Anti-Grav?

[Steve Schear <schear@lvdi.net>]

I must have been sleeping, but it appears I missed the emergence of another Fleischman-Pons ("cold fusion") style episode, this time having to do with antigravity.  Experiments in 1992 in Finland seemed to show that the Earth's gravity could be shielded with a superconductor.  This experiment, by Eugene Podkletnov, at Finland's Tampere University of Technology, apparently displayed a reduction in the weight of objects placed above a levitating, rotating high Tc superconducting disk, exposed to high frequency magnetic fields. 

http://www.virtualpet.com/rbbi/folders/tech/basic/gravity.htm

http://www.inetarena.com/~noetic/pls/gravity.html#pandb

There are at least three different theoretical models for the effect -- gravitomagnetism, local change to cosmological constant, and outright shielding.  Detractors have pointed to possible experimental errors as the cause for the apparent levitation.  

Gravitomagnetism
The coupling of supercurrents to the classical gravitational field is extremely weak. The reason, of course, stems from the smallness of the coupling between gravity and the energy-momentum tensor of matter. One might wonder whether in a quantum theory of gravity - or at least in an approximation of the theory for weak fields - the Bose condensate of the Cooper pairs, due to its macroscopic quantum character, can play a more subtle role than as a simple contribution to the energy-momentum tensor. 

In other words, we wonder if the macroscopic quantum coherence of the condensate can be taken into account at a fundamental level in computing the interaction between the superconductor and the external gravitational field.  Results might then differ from those obtained for the gravitational coupling of "regular", incoherent matter.

Shielding
It appears that a theory is being developed for simple shielding of gravity, in analogy with the shielding of microwaves by metal.  Different materials shield or don't  shield EM ratiation at various frequencies; metal shields microwaves, but plastic does not. Pure YBCO superconductors do not shield microwaves, but YBCO  doped with small amounts of lead or silver does.  They relate this to gravity shielding by virtue of two ideas -- that gravity might have a frequency (very high, on the order of the Planck length, or 10^34) -- a very speculative idea -- and that the bose condensate within a superconductor could radically lower the effective interaction frequency of gravity so that it could be shielded by ordinary matter. 

On a related note, NASA has Breakthrough Propusion page http://www.lerc.nasa.gov/WWW/bpp which outlines their plans and activities to explore (and hopefully perfect) non-mass based propusion technologies.  They seem to be taking this seriously enough to form a Delta-G group at their Marshall Space Flight Center to try and reproduce Podkletnov's (and others) experiments.  

--Steve

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