The zero point on the absolute temperature scale, -273.15°C or 0 K, theoretically, the temperature at which molecular motion ceases. The concept of an absolute zero temperature was first deduced from experiments with gases. When a fixed volume of gas is cooled, its pressure decreases with its temperature. Absolute zero physically possesses quantum mechanical zero-point energy. Absolute zero is equivalent to 0 °R on the Rankine scale and -459.67° on the Fahrenheit scale. Absolute zero can't be reached through experiments, although it can be closely approached. According to the third law of thermodynamics the entropy of a pure crystal is zero at absolute zero temperature.
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