Re: Physical mythology

[Joseph Bellina <jbellina@SAINTMARYS.EDU>]

Perhaps part of the problem here has to do with arc inititation, which
may depend as much on the choice a material as on its overall shape.  In
many materials, a high electric field will result in very fine fingers
of material rising up from the surface.  These fingers have a very small
radius of curvature, and hence lead to large fields and efficient arc
formation.  If a sphere was made of such a material, it might indeed act
as a better arc initiator than a pointed rod, given that the point rod
was probably wrought, and hence less prone to producing such fine
fingers.

just a thought,

cheers,

joe

On Wed, 7 Feb 2001, Daniel L. MacIsaac wrote:

> [edits]
> > > Well, tell me, which kind of
> > > lightning rod do you think is superior? What informed your opinion on
> > > this topic, and at what age did you first learn the correct answer?
> > > The inquiring mind wants to know.
> >
> > PERHAPS pointed lightning rods are no more effective than spherically
> > ended ones. If so, I would expect that the UK would still be using
> > the spherical ones. (are they? why or why not?)
> [edit]
> > Ancient myths do indeed die hard!
> >
> > My experience with the van de Graaf dome shows me that
> > sphere-to-sphere discharges are less frequent and much more 'fat'.
> > Point-to-point sparks are much more continuous and feeble. Is this
> > relevant to the thunderstorm generator??
> >
> > I HAVE read that alpha-augmented pointed tips are not significantly
> > better than non-radioactive points as lightning protection. But alpha
> > doped points ARE often used in atmospheric measuring set-ups.
> ...I believe there was a great deal of religious-inspired turmoil on this
> topic in the 1700s; the problem was pointed rods 'pierced the heavens' and
> constituted an assault on God's residence at the hands of science (sounds
> like evolution, no?)  Hence communities were influenced by ministers to
> use no or ball-tipped lightning rods.
>
> Dan MacIsaac, Assistant Professor of Physics and Astronomy, Northern AZ Univ
> danmac@nau.edu          http://purcell.phy.nau.edu         PHYS-L list owner