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Absolute zero

Absolute zero is the lowest limit of the thermodynamic temperature scale; a state at which the enthalpy and entropy of a cooled ideal gas reach their minimum value, taken as zero kelvin. The fundamental particles of nature have minimum vibrational motion, retaining only quantum mechanical, zero-point energy-induced particle motion. The theoretical temperature is determined by extrapolating the ideal gas law; by international agreement, absolute zero is taken as −273.15 degrees on the Celsius scale (International System of Units), which equals −459.67 degrees on the Fahrenheit scale (United States customary units or imperial units). The corresponding Kelvin and Rankine temperature scales set their zero points at absolute zero by definition.

It is commonly thought of as the lowest temperature possible, but it is not the lowest enthalpy state possible, because all real substances begin to depart from the ideal gas when cooled as they approach the change of state to liquid, and then to solid; and the sum of the enthalpy of vaporization (gas to liquid) and enthalpy of fusion (liquid to solid) exceeds the ideal gas's change in enthalpy to absolute zero. In the quantum-mechanical description, matter at absolute zero is in its ground state, the point of lowest internal energy.

The laws of thermodynamics indicate that absolute zero cannot be reached using only thermodynamic means, because the temperature of the substance being cooled approaches the temperature of the cooling agent asymptotically. Even a system at absolute zero, if it could somehow be achieved, would still possess quantum mechanical zero-point energy, the energy of its ground state at absolute zero; the kinetic energy of the ground state cannot be removed. Scientists and technologists routinely achieve temperatures close to absolute zero, where matter exhibits quantum effects such as Bose–Einstein condensate, superconductivity and superfluidity.

Thermodynamics near absolute zero
At temperatures near 0 K, nearly all molecular motion ceases and ΔS = 0 for any adiabatic process, where S is the entropy. In such a circumstance, pure substances can (ideally) form perfect crystals with no structural imperfections as T → 0. Max Planck's strong form of the third law of thermodynamics states the entropy of a perfect crystal vanishes at absolute zero. The original Nernst heat theorem makes the weaker and less controversial claim that the entropy change for any isothermal process approaches zero as T → 0:
 * $$ \lim_{T \to 0} \Delta S = 0 $$

The implication is that the entropy of a perfect crystal approaches a constant value. An adiabat is a state with constant entropy, typically represented on a graph as a curve in a manner similar to isotherms and isobars.

"The Nernst postulate identifies the isotherm T = 0 as coincident with the adiabat S = 0, although other isotherms and adiabats are distinct. As no two adiabats intersect, no other adiabat can intersect the T = 0 isotherm. Consequently no adiabatic process initiated at nonzero temperature can lead to zero temperature. (≈ Callen, pp. 189–190)"

A perfect crystal is one in which the internal lattice structure extends uninterrupted in all directions. The perfect order can be represented by translational symmetry along three (not usually orthogonal) axes. Every lattice element of the structure is in its proper place, whether it is a single atom or a molecular grouping. For substances that exist in two (or more) stable crystalline forms, such as diamond and graphite for carbon, there is a kind of chemical degeneracy. The question remains whether both can have zero entropy at T = 0 even though each is perfectly ordered.

Perfect crystals never occur in practice; imperfections, and even entire amorphous material inclusions, can and do get "frozen in" at low temperatures, so transitions to more stable states do not occur.

Using the Debye model, the specific heat and entropy of a pure crystal are proportional to T3, while the enthalpy and chemical potential are proportional to T4. (Guggenheim, p. 111) These quantities drop toward their T = 0 limiting values and approach with zero slopes. For the specific heats at least, the limiting value itself is definitely zero, as borne out by experiments to below 10 K. Even the less detailed Einstein model shows this curious drop in specific heats. In fact, all specific heats vanish at absolute zero, not just those of crystals. Likewise for the coefficient of thermal expansion. Maxwell's relations show that various other quantities also vanish. These phenomena were unanticipated.

Since the relation between changes in Gibbs free energy (G), the enthalpy (H) and the entropy is

 * $$ \Delta G = \Delta H - T \Delta S \,$$

thus, as T decreases, ΔG and ΔH approach each other (so long as ΔS is bounded). Experimentally, it is found that all spontaneous processes (including chemical reactions) result in a decrease in G as they proceed toward equilibrium. If ΔS and/or T are small, the condition ΔG < 0 may imply that ΔH < 0, which would indicate an exothermic reaction. However, this is not required; endothermic reactions can proceed spontaneously if the TΔS term is large enough.

Moreover, the slopes of the derivatives of ΔG and ΔH converge and are equal to zero at T = 0. This ensures that ΔG and ΔH are nearly the same over a considerable range of temperatures and justifies the approximate empirical Principle of Thomsen and Berthelot, which states that the equilibrium state to which a system proceeds is the one that evolves the greatest amount of heat, i.e., an actual process is the most exothermic one. (Callen, pp. 186–187)

One model that estimates the properties of an electron gas at absolute zero in metals is the Fermi gas. The electrons, being fermions, must be in different quantum states, which leads the electrons to get very high typical velocities, even at absolute zero. The maximum energy that electrons can have at absolute zero is called the Fermi energy. The Fermi temperature is defined as this maximum energy divided by the Boltzmann constant, and is on the order of 80,000 K for typical electron densities found in metals. For temperatures significantly below the Fermi temperature, the electrons behave in almost the same way as at absolute zero. This explains the failure of the classical equipartition theorem for metals that eluded classical physicists in the late 19th century.

Relation with Bose–Einstein condensate
A Bose–Einstein condensate (BEC) is a state of matter of a dilute gas of weakly interacting bosons confined in an external potential and cooled to temperatures very near absolute zero. Under such conditions, a large fraction of the bosons occupy the lowest quantum state of the external potential, at which point quantum effects become apparent on a macroscopic scale.

This state of matter was first predicted by Satyendra Nath Bose and Albert Einstein in 1924–25. Bose first sent a paper to Einstein on the quantum statistics of light quanta (now called photons). Einstein was impressed, translated the paper from English to German and submitted it for Bose to the Zeitschrift für Physik, which published it. Einstein then extended Bose's ideas to material particles (or matter) in two other papers.

Seventy years later, in 1995, the first gaseous condensate was produced by Eric Cornell and Carl Wieman at the University of Colorado at Boulder NIST-JILA lab, using a gas of rubidium atoms cooled to 170 nanokelvin (nK) ($1.7 K$).

In 2003, researchers at the Massachusetts Institute of Technology (MIT) achieved a temperature of 450 ± 80 picokelvin (pK) ($4.5 K$) in a BEC of sodium atoms. The associated black-body (peak emittance) wavelength of 6.4 megameters is roughly the radius of Earth.

In 2021, University of Bremen physicists achieved a BEC with a temperature of only 38 pK, the current coldest temperature record.

Absolute temperature scales
Absolute, or thermodynamic, temperature is conventionally measured in kelvin (Celsius-scaled increments) and in the Rankine scale (Fahrenheit-scaled increments) with increasing rarity. Absolute temperature measurement is uniquely determined by a multiplicative constant which specifies the size of the degree, so the ratios of two absolute temperatures, T2/T1, are the same in all scales. The most transparent definition of this standard comes from the Maxwell–Boltzmann distribution. It can also be found in Fermi–Dirac statistics (for particles of half-integer spin) and Bose–Einstein statistics (for particles of integer spin). All of these define the relative numbers of particles in a system as decreasing exponential functions of energy (at the particle level) over kT, with k representing the Boltzmann constant and T representing the temperature observed at the macroscopic level.

Negative temperatures
Temperatures that are expressed as negative numbers on the familiar Celsius or Fahrenheit scales are simply colder than the zero points of those scales. Certain systems can achieve truly negative temperatures; that is, their thermodynamic temperature (expressed in kelvins) can be of a negative quantity. A system with a truly negative temperature is not colder than absolute zero. Rather, a system with a negative temperature is hotter than any system with a positive temperature, in the sense that if a negative-temperature system and a positive-temperature system come in contact, heat flows from the negative to the positive-temperature system.

Most familiar systems cannot achieve negative temperatures because adding energy always increases their entropy. However, some systems have a maximum amount of energy that they can hold, and as they approach that maximum energy their entropy actually begins to decrease. Because temperature is defined by the relationship between energy and entropy, such a system's temperature becomes negative, even though energy is being added. As a result, the Boltzmann factor for states of systems at negative temperature increases rather than decreases with increasing state energy. Therefore, no complete system, i.e. including the electromagnetic modes, can have negative temperatures, since there is no highest energy state, so that the sum of the probabilities of the states would diverge for negative temperatures. However, for quasi-equilibrium systems (e.g. spins out of equilibrium with the electromagnetic field) this argument does not apply, and negative effective temperatures are attainable.

On 3 January 2013, physicists announced that for the first time they had created a quantum gas made up of potassium atoms with a negative temperature in motional degrees of freedom.

History
One of the first to discuss the possibility of an absolute minimal temperature was Robert Boyle. His 1665 New Experiments and Observations touching Cold, articulated the dispute known as the primum frigidum. The concept was well known among naturalists of the time. Some contended an absolute minimum temperature occurred within earth (as one of the four classical elements), others within water, others air, and some more recently within nitre. But all of them seemed to agree that, "There is some body or other that is of its own nature supremely cold and by participation of which all other bodies obtain that quality."

Limit to the "degree of cold"
The question of whether there is a limit to the degree of coldness possible, and, if so, where the zero must be placed, was first addressed by the French physicist Guillaume Amontons in 1703, in connection with his improvements in the air thermometer. His instrument indicated temperatures by the height at which a certain mass of air sustained a column of mercury—the pressure, or "spring" of the air varying with temperature. Amontons therefore argued that the zero of his thermometer would be that temperature at which the spring of the air was reduced to nothing. He used a scale that marked the boiling point of water at +73 and the melting point of ice at +$51 1/2$, so that the zero was equivalent to about −240 on the Celsius scale. Amontons held that the absolute zero cannot be reached, so never attempted to compute it explicitly. The value of −240 °C, or "431 divisions [in Fahrenheit's thermometer] below the cold of freezing water" was published by George Martine in 1740.

This close approximation to the modern value of −273.15 °C for the zero of the air thermometer was further improved upon in 1779 by Johann Heinrich Lambert, who observed that -270 C might be regarded as absolute cold.

Values of this order for the absolute zero were not, however, universally accepted about this period. Pierre-Simon Laplace and Antoine Lavoisier, in their 1780 treatise on heat, arrived at values ranging from 1,500 to 3,000 below the freezing point of water, and thought that in any case it must be at least 600 below. John Dalton in his Chemical Philosophy gave ten calculations of this value, and finally adopted −3,000 °C as the natural zero of temperature.

Charles's law
From 1787 to 1802, it was determined by Jacques Charles (unpublished), John Dalton, and Joseph Louis Gay-Lussac that, at constant pressure, ideal gases expanded or contracted their volume linearly (Charles's law) by about 1/273 parts per degree Celsius of temperature's change up or down, between 0° and 100° C. This suggested that the volume of a gas cooled at about −273 °C would reach zero.

Lord Kelvin's work
After James Prescott Joule had determined the mechanical equivalent of heat, Lord Kelvin approached the question from an entirely different point of view, and in 1848 devised a scale of absolute temperature that was independent of the properties of any particular substance and was based on Carnot's theory of the Motive Power of Heat and data published by Henri Victor Regnault. It followed from the principles on which this scale was constructed that its zero was placed at −273 °C, at almost precisely the same point as the zero of the air thermometer, where the air volume would reach "nothing". This value was not immediately accepted; values ranging from -271.1 C to -274.5 C, derived from laboratory measurements and observations of astronomical refraction, remained in use in the early 20th century.

The race to absolute zero
With a better theoretical understanding of absolute zero, scientists were eager to reach this temperature in the lab. By 1845, Michael Faraday had managed to liquefy most gases then known to exist, and reached a new record for lowest temperatures by reaching -130 C. Faraday believed that certain gases, such as oxygen, nitrogen, and hydrogen, were permanent gases and could not be liquefied. Decades later, in 1873 Dutch theoretical scientist Johannes Diderik van der Waals demonstrated that these gases could be liquefied, but only under conditions of very high pressure and very low temperatures. In 1877, Louis Paul Cailletet in France and Raoul Pictet in Switzerland succeeded in producing the first droplets of liquid air at -195 C. This was followed in 1883 by the production of liquid oxygen -218 C by the Polish professors Zygmunt Wróblewski and Karol Olszewski.

Scottish chemist and physicist James Dewar and Dutch physicist Heike Kamerlingh Onnes took on the challenge to liquefy the remaining gases, hydrogen and helium. In 1898, after 20 years of effort, Dewar was the first to liquefy hydrogen, reaching a new low-temperature record of -252 C. However, Kamerlingh Onnes, his rival, was the first to liquefy helium, in 1908, using several precooling stages and the Hampson–Linde cycle. He lowered the temperature to the boiling point of helium -269 C. By reducing the pressure of the liquid helium, he achieved an even lower temperature, near 1.5 K. These were the coldest temperatures achieved on Earth at the time and his achievement earned him the Nobel Prize in 1913. Kamerlingh Onnes would continue to study the properties of materials at temperatures near absolute zero, describing superconductivity and superfluids for the first time.

Very low temperatures

The average temperature of the universe today is approximately 2.73 K, or about −270.42 °C, based on measurements of cosmic microwave background radiation. Standard models of the future expansion of the universe predict that the average temperature of the universe is decreasing over time. This temperature is calculated as the mean density of energy in space; it should not be confused with the mean electron temperature (total energy divided by particle count) which has increased over time.

Absolute zero cannot be achieved, although it is possible to reach temperatures close to it through the use of evaporative cooling, cryocoolers, dilution refrigerators, and nuclear adiabatic demagnetization. The use of laser cooling has produced temperatures of less than a billionth of a kelvin. At very low temperatures in the vicinity of absolute zero, matter exhibits many unusual properties, including superconductivity, superfluidity, and Bose–Einstein condensation. To study such phenomena, scientists have worked to obtain even lower temperatures.
 * In November 2000, nuclear spin temperatures below 100 pK were reported for an experiment at the Helsinki University of Technology's Low Temperature Lab in Espoo, Finland. However, this was the temperature of one particular degree of freedom—a quantum property called nuclear spin—not the overall average thermodynamic temperature for all possible degrees in freedom.
 * In February 2003, the Boomerang Nebula was observed to have been releasing gases at a speed of 500000 km/h for the last 1,500 years. This has cooled it down to approximately 1 K, as deduced by astronomical observation, which is the lowest natural temperature ever recorded.
 * In November 2003, 90377 Sedna was discovered and is one of the coldest known objects in the Solar System. With an average surface temperature of -400°F (-240°C), due to its extremely far orbit of 903 astronomical units.
 * In May 2005, the European Space Agency proposed research in space to achieve femtokelvin temperatures.
 * In May 2006, the Institute of Quantum Optics at the University of Hannover gave details of technologies and benefits of femtokelvin research in space.
 * In January 2013, physicist Ulrich Schneider of the University of Munich in Germany reported to have achieved temperatures formally below absolute zero ("negative temperature") in gases. The gas is artificially forced out of equilibrium into a high potential energy state, which is, however, cold. When it then emits radiation it approaches the equilibrium, and can continue emitting despite reaching formal absolute zero; thus, the temperature is formally negative.
 * In September 2014, scientists in the CUORE collaboration at the Laboratori Nazionali del Gran Sasso in Italy cooled a copper vessel with a volume of one cubic meter to 0.006 K for 15 days, setting a record for the lowest temperature in the known universe over such a large contiguous volume.
 * In June 2015, experimental physicists at MIT cooled molecules in a gas of sodium potassium to a temperature of 500 nanokelvin, and it is expected to exhibit an exotic state of matter by cooling these molecules somewhat further.
 * In 2017, Cold Atom Laboratory (CAL), an experimental instrument was developed for launch to the International Space Station (ISS) in 2018. The instrument has created extremely cold conditions in the microgravity environment of the ISS leading to the formation of Bose–Einstein condensates. In this space-based laboratory, temperatures as low as 1 picokelvin (10−12 K) are projected to be achievable, and it could further the exploration of unknown quantum mechanical phenomena and test some of the most fundamental laws of physics.
 * The current world record for effective temperatures was set in 2021 at 38 picokelvin (pK) through matter-wave lensing of rubidium Bose–Einstein condensates.

title: Absolute zero


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Adiabatic process

An adiabatic process (adiabatic ) is a type of thermodynamic process that occurs without transferring heat or mass between the thermodynamic system and its environment. Unlike an isothermal process, an adiabatic process transfers energy to the surroundings only as work. As a key concept in thermodynamics, the adiabatic process supports the theory that explains the first law of thermodynamics. The opposite term to "adiabatic" is diabatic.

Some chemical and physical processes occur too rapidly for energy to enter or leave the system as heat, allowing a convenient "adiabatic approximation". For example, the adiabatic flame temperature uses this approximation to calculate the upper limit of flame temperature by assuming combustion loses no heat to its surroundings.

In meteorology, adiabatic expansion and cooling of moist air, which can be triggered by winds flowing up and over a mountain for example, can cause the water vapor pressure to exceed the saturation vapor pressure. Expansion and cooling beyond the saturation vapor pressure is often idealized as a pseudo-adiabatic process whereby excess vapor instantaneously precipitates into water droplets. The change in temperature of an air undergoing pseudo-adiabatic expansion differs from air undergoing adiabatic expansion because latent heat is released by precipitation.

Description
A process without transfer of heat to or from a system, so that $Q = 0$, is called adiabatic, and such a system is said to be adiabatically isolated. The simplifying assumption frequently made is that a process is adiabatic. For example, the compression of a gas within a cylinder of an engine is assumed to occur so rapidly that on the time scale of the compression process, little of the system's energy can be transferred out as heat to the surroundings. Even though the cylinders are not insulated and are quite conductive, that process is idealized to be adiabatic. The same can be said to be true for the expansion process of such a system.

The assumption of adiabatic isolation is useful and often combined with other such idealizations to calculate a good first approximation of a system's behaviour. For example, according to Laplace, when sound travels in a gas, there is no time for heat conduction in the medium, and so the propagation of sound is adiabatic. For such an adiabatic process, the modulus of elasticity (Young's modulus) can be expressed as $E = γP$, where $γ$ is the ratio of specific heats at constant pressure and at constant volume ($γ = C_{p}⁄C_{v}$) and $P$ is the pressure of the gas.

Various applications of the adiabatic assumption
For a closed system, one may write the first law of thermodynamics as $ΔU = Q − W$, where $ΔU$ denotes the change of the system's internal energy, $Q$ the quantity of energy added to it as heat, and $W$ the work done by the system on its surroundings.

 * If the system has such rigid walls that work cannot be transferred in or out ($W = 0$), and the walls are not adiabatic and energy is added in the form of heat ($Q > 0$), and there is no phase change, then the temperature of the system will rise.
 * If the system has such rigid walls that pressure–volume work cannot be done, but the walls are adiabatic ($Q = 0$), and energy is added as isochoric (constant volume) work in the form of friction or the stirring of a viscous fluid within the system ($W < 0$), and there is no phase change, then the temperature of the system will rise.
 * If the system walls are adiabatic ($Q = 0$) but not rigid ($W ≠ 0$), and, in a fictive idealized process, energy is added to the system in the form of frictionless, non-viscous pressure–volume work ($W < 0$), and there is no phase change, then the temperature of the system will rise. Such a process is said to be "reversible". Ideally, if the process were reversed the energy could be recovered entirely as work done by the system. Should the work be added in such a way that friction or viscous forces are operating within the system, and if there is no phase change, then the temperature of the system will rise, the process is said to be "irreversible", and the work added to the system is not entirely recoverable in the form of work.
 * If the walls of a system are not adiabatic, and energy is transferred in as heat, the process is not adiabatic, having $Q > 0$, and $ΔS > 0$ according to the second law of thermodynamics.

Naturally occurring adiabatic processes are irreversible.

The transfer of energy as work into an adiabatically isolated system can be imagined as being of two idealized extreme kinds. In one such kind, no friction, viscous dissipation, etc., and the work is only pressure-volume work (denoted by $P dV$). In nature, this ideal kind occurs only approximately because it demands an infinitely slow process and no sources of dissipation.

The other extreme kind of work is isochoric work ($dV = 0$), for which energy is added as work solely through friction or viscous dissipation within the system. A stirrer that transfers energy to a viscous fluid of an adiabatically isolated system with rigid walls, without phase change, will cause a rise in temperature of the fluid, but that work is not recoverable. Isochoric work is irreversible. The second law of thermodynamics observes that a natural process, of transfer of energy as work, always consists at least of isochoric work and often both of these extreme kinds of work. Every natural process, adiabatic or not, is irreversible, with $ΔS > 0$, as friction or viscosity are always present to some extent.

Adiabatic compression and expansion
The adiabatic compression of a gas causes a rise in temperature of the gas. Adiabatic expansion against pressure, or a spring, causes a drop in temperature. In contrast, free expansion is an isothermal process for an ideal gas.

Adiabatic compression occurs when the pressure of a gas is increased by work done on it by its surroundings, e.g., a piston compressing a gas contained within a cylinder and raising the temperature where in many practical situations heat conduction through walls can be slow compared with the compression time. This finds practical application in diesel engines which rely on the lack of heat dissipation during the compression stroke to elevate the fuel vapor temperature sufficiently to ignite it.

Adiabatic compression occurs in the Earth's atmosphere when an air mass descends, for example, in a Katabatic wind, Foehn wind, or Chinook wind flowing downhill over a mountain range. When a parcel of air descends, the pressure on the parcel increases. Because of this increase in pressure, the parcel's volume decreases and its temperature increases as work is done on the parcel of air, thus increasing its internal energy, which manifests itself by a rise in the temperature of that mass of air. The parcel of air can only slowly dissipate the energy by conduction or radiation (heat), and to a first approximation it can be considered adiabatically isolated and the process an adiabatic process.

Adiabatic expansion occurs when the pressure on an adiabatically isolated system is decreased, allowing it to expand in size, thus causing it to do work on its surroundings. When the pressure applied on a parcel of gas is reduced, the gas in the parcel is allowed to expand; as the volume increases, the temperature falls as its internal energy decreases. Adiabatic expansion occurs in the Earth's atmosphere with orographic lifting and lee waves, and this can form pilei or lenticular clouds.

Due in part to adiabatic expansion in mountainous areas, snowfall infrequently occurs in some parts of the Sahara desert.

Adiabatic expansion does not have to involve a fluid. One technique used to reach very low temperatures (thousandths and even millionths of a degree above absolute zero) is via adiabatic demagnetisation, where the change in magnetic field on a magnetic material is used to provide adiabatic expansion. Also, the contents of an expanding universe can be described (to first order) as an adiabatically expanding fluid. (See heat death of the universe.)

Rising magma also undergoes adiabatic expansion before eruption, particularly significant in the case of magmas that rise quickly from great depths such as kimberlites.

In the Earth's convecting mantle (the asthenosphere) beneath the lithosphere, the mantle temperature is approximately an adiabat. The slight decrease in temperature with shallowing depth is due to the decrease in pressure the shallower the material is in the Earth.

Such temperature changes can be quantified using the ideal gas law, or the hydrostatic equation for atmospheric processes.

In practice, no process is truly adiabatic. Many processes rely on a large difference in time scales of the process of interest and the rate of heat dissipation across a system boundary, and thus are approximated by using an adiabatic assumption. There is always some heat loss, as no perfect insulators exist.

Ideal gas (reversible process)
The mathematical equation for an ideal gas undergoing a reversible adiabatic process can be represented by the polytropic process equation
 * $$ P V^\gamma = \text{constant}, $$

where $P$ is pressure, $V$ is volume, and $γ$ is the adiabatic index or heat capacity ratio defined as
 * $$ \gamma = \frac{C_P}{C_V} = \frac{f + 2}{f}. $$

Here $C_{P}$ is the specific heat for constant pressure, $C_{V}$ is the specific heat for constant volume, and $f$ is the number of degrees of freedom (3 for a monatomic gas, 5 for a diatomic gas or a gas of linear molecules such as carbon dioxide).

For a monatomic ideal gas, $γ = 5⁄3$, and for a diatomic gas (such as nitrogen and oxygen, the main components of air), $γ = 7⁄5$. Note that the above formula is only applicable to classical ideal gases (that is, gases far above absolute zero temperature) and not Bose–Einstein or Fermi gases.

One can also use the ideal gas law to rewrite the above relationship between $P$ and $V$ as

 * $$ P^{1-\gamma} T^\gamma = \text{constant},$$

 * $$ TV^{\gamma - 1} = \text{constant}.$$

where T is the absolute or thermodynamic temperature.

Example of adiabatic compression
The compression stroke in a gasoline engine can be used as an example of adiabatic compression. The model assumptions are: the uncompressed volume of the cylinder is one litre (1 L = 1000 cm3 = 0.001 m3); the gas within is the air consisting of molecular nitrogen and oxygen only (thus a diatomic gas with 5 degrees of freedom, and so $γ = 7⁄5$); the compression ratio of the engine is 10:1 (that is, the 1 L volume of uncompressed gas is reduced to 0.1 L by the piston); and the uncompressed gas is at approximately room temperature and pressure (a warm room temperature of ~27 °C, or 300 K, and a pressure of 1 bar = 100 kPa, i.e. typical sea-level atmospheric pressure).

 * $$\begin{align}

& P_1 V_1^\gamma = \mathrm{constant}_1 = 100\,000~\text{Pa} \times (0.001~\text{m}^3)^\frac75 \\ & = 10^5 \times 6.31 \times 10^{-5}~\text{Pa}\,\text{m}^{21/5} = 6.31~\text{Pa}\,\text{m}^{21/5}, \end{align}$$

so the adiabatic constant for this example is about 6.31 Pa m4.2.

The gas is now compressed to a 0.1 L (0.0001 m3) volume, which we assume happens quickly enough that no heat enters or leaves the gas through the walls. The adiabatic constant remains the same, but with the resulting pressure unknown

 * $$ P_2 V_2^\gamma = \mathrm{constant}_1 = 6.31~\text{Pa}\,\text{m}^{21/5} = P \times (0.0001~\text{m}^3)^\frac75, $$

We can now solve for the final pressure
 * $$ P_2 = P_1\left (\frac{V_1}{V_2}\right)^\gamma = 100\,000~\text{Pa} \times \text{10}^{7/5} = 2.51 \times 10^6~\text{Pa}$$

or 25.1 bar. This pressure increase is more than a simple 10:1 compression ratio would indicate; this is because the gas is not only compressed, but the work done to compress the gas also increases its internal energy, which manifests itself by a rise in the gas temperature and an additional rise in pressure above what would result from a simplistic calculation of 10 times the original pressure.

We can solve for the temperature of the compressed gas in the engine cylinder as well, using the ideal gas law, PV = nRT (n is amount of gas in moles and R the gas constant for that gas). Our initial conditions being 100 kPa of pressure, 1 L volume, and 300 K of temperature, our experimental constant (nR) is:

 * $$ \frac{PV}{T} = \mathrm{constant}_2 = \frac{10^5~\text{Pa} \times 10^{-3}~\text{m}^3}{300~\text{K}} = 0.333~\text{Pa}\,\text{m}^3\text{K}^{-1}.$$

We know the compressed gas has $V$ = 0.1 L and $P$ = $2.51 Pa$, so we can solve for temperature:

 * $$ T = \frac{P V}{\mathrm{constant}_2} = \frac{2.51 \times 10^6~\text{Pa} \times 10^{-4}~\text{m}^3}{0.333~\text{Pa}\,\text{m}^3\text{K}^{-1}} = 753~\text{K}. $$

That is a final temperature of 753 K, or 479 °C, or 896 °F, well above the ignition point of many fuels. This is why a high-compression engine requires fuels specially formulated to not self-ignite (which would cause engine knocking when operated under these conditions of temperature and pressure), or that a supercharger with an intercooler to provide a pressure boost but with a lower temperature rise would be advantageous. A diesel engine operates under even more extreme conditions, with compression ratios of 16:1 or more being typical, in order to provide a very high gas pressure, which ensures immediate ignition of the injected fuel.

Adiabatic free expansion of a gas
For an adiabatic free expansion of an ideal gas, the gas is contained in an insulated container and then allowed to expand in a vacuum. Because there is no external pressure for the gas to expand against, the work done by or on the system is zero. Since this process does not involve any heat transfer or work, the first law of thermodynamics then implies that the net internal energy change of the system is zero. For an ideal gas, the temperature remains constant because the internal energy only depends on temperature in that case. This process is irreversible.

Derivation of P–V relation for adiabatic compression and expansion
The definition of an adiabatic process is that heat transfer to the system is zero, $δQ = 0$. Then, according to the first law of thermodynamics,

where $dU$ is the change in the internal energy of the system and $δW$ is work done by the system. Any work ($δW$) done must be done at the expense of internal energy $U$, since no heat $δQ$ is being supplied from the surroundings. Pressure–volume work $δW$ done by the system is defined as

However, $P$ does not remain constant during an adiabatic process but instead changes along with $V$.

It is desired to know how the values of $dP$ and $dV$ relate to each other as the adiabatic process proceeds. For an ideal gas (recall ideal gas law $PV = nRT$) the internal energy is given by

where $α$ is the number of degrees of freedom divided by 2, $R$ is the universal gas constant and $n$ is the number of moles in the system (a constant).

Differentiating equation (a3) yields

Equation (a4) is often expressed as $dU = nC_{V} dT$ because $C_{V} = αR$.

Now substitute equations (a2) and (a4) into equation (a1) to obtain

 * $$ -P \, dV = \alpha P \, dV + \alpha V \, dP,$$

factorize $−P dV$:

 * $$ -(\alpha + 1) P \, dV = \alpha V \, dP,$$

and divide both sides by $PV$:

 * $$ -(\alpha + 1) \frac{dV}{V} = \alpha \frac{dP}{P}. $$

After integrating the left and right sides from $V_{0}$ to $V$ and from $P_{0}$ to $P$ and changing the sides respectively,

 * $$ \ln \left( \frac{P}{P_0} \right) = -\frac{\alpha + 1}{\alpha} \ln \left( \frac{V}{V_0} \right). $$

Exponentiate both sides, substitute $α + 1⁄α$ with $γ$, the heat capacity ratio

 * $$ \left( \frac{P}{P_0} \right) = \left( \frac{V}{V_0} \right)^{-\gamma}, $$

and eliminate the negative sign to obtain

 * $$ \left( \frac{P}{P_0} \right) = \left( \frac{V_0}{V} \right)^\gamma. $$

Therefore,

 * $$ \left( \frac{P}{P_0} \right) \left( \frac{V}{V_0} \right)^\gamma = 1,$$

and

 * $$ P_0 V_0^\gamma = P V^\gamma = \mathrm{constant}. $$

At the same time, the work done by the pressure–volume changes as a result from this process, is equal to

Since we require the process to be adiabatic, the following equation needs to be true

By the previous derivation,

Rearranging (b4) gives

 * $$ P = P_1 \left(\frac{V_1}{V} \right)^\gamma. $$

Substituting this into (b2) gives

 * $$ W = \int_{V_1}^{V_2} P_1 \left(\frac{V_1}{V} \right)^\gamma \,dV. $$

Integrating we obtain the expression for work,

 * $$ W = P_1 V_1^\gamma \frac{V_2^{1-\gamma} - V_1^{1-\gamma}}{1 - \gamma} = \frac{P_2 V_2 - P_1 V_1}{1 - \gamma}. $$

Substituting $γ = α + 1⁄α$ in second term,

 * $$ W = -\alpha P_1 V_1^\gamma \left( V_2^{1-\gamma} - V_1^{1-\gamma} \right). $$

Rearranging,

 * $$ W = -\alpha P_1 V_1 \left( \left( \frac{V_2}{V_1} \right)^{1-\gamma} - 1 \right). $$

Using the ideal gas law and assuming a constant molar quantity (as often happens in practical cases),

 * $$ W = -\alpha n R T_1 \left( \left( \frac{V_2}{V_1} \right)^{1-\gamma} - 1 \right). $$

By the continuous formula,

 * $$ \frac{P_2}{P_1} = \left(\frac{V_2}{V_1}\right)^{-\gamma}, $$

or

 * $$ \left(\frac{P_2}{P_1}\right)^{-\frac{1}{\gamma}} = \frac{V_2}{V_1}. $$

Substituting into the previous expression for $W$,

 * $$ W = -\alpha n R T_1 \left( \left( \frac{P_2}{P_1} \right)^{\frac{\gamma-1}{\gamma}} - 1 \right). $$

Substituting this expression and (b1) in (b3) gives

 * $$ \alpha n R (T_2 - T_1) = \alpha n R T_1 \left( \left( \frac{P_2}{P_1} \right)^{\frac{\gamma-1}{\gamma}} - 1 \right). $$

Simplifying,

 * $$ T_2 - T_1 = T_1 \left( \left( \frac{P_2}{P_1} \right)^{\frac{\gamma-1}{\gamma}} - 1 \right), $$

 * $$ \frac{T_2}{T_1} - 1 = \left( \frac{P_2}{P_1} \right)^{\frac{\gamma-1}{\gamma}} - 1, $$

 * $$ T_2 = T_1 \left( \frac{P_2}{P_1} \right)^{\frac{\gamma-1}{\gamma}}. $$

Derivation of discrete formula and work expression
The change in internal energy of a system, measured from state 1 to state 2, is equal to

At the same time, the work done by the pressure–volume changes as a result from this process, is equal to

Since we require the process to be adiabatic, the following equation needs to be true

By the previous derivation,

Rearranging (c4) gives

 * $$ P = P_1 \left(\frac{V_1}{V} \right)^\gamma. $$

Substituting this into (c2) gives

 * $$ W = \int_{V_1}^{V_2} P_1 \left(\frac{V_1}{V} \right)^\gamma \,dV. $$

Integrating we obtain the expression for work,

 * $$ W = P_1 V_1^\gamma \frac{V_2^{1-\gamma} - V_1^{1-\gamma}}{1 - \gamma} = \frac{P_2 V_2 - P_1 V_1}{1 - \gamma}. $$

Substituting $γ = α + 1⁄α$ in second term,

 * $$ W = -\alpha P_1 V_1^\gamma \left( V_2^{1-\gamma} - V_1^{1-\gamma} \right). $$

Rearranging,

 * $$ W = -\alpha P_1 V_1 \left( \left( \frac{V_2}{V_1} \right)^{1-\gamma} - 1 \right). $$

Using the ideal gas law and assuming a constant molar quantity (as often happens in practical cases),

 * $$ W = -\alpha n R T_1 \left( \left( \frac{V_2}{V_1} \right)^{1-\gamma} - 1 \right). $$

By the continuous formula,

 * $$ \frac{P_2}{P_1} = \left(\frac{V_2}{V_1}\right)^{-\gamma}, $$

or

 * $$ \left(\frac{P_2}{P_1}\right)^{-\frac{1}{\gamma}} = \frac{V_2}{V_1}. $$

Substituting into the previous expression for $W$,

 * $$ W = -\alpha n R T_1 \left( \left( \frac{P_2}{P_1} \right)^{\frac{\gamma-1}{\gamma}} - 1 \right). $$

Substituting this expression and (c1) in (c3) gives

 * $$ \alpha n R (T_2 - T_1) = \alpha n R T_1 \left( \left( \frac{P_2}{P_1} \right)^{\frac{\gamma-1}{\gamma}} - 1 \right). $$

Simplifying,

 * $$ T_2 - T_1 = T_1 \left( \left( \frac{P_2}{P_1} \right)^{\frac{\gamma-1}{\gamma}} - 1 \right), $$

 * $$ \frac{T_2}{T_1} - 1 = \left( \frac{P_2}{P_1} \right)^{\frac{\gamma-1}{\gamma}} - 1, $$

 * $$ T_2 = T_1 \left( \frac{P_2}{P_1} \right)^{\frac{\gamma-1}{\gamma}}. $$

Etymology
The term adiabatic is an anglicization of the Greek term ἀδιάβατος "impassable" (used by Xenophon of rivers). It is used in the thermodynamic sense by Rankine (1866), and adopted by Maxwell in 1871 (explicitly attributing the term to Rankine). The etymological origin corresponds here to an impossibility of transfer of energy as heat and of transfer of matter across the wall.

The Greek word ἀδιάβατος is formed from privative ἀ- ("not") and διαβατός, "passable", in turn deriving from διά ("through"), and βαῖνειν ("to walk, go, come").

Conceptual significance in thermodynamic theory
The adiabatic process has been important for thermodynamics since its early days. It was important in the work of Joule because it provided a way of nearly directly relating quantities of heat and work.

Energy can enter or leave a thermodynamic system enclosed by walls that prevent mass transfer only as heat or work. Therefore, a quantity of work in such a system can be related almost directly to an equivalent quantity of heat in a cycle of two limbs. The first limb is an isochoric adiabatic work process increasing the system's internal energy; the second, an isochoric and workless heat transfer returning the system to its original state. Accordingly, Rankine measured quantity of heat in units of work, rather than as a calorimetric quantity. In 1854, Rankine used a quantity that he called "the thermodynamic function" that later was called entropy, and at that time he wrote also of the "curve of no transmission of heat", which he later called an adiabatic curve. Besides its two isothermal limbs, Carnot's cycle has two adiabatic limbs.

For the foundations of thermodynamics, the conceptual importance of this was emphasized by Bryan, by Carathéodory, and by Born. The reason is that calorimetry presupposes a type of temperature as already defined before the statement of the first law of thermodynamics, such as one based on empirical scales. Such a presupposition involves making the distinction between empirical temperature and absolute temperature. Rather, the definition of absolute thermodynamic temperature is best left till the second law is available as a conceptual basis.

In the eighteenth century, the law of conservation of energy was not yet fully formulated or established, and the nature of heat was debated. One approach to these problems was to regard heat, measured by calorimetry, as a primary substance that is conserved in quantity. By the middle of the nineteenth century, it was recognized as a form of energy, and the law of conservation of energy was thereby also recognized. The view that eventually established itself, and is currently regarded as right, is that the law of conservation of energy is a primary axiom, and that heat is to be analyzed as consequential. In this light, heat cannot be a component of the total energy of a single body because it is not a state variable but, rather, a variable that describes a transfer between two bodies. The adiabatic process is important because it is a logical ingredient of this current view.

Divergent usages of the word adiabatic
This present article is written from the viewpoint of macroscopic thermodynamics, and the word adiabatic is used in this article in the traditional way of thermodynamics, introduced by Rankine. It is pointed out in the present article that, for example, if a compression of a gas is rapid, then there is little time for heat transfer to occur, even when the gas is not adiabatically isolated by a definite wall. In this sense, a rapid compression of a gas is sometimes approximately or loosely said to be adiabatic, even when the gas is not adiabatically isolated by a definite wall.

Some authors, like Pippard, recommend using "adiathermal" to refer to processes where no heat-exchange occurs (such as Joule expansion), and "adiabatic" to reversible quasi-static adiathermal processes (so that rapid compression of a gas is not "adiabatic"). And Laidler has summarized the complicated etymology of "adiabatic".

Quantum mechanics and quantum statistical mechanics, however, use the word adiabatic in a very different sense, one that can at times seem almost opposite to the classical thermodynamic sense. In quantum theory, the word adiabatic can mean something perhaps near quasi-static, but the usage of the word is very different between the two disciplines.

On the one hand, in quantum theory, if a perturbative element of compressive work is done almost infinitely slowly (that is to say quasi-statically), it is said to have been done adiabatically. The idea is that the shapes of the eigenfunctions change slowly and continuously, so that no quantum jump is triggered, and the change is virtually reversible. While the occupation numbers are unchanged, nevertheless there is change in the energy levels of one-to-one corresponding, pre- and post-compression, eigenstates. Thus a perturbative element of work has been done without heat transfer and without introduction of random change within the system. For example, Max Born writes "Actually, it is usually the 'adiabatic' case with which we have to do: i.e. the limiting case where the external force (or the reaction of the parts of the system on each other) acts very slowly. In this case, to a very high approximation

 * $$c_1^2=1,\,\,c_2^2=0,\,\,c_3^2=0,\,...\,,$$

that is, there is no probability for a transition, and the system is in the initial state after cessation of the perturbation. Such a slow perturbation is therefore reversible, as it is classically."

On the other hand, in quantum theory, if a perturbative element of compressive work is done rapidly, it changes the occupation numbers and energies of the eigenstates in proportion to the transition moment integral and in accordance with time-dependent perturbation theory, as well as perturbing the functional form of the eigenstates themselves. In that theory, such a rapid change is said not to be adiabatic, and the contrary word diabatic is applied to it.

Recent research suggests that the power absorbed from the perturbation corresponds to the rate of these non-adiabatic transitions. This corresponds to the classical process of energy transfer in the form of heat, but with the relative time scales reversed in the quantum case. Quantum adiabatic processes occur over relatively long time scales, while classical adiabatic processes occur over relatively short time scales. It should also be noted that the concept of 'heat' (in reference to the quantity of thermal energy transferred) breaks down at the quantum level, and the specific form of energy (typically electromagnetic) must be considered instead. The small or negligible absorption of energy from the perturbation in a quantum adiabatic process provides a good justification for identifying it as the quantum analogue of adiabatic processes in classical thermodynamics, and for the reuse of the term.

Furthermore, in atmospheric thermodynamics, a diabatic process is one in which heat is exchanged.

In classical thermodynamics, such a rapid change would still be called adiabatic because the system is adiabatically isolated, and there is no transfer of energy as heat. The strong irreversibility of the change, due to viscosity does not impinge on this classical usage.

Thus for a mass of gas, in macroscopic thermodynamics, words are so used that a compression is sometimes loosely or approximately said to be adiabatic if it is rapid enough to avoid significant heat transfer, even if the system is not adiabatically isolated. But in quantum statistical theory, a compression is not called adiabatic if it is rapid, even if the system is adiabatically isolated in the classical thermodynamic sense of the term. The words are used differently in the two disciplines, as stated just above.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Adiabatic process


text:
Talk:Antoni van Leeuwenhoek

Historical note
''The previous discussion that was here was moved to Wikipedia talk:Naming conventions (anglicization). The discussion was about the "correct" spelling of Leeuwenhook's first name. One person insisted that the Dutch spelling of "Antoni" should only be used because Leeuwenhoek was Dutch and that is the spelling that scholars use. Several others cited naming conventions that state that the name most recognizable to the greatest number of English speakers is the correct name in the English wikipedia. Anton is the Anglicized form of Antoni and the article was moved to Anton van Leeuwenhoek with Antoni van Leeuwenhoek being redirected there and a mention of the Antoni spelling was inserted into the article.''

title: Talk:Antoni van Leeuwenhoek


text:
Amide

In organic chemistry, an amide,  also known as an organic amide or a carboxamide, is a compound with the general formula R\sC(\dO)\sNR′R″, where R, R', and R″ represent any group, typically organyl groups or hydrogen atoms. The amide group is called a peptide bond when it is part of the main chain of a protein, and an isopeptide bond when it occurs in a side chain, as in asparagine and glutamine. It can be viewed as a derivative of a carboxylic acid (R\sC(\dO)\sOH) with the hydroxyl group (\sOH) replaced by an amine group (\sNR′R″); or, equivalently, an acyl (alkanoyl) group (R\sC(\dO)\s) joined to an amine group.

Common of amides are formamide (H\sC(\dO)\sNH2), acetamide (H3C\sC(\dO)\sNH2), benzamide (C6H5\sC(\dO)\sNH2), and dimethylformamide (H\sC(\dO)\sN(\sCH3)2). Some uncommon examples of amides are N-chloroacetamide (H3C\sC(\dO)\sNH\sCl) and chloroformamide (Cl\sC(\dO)\sNH2).

Amides are qualified as primary, secondary, and tertiary according to whether the amine subgroup has the form \sNH2, \sNHR, or \sNRR', where R and R' are groups other than hydrogen.

Nomenclature
The core \sC(\dO)\s(N) of amides is called the amide group (specifically, carboxamide group).

In the usual nomenclature, one adds the term "amide" to the stem of the parent acid's name. For instance, the amide derived from acetic acid is named acetamide (CH3CONH2). IUPAC recommends ethanamide, but this and related formal names are rarely encountered. When the amide is derived from a primary or secondary amine, the substituents on nitrogen are indicated first in the name. Thus, the amide formed from dimethylamine and acetic acid is N,N-dimethylacetamide (CH3CONMe2, where Me = CH3). Usually even this name is simplified to dimethylacetamide. Cyclic amides are called lactams; they are necessarily secondary or tertiary amides.

Applications
Amides are pervasive in nature and technology. Proteins and important plastics like Nylons, Aramid, Twaron, and Kevlar are polymers whose units are connected by amide groups (polyamides); these linkages are easily formed, confer structural rigidity, and resist hydrolysis. Amides include many other important biological compounds, as well as many drugs like paracetamol, penicillin and LSD. Low-molecular-weight amides, such as dimethylformamide, are common solvents.

Structure and bonding
The lone pair of electrons on the nitrogen atom is delocalized into the carbonyl group, thus forming a partial double bond between nitrogen and carbon. In fact the O, C and N atoms have molecular orbitals occupied by delocalized electrons, forming a conjugated system. Consequently, the three bonds of the nitrogen in amides is not pyramidal (as in the amines) but planar. This planar restriction prevents rotations about the N linkage and thus has important consequences for the mechanical properties of bulk material of such molecules, and also for the configurational properties of macromolecules built by such bonds. The inability to rotate distinguishes amide groups from ester groups which allow rotation and thus create more flexible bulk material.

The C-C(O)NR2 core of amides is planar. The C=O distance is shorter than the C-N distance by almost 10%. The structure of an amide can be described also as a resonance between two alternative structures: neutral (A) and zwitterionic (B).
 * Amide resonance v2.svg

It is estimated that for acetamide, structure A makes a 62% contribution to the structure, while structure B makes a 28% contribution (these figures do not sum to 100% because there are additional less-important resonance forms that are not depicted above). There is also a hydrogen bond present between the hydrogen and nitrogen atoms in the active groups. Resonance is largely prevented in the very strained quinuclidone.

In their IR spectra, amides exhibit a moderately intense νCO band near 1650 cm−1. The energy of this band is about 60 cm-1 lower than for the νCO of esters and ketones. This difference reflects the contribution of the zwitterionic resonance structure.

Basicity
Compared to amines, amides are very weak bases. While the conjugate acid of an amine has a pKa of about 9.5, the conjugate acid of an amide has a pKa around −0.5. Therefore, compared to amines, amides do not have acid–base properties that are as noticeable in water. This relative lack of basicity is explained by the withdrawing of electrons from the amine by the carbonyl. On the other hand, amides are much stronger bases than carboxylic acids, esters, aldehydes, and ketones (their conjugate acids' pKas are between −6 and −10).

The proton of a primary or secondary amide does not dissociate readily; its pKa is usually well above 15. Conversely, under extremely acidic conditions, the carbonyl oxygen can become protonated with a pKa of roughly −1. It is not only because of the positive charge on the nitrogen but also because of the negative charge on the oxygen gained through resonance.

Hydrogen bonding and solubility
Because of the greater electronegativity of oxygen than nitrogen, the carbonyl (C=O) is a stronger dipole than the N–C dipole. The presence of a C=O dipole and, to a lesser extent a N–C dipole, allows amides to act as H-bond acceptors. In primary and secondary amides, the presence of N–H dipoles allows amides to function as H-bond donors as well. Thus amides can participate in hydrogen bonding with water and other protic solvents; the oxygen atom can accept hydrogen bonds from water and the N–H hydrogen atoms can donate H-bonds. As a result of interactions such as these, the water solubility of amides is greater than that of corresponding hydrocarbons. These hydrogen bonds also have an important role in the secondary structure of proteins.

The solubilities of amides and esters are roughly comparable. Typically amides are less soluble than comparable amines and carboxylic acids since these compounds can both donate and accept hydrogen bonds. Tertiary amides, with the important exception of N,N-dimethylformamide, exhibit low solubility in water.

Reactions

 * Acid-CatAmideHydrolMarch.png

Amides undergo many chemical reactions, although they are less reactive than esters. Amides hydrolyse in hot alkali as well as in strong acidic conditions. Acidic conditions yield the carboxylic acid and the ammonium ion while basic hydrolysis yield the carboxylate ion and ammonia. The protonation of the initially generated amine under acidic conditions and the deprotonation of the initially generated carboxylic acid under basic conditions render these processes non-catalytic and irreversible. Amides are also versatile precursors to many other functional groups. Electrophiles react with the carbonyl oxygen. This step often precedes hydrolysis, which is catalyzed by both Brønsted acids and Lewis acids. Enzymes, e.g. peptidases and artificial catalysts, are known to accelerate the hydrolysis reactions.

From carboxylic acids and related compounds
Amides are usually prepared by coupling a carboxylic acid with an amine. The direct reaction generally requires high temperatures to drive off the water:
 * RCO2H + R'2NH → RCO2- + R'2NH2+
 * RCO2- + R'2NH2 → RC(O)NR'2 + H2O

Esters are far superior substrates relative to carboxylic acids.

Further "activating" both acid chlorides (Schotten-Baumann reaction) and anhydrides (Lumière–Barbier method) react with amines to give amides:
 * RCO2R" + R'2NH → RC(O)NR'2 + R"OH
 * RCOCl + 2R'2NH → RC(O)NR'2 + R'2NH2+Cl-
 * (RCO)2O + R'2NH → RC(O)NR'2 + RCO2H

Peptide synthesis use coupling agents such as HATU, HOBt, or PyBOP.

From nitriles
The hydrolysis of nitriles is conducted on an industrial scale to produce fatty amides. Laboratory procedures are also available.

Specialty routes
Many specialized methods also yield amides. A variety of reagents, e.g. tris(2,2,2-trifluoroethyl) borate have been developed for specialized applications.

title: Amide


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Animism

Animism (from anima meaning 'breath, spirit, life') is the belief that objects, places, and creatures all possess a distinct spiritual essence. Animism perceives all things—animals, plants, rocks, rivers, weather systems, human handiwork, and in some cases words—as being animated, having agency and free will. Animism is used in anthropology of religion as a term for the belief system of many Indigenous peoples in contrast to the relatively more recent development of organized religions. Animism is a metaphysical belief which focuses on the supernatural universe (beyond logical foundations and procedures): specifically, on the concept of the immaterial soul.

Although each culture has its own mythologies and rituals, animism is said to describe the most common, foundational thread of indigenous peoples' "spiritual" or "supernatural" perspectives. The animistic perspective is so widely held and inherent to most indigenous peoples that they often do not even have a word in their languages that corresponds to "animism" (or even "religion"). The term "animism" is an anthropological construct.

Largely due to such ethnolinguistic and cultural discrepancies, opinions differ on whether animism refers to an ancestral mode of experience common to indigenous peoples around the world or to a full-fledged religion in its own right. The currently accepted definition of animism was only developed in the late 19th century (1871) by Edward Tylor. It is "one of anthropology's earliest concepts, if not the first."

Animism encompasses beliefs that all material phenomena have agency, that there exists no categorical distinction between the spiritual and physical world, and that soul, spirit, or sentience exists not only in humans but also in other animals, plants, rocks, geographic features (such as mountains and rivers), and other entities of the natural environment. Examples include water sprites, vegetation deities, and tree spirits, among others. Animism may further attribute a life force to abstract concepts such as words, true names, or metaphors in mythology. Some members of the non-tribal world also consider themselves animists, such as author Daniel Quinn, sculptor Lawson Oyekan, and many contemporary Pagans.

Etymology
English anthropologist Sir Edward Tylor initially wanted to describe the phenomenon as spiritualism, but he realized that it would cause confusion with the modern religion of spiritualism, which was then prevalent across Western nations. He adopted the term animism from the writings of German scientist Georg Ernst Stahl, who had developed the term animismus in 1708 as a biological theory that souls formed the vital principle, and that the normal phenomena of life and the abnormal phenomena of disease could be traced to spiritual causes.

The origin of the word comes from the Latin word anima, which means life or soul.

The first known usage in English appeared in 1819.

"Old animism" definitions
Earlier anthropological perspectives, which have since been termed the old animism, were concerned with knowledge on what is alive and what factors make something alive. The old animism assumed that animists were individuals who were unable to understand the difference between persons and things. Critics of the old animism have accused it of preserving "colonialist and dualistic worldviews and rhetoric."

Edward Tylor's definition
The idea of animism was developed by anthropologist Sir Edward Tylor through his 1871 book Primitive Culture, in which he defined it as "the general doctrine of souls and other spiritual beings in general." According to Tylor, animism often includes "an idea of pervading life and will in nature;" a belief that natural objects other than humans have souls. This formulation was little different from that proposed by Auguste Comte as "fetishism", but the terms now have distinct meanings.

For Tylor, animism represented the earliest form of religion, being situated within an evolutionary framework of religion that has developed in stages and which will ultimately lead to humanity rejecting religion altogether in favor of scientific rationality. Thus, for Tylor, animism was fundamentally seen as a mistake, a basic error from which all religions grew. He did not believe that animism was inherently illogical, but he suggested that it arose from early humans' dreams and visions and thus was a rational system. However, it was based on erroneous, unscientific observations about the nature of reality. Stringer notes that his reading of Primitive Culture led him to believe that Tylor was far more sympathetic in regard to "primitive" populations than many of his contemporaries and that Tylor expressed no belief that there was any difference between the intellectual capabilities of "savage" people and Westerners.

The idea that there had once been "one universal form of primitive religion" (whether labelled animism, totemism, or shamanism) has been dismissed as "unsophisticated" and "erroneous" by archaeologist Timothy Insoll, who stated that "it removes complexity, a precondition of religion now, in all its variants."

Social evolutionist conceptions
Tylor's definition of animism was part of a growing international debate on the nature of "primitive society" by lawyers, theologians, and philologists. The debate defined the field of research of a new science: anthropology. By the end of the 19th century, an orthodoxy on "primitive society" had emerged, but few anthropologists still would accept that definition. The "19th-century armchair anthropologists" argued that "primitive society" (an evolutionary category) was ordered by kinship and divided into exogamous descent groups related by a series of marriage exchanges. Their religion was animism, the belief that natural species and objects had souls.

With the development of private property, the descent groups were displaced by the emergence of the territorial state. These rituals and beliefs eventually evolved over time into the vast array of "developed" religions. According to Tylor, as society became more scientifically advanced, fewer members of that society would believe in animism. However, any remnant ideologies of souls or spirits, to Tylor, represented "survivals" of the original animism of early humanity.

Confounding animism with totemism
In 1869 (three years after Tylor proposed his definition of animism), Edinburgh lawyer John Ferguson McLennan, argued that the animistic thinking evident in fetishism gave rise to a religion he named totemism. Primitive people believed, he argued, that they were descended from the same species as their totemic animal. Subsequent debate by the "armchair anthropologists" (including J. J. Bachofen, Émile Durkheim, and Sigmund Freud) remained focused on totemism rather than animism, with few directly challenging Tylor's definition. Anthropologists "have commonly avoided the issue of animism and even the term itself, rather than revisit this prevalent notion in light of their new and rich ethnographies."

According to anthropologist Tim Ingold, animism shares similarities with totemism but differs in its focus on individual spirit beings which help to perpetuate life, whereas totemism more typically holds that there is a primary source, such as the land itself or the ancestors, who provide the basis to life. Certain indigenous religious groups such as the Australian Aboriginals are more typically totemic in their worldview, whereas others like the Inuit are more typically animistic.

From his studies into child development, Jean Piaget suggested that children were born with an innate animist worldview in which they anthropomorphized inanimate objects and that it was only later that they grew out of this belief. Conversely, from her ethnographic research, Margaret Mead argued the opposite, believing that children were not born with an animist worldview but that they became acculturated to such beliefs as they were educated by their society.

Stewart Guthrie saw animism—or "attribution" as he preferred it—as an evolutionary strategy to aid survival. He argued that both humans and other animal species view inanimate objects as potentially alive as a means of being constantly on guard against potential threats. His suggested explanation, however, did not deal with the question of why such a belief became central to the religion. In 2000, Guthrie suggested that the "most widespread" concept of animism was that it was the "attribution of spirits to natural phenomena such as stones and trees."

"New animism" non-archaic definitions
Many anthropologists ceased using the term animism, deeming it to be too close to early anthropological theory and religious polemic. However, the term had also been claimed by religious groups—namely, Indigenous communities and nature worshippers—who felt that it aptly described their own beliefs, and who in some cases actively identified as "animists." It was thus readopted by various scholars, who began using the term in a different way, placing the focus on knowing how to behave toward other beings, some of whom are not human. As religious studies scholar Graham Harvey stated, while the "old animist" definition had been problematic, the term animism was nevertheless "of considerable value as a critical, academic term for a style of religious and cultural relating to the world."

Hallowell and the Ojibwe
The new animism emerged largely from the publications of anthropologist Irving Hallowell, produced on the basis of his ethnographic research among the Ojibwe communities of Canada in the mid-20th century. For the Ojibwe encountered by Hallowell, personhood did not require human-likeness, but rather humans were perceived as being like other persons, who for instance included rock persons and bear persons. For the Ojibwe, these persons were each willful beings, who gained meaning and power through their interactions with others; through respectfully interacting with other persons, they themselves learned to "act as a person".

Hallowell's approach to the understanding of Ojibwe personhood differed strongly from prior anthropological concepts of animism. He emphasized the need to challenge the modernist, Western perspectives of what a person is, by entering into a dialogue with different worldwide views. Hallowell's approach influenced the work of anthropologist Nurit Bird-David, who produced a scholarly article reassessing the idea of animism in 1999. Seven comments from other academics were provided in the journal, debating Bird-David's ideas.

Postmodern anthropology
More recently, postmodern anthropologists are increasingly engaging with the concept of animism. Modernism is characterized by a Cartesian subject-object dualism that divides the subjective from the objective, and culture from nature. In the modernist view, animism is the inverse of scientism, and hence, is deemed inherently invalid by some anthropologists. Drawing on the work of Bruno Latour, some anthropologists question modernist assumptions and theorize that all societies continue to "animate" the world around them. In contrast to Tylor's reasoning, however, this "animism" is considered to be more than just a remnant of primitive thought. More specifically, the "animism" of modernity is characterized by humanity's "professional subcultures", as in the ability to treat the world as a detached entity within a delimited sphere of activity.

Human beings continue to create personal relationships with elements of the aforementioned objective world, such as pets, cars, or teddy bears, which are recognized as subjects. As such, these entities are "approached as communicative subjects rather than the inert objects perceived by modernists." These approaches aim to avoid the modernist assumption that the environment consists of a physical world distinct from the world of humans, as well as the modernist conception of the person being composed dualistically of a body and a soul.

Nurit Bird-David argues that:

"Positivistic ideas about the meaning of 'nature', 'life', and 'personhood' misdirected these previous attempts to understand the local concepts. Classical theoreticians (it is argued) attributed their own modernist ideas of self to 'primitive peoples' while asserting that the 'primitive peoples' read their idea of self into others!"

She explains that animism is a "relational epistemology" rather than a failure of primitive reasoning. That is, self-identity among animists is based on their relationships with others, rather than any distinctive features of the "self". Instead of focusing on the essentialized, modernist self (the "individual"), persons are viewed as bundles of social relationships ("dividuals"), some of which include "superpersons" (i.e. non-humans).

Stewart Guthrie expressed criticism of Bird-David's attitude towards animism, believing that it promulgated the view that "the world is in large measure whatever our local imagination makes it." This, he felt, would result in anthropology abandoning "the scientific project."

Like Bird-David, Tim Ingold argues that animists do not see themselves as separate from their environment:

"Hunter-gatherers do not, as a rule, approach their environment as an external world of nature that has to be 'grasped' intellectually ... indeed the separation of mind and nature has no place in their thought and practice."

Rane Willerslev extends the argument by noting that animists reject this Cartesian dualism and that the animist self identifies with the world, "feeling at once within and apart from it so that the two glide ceaselessly in and out of each other in a sealed circuit". The animist hunter is thus aware of himself as a human hunter, but, through mimicry, is able to assume the viewpoint, senses, and sensibilities of his prey, to be one with it. Shamanism, in this view, is an everyday attempt to influence spirits of ancestors and animals, by mirroring their behaviors, as the hunter does its prey.

Ethical and ecological understanding
Cultural ecologist and philosopher David Abram proposed an ethical and ecological understanding of animism, grounded in the phenomenology of sensory experience. In his books The Spell of the Sensuous and Becoming Animal, Abram suggests that material things are never entirely passive in our direct perceptual experience, holding rather that perceived things actively "solicit our attention" or "call our focus", coaxing the perceiving body into an ongoing participation with those things.

In the absence of intervening technologies, he suggests that sensory experience is inherently animistic in that it discloses a material field that is animate and self-organizing from the beginning. David Abram used contemporary cognitive and natural science, as well as the perspectival worldviews of diverse indigenous oral cultures, to propose a richly pluralist and story-based cosmology in which matter is alive. He suggested that such a relational ontology is in close accord with humanity's spontaneous perceptual experience by drawing attention to the senses, and to the primacy of sensuous terrain, enjoining a more respectful and ethical relation to the more-than-human community of animals, plants, soils, mountains, waters, and weather-patterns that materially sustains humanity.

In contrast to a long-standing tendency in the Western social sciences, which commonly provide rational explanations of animistic experience, Abram develops an animistic account of reason itself. He holds that civilised reason is sustained only by intensely animistic participation between human beings and their own written signs. For instance, as soon as someone reads letters on a page or screen, they can "see what it says"—the letters speak as much as nature spoke to pre-literate peoples. Reading can usefully be understood as an intensely concentrated form of animism, one that effectively eclipses all of the other, older, more spontaneous forms of animistic participation in which humans were once engaged.

"To tell the story in this manner—to provide an animistic account of reason, rather than the other way around—is to imply that animism is the wider and more inclusive term and that oral, mimetic modes of experience still underlie, and support, all our literate and technological modes of reflection. When reflection's rootedness in such bodily, participatory modes of experience is entirely unacknowledged or unconscious, reflective reason becomes dysfunctional, unintentionally destroying the corporeal, sensuous world that sustains it."

Relation to the concept of 'I-thou'
Religious studies scholar Graham Harvey defined animism as the belief "that the world is full of persons, only some of whom are human, and that life is always lived in relationship with others." He added that it is therefore "concerned with learning how to be a good person in respectful relationships with other persons."

In his Handbook of Contemporary Animism (2013), Harvey identifies the animist perspective in line with Martin Buber's "I-thou" as opposed to "I-it". In such, Harvey says, the animist takes an I-thou approach to relating to the world, whereby objects and animals are treated as a "thou", rather than as an "it".

Religion

There is ongoing disagreement (and no general consensus) as to whether animism is merely a singular, broadly encompassing religious belief or a worldview in and of itself, comprising many diverse mythologies found worldwide in many diverse cultures. This also raises a controversy regarding the ethical claims animism may or may not make: whether animism ignores questions of ethics altogether; or, by endowing various non-human elements of nature with spirituality or personhood, it in fact promotes a complex ecological ethics.

Distinction from pantheism
Animism is not the same as pantheism, although the two are sometimes confused. Moreover, some religions are both pantheistic and animistic. One of the main differences is that while animists believe everything to be spiritual in nature, they do not necessarily see the spiritual nature of everything in existence as being united (monism) the way pantheists do. As a result, animism puts more emphasis on the uniqueness of each individual soul. In pantheism, everything shares the same spiritual essence, rather than having distinct spirits or souls. For example, Giordano Bruno equated the world soul with God and espoused a pantheistic animism.

Fetishism / totemism
In many animistic world views, the human being is often regarded as on a roughly equal footing with other animals, plants, and natural forces.

African indigenous religions
Traditional African religions: most religious traditions of Sub-Saharan Africa are basically a complex form of animism with polytheistic and shamanistic elements and ancestor worship.

In East Africa the Kerma culture display Animistic elements similar to other Traditional African religions. In contrast, the later polytheistic Napatan and Meroitic periods, with displays of animals in Amulets and the esteemed antiques of Lions, appear to be an Animistic culture rather than a polytheistic culture. The Kermans likely treated Jebel Barkal as a special sacred site, and passed it on to the Kushites and Egyptians who venerated the mesa.

In North Africa, the traditional Berber religion includes the traditional polytheistic, animist, and in some rare cases, shamanistic, religions of the Berber people.

Indian-origin religions
In the Indian-origin religions, namely Hinduism, Buddhism, Jainism, and Sikhism, the animistic aspects of nature worship and ecological conservation are part of the core belief system.

Matsya Purana, a Hindu text, has a Sanskrit language shloka (hymn), which explains the importance of reverence of ecology. It states: "A pond equals ten wells, a reservoir equals ten ponds, while a son equals ten reservoirs, and a tree equals ten sons." Indian religions worship trees such as the Bodhi Tree and numerous superlative banyan trees, conserve the sacred groves of India, revere the rivers as sacred, and worship the mountains and their ecology.

Panchavati are the sacred trees in Indic religions, which are sacred groves containing five type of trees, usually chosen from among the Vata (Ficus benghalensis, Banyan), Ashvattha (Ficus religiosa, Peepal), Bilva (Aegle marmelos, Bengal Quince), Amalaki (Phyllanthus emblica, Indian Gooseberry, Amla), Ashoka (Saraca asoca, Ashok), Udumbara (Ficus racemosa, Cluster Fig, Gular), Nimba (Azadirachta indica, Neem) and Shami (Prosopis spicigera, Indian Mesquite).

The banyan is considered holy in several religious traditions of India. The Ficus benghalensis is the national tree of India. Vat Purnima is a Hindu festival related to the banyan tree, and is observed by married women in North India and in the Western Indian states of Maharashtra, Goa, Gujarat. For three days of the month of Jyeshtha in the Hindu calendar (which falls in May–June in the Gregorian calendar) married women observe a fast, tie threads around a banyan tree, and pray for the well-being of their husbands. Thimmamma Marrimanu, sacred to Indian religions, has branches spread over five acres and was listed as the world's largest banyan tree in the Guinness World Records in 1989.

In Hinduism, the leaf of the banyan tree is said to be the resting place for the god Krishna. In the Bhagavat Gita, Krishna said, "There is a banyan tree which has its roots upward and its branches down, and the Vedic hymns are its leaves. One who knows this tree is the knower of the Vedas." (Bg 15.1)

In Buddhism's Pali canon, the banyan (Pali: nigrodha) is referenced numerous times. Typical metaphors allude to the banyan's epiphytic nature, likening the banyan's supplanting of a host tree as comparable to the way sensual desire (kāma) overcomes humans.

Mun (also known as Munism or Bongthingism) is the traditional polytheistic, animist, shamanistic, and syncretic religion of the Lepcha people.

Sanamahism is an ethnic religion of the Meitei people of in Northeast India. It is a polytheistic and animist religion and is named after Lainingthou Sanamahi, one of the most important deities of the Meitei faith.

Chinese religions
Shendao is a term originated by Chinese folk religions influenced by, Mohist, Confucian and Taoist philosophy, referring to the divine order of nature or the Wuxing.

The Shang dynasty's state religion was practiced from 1600 BCE to 1046 BCE, and was built on the idea of spiritualizing natural phenomena.

Japan and Shinto
Shinto is the traditional Japanese folk religion and has many animist aspects. The, a class of supernatural beings, are central to Shinto. All things, including natural forces and well-known geographical locations, are thought to be home to the kami. The kami are worshipped at kamidana household shrines, family shrines, and jinja public shrines.

The Ryukyuan religion of the Ryukyu islands is distinct from Shinto, but shares similar characteristics.

Kalash people
Kalash people of Northern Pakistan follow an ancient animistic religion identified with an ancient form of Hinduism.

The Kalash (Kalasha: کالؕاشؕا, romanised: Kaḷaṣa, Devanagari: कळष), or Kalasha, are an Indo-Aryan indigenous people residing in the Chitral District of the Khyber-Pakhtunkhwa province of Pakistan.

They are considered unique among the people of Pakistan. They are also considered to be Pakistan's smallest ethnoreligious group, and traditionally practice what authors characterise as a form of animism. During the mid-20th century an attempt was made to force a few Kalasha villages in Pakistan to convert to Islam, but the people fought the conversion and, once official pressure was removed, the vast majority resumed the practice of their own religion. Nevertheless, some Kalasha have since converted to Islam, despite being shunned afterward by their community for having done so.

The term is used to refer to many distinct people including the Väi, the Čima-nišei, the Vântä, plus the Ashkun- and Tregami-speakers. The Kalash are considered to be an indigenous people of Asia, with their ancestors migrating to Chitral Valley from another location possibly further south, which the Kalash call "Tsiyam" in their folk songs and epics.

They claim to descend from the armies of Alexander who were left behind from his armed campaign, though no evidence exists for him to have passed the area. {{efn|

The neighbouring Nuristani people of the adjacent Nuristan (historically known as Kafiristan) province of Afghanistan once had the same culture and practised a faith very similar to that of the Kalash, differing in a few minor particulars.

The first historically recorded Islamic invasions of their lands were by the Ghaznavids in the 11th century while they themselves are first attested in 1339 during Timur's invasions. Nuristan had been forcibly converted to Islam in 1895–96, although some evidence has shown the people continued to practice their customs. The Kalash of Chitral have maintained their own separate cultural traditions.

Korea
Muism, the native Korean belief, has many animist aspects. The various deities, called kwisin, are capable of interacting with humans and causing problems if they are not honoured appropriately.

Philippines indigenous religions
In the indigenous Philippine folk religions, pre-colonial religions of Philippines and Philippine mythology, animism is part of their core beliefs as demonstrated by the belief in Anito and Bathala as well as their conservation and veneration of sacred Indigenous Philippine shrines, forests, mountains and sacred grounds.

Anito (lit. '[ancestor] spirit') refers to the various indigenous shamanistic folk religions of the Philippines, led by female or feminized male shamans known as babaylan. It includes belief in a spirit world existing alongside and interacting with the material world, as well as the belief that everything has a spirit, from rocks and trees to animals and humans to natural phenomena.

In indigenous Filipino belief, the Bathala is the omnipotent deity which was derived from Sanskrit word for the Hindu supreme deity bhattara, as one of the ten avatars of the Hindu god Vishnu. The omnipotent Bathala also presides over the spirits of ancestors called Anito. Anitos serve as intermediaries between mortals and the divine, such as Agni (Hindu) who holds the access to divine realms; for this reason they are invoked first and are the first to receive offerings, regardless of the deity the worshipper wants to pray to.

Abrahamic religions
Animism also has influences in Abrahamic religions.

The Old Testament and the Wisdom literature preach the omnipresence of God (Jeremiah 23:24; Proverbs 15:3; 1 Kings 8:27), and God is bodily present in the incarnation of his Son, Jesus Christ. (Gospel of John 1:14, Colossians 2:9). Animism is not peripheral to Christian identity but is its nurturing home ground, its axis mundi. In addition to the conceptual work the term animism performs, it provides insight into the relational character and common personhood of material existence.

With rising awareness of ecological preservation, recently theologians like Mark I. Wallace argue for animistic Christianity with a biocentric approach that understands God being present in all earthly objects, such as animals, trees, and rocks.

Pre-Islamic Arab religion
Pre-Islamic Arab religion can refer to the traditional polytheistic, animist, and in some rare cases, shamanistic, religions of the peoples of the Arabian Peninsula. The belief in jinn, invisible entities akin to spirits in the Western sense dominant in the Arab religious systems, hardly fit the description of Animism in a strict sense. The jinn are considered to be analogous to the human soul by living lives like that of humans, but they are not exactly like human souls neither are they spirits of the dead. It is unclear if belief in jinn derived from nomadic or sedentary populations.

New religious movements
Some modern pagan groups, including Eco-pagans, describe themselves as animists, meaning that they respect the diverse community of living beings and spirits with whom humans share the world and cosmos.

The New Age movement commonly demonstrates animistic traits in asserting the existence of nature spirits.

Shamanism
A shaman is a person regarded as having access to, and influence in, the world of benevolent and malevolent spirits, who typically enters into a trance state during a ritual, and practices divination and healing.

According to Mircea Eliade, shamanism encompasses the premise that shamans are intermediaries or messengers between the human world and the spirit worlds. Shamans are said to treat ailments and illnesses by mending the soul. Alleviating traumas affecting the soul or spirit restores the physical body of the individual to balance and wholeness. The shaman also enters supernatural realms or dimensions to obtain solutions to problems afflicting the community. Shamans may visit other worlds or dimensions to bring guidance to misguided souls and to ameliorate illnesses of the human soul caused by foreign elements. The shaman operates primarily within the spiritual world, which in turn affects the human world. The restoration of balance results in the elimination of the ailment.

Abram, however, articulates a less supernatural and much more ecological understanding of the shaman's role than that propounded by Eliade. Drawing upon his own field research in Indonesia, Nepal, and the Americas, Abram suggests that in animistic cultures, the shaman functions primarily as an intermediary between the human community and the more-than-human community of active agencies—the local animals, plants, and landforms (mountains, rivers, forests, winds, and weather patterns, all of which are felt to have their own specific sentience). Hence, the shaman's ability to heal individual instances of disease (or imbalance) within the human community is a byproduct of their more continual practice of balancing the reciprocity between the human community and the wider collective of animate beings in which that community is embedded.

Non-human animals
Animism entails the belief that all living things have a soul, and thus, a central concern of animist thought surrounds how animals can be eaten, or otherwise used for humans' subsistence needs. The actions of non-human animals are viewed as "intentional, planned and purposive", and they are understood to be persons, as they are both alive, and communicate with others.

In animist worldviews, non-human animals are understood to participate in kinship systems and ceremonies with humans, as well as having their own kinship systems and ceremonies. Graham Harvey cited an example of an animist understanding of animal behavior that occurred at a powwow held by the Conne River Mi'kmaq in 1996; an eagle flew over the proceedings, circling over the central drum group. The assembled participants called out kitpu ('eagle'), conveying welcome to the bird and expressing pleasure at its beauty, and they later articulated the view that the eagle's actions reflected its approval of the event, and the Mi'kmaq's return to traditional spiritual practices.

In animism, rituals are performed to maintain relationships between humans and spirits. Indigenous peoples often perform these rituals to appease the spirits and request their assistance during activities such as hunting and healing. In the Arctic region, certain rituals are common before the hunt as a means to show respect for the spirits of animals.

Flora
Some animists also view plant and fungi life as persons and interact with them accordingly. The most common encounter between humans and these plant and fungi persons is with the former's collection of the latter for food, and for animists, this interaction typically has to be carried out respectfully. Harvey cited the example of Māori communities in New Zealand, who often offer karakia invocations to sweet potatoes as they dig up the latter. While doing so, there is an awareness of a kinship relationship between the Māori and the sweet potatoes, with both understood as having arrived in Aotearoa together in the same canoes.

In other instances, animists believe that interaction with plant and fungi persons can result in the communication of things unknown or even otherwise unknowable. Among some modern Pagans, for instance, relationships are cultivated with specific trees, who are understood to bestow knowledge or physical gifts, such as flowers, sap, or wood that can be used as firewood or to fashion into a wand; in return, these Pagans give offerings to the tree itself, which can come in the form of libations of mead or ale, a drop of blood from a finger, or a strand of wool.

The elements
Various animistic cultures also comprehend stones as persons. Discussing ethnographic work conducted among the Ojibwe, Harvey noted that their society generally conceived of stones as being inanimate, but with two notable exceptions: the stones of the Bell Rocks and those stones which are situated beneath trees struck by lightning, which were understood to have become Thunderers themselves. The Ojibwe conceived of weather as being capable of having personhood, with storms being conceived of as persons known as 'Thunderers' whose sounds conveyed communications and who engaged in seasonal conflict over the lakes and forests, throwing lightning at lake monsters. Wind, similarly, can be conceived as a person in animistic thought.

The importance of place is also a recurring element of animism, with some places being understood to be persons in their own right.

Spirits
Animism can also entail relationships being established with non-corporeal spirit entities.

Science
In the early 20th century, William McDougall defended a form of animism in his book Body and Mind: A History and Defence of Animism (1911).

Physicist Nick Herbert has argued for "quantum animism" in which the mind permeates the world at every level:

"The quantum consciousness assumption, which amounts to a kind of 'quantum animism' likewise asserts that consciousness is an integral part of the physical world, not an emergent property of special biological or computational systems. Since everything in the world is on some level a quantum system, this assumption requires that everything be conscious on that level. If the world is truly quantum animated, then there is an immense amount of invisible inner experience going on all around us that is presently inaccessible to humans, because our own inner lives are imprisoned inside a small quantum system, isolated deep in the meat of an animal brain."

Werner Krieglstein wrote regarding his quantum Animism:

"Herbert's quantum Animism differs from traditional Animism in that it avoids assuming a dualistic model of mind and matter. Traditional dualism assumes that some kind of spirit inhabits a body and makes it move, a ghost in the machine. Herbert's quantum Animism presents the idea that every natural system has an inner life, a conscious center, from which it directs and observes its action."

In Error and Loss: A Licence to Enchantment, Ashley Curtis (2018) has argued that the Cartesian idea of an experiencing subject facing off with an inert physical world is incoherent at its very foundation and that this incoherence is consistent with rather than belied by Darwinism. Human reason (and its rigorous extension in the natural sciences) fits an evolutionary niche just as echolocation does for bats and infrared vision does for pit vipers, and is epistemologically on a par with, rather than superior to, such capabilities. The meaning or aliveness of the "objects" we encounter, rocks, trees, rivers, and other animals, thus depends for its validity not on a detached cognitive judgment, but purely on the quality of our experience. The animist experience, or the wolf's or raven's experience, thus become licensed as equally valid worldviews to the modern western scientific one; they are indeed more valid, since they are not plagued with the incoherence that inevitably arises when "objective existence" is separated from "subjective experience."

Socio-political impact
Harvey opined that animism's views on personhood represented a radical challenge to the dominant perspectives of modernity, because it accords "intelligence, rationality, consciousness, volition, agency, intentionality, language, and desire" to non-humans. Similarly, it challenges the view of human uniqueness that is prevalent in both Abrahamic religions and Western rationalism.

Art and literature
Animist beliefs can also be expressed through artwork. For instance, among the Māori communities of New Zealand, there is an acknowledgement that creating art through carving wood or stone entails violence against the wood or stone person and that the persons who are damaged therefore have to be placated and respected during the process; any excess or waste from the creation of the artwork is returned to the land, while the artwork itself is treated with particular respect. Harvey, therefore, argued that the creation of art among the Māori was not about creating an inanimate object for display, but rather a transformation of different persons within a relationship.

Harvey expressed the view that animist worldviews were present in various works of literature, citing such examples as the writings of Alan Garner, Leslie Silko, Barbara Kingsolver, Alice Walker, Daniel Quinn, Linda Hogan, David Abram, Patricia Grace, Chinua Achebe, Ursula Le Guin, Louise Erdrich, and Marge Piercy.

Animist worldviews have also been identified in the animated films of Hayao Miyazaki.

title: Animism