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83-493: The green flash and green ray are meteorological optical phenomena that sometimes occur transiently around the moment of sunset or sunrise . When the conditions are right, a distinct green spot is briefly visible above the Sun 's upper limb ; the green appearance usually lasts for no more than two seconds. Rarely, the green flash can resemble a green ray shooting up from the sunset or sunrise point. Green flashes occur because

166-427: A supermassive black hole , which may result in an active galactic nucleus . Galaxies can also have satellites in the form of dwarf galaxies and globular clusters . The constituents of a galaxy are formed out of gaseous matter that assembles through gravitational self-attraction in a hierarchical manner. At this level, the resulting fundamental components are the stars, which are typically assembled in clusters from

249-466: A telescope to look directly at the Sun without potential harm to the eyes. (Of course, a magnified image might be projected onto a sheet of paper for safe viewing.) As the Sun gets closer to the horizon, the green rim becomes fainter due to atmospheric reddening. According to the above, it is probably correct to conclude that although a green rim is present during every sunset, a green flash is rarer because of

332-458: A variable star . An example of this is the instability strip , a region of the H-R diagram that includes Delta Scuti , RR Lyrae and Cepheid variables . The evolving star may eject some portion of its atmosphere to form a nebula, either steadily to form a planetary nebula or in a supernova explosion that leaves a remnant . Depending on the initial mass of the star and the presence or absence of

415-406: A body and an object: It is a body when referring to the frozen nucleus of ice and dust, and an object when describing the entire comet with its diffuse coma and tail . Astronomical objects such as stars , planets , nebulae , asteroids and comets have been observed for thousands of years, although early cultures thought of these bodies as gods or deities. These early cultures found

498-542: A companion, a star may spend the last part of its life as a compact object ; either a white dwarf , neutron star , or black hole . The IAU definitions of planet and dwarf planet require that a Sun-orbiting astronomical body has undergone the rounding process to reach a roughly spherical shape, an achievement known as hydrostatic equilibrium . The same spheroidal shape can be seen on smaller rocky planets like Mars to gas giants like Jupiter . Any natural Sun-orbiting body that has not reached hydrostatic equilibrium

581-459: A green rim on the top of the solar disk may be seen on most clear-day sunsets, although the flash or ray effects require a stronger layering of the atmosphere and a mirage, which serves to magnify the green from a fraction of a second to a couple of seconds. While simple atmospheric refraction or lensing explains the background gradient of red-amber twilight, the primary potential cause of the bright, verdant discontinuity from that gradient known as

664-673: A green rim, which at times could have been a green flash. It was seen on and off for 35 minutes by members of the Richard Evelyn Byrd party from the Antarctic Little America exploration base in 1934: There was a rush for the surface and as eyes turned southward, they saw a tiny but brilliant green spot where the last ray of the upper rim of the sun hung on the skyline. It lasted an appreciable length of time, several seconds at least, and no sooner disappeared than it flashed forth again. Altogether it remained on

747-441: A percentage of the light which enters the cloud is not reflected back out before it is absorbed. A simple example of this is being able to see farther in heavy rain than in heavy fog. This process of reflection / absorption is what causes the range of cloud color from white to black. Other colors occur naturally in clouds. Bluish-grey is the result of light scattering within the cloud. In the visible spectrum, blue and green are at

830-521: A real optical phenomenon which can be captured on camera, since light rays actually are refracted to form the false image at the observer's location. What the image appears to represent, however, is determined by the interpretive faculties of the human mind. For example, inferior images on land are very easily mistaken for the reflections from a small body of water. Mirages can be categorized as "inferior" (meaning lower), "superior" (meaning higher) and " Fata Morgana ", one kind of superior mirage consisting of

913-550: A series of both inverted and erect images. A Fata Morgana is an unusual and very complex form of mirage, a form of superior mirage , which, like many other kinds of superior mirages, is seen in a narrow band right above the horizon. It is an Italian phrase derived from the vulgar Latin for "fairy" and the Arthurian sorcerer Morgan le Fay , from a belief that the mirage, often seen in the Strait of Messina , were fairy castles in

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996-514: A series of flashes. While observing at the Vatican Observatory in 1960, D.J.K. O'Connell produced the first color photograph of the green flash at sunset. Green flash occurs because the atmosphere causes the light from the Sun to separate , or refract , into different frequencies. Green flashes are enhanced by mirages , which increase refraction . A green flash is more likely to be seen in stable, clear air, when more of

1079-602: A series of unusually elaborate, vertically stacked images, which form one rapidly changing mirage. Green flashes and green rays are optical phenomena that occur shortly after sunset or before sunrise, when a green spot is visible, usually for no more than a second or two, above the Sun, or a green ray shoots up from the sunset point. Green flashes are actually a group of phenomena stemming from different causes, and some are more common than others. Green flashes can be observed from any altitude (even from an aircraft). They are usually seen at an unobstructed horizon , such as over

1162-405: A tropospheric cloud matures, the dense water droplets may combine to produce larger droplets, which may combine to form droplets large enough to fall as rain. By this process of accumulation, the space between droplets becomes increasingly larger, permitting light to penetrate farther into the cloud. If the cloud is sufficiently large and the droplets within are spaced far enough apart, it may be that

1245-426: A web that spans the observable universe. Galaxies have a variety of morphologies , with irregular , elliptical and disk-like shapes, depending on their formation and evolutionary histories, including interaction with other galaxies, which may lead to a merger . Disc galaxies encompass lenticular and spiral galaxies with features, such as spiral arms and a distinct halo . At the core, most galaxies have

1328-549: Is a polar mirage caused by high refraction of sunlight between atmospheric thermoclines . The Novaya Zemlya effect will give the impression that the sun is rising earlier or setting later than it actually should (astronomically speaking). Depending on the meteorological situation the effect will present the Sun as a line or a square (which is sometimes referred to as the "rectangular sun"), made up of flattened hourglass shapes. The mirage requires rays of sunlight to have an inversion layer for hundreds of kilometres, and depends on

1411-683: Is a naturally occurring physical entity , association, or structure that exists within the observable universe . In astronomy , the terms object and body are often used interchangeably. However, an astronomical body or celestial body is a single, tightly bound, contiguous entity, while an astronomical or celestial object is a complex, less cohesively bound structure, which may consist of multiple bodies or even other objects with substructures. Examples of astronomical objects include planetary systems , star clusters , nebulae , and galaxies , while asteroids , moons , planets , and stars are astronomical bodies. A comet may be identified as both

1494-555: Is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky. The word comes to English via the French mirage , from the Latin mirare , meaning "to look at, to wonder at". This is the same root as for "mirror" and "to admire". Also, it has its roots in the Arabic mirage . In contrast to a hallucination , a mirage is

1577-424: Is always red. A green rim is very thin and is difficult or impossible to see with the naked eye. In usual conditions, a green rim of an astronomical object gets fainter when an astronomical object is very low above the horizon because of atmospheric reddening, but sometimes the conditions are right to see a green rim just above the horizon. The following quote describes what was probably the longest observation of

1660-419: Is an atmospheric condition where warmer air exists in a well-defined layer above a layer of significantly cooler air. This temperature inversion is the opposite of what is normally the case; air is usually warmer close to the surface, and cooler higher up. In calm weather, a layer of significantly warmer air can rest over colder dense air, forming an atmospheric duct which acts like a refracting lens , producing

1743-587: Is classified by the IAU as a small Solar System body (SSSB). These come in many non-spherical shapes which are lumpy masses accreted haphazardly by in-falling dust and rock; not enough mass falls in to generate the heat needed to complete the rounding. Some SSSBs are just collections of relatively small rocks that are weakly held next to each other by gravity but are not actually fused into a single big bedrock . Some larger SSSBs are nearly round but have not reached hydrostatic equilibrium. The small Solar System body 4 Vesta

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1826-488: Is due to two internal reflections within a drop. The resulting secondary arc is some 3° wide and the colours are reversed, with blue/violet on the outside. Two internal reflections produce a bow with angular size of 50.5° to 54° with blue/violet on the outside. The region between a double rainbow is often noticeably darker that the sky withinthe primary bow and that beyond the seconday bow. It known an Alexander's Dark Band. The reason for this apparent reduction in sky brightness

1909-399: Is going on inside the cloud. Dense deep tropospheric clouds exhibit a high reflectance (70% to 95%) throughout the visible spectrum . Tiny particles of water are densely packed and sunlight cannot penetrate far into the cloud before it is reflected out, giving a cloud its characteristic white color, especially when viewed from the top. Cloud droplets tend to scatter light efficiently, so that

1992-468: Is greater in the forward and backward directions than it is in the lateral direction. 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. Dust from the Sahara moves around the southern periphery of the subtropical ridge moves into

2075-425: Is much like if a person were to shine a red spotlight on a white sheet. In combination with large, mature thunderheads this can produce blood-red clouds. Clouds look darker in the near- infrared because water absorbs solar radiation at those wavelengths . A halo (ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by the interaction of light from the Sun or Moon with ice crystals in

2158-515: Is much smaller than a rainbow, ranging between 5° and 20°, depending on the size of the droplets. The glory can only be seen when the observer is directly between the Sun and cloud of refracting water droplets. Hence, it is commonly observed while airborne, with the glory surrounding the airplane's shadow on clouds (this is often called The Glory of the Pilot ). Glories can also be seen from mountains and tall buildings, when there are clouds or fog below

2241-501: Is still unknown, but it could be due to the combination of reddened sunlight passing through very optically thick clouds. Yellowish clouds may occur in the late spring through early fall months during forest fire season. The yellow color is due to the presence of pollutants in the smoke. Yellowish clouds caused by the presence of nitrogen dioxide are sometimes seen in urban areas with high air pollution levels. Red, orange and pink clouds occur almost entirely at sunrise and sunset and are

2324-420: Is that, while light from the sky enclosed within the primary bow comes from droplet reflection, and light beyond the secondary bow also comes from droplet reflection, there is no mechanism for the region between the bows to reflect light in the direction of the observer. Generally speaking, larger the droplets make for brighter bows. A rainbow spans a continuous spectrum of colors; the distinct bands (including

2407-435: Is the glory. A glory is an optical phenomenon, appearing much like an iconic Saint 's halo about the head of the observer, produced by light backscattered (a combination of diffraction , reflection and refraction ) towards its source by a cloud of uniformly sized water droplets. A glory has multiple colored rings, with red colors on the outermost ring and blue/violet colors on the innermost ring. The angular distance

2490-517: The Andromeda nebula as a different galaxy, along with many others far from the Milky Way. The universe can be viewed as having a hierarchical structure. At the largest scales, the fundamental component of assembly is the galaxy . Galaxies are organized into groups and clusters , often within larger superclusters , that are strung along great filaments between nearly empty voids , forming

2573-552: The Earth's atmosphere can cause the light from the Sun to separate , or refract , into different colors. Green flashes are a group of similar phenomena that stem from slightly different causes, and therefore, some types of green flashes are more common than others. Green flashes may be observed from any altitude. They usually are seen at an unobstructed horizon , such as over the ocean, but are possible over cloud tops and mountain tops as well. They may occur at any latitude, although at

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2656-459: The Sun located in the center of the Solar System . Johannes Kepler discovered Kepler's laws of planetary motion , which are properties of the orbits that the astronomical bodies shared; this was used to improve the heliocentric model. In 1584, Giordano Bruno proposed that all distant stars are their own suns, being the first in centuries to suggest this idea. Galileo Galilei was one of

2739-493: The photoelectric photometer allowed astronomers to accurately measure the color and luminosity of stars, which allowed them to predict their temperature and mass. In 1913, the Hertzsprung-Russell diagram was developed by astronomers Ejnar Hertzsprung and Henry Norris Russell independently of each other, which plotted stars based on their luminosity and color and allowed astronomers to easily examine stars. It

2822-491: The protoplanetary disks that surround newly formed stars. The various distinctive types of stars are shown by the Hertzsprung–Russell diagram (H–R diagram)—a plot of absolute stellar luminosity versus surface temperature. Each star follows an evolutionary track across this diagram. If this track takes the star through a region containing an intrinsic variable type, then its physical properties can cause it to become

2905-603: The Green Flash may be due to naturally-occurring coherent (laser) light . Part of this phenomenon was recently discovered by researchers at the Washington University School of Medicine , regarding infrared-laser light converting-up (or upconverting) to visible-green laser light, causing what researchers there call "a double hit" of photons on the retina, creating the perception of bright neon green from an originally invisible infrared laser. Doubling

2988-614: The Moon illusion gradually came to be accepted as a psychological phenomenon, with Ptolemy's theory being rejected in the 17th century. For over 100 years, research on the Moon illusion has been conducted by vision scientists who invariably have been psychologists specializing in human perception . After reviewing the many different explanations in their 2002 book The Mystery of the Moon Illusion , Ross and Plug concluded "No single theory has emerged victorious". The color of light from

3071-477: The Sun and Moon larger at the horizon than when they are higher in the sky, he redefined the problem in terms of perceived, rather than real, enlargement. He said that judging the distance of an object depends on there being an uninterrupted sequence of intervening bodies between the object and the observer. Critically, Ibn al-Haytham said that judging the size of an object depends on its judged distance: an object that appears near appears smaller than an object having

3154-431: The Sun. For an observer on the ground, the amount of the arc that is visible depends on the height of the sun above the horizon. It is a full semicircle with an angular radius of 42° when the sun is at the horizon. But as the sun rises in the sky, the arc grows smaller and ceases to be visible when the sun is more than 42° above the horizon. To see more than a semicircular bow, an observer would have to be able to look down on

3237-420: The air, or false land designed to lure sailors to their death created by her witchcraft. Although the term Fata Morgana is sometimes incorrectly applied to other, more common kinds of mirages, the true Fata Morgana is not the same as an ordinary superior mirage, and is certainly not the same as an inferior mirage . Fata Morgana mirages tremendously distort the object or objects which they are based on, such that

3320-521: The amount of blue light is sufficient to be visible as a "blue flash". As an astronomical object sets or rises in relation to the horizon, the light it emits travels through Earth's atmosphere , which works as a prism separating the light into different colors. The color of the upper rim of an astronomical object could go from green to blue to violet depending on the decrease in concentration of pollutants as they spread throughout an increasing volume of atmosphere. The lower rim of an astronomical object

3403-455: The atmosphere, resulting in colored or white arcs, rings or spots in the sky. Many halos are positioned near the Sun or Moon, but others are elsewhere and even in the opposite part of the sky. They can also form around artificial lights in very cold weather when ice crystals called diamond dust are floating in the nearby air. There are many types of ice halos. They are produced by the ice crystals in cirrus or cirrostratus clouds high in

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3486-445: The conditions are met). The "green flash" description relates to a group of optical phenomena, some of which are listed below: The majority of flashes observed are inferior-mirage or mock-mirage effects, with the others constituting only 1% of reports. Some types not listed in the table above, such as the cloud-top flash (seen as the Sun sinks into a coastal fog , or at distant cumulus clouds ), are not understood. On rare occasion,

3569-410: The crystals are increasingly skewed from the horizontal plane. Their angle of deviation increases and the sundogs move further from the Sun. However, they always stay at the same elevation as the Sun. Sun dogs are red-colored at the side nearest the Sun. Farther out the colors grade to blue or violet. However, the colors overlap considerably and so are muted, rarely pure or saturated. The colors of

3652-408: The direction opposite the sun. They appear to converge again at the distant horizon. Atmospheric refraction influences the apparent position of astronomical and terrestrial objects, usually causing them to appear higher than they actually are. For this reason navigators, astronomers, and surveyors observe positions when these effects are minimal. Sailors will only shoot a star when 20° or more above

3735-412: The drops, say from an airplane or a mountaintop. Rainbows are most common during afternoon rain showers in summer. A single reflection off the backs of an array of raindrops produces a rainbow with an angular size that ranges from 40° to 42° with red on the outside and blue/violet on the inside. This is known as the primary bow. A fainter secondary bow is often visible some 10° outside the primary bow. It

3818-461: The equator, the flash rarely lasts longer than a second. The green flash also may be observed in association with the Moon and bright planets at the horizon, including Venus and Jupiter . With an unrestricted view of the horizon, green flashes are regularly seen by airline pilots , particularly when flying westwards as the sunset is slowed. If the atmosphere is layered, the green flash may appear as

3901-426: The explorers to have seen a green rim on and off for 35 minutes, there must have been some mirage effect present. A green rim is present at every sunset, but it is too thin to be seen with the naked eye. Often a green rim changes to a green flash and back again during the same sunset. The best time to observe a green rim is about 10 minutes before sunset. That is too early to use any magnification like binoculars or

3984-480: The first astronomers to use telescopes to observe the sky, in 1610 he observed the four largest moons of Jupiter , now named the Galilean moons . Galileo also made observations of the phases of Venus , craters on the Moon , and sunspots on the Sun. Astronomer Edmond Halley was able to successfully predict the return of Halley's Comet , which now bears his name, in 1758. In 1781, Sir William Herschel discovered

4067-455: The first season of Arthur in 1996, Arthur Read, having never stayed up until midnight on New Year's Eve before, talks with his friends about what happens when the New Year comes. Despite not actually having stayed up themselves, they each share their take on the matter, Prunella Deegan telling him that there is an amazing green flash at midnight, but if it doesn't happen, then it has to stay

4150-439: The horizon with short interruptions for thirty-five minutes. When it disappeared momentarily it seemed to have been shut off by a tiny spurt, an inequality in the skyline caused by the barrier surface. Even by moving the head up a few inches it would disappear and reappear again and after it had finally disappeared from view it could be recaptured by climbing up the first few steps of the antanea [ sic ] post. For

4233-431: The horizon, astronomers try to schedule observations when an object is highest in the sky, and surveyors try to observe in the afternoon when refraction is minimum. Atmospheric diffraction is a visual effect caused when sunlight is bent by particles suspended in the air. Atmospheric optical phenomena include: Astronomical object An astronomical object , celestial object , stellar object or heavenly body

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4316-521: The human eye were discovered, and new telescopes were made that made it possible to see astronomical objects in other wavelengths of light. Joseph von Fraunhofer and Angelo Secchi pioneered the field of spectroscopy , which allowed them to observe the composition of stars and nebulae, and many astronomers were able to determine the masses of binary stars based on their orbital elements . Computers began to be used to observe and study massive amounts of astronomical data on stars, and new technologies such as

4399-403: The ice. Also they are also viewed in days when the sun hits the clouds in a perfect angle shining upon the area. There are three primary forms of crepuscular rays : They are commonly seen near sunrise and sunset, when tall clouds such as cumulonimbus and mountains can be most effective at creating these rays. Anticrepuscular rays while parallel in reality are sometimes visible in the sky in

4482-508: The intensity of the solar radiation decreases with depth into the gases. As a result, the cloud base can vary from a very light to very dark grey depending on the cloud's thickness and how much light is being reflected or transmitted back to the observer. Thin clouds may look white or appear to have acquired the color of their environment or background. High tropospheric and non-tropospheric clouds appear mostly white if composed entirely of ice crystals and/or supercooled water droplets. As

4565-464: The inversion layer's temperature gradient . The sunlight must bend to the Earth's curvature at least 400 kilometres (250 mi) to allow an elevation rise of 5 degrees for sight of the sun disk. The first person to record the phenomenon was Gerrit de Veer , a member of Willem Barentsz ' ill-fated third expedition into the polar region. Novaya Zemlya , the archipelago where de Veer first observed

4648-400: The left and right of the Sun, at a distance of about 22° and at the same elevation above the horizon. They are commonly caused by plate-shaped hexagonal ice crystals . These crystals tend to become horizontally aligned as they sink through the air, causing them to refract the sunlight to the left and right, resulting in the two sun dogs. As the Sun rises higher, the rays passing through

4731-405: The level of the observer, or on days with ground fog. The glory is related to the optical phenomenon anthelion . A rainbow is a narrow, multicoloured semicircular arc due to dispersion of white light by a multitude of drops of water, usually in the form of rain, when they are illuminated by sunlight. Hence, when conditions are right, a rainbow always appears in the section of sky directly opposite

4814-401: The light from the setting sun reaches the observer without being scattered. One might expect to see a blue flash, since blue light is refracted most of all and the blue component of the sun's light is therefore the last to disappear below the horizon, but the blue is preferentially scattered out of the line of sight , and the remaining light ends up appearing green. With slight magnification ,

4897-417: The longest-possible path through the air, yielding more scattering. The blueness is at the horizon because the blue light coming from great distances is also preferentially scattered. This results in a red shift of the distant light sources that is compensated by the blue hue of the scattered light in the line of sight. In other words, the red light scatters also; if it does so at a point a great distance from

4980-530: The movements of the bodies very important as they used these objects to help navigate over long distances, tell between the seasons, and to determine when to plant crops. During the Middle-Ages , cultures began to study the movements of these bodies more closely. Several astronomers of the Middle-East began to make detailed descriptions of stars and nebulae, and would make more accurate calendars based on

5063-508: The movements of these stars and planets. In Europe , astronomers focused more on devices to help study the celestial objects and creating textbooks, guides, and universities to teach people more about astronomy. During the Scientific Revolution , in 1543, Nicolaus Copernicus's heliocentric model was published. This model described the Earth , along with all of the other planets as being astronomical bodies which orbited

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5146-452: The new planet Uranus , being the first discovered planet not visible by the naked eye. In the 19th and 20th century, new technologies and scientific innovations allowed scientists to greatly expand their understanding of astronomy and astronomical objects. Larger telescopes and observatories began to be built and scientists began to print images of the Moon and other celestial bodies on photographic plates. New wavelengths of light unseen by

5229-552: The number of bands) are an artifact of human color vision , and no banding of any type is seen in a black-and-white photograph of a rainbow (only a smooth gradation of intensity to a maxima, then fading to a minima at the other side of the arc). For colors seen by a normal human eye, the most commonly cited and remembered sequence, in English, is Isaac Newton 's sevenfold red, orange, yellow, green, blue, indigo and violet (popularly memorized by mnemonics like Roy G. Biv ). A mirage

5312-619: The object often appears to be very unusual, and may even be transformed in such a way that it is completely unrecognizable. A Fata Morgana can be seen on land or at sea, in polar regions or in deserts. This kind of mirage can involve almost any kind of distant object, including such things as boats, islands, and coastline. A Fata Morgana is not only complex, but also rapidly changing. The mirage comprises several inverted (upside down) and erect (right side up) images that are stacked on top of one another. Fata Morgana mirages also show alternating compressed and stretched zones. The Novaya Zemlya effect

5395-440: The observer it has a much higher chance of reaching the observer than blue light. At distances nearing infinity, the scattered light is therefore white. Distant clouds or snowy mountaintops will seem yellow for that reason; that effect is not obvious on clear days, but very pronounced when clouds are covering the line of sight reducing the blue hue from scattered sunlight. The scattering due to molecule sized particles (as in air)

5478-418: The ocean, but are possible over cloud tops and mountain tops as well. A green flash from the Moon and bright planets at the horizon, including Venus and Jupiter , can also be observed. This optical phenomenon occurs because rays of light are strongly bent when they pass through air layers of different temperatures in a steep thermal inversion where an atmospheric duct has formed. A thermal inversion

5561-412: The optical properties of Earth's atmosphere cause a wide range of optical phenomena and visual perception phenomena. Examples of meteorological phenomena include: Other phenomena that are remarkable because they are forms of visual illusions include: A book on meteorological optics was published in the sixteenth century, but there have been numerous books on the subject since about 1950. The topic

5644-576: The phenomenon, lends its name to the effect. Crepuscular rays are near-parallel rays of sunlight moving through the Earth's atmosphere, but appear to diverge because of linear perspective . They often occur when objects such as mountain peaks or clouds partially shadow the Sun's rays like a cloud cover . Various airborne compounds scatter the sunlight and make these rays visible, due to diffraction , reflection, and scattering. Crepuscular rays can also occasionally be viewed underwater, particularly in arctic areas, appearing from ice shelves or cracks in

5727-413: The preferred angular distance are 22 and 46 degrees from the ice crystals which create them. Atmospheric phenomena such as halos have been used as part of weather lore as an empirical means of weather forecasting , with their presence indicating an approach of a warm front and its associated rain . Sun dogs are a common type of halo, with the appearance of two subtly-colored bright spots to

5810-422: The required mirage . Jules Verne 's 1882 novel The Green Ray helped to popularize the green flash phenomenon. In Éric Rohmer's 1986 film The Green Ray (French: Le rayon vert ), the main character, Delphine, eavesdrops on a conversation about Jules Verne's novel and the significance of the green flash, eventually witnessing the phenomenon herself in the final scene. In "Arthur's New Year's Eve" from

5893-443: The result of the scattering of sunlight by the atmosphere. When the angle between the Sun and the horizon is less than 10 percent, as it is just after sunrise or just prior to sunset, sunlight becomes too red due to refraction for any colors other than those with a reddish hue to be seen. The clouds do not become that color; they are reflecting long and unscattered rays of sunlight, which are predominant at those hours. The effect

5976-432: The same image size on the retina that appears far. With the overhead Moon, there is no uninterrupted sequence of intervening bodies. Hence it appears far and small. With a horizon Moon, there is an uninterrupted sequence of intervening bodies: all the objects between the observer and the horizon, so the Moon appears far and large. Through works by Roger Bacon , John Pecham , and Witelo based on Ibn al-Haytham's explanation,

6059-653: The same year for another whole year. Walt Disney Pictures ' 2007 movie Pirates of the Caribbean: At World's End references the green flash as a signal that a soul had returned from the dead. The episode Trials and Determinations! of Pokémon the Series: Sun & Moon references the green flash when Ash's Rockruff evolves into Dusk Form Lycanroc after witnessing a green flash at sunset. Atmospheric optics Meteorological optical phenomena, as described in this article, are concerned with how

6142-497: The short end of light's visible wavelengths, while red and yellow are at the long end. The short rays are more easily scattered by water droplets, and the long rays are more likely to be absorbed. The bluish color is evidence that such scattering is being produced by rain-sized droplets in the cloud. A cumulonimbus cloud emitting green is a sign that it is a severe thunderstorm , capable of heavy rain, hail , strong winds and possible tornadoes . The exact cause of green thunderstorms

6225-405: The sky is a result of Rayleigh scattering of sunlight , which results in a perceived blue color. On a sunny day, Rayleigh scattering gives the sky a blue gradient , darkest around the zenith and brightest near the horizon. Light rays coming from the zenith take the shortest-possible path ( 1 ⁄ 38 ) through the air mass , yielding less scattering. Light rays coming from the horizon take

6308-498: The sky, most pronounced at an angle 90° from the Sun. 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 . The color of a cloud, as seen from the Earth, tells much about what

6391-458: The southeastern United States during the summer, which changes the sky from a blue to a white appearance and leads to an increase in red sunsets. Its presence negatively affects air quality during the summer since it adds to the count of airborne particulates. The sky can turn a multitude of colors such as red, orange, pink and yellow (especially near sunset or sunrise) and black at night. Scattering effects also partially polarize light from

6474-527: The sun dog finally merge into the white of the parhelic circle (if the latter is visible). It is theoretically possible to predict the forms of sun dogs as would be seen on other planets and moons. Mars might have sundogs formed by both water-ice and CO 2 -ice. On the giant gas planets — Jupiter , Saturn , Uranus and Neptune — other crystals form the clouds of ammonia , methane , and other substances that can produce halos with four or more sundogs. A common optical phenomenon involving water droplets

6557-597: The upper troposphere , at an altitude of 5 kilometres (3.1 mi) to 10 kilometres (6.2 mi), or, during very cold weather, by ice crystals called diamond dust drifting in the air at low levels. The particular shape and orientation of the crystals are responsible for the types of halo observed. Light is reflected and refracted by the ice crystals and may split into colors because of dispersion . The crystals behave like prisms and mirrors , refracting and reflecting sunlight between their faces, sending shafts of light in particular directions. For circular halos,

6640-399: The various condensing nebulae. The great variety of stellar forms are determined almost entirely by the mass, composition and evolutionary state of these stars. Stars may be found in multi-star systems that orbit about each other in a hierarchical organization. A planetary system and various minor objects such as asteroids, comets and debris, can form in a hierarchical process of accretion from

6723-410: The wavelength of green light yields roughly 1000-1100 nm infrared light, so the most likely hypothesis is that the Green Flash is coherent upconverted infrared (laser) light that "double-hits" the retina or camera lens, creating the effect of bright green (additionally, this explains why the Green Flash is also sometimes blue or purple; coherent infrared light can upconvert to any color of visible light if

6806-592: Was found that stars commonly fell on a band of stars called the main-sequence stars on the diagram. A refined scheme for stellar classification was published in 1943 by William Wilson Morgan and Philip Childs Keenan based on the Hertzsprung-Russel Diagram. Astronomers also began debating whether other galaxies existed beyond the Milky Way , these debates ended when Edwin Hubble identified

6889-518: Was popularised by the wide circulation of a book by Marcel Minnaert , Light and Color in the Open Air , in 1954. In the Book of Optics (1011–22 AD), Ibn al-Haytham argued that vision occurs in the brain, and that personal experience has an effect on what people see and how they see, and that vision and perception are subjective. Arguing against Ptolemy 's refraction theory for why people perceive

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