MadSci Network: Physics
Query:

Re: machines to produce energy from gravity

Date: Tue Feb 20 08:40:19 2001
Posted By: Emilson Leite, Grad student, Dept. of Geophysics, Institute of Astronomy and Geophysics - University of São Paulo
Area of science: Physics
ID: 981687025.Ph
Message:

Dear Joseph,

   It seems to me that the concept of generating anti-gravity, or 
shielding from the affect of Earth's gravity, is a romantic idea in the 
science fiction sense.  Imagine launching satellites by cancelling their 
weight and then gently tapping them into orbit with your finger; or a 
wheel chair that suspends its rider in a zero gravitational field.  How 
about anti-gravity running shoes?

   Ok, thats is a point. In 1992, experiments in Finland seemed to show 
that the Earth's gravity could be shielded or modified with a 
superconductor.  This experiment, by Eugene Podkletnov, at Finland's 
Tampere University of Technology, apparently displayed the reduction in 
the weight of objects placed above a levitating, rotating high 
superconducting disk, exposed to high frequency magnetic fields. 

   Did his device truely shield gravity, or was it a fluke, a mistake in 
experiment design?  Podkletnov maintains that his experiments were 
complete.  However, he apparently did not share his findings nor the 
details of his apparatus with the university or his coworkers at the time, 
so he perhaps unwittingly, perhaps permanently, cast doubt on the accuracy 
of his claims. 

   One physicist has tried to explain Podkletnov's surprising results; 
papers written by G. Modanese offer theories as to why this effect might 
occur via quantum gravitational effects: specifically, a local change to 
the cosmological constant.  Other physicists, including Unnikrishnan and 
De Podesta and Bull, offer alternative, non-gravitational explanations 
based on normal physical effects missed by Podkletnov.  Two other 
physicists, Li and Torr, have written papers (2 papers before Podkletnov 
published his results, and 1 after) that predicted rotating 
superconductors in an alternating magnetic field would generate gravity -- 
perhaps Podkletnov has detected the effect they predicted.  NASA have had 
a program in place researching this for nearly 3 years. 

   Many other physicists simply laugh and say it's impossible due to 
conservation of energy, general relativity, or the fact that gravity 
really isn't a force -- it's just an implication of the 4 dimensional 
space we live in, and leave it at that. 

   According to known physical principles, gravity cannot be shielded or 
modified.  No combination of electromagnetic fields of any conceivable 
strength (that could be generated on Earth with conventional technology), 
near a superconductor or not, could modify gravity in any discernable 
way.  In fact, there are so many known ways in which strong electric and 
magnetic fields can exert strong forces on nearby objects, that these 
sorts of effects almost always dominate weight measurements over even 
moderate changes in gravity.  Thus, the design of any experiment to test 
for gravity changes in the vicinity of strong magnetic and/or electric 
fields (as in the Podkletnov device) must always be done very carefully.  
Attention must be paid to all of the forces present.  It is not clear at 
all that Podkletnov's claims of having taken care of all that is valid.  
It is these sorts of issues that have stymied NASA so far. 

   Because Podkletnov's claims have such far-reaching implications, a 
number of different groups are conducting experiments to reproduce the 
effect.

   Best regards,

   Emilson P. Leite
   IAG/USP - Brazil


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