Sky

July night sky (35972569256)

Sky over Munich 02

Blue Sky, Dhaka, Bangladesh

Rayleigh sunlight scattering

Moon in Sunrise Sky 2

Sky refers to the expanse of atmosphere and outer space visible from the Earth's surface. It is observed as a dome-like structure arching over the planet, changing in appearance due to the light from the Sun, the Moon, and the stars. The color of the sky varies, primarily due to the scattering of sunlight by the molecules in the atmosphere, which explains why the sky appears blue during the day and takes on shades of orange, pink, or red during sunrise and sunset.

Composition and Appearance

The sky is composed of several layers of the Earth's atmosphere, including the troposphere, stratosphere, mesosphere, thermosphere, and the exosphere. Each layer has distinct characteristics and plays a role in the Earth's climate and in the transmission of radio waves. The troposphere is the lowest layer of the atmosphere and is where all weather conditions take place.

The appearance of the sky changes not only with the time of day but also with the weather conditions. Cloud formations, varying from thin cirrus to thick cumulus clouds, can significantly alter the sky's appearance. Atmospheric phenomena such as rainbows, auroras (northern and southern lights), and halos are also visible under certain conditions.

Celestial Observations

The sky serves as a backdrop for a variety of celestial bodies and phenomena. During the day, the Sun is the most prominent feature, providing light and warmth to the Earth. At night, the sky becomes a window to the universe, showcasing the Moon, planets, stars, and galaxies. The study of these celestial bodies and phenomena is known as astronomy.

Cultural Significance

Throughout history, the sky has held significant cultural, spiritual, and religious importance. Many ancient civilizations built monuments aligned with the stars, such as Stonehenge and the Pyramids of Giza. The sky and its elements have been personified in mythology and folklore, with many cultures attributing divine qualities to celestial phenomena.

Environmental and Pollution Concerns

The clarity and visibility of the sky are increasingly affected by air pollution and light pollution. Airborne particulates and chemicals can lead to smoggy conditions, obscuring the view of the sky and posing health risks. Light pollution, caused by excessive and misdirected artificial light, significantly diminishes the visibility of stars and planets in urban areas.

See Also

• Atmospheric optics
• Blue sky law
• Climate change
• Meteorology

Sky Resources
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