Time capsule

A time capsule is a historic cache of goods and/or information, usually intended as a method of communication with people in the future. Time capsules are sometimes created and buried during celebrations such as a World Fair, cornerstone laying for a building, or at other events. The phrase "time capsule" has been in use since about 1939.

Background

Time capsules can be classified into two types: intentional and unintentional. Intentional time capsules are placed on purpose and are usually intended to be opened at a particular future date. Unintentional time capsules are usually archaeological in nature. Discoveries of cultural significance are often found in standard archaeological digs as well as those from volcanic eruptions such as Pompeii and Vesuvius.
The concept of time capsules is not recent. The Epic of Gilgamesh, among humanity's earliest literary works, begins with instructions on how to find a box of copper inside a foundation stone in the great walls of Uruk - in the box is Gilgamesh's tale, written on a lapis tablet. There were other time capsules 5,000 years ago as vaults of artifacts hidden inside the walls of Mesopotamian cities. Egyptian and other ancient tombs are effectively time capsules as well.
What is now thought of as a "time capsule" has more recent origins. In 1937, during preparations for the 1939 New York World's Fair, it was suggested to bury a "time bomb" for 5,000 years (until 6939)—the less inflammatory name of "time capsule" was suggested, and the name has stuck since. The 1939 New York World's Fair time capsule was created by Westinghouse as part of their exhibit, It was 90" long, with an interior diameter of 6.5 inches, and weighed 800 pounds. Westinghouse named the copper, chromium and silver alloy "Cupaloy", claiming it had the same strength as mild steel. It contained everyday items such as a spool of thread and doll, a Book of Record (description of the capsule and its creators), a vial of staple food crop seeds, a microscope and a 15-minute RKO Pathe Pictures newsreel. Microfilm spools condensed the contents of a Sears Roebuck catalog, dictionary, almanac, and other texts. This first modern time capsule was followed in 1965 by a second capsule at the same site, but 10 feet to the north of the original. Both capsules are buried 50 feet below Flushing Meadows Park, site of the Fair. Both the 1939 and 1965 Westinghouse Time Capsules are meant to be opened in 6939. More recently, in 1985, Westinghouse created a smaller, Plexiglas shell to be buried beneath the New York Marriott Marquis hotel, in the heart of New York's theater district. However, this time capsule was never put in place.
The Crypt of Civilization (1936) at Oglethorpe University, scheduled to be opened in 8113, is generally regarded to be the first successful implementation of a modern time capsule, although it was not called a time capsule at the time. George Edward Pendray is responsible for coining the term "time capsule." The Crypt of Civilization is a sealed airtight chamber located at Oglethorpe University in Atlanta, Georgia. The crypt consists of preserved artifacts scheduled to be opened in the year 8113 CE. The 1990 Guinness Book of World Records cites the crypt as the "first successful attempt to bury a record of this culture for any future inhabitants or visitors to the planet Earth." The Crypt of Civilization chamber is positioned on Appalachian granite bedrock located in the foundation of Phoebe Hearst Memorial Hall, a granite Gothic style academic building at Oglethorpe University. The room was converted from a swimming pool from 1937 to 1940 and the walls were lined with enamel plates embedded in pitch.
The Crypt room is 20 feet (6 m) long, 10 feet (3 m) high and 10 feet (3 m) wide. The chamber is under a stone roof seven feet thick and lies over a two-foot stone floor. It is sealed with a stainless steel door welded in place.
Thomas Kimmwood Peters (1884–1973) supervised construction and served as its archivist
During the socialist period in the USSR, many time capsules were buried with messages to the people who would live in the future communist society.
New Zealand developed a time capsule project called "Millennium Vault" for the turn of the 20th-century century. The project developers buried it beneath a pyramid.
Currently, four time capsules are "buried" in space. The two Pioneer Plaques and the two Voyager Golden Records have been attached to spacecraft for the possible benefit of spacefarers in the distant future. A fifth time capsule, the KEO satellite, will be launched in 2009 or 2010, carrying individual messages from Earth's inhabitants addressed to earthlings around the year 52,000, when KEO will return to Earth.
The International Time Capsule Society was created to maintain a global database of all existing time capsules.

Construction of a time capsule

The International Time Capsule Society provides tips for building a time capsule.
1. Select a retrieval date
2. Choose an "archivist" or director
3. Select a container
4. Find a secure indoor location, not "buried"
5. Secure items for time storage.
6. Have a solemn "sealing ceremony"
7. Don't forget the capsule's existence
8. Inform the International Time Capsule Society of your completed time capsule project.

Criticism

According to time capsule historian William Jarvis, most intentional time capsules usually do not provide much useful historical information: they are typically filled with "useless junk", new and pristine in condition, that tells little about the people of the time. Many time capsules today contain only artifacts of limited value to future historians. Historians suggest that items which describe the daily lives of the people who created them, such as personal notes, pictures, and documents, would greatly increase the value of the time capsule to future historians.
If time capsules have a museum-like goal of preserving the culture of a particular time and place for study, they fulfill this goal very poorly in that they, by definition, are kept sealed for a particular length of time. Subsequent generations between the launch date and the target date will have no direct access to the artifacts and therefore these generations are prevented from learning from the contents directly. Therefore, time capsules can be seen, in respect to their usefulness to historians, as poorly implemented museums.
Historians also concede that there are many preservation issues surrounding the selection of the media to transmit this information to the future. Some of these issues include the obsolescence of technology and the deterioration of electronic and magnetic storage media, and possible language problems if the capsule is dug up in the distant future. Many buried time capsules are lost, as interest in them fades and the exact location is forgotten, or are destroyed within a few years by groundwater. A proposed deep time capsule, The Ozymandias Project addresses many of these issues.

Crepuscular rays

Crepuscular rays, in atmospheric optics are rays of sunlight that appear to radiate from a single point in the sky. These rays, which stream through gaps in clouds or between other objects, are columns of sunlit air separated by darker cloud-shadowed regions. The name comes from their frequent occurrences during crepuscular hours (those around dawn and dusk), when the contrasts between light and dark are the most obvious. Crepuscular is a term used to describe some animals that are primarily active during twilight, that is at dawn and at dusk. The word is derived from the Latin word crepusculum, meaning "twilight." Crepuscular is thus in contrast with diurnal and nocturnal behavior. Crepuscular animals may also be active on a bright moonlit night. Many animals that are casually described as nocturnal are in fact crepuscular. Within the definition of crepuscular are the terms matutinal (or "matinal") and vespertine, denoting species active in the dawn and dusk respectively.
The patterns of activity are thought to be an antipredator adaptation. Many predators forage most intensely at night, while others are active at mid-day and see best in full sun. Thus the crepuscular habit may reduce predation. Additionally, in hot areas, it may be a way of avoiding thermal stress while capitalizing on available light. Some crepuscular mammals include the Red Panda, cats, deer, moose, rabbits, chinchillas, ferrets, guinea pigs, hamsters, the common mouse, skunks, rats, wombats, quolls and capybaras. Crepuscular birds include the Common Nighthawk, Chimney Swift, American Woodcock, and Spotted Crake.
Some animals that are extinct were also crepuscular such as the Tasmanian Tiger.
Some species have different habits in the absence of predators. For example, the Short-eared Owl is crepuscular on those of the Galápagos Islands that have buzzard species, but diurnal on those without.
Many moths, beetles, flies, and other insects are crepuscular as well.

Appearance
Crepuscular rays are near-parallel, 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 the ice.
There are three primary forms of crepuscular rays:
i. Rays of light penetrating holes in low clouds (also called "Jacob's Ladder").
ii. Beams of light diverging from behind a cloud.
iii. Pale, pinkish or reddish rays that radiate from below the horizon. These are often mistaken for light pillars.
They are most common in Antarctica.

Anticrepuscular Rays
Crepuscular and anticrepuscular rays are generated in the same way. The rays in some cases may extend across the sky and appear to converge at the antisolar point, which is the point on the sky sphere directly opposite the sun, and they are called anticrepuscular rays. Like crepuscular rays, they are parallel shafts of sunlight from holes in the clouds, and their apparent convergence is a perspective effect.
Anticrepuscular rays are similar to crepuscular rays, but seen opposite the sun in the sky. Sunlight travels in straight lines, but the projections of these lines on Earth's spherical atmosphere are great circles. Hence, straight-line crepuscular rays from a setting (or rising) sun can appear to re-converge at the antisolar point. Anticrepuscular rays are most frequently visible near sunrise or sunset. Crepuscular rays are usually much brighter than anticrepuscular rays. This is because for crepuscular rays, seen on the same side of the sky as the sun, the atmospheric light scattering and making them visible is taking place at small angles (see Mie theory).
Although anticrepuscular rays appear to converge onto a point opposite the sun, the convergence is actually an illusion. The rays are in fact parallel, and the apparent convergence is to the vanishing point at infinity.

Color
Crepuscular rays are usually red or yellow in appearance because the path through the atmosphere at sunrise and sunset pass through up to 40 times as much air as rays from a high midday sun. Particles in the air scatter short wavelength light (blue and green) through Rayleigh scattering much more strongly than longer wavelength yellow and red light.

Alternative names
a) Sunbeams
b) Sunburst
c) Sun rays
d) Sun drawing water - from the ancient Greek belief that sunbeams drew water into the sky (an early description of evaporation)
e) Backstays of the sun - a nautical term, from the fact that backstays that brace the mast of a sailing ship converge in a similar way
f) Ropes of Maui - (originally. taura a Maui) from the Maori tale of Maui Potiki restraining the sun with ropes to make the days longer
g) Jacob's Ladder
h) Gateways to Heaven and Stairways to Heaven
i) God Rays
j) Cloud breaks
k) Fingers of God (or God's Fingers)
l) Volumetric lighting (used by the computer graphics industry

Karst topography

Karst topography is a landscape shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rock such as limestone or dolomite.
Due to subterranean drainage, there may be very limited surface water, even to the absence of all rivers and lakes. Many karst regions display distinctive surface features, with sinkholes or dolines being the most common. However, distinctive karst surface features may be completely absent where the soluble rock is mantled, such as by glacial debris, or confined by a superimposed non-soluble rock strata. Some karst regions include thousands of caves, even though evidence of caves that are big enough for human exploration is not a required characteristic of karst.

Background
The geographer Jovan Cvijić (1865–1927) was born in western Serbia and studied widely in the Dinaric Kras region. His publication of Das Karstphänomen (1893) established that rock dissolution was the key process and that it created most types of dolines, "the diagnostic karst landforms". The Dinaric Kras thus became the type area for dissolutional landforms and aquifers; the regional name kras, Germanicised as "karst", is now applied to modern and paleo-dissolutional phenomena worldwide. Cvijić related the complex behaviour of karstic aquifers to development of solutional conduit networks and linked it to a cycle of landform evolution. He is recognized as "the father of karst geomorphology".
Different terms for karst topography exist in other languages—for example, yanrong in Chinese and tsingy in Malagasy. The international community has settled on karst, the German name for Kras, a region in Slovenia partially extending into Italy, where it is called "Carso" and where the first scientific research of a karst topography was made. The name has a pre-Indo-European origin (from karra meaning "stone"), and in antiquity it was called "Carusardius" in Latin. The Slovene form grast is attested since 1177, and the Croatian kras since 1230

Chemistry

Karst landforms are generally the result of mildly acidic water acting on soluble bedrock such as limestone or dolostone. The carbonic acid that causes these features is formed as rain passes through the atmosphere picking up CO2, which dissolves in the water. Once the rain reaches the ground, it may pass through soil that may provide further CO2 to form a weak carbonic acid solution: H2O + CO2 → H2CO3 (the acid). Recent studies of sulfates, in karst waters, suggests sulfuric acid and hydrosulfuric acid may also play an important role in karst formation.
This mildly acidic water begins to dissolve the surface along with any fractures or bedding planes in the limestone bedrock. Over time, these fractures enlarge as the bedrock continues to dissolve. Openings in the rock increase in size, and an underground drainage system begins to develop, allowing more water to pass through the area, and accelerating the formation of underground karst features.
Somewhat less common than this limestone karst is gypsum karst, where the solubility of the mineral gypsum provides many similar structures to the dissolution and redeposition of calcium carbonate.

Formations

The karstification of a landscape may result in a variety of large or small scale features both on the surface and beneath. On exposed surfaces, small features may include flutes, runnels, clints and grikes, collectively called karren or lapiez. Medium-sized surface features may include sinkholes or cenotes (closed basins), vertical shafts, foibe (inverted funnel shaped sinkholes), disappearing streams, and reappearing springs. Large-scale features may include limestone pavements, poljes and blind valleys. Mature karst landscapes, where more bedrock has been removed than remains, may result in karst towers or haystack/eggbox landscapes. Beneath the surface, complex underground drainage systems (such as karst aquifers) and extensive caves and cavern systems may form.

Erosion along limestone shores, notably in the tropics, produces karst topography that includes a sharp makatea surface above the normal reach of the sea and undercuts that are mostly the result of biological activity or bioerosion at or a little above mean sea level. Some of the most dramatic of these formations can be seen in Thailand's Phangnga Bay and Halong Bay in Vietnam.
Calcium carbonate dissolved into water may precipitate out where the water discharges some of its dissolved carbon dioxide. Rivers which emerge from springs may produce tufa terraces, consisting of layers of calcite deposited over extended periods of time. In caves, a variety of features collectively called speleothems are formed by deposition of calcium carbonate and other dissolved minerals.
A karst river may disappear underground a number of times and spring up again in different places, usually under a different name (like Ljubljanica, the river of seven names).
An example of this is the Popo Agie River in Fremont County, Wyoming. Simply named "The Sinks" and Sinks Canyon State Park, the river flows into a cave in a formation known as the Madison Limestone, and then rises again a half-mile down the canyon in a placid pool. When the river was dyed, it took two hours for the dye to reach the rising a short distance away.

Hydrology

Farming in karst areas must take into account the lack of surface water. The soils may be fertile enough, and rainfall may be adequate, but rainwater quickly moves through the crevices into the ground, sometimes leaving the surface soil parched between rains.
A karst fenster is where an underground stream emerges onto the surface between layers of rock, cascades some feet, and then disappears back down, often into a sinkhole.
Water supplies from wells in karst topography may be unsafe, as the water may have run unimpeded from a sinkhole in a cattle pasture, through a cave and to the well, bypassing the normal filtering that occurs in a porous aquifer. Karst formations are cavernous and therefore have high rates of permeability, resulting in reduced opportunity for contaminants to be filtered out.
Groundwater in karst areas is just as easily polluted as surface streams. Sinkholes have often been used as farmstead or community trash dumps. Overloaded or malfunctioning septic tanks in karst landscapes may dump raw sewage directly into underground channels.
The karst topography itself also poses difficulties for human inhabitants. Sinkholes can develop gradually as surface openings enlarge, but quite often progressive erosion is unseen and the roof of an underground cavern suddenly collapses. Such events have swallowed homes, cattle, cars, and farm machinery.
The Driftless Area National Wildlife Refuge in Iowa protects Discus macclintocki, a species of ice age snail surviving in air chilled by flowing over buried karst ice formations.

Lithography

Lithography (from Greek λίθος - lithos, 'stone' + γράφω - graphο, 'to write') is a method for printing using a stone (lithographic limestone) or a metal plate with a completely smooth surface. Lithography uses oil or fat and gum arabic to divide the smooth surface into hydrophilic regions which accept the ink, and hydrophobic regions which reject it and thus become the background. By contrast, in intaglio printing a plate is engraved, etched or stippled to make cavities to contain the printing ink, and in woodblock printing and letterpress ink is applied to the raised surfaces of letters or images.
Invented by Bavarian author Alois Senefelder in 1796, lithography can be used to print text or artwork onto paper or another suitable material. Most books, indeed all types of high-volume text, are now printed using offset lithography, the most common form of printing production. The word "lithography" also refers to photolithography, a microfabrication technique used to make integrated circuits and microelectromechanical systems, although those techniques have more in common with etching than with lithography.

The principle of lithography

Lithography uses simple chemical processes to create an image. For instance, the positive part of an image would be a hydrophobic, or "water hating" chemical, while the negative image would be hydrophilic or "water loving". Thus, when the plate is introduced to a compatible printing ink and water mixture, the ink will adhere to the positive image and the water will clean the negative image. This allows a flat print plate to be used, enabling much longer and more detailed print runs than the older physical methods of printing (e.g., intaglio printing, Letterpress printing).

In the early days of lithography, a smooth piece of limestone was used (hence the name "lithography"—"lithos" (λιθος) is the ancient Greek word for stone). After the oil-based image was put on the surface, a solution of gum arabic in water was applied, the gum sticking only to the non-oily surface. During printing, water adhered to the gum arabic surfaces and avoided the oily parts, while the oily ink used for printing did the opposite.

Lithography on limestone

Lithography works because of the mutual repulsion of oil and water. The image is drawn on the surface of the print plate with a fat or oil-based medium (hydrophobic), which may be pigmented to make the drawing visible. A wide range of oil-based media is available, but the durability of the image on the stone depends on the lipid content of the material being used, and its ability to withstand water and acid. Following the drawing of the image, an aqueous solution of gum arabic, weakly acidified with nitric acid HNO3 is applied to the stone. The function of this solution is to create a hydrophilic layer of calcium nitrate salt, Ca(NO3)2, and gum arabic on all non-image surfaces. The gum solution penetrates into the pores of the stone, completely surrounding the original image with a hydrophilic layer that will not accept the printing ink. Using lithographic turpentine, the printer then removes any excess of the greasy drawing material, but a hydrophobic molecular film of it remains tightly bonded to the surface of the stone, rejecting the gum arabic and water, but ready to accept the oily ink.
When printing, the stone is kept wet with water. Naturally the water is attracted to the layer of gum and salt created by the acid wash. Printing ink based on drying oils such as linseed oil and varnish loaded with pigment is then rolled over the surface. The water repels the greasy ink but the hydrophobic areas left by the original drawing material accept it. When the hydrophobic image is loaded with ink, the stone and paper are run through a press which applies even pressure over the surface, transferring the ink to the paper and off the stone.

Senefelder had experimented in the early 1800s with multicolor lithography; in his 1819 book, he predicted that the process would eventually be perfected and used to reproduce paintings. Multi-color printing was introduced through a new process developed by Godefroy Engelmann (France) in 1837 known as Chromolithography. A separate stone was used for each colour, and a print went through the press separately for each stone. The main challenge was of course to keep the images aligned (in register). This method lent itself to images consisting of large areas of flat color, and led to the characteristic poster designs of this period.

The modern lithographic process

The earliest regular use of lithography for text was in countries using Arabic, Turkish and similar scripts, where books, especially the Qu'ran, were sometimes printed by lithography in the nineteenth century, as the links between the characters require compromises when movable type is used which were considered inappropriate for sacred texts.
High-volume lithography is used today to produce posters, maps, books, newspapers, and packaging — just about any smooth, mass-produced item with print and graphics on it. Most books, indeed all types of high-volume text, are now printed using offset lithography.
In offset lithography, which depends on photographic processes, flexible aluminum, polyester, mylar or paper printing plates are used in place of stone tablets. Modern printing plates have a brushed or roughened texture and are covered with a photosensitive emulsion. A photographic negative of the desired image is placed in contact with the emulsion and the plate is exposed to ultraviolet light. After development, the emulsion shows a reverse of the negative image, which is thus a duplicate of the original (positive) image. The image on the plate emulsion can also be created through direct laser imaging in a CTP (Computer-To-Plate) device called a platesetter. The positive image is the emulsion that remains after imaging. For many years, chemicals have been used to remove the non-image emulsion, but now plates are available that do not require chemical processing.

The plate is affixed to a cylinder on a printing press. Dampening rollers apply water, which covers the blank portions of the plate but is repelled by the emulsion of the image area. Ink, which is hydrophobic, is then applied by the inking rollers, which is repelled by the water and only adheres to the emulsion of the image area--such as the type and photographs on a newspaper page.
If this image were directly transferred to paper, it would create a mirror image and the paper would become too wet. Instead, the plate rolls against a cylinder covered with a rubber blanket, which squeezes away the water, picks up the ink and transfers it to the paper with uniform pressure. The paper rolls across the blanket drum and the image is transferred to the paper. Because the image is first transferred, or offset to the rubber drum, this reproduction method is known as offset lithography or offset printing. http://www.compassrose.com/static/Offset.jpg
Many innovations and technical refinements have been made in printing processes and presses over the years, including the development of presses with multiple units (each containing one printing plate) that can print multi-color images in one pass on both sides of the sheet, and presses that accommodate continuous rolls (webs) of paper, known as web presses. Another innovation was the continuous dampening system first introduced by Dahlgren instead of the old method which is still used today on older presses (conventional dampening), which are rollers covered in molleton (cloth) which absorbs the water. This increased control over the water flow to the plate and allowed for better ink and water balance. Current dampening systems include a "delta effect or vario " which slows the roller in contact with the plate, thus creating a sweeping movement over the ink image to clean impurities known as "hickies".
The advent of desktop publishing made it possible for type and images to be manipulated easily on personal computers for eventual printing on desktop or commercial presses. The development of digital imagesetters enabled print shops to produce negatives for platemaking directly from digital input, skipping the intermediate step of photographing an actual page layout. The development of the digital platesetter in the late twentieth century eliminated film negatives altogether by exposing printing plates directly from digital input, a process known as computer to plate printing.

Virtual world

A virtual world is a computer-based simulated environment intended for its users to inhabit and interact via avatars. These avatars are usually depicted as textual, two-dimensional, or three-dimensional graphical representations, although other forms are possible (auditory and touch sensations for example). Some, but not all, virtual worlds allow for multiple users.
The computer accesses a computer-simulated world and presents perceptual stimuli to the user, who in turn can manipulate elements of the modeled world and thus experiences telepresence to a certain degree. Such modeled worlds may appear similar to the real world or instead depict fantasy worlds. The model world may simulate rules based on the real world or some hybrid fantasy world. Example rules are gravity, topography, locomotion, real-time actions, and communication. Communication between users has ranged from text, graphical icons, visual gesture, sound, and rarely, forms using touch, voice command, and balance senses.
Massively multiplayer online games commonly depict a world very similar to the real world, with real world rules and real-time actions, and communication. Players create a character to travel between buildings, towns, and even worlds to carry out business or leisure activities. Communication is usually textual, with real-time voice communication using VOIP also possible.
Virtual worlds are not limited to games but, depending on the degree of immediacy presented, can encompass computer conferencing and text based chatrooms. Sometimes, emoticons or 'smilies' are available, to show feeling or facial expression. Emoticons often have a keyboard shortcut. Edward Castronova is an economist who has argued that "synthetic worlds" is a better term for these cyberspaces, but this term has not been widely adopted.

Virtual world concepts

One perception of virtual worlds requires an online persistent world, active and available 24 hours a day and seven days a week, to qualify as a true virtual world. Although this is possible with smaller virtual worlds, especially those that are not actually online, no massively multiplayer game runs all day, every day. All the online games include downtime for maintenance that is not included as time passing in the virtual world. While the interaction with other participants is done in real-time, time consistency is not always maintained in online virtual worlds. For example, EverQuest time passes faster than real-time despite using the same calendar and time units to present game time.
As virtual world is a fairly vague and inclusive term, the above can generally be divided along a spectrum ranging from:
a) massively multiplayer online role-playing games or MMORPGs where the user playing a specific character is a main feature of the game (World Of Warcraft for example).
b) massively multiplayer online real-life/rogue-like games or MMORLGs, the user can edit and alter their avatar at will, allowing them to play a more dynamic role, or multiple roles.
Some would argue that the MMO versions of RTS and FPS games are also virtual worlds if the world editors allow for open editing of the terrains if the "source file" for the terrain is shared. Emerging concepts include basing the terrain of such games on real satellite photos, such as those available through the Google Maps API or through a simple virtual geocaching of "easter eggs" on WikiMapia or similar mashups, where permitted.

Economy

A virtual economy is the emergent property of the interaction between participants in a virtual world. While the designers have a great deal of control over the economy by the encoded mechanics of trade, it is nonetheless the actions of players that define the economic conditions of a virtual world. The economy arises as a result of the choices that players make under the scarcity of real and virtual resources such as time or currency. Participants have a limited time in the virtual world, as in the real world, which they must divide between task such as collecting resources, practicing trade skills, or engaging in less productive fun play. The choices they make in their interaction with the virtual world, along with the mechanics of trade and wealth acquisition, dictate the relative values of items in the economy. The economy in virtual worlds is typically driven by in-game needs such as equipment, food, or trade goods. Virtual economies like that of Second Life, however, are almost entirely player-produced with very little link to in-game needs.
The value of objects in a virtual economy is usually linked to their usefulness and the difficulty of obtaining them. The investment of real world resources (time, membership fees, etc) in acquisition of wealth in a virtual economy may contribute to the real world value of virtual objects. This real world value is made obvious by the trade of virtual items on online market sites like eBay. Recent legal disputes also acknowledge the value of virtual property, even overriding the mandatory EULA which many software companies use to establish that virtual property has no value and/or that users of the virtual world have no legal claim to property therein.
Some industry analysts have moreover observed that there is a secondary industry growing behind the virtual worlds, made up by social networks, websites and other projects completely devoted to virtual worlds communities and gamers. Special websites as GamerDNA, Koinup and others which serve as social networks for virtual worlds users are facing some crucial issue as the DataPortability of avatars across many virtual worlds and MMORPGs.

Furthermore, economical actors are interested by virtual world like 3D video games, instant messaging, search engines and blogs because these are places where they can display targeted advertising, adapted to the people who will see it. Projects about coming video games planned to include advertisements inside the 3D environment.

Virtual worlds and real life

Some virtual worlds have off-line, real world components and applications. Handipoints, for example, is a children's virtual world that tracks chores via customizable chore charts and lets children get involved in their household duties offline. They complete chores and use the website and virtual world to keep track of their progress and daily tasks.

Application domains

Social

Even though Virtual Worlds are often seen as 3D Games, there are many different kinds: forums, blogs, wikis and chatrooms where communities are born. Places which have their own world, their own rules, topics, jokes, members, etc... Each person who belongs to these kinds of communities can find like-minded people to talk to, whether this be a passion, the wish to share information about or just to meet new people and experience new things. Some users develop a double personality depending on which world they are interacting with. Depending on whether that person is in the real or virtual world can impact on the way they think and act. It is not all about video games and communities, virtual world also plays a part in the social as it can allow people to speak or share knowledge with each other. Best examples are instant messaging and visio-conferences which allow people to create their own virtual world.
Systems that have been designed for a social application include:
a) Active Worlds

b) Second Life
c) Smallworlds

Medical

Virtual worlds can also be used, for instance by the Starlight Children's Foundation, to help hospitalised children (suffering from painful diseases or autism for example) to create a comfortable and safe environment which can expand their situation, experience interactions (when you factor in the involvement of a multiple cultures and players from around the world) they may not have been able to experience without a virtual world, healthy or sick. Virtual worlds also enable them to experience and act beyond the restrictions of their illness and help to relieve stress. Disabled or chronically invalided people of any age can also benefit enormously from experiencing the mental and emotional freedom gained by temporarily leaving their disabilities behind and doing, through the medium of their avatars, things as simple and potentially accessible to able, healthy people as walking, running, dancing, sailing, fishing, swimming, surfing, flying, skiing, gardening, exploring and other physical activities which their illnesses or disabilities prevent them from doing in real life. They may also be able to socialise, form friendships and relationships much more easily and avoid the stigma and other obstacles which would normally be attached to their disabilities. This can be much more constructive, emotionally satisfying and mentally fulfilling than passive pastimes such as television watching, playing computer games, reading or more conventional types of internet use.
Psychologically virtual worlds can help players become more familiar and comfortable with actions they may in real-life feel reluctant or embarrassed. For example, in World of Warcraft, /dance is the emote for a dance move which a player in the virtual world can "emote" quite simply. And a familiarization with said or similar "emotes" or social skills (such as, encouragement, gratitude, problem-solving, and even kissing) in the virtual world via avatar can make the assimilation to similar forms of expression, socialization, interaction in real life smooth. Interaction with humans through avatars in the virtual world has potential to seriously expand the mechanics of one's interaction with real-life interactions.

Cyborg

A cyborg is a cybernetic organism (i.e., an organism that has both artificial and natural systems). The term was coined in 1960 when Manfred Clynes and Nathan Kline used it in an article about the advantages of self-regulating human-machine systems in outer space. D. S. Halacy's Cyborg: Evolution of the Superman in 1965 featured an introduction which spoke of a "new frontier" that was "not merely space, but more profoundly the relationship between 'inner space' to 'outer space' -a bridge...between mind and matter." The cyborg is often seen today merely as an organism that has enhanced abilities due to technology, but this perhaps oversimplifies the category of feedback.
Fictional cyborgs are portrayed as a synthesis of organic and synthetic parts, and frequently pose the question of difference between human and machine as one concerned with morality, free will, and empathy. Fictional cyborgs may be represented as visibly mechanical (e.g. the Cybermen in the Doctor Who franchise or The Borg from Star Trek); or as almost indistinguishable from humans (e.g. the "Human" Cylons from the re-imagining of Battlestar Galactica). The 1970s television series the Six Million Dollar Man featured one of the most famous fictional cyborgs. Cyborgs in fiction often play up a human contempt for over-dependence on technology, particularly when used for war, and when used in ways that seem to threaten free will. Cyborgs are also often portrayed with physical or mental abilities far exceeding a human counterpart (military forms may have inbuilt weapons, among other things).
Real (as opposed to fictional) cyborgs are more frequently people who use cybernetic technology to repair or overcome the physical and mental constraints of their bodies. While cyborgs are commonly thought of as mammals, they can be any kind of organism.

Individual cyborgs
Generally, the term "cyborg" is used to refer to a man or woman with bionic, or robotic, implants.
In current prosthetic applications, the C-Leg system developed by Otto Bock HealthCare is used to replace a human leg that has been amputated because of injury or illness. The use of sensors in the artificial C-Leg aids in walking significantly by attempting to replicate the user's natural gait, as it would be prior to amputation. Prostheses like the C-Leg and the more advanced iLimb are considered by some to be the first real steps towards the next generation of real-world cyborg applications. Additionally cochlear implants and magnetic implants which provide people with a sense that they would not otherwise have had can additionally be thought of as creating cyborgs.
In 2002, under the heading Project Cyborg, a British scientist, Kevin Warwick, had an array of 100 electrodes fired in to his nervous system in order to link his nervous system into the internet. With this in place he successfully carried out a series of experiments including extending his nervous system over the internet to control a robotic hand, a loudspeaker and amplifier. This is a form of extended sensory input and the first direct electronic communication between the nervous systems of two humans.

Cyborg proliferation in society

In medicine

In medicine, there are two important and different types of cyborgs: these are the restorative and the enhanced. Restorative technologies “restore lost function, organs, and limbs”. The key aspect of restorative cyborgization is the repair of broken or missing processes to revert to a healthy or average level of function. There is no enhancement to the original faculties and processes that were lost.
On the contrary, the enhanced cyborg “follows a principle, and it is the principle of optimal performance: maximising output (the information or modifications obtained) and minimising input (the energy expended in the process) ”. Thus, the enhanced cyborg intends to exceed normal processes or even gain new functions that were not originally present.
Although prostheses in general supplement lost or damaged body parts with the integration of a mechanical artifice, bionic implants in medicine allow model organs or body parts to mimic the original function more closely. Michael Chorost wrote a memoir of his experience with cochlear implants, or bionic ear, titled "Rebuilt: How Becoming Part Computer Made Me More Human." Jesse Sullivan became one of the first people to operate a fully robotic limb through a nerve-muscle graft, enabling him a complex range of motions beyond that of previous prosthetics. By 2004, a fully functioning artificial heart was developed. The continued technological development of bionic and nanotechnologies begins to raise the question of enhancement, and of the future possibilities for cyborgs which surpass the original functionality of the biological model. The ethics and desirability of "enhancement prosthetics" have been debated; their proponents include the transhumanist movement, with its belief that new technologies can assist the human race in developing beyond its present, normative limitations such as aging and disease, as well as other, more general incapacities, such as limitations on speed, strength, endurance, and intelligence. Opponents of the concept describe what they believe to be biases which propel the development and acceptance of such technologies; namely, a bias towards functionality and efficiency that may compel assent to a view of human people which de-emphasises as defining characteristics actual manifestations of humanity and personhood, in favour of definition in terms of upgrades, versions, and utility.
One of the more common and accepted forms of temporary modification occurs as a result of prenatal diagnosis technologies. Some modern parents willingly use testing methods such as ultrasounds and amniocentesis to determine the sex or health of the fetus. The discovery of birth defects or other congenital problems by these procedures may lead to neonatal treatment in the form of open fetal surgery or the less invasive fetal intervention.
A brain-computer interface, or BCI, provides a direct path of communication from the brain to an external device, effectively creating a cyborg. Research of Invasive BCIs, which utilize electrodes implanted directly into the grey matter of the brain, has focused on restoring damaged eye sight in the blind and providing functionality to paralysed people, most notably those with severe cases, such as Locked-In syndrome.
Retinal implants are another form of cyborgization in medicine. The theory behind retinal stimulation to restore vision to people suffering from retinitis pigmentosa and vision loss due to aging (conditions in which people have an abnormally low amount of ganglion cells) is that the retinal implant and electrical stimulation would act as a substitute for the missing ganglion cells (cells which connect the eye to the brain).
While work to perfect this technology is still being done, there have already been major advances in the use of electronic stimulation of the retina to allow the eye to sense patterns of light. A specialized camera is worn by the subject (possibly on the side of a their glasses frames) the camera converts the image into a pattern of electrical stimulation. A chip located in the users eye would then electrically stimulate the retina with this pattern and the image appears to the user. Current prototypes have the camera being powered by a hand sized power supply that could be placed in a pocket or on the waist.
Currently the technology has only been tested on human subject for brief amounts of time and the amount of light picked up by the subject has been minimal. However, if technological advances proceed as planned this technology may be used by thousands of blind people and restore vision to most of them. Robot assisted surgery is another way cyborgs are being integrated into medicine

In the military

Military organizations' research has recently focused on the utilization of cyborg animals for inter-species relationships for the purposes of a supposed a tactical advantage. DARPA has announced its interest in developing "cyborg insects" to transmit data from sensors implanted into the insect during the pupal stage. The insect's motion would be controlled from a MEMS, or Micro-Electro-Mechanical System, and would conceivably surveil an environment and detect explosives or gas. Similarly, DARPA is developing a neural implant to remotely control the movement of sharks. The shark's unique senses would be exploited to provide data feedback in relation to enemy ship movement and underwater explosives.

Cloud

A cloud is a visible mass of droplets or frozen crystals suspended in the atmosphere above the surface of the Earth or another planetary body. A cloud is also a visible mass attracted by gravity, such as masses of material in space called interstellar clouds and nebulae. Clouds are studied in the nephology or cloud physics branch of meteorology.
On Earth the condensing substance is typically water vapor, which forms small droplets or ice crystals, typically 0.01 mm in diameter. When surrounded by billions of other droplets or crystals they become visible as clouds. Dense deep clouds exhibit a high reflectance (70% to 95%) throughout the visible range of wavelengths. They thus appear white, at least from the top. Cloud droplets tend to scatter light efficiently, so that the intensity of the solar radiation decreases with depth into the gases, hence the gray or even sometimes dark appearance at the cloud base. Thin clouds may appear to have acquired the color of their environment or background and clouds illuminated by non-white light, such as during sunrise or sunset, may appear colored accordingly. Clouds look darker in the near-infrared because water absorbs solar radiation at those wavelengths.

Condensation

As air parcels cool due to expansion of the rising air mass, water vapor begins to condense on condensation nuclei such as dust, ice and salt. This process forms clouds. Sometimes an elevated portion of a frontal zone forces broad areas of lift, which form cloud decks such as altostratus or cirrostratus. Stratus is a large dark low cloud deck that tends to form when a stable cool air mass is trapped underneath a warm air mass. It can also form due to the lifting of advection fog during breezy conditions. Clouds can also be formed due to lifting over mountains and other topography

Cirrostratus cloud

Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals, capable of forming halos. They are usually located above 5.5 km . When thick enough to be seen, they are whitish, usually with no distinguishing features. When covering the whole sky and sometimes so thin as to be hardly discernible, this may indicate a large amount of moisture in the upper atmosphere. Cirrostratus clouds sometimes signal the beginning of a warm front and thus may be signs that precipitation might follow in the next 12 to 24 hours.

Circumhorizontal arc

A circumhorizontal arc is an optical phenomenon, an ice-halo formed by plate shaped ice crystals in high level cirrus clouds.
The current accepted technical names are circumhorizon arc or Lower symmetric 46° plate arc. The term 'fire rainbow' coined recently by a journalist is not recognised. It is misleading as the arc is not a rainbow and is not related to fires.
The complete halo is a huge and beautiful multi-coloured band running parallel to the horizon with its center beneath the sun. The distance below the sun is twice as far as the common 22-degree halo. Red is the uppermost colour. Often, when the halo forming cloud is small or patchy, only fragments of the arc are seen.
There is a myth that the halo is rare. How often it is seen depends on location and in particular latitude. In the United States it is a relatively common halo seen several times each summer in any one place. In contrast, it is rare in mid-latitude and northern Europe.
For the halo to form the sun must be very high in the sky, at an elevation of 58° or more. Cirrus cloud or haze containing relatively large plate-shaped ice crystals must also be present. The sun altitude requirement has the consequence that the halo is impossible to see at locations north of 55°N or south of 55°S (although a lunar circumhorizon arc might be visible). In other latitudes it is visible for a greater or lesser time around the summer solstice. Slots of visibility for different latitudes and locations can be looked up on graph. For example, in London, England the sun is only high enough for 140 hours between mid May and late July. Contrast that with Los Angeles with the sun higher than 58 degrees for 670 hours between late March and late September. When the cloudiness of Europe is also taken into account, the halo becomes more than 10-20X more likely to be seen in the United States.
The halo is formed by sunlight entering horizontally-oriented flat hexagon ice crystals through a vertical side face and leaving through the near horizontal bottom face. There is no requirement that the plates be thick. In principle, Parry oriented column crystals can also produce the arc although this is rare.
The 90° inclination between the ray entrance and exit faces produces the well-separated spectral colours and, if the crystal alignment is just right, makes the entire cirrus cloud appear to shine.
A circumhorizontal arc can be difficult to distiguish from an infralateral arc when the sun is high in the sky. The former is always parallel to the horizon whereas the latter curves upwards at its ends.

Cloud iridescence

Cloud iridescence or irisation is the occurrence of colors in a cloud not dissimilar to those seen in oil films on puddles. It is fairly common. The colors are usually pastel and need searching for but sometimes they can be very vivid. Iridescence is most frequent near to the sun and the glare masks it. It is most easily seen by hiding the sun behind a tree or building. Other aids are dark glasses or observing the sky by its reflection in a convex mirror or in a pool of water.
Iridescent clouds are a diffraction phenomenon. Small water droplets or even small ice crystals in clouds individually scatter light. Large ice crystals produce halos - the latter are refraction phenomena not iridescence. Iridescence should similarly be distinguished from the refraction in larger raindrops that gives a rainbow.
If parts of the clouds have droplets (or crystals) of similar size the cumulative effect is seen as colors. The cloud must be optically thin so that most rays encounter only a single droplet. Iridescence is therefore mostly seen at cloud edges or in semi transparent clouds. Newly forming clouds produce the brightest and most colorful iridescence because their droplets are of the same size. When a thin cloud has droplets of similar size over a large extent the iridescence takes on a structured form to give a corona - a central bright disk around the sun or moon surrounded by one or more colored rings.