From: palmer@sfu.ca (Leigh Palmer)
Subject: Re: Detecting Second-Order GR Effects in Binary Pulsars
Organization: Simon Fraser University
Date: Tue, 15 Dec 1992 01:22:30 GMT

In article <MATT.92Dec14125234@physics2.berkeley.edu>
matt@physics2.berkeley.edu (Matt Austern) writes, in response to Tom Van
Flandern:

>The [your] claim, then, is that gravitational radiation is *not* a solution
>to the vacuum form of the Einstein field equations?

>Frankly, I find that claim very difficult to accept.  The vacuum
>Einstein equations just aren't all that complicated, and I don't see
>any way that you could fail to get waves from them.  Can you provide
>some more details?

Sorry to stick my oar in here, Matt, but I feel I must play referee. I'm not a
GR guru, but you aren't hearing what Tom is saying. He is making the entirely
defensible claim that gravitational radiation has neither been detected nor
seen to be emitted. Empirical verification of the phenomenon seems to be
lacking, and the canons of physics require such observation before we accept
its *demonstrated* existence.

The understandable hubris of theoreticians culminates in the "totalitarian
principle" articulated by Murray Gell-Mann: 

                "That which is not forbidden is compulsory."

The dramatic successes of Maxwell, Einstein, and the quantum mechanics have led
us to expect this means that if a theory predicts it, it will be found. 

Well, we also occasionally must invent an ad hoc principle to explain the
absence of some predicted effect. Consider the Pauli exclusion principle and
other "selection rules". Is it entirely beyond the realm of plausibility that,
though a wavelike solution to GR exists (which I'm willing to accept on your
word) it may correspond to no physically consequential observation (or, for the
left-handed, no physically observable consequence)?

A couple of decades ago it was pointed out (I might even say "promoted") that
there exist solutions to SRT corresponding to faster-than-light particles. The
proponent of these beasts even had the temerity to name them; he called them
"tachyons". Subsequently their principal manifestations have been in science
fiction. There is no shred of evidence that they are isomorphic to any
physically observable corpuscle. I've even heard it argued that unobservability
is one of the expected properties of these objects! Such nonsense does not
advance physics, and it certainly does not serve to improve our understanding
of the universe in which we live.

Physics is *description* of the physical universe. The most elegant of theories
is flawed if it predicts what does not exist. Apparently Einstein did not
predict gravitational radiation even though, as you say, "The vacuum Einstein
equations just aren't all that complicated, and I don't see any way that you
could fail to get waves from them." I must also point out that Maxwell did not
predict electromegnetic waves, either; he observed that his synthesis described
a known phenomenon, light, and made therefrom a reasonable extrapolation.

Let's listen to what Tom's saying. He has certainly opened my eyes to some
physics I didn't know before, and he doesn't make claims he can't back up.

Leigh

"Remember that the man whose birth we celebrate this season died a virgin."
                                                         - me
Newsgroups: sci.astro