It has come to my attention that some people are claiming that the below graphic is consistent with the belief that the Earth is flat.

I am sad and amused.

This web site uses spherical trigonometry in its calculations, and not a single formula on this web site would work if the Earth were not a sphere (it's not a perfect sphere, of course, it's technically an ellipsoid...but the calculations herein correct for the very small, natural deviations from sphericity caused by the Earth spinning and a few minor geologic factors).

Humans have known and proven that the Earth is a sphere since about the 6th century B.C. If you still harbor the belief that the Earth is flat, you have about 2,500 years of catching up to do.

(The Earth is effectively flat, locally, of course, as a reasonable approximation, which is perhaps why some people have misinterpreted this graphic. At least on the human scale of rooms and houses and towns, the Earth's curvature is generally too small to be relevant. But please don't apply this approximation to larger distances.)

The altitude angle (sometimes referred to as the "solar elevation angle") describes how high the sun appears in the sky. The angle is measured between an imaginary line between the observer and the sun and the (also imaginary) horizontal plane the observer is standing on. The altitude angle is negative when the sun drops below the horizon. (In this graphic, replace "N" with "S" for observers in the Southern Hemisphere.)

The altitude angle is calculated as follows:

sin (Al) = [cos (L) * cos (D) * cos (H)] + [sin (L) * sin (D)]

where:

Al = Solar altitude angle

L = Latitude (negative for Southern Hemisphere)

D = Declination (negative for Southern Hemisphere)

H = Hour angle