Proposals to measure speed of gravity?
z@z
| upthink wrote:
| > Newton thought that gravity acted instantaneously.
|
| Newton was never so rash. He thought:
|
| That one body may act upon another at a distance through a vacuum
| without the mediation of any thing else, by and through which their
| action and force may be conveyed from one to the other, is to me so
| great an absurdity, that I believe no man, who has in philosophical
| matters a competent faculty of thinking, can ever fall into it.
This prejudice of Newton is responsible for the fact that actions
at a distance were forcefully eliminated from physics at the end
of the last and at the beginning of this century.
Already Occam, the first consequent advocate of Galilean relativity
I know of, had developed three centuries before Newton a much sounder
and more modern epistemology according to which actions at a distance
are a completely reasonable assumption.
We must judge hypotheses and theories only by verifiable consequences
and predictions and never by metaphysical claims such as Newton's
prejudice concerning actions at a distance !!!
Kepler accepted instantanous effects over huge distances. This
allowed him not only to assume that the moon affects the tides
but also to postulate a universal gravitational force. Newton's
precursor Galilei ridiculed Kepler's notion that the moon affects
the tides, because the assumption that particles from the moon
come to the earth and affect the tides is really a bit strange.
One should also take into account that (the successful part of)
Newton's theory of gravitation is based on Kepler and that the
assumption that gravity propagates at c would have completely
spoiled the theory.
The faq concerning the problem of finite propagation speed
of gravitity shows once more very elegantly that modern physics
is completely unfalsifiable:
"This cancellation may seem less strange if one notes that a
similar effect occurs in electromagnetism. If a charged particle
is moving at a constant velocity, it exerts a force that points
toward its present position, not its retarded position, even
though electromagnetic interactions certainly move at the speed
of light. HERE, AS IN GENERAL RELATIVITY, SUBTLETIES IN THE
NATURE OF THE INTERACTION "CONSPIRE" TO DISGUISE THE EFFECT OF
PROGAGATION DELAY. ... [emphasis mine]
Since this point can be confusing, it's worth exploring a little
further, in a slightly more technical manner. Consider two bodies
-- call them A and B -- held in orbit by either electrical or
gravitational attraction. As long as the force on A points
directly towards B and vice versa, a stable orbit is possible. If
the force on A points instead towards the retarded (propagation-
time-delayed) position of B, on the other hand, the effect is to
add a new component of force in the direction of A's motion,
causing instability of the orbit. This instability, in turn,
leads to a change in the mechanical angular momentum of the A-B
system. But total angular momentum is conserved, so this change
can only occur if some of the angular momentum of the A-B system
is carried away by electromagnetic or gravitational radiation."
http://www.corepower.com/~relfaq/grav_speed.html
These reasonings can be considered either a refutation of the
the theory or a proof of gravitational radiation which is
assumed to exactly compensate the effects resulting from the
finite propagation speed of gravity, so that the result is the
same as in the case of instantanous propagation.
Momentum conservation without actions at distance is almost
impossible. A lot of faith is needed for believing that in all
possible situations secundary effects emerge cancelling exactly
out the violations of momentum conservation resulting from the
primary effects.
| If Einstein did not like the Copenhagen interpretation of quantum
| mechanics, one dreads to think of the contempt in which Newton would
| have held it.
That Einstein did not like QM actions at distance is easy to
understand: if actions at a distance are possible, then many
reasonings which have led him and others to relativity lose
their logical necessity.
Einstein wrote in 1920:
"In setting up the special relativity, the following ... idea
about Faraday's electromagnetic induction played a guiding
role. According to Faraday, relative motion of a magnet and
a closed electric circuit induces an electric current in the
latter. Whether the magnet is moved or the conductor doesn't
matter; only the relative motion is significant. ... The
phenomena of electromagnetic induction ... compelled me to
postulate the principle of (special) relativity."
(Collected Papers of A.E., Volume 2, p.262)
If even such (IMO absurd) EPR actions at a distance could exist
then also 'common sense' actions at distance should be possible
and Einstein's above reasoning becomes almost meaningless,
because the explanation of electromagnetic induction by actions
at a distance is much simpler and much more consistent than the
SR explanation.
Wolfgang Gottfied G.
Relationality instead of Relativity:
http://members.lol.li/twostone/E/physics1.html
bilge
>If even such (IMO absurd) EPR actions at a distance could exist
>then also 'common sense' actions at distance should be possible
>and Einstein's above reasoning becomes almost meaningless,
>because the explanation of electromagnetic induction by actions
>at a distance is much simpler and much more consistent than the
>SR explanation.
>
Here's a way to try and compare the speed of gravity to the
speed of light. Unfortunately, it's also expensive despite
the fact that I dont have a cheaper method and you'll need to
handle a few details. A few years back, CERN reported that
they were able to to track the gravitational pull of the moon
by the amount it stretched the accelerator ring and consequently
the resonance point. You should also be able to track the
position of the moon optically. Wasnt a mirror left there?
At the point of closest approach, if the speed of gravity
were infinite, you should see the accelerator resonance shift
back a bit before the optical path. Obviously, this is a
precision measurement, and only if you can be assured of some
relationship between the optical path length and the tidal
forces. I personally think gravity and light travel at c,
so I leave the feasibility study to the doubters.
Charles Francis
>Charles Francis wrote:
>| upthink wrote:
>
>| > Newton thought that gravity acted instantaneously.
>|
>| Newton was never so rash. He thought:
>|
>| That one body may act upon another at a distance through a vacuum
>| without the mediation of any thing else, by and through which their
>| action and force may be conveyed from one to the other, is to me so
>| great an absurdity, that I believe no man, who has in philosophical
>| matters a competent faculty of thinking, can ever fall into it.
>
>This prejudice of Newton is responsible for the fact that actions
>at a distance were forcefully eliminated from physics at the end
>of the last and at the beginning of this century.
>
>Already Occam, the first consequent advocate of Galilean relativity
>I know of, had developed three centuries before Newton a much sounder
>and more modern epistemology according to which actions at a distance
>are a completely reasonable assumption.
>
>We must judge hypotheses and theories only by verifiable consequences
>and predictions and never by metaphysical claims such as Newton's
>prejudice concerning actions at a distance !!!
It is no prejudice, but clear thinking about what is possible in a
description of matter. It is not only a principle of relativity, but
also a principle of quantum electrodynamics, which does indeed make
verifiable predictions covering every observable physical phenomena bar
strong interactions and gravity. QED already extends to electroweak
theory, and when QED is reformulated as a discrete theory of particle
interactions with no ontological space-time then it encompasses and
explains gravity too. A number of extensions to the strong interactions
are possible, but they all incorporate the same principle.
--
Charles Francis
cha...@clef.demon.co.uk