[philman_36]

Rayleigh scattering can contribute to purple sunsets
by scattering blue and red light simultaneously.

Nothing to do with shadows or Venus.

[Pete from Shawnee Mission]

I am saying that the Earth is round, and because it is round, at certain times it casts a shadow in the atmosphere that can be seen. See the link in my original post.

I am not sure what you are saying with the 8 Inches per mile squared unless it is to describe the curvature of the earth relative to the observer.