The temperature at which a system would undergo a reversible isothermal process without transfer of heat and at which the volume of an ideal gas would become zero, calculated to be -273.16°C (-459.7°F) or zero degree Kelvin.
Absolute zero is the lowest possible temperature where nothing could be colder and no heat energy remains in a substance.
Absolute zero is the point at which the fundamental particles of nature have minimal vibrational motion, retaining only quantum mechanical, zero-point energy-induced particle motion. By international agreement, absolute zero is defined as precisely; 0 K on the Kelvin scale, which is a thermodynamic (absolute) temperature scale; and –273.15 degrees Celsius on the Celsius scale.
Absolute zero is also precisely equivalent to; 0 degrees R on the Rankine scale (also a thermodynamic temperature scale); and –459.67 degrees F on the Fahrenheit scale. While scientists can not fully achieve a state of “zero” heat energy in a substance, they have made great advancements in achieving temperatures ever closer to absolute zero (where matter exhibits odd quantum effects).
In 1994, the NIST achieved a record cold temperature of 700 nK (billionths of a kelvin).
In 2003, researchers at MIT eclipsed this with a new record of 450 pK (0.45 nK).