Azimuthally symmetric theory of gravitation
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From: Surfer on 16 Jun 2010 22:59 Azimuthally symmetric theory of gravitation - I. On the perihelion precession of planetary orbits Nyambuya, G. G. Monthly Notices of the Royal Astronomical Society, Volume 403, Number 3, April 2010 , pp. Preprint http://arxiv.org/abs/0912.2966 <Start extract> Abstract: From a purely none-general relativistic standpoint, we solve the empty space Poisson equation (nabla^2 Phi=0) for an azimuthally symmetric setting, i.e., for a spinning gravitational system like the Sun. We seek the general solution of the form Phi=Phi(r, theta). This general solution is constrained such that in the zeroth order approximation it reduces to Newton's well known inverse square law of gravitation. For this general solution, it is seen that it has implications on the orbits of test bodies in the gravitational field of this spinning body. We show that to second order approximation, this azimuthally symmetric gravitational field is capable of explaining at least two things (1) the observed perihelion shift of solar planets (2) that the mean Earth-Sun distance must be increasing -- this resonates with the observations of two independent groups of astronomers (Krasinsky & Brumberg 2004; Standish 2005) who have measured that the mean Earth-Sun distance must be increasing at a rate of about 7.0 +/- 0.2 m/century (Standish 2005) to 15.0 +/- 0.3 m/cy (Krasinsky & Brumberg 2004). In-principle, we are able to explain this result as a consequence of loss of orbital angular momentum -- this loss of orbital angular momentum is a direct prediction of the theory. Further, we show that the theory is able to explain at a satisfactory level the observed secular increase Earth Year (1.70 +/- 0.05 ms/yr; Miura et al. 2009). Furthermore, we show that the theory makes a significant and testable prediction to the effect that the period of the solar spin must be decreasing at a rate of at least 8.00 +/- 2.00 s/cy. <End extract>
From: eric gisse on 16 Jun 2010 23:41 Surfer wrote: > Azimuthally symmetric theory of gravitation - I. On the perihelion > precession of planetary orbits > Nyambuya, G. G. [...] I remember this shitheap in MNRAS. I still don't get why it was published. The solution of the LAPLACIAN (not the Poisson) equation in empty space is something anyone who passed a junior level physics course is expected to be able to do. The decomposition of the angular part into their harmonics is also equally standard. Reading further, he makes a fundamental error regarding basic differential equation theory by opining that there should be "two independent solutions for every l". I do like how he writes the gravitational field in terms of its' multipole moments as if it were a feat of anything other than passing some undergrad courses. He does not understand that the LAPLACIAN does not contain time derivatives, thus making his claim that the multipole moment decomposition 'takes into account' spin of an object pretty stupid. This paper is just as idiotic as when I first saw it in MNRAS.
From: Surfer on 18 Jun 2010 21:18 On Wed, 16 Jun 2010 20:41:03 -0700, eric gisse <jowr.pi.nospam(a)gmail.com> wrote: > >He does not understand that the LAPLACIAN does not contain time derivatives, >thus making his claim that the multipole moment decomposition 'takes into >account' spin of an object pretty stupid. > I think he is hypothesizing that spin might cause unknown effects that could break spherical symmetry, but with it being impractical to model unknown effects, he only models the hypothesized loss of spherical symmetry. I think that is valid, however since there are multiple reasons to believe that relativistic effects are real and since such effects can adequately account for precession of planetary orbits, I don't see much chance of his hypothesis replacing relativistic effects as the cause of precession.
From: eric gisse on 18 Jun 2010 22:23
Surfer wrote: > On Wed, 16 Jun 2010 20:41:03 -0700, eric gisse > <jowr.pi.nospam(a)gmail.com> wrote: > >> >>He does not understand that the LAPLACIAN does not contain time >>derivatives, thus making his claim that the multipole moment decomposition >>'takes into account' spin of an object pretty stupid. >> > I think he is hypothesizing that spin might cause unknown effects that > could break spherical symmetry, but with it being impractical to model > unknown effects, he only models the hypothesized loss of spherical > symmetry. > He doesn't know what the hell he is doing. That much is obvious. > I think that is valid, however since there are multiple reasons to > believe that relativistic effects are real and since such effects can > adequately account for precession of planetary orbits, I don't see > much chance of his hypothesis replacing relativistic effects as the > cause of precession. Except he's not doing relativity, or anything like it. All he's doing is taking the highly standard multipole expansion of Earth's gravitational field while assuming rotational symmetry, and making the identification that it must reduce to the correct 1/r and 1/r^2 potentials that relativity predicts. He does that by putting in arbitrary constants, which is not really all that impressive. It is well known that a perturbation to the regular Newtonian force of the form k/r^3 is able to reproduce the perihelion advance of Mercury. This is in Goldstein, for fucks sake. There's nothing new or interesting here. |