Re: Opposite phase + same size = attraction

John Berry ( antigrav@ihug.co.nz )
Wed, 14 Jul 1999 01:05:10 +1200

These oscillons (or any other name they go under) remind me of the what
you get when you tap a plastic 1.5 or 2 litre coke bottle at the right
pressure and when it is a bit more than half full, a large (50 or so)
drops of coke spring into the air and scoot round as antibubbles for a
while.
It has to be the right pressure and frequency but it is quite
interesting to see.

I wonder if there is any relation....

John Berry

Jerry Wayne Decker wrote:

> Hi Folks!
>
> 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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