No, it is Tyger turn - he is correct.Originally posted by marcus
That's really a second question. So I will put in a thought----it will still be nbo's turn because he said Rayleigh scattering.
Molecule of N2 is too small (d~0.3 nm) to give any essential contribution into blue sky color. Recall that intensity of scattered light is proportional to (d/[lamb])4, so it drops dramatically with size. It would take about hundred times more air to get essential contribution into scattering from individual molecules. But the distribution of molecules in air is fluctuating, and it turns out that most contribution into intensity of scattered light comes from fluctuating pockets of air of order of 10-100 nm in size. These pockets can have dramatically different number of molecules per unit volume.
Density of larger pockets does not fluctuates essentially, and there are less of those pockets, so despite their larger cross section their contribution is less.
Kinda interesting how interplay of math factors creates tangible phenomenon (blue sky) from something which is not very tangible itself (fluctuating due to thermal motion voids/concentration of certain size range).
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