0_Wizard
Do you know why the sky is blue?
The clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering.
chosen_Blue_0
Blue
chosen_topic_0_Blue
Diné Bahaneʼ
This story forms the basis for the traditional Navajo way of life. The basic outline of begins with the (Holy Wind) being created, the mists of lights which arose through the darkness to animate and bring purpose to the four (Holy People), supernatural and sacred in the different three lower worlds. All these things were spiritually created in the time before the Earth existed and the physical aspect of humans did not exist yet, but the spiritual did. The First or Dark World, , was small and centered on an island floating in the middle of four seas. The inhabitants of the first world were the four , the two Coyotes, the four rulers of the four seas, mist beings and various insect and bat people, the latter being the Air-Spirit People.
Blue–green distinction in language
Many languages do not distinguish between what in English are described as "blue" and "green" and instead use a cover term spanning both. To describe this English lexical gap, linguists use the portmanteau word "grue", from "green" and "blue", which the philosopher Nelson Goodman coined in his 1955 "Fact, Fiction, and Forecast" to illustrate the "new riddle of induction". The exact definition of "blue" and "green" may be complicated by the speakers not primarily distinguishing the hue, but using terms that describe other color components such as saturation and luminosity, or other properties of the object being described.
List of Warriors characters
The "Warriors" novel series is written by Erin Hunter. Due to the large number of characters present in the novel series, this list is divided by Clan, e.g., all characters in ThunderClan are listed together. Each cat has a prefix. Eg: Dawn, Violet etc. As a young kit they will have -kit at the end of their name. Eg: Dawnkit Violetkit. When they are an apprentice -paw will be at the end of their name. Eg: Dawnpaw Violetpaw. When that cat is a warrior or medicine cat they will have a suffix. Eg: -fur -pelt -cloud -flame -wing -song etc. Eg: Dawnsong Violetflame. That is if they are in one of the clans like ThunderClan, RiverClan, WindClan, ShadowClan, Skyclan.
2009 Sky Blue FC season
The 2009 Sky Blue FC season was the first season for Sky Blue FC in Women's Professional Soccer (WPS). In the league's inaugural season, the club finished fourth in the regular season with 26 points, qualifying for the playoffs. After victories over the Washington Freedom and Saint Louis Athletica, Sky Blue FC defeated the Los Angeles Sol, the top team in the regular season, in the championship match to become the first WPS champions. Sky Blue FC was the WPS franchise in the New York City/New Jersey region. Players from the U.S. national team were allocated to the seven WPS clubs in September 2008; each side was allotted the rights to three national team players.
Sky Mangel
Sky Mangel (also Bishop) is a fictional character from the Australian soap opera "Neighbours". She made her first screen appearance during the episode broadcast on 1 February 1989. The character was originally played by Miranda Fryer until 1991. When Sky was reintroduced on 13 August 2003, Stephanie McIntosh took over the role. She departed on 3 August 2007. McIntosh reprised her role as part of the show's 30th anniversary celebrations and Sky appeared via Skype on 20 March 2015. Miranda Fryer was cast in the role of an infant Sky after being spotted in a supermarket. When the character was brought back in 2003, Stephanie McIntosh was cast in the role.
Sky Sports
Sky Sports is a group of sports television channels operated by the satellite pay-TV company Sky plc. Sky Sports is the dominant subscription television sports brand in the United Kingdom and Ireland. It has played a major role in the increased commercialisation of British sport since 1991, sometimes playing a large role in inducing organisational changes in the sports it broadcasts, most notably when it encouraged the Premier League to break away from the Football League in 1992. Sky Sports Main Event, Premier League, Football, Cricket, Golf, F1, Action and Arena are available as a premium package on top of the basic Sky package.
Blue
Blue is one of the three primary colours of pigments in painting and traditional colour theory, as well as in the RGB colour model. It lies between violet and green on the spectrum of visible light. The eye perceives blue when observing light with a dominant wavelength between approximately 450 and 495 nanometres. Most blues contain a slight mixture of other colors; azure contains some green, while ultramarine contains some violet. The clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering. An optical effect called Tyndall scattering explains blue eyes.
Sky Blue FC
Sky Blue FC is a professional soccer club based in Piscataway Township, New Jersey, which has participated in the National Women's Soccer League since 2013. From 2009 to 2011, the team played in Women's Professional Soccer (WPS). Sky Blue FC is part of the larger Sky Blue Soccer organization, based in Somerset County, New Jersey, an integrated program that allows players to progress in soccer from a young age with an opportunity for long-term growth. Sky Blue FC named Ian Sawyers as its first head coach and general manager on March 5, 2008. However, it wasn't until September 9, 2008 that the New York/New Jersey outfit was officially unveiled under the name Sky Blue FC.
Sky Blue Sky
Sky Blue Sky is the sixth studio album by American rock band Wilco, released on May 15, 2007 by Nonesuch Records. Originally announced on January 17, 2007 at a show in Nashville, Tennessee, it was the band's first studio album with guitarist Nels Cline and multi-instrumentalist Pat Sansone. Before its release, the band streamed the entire album on its official website and offered a free download of "What Light". "Sky Blue Sky" was Wilco's highest debuting album on the "Billboard" 200 at number four. The self-produced album received mostly favorable reviews by critics. Publications such as PopMatters and "Rolling Stone" praised its maturity, while Playlouder and Pitchfork criticized its "dad-rock" sound.
Blue Sky Solar Racing
Blue Sky Solar Racing is a student-run initiative at the University of Toronto. The team aims to promote environmentally friendly technologies through the design, construction and showcasing of world class solar powered vehicles. The project encourages students to participate in a long-term multidisciplinary project to augment their skills learned in class, and to make a positive impact on their community. Since its foundation in 1997, the team has produced eight vehicles that competed in a total of nine international solar car racing competitions. Their most recent vehicle, Horizon, was ranked 12th at World Solar Challenge 2015, and 1st in Canada.
1_Apprentice
That's a great question, why is the sky blue?
0_Wizard
It is blue because of an optical effect known as Rayleigh scattering. 
The clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering.
chosen_Blue_0
Blue
chosen_topic_0_Blue
Rayleigh scattering
Rayleigh scattering (pronounced ), named after the British physicist Lord Rayleigh (John William Strutt), is the (dominantly) elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation. Rayleigh scattering does not change the state of material and is, hence, a parametric process. The particles may be individual atoms or molecules. It can occur when light travels through transparent solids and liquids, but is most prominently seen in gases. Rayleigh scattering results from the electric polarizability of the particles. The oscillating electric field of a light wave acts on the charges within a particle, causing them to move at the same frequency.
Blue
Blue is one of the three primary colours of pigments in painting and traditional colour theory, as well as in the RGB colour model. It lies between violet and green on the spectrum of visible light. The eye perceives blue when observing light with a dominant wavelength between approximately 450 and 495 nanometres. Most blues contain a slight mixture of other colors; azure contains some green, while ultramarine contains some violet. The clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering. An optical effect called Tyndall scattering explains blue eyes.
Mie scattering
The Mie solution to Maxwell's equations (also known as the Lorenz–Mie solution, the Lorenz–Mie–Debye solution or Mie scattering) describes the scattering of an electromagnetic plane wave by a homogeneous sphere. The solution takes the form of an infinite series of spherical multipole partial waves. It is named after Gustav Mie. The term "Mie solution" is also used for solutions of Maxwell's equations for scattering by stratified spheres or by infinite cylinders, or other geometries where one can write separate equations for the radial and angular dependence of solutions. The term "Mie theory" is sometimes used for this collection of solutions and methods; it does not refer to an independent physical theory or law.
Scattering
Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more paths due to localized non-uniformities in the medium through which they pass. In conventional use, this also includes deviation of reflected radiation from the angle predicted by the law of reflection. Reflections that undergo scattering are often called "diffuse reflections" and unscattered reflections are called "specular" (mirror-like) reflections. Scattering may also refer to particle-particle collisions between molecules, atoms, electrons, photons and other particles.
Raman scattering
Raman scattering or the Raman effect is the inelastic scattering of a photon by molecules which are excited to higher vibrational or rotational energy levels. It was discovered by C. V. Raman and K. S. Krishnan (who was a student of C.V. Raman) in liquids,  and independently by Grigory Landsberg and Leonid Mandelstam in crystals. The effect had been predicted theoretically by Adolf Smekal in 1923. When photons are scattered from an atom or molecule, most of them are elastically scattered (Rayleigh scattering), such that the scattered photons have the same energy (frequency and wavelength) as the incident photons.
Optics
Optics is the branch of physics which involves the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties. Most optical phenomena can be accounted for using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice.
Skyglow
Skyglow (or sky glow) is the diffuse luminance of the night sky, apart from discrete light sources such as the Moon and visible individual stars. It is a commonly noticed aspect of light pollution. While usually referring to sky luminance arising from artificial lighting, skyglow may also involve any nighttime sources of diffuse light, including natural ones like the zodiacal light, starlight, and airglow. In the context of light pollution, skyglow arises from the use of artificial light sources, including electrical (or rarely gas) lighting used for illumination and advertisement, and from gas flares.
Eye color
Eye color is a polygenic phenotypic character determined by two distinct factors: the pigmentation of the eye's iris and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris. In humans, the pigmentation of the iris varies from light brown to black, depending on the concentration of melanin in the iris pigment epithelium (located on the back of the iris), the melanin content within the iris stroma (located at the front of the iris), and the cellular density of the stroma. The appearance of blue and green, as well as hazel eyes, results from the Tyndall scattering of light in the stroma, a phenomenon similar to that which accounts for the blueness of the sky called Rayleigh scattering.
Tyndall effect
The Tyndall effect, also known as Willis–Tyndall scattering, is light scattering by particles in a colloid or else particles in a very fine suspension. It is named after the 19th-century physicist John Tyndall. It is similar to Rayleigh scattering, in that the intensity of the scattered light depends on the fourth power of the frequency, so blue light is scattered much more strongly than red light. An example in everyday life is the blue colour sometimes seen in the smoke emitted by motorcycles, in particular two-stroke machines where the burnt engine oil provides these particles. Under the Tyndall effect, the longer-wavelength light is more transmitted while the shorter-wavelength light is more reflected via scattering.
Atmospheric optics
Atmospheric optics deals with how the unique optical properties of Earth's atmosphere cause a wide range of spectacular optical phenomena. The blue color of the sky is a direct result of Rayleigh scattering, which redirects higher frequency (blue) sunlight back into the field of view of the observer. Because blue light is scattered more easily than red light, the Sun takes on a reddish hue when it is observed through a thick atmosphere, as during a sunrise or sunset. Additional particulate matter in the sky can scatter different colors at different angles, creating colorful, glowing skies at dusk and dawn.
1_Apprentice
Can you describe this optical effect more?
0_Wizard
Scattering is light particles that we can see, and blue is the shortest and fastest meaning we see it more.
The eye perceives blue when observing light with a dominant wavelength between approximately 450 and 495 nanometres.
self_Cross_section_(physics)_2
Blue
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Tachyon
A tachyon or tachyonic particle is a hypothetical particle that always moves faster than light. Most physicists believe that faster-than-light particles cannot exist because they are not consistent with the known laws of physics. If such particles did exist, they could be used to build a tachyonic antitelephone and send signals faster than light, which (according to special relativity) would lead to violations of causality. The possibility of particles moving faster than light was first proposed by O. M. P. Bilaniuk, V. K. Deshpande, and E. C. G. Sudarshan in 1962, although the term they used for it was "meta-particle".
Cross section (physics)
When two particles interact, their mutual cross section is the area transverse to their relative motion within which they must meet in order to scatter from each other. If the particles are hard spheres that interact only upon contact, their scattering cross section is related to their geometric size. If the particles interact through some action-at-a-distance force, such as electromagnetism or gravity, their scattering cross section is generally larger than their geometric size. When a cross section is specified as a function of some final-state variable, such as particle angle or energy, it is called a "differential cross section".
Higgs boson
The Higgs boson is an elementary particle in the Standard Model of particle physics. First suspected to exist in the 1960s, it is the quantum excitation of the Higgs field, a fundamental field of crucial importance to particle physics theory. Unlike other known fields such as the electromagnetic field, it has a non-zero constant value in vacuum. The question of the existence of the Higgs field became the last unverified part of the Standard Model of particle physics, and for several decades, was considered "the central problem in particle physics". The presence of the field, now confirmed by experimental investigation, explains why some fundamental particles have mass when, based on the symmetries controlling their interactions, they should be massless.
Elastic recoil detection
Elastic Recoil Detection Analysis (ERDA), also referred to as forward recoil scattering (or, contextually, spectrometry), is an Ion Beam Analysis technique in materials science to obtain elemental concentration depth profiles in thin films. This technique is known by several different names. These names are listed below. In the technique of ERDA, an energetic ion beam is directed at a sample to be characterized and (as in Rutherford backscattering) there is an elastic nuclear interaction between the ions of beam and the atoms of the target sample. Such interactions are commonly of Coulomb nature.
Mie scattering
The Mie solution to Maxwell's equations (also known as the Lorenz–Mie solution, the Lorenz–Mie–Debye solution or Mie scattering) describes the scattering of an electromagnetic plane wave by a homogeneous sphere. The solution takes the form of an infinite series of spherical multipole partial waves. It is named after Gustav Mie. The term "Mie solution" is also used for solutions of Maxwell's equations for scattering by stratified spheres or by infinite cylinders, or other geometries where one can write separate equations for the radial and angular dependence of solutions. The term "Mie theory" is sometimes used for this collection of solutions and methods; it does not refer to an independent physical theory or law.
Rayleigh scattering
Rayleigh scattering (pronounced ), named after the British physicist Lord Rayleigh (John William Strutt), is the (dominantly) elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation. Rayleigh scattering does not change the state of material and is, hence, a parametric process. The particles may be individual atoms or molecules. It can occur when light travels through transparent solids and liquids, but is most prominently seen in gases. Rayleigh scattering results from the electric polarizability of the particles. The oscillating electric field of a light wave acts on the charges within a particle, causing them to move at the same frequency.
Faster-than-light
Faster-than-light (also superluminal or FTL) communication and travel refer to the propagation of information or matter faster than the speed of light. The special theory of relativity implies that only particles with zero rest mass may travel at the speed of light. Tachyons, particles whose speed exceeds that of light, have been hypothesized but the existence of such particles would violate causality and the consensus of physicists is that such particles cannot exist. On the other hand, what some physicists refer to as "apparent" or "effective" FTL depends on the hypothesis that unusually distorted regions of spacetime might permit matter to reach distant locations in less time than light could in normal or undistorted spacetime.
Dynamic light scattering
Dynamic light scattering (DLS) is a technique in physics that can be used to determine the size distribution profile of small particles in suspension or polymers in solution. In the scope of DLS, temporal fluctuations are usually analyzed by means of the intensity or photon auto-correlation function (also known as photon correlation spectroscopy or quasi-elastic light scattering). In the time domain analysis, the autocorrelation function (ACF) usually decays starting from zero delay time, and faster dynamics due to smaller particles lead to faster decorrelation of scattered intensity trace. It has been shown that the intensity ACF is the Fourier transformation of the power spectrum, and therefore the DLS measurements can be equally well performed in the spectral domain.
Scattering
Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more paths due to localized non-uniformities in the medium through which they pass. In conventional use, this also includes deviation of reflected radiation from the angle predicted by the law of reflection. Reflections that undergo scattering are often called "diffuse reflections" and unscattered reflections are called "specular" (mirror-like) reflections. Scattering may also refer to particle-particle collisions between molecules, atoms, electrons, photons and other particles.
Multiangle light scattering
Multiangle light scattering (MALS) describes a technique for measuring the light scattered by a sample into a plurality of angles. It is used for determining both the absolute molar mass and the average size of molecules in solution, by detecting how they scatter light. Collimated light from a laser source is most often used, in which case the technique can be referred to as multiangle laser light scattering (MALLS). The insertion of the word “laser” was intended to reassure those used to making light scattering measurements with conventional light sources such as Hg-arc lamps that low angle measurements could now be made.
1_Apprentice
So this means there are also other colors in the sky, but we just see blue?
0_Wizard
Correct. And when we see different colors, it is because additional particulate matter scatters as well, usually at dusk or dawn.
Additional particulate matter in the sky can scatter different colors at different angles, creating colorful, glowing skies at dusk and dawn.
partner_Wildfire_3
Atmospheric optics
partner_7_Atmospheric_optics
Particulates
Atmospheric aerosol particles, also known as atmospheric particulate matter, particulate matter (PM), particulates, or suspended particulate matter (SPM) are microscopic solid or liquid matter suspended in Earth's atmosphere. The term "aerosol" commonly refers to the particulate/air mixture, as opposed to the particulate matter alone. Sources of particulate matter can be natural or anthropogenic. They have impacts on climate and precipitation that adversely affect human health. Subtypes of atmospheric particles include suspended particulate matter (SPM), thoracic and respirable particles, inhalable coarse particles, which are [coarse] particles with a diameter between 2.5 and 10 micrometers (μm) (PM), fine particles with a diameter of 2.5 μm or less (PM), ultrafine particles, and soot  The IARC and WHO designate airborne particulates a Group 1 carcinogen.
Black carbon
Chemically, black carbon (BC) is a component of fine particulate matter (PM ≤ 2.5 µm in aerodynamic diameter). Black carbon consists of pure carbon in several linked forms. It is formed through the incomplete combustion of fossil fuels, biofuel, and biomass, and is emitted in both anthropogenic and naturally occurring soot. Black carbon causes human morbidity and premature mortality. In climatology, black carbon is a climate forcing agent. Black carbon warms the Earth by absorbing sunlight and heating the atmosphere and by reducing albedo when deposited on snow and ice (direct effects) and indirectly by interaction with clouds, with the total forcing of 1.1 W/m.
Atmospheric optics
Atmospheric optics deals with how the unique optical properties of Earth's atmosphere cause a wide range of spectacular optical phenomena. The blue color of the sky is a direct result of Rayleigh scattering, which redirects higher frequency (blue) sunlight back into the field of view of the observer. Because blue light is scattered more easily than red light, the Sun takes on a reddish hue when it is observed through a thick atmosphere, as during a sunrise or sunset. Additional particulate matter in the sky can scatter different colors at different angles, creating colorful, glowing skies at dusk and dawn.
Diesel exhaust
Diesel exhaust is the gaseous exhaust produced by a diesel type of internal combustion engine, plus any contained particulates. Its composition may vary with the fuel type or rate of consumption, or speed of engine operation (e.g., idling or at speed or under load), and whether the engine is in an on-road vehicle, farm vehicle, locomotive, marine vessel, or stationary generator or other application. Diesel exhaust is a Group 1 carcinogen, which causes lung cancer and has a positive association with bladder cancer. It contains several substances that are also listed individually as human carcinogens by the IARC.
Fossil fuel power station
A fossil fuel power station is a power station which burns a fossil fuel such as coal, natural gas, or petroleum to produce electricity. Central station fossil fuel power plants are designed on a large scale for continuous operation. In many countries, such plants provide most of the electrical energy used. Fossil fuel power stations have machinery to convert the heat energy of combustion into mechanical energy, which then operates an electrical generator. The may be a steam turbine, a gas turbine or, in small plants, a reciprocating internal combustion engine. All plants use the energy extracted from expanding gas, either steam or combustion gases.
Diesel particulate filter
A diesel particulate filter (or DPF) is a device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine. Wall-flow diesel particulate filters usually remove 85% or more of the soot, and under certain conditions can attain soot removal efficiencies approaching 100%. Some filters are single-use, intended for disposal and replacement once full of accumulated ash. Others are designed to burn off the accumulated particulate either passively through the use of a catalyst or by active means such as a fuel burner which heats the filter to soot combustion temperatures.
2008 California Statewide Truck and Bus Rule
The California Statewide Truck and Bus Rule was initially adopted in December 2008 by the California Air Resources Board (CARB) and requires all heavy-duty diesel trucks and buses that operate in California to retrofit or replace engines in order to reduce diesel emissions. All privately and federally owned diesel-fueled trucks and buses, and privately and publicly owned school buses with a gross vehicle weight rating (GVWR) greater than 14,000 pounds, are covered by the regulation. Implementation was originally scheduled for January 1, 2011 but recent amendments were considered in December 2010.
Wildfire
A wildfire or wildland fire is a fire in an area of combustible vegetation that occurs in the countryside or rural area. Depending on the type of vegetation where it occurs, a wildfire can also be classified more specifically as a brush fire, bush fire, desert fire, forest fire, grass fire, hill fire, peat fire, vegetation fire, or veld fire. Fossil charcoal indicates that wildfires began soon after the appearance of terrestrial plants 420 million years ago. Wildfire’s occurrence throughout the history of terrestrial life invites conjecture that fire must have had pronounced evolutionary effects on most ecosystems' flora and fauna.
Air pollution in the United States
Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or damages the natural environment into the atmosphere. Ever since the beginning of the Industrial Revolution in the United States, America has had much trouble with environmental issues, air pollution in particular. According to a 2009 report, around "60 percent of Americans live in areas where air pollution has reached unhealthy levels that can make people sick". Pollution in the United States has plummeted in the recent decade, with pollutants such as nitrogen dioxide decreasing despite the fact the number of vehicles on the road isn't.
Airborne particulate radioactivity monitoring
Continuous particulate air monitors (CPAMs) have been used for years in nuclear facilities to assess airborne particulate radioactivity (APR). In more recent times they may also be used to monitor people in their homes for the presence of manmade radioactivity. These monitors can be used to trigger alarms, indicating to personnel that they should evacuate an area. This article will focus on CPAM use in nuclear power plants, as opposed to other nuclear fuel-cycle facilities, or laboratories, or public-safety applications. In nuclear power plants, CPAMs are used for measuring releases of APR from the facility, monitoring levels of APR for protection of plant personnel, monitoring the air in the reactor containment structure to detect leakage from the reactor systems, and to control ventilation fans, when the APR level has exceeded a defined threshold in the ventilation system.
1_Apprentice
Speaking of the sky, how do clouds float in the sky?