Absolute zero

Absolute zero is the lowest temperature possible, at zero kelvins (−273.15° celcius), where the fundamental particles of nature have only zero-point energy particle motion via quantum fluctuations.

At temperatures close to absolute zero, matter exhibits quantum effects such as:

 * Bose–Einstein condensate - the fifth state of matter
 * superconductivity - where electrical resistance vanishes and magnetic flux fields are expelled from a material - used for example in powerful electromagnets and vactrains
 * superfluidity - where a fluid has zero viscosity and therefore flows without any loss of kinetic energy - and can even flow uphill

Cryogenics is the production and behaviour of materials at very low temperatures, compared to cryonics which is the cryopreserving of humans and animals with the intention of future revival. Cryonics is used by the occupants of 'world ships' travelling at sub-light speed where long journeys would outlive them and the technology for faster-than-light has not yet been invented.

The old laws of thermodynamics indicate that absolute zero cannot be reached. Once the quantum dimension is understood, technology achieving absolute zero is invented. Absolute zero is used in some perpetual motion devices.