mass-energy distribution...

*  Steinn Sigurdsson   			Lick Observatory      	*
*  steinly@lick.ucsc.edu		"standard disclaimer"  	*
*  The laws of gravity are very,very strict			*
*  And you're just bending them for your own benefit - B.B. 1988*