Minggu, 08 April 2012

Weather

From Wikipedia, the free encyclopedia

Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy.[1] Most weather phenomena occur in the troposphere,[2][3] just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate is the term for the average atmospheric conditions over longer periods of time.[4] When used without qualification, "weather" is understood to be the weather of Earth.
Weather is driven by density (temperature and moisture) differences between one place and another. These differences can occur due to the sun angle at any particular spot, which varies by latitude from the tropics. The strong temperature contrast between polar and tropical air gives rise to the jet stream. Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow. Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. On Earth's surface, temperatures usually range ±40 °C (100 °F to −40 °F) annually. Over thousands of years, changes in Earth's orbit affect the amount and distribution of solar energy received by the Earth and influence long-term climate and global climate change.
Surface temperature differences in turn cause pressure differences. Higher altitudes are cooler than lower altitudes due to differences in compressional heating. Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. The atmosphere is a chaotic system, so small changes to one part of the system can grow to have large effects on the system as a whole. Human attempts to control the weather have occurred throughout human history, and there is evidence that human activity such as agriculture and industry has inadvertently modified weather patterns.
Studying how the weather works on other planets has been helpful in understanding how weather works on Earth. A famous landmark in the Solar System, Jupiter's Great Red Spot, is an anticyclonic storm known to have existed for at least 300 years. However, weather is not limited to planetary bodies. A star's corona is constantly being lost to space, creating what is essentially a very thin atmosphere throughout the Solar System. The movement of mass ejected from the Sun is known as the solar wind.

Cause

On Earth, common weather phenomena include wind, cloud, rain, snow, fog and dust storms. Less common events include natural disasters such as tornadoes, hurricanes, typhoons and ice storms. Almost all familiar weather phenomena occur in the troposphere (the lower part of the atmosphere).[3] Weather does occur in the stratosphere and can affect weather lower down in the troposphere, but the exact mechanisms are poorly understood.[5]
Weather occurs primarily due to density (temperature and moisture) differences between one place to another. These differences can occur due to the sun angle at any particular spot, which varies by latitude from the tropics. In other words, the farther from the tropics you lie, the lower the sun angle is, which causes those locations to be cooler due to the indirect sunlight.[6] The strong temperature contrast between polar and tropical air gives rise to the jet stream.[7] Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow (see baroclinity).[8] Weather systems in the tropics, such as monsoons or organized thunderstorm systems, are caused by different processes.
Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. In June the Northern Hemisphere is tilted towards the sun, so at any given Northern Hemisphere latitude sunlight falls more directly on that spot than in December (see Effect of sun angle on climate).[9] This effect causes seasons. Over thousands to hundreds of thousands of years, changes in Earth's orbital parameters affect the amount and distribution of solar energy received by the Earth and influence long-term climate. (see Milankovitch cycles).[10]
The uneven solar heating (the formation of zones of temperature and moisture gradients, or frontogenesis) can also be due to the weather itself in the form of cloudiness and precipitation.[11] Higher altitudes are cooler than lower altitudes, which is explained by the lapse rate.[12][13] On local scales, temperature differences can occur because different surfaces (such as oceans, forests, ice sheets, or man-made objects) have differing physical characteristics such as reflectivity, roughness, or moisture content.
Surface temperature differences in turn cause pressure differences. A hot surface heats the air above it and the air expands, lowering the air pressure and its density.[14] The resulting horizontal pressure gradient accelerates the air from high to low pressure, creating wind, and Earth's rotation then causes curvature of the flow via the Coriolis effect.[15] The simple systems thus formed can then display emergent behaviour to produce more complex systems and thus other weather phenomena. Large scale examples include the Hadley cell while a smaller scale example would be coastal breezes.
The atmosphere is a chaotic system, so small changes to one part of the system can grow to have large effects on the system as a whole.[16] This makes it difficult to accurately predict weather more than a few days in advance, though weather forecasters are continually working to extend this limit through the scientific study of weather, meteorology. It is theoretically impossible to make useful day-to-day predictions more than about two weeks ahead, imposing an upper limit to potential for improved prediction skill.[17]

Shaping the planet Earth

Weather is one of the fundamental processes that shape the Earth. The process of weathering breaks down the rocks and soils into smaller fragments and then into their constituent substances.[18] These are then free to take part in chemical reactions that can affect the surface further (such as acid rain) or are reformed into other rocks and soils. In this way, weather plays a major role in erosion of the surface.[19]

Effect on humans

Effects on populations

Weather has played a large and sometimes direct part in human history. Aside from climatic changes that have caused the gradual drift of populations (for example the desertification of the Middle East, and the formation of land bridges during glacial periods), extreme weather events have caused smaller scale population movements and intruded directly in historical events. One such event is the saving of Japan from invasion by the Mongol fleet of Kublai Khan by the Kamikaze winds in 1281.[20] French claims to Florida came to an end in 1565 when a hurricane destroyed the French fleet, allowing Spain to conquer Fort Caroline.[21] More recently, Hurricane Katrina redistributed over one million people from the central Gulf coast elsewhere across the United States, becoming the largest diaspora in the history of the United States.[22]
The Little Ice Age caused crop failures and famines in Europe. The 1690s saw the worst famine in France since the
Middle Ages. Finland suffered a severe famine in 1696–1697, during which about one-third of the Finnish population died.[23]

Effects on individuals

The human body is negatively affected by extremes in temperature, humidity, and wind.[24]

Forecasting

Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. Human beings have attempted to predict the weather informally for millennia, and formally since at least the nineteenth century.[25][26] Weather forecasts are made by collecting quantitative data about the current state of the atmosphere and using scientific understanding of atmospheric processes to project how the atmosphere will evolve.[27]
Once an all-human endeavor based mainly upon changes in barometric pressure, current weather conditions, and sky condition,[28][29] forecast models are now used to determine future conditions. Human input is still required to pick the best possible forecast model to base the forecast upon, which involves pattern recognition skills, teleconnections, knowledge of model performance, and knowledge of model biases. The chaotic nature of the atmosphere, the massive computational power required to solve the equations that describe the atmosphere, error involved in measuring the initial conditions, and an incomplete understanding of atmospheric processes mean that forecasts become less accurate as the difference in current time and the time for which the forecast is being made (the range of the forecast) increases. The use of ensembles and model consensus helps to narrow the error and pick the most likely outcome.[30][31][32]
There are a variety of end users to weather forecasts. Weather warnings are important forecasts because they are used to protect life and property.[33][34] Forecasts based on temperature and precipitation are important to agriculture,[35][36][37][38] and therefore to commodity traders within stock markets. Temperature forecasts are used by utility companies to estimate demand over coming days.[39][40][41] On an everyday basis, people use weather forecasts to determine what to wear on a given day. Since outdoor activities are severely curtailed by heavy rain, snow and the wind chill, forecasts can be used to plan activities around these events, and to plan ahead and survive them.

Modification

The aspiration to control the weather is evident throughout human history: from ancient rituals intended to bring rain for crops to the U.S. Military Operation Popeye, an attempt to disrupt supply lines by lengthening the North Vietnamese monsoon. The most successful attempts at influencing weather involve cloud seeding; they include the fog- and low stratus dispersion techniques employed by major airports, techniques used to increase winter precipitation over mountains, and techniques to suppress hail.[42] A recent example of weather control was China's preparation for the 2008 Summer Olympic Games. China shot 1,104 rain dispersal rockets from 21 sites in the city of Beijing in an effort to keep rain away from the opening ceremony of the games on 8 August 2008. Guo Hu, head of the Beijing Municipal Meteorological Bureau (BMB), confirmed the success of the operation with 100 millimeters falling in Baoding City of Hebei Province, to the southwest and Beijing's Fangshan District recording a rainfall of 25 millimeters.[43]
Whereas there is inconclusive evidence for these techniques' efficacy, there is extensive evidence that human activity such as agriculture and industry results in inadvertent weather modification:[42]
The effects of inadvertent weather modification may pose serious threats to many aspects of civilization, including ecosystems, natural resources, food and fiber production, economic development, and human health.[45]

Extremes on Earth

On Earth, temperatures usually range ±40 °C (100 °F to −40 °F) annually. The range of climates and latitudes across the planet can offer extremes of temperature outside this range. The coldest air temperature ever recorded on Earth is −89.2 °C (−128.6 °F), at Vostok Station, Antarctica on 21 July 1983. The hottest air temperature ever recorded was 57.7 °C (135.9 °F) at 'Aziziya, Libya, on 13 September 1922,[46] but that reading is queried. The highest recorded average annual temperature was 34.4 °C (93.9 °F) at Dallol, Ethiopia.[47] The coldest recorded average annual temperature was −55.1 °C (−67.2 °F) at Vostok Station, Antarctica.[48] The coldest average annual temperature in a permanently inhabited location is at Eureka, Nunavut, in Canada, where the annual average temperature is −19.7 °C (−3.5 °F).[49]

Extraterrestrial within the Solar System

Studying how the weather works on other planets has been seen as helpful in understanding how it works on Earth.[50] Weather on other planets follows many of the same physical principles as weather on Earth, but occurs on different scales and in atmospheres having different chemical composition. The Cassini–Huygens mission to Titan discovered clouds formed from methane or ethane which deposit rain composed of liquid methane and other organic compounds.[51] Earth's atmosphere includes six latitudinal circulation zones, three in each hemisphere.[52] In contrast, Jupiter's banded appearance shows many such zones,[53] Titan has a single jet stream near the 50th parallel north latitude,[54] and Venus has a single jet near the equator.[55]
One of the most famous landmarks in the Solar System, Jupiter's Great Red Spot, is an anticyclonic storm known to have existed for at least 300 years.[56] On other gas giants, the lack of a surface allows the wind to reach enormous speeds: gusts of up to 600 metres per second (about 2,100 km/h or 1,300 mph) have been measured on the planet Neptune.[57] This has created a puzzle for planetary scientists. The weather is ultimately created by solar energy and the amount of energy received by Neptune is only about 1⁄900 of that received by Earth, yet the intensity of weather phenomena on Neptune is far greater than on Earth.[58] The strongest planetary winds discovered so far are on the extrasolar planet HD 189733 b, which is thought to have easterly winds moving at more than 9,600 kilometres per hour (6,000 mph).[59]

Space weather

Weather is not limited to planetary bodies. Like all stars, the sun's corona is constantly being lost to space, creating what is essentially a very thin atmosphere throughout the Solar System. The movement of mass ejected from the Sun is known as the solar wind. Inconsistencies in this wind and larger events on the surface of the star, such as coronal mass ejections, form a system that has features analogous to conventional weather systems (such as pressure and wind) and is generally known as space weather. Coronal mass ejections have been tracked as far out in the solar system as Saturn.[60] The activity of this system can affect planetary atmospheres and occasionally surfaces. The interaction of the solar wind with the terrestrial atmosphere can produce spectacular aurorae,[61] and can play havoc with electrically sensitive systems such as electricity grids and radio signals.[62]
Diposting oleh di 08.35 0 komentar

Fire dancing


Fire dancing (also known as "fire twirling," "fire spinning," "fire performance," or "fire manipulation") is a group of performance arts or disciplines that involve manipulation of objects on fire. Typically these objects have one or more bundles of wicking, which are soaked in fuel and ignited.
Some of these disciplines are related to juggling or baton twirling (both forms of object manipulation), and there is also an affinity between fire dancing and rhythmic gymnastics. Firedancing is often performed to music. Fire dancing has been a traditional part of cultures from around the world, and modern fire performance often includes visual and stylistic elements from many traditions.
Fire dancing is a very dangerous performance art, and fire safety precautions should always be taken.

Fire apparatuses

The various tools used by the fire performance community borrow from a variety of sources. many have martial sources like swords, staves, poi, and whips, where some seem specifically designed for the fire community. The use of these tools is limited only by the imagination of their users. Some tools lend themselves to rhythmic swinging and twirling, others to martial kata, and others to more subtle use. Some common tools are:
  • Poi - A pair of roughly arm-length chains with handles attached to one end, and bundle of wicking material on the other.
  • Staff - A rod of wood or metal, with wicking material applied to one or both ends. Staves are generally used in pairs or individually, though many performers are now experimenting with three or more staves.
  • Fire hoop - hoop with spokes and wicking material attached.
  • Fans - A large metal fan with one or more wicks attached to the edges.
  • Fire umbrella - an umbrella that has the cloth removed, with kevlar tips.
  • Fire meteor - A long length of chain or rope with wicks, or small bowls of liquid fuel, attached to both ends.
  • Nunchaku - Nunchaku with wicking material, usually at either end.
  • Batons
  • Fire stick - Like a traditional devil stick, with wicks on both ends of the central stick.
  • Torch - A short club or torch, with a wick on one end, and swung like Indian clubs or tossed end-over-end like juggling clubs.
  • Fire-knives - Short staves with blades attached to the ends and wicking material applied to the blade. Fireknives are the traditional Polynesian fire implement and have been in use since the 1940s.
  • Fire rope dart - A wick, sometimes wrapped around a steel spike, at the end of a rope or chain ranging from 6–15 feet long, with a ring or other handle on the opposite end.
  • Fire sword - either a real sword modified for fire, or one specifically built for the purpose of fire shows.
  • Chi ball/Fire orb - 2 rings or handles with a wick attached between them by a thin wire.
  • Finger wands - Short torches attached to individual fingers.
  • Palm torches - Small torches with a flat base meant to be held upright in the palm of the hand.
  • Fire whips - Lengths of braided aramid fibre tapered to make a bullwhip, usually with a metal handle about 12 inches long.
  • Jumblymambas - a triple ended fire object for juggling, twirling and manipulation
  • Fire cannons - a propane flame effect device; larger ones can shoot a pillar of fire up to 200+ feet in the air, although they usually are mounted to a base or vehicle.
  • Fire poofers - Similar to fire cannons, but much smaller and made to be held, with fuel stored in a "backpack" fashioned of one or more propane tanks.
  • Fire Balls - Specially constructed juggling balls, either solid balls dipped in fuel and juggled with protective gloves, or ones designed to contain the flame in the centre of the ball.
  • Wearable Fire- Headdresses, hip belts, arm bands, or other garments made typically of metal with kevlar torches attached. Can be worn while fire dancing.
The variety of available tools took a sharp swing upwards in 2000, and as the numbers of dedicated fire tool makers increased, many makers added their own ingenuity to the art and expand the performance potential even more. Frequently, new tools appear from home tinkering and enter the public domain after a few performances.

Materials and construction

The typical construction of fire performance tools involves a metallic structure with wicking material made from fibreglass, cotton, or Kevlar blended with fibreglass, Nomex, and other poly-aramids. Kevlar-blend wicks are the most common, and are considered standard equipment in modern fire performance. Though most wick suppliers refer to their wick simply as Kevlar, almost no suppliers sell a 100% Kevlar wick, which is both expensive and not particularly absorbent. Most serious contemporary performers avoid cotton and other natural materials because such wicks disintegrate after relatively few uses, and can come apart during use, showering the performer and audience with flaming debris.
A typical poi construction would consist of a single or double-looped handle made of webbing, Kevlar fabric, or leather. This is connected to a swivel and a length of chain or cable. This chain or cable then connects to another swivel, and then to the wick, which is made out of tape wick (a wide, flat webbing made of wick material), or rope wick. The wick material is typically folded or tied to a central core in either a knot or lanyard-type fold.
The chain or cable can be anything from stainless steel wire rope (preferred by some for its low cost, light weight, high strength, and almost invisible profile, but not by others because it tangles easily) to dog chain (preferred by some for its heft and low cost) to industrial ball chain, which is the most common chain for fire performance equipment. Made of nickel-plated steel, stainless steel, or black-oxide brass, ball chain in the #13 to #20 size ranges provides excellent strength, a fluid feel, and great tangle prevention. Since every link on the chain swivels, one can eliminate dedicated swivels from a design, and body wrapping and chain wrapping moves become much easier. Extra cost and a higher weight to durability ratio are the biggest downsides to ball chain.
A fire staff typically consists of a long cylindrical section of either aluminium tube (lighter, more suitable for fast-spinning tricks) or wood (heavier, more suited to 'contact' moves in which the staff retains contact with the performer throughout the trick; see contact juggling) with a length of wick secured at either end, usually with screws. Wooden-cored staves often have thin sheet metal wrapped around the ends to prevent charring of the wood from the heat - this will have holes drilled through it to allow the wick to be screwed securely into the core. Metal staves generally have a length of wooden dowel inserted into each end; holes are drilled through the metal to allow the wicks' screws to gain firm purchase on the wooden core. A grip of some sort is usually fashioned in the centre of the staff to provide a comfortable hand-hold - most commonly leather, or a soft, self-adhesive grip of a type designed for hockey sticks or tennis rackets.

Important factors in equipment construction

Building high quality fire performance equipment involves the balancing of a number of factors to achieve performance suited for the specific intended use by the performer. Even if you are planning on buying prefabricated equipment, understanding the following factors and how they interrelate will allow you to best purchase the right implement.
  • Balance - Balance is how the weight is distributed in the implement. It is critical when making staffs, torches, hula hoops, clubs and swords, as balance will determine the axis around which the implement rotates.
  • Weight- Making implements heavier will, up to a certain point, allow you to spin them faster. However weight will also make the implement increasingly unwieldy. Also, heavy implements are more likely to lead to repetitive stress disorder, and cause injuries if you make mistakes. Heavier implements make certain types of contact juggling much easier, and certain high speed manipulation more difficult.
  • Wick size - Generally, the more exposed surface area of wick on the prop, the larger the flame. More wick will increase the fuel the implement will hold and if wick is layered increase burn time. The prop will also be heavier, and more expensive to construct. The more fuel the prop holds the larger the increase in weight after fuelling.
  • Cost - The fourth factor is cost. Frequently new prop development, and sometimes even building standard designs, require extra materials and tools that are not readily available. Even dedicated home tinkerers find themselves weighing the cost of purchasing versus the cost and time of build at home.

Fuels

Nearly all modern fire dancing apparatus rely on a liquid fuel held in the wick. There are many choices for fuels, each differing in properties. Individuals select a fuel or a blend of fuels based on safety, cost, availability, and the desirability of various characteristics like colour of flame, heat of flame, and solubility. There are also geographic variances in fuels used, based on local availability, pricing and community perception. For example, American firespinners commonly use coleman gas or 50/50 mixes whilst British firespinners almost exclusively use paraffin oil (which the Americans call kerosene or jet fuel). Frequently, particularly in areas not fully industrialized, the fuel available is the residue from productions of more refined fuels. Travelling performers can find themselves spinning highly toxic, smokey, or carcinogenic fuels.
  • Isoparaffin oil, some known types include Pegasol 3440 special, Shellsol T, Isopar G. MSDS lists them as Naphtha (petroleum), heavy alkylates. Performers seek isoparaffins with low aromatic, benzene and sulfur contents. These can be odourless, burn clean with little smoke and are available in a range of flash points. Little known or used in the US.
  • White gas, also known as Coleman fuel, naphtha, or petroleum ether - This hot, volatile fuel is popular because it is easy to ignite, burns brightly, evaporates cleanly, and does not leave smoke or residues on wicks and bodies. However, it burns hot and quick, limiting the burn time, and potentially increasing the risk of burns. This is the preferred fuel for performers who do indoor shows in the US. Becoming increasingly more difficult to obtain in the US due to its alternate use in Meth-amphetamine production.
  • Kerosene/paraffin oil - This is a popular fuel due to its low cost and long burn times. Kerosene is a generic term that covers a broad range of fuels ranging from gasoline to diesel fuel. It is normally a mixture of hydrocarbons. Almost every maker of kerosene has different purity standards and different flash points. Some home fuel oils are nearly pure paraffins (alkanes and iso-alkanes) whereas others are almost completely benzene and refinery residue.
  • Lamp oil - Lamp oil is an oily, non-volatile fuel. Typically sporting the highest flash point of all the petrol distillates in liquid form, lamp oils are the most difficult to light and longest burning fuels. Many products sold as lamp oil contain a limited amount of non-alkane petrol distillates (benzene, et al.), and many have colourings and scent additives that have some toxic potential. Even the purest grades of lamp oil burn quite smokily (though less irritating and toxic), and thus make it preferred for outdoor use. The soot from burned lamp oil can be difficult to wash out of clothing.
  • Alcohol fuels are usually ethanol, methanol, or isopropyl. Industrial or lab alcohol is usually ethanol with methanol, acetone or other denaturing agents added. Denatured alcohols can be up to 95% ethanol, or as little as 50%. An MSDS sheet of the mixture will indicate the exact contents.
Note: The flame is blue to orange, depending on methanol content, and fairly dim. However, when mixed with chemicals such as lithium chloride, copper chloride and boric acid, various colours of flame can be created. Lithium compounds produce pinks, copper compounds produce greens and blues, and boric acid produces green. Other chemicals may produce other colours, and performers often experiment with various choices. Use of chemicals like these may produce some toxic vapours, and have a tendency to destroy wicks. Due to the weak flame, price and toxicity of methanol, it is usually only used for coloured flame production and in mixes.
  • Biodiesel - Biodiesel is a fuel produced by refinement or transesterification of vegetable oil (used or virgin) using methoxide composed of methanol and lye. Both KOH, potassium hydroxide and NaOH, sodium hydroxide can be used in the process but only one or the other, never both in the same batch. This produces glycerin and methyl esters, aka Biodiesel. The fuel is designed for use in diesel vehicles, but is a fairly safe and practical fuel for fire performance. Like kerosene, it is difficult to ignite by itself, and produces a dim, long-lasting flame that may smell a bit like French fries, depending on the source. It is often mixed with white gas to produce an easy-to-ignite, long-burning fuel.

Safety

Metal parts on fire tools have a high heat transfer coefficient and may burn on contact; the wick has a lower coefficient and is less likely to cause burns directly, but can spray or spread fuel. Costumes from non-flammable or flame retardant materials, such as leather or treated cotton, are preferred when employing fire; synthetic materials tend to melt when burned, resulting in severe burns to the wearer.
Fire tools require a safety regime to address the risks of setting fire to the user, bystanders, or the surroundings. Typical elements of such a regimen include a sober, rested, and alert spotter who has access to an ABC Dry Chemical fire extinguisher for putting out material and fuel fires (water-based extinguishers may spread oil fires), a damp towel or woolen/duvetyne fire retardant blanket (for extinguishing burning clothes and fire toys), a bucket of water (for the eventuality of out-of-control fires), and plastic wrap (for protecting burns that require hospitalisation).[1] Typically, a metal container (located away from the performance area) that can quickly be sealed (so as to be airtight) is used as a fuel dump; with the lid in place, fuel fires may be extinguished.

History

Fire dancing using different techniques is a part of the historic culture of some areas of the world. Ancient Aztecs performed a fire dance dedicated to Xiuhtecuhtli, the god of fire.[2] The Aztec fire dance is performed today for tourists in Mexico. In Bali, the Angel Dance and the Fire Dance, regularly performed for tourists, have origins in ancient rituals. Both the Angel Dance and the Fire Dance originated in a trance ritual called the sanghyang, a ritual dance "performed to ward off witches at the time of an epidemic."[3] Also known as the "horse dance" men perform the dance by holding rods representing horses, while leaping around burning coconut husks, and walking through the flames. French Polynesia, Antigua, Cuba and Saint Lucia are other locations where fire dances are recreated for tourists. The Siddha Jats of the Thar Desert in India perform traditional fire dances as part of the Spring festival. Fire dancing is performed to music played on drums and the behr. There are variations of the fire dancing; men often perform a dance that involves walking on hot coals,[4] while women perform a dance while balancing flaming tin pots on their heads. Today this ritual is often performed for tourists.

Modern developments in fire performance

During the period from the mid-1990s to the early 2000s, fire dancing grew from a relatively obscure and marginalized native tradition,[citation needed] and a talent and skill of the baton twirler or circus artist, to a widespread and almost commonplace occurrence at raves, rock concerts, night clubs, beach parties, camping festivals, cabarets and hotel shows. Many[who?] attribute the discipline's rapid growth in popularity to the Burning Man festival, where many thousands were exposed to fire dancing who had never seen or heard of it before. Another powerful force was the rise of internet chat and bulletin board cultures, which allowed aspiring dancers in isolated areas to communicate with the then-limited pool of skilled performers far outside of their geographic confines.
As the number of fire dancers multiplied exponentially[citation needed], individual performers and troupes began to experiment with new equipment concepts (i.e., beyond the traditional staff, fireknives and poi) and with hybrid performance art concepts. The following is an incomplete list of such show varieties, whose categories are general and tend to overlap.
  • Traditional fire shows: Traditional shows often incorporate Polynesian costuming and other cultural elements. Many conform to the guidelines or are inspired by the annual World Fireknife Competition and Samoa Festival.
  • Standard modern shows: These usually include performers in tight and perhaps even risqué costumes with elaborate face paint, performing with poi, staffs, and other standard implements. Such shows often include fire breathing techniques as well. Most people think of this type of performance when they think of fire dancing.
  • Fire theatre: Such shows are theatrical shows which include fire and fire performance as elements of staged dramatic presentations. Often the fire performance is a small element of the larger show. These shows tend to use more elaborate props and costuming and focus less on technical skill.
  • Fire fetish show: Such shows are recognizable by more overt sexuality in the performance and often extremely risqué costuming, nudity, and implied or actual sexual contact between performers, and are often seen as a fusion between exotic dancing or burlesque with fire dancing. Thus, fire fetish refers to a particular style of performance, and not a sexual fetish on the part of the performer, as would pyrophilia.
  • Erotic fire show: Such shows may be seen as simply a normal improvised fire dance but with emphasis on sexually arousing body gyrations, seductive facial expressions, an eroticised musical selection (such as R&B or downtempo music), and minimal clothing of the performer, thus promoting sexual arousal or desire in addition to the expected visual entertainment for an audience. Unlike a fire fetish show, this performance is generally more low-key, slower in tempo, and may be performed by a solo dancer in front of a small and select audience, often a spouse or romantic partner. This performance is considered[by whom?] to be an active and visually exciting form of ritual foreplay. However this type of show is usually only enticing to a select audience and is generally unpopular by the mainstream community.
  • Ritual fire show: Such shows are usually a fusion of pagan or occult ceremony with fire and fire performance. They focus less on technical skill, and more on the use of the fire dancer to highlight the ritual.
  • Fire and belly dance: Such shows are a fusion of Middle Eastern belly dancing (raqs sharqi) and combine elements of fire dancing and belly dancing. Often the dancers use palm torches and fire swords made to resemble scimitars.
  • Fire comedy jugglers combine many of the skills of other fire performers but also include juggling, which is rarer in other spinners[citation needed]. The juggler also includes comedy to round out their routines, like lighting their behinds on fire.
Other performance variations continue to emerge as fire dancing becomes more widespread and commonplace.
  • Cirque Du Soleil has for the first time incorporated contemporary fire dance techniques in its Zaia production in Macau. Previous Cirque Du Soleil shows 'Alegria' and 'O' relied on the skills of traditional fire knife artists for fire performances. Recognition of contemporary fire dance and modern prop techniques has previously been very limited in the professional circus community. Dan Miethke[1] is the current fire coach and lead fire artist in Zaia.
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Whale Shark - The World's Biggest Fish

The whale shark is the world's biggest fish. Here are some other details about the whale shark.
Sharks are fish who have some of the largest sizes as compared to all aquatic life. Sharks come in all sizes, ranging from twenty two centimeters, and aptly named the pygmy shark to the largest fish in the world, the whale shark.

The Whale Shark scientific name Rhincodon typus is from the family Rhincodontidae and genus Rhinocodon. It is of the class Chondrichthyes and subclass Elasmobranichii. It is believed to trace it's origins some sixty million years ago. The Whale shark is the largest living fish species.

The Whale Shark is feeds by straining food particles from water and therefore is termed as a filter feeder or a suspension feeder. They typically pass water or a specialized structure to feed. The mouth of the Whale Shark measure up to five feet. It's mouth can contain up to three hundred and fifty rows of teeth. The shark has a flat and wide head and its eyes are located towards the front of the head.

Its body is mostly gray and it has a white patch on its belly. The whale shark is characterized by the three prominent ridges that run along each side of its body. It also has a checkerboard pattern of yellow spots and stripes.The whale shark has two pairs of pectoral and dorsal fins. Its skin can be up to ten centimeters thick.
This size makes the whale shark the biggest fish in the world. However, the whale shark uses its entire body for swimming, and therefore, it is not as good a swimmer as compared to other sharks and fishes. This unusual trait gives the whale shark a unimpressive speed of about five kilometers per hour.

The Whale Shark normally inhabits the warm temperature and tropical climates. It was first identified in the year 1828, with the harpooning of a fifteen feet long member of the species in Table Bay, South Africa. The Whale Shark is the largest specimen of aquatic life ever caught.

The largest fish ever caught was caught on November 11, 1947 near the island of Baba. It was about forty two feet long and weighed more than twenty tons. It had a girth of about twenty three feet.

Though the whale shark is the largest shark ever, it is a misunderstood predator. It's massive size creates an illusion about the dangers to humankind, however, the whale shark does not pose any significant danger to uses. Whale Sharks are not man-eaters and can actually be playful and gentle with divers. The whale shark attacks humans only when provoked, and divers can actually dive alongside this great fish, with the only risk of being accidentally heat by its large tail fin.

The whale shark feeds on squids, other aquatic vertebrates, drifting aquatic organisms known as phytoplanktons, planktons, macro-algae and krill. Contrary to popular belief, their immense rows of teeth play no role in their feeding. The shark gulps in a mouthful of water and then exhales the water through its gills. The plankton is trapped in the whale shark's mouth during this procedure. The whale shark also has a sieve like apparatus, which is unique to the whale shark. This prevents the escape of anything except fluid through the gills. The whale shark can therefore trap anything up to three millimeters.
There have been many rumors about the size of the whale shark and the largest fish ever caught or seen. Some claims even say that whale sharks the size of about seventy five feet have been found. One famous rumor is about the ship Maurguni, which rammed against a whale shark, which resulted in the whale being stuck in the prow of the ship, being four to five meters on one side and about thirteen meters on the other. 

from: http://www.buzzle.com/articles/whale-shark-worlds-biggest-fish.html 
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Selasa, 03 April 2012

Marine biology


Marine biology is the scientific study of organisms in the ocean or other marine or brackish bodies of water. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather than on taxonomy. Marine biology differs from marine ecology as marine ecology is focused on how organisms interact with each other and the environment, and biology is the study of the organisms themselves.
Marine life is a vast resource, providing food, medicine, and raw materials, in addition to helping to support recreation and tourism all over the world. At a fundamental level, marine life helps determine the very nature of our planet. Marine organisms contribute significantly to the oxygen cycle, and are involved in the regulation of the Earth's climate.[1] Shorelines are in part shaped and protected by marine life, and some marine organisms even help create new land.[2]
Marine biology covers a great deal, from the microscopic, including most zooplankton and phytoplankton to the huge cetaceans (whales) which reach up to a reported 30 meters (98 feet) in length.
The habitats studied by marine biology include everything from the tiny layers of surface water in which organisms and abiotic items may be trapped in surface tension between the ocean and atmosphere, to the depths of the oceanic trenches, sometimes 10,000 meters or more beneath the surface of the ocean. It studies habitats such as coral reefs, kelp forests, tidepools, muddy, sandy and rocky bottoms, and the open ocean (pelagic) zone, where solid objects are rare and the surface of the water is the only visible boundary.
A large proportion of all life on Earth exists in the oceans. Exactly how large the proportion is unknown, since many ocean species are still to be discovered. While the oceans constitute about 71% of the Earth's surface, due to their depth they encompass about 300 times the habitable volume of the terrestrial habitats on Earth.
Many species are economically important to humans, including food fish. It is also becoming understood that the well-being of marine organisms and other organisms are linked in very fundamental ways. The human body of knowledge regarding the relationship between life in the sea and important cycles is rapidly growing, with new discoveries being made nearly every day. These cycles include those of matter (such as the carbon cycle) and of air (such as Earth's respiration, and movement of energy through ecosystems including the ocean). Large areas beneath the ocean surface still remain effectively unexplored.

Subfields

The marine ecosystem is large, and thus there are many sub-fields of marine biology. Most involve studying specializations of particular animal groups, such as phycology, invertebrate zoology and ichthyology.
Other subfields study the physical effects of continual immersion in sea water and the ocean in general, adaptation to a salty environment, and the effects of changing various oceanic properties on marine life. A subfield of marine biology studies the relationships between oceans and ocean life, and global warming and environmental issues (such as carbon dioxide displacement).
Recent marine biotechnology has focused largely on marine biomolecules, especially proteins, that may have uses in medicine or engineering. Marine environments are the home to many exotic biological materials that may inspire biomimetic materials.

Related fields

Marine biology is a branch of oceanography and is closely linked to biology. It also encompasses many ideas from ecology. Fisheries science and marine conservation can be considered partial offshoots of marine biology (as well as environmental studies).

Animals

Birds

Birds adapted to living in the marine environment are often referred to as seabirds. Examples include albatross, penguins, gannets, and auks. Although they spend most of their lives in the ocean, species such as gulls can often be found thousands of miles inland.

Fish

Fish anatomy includes a two-chambered heart, operculum, swim bladder, scales, fins, lips, eyes and secretory cells that produce mucous. Fish breathe by extracting oxygen from water through their gills. Fins propel and stabilize the fish in the water.
Well known fish include: sardines, anchovy, ling cod, clownfish (also known as anemonefish), and bottom fish which include halibut or ling cod. Predators include sharks and barracuda.

Invertebrates

As on land, invertebrates make up a huge portion of all life in the sea. Invertebrate sea life includes Cnidaria such as jellyfish and sea anemones; Ctenophora; sea worms including the phyla Platyhelminthes, Nemertea, Annelida, Sipuncula, Echiura, Chaetognatha, and Phoronida; Mollusca including shellfish, squid, octopus; Arthropoda including Chelicerata and Crustacea; Porifera; Bryozoa; Echinodermata including starfish; and Urochordata including sea squirts or tunicates.

Mammals

There are five main types of marine mammals.

Reptiles

Reptiles which inhabit or frequent the sea include sea turtles, sea snakes, terrapins, the marine iguana, and the saltwater crocodile. Most extant marine reptiles, except for some sea snakes, are oviparous and need to return to land to lay their eggs. Thus most species, excepting sea turtles, spend most of their lives on or near land rather than in the ocean. Despite their marine adaptations, most sea snakes prefer shallow waters nearby land, around islands, especially waters that are somewhat sheltered, as well as near estuaries.[3][4] Some extinct marine reptiles, such as ichthyosaurs, evolved to be viviparous and had no requirement to return to land.

Fungi

Over 1500 species of fungi are known from marine environments.[5] These parasitize marine algae or animals, or are saprobes on algae, corals, protozoan cysts, sea grasses, wood and other substrata, and can also be found in sea foam.[6] Spores of many species have special appendages which facilitate attachment to the substratum.[7] A very diverse range of unusual secondary metabolites is produced by marine fungi.[8]

Plants and algae

Plant life is widespread and very diverse under the ocean. Microscopic photosynthetic algae contribute a larger proportion of the worlds photosynthetic output than all the terrestrial forests combined. Most of the niche occupied by sub plants on land is actually occupied by macroscopic algae in the ocean, such as Sargassum and kelp, which are commonly known as seaweeds that creates kelp forests. The non algae plants that survive in the sea are often found in shallow waters, such as the seagrasses (examples of which are eelgrass, Zostera, and turtle grass, Thalassia). These plants have adapted to the high salinity of the ocean environment. The intertidal zone is also a good place to find plant life in the sea, where mangroves or cordgrass or beach grass might grow. Microscopic algae and plants provide important habitats for life, sometimes acting as hiding and foraging places for larval forms of larger fish and invertebrates.

Microscopic life

Microscopic life undersea is incredibly diverse and still poorly understood. For example, the role of viruses in marine ecosystems is barely being explored even in the beginning of the 21st century.
The role of phytoplankton is better understood due to their critical position as the most numerous primary producers on Earth. Phytoplankton are categorized into cyanobacteria (also called blue-green algae/bacteria), various types of algae (red, green, brown, and yellow-green), diatoms, dinoflagellates, euglenoids, coccolithophorids, cryptomonads, chrysophytes, chlorophytes, prasinophytes, and silicoflagellates.
Zooplankton tend to be somewhat larger, and not all are microscopic. Many Protozoa are zooplankton, including dinoflagellates, zooflagellates, foraminiferans, and radiolarians. Some of these (such as dinoflagellates) are also phytoplankton; the distinction between plants and animals often breaks down in very small organisms. Other zooplankton include cnidarians, ctenophores, chaetognaths, molluscs, arthropods, urochordates, and annelids such as polychaetes. Many larger animals begin their life as zooplankton before they become large enough to take their familiar forms. Two examples are fish larvae and sea stars (also called starfish).

Marine habitats

Marine habitats can be divided into coastal and open ocean habitats. Coastal habitats are found in the area that extends from the shoreline to the edge of the continental shelf. Most marine life is found in coastal habitats, even though the shelf area occupies only seven percent of the total ocean area. Open ocean habitats are found in the deep ocean beyond the edge of the continental shelf
Alternatively, marine habitats can be divided into pelagic and demersal habitats. Pelagic habitats are found near the surface or in the open water column, away from the bottom of the ocean. Demersal habitats are near or on the bottom of the ocean. An organism living in a pelagic habitat is said to be a pelagic organism, as in pelagic fish. Similarly, an organism living in a demersal habitat is said to be a demersal organism, as in demersal fish. Pelagic habitats are intrinsically shifting and ephemeral, depending on what ocean currents are doing.
Marine habitats can be modified by their inhabitants. Some marine organisms, like corals, kelp and seagrasses, are ecosystem engineers which reshape the marine environment to the point where they create further habitat for other organisms.

Intertidal and shore

Intertidal zones, those areas close to shore, are constantly being exposed and covered by the ocean's tides. A huge array of life lives within this zone.
Shore habitats span from the upper intertidal zones to the area where land vegetation takes prominence. It can be underwater anywhere from daily to very infrequently. Many species here are scavengers, living off of sea life that is washed up on the shore. Many land animals also make much use of the shore and intertidal habitats. A subgroup of organisms in this habitat bores and grinds exposed rock through the process of bioerosion.

Reefs

Reefs comprise some of the densest and most diverse habitats in the world. The best-known types of reefs are tropical coral reefs which exist in most tropical waters; however, reefs can also exist in cold water. Reefs are built up by corals and other calcium-depositing animals, usually on top of a rocky outcrop on the ocean floor. Reefs can also grow on other surfaces, which has made it possible to create artificial reefs. Coral reefs also support a huge community of life, including the corals themselves, their symbiotic zooxanthellae, tropical fish and many other organisms.
Much attention in marine biology is focused on coral reefs and the El Niño weather phenomenon. In 1998, coral reefs experienced the most severe mass bleaching events on record, when vast expanses of reefs across the world died because sea surface temperatures rose well above normal.[9][10] Some reefs are recovering, but scientists say that between 50% and 70% of the world's coral reefs are now endangered and predict that global warming could exacerbate this trend.[11][12][13][14]

Open ocean

The open ocean is relatively unproductive because of a lack of nutrients, yet because it is so vast, in total it produces the most primary productivity. Much of the aphotic zone's energy is supplied by the open ocean in the form of detritus. The open ocean consists mostly of jellyfish and its predators such as the mola mola.

Deep sea and trenches

The deepest recorded oceanic trenches measure to date is the Mariana Trench, near the Philippines, in the Pacific Ocean at 10,924 m (35,838 ft). At such depths, water pressure is extreme and there is no sunlight, but some life still exists. A white flatfish, a shrimp and a jellyfish were seen by the American crew of the bathyscaphe Trieste when it dove to the bottom in 1960.[15]
Other notable oceanic trenches include Monterey Canyon, in the eastern Pacific, the Tonga Trench in the southwest at 10,882 m (35,702 ft), the Philippine Trench, the Puerto Rico Trench at 8,605 m (28,232 ft), the Romanche Trench at 7,760 m (24,450 ft), Fram Basin in the Arctic Ocean at 4,665 m (15,305 ft), the Java Trench at 7450 m (24,442 ft), and the South Sandwich Trench at 7,235 m (23,737 ft).
In general, the deep sea is considered to start at the aphotic zone, the point where sunlight loses its power of transference through the water.[citation needed] Many life forms that live at these depths have the ability to create their own light known as bio-luminescence.
Marine life also flourishes around seamounts that rise from the depths, where fish and other sea life congregate to spawn and feed. Hydrothermal vents along the mid-ocean ridge spreading centers act as oases, as do their opposites, cold seeps. Such places support unique biomes and many new microbes and other lifeforms have been discovered at these locations .[citation needed]

Distribution factors

An active research topic in marine biology is to discover and map the life cycles of various species and where they spend their time. Marine biologists study how the ocean currents, tides and many other oceanic factors affect ocean lifeforms, including their growth, distribution and well-being. This has only recently become technically feasible with advances in GPS and newer underwater visual devices.[citation needed]
Most ocean life breeds in specific places, nests or not in others, spends time as juveniles in still others, and in maturity in yet others. Scientists know little about where many species spend different parts of their life cycles. For example, it is still largely unknown where sea turtles and some sharks travel. Tracking devices do not work for some life forms, and the ocean is not friendly to technology. This is important to scientists and fishermen because they are discovering that by restricting commercial fishing in one small area they can have a large impact in maintaining a healthy fish population in a much larger area far away.
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