Earlier, I wrote a post on why people know that the earth is round. Evidence such as star movement, the obscuring of distant objects by the earth’s curvature, and aircraft flight times shows that the earth is not flat:
In this post, I want to temporarily put on the “hat” of a flat-earther. They claim that the sun is a “spotlight” which travels across a circular flat earth like this:
That is at least a well-defined model, crazy though it might be, and therefore can be tested. Here is a computer render of the spring sun at sunset on that assumption (as seen from, say, San Francisco, at the moment that the sun disappears from view):
Three obvious problems with the flat-earth model are visible in this picture:
- The sun is much too small: only 40% of its noontime diameter (because it is 2.5 times as far away as at noon)
- The sun appears oval, rather than circular, because the “spotlight” is being seen obliquely (click to zoom if you can’t see the shape)
- The sun is much too high in the sky (24° above the horizon)
In reality, of course, the sun at sunset is a circular disk that gradually slips under the horizon. Oops. No, the earth is not flat.