Interesting picture. I can't quite make out what is supposed to be 140 miles away and what 190 miles away. At 140 miles away (starting at an elevation of 500 feet), 8400+ feet should be hidden from view by curvature; at 190 miles, 17,600+ feet. I doubt that refraction could explain this.
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No refraction is needed for an explanation. There doesn't seem to be any refraction going on, not unusual for cold climates.
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You're not using the curvature calculation correctly.
The
elevation of the viewer is (supposedly)
500 feet (actually it's probably more like 550 feet but we'll ignore the 50' of error.)
The
distance to Denali is not 140 miles (the correct distance is 120) because the flat-earther's scribbling on the photo is wrong.
Check the maps. It's
120 miles.
Therefore, using an accurate calculator that takes these into account, such as
this one, you get:
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5,720 ft obscured. .
Take that away from 20,310 ft and you have
14,690 ft visible -- well within reasonable in the picture shown, especially considering the base of Denali mountain range is right about the same as the obscured calculated. (The peaks of the
Dutch Hills at Denali's base are 4,500 ft tall and they're not visible in the photo, because they're under the curvature horizon.)
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The only thing flat-earthers have to fear is sphere itself. .