Re: Gravity Carrier - could gravity be push with shadows not pull?

From: Hal Finney <hal.domain.name.hidden>
Date: Thu, 26 Feb 2004 09:57:29 -0800

Eric Hawthorne, <egh.domain.name.hidden>, writes:
> Is it possible to model gravity as space being filled with an
> all-directional flux of "inverse gravitons"?

Again, this is not really a multiverse question. I hate to be negative,
but there are other forums for exploring nonstandard physics concepts.
Try the Usenet group sci.physics.relativity, where you will find no end
of discussions on this and similar topics. If there is some connection
I am missing between this particular model and multiverse theory, then
I apologize.

These "push gravity" theories have been around for a long time.
There is a book out by a small Canadian press called "Pushing Gravity:
New Perspectives on Le Sage's Theory of Gravitation" by Matthew Edwards,
which summarizes centuries of thought on the matter. The idea goes back
to Georges-Louis Le Sage in the mid 1700s.

Below is a posting to sci.physics.relativity from 2002 by Steve Carlip
which lists some immediate problems with the theory.

Hal Finney

> In sci.physics.relativity Lawson English <english7.domain.name.hidden> wrote:
>
> > Since the "push" theory is (or can be made) 100% compatible
> > (corrections welcome) with the more commonly accepted Newtonian
> > model of gravity-as-pull, how could it be "crap" unless the Newtonian
> > model is also?
>
> It's not at all clear that the "push" theory can be made compatible
> with Newtonian gravity. It's certainly true that no one has managed
> to do so yet.
>
> Here are three major problems:
>
> 1. Drag: Planets are not at rest with respect to the hypothetical
> pushing particles, and as a consequence, would experience drag.
> (Standard analogy: if you run through the rain, you experience
> a net force on your front side.) It's not hard to compute this drag
> quantitatively; it's much too large to be compatible with Solar
> System observations. This was Feynman's objection in the
> Feynman Lectures.
>
> 2. Aberration: in a ``push'' theory, the Earth experiences a net
> force toward the Sun because the Sun blocks some of the pushing
> particles, casting a ``shadow.'' But the Sun is not stationary; its
> position changes with time, and the ``shadow'' points to its past
> position, not its present position. If, for example, the hypothetical
> pushing particles traveled at the speed of light, the Earth ``now''
> would be pushed toward where the Sun had been a bit more than
> eight minutes ago. This might seem like a small effect, but in fact
> it would drastically destabilize planetary orbits, in a way that is
> easily ruled out by observation.
>
> 3. Equivalence principle: we know from experiment that not only
> rest mass, but all forms of energy contribute to gravitational mass.
> A hot brick weighs more than a cold one, because of the kinetic
> energy of the molecules. A push theory would have to explain why
> the hypothetical pushing particles ``push'' against kinetic energy
> (and nuclear binding energy, and electrostatic and magnetostatic
> energy, and even gravitational binding energy) in exactly the way
> they would if that energy had a mass E/c^2. No one, as far as I
> know, has come even close to an explanation for this.
>
> Now, points 1 and 2 operate in opposite directions---drag gives an
> acceleration opposed to a planet's motion, while aberration gives
> an acceleration in the direction of motion---and one might hope
> that they could be made to cancel. But in fact they have drastically
> different dependences on masses and distances, so even if they
> could be ``fine tuned'' to cancel for one orbit, they would not
> cancel for others.
>
> > Surely someone, somewhere has examined the QM/GR
> > implications of the alternative view and found them wanting,
> > or at least, a dead end?
>
> I don't think the theory has ever been formulated clearly enough,
> and in a way that isn't already ruled out by observation, to
> look at GR implications. But my immediate reaction is that it
> simply doesn't have enough local degrees of freedom to be
> compatible with GR. For instance, how do you get quadrupole
> gravitational waves? And what prevents monopole and dipole
> waves?
>
> Steve Carlip
Received on Thu Feb 26 2004 - 12:59:34 PST