The sun does not sink below the horizon.
False.
It is plainly visible from a private airplane, when flying westward at sunset, to see the sun dip below the horizon, all one needs to do is to gain elevation a few hundred feet to see the sun re-appear where it went down, and then by descending one can see the sun set again over the horizon.
On a clear day, standing in a valley with mountains to the east, anyone with eyes to see can follow the shadow of the setting sun cast on the mountainside as it moves up the hillside. You can actually watch it move -- but it moves slowly. On an open field, such as Death Valley, you cannot run fast enough to keep up with the shadow it moves so fast.
Of course, some people (generally Modernists) cannot believe what they see with their own eyes.