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. Enthalpy, the total heat content of a particular system, is zero. Entropy, the disorderliness or change in enthalpy of a system, is zero or even nothing.
Fermi energy is the highest energy level that electrons can occupy in a material at absolute zero. In quantum mechanics, it is the energy difference between the highest and lowest occupied single-particle states in a quantum system of non-interacting fermions.
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
Current tech[]
- Laser Cooling involves using lasers to slow down the motion of atoms, effectively reducing their kinetic energy and thus their temperature.
- Evaporative Cooling works by selectively removing the most energetic atoms from a system, leaving behind the cooler ones.
- Dilution Refrigeration uses the properties of helium isotopes to achieve very low temperatures, often down to the millikelvin range.
- Nuclear Adiabatic Demagnetization uses a magnetic field to align the nuclear spins in a material, and then the field is slowly reduced, leading to a decrease in temperature.
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.