From: noelturntive@live.co.uk   
      
   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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