id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
work_prhcxmj2lfgura6jpzx2tayfgy	David K. Lynch	Visually discerning the curvature of the Earth	2008.0	5	.pdf	application/pdf	3159	272	72	Reports and photographs claiming that visual observers can detect the curvature of the Earth from high the minimum altitude at which curvature of the horizon can be detected is at or slightly below 35; 000 ft, the horizon must be placed precisely in the center of the image, i.e., on the optical axis. High-altitude physicist and experienced sky observer David Gutierrez [6] reported that The apparent horizon from commercial altitudes is not a sharp line, but rather a lowcontrast transition from bright sky above to a slightly The brightness change for the high-elevation horizon The sea-level horizon is sharp and has a high contrast. The high-elevation horizon is almost as sharp, but its contrast is low, less than 10% of the detect the curvature of the horizon by using geometrical optics, simple models of the eye, and known Model of the horizon and the Earth's curvature as seen by	./cache/work_prhcxmj2lfgura6jpzx2tayfgy.pdf	./txt/work_prhcxmj2lfgura6jpzx2tayfgy.txt