Published on Jul 30, 2020

Evening Sky Background Images

License Info: Creative Commons 4.0 BY-NC

The sky (or celestial dome) is everything that lies above the surface of the Earth, including the atmosphere and outer space.

In the field of astronomy, the sky is also called the celestial sphere. This is an abstract sphere, centred on the earth, on which the Sun, stars, planets, and the Moon appear to be traveling. The celestial sphere is conventionally divided into designated areas called constellations. Usually, the term sky is used informally as the point of view from the Earth’s surface; however, the meaning and usage can vary. An observer on the surface of the earth can see a small part of the sky, which appears to be a dome, also known as the sky bowl, flatter during the day than at night. In some cases, such as in discussing the weather, the sky refers to only the lower, more dense portions of the atmosphere.

During daylight, the sky appears to be blue because air scatters more blue sunlight than red. At night, the sky appears to be a mostly dark surface or region spangled with stars. During the day, the Sun, and sometimes the Moon, can be seen in the sky unless obscured by clouds. In the night sky the Moon, planets, and stars can be similarly visible in the sky. Some of the natural phenomena seen in the sky are clouds, rainbows, and aurorae. Lightning and precipitation can also be seen in the sky. Birds, insects, aircraft, and kites fly in the sky. Due to human activities, smog during the day and light pollution during the night are often seen above large cities.


Except for light that comes directly from the sun, most of the light in the day sky is caused by scattering, which is dominated by a small-particle limit called Rayleigh Scattering. The scattering due to molecule sized particles (as in air) is greater in the direction toward and away from the source of light, than it is in directions perpendicular to the arrival path. Scattering is significant for light at all visible wavelengths but is stronger at the shorter (bluer) end of the visible spectrum, meaning that the scattered light is bluer than its source, the sun. The remaining sunlight, having lost some of its short wavelength components, appears slightly less blue.

Scattering also occurs even more strongly in clouds. Individual water droplets exposed to white light will create a set of colored rings. If a cloud is thick enough, scattering from multiple water droplets will wash out the set of colored rings and create a washed-out white color.

Evening Sky Background images gallery for free download


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