Fun_People Archive
18 Jul
ATTN JMS: Direction of Toilet Swirl?

Date: Tue, 18 Jul 95 12:48:20 -0700
From: Peter Langston <psl>
To: Fun_People
Subject: ATTN JMS: Direction of Toilet Swirl?

Forwarded-by: (m.b.komor)

In <> (Keith Thompson) writes:
> My understanding is that the Coriolis force caused by the Earth's rotation
> is far too weak to have any significant effect on the swirling of water
> in toilets and sinks.  The effect might be measurable with sufficiently
> sensitive instruments under ideal circumstances, but it's normally masked
> by the effects of the shape of the toilet or sink and any initial motion
> in the water.  Remember that the Earth will rotate only about one minute
> of arc in the time it takes to flush.

Your "understanding" is correct.   In one of the more classic bored-physicist
experiments (a group of physicists bound for Antarctica during the now-
forgotten "International Geophysical Year," about 37 years ago) a group
of PhD's tried to design an experiment using a very large tank of very
still water on shipboard, trying to see if they could determine with
reasonable accuracy when they crossed the Equator.  With the time and
equipment they had available, they were unable to invent an experimental
regime that came anywhere close to producing reasonable results.

As an aside, you might also try paying attention to any whirlwinds you
encounter; a good percentage are spinning in the opposite direction
than the Myth would lead you to expect.

In practice, the direction of spin in a fluid medium, air or water,
seems to be more based on the original motion components of the fluid
than on which hemisphere the funnel happens to be in.

I notice that Chris Carter, at the "X-FILES," subscribes to this Urban
Myth as well; in tonight's re-run (one of their better shows) Agent
Mulder detects the Presence Of Evil by noticing that the water in a
drain is spinning what he thinks is the wrong way.  (Oh, well; at
least he was polite to the Wiccans, and didn't confuse them with
demon-worshipping psychos; you can't win 'em all.)

> Some friends and I once performed an experiment at a party.  We filled
> the bathroom sink with water and added a few bits of paper to show any
> motion of the water.  We let the water sit for an hour or so, to let
> any currents die out, and then opened the drain.  It drained straight
> down with no swirling.  (Yes, it was a fun party; why do you ask?)

Sounds like you go to the same kind of parties I do.   The last really
good party I attended, the hostess had arranged for us to see a preview
copy of a movie we'd all contributed material to, but her VCR/projector
was very crudely aligned.   So the bunch of us tore it down, matched
the adjustments, and did a *proper* convergence on it before we
watched the video tape.    There was a moment of acute panic on the
part of the hostess when she came back down to the screening room to see
how we were getting along, and found twenty kilobucks' worth of Home
Theater System spread all over the floor in pieces.

  Hostess' Husband:  "I *TOLD* you not to leave any tools out, with
		      this bunch in the house!"

  Hostess:           "I didn't!   They all had Swiss Army Knives and
		      Little Screwdrivers!"

  Hostess' Husband:  "God, look at this mess.   Can't they just drink
		      and bust things, like normal party guests?"

....The front-projection unit was at better-than-factory alignment when
we were done with it.  It really was the best sixty-inch projection
TV display I'd ever seen, after it was properly degaussed, compensated,
and converged.  (And our movie looked great, thank you very much.)
However, at the next party at that house, the butler requested that
we check "weapons and tools" at the door.   (We ignored him.)

> Hopefully someone who knows more than I do will correct me if I'm wrong.

You weren't.

> Inevitably someone who knows less than I do will correct me if I'm right.

Count on it; if it's a form of behavior indistinguishable from bull-headed
obtusity, it's normal for the Net.

[=] © 1995 Peter Langston []