Absolute Zero
The theoretical lower limit of thermodynamic temperature, defined as 0 Kelvin (-273.15°C or -459.67°F).
Governing formula
0 K = -273.15°C
SI unit
K
In depth
At absolute zero, classical particle motion ceases completely, and the system reaches its minimum possible quantum ground state energy (zero-point energy). According to the Third Law of Thermodynamics, absolute zero cannot be reached in a finite number of steps.
Examples in the real world
Cryogenic laboratories using laser cooling and magnetic trapping have cooled gas clouds to within a few hundred picokelvins above absolute zero.