Published on Feb 19, 2020

Pretty Sunset Wallpapers HD Background

Download best high-quality free Pretty Sunset Wallpapers HD Background available in different sizes. To view the full image size resolution click on the below image thumbnail.

License Info: Creative Commons 4.0 BY-NC

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Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth’s rotation. As viewed from the Equator, the equinox Sun sets exactly due west in both Spring and Autumn. As viewed from the middle latitudes, the local summer Sun sets to the southwest for the Northern Hemisphere, but to the northwest for the Southern Hemisphere.

The time of sunset is defined in astronomy as the moment when the upper limb of the Sun disappears below the horizon. Near the horizon, atmospheric refraction causes sunlight rays to be distorted to such an extent that geometrically the solar disk is already about one diameter below the horizon when a sunset is observed.

Sunset is distinct from twilight, which is divided into three stages, the first being civil twilight, which begins once the Sun has disappeared below the horizon, and continues until it descends to 6 degrees below the horizon; the second phase is nautical twilight, between 6 and 12 degrees below the horizon; and the third is astronomical twilight, which is the period when the Sun is between 12 and 18 degrees below the horizon.

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Dusk is at the very end of astronomical twilight, and is the darkest moment of twilight just before night. Night occurs when the Sun reaches 18 degrees below the horizon and no longer illuminates the sky.

Locations further North than the Arctic Circle and further South than the Antarctic Circle experience no full sunset or sunrise on at least one day of the year, when the polar day or the polar night persists continuously for 24 hours.

As a ray of white sunlight travels through the atmosphere to an observer, some of the colors are scattered out of the beam by air molecules and airborne particles, changing the final color of the beam the viewer sees. Because the shorter wavelength components, such as blue and green, scatter more strongly, these colors are preferentially removed from the beam.

At sunrise and sunset, when the path through the atmosphere is longer, the blue and green components are removed almost completely, leaving the longer wavelength orange and red hues we see at those times. The remaining reddened sunlight can then be scattered by cloud droplets and other relatively large particles to light up the horizon red and orange.

Some of the most varied colors at sunset can be found in the opposite or eastern sky after the Sun has set during twilight. Depending on weather conditions and the types of clouds present, these colors have a wide spectrum, and can produce unusual results.

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