Absolute zero: Difference between revisions

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'''Absolute zero''' is the point at which no further [[heat]] can be removed from an object. Commonly used temperature scales, such as [[Celsius (unit)|Celsius]] and [[Fahrenheit (unit)|Fahrenheit]], are based around every-day experience and thus have zero points vastly above this theoretical lowest possible temperature.  Absolute zero corresponds to −273.15 °C on the Celsius temperature scale and to −459.67 °F on the Fahrenheit scale. It is expressed as O ° in specialist scales such as the [[Kelvin (unit)|Kelvin]]. Achieving absolute zero is generally regarded as an impossibility under real world conditions.
'''Absolute zero''' is the point at which no further [[heat]] can be removed from an object. In classical terms, at zero temperature all molecules are standing still, there is no translation, rotation or vibration. In [[quantum mechanics|quantum mechanical]] terms all possible motions are in their lowest-energy (ground) state.
 
Commonly used temperature scales, such as [[Celsius (unit)|Celsius]] and [[Fahrenheit (unit)|Fahrenheit]], are based around everyday experience and thus have zero points vastly above this theoretical lowest possible temperature.  Absolute zero corresponds to −273.15 °C on the Celsius temperature scale and to −459.67 °F on the Fahrenheit scale. It is expressed as in specialist scales such as the [[Kelvin (unit)|Kelvin]] and the [[Rankine (unit)|Rankine]] scales. The Kelvin scale is identical to the Celsius scale shifted downward by 273.15. That is, a temperature difference of 1 K is by definition identical to a temperature difference of 1 °C. Similarly, the  Rankine scale is identical to the Fahrenheit scale shifted downward by 459.67 and a temperature difference of 1 °R is by definition identical to a temperature difference of 1 °F.
 
The [[third law of thermodynamics]] asserts that it is impossible to reduce the temperature of any system to exactly zero temperature. However, it is possible in the laboratory to reduce the speed of gas molecules to such an extent that their [[kinetic energy]] corresponds to a temperature of less than a nanokelvin (10<sup>&minus;9</sup> K) above the absolute zero. Although the absolute zero is theoretically unattainable, a nanokelvin temperature is very close to it.

Latest revision as of 20:01, 18 September 2021

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Absolute zero is the point at which no further heat can be removed from an object. In classical terms, at zero temperature all molecules are standing still, there is no translation, rotation or vibration. In quantum mechanical terms all possible motions are in their lowest-energy (ground) state.

Commonly used temperature scales, such as Celsius and Fahrenheit, are based around everyday experience and thus have zero points vastly above this theoretical lowest possible temperature. Absolute zero corresponds to −273.15 °C on the Celsius temperature scale and to −459.67 °F on the Fahrenheit scale. It is expressed as 0° in specialist scales such as the Kelvin and the Rankine scales. The Kelvin scale is identical to the Celsius scale shifted downward by 273.15. That is, a temperature difference of 1 K is by definition identical to a temperature difference of 1 °C. Similarly, the Rankine scale is identical to the Fahrenheit scale shifted downward by 459.67 and a temperature difference of 1 °R is by definition identical to a temperature difference of 1 °F.

The third law of thermodynamics asserts that it is impossible to reduce the temperature of any system to exactly zero temperature. However, it is possible in the laboratory to reduce the speed of gas molecules to such an extent that their kinetic energy corresponds to a temperature of less than a nanokelvin (10−9 K) above the absolute zero. Although the absolute zero is theoretically unattainable, a nanokelvin temperature is very close to it.