Temperature is a physical quantity that measures the degree of hotness or coldness of a substance, which, on a microscopic level, represents the intensity of the thermal motion of its molecules. At high temperatures, the theoretical upper limit is when the heaviest microscopic particles move at the speed of light, known as the Planck Temperature, with a value reaching 1032 K. On the other end of the spectrum lies the ultimate low temperature, termed “absolute zero”, corresponding to 0 K. When converted to the commonly used temperature unit, this is equivalent to − 273.15 °C, a theoretical limit that cannot be physically attained.