Temperature is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy, present in all matter, which is the source of the occurrence of heat, a flow of energy, when a body is in contact with another that is colder.
Temperature is by far the most measured parameter. It impacts the physical, chemical and biological world in numerous ways. Yet, a full appreciation of the complexities of temperature and its measurement has been relatively slow to develop.
Intuitively, people have known about temperature for a long time: fire is hot and snow is cold. Greater knowledge was gained as man attempted to work with metals through the bronze and iron ages. Some of the technological processes required a degree of control over temperature, but to control temperature you need to be able to measure what you are controlling.

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