58:2.2
The earth’s atmosphere is all but opaque to much of the solar radiation at the extreme ultraviolet end of the spectrum. Most of these short wave lengths are absorbed by a layer of ozone which exists throughout a level about ten miles above the surface of the earth, and which extends spaceward for another ten miles. The ozone permeating this region, at conditions prevailing on the earth’s surface, would make a layer only one tenth of an inch thick; nevertheless, this relatively small and apparently insignificant amount of ozone protects Urantia inhabitants from the excess of these dangerous and destructive ultraviolet radiations present in sunlight. But were this ozone layer just a trifle thicker, you would be deprived of the highly important and health-giving ultraviolet rays which now reach the earth’s surface, and which are ancestral to one of the most essential of your vitamins.