1.
Farallon Islands
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The Farallon Islands, or Farallones, are a group of islands and sea stacks in the Gulf of the Farallones, off the coast of San Francisco, California, United States. They lie 30 miles outside the Golden Gate and 20 miles south of Point Reyes, the islands are officially part of the City and County of San Francisco. The only inhabited portion of the islands is on Southeast Farallon Island, where researchers from Point Blue Conservation Science, the islands are closed to the public. The Farallon National Wildlife Refuge is one of 63 National Wildlife Refuges that have designated wilderness status. In 1974 the Farallon Wilderness was established and includes all islands except the Southeast Island for a total of 141 acres. The first European to land and record the islands was Spanish explorer Juan Rodriguez Cabrillo in 1539, the expedition missed the entrance to San Francisco Bay, but it sighted and named nearby places such as Punta de los Pinos, and Bahia de los Pinos. On July 24,1579, English privateer and explorer Sir Francis Drake landed on the islands, in order to collect seal meat and he named them the Islands of Saint James because the day after his arrival was the feast day of St James the Great. The name of St James is now applied to one of the rocky islets of the North Farallones. The islands were given the name Los Frayles by Spanish explorer Sebastián Vizcaíno, in the years following their discovery, during the Maritime Fur Trade era, the islands were exploited by seal hunters, first from New England and later from Russia. The Russians maintained a station in the Farallones from 1812 to 1840, taking 1,200 to 1,500 fur seals annually. In 1810, they met up with two other American ships at the Farallon Islands, the Mercury and the Isabella, and at least 30,000 seal skins were taken. By 1818 the seals diminished rapidly until only about 500 could be taken annually and within the few years. It is not known whether the fur seal or the Guadalupe fur seal were the islands native fur seal. After Alta California was ceded by Mexico to the United States in 1848 with the Treaty of Guadalupe Hidalgo, beginning in 1853, a lighthouse was constructed on SEFI. As the city grew, the colonies came under severe threat as eggs were collected in the millions for San Francisco markets. The trade, which in its heyday could yield 500,000 eggs a month, was the source of conflict between the egg collecting companies and the lighthouse keepers and this conflict turned violent in a confrontation between rival companies in 1863. The clash between two companies, known as the Egg War, left two men dead and marked the end of private companies on the islands, although the lighthouse keepers continued egging. This was expanded to the islands in 1969 when it became a National Wildlife Refuge
2.
Green flash
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Green flashes and green rays are optical phenomena that sometimes occur right before sunset or right after sunrise. When the conditions are right, a spot is visible above the upper rim of the disk of the sun. The green appearance usually lasts for no more than a second or two, rarely, the green flash can resemble a green ray shooting up from the sunset point. Green flashes occur because the atmosphere can cause the light from the sun to separate out into different colors, Green flashes are a group of phenomena which 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 and 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 the equator the flash rarely lasts longer than a second, a 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, if the atmosphere is layered the green flash may appear as a series of flashes. While observing at the Vatican Observatory in 1960 D. K. J, oConnell produced the first color photographs of a green flash at sunset. Green flashes are enhanced by mirage, which increase refraction, a green flash is more likely to be seen in stable, clear air, when more of the light from the setting sun reaches the observer without being scattered. Some types not listed in the table above, such as the flash, are not understood. Rarely, the amount of light is sufficient to be visible as a blue flash. An explanation for the blue flash has not yet been identified, as an astronomical object sets or rises in relation to the horizon, the light it emits travels through Earths atmosphere, which works as a prism separating the light into different colors. The lower rim of an object is always red. A green rim is thin and is difficult or impossible to see with the naked eye. The following quote describes what was probably the longest observation of a green rim and it lasted an appreciable length of time, several seconds at least, and no sooner disappeared than it flashed forth again. Altogether it remained on 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. For 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 flash and back again during the same sunset
3.
Fata Morgana (mirage)
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A Fata Morgana is an unusual and complex form of superior mirage that is seen in a narrow band right above the horizon. Although the term Fata Morgana is sometimes applied to other, more kinds of mirages. Fata Morgana mirages significantly distort the object or objects on which they are based, a Fata Morgana can be seen on land or at sea, in polar regions or in deserts. It can involve almost any kind of distant object, including boats, islands, a Fata Morgana is often rapidly changing. The mirage comprises several inverted and erect images that are stacked on top of one another, Fata Morgana mirages also show alternating compressed and stretched zones. The optical phenomenon occurs because rays of light are bent when they pass through air layers of different temperatures in a thermal inversion where an atmospheric duct has formed. A Fata Morgana requires a duct to be present, thermal inversion alone is not enough to produce this kind of mirage, while a thermal inversion often takes place without there being an atmospheric duct, an atmospheric duct cannot exist without there first being a thermal inversion. A Fata Morgana is most commonly seen in regions, especially over large sheets of ice which have a uniform low temperature. It can, however, be observed in almost any area, in polar regions the Fata Morgana phenomenon is observed on relatively cold days. However, in deserts, over oceans, and over lakes, to generate the Fata Morgana phenomenon, the thermal inversion has to be strong enough that the curvature of the light rays within the inversion layer is stronger than the curvature of the Earth. Under these conditions, the bend and create arcs. An observer needs to be within or below an atmospheric duct in order to be able to see a Fata Morgana, a Fata Morgana can be observed from any altitude within the Earths atmosphere, from sea level up to mountaintops, and even including the view from airplanes. A Fata Morgana can be described as a very complex superior mirage with more than three distorted erect and inverted images. The sequential image here shows sixteen photographic frames of a mirage of the Farallon Islands as seen from San Francisco, in the first fourteen frames, elements of the Fata Morgana mirage display alternations of compressed and stretched zones. The last two frames were photographed few hours later, around sunset time, at that point in time, the air was cooler while the ocean was probably a little bit warmer, which caused the thermal inversion to be not as extreme as it was few hours before. A mirage was still present at that point, but it was not as complex as few hours before sunset, the mirage was no longer a Fata Morgana, but instead had become a simple superior mirage. Gabriel Gruber and Tobias Gruber, who observed Fata Morgana above Lake Cerknica, were the first to study it in a laboratory setting, la Fata Morgana is the name of Morgan le Fay in Italian. Morgan le Fay, alternately known as Morgane, Morgain, Morgana and other variants, was described as a sorceress and antagonist of King Arthur
4.
Optical phenomena
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Optical phenomena are any observable events that result from the interaction of light and matter. See also list of topics and optics. A mirage is an example of an optical phenomenon, common optical phenomena are often due to the interaction of light from the sun or moon with the atmosphere, clouds, water, dust, and other particulates. One common example is the rainbow, when light from the sun is reflected and refracted by water droplets, some, such as the green ray, are so rare they are sometimes thought to be mythical. Others, such as Fata Morganas, are commonplace in favored locations, other phenomena are simply interesting aspects of optics, or optical effects. For instance, the colors generated by a prism are often shown in classrooms, optical phenomena include those arising from the optical properties of the atmosphere, the rest of nature, of objects, whether natural or human-made, and of our eyes. Also listed here are unexplained phenomena that could have an optical explanation, there are many phenomena that result from either the particle or the wave nature of light. Some are quite subtle and observable only by precise measurement using scientific instruments, one famous observation is of the bending of light from a star by the Sun observed during a solar eclipse. This demonstrates that space is curved, as the theory of relativity predicts, afterglow Airglow Alexanders band, the dark region between the two bows of a double rainbow. Some consider many of these mysteries to simply be local tourist attractions that are not worthy of thorough investigation. Minnaert, Light and Color in the Outdoors, ISBN 0-387-97935-2 John Naylor Out of the Blue, A 24-hour Skywatchers Guide, CUP,2002, ISBN 0-521-80925-8 Abenteuer im Erdschatten
5.
Mirror
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This is different from other light-reflecting objects that do not preserve much of the original wave signal other than color and diffuse reflected light. The most familiar type of mirror is the mirror, which has a flat screen surface. Curved mirrors are used, to produce magnified or diminished images or focus light or simply distort the reflected image. Mirrors are commonly used for personal grooming or admiring oneself, decoration, Mirrors are also used in scientific apparatus such as telescopes and lasers, cameras, and industrial machinery. Most mirrors are designed for light, however, mirrors designed for other wavelengths of electromagnetic radiation are also used. The first mirrors used by people were most likely pools of dark, still water, the requirements for making a good mirror are a surface with a very high degree of flatness, and a surface roughness smaller than the wavelength of the light. The earliest manufactured mirrors were pieces of polished stone such as obsidian, examples of obsidian mirrors found in Anatolia have been dated to around 6000 BC. Mirrors of polished copper were crafted in Mesopotamia from 4000 BC, polished stone mirrors from Central and South America date from around 2000 BC onwards. In China, bronze mirrors were manufactured from around 2000 BC, some of the earliest bronze, Mirrors made of other metal mixtures such as copper and tin speculum metal may have also been produced in China and India. Mirrors of speculum metal or any precious metal were hard to produce and were owned by the wealthy. Stone mirrors often had poor reflectivity compared to metals, yet metals scratch or tarnish easily, depending upon the color, both often yielded reflections with poor color rendering. The poor image quality of ancient mirrors explains 1 Corinthians 13s reference to seeing as in a mirror, glass was a desirable material for mirrors. Because the surface of glass is smooth, it produces reflections with very little blur. In addition, glass is very hard and scratch resistant, however, glass by itself has little reflectivity, so people began coating it with metals to increase the reflectivity. According to Pliny, the people of Sidon developed a technique for creating crude mirrors by coating glass with molten lead. Glass mirrors backed with gold leaf are mentioned by Pliny in his Natural History and these circular mirrors were typically small, from only a fraction of an inch to as much as eight inches in diameter. These small mirrors produced distorted images, yet were prized objects of high value and these ancient glass mirrors were very thin, thus very fragile, because the glass needed to be extremely thin to prevent cracking when coated with a hot, molten metal. Due to the quality, high cost, and small size of these ancient glass mirrors
6.
Mojave Desert
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The Mojave Desert is an arid rain-shadow desert and the driest desert in North America. It is located in the southwestern United States, primarily within southeastern California and southern Nevada, very small areas also extend into Utah and Arizona. The central part of the desert is sparsely populated, while its peripheries support large communities such as Las Vegas, Lancaster, Palmdale, Victorville, the Mojave Desert is bordered by the Great Basin Desert to its north and the Sonoran Desert to its south and east. Topographical boundaries include the Tehachapi Mountains to the west, and the San Gabriel Mountains, the mountain boundaries are distinct because they are outlined by the two largest faults in California – the San Andreas and Garlock faults. The Mojave Desert displays typical basin and range topography and it occupies less than 50,000 sq mi, making it the smallest of the North American deserts. The Mojave Desert is often referred to as the desert, in contrast to the low desert. However, the Mojave Desert is generally lower than the Great Basin Desert to the north, the spelling Mojave originates from the Spanish language while the spelling Mohave comes from modern English. The Mojave Desert receives less than 13 in of rain a year and is generally between 2,000 and 5,000 feet in elevation, zion National Park in Utah lies at the junction of the Mojave, the Great Basin Desert, and the Colorado Plateau. Despite its aridity, the Mojave has long been a center of production, fed by irrigation coming from groundwater. The Mojave is a desert of temperature extremes and two distinct seasons, winter months bring comfortable daytime temperatures, which dip precipitously to around 20 °F on valley floors, and below 0 °F at higher elevations. Storms moving from the Pacific Northwest can bring rain and in places even snow. More often, the shadow created by the Sierra Nevada as well as mountain ranges within the desert such as the Spring Mountains, bring only clouds. By early June, it is rare for another Pacific storm to have a significant impact on the regions weather, summer weather is dominated by heat. Temperatures on valley floors can soar above 120 °F and above 130 °F at the lowest elevations, low humidity, high temperatures, and low pressure, draw in moisture from the Gulf of Mexico creating thunderstorms across the desert southwest known as the North American monsoon. Autumn is generally pleasant, with one to two Pacific storm systems creating regional rain events, october is one of the driest and sunniest months in the Mojave, and temperatures usually remain between 70 °F and 90 °F on the valley floors. After temperature, wind is the most significant weather phenomenon in the Mojave, during the June Gloom, cooler air can be pushed out into the desert from Southern California. In Santa Ana wind events, hot air from the desert blows out into the Los Angeles basin, wind farms in these areas generate power from these winds. The other major factor in the region is elevation
7.
Desert
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A desert is a barren area of land where little precipitation occurs and consequently living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation, about one third of the land surface of the world is arid or semi-arid. This includes much of the regions where little precipitation occurs. Deserts can be classified by the amount of precipitation falls, by the temperature that prevails. Deserts are formed by weathering processes as large variations in temperature between day and night put strains on the rocks which consequently break in pieces, although rain seldom occurs in deserts, there are occasional downpours that can result in flash floods. Rain falling on hot rocks can cause them to shatter and the resulting fragments and this picks up particles of sand and dust and wafts them aloft in sand or dust storms. Wind-blown sand grains striking any solid object in their path can abrade the surface, rocks are smoothed down, and the wind sorts sand into uniform deposits. The grains end up as level sheets of sand or are piled high in billowing sand dunes, other deserts are flat, stony plains where all the fine material has been blown away and the surface consists of a mosaic of smooth stones. These areas are known as desert pavements and little further erosion takes place, other desert features include rock outcrops, exposed bedrock and clays once deposited by flowing water. Temporary lakes may form and salt pans may be left when waters evaporate, there may be underground sources of water in the form of springs and seepages from aquifers. Where these are found, oases can occur, plants and animals living in the desert need special adaptations to survive in the harsh environment. Plants tend to be tough and wiry with small or no leaves, water-resistant cuticles, some annual plants germinate, bloom and die in the course of a few weeks after rainfall while other long-lived plants survive for years and have deep root systems able to tap underground moisture. Animals need to cool and find enough food and water to survive. Many are nocturnal and stay in the shade or underground during the heat of the day and they tend to be efficient at conserving water, extracting most of their needs from their food and concentrating their urine. Some animals remain in a state of dormancy for long periods and they then reproduce rapidly while conditions are favorable before returning to dormancy. People have struggled to live in deserts and the surrounding lands for millennia. Nomads have moved their flocks and herds to wherever grazing is available, the cultivation of semi-arid regions encourages erosion of soil and is one of the causes of increased desertification. Many trade routes have been forged across deserts, especially across the Sahara Desert, large numbers of slaves were also taken northwards across the Sahara
8.
Asphalt
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Asphalt, also known as bitumen is a sticky, black and highly viscous liquid or semi-solid form of petroleum. It may be found in deposits or may be a refined product. Until the 20th century, the term asphaltum was also used, the word is derived from the Ancient Greek ἄσφαλτος ásphaltos. The primary use of asphalt/bitumen is in construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt, the terms asphalt and bitumen are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, asphalt is the carefully refined residue from the process of selected crude oils. Outside the United States, the product is often called bitumen, geologists often prefer the term bitumen. Common usage often refers to forms of asphalt/bitumen as tar. Naturally occurring asphalt/bitumen is sometimes specified by the crude bitumen. Its viscosity is similar to that of cold molasses while the material obtained from the distillation of crude oil boiling at 525 °C is sometimes referred to as refined bitumen. The Canadian province of Alberta has most of the reserves of natural bitumen, covering 142,000 square kilometres. Additionally, most natural bitumens contain organosulfur compounds, resulting in a sulfur content of up to 4%. Nickel and vanadium are found in the <10 ppm level, as is typical of some petroleum, the substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase, and it is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large. Asphalt/bitumen can sometimes be confused with tar, which is a visually similar black. During the early and mid-20th century when town gas was produced, coal tar was a readily available byproduct, the addition of tar to macadam roads led to the word tarmac, which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. Pitch is another term used at times to refer to asphalt/bitumen
9.
Jet engine
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A jet engine is a reaction engine discharging a fast-moving jet that generates thrust by jet propulsion. This broad definition includes airbreathing jet engines and non-airbreathing jet engines, in general, jet engines are combustion engines. In common parlance, the jet engine loosely refers to an internal combustion airbreathing jet engine. These typically feature an air compressor powered by a turbine. Jet aircraft use such engines for long-distance travel, early jet aircraft used turbojet engines which were relatively inefficient for subsonic flight. Modern subsonic jet aircraft usually use more complex high-bypass turbofan engines and these engines offer high speed and greater fuel efficiency than piston and propeller aeroengines over long distances. Jet engines date back to the invention of the aeolipile before the first century AD and this device directed steam power through two nozzles to cause a sphere to spin rapidly on its axis. So far as is known, it did not supply mechanical power, instead, it was seen as a curiosity. However, although powerful, at reasonable flight speeds rockets are very inefficient. The earliest attempts at airbreathing jet engines were hybrid designs in which a power source first compressed air. In one such system, called a thermojet by Secondo Campini but more commonly, motorjet, examples of this type of design were the Caproni Campini N.1, and the Japanese Tsu-11 engine intended to power Ohka kamikaze planes towards the end of World War II. None were entirely successful and the N.1 ended up being slower than the design with a traditional engine. If aircraft performance were ever to increase beyond such a barrier and this was the motivation behind the development of the gas turbine engine, commonly called a jet engine. The key to a jet engine was the gas turbine. The gas turbine was not an idea developed in the 1930s, the first gas turbine to successfully run self-sustaining was built in 1903 by Norwegian engineer Ægidius Elling. Limitations in design and practical engineering and metallurgy prevented such engines reaching manufacture, the main problems were safety, reliability, weight and, especially, sustained operation. The first patent for using a gas turbine to power an aircraft was filed in 1921 by Frenchman Maxime Guillaume and his engine was an axial-flow turbojet. Alan Arnold Griffith published An Aerodynamic Theory of Turbine Design in 1926 leading to work at the RAE
10.
Telescope
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A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation. The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s and they found use in both terrestrial applications and astronomy. Within a few decades, the telescope was invented, which used mirrors to collect. In the 20th century many new types of telescopes were invented, including radio telescopes in the 1930s, the word telescope now refers to a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors. The word telescope was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galileis instruments presented at a banquet at the Accademia dei Lincei, in the Starry Messenger, Galileo had used the term perspicillum. The earliest recorded working telescopes were the telescopes that appeared in the Netherlands in 1608. Their development is credited to three individuals, Hans Lippershey and Zacharias Janssen, who were spectacle makers in Middelburg, Galileo heard about the Dutch telescope in June 1609, built his own within a month, and improved upon the design in the following year. Also in 1609, Thomas Harriot became the first person known to point a telescope skyward in order to make observations of a celestial object. The idea that the objective, or light-gathering element, could be a mirror instead of a lens was being investigated soon after the invention of the refracting telescope. The potential advantages of using parabolic mirrors—reduction of spherical aberration and no chromatic aberration—led to many proposed designs, in 1668, Isaac Newton built the first practical reflecting telescope, of a design which now bears his name, the Newtonian reflector. The invention of the lens in 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter. The largest reflecting telescopes currently have objectives larger than 10 m, the 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio to gamma-rays. The first purpose built radio telescope went into operation in 1937, since then, a tremendous variety of complex astronomical instruments have been developed. The name telescope covers a range of instruments. Most detect electromagnetic radiation, but there are differences in how astronomers must go about collecting light in different frequency bands. The near-infrared can be collected much like light, however in the far-infrared and submillimetre range. For example, the James Clerk Maxwell Telescope observes from wavelengths from 3 μm to 2000 μm, on the other hand, the Spitzer Space Telescope, observing from about 3 μm to 180 μm uses a mirror. Also using reflecting optics, the Hubble Space Telescope with Wide Field Camera 3 can observe in the range from about 0.2 μm to 1.7 μm
11.
Telephoto lens
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In photography and cinematography, a telephoto lens is a specific type of a long-focus lens in which the physical length of the lens is shorter than the focal length. This is achieved by incorporating a special group known as a telephoto group that extends the light path to create a long-focus lens in a much shorter overall design. The angle of view and other effects of long-focus lenses are the same for telephoto lenses of the same specified focal length, long-focal-length lenses are often informally referred to as telephoto lenses although this is technically incorrect, a telephoto lens specifically incorporates the telephoto group. In contrast to a lens, for any given focal length a simple lens of non-telephoto design is constructed from one lens. To focus on an object at infinity, the distance from this single lens to focal plane of the camera has to be adjusted to this focal length, for example, given a focal length of 500 mm, the distance between lens and focal plane is 500 mm. The farther the focal length is increased, the more the length of such a simple lens makes it unwieldy. But such simple lenses are not telephoto lenses, no matter how extreme the focal length – they are known as long-focus lenses, while the optical centre of a simple lens is within the construction, the telephoto lens moves the optical centre in front of the construction. The basic construction of a telephoto lens consists of front lens elements that, the focal length of this group is shorter than the effective focal length of the lens. The converging rays from this group are intercepted by the rear lens group, sometimes called the telephoto group, the simplest telephoto designs could consist of one element in each group, but in practice, more than one element is used in each group to correct for various aberrations. The combination of two groups produces a lens assembly that is physically shorter than a long-focus lens producing the same image size. This same property is achieved in camera lenses that combine mirrors with lenses and these designs, called catadioptric, reflex, or mirror lenses, have a curved mirror as the primary objective with some form of negative lens in front of the mirror to correct optical aberrations. They also use a secondary mirror to relay the image that extends the light cone the same way the negative lens telephoto group does. The mirrors also fold the light path, the heaviest non-Catadioptric telephoto lens for civilian use was made by Carl Zeiss and has a focal length of 1700 mm with a maximum aperture of f/4, implying a 425 mm entrance pupil. It is designed for use with a medium format Hasselblad 203 FE camera, the telephoto lens design has also been used for wide angles, at least once in the case of the Olympus XA where it permitted a 35mm focal length to fit in an extra compact camera body. Inverting the telephoto configuration, employing one or more negative lens groups in front of a positive lens group and this allows for greater clearance for other optical or mechanical parts such as the mirror parts in a single-lens reflex camera. Zoom lenses that are telephotos at one extreme of the zoom range, the concept of the telephoto lens, in reflecting form, was first described by Johannes Kepler in his Dioptrice of 1611, and re-invented by Peter Barlow in 1834. Some of his photographs are preserved in the holdings of the Turnbull Library in Wellington, one of McKay’s photographs shows the Russian warship Vjestnik anchored in Wellington harbour about two and a half kilometres away, with its rigging lines and gun ports clearly visible. The other, taken from the point, is of a local hotel
12.
Sky
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The sky is everything that lies above the surface of the Earth, including the atmosphere and outer space. In the field of astronomy, the sky is called the celestial sphere. This is viewed from Earths surface as a dome where the Sun, stars, planets. The celestial sphere is divided into regions called constellations. Usually, the sky is used informally as the point of view from the Earths surface, however. In some cases, such as in discussing the weather, the sky refers to only the lower, during daylight, the sky appears to be blue because air scatters blue sunlight more than it scatters red. At night, the sky appears to be a dark surface or region scattered with stars. During the day, the Sun can be seen in the sky obscured by clouds. In the night sky 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, birds, insects, aircraft, and kites are often considered to 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 directly from the sun, most of the light in the day sky is caused by scattering. The scattering due to molecule sized particles is greater in the forward and backward directions than it is in the lateral direction. Scattering is significant for light at all visible wavelengths but is stronger at the end of the visible spectrum, meaning that the scattered light is bluer than its source. The remaining sunlight, having lost some of its wavelength components. Scattering also occurs more strongly in clouds. Individual water droplets exposed to light will create a set of colored rings. If a cloud is thick enough, scattering from water droplets will wash out the set of colored rings
