Cold
Cold is the presence of low temperature, especially in the atmosphere. In common usage, cold is often a subjective perception. A lower bound to temperature is absolute zero, defined as 0.00K on the Kelvin scale, an absolute thermodynamic temperature scale. This corresponds to on the Celsius scale, on the Fahrenheit scale, and on the Rankine scale. Since temperature relates to the thermal energy held by an object or a sample of matter, which is the kinetic energy of the random motion of the particle constituents of matter, an object will have less thermal energy when it is colder and more when it is hotter. If it were possible to cool a system to absolute zero, all motion of the particles in a sample of matter would cease and they would be at complete rest in the classical sense. The object could be described as having zero thermal energy. Microscopically in the description of quantum mechanics, however, matter still has zero-point energy even at absolute zero, because of the uncertainty principle. Cooling Cooling refers to the process of becoming cold, or lowering in temperature. This could be accomplished by removing heat from a system, or exposing the system to an environment with a lower temperature. Coolants are fluids used to cool objects, prevent freezing and prevent erosion in machines. Air cooling is the process of cooling an object by exposing it to air. This will only work if the air is at a lower temperature than the object, and the process can be enhanced by increasing the surface area, increasing the coolant flow rate, or decreasing the mass of the object. Another common method of cooling is exposing an object to ice, dry ice, or liquid nitrogen. This works by conduction; the heat is transferred from the relatively warm object to the relatively cold coolant. Laser cooling and magnetic evaporative cooling are techniques used to reach very low temperatures. History Early history In ancient times, ice was not adopted for food preservation but used to cool wine which the Romans had also done. According to Pliny, Emperor Nero invented the ice bucket to chill wines instead of adding it to wine to make it cold as it would dilute it. Some time around 1700 BC Zimri-Lim, king of Mari Kingdom in northwest Iraq had created an "icehouse" called bit shurpin at a location close to his capital city on the banks of the Euphrates. In the 7th century BC the Chinese had used icehouses to preserve vegetables and fruits. During the Tang dynastic rule in China (618 -907 AD) a document refers to the practice of using ice that was in vogue during the Eastern Chou Dynasty (770 -256 BC) by 94 workmen employed for "Ice-Service" to freeze everything from wine to dead bodies. Shachtman says that in the 4th century AD, the brother of the Japanese emperor Nintoku gave him a gift of ice from a mountain. The Emperor was so happy with the gift that he named the first