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Re: Squeeky Snow



On Tue, 19 Dec 2000, Paul O. Johnson wrote:

You've struck another chord, Brother Beaty. I can't remember much of my five
years in Lawrence, Kansas, either from classes or from walking across the
snow. But I vividly remember walking on the beach at Surfers Paradise,
Queensland. The sand felt like talcum powder, and it definitely and loudly
squeaked with each step.

Squeeking snow happened too long ago in my childhood, but I remember that
the Gulf Breeze FL sand and the Oregon sand both made a "wheeeeOOOOP"
noise as my feet moved along. I couldn't tell whether the frequency of
the sound was proportional to the horizontal velocity of my foot, or to
the downward force. In both cases the sand appeared to be silica based,
as opposed to the coral sands in other places (I grew up on Guam, and
never encountered any sand-squeeks.) Maybe silica makes a difference?
With snow available, I wonder if a sled-like "foot analog" could be built
which would generate the sound as it's dragged along.

Last I heard, the sand phenomenon is still unexplained. Some people even
think that it's electrostatic. Also, I remember hearing that silica sand
supports a very thin layer of silica gel which varies with humidity. And
ice supports a water layer which varies with temperature below freezing.
If particle size is made smaller, these layers would act proportionally
larger, so maybe the powder must be small enough to behave like rubbery
spheres with heavy masses inside. Maybe both effects are collective
emergent phenomena caused by the physics of powders combined with surface
physics? Not that that tells us much! But if it's based on Complexity,
then perhaps any explanations will have to wait for analysis techniques
which can also crack the Turbulence problem.

Hey, is water-ice piezoelectric?

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William J. Beaty SCIENCE HOBBYIST website
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