anti-gravity from spinning gravito-magnetic field?

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hanelyp
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anti-gravity from spinning gravito-magnetic field?

Post by hanelyp »

Let's start with an electrical analog. A charged particle spinning generates a magnetic field. If a collection of such particles are spin polarized, the the collection as a whole is spun, we can get a spinning magnetic field. This magnetic field sweeping past charged test particle can induce a qVxB force towards or away from the collection of particles producing the field.

How strong can this induced force be relative to the electrostatic field between the test particle and the generator composed of all like charges? I suspect the electrostatic force will dominate, but would be interested to hear reasoned arguments to the contrary.

How well does this translate to gravitation?

kcdodd
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Post by kcdodd »

I assume you mean a moving charge past the collection has VxB force opposing the electric force. The closest thing to a "moving" electromagnetic field is the EM momentum proportional to ExB, in this case the angular momentum about the collection since E is radial and B is axial. Fields themselves don't "sweep".
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chrismb
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Re: anti-gravity from spinning gravito-magnetic field?

Post by chrismb »

hanelyp wrote: How well does this translate to gravitation?
I don't understand what you're saying.

Are you saying that a 'gravito-magnetic' field can be created, or are you [correctly] asuming ne'er the twain shall meet but that you're asking what if a gravity field was rotated?

If so then, as with any rotating field, you can induce a transient compression/rarefaction which may have consequent effects depending on the media affected, but it can only result in a 'wave' in the field, not in a 'new field'. If this relates to what you're asking, then I think the answer lies in the theories on how gravitational waves are generated and you might seek your answer in that research.

As far as I am aware no gravity waves have been measured. I am ignorant on this subject but as a casual observer I would suggest to such researchers that they're wasting their time. It is not a wave in our space, gravity waves would be waves on our space, so of course we're not going to be able to measure them as the measurement kit's time-space distorts along with the space itself!! No-one makes rulers made out of elastic string, and there's a reason for that!

kcdodd
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Post by kcdodd »

I think he is talking about something like a relative gravitational field, depending on the relative motion of an observer. I think a "matter current" would just increase the gravitational field for a stationary observer, so it could never repel.
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rcain
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Post by rcain »

... whether wave-like or not, a related observation (and a question that has always intrigued me), the effects of gravitation do now appear to 'propagate' at the speed of light +/- 20%:: http://www.nrao.edu/pr/2003/gravity/

Giorgio
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Post by Giorgio »

rcain wrote:... whether wave-like or not, a related observation (and a question that has always intrigued me), the effects of gravitation do now appear to 'propagate' at the speed of light +/- 20%:: http://www.nrao.edu/pr/2003/gravity/
I do not agree, their test just proved that radio waves are bended by a gravitational field. At the most they proved that light moves at the "speed of light", but this experiment gives no clues in regards to the speed of gravity.

chrismb
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Post by chrismb »

"The strongest of these experiments sets a lower limit to the speed of gravity of 2x10^10 c"

from http://metaresearch.org/cosmology/gravi ... _limit.asp

alexjrgreen
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Post by alexjrgreen »

chrismb wrote:"The strongest of these experiments sets a lower limit to the speed of gravity of 2x10^10 c"

from http://metaresearch.org/cosmology/gravi ... _limit.asp
You don't agree with Carlip, then?

Aberration and the Speed of Gravity
The observed absence of gravitational aberration requires that "Newtonian" gravity propagate at a speed c_g>2x10^10 c. By evaluating the gravitational effect of an accelerating mass, I show that aberration in general relativity is almost exactly canceled by velocity-dependent interactions, permitting c_g=c. This cancellation is dictated by conservation laws and the quadrupole nature of gravitational radiation.
Ars artis est celare artem.

chrismb
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Post by chrismb »

alexjrgreen wrote:
chrismb wrote:"The strongest of these experiments sets a lower limit to the speed of gravity of 2x10^10 c"

from http://metaresearch.org/cosmology/gravi ... _limit.asp
You don't agree with Carlip, then?
Me?! I have no opinion. I am a blank canvas. I simply repeat what I read. :wink:

Giorgio
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Post by Giorgio »

All those theories are just long shots to define something we did not observe nor we did fully understand until now.

In a much smaller scale, you can make a comparision with 19th-20th century scientists trying to come up with the possibility of something moving at a speed greater than sound.

I should go back to dig into my collection to find some of those papers where scientists was disgressing that nothing could go faster than the speed of sound becouse the "sound" was unable to go at an higher speed than the observed one.
:roll:

alexjrgreen
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Post by alexjrgreen »

chrismb wrote:Me?! I have no opinion. I am a blank canvas. I simply repeat what I read. :wink:
I recommend

James Clerk Maxwell, A Treatise on Electricity And Magnetism Vols 1 and 2
Ars artis est celare artem.

chrismb
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Post by chrismb »

Ampere and Weber dismissed "Maxwell's equations" as being too simplistic long before Maxwell even wrote anything, because they saw such a solution as trivial and not properly accounting for all phoenomenon, specifically "longitudinal forces" that are not essentially included in Maxwell and aren't really derivative either.

Then Einstein stepped in and we realised magnetism and electricity are the same thing, just in different inertial frames.

alexjrgreen
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Post by alexjrgreen »

"Note on the Attraction of Gravitation" in
James Clerk Maxwell, "A Dynamical Theory of the Electromagnetic Field," Phil. Trans. 155, 1865, pp. 459-512, sec. 82, pp. 492-3
http://www.zpenergy.com/downloads/Maxwell_1864_4.pdf (pp. 4-5)
Ars artis est celare artem.

rcain
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Post by rcain »

Giorgio wrote:
rcain wrote:... whether wave-like or not, a related observation (and a question that has always intrigued me), the effects of gravitation do now appear to 'propagate' at the speed of light +/- 20%:: http://www.nrao.edu/pr/2003/gravity/
I do not agree, their test just proved that radio waves are bended by a gravitational field. At the most they proved that light moves at the "speed of light", but this experiment gives no clues in regards to the speed of gravity.
thats what i thought at first, but reconsidered, i conclude they must have made reference to the 'rate' of bending (dt) relative to movement/acceleration of jupiter. otherwise, i agree their conclusions would not make sense.
chrismb wrote:"The strongest of these experiments sets a lower limit to the speed of gravity of 2x10^10 c"

from http://metaresearch.org/cosmology/gravi ... _limit.asp
very interesting paper, thanks chrismb. (though it'll take me a while to read though completely). certainly a VERY different conclusion (by many orders of magnitude).

noteably however, it predates the NRAO observations by a year or so and admits extremely wide variation (and doubt) in both experimental findings (to that date) as well as in the various competing theoretical predictions.
alexjrgreen wrote:Aberration and the Speed of Gravity...permitting c_g=c. This cancellation is dictated by conservation laws and the quadrupole nature of gravitational radiation.
would it be true to say that there is still (a root) debate over the 'quadrupole nature of gravitational "radiation"'?

maybe the LHC will give us some answers (sometime around 2012 i believe is the date set for the 'big' one).
Giorgio wrote:...
In a much smaller scale, you can make a comparision with 19th-20th century scientists trying to come up with the possibility of something moving at a speed greater than sound.
...
even at that time however they had determined that sound required a medium to propagate within. by contrast, the proposition that light/gravity requires a medium to propagate within is more or less verboten (i think i'm still right in saying).

like chrismb, i have no opinion. indeed i have a big problem in even conceiving of any experimental setup that would be capable of deciding such a matter. though worthy grist for day dreaming...

pfrit
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Post by pfrit »

rcain wrote:even at that time however they had determined that sound required a medium to propagate within. by contrast, the proposition that light/gravity requires a medium to propagate within is more or less verboten (i think i'm still right in saying).
Actually, they need to travel in a frame of reference and that requires a second "object". That means space-time. To consider "Aether" to be the same thing as space-time requires a pretty silly "Aether".
What is the difference between ignorance and apathy? I don't know and I don't care.

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