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Absolute zero is the practical minimum of [[Temperature|temperature]], defined as 0 [[Kelvin]] on the absolute temperature scale (the zero on the Kelvin scale has had to adjust, slightly, as measurements of absolute zero are refined).  This corresponds to -273.15 degrees [[Celsius]] and -459.67 degrees [[Fahrenheit]]. At absolute zero, all thermal motion (i.e. the movement of [[Molecule|molecules]] in a [[States of matter#gaseous|gas]], [[Atom|atoms]] in a [[Crystal|crystal]]) ceases.

'''Absolute zero''' is the minimum [[temperature]], defined as 0 [[Kelvin]] on the [[absolute temperature scale]]s (the zero on the Kelvin scale has had to adjust, slightly, as measurements of absolute zero are refined).  This corresponds to -273.15 degrees [[Celsius]] and -459.67 degrees [[Fahrenheit]]. At absolute zero, all motion (i.e. the movement of [[molecules]] in a [[gas]], [[atom]]s in a [[crystal]]) would cease.

 

No place in our universe is at absolute zero, but there are places that get close. [[Outer space|Space]] is approximately 2.73 kelvin. This is not because heat from [[star]]s in the universe keep the temperature up, but because of cosmic background radiation. The [[COBE|Cosmic Background Explorer]] (CBE) measured this value. The [[Big Bang theory]] predicts a leftover background radiation and that such radiation would have a relative uniformity, which is reinforced by the evidence presented by the CBE's observations.  However, these observations cannot account for the [[horizon problem]].

 

 

 

[http://www.ph.rhul.ac.uk/schools/ZeroT/Absolute.html http://www.ph.rhul.ac.uk/schools/ZeroT/Absolute.html]