Absolute zero

Absolute aught is the abstract temperature at which anarchy alcove its minimum value. The laws of thermodynamics accompaniment that complete aught cannot be accomplished application alone thermodynamic means. A arrangement at complete aught still possesses breakthrough automated zero-point energy, the activity of its arena state. The active

activity of the arena accompaniment cannot be removed. However, in the classical estimation it is aught and the thermal activity of amount vanishes

.

The aught point of any thermodynamic temperature scale, such as Kelvin or Rankine, is set at complete zero. By all-embracing agreement, complete aught is authentic as 0K on the Kelvin calibration and as −273.15° on the Celsius scale.12 This equates to −459.67° on the Fahrenheit scale3 and 0 R on the Rankine scale.2 Scientists accept accomplished temperatures actual abutting to complete zero, area amount exhibits breakthrough furnishings such as superconductivity and superfluidity.

History

One of the aboriginal to altercate the achievability of an complete basal temperature was Robert Boyle. His 1665 New Experiments and Observations affecting Cold, articulate the altercation accepted as the primum frigidum. The abstraction was able-bodied accepted amid naturalists of the time. Some arguable an complete minimum temperature occurred aural apple (as one of the four alleged 'elements'), others aural water, others air, and some added afresh aural nitre.4 But all of them seemed to accede that, "There is some anatomy or added that is of its own attributes chiefly algid and by accord of which all added bodies access that quality."5

Lord Kelvin's work

After J.P. Joule had bent the automated agnate of heat, Lord Kelvin approached the catechism from an absolutely altered point of view, and in 1848 devised a calibration of complete temperature which was absolute of the backdrop of any accurate actuality and was based alone on the axiological laws of thermodynamics. It followed from the attempt on which this calibration was complete that its aught was placed at −273.15 °C, at about absolutely the aforementioned point as the aught of the air-thermometer.7

Relation with Bose–Einstein condensates

A Bose–Einstein condensate (BEC) is a accompaniment of amount of a adulterate gas of abominably interacting bosons bedfast in an alien abeyant and cooled to temperatures actual abreast to complete zero. Under such conditions, a ample atom of the bosons absorb the everyman breakthrough accompaniment of the alien potential, at which point breakthrough furnishings become credible on a arresting scale.

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This accompaniment of amount was aboriginal predicted by Satyendra Nath Bose and Albert Einstein in 1924–25. Bose aboriginal beatific a cardboard to Einstein on the breakthrough statistics of ablaze quanta (now alleged photons). Einstein was impressed, translated the cardboard himself from English to German and submitted it for Bose to the Zeitschrift für Physik which appear it. Einstein again continued Bose's account to actual particles (or matter) in two added papers.16



Seventy years later, the aboriginal aerial condensate was produced by Eric Cornell and Carl Wieman in 1995 at the University of Colorado at Boulder NIST-JILA lab, application a gas of rubidium atoms cooled to 170 nanokelvin (nK)17 (1.7×10−7 K).18



A almanac algid temperature of 450 ±80 pK in a Bose–Einstein condensate (BEC) of sodium atoms was accomplished in 2003 by advisers at MIT.19 It's noteworthy that this record's aiguille emittance black-body amicableness of 6,400 kilometers is almost the ambit of Earth.

Absolute temperature scales

Absolute, or thermodynamic, temperature is commonly abstinent in kelvins (Celsius-scaled increments) and in the Rankine calibration (Fahrenheit-scaled increments) with accretion rarity. Complete temperature altitude is abnormally bent by a multiplicative connected which specifies the admeasurement of the "degree", so the ratios of two complete temperatures, T2/T1, are the aforementioned in all scales. The best cellophane analogue of this accepted comes from the Maxwell–Boltzmann distribution. It can additionally be begin in Fermi–Dirac statistics (for particles of half-integer spin) and Bose–Einstein statistics (for particles of accumulation spin). All of these ascertain the about numbers of particles in a arrangement as abbreviating exponential functions of activity (at the atom level) over kT, with k apery the Boltzmann connected and T apery the temperature empiric at the arresting level.1

Negative temperatures

Temperatures that are bidding as abrogating numbers on the accustomed Celsius or Fahrenheit scales are artlessly colder than the aught credibility of those scales. Certain systems can accomplish absolutely abrogating temperatures; that is, their thermodynamic temperature (expressed in kelvin) can be of a abrogating quantity. A arrangement with a absolutely abrogating temperature is not colder than complete zero. Rather, a arrangement with a abrogating temperature is hotter than any arrangement with a absolute temperature in the faculty that if a negative-temperature arrangement and a positive-temperature arrangement appear in contact, calefaction will breeze from the negative- to the positive-temperature system.20

Most accustomed systems cannot accomplish abrogating temperatures because abacus activity consistently increases their entropy. However, some systems accept a best bulk of activity that they can hold, and as they access that best activity their anarchy absolutely begins to decrease. Because temperature is authentic by the accord amid activity and entropy, such a system's temperature becomes negative, alike admitting activity is actuality added.20 As a result, the Boltzmann

agency for states of systems at abrogating temperature increases rather than decreases with accretion accompaniment energy. Therefore no complete system, i.e. including the electromagnetic modes, can accept abrogating temperatures, back there is no accomplished activity state, so that the sum of the probabilities of the states would bend for abrogating temperatures. However, for quasi-equilibrium systems (e.g. spins out of calm with the electromagnetic field) this altercation does not apply, and abrogating able temperatures are attainable.