Carlip's paper on the speed of gravity

[Max] " ... if the gravitational "waves", being fourth order, can anticipate constant acceleration ... "

Even if they could, it is irrelevant. Gravitational force is a longitudinal, always attractive phenomenon. The forces created by gravitational waves are transverse and alternate periodically between stretching and compressing.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Max</i>
<br />what do you make of the paper by S. Carlip ... that claims to answer questions posed in your paper about the speed of gravity?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Carlip fixed some problems in that preprint paper and eventually got it published as “Aberration and the speed of gravity” in Phys.Lett.A 267:81-87 (2000).

I wrote a response to him and to several other objectors, and was joined by the late senior physicist J.P. Vigier in a comprehensive review article: “Experimental Repeal of the Speed Limit for Gravitational, Electrodynamic, and Quantum Field Interactions”, T. Van Flandern and J.P. Vigier, Found.Phys. 32:1031-1068 (2002). If you don't have easy access to a technical library, you can find a preprint on this site under title “The speed of gravity – Repeal of the speed limit” at metaresearch.org/cosmology/gravity/speed_limit.asp
Sections 7 and 8 are directly relevant to rebutting Carlip's claims.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Would be interesting to see how you guy duke it out.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Indeed. But Carlip gave up the battle at that point. However, you can find many years of prior fencing preserved in USENET archives. These discussions are also on our "Gravity" CD, available in our web site store.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">I always wondered though, if the gravitational "waves", being fourth order, can anticipate constant acceleration, that can answer the question why the solar system is stable<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">It is important to know that gravitational waves have nothing to do with ordinary gravitational force. Such waves are more akin to frictional kinetic energy losses by the orbital motions of bodies, and are so weak that no trace of them has yet been found anywhere in our solar system.

The stability of the solar system is easily answered by the propagation speed of gravitational force being very high, which makes the instability from aberration comparable to other known instability sources, such as solar mass loss through solar wind.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">but then it follows that any dynamic system more complicated than a binary one, for example, a three-body system with arbitrary initial conditions, would quite quickly radiate it's gravitational energy away. In your experience as an astronomer - do three-body systems radiate away gravitational energy?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">No, they don't radiate away any gravitational energy at a detectable level yet. Bnd I don't see why three bodies would be expected to radiate more than two bodies. The radiation just depends on relative velocities. -|Tom|-

The reason I mentioned tertiary systems is that the mainstream explanation for the absence of gravitational aberration in two-body systems is that gravity can only radiate if a quadrupole moment is present, which is absent in two-body systems (because acceleration of bodies is constant). Therefore, I asked, if this is so, then a multiple-body systems, where acceleration in general is not constant, must possess a quadrupole moment, and therefore emit gravitational energy through waves, with the side effect of the aberration.

So, if you assert that many known three-body systems do not display aberration as well, then there is a conflict with the mainstream understanding of gravity, no?

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Max</i>
<br />The reason I mentioned tertiary systems is that the mainstream explanation for the absence of gravitational aberration in two-body systems is that gravity can only radiate if a quadrupole moment is present, which is absent in two-body systems (because acceleration of bodies is constant).<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">There are two confusions here. First, gravitational radiation, even when present at an observable level (as in certain binary pulsars), is way too small an effect to possibly cancel aberration. And in the solar system, where aberration is 20" for the Sun-Earth system and would double the size of the Earth's orbit in 1200 years if it existed for gravity, gravitational radiation is not detectable even with the highest precision VLBI/radar/laser/spacecraft observations.

Remember, aberration is a v/c effect. Light-bending and perihelion advance are (v/c)^2 effects. Gravitational radiation is a (v/c)^5 effect, which for Sun-Earth would be of order 10^-20. This shows both why it has never been detected and why it is incapable of putting a dent into aberration.

The second confusion is in your remark that acceleration is constant in 2-body systems. Acceleration is a vector, and is therefore continually changing direction even for circular motion, but changes both magnitude and direction for elliprical motion such as Earth's orbit (with no detectable gravitational radiation) or in binary pulsars (with detectable-but-small gravitational radiation). However, once again, gravitational radiation is unrelated to gravitational force, so neither of those effects matters to the aberration argument.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Therefore, I asked, if this is so, then a multiple-body systems, where acceleration in general is not constant, must possess a quadrupole moment, and therefore emit gravitational energy through waves, with the side effect of the aberration.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Besides all the preceding arguments, observations of 3-body systems such as Sun-Earth-Moon also support near-instantaneous gravitational force propagation because of the observed absence of gravtational aberration. This is especially evident during solar eclipses, where mid-eclipse occurs (on average) 40 seconds before the meximum gravitational force on Earth from the combined pulls of Sun and Moon. This difference is caused by the presence of optical aberration and the absence of gravitational aberration, with gravitational radiation too insignificant to detect.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">So, if you assert that many known three-body systems do not display aberration as well, then there is a conflict with the mainstream understanding of gravity, no?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Yes. The geometric interpretation of GR is flawed. But the field interpretation works just fine, and greatly improves our understanding of both gravity in particular and physics in general because of the lifting of the universal speed limit that it implies. -|Tom|-

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">No, they don't radiate away any gravitational energy at a detectable level yet. Bnd I don't see why three bodies would be expected to radiate more than two bodies. The radiation just depends on relative velocities. -|Tom|-<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Just as electrons changing orbits emit photons, planets swapping orbits with one another should emit gravity waves. This cannot happen in a two-body system.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by PhilJ</i>
<br />Just as electrons changing orbits emit photons, planets swapping orbits with one another should emit gravity waves. This cannot happen in a two-body system.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">You better rush that news to the Nobel committee so they can take back Joe Taylor's Prize for indirect evidence of gravitational waves in the two-body binary pulsar PSR 113+16. [}] -|Tom|-