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From: jim@alberta.UUCP (Jim Easton)
Newsgroups: net.physics
Subject: Re: The wild ride down the drain...
Message-ID: <757@alberta.UUCP>
Date: Fri, 13-Dec-85 12:57:19 EST
Article-I.D.: alberta.757
Posted: Fri Dec 13 12:57:19 1985
Date-Received: Sat, 14-Dec-85 23:43:32 EST
References: <16@drutx.UUCP>
Organization: U. of Alberta, Edmonton, AB
Lines: 33

>
> Does anyone out there know why water in the sink spins in one direction
> in the Northern Hemisphere when draining, and in the other direction
> in the Southern Hemisphere? 

It doesn't.  The idea is perpetrated by people who find the idea attractive
and are ignorant about the magnitude of the forces involved.  Weather systems
and long range ballistics are affected because of their size and the speed
which gun shells travel but water in a sink is too small a system for Coriolis
acceleration to have any significant effect.

> Does this phenomenon have anything to do with the Corealis (sp?) force?

No - It has to do with conservation of angular momentum.

You don't feel Coriolis acceleration when you're walking down the street or
driving on the highway.  Why would you expect the water in a sink to feel
it.  Granted that it is not zero but is overwhelmed by orders of magnitude
by other forces.

Given a circular tub with a drain hole in the middle.  Water draining out
of that hole will almost always form a whirlpool but that is because the
body of water almost always has some initial (albeit small) angular momentum
about the hole which determines the direction.

Don't take my word for it.  There is nothing like a good experiment to 
debunk this sort of nonsense.  The tub I tried it on was circular with the
drain hole in the middle about a foot deep and about 3 feet across.  The
barest perceptible motion would determine the direction of any whirlpool
that developed.  It literally took hours for the water to settle sufficiently
to not form any whirlpool.

	Jim Easton (..!alberta!jim)