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143-405: While an individual thermometer is able to measure degrees of hotness, the readings on two thermometers cannot be compared unless they conform to an agreed scale. Today there is an absolute thermodynamic temperature scale. Internationally agreed temperature scales are designed to approximate this closely, based on fixed points and interpolating thermometers. The most recent official temperature scale

286-501: A clinical thermometer that produced a body temperature reading in five minutes as opposed to twenty. In 1999, Dr. Francesco Pompei of the Exergen Corporation introduced the world's first temporal artery thermometer, a non-invasive temperature sensor which scans the forehead in about two seconds and provides a medically accurate body temperature. Traditional thermometers were all non-registering thermometers. That is,

429-418: A more ordered state to a less ordered state . In Fig. 7 , the melting of ice is shown within the lower left box heading from blue to green. At one specific thermodynamic point, the melting point (which is 0 °C across a wide pressure range in the case of water), all the atoms or molecules are, on average, at the maximum energy threshold their chemical bonds can withstand without breaking away from

572-466: A relative standard uncertainty of 0.37 ppm. Afterwards, by defining the Boltzmann constant as exactly 1.380 649 × 10  J/K , the 0.37 ppm uncertainty was transferred to the triple point of water, which became an experimentally determined value of 273.1600 ± 0.0001 K ( 0.0100 ± 0.0001 °C ). That the triple point of water ended up being exceedingly close to 273.16 K after

715-400: A thermoscope because they provide an observable indication of sensible heat (the modern concept of temperature was yet to arise). The difference between a thermoscope and a thermometer is that the latter has a scale. A thermometer is simply a thermoscope with a scale. ... I propose to regard it as axiomatic that a “meter” must have a scale or something equivalent. ... If this is admitted,

858-407: A certain temperature. Nonetheless, all those degrees of freedom that are available to the molecules under a particular set of conditions contribute to the specific heat capacity of a substance; which is to say, they increase the amount of heat (kinetic energy) required to raise a given amount of the substance by one kelvin or one degree Celsius. The relationship of kinetic energy, mass, and velocity

1001-445: A constant volume air thermometer. Constant volume thermometers do not provide a way to avoid the problem of anomalous behaviour like that of water at approximately 4 °C. Planck's law very accurately quantitatively describes the power spectral density of electromagnetic radiation, inside a rigid walled cavity in a body made of material that is completely opaque and poorly reflective, when it has reached thermodynamic equilibrium, as

1144-538: A fixed reference temperature, a mixture of equal amounts of ice and boiling water, with four degrees of heat above this point and four degrees of cold below. 16th century physician Johann Hasler developed body temperature scales based on Galen's theory of degrees to help him mix the appropriate amount of medicine for patients. In the late 16th and early 17th centuries, several European scientists, notably Galileo Galilei and Italian physiologist Santorio Santorio developed devices with an air-filled glass bulb, connected to

1287-432: A function of absolute thermodynamic temperature alone. A small enough hole in the wall of the cavity emits near enough blackbody radiation of which the spectral radiance can be precisely measured. The walls of the cavity, provided they are completely opaque and poorly reflective, can be of any material indifferently. This provides a well-reproducible absolute thermometer over a very wide range of temperatures, able to measure

1430-574: A gas contributes to the pressure and volume of that gas is a proportional function of thermodynamic temperature as established by the Boltzmann constant (symbol:  k B ). The Boltzmann constant also relates the thermodynamic temperature of a gas to the mean kinetic energy of an individual particles' translational motion as follows: E ~ = 3 2 k B T {\displaystyle {\tilde {E}}={\frac {3}{2}}k_{\text{B}}T} where: While

1573-410: A good job of establishing—within the uncertainties due to isotopic variations between water samples—temperatures around the freezing and triple points of water, but required that intermediate values between the triple point and absolute zero, as well as extrapolated values from room temperature and beyond, to be experimentally determined via apparatus and procedures in individual labs. This shortcoming

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1716-524: A kelvin) in 1994, they used optical lattice laser equipment to adiabatically cool cesium atoms. They then turned off the entrapment lasers and directly measured atom velocities of 7 mm per second to in order to calculate their temperature. Formulas for calculating the velocity and speed of translational motion are given in the following footnote. It is neither difficult to imagine atomic motions due to kinetic temperature, nor distinguish between such motions and those due to zero-point energy. Consider

1859-413: A large amount of heat energy per mole with only a modest temperature change because each molecule comprises an average of 21 atoms and therefore has many internal degrees of freedom. Even larger, more complex molecules can have dozens of internal degrees of freedom. Heat conduction is the diffusion of thermal energy from hot parts of a system to cold parts. A system can be either a single bulk entity or

2002-529: A plurality of discrete bulk entities. The term bulk in this context means a statistically significant quantity of particles (which can be a microscopic amount). Whenever thermal energy diffuses within an isolated system, temperature differences within the system decrease (and entropy increases). One particular heat conduction mechanism occurs when translational motion, the particle motion underlying temperature, transfers momentum from particle to particle in collisions. In gases, these translational motions are of

2145-478: A pressure of at least 2.5  MPa (25  bar )), ZPE is very much a form of thermal energy and may properly be included when tallying a substance's internal energy. Though there have been many other temperature scales throughout history, there have been only two scales for measuring thermodynamic temperature which have absolute zero as their null point (0): The Kelvin scale and the Rankine scale. Throughout

2288-839: A range of physical effects to measure temperature. Temperature sensors are used in a wide variety of scientific and engineering applications, especially measurement systems. Temperature systems are primarily either electrical or mechanical, occasionally inseparable from the system which they control (as in the case of a mercury-in-glass thermometer). Thermometers are used in roadways in cold weather climates to help determine if icing conditions exist. Indoors, thermistors are used in climate control systems such as air conditioners , freezers, heaters , refrigerators , and water heaters . Galileo thermometers are used to measure indoor air temperature, due to their limited measurement range. Such liquid crystal thermometers (which use thermochromic liquid crystals) are also used in mood rings and used to measure

2431-448: A rest mass only 1 ⁄ 1836 that of a proton . This is about the same ratio as a .22 Short bullet (29 grains or 1.88  g ) compared to the rifle that shoots it. As Isaac Newton wrote with his third law of motion , Law #3: All forces occur in pairs, and these two forces are equal in magnitude and opposite in direction. However, a bullet accelerates faster than a rifle given an equal force. Since kinetic energy increases as

2574-399: A specific subset of the possible motions that can occur in matter: that comprising the three translational degrees of freedom . The translational degrees of freedom are the familiar billiard ball-like movements along the X, Y, and Z axes of 3D space (see Fig. 1 , below). This is why the noble gases all have the same specific heat capacity per atom and why that value is lowest of all

2717-413: A substance are as close as possible to complete rest and retain only ZPE (zero-point energy)-induced quantum mechanical motion, the substance is at the temperature of absolute zero ( T  = 0). Whereas absolute zero is the point of zero thermodynamic temperature and is also the point at which the particle constituents of matter have minimal motion, absolute zero is not necessarily the point at which

2860-521: A substance as the photons are absorbed by neighboring atoms, transferring momentum in the process. Black-body photons also easily escape from a substance and can be absorbed by the ambient environment; kinetic energy is lost in the process. As established by the Stefan–Boltzmann law , the intensity of black-body radiation increases as the fourth power of absolute temperature. Thus, a black-body at 824 K (just short of glowing dull red) emits 60 times

3003-672: A substance at equilibrium, black-body photons are emitted across a range of wavelengths in a spectrum that has a bell curve-like shape called a Planck curve (see graph in Fig. 5 at right). The top of a Planck curve ( the peak emittance wavelength ) is located in a particular part of the electromagnetic spectrum depending on the temperature of the black-body. Substances at extreme cryogenic temperatures emit at long radio wavelengths whereas extremely hot temperatures produce short gamma rays (see § Table of thermodynamic temperatures ). Black-body radiation diffuses thermal energy throughout

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3146-454: A substance contains zero internal energy; one must be very precise with what one means by internal energy . Often, all the phase changes that can occur in a substance, will have occurred by the time it reaches absolute zero. However, this is not always the case. Notably, T  = 0 helium remains liquid at room pressure ( Fig. 9 at right) and must be under a pressure of at least 25  bar (2.5  MPa ) to crystallize. This

3289-425: A substance in equilibrium, the kinetic energy of particle motion is evenly distributed among all the active degrees of freedom available to the particles. Since the internal temperature of molecules are usually equal to their kinetic temperature, the distinction is usually of interest only in the detailed study of non- local thermodynamic equilibrium (LTE) phenomena such as combustion , the sublimation of solids, and

3432-538: A temperature scale is not bound to the absolute zero of temperature. Nevertheless, some temperature scales have their numerical zero coincident with the absolute zero of temperature. Examples are the International SI temperature scale, the Rankine temperature scale , and the thermodynamic temperature scale. Other temperature scales have their numerical zero far from the absolute zero of temperature. Examples are

3575-411: A tube, partially filled with water. As the air in the bulb warms or cools, the height of the column of water in the tube falls or rises, allowing an observer to compare the current height of the water to previous heights to detect relative changes of the heat in the bulb and its immediate environment. Such devices, with no scale for assigning a numerical value to the height of the liquid, are referred to as

3718-489: A virtual standstill (off the x –axis to the right). This graph uses inverse speed for its x -axis so the shape of the curve can easily be compared to the curves in Fig. 5 below. In both graphs, zero on the x -axis represents infinite temperature. Additionally, the x - and y -axes on both graphs are scaled proportionally. Although very specialized laboratory equipment is required to directly detect translational motions,

3861-452: Is 491.67 °R. To convert temperature intervals (a span or difference between two temperatures), the formulas from the preceding paragraph are applicable; for instance, an interval of 5 kelvin is precisely equal to an interval of 9 degrees Rankine. For 65 years, between 1954 and the 2019 revision of the SI , a temperature interval of one kelvin was defined as ⁠ 1 / 273.16 ⁠

4004-444: Is a diatomic molecule, has five active degrees of freedom: the three comprising translational motion plus two rotational degrees of freedom internally. Not surprisingly, in accordance with the equipartition theorem, nitrogen has five-thirds the specific heat capacity per mole (a specific number of molecules) as do the monatomic gases. Another example is gasoline (see table showing its specific heat capacity). Gasoline can absorb

4147-467: Is a byproduct of the collisions arising from various vibrational motions of atoms. These collisions cause the electrons of the atoms to emit thermal photons (known as black-body radiation ). Photons are emitted anytime an electric charge is accelerated (as happens when electron clouds of two atoms collide). Even individual molecules with internal temperatures greater than absolute zero also emit black-body radiation from their atoms. In any bulk quantity of

4290-413: Is a single levitated argon atom (argon comprises about 0.93% of air) that is illuminated and glowing against a dark backdrop. If this argon atom was at a beyond-record-setting one-trillionth of a kelvin above absolute zero, and was moving perpendicular to the field of view towards the right, it would require 13.9 seconds to move from the center of the image to the 200-micron tick mark; this travel distance

4433-445: Is about the same as the width of the period at the end of this sentence on modern computer monitors. As the argon atom slowly moved, the positional jitter due to zero-point energy would be much less than the 200-nanometer (0.0002 mm) resolution of an optical microscope. Importantly, the atom's translational velocity of 14.43 microns per second constitutes all its retained kinetic energy due to not being precisely at absolute zero. Were

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4576-399: Is an energy field that jostles particles in ways described by the mathematics of quantum mechanics. In atomic and molecular collisions in gases, ZPE introduces a degree of chaos , i.e., unpredictability, to rebound kinetics; it is as likely that there will be less ZPE-induced particle motion after a given collision as more . This random nature of ZPE is why it has no net effect upon either

4719-445: Is because helium's heat of fusion (the energy required to melt helium ice) is so low (only 21 joules per mole) that the motion-inducing effect of zero-point energy is sufficient to prevent it from freezing at lower pressures. Giuseppe Biancani Giuseppe Biancani , SJ ( Latin : Josephus Blancanus ; 8 March 1566 – 7 June 1624) was an Italian Jesuit astronomer , mathematician , and selenographer , after whom

4862-418: Is because in solids, atoms and molecules are locked into place relative to their neighbors and are not free to roam. Metals however, are not restricted to only phonon-based heat conduction. Thermal energy conducts through metals extraordinarily quickly because instead of direct molecule-to-molecule collisions, the vast majority of thermal energy is mediated via very light, mobile conduction electrons . This

5005-401: Is called the 'universal hotness manifold'." To this information there needs to be added a sense of greater hotness; this sense can be had, independently of calorimetry , of thermodynamics , and of properties of particular materials, from Wien's displacement law of thermal radiation : the temperature of a bath of thermal radiation is proportional , by a universal constant, to the frequency of

5148-400: Is certified to an accuracy of ±0.2 °C. According to British Standards , correctly calibrated, used and maintained liquid-in-glass thermometers can achieve a measurement uncertainty of ±0.01 °C in the range 0 to 100 °C, and a larger uncertainty outside this range: ±0.05 °C up to 200 or down to −40 °C, ±0.2 °C up to 450 or down to −80 °C. Thermometers utilize

5291-464: Is defined and measured, this microscopic kinetic definition is regarded as an "empirical" temperature. It was adopted because in practice it can generally be measured more precisely than can Kelvin's thermodynamic temperature. A thermodynamic temperature of zero is of particular importance for the third law of thermodynamics . By convention, it is reported on the Kelvin scale of temperature in which

5434-404: Is experienced. Electronic registering thermometers may be designed to remember the highest or lowest temperature, or to remember whatever temperature was present at a specified point in time. Thermometers increasingly use electronic means to provide a digital display or input to a computer. Thermometers may be described as empirical or absolute. Absolute thermometers are calibrated numerically by

5577-458: Is false," Biancani wrote, during his discussion on Copernican and Keplerian theories, "and should be rejected (even though it is established by better proofs and arguments) has nevertheless become much more certain in our day when it has been condemned by the authority of the Church as contrary to Sacred Scripture" ( Sphaera , IV, 37). The work not only included studies on the natural phenomenon of

5720-422: Is given by the formula E k  =  ⁠ 1 / 2 ⁠ mv . Accordingly, particles with one unit of mass moving at one unit of velocity have precisely the same kinetic energy, and precisely the same temperature, as those with four times the mass but half the velocity. The extent to which the kinetic energy of translational motion in a statistically significant collection of atoms or molecules in

5863-531: Is hotter than the initial state. There are several principles on which empirical thermometers are built, as listed in the section of this article entitled "Primary and secondary thermometers". Several such principles are essentially based on the constitutive relation between the state of a suitably selected particular material and its temperature. Only some materials are suitable for this purpose, and they may be considered as "thermometric materials". Radiometric thermometry, in contrast, can be only slightly dependent on

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6006-417: Is just one contributor to the total thermal energy in a substance; another is phase transitions , which are the potential energy of molecular bonds that can form in a substance as it cools (such as during condensing and freezing ). The thermal energy required for a phase transition is called latent heat . This phenomenon may more easily be grasped by considering it in the reverse direction: latent heat

6149-408: Is liberated or absorbed during phase transitions, pure chemical elements , compounds , and eutectic alloys exhibit no temperature change whatsoever while they undergo them (see Fig. 7 , below right). Consider one particular type of phase transition: melting. When a solid is melting, crystal lattice chemical bonds are being broken apart; the substance is transitioning from what is known as

6292-455: Is more modest, ranging from 0.021 to 2.3 kJ per mole. Relatively speaking, phase transitions can be truly energetic events. To completely melt ice at 0 °C into water at 0 °C, one must add roughly 80 times the thermal energy as is required to increase the temperature of the same mass of liquid water by one degree Celsius. The metals' ratios are even greater, typically in the range of 400 to 1200 times. The phase transition of boiling

6435-429: Is much more energetic than freezing. For instance, the energy required to completely boil or vaporize water (what is known as enthalpy of vaporization ) is roughly 540 times that required for a one-degree increase. Water's sizable enthalpy of vaporization is why one's skin can be burned so quickly as steam condenses on it (heading from red to green in Fig. 7  above); water vapors (gas phase) are liquefied on

6578-511: Is named), Biancani wrote of his certainty that there could not be any mountains on the Moon. This, according to Biancani, was demonstrated by the observation that the outer circle of the Moon is "entirely lucid, without any shadow or sign of inequality". Biancani opined that the Copernican system was an opinionem falsam... ac rejeciendam . Nevertheless, he remained ambivalent in the midst of

6721-402: Is no surviving document that he actually produced any such instrument. The first clear diagram of a thermoscope was published in 1617 by Giuseppe Biancani (1566 – 1624); the first showing a scale and thus constituting a thermometer was by Santorio Santorio in 1625. This was a vertical tube, closed by a bulb of air at the top, with the lower end opening into a vessel of water. The water level in

6864-470: Is smaller than a micrometre , and new methods and materials have to be used. Nanothermometry is used in such cases. Nanothermometers are classified as luminescent thermometers (if they use light to measure temperature) and non-luminescent thermometers (systems where thermometric properties are not directly related to luminescence). Thermometers used specifically for low temperatures. Various thermometric techniques have been used throughout history such as

7007-536: Is the International Temperature Scale of 1990 . It extends from 0.65  K (−272.5 °C; −458.5 °F) to approximately 1,358 K (1,085 °C; 1,985 °F). Sparse and conflicting historical records make it difficult to pinpoint the invention of the thermometer to any single person or date with certitude. In addition, given the many parallel developments in the thermometer's history and its many gradual improvements over time,

7150-423: Is the energy required to break chemical bonds (such as during evaporation and melting ). Almost everyone is familiar with the effects of phase transitions; for instance, steam at 100 °C can cause severe burns much faster than the 100 °C air from a hair dryer . This occurs because a large amount of latent heat is liberated as steam condenses into liquid water on the skin. Even though thermal energy

7293-441: Is to say, the material must be able to be heated and cooled indefinitely often by the same increment and decrement of heat, and still return to its original pressure, volume and temperature every time. Some plastics do not have this property; (3) Its heating and cooling must be monotonic. That is to say, throughout the range of temperatures for which it is intended to work, At temperatures around about 4 °C, water does not have

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7436-401: Is typically used in cryogenics and related phenomena like superconductivity , as per the following example usage: "Conveniently, tantalum's transition temperature ( T c ) of 4.4924 kelvin is slightly above the 4.2221 K boiling point of helium." The Boltzmann constant and its related formulas describe the realm of particle kinetics and velocity vectors whereas ZPE ( zero-point energy )

7579-404: Is used for its relation between pressure and volume and temperature, a thermometric material must have three properties: (1) Its heating and cooling must be rapid. That is to say, when a quantity of heat enters or leaves a body of the material, the material must expand or contract to its final volume or reach its final pressure and must reach its final temperature with practically no delay; some of

7722-420: Is what gives substances their temperature). The effect is rather like popcorn : at a certain temperature, additional thermal energy cannot make the kernels any hotter until the transition (popping) is complete. If the process is reversed (as in the freezing of a liquid), thermal energy must be removed from a substance. As stated above, the thermal energy required for a phase transition is called latent heat . In

7865-439: Is why there is a near-perfect correlation between metals' thermal conductivity and their electrical conductivity . Conduction electrons imbue metals with their extraordinary conductivity because they are delocalized (i.e., not tied to a specific atom) and behave rather like a sort of quantum gas due to the effects of zero-point energy (for more on ZPE, see Note 1 below). Furthermore, electrons are relatively light with

8008-533: The Boltzmann constant at exactly 1.380 649 × 10  joules per kelvin (J/K). The microscopic property that imbues material substances with a temperature can be readily understood by examining the ideal gas law , which relates, per the Boltzmann constant, how heat energy causes precisely defined changes in the pressure and temperature of certain gases. This is because monatomic gases like helium and argon behave kinetically like freely moving perfectly elastic and spherical billiard balls that move only in

8151-551: The Galileo thermometer to thermal imaging. Medical thermometers such as mercury-in-glass thermometers, infrared thermometers, pill thermometers , and liquid crystal thermometers are used in health care settings to determine if individuals have a fever or are hypothermic . Thermodynamic temperature Thermodynamic temperature is a quantity defined in thermodynamics as distinct from kinetic theory or statistical mechanics . Historically, thermodynamic temperature

8294-745: The Scientific Revolution , as he cited Galileo's opinions on the surface of the Moon while also discussing those of the ancients, such as Posidonius and Cleomedes . Biancani adopted the Tychonic system battling the Aristotelianism of Mutio Vitelleschi , General of the Jesuit Order. He also maintained that the heavens were composed of fluid matter, not solid spheres, another anti-Aristotelian view. Biancani's Constructio instrumenti ad horologia solaria discusses how to make

8437-495: The degree Fahrenheit (symbol: °F). A unit increment of one kelvin is exactly 1.8 times one degree Rankine; thus, to convert a specific temperature on the Kelvin scale to the Rankine scale, x K = 1.8 x °R , and to convert from a temperature on the Rankine scale to the Kelvin scale, x °R = x /1.8 K . Consequently, absolute zero is "0" for both scales, but the melting point of water ice (0 °C and 273.15 K)

8580-464: The diffusion of hot gases in a partial vacuum. The kinetic energy stored internally in molecules causes substances to contain more heat energy at any given temperature and to absorb additional internal energy for a given temperature increase. This is because any kinetic energy that is, at a given instant, bound in internal motions, is not contributing to the molecules' translational motions at that same instant. This extra kinetic energy simply increases

8723-466: The echo and on sundials , but also included a diagram of the Moon. Giuseppe Biancani's map was not drawn up in support of new Copernican ideas but those berthed in traditional geocentric cosmology and in support of Aristotelian thought. Biancani disagreed with Galileo, who believed in the existence of lunar mountains . In a 1611 letter to Christoph Grienberger (after whom the Gruemberger crater

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8866-400: The noble gases helium and argon , which have only the three translational degrees of freedom (the X, Y, and Z axis). Kinetic energy is stored in molecules' internal degrees of freedom, which gives them an internal temperature . Even though these motions are called "internal", the external portions of molecules still move—rather like the jiggling of a stationary water balloon . This permits

9009-483: The unit of measurement is the kelvin (unit symbol: K). For comparison, a temperature of 295 K corresponds to 21.85 °C and 71.33 °F. Thermodynamic temperature, as distinct from SI temperature, is defined in terms of a macroscopic Carnot cycle . Thermodynamic temperature is of importance in thermodynamics because it is defined in purely thermodynamic terms. SI temperature is conceptually far different from thermodynamic temperature. Thermodynamic temperature

9152-834: The Academy of Mathematics in the Roman College with Clavius . Between 1596 and 1599 he lived in Padua , where he completed his studies and befriended Galileo, who had been appointed professor of mathematics at the local university in 1592. When the Jesuits were expelled from the Republic of Venice in 1606 Biancani was sent to the College of Parma, where he taught mathematics in the Jesuit College until his death in 1624, and

9295-435: The Boltzmann constant a precisely defined value had no practical effect on modern thermometry except for the most exquisitely precise measurements. Before the revision, the triple point of water was exactly 273.16 K and 0.01 °C and the Boltzmann constant was experimentally determined to be 1.380 649 03 (51) × 10  J/K , where the "(51)" denotes the uncertainty in the two least significant digits (the 03) and equals

9438-432: The Boltzmann constant is useful for finding the mean kinetic energy in a sample of particles, it is important to note that even when a substance is isolated and in thermodynamic equilibrium (all parts are at a uniform temperature and no heat is going into or out of it), the translational motions of individual atoms and molecules occurs across a wide range of speeds (see animation in Fig. 1 above). At any one instant,

9581-517: The Fahrenheit scale and the Celsius scale. At the zero point of thermodynamic temperature, absolute zero , the particle constituents of matter have minimal motion and can become no colder. Absolute zero, which is a temperature of zero kelvins (0 K), precisely corresponds to −273.15 °C and −459.67 °F. Matter at absolute zero has no remaining transferable average kinetic energy and

9724-418: The SI revision was no accident; the final value of the Boltzmann constant was determined, in part, through clever experiments with argon and helium that used the triple point of water for their key reference temperature. Notwithstanding the 2019 revision, water triple-point cells continue to serve in modern thermometry as exceedingly precise calibration references at 273.16 K and 0.01 °C. Moreover,

9867-501: The SI was primarily for the purpose of decoupling much of the SI system's definitional underpinnings from the kilogram , which was the last physical artifact defining an SI base unit (a platinum/iridium cylinder stored under three nested bell jars in a safe located in France) and which had highly questionable stability. The solution required that four physical constants, including the Boltzmann constant, be definitionally fixed. Assigning

10010-402: The absolute temperature of a body inside the cavity. A thermometer is called primary or secondary based on how the raw physical quantity it measures is mapped to a temperature. As summarized by Kauppinen et al., "For primary thermometers the measured property of matter is known so well that temperature can be calculated without any unknown quantities. Examples of these are thermometers based on

10153-504: The amount of internal energy that substance absorbs for a given temperature rise. This property is known as a substance's specific heat capacity . Different molecules absorb different amounts of internal energy for each incremental increase in temperature; that is, they have different specific heat capacities. High specific heat capacity arises, in part, because certain substances' molecules possess more internal degrees of freedom than others do. For instance, room-temperature nitrogen , which

10296-447: The ancient work Pneumatics were introduced to late 16th century Italy and studied by many, including Galileo Galilei , who had read it by 1594. The Roman Greek physician Galen is given credit for introducing two concepts important to the development of a scale of temperature and the eventual invention of the thermometer. First, he had the idea that hotness or coldness may be measured by "degrees of hot and cold." He also conceived of

10439-421: The atom precisely at absolute zero, imperceptible jostling due to zero-point energy would cause it to very slightly wander, but the atom would perpetually be located, on average, at the same spot within the field of view. This is analogous to a boat that has had its motor turned off and is now bobbing slightly in relatively calm and windless ocean waters; even though the boat randomly drifts to and fro, it stays in

10582-494: The book are described in Latin as: Sphaera Mundi seu Cosmographia. Demonstrativa, ac facili Methodo tradita: In qua totius Mundi fabrica, una cum novis, Tychonis, Kepleri, Galilaei, aliorumque; Astronomorum adinventis continetur. Accessere I. Brevis introductio ad Geographiam. II. Apparatus ad Mathematicarum studium. III. Echometria, idest Geometrica tractatio de Echo. IV. Novum instrumentum ad horologia describenda . As evidenced in

10725-546: The constitutive relations of materials. In a sense then, radiometric thermometry might be thought of as "universal". This is because it rests mainly on a universality character of thermodynamic equilibrium, that it has the universal property of producing blackbody radiation. There are various kinds of empirical thermometer based on material properties. Many empirical thermometers rely on the constitutive relation between pressure, volume and temperature of their thermometric material. For example, mercury expands when heated. If it

10868-586: The crater Blancanus on the Moon is named. Biancani was one of the most able and respected Catholic astronomers of his day, and his main work, Sphaera Mundi , was republished at least four times in the seventeenth century, 1620, 1630, 1635, and 1653. Giuseppe Biancani was born in Bologna in 1566, entered the Jesuit Order in 1592, and studied at the College of Brescia with Marco Antonio De Dominis , and at

11011-455: The defining points in the International Temperature Scale of 1990 , though in practice the melting point of water is more commonly used than its triple point, the latter being more difficult to manage and thus restricted to critical standard measurement. Nowadays manufacturers will often use a thermostat bath or solid block where the temperature is held constant relative to a calibrated thermometer. Other thermometers to be calibrated are put into

11154-565: The difference between the triple point of water and absolute zero. The 1954 resolution by the International Bureau of Weights and Measures (known by the French-language acronym BIPM), plus later resolutions and publications, defined the triple point of water as precisely 273.16 K and acknowledged that it was "common practice" to accept that due to previous conventions (namely, that 0 °C had long been defined as

11297-663: The disadvantage that they were also barometers , i.e. sensitive to air pressure. In 1629, Joseph Solomon Delmedigo , a student of Galileo and Santorio in Padua, published what is apparently the first description and illustration of a sealed liquid-in-glass thermometer. It is described as having a bulb at the bottom of a sealed tube partially filled with brandy. The tube had a numbered scale. Delmedigo did not claim to have invented this instrument. Nor did he name anyone else as its inventor. In about 1654, Ferdinando II de' Medici, Grand Duke of Tuscany (1610–1670) did produce such an instrument,

11440-496: The effect of precisely establishing the magnitude of the unit interval of SI temperature, the kelvin, in terms of the average kinetic behavior of the noble gases. Moreover, the starting point of the thermodynamic temperature scale, absolute zero, was reaffirmed as the point at which zero average kinetic energy remains in a sample; the only remaining particle motion being that comprising random vibrations due to zero-point energy. Temperature scales are numerical. The numerical zero of

11583-690: The effects of zero-point energy. Such are the consequences of statistical mechanics and the nature of thermodynamics. As mentioned above, there are other ways molecules can jiggle besides the three translational degrees of freedom that imbue substances with their kinetic temperature. As can be seen in the animation at right, molecules are complex objects; they are a population of atoms and thermal agitation can strain their internal chemical bonds in three different ways: via rotation, bond length, and bond angle movements; these are all types of internal degrees of freedom . This makes molecules distinct from monatomic substances (consisting of individual atoms) like

11726-445: The equation of state of a gas, on the velocity of sound in a gas, on the thermal noise voltage or current of an electrical resistor, and on the angular anisotropy of gamma ray emission of certain radioactive nuclei in a magnetic field ." In contrast, "Secondary thermometers are most widely used because of their convenience. Also, they are often much more sensitive than primary ones. For secondary thermometers knowledge of

11869-475: The evaporation of just 20 mm of water from a 1.29-meter-deep pool chills its water 8.4 °C (15.1 °F). The total energy of all translational and internal particle motions, including that of conduction electrons, plus the potential energy of phase changes, plus zero-point energy of a substance comprise the internal energy of it. As a substance cools, different forms of internal energy and their related effects simultaneously decrease in magnitude:

12012-424: The first modern-style thermometer, dependent on the expansion of a liquid and independent of air pressure. Many other scientists experimented with various liquids and designs of thermometer. However, each inventor and each thermometer was unique — there was no standard scale . Early attempts at standardization added a single reference point such as the freezing point of water. The use of two references for graduating

12155-415: The following example usage: "A 60/40 tin/lead solder is non-eutectic and is plastic through a range of 5 kelvins as it solidifies." A temperature interval of one degree Celsius is the same magnitude as one kelvin. The magnitude of the kelvin was redefined in 2019 in relation to the physical property underlying thermodynamic temperature: the kinetic energy of atomic free particle motion. The revision fixed

12298-413: The following hypothetical thought experiment, as illustrated in Fig. 2.5 at left, with an atom that is exceedingly close to absolute zero. Imagine peering through a common optical microscope set to 400 power, which is about the maximum practical magnification for optical microscopes. Such microscopes generally provide fields of view a bit over 0.4 mm in diameter. At the center of the field of view

12441-485: The form of phonons (see Fig. 4 at right). Phonons are constrained, quantized wave packets that travel at the speed of sound of a given substance. The manner in which phonons interact within a solid determines a variety of its properties, including its thermal conductivity. In electrically insulating solids, phonon-based heat conduction is usually inefficient and such solids are considered thermal insulators (such as glass, plastic, rubber, ceramic, and rock). This

12584-461: The gases. Molecules (two or more chemically bound atoms), however, have internal structure and therefore have additional internal degrees of freedom (see Fig. 3 , below), which makes molecules absorb more heat energy for any given amount of temperature rise than do the monatomic gases. Heat energy is born in all available degrees of freedom; this is in accordance with the equipartition theorem , so all available internal degrees of freedom have

12727-482: The hand of God, " natural law " would have allowed the Earth to remain in that form. Biancani believed, however, that God had created the depths of the sea and formed the mountains of the Earth. Moreover, if left to "natural law," the Earth would be consumed in water, in imitation of how it was created. However, the hand of God would intervene in order to cause the Earth to be destroyed entirely by fire . The contents of

12870-493: The heat that enters can be considered to change the volume of the body at constant temperature, and is called the latent heat of expansion at constant temperature ; and the rest of it can be considered to change the temperature of the body at constant volume, and is called the specific heat at constant volume . Some materials do not have this property, and take some time to distribute the heat between temperature and volume change. (2) Its heating and cooling must be reversible. That

13013-461: The instrument is best viewed not as a single invention, but an evolving technology . Early pneumatic devices and ideas from antiquity provided inspiration for the thermometer's invention during the Renaissance period. In the 3rd century BC, Philo of Byzantium documented his experiment with a tube submerged in a container of liquid on one end and connected to an air-tight, hollow sphere on

13156-444: The instrument, e.g. in a liquid-in-glass thermometer if the capillary tube varies in diameter. For many purposes reproducibility is important. That is, does the same thermometer give the same reading for the same temperature (or do replacement or multiple thermometers give the same reading)? Reproducible temperature measurement means that comparisons are valid in scientific experiments and industrial processes are consistent. Thus if

13299-541: The latent heat of available phase transitions is liberated as a substance changes from a less ordered state to a more ordered state; the translational motions of atoms and molecules diminish (their kinetic energy or temperature decreases); the internal motions of molecules diminish (their internal energy or temperature decreases); conduction electrons (if the substance is an electrical conductor) travel somewhat slower; and black-body radiation's peak emittance wavelength increases (the photons' energy decreases). When particles of

13442-407: The lattice. Chemical bonds are all-or-nothing forces: they either hold fast, or break; there is no in-between state. Consequently, when a substance is at its melting point, every joule of added thermal energy only breaks the bonds of a specific quantity of its atoms or molecules, converting them into a liquid of precisely the same temperature; no kinetic energy is added to translational motion (which

13585-450: The maximum of its frequency spectrum ; this frequency is always positive, but can have values that tend to zero . Another way of identifying hotter as opposed to colder conditions is supplied by Planck's principle , that when a process of isochoric adiabatic work is the sole means of change of internal energy of a closed system, the final state of the system is never colder than the initial state; except for phase changes with latent heat, it

13728-467: The mean average kinetic energy of a specific kind of particle motion known as translational motion . These simple movements in the three X, Y, and Z–axis dimensions of space means the particles move in the three spatial degrees of freedom . This particular form of kinetic energy is sometimes referred to as kinetic temperature . Translational motion is but one form of heat energy and is what gives gases not only their temperature, but also their pressure and

13871-477: The measured property is not sufficient to allow direct calculation of temperature. They have to be calibrated against a primary thermometer at least at one temperature or at a number of fixed temperatures. Such fixed points, for example, triple points and superconducting transitions, occur reproducibly at the same temperature." Thermometers can be calibrated either by comparing them with other calibrated thermometers or by checking them against known fixed points on

14014-432: The melting point of ice and body temperature . In 1714, scientist and inventor Daniel Gabriel Fahrenheit invented a reliable thermometer, using mercury instead of alcohol and water mixtures . In 1724, he proposed a temperature scale which now (slightly adjusted) bears his name . In 1742, Anders Celsius (1701–1744) proposed a scale with zero at the boiling point and 100 degrees at the freezing point of water, though

14157-440: The melting point of water and that the triple point of water had long been experimentally determined to be indistinguishably close to 0.01 °C), the difference between the Celsius scale and Kelvin scale is accepted as 273.15 kelvins; which is to say, 0 °C corresponds to 273.15 kelvins. The net effect of this as well as later resolutions was twofold: 1) they defined absolute zero as precisely 0 K, and 2) they defined that

14300-458: The nature of the mathematical sciences. The work suffered censorship whilst undergoing peer review , a common Jesuit practice. The reviewer, Giovanni Camerota, wrote: "It does not seem to be either proper or useful for the books of our members to contain the ideas of Galileo Galilei , especially when they are contrary to Aristotle." Biancani wrote his Sphaera mundi, seu cosmographia demonstrativa, ac facili methodo tradita in 1615. However, it

14443-496: The nature shown above in Fig. 1 . As can be seen in that animation, not only does momentum (heat) diffuse throughout the volume of the gas through serial collisions, but entire molecules or atoms can move forward into new territory, bringing their kinetic energy with them. Consequently, temperature differences equalize throughout gases very quickly—especially for light atoms or molecules; convection speeds this process even more. Translational motion in solids , however, takes

14586-440: The nearest 10 °C or more. Clinical thermometers and many electronic thermometers are usually readable to 0.1 °C. Special instruments can give readings to one thousandth of a degree. However, this precision does not mean the reading is true or accurate, it only means that very small changes can be observed. A thermometer calibrated to a known fixed point is accurate (i.e. gives a true reading) at that point. The invention of

14729-436: The only remaining particle motion is due to an ever-pervasive quantum mechanical phenomenon called ZPE ( zero-point energy ). Though the atoms in, for instance, a container of liquid helium that was precisely at absolute zero would still jostle slightly due to zero-point energy, a theoretically perfect heat engine with such helium as one of its working fluids could never transfer any net kinetic energy ( heat energy ) to

14872-542: The original ancient Greek were utilized by Robert Fludd sometime around 1617 and used as the basis for his air thermometer. In his book, Pneumatics , Hero of Alexandria (10–70 AD) provides a recipe for building a "Fountain which trickles by the Action of the Sun's Rays," a more elaborate version of Philo's pneumatic experiment but which worked on the same principle of heating and cooling air to move water around. Translations of

15015-488: The other working fluid and no thermodynamic work could occur. Temperature is generally expressed in absolute terms when scientifically examining temperature's interrelationships with certain other physical properties of matter such as its volume or pressure (see Gay-Lussac's law ), or the wavelength of its emitted black-body radiation . Absolute temperature is also useful when calculating chemical reaction rates (see Arrhenius equation ). Furthermore, absolute temperature

15158-406: The other. When air in the sphere is heated with a candle or by exposing it to the sun, expanding air exits the sphere and generates bubbles in the vessel. As air in the sphere cools, a partial vacuum is created, sucking liquid up into the tube. Any changes in the position of the liquid will now indicate whether the air in the sphere is getting hotter or colder. Translations of Philo's experiment from

15301-440: The pressure or volume of any bulk quantity (a statistically significant quantity of particles) of gases. However, in temperature T = 0 condensed matter ; e.g., solids and liquids, ZPE causes inter-atomic jostling where atoms would otherwise be perfectly stationary. Inasmuch as the real-world effects that ZPE has on substances can vary as one alters a thermodynamic system (for example, due to ZPE, helium won't freeze unless under

15444-399: The problem of the invention of the thermometer becomes more straightforward; that of the invention of the thermoscope remains as obscure as ever. Given this, the possible inventors of the thermometer are usually considered to be Galileo, Santorio, Dutch inventor Cornelis Drebbel , or British mathematician Robert Fludd . Though Galileo is often said to be the inventor of the thermometer, there

15587-562: The property (3), and is said to behave anomalously in this respect; thus water cannot be used as a material for this kind of thermometry for temperature ranges near 4 °C. Gases, on the other hand, all have the properties (1), (2), and (3)(a)(α) and (3)(b)(α). Consequently, they are suitable thermometric materials, and that is why they were important in the development of thermometry. According to Preston (1894/1904), Regnault found constant pressure air thermometers unsatisfactory, because they needed troublesome corrections. He therefore built

15730-525: The proportion of particles moving at a given speed within this range is determined by probability as described by the Maxwell–Boltzmann distribution . The graph shown here in Fig. 2 shows the speed distribution of 5500 K helium atoms. They have a most probable speed of 4.780 km/s (0.2092 s/km). However, a certain proportion of atoms at any given instant are moving faster while others are moving relatively slowly; some are momentarily at

15873-456: The radiant power as it does at 296 K (room temperature). This is why one can so easily feel the radiant heat from hot objects at a distance. At higher temperatures, such as those found in an incandescent lamp , black-body radiation can be the principal mechanism by which thermal energy escapes a system. The table below shows various points on the thermodynamic scale, in order of increasing temperature. The kinetic energy of particle motion

16016-478: The resultant collisions by atoms or molecules with small particles suspended in a fluid produces Brownian motion that can be seen with an ordinary microscope. The translational motions of elementary particles are very fast and temperatures close to absolute zero are required to directly observe them. For instance, when scientists at the NIST achieved a record-setting cold temperature of 700 nK (billionths of

16159-463: The same bath or block and allowed to come to equilibrium, then the scale marked, or any deviation from the instrument scale recorded. For many modern devices calibration will be stating some value to be used in processing an electronic signal to convert it to a temperature. The precision or resolution of a thermometer is simply to what fraction of a degree it is possible to make a reading. For high temperature work it may only be possible to measure to

16302-416: The same spot in the long term and makes no headway through the water. Accordingly, an atom that was precisely at absolute zero would not be "motionless", and yet, a statistically significant collection of such atoms would have zero net kinetic energy available to transfer to any other collection of atoms. This is because regardless of the kinetic temperature of the second collection of atoms, they too experience

16445-435: The same temperature as their three external degrees of freedom. However, the property that gives all gases their pressure , which is the net force per unit area on a container arising from gas particles recoiling off it, is a function of the kinetic energy borne in the freely moving atoms' and molecules' three translational degrees of freedom. Fixing the Boltzmann constant at a specific value, along with other rule making, had

16588-440: The same type of thermometer is calibrated in the same way its readings will be valid even if it is slightly inaccurate compared to the absolute scale. An example of a reference thermometer used to check others to industrial standards would be a platinum resistance thermometer with a digital display to 0.1 °C (its precision) which has been calibrated at 5 points against national standards (−18, 0, 40, 70, 100 °C) and which

16731-442: The scale which now bears his name has them the other way around. French entomologist René Antoine Ferchault de Réaumur invented an alcohol thermometer and, temperature scale in 1730, that ultimately proved to be less reliable than Fahrenheit's mercury thermometer. The first physician to use thermometer measurements in clinical practice was Herman Boerhaave (1668–1738). In 1866, Sir Thomas Clifford Allbutt (1836–1925) invented

16874-487: The scientific world where modern measurements are nearly always made using the International System of Units, thermodynamic temperature is measured using the Kelvin scale. The Rankine scale is part of English engineering units and finds use in certain engineering fields, particularly in legacy reference works. The Rankine scale uses the degree Rankine (symbol: °R) as its unit, which is the same magnitude as

17017-420: The skin with releasing a large amount of energy (enthalpy) to the environment including the skin, resulting in skin damage. In the opposite direction, this is why one's skin feels cool as liquid water on it evaporates (a process that occurs at a sub-ambient wet-bulb temperature that is dependent on relative humidity ); the water evaporation on the skin takes a large amount of energy from the environment including

17160-403: The skin, reducing the skin temperature. Water's highly energetic enthalpy of vaporization is also an important factor underlying why solar pool covers (floating, insulated blankets that cover swimming pools when the pools are not in use) are so effective at reducing heating costs: they prevent evaporation. (In other words, taking energy from water when it is evaporated is limited.) For instance,

17303-416: The specific cases of melting and freezing, it is called enthalpy of fusion or heat of fusion . If the molecular bonds in a crystal lattice are strong, the heat of fusion can be relatively great, typically in the range of 6 to 30 kJ per mole for water and most of the metallic elements. If the substance is one of the monatomic gases (which have little tendency to form molecular bonds) the heat of fusion

17446-472: The square of velocity, nearly all the kinetic energy goes into the bullet, not the rifle, even though both experience the same force from the expanding propellant gases. In the same manner, because they are much less massive, thermal energy is readily borne by mobile conduction electrons. Additionally, because they are delocalized and very fast, kinetic thermal energy conducts extremely quickly through metals with abundant conduction electrons. Thermal radiation

17589-495: The statement of the zeroth law of thermodynamics by James Serrin in 1977, though rather mathematically abstract, is more informative for thermometry: "Zeroth Law – There exists a topological line M {\displaystyle M} which serves as a coordinate manifold of material behaviour. The points L {\displaystyle L} of the manifold M {\displaystyle M} are called 'hotness levels', and M {\displaystyle M}

17732-476: The table of contents, this work also presented a summary of the discoveries made with the telescope by Tycho Brahe , Johannes Kepler , Galileo , Copernicus , and others. Biancani gave very favourable evaluations of Galileo's Sidereus Nuncius , De maculis solaribus , and De iis quae natantur aut moventur in aqua . The censorship of Biancani's previous work, however, affected the manner in which he wrote Sphaera mundi . "But that this opinion [heliocentrism]

17875-543: The technology to measure temperature led to the creation of scales of temperature . In between fixed calibration points, interpolation is used, usually linear. This may give significant differences between different types of thermometer at points far away from the fixed points. For example, the expansion of mercury in a glass thermometer is slightly different from the change in resistance of a platinum resistance thermometer, so these two will disagree slightly at around 50 °C. There may be other causes due to imperfections in

18018-455: The temperature of its new conditions (in this case, the air temperature). Registering thermometers are designed to hold the temperature indefinitely, so that the thermometer can be removed and read at a later time or in a more convenient place. Mechanical registering thermometers hold either the highest or lowest temperature recorded until manually re-set, e.g., by shaking down a mercury-in-glass thermometer, or until an even more extreme temperature

18161-407: The temperature of water in fish tanks. Fiber Bragg grating temperature sensors are used in nuclear power facilities to monitor reactor core temperatures and avoid the possibility of nuclear meltdowns . Nanothermometry is an emergent research field dealing with the knowledge of temperature in the sub-micrometric scale. Conventional thermometers cannot measure the temperature of an object which

18304-407: The temperature scale. The best known of these fixed points are the melting and boiling points of pure water. (Note that the boiling point of water varies with pressure, so this must be controlled.) The traditional way of putting a scale on a liquid-in-glass or liquid-in-metal thermometer was in three stages: Other fixed points used in the past are the body temperature (of a healthy adult male) which

18447-437: The thermodynamic absolute temperature scale. Empirical thermometers are not in general necessarily in exact agreement with absolute thermometers as to their numerical scale readings, but to qualify as thermometers at all they must agree with absolute thermometers and with each other in the following way: given any two bodies isolated in their separate respective thermodynamic equilibrium states, all thermometers agree as to which of

18590-410: The thermometer did not hold the temperature reading after it was moved to a place with a different temperature. Determining the temperature of a pot of hot liquid required the user to leave the thermometer in the hot liquid until after reading it. If the non-registering thermometer was removed from the hot liquid, then the temperature indicated on the thermometer would immediately begin changing to reflect

18733-419: The thermometer is said to have been introduced by Joachim Dalence in 1668, although Christiaan Huygens (1629–1695) in 1665 had already suggested the use of graduations based on the melting and boiling points of water as standards and, in 1694, Carlo Renaldini (1615–1698) proposed using them as fixed points along a universal scale. In 1701, Isaac Newton (1642–1726/27) proposed a scale of 12 degrees between

18876-402: The triple point of special isotopically controlled water called Vienna Standard Mean Ocean Water occurred at precisely 273.16 K and 0.01 °C. One effect of the aforementioned resolutions was that the melting point of water, while very close to 273.15 K and 0 °C, was not a defining value and was subject to refinement with more precise measurements. The 1954 BIPM standard did

19019-422: The triple point of water remains one of the 14 calibration points comprising ITS‑90, which spans from the triple point of hydrogen (13.8033 K) to the freezing point of copper (1,357.77 K), which is a nearly hundredfold range of thermodynamic temperature. The thermodynamic temperature of any bulk quantity of a substance (a statistically significant quantity of particles) is directly proportional to

19162-568: The tube was controlled by the expansion and contraction of the air, so it was what we would now call an air thermometer. The word thermometer (in its French form) first appeared in 1624 in La Récréation Mathématique by Jean Leurechon , who describes one with a scale of 8 degrees. The word comes from the Greek words θερμός , thermos , meaning "hot" and μέτρον, metron , meaning "measure". The above instruments suffered from

19305-472: The two has the higher temperature, or that the two have equal temperatures. For any two empirical thermometers, this does not require that the relation between their numerical scale readings be linear, but it does require that relation to be strictly monotonic . This is a fundamental character of temperature and thermometers. As it is customarily stated in textbooks, taken alone, the so-called " zeroth law of thermodynamics " fails to deliver this information, but

19448-436: The two-way exchange of kinetic energy between internal motions and translational motions with each molecular collision. Accordingly, as internal energy is removed from molecules, both their kinetic temperature (the kinetic energy of translational motion) and their internal temperature simultaneously diminish in equal proportions. This phenomenon is described by the equipartition theorem , which states that for any bulk quantity of

19591-683: The vast majority of their volume. This relationship between the temperature, pressure, and volume of gases is established by the ideal gas law 's formula pV = nRT and is embodied in the gas laws . Though the kinetic energy borne exclusively in the three translational degrees of freedom comprise the thermodynamic temperature of a substance, molecules, as can be seen in Fig. 3 , can have other degrees of freedom, all of which fall under three categories: bond length, bond angle, and rotational. All three additional categories are not necessarily available to all molecules, and even for molecules that can experience all three, some can be "frozen out" below

19734-463: Was addressed by the International Temperature Scale of 1990 , or ITS‑90, which defined 13 additional points, from 13.8033 K, to 1,357.77 K. While definitional, ITS‑90 had—and still has—some challenges, partly because eight of its extrapolated values depend upon the melting or freezing points of metal samples, which must remain exceedingly pure lest their melting or freezing points be affected—usually depressed. The 2019 revision of

19877-449: Was defined by Lord Kelvin in terms of a macroscopic relation between thermodynamic work and heat transfer as defined in thermodynamics, but the kelvin was redefined by international agreement in 2019 in terms of phenomena that are now understood as manifestations of the kinetic energy of free motion of microscopic particles such as atoms, molecules, and electrons. From the thermodynamic viewpoint, for historical reasons, because of how it

20020-672: Was not published until 1619 in Bologna, after the Decree of the Congregation of the Index in 1616. In his Sphaera mundi , Biancani expounded on his belief that God had made the Earth a perfect symmetrical world: the highest mountain on land had its proportional equivalent in the lowest depth of the ocean. The original Earth emerged on the third day of Genesis creation narrative as a perfectly smooth sphere , Biancani reasoned. If not for

20163-470: Was originally used by Fahrenheit as his upper fixed point (96 °F (35.6 °C) to be a number divisible by 12) and the lowest temperature given by a mixture of salt and ice, which was originally the definition of 0 °F (−17.8 °C). (This is an example of a frigorific mixture .) As body temperature varies, the Fahrenheit scale was later changed to use an upper fixed point of boiling water at 212 °F (100 °C). These have now been replaced by

20306-458: Was rigorously defined historically long before there was a fair knowledge of microscopic particles such as atoms, molecules, and electrons. The International System of Units (SI) specifies the international absolute scale for measuring temperature, and the unit of measure kelvin (unit symbol: K) for specific values along the scale. The kelvin is also used for denoting temperature intervals (a span or difference between two temperatures) as per

20449-485: Was the teacher of a group of Jesuit scientists who distinguished themselves for their scientific contributions, such as Niccolò Cabeo , Niccolò Zucchi , Mario Bettinus and Giovanni Battista Riccioli . In his Aristotelis loca mathematica ex universis ipsius operibus collecta et explicata , published in Bologna in 1615, Biancani discussed all Aristotle's references to mathematics as a science, and gave his own view of

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