Re: Is Einstein's Principle of Equivalence true?
From: Tom Roberts (tjroberts_at_lucent.com)
Date: 11/09/04
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Date: Tue, 09 Nov 2004 08:57:06 -0600
RP wrote:
> Tom Roberts wrote:
>> The situation is similar for GR vs NM. To "explain" the precession of
>> mercury an adherent of NM would have to assume some unknown "Torque",
>> which would have no predictive power -- the assumed Torque must be fit
>> to the observations. And such a die-hard adherent of NM would have to
>> invent additional "Torques" for all the other tests of GR.... GR fits
>> the observations without any additional assumptions. And GR has a
>> larger domain of validity.
>
> Only one additional assumption must be incorporated into NM to account
> for these effects: Long range forces, and the impossibility of "closed
> systems".
No, you must also postulate that there are additional "Torques" that
JUST HAPPEN to behave in a manner indistinguishable from the way GR
predicts the non-Newtonian terms behave. And you need one additional
"Torque" for each test of GR, because you have no theoretical basis to
relate them to each other. That is not science, that is the way
"Creationists" attempt to "explain" evolution.
> Moreover [Newton] never postulated instantaneous
> action at a distance, but rather thought such a notion was the greatest
> absurdity.
And yet, in Newtonian gravitation the potential here and now depends on
the distribution of matter everywhere in the universe RIGHT NOW. While
Newton may have disliked instantaneous action at a distance, it appears
in his equations. GR, on the other hand, does not have instantaneous
propagation (at least in the PPN approximation where this can be
addressed)....
> Now as for your torque, it need not be assumed, it is rather "derived"
> as a necessary direct result of the application of Newton.
Not true. You have no way to predict the motion of a planet without
first postulating the "Torque" on it. If you determine the "Torque" from
the planet's motion, then you have no predictive power, and are not
doing science (look up "Creationism" for examples of that approach).
> Moreover it
> is you who are making the baseless assumption, namely, that there is no
> counter torque generated on the Sun.
No. People have looked long and hard. But yes, the standard attitude is:
calculate all forces on the planet using all known physics. Do that and
GR provides a prediction of its motion in agreement with observations --
No additional "Torques" are needed. NM, on the other hand, needs
additional "Torques" that JUST HAPPEN to behave as GR predicts....
> A variation of the inverse square
> law of gravity over r is sufficient to account for advancing
> periheilions,
Yes, you can postulate may kinds of invisible blue fairies ("Torques",
"variation of the inverse square law of gravity over r"). The rest of us
want to do physics.
Such an assumption, for instance, cannot account for the
Lense-Thirring effect, or the emission of gravitational
waves from binary pulsars, or the variation in clock rates
with altitude, or....
> IOW, Newton may simply not be a complete theory.
RIGHT! And GR is by far the leading contender as a replacement. Sure you
can make all sorts of other guesses about invisible blue fairies, but
none of them have the elegance, consistency with experiment, generality,
and scope of GR.
> And lastly, it
> cannot be falsified, period, because it is a tautology. Any variations
> that you observer (from Newtonian predictions) are not the fault of
> Newton, but of your own omission or misapplication of the parameters.
That is YOUR approach, not GR's. GR makes specific and detailed
predictions that could be falsified, but are in good agreement with
observations. Your method of guessing arbitrary invisible blue fairies
("Torques") can never be falsified, and is therefore not science.
Science is about finding theories with predictive power, not just
guessing how observations could be fit to arbitrary assumptions.
Tom Roberts tjroberts@lucent.com
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