It's no wonder that some HS teacher continue to promulgate such
blatantly dangerous notions as entropy being related to disorder.
SOMEBODY working for the AIP has similar misconceptions!
e.g.
Number 469 (Story #1), February 2, 2000 by Phillip F. Schewe and Ben Stein
DIGITAL ENTROPY How much information does it take to control
something? By combining thermodynamics with information theory, MIT
researchers (contact
Seth Lloyd, 617-252-1803, slloyd@mit.edu) have determined the minimum
amount of information one needs to bring an unruly object under
control, providing quantitative answers to such subjects as taming
chaos.
From the perspective of thermodynamics, controlling an object means
reducing its
disorder, or entropy. Lowering the disorder of a hot gas, for
example, decreases the
^^^^^^^^ ^^^^^^^
number of possible microscopic arrangements in the gas. This in turn
removes some of the uncertainty from the gas's detailed properties.
According to information theory, this reduced uncertainty is
tantamount to increased information about the gas. Applying this
"digital entropy" perspective to the notion
of control, the researchers found that controlling an object becomes
possible when one acquires enough information about it (and then
applies this information to the
object) to keep the uncertainties in its properties at manageable levels.
Chaotic systems are particularly hard to control because they
constantly manifest new amounts of uncertainty in their properties.
Perhaps there is no better everyday
example of chaos than steering a car: a tiny change in steering can
quickly be amplified into a huge change in course. For example, if a
blindfolded driver initially
knows that her car is within two feet from a curb, tiny fluctuations
in steering can make this uncertainty 4 feet after one second, 8 feet
after two seconds, and so on.
Only if the driver receives second-by-second instructions for
adjusting the steering to keep the uncertainty down to the two-feet
level does she have any hope of
controlling it. If the driver makes such steering adjustments only
half as frequently, her car will go out of control (crash into the
curb) but it will take exactly twice the
amount of time than if no adjustments were made. (Touchette and
Lloyd, Physical Review Letters, 7 February 2000; Select Articles.)
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Chuck Britton Education is what is left when
britton@academic.ncssm.edu you have forgotten everything
North Carolina School of Science & Math you learned in school.
(919) 286-3366 x224 Albert Einstein, 1936