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Ceramic

A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, and brick.

The earliest ceramics made by humans were brick walls used for building houses and other structures, while pottery objects (pots, vessels, or vases) or figurines made from clay, either by itself or mixed with other materials like silica, hardened and sintered in fire is the common belief of how ceramic was made. Later, ceramics were glazed and fired to create smooth, colored surfaces, decreasing porosity through the use of glassy, amorphous ceramic coatings on top of the crystalline ceramic substrates. Ceramics now include domestic, industrial, and building products, as well as a wide range of materials developed for use in advanced ceramic engineering, such as semiconductors.

The word ceramic comes from the Ancient Greek word, meaning "of or for pottery". The earliest known mention of the root ceram- is the Mycenaean Greek ke-ra-me-we, workers of ceramic, written in Linear B syllabic script. The word ceramic can be used as an adjective to describe a material, product, or process, or it may be used as a noun, either singular or, more commonly, as the plural noun ceramics.

Materials
Ceramic material is an inorganic, metallic oxide, nitride, or carbide material. Some elements, such as carbon or silicon, may be considered ceramics. Ceramic materials are brittle, hard, strong in compression, and weak in shearing and tension. They withstand the chemical erosion that occurs in other materials subjected to acidic or caustic environments. Ceramics generally can withstand very high temperatures, ranging from 1,000 °C to 1,600 °C (1,800 °F to 3,000 °F).

The crystallinity of ceramic materials varies widely. Most often, fired ceramics are either vitrified or semi-vitrified, as is the case with earthenware, stoneware, and porcelain. Varying crystallinity and electron composition in the ionic and covalent bonds cause most ceramic materials to be good thermal and electrical insulators (researched in ceramic engineering). With such a large range of possible options for the composition/structure of a ceramic (nearly all of the elements, nearly all types of bonding, and all levels of crystallinity), the breadth of the subject is vast, and identifiable attributes (hardness, toughness, electrical conductivity) are difficult to specify for the group as a whole. General properties such as high melting temperature, high hardness, poor conductivity, high moduli of elasticity, chemical resistance, and low ductility are the norm, with known exceptions to each of these rules (piezoelectric ceramics, glass transition temperature, superconductive ceramics).

Composites such as fiberglass and carbon fiber, while containing ceramic materials, are not considered to be part of the ceramic family.

Highly oriented crystalline ceramic materials are not amenable to a great range of processing. Methods for dealing with them tend to fall into one of two categories: either making the ceramic in the desired shape by reaction in situ or "forming" powders into the desired shape and then sintering to form a solid body. Ceramic forming techniques include shaping by hand (sometimes including a rotation process called "throwing"), slip casting, tape casting (used for making very thin ceramic capacitors), injection molding, dry pressing, and other variations.

Many ceramics experts do not consider materials with an amorphous (noncrystalline) character (i.e., glass) to be ceramics, even though glassmaking involves several steps of the ceramic process and its mechanical properties are similar to those of ceramic materials. However, heat treatments can convert glass into a semi-crystalline material known as glass-ceramic.

Traditional ceramic raw materials include clay minerals such as kaolinite, whereas more recent materials include aluminium oxide, more commonly known as alumina. Modern ceramic materials, which are classified as advanced ceramics, include silicon carbide and tungsten carbide. Both are valued for their abrasion resistance and are therefore used in applications such as the wear plates of crushing equipment in mining operations. Advanced ceramics are also used in the medical, electrical, electronics, and armor industries.

History
Human beings appear to have been making their own ceramics for at least 26,000 years, subjecting clay and silica to intense heat to fuse and form ceramic materials. The earliest found so far were in southern central Europe and were sculpted figures, not dishes. The earliest known pottery was made by mixing animal products with clay and firing it at up to 800 °C. While pottery fragments have been found up to 19,000 years old, it was not until about 10,000 years later that regular pottery became common. An early people that spread across much of Europe is named after its use of pottery: the Corded Ware culture. These early Indo-European peoples decorated their pottery by wrapping it with rope while it was still wet. When the ceramics were fired, the rope burned off but left a decorative pattern of complex grooves on the surface.

The invention of the wheel eventually led to the production of smoother, more even pottery using the wheel-forming (throwing) technique, like the pottery wheel. Early ceramics were porous, absorbing water easily. It became useful for more items with the discovery of glazing techniques, which involved coating pottery with silicon, bone ash, or other materials that could melt and reform into a glassy surface, making a vessel less pervious to water.

Archaeology
Ceramic artifacts have an important role in archaeology for understanding the culture, technology, and behavior of peoples of the past. They are among the most common artifacts to be found at an archaeological site, generally in the form of small fragments of broken pottery called sherds. The processing of collected sherds can be consistent with two main types of analysis: technical and traditional.

The traditional analysis involves sorting ceramic artifacts, sherds, and larger fragments into specific types based on style, composition, manufacturing, and morphology. By creating these typologies, it is possible to distinguish between different cultural styles, the purpose of the ceramic, and the technological state of the people, among other conclusions. Besides, by looking at stylistic changes in ceramics over time, it is possible to separate (seriate) the ceramics into distinct diagnostic groups (assemblages). A comparison of ceramic artifacts with known dated assemblages allows for a chronological assignment of these pieces.

The technical approach to ceramic analysis involves a finer examination of the composition of ceramic artifacts and sherds to determine the source of the material and, through this, the possible manufacturing site. Key criteria are the composition of the clay and the temper used in the manufacture of the article under study: the temper is a material added to the clay during the initial production stage and is used to aid the subsequent drying process. Types of temper include shell pieces, granite fragments, and ground sherd pieces called 'grog'. Temper is usually identified by microscopic examination of the tempered material. Clay identification is determined by a process of refiring the ceramic and assigning a color to it using Munsell Soil Color notation. By estimating both the clay and temper compositions and locating a region where both are known to occur, an assignment of the material source can be made. Based on the source assignment of the artifact, further investigations can be made into the site of manufacture.

Properties
The physical properties of any ceramic substance are a direct result of its crystalline structure and chemical composition. Solid-state chemistry reveals the fundamental connection between microstructure and properties, such as localized density variations, grain size distribution, type of porosity, and second-phase content, which can all be correlated with ceramic properties such as mechanical strength σ by the Hall-Petch equation, hardness, toughness, dielectric constant, and the optical properties exhibited by transparent materials.

Ceramography is the art and science of preparation, examination, and evaluation of ceramic microstructures. Evaluation and characterization of ceramic microstructures are often implemented on similar spatial scales to that used commonly in the emerging field of nanotechnology: from nanometers to tens of micrometers (µm). This is typically somewhere between the minimum wavelength of visible light and the resolution limit of the naked eye.

The microstructure includes most grains, secondary phases, grain boundaries, pores, micro-cracks, structural defects, and hardness micro indentions. Most bulk mechanical, optical, thermal, electrical, and magnetic properties are significantly affected by the observed microstructure. The fabrication method and process conditions are generally indicated by the microstructure. The root cause of many ceramic failures is evident in the cleaved and polished microstructure. Physical properties which constitute the field of materials science and engineering include the following:

Mechanical properties
Mechanical properties are important in structural and building materials as well as textile fabrics. In modern materials science, fracture mechanics is an important tool in improving the mechanical performance of materials and components. It applies the physics of stress and strain, in particular the theories of elasticity and plasticity, to the microscopic crystallographic defects found in real materials in order to predict the macroscopic mechanical failure of bodies. Fractography is widely used with fracture mechanics to understand the causes of failures and also verify the theoretical failure predictions with real-life failures.

Ceramic materials are usually ionic or covalent bonded materials. A material held together by either type of bond will tend to fracture before any plastic deformation takes place, which results in poor toughness in these materials. Additionally, because these materials tend to be porous, the pores and other microscopic imperfections act as stress concentrators, decreasing the toughness further, and reducing the tensile strength. These combine to give catastrophic failures, as opposed to the more ductile failure modes of metals.

These materials do show plastic deformation. However, because of the rigid structure of crystalline material, there are very few available slip systems for dislocations to move, and so they deform very slowly.

To overcome the brittle behavior, ceramic material development has introduced the class of ceramic matrix composite materials, in which ceramic fibers are embedded and with specific coatings are forming fiber bridges across any crack. This mechanism substantially increases the fracture toughness of such ceramics. Ceramic disc brakes are an example of using a ceramic matrix composite material manufactured with a specific process.

Scientists are working on developing ceramic materials that can withstand significant deformation without breaking. A first such material that can deform in room temperature was found in 2024.

Ice-templating for enhanced mechanical properties
If a ceramic is subjected to substantial mechanical loading, it can undergo a process called ice-templating, which allows some control of the microstructure of the ceramic product and therefore some control of the mechanical properties. Ceramic engineers use this technique to tune the mechanical properties to their desired application. Specifically, the strength is increased when this technique is employed. Ice templating allows the creation of macroscopic pores in a unidirectional arrangement. The applications of this oxide strengthening technique are important for solid oxide fuel cells and water filtration devices.

To process a sample through ice templating, an aqueous colloidal suspension is prepared to contain the dissolved ceramic powder evenly dispersed throughout the colloid, for example Yttria-stabilized zirconia (YSZ). The solution is then cooled from the bottom to the top on a platform that allows for unidirectional cooling. This forces ice crystals to grow in compliance with the unidirectional cooling, and these ice crystals force the dissolved YSZ particles to the solidification front of the solid-liquid interphase boundary, resulting in pure ice crystals lined up unidirectionally alongside concentrated pockets of colloidal particles. The sample is then heated and at the same the pressure is reduced enough to force the ice crystals to sublime and the YSZ pockets begin to anneal together to form macroscopically aligned ceramic microstructures. The sample is then further sintered to complete the evaporation of the residual water and the final consolidation of the ceramic microstructure.

During ice-templating, a few variables can be controlled to influence the pore size and morphology of the microstructure. These important variables are the initial solids loading of the colloid, the cooling rate, the sintering temperature and duration, and the use of certain additives which can influence the microstructural morphology during the process. A good understanding of these parameters is essential to understanding the relationships between processing, microstructure, and mechanical properties of anisotropically porous materials.

Semiconductors
Some ceramics are semiconductors. Most of these are transition metal oxides that are II-VI semiconductors, such as zinc oxide. While there are prospects of mass-producing blue LEDs from zinc oxide, ceramicists are most interested in the electrical properties that show grain boundary effects. One of the most widely used of these is the varistor. These are devices that exhibit the property that resistance drops sharply at a certain threshold voltage. Once the voltage across the device reaches the threshold, there is a breakdown of the electrical structure in the vicinity of the grain boundaries, which results in its electrical resistance dropping from several megohms down to a few hundred ohms. The major advantage of these is that they can dissipate a lot of energy, and they self-reset; after the voltage across the device drops below the threshold, its resistance returns to being high. This makes them ideal for surge-protection applications; as there is control over the threshold voltage and energy tolerance, they find use in all sorts of applications. The best demonstration of their ability can be found in electrical substations, where they are employed to protect the infrastructure from lightning strikes. They have rapid response, are low maintenance, and do not appreciably degrade from use, making them virtually ideal devices for this application. Semiconducting ceramics are also employed as gas sensors. When various gases are passed over a polycrystalline ceramic, its electrical resistance changes. With tuning to the possible gas mixtures, very inexpensive devices can be produced.

Superconductivity
Under some conditions, such as extremely low temperatures, some ceramics exhibit high-temperature superconductivity (in superconductivity, "high temperature" means above 30 K). The reason for this is not understood, but there are two major families of superconducting ceramics.

Ferroelectricity and supersets
Piezoelectricity, a link between electrical and mechanical response, is exhibited by a large number of ceramic materials, including the quartz used to measure time in watches and other electronics. Such devices use both properties of piezoelectrics, using electricity to produce a mechanical motion (powering the device) and then using this mechanical motion to produce electricity (generating a signal). The unit of time measured is the natural interval required for electricity to be converted into mechanical energy and back again.

The piezoelectric effect is generally stronger in materials that also exhibit pyroelectricity, and all pyroelectric materials are also piezoelectric. These materials can be used to inter-convert between thermal, mechanical, or electrical energy; for instance, after synthesis in a furnace, a pyroelectric crystal allowed to cool under no applied stress generally builds up a static charge of thousands of volts. Such materials are used in motion sensors, where the tiny rise in temperature from a warm body entering the room is enough to produce a measurable voltage in the crystal.

In turn, pyroelectricity is seen most strongly in materials that also display the ferroelectric effect, in which a stable electric dipole can be oriented or reversed by applying an electrostatic field. Pyroelectricity is also a necessary consequence of ferroelectricity. This can be used to store information in ferroelectric capacitors, elements of ferroelectric RAM.

The most common such materials are lead zirconate titanate and barium titanate. Aside from the uses mentioned above, their strong piezoelectric response is exploited in the design of high-frequency loudspeakers, transducers for sonar, and actuators for atomic force and scanning tunneling microscopes.

Positive thermal coefficient
Temperature increases can cause grain boundaries to suddenly become insulating in some semiconducting ceramic materials, mostly mixtures of heavy metal titanates. The critical transition temperature can be adjusted over a wide range by variations in chemistry. In such materials, current will pass through the material until joule heating brings it to the transition temperature, at which point the circuit will be broken and current flow will cease. Such ceramics are used as self-controlled heating elements in, for example, the rear-window defrost circuits of automobiles.

At the transition temperature, the material's dielectric response becomes theoretically infinite. While a lack of temperature control would rule out any practical use of the material near its critical temperature, the dielectric effect remains exceptionally strong even at much higher temperatures. Titanates with critical temperatures far below room temperature have become synonymous with "ceramic" in the context of ceramic capacitors for just this reason.

Optical properties
Optically transparent materials focus on the response of a material to incoming light waves of a range of wavelengths. Frequency selective optical filters can be utilized to alter or enhance the brightness and contrast of a digital image. Guided lightwave transmission via frequency selective waveguides involves the emerging field of fiber optics and the ability of certain glassy compositions as a transmission medium for a range of frequencies simultaneously (multi-mode optical fiber) with little or no interference between competing wavelengths or frequencies. This resonant mode of energy and data transmission via electromagnetic (light) wave propagation, though low powered, is virtually lossless. Optical waveguides are used as components in Integrated optical circuits (e.g. light-emitting diodes, LEDs) or as the transmission medium in local and long haul optical communication systems. Also of value to the emerging materials scientist is the sensitivity of materials to radiation in the thermal infrared (IR) portion of the electromagnetic spectrum. This heat-seeking ability is responsible for such diverse optical phenomena as night-vision and IR luminescence.

Thus, there is an increasing need in the military sector for high-strength, robust materials which have the capability to transmit light (electromagnetic waves) in the visible (0.4 – 0.7 micrometers) and mid-infrared (1 – 5 micrometers) regions of the spectrum. These materials are needed for applications requiring transparent armor, including next-generation high-speed missiles and pods, as well as protection against improvised explosive devices (IED).

In the 1960s, scientists at General Electric (GE) discovered that under the right manufacturing conditions, some ceramics, especially aluminium oxide (alumina), could be made translucent. These translucent materials were transparent enough to be used for containing the electrical plasma generated in high-pressure sodium street lamps. During the past two decades, additional types of transparent ceramics have been developed for applications such as nose cones for heat-seeking missiles, windows for fighter aircraft, and scintillation counters for computed tomography scanners. Other ceramic materials, generally requiring greater purity in their make-up than those above, include forms of several chemical compounds, including:

 * 1) Barium titanate: (often mixed with strontium titanate) displays ferroelectricity, meaning that its mechanical, electrical, and thermal responses are c
 * 2) Sialon (silicon aluminium oxynitride) has high strength; resistance to thermal shock, chemical and wear resistance, and low density. These ceramics are used in non-ferrous molten metal handling, weld pins, and the chemical industry.
 * 3) Silicon carbide (SiC) is used as a susceptor in microwave furnaces, a commonly used abrasive, and as a refractory material.
 * 4) Silicon nitride (Si3N4) is used as an abrasive powder.
 * 5) Steatite (magnesium silicates) is used as an electrical insulator.
 * 6) Titanium carbide Used in space shuttle re-entry shields and scratchproof watches.
 * 7) Uranium oxide (UO2), used as fuel in nuclear reactors.
 * 8) Yttrium barium copper oxide (YBa2Cu3O7−x), a high-temperature superconductor.
 * 9) Zinc oxide (ZnO), which is a semiconductor, and used in the construction of varistors.
 * 10) Zirconium dioxide (zirconia), which in pure form undergoes many phase changes between room temperature and practical sintering temperatures, can be chemically "stabilized" in several different forms. Its high oxygen ion conductivity recommends it for use in fuel cells and automotive oxygen sensors. In another variant, metastable structures can impart transformation toughening for mechanical applications; most ceramic knife blades are made of this material. Partially stabilised zirconia (PSZ) is much less brittle than other ceramics and is used for metal forming tools, valves and liners, abrasive slurries, kitchen knives and bearings subject to severe abrasion.

By usage
For convenience, ceramic products are usually divided into four main types; these are shown below with some examples:
 * 1) Structural, including bricks, pipes, floor and roof tiles
 * 2) Refractories, such as kiln linings, gas fire radiants, steel and glass making crucibles
 * 3) Whitewares, including tableware, cookware, wall tiles, pottery products and sanitary ware
 * 4) Technical, also known as engineering, advanced, special, and fine ceramics. Such items include:
 * 5) *gas burner nozzles
 * 6) *ballistic protection, vehicle armor
 * 7) *nuclear fuel uranium oxide pellets
 * 8) *biomedical implants
 * 9) *coatings of jet engine turbine blades
 * 10) *ceramic matrix composite gas turbine parts
 * 11) *reinforced carbon–carbon ceramic disc brakes
 * 12) *missile nose cones
 * 13) *bearings
 * 14) *tiles used in the Space Shuttle program

Ceramics made with clay
Frequently, the raw materials of modern ceramics do not include clays. Those that do have been classified as:
 * 1) Earthenware, fired at lower temperatures than other types
 * 2) Stoneware, vitreous or semi-vitreous
 * 3) Porcelain, which contains a high content of kaolin
 * 4) Bone china

Classification
Ceramics can also be classified into three distinct material categories:
 * 1) Oxides: alumina, beryllia, ceria, zirconia
 * 2) Non-oxides: carbide, boride, nitride, silicide
 * 3) Composite materials: particulate reinforced, fiber reinforced, combinations of oxides and nonoxides.

Each one of these classes can be developed into unique material properties.

Applications

 * 1) Knife blades: the blade of a ceramic knife will stay sharp for much longer than that of a steel knife, although it is more brittle and susceptible to breakage.
 * 2) Carbon-ceramic brake disks for vehicles: highly resistant to brake fade at high temperatures.
 * 3) Advanced composite ceramic and metal matrices have been designed for most modern Armoured fighting vehicles because they offer superior penetrating resistance against shaped charge (HEAT rounds) and kinetic energy penetrators.
 * 4) Ceramics such as alumina and boron carbide have been used as plates in ballistic armored vests to repel high-velocity rifle fire. Such plates are known commonly as small arms protective inserts, or SAPIs. Similar low-weight material is used to protect the cockpits of some military aircraft.
 * 5) Ceramic ball bearings can be used in place of steel. Their greater hardness results in lower susceptibility to wear. Ceramic bearings typically last triple the lifetime of steel bearings. They deform less than steel under load, resulting in less contact with the bearing retainer walls and lower friction. In very high-speed applications, heat from friction causes more problems for metal bearings than ceramic bearings. Ceramics are chemically resistant to corrosion and are preferred for environments where steel bearings would rust. In some applications their electricity-insulating properties are advantageous. Drawbacks to ceramic bearings include significantly higher cost, susceptibility to damage under shock loads, and the potential to wear steel parts due to ceramics' greater hardness.
 * 6) In the early 1980s Toyota researched production of an adiabatic engine using ceramic components in the hot gas area. The use of ceramics would have allowed temperatures exceeding 1650 °C. Advantages would include lighter materials and a smaller cooling system (or no cooling system at all), leading to major weight reduction. The expected increase of fuel efficiency (due to higher operating temperatures, demonstrated in Carnot's theorem) could not be verified experimentally. It was found that heat transfer on the hot ceramic cylinder wall was greater than the heat transfer to a cooler metal wall. This is because the cooler gas film on a metal surface acts as a thermal insulator. Thus, despite the desirable properties of ceramics, prohibitive production costs and limited advantages have prevented widespread ceramic engine component adoption. In addition, small imperfections in ceramic material along with low fracture toughness can lead to cracking and potentially dangerous equipment failure. Such engines are possible experimentally, but mass production is not feasible with current technology.
 * 7) Experiments with ceramic parts for gas turbine engines are being conducted. Currently, even blades made of advanced metal alloys used in the engines' hot section require cooling and careful monitoring of operating temperatures. Turbine engines made with ceramics could operate more efficiently, providing for greater range and payload.
 * 8) Recent advances have been made in ceramics which include bioceramics such as dental implants and synthetic bones. Hydroxyapatite, the major mineral component of bone, has been made synthetically from several biological and chemical components and can be formed into ceramic materials. Orthopedic implants coated with these materials bond readily to bone and other tissues in the body without rejection or inflammatory reaction. They are of great interest for gene delivery and tissue engineering scaffolding. Most hydroxyapatite ceramics are quite porous and lack mechanical strength and are therefore used solely to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. They are also used as fillers for orthopedic plastic screws to aid in reducing inflammation and increase the absorption of these plastic materials. Work is being done to make strong, fully dense nanocrystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic but naturally occurring bone mineral. Ultimately, these ceramic materials may be used as bone replacement, or with the incorporation of protein collagens, the manufacture of synthetic bones.
 * 9) Applications for actinide-containing ceramic materials include nuclear fuels for burning excess plutonium (Pu), or a chemically-inert source of alpha radiation in power supplies for uncrewed space vehicles or microelectronic devices. Use and disposal of radioactive actinides require immobilization in a durable host material. Long half-life radionuclides such as actinide are immobilized using chemically-durable crystalline materials based on polycrystalline ceramics and large single crystals.
 * 10) High-tech ceramics are used for producing watch cases. The material is valued by watchmakers for its light weight, scratch resistance, durability, and smooth touch. IWC is one of the brands that pioneered the use of ceramic in watchmaking.
 * 11) Ceramics are used in the design of mobile phone bodies due to their high hardness, resistance to scratches, and ability to dissipate heat. Ceramic's thermal management properties help in maintaining optimal device temperatures during heavy use enhancing performance. Additionally, ceramic materials can support wireless charging and offer better signal transmission compared to metals, which can interfere with antennas. Companies like Apple and Samsung have incorporated ceramic in their devices.
 * 12) Ceramics made of Silicon Carbide are used in pump and valve components because of their corrosion resistance characteristics. It is also used in nuclear reactors as fuel cladding materials due to their ability to withstand radiation and thermal stress. Other uses of Silicon carbide ceramics include paper manufacturing, ballistics, chemical production, and as pipe system components.

title: Ceramic


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Wuxing (Chinese philosophy)

, usually translated as Five Phases or Five Agents, is a fivefold conceptual scheme used in many traditional Chinese fields of study to explain a wide array of phenomena, including cosmic cycles, the interactions between internal organs, the succession of political regimes, and the properties of herbal medicines.

The agents are Fire, Water, Wood, Metal, and Earth. The wuxing system has been in use since it was formulated in the second or first century BCE during the Han dynasty. It appears in many seemingly disparate fields of early Chinese thought, including music, feng shui, alchemy, astrology, martial arts, military strategy, I Ching divination, and traditional medicine, serving as a metaphysics based on cosmic analogy.

Etymology
Wuxing originally referred to the five major planets (Jupiter, Saturn, Mercury, Mars, Venus), which were with the combination of the Sun and the Moon, conceived as creating five forces of earthly life. This is why the word is composed of Chinese characters meaning "five" and "moving". "Moving" is shorthand for "planets", since the word for planets in Chinese literally translates as "moving stars". Some of the Mawangdui Silk Texts (before 168 BC) also connect the wuxing to the wude, the Five Virtues and Five Emotions. Scholars believe that various predecessors to the concept of wuxing were merged into one system with many interpretations during the Han dynasty.

Wuxing was first translated into English as "the Five Elements", drawing deliberate parallels with the Greek arrangement of the four elements. This translation is still in common use among practitioners of Traditional Chinese medicine, such as in the name of Five Element acupuncture. However, this analogy is misleading. The four elements are concerned with form, substance and quantity, whereas wuxing are "primarily concerned with process, change, and quality". For example, the wuxing element "Wood" is more accurately thought of as the "vital essence" of trees rather than the physical substance wood. This led sinologist Nathan Sivin to propose the alternative translation "five phases" in 1987. But "phase" also fails to capture the full meaning of wuxing. In some contexts, the wuxing are indeed associated with physical substances. Historian of Chinese medicine Manfred Porkert proposed the (somewhat unwieldy) term "Evolutive Phase". Perhaps the most widely accepted translation among modern scholars is "the five agents", proposed by Marc Kalinowski.

Cycles
In traditional doctrine, the five phases are connected in two cycles of interactions: a generating or creation ( shēng) cycle, also known as "mother-son"; and an overcoming or destructive ( kè) cycle, also known as "grandfather-grandson" (see diagram). Each of the two cycles can be analyzed going forward or reversed. There is also an "overacting" or excessive version of the destructive cycle.

Inter-promoting
The generating cycle ( xiāngshēng) is:
 * Wood feeds Fire
 * Fire produces Earth (ash, lava)
 * Earth bears Metal (geological processes produce minerals)
 * Metal collects Water (water vapor condenses on metal, for example)
 * Water nourishes Wood (Water flowers, plants and other changes in forest)

Weakening
The reverse generating cycle (/ xiāngxiè) is:
 * Wood depletes Water
 * Water rusts Metal
 * Metal impoverishes Earth (erosion, destructive mining of minerals)
 * Earth smothers Fire
 * Fire burns Wood (forest fires)

Inter-regulating
The destructive cycle ( xiāngkè) is:
 * Wood grasps (or stabilizes) Earth (roots of trees can prevent soil erosion)
 * Earth contains (or directs) Water (dams or river banks)
 * Water dampens (or regulates) Fire
 * Fire melts (or refines or shapes) Metal
 * Metal chops (or carves) Wood

Overacting
The excessive destructive cycle ( xiāngchéng) is:
 * Wood depletes Earth (depletion of nutrients in soil, over-farming, overcultivation)
 * Earth obstructs Water (over-damming)
 * Water extinguishes Fire
 * Fire melts Metal (affecting its integrity)
 * Metal makes Wood rigid to easily snap.

Counteracting
A reverse or deficient destructive cycle ( xiāngwǔ or xiānghào) is:
 * Wood dulls Metal
 * Metal de-energizes Fire (conducting heat away)
 * Fire evaporates Water
 * Water muddies (or destabilizes) Earth
 * Earth rots Wood (buried wood rots)

Ming neiyin
In Ziwei divination, neiyin (納音) further classifies the Five Elements into 60 ming (命), or life orders, based on the ganzhi. Similar to the astrology zodiac, the ming is used by fortune-tellers to analyse individual personality and destiny.

Applications
The wuxing schema is applied to explain phenomena in various fields.

Phases of the Year
The five phases are around 73 days each and are usually used to describe the transformations of nature rather than their formative states.
 * Wood/Spring: a period of growth, expanding which generates abundant vitality, movement and wind.
 * Fire/Summer: a period of swollen, flowering, expanded with heat.
 * Earth can be seen as a period of stillness transitioning between the other phases or seasons or when relating to transformative seasonal periods it can be seen as late Summer. This period is associated with stability, leveling and dampness.
 * Metal/Autumn: a period of harvesting, transmuting, contracting, collecting and dryness.
 * Water/Winter: a period of retreat, stillness, consolidation and coolness.

Cosmology and feng shui
The art of feng shui (Chinese geomancy) is based on wuxing, with the structure of the cosmos mirroring the five phases, as well as the eight trigrams. Each phase has a complex network of associations with different aspects of nature (see table): colors, seasons and shapes all interact according to the cycles.

An interaction or energy flow can be expansive, destructive, or exhaustive, depending on the cycle to which it belongs. By understanding these energy flows, a feng shui practitioner attempts to rearrange energy to benefit the client.

Dynastic transitions
According to the Warring States period political philosopher Zou Yan (c. 305–240 BCE), each of the five elements possesses a personified virtue, which indicates the foreordained destiny of a dynasty; hence the cyclic succession of the elements also indicates dynastic transitions. Zou Yan claims that the Mandate of Heaven sanctions the legitimacy of a dynasty by sending self-manifesting auspicious signs in the ritual color (yellow, blue, white, red, and black) that matches the element of the new dynasty (Earth, Wood, Metal, Fire, and Water). From the Qin dynasty onward, most Chinese dynasties invoked the theory of the Five Elements to legitimize their reign.

Chinese medicine

The interdependence of zangfu networks in the body was said to be a circle of five things, and so mapped by the Chinese doctors onto the five phases.

In order to explain the integrity and complexity of the human body, Chinese medical scientists and physicians use the Five Elements theory to classify the human body's endogenous influences on organs, physiological activities, pathological reactions, and environmental or exogenous (external, environmental) influences. This diagnostic capacity is extensively used in traditional five phase acupuncture today, as opposed to the modern Confucian styled eight principles based Traditional Chinese medicine. Furthermore, in combination the two systems are a formative and functional study of postnatal and prenatal influencing on genetics, psychology, sociology and ecology.

Music
The Huainanzi and the Yueling chapter of the Book of Rites make the following correlations:

 * Qing is a Chinese color word used for both green and blue. Modern Mandarin has separate words for each, but like many other languages, older forms of Chinese did not distinguish between green and blue.
 * In most modern music, various five note or seven note scales (e.g., the major scale) are defined by selecting five or seven frequencies from the set of twelve semi-tones in the Equal tempered tuning. The Chinese shi'er lü system of tuning is closest to the ancient Greek tuning of Pythagoras.

Martial arts
Tai chi uses the five elements to designate different directions, positions or footwork patterns: forward, backward, left, right and centre, or three steps forward (attack) and two steps back (retreat).

The Five Steps :
 * Jinbu – forward step
 * Tuibu – backward step
 * Zuogu – left step
 * Youpan – right step
 * Zhongding – central position, balance, equilibrium

The martial art of xingyiquan uses the five elements metaphorically to represent five different states of combat.

Wuxing heqidao, Gogyo Aikido (五行合气道) is a life art with roots in Confucian, Taoists and Buddhist theory. It centers around applied peace and health studies rather than defence or physical action. It emphasizes the unification of mind, body and environment using the physiological theory of yin, yang and five-element Traditional Chinese medicine. Its movements, exercises, and teachings cultivate, direct, and harmonise the qi.

Gogyo
The Japanese term is gogyo (Japanese:五行, romanized: gogyō). During the 5th and 6th centuries (Kofun period), Japan adopted various philosophical disciplines such as Taoism, Chinese Buddhism and Confucianism through monks and physicians from China. As opposed to theory of Godai that is form based and was introduced to Japan through India and Tibetan Buddhism evolving the Onmyōdō system. In particular, wuxing was adapted into gogyo. These theories have been extensively practiced in Japanese acupuncture and traditional Kampo medicine.

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title: Wuxing (Chinese philosophy)


text:
Talk:Wuxing (Chinese philosophy)

Theory

 * Even when we know now the electrons, not the positive charge flow in the circuit, the definition of electric current is not abandoned because the model still works despite the invalid underlying theory.

This is a misrepresentation of the theory of electromagnetism. The definition of electric current is in no way invalidated by the fact that electrons are negatively charged. The definition is J=dρ/dt, and this definition gives no special place to either positive or negative charge.

I'm changing it to an example that hardly anyone will understand, but at least it's factually accurate. -- Tim Starling

-- This is incomprehensible. The statement that a scientific model does not have to be valid to be useful makes no sense.

 * At first sight, the theory behind the five elements seems to be very unscientific. However, if one thinks of it as a model and scaffolding to build knowledge on, one may find the system intriguing.  Even the western scientific model does not have to be valid to be useful.  One example is classical electrodynamics - even though it suffers fundamental problems such as infinite field energy and acausal acceleration, it is still widely used. By the same token, the five elements system is a useful model regardless how unscientific it may seem to be

-- User:Roadrunner

5 "Elemental" Phases Are All the Same Around the World
This is a theory..

In understanding the cyclical elements, we shall rely on the traditional Wu Xing arrangement alongside the contemporary Wiccan arrangement of the classical Greek Phases. I shall use parallel examples of the classical Babylonian 'elemental' phases.

The question of 'physical' elements is not of consequence in any philosophical arrangement of cycles, whether eastern or western. Rather than labeling the "phases" or "walks" with physical substance, we can instead "colour" these cyclical patterns. Before we break into this, first, one must understand the true orbital flow of our planet relative to our season changes. It is after the Winter solstice in which the initial spark of Yang (projective) energy is truly born, considering that the days become longer after the beginning of Winter. Thus, climatic changes observed during Spring had already taken place on a "cosmic" scale back in Winter...

During Winter, we enter the 'Green' spectral energy phase. It's climatic traits manifest during the Spring, but during Winter, its cosmic energy traits are occurring. This 'Green' flow may correlate with either the Chinese phase of Water (Stream on the Pakua), the Greek element of Earth or the Chaldean element of the Sea. During the Spring, we enter the energy spectral phase of the 'Yellow.' Its energies climatically manifest during the summer when the sun is strongest. "Yellow" energy may be associated with the Chinese element of Wood (Lightning and Wind) and the Greek and Babylonian elements of Air. The hallmarks of this energy phase is forward optimistic thinking and cognitive awakeness.. During the Summer, our world enters the "Red" energy phase. This phase of transformation is representative of the light and warmth which follows combustion, thus it is a period of relative stillness and inner stability when compared to the flammable 'yellow' phase. Its traits correspond with seasonal changes observed visibly during Autumn. "Red" is associated with the philosophical Chinese and Greek elements of Fire and the Chaldean element of Light. During Autumn, our planet enters the "Blue" energy phase. "Blue" is a colour of internal serenity, slumber and rest. During the Winter, reminiscent climatic traits become visible. "Blue" energy is associated with the Chinese element of Metal (Heaven and Lake), the Greek element of Water and the Babylonian element of Heaven. It is associated with the theoretical substance of aether in modern physics. This "element" represents substance of formless potential. Both the Chinese in some respect (through the Lake) and the Greeks have associated this phase with Water. However, this "phase" also enacts traits reminiscent of physical characteristics of pure metals such as iron, silver and platinum- hence the Chinese proper association. Neither the Chinese nor the Greeks wished to associate their elements with theoretical forms of matter which were then beyond grasp, hence the Greeks called this phase "water" and the Chinese "metal."

Safe to believe, the Chinese signs of the Ox, Snake and Rooster are "Green" as they correspond to the Earth ptolemaic astrolgical signs. The Tiger, Horse and Dog are "Yellow" as they correspond to the ptolemaic air signs. The Dragon, Monkey and Rat are "Red" as they correspond to the Fire ptolemaic signs. The Rabbit, Goat and Pig are "Blue" as they correspond to the ptolemaic Water star signs.

Did some editing
I considered it somewhat inappropriate that this page and Zang Fu theory were linking to Western medicine entries about organs, and have threfore created corresponding (Zang) and (Fu) stubs, linked to those where I considered it appropriate and moved some content from Pericardium to Pericardium (Zang), putting in some appropriate linking text instead.

Also deleted 'hair' from the list corresponding to the Metal element, since the body hair is Metal and the head hair is Water (Maciocia, The Foundations of Chinese Medicine) - leaving it there could create potential for confusion. User:NickArgall

add
wood matter is yin metal air energy is yang left months table information arctic antarctic difference etc.

Countries
In an old version of this article, the following correspondence between the elements and some countries were noted:

Earth - China

Metal - Hong Kong

Water - Japan

Wood - Taiwan

Fire - South Korea

Why was this removed? Answer: The correspondence is wrong and probably has no source. Hong Kong is not West of China so it can't be Metal. Similarly, Japan is not North, and South Korea is not South. Taiwan is East, but I highly doubt it's big enough to warrant an entire phase/agent for. — Preceding unsigned comment added by 72.216.186.113 (talk) 09:29, 19 September 2023 (UTC)

Merger proposal
I propose merging Gogyo into Wuxing (Chinese philosophy), as per the earlier Talk:Gogyo suggestion of User:Mazamadao. Gogyo is simply the Japanese language translation of the Chinese Wuxing and no compelling argument for its retention as a separate article has been made. As Gogyo is only a stub, created by a (now blocked) disruptive editor and maintained by their socks, it seems sensible to merge the two articles. Midnightblueowl (talk) 13:27, 1 April 2022 (UTC)
 * I would endorse your proposal, since, as the article itself said, "Gogyo" is just Japanese for "Wuxing". In fact, it is the only thing this entire article says! Furthermore, I checked the history of the article, and I found that it was a redirect to Wuxing from 2007 to 2014, and a disambiguation page until 2020! Maybe we can mention the Japanese term at the beginning of the Wuxing article? Either way, the "Gogyo" article isn't very useful! SleepTrain456 (talk) 02:16, 19 April 2022 (UTC)
 * Support The previous edits on Gogyo by User talk:Zongqi were moot at all, merging to Wuxing (Chinese philosophy) is more understandable. UU (talk) 15:52, 20 May 2022 (UTC)
 * ✅ Klbrain (talk) 07:06, 29 August 2022 (UTC)

Sources for Section on Ming Neiyin?
I cannot find a source for the chart under the heading Ming Neiyin. There is no source listed in this article, nor is this chart referenced in the main article "Heavenly Stems", nor does the book from which the "Heavenly Stems" article is sourced mention anything about "Fortress Earth" or "Forest Wood" (or any of the other listed names, as far as I can tell). Finally, I have failed to find any source on the web that discusses this information (except for a few dozen sites that have simply copy/pasted this article).

At the very least, there needs to be a "citation needed" note, but I can find no evidence that this information is accurate, historically or otherwise. VoxAdActa (talk) 21:23, 9 August 2023 (UTC)

The Days and Planets don't make sense
There's a table under the "Cosmology and feng shui" section. In antiquity, only Mercury, Venus, Mars, Jupiter, and Saturn were visible in the sky. And even if there were eight planets, Bagua has no association with them. Also, the Chinese Calendar uses nine or ten day weeks, not five days as this table seems to suggest. My guess is that someone tried connecting the days of the week with the planets, but that was done in western culture as part of Hellenistic astronomy. 72.216.186.113 (talk) 09:21, 19 September 2023 (UTC)

Quincunx or pentagram?
After scrolling through pages of images relating to the wuxing, I noticed that the pentagram arrangement shown in the article only ever appears in computer-illustrated diagrams, while any diagrams of the wuxing featured in older documents and emblems use a quincunx arrangement with Earth in the centre and the other phases in the four corners, corresponding to the cardinal directions. This suggests that the pentagram is just a convenient representation of the traditionally tabulated relationships between the phases, but not a traditional representation itself. If sources discussing the iconography could be found, it would make sense to replace the current image with a more traditional one. Albie's relation of misfortune (talk) 12:02, 25 May 2024 (UTC)

 * Update: ofc. this is not a reliable source, but there are some good pointers at https://elementaljapan.com/2021/09/23/solving-the-puzzle-of-the-pentagram-and-the-five-phases-in-japan/. Albie's relation of misfortune (talk) 14:55, 25 May 2024 (UTC)

title: Talk:Wuxing (Chinese philosophy)


text:
Church of Christ, Scientist

The Church of Christ, Scientist was founded in 1879 in Boston, Massachusetts, by Mary Baker Eddy, author of Science and Health with Key to the Scriptures, and founder of Christian Science. The church was founded "to commemorate the word and works of Christ Jesus" and "reinstate primitive Christianity and its lost element of healing".

In the early decades of the 20th century, Christian Science churches were founded in communities around the world, though in the last several decades of that century, there was a marked decline in membership, except in Africa, where there has been growth. Headquartered in Boston, the church does not officially report membership, and estimates as to worldwide membership range from under 100,000 to about 400,000.

History
The church was incorporated by Mary Baker Eddy in 1879, following a claimed personal healing in 1866, which she said resulted from reading the Bible. The Bible and Eddy's textbook on Christian healing, Science and Health with Key to the Scriptures, are together the church's key doctrinal sources and have been ordained as the church's "dual impersonal pastor".

The First Church of Christ, Scientist publishes the weekly newspaper The Christian Science Monitor in print and online.

Beliefs and practices
Christian Scientists believe that prayer is effective for healing diseases. The Church has collected over 50,000 testimonies of incidents that it considers healing through Christian Science treatment alone. While most of these testimonies represent ailments neither diagnosed nor treated by medical professionals, the Church requires three other people to vouch for any testimony published in any of its official organs, including the Christian Science Journal, Christian Science Sentinel, and Herald of Christian Science; verifiers say that they witnessed the healing or know the testifier well enough to vouch for them.

Christian Scientists may take an intensive two-week "Primary" class from an authorized Christian Science teacher. Those who wish to become "Journal-listed" (accredited) practitioners, devoting themselves full-time to the practice of healing, must first have Primary class instruction. When they have what the church regards as a record of healing, they may submit their names for publication in the directory of practitioners and teachers in the Christian Science Journal. A practitioner who has been listed for at least three years may apply for "Normal" class instruction, given once every three years. Those who receive a certificate are authorized to teach. Both Primary and Normal classes are based on the Bible and the writings of Mary Baker Eddy. The Primary class focuses on the chapter "Recapitulation" in Science and Health with Key to the Scriptures. This chapter uses the Socratic method of teaching and contains the "Scientific Statement of Being". The "Normal" class focuses on the platform of Christian Science, contained on pages 330-340 of Science and Health.

Organization
The First Church of Christ, Scientist is the legal title of The Mother Church and administrative headquarters of the Christian Science Church. The Mary Baker Eddy Library for the Betterment of Humanity is housed in an 11-story structure originally built for The Christian Science Publishing Society.

An international newspaper, The Christian Science Monitor, founded by Eddy in 1908 and winner of seven Pulitzer prizes, is published by the church through the Christian Science Publishing Society.

Board of directors
The Christian Science Board of Directors is a five-person executive entity created by Mary Baker Eddy to conduct the business of the Christian Science Church under the terms defined in the by-laws of the Church Manual. Its functions and restrictions are defined by the Manual.

Broadcasting
Beginning in the mid-1980s, church executives undertook a controversial and ambitious foray into electronic broadcast media. The first significant effort was to create a weekly half-hour syndicated television program, The Christian Science Monitor Reports. "Monitor Reports" was anchored in its first season by newspaper veteran Rob Nelson. He was replaced in the second by the Christian Science Monitor's former Moscow correspondent, David Willis.

In October 1991, after a series of conflicts over the boundaries between Christian Science teachings and his journalistic independence, John Hart resigned.

The hundreds of millions lost on broadcasting brought the church to the brink of bankruptcy. However, with the 1991 publication of The Destiny of The Mother Church by the late Bliss Knapp, the church secured a $90 million bequest from the Knapp trust. The trust dictated that the book be published as "Authorized Literature", with neither modification nor comment. Historically, the church had censured Knapp for deviating at several points from Eddy's teaching, and had refused to publish the work. The church's archivist, fired in anticipation of the book's publication, wrote to branch churches to inform them of the book's history. Many Christian Scientists thought the book violated the church's by-laws, and the editors of the church's religious periodicals and several other church employees resigned in protest. Alternate beneficiaries subsequently sued to contest the church's claim it had complied fully with the will's terms, and the church ultimately received only half of the original sum.

The fallout of the broadcasting debacle also sparked a minor revolt among some prominent church members. In late 1993, a group of Christian Scientists filed suit against the Board of Directors, alleging a willful disregard for the Manual of The Mother Church in its financial dealings. The suit was thrown out by the Supreme Judicial Court of Massachusetts in 1997, but a lingering discontent with the church's financial matters persists to this day. The Destiny Of The Mother Church ceased publication in September 2023.

Membership decline and financial setbacks
In spite of its early meteoric rise, church membership has declined over the past eight decades, according to the church's former treasurer, J. Edward Odegaard. Though the Church is prohibited by the Manual from publishing membership figures, the number of branch churches in the United States has fallen steadily since World War II. In 2009, for the first time in church history, more new members came from Africa than the United States.

In 2005, The Boston Globe reported that the church was considering consolidating Boston operations into fewer buildings and leasing out space in buildings it owned. Church official Philip G. Davis noted that the administration and Colonnade buildings had not been fully used for many years and that vacancy increased after staff reductions in 2004. The church posted an $8 million financial loss in fiscal 2003, and in 2004 cut 125 jobs, a quarter of the staff, at the Christian Science Monitor. Conversely, Davis noted that "the financial situation right now is excellent" and stated that the church was not facing financial problems.

Use of spiritual healing in place of medical treatment
In the United States, Christian Scientist parents whose children have died for lack of access to medical treatment have been the subject of considerable controversy. At least 50 Christian Scientists have been charged with manslaughter or even murder of children whose illnesses were otherwise curable using standard medical techniques. The outcomes of these cases have been inconsistent. Some courts have held that parents are free to refuse treatment for themselves on religious grounds, but cannot refuse treatment for their children, while others have found that religious liberty empowers parents to forgo seeking medical care for a child in favor of spiritual healing.

The lack of consensus on whether Christian Scientist parents can be compelled to obtain medical care for their children is reflected in the laws of various U.S. states. As of 2016, 34 states and the District of Columbia recognized religious exemptions to state child neglect laws. Of those 34, 16 permitted courts to order treatment. A total of 16 states did not recognize any religious exemption.

title: Church of Christ, Scientist


text:
Talk:Timeline of computing

New Application Area
I think YouTube and its contemporaries revolutionized the interaction with Internet which people new use as a gigantic digital video recorder leaving aside telvision. DynV (talk) 01:35, 11 July 2010 (UTC)
 * ✅--greenrd (talk) 16:23, 26 August 2017 (UTC)

How is/was this image produced
I may be overlooking something, but how was the image and imagemap produced?

Any links for recreating so I can add the updates mentioned above and some more of my own? (I want to add a link to the Go programming language in 2007, but once I start I'm sure there will be many other updates).

Is there a general HOWTO wikipedia doc, if not, I shall create one. — Preceding unsigned comment added by Ganly (talk • contribs) 21:17, 15 February 2017 (UTC)
 * The actual image is generated by Template:Timeline History of Computing. That page uses a very obscure undocumented language, which is used almost nowhere else on Wikipedia! If you need any help, just @ mention me or write a message on my talk page.--greenrd (talk) 15:18, 26 August 2017 (UTC)

Graphic Missing
The graphical timeline is now missing. Was this purposefully removed? 38.108.59.142 (talk) 15:21, 6 September 2019 (UTC)

title: Talk:Timeline of computing