On Thursday, 25 May 2006 at 21:00:38 UTC+1, carlip...@physics.ucdavis.edu wrote:

Blaze Labs <sav...@blazelabs.com> wrote:

Hello guys,
I would like to know the main reasons why the push gravity concept is
not considered as a viable concept by mainstream science.

There are a few generic objections, along with particular problems with particular models. The main generic objections I know of are
1. Drag: As Feynman pointed out in the Feynman Lectures, anything
that's capable of "pushing" will also create drag on a moving object.
There are very strong observational limits on such drag, in the
Solar System and in binary pulsar systems.

It's hard to defend a EMR push gravity model if critics \_give_/ push
gravity effects that the model itself does not predict. Why exactly
would push gravity as EMR give \_drag_/ to an orbitting satelitte?
Notice any force felt in push gravity is only observed if another mass
throws a *shadow* on the first body. Otherwise the object floating in
space is always subject to an equal `push' from all directions of the
universe. Regardless of its motion relative to any other object.

Steve and others assume push gravity as EMR would create drag. But no explanation as to how this drag is created. For instance an object in a
push gravity universe always has uniform EMR pressure coming in from all
sides. (Except of course if it's experiencing a shadow from another
nearby mass.) This is the basics of the model. In the same way that an
object will continue in an inertial path unless acted upon by an
external force. Which can only be another objects gravitational shadow.
So an object travelling through the solar system that from our
perspective is moving...is actually at rest in its own frame. With an
equal push of universal EMR push gravity from all directions. And the
solar system is moving.

This is possible because in a push EMR model a BB is not neccesary. And
being a novel gravitational model, GR does not apply. Which means any
atom in an infinite universe is always subject to an even push from all directions. Any point in a infinite universe, ALWAYS has an equal and
infinite amount of universe in all directions. Regardless of its motion relative to any other atom.

You immediately run into trouble with the principle of equivalence,
for one thing. Electromagnetic waves don't interact with other electromagnetic waves (except by truly tiny quantum effects); but
gravity bends light. Nor do electromagnetic waves interact with
internal energy, not with neutrinos; but these *are* affected by
gravity. You also run into grave problems with aberration (see above),
and very probably with drag. You would *further* have to explain why
this high frequency radiation is not absorbed by the Earth enough to
lead to gravitational screening of the type ruled out by experiment.

This is not a problem in a EMR push model. The push model assumes much
greater energies than those observed exist. And generally they pass
through all mass, like the earth. But a small amount interacts with each
atom. We know this happens because we can observe small amounts of
visible light reflects off atoms. And \_pushes_/ the atom. As in solar
sails. This is evidence that EMR does interact with atoms and can give
observed push. The very basics of a push model are confirmed.

[Moderator's note: The above is an amalgamation of two overlapping
posts. I have also removed superfluous quoted text and reformatted it somewhat. Also, note that Stever Carlip's original reply addressed
several arguments against such theories; at the very least, one would
have to refute them all, not just the ones mentioned above. -P.H.]

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On Thursday, 25 May 2006 at 21:00:38 UTC+1, carlip.. wrote:

Blaze Labs <> wrote:

Hello guys,
I would like to know the main reasons why the push gravity concept is
not considered as a viable concept by mainstream science.

There are a few generic objections, along with particular problems with particular models. The main generic objections I know of are

( Moderator: Thanks for the format edits on my last post. I’ve tried to better follow The formatting rules here and answer some of the other
points you suggested I address. )

2. Aberration: Suppose "pushing" particles move at a speed v, and
look at the effect on the Solar System. For a planet at distance d
from the Sun, the "push" will not be toward the instantaneous
position of the Sun, but towards its position at a time d/v in the
past. This is a drastic effect -- if v is the speed of light, the
Solar System would be drastically unstable over a thousand-year
time scale.
(The effect of aberration is to increase the velocity of a planet,
and you might hope that drag would cancel it. But it's easy to
check that such cancellation can occur at, at most, one radial
distance from the Sun.)

Instantaneous gravity or at least the appearance of it is not a
problem for emr push gravity.
So for example: A point distance d from the sun. Radiation
pushes from above at distance d. You don’t have to wait for it to
come across the universe. It’s already arrived and is present
everywhere. Not just at point distance d. Otherwise push gravity
wouldn’t work.
The Same applies with the slightly less “push” coming up from the
sun. The suns “shadow” as it is called by some. If you suddenly materialised at point distance d from the sun you don’t have to
wait for this radiation to come from the suns interior. It’s already
there at that point defined by distance d. Or at any other point
outside the suns surface. The suns push gravity shadow pushing
out, in the suns frame, has been there and propagating outwards,
for the billions of years of its life. Essentially this allows the push
model to appear “instantaneous” at any point, even though the
speed v of the emr gravity itself is finite.

3. Principle of equivalence: It is observed that gravity acts not
only on mass, but on all forms of energy. A "push gravity" theory
would have to come with an explanation of how the particles that do
the pushing manage to push against, for example, electrostatic binding
energy and the kinetic energy of electrons in an atom, and why that
"push" exactly matches the "push" against ordinary matter.
In particular, we observe that gravitational binding energy itself gravitates. This seems to require self-interaction among the
pushing particles. On the other hand, the accuracy of the inverse
square law over long distances requires that the self-interaction
be very small -- you certainly need a mean free path larger than
the size of the Solar System if you don't want to mess up Pluto's
orbit.

I can’t see any incompatibility with Newtonian or Keplerian Principle
of Equivelence. And Steve doesn’t actually cite any specific problems.
And regarding any problems with relativistic PoE, its important to note
Push Gravity and GR are two seperate theories of gravity. Neither needs
to be bound by assumptions made by the other.

4. Gravitational screening: There are very strong limits on the kind
of "gravitational screening" one would expect from a "push gravity"
model -- see, for example, Unnikrishnan et al., Phys. Rev. D 63 (2001) 062002.

Gravitational screening. I’ve checked the paper abstract... it’s paywalled. I think Steve didn’t read it properly though. It mentions shielding but
no reference to push gravity. Rather an anomolus observation that
the moon may block some of the suns gravity.

[...]

Please note, I am NOT asking about Le Sage ultramundane particles
theory (which also falls under the push gravity category), which I can
easiely discredit myself. I'm mostly interested in the concept of
electromagnetic radiation pressure of high frequency radiation acting
as the gravitational mechanism, and its shadowing creating the inverse
square law, low pressure areas.

You immediately run into trouble with the principle of equivalence,
for one thing. Electromagnetic waves don't interact with other electromagnetic waves (except by truly tiny quantum effects); but
gravity bends light. Nor do electromagnetic waves interact with
internal energy, not with neutrinos; but these *are* affected by
gravity. You also run into grave problems with aberration (see above),

This is an odd criticism. Push emr gravity does not need to have emr interacting with emr. And I won’t broach gravitational bending. It’s a hot perennial topic with refraction vs GR and needs its own thread.
And as far as I’m aware neutrinoes are not considered EMR. Regarding “Internal energy”.(atoms?) this is not specified but if an atom already
can be shown to be pushed by emr via solar sails (IKAROS) then
by association the atoms internal energy has been affected by emr.

and very probably with drag. You would *further* have to explain why
this high frequency radiation is not absorbed by the Earth enough to
lead to gravitational screening of the type ruled out by experiment.
Note that "high frequency [electromagnetic] radiation" is gamma radiation. There are experimental measurements of very high energy gamma rays, and
a fair amount is known about their spectrum. I suspect you would have
a very hard time reconciling your model with these observations

Once again an odd claim. Push gravity predicts push comes from very
high energies beyond the upper energies of the known spectrum.
To say that these energies don’t exist because they haven’t yet been observed yet is in itself not a very good assumption in my opinion.
Notice also that EMR push gravity predicts these energies do exist and
states that the observed interaction of hi energy radiation with atoms
will manifest as gravity. Which is observed.

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It was proven (by Feynman?) that push gravity cannot work if whatever
flux does the pushing is reflected from a mass. That is because the
shadow of any body is exactly balanced by reflections from that body
from the other side. Therefore push *cannot* work by reflection.

The other possibility is push by absorption of the flux. This shows much
more promise because:

1. Such absorption would need to happen at the level of atomic particles
and would therefore cause increase in mass of particles as described in Narlikar's variable mass hypothesis (VMH).

2. Such a change in particle masses over time would lead to a blue shift
of atomic spectra over time. This looks exactly like a red shift of
spectral lines with distance because distance is a measure of how far
back in time we look. So VMH automatically offers an explanation for the cosmological redshift.

3. The rate of absorption must exactly explain the cosmological
redshift, and that rate will give exactly the correct strength of
gravity relative to e/m forces as 10^40 weaker.

4. It helps if it is understood that particles are some special form of standing waves of e/m as described my Milo Wollfe who proved that all of
the properties of the electron were excactly matched by the Wave
Structure of Matter (WSM) model. The exact e/m wave structure of
nucleons has not been determined as far as I know.

5. When the particle standing wave is understood as an incoming and
outgoing (after it passes through the centre) wave as Feynman and
Wheeler almost came to understand for an electron then we can observe
the true meaning of the Large Numbers Hypothesis (LNH) as favoured by
Dirac and Eddington. When a wave has traveled 10^40 (Compton)
wavelengths of a nucleon then it spreads over a sphere of area of 10^80
times a nucleon by which point it becomes the incoming wave of all other nucleons in the Universe. It is fully absorbed and re radiated at the
Hubble scale.

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