[interroboink]

I went down this rabbit hole a while back — there's a fascinating history of various scientists' investigations into the blue sky, across many decades, with some back-and-forth between Russia and Europe. Einstein eventually made a connection between it and the seemingly-unrelated issue of "critical opalescence," by showing that the fluctuations of densities is responsible for the scattering, not just a simple "individual molecules floating in space" analysis that Rayleigh originally performed. But funnily, for an ideal gas (such as our atmosphere), the formula works out to be the same.

So, "Rayleigh scattering" is the common term still used today, but there is a deeper reason for the formula being correct — it remains correct even when molecules are relatively close together, such as in the lower layers of our atmosphere.

I found this nice paper[1] giving an overview of the timeline, various discoveries, etc: http://users.df.uba.ar/bragas/Web%20roberto/Papers/sobelman%...