At http://hometown.aol.com/djmenck/gravity.html  there's an attempt at a materialistic derivation of gravity, including inverse square, perihelions, and new predictions.  The model used is Steven Rado's ideal gas sink theory. If correct, then gravitational constant, relationship of force to mass, all mathematical relationships follow from ideal gas mechanics.

At http://hometown.aol.com/djmenck/gravity.html  there's an attempt at a materialistic derivation of gravity, including inverse square, perihelions, and new predictions.  The model used is Steven Rado's ideal gas sink theory. If correct, then gravitational constant, relationship of force to mass, all mathematical relationships follow from ideal gas mechanics. 1) The derivation of 1/r^2 gravitational forces First let me summarize the idea of Dennis McCarthy. He considered a radial flow of Ether converging toward a point O. He claimed that the pressure forces experienced by an _object_ of mass m at a point P in this flow gives a radial attractive force proportional to G M m / OP^2. This reproduce therefore the gravitational forces which would be created by a mass M placed in O. This presentation is naive and oversimplified but it is enough in order to understand my forthcoming criticisms. a) this demonstration forgot completly sail effects . Indeed imagine a coin placed such that its plane makes an angle of 45 degrees with the local flow. Then the coin will not only be pushed toward O but also in an orthoradial direction, these two forces being of equal strength. Therefore an initialy motionless coin at a point P in the _frame_ where the flow is radial will start to move with an angle of 45 degrees with respect to the direction OP !!!!! This a) is enough to demolish the whole thing but let's pretend I have not seen this problem. b) Let's now consider the system Moon-Earth for example. With the Moon in the middle of the radial flow which is supposed to reproduce Earth's gravitational field, this flow can not be radial anymore because it will be heavily perturbated by such a big obstacle. Therefore the toy model presented on this web page is not able to treat even the simplest possible gravitational system. c) A more elaborate treatment is therefore required. For a system such as Sun + Jupiter and its satellites, I am pretty sure that no analytic solution can be found to such a complicated hydrodynamical system. Therefore numerical analyses are needed and unless Dennis McCarthy has a few supercomputer in his cave, I doubt we will see any result for real systems such as the one I have just described. 2) Advance of perihelion Considering not only a radial flow but also a vortex of Ether, it is claimed that an hydrodynamical model can give a radial force of strength         F=G M m/r^2 + L m/r^3 where L is some constant. It is then claimed that  such a force can account for the advance of the perihelion of the planets in our solar system and therefore that there is a hydrodynamical alternative to General Relativity for this effect. Le's believe that the above force can indeed with the same value of L for all orbits reproduce the prediction of GR. a) First, the criticisms made in 1) can be reproduce here. Again I could then stop here but let's imagine that these problems are solved. b) Then even if the above model is able to give the same results as GR, it is obviously an inferior one since it relies on two free parameters (G and L) whereas GR has only one relevant one (G) for the class of astronomical phenomena studied here. Moreover it turns out that L is obtained from the experimental measurements of the advances whereas G is determined independently by using high precision laboratory experiment on Earth. The existence of the underlying hydrodynamical explanation turns out to make things even worse since it introduces a dozen of completly unknown parameters which are hidden behind G, M and L in the above formula for the force F. 3) conclusion So it appears that what is proposed by Dennis McCarthy is at best a kindergarten model. There are some situations in science when even very sketchy models can have an interest. One of them is when a leading theory is in crisis because of new unexplained experimental results. In these conditions, and in an exploratory phase, one can try wild and incomplete approaches. However General Relativity is not in crisis at all and therefore Mr. McCarthy's models have no interest at all.

3) conclusion So it appears that what is proposed by Dennis McCarthy is at best a kindergarten model. There are some situations in science when even very sketchy models can have an interest. One of them is when a leading theory is in crisis because of new unexplained experimental results. In these conditions, and in an exploratory phase, one can try wild and incomplete approaches. However General Relativity is not in crisis at all and therefore Mr. McCarthy's models have no interest at all. BTW, RFD, induced heating (due to energy deposition), the drag force on spacecraft and other observed effects are a 'direct' consequence of such physical causal model.  GR doesn't even predict gravitational induction heating which is both observed and matches the expected magnitude for such. I think that as usual, you egotistical bias is precluding proper judgement. Paul Stowe

I think that as usual, you egotistical bias is precluding proper judgement. Instead of this personal attack, you could have made meaningful comments about my criticisms. Anyway I would be delighted if you could give the references and precisions I asked for.

So it appears that what is proposed by Dennis McCarthy is at best a kindergarten model. There are some situations in science when even very sketchy models can have an interest. One of them is when a leading theory is in crisis because of new unexplained experimental results. In these conditions, and in an
... read more »

If particles colliding the coin are able to transfer to it some momentum, which is the fundamental premise of this model, then if the coin makes an angle of 45 degrees with the flow, it will be pushed in a direction orthogonal to the plane of the coin. Frankly your comment is quite strange. Well, while I understand that the nuances of radiation transport may be outside your area of expertise, I would think that you would comprehend the fact that, on a subatomic level, the 'number' of collisions (interactions) is only a function of the number and spacing of said entities.  Thus the old saw, same mass, same shielding.  Rotate the above disk 45 degrees, the cross-sectional area exposed to the fluence is reduced, but the effective thickness increases by the same ratio. The result, no change in the induced acceleration! I am sorry but I do not get this. Look at the following sketch : the incident particles are deflected at an angle of 90 degrees if their incident speed make an angle of 45 degrees with the plane of the coin. In fact since the surface of the coin is not perfect, this is not exactly 90 degrees everywhere but the average value is 90 degrees and therefore the average transferred momentum is at 45 degrees with the incident speed. This is how one computes the pressure forces created by an ideal gas on a wall, isn't it ? And in Dennis's model the Ether is such an ideal gas, isn't it ? So you was not discussing the model proposed by Dennis McCarthy on his web page. Did you even read it ?                                                                                                                           P