Absolute zero is the coldest possible temperature, at which no heat is left in a substance and its particles display no motion whatsoever. Absolute zero is equal to 0 K on the Kelvin scale, which is equivalent to negative 273.15 degrees Celsius or negative 459.67 degrees Fahrenheit.
The temperature of a substance is determined by the amount of movement its particles exhibit. Particles move more quickly and over a greater area at higher temperatures than at lower temperatures. As the temperature approaches absolute zero, particle movement eventually slows to the point that it becomes just a vibration.
As of 2014, scientists have not yet been able to bring a substance all of the way down to absolute zero, but they have come close. In 2003, researchers at MIT were able to achieve a record low temperature of 0.45 billionths of a Kelvin using laser-cooling methods. Substances near absolute zero begin to display unusual properties such as superconductivity or superfluidity.
Absolute zero is the basis for the Kelvin scale, which defines 0 K as absolute zero. Created in 1848 by William Thomson, also known as Lord Kelvin, this temperature scale remains the predominant scale used in thermodynamic chemistry and physics. It is a convenient scale to use when dealing with very cold temperatures, since the absence of negative values simplifies calculations.