When seen from altitude, as here from an airplane, the sky's color varies from pale to dark at elevations approaching the zenith

Turbulent skies

The sky's zenith appears centered in this daytime photograph taken looking up though trees

Clear night sky

Clouds made orange by a sunset

The sky is the part of the atmosphere or of outer space visible from the surface of any astronomical object. It is difficult to define precisely for several reasons. During daylight the sky of Earth has the appearance of a deep blue surface, as the result of the air's scattering of sunlight.^[1][2][3][4] The sky is sometimes defined as the denser gaseous zone of a planet's atmosphere. At night the sky has the appearance of a black surface or region scattered with stars. Sky has several uses: The sky is the area above Earth. ... Image File history File links Metadata No higher resolution available. ... Image File history File links Metadata No higher resolution available. ... Image File history File links Download high resolution version (1024x715, 58 KB)Turbulent Skies Taken by User:Fir0002 File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high resolution version (1024x715, 58 KB)Turbulent Skies Taken by User:Fir0002 File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high resolution version (1003x670, 302 KB)From: http://firepix. ... Image File history File links Download high resolution version (1003x670, 302 KB)From: http://firepix. ... It has been suggested that this article or section be merged with Tree (disambiguation). ... Download high resolution version (1280x960, 153 KB)A dramatic sunset Taken by User:Fir0002 File links The following pages link to this file: Color Rayleigh scattering Sunset Sky Wikipedia:Featured picture candidates/Sunsets Wikipedia:Featured pictures candidates/April-2005 User:Fir0002/Fir0002 gallery Categories: GFDL images ... Download high resolution version (1280x960, 153 KB)A dramatic sunset Taken by User:Fir0002 File links The following pages link to this file: Color Rayleigh scattering Sunset Sky Wikipedia:Featured picture candidates/Sunsets Wikipedia:Featured pictures candidates/April-2005 User:Fir0002/Fir0002 gallery Categories: GFDL images ... The orange, the fruit from which the modern name of the orange colour comes. ... Atmospheres redirects here. ... Layers of Atmosphere - not to scale (NOAA)[1] Outer space, sometimes simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. ... Astronomical objects are significant physical entities, associations or structures which current science has confirmed to exist in space. ... Look up daylight in Wiktionary, the free dictionary. ... This article is about Earth as a planet. ... This article is about the colour. ... Look up air in Wiktionary, the free dictionary. ... Scattering is a general physical process whereby some forms of radiation, such as light, sound or moving particles, for example, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which it passes. ... Prism splitting light High Resolution Solar Spectrum Sunlight in the broad sense is the total spectrum of the electromagnetic radiation given off by the Sun. ... For other uses, see Gas (disambiguation). ... This article is about the astronomical term. ... Atmosphere is the general name for a layer of gases that may surround a material body of sufficient mass. ... This article is about the astronomical object. ...

During the day the Sun can be seen in the sky, unless covered by clouds. In the night sky (and to some extent during the day) the moon, planets and stars are 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 during storms. On Earth, birds, insects, aircraft, and kites are often considered to fly in the sky. As a result of human activities, smog during the day and light radiance during the night are often seen above large cities (see also light pollution). Sol redirects here. ... For other uses, see Cloud (disambiguation). ... Amateur astronomy, often called back yard astronomy, is a hobby whose participants enjoy observing celestial objects. ... This article is about Earths moon. ... This article is about the astronomical term. ... This article is about the astronomical object. ... Natural is defined as of or relating to nature; this applies to both definitions of nature: essence (ones true nature) and the untouched world (force of nature). Natural is often used meaning good, healthy, or belonging to human nature. This use can be questioned, as many freely growing plants... For other uses, see Cloud (disambiguation). ... For other uses, see Rainbow (disambiguation). ... Aurora borealis Polar aurorae are optical phenomena characterized by colorful displays of light in the night sky. ... Not to be confused with lighting. ... For other uses, see Storm (disambiguation). ... This article is about Earth as a planet. ... For other uses, see Bird (disambiguation). ... Orders Subclass Apterygota Archaeognatha (bristletails) Thysanura (silverfish) Subclass Pterygota Infraclass Paleoptera (Probably paraphyletic) Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Superorder Exopterygota Grylloblattodea (ice-crawlers) Mantophasmatodea (gladiators) Plecoptera (stoneflies) Embioptera (webspinners) Zoraptera (angel insects) Dermaptera (earwigs) Orthoptera (grasshoppers, etc) Phasmatodea (stick insects) Blattodea (cockroaches) Isoptera (termites) Mantodea (mantids) Psocoptera... Flying machine redirects here. ... Yokaichi Giant Kite Festival held on the fourth Sunday every May in Higashiomi, Shiga, Japan Kite flying is the activity of flying tethered man-made objects in wind. ... For other uses, see Flight (disambiguation). ... This article is about modern humans. ... For other uses, see Smog (disambiguation). ... For other uses, see City (disambiguation). ... This time exposure photo of New York City shows sky glow, one form of light pollution. ...

In the field of astronomy, the sky is also called the celestial sphere. This is an imaginary dome where the sun, stars, planets, and the moon are seen to be travelling. The celestial sphere is divided into regions called constellations. For other uses, see Astronomy (disambiguation). ... The celestial sphere is divided by the celestial equator. ... Sol redirects here. ... This article is about the astronomical object. ... This article is about the astronomical term. ... This article is about Earths moon. ... This article is about the star grouping. ...

See skies of other planets for descriptions of the skies of various planets and moons in the solar system. The sky of a world refers to the view of the heavens from its surface. ... This article is about the Solar System. ...

Sky luminance and colors

The light from the sky is a result of the scattering of sunlight, which results in a light blue color perceived by the human eye. On a sunny day Rayleigh Scattering gives the sky a blue gradient — dark in the zenith, light near the horizon. Light that comes in from overhead encounters an air mass 1/38th of the mass that of a sunbeam coming along a horizon paths. So, fewer particles scatter the zenith sunbeam, and, therefore the light remains a darker blue.^[5] Spectrum of blue sky clearly showing solar Fraunhofer lines and atmospheric water absorption band. ... Color is an important part of the visual arts. ... Rayleigh scattering causing the blue hue of the sky and the reddening at sunset Rayleigh scattering (named after Lord Rayleigh) is the scattering of light, or other electromagnetic radiation, by particles much smaller than the wavelength of the light. ... In graphics programs for digital image editing such as Photoshop (a bitmap graphics editor) and Adobe Illustrator (a vector graphics editor), the term gradient is used for a gradual blend of colour which can be considered as an even gradation from low to high values, as used from white to... In broad terms, the zenith is the direction pointing directly above a particular location (perpendicular, orthogonal). ... Horizon. ...

The sky can turn a multitude of colors such as red, orange and yellow (especially near sunset or sunrise) and black at night. Scattering effects also partially polarize light from the sky. A composite image showing the terminator dividing night from day, running across Europe and Africa. ... A typical sunrise, in New Zealand A sunrise through clouds over Oakland, California. ... This article is about the time of day. ... In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves, such as light, that describes the direction of their transverse electric field. ...

Sky luminance distribution models have been recommended by the International Commission on Illumination (CIE) for the design of daylighting schemes. Recent developments relate to “all sky models” for modelling sky luminance under weather conditions ranging from clear sky to overcast.^[6] Luminance (also called luminosity) is a photometric measure of the density of luminous intensity in a given direction. ... The CIE 1931 color space chromaticity diagram with wavelengths in nanometers. ... Daylighting is the practice of placing windows, or other transparent media, and reflective surfaces so that, during the day, natural light provides effective internal illumination. ... Luminance (also called luminosity) is a photometric measure of the density of luminous intensity in a given direction. ... For the geological process, see Weathering or Erosion. ...

Dark Skies

Dark Skies is the name usually given to the campaign to reduce and eventually eliminate light pollution from as much of the planet as possible. The campaign is led by the International Dark Sky Association (IDA) and supported by organizations in many countries such as The Royal Astronomical Society of New Zealand - RASNZ and Dark Sky Taonga. Light pollution is defined by the IDA as; "Any adverse effect of artificial light including sky glow, glare, light trespass, light clutter, decreased visibility at night, and energy waste. This time exposure photo of New York City shows sky glow, one form of light pollution. ...

See also

• Air
• Diffuse sky radiation — Why the sky is blue.
• Sky brightness
• Skygazing

Look up air in Wiktionary, the free dictionary. ... Spectrum of blue sky clearly showing solar Fraunhofer lines and atmospheric water absorption band. ... Airglow made visible from aboard the ISS (NASA) The fact that the sky isnt absolutely dark at night can easily be observed. ... This article or section needs copy editing for grammar, style, cohesion, tone and/or spelling. ...

References

1. ^ Tyndall, John (December 1868). "On the Blue Colour of the Sky, the Polarization of Skylight, and on the Polarization of Light by Cloudy Matter Generally". Proceedings of the Royal Society of London 17: pp. 223-233. 
2. ^ Rayleigh, Lord (June 1871). "On the scattering of light by small particles". Philosophical Magazine 41, 275: pp. 447-451. 
3. ^ Watson, JG (June 2002). "Visibility: Science and Regulation". J. Air & Waste Manage. Assoc 52: pp. 628-713. Retrieved on 2007-04-19. 
4. ^ Why is the sky Blue?
5. ^ Why is the sky bluer on top than at the horizon
6. ^ CIE General Sky Standard Defining Luminance DistributionsPDF (710 KiB)

John Tyndall. ... The Proceedings of the Royal Society of London are a scientific journal published by the Royal Society of London. ... See also Rayleigh fading Rayleigh scattering Rayleigh number Rayleigh waves Rayleigh-Jeans law External links Nobel website bio of Rayleigh About John William Strutt MacTutor biography of Lord Rayleigh Categories: People stubs | 1842 births | 1919 deaths | Nobel Prize in Physics winners | Peers | British physicists | Discoverer of a chemical element ... The Philosophical Magazine is arguably the world’s oldest commercially published scientific journal. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 109th day of the year (110th in leap years) in the Gregorian calendar. ... “PDF” redirects here. ... A kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage, commonly abbreviated KiB (never kiB). 1 kibibyte = 210 bytes = 1,024 bytes The kibibyte is closely related to the kilobyte, which can be used either as a synonym for kibibyte or to refer to...

External links

Wikimedia Commons has media related to:

Sky

• Day Sky Images
• Night Sky Images
• Sky Photo Gallery
• Why is the sky blue?