Most flat earthers think that the sun orbits roughly 5000km above the earth in a circular motion.
This theory is absolutely ridiculous. Using simple trigonometry I can easily disprove the theory:
On the winter solstice the sun is 7213.8km away from the tropic of cancer on the flat earth. This can be calculated by using the pythagorean theorem. We can now calculate the actual diameter of the sun. Assume that the center of the sun is 5000km away from the flat earth. The angular diameter of the sun is 0.5 degrees, so we can calculate the actual diameter of the sun by solving for d in this equation:
a = 2 * arctan(d/2D)
Where a is the angular diameter in radians, d is the actual diameter of the sun and D is the distance to the sun.
I found a calculator that did it online so I didn't have to change the values manually. I got x = 43.63km. Now let us change the values of D for it to be 7213.8km. If the flat earth theorem is true then the suns angular diameter is 0.34 degrees. Or in other words, 32% smaller.
It gets much, much worse from London. London is approximately 8340km away from the tropic of capricorn. That means that in the pizza world, London can be found 9720km away from the sun. London would have a sun that is 50% smaller than the sun over the Tropic of Capricorn.
Here is a picture of what the sun would look like on the 21st of december at noon from London, the tropic of capricorn and the tropic of cancer. I compared these results with the “observed” results:
The same goes for the moon as it is about the same size as the sun is in the sky.