Snow Blindness
Fresh snow reflects 90% or more of ultraviolet radiation, which causes snow blindness, also reducing absorption of sunlight by the ground. Snow blindness (also known as ultraviolet keratitis, photokeratitis or niphablepsia) is a painful eye condition, caused by exposure of unprotected eyes to the ultraviolet (UV) rays in bright sunlight reflected from snow or ice. This condition is a problem in polar regions and at high altitudes, as with every 1,000 feet (300 m) of elevation (above sea level), the intensity of UV rays increases by 4%. Snow's large reflection of light makes night skies much brighter, since reflected light is directed back up into the sky. However, when there is also cloud cover, light is then reflected back to the ground. This greatly amplifies light emitted from city lights, causing the 'bright night' effect. A similar brightening effect occurs when no snow is falling and there is a full moon and a large amount of snow.
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Famous quotes containing the words snow and/or blindness:
“Every winter the liquid and trembling surface of the pond, which was so sensitive to every breath, and reflected every light and shadow, becomes solid to the depth of a foot or a foot and a half, so that it will support the heaviest teams, and perchance the snow covers it to an equal depth, and it is not to be distinguished from any level field. Like the marmots in the surrounding hills, it closes its eyelids and becomes dormant for three months or more.”
—Henry David Thoreau (1817–1862)
“Oh blindness to the future! kindly giv’n,
That each may fill the circle mark’d by Heav’n:”
—Alexander Pope (1688–1744)