Re: blue sky: Bohren&Fraser +- Einstein

["John S. Denker" <jsd@MONMOUTH.COM>]

At 06:51 PM 9/1/00 -0700, Daniel Schroeder wrote:
> Now that I've read [the Bohren and Fraser] article in The Physics Teacher
> (May, 1985, page 267), I can recommend it with unreserved
> enthusiasm.  Please, don't take my word for it, go read it
> for yourself.

I recently read this paper.  I too recommend it, although with some
reservations.

+) The bibliography is good;  it contains pointers that I had previously
obtained only with difficulty.

+) The paper properly punctures a number of common misconceptions.

-) On the other hand, the right-hand half of page 269 seems goofy.  It
makes a fuss about the distinction between scattering by molecules and
scattering by density fluctuations.  In particular, B&F try to tar Einstein
with this brush, implying that he "pretends" matter is continuous.  But if
you actually read Einstein's paper (1910, Annalen der Physik) he pretends
no such thing; all the relevant equations have a factor of N (Avogadro's
number) right out front, and indeed N is the subject of the concluding
paragraph.  (As if somebody who had published an epochal paper on Brownian
motion just 5 years earlier was going to misunderstand the nature of the
fluctuations!)

Oh, by the way, I recommend Einstein's paper without reservation.

1) Don't be put off by the title, which suggests it's all about critical
opalescence.... A huge part of it applies to the plain old blue sky (far
from the critical point).

2) Nowadays some people try to show how "smart" they are by making their
writing heavy and hard to understand.  But in contrast Uncle Al's writing
(except for the title :-) is remarkably light and bright and clear.