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First real challenge to General Relativity?, (and not from Gravity Probe-B)
Guest_BruceMoomaw_*
post Mar 23 2006, 09:50 PM
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...in the form of what may be an accidentally discovered artificial gravity generator, with possible practical applications!:
http://www.esa.int/SPECIALS/GSP/SEM0L6OVGJE_0.html

If this effect is real, it's fully 1/10,000 G -- which is not to be sneezed at, and might conceivably lead us to Bigger Things.
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Guest_BruceMoomaw_*
post Mar 23 2006, 10:14 PM
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The actual paper ( http://esamultimedia.esa.int/docs/gsp/Expe...l_Detection.pdf ) says that the effect appears to be "directly proportional to the applied angular acceleration of thesuperconductor following our theoretical motivations" -- that is, the gravity generated is in direct proportion to how fast you spin the superconducting ring. Spin it at 65 million rpm and you'd generate a 1-G field. And -- to repeat -- the scientists involved apparently have rather bigger reputations than Poletnikov, and were researching a puzzling already-observed phenomenon in superconductors. IF this works out -- and, needless to say, that is an extremely big "if" -- the analogy to James Blish's "spindizzies" is rather eerie.
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ugordan
post Mar 23 2006, 10:17 PM
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Weren't there experiments and claims (by a russian scientist ?) that spinning superconducting plates "reduce" gravity felt above them years ago? And these claims were pretty much dismissed as bull since they couldn't be properly reproduced.

Well, whaddya know...

EDIT: Yes, his name is Podkletnov (not Poletnikov)


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Guest_BruceMoomaw_*
post Mar 23 2006, 10:29 PM
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Sorry about the misspelling. Their actual passage on him is as follows:

"The reported results are very different from previous claims in the literature from Podkletnov claiming gravitational shielding effects above rotating superconductors. As we have not observed any change in the vertical sensors ( 5 μg) above any superconductors during their phase transition and during rotation, our results even put new limits on any possible shielding effects (effect must be < 0.0005% compared to claims of up to 2% of weight change for samples above a rotating superconductor)." (pg. 16-17)

These guys are two bigwigs in the ESA and GmbH, and they were doing further research into aspects of an apparent phenomenon already observed by another team. It will, at any rate, be interesting to see if this develops into anything.
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ugordan
post Mar 23 2006, 10:38 PM
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Very interesting, indeed. Though I have a hard time swallowing concepts like gravitomagnetic and gravitoelectric fields...

QUOTE
This gravitomagnetic London moment is equivalent to a frame-dragging or Lense-Thirring field and is of great interest since gravitational effects of measurable magnitudes could be produced in a laboratory environment

Are we finally on the verge of figuring out this thing called gravity?

Time will tell.


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tty
post Mar 23 2006, 10:52 PM
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If the effect is proportional to speed of rotation it should be noted that APU's and small jet engines routinely run at up to 60 - 70,000 rpm and ultracentrifuges at twice that. That would equal 0,001-0,002 g. Now that is a really appreciable acceleration!
One small thing, "Gmbh" means "Limited Liability Company", it's the bit before that is the name of the firm.

tty
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ugordan
post Mar 23 2006, 10:57 PM
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QUOTE (tty @ Mar 23 2006, 11:52 PM) *
If the effect is proportional to speed of rotation it should be noted that APU's and small jet engines routinely run at up to 60 - 70,000 rpm and ultracentrifuges at twice that. That would equal 0,001-0,002 g. Now that is a really appreciable acceleration!

I don't have time to read the entire paper right now, but from what I read so far, the effect is actually present when the superconductor accelerates its rotation. It apparently has nothing to do with the actual speed of rotation, only the angular acceleration of the disk.


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Guest_BruceMoomaw_*
post Mar 24 2006, 02:32 AM
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I believe -- although I may be wrong, given my Mr. Wizard level of scientific understanding -- that "angular acceleration" just refers to the acceleration produced by the simple fact that the different parts of the disk keep changing their direction of motion as it turns: i.e., slowing down along one straight-line direction at the same time that they start moving in another. This, after all, is what centrifugal "force" really is: the power of inertia operating because the parts of a spinning object keep changing their velocity of motion along straight-line directions.

I imagine this will turn out to be nothing, just like the Aviation Week "Spaceplane" article -- but who knows? Maybe we'll luck out and it will actually amount to something.

QUOTE (tty @ Mar 23 2006, 10:52 PM) *
One small thing, "Gmbh" means "Limited Liability Company", it's the bit before that is the name of the firm.

Oops. Actually, it ain't that small; I've never heard of "ARC Seibersdorf" and have no idea what kind of reputation it has, even given that it's supposedly "Austria's largest research institution". (Tajmar turns out to have been interested in research into gravity control for some time: http://ilfb.tuwien.ac.at/~tajmar/ .) Still, the other guy is General Studies Officer for ESA's Advanced Concepts & Studies Office, which implies some kind of reputation.
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The Messenger
post Mar 24 2006, 06:18 AM
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This is going to be very difficult to confirm, and very difficult to assign the force strictly to a gravitational vector. I question whether the effect, if real, would be totally different from what Podkletnov claimed: If you can create a magnogravimetric field, you can shield it - frankly I think the fickle gravity anomalies observe during total eclipses proved this fifty years ago. And I don-t think they have as yet realize the full implications of this relationship.\\\

Speaking of the B probe, and hint of any results?
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ugordan
post Mar 24 2006, 08:14 AM
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QUOTE (BruceMoomaw @ Mar 24 2006, 03:32 AM) *
I believe -- although I may be wrong, given my Mr. Wizard level of scientific understanding -- that "angular acceleration" just refers to the acceleration produced by the simple fact that the different parts of the disk keep changing their direction of motion as it turns: i.e., slowing down along one straight-line direction at the same time that they start moving in another.

Nope, that would be radial acceleration as the acceleration vector points to the center of rotation. The angular velocity remains the same. Angular acceleration is the change (or derivation) of omega, which is the angular velocity. They even mentioned in one part of the paper thew were using two electric motors, one could go up to 6500 RPM but provided a slower spin-up speed and the other could go to (IIRC) 4500 but had a faster spin-up. They wouldn't mention that if the effect is totally determined by RPMs alone, IMHO.

QUOTE (The Messenger @ Mar 24 2006, 07:18 AM) *
This is going to be very difficult to confirm, and very difficult to assign the force strictly to a gravitational vector.

Have you read the paper? Apparently they conducted numerous experiments because they were as well reluctant to believe what they were seeing. They did isolate the accelerometers inside Faraday cages to get rid of electromagnetic side-effects. As Bruce points out, they think this is totally independent of Podkletnov's claims.


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Guest_Richard Trigaux_*
post Mar 24 2006, 08:32 AM
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The Lens-Thiring effect, or magnetogravitationnal field, is the exact equivalent to gravitation and mass of what the magnetic field is to electric field and charge.

This is because the two domains mostly obey to the same equations.

When electric charges move, for instance rotate in a transformer coil (say to simplify a ring) they produce a magnetic field, with a north pole at one side of the ring, and a south pole at the other side. This magnetic field can in turn induce an electric field and a current into a secondary ring (coil).
Similarly, a ring of matter rotating produces a magnetogravitationnal field, which can in turn induce the rotation of a secondary ring besides the first.
This is a known consequence of the relativity. At a pinch, that relativity predicts the existence of the magnetogravitationnal field makes that it predicts too... the magnetic field, which is thus a BIG consequence of relativity at human scale.

Alas for us, the gravitomagnetic field is so weak that any human scale test is still unable to detect it, only at space scale the gravity probe B could detect it (results please?). But it may play an important role in the realm of neutron stars and black holes, for instance the rotation energy of a black hole could be extracted to accelerate an accretion disk. (and for instance produce jets)

What is new with this experiment is that a magnetogravitationnal field is said to result from electromagnetic effects alone, a thing hich is not predicted by relativity and is said (in the paper) to result from the violation of a basic physical symmetry.

If it is true, it may be a breakthrough into our understanding of the relation between relativity and the quantum world. But I wait for others reproducing the results before inflating imagination.

Anyway the gravitationnal field resulting from a Lens-Thiring field is ROTATING, so that it cannot be used to produce anti-gravitation or any propulsive gravitationnal field. At least not directly. At a pinch two Lens-Thiring rings repell each other, if they show both the same pole to the other. But it is much more complicated than using simply the magnetic properties of superconducting rings. And we are still far of producing a 1 G effect, if we need for this a rotation at 64 MILLIONS RPM...

So the thing is anyway to follow carefully, as soon as the primary results are reproduced.
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ugordan
post Mar 24 2006, 09:05 AM
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QUOTE (Richard Trigaux @ Mar 24 2006, 09:32 AM) *
And we are still far of producing a 1 G effect, if we need for this a rotation at 64 MILLIONS RPM...

Once again, people, RPMs have nothing to do with it! The first page of the paper clearly states:
QUOTE
The field appears to be directly proportional to the applied angular acceleration of the superconductor following our theoretical motivations.


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Guest_Richard Trigaux_*
post Mar 24 2006, 09:49 AM
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QUOTE (ugordan @ Mar 24 2006, 10:05 AM) *
Once again, people, RPMs have nothing to do with it! The first page of the paper clearly states:
The field appears to be directly proportional to the applied angular acceleration of the superconductor following our theoretical motivations.


Yes, but strong acceleration sustained in time leads to many RPM. I read somewhere in the paper that such speed would be necessary to produce a 1g field.

The analogy with the electrical transformer stills hold: it is the change the into primary current (equivalent of acceleration here) which produces the secondary electromotrice force (eequivalent of gravitationnal acceleration)
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ugordan
post Mar 24 2006, 09:55 AM
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QUOTE (Richard Trigaux @ Mar 24 2006, 10:49 AM) *
Yes, but strong acceleration sustained in time leads to many RPM. I read somewhere in the paper that such speed would be necessary to produce a 1g field.

Such a speed isn't necessary for a 1 g field, a very rapid acceleration is. As you point out, only if you want to sustain the 1g field long enough will you reach such high RPMs.


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dtolman
post Mar 24 2006, 03:02 PM
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QUOTE (ugordan @ Mar 24 2006, 04:55 AM) *
Such a speed isn't necessary for a 1 g field, a very rapid acceleration is. As you point out, only if you want to sustain the 1g field long enough will you reach such high RPMs.


So basically, unless someone invents a perpetual motion machine, this can be used to create strong, but short lasting gravity fields or weaker, but relatively longer lasting gravity fields (depending on how quickly you ramp up to the maximum RPM).

Even if this can't be used to make artificial gravity plating in my space yaucht - its exciting to think that General Relativity has finally had a hole poked into it within my lifetime!
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