"Cold Cold is the presence of low temperature, especially in the atmosphere. In common usage, cold is often a subjective perception. A lower bound to temperature is absolute zero, defined as 0.00K on the Kelvin scale, an absolute thermodynamic temperature scale. This corresponds to on the Celsius scale, on the Fahrenheit scale, and on the Rankine scale. Since temperature relates to the thermal energy held by an object or a sample of matter, which is the kinetic energy of the random motion of the particle constituents of matter, an object will have less thermal energy when it is colder and"
"worked to obtain even lower temperatures. 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 0. The fundamental particles of nature have minimal 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° on the Celsius scale (International System of Units), which equals −459.67° on the Fahrenheit scale (United States customary units or Imperial units). The corresponding"
"relative motion of its component molecules/atoms decreases - its temperature decreases. Cooling can continue until all motion ceases, and its kinetic energy, or energy of motion, disappears. This condition is known as absolute zero and it forms the basis for the Kelvin temperature scale, which measures the temperature above absolute zero. Zero degrees Celsius (°C) coincides with 273 Kelvin. At absolute zero most elements become a solid, but not all behave as predictably as this; for instance, helium becomes a highly unusual liquid. The chemistry between substances, however, does not disappear, even near absolute zero temperatures, since separated molecules/atom can"
"statistical law of nature regarding entropy and the impossibility of reaching absolute zero of temperature. This law provides an absolute reference point for the determination of entropy. The entropy determined relative to this point is the absolute entropy. Alternate definitions are, ""the entropy of all systems and of all states of a system is smallest at absolute zero,"" or equivalently ""it is impossible to reach the absolute zero of temperature by any finite number of processes"". Absolute zero, at which all activity would stop if it were possible to happen, is −273.15 °C (degrees Celsius), or −459.67 °F (degrees Fahrenheit),"
"Freezing level The freezing level, or 0 °C (zero-degree) isotherm, represents the altitude in which the temperature is at 0 °C (the freezing point of water) in a free atmosphere (i.e. allowing reflection of the sun by snow, etc.). Any given measure is valid for only a short period of time, often less than a day. Above the freezing altitude, the temperature of the air is below freezing. Below it, the temperature is above freezing. The profile of this frontier, and its variations, are studied in meteorology, and are used for a variety of forecasts and predictions. Whilst not given"
"Planck temperature scale The Planck temperature scale is an absolute temperature scale using natural units. On this scale, 0 is absolute zero, and 1 is the Planck temperature. Quantum Theory states that the Planck temperature is the hottest possible temperature. The symbol used for this scale is ""T"". The freezing/melting point of water on this scale would be written 1.928 × 10""T"". A way of expressing temperatures in more familiar sized units is to use centimicroyocto plank temperatures (cµy""T""). The freezing point of water is 1.928 × 10""T"". By simply moving the decimal point 32 places to the right, you"
"the zero was equivalent to about −240 on the Celsius scale. 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 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"
"Absolute hot Absolute hot is a concept of temperature that postulates the existence of a highest attainable temperature of matter. The concept has been popularized by the television series ""Nova"". In this article, absolute hot is assumed to be the high end of a temperature scale starting at absolute zero, which is the temperature at which entropy is minimal and classical thermal energy is zero. Contemporary models of physical cosmology postulate that the highest possible temperature is the Planck temperature, which has the value . Above about , particle energies become so large that gravitational forces between them would become"
"actually reach the infinite temperature. Absolute hot Absolute hot is a concept of temperature that postulates the existence of a highest attainable temperature of matter. The concept has been popularized by the television series ""Nova"". In this article, absolute hot is assumed to be the high end of a temperature scale starting at absolute zero, which is the temperature at which entropy is minimal and classical thermal energy is zero. Contemporary models of physical cosmology postulate that the highest possible temperature is the Planck temperature, which has the value . Above about , particle energies become so large that gravitational"
"Scale of temperature Scale of temperature is a way to measure temperature quantitatively. Empirical scales measure the quantity of heat in a system in relation to a fixed parameter, a thermometer. They are not absolute measures, that is why scales vary. Absolute temperature is thermodynamic temperature because it is directly related to thermodynamics. It is the Zeroth Law of Thermodynamics that leads to a formal definition of thermodynamic temperature. According to the zeroth law of thermodynamics, being in thermal equilibrium is an equivalence relation. Thus all thermal systems may be divided into a quotient set by this equivalence relation, denoted"
"temperature scale matches the Celsius scale, except that absolute zero is 0 K. The Fahrenheit scale uses the symbol ° to denote a point on the temperature scale (as does Celsius) and the letter F to indicate the use of the Fahrenheit scale (""e.g."" ""Gallium melts at 85.5763 °F""), as well as to denote a difference between temperatures or an uncertainty in temperature (""e.g."" ""The output of the heat exchanger experiences an increase of 72 °F"" and ""Our standard uncertainty is ±5 °F""). For an exact conversion, the following formulas can be applied. Here, is the value in Fahrenheit and"
"the value in Celsius: This is also an exact conversion making use of the identity -40 °F = -40 °C. Again, is the value in Fahrenheit and the value in Celsius: Fahrenheit proposed his temperature scale in 1724, basing it on two reference points of temperature. In his initial scale (which is not the final Fahrenheit scale), the zero point was determined by placing the thermometer in a mixture of ice, water, and ammonium chloride (""salis Armoniaci""). This is a frigorific mixture which stabilizes its temperature automatically: that stable temperature was defined as 0 °F (−17.78 °C). The second point,"
"Rømer scale The Rømer scale (; notated as °Rø), also known as Romer or Roemer, is a temperature scale named after the Danish astronomer Ole Christensen Rømer, who proposed it in 1701. It is based on the freezing point of pure water being 7.5 degrees and the boiling point of water as 60 degrees. In this scale, the zero was initially set using freezing brine. The boiling point of water was defined as 60 degrees. Rømer then saw that the freezing point of pure water was roughly one eighth of the way (about 7.5 degrees) between these two points, so"
"of a system at absolute zero is a well defined constant. This is because a system at zero temperature exists in its ground state. Furthermore, Δ""S"" will reach zero at zero temperature, but ""S"" itself will also reach (0)zero, at least for perfect crystalline substances. No experimentally verified violations of the laws of thermodynamics are known yet. The four laws of black-hole mechanics suggest that one should identify the surface gravity of a black hole with temperature and the area of the event horizon with entropy, at least up to some multiplicative constants. If one only considers black holes classically,"
"area. It varies under two conditions: These conditions imply that the 0 °C isotherm varies globally. Freezing level The freezing level, or 0 °C (zero-degree) isotherm, represents the altitude in which the temperature is at 0 °C (the freezing point of water) in a free atmosphere (i.e. allowing reflection of the sun by snow, etc.). Any given measure is valid for only a short period of time, often less than a day. Above the freezing altitude, the temperature of the air is below freezing. Below it, the temperature is above freezing. The profile of this frontier, and its variations, are"
"Degree of frost A degree of frost is a non-standard unit of measure for air temperature meaning degrees below melting point (also known as ""freezing point"") of water (0 degrees Celsius or 32 degrees Fahrenheit). ""Degree"" in this case can refer to degree Celsius or degree Fahrenheit. When based on Celsius, 0 degrees of frost is the same as 0 °C, and any other value is simply the negative of the Celsius temperature. When based on Fahrenheit, 0 degrees of frost is equal to 32 °F. Conversion formulas: The term ""degrees of frost"" was widely used in accounts of the"
"cool a system to absolute zero, all classical motion of its particles would cease and they would be at complete rest in this classical sense. Microscopically in the description of quantum mechanics, however, matter still has zero-point energy even at absolute zero, because of the uncertainty principle. Temperature is a measure of a quality of a state of a material. The quality may be regarded as a more abstract entity than any particular temperature scale that measures it, and is called ""hotness"" by some writers. The quality of hotness refers to the state of material only in a particular locality,"
"if so, where the zero must be placed, was first addressed by the French physicist Guillaume Amontons in 1702, 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 volume, 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 +, so that"
"According to the third law of thermodynamics, a system at absolute zero temperature exists in its ground state; thus, its entropy is determined by the degeneracy of the ground state. Many systems, such as a perfect crystal lattice, have a unique ground state and therefore have zero entropy at absolute zero. It is also possible for the highest excited state to have absolute zero temperature for systems that exhibit negative temperature. In one dimension, the ground state of the Schrödinger equation can be proven to have no nodes. Consider the average energy of a state with a node at ="
"0.01 °C. However, current measurements show that the difference between the triple and melting points of VSMOW is actually very slightly (<0.001 °C) greater than 0.01 °C. Thus, the actual melting point of ice is very slightly (less than a thousandth of a degree) below 0 °C. Also, defining water's triple point at 273.16 K precisely defined the magnitude of each 1 °C increment in terms of the absolute thermodynamic temperature scale (referencing absolute zero). Now decoupled from the actual boiling point of water, the value ""100 °C"" is hotter than 0 °C – in absolute terms – by a"
"and redefined the ohm in terms of other base units. The definitions for absolute electrical system based on the ampere was formalised in 1948. The draft proposal units with these names are very close, but not identical to the International units. In the Celsius scale from the 18th century, temperature was expressed in degrees Celsius with the definition that ice melted at 0 °C and at standard atmospheric pressure, water boiled at 100 °C. A series of lookup tables defined temperature in terms of inter-related empirical measurements made using various devices. In 1948, definitions relating to temperature had to be"
"the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale two years before his death. The degree Celsius (°C) can refer to a specific temperature on the Celsius scale as well as a unit to indicate a temperature ""interval ""(a difference between two temperatures or an uncertainty). From 1744 until 1954, 0 °C was defined as the freezing point of water and 100 °C was defined as the boiling point of water, both at a pressure of one standard atmosphere. Although these defining correlations are commonly taught in schools today, by international agreement the unit ""degree Celsius"" and"
"(1701–1744) created a temperature scale that was the reverse of the scale now known as ""Celsius"": 0 represented the boiling point of water, while 100 represented the freezing point of water. In his paper ""Observations of two persistent degrees on a thermometer"", he recounted his experiments showing that the melting point of ice is essentially unaffected by pressure. He also determined with remarkable precision how the boiling point of water varied as a function of atmospheric pressure. He proposed that the zero point of his temperature scale, being the boiling point, would be calibrated at the mean barometric pressure at"
"is not the origin 0 in some scales. For absolute zero, but for temperature differences, (Here °R refers to the Rankine scale, not the Réaumur scale). Unit conversion for temperature differences is simply a matter of multiplying by, e.g., 1 °F / 1 K (although the ratio is not a constant value). But because some of these scales have origins that do not correspond to absolute zero, conversion from one temperature scale to another requires accounting for that. As a result, simple dimensional analysis can lead to errors if it is ambiguous whether 1 K means the absolute temperature equal"
"Celsius scale at the triple point of Vienna Standard Mean Ocean Water (VSMOW, 273.16 K and 0.01 °C), and at absolute zero (0 K and −273.15 °C), is that neither the melting nor boiling point of water under one standard atmosphere (101.325 kPa) remains a defining point for the Celsius scale. In 1948 when the 9th General Conference on Weights and Measures (CGPM) in Resolution 3 first considered using the triple point of water as a defining point, the triple point was so close to being 0.01 °C greater than water's known melting point, it was simply defined as precisely"
"energy states than in the lower ones. The system can then be characterised as having a negative temperature. A substance with a negative temperature is not colder than absolute zero, but rather it is hotter than infinite temperature. As Kittel and Kroemer (p. 462) put it, ""The temperature scale from cold to hot runs: The corresponding inverse temperature scale, for the quantity ""β"" = 1/""kT"" (where ""k"" is Boltzmann's constant), runs continuously from low energy to high as +∞, … , 0, …, −∞. Because it avoids the abrupt jump from +∞ to −∞, β is considered more natural than"
"Lord Kelvin) in 1848: This is what we might anticipate, when we reflect that infinite cold must correspond to a finite number of degrees of the air-thermometer below zero; since if we push the strict principle of graduation, stated above, sufficiently far, we should arrive at a point corresponding to the volume of air being reduced to nothing, which would be marked as −273° of the scale (−100/.366, if .366 be the coefficient of expansion); and therefore −273° of the air-thermometer is a point which cannot be reached at any finite temperature, however low. However, the ""absolute zero"" on the"
"clarified. The ""Celsius"", as an angular measure, was adopted for general use in a number of countries, so in 1948 the General Conference on Weights and Measures (CGPM) recommended that the degree Celsius, as used for the measurement of temperature, be renamed the degree Celsius. The SI Brochure (2006) notes that the gon is now a little-used alternative to the degree. At the 9th CGPM, the Celsius temperature scale was renamed the Celsius scale and the scale itself was fixed by defining the triple point of water as 0.01 °C, though the CGPM left the formal definition of absolute zero"
"the definitions of many different empirical scales of temperature, the second law of thermodynamics selects the definition of a single preferred, absolute temperature, unique up to an arbitrary scale factor, whence called the thermodynamic temperature. If internal energy is considered as a function of the volume and entropy of a homogeneous system in thermodynamic equilibrium, thermodynamic absolute temperature appears as the partial derivative of internal energy with respect the entropy at constant volume. Its natural, intrinsic origin or null point is absolute zero at which the entropy of any system is at a minimum. Although this is the lowest absolute"
"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, ""T""/""T"", 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"
"""below freezing"". In statistical mechanics, one sometimes uses negative temperatures to describe systems with population inversion, which can be considered to have a temperature greater than positive infinity, because the coefficient of energy in the population distribution function is −1/Temperature. In this context, a temperature of −0 is a (theoretical) temperature larger than any other negative temperature, corresponding to the (theoretical) maximum conceivable extent of population inversion, the opposite extreme to +0. Signed zero Signed zero is zero with an associated sign. In ordinary arithmetic, the number 0 does not have a sign, so that −0, +0 and 0 are"
"(CDT) and highlights why a method for cooling the air after the compressor is so important. Note: in the example above, the ambient air pressure (1.01 bar) is added to the boost (0.69 bar) to get total pressure (1.70 bar), which is the value used for formula_4 in the equation. The temperatures must be in absolute values, using the Kelvin scale, which begins at absolute zero (0 Kelvin) and where 0 °C is 273.15 K. A Kelvin unit is the same size as a Celsius degree (so 24 °C added to absolute zero is simply 273.15 K + 24 K)."
"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 they had created a quantum gas made up of potassium atoms with a negative temperature in motional degrees of freedom for the first time. One of the first to discuss the possibility of an absolute minimal temperature was Robert Boyle."