Re: curvature of buckets of water

[John Denker <jsd@MONMOUTH.COM>]

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