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...

alistair wrote:

[...]
shouldn't we
look at the possibility that some forms of energy do not curve
space-time?

Of course we should. This is a *major* experimental program,
with easily a dozen groups investigating the question of whether
composition affects gravitational fields.

So far, though, not one speck of evidence has been found to
suggest that ``some forms of energy do not curve space-time.''
There are strong limits for electrostatic and magnetstatic
energy,

Reference, please.

strong interaction energy,

Reference, please.

and gravitational binding energy,

Reference, please.

with somewhat weaker limits on kinetic energy and the
energy of the parity-conserving part of the weak interactions.

Reference, please.

For these, we have experimentally ruled out the possibility
that they don't gravitate.

Did you have some other kind of energy in mind?

How about thermal energy? The last reference you gave for this (Will,
section 2.4) did not contain anything on the subject.
http://www.google.com/groups?selm=vg....supernews.com

Hmmm, I missed your response where you abandoned Will, and went to your own
1988 paper, where you note:
"Surprisingly, the observational evidence for this prediction does not seem
to be discussed in the literature."

But this paper is still not available online to nonsubscribers. So, another
trip to the library will be needed to see if there is actually any support
for your conclusion. "Reanalysis" of "existing experiments" is always a
tricky effort.

--
greywolf42
ubi dubium ibi libertas
{remove planet for e-mail}