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While differing traditions exist among groups, they overlap in the way the stars, weather, and folk tales assist in hunting, navigation and teaching their young about the world. [ 1 ] Their astronomy and relationship to the sky is heavily influenced by their spiritual and pragmatic needs, as well as the high northerly latitudes where they reside.
The blue sky spectrum contains light at all visible wavelengths with a broad maximum around 450–485 nm, the wavelengths of the color blue. Diffuse sky radiation is solar radiation reaching the Earth 's surface after having been scattered from the direct solar beam by molecules or particulates in the atmosphere .
Diagram showing displacement of the Sun's image at sunrise and sunset Comparison of inferior and superior mirages due to differing air refractive indices, n. Atmospheric refraction is the deviation of light or other electromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of height. [1]
Sky-gazers on the east coast of North America may see up to 25 meteors streaking across the skies, while those on the west coast could see double that amount due to a later sunrise, Lunsford said.
With a conventional telescope, an extremely dark filter at the opening of the primary tube is used to reduce the light of the Sun to tolerable levels. Since the full available spectrum is observed, this is known as "white-light" viewing, and the opening filter is called a "white-light filter".
World map showing the areas of Earth receiving daylight around 13:00 UTC in April. Daylight is the combination of all direct and indirect sunlight during the daytime.This includes direct sunlight, diffuse sky radiation, and (often) both of these reflected by Earth and terrestrial objects, like landforms and buildings.
However, this doesn't mean it is completely dark for 24 hours a day for areas experiencing polar night. This is due to a time of day called "civil twilight," according to the Weather Channel.
During the blue "hour", red light passes through space while blue light is scattered in the atmosphere, and thus reaches Earth's surface. Blue hour usually lasts about 20–96 minutes right after sunset and right before sunrise. Time of year, location, and air quality all have an influence on the exact time of blue hour. [7]