Why doesn't sunlight behave like light thru a prism as it hits the earth's atmosphere?

Here is what is happening.

It is originally from Einstein equations.. he sought to answer why the sky is blue. It does something called Rayleigh scattering.. or that's the math behind it.

But this is the best "theory" they have.. truth is no one really knows why the sky is blue or not a rainbow.

[link to hyperphysics.phy-astr.gsu.edu]