Are temps. below 0 kelvin possible?

Question

First please read the following site:
http://www2.corepower.com:8080/~relfaq/neg_temperature.html

Support all answers with documented evidence please.

Answer 1

This is kind of a question of semantics. What do you mean by 'temperature'?

You can't cool a system to (or past) zero Kelvin -- the MIT experiments (and other laser-cooling experiments) are all trying to cool matter as much as possible, that is, minimize its kinetic energy, which clearly can't be negative.

However, the statistical definition of temperature is
T=dE/dS
so you might imagine a system in which energy decreases with increasing entropy, producing 'negative' temperature. This is what the author of your link is explaining, a two-state system that lowers its energy when entropy increases. However, that system won't be "colder" than the supercooling experiments.

Here is the long explanation:
http://www.maxwellian.demon.co.uk/art/esa/negkelvin/negkelvin.html

Answer 2

0 kelvin (absolute zero) = -273 degrees celsius. You can't go below 0 degrees kelvin because that's the theoretical poin t wehre matter has *no* movement what so ever (temperature being hte measurement of how much particles in a substance move.) i say theoretical because it's never been reached, and *technically* it would be impossible to measure accurately if we *did* reach it.

Answer 3

Absolute zero is the lowest possible temperature, occurring when no heat energy remains in a substance. Absolute zero is the point at which particles have a minimum energy, determined by quantum mechanical effects, which is called the zero-point energy. By international agreement, absolute zero is defined as precisely 0 K on the Kelvin scale, which is a thermodynamic (absolute) temperature scale, and -273.15°C on the Celsius scale. Absolute zero is also precisely equivalent to 0 °R on the Rankine scale (also a thermodynamic temperature scale), and –459.67 °F on the Fahrenheit scale.

Space is the coldest place in the universe and its only 3 degrees hotter than "Absolute zero"

To establish an instrument to measure a range of temperatures, in 1593 Galileo Galilei invented a rudimentary water thermometer. One of the first to discuss the possibility of an “absolute cold” on such a scale was Robert Boyle who in his 1665 New Experiments and Observations touching Cold, stated the dispute which is the primum frigidum is very well known among naturalists, some contending for the earth, others for water, others for the air, and some of the moderns for nitre, but all seeming to agree that:

“ There is some body or other that is of its own nature supremely cold and by participation of which all other bodies obtain that quality. ”

The question whether there is a limit to the degree of cold possible, and, if so, where the zero must be placed, was first attacked by the French physicist Guillaume Amontons, in 1702-1703, in connection with his improvements in the air thermometer. In his instrument temperatures were indicated by the height at which a column of mercury was sustained by a certain mass of air, the volume or " spring " of which of course varied with the heat to which it was exposed. Amontons therefore argued that the zero of his thermometer would be that temperature at which the spring of the air in it was reduced to nothing. On the scale he used the boiling-point of water was marked at +73 and the melting-point of ice at 511, so that the zero of his scale was equivalent to about -240 on the centigrade scale.

This remarkably close approximation to the modern value of - 273° for the zero of the air-thermometer was further improved on by Johann Heinrich Lambert (Pyrometrie, 1779), who gave the value -270 and observed that this temperature might be regarded as absolute cold. Values of this order for the absolute zero were not, however, universally accepted about this period. Laplace and Lavoisier, for instance, in their treatise on heat (1780), arrived at values ranging from 1500 to 3000 below the freezing-point of water, and thought that in any case it must be at least 600 below, while John Dalton in his Chemical Philosophy gave ten calculations of this value, and finally adopted - 3000° C. as the natural zero of temperature. After J. P. Joule had determined the mechanical equivalent of heat, Lord Kelvin approached the question from an entirely different point of view, and in 1848 devised a scale of absolute temperature which was independent of the properties of any particular substance and was based solely on the fundamental laws of thermodynamics. It followed from the principles on which this scale was constructed that its zero was placed at -273°, at almost precisely the same point as the zero of the air-thermometer.

While scientists cannot fully achieve a state of “zero” heat energy in a substance, they have made great advancements in achieving temperatures ever closer to absolute zero (where matter exhibits odd quantum effects). In 1994, the NIST achieved a record cold temperature of 700 nK (billionths of a kelvin). In 2003, researchers at MIT eclipsed this with a new record of 450 pK (0.45 nK).

Answer 4

No, zero Kelvin is absolute zero and it's the coldest temperature physically possible. Temperature is a measure of the average kinetic energy of molecules, and at absolute zero the molecules come to a complete halt. You can't go slower than zero; you can't get colder than zero.

Answer 5

No the closest we've ever gotten is one nanoKelvin at MIT

http://www.eurekalert.org/pub_releases/2003-09/miot-mta090903.php