🚀 go-pugleaf

In article <STEINLY.92Sep29131347@topaz.ucsc.edu> steinly@topaz.ucsc.edu (Steinn Sigurdsson) writes:
>In article <MATT.92Sep29114552@physics.berkeley.edu> matt@physics.berkeley.edu (Matt Austern) writes:
>
>   I contend that in a static situation (i.e., one where there is no
>   gravitational radiation), it is meaningless to talk about the speed of
>   propagation of gravity, since nothing is propagating.  I contend,
>   then, that detecting a finite speed of gravitation is equivalent to
>   detecting the effects of gravitational radiation.
>
>I agree absolutely, there is however a point that - as Tom van
>Flandern is happy to note - is often glossed over, namely that
>if you do the calculation in a retarded potential formalism
>the first two (1/2) order terms in (r - v/c) cancel - there is
>no aberration, and hence the L-W formalism is not very useful.
>You can look at it as either a very neat and not unexpected
>feature of GR or as a Profound Mystery indicating something very
>basic ;-)

Hmm, this is peculiar.  My feeble Quayle's-eye view of gravity led me
to the thought that finite propagation of gravity was only detectable
in accelerating situations (such as two stars rotating about each
other).  I am now hearing an equivalent statement, but expressed in
terms of a distinction between gravitation and gravitational
radiation.  So I'm guessing that the above first-order cancellation
must be making precise the obvious intuition here.

But in that case, is "static gravitation without radiation" a real
distinction, or just (a corollary of) one of the above views (L-W? What
is the lineup?).  (Scott: maybe you could update your FAQ on
gravitational radiation to address "static gravity" as well, and mention
L-W if appropriate...)

Granted that it would be convenient if gravitational radiation turned
out to be quantized, what about "static gravitation"?  Can the GR view
of gravity as space warp be reconciled with a force field view of
gravity?  (For this not to be possible would make gravity truly
mysterious to me.)  And if so, then would it be any less convenient for
this "static" field not to turn out to be quantized?  And if you made
it through that double negative, are the gravitons of "static gravity"
at all different from the gravitons of gravitational radiation?

Sounds like I should retire to read MTW and friends before I spout too
much more of this nonsense.  Where are these questions addressed?

-- 
=================================================== In short, I am floundering
Vaughan Pratt   pratt@cs.Stanford.EDU  415-494-2545 around and don't take what
=================================================== I say seriously.