absolute zero


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absolute zero,

the zero point of the ideal gas temperature scale, denoted by 0 degrees on the KelvinKelvin temperature scale,
a temperature scale having an absolute zero below which temperatures do not exist. Absolute zero, or 0°K;, is the temperature at which molecular energy is a minimum, and it corresponds to a temperature of −273.
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 and RankineRankine temperature scale,
temperature scale having an absolute zero, below which temperatures do not exist, and using a degree of the same size as that used by the Fahrenheit temperature scale.
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 temperature scales, which is equivalent to −273.15°C; and −459.67°F;. For most gases there is a linear relationship between temperature and pressure (see gas lawsgas laws,
physical laws describing the behavior of a gas under various conditions of pressure, volume, and temperature. Experimental results indicate that all real gases behave in approximately the same manner, having their volume reduced by about the same proportion of the
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), i.e., gases contract indefinitely as the temperature is decreased. Theoretically, at absolute zero the volume of an ideal gas would be zero and all molecular motion would cease. In actuality, all gases condense to solids or liquids well above this point. Although absolute zero cannot be reached, temperatures within a few billionths of a degree above absolute zero have been achieved in the laboratory. At such low temperatures, gases assume nontraditional states, the Bose-Einstein and fermionic condensatescondensate,
matter in the form of a gas of atoms, molecules, or elementary particles that have been so chilled that their motion is virtually halted and as a consequence they lose their separate identities and merge into a single entity.
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. See also low-temperature physicslow-temperature physics,
science concerned with the production and maintenance of temperatures much below normal, down to almost absolute zero, and with various phenomena that occur only at such temperatures.
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; temperaturetemperature,
measure of the relative warmth or coolness of an object. Temperature is measured by means of a thermometer or other instrument having a scale calibrated in units called degrees. The size of a degree depends on the particular temperature scale being used.
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.

Absolute zero

The temperature at which an ideal gas would exert no pressure. The Kelvin scale of temperatures is defined in terms of the triple point of water, T3 = 273.16° (where the solid, liquid, and vapor phases coexist), and absolute zero. Temperature is measured most simply via the constant-volume ideal-gas thermometer, in which a small amount of gas is introduced (in order to limit the effect of interactions between molecules) and then sealed off, and the gas pressure P referenced to its value at the triple point P(T3) is measured. The ideal-gas law applies if the molecules in a gas exert no forces on one another and if they are not attracted to the walls. Absolute zero is the temperature at which the pressure of a truly ideal gas would vanish. See Temperature measurement

According to classical physics, all motion would cease at absolute zero; however, the quantum-mechanical uncertainty principle requires that there be a small amount of residual motion (zero-point motion) even at absolute zero. See Kinetic theory of matter, Uncertainty principle

Temperature can also be defined from the Boltzmann distribution. If a collection of spin-1/2 magnetic ions is placed in a magnetic field, the ratio of the occupancy of the lower to the higher energy state is given by the equation below.

Here k is Boltzmann's constant, ΔE is the magnitude of the difference in energy between the states, and T is the Kelvin temperature. Thus, at high temperatures the two states have nearly equal occupation probability, while the lower energy state is progressively favored at lower temperatures. At absolute zero, only the lower energy level is occupied. This relation allows for the possibility of negative temperatures when the population of the higher energy state exceeds that of the lower state. See Boltzmann constant, Boltzmann statistics

Negative temperatures notwithstanding, the third law of thermodynamics states that the absolute zero of temperature cannot be attained by any finite number of steps. The lowest (and hottest) temperatures that have been achieved are on the order of a picokelvin (10-12K). These are spin temperatures of nuclei which are out of equilibrium with the lattice vibrations and electrons of a solid. The lowest temperatures to which the electrons have been cooled are on the order of 10 microkelvins in metallic systems. See Low-temperature physics, Temperature

absolute zero

The zero value of the thermodynamic temperature scale, i.e. 0 K (–273.15 °C). Absolute zero is the lowest temperature theoretically possible. At absolute zero molecular motion almost ceases.

Absolute Zero

 

the point from which absolute temperatures are measured; it lies at 273.16°K below the temperature of the triple point of water. The existence of absolute temperature and of absolute zero follows from the second law of thermodynamics; the third law of thermodynamics indicates that absolute zero cannot be attained. As the temperature approaches absolute zero, the thermal characteristics of matter such as the entropy, heat capacity, and coefficient of thermal expansion tend to zero. The sharp drop in the intensity of the thermal motion of atoms and molecules near absolute zero results in the ordered crystalline structure that all substances, with the exception of liquid helium, have under these conditions.

According to classical physics, at absolute zero the energy of thermal (random) motion of molecules and atoms in a substance is equal to zero. According to quantum mechanics, however, at absolute zero the atoms or molecules at sites in a crystalline lattice are not completely at rest but undergo “zero” vibrations and have so-called zero energy. If the atomic mass and the interaction energy between atoms are very small, the zero vibrations may hinder the formation of a crystalline lattice. This is the case in the helium isotopes 3He and 4He, which remain liquid right down to the lowest attainable temperatures.

Obtaining temperatures that are as close as possible to absolute zero is a complicated experimental problem, but temperatures have been reached which are within millionths of a degree of absolute zero.

absolute zero

[′ab·sə‚lüt ′zir·ō]
(thermodynamics)
The temperature of -273.16°C, or -459.69°F, or 0 K, thought to be the temperature at which molecular motion vanishes and a body would have no heat energy.

absolute zero

the lowest temperature theoretically attainable, at which the particles constituting matter would be in the lowest energy states available; the zero of thermodynamic temperature; zero on the International Practical Scale of Temperature: equivalent to --273.15°C or --459.67°F

absolute zero

The temperature at which molecular activity is at a minimum. Absolute zero is -273.15 degrees Celsius and -459.67 degrees Fahrenheit. See Kelvin.
References in periodicals archive ?
In awarding Cirrus the Absolute Zero Defect Award, Delphi recognized Cirrus for its high quality of analog audio chipsets, which Cirrus supplies to Delphi for use in a wide range of automotive audio systems.
From the 1930s into the 1990s, Science News printed at least three dozen stories on the race to low temperatures, tracking new records as they fell from thousandths of a degree above absolute zero (millikelvins) to millionths (microkelvins) to billionths (nanokelvins).
It seemed to Kamerlingh Onnes that this lessening must continue all the way down to absolute zero, where it must disappear altogether.
Instead of lining up neatly (as in magnets and in an antiferromagnet, left, seen in superconductors), the spins move around uncomfortably thanks to quantum fluctuations that keep them twitching even at absolute zero.
1 degrees C above absolute zero - the coldest temperature theoretically possible in our Universe.
Debye and Giauque had suggested a way of approaching absolute zero more closely by using magnetic techniques (see 1925).
For example, the experiments had to be carried out at temperatures just a few degrees above absolute zero, at minus 273 degrees Celsius (minus 459 degrees Fahrenheit) -- the lowest possible temperature that can be achieved.
But it wasn't until 1995 that scientists made a Bose-Einstein condensate, using lasers to carefully cool rubidium-87 atoms down to temperatures less than a millionth of a degree above absolute zero.
Many materials become superconductors at temperatures approaching absolute zero, capable of carrying vast amounts of electrical current with no resistance.
However, the Mirror mathematician says for a temperature to drop by 100 per cent it would have to go down to absolute zero, which is -275.
Martini drinkers who shake can approach temperatures of absolute zero by packing a shaker with ice and working the thing back and forth until it develops a thick coating of frost on the outside.