This particularly interesting news article deals with
Chladni like oscillations where similarly sized
particles attract when oppositely phased. Dr. Henry
Monteith had done experiments with bubbles and noticed
similar phenomena.
It is important because from such simple patterns come
complex geometries which is clearly shown on the
superb cymatics video by the late Dr. Hans Jenny and
carried on by Dr. Peter Guy Manners.
http://www.aip.org/enews/physnews/1996/split/pnu286-1.htm
PARTICLE-LIKE LOCALIZED EXCITATIONS IN A BED OF SAND
can form into molecules and even crystals. University
of Texas physicist Harry Swinney shakes an evacuated
container of sand (actually a lake of tiny bronze
balls ) up and down.
At a certain frequency the energy put into the system
manifests itself as small isolated heaps of sand
(about thirty grains in diameter) which also bob up
and down.
These heaps, which Swinney calls "oscillons," are
stable (holding together for thousands of shakings)
and able to slowly drift across the sand bed.
And just as with electrical charges, when it comes to
oscillons opposites attract.
As long as their centers are within 1.4 diameters of
each other, oscillons of opposite phase (one at its
peak height and one at its shallowest depth) can enter
into a dipole state.
These peak-crater pairs in turn were observed to form
chains and other configurations including extended
lattices. Swinney and his colleagues have no definite
answer as to how and why the oscillons form and
interact, but he feels that such localized structures
may exist in other dissipative systems (systems which
steadily lose energy), and not just in granular
materials (see Update 264).
( Paul. B. Umbanhowar, Francisco Melo, and Harry L.
Swinney, Nature, 29 August 1996. Some associated
figures can be viewed on our Physics News Graphics
website: http://www.aip.org/enews/physnews/graphics/ )
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