Absolute Zero

Physics Theoretical lowest temperature that can be attained by matter. Below this temperature, all molecular activity would cease.

It is precisely 0 Kelvin, -273,15º Celsius or -459,67º Fahrenheit.

Origin
Robert Boyle was one of the first physicists that studied the possibility of an absolute minimal temperature. Another physicist, Guillaume Amontons, raised the question whether there is a limit to the degree of cold possible and where the zero should be placed.

Amontons achieved a close approximation to the modern value of -273,15º Celsius by using an air thermometer. This calculation was later improved by Johann Heinrich Lambert, Swiss physician and mathematician. But these values were not universally accepted and scientists such as Pierre-Simon Laplace and Antoine Lavoisier rejected them.

In 1848, Lord Kelvin (after whom the unit of temperature is named) approached this question from a different point of view and devised a scale based on the fundamental laws of thermodynamics. This scale of absolute temperature was independent of the properties of any particular substance. Zero was placed at -273.15 °C, at almost precisely the same point as the zero of the air thermometer.

Comment
It is not possible to achieve absolute zero artificially, although temperatures close to zero can be reached through the use of cryocoolers or by using the laser-cooling technique.

The matter that achieves temperatures close to absolute zero exhibits quantum effects such as superconductivity (no electrical resistance) and superfluidity (no viscosity). Scientists have been able to create environments really close to absolute zero, which are used to study matter.