Temperature depends on the energy landscape
(Image: Ludwig Maximilian University of Munich)

Cloud of atoms goes beyond absolute zero

19:00 03 January 2013 by Jacob Aron

Nothing is colder than absolute zero, so it seems nonsensical to talk about negative temperature – but now there is a substance that must have just that. The revelation could shake up our ideas about temperature and help us understand strange entities such as dark energy, as well as the interactions of subatomic particles.

Although we’re used to talking about negative temperatures, such as ?10°C, all temperatures on an ordinary thermometer are actually positive when measured in kelvin, the scientific temperature scale that starts at absolute zero (?273.15°C).

On the kelvin scale, temperature is determined by the kinetic energy of particles, so a gas of slow particles is colder than a gas of fast-moving ones. Absolute zero corresponds to the point at which particles stop moving completely, which is why nothing can be colder.

That does not tell the whole story, however. Temperature also depends on the way in which the particle energies are distributed within the gas, which determines their entropy, or disorder.

Read more: Cloud of atoms goes beyond absolute zero – physics-math – 03 January 2013 – New Scientist.

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