Kopeikin and "the speed of gravity"

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[tvanflandern]
I have amended the press release several times in response to suggestions to make it easier to read and understand. I'd like to simplify it more. Any specific suggestions about what still needs more work? -|Tom|-
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Dr. Van Flandern,

In a Usenet discussion I had with Chris Hillman several years ago* I became aware of an exotic difference between gravitational acceleration and gravity waves. I've not seen any mention of it anywhere else besides MTW's text book. But since they DO talk about it, I'm pretty sure it is 'real' (as a feature of GTR at least, if not of reality).

Everyone knows that the force associated with gravitational radiation (gravity waves) is exceedingly small. So small that $pecial, very $en$itive equipment is being/has been built in the hope of finally detecting this phenomenon. You have pointed out on numerous occasions that the force associated with gravitational acceleration is enormous in comparison. It is so large that we have been able to detect and measure it for a long time. We have accelerometers that can measure the difference in gravitational accleration caused by one person moving around in an adjacent room.

Still, many seemingly knowledgeable people say things that make it clear that they believe that gravity waves are either the direct cause of gravitational acceleration or that gravity waves are at least deeply involved in the phenomenon of gravitational acceleration.

I asked Dr Hillman how this could be, given these differences between the two. At first he said categorically that gravity waves CAUSE gravitational acceleration. But then he began wavering and complaining of some sort of "brain blip" so I'm not sure exactly where he stands on this issue right now. He went off on a tangent about some minute detail and I got busy in my real life and the discussion just died out. I've been thinking about this difference ever since, and it seems like this might be a good time to talk about it some more.

Anyway - the force associated with gravitational acceleration acts in the direction of the line joining two masses. But the force associated with gravity waves acts perpendicularly to this line. There is NO COMPONENT of the force from gravity waves that acts in the direction of travel of the wave.

As a consequence of this difference there is NO NET FORCE on a mass created by the wave. When a gravity wave moves through a mass it causes the mass to alternately stretch and compress in directions that are <b>perpendicular</b> to the direction of travel of the wave (the line between the masses). A little heat is generated, but no motion.

Now, if the argument about the amplitude difference of these forces doesn't alert most people to the unreasonableness of believing that gravity waves have something to do with gravitational acceleration, it is likely that an argument about the directional difference will also be mostly fruitless. But maybe it would cause a few people to reconsider, and maybe those few will be different than the few who already grok the amplitude argument.

A small step in the right direction? What if Kopekin were one of them?

Regards,
LB

*
sci.physics.relativity, "RE: How fast is gravity", July 2000, post numbers from about 180 to about 190
(I am "gamemaster" in that thread)

All good points, Larry. The most recent publication to deal with this subject [“Experimental Repeal of the Speed Limit for Gravitational, Electrodynamic, and Quantum Field Interactions”, T. Van Flandern and J.P. Vigier, Found.Phys. 32(#7), 1031-1068 (2002)] uses an anchor-and-buoy analogy to illustrate the difference between gravitational waves and gravitational force. That part of the discussion also appears in section 3 of the paper on this web site at [url] metaresearch.org/cosmology/gravity/speed_limit.asp [/url].

IMO, Kopeikin is now too committed to his sponsors, colleagues, and the media to back off his claims. But sometimes people still surprise me and rise above their circumstances. In any case, the approach would have to come from someone else. Once a dispute starts getting aired in public, principals can become reluctant to speak frankly to critics for fear of being quoted in the media. -|Tom|-

From Larry:

Anyway - the force associated with gravitational acceleration acts in the direction of the line joining two masses. But the force associated with gravity waves acts perpendicularly to this line. There is NO COMPONENT of the force from gravity waves that acts in the direction of travel of the wave.

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I think you're mixing dot and cross products of vectors. Remember FBI in EM? Magnetic field is perpendicular to force and current. There aren't TWO forces, only One. The field has to be in a mathematical sense perpendicular to force. There is only one force you get from that field. That forces gives you acceleration. When you make water waves, the wave vector is perpendicular to the current and force vector, then you get an acceleration along the direction of the force vector. Torque is also a vector perpendicular to the plane of force and distance and actually doesn't matter where you put it. That's because Torque is a cross product.

Because you have a wave vector perpendicular to separation it doesn't mean you have two forces. When you have coupling effects from two fields you can get a "side force". Is that maybe what causes the confusion?

Time to wave out some cars.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[mechanic]
There aren't TWO forces, only One.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

??? I guess I don't understand.

One of these forces is always present. The other comes and goes depending on whether or not the mass is being shoved around.

One of these forces is always attractive. The other (when present) neither attracts nor repels.

One of them is large and easy to detect. The other is still just a theoretical possibility - if it does exist it is very small and very difficult to detect.

<b>If</b> the mass is being shoved around - one of these forces has a large constant amplitude with a small variation riding on top of it (much like the control signals in an X-10 Home Automation System, if you are familliar with that - OR - visualize a one volt sine wave riding on top of 1000 volts DC), the other has a true alternating amplitude that goes from zero to maximum in one direction, back to zero, then to maximum in the opposite direction, then back to zero for a complete cycle.

In what sense are you suggesting that they are a single force?

Regards,
LB

One of them is large and easy to detect. The other is still just a theoretical possibility - if it does exist it is very small and very difficult to detect.

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You must be talking of GR speculating oscilating double stars generating gravity waves. I am not sure if Einstein himself predicted that or others interpet it that way. Because of the small value of G these would be hard to measure of present. Some guy named Weber in 1971 reported arrival of such waves from outer space. I still insist that this speculation arises from a mistake in mathematics. Maybe that's related to what Van Flandern says about Kopeikin's math and maybe not. From a common sense perspective, why should gravity be the cause of two different effects. Is that maybe a math trick to justify some effects GR cannot do by a sole geometric representation of gravity? I don't know but I think with that tensor game something went wrong.

Mechanic

On 10-Jan, AgoraBasta suggested an empirical way to measure the speed of gravity with large quartz crystals. Another approach might be to use gravimeters (mentioned by Larry Burford), as long as they have very fast responses or at least reliable latencies (e.g., within a few nanoseconds). If we have a mass, detected both up close as well as a few meters away by two identical gravimeters, couldn't we bump (accelerate) the mass and measure the delay between the gravimeter readings? Couldn't this enable us to determine quite easily whether gravitational force travels at close to c or not?

John