From: "James F. Tims" <p00168@psilink.com>
Subject: Re: Wwy is the sky blue? (was Re: Daytime Stars - Not Donahue or Oprah)
Organization: Semper Excelsior
Date: Mon, 21 Dec 1992 17:33:43 GMT
X-Mailer: PSILink (3.2)

>DATE:   21 Dec 92 01:24:15 GMT
>FROM:   Kevin Moore <kjm@buc.edu.au>
>
>In article <1992Dec16.083550.11767@msc.cornell.edu> maynard@leah.msc.cornell.edu (Maynard J. Handley) writes:
>
>>So I'm not sure quite what the above dude means by electron scattering in
>>molecules not being affected by frequency. Maybe this statement refers to
>>resonant scattering, whereas what we care about is non-resonant.
>
>>Maynard
>
>All that stuff in Jackson essentially reduces to treating air molecules as 
>classical harmonic oscillators, excited by the incident light, and radiating 
>as dipole radiators.
>
>The frequency of light is well below the natural frequency of the air 
>molecules. When sufficiently outside the resonant region, a harmonic 
>oscillator's amplitude is approximately constant ( A = F_0/k ) for 
>frequencies below resonance. For frequencies well above resonance, 
>A = F_0/ m omega^2 . In the resonance region, it is a lot more complicated, 
>and is certainly frequency dependent.
>
>The Rayleigh scattering case is below resonant frequency. The amplitude of 
>the oscillator is constant with frequency, so from the dipole radiation 
>formula, we get the omega^4 dependence.
>
>As far as seeing stars from the bottom of wells is concerned, I've looked up 
>at the sky from the bottom of slot canyons, and it looks blue, just like a 
>normal daytime sky. No stars. 
>
>Bah, Humbug! to you all,
>
>Kevin
>
>******************************************************************************
>The reason is that the program was written in  	*	Kevin Moore
>BASIC, a sort of computer baby-talk.            *     kjm@buc.edu.au
>                              Richard Dawkins	*
>******************************************************************************

I'm still confused.  Sorry.  I'm really trying to understand this.
Some of the posts seem to confirm my vague recollections that the sky is
glowing, although my reasons for it were incorrect.

I can't figure out whether the atmosphere is a lens or a radiator; whether 
the photon originally came from the sun (no glowing) or whether it came from
the air molecules (glowing); whether a different atmosphere would be a
different color because of its spectral signature or because of its optical
properties; whether the air molecules in the viewed part of the sky are even
receiving their fair share of red (!glowing) or whether the red is being absorbed
and re-radiated (glowing).  I had diff-eq over 30 years ago.  I had one
miserable year of highschool and one stinking semester of college physics 
over 30 years ago.  I love physics.  I do.  I am simply too thick to get 
very far into its abstruse realms.  Surely, there is some succinct 
statement that a laymen can understand, that would imply that it acts 
like thus-and-so, that would make an analogy sufficiently comprehensible 
that I can finally get a feel for why the sky is blue.

Maybe we need a dissertation on Rayleigh (John Strutt -- see...I'm really
trying) Scattering.  In that case, I may be doomed never to know why the
sky is blue. 8^(

  ,...,.,,
 /666;    ',    jim tims
////;    _~ -   p00168@psilink.com
(/@/----0-~-0
 ;'  . `` ~ \'
  , `    ' , >
;;|\..((   -C---->> So is it glowing, or what?  I almost thought I had
;;| >-  `.__),;;    there for a second, but now it's gone again.






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