Part 6/10:
Refraction involves light bending when passing through mediums of varying densities. However, the amount of bending is limited by the physical properties of Earth's atmosphere, which decreases in density with altitude. To produce the kind of magnification flat earthers argue for—such as the Sun appearing larger at the horizon—would require an atmospheric shape that is improbably convex on a planetary scale, or a density profile incompatible with known physics.
Moreover, the atmosphere's pressure gradient, proportional to altitude, strongly supports a spherical or at least curved model, where air pressure decreases predictably with height. Flat Earth models would need to posit an impossibly curved atmosphere to match observations, which contradicts existing physics and atmospheric science.