Absolute Zero
. Absolute Zero, lowest temperature theoretically possible, characterized by complete absence of heat . Absolute zero is approximately -273.16° C (-459.69° F), or zero degree on the Kelvin scale (0 K). The concept of absolute zero temperature was first deduced from experiments with gases; when a fixed volume of gas is cooled, its pressure decreases with its temperature. Although this experiment cannot be conducted below the liquefaction point of the gas, a plot of the experimental values of pressure versus temperature can be extrapolated to zero pressure. The temperature at which the pressure would be zero is the absolute zero temperature. This experimental concept of a gas-thermometer temperature scale and of absolute zero was subsequently shown to be consistent with the theoretical definitions of absolute zero. Absolute zero cannot be reached experimentally, although it can be closely approached. Special procedures are needed to reach very low, or cryogenic , temperatures. Liquid he