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85-425: The hypothesis describes a feedback loop that begins with an increase in the available energy from the sun acting to increase the growth rates of phytoplankton by either a physiological effect (due to elevated temperature) or enhanced photosynthesis (due to increased irradiance ). Certain phytoplankton, such as coccolithophorids , synthesise dimethylsulfoniopropionate (DMSP), and their enhanced growth increases

170-548: A basal metabolic rate of 80 watts. For example, if our bodies run (on average) at 80 watts, then a light bulb running at 100 watts is running at 1.25 human equivalents (100 ÷ 80) i.e. 1.25 H-e. For a difficult task of only a few seconds' duration, a person can put out thousands of watts, many times the 746 watts in one official horsepower. For tasks lasting a few minutes, a fit human can generate perhaps 1,000 watts. For an activity that must be sustained for an hour, output drops to around 300; for an activity kept up all day, 150 watts

255-462: A battery (from chemical energy to electric energy ), a dam (from gravitational potential energy to kinetic energy of moving water (and the blades of a turbine ) and ultimately to electric energy through an electric generator ), and a heat engine (from heat to work). Examples of energy transformation include generating electric energy from heat energy via a steam turbine, or lifting an object against gravity using electrical energy driving

340-415: A system can be subdivided and classified into potential energy , kinetic energy , or combinations of the two in various ways. Kinetic energy is determined by the movement of an object – or the composite motion of the object's components – while potential energy reflects the potential of an object to have motion, generally being based upon the object's position within a field or what is stored within

425-467: A thermodynamic system , and rest energy associated with an object's rest mass . All living organisms constantly take in and release energy. The Earth's climate and ecosystems processes are driven primarily by radiant energy from the sun . The energy industry provides the energy required for human civilization to function, which it obtains from energy resources such as fossil fuels , nuclear fuel , and renewable energy . The total energy of

510-435: A Lagrangian; for example, dissipative systems with continuous symmetries need not have a corresponding conservation law. In the context of chemistry , energy is an attribute of a substance as a consequence of its atomic, molecular, or aggregate structure. Since a chemical transformation is accompanied by a change in one or more of these kinds of structure, it is usually accompanied by a decrease, and sometimes an increase, of

595-474: A biological cell or organelle of a biological organism. Energy used in respiration is stored in substances such as carbohydrates (including sugars), lipids , and proteins stored by cells . In human terms, the human equivalent (H-e) (Human energy conversion) indicates, for a given amount of energy expenditure, the relative quantity of energy needed for human metabolism , using as a standard an average human energy expenditure of 12,500 kJ per day and

680-515: A bound system is discrete (a set of permitted states, each characterized by an energy level ) which results in the concept of quanta . In the solution of the Schrödinger equation for any oscillator (vibrator) and for electromagnetic waves in a vacuum, the resulting energy states are related to the frequency by Planck's relation : E = h ν {\displaystyle E=h\nu } (where h {\displaystyle h}

765-424: A century until this was generally accepted. The modern analog of this property, kinetic energy , differs from vis viva only by a factor of two. Writing in the early 18th century, Émilie du Châtelet proposed the concept of conservation of energy in the marginalia of her French language translation of Newton's Principia Mathematica , which represented the first formulation of a conserved measurable quantity that

850-417: A core concept. Work , a function of energy, is force times distance. This says that the work ( W {\displaystyle W} ) is equal to the line integral of the force F along a path C ; for details see the mechanical work article. Work and thus energy is frame dependent . For example, consider a ball being hit by a bat. In the center-of-mass reference frame, the bat does no work on

935-492: A crane motor. Lifting against gravity performs mechanical work on the object and stores gravitational potential energy in the object. If the object falls to the ground, gravity does mechanical work on the object which transforms the potential energy in the gravitational field to the kinetic energy released as heat on impact with the ground. The Sun transforms nuclear potential energy to other forms of energy; its total mass does not decrease due to that itself (since it still contains

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1020-556: A few exceptions, like those generated by volcanic events for example. An example of a solar-mediated weather event is a hurricane, which occurs when large unstable areas of warm ocean, heated over months, suddenly give up some of their thermal energy to power a few days of violent air movement. In a slower process, radioactive decay of atoms in the core of the Earth releases heat. This thermal energy drives plate tectonics and may lift mountains, via orogenesis . This slow lifting represents

1105-455: A force of one newton through a distance of one metre. However energy can also be expressed in many other units not part of the SI, such as ergs , calories , British thermal units , kilowatt-hours and kilocalories , which require a conversion factor when expressed in SI units. The SI unit of power , defined as energy per unit of time, is the watt , which is a joule per second. Thus, one joule

1190-474: A given temperature  T . This exponential dependence of a reaction rate on temperature is known as the Arrhenius equation . The activation energy necessary for a chemical reaction can be provided in the form of thermal energy. In biology , energy is an attribute of all biological systems, from the biosphere to the smallest living organism. Within an organism it is responsible for growth and development of

1275-477: A kind of gravitational potential energy storage of the thermal energy, which may later be transformed into active kinetic energy during landslides, after a triggering event. Earthquakes also release stored elastic potential energy in rocks, a store that has been produced ultimately from the same radioactive heat sources. Thus, according to present understanding, familiar events such as landslides and earthquakes release energy that has been stored as potential energy in

1360-400: A physical quantity Z is expressed as the product of a numerical value { Z } (a pure number) and a unit [ Z ]: For example, let Z {\displaystyle Z} be "2 metres"; then, { Z } = 2 {\displaystyle \{Z\}=2} is the numerical value and [ Z ] = m e t r e {\displaystyle [Z]=\mathrm {metre} }

1445-489: A quantity like Δ in Δ y or operators like d in d x , are also recommended to be printed in roman type. Examples: A scalar is a physical quantity that has magnitude but no direction. Symbols for physical quantities are usually chosen to be a single letter of the Latin or Greek alphabet , and are printed in italic type. Vectors are physical quantities that possess both magnitude and direction and whose operations obey

1530-540: A quantity of mass might be represented by the symbol m , and could be expressed in the units kilograms (kg), pounds (lb), or daltons (Da). Dimensional homogeneity is not necessarily sufficient for quantities to be comparable; for example, both kinematic viscosity and thermal diffusivity have dimension of square length per time (in units of m /s ). Quantities of the same kind share extra commonalities beyond their dimension and units allowing their comparison; for example, not all dimensionless quantities are of

1615-425: A system. This property is responsible for the inertia and strength of gravitational interaction of the system ("mass manifestations"), and is also responsible for the potential ability of the system to perform work or heating ("energy manifestations"), subject to the limitations of other physical laws. In classical physics , energy is a scalar quantity, the canonical conjugate to time. In special relativity energy

1700-426: A tiny fraction of the original chemical energy is used for work : It would appear that living organisms are remarkably inefficient (in the physical sense) in their use of the energy they receive (chemical or radiant energy); most machines manage higher efficiencies. In growing organisms the energy that is converted to heat serves a vital purpose, as it allows the organism tissue to be highly ordered with regard to

1785-677: Is a n -variable function X ≡ X ( x 1 , x 2 ⋯ x n ) {\displaystyle X\equiv X\left(x_{1},x_{2}\cdots x_{n}\right)} , then Differential The differential n -space volume element is d n x ≡ d V n ≡ d x 1 d x 2 ⋯ d x n {\displaystyle \mathrm {d} ^{n}x\equiv \mathrm {d} V_{n}\equiv \mathrm {d} x_{1}\mathrm {d} x_{2}\cdots \mathrm {d} x_{n}} , No common symbol for n -space density, here ρ n

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1870-460: Is about the maximum. The human equivalent assists understanding of energy flows in physical and biological systems by expressing energy units in human terms: it provides a "feel" for the use of a given amount of energy. Sunlight's radiant energy is also captured by plants as chemical potential energy in photosynthesis , when carbon dioxide and water (two low-energy compounds) are converted into carbohydrates, lipids, proteins and oxygen. Release of

1955-434: Is also a scalar (although not a Lorentz scalar but a time component of the energy–momentum 4-vector ). In other words, energy is invariant with respect to rotations of space , but not invariant with respect to rotations of spacetime (= boosts ). Energy may be transformed between different forms at various efficiencies . Items that transform between these forms are called transducers . Examples of transducers include

2040-575: Is called the Lagrangian , after Joseph-Louis Lagrange . This formalism is as fundamental as the Hamiltonian, and both can be used to derive the equations of motion or be derived from them. It was invented in the context of classical mechanics , but is generally useful in modern physics. The Lagrangian is defined as the kinetic energy minus the potential energy. Usually, the Lagrange formalism

2125-473: Is defined in terms of the energy operator (Hamiltonian) as a time derivative of the wave function . The Schrödinger equation equates the energy operator to the full energy of a particle or a system. Its results can be considered as a definition of measurement of energy in quantum mechanics. The Schrödinger equation describes the space- and time-dependence of a slowly changing (non-relativistic) wave function of quantum systems. The solution of this equation for

2210-418: Is directly proportional to the mass of the body: E 0 = m 0 c 2 , {\displaystyle E_{0}=m_{0}c^{2},} where For example, consider electron – positron annihilation, in which the rest energy of these two individual particles (equivalent to their rest mass) is converted to the radiant energy of the photons produced in the process. In this system

2295-516: Is either from gravitational collapse of matter (usually molecular hydrogen) into various classes of astronomical objects (stars, black holes, etc.), or from nuclear fusion (of lighter elements, primarily hydrogen). The nuclear fusion of hydrogen in the Sun also releases another store of potential energy which was created at the time of the Big Bang . At that time, according to theory, space expanded and

2380-510: Is extremely large relative to ordinary human scales, the conversion of an everyday amount of rest mass (for example, 1 kg) from rest energy to other forms of energy (such as kinetic energy, thermal energy, or the radiant energy carried by light and other radiation) can liberate tremendous amounts of energy (~ 9 × 10 16 {\displaystyle 9\times 10^{16}} joules = 21 megatons of TNT), as can be seen in nuclear reactors and nuclear weapons. Conversely,

2465-623: Is mathematically more convenient than the Hamiltonian for non-conservative systems (such as systems with friction). Noether's theorem (1918) states that any differentiable symmetry of the action of a physical system has a corresponding conservation law. Noether's theorem has become a fundamental tool of modern theoretical physics and the calculus of variations. A generalisation of the seminal formulations on constants of motion in Lagrangian and Hamiltonian mechanics (1788 and 1833, respectively), it does not apply to systems that cannot be modeled with

2550-412: Is necessarily required for the gradient of a scalar field, since only the nabla/del operator ∇ or grad needs to be written. For spatial density, current, current density and flux, the notations are common from one context to another, differing only by a change in subscripts. For current density, t ^ {\displaystyle \mathbf {\hat {t}} } is a unit vector in

2635-402: Is no friction or other losses, the conversion of energy between these processes would be perfect, and the pendulum would continue swinging forever. Energy is also transferred from potential energy ( E p {\displaystyle E_{p}} ) to kinetic energy ( E k {\displaystyle E_{k}} ) and then back to potential energy constantly. This

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2720-436: Is one watt-second, and 3600 joules equal one watt-hour. The CGS energy unit is the erg and the imperial and US customary unit is the foot pound . Other energy units such as the electronvolt , food calorie or thermodynamic kcal (based on the temperature change of water in a heating process), and BTU are used in specific areas of science and commerce. In 1843, French physicist James Prescott Joule , namesake of

2805-415: Is referred to as conservation of energy. In this isolated system , energy cannot be created or destroyed; therefore, the initial energy and the final energy will be equal to each other. This can be demonstrated by the following: The equation can then be simplified further since E p = m g h {\displaystyle E_{p}=mgh} (mass times acceleration due to gravity times

2890-696: Is the Planck constant and ν {\displaystyle \nu } the frequency). In the case of an electromagnetic wave these energy states are called quanta of light or photons . When calculating kinetic energy ( work to accelerate a massive body from zero speed to some finite speed) relativistically – using Lorentz transformations instead of Newtonian mechanics – Einstein discovered an unexpected by-product of these calculations to be an energy term which does not vanish at zero speed. He called it rest energy : energy which every massive body must possess even when being at rest. The amount of energy

2975-418: Is the quantitative property that is transferred to a body or to a physical system , recognizable in the performance of work and in the form of heat and light . Energy is a conserved quantity —the law of conservation of energy states that energy can be converted in form, but not created or destroyed; matter and energy may also be converted to one another. The unit of measurement for energy in

3060-445: Is the main input to Earth's energy budget which accounts for its temperature and climate stability. Sunlight may be stored as gravitational potential energy after it strikes the Earth, as (for example when) water evaporates from oceans and is deposited upon mountains (where, after being released at a hydroelectric dam, it can be used to drive turbines or generators to produce electricity). Sunlight also drives most weather phenomena, save

3145-512: Is the unit. Conversely, the numerical value expressed in an arbitrary unit can be obtained as: The multiplication sign is usually left out, just as it is left out between variables in the scientific notation of formulas. The convention used to express quantities is referred to as quantity calculus . In formulas, the unit [ Z ] can be treated as if it were a specific magnitude of a kind of physical dimension : see Dimensional analysis for more on this treatment. International recommendations for

3230-424: Is transformed to what other kind) is often determined by entropy (equal energy spread among all available degrees of freedom ) considerations. In practice all energy transformations are permitted on a small scale, but certain larger transformations are not permitted because it is statistically unlikely that energy or matter will randomly move into more concentrated forms or smaller spaces. Energy transformations in

3315-433: Is trapped in a system with zero momentum, where it can be weighed. It is also equivalent to mass, and this mass is always associated with it. Mass is also equivalent to a certain amount of energy, and likewise always appears associated with it, as described in mass–energy equivalence . The formula E  =  mc ², derived by Albert Einstein (1905) quantifies the relationship between relativistic mass and energy within

3400-568: The Cauchy stress tensor possesses magnitude, direction, and orientation qualities. The notion of dimension of a physical quantity was introduced by Joseph Fourier in 1822. By convention, physical quantities are organized in a dimensional system built upon base quantities, each of which is regarded as having its own dimension. There is often a choice of unit, though SI units are usually used in scientific contexts due to their ease of use, international familiarity and prescription. For example,

3485-528: The Gaia hypothesis framed by one of the original authors of the CLAW hypothesis, James Lovelock. Some subsequent studies of the CLAW hypothesis have uncovered evidence to support its mechanism, although this is not unequivocal. Other researchers have suggested that a CLAW-like mechanism may operate in the Earth's sulfur cycle without the requirement of an active biological component. A 2014 review article criticised

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3570-493: The International System of Units (SI) is the joule (J). Forms of energy include the kinetic energy of a moving object, the potential energy stored by an object (for instance due to its position in a field ), the elastic energy stored in a solid object, chemical energy associated with chemical reactions , the radiant energy carried by electromagnetic radiation , the internal energy contained within

3655-493: The axioms of a vector space . Symbols for physical quantities that are vectors are in bold type, underlined or with an arrow above. For example, if u is the speed of a particle, then the straightforward notations for its velocity are u , u , or u → {\displaystyle {\vec {u}}} . Scalar and vector quantities are the simplest tensor quantities , which are tensors can be used to describe more general physical properties. For example,

3740-487: The gravitational collapse of supernovae to "store" energy in the creation of heavy isotopes (such as uranium and thorium ), and nuclear decay , a process in which energy is released that was originally stored in these heavy elements, before they were incorporated into the Solar System and the Earth. This energy is triggered and released in nuclear fission bombs or in civil nuclear power generation. Similarly, in

3825-416: The matter and antimatter (electrons and positrons) are destroyed and changed to non-matter (the photons). However, the total mass and total energy do not change during this interaction. The photons each have no rest mass but nonetheless have radiant energy which exhibits the same inertia as did the two original particles. This is a reversible process – the inverse process is called pair creation – in which

3910-526: The nuclear force or the weak force , among other examples. The word energy derives from the Ancient Greek : ἐνέργεια , romanized :  energeia , lit.   'activity, operation', which possibly appears for the first time in the work of Aristotle in the 4th century BC. In contrast to the modern definition, energeia was a qualitative philosophical concept, broad enough to include ideas such as happiness and pleasure. In

3995-571: The Earth's gravitational field or elastic strain (mechanical potential energy) in rocks. Prior to this, they represent release of energy that has been stored in heavy atoms since the collapse of long-destroyed supernova stars (which created these atoms). In cosmology and astronomy the phenomena of stars , nova , supernova , quasars and gamma-ray bursts are the universe's highest-output energy transformations of matter. All stellar phenomena (including solar activity) are driven by various kinds of energy transformations. Energy in such transformations

4080-423: The amount of solar energy reaching the Earth's surface. A significant feature of the chain of interactions described above is that it creates a negative feedback loop, whereby a change to the climate system (increased/decreased solar input) is ultimately counteracted and damped by the loop. As such, the CLAW hypothesis posits an example of planetary-scale homeostasis or complex adaptive system , consistent with

4165-510: The ball. But, in the reference frame of the person swinging the bat, considerable work is done on the ball. The total energy of a system is sometimes called the Hamiltonian , after William Rowan Hamilton . The classical equations of motion can be written in terms of the Hamiltonian, even for highly complex or abstract systems. These classical equations have direct analogs in nonrelativistic quantum mechanics. Another energy-related concept

4250-447: The case of a chemical explosion , chemical potential energy is transformed to kinetic and thermal energy in a very short time. Yet another example is that of a pendulum . At its highest points the kinetic energy is zero and the gravitational potential energy is at its maximum. At its lowest point the kinetic energy is at its maximum and is equal to the decrease in potential energy . If one (unrealistically) assumes that there

4335-965: The case of animals. The daily 1500–2000  Calories (6–8 MJ) recommended for a human adult are taken as food molecules, mostly carbohydrates and fats, of which glucose (C 6 H 12 O 6 ) and stearin (C 57 H 110 O 6 ) are convenient examples. The food molecules are oxidized to carbon dioxide and water in the mitochondria C 6 H 12 O 6 + 6 O 2 ⟶ 6 CO 2 + 6 H 2 O {\displaystyle {\ce {C6H12O6 + 6O2 -> 6CO2 + 6H2O}}} C 57 H 110 O 6 + ( 81 1 2 ) O 2 ⟶ 57 CO 2 + 55 H 2 O {\displaystyle {\ce {C57H110O6 + (81 1/2) O2 -> 57CO2 + 55H2O}}} and some of

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4420-433: The complete conversion of matter (such as atoms) to non-matter (such as photons) is forbidden by conservation laws . Physical quantity A physical quantity (or simply quantity ) is a property of a material or system that can be quantified by measurement . A physical quantity can be expressed as a value , which is the algebraic multiplication of a numerical value and a unit of measurement . For example,

4505-451: The complex organisms can occupy ecological niches that are not available to their simpler brethren. The conversion of a portion of the chemical energy to heat at each step in a metabolic pathway is the physical reason behind the pyramid of biomass observed in ecology . As an example, to take just the first step in the food chain : of the estimated 124.7 Pg/a of carbon that is fixed by photosynthesis , 64.3 Pg/a (52%) are used for

4590-553: The concept of special relativity. In different theoretical frameworks, similar formulas were derived by J.J. Thomson (1881), Henri Poincaré (1900), Friedrich Hasenöhrl (1904) and others (see Mass–energy equivalence#History for further information). Part of the rest energy (equivalent to rest mass) of matter may be converted to other forms of energy (still exhibiting mass), but neither energy nor mass can be destroyed; rather, both remain constant during any process. However, since c 2 {\displaystyle c^{2}}

4675-461: The direction of flow, i.e. tangent to a flowline. Notice the dot product with the unit normal for a surface, since the amount of current passing through the surface is reduced when the current is not normal to the area. Only the current passing perpendicular to the surface contributes to the current passing through the surface, no current passes in the (tangential) plane of the surface. The calculus notations below can be used synonymously. If X

4760-428: The early 19th century, and applies to any isolated system . It was argued for some years whether heat was a physical substance, dubbed the caloric , or merely a physical quantity, such as momentum . In 1845 James Prescott Joule discovered the link between mechanical work and the generation of heat. These developments led to the theory of conservation of energy, formalized largely by William Thomson ( Lord Kelvin ) as

4845-473: The energy is used to convert ADP into ATP : The rest of the chemical energy of the carbohydrate or fat are converted into heat: the ATP is used as a sort of "energy currency", and some of the chemical energy it contains is used for other metabolism when ATP reacts with OH groups and eventually splits into ADP and phosphate (at each stage of a metabolic pathway , some chemical energy is converted into heat). Only

4930-457: The energy stored during photosynthesis as heat or light may be triggered suddenly by a spark in a forest fire, or it may be made available more slowly for animal or human metabolism when organic molecules are ingested and catabolism is triggered by enzyme action. All living creatures rely on an external source of energy to be able to grow and reproduce – radiant energy from the Sun in the case of green plants and chemical energy (in some form) in

5015-438: The fact that the laws of physics do not change over time. Thus, since 1918, theorists have understood that the law of conservation of energy is the direct mathematical consequence of the translational symmetry of the quantity conjugate to energy, namely time. In the International System of Units (SI), the unit of energy is the joule . It is a derived unit that is equal to the energy expended, or work done, in applying

5100-436: The field itself. While these two categories are sufficient to describe all forms of energy, it is often convenient to refer to particular combinations of potential and kinetic energy as its own form. For example, the sum of translational and rotational kinetic and potential energy within a system is referred to as mechanical energy , whereas nuclear energy refers to the combined potentials within an atomic nucleus from either

5185-413: The field of thermodynamics . Thermodynamics aided the rapid development of explanations of chemical processes by Rudolf Clausius , Josiah Willard Gibbs , and Walther Nernst . It also led to a mathematical formulation of the concept of entropy by Clausius and to the introduction of laws of radiant energy by Jožef Stefan . According to Noether's theorem , the conservation of energy is a consequence of

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5270-674: The following table. Other conventions may have a different number of base units (e.g. the CGS and MKS systems of units). The angular quantities, plane angle and solid angle , are defined as derived dimensionless quantities in the SI. For some relations, their units radian and steradian can be written explicitly to emphasize the fact that the quantity involves plane or solid angles. Derived quantities are those whose definitions are based on other physical quantities (base quantities). Important applied base units for space and time are below. Area and volume are thus, of course, derived from

5355-413: The height) and E k = 1 2 m v 2 {\textstyle E_{k}={\frac {1}{2}}mv^{2}} (half mass times velocity squared). Then the total amount of energy can be found by adding E p + E k = E total {\displaystyle E_{p}+E_{k}=E_{\text{total}}} . Energy gives rise to weight when it

5440-418: The hypothesis for being an oversimplification and that the effect might be much weaker than proposed. In his 2006 book The Revenge of Gaia , Lovelock proposed that instead of providing negative feedback in the climate system, the components of the CLAW hypothesis may act to create a positive feedback loop . Under future global warming , increasing temperature may stratify the world ocean , decreasing

5525-408: The late 17th century, Gottfried Leibniz proposed the idea of the Latin : vis viva , or living force, which defined as the product of the mass of an object and its velocity squared; he believed that total vis viva was conserved. To account for slowing due to friction, Leibniz theorized that thermal energy consisted of the motions of the constituent parts of matter, although it would be more than

5610-613: The length, but included for completeness as they occur frequently in many derived quantities, in particular densities. Important and convenient derived quantities such as densities, fluxes , flows , currents are associated with many quantities. Sometimes different terms such as current density and flux density , rate , frequency and current , are used interchangeably in the same context; sometimes they are used uniquely. To clarify these effective template-derived quantities, we use q to stand for any quantity within some scope of context (not necessarily base quantities) and present in

5695-437: The liquid water content of clouds and cloud area. This acts to increase cloud albedo , leading to greater reflection of incident sunlight , and a decrease in the forcing that initiated this chain of events. The figure to the right shows a summarising schematic diagram . Note that the feedback loop can operate in the reverse direction, such that a decline in solar energy leads to reduced cloud cover and thus to an increase in

5780-424: The mass equivalent of an everyday amount energy is minuscule, which is why a loss of energy (loss of mass) from most systems is difficult to measure on a weighing scale, unless the energy loss is very large. Examples of large transformations between rest energy (of matter) and other forms of energy (e.g., kinetic energy into particles with rest mass) are found in nuclear physics and particle physics . Often, however,

5865-474: The metabolism of green plants, i.e. reconverted into carbon dioxide and heat. In geology , continental drift , mountain ranges , volcanoes , and earthquakes are phenomena that can be explained in terms of energy transformations in the Earth's interior, while meteorological phenomena like wind, rain, hail , snow, lightning, tornadoes and hurricanes are all a result of energy transformations in our atmosphere brought about by solar energy . Sunlight

5950-427: The molecules it is built from. The second law of thermodynamics states that energy (and matter) tends to become more evenly spread out across the universe: to concentrate energy (or matter) in one specific place, it is necessary to spread out a greater amount of energy (as heat) across the remainder of the universe ("the surroundings"). Simpler organisms can achieve higher energy efficiencies than more complex ones, but

6035-409: The physical quantity mass , symbol m , can be quantified as m = n   kg, where n is the numerical value and kg is the unit symbol (for kilogram ). Quantities that are vectors have, besides numerical value and unit, direction or orientation in space. Following ISO 80000-1 , any value or magnitude of a physical quantity is expressed as a comparison to a unit of that quantity. The value of

6120-417: The production of this osmolyte . In turn, this leads to an increase in the concentration of its breakdown product, dimethyl sulfide (DMS), first in seawater, and then in the atmosphere. DMS is oxidised in the atmosphere to form sulfur dioxide , and this leads to the production of sulfate aerosols . These aerosols act as cloud condensation nuclei and increase cloud droplet number, which in turn elevate

6205-405: The rest mass of particles is created from the radiant energy of two (or more) annihilating photons. In general relativity, the stress–energy tensor serves as the source term for the gravitational field, in rough analogy to the way mass serves as the source term in the non-relativistic Newtonian approximation. Energy and mass are manifestations of one and the same underlying physical property of

6290-521: The right shows a summarising schematic diagram. Evidence for the anti-CLAW hypothesis is constrained by similar uncertainties as those of the sulfur cycle feedback loop of the CLAW hypothesis. However, researchers simulating future oceanic primary production have found evidence of declining production with increasing ocean stratification, leaving open the possibility that such a mechanism may exist. Energy Energy (from Ancient Greek ἐνέργεια ( enérgeia )  'activity')

6375-508: The same kind. A systems of quantities relates physical quantities, and due to this dependence, a limited number of quantities can serve as a basis in terms of which the dimensions of all the remaining quantities of the system can be defined. A set of mutually independent quantities may be chosen by convention to act as such a set, and are called base quantities. The seven base quantities of the International System of Quantities (ISQ) and their corresponding SI units and dimensions are listed in

6460-474: The same total energy even in different forms) but its mass does decrease when the energy escapes out to its surroundings, largely as radiant energy . There are strict limits to how efficiently heat can be converted into work in a cyclic process, e.g. in a heat engine, as described by Carnot's theorem and the second law of thermodynamics . However, some energy transformations can be quite efficient. The direction of transformations in energy (what kind of energy

6545-467: The situation is the reverse. Chemical reactions are usually not possible unless the reactants surmount an energy barrier known as the activation energy . The speed of a chemical reaction (at a given temperature  T ) is related to the activation energy  E by the Boltzmann's population factor e ; that is, the probability of a molecule to have energy greater than or equal to  E at

6630-525: The supply of nutrients from the deep ocean to its productive euphotic zone . Consequently, phytoplankton activity will decline with a concomitant fall in the production of DMS. In a reverse of the CLAW hypothesis, this decline in DMS production will lead to a decrease in cloud condensation nuclei and a fall in cloud albedo . The consequence of this will be further climate warming which may lead to even less DMS production (and further climate warming). The figure to

6715-452: The table below some of the most commonly used symbols where applicable, their definitions, usage, SI units and SI dimensions – where [ q ] denotes the dimension of q . For time derivatives, specific, molar, and flux densities of quantities, there is no one symbol; nomenclature depends on the subject, though time derivatives can be generally written using overdot notation. For generality we use q m , q n , and F respectively. No symbol

6800-420: The total energy of the substances involved. Some energy may be transferred between the surroundings and the reactants in the form of heat or light; thus the products of a reaction have sometimes more but usually less energy than the reactants. A reaction is said to be exothermic or exergonic if the final state is lower on the energy scale than the initial state; in the less common case of endothermic reactions

6885-406: The unit of measure, discovered that the gravitational potential energy lost by a descending weight attached via a string was equal to the internal energy gained by the water through friction with the paddle. In classical mechanics, energy is a conceptually and mathematically useful property, as it is a conserved quantity . Several formulations of mechanics have been developed using energy as

6970-421: The universe cooled too rapidly for hydrogen to completely fuse into heavier elements. This meant that hydrogen represents a store of potential energy that can be released by fusion. Such a fusion process is triggered by heat and pressure generated from gravitational collapse of hydrogen clouds when they produce stars, and some of the fusion energy is then transformed into sunlight. In quantum mechanics , energy

7055-401: The universe over time are characterized by various kinds of potential energy, that has been available since the Big Bang , being "released" (transformed to more active types of energy such as kinetic or radiant energy) when a triggering mechanism is available. Familiar examples of such processes include nucleosynthesis , a process ultimately using the gravitational potential energy released from

7140-706: The use of symbols for quantities are set out in ISO/IEC 80000 , the IUPAP red book and the IUPAC green book . For example, the recommended symbol for the physical quantity "mass" is m , and the recommended symbol for the quantity "electric charge" is Q . Physical quantities are normally typeset in italics. Purely numerical quantities, even those denoted by letters, are usually printed in roman (upright) type, though sometimes in italics. Symbols for elementary functions (circular trigonometric, hyperbolic, logarithmic etc.), changes in

7225-409: Was distinct from momentum , and which would later be called "energy". In 1807, Thomas Young was possibly the first to use the term "energy" instead of vis viva , in its modern sense. Gustave-Gaspard Coriolis described " kinetic energy " in 1829 in its modern sense, and in 1853, William Rankine coined the term " potential energy ". The law of conservation of energy was also first postulated in

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