{Chaotic Determinism (+ Extracts) [continued (20)]}[4th August 1988]

[Redbook5:258-259][19880804:1705g]{Chaotic Determinism (+ Extracts) [continued (20)]}[4th August 1988]

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[continued]

Nevertheless,* it may have its limits. Tritton** writes: ‘This “sensitivity to initial conditions” is the key to understanding why determinism does not necessarily imply predictability. If we knew exactly how the pendulum is moving at a given time, then we could predict future motion exactly. But we never do know anything exactly – the slightest vibration in the drive or the slightest draught in the room prevents that. The feature that distinguishes systems that behave chaotically from those that do not, is that the smallest change leads ultimately to quite different detailed development.’**

The point, if I understand it right, is that although the pattern does not repeat itself, once running, and seems to be unpredictable except by perfectly controlled experiment (eg in a computer), the experiment is repeatable: given exactly the same start and conditions, exactly the same internally unrepeating patterns will be repeated, for so long as exactly the same conditions hold, as occurred the last time the experiment was run. This is not, of course, true Chaos, although it may be the nearest we can come to it.***

*[See last previous entry]

**[Tritton, D, ‘Chaos in the Swing of a Pendulum’, N[ew] S[cientist], 24/07/86, 1518, p37, presumably, as this was read on the same day according to a marginal note in the ms]

[Presumably D. J. Tritton, Senior Lecturer in Physics, University of Newcastle upon Tyne, and author of Physical Fluid Dynamics (Clarendon Press)]

***[But see next entry]

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