Sigh....
Truth is a lot simpler and requires no complex explanations. (unlike the globe models)
Do you even know what atmospheric refraction is????
If it was "refraction" the image of the skyline would be angled differently.
Also, refraction works only through a fluid or lens of some sort, the atmosphere has enough density to allow this, but what most people do not understand is the fact that you would still require uninterrupted line of sight for refraction to take place.
At 40 miles of distance, and according to the curvature equation, there would be over 1000ft of earth that gets in the way.
If it was a "mirage" the image of the skyline would be flipped.
So no, it definitely is not refraction.
There is a circumference, but only in a 2D plane, not 3D like a sphere would be.....
The earth is a flat disk, not a ball.
The bible even says the earth is a CIRCLE...
Not a BALL........
King James Bible Isaiah 40:22
It is he that sitteth upon the circle of the earth, and the inhabitants thereof are as grasshoppers; that stretcheth out the heavens as a curtain, and spreadeth them out as a tent to dwell in: