Re: Interesting article in Science
Brian D. Harper (bharper@magnus.acs.ohio-state.edu)
Thu, 25 Jan 1996 22:36:58 -0500 Nothing, it seems, could be simpler than a sandpile-this was
certainly the general view of physicists until recently.
Sandpiles were therefore used as illustrations for complicated
physical systems and concepts with the implicit assumption that
their innate simplicity would illuminate the difficulties of
the system or concept being explained. The most recent example
of this arose about 5 years ago, when Bak, Tang, and Wiesenfeld
(BTW) proposed their theory of self-organised criticality (SOC),
using "a simple pile of sand" for purposes of illustration
(Bak et al, 1987). This has proved to be a rather perilous
paradigm in retrospect, because it is now almost universally
accepted that real sandpiles are in fact much more complicated
than that model; in fact, the avalanche of interest in these
systems in recent years has not resulted in anything approaching
even a crude understanding of their microscopic behaviour.
Whatever the relevance of theories of self-organised criticality
to real physical systems may turn out to be, there is no doubt
at all that their choice of the "wrong" paradigm has led to a
positive outcome; there has been an explosion of interest in
the physics of real sandpiles, as physicists have responded in
increasing numbers to the challenges of describing the many
hidden complexities of what can no longer he regarded as a
"simple" pile of sand.
-- Mehta, A. (1994). "Relaxational Dynamics, Avalanches, and
Disorder in Real Sandpiles," in Granular Matter: An
Interdisciplinary Approach, Ed. A. Mehta, Springer-Verlag,
New York.
I think this makes my point very well. SOC may have many important
applications but it is just too simple a model to be considered
paradigmatic for *complex* systems.
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Brian Harper |
Associate Professor | "It is not certain that all is uncertain,
Applied Mechanics | to the glory of skepticism" -- Pascal
Ohio State University |
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