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From: chesler@netrix.nac.dec.com (David Chesler)
Newsgroups: sci.bio,sci.misc
Subject: Re: Textbook errors - OSMOSIS
Summary: Dynamic Equilibrium != Perpetual Motion
Keywords: osmosis
Message-ID: <17302@shlump.nac.dec.com>
Date: 14 Nov 90 19:56:14 GMT
References: <1990Nov12.211609.23489@cunixf.cc.columbia.edu> <1990Nov13.111721.12306@newcastle.ac.uk> <1765@ruunsa.fys.ruu.nl>
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In article <1765@ruunsa.fys.ruu.nl> hooft@ruunsa.fys.ruu.nl (Rob Hooft) writes:
>In <1990Nov13.111721.12306@newcastle.ac.uk> william@lorien.newcastle.ac.uk 
         (William Coyne) writes:
>>In fig 1 in the AFTER part won't the water be cascading down
>>the area of membrane not exposed to the lo side, and would this not have an
>>effect on the equilibrium position?
>
>Wieeeee! There we have it again. Perpetual motion!! No, the water wouldn't be
>dropping to the low side.

  Nobody denies that at equilibrium molecules are going back and forth across
the membrane below the low water mark.  And nobody claims this is perpetual
motion.

  Why should the water on the high side "know" that if it crosses membrane
it will fall?  Fear of heights?

  Dynamic equilibrium is not the same as fallacious perpetual motion.

  (But why couldn't energy be taken off the falling water?  I don't know.
Maybe taking the energy would shift the equilibrium, or maybe through
capillary action and stuff the water is as likely to move up the dry side
of the membrane as down.)

-- David Chesler (chesler@netrix.enet.dec.com) formerly david@prism.tmc.com
    Earning my living at Digital in Littleton, Mass; speaking for myself.
    "Video meliora proboque, Deteriora sequor." Ovid, Metam., VII, 20.