On 12/08/2009 10:18 PM, Jones Beene wrote:
The sound level is certainly intense from helicopter blades... not
ultrasonic, but sonoluminescence does not demand ultrasound.
Yellow is a characteristic color of salinity and many sandy deserts are
highly saline.
Instead of sand, per se, the emission could be caused by cavitation in
saline air.
Waitaminnit -- cavitation in *air*?
I thought you needed an incompressible fluid -- i.e., a liquid -- to get
cavitation, or at least to observe the effects commonly associated with
cavitation.
With cavitation you've got regions of extreme low pressure side by side
with regions of normal pressure. With a gas, that just doesn't happen,
because there's no abrupt boundary between a gas and not-a-gas -- it
just gets thinner.
And even if "bubbles of nothing" could form in air, when they collapsed,
the pressure spike which occurs when a cavity collapses in a liquid
would be absent, because, once again, air is compressible. Viewed a
little differently, what that means is that air doesn't have the sort of
"exclusion property" water has: Two volumes of water can't occupy the
same space at the same time, and if they try to do so, the pressure goes
through the roof. Two volumes of air, OTOH, can occupy the same space
at the same time and if the diameter of the space is less than the mean
free path, they won't even notice each other. Consequently when two
walls of water smash into each other, as in a collapsing cavity, the
pressure at the interface may be instantaneously enormous. When two
walls of air smash into each other, on the other hand, nothing much
happens; where the walls interpenetrate the pressure will momentarily
double, but that's about it. (Blow your ear drums out, sure, if you
happen to be standing in the middle -- but set off a fusion reaction?
Don't think so!)
-----Original Message-----
From: Steven Krivit
cavitation???
Dust impact? Glow discharge? Dust contaminates the N2O2 plasma?
Bright yellow glow from helicopter rotors
http://www.michaelyon-online.com/the-kopp-etchells-effect.htm
(from http://sprott.physics.wisc.edu/pickover/pc/realitycarnival.html)
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