Re: curvature of buckets of water

[Herbert H Gottlieb <herbgottlieb@JUNO.COM>]

The spinning bucket reminds me of a nice corridor display that I saw
at Lake Forest College about 35 years ago.

Grow some grass seed on a phonograph turntable. After a few
days, the seeds will germinate and the grass blades will all
slant to the center of the turntable instead of growing vertically erect.

Herb Gottlieb from New York City
(Where we enjoy fooling Mother Nature's planned geotropism)

On Sun, 04 Jul 1999 09:28:55 -0400 John Denker <jsd@MONMOUTH.COM> writes:
> At 01:21 PM 7/3/99 -0400, Bob Sciamanda wrote:
>
> > I'm sure you know the phenomenon to which I am referring and the
> > point involved.
>
> Indeed I knew what you were referring to, and I thought it was a nice
> exposition of the relevant physics.
>
> > Before I am consumed in flames, let me correct an error in
> terminology :  in
> > my last post replace the word "meniscus"  ...
>
> Hee, hee.  Perhaps you could use a bucket of spinning water to put out
> the
> flames?
>
>
>
> Now... to move beyond vocabulary, let me pick a nit of real physics:
>
> At 01:02 PM 7/3/99 -0400, Bob Sciamanda wrote:
> > To paraphrase Mach, you can
> > only produce a curved [] surface in a pail of water by rotating the
> > water in  this "absolute" sense
>
> Ahem.  I'd say that strictly speaking, spinning the bucket is not
> actually
> the *only* way to produce a curved surface.  Putting some
> artfully-arranged
> gravitational sources under the bucket could do it, especially if we
> consider slow rotations and/or really dense sources.
>
> I'm just beating the drum for the equivalence principle:  at any
> particular
> point in space, an accelerated reference frame is indistinguishable
> from a
> gravitational field.
>
> OTOH the point remains 100% valid that rotation is absolute and not
> relative, and can be detected by a bucket of water.  You just need to
> make
> a couple of extra checks to make sure some wise guy hasn't slipped you
> a
> funky bucket.
>
> Cheers --- jsd