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James Van Allen journal, 1951?-December 1954

Page 17

Also:
   Probability of a collision = (μ) (d) (x) = (((d)(x)  {thickness  (gm/(cm exponent 2))})/(L {mean [frequency?] path  (gm/(cm exponent 2))})) , L_=(1/μ)

therefore, (1/L) = (sigma)(N/A) = μ

[red ink box below here:]
(L  {M.F.P. (gm/(cm exponent 2))}) = (A {atomic #})/((sigma  {cross section ((cm exponent 2)/(atom))})N  {Avogadro #})
[red ink box above here]
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Hynek on 21 March 1950

Astronomical Magnitufe per square second of sky at the zenith: --

+22 on a moonless night
+4 daylight sun at a moderate elevation

Hynek has photographed a +4 magnitude star in daytime (best yet achieval with Perkins telescope)

See Pettit and Nicholson (Astrophysical Journal ?) for absolute comparison of starlight and skylight and sunlight.
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Total direct sunlight = 6 times skylight typically falling on a horizontal area.

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Also: Probability of a collision = (μ) (d) (x) = (((d)(x) {thickness (gm/(cm exponent 2))})/(L {mean [frequency?] path (gm/(cm exponent 2))})) , L_=(1/μ) therefore, (1/L) = (sigma)(N/A) = μ [red ink box below here:] (L {M.F.P. (gm/(cm exponent 2))}) = (A {atomic #})/((sigma {cross section ((cm exponent 2)/(atom))})N {Avogadro #}) [red ink box above here] ------------------------------------------------------------------- Hynek on 21 March 1950 Astronomical Magnitufe per square second of sky at the zenith: -- +22 on a moonless night +4 daylight sun at a moderate elevation Hynek has photographed a +4 magnitude star in daytime (best yet achieval with Perkins telescope) See Pettit and Nicholson (Astrophysical Journal ?) for absolute comparison of starlight and skylight and sunlight. -------------------------------------------------------------------- Total direct sunlight = 6 times skylight typically falling on a horizontal area.