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On Tuesday, April 02, 2002, 2:22:17 AM, John Cappello wrote:
JC> The preponderance of sky particles are in the blue wave length and
JC> not violet.
Irrelevant babble.
First, the mechanism we are talking about is scattering, and has
nothing to do with the color of "sky particles" in the atmosphere.
Also, the predominant scattering is from *molecules*, not "sky
particles." The sky would be the color it is even if it contained NO
aerosol particles.
This molecular scattering (Raleigh scattering) is *strongly* dependent
on wavelength (inv 4th power), and thus violet is more strongly
scattered than blue, as I said. With just this simple explanation, the
sky would be violet, not blue.
To understand why the sky is blue, you have to go beyond this
simplistic explanation. First, sunlight does not have a flat spectrum,
it is a 6000 degree 'black body' radiator. This means, among other
things, :-) that there is not as much violet light as blue in sunlight
- one of the factors that makes the sky blue.
Then there is atmospheric attenuation. Not a big factor, but if you
want the *correct* answer, you have to allow for a bit greater
absorption of violet than blue in the atmosphere.
Last, but *certainly* not least, is the response of the eye. This gets
a bit complicated (as I SAID) because the three kinds of 'cones' in
the eye each have their *own* spectral response that must be
considered. To further complicate matters, the red cones also respond
significantly to blue light, thus making the perceived sky color more
"blue" than it 'really' is.
I would have thought that you, as a medical doctor, might know this
and take such things into account.
There are also aerosol particles in the atmosphere. They scatter
according to a different theory devised by Mie, who showed how to
calculate scattering from spherical particles whose size is comparable
to the illuminating wavelength. This kind of scattering is
considerably more complex than Rayleigh scattering, but not nearly as
complex as scattering from arbitrarily-shaped particles. Mie scatter
has a much weaker spectral dependence, but is *very* dependent on the
aerosol particle size distribution. The color effects can vary widely,
from a beautiful red sunset caused,in part, by the strong
forward-scatter behavior of Mie scattering from typical 'haze' aerosol
particles, to the grey color of clouds and fog.
A complete discussion of the significant effects of aerosol particle
scatter on the sky color is beyond this short note.
JC> I stand by my explanation previously posted .
You can stand by it as much as you want, but it is WRONG, and will not
become more correct by inserting irrelevant babble about "sky
particles".
You seem to stand by a number of other things, too. Hmmm...
JC> It is not complicated.
It is, as I said, a bit more complex than the simplistic 'scatter'
view - especially if you want to get the *right* answer. :-)
JC> The plague was the Bubonic plague spread by rats somewhat like vermin
JC> multiplying on this board as anticipated.
Pneumonic plague is caused by the same bacillus, Yersinia pestis, as
Bubonic plague, but is caused by the inhalation of contaminated
aerosols instead of flea bites. (there's those pesky aerosols, causing
trouble again.) :-)
As a medical doctor, I would have thought you would know about such
things. Hmmm....
You might want to tell us what's behind your trading 'predictions'. If
it is as flawed as the above.... Hmmm....
ztrader
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