Absolute Zero (Video)

What is cold? How do you achieve it, and how cold can it get?

Absolute zero is the theoretical temperature at which entropy would reach its minimum value. The laws of thermodynamics state that absolute zero cannot be reached because this would require a thermodynamic system to be fully removed from the rest of the universe.

A system at absolute zero would still possess quantum mechanical zero-point energy. While molecular motion would not cease entirely at absolute zero, the system would not have enough energy for transference to other systems. It is therefore correct to say that molecular kinetic energy is minimal at absolute zero.

By international agreement, absolute zero is defined as 0K on the Kelvin scale and as −273.15°C on the Celsius scale. This equates to −459.67°F on the Fahrenheit scale. Scientists have achieved temperatures very close to absolute zero, where matter exhibits quantum effects such as superconductivity and superfluidity.