From: Hal Finney (hal@rain.org)
Date: Fri Jun 12 1998 - 10:14:10 MDT
Damien Broderick, <damien@ariel.ucs.unimelb.edu.au>, writes:
> I just visited ace physicist John Cramer's site after an absence, and found
> this interesting piece from March 1997 Analog
>
> http://www.npl.washington.edu/AV/altvw83.html
>
> on possible antigravity devices that aren't self-evidently silly. There
> are some other recent tasty essays posted there.
I agree that John Cramer's articles are interesting and worth reading.
I'm pretty skeptical about this particular antigravity model though.
Anything which violates conservation of momentum is highly suspicious
in my book. It seems that the claim is that it doesn't "really" violate
momentum conservation because (apparently) instantaneous nonlocal
(i.e. faster than light?) changes occur elsewhere to bring about balance.
Handwaving about quantum nonlocality is a long way from justifying this
claim.
As for the measurements, it is notoriously difficult to get good
measurements on these kinds of devices. The article refers to the
misleading results from the Dean drive. There was a recent Wired article
about someone (not Podkletnov) using rotating superconducting disks, and
the reporter pointed out problems with air currents caused by bubbling
liquid nitrogen.
In the experiment Cramer describes, running heavy oscillating currents
into a capacitor can cause all kinds of EM interference. Plus, the
capacitor itself will be subject to mechanical vibrations as its internal
electrodes alternately attract and repel each other. It all adds up to
a messy system that is going to be very hard to get clean measurements on.
Hal
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