And the reason why you have the blue line, curved?
This one question just shows your total inability to understand the most basic concepts. This is one of the reasons no-one takes you seriously.
Explain it then.
And the reason why you have the blue line, curved?
Because it shows the 8 inches per mile squared.
It shows the approximation for the curvature of Earth, and it is compared to a circle representing Earth.\
No reason for a curved line.
So do you really have no idea at all what you are talking about, or are you just trolling/knowingly spouting BS?
The reason is quite simple, the drop is 8 inches per mile squared.
i.e. to find the drop, take the distance, divide it by mile, square the result and then multiply it by 8 inches.
Or, to express it more correctly and as a simple formula: h=d^2/(2*R)
Notice the square part?
That is what makes the curve.
For a distance of 0 miles, the drop is 8*0^2 = 0 inches.
For a distance of 1 mile, the drop is 8*1^2 = 8 inches.
For a distance of 2 miles, the drop is 8*2^2 = 32 inches.
For a distance of 3 miles, the drop is 8*3^2 = 72 inches.
If you plot these (and the other numbers produced by the same formula) you will get a curve.
Now do you understand why the curve is there?
And again, which of the rods in the image I gave are vertical, which are leaning forwards and which are leaning backwards?