Sun observation models
Sun observation models compare what the Sun should look like on a globe versus a flat Earth — angular size, elevation, path. Flerfs say "perspective." These tools make them pick numbers.
Sunset Visualiser
sunset.observable.science — interactive sunset, globe vs flat, side by side. By James DeBono (source).
Claim it kills: on flat Earth a nearby Sun sliding toward the horizon must shrink. On a globe it basically doesn't; it sets because the horizon tips past it. Real sunsets match the globe pane.
Four views (globe/flat × camera/side), local-plane or Gleason-map flat paths, location/date/refraction controls. Maths and in-browser tests linked from the site.