1.
Mantle (geology)
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The mantle is a layer inside a terrestrial planet and some other rocky planetary bodies. For a mantle to form, the body must be large enough to have undergone the process of planetary differentiation by density. The mantle surrounds the planetary core, the mantle is surrounded by the crust. The terrestrial planets, the Moon, two of Jupiters moons and the asteroid Vesta each have a made of silicate rock. Interpretation of spacecraft data suggests that at least two moons of Jupiter, as well as Titan and Triton each have a mantle made of ice or other solid volatile substances. The interior of Earth, similar to the terrestrial planets, is divided into layers of different composition. The mantle is a layer between the crust and the outer core, Earths mantle is a silicate rocky shell with an average thickness of 2,886 kilometres. The mantle makes up about 84% of Earths volume and it is predominantly solid but in geological time it behaves as a very viscous fluid. The mantle encloses the hot core rich in iron and nickel, past episodes of melting and volcanism at the shallower levels of the mantle have produced a thin crust of crystallized melt products near the surface. A thin crust, the part of the lithosphere, surrounds the mantle and is about 5 to 75 km thick. In some places under the ocean the mantle is exposed on the surface of Earth. The mantle is divided into sections which are based upon results from seismology and these layers are the following, the upper mantle, the transition zone, the lower mantle, and anomalous core–mantle boundary with a variable thickness. The uppermost mantle plus overlying crust are relatively rigid and form the lithosphere, below the lithosphere the upper mantle becomes notably more plastic. In some regions below the lithosphere, the shear velocity is reduced. Inge Lehmann discovered a seismic discontinuity at about 220 km depth, although this discontinuity has been found in other studies, the transition zone is an area of great complexity, it physically separates the upper and lower mantle. Very little is known about the lower mantle apart from that it appears to be relatively seismically homogeneous, the D layer at the core–mantle boundary separates the mantle from the core. A principal source of the heat that drives plate tectonics is the decay of uranium, thorium. The mantle differs substantially from the crust in its properties as the direct consequence of the difference in composition
2.
Molecule
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A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge, however, in quantum physics, organic chemistry, and biochemistry, the term molecule is often used less strictly, also being applied to polyatomic ions. In the kinetic theory of gases, the molecule is often used for any gaseous particle regardless of its composition. According to this definition, noble gas atoms are considered molecules as they are in fact monoatomic molecules. A molecule may be homonuclear, that is, it consists of atoms of one element, as with oxygen, or it may be heteronuclear. Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are not considered single molecules. Molecules as components of matter are common in organic substances and they also make up most of the oceans and atmosphere. Also, no typical molecule can be defined for ionic crystals and covalent crystals, the theme of repeated unit-cellular-structure also holds for most condensed phases with metallic bonding, which means that solid metals are also not made of molecules. In glasses, atoms may also be together by chemical bonds with no presence of any definable molecule. The science of molecules is called molecular chemistry or molecular physics, in practice, however, this distinction is vague. In molecular sciences, a molecule consists of a system composed of two or more atoms. Polyatomic ions may sometimes be thought of as electrically charged molecules. The term unstable molecule is used for very reactive species, i. e, according to Merriam-Webster and the Online Etymology Dictionary, the word molecule derives from the Latin moles or small unit of mass. Molecule – extremely minute particle, from French molécule, from New Latin molecula, diminutive of Latin moles mass, a vague meaning at first, the vogue for the word can be traced to the philosophy of Descartes. The definition of the molecule has evolved as knowledge of the structure of molecules has increased, earlier definitions were less precise, defining molecules as the smallest particles of pure chemical substances that still retain their composition and chemical properties. Molecules are held together by covalent bonding or ionic bonding. Several types of non-metal elements exist only as molecules in the environment, for example, hydrogen only exists as hydrogen molecule. A molecule of a compound is made out of two or more elements, a covalent bond is a chemical bond that involves the sharing of electron pairs between atoms
3.
Gas
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Gas is one of the four fundamental states of matter. A pure gas may be made up of atoms, elemental molecules made from one type of atom. A gas mixture would contain a variety of pure gases much like the air, what distinguishes a gas from liquids and solids is the vast separation of the individual gas particles. This separation usually makes a colorless gas invisible to the human observer, the interaction of gas particles in the presence of electric and gravitational fields are considered negligible as indicated by the constant velocity vectors in the image. One type of commonly known gas is steam, the gaseous state of matter is found between the liquid and plasma states, the latter of which provides the upper temperature boundary for gases. Bounding the lower end of the temperature scale lie degenerative quantum gases which are gaining increasing attention, high-density atomic gases super cooled to incredibly low temperatures are classified by their statistical behavior as either a Bose gas or a Fermi gas. For a comprehensive listing of these states of matter see list of states of matter. The only chemical elements which are stable multi atom homonuclear molecules at temperature and pressure, are hydrogen, nitrogen and oxygen. These gases, when grouped together with the noble gases. Alternatively they are known as molecular gases to distinguish them from molecules that are also chemical compounds. The word gas is a neologism first used by the early 17th-century Flemish chemist J. B. van Helmont, according to Paracelsuss terminology, chaos meant something like ultra-rarefied water. An alternative story is that Van Helmonts word is corrupted from gahst and these four characteristics were repeatedly observed by scientists such as Robert Boyle, Jacques Charles, John Dalton, Joseph Gay-Lussac and Amedeo Avogadro for a variety of gases in various settings. Their detailed studies ultimately led to a relationship among these properties expressed by the ideal gas law. Gas particles are separated from one another, and consequently have weaker intermolecular bonds than liquids or solids. These intermolecular forces result from interactions between gas particles. Like-charged areas of different gas particles repel, while oppositely charged regions of different gas particles attract one another, transient, randomly induced charges exist across non-polar covalent bonds of molecules and electrostatic interactions caused by them are referred to as Van der Waals forces. The interaction of these forces varies within a substance which determines many of the physical properties unique to each gas. A comparison of boiling points for compounds formed by ionic and covalent bonds leads us to this conclusion, the drifting smoke particles in the image provides some insight into low pressure gas behavior
4.
Liquid
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A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a constant volume independent of pressure. As such, it is one of the four states of matter. A liquid is made up of tiny vibrating particles of matter, such as atoms, water is, by far, the most common liquid on Earth. Like a gas, a liquid is able to flow and take the shape of a container, most liquids resist compression, although others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, a distinctive property of the liquid state is surface tension, leading to wetting phenomena. The density of a liquid is usually close to that of a solid, therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, although liquid water is abundant on Earth, this state of matter is actually the least common in the known universe, because liquids require a relatively narrow temperature/pressure range to exist. Most known matter in the universe is in form as interstellar clouds or in plasma form within stars. Liquid is one of the four states of matter, with the others being solid, gas. Unlike a solid, the molecules in a liquid have a greater freedom to move. The forces that bind the molecules together in a solid are only temporary in a liquid, a liquid, like a gas, displays the properties of a fluid. A liquid can flow, assume the shape of a container, if liquid is placed in a bag, it can be squeezed into any shape. These properties make a suitable for applications such as hydraulics. Liquid particles are bound firmly but not rigidly and they are able to move around one another freely, resulting in a limited degree of particle mobility. As the temperature increases, the vibrations of the molecules causes distances between the molecules to increase. When a liquid reaches its point, the cohesive forces that bind the molecules closely together break. If the temperature is decreased, the distances between the molecules become smaller, only two elements are liquid at standard conditions for temperature and pressure, mercury and bromine. Four more elements have melting points slightly above room temperature, francium, caesium, gallium and rubidium, metal alloys that are liquid at room temperature include NaK, a sodium-potassium metal alloy, galinstan, a fusible alloy liquid, and some amalgams
5.
Diffusion
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Diffusion is the net movement of molecules or atoms from a region of high concentration to a region of low concentration. This is also referred to as the movement of a substance down a concentration gradient, a gradient is the change in the value of a quantity with the change in another variable. The word diffusion derives from the Latin word, diffundere, which means to spread out, a distinguishing feature of diffusion is that it results in mixing or mass transport, without requiring bulk motion. Thus, diffusion should not be confused with convection, or advection, an example of a situation in which bulk flow and diffusion can be differentiated is the mechanism by which oxygen enters the body during external respiration. The lungs are located in the cavity, which expands as the first step in external respiration. This expansion leads to an increase in volume of the alveoli in the lungs and this creates a pressure gradient between the air outside the body and the alveoli. The air moves down the gradient through the airways of the lungs and into the alveoli until the pressure of the air. The air arriving in the alveoli has a concentration of oxygen than the “stale” air in the alveoli. The increase in oxygen concentration creates a concentration gradient for oxygen between the air in the alveoli and the blood in the capillaries that surround the alveoli, oxygen then moves by diffusion, down the concentration gradient, into the blood. The other consequence of the air arriving in alveoli is that the concentration of carbon dioxide in the alveoli decreases and this creates a concentration gradient for carbon dioxide to diffuse from the blood into the alveoli. The pumping action of the heart then transports the blood around the body, as the left ventricle of the heart contracts, the volume decreases, which increases the pressure in the ventricle. This creates a gradient between the heart and the capillaries, and blood moves through blood vessels by bulk flow. The concept of diffusion is widely used in, physics, chemistry, biology, sociology, economics, however, in each case, the object that is undergoing diffusion is “spreading out” from a point or location at which there is a higher concentration of that object. In the phenomenological approach, diffusion is the movement of a substance from a region of high concentration to a region of low concentration without bulk motion, according to Ficks laws, the diffusion flux is proportional to the negative gradient of concentrations. It goes from regions of higher concentration to regions of lower concentration, some time later, various generalizations of Ficks laws were developed in the frame of thermodynamics and non-equilibrium thermodynamics. From the atomistic point of view, diffusion is considered as a result of the walk of the diffusing particles. In molecular diffusion, the molecules are self-propelled by thermal energy. Random walk of small particles in suspension in a fluid was discovered in 1827 by Robert Brown, the theory of the Brownian motion and the atomistic backgrounds of diffusion were developed by Albert Einstein
6.
Kelly Kettle
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Kelly Kettle and Volcano Kettle are registered trademarks of the Kelly Kettle company which first produced the product in Ireland in the early 1900s. The Thermette was first manufactured in New Zealand in 1929 and was standard issue for the New Zealand Army during World War II where it was known as a Benghazi boiler, other companies, including the Eydon Kettle Company started manufacture at later dates. Earlier examples of water using a water jacket include heavier samovar tea urns from Eastern, Central. Early examples of devices that heat water surrounding a fire include samovar tea urns from Eastern, Central, the Kelly Kettle Company first manufactured portable devices of this type four generations ago in the early 1900s. The Thermette was invented in 1929 in New Zealand by John Ashley Hart and it was standard issue to the New Zealand army serving in the North Africa during WW2 when it was known as the Benghasi Boiler. In 1939 the New Zealand Army asked Hart to waive his patent so they could make their own Thermettes, he agreed, a modified version of the idea was created by the Eydon Kettle Company in the early 1970s and sold as the Storm Kettle. Fixed rocket stoves used for cooking were developed in 1980s, with variants for heating water, the kettles are normally constructed from a durable heat-conductive metal, such as aluminium, stainless steel, copper or tin. The source of heat is typically from small items of material such as paper. A base placed below the body section holds the fuel. Additional fuel can be added to the fire without removing the kettle by dropping it down the chimney, common among all designs is the principle of internal chimney to create the efficient upward draught of heat. Variations around a core design have been produced by a number of manufacturers, typical water capacities are between 0. 5–1.5 litres. Some kettles have the flame holder at the base integral and some allow it to be removed, if the base is removable, it may be possible to store other items, or specially designed cook sets within the chimney during transport. Devices normally come with a swinging or fixed handle depending on the design. If left in place even loosely the hot water vapor can make the cork swell and hold fast and these add-ons typically store inside the chimney for transport. Further add-ons can turn the chimney into a cooking range, with the cooking containers. The fire bases may be inverted and stored inside the chimney, the Dingo Bush Kettle, has a removable bottom plate for the fire base, which is integral to the kettle. It has a different shape, being more rounded than the other kettles. The Volcano Kettle from the Kelly Kettle Company, the Storm Kettle by the Eydon Kettle Company, the common design has a removable base, inside which the fire is lit
7.
Bunsen burner
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A Bunsen burner, named after Robert Bunsen, is a common piece of laboratory equipment that produces a single open gas flame, which is used for heating, sterilization, and combustion. The gas can be gas or a liquefied petroleum gas, such as propane, butane. In 1852 the University of Heidelberg hired Bunsen and promised him a new laboratory building, the city of Heidelberg had begun to install coal-gas street lighting, and so the university laid gas lines to the new laboratory. The designers of the building intended to use the gas not just for illumination, for any burner lamp, it was desirable to maximize the temperature and minimize luminosity. However, existing laboratory burner lamps left much to be desired not just in terms of the heat of the flame, but also regarding economy and simplicity. While the building was still under construction in late 1854 Bunsen suggested certain design principles to the mechanic, Peter Desaga. The Bunsen/Desaga design succeeded in generating a hot, sootless, non-luminous flame by mixing the gas with air in a controlled fashion before combustion, Desaga created adjustable slits for air at the bottom of the cylindrical burner, with the flame igniting at the top. By the time the building opened early in 1855 Desaga had made fifty of the burners for Bunsens students, two years later Bunsen published a description, and many of his colleagues soon adopted the design. Bunsen burners are now used in all around the world. The device in use today safely burns a continuous stream of a gas such as natural gas or a liquefied petroleum gas such as propane, butane. The hose barb is connected to a gas nozzle on the bench with rubber tubing. Most laboratory benches are equipped with multiple gas nozzles connected to a gas source, as well as vacuum, nitrogen. The gas then flows up through the base through a hole at the bottom of the barrel and is directed upward. There are open slots in the side of the bottom to admit air into the stream via the venturi effect. The most common methods of lighting the burner are using a match or a spark lighter, the amount of air mixed with the gas stream affects the completeness of the combustion reaction. Less air yields an incomplete and thus cooler reaction, while a gas stream well mixed with air provides oxygen in an amount and thus a complete. The air flow can be controlled by opening or closing the openings at the base of the barrel. If the collar at the bottom of the tube is adjusted so more air can mix with the gas before combustion, the flame will burn hotter, appearing blue as a result
8.
Convective heat transfer
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Convective heat transfer, often referred to simply as convection, is the transfer of heat from one place to another by the movement of fluids. Convection is usually the dominant form of transfer in liquids. Although often discussed as a method of heat transfer, convective heat transfer involves the combined processes of unknown conduction and advection. Convection can be forced by movement of a fluid by means other than buoyancy forces, Thermal expansion of fluids may also force convection. In other cases, natural buoyancy forces alone are responsible for fluid motion when the fluid is heated. An example is the draft in a chimney or around any fire, for example, when water is heated on a stove, hot water from the bottom of the pan rises, displacing the colder denser liquid, which falls. After heating has stopped, mixing and conduction from this natural convection eventually result in a nearly homogeneous density, without the presence of gravity, natural convection does not occur, and only forced-convection modes operate. The convection heat transfer mode comprises one mechanism, in addition to energy transfer due to specific molecular motion, energy is transferred by bulk, or macroscopic, motion of the fluid. This motion is associated with the fact that, at any instant, such motion, in the presence of a temperature gradient, contributes to heat transfer. It is customary to use the term convection when referring to this cumulative transport, in the absence of an external source, when the fluid is in contact with a hot surface, its molecules separate and scatter, causing the fluid to be less dense. As a consequence, the fluid is displaced while the cooler fluid gets denser, thus, the hotter volume transfers heat towards the cooler volume of that fluid. Familiar examples are the flow of air due to a fire or hot object. Forced convection, when a fluid is forced to flow over the surface by a source such as fans, by stirring. Internal and external flow can also classify convection, internal flow occurs when a fluid is enclosed by a solid boundary such when flowing through a pipe. An external flow occurs when a fluid extends indefinitely without encountering a solid surface, both of these types of convection, either natural or forced, can be internal or external because they are independent of each other. Further classification can be made depending on the smoothness and undulations of the solid surfaces, not all surfaces are smooth, though a bulk of the available information deals with smooth surfaces. Wavy irregular surfaces are commonly encountered in heat transfer devices which include solar collectors, regenerative heat exchangers and they have a significant role to play in the heat transfer processes in these applications. Since they bring in an added complexity due to the undulations in the surfaces, also they do affect the flow and heat transfer characteristics, thereby behaving differently from straight smooth surfaces
9.
Heat transfer
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Heat transfer is the exchange of thermal energy between physical systems. The rate of transfer is dependent on the temperatures of the systems. The three fundamental modes of transfer are conduction, convection and radiation. Heat transfer, the flow of energy in the form of heat, is a process by which an internal energy is changed. Conduction is also known as diffusion, not to be confused with related to the mixing of constituents of a fluid. The direction of transfer is from a region of high temperature to another region of lower temperature. Heat transfer changes the energy of the systems from which. Heat transfer will occur in a direction that increases the entropy of the collection of systems, Heat transfer ceases when thermal equilibrium is reached, at which point all involved bodies and the surroundings reach the same temperature. Thermal expansion is the tendency of matter to change in volume in response to a change in temperature, Heat is defined in physics as the transfer of thermal energy across a well-defined boundary around a thermodynamic system. The thermodynamic free energy is the amount of work that a system can perform. Enthalpy is a potential, designated by the letter H. Joule is a unit to quantify energy, work, or the amount of heat, thermodynamic and mechanical heat transfer is calculated with the heat transfer coefficient, the proportionality between the heat flux and the thermodynamic driving force for the flow of heat. Heat flux is a quantitative, vectorial representation of heat-flow through a surface, in engineering contexts, the term heat is taken as synonymous to thermal energy. This usage has its origin in the interpretation of heat as a fluid that can be transferred by various causes. Thermal engineering concerns the generation, use, conversion, and exchange of heat transfer, as such, heat transfer is involved in almost every sector of the economy. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. The fundamental modes of transfer are, Advection Advection is the transport mechanism of a fluid from one location to another. Conduction or diffusion The transfer of energy between objects that are in physical contact, thermal conductivity is the property of a material to conduct heat and evaluated primarily in terms of Fouriers Law for heat conduction
10.
Mass transfer
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Mass transfer is the net movement of mass from one location, usually meaning stream, phase, fraction or component, to another. Mass transfer occurs in many processes, such as absorption, evaporation, drying, precipitation, membrane filtration, mass transfer is used by different scientific disciplines for different processes and mechanisms. The phrase is used in engineering for physical processes that involve diffusive and convective transport of chemical species within physical systems. Some common examples of mass transfer processes are the evaporation of water from a pond to the atmosphere, the purification of blood in the kidneys and liver, mass transfer is often coupled to additional transport processes, for instance in industrial cooling towers. These towers couple heat transfer to transfer by allowing hot water to flow in contact with hotter air. It is a phenomenon in binary systems, and may play an important role in some types of supernovae. Mass transfer finds extensive application in engineering problems. It is used in engineering, separations engineering, heat transfer engineering. The driving force for mass transfer is typically a difference in chemical potential, a chemical species moves from areas of high chemical potential to areas of low chemical potential. Thus, the theoretical extent of a given mass transfer is typically determined by the point at which the chemical potential is uniform. This rate can be quantified through the calculation and application of mass transfer coefficients for an overall process and these mass transfer coefficients are typically published in terms of dimensionless numbers, often including Péclet numbers, Reynolds numbers, Sherwood numbers and Schmidt numbers, among others. There are notable similarities in the commonly used approximate differential equations for momentum, heat, a great deal of effort has been devoted to developing analogies among these three transport processes so as to allow prediction of one from any of the others
11.
Brownian motion
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Brownian motion or pedesis is the random motion of particles suspended in a fluid resulting from their collision with the fast-moving atoms or molecules in the gas or liquid. This transport phenomenon is named after the botanist Robert Brown and this explanation of Brownian motion served as convincing evidence that atoms and molecules exist, and was further verified experimentally by Jean Perrin in 1908. Perrin was awarded the Nobel Prize in Physics in 1926 for his work on the structure of matter. Brownian motion is among the simplest of the stochastic processes. This universality is closely related to the universality of the normal distribution, in both cases, it is often mathematical convenience, rather than the accuracy of the models, that motivates their use. The Roman Lucretiuss scientific poem On the Nature of Things has a description of Brownian motion of dust particles in verses 113 –140 from Book II. He uses this as a proof of the existence of atoms, Observe what happens when sunbeams are admitted into a building and you will see a multitude of tiny particles mingling in a multitude of ways. Their dancing is an indication of underlying movements of matter that are hidden from our sight. It originates with the atoms which move of themselves, then those small compound bodies that are least removed from the impetus of the atoms are set in motion by the impact of their invisible blows and in turn cannon against slightly larger bodies. So the movement mounts up from the atoms and gradually emerges to the level of our senses, so that those bodies are in motion that we see in sunbeams, moved by blows that remain invisible. Although the mingling motion of dust particles is caused largely by air currents, while Jan Ingenhousz described the irregular motion of coal dust particles on the surface of alcohol in 1785, the discovery of this phenomenon is often credited to the botanist Robert Brown in 1827. Brown was studying pollen grains of the plant Clarkia pulchella suspended in water under a microscope when he observed minute particles, ejected by the pollen grains, executing a jittery motion. By repeating the experiment with particles of matter he was able to rule out that the motion was life-related. The first person to describe the mathematics behind Brownian motion was Thorvald N. Thiele in a paper on the method of least squares published in 1880. This was followed independently by Louis Bachelier in 1900 in his PhD thesis The theory of speculation, in which he presented an analysis of the stock. The Brownian motion model of the market is often cited. Albert Einstein and Marian Smoluchowski brought the solution of the problem to the attention of physicists and their equations describing Brownian motion were subsequently verified by the experimental work of Jean Baptiste Perrin in 1908. In this way Einstein was able to determine the size of atoms, in accordance to Avogadros law this volume is the same for all ideal gases, which is 22.414 liters at standard temperature and pressure
12.
Natural convection
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In natural convection, fluid surrounding a heat source receives heat, becomes less dense and rises. The surrounding, cooler fluid then moves to replace it and this cooler fluid is then heated and the process continues, forming a convection current, this process transfers heat energy from the bottom of the convection cell to top. The driving force for natural convection is buoyancy, a result of differences in fluid density, because of this, the presence of a proper acceleration such as arises from resistance to gravity, or an equivalent force, is essential for natural convection. Natural convection has attracted a deal of attention from researchers because of its presence both in nature and engineering applications. In nature, convection cells formed from air raising above sunlight-warmed land or water are a feature of all weather systems. Convection is also seen in the plume of hot air from fire, oceanic currents. A very common application of natural convection is free air cooling without the aid of fans. The onset of natural convection is determined by the Rayleigh number, Convection will be less likely and/or less rapid with more rapid diffusion and/or a more viscous fluid. For thermal convection due to heating from below, as described in the pot above. The general diffusivity, D, is redefined as a thermal diffusivity, D = α Inserting these substitutions produces a Rayleigh number that can be used to predict thermal convection. Ra = ρ0 g β Δ T L3 α μ The tendency of a particular naturally convective system towards turbulence relies on the Grashof number. G r = g β Δ T L3 ν2 In very sticky, viscous fluids, fluid movement is restricted, and natural convection will be non-turbulent. Following the treatment of the subsection, the typical fluid velocity is of the order of g Δ ρ L2 / μ. Therefore, Grashof number can be thought of as Reynolds number with the velocity of natural convection replacing the velocity in Reynolds numbers formula. However In practice, when referring to the Reynolds number, it is understood that one is considering forced convection, the Grashof number can be formulated for natural convection occurring due to a concentration gradient, sometimes termed thermo-solutal convection. In this case, a concentration of hot fluid diffuses into a cold fluid, in much the same way that ink poured into a container of water diffuses to dye the entire space. Then, G r = g β Δ C L3 ν2 Natural convection is highly dependent on the geometry of the hot surface, in this system heat is transferred from a vertical plate to a fluid moving parallel to it by natural convection. This will occur in any system wherein the density of the fluid varies with position
13.
Combustion
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Combustion in a fire produces a flame, and the heat produced can make combustion self-sustaining. Combustion is often a sequence of elementary radical reactions. Solid fuels, such as wood, first undergo endothermic pyrolysis to produce gaseous fuels whose combustion then supplies the required to produce more of them. Combustion is often hot enough that light in the form of either glowing or a flame is produced, a simple example can be seen in the combustion of hydrogen and oxygen into water vapor, a reaction commonly used to fuel rocket engines. The bond energies in the play only a minor role, since they are similar to those in the combustion products. The heat of combustion is approximately -418 kJ per mole of O2 used up in the combustion reaction, uncatalyzed combustion in air requires fairly high temperatures. Complete combustion is stoichiometric with respect to the fuel, where there is no remaining fuel, thermodynamically, the chemical equilibrium of combustion in air is overwhelmingly on the side of the products. Thus, the smoke is usually toxic and contains unburned or partially oxidized products. Since combustion is rarely clean, flue gas cleaning or catalytic converters may be required by law, fires occur naturally, ignited by lightning strikes or by volcanic products. Combustion was the first controlled chemical reaction discovered by humans, in the form of campfires and bonfires, usually, the fuel is carbon, hydrocarbons or more complicated mixtures such as wood that contains partially oxidized hydrocarbons. Combustion is also currently the only used to power rockets. Combustion is also used to destroy waste, both nonhazardous and hazardous, oxidants for combustion have high oxidation potential and include atmospheric or pure oxygen, chlorine, fluorine, chlorine trifluoride, nitrous oxide and nitric acid. For instance, hydrogen burns in chlorine to form hydrogen chloride with the liberation of heat, although usually not catalyzed, combustion can be catalyzed by platinum or vanadium, as in the contact process. In complete combustion, the reactant burns in oxygen, producing a number of products. When a hydrocarbon burns in oxygen, the reaction will yield carbon dioxide. When elements are burned, the products are primarily the most common oxides, carbon will yield carbon dioxide, sulfur will yield sulfur dioxide, and iron will yield iron oxide. Nitrogen is not considered to be a combustible substance when oxygen is the oxidant, Combustion is not necessarily favorable to the maximum degree of oxidation, and it can be temperature-dependent. For example, sulfur trioxide is not produced quantitatively by the combustion of sulfur, NOx species appear in significant amounts above about 2,800 °F, and more is produced at higher temperatures
14.
Capillary action
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Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. It occurs because of forces between the liquid and surrounding solid surfaces. If the diameter of the tube is sufficiently small, then the combination of surface tension, the first recorded observation of capillary action was by Leonardo da Vinci. A former student of Galileo, Niccolò Aggiunti, was said to have investigated capillary action, boyle then reported an experiment in which he dipped a capillary tube into red wine and then subjected the tube to a partial vacuum. Some thought that liquids rose in capillaries because air couldnt enter capillaries as easily as liquids, others thought that the particles of liquid were attracted to each other and to the walls of the capillary. They derived the Young–Laplace equation of capillary action, by 1830, the German mathematician Carl Friedrich Gauss had determined the boundary conditions governing capillary action. In 1871, the British physicist William Thomson determined the effect of the meniscus on a liquids vapor pressure—a relation known as the Kelvin equation, German physicist Franz Ernst Neumann subsequently determined the interaction between two immiscible liquids. Albert Einsteins first paper, which was submitted to Annalen der Physik in 1900, was on capillarity, a common apparatus used to demonstrate the first phenomenon is the capillary tube. When the lower end of a glass tube is placed in a liquid, such as water. Adhesion occurs between the fluid and the inner wall pulling the liquid column up until there is a sufficient mass of liquid for gravitational forces to overcome these intermolecular forces. So, a tube will draw a liquid column higher than a wider tube will. Capillary action is essential for the drainage of constantly produced tear fluid from the eye, wicking is the absorption of a liquid by a material in the manner of a candle wick. Paper towels absorb liquid through capillary action, allowing a fluid to be transferred from a surface to the towel, the small pores of a sponge act as small capillaries, causing it to absorb a large amount of fluid. Some textile fabrics are said to use capillary action to wick sweat away from the skin and these are often referred to as wicking fabrics, after the capillary properties of candle and lamp wicks. Capillary action is observed in thin layer chromatography, in which a solvent moves vertically up a plate via capillary action, in this case the pores are gaps between very small particles. Capillary action draws ink to the tips of fountain pen nibs from a reservoir or cartridge inside the pen, in hydrology, capillary action describes the attraction of water molecules to soil particles. Capillary action is responsible for moving groundwater from wet areas of the soil to dry areas, differences in soil potential drive capillary action in soil. Thus the thinner the space in which the water can travel, for a water-filled glass tube in air at standard laboratory conditions, γ =0.0728 N/m at 20 °C, ρ =1000 kg/m3, and g =9.81 m/s2
15.
Marangoni effect
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The Marangoni effect is the mass transfer along an interface between two fluids due to surface tension gradient. In the case of temperature dependence, this phenomenon may be called thermo-capillary convection and this phenomenon was first identified in the so-called tears of wine by physicist James Thomson in 1855. The general effect is named after Italian physicist Carlo Marangoni, who studied it for his dissertation at the University of Pavia. A complete theoretical treatment of the subject was given by J. Willard Gibbs in his work On the Equilibrium of Heterogeneous Substances, the surface tension gradient can be caused by concentration gradient or by a temperature gradient. As an example, wine may exhibit an effect called tears. The effect is a consequence of the fact that alcohol has a surface tension than water. If alcohol is mixed with water inhomogeneously, a region with a concentration of alcohol will pull on the surrounding fluid more strongly than a region with a higher alcohol concentration. The result is that the liquid tends to flow away from regions with higher alcohol concentration—along the tension gradient. This can also be demonstrated by spreading a thin film of water on a smooth surface. The liquid will rush out of the region where the drop of alcohol fell, the Marangoni number, a dimensionless value, can be used to characterize the relative effects of surface tension and viscous forces. Many experiments have been conducted under microgravity conditions aboard sounding rockets to observe the Marangoni effect without the influence of gravity and this is due to the very weak Marangoni effect within a mixture of almost identical surface tensions which is normally masked by the fluids inertia due to gravity. A familiar example is in soap films, the Marangoni effect stabilizes soap films, another instance of the Marangoni effect appears in the behavior of convection cells, the so-called Bénard cells. One important application of the Marangoni effect is the use for drying silicon wafers after a wet processing step during the manufacture of integrated circuits, liquid spots left on the wafer surface can cause oxidation that damages components on the wafer. A similar phenomenon has been utilized to self-assemble nanoparticles into ordered arrays. An alcohol containing nanoparticles is spread on the substrate, followed by blowing the substrate with an air flow. The alcohol is evaporated under the flow, simultaneously, water condenses and forms microdroplets on the substrate. Meanwhile, the nanoparticles in alcohol are transferred into the microdroplets, the Marangoni effect is also important to the fields of welding, crystal growth and electron beam melting of metals
16.
Thunderstorm
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Thunderstorms occur in association with a type of cloud known as a cumulonimbus. They are usually accompanied by winds, heavy rain, and sometimes snow, sleet, hail, or, in contrast. Thunderstorms may line up in a series or become a rainband, strong or severe thunderstorms, known as supercells, rotate as do cyclones. Thunderstorms result from the upward movement of warm, moist air. As the warm, moist air moves upward, it cools, condenses, as the rising air reaches its dew point temperature, water vapor condenses into water droplets or ice, reducing pressure locally within the thunderstorm cell. Any precipitation falls the long distance through the clouds towards the Earths surface, as the droplets fall, they collide with other droplets and become larger. Thunderstorms can form and develop in any location but most frequently within the mid-latitude. Thunderstorms are responsible for the development and formation of many weather phenomena. Thunderstorms, and the phenomena that occur along them, pose great hazards. Damage that results from thunderstorms is mainly inflicted by downburst winds, large hailstones, stronger thunderstorm cells are capable of producing tornadoes and waterspouts. There are four types of thunderstorms, single-cell, multi-cell cluster, multi-cell lines, supercell thunderstorms are the strongest and the most associated with severe weather phenomena. Mesoscale convective systems formed by vertical wind shear within the tropics and subtropics can be responsible for the development of hurricanes. Dry thunderstorms, with no precipitation, can cause the outbreak of wildfires from the heat generated from the lightning that accompanies them. Several means are used to study thunderstorms, weather radar, weather stations, past civilizations held various myths concerning thunderstorms and their development as late as the 18th century. Beyond the Earths atmosphere, thunderstorms have also observed on the planets of Jupiter, Saturn, Neptune. Warm air has a lower density than air, so warmer air rises upwards. Clouds form as relatively warmer air, carrying moisture, rises within cooler air, the moist air rises, and, as it does so, it cools and some of the water vapor in that rising air condenses. If enough instability is present in the atmosphere, this process will continue long enough for cumulonimbus clouds to form and produce lightning, Meteorological indices such as convective available potential energy and the lifted index can be used to assist in determining potential upward vertical development of clouds
17.
Fluid mechanics
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Fluid mechanics is a branch of physics concerned with the mechanics of fluids and the forces on them. Fluid mechanics has a range of applications, including for mechanical engineering, civil engineering, chemical engineering, geophysics, astrophysics. Fluid mechanics can be divided into fluid statics, the study of fluids at rest, and fluid dynamics, fluid mechanics, especially fluid dynamics, is an active field of research with many problems that are partly or wholly unsolved. Fluid mechanics can be complex, and can best be solved by numerical methods. A modern discipline, called computational fluid dynamics, is devoted to this approach to solving fluid mechanics problems, Particle image velocimetry, an experimental method for visualizing and analyzing fluid flow, also takes advantage of the highly visual nature of fluid flow. Inviscid flow was further analyzed by mathematicians and viscous flow was explored by a multitude of engineers including Jean Léonard Marie Poiseuille. Fluid statics or hydrostatics is the branch of mechanics that studies fluids at rest. It embraces the study of the conditions under which fluids are at rest in stable equilibrium, and is contrasted with fluid dynamics, hydrostatics is fundamental to hydraulics, the engineering of equipment for storing, transporting and using fluids. It is also relevant to some aspect of geophysics and astrophysics, to meteorology, to medicine, fluid dynamics is a subdiscipline of fluid mechanics that deals with fluid flow—the science of liquids and gases in motion. The solution to a fluid dynamics problem typically involves calculating various properties of the fluid, such as velocity, pressure, density and it has several subdisciplines itself, including aerodynamics and hydrodynamics. Some fluid-dynamical principles are used in engineering and crowd dynamics. Fluid mechanics is a subdiscipline of continuum mechanics, as illustrated in the following table, in a mechanical view, a fluid is a substance that does not support shear stress, that is why a fluid at rest has the shape of its containing vessel. A fluid at rest has no shear stress, the assumptions inherent to a fluid mechanical treatment of a physical system can be expressed in terms of mathematical equations. This can be expressed as an equation in integral form over the control volume, the continuum assumption is an idealization of continuum mechanics under which fluids can be treated as continuous, even though, on a microscopic scale, they are composed of molecules. Fluid properties can vary continuously from one element to another and are average values of the molecular properties. The continuum hypothesis can lead to results in applications like supersonic speed flows. Those problems for which the continuum hypothesis fails, can be solved using statistical mechanics, to determine whether or not the continuum hypothesis applies, the Knudsen number, defined as the ratio of the molecular mean free path to the characteristic length scale, is evaluated. Problems with Knudsen numbers below 0.1 can be evaluated using the continuum hypothesis, the Navier–Stokes equations are differential equations that describe the force balance at a given point within a fluid
18.
Thermodynamics
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Thermodynamics is a branch of science concerned with heat and temperature and their relation to energy and work. The behavior of these quantities is governed by the four laws of thermodynamics, the laws of thermodynamics are explained in terms of microscopic constituents by statistical mechanics. Thermodynamics applies to a variety of topics in science and engineering, especially physical chemistry, chemical engineering. The initial application of thermodynamics to mechanical heat engines was extended early on to the study of chemical compounds, Chemical thermodynamics studies the nature of the role of entropy in the process of chemical reactions and has provided the bulk of expansion and knowledge of the field. Other formulations of thermodynamics emerged in the following decades, statistical thermodynamics, or statistical mechanics, concerned itself with statistical predictions of the collective motion of particles from their microscopic behavior. In 1909, Constantin Carathéodory presented a mathematical approach to the field in his axiomatic formulation of thermodynamics. A description of any thermodynamic system employs the four laws of thermodynamics that form an axiomatic basis, the first law specifies that energy can be exchanged between physical systems as heat and work. In thermodynamics, interactions between large ensembles of objects are studied and categorized, central to this are the concepts of the thermodynamic system and its surroundings. A system is composed of particles, whose average motions define its properties, properties can be combined to express internal energy and thermodynamic potentials, which are useful for determining conditions for equilibrium and spontaneous processes. With these tools, thermodynamics can be used to describe how systems respond to changes in their environment and this can be applied to a wide variety of topics in science and engineering, such as engines, phase transitions, chemical reactions, transport phenomena, and even black holes. This article is focused mainly on classical thermodynamics which primarily studies systems in thermodynamic equilibrium, non-equilibrium thermodynamics is often treated as an extension of the classical treatment, but statistical mechanics has brought many advances to that field. Guericke was driven to make a vacuum in order to disprove Aristotles long-held supposition that nature abhors a vacuum. Shortly after Guericke, the English physicist and chemist Robert Boyle had learned of Guerickes designs and, in 1656, in coordination with English scientist Robert Hooke, using this pump, Boyle and Hooke noticed a correlation between pressure, temperature, and volume. In time, Boyles Law was formulated, which states that pressure, later designs implemented a steam release valve that kept the machine from exploding. By watching the valve rhythmically move up and down, Papin conceived of the idea of a piston and he did not, however, follow through with his design. Nevertheless, in 1697, based on Papins designs, engineer Thomas Savery built the first engine, although these early engines were crude and inefficient, they attracted the attention of the leading scientists of the time. Black and Watt performed experiments together, but it was Watt who conceived the idea of the condenser which resulted in a large increase in steam engine efficiency. Drawing on all the work led Sadi Carnot, the father of thermodynamics, to publish Reflections on the Motive Power of Fire
19.
Atmosphere of Earth
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The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earths gravity. The atmosphere of Earth protects life on Earth by absorbing solar radiation, warming the surface through heat retention. By volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor, on average around 1% at sea level. The atmosphere has a mass of about 5. 15×1018 kg, the atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km, or 1. 57% of Earths radius, is used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km, several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earths atmosphere and its processes is called atmospheric science, early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The three major constituents of air, and therefore of Earths atmosphere, are nitrogen, oxygen, water vapor accounts for roughly 0. 25% of the atmosphere by mass. The remaining gases are often referred to as gases, among which are the greenhouse gases, principally carbon dioxide, methane, nitrous oxide. Filtered air includes trace amounts of other chemical compounds. Various industrial pollutants also may be present as gases or aerosols, such as chlorine, fluorine compounds, sulfur compounds such as hydrogen sulfide and sulfur dioxide may be derived from natural sources or from industrial air pollution. In general, air pressure and density decrease with altitude in the atmosphere, however, temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions. In this way, Earths atmosphere can be divided into five main layers, excluding the exosphere, Earth has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. It extends from the exobase, which is located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km where it merges into the solar wind. This layer is composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen. The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another, thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind, the exosphere is located too far above Earth for any meteorological phenomena to be possible
20.
Planet
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The term planet is ancient, with ties to history, astrology, science, mythology, and religion. Several planets in the Solar System can be seen with the naked eye and these were regarded by many early cultures as divine, or as emissaries of deities. As scientific knowledge advanced, human perception of the planets changed, in 2006, the International Astronomical Union officially adopted a resolution defining planets within the Solar System. This definition is controversial because it excludes many objects of mass based on where or what they orbit. The planets were thought by Ptolemy to orbit Earth in deferent, at about the same time, by careful analysis of pre-telescopic observation data collected by Tycho Brahe, Johannes Kepler found the planets orbits were not circular but elliptical. As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes, and some shared such features as ice caps and seasons. Since the dawn of the Space Age, close observation by space probes has found that Earth and the planets share characteristics such as volcanism, hurricanes, tectonics. Planets are generally divided into two types, large low-density giant planets, and smaller rocky terrestrials. Under IAU definitions, there are eight planets in the Solar System, in order of increasing distance from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four giant planets, Jupiter, Saturn, Uranus, and Neptune. Six of the planets are orbited by one or more natural satellites, several thousands of planets around other stars have been discovered in the Milky Way. e. in the habitable zone. On December 20,2011, the Kepler Space Telescope team reported the discovery of the first Earth-sized extrasolar planets, Kepler-20e and Kepler-20f, orbiting a Sun-like star, Kepler-20. A2012 study, analyzing gravitational microlensing data, estimates an average of at least 1.6 bound planets for every star in the Milky Way, around one in five Sun-like stars is thought to have an Earth-sized planet in its habitable zone. The idea of planets has evolved over its history, from the lights of antiquity to the earthly objects of the scientific age. The concept has expanded to include not only in the Solar System. The ambiguities inherent in defining planets have led to much scientific controversy, the five classical planets, being visible to the naked eye, have been known since ancient times and have had a significant impact on mythology, religious cosmology, and ancient astronomy. In ancient times, astronomers noted how certain lights moved across the sky, as opposed to the fixed stars, ancient Greeks called these lights πλάνητες ἀστέρες or simply πλανῆται, from which todays word planet was derived. In ancient Greece, China, Babylon, and indeed all pre-modern civilizations, it was almost universally believed that Earth was the center of the Universe and that all the planets circled Earth. The first civilization known to have a theory of the planets were the Babylonians
21.
Tropical cyclone
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Depending on its location and strength, a tropical cyclone is referred to by names such as hurricane, typhoon /taɪˈfuːn/, tropical storm, cyclonic storm, tropical depression, and simply cyclone. A hurricane is a storm that occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, Tropical cyclones typically form over large bodies of relatively warm water. They derive their energy through the evaporation of water from the ocean surface and this energy source differs from that of mid-latitude cyclonic storms, such as noreasters and European windstorms, which are fueled primarily by horizontal temperature contrasts. The strong rotating winds of a tropical cyclone are a result of the conservation of momentum imparted by the Earths rotation as air flows inwards toward the axis of rotation. As a result, they form within 5° of the equator. Tropical cyclones are typically between 100 and 2,000 km in diameter, Tropical refers to the geographical origin of these systems, which form almost exclusively over tropical seas. Cyclone refers to their nature, with wind blowing counterclockwise in the Northern Hemisphere. The opposite direction of circulation is due to the Coriolis effect, in addition to strong winds and rain, tropical cyclones are capable of generating high waves, damaging storm surge, and tornadoes. They typically weaken rapidly over land where they are cut off from their energy source. For this reason, coastal regions are vulnerable to damage from a tropical cyclone as compared to inland regions. Heavy rains, however, can cause significant flooding inland, though their effects on human populations are often devastating, tropical cyclones can relieve drought conditions. They also carry heat away from the tropics and transport it toward temperate latitudes. Tropical cyclones are areas of low pressure in the troposphere. On Earth, the pressures recorded at the centers of tropical cyclones are among the lowest ever observed at sea level, the environment near the center of tropical cyclones is warmer than the surroundings at all altitudes, thus they are characterized as warm core systems. The near-surface wind field of a cyclone is characterized by air rotating rapidly around a center of circulation while also flowing radially inwards. At the outer edge of the storm, air may be nearly calm, however, due to the Earths rotation, as air flows radially inward, it begins to rotate cyclonically in order to conserve angular momentum. At an inner radius, air begins to ascend to the top of the troposphere and this radius is typically coincident with the inner radius of the eyewall, and has the strongest near-surface winds of the storm, consequently, it is known as the radius of maximum winds. Once aloft, air flows away from the center, producing a shield of cirrus clouds
22.
Black hole
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A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light—can escape from inside it. The theory of relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of the region from which no escape is possible is called the event horizon, although the event horizon has an enormous effect on the fate and circumstances of an object crossing it, no locally detectable features appear to be observed. In many ways a black hole acts like a black body. Moreover, quantum theory in curved spacetime predicts that event horizons emit Hawking radiation. This temperature is on the order of billionths of a kelvin for black holes of stellar mass, objects whose gravitational fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. Black holes were considered a mathematical curiosity, it was during the 1960s that theoretical work showed they were a generic prediction of general relativity. The discovery of neutron stars sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality, black holes of stellar mass are expected to form when very massive stars collapse at the end of their life cycle. After a black hole has formed, it can continue to grow by absorbing mass from its surroundings, by absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses may form. There is general consensus that supermassive black holes exist in the centers of most galaxies, despite its invisible interior, the presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as visible light. Matter that falls onto a black hole can form an accretion disk heated by friction. If there are other stars orbiting a black hole, their orbits can be used to determine the black holes mass, such observations can be used to exclude possible alternatives such as neutron stars.3 million solar masses. On 15 June 2016, a detection of a gravitational wave event from colliding black holes was announced. The idea of a body so massive that light could not escape was briefly proposed by astronomical pioneer John Michell in a letter published in 1783-4. Michell correctly noted that such supermassive but non-radiating bodies might be detectable through their effects on nearby visible bodies. In 1915, Albert Einstein developed his theory of general relativity, only a few months later, Karl Schwarzschild found a solution to the Einstein field equations, which describes the gravitational field of a point mass and a spherical mass. A few months after Schwarzschild, Johannes Droste, a student of Hendrik Lorentz, independently gave the solution for the point mass. This solution had a peculiar behaviour at what is now called the Schwarzschild radius, the nature of this surface was not quite understood at the time
23.
Heat
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In physics, heat is the amount of energy flowing from one body to another spontaneously due to their temperature difference, or by any means other than through work or the transfer of matter. Thus, energy exchanged as heat during a process changes the energy of each body by equal. The sign of the quantity of heat can indicate the direction of the transfer, for example from system A to system B, negation indicates energy flowing in the opposite direction. While heat flows spontaneously from hot to cold, it is possible to construct a heat pump or refrigeration system that does work to increase the difference in temperature between two systems, conversely, a heat engine reduces an existing temperature difference to do work on another system. Heat is a consequence of the motion of particles. When heat is transferred between two objects or systems, the energy of the object or systems particles increases, as this occurs, the arrangement between particles becomes more and more disordered. In other words, heat is related to the concept of entropy, historically, many energy units for measurement of heat have been used. The standards-based unit in the International System of Units is the joule, Heat is measured by its effect on the states of interacting bodies, for example, by the amount of ice melted or a change in temperature. The quantification of heat via the change of a body is called calorimetry. In calorimetry, sensible heat is defined with respect to a specific chosen state variable of the system, sensible heat causes a change of the temperature of the system while leaving the chosen state variable unchanged. Heat transfer that occurs at a constant system temperature but changes the state variable is called latent heat with respect to the variable, for infinitesimal changes, the total incremental heat transfer is then the sum of the latent and sensible heat. Physicist James Clerk Maxwell, in his 1871 classic Theory of Heat, was one of many who began to build on the established idea that heat has something to do with matter in motion. This was the idea put forth by Benjamin Thompson in 1798. One of Maxwells recommended books was Heat as a Mode of Motion, Maxwell outlined four stipulations for the definition of heat, It is something which may be transferred from one body to another, according to the second law of thermodynamics. It is a quantity, and so can be treated mathematically. It cannot be treated as a substance, because it may be transformed into something that is not a material substance. Heat is one of the forms of energy and this was the way of the historical pioneers of thermodynamics. Maxwell writes that convection as such is not a purely thermal phenomenon, in thermodynamics, convection in general is regarded as transport of internal energy
24.
Thermal radiation
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Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a greater than absolute zero emits thermal radiation. When the temperature of a body is greater than absolute zero, Thermal radiation is different from thermal convection and thermal conduction—a person near a raging bonfire feels radiant heating from the fire, even if the surrounding air is very cold. Sunlight is part of thermal radiation generated by the hot plasma of the Sun, the Earth also emits thermal radiation, but at a much lower intensity and different spectral distribution because it is cooler. The Earths absorption of radiation, followed by its outgoing thermal radiation are the two most important processes that determine the temperature and climate of the Earth. If a radiation-emitting object meets the physical characteristics of a body in thermodynamic equilibrium. Plancks law describes the spectrum of radiation, which depends only on the objects temperature. Wiens displacement law determines the most likely frequency of the radiation. Thermal radiation is one of the mechanisms of heat transfer. Thermal radiation is the emission of electromagnetic waves from all matter that has a greater than absolute zero. It represents a conversion of energy into electromagnetic energy. Thermal energy consists of the energy of random movements of atoms. All matter with a temperature by definition is composed of particles which have kinetic energy, and these atoms and molecules are composed of charged particles, i. e. protons and electrons, and kinetic interactions among matter particles result in charge-acceleration and dipole-oscillation. This results in the generation of coupled electric and magnetic fields, resulting in the emission of photons. Electromagnetic radiation, including light, does not require the presence of matter to propagate, the radiation is not monochromatic, i. e. it does not consist of just a single frequency, but comprises a continuous dispersion of photon energies, its characteristic spectrum. If the radiating body and its surface are in thermodynamic equilibrium, a black body is also a perfect emitter. The radiation of such perfect emitters is called black-body radiation, the ratio of any bodys emission relative to that of a black body is the bodys emissivity, so that a black body has an emissivity of unity. Absorptivity, reflectivity, and emissivity of all bodies are dependent on the wavelength of the radiation, the temperature determines the wavelength distribution of the electromagnetic radiation
25.
Electromagnetic radiation
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In physics, electromagnetic radiation refers to the waves of the electromagnetic field, propagating through space carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, light, ultraviolet, X-, classically, electromagnetic radiation consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields that propagate at the speed of light through a vacuum. The oscillations of the two fields are perpendicular to other and perpendicular to the direction of energy and wave propagation. The wavefront of electromagnetic waves emitted from a point source is a sphere, the position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength. Electromagnetic waves are produced whenever charged particles are accelerated, and these waves can interact with other charged particles. EM waves carry energy, momentum and angular momentum away from their source particle, quanta of EM waves are called photons, whose rest mass is zero, but whose energy, or equivalent total mass, is not zero so they are still affected by gravity. Thus, EMR is sometimes referred to as the far field, in this language, the near field refers to EM fields near the charges and current that directly produced them, specifically, electromagnetic induction and electrostatic induction phenomena. In the quantum theory of electromagnetism, EMR consists of photons, quantum effects provide additional sources of EMR, such as the transition of electrons to lower energy levels in an atom and black-body radiation. The energy of a photon is quantized and is greater for photons of higher frequency. This relationship is given by Plancks equation E = hν, where E is the energy per photon, ν is the frequency of the photon, a single gamma ray photon, for example, might carry ~100,000 times the energy of a single photon of visible light. The effects of EMR upon chemical compounds and biological organisms depend both upon the power and its frequency. EMR of visible or lower frequencies is called non-ionizing radiation, because its photons do not individually have enough energy to ionize atoms or molecules, the effects of these radiations on chemical systems and living tissue are caused primarily by heating effects from the combined energy transfer of many photons. In contrast, high ultraviolet, X-rays and gamma rays are called ionizing radiation since individual photons of high frequency have enough energy to ionize molecules or break chemical bonds. These radiations have the ability to cause chemical reactions and damage living cells beyond that resulting from simple heating, Maxwell derived a wave form of the electric and magnetic equations, thus uncovering the wave-like nature of electric and magnetic fields and their symmetry. Because the speed of EM waves predicted by the wave equation coincided with the speed of light. Maxwell’s equations were confirmed by Heinrich Hertz through experiments with radio waves, according to Maxwells equations, a spatially varying electric field is always associated with a magnetic field that changes over time. Likewise, a varying magnetic field is associated with specific changes over time in the electric field. In an electromagnetic wave, the changes in the field are always accompanied by a wave in the magnetic field in one direction
26.
Heat sink
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In computers, heat sinks are used to cool central processing units or graphics processors. A heat sink is designed to maximize its surface area in contact with the medium surrounding it. Air velocity, choice of material, protrusion design and surface treatment are factors that affect the performance of a heat sink, heat sink attachment methods and thermal interface materials also affect the die temperature of the integrated circuit. Thermal adhesive or thermal grease improve the heat sinks performance by filling air gaps between the sink and the heat spreader on the device. A heat sink is made out of copper and/or aluminium. Copper is used because it has many desirable properties for thermally efficient, first and foremost, copper is an excellent conductor of heat. This means that high thermal conductivity allows heat to pass through it quickly. Aluminum is used in applications where weight is a big concern, a heat sink transfers thermal energy from a higher temperature device to a lower temperature fluid medium. The fluid medium is air, but can also be water. If the fluid medium is water, the sink is frequently called a cold plate. In thermodynamics a heat sink is a reservoir that can absorb an arbitrary amount of heat without significantly changing temperature. Practical heat sinks for electronic devices must have a higher than the surroundings to transfer heat by convection, radiation. The power supplies of electronics are not 100% efficient, so heat is produced that may be detrimental to the function of the device. As such, a sink is included in the design to disperse heat to improve efficient energy use. To understand the principle of a sink, consider Fouriers law of heat conduction. The rate at which heat is transferred by conduction, q k, is proportional to the product of the temperature gradient, Q k = − k A d T d x Consider a heat sink in a duct, where air flows through the duct. It is assumed that the heat sink base is higher in temperature than the air, when compact heat exchangers are calculated, the logarithmic mean air temperature is used. M ˙ is the air flow rate in kg/s
27.
Central processing unit
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The computer industry has used the term central processing unit at least since the early 1960s. The form, design and implementation of CPUs have changed over the course of their history, most modern CPUs are microprocessors, meaning they are contained on a single integrated circuit chip. An IC that contains a CPU may also contain memory, peripheral interfaces, some computers employ a multi-core processor, which is a single chip containing two or more CPUs called cores, in that context, one can speak of such single chips as sockets. Array processors or vector processors have multiple processors that operate in parallel, there also exists the concept of virtual CPUs which are an abstraction of dynamical aggregated computational resources. Early computers such as the ENIAC had to be rewired to perform different tasks. Since the term CPU is generally defined as a device for software execution, the idea of a stored-program computer was already present in the design of J. Presper Eckert and John William Mauchlys ENIAC, but was initially omitted so that it could be finished sooner. On June 30,1945, before ENIAC was made, mathematician John von Neumann distributed the paper entitled First Draft of a Report on the EDVAC and it was the outline of a stored-program computer that would eventually be completed in August 1949. EDVAC was designed to perform a number of instructions of various types. Significantly, the programs written for EDVAC were to be stored in high-speed computer memory rather than specified by the wiring of the computer. This overcame a severe limitation of ENIAC, which was the considerable time, with von Neumanns design, the program that EDVAC ran could be changed simply by changing the contents of the memory. Early CPUs were custom designs used as part of a larger, however, this method of designing custom CPUs for a particular application has largely given way to the development of multi-purpose processors produced in large quantities. This standardization began in the era of discrete transistor mainframes and minicomputers and has accelerated with the popularization of the integrated circuit. The IC has allowed increasingly complex CPUs to be designed and manufactured to tolerances on the order of nanometers, both the miniaturization and standardization of CPUs have increased the presence of digital devices in modern life far beyond the limited application of dedicated computing machines. Modern microprocessors appear in electronic devices ranging from automobiles to cellphones, the so-called Harvard architecture of the Harvard Mark I, which was completed before EDVAC, also utilized a stored-program design using punched paper tape rather than electronic memory. Relays and vacuum tubes were used as switching elements, a useful computer requires thousands or tens of thousands of switching devices. The overall speed of a system is dependent on the speed of the switches, tube computers like EDVAC tended to average eight hours between failures, whereas relay computers like the Harvard Mark I failed very rarely. In the end, tube-based CPUs became dominant because the significant speed advantages afforded generally outweighed the reliability problems, most of these early synchronous CPUs ran at low clock rates compared to modern microelectronic designs. Clock signal frequencies ranging from 100 kHz to 4 MHz were very common at this time, the design complexity of CPUs increased as various technologies facilitated building smaller and more reliable electronic devices
28.
Computer fan
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Generally these are found in axial and sometimes centrifugal forms. The former is called a muffin fan, after the Rotron Muffin line. These components need to be kept within a temperature range to prevent overheating, instability, malfunction. While in earlier personal computers it was possible to cool most components using natural convection, to cool these components, fans are used to move heated air away from the components and draw cooler air over them. Fans attached to components are used in combination with a heatsink to increase the area of heated surface in contact with the air. In the IBM compatible PC market, the power supply unit almost always uses an exhaust fan to expel warm air from the PSU. Active cooling on CPUs started to appear on the Intel 80486, a third vent fan in the side of the PC, often located over the CPU, is also common. The graphics processing unit on most modern graphics cards require a heatsink. In some cases, the chip on the motherboard has another heatsink. Other components such as the drives and RAM may also be actively cooled. It is not uncommon to find five or more fans in a modern PC, used to aerate the case of the computer. The components inside the case cannot dissipate heat efficiently if the air is too hot. Case fans move air through the case, usually drawing cooler air in through the front or bottom. Standard axial case fans are 80,92,120,140,200 and 230 mm in width and length, decorative fans and accessories are popular with case modders. Air filters are used over intake fans, to prevent dust from entering the case. Heatsinks are especially vulnerable to being clogged up, as the effect of the dust will rapidly degrade the heatsinks ability to dissipate heat. While the power supply contains a fan with few exceptions, it is not to be used for case ventilation, the hotter the PSUs intake air is, the hotter the PSU gets. As the PSU temperature rises, the conductivity of its internal components decrease, decreased conductivity means that the PSU will convert more of the input electric energy into thermal energy
29.
Convection cell
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In the field of fluid dynamics, a convection cell is the phenomenon that occurs when density differences exist within a body of liquid or gas. These density differences result in rising and/or falling currents, which are the key characteristics of a convection cell, when a volume of fluid is heated, it expands and becomes less dense and thus more buoyant than the surrounding fluid. The colder, denser part of the fluid descends to settle below the warmer, less-dense fluid, such movement is called convection, and the moving body of liquid is referred to as a convection cell. This particular type of convection, where a layer of fluid is heated from below, is known as Rayleigh-Bénard convection. Convection usually requires a field, but in microgravity experiments. Fluids are generalized as materials that exhibit the property of flow, however, fluid properties can also be observed in gases and even in particulate solids. A convection cell is most notable in the formation of clouds with its release, as air moves along the ground it absorbs heat, loses density and moves up into the atmosphere. When it is forced into the atmosphere, which has an air pressure, it cannot contain as much fluid as at a lower altitude, so it releases its moist air. In this process the warm air is cooled, it gains density and falls towards the earth, convection cells can form in any fluid, including the Earths atmosphere, boiling water, soup, the ocean, or the surface of the sun. The size of cells is largely determined by the fluids properties. Convection cells can occur when the heating of a fluid is uniform. At some point the fluid becomes denser than the fluid beneath it, since it cannot descend through the rising fluid, it moves to one side. At some distance, its downward force overcomes the rising force beneath it, as it descends, it warms again through surface contact or conductivity and the cycle repeats. Air warms, becomes less dense, rises, then air cools, becomes more dense, sinks. Then cool air at the bottom, warm air has a lower density than cool air, so warm air rises within cooler air, similar to hot air balloons. Clouds form as relatively warmer air carrying moisture rises within cooler air, as the moist air rises, it cools, causing some of the water vapor in the rising packet of air to condense. When the moisture condenses, it releases energy known as the latent heat of fusion, if enough instability is present in the atmosphere, this process will continue long enough for cumulonimbus clouds to form, which support lightning and thunder. Generally, thunderstorms require three conditions to form, moisture, an air mass, and a lifting force
30.
Atmospheric circulation
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Atmospheric circulation is the large-scale movement of air, and together with ocean circulation is the means by which thermal energy is redistributed on the surface of the Earth. The Earths atmospheric circulation varies from year to year, but the scale structure of its circulation remains fairly constant. The Earths weather is a consequence of its illumination by the Sun, the atmospheric circulation can be viewed as a heat engine driven by the Suns energy, and whose energy sink, ultimately, is the blackness of space. Over very long periods, a tectonic uplift can significantly alter their major elements, such as the jet stream. During the extremely hot climates of the Mesozoic, a third desert belt may have existed at the Equator, the wind belts girdling the planet are organised into three cells in each hemisphere, the Hadley cell, the Ferrel cell, and the Polar cell. Those cells exist in both the northern and southern hemispheres, the vast bulk of the atmospheric motion occurs in the Hadley cell. The high pressure systems acting on the Earths surface are balanced by the low pressure systems elsewhere, as a result, there is a balance of forces acting on the Earths surface. The atmospheric circulation pattern that George Hadley described was an attempt to explain the trade winds, the Hadley cell is a closed circulation loop which begins at the equator. There, moist air is warmed by the Earths surface, decreases in density, a similar air mass rising on the other side of the equator forces those rising air masses to move poleward. The rising air creates a low pressure zone near the equator, as the air moves poleward, it cools, becomes more dense, and descends at about the 30th parallel, creating a high-pressure area. The descended air then travels toward the equator along the surface, replacing the air that rose from the equatorial zone, the poleward movement of the air in the upper part of the troposphere deviates toward the east, caused by the coriolis acceleration. At the ground however, the movement of the air toward the equator in the lower troposphere deviates toward the west. The winds that flow to the west at the level in the Hadley cell are called the Trade Winds. The zone where the greatest heating takes place is called the thermal equator, as the southern hemisphere summer is December to March, the movement of the thermal equator to higher southern latitudes takes place then. The Hadley system provides an example of a thermally direct circulation, the thermodynamic efficiency and power of the Hadley system, considered as a heat engine, is estimated at 200 terawatts. The Polar cell, likewise, is a simple system, though cool and dry relative to equatorial air, the air masses at the 60th parallel are still sufficiently warm and moist to undergo convection and drive a thermal loop. At the 60th parallel, the air rises to the tropopause, as it does so, the upper level air mass deviates toward the east. When the air reaches the areas, it has cooled and is considerably denser than the underlying air
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Latitude
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In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earths surface. Latitude is an angle which ranges from 0° at the Equator to 90° at the poles, lines of constant latitude, or parallels, run east–west as circles parallel to the equator. Latitude is used together with longitude to specify the location of features on the surface of the Earth. Without qualification the term latitude should be taken to be the latitude as defined in the following sections. Also defined are six auxiliary latitudes which are used in special applications, there is a separate article on the History of latitude measurements. Two levels of abstraction are employed in the definition of latitude and longitude, in the first step the physical surface is modelled by the geoid, a surface which approximates the mean sea level over the oceans and its continuation under the land masses. The second step is to approximate the geoid by a mathematically simpler reference surface, the simplest choice for the reference surface is a sphere, but the geoid is more accurately modelled by an ellipsoid. The definitions of latitude and longitude on such surfaces are detailed in the following sections. Lines of constant latitude and longitude together constitute a graticule on the reference surface, latitude and longitude together with some specification of height constitute a geographic coordinate system as defined in the specification of the ISO19111 standard. This is of importance in accurate applications, such as a Global Positioning System, but in common usage, where high accuracy is not required. In English texts the latitude angle, defined below, is denoted by the Greek lower-case letter phi. It is measured in degrees, minutes and seconds or decimal degrees, the precise measurement of latitude requires an understanding of the gravitational field of the Earth, either to set up theodolites or to determine GPS satellite orbits. The study of the figure of the Earth together with its field is the science of geodesy. These topics are not discussed in this article and this article relates to coordinate systems for the Earth, it may be extended to cover the Moon, planets and other celestial objects by a simple change of nomenclature. The primary reference points are the poles where the axis of rotation of the Earth intersects the reference surface, the plane through the centre of the Earth and perpendicular to the rotation axis intersects the surface at a great circle called the Equator. Planes parallel to the plane intersect the surface in circles of constant latitude. The Equator has a latitude of 0°, the North Pole has a latitude of 90° North, the latitude of an arbitrary point is the angle between the equatorial plane and the radius to that point. The latitude, as defined in this way for the sphere, is termed the spherical latitude
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Hadley cell
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This circulation creates the trade winds, tropical rain-belts and hurricanes, subtropical deserts and the jet streams. Each Hadley cell operates between zero and 30 to 40 degrees north and south and is responsible for the weather in the equatorial regions of the world. The major driving force of atmospheric circulation is solar heating, which is greatest near the equator, the atmospheric circulation transports energy polewards, thus reducing the resulting equator-to-pole temperature gradient. The mechanisms by which this is accomplished differs in tropical and extratropical latitudes, Hadley cells exist on either side of the equator. Each cell encircles the globe and acts to transport energy from the equator to 30th latitude, on the smaller synoptic scale, the energy transport is also accomplished by cyclones and anticyclones that cause relatively warm air to move polewards and cold air to move equatorwards. The large scale tropical overturning cell is referred to as the Hadley cell, why it extends only to 30 degrees latitude and what determines its strength are questions addressed by dynamical meteorology. Near the tropopause, as the air moves polewards in the Hadley cell, it is turned eastward by the Coriolis effect, analogously, near the surface, the equatorward return flow is turned to the west by the Coriolis effect. These resulting surface winds, with both an equatorward and a component, are referred to as the trade winds. The Hadley system provides an example of a thermally direct circulation, the thermodynamic efficiency of the Hadley system, considered as a heat engine, has been relatively constant over the 1979~2010 period, averaging 2. 6%. In the early 18th century, George Hadley, an English lawyer, what was no doubt correct in Halleys theory was that solar heating creates upward motion of equatorial air, and air mass from neighboring latitudes must flow in to replace the risen air mass. But for the component of the trade winds Halley had proposed that in moving across the sky the Sun heats the air mass differently over the course of the day. Hadley was not satisfied with that part of Halleys theory and rightly so, Hadley was the first to recognize that Earths rotation plays a role in the direction taken by an air mass as it moves relative to the Earth. Hadleys theory, published in 1735, remained unknown, but it was rediscovered several times. Among the re-discoverers was John Dalton, who learned of Hadleys priority. Over time the proposed by Hadley became accepted, and over time his name was increasingly attached to it. By the end of the 19th century it was shown that Hadleys theory was deficient in several respects, one of the first who accounted for the dynamics correctly was William Ferrel. It took many decades for the theory to become accepted. Hadleys theory was the accepted theory long enough to make his name become universally attached to the circulation pattern in the tropical atmosphere
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Polar vortex
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A polar vortex is an upper level low-pressure area lying near the Earths pole. There are two polar vortices in the Earths atmosphere, which overlie the North, and South Poles, each polar vortex is a persistent, large-scale, low pressure zone that rotates counter-clockwise at the North Pole, and clockwise at the South Pole. The bases of the two vortices are located in the middle and upper troposphere and extend into the stratosphere. Beneath that lies a large mass of cold, dense arctic air, the vortices weaken and strengthen from year to year. The interface between the dry air mass of the pole and the warm moist air mass further south defines the location of the polar front. The polar front is centered, roughly at 60° latitude, a polar vortex strengthens in the winter and weakens in the summer due to its dependence on the temperature difference between the equator and the poles. The vortices span less than 1,000 kilometers in diameter within which they rotate counter-clockwise in the Northern Hemisphere, as with other cyclones, their rotation is driven by the Coriolis effect. When the polar vortex is strong, there is a vortex with a jet stream that is well constrained near the polar front. When the northern vortex weakens, it separates into two or more vortices, the strongest of which are near Baffin Island, Canada and the other over northeast Siberia. The Antarctic vortex of the Southern Hemisphere is a low pressure zone that is found near the edge of the Ross ice shelf near 160 west longitude. When the polar vortex is strong, the mid-latitude Westerlies increase in strength and are persistent, when the polar vortex is weak, high pressure zones of the mid latitudes may push poleward, moving the polar vortex, jet stream, and polar front equatorward. The jet stream is seen to buckle and deviate south and this rapidly brings cold dry air into contact with the warm, moist air of the mid latitudes, resulting in a rapid and dramatic change of weather known as a cold snap. Ozone depletion occurs within the polar vortices – particularly over the Southern Hemisphere – reaching a maximum depletion in the spring, the polar vortex was first described as early as 1853. The phenomenons sudden stratospheric warming develops during the winter in the Northern Hemisphere and was discovered in 1952 with radiosonde observations at higher than 20 km. The phenomenon was mentioned frequently in the news and weather media in the cold North American winter of 2013-2014, Polar cyclones are low pressure zones embedded within the polar air masses, and exist year-round. The stratospheric polar vortex develops at latitudes above the jet stream. Horizontally, most polar vortices have a radius of less than 1,000 kilometres, since polar vortices exist from the stratosphere downward into the mid-troposphere, a variety of heights/pressure levels are used to mark its position. The 50 mb pressure surface is most often used to identify its stratospheric location, at the level of the tropopause, the extent of closed contours of potential temperature can be used to determine its strength
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Latent heat
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Latent heat is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process. An example is latent heat of fusion for a change, melting. The term was introduced around 1762 by British chemist Joseph Black and it is derived from the Latin latere. Black used the term in the context of calorimetry where a transfer caused a volume change while the thermodynamic systems temperature was constant. In contrast to latent heat, sensible heat involves a transfer that results in a temperature change of the system. The terms ″sensible heat″ and ″latent heat″ are specific forms of energy, ″Sensible heat″ is a bodys internal energy that may be ″sensed″ or felt. ″Latent heat″ is internal energy concerning the phase of a material, both sensible and latent heats are observed in many processes of transport of energy in nature. The original usage of the term, as introduced by Black, was applied to systems that were held at constant temperature. Such usage referred to latent heat of expansion and several other related latent heats and these latent heats are defined independently of the conceptual framework of thermodynamics. Two common forms of latent heat are latent heat of fusion and these names describe the direction of energy flow when changing from one phase to the next, from solid to liquid, and liquid to gas. In both cases the change is endothermic, meaning that the system absorbs energy, for example, when water evaporates, energy is required for the water molecules to overcome the forces of attraction between them, the transition from water to vapor requires an input of energy. If the vapor condenses to a liquid on a surface. The large value of the enthalpy of condensation of vapor is the reason that steam is a far more effective heating medium than boiling water. It is an important component of Earths surface energy budget, latent heat flux has been commonly measured with the Bowen ratio technique, or more recently since the mid-1900s by the Jonathan Beaver method. The English word latent comes from Latin latēns, meaning lying hidden, intensive properties are material characteristics and are not dependent on the size or extent of the sample. Commonly quoted and tabulated in the literature are the specific latent heat of fusion, the following table shows the specific latent heats and change of phase temperatures of some common fluids and gases. Bowen ratio Eddy covariance flux Sublimation Specific heat capacity Enthalpy of fusion Enthalpy of vaporization
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Condensation
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Condensation is the change of the physical state of matter from gas phase into liquid phase, and is the reverse of evaporation. The word most often refers to the water cycle and it can also be defined as the change in the state of water vapour to liquid water when in contact with a liquid or solid surface or cloud condensation nuclei within the atmosphere. When the transition happens from the phase into the solid phase directly. A few distinct reversibility scenarios emerge here with respect to the nature of the surface, absorption into the surface of a liquid —is reversible as evaporation. Adsorption onto solid surface at pressures and temperatures higher than the species triple point—also reversible as evaporation, adsorption onto solid surface at pressures and temperatures lower than the species triple point—is reversible as sublimation. Condensation commonly occurs when a vapor is cooled and/or compressed to its limit when the molecular density in the gas phase reaches its maximal threshold. Vapor cooling and compressing equipment that collects condensed liquids is called a condenser, psychrometry measures the rates of condensation through evaporation into the air moisture at various atmospheric pressures and temperatures. Water is the product of its vapor condensation—condensation is the process of such phase conversion, condensation is a crucial component of distillation, an important laboratory and industrial chemistry application. Because condensation is a naturally occurring phenomenon, it can often be used to water in large quantities for human use. Many structures are made solely for the purpose of collecting water from condensation, such as air wells and it is also a crucial process in forming particle tracks in a cloud chamber. In this case, ions produced by an incident particle act as centers for the condensation of the vapor producing the visible cloud trails. Furthermore, condensation is a step in many industrial processes, such as power generation, water desalination, thermal management, refrigeration. Numerous living beings use water made accessible by condensation, a few examples of these are the Australian Thorny Devil, the darkling beetles of the Namibian coast, and the Coast Redwoods of the West Coast of the United States. To alleviate these issues, the air humidity needs to be lowered. This can be done in a number of ways, for example opening windows, turning on extractor fans, using dehumidifiers, drying clothes outside and covering pots and pans whilst cooking. Air conditioning or ventilation systems can be installed that help remove moisture from the air, the amount of water vapour that can be stored in the air can be increased simply by increasing the temperature. However, this can be a double edged sword as most condensation in the home occurs when warm, as the air is cooled, it can no longer hold as much water vapour. This leads to deposition of water on the cool surface and this is very apparent when central heating is used in combination with single glazed windows in winter
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Water vapor
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Water vapor, water vapour or aqueous vapor, is the gaseous phase of water. It is one state of water within the hydrosphere, water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Unlike other forms of water, water vapor is invisible, under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is lighter than air and triggers convection currents that can lead to clouds, use of water vapor, as steam, has been important to humans for cooking and as a major component in energy production and transport systems since the industrial revolution. Likewise the detection of water vapor would indicate a similar distribution in other planetary systems. Water vapor is significant in that it can be evidence supporting the presence of extraterrestrial liquid water in the case of some planetary mass objects. Whenever a water molecule leaves a surface and diffuses into a surrounding gas, each individual water molecule which transitions between a more associated and a less associated state does so through the absorption or release of kinetic energy. The aggregate measurement of kinetic energy transfer is defined as thermal energy. Liquid water that becomes water vapor takes a parcel of heat with it, the amount of water vapor in the air determines how fast each molecule will return to the surface. When a net evaporation occurs, the body of water will undergo a net cooling directly related to the loss of water, in the US, the National Weather Service measures the actual rate of evaporation from a standardized pan open water surface outdoors, at various locations nationwide. Others do likewise around the world, the US data is collected and compiled into an annual evaporation map. The measurements range from under 30 to over 120 inches per year, formulas can be used for calculating the rate of evaporation from a water surface such as a swimming pool. In some countries, the evaporation rate far exceeds the precipitation rate, evaporative cooling is restricted by atmospheric conditions. Humidity is the amount of vapor in the air. The vapor content of air is measured with devices known as hygrometers, the measurements are usually expressed as specific humidity or percent relative humidity. This condition is referred to as complete saturation. Humidity ranges from 0 gram per cubic metre in dry air to 30 grams per cubic metre when the vapor is saturated at 30 °C, another form of evaporation is sublimation, by which water molecules become gaseous directly, leaving the surface of ice without first becoming liquid water. Sublimation accounts for the slow disappearance of ice and snow at temperatures too low to cause melting
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Walker circulation
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The Walker circulation, also known as the Walker cell, is a conceptual model of the air flow in the tropics in the lower atmosphere. According to this model, parcels of air follow a closed circulation in the zonal and vertical directions and this circulation, which is roughly consistent with observations, is caused by differences in heat distribution between ocean and land. It was discovered by Gilbert Walker, in addition to motions in the zonal and vertical direction the tropical atmosphere also has considerable motion in the meridional direction as part of, for example, the Hadley Circulation. The term Walker circulation was coined in 1969 by the Norwegian-American meteorologist Jacob Bjerknes, Gilbert Walker was an established applied mathematician at the University of Cambridge when he became director-general of observatories in India in 1904. While there, he studied the characteristics of the Indian Ocean monsoon and he also worked with the Indian Meteorological Department especially in linking the monsoon with Southern Oscillation phenomenon. He was made a Companion of the Order of the Star of India in 1911, Walker determined that the time scale of a year was unsuitable because geospatial relationships could be entirely different depending on the season. Thus, Walker broke his temporal analysis into December–February, March–May, June–August, Walker then selected a number of centers of action, which included areas such as the Indian Peninsula. The centers were in the hearts of regions with permanent or seasonal high. He also added points for regions where rainfall, wind or temperature was an important control and he examined the relationships of the summer and winter values of pressure and rainfall, first focusing on summer and winter values, and later extending his work to the spring and autumn. He concludes that variations in temperature are generally governed by variations in pressure, Walker made it a point to publish all of his correlation findings, both of relationships found to be important as well as relationships that were found to be unimportant. He did this for the purpose of dissuading researchers from focusing on correlations that did not exist. The Walker Circulations of the tropical Indian, Pacific, and Atlantic basins result in surface winds in Northern Summer in the first basin and easterly winds in the second. As a result, the structure of the three oceans display dramatic asymmetries. The equatorial Pacific and Atlantic both have cool surface temperatures in Northern Summer in the east, while cooler temperatures prevail only in the western Indian Ocean. These changes in surface temperature changes in the depth of the thermocline. Changes in the Walker Circulation with time occur in conjunction with changes in surface temperature, some of these changes are forced externally, such as the seasonal shift of the Sun into the Northern Hemisphere in summer. These anomalous easterlies induce more equatorial upwelling and raise the thermocline in the east and this coupled ocean-atmosphere feedback was originally proposed by Bjerknes. From an oceanographic point of view, the cold tongue is caused by easterly winds
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