Absolute zero – or 0 Kelvin – is the theoretical coldest temperature it is possible to achieve, a point where atoms stop moving and have no energy.
It is the lowest limit of the thermodynamic temperature scale, a state at which the enthalpy and entropy of a cooled gas reach their minimum value.
Fundamental particles of nature have minimum motion and vibration at this temperature point, and only retain quantum mechanical, zero-point energy-induced particle motion – creating for unusual behaviours and conditions.
It is measured in Kelvin, with absolute zero being 0 Kelvin, or −273.15 degrees on the Celsius scale and −459.67 degrees on the Fahrenheit scale.
So the boiling point of water at sea level on Earth is 373.2 Kelvin (K).
Scientists have achieved temperatures close to absolute zero, including through the creation of unusual states of matter such as Bose–Einstein condensate, superconductivity and superfluidity.