# Absolute zero

In theory, absolute zero is the temperature at which the particles of matter (molecules and atoms) stop moving. In practice, it is impossible to arrive at absolute zero, because all particles move, even if it is just a small vibration. Some people have created temperatures very close to absolute zero: the record temperature was 100 pK (one hundred picokelvin, equal to 10−10 kelvin) above absolute zero.[1] Even getting close to absolute zero is difficult because anything that touches an object being cooled near absolute zero would give heat to the objects. Scientists use lasers to slow atoms when cooling objects to very low temperatures.[2]

The kelvin and Rankine temperature scales are defined so that absolute zero is 0 kelvin (K) or 0 degrees Rankine (°R). The Celsius and Fahrenheit scales are defined so that absolute zero is −273.15 °C or −459.67 °F.[3]

At this stage the pressure of the particles is zero. If we plot a graph to it, we can see that the temperature of the particles is zero. The temperature cannot go down any further. Also, the particles cannot move in "reverse" either because as the movement of particles is vibration, vibrating in reverse would be nothing but simply vibrating again. The closer the temperature of an object gets to absolute zero, the less resistive the material is to electricity therefore it will conduct electricity almost perfectly, with no measurable resistance.

The Third Law of Thermodynamics says that nothing can ever have a temperature of absolute zero.

The Second Law of Thermodynamics says that all engines that are powered by heat (like car engines and steam train engines) must release waste heat and can not be 100% efficient. This is because the efficiency (percent of energy the engine uses up that is actually used to do the engine's job) is 100%×(1-Toutside/Tinside), which only is 100% if the outside temperature is absolute zero which it cannot be. So, an engine cannot be 100% efficient, but you can make its efficiency closer to 100% by making the inside temperature hotter and/or the outside temperature colder.

## References

1. reported in the Helsinki University of Technology in 2000.
2. "Verging on absolute zero". cosmosmagazine.com. Retrieved February 2, 2011.
3. "Unit of thermodynamic temperature (kelvin)". SI Brochure, 8th edition. Bureau International des Poids et Mesures. 1967. pp. Section 2.1.1.5. Retrieved October 24, 2008.