I mean, the reason the sky is blue is due to the atmosphere’s effects on light and the fact that it’s not fully transparent.
Earth’s atmosphere is also the reason why we see some stars flickering. The light of the star is constant, but our atmosphere creates diffusion, so some of the photons don’t reach our retinas. Technically, if you and your next door neighbor look at the same star, it’s flickering for both of you, but the flickering is not synchronous since position of observation matters.
Its blue because of Nitrogen more than Oxygen, considering the relative densities.
And also, ofc, because of Avagadro’s Number.
The fact that blue light gets scattered by the atmosphere is due to the fact that there’s just so much of it and not bcoz the atmosphere inherently is non-transparent
So the atmosphere interacts with light because it’s there, not because it interacts with light??
I’m saying if the atmosphere was smaller, scattering would be less and blue colour may not appear. So the blue colour is not because the atmosphere is “not entirely transparent” like the commenter said, but because there is enough of the atmosphere that the scattering effect is prominent.