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1742 — Anders Celsius proposed a temperature scale in which 100 represented the temperature of melting ice and 0 represented the boiling point of water at 25 inches and 3 lines of barometric mercury height. [8] This corresponds to 751.16 mm, [9] so that on the present-day definition, this boiling point is 99.67 degrees Celsius. [10]
A medical/clinical thermometer showing the temperature of 38.7 °C (101.7 °F) Temperature measurement (also known as thermometry) describes the process of measuring a current temperature for immediate or later evaluation. Datasets consisting of repeated standardized measurements can be used to assess temperature trends.
Other fixed points used in the past are the body temperature (of a healthy adult male) which was originally used by Fahrenheit as his upper fixed point (96 °F (35.6 °C) to be a number divisible by 12) and the lowest temperature given by a mixture of salt and ice, which was originally the definition of 0 °F (−17.8 °C). [37]
1850 – Rankine uses his vortex theory to establish accurate relationships between the temperature, pressure, and density of gases, and expressions for the latent heat of evaporation of a liquid; he accurately predicts the surprising fact that the apparent specific heat of saturated steam will be negative
The history of thermodynamics is a fundamental strand in the history of physics, the history of chemistry, and the history of science in general. Due to the relevance of thermodynamics in much of science and technology, its history is finely woven with the developments of classical mechanics, quantum mechanics, magnetism, and chemical kinetics, to more distant applied fields such as ...
When two systems with different temperatures are put into purely thermal connection, heat will flow from the higher temperature system to the lower temperature one; thermodynamically this is understood by the second law of thermodynamics: The total change in entropy following a transfer of energy from system 1 to system 2 is:
This definition also precisely related the Celsius scale to the Kelvin scale, which defines the SI base unit of thermodynamic temperature with symbol K. Absolute zero, the lowest temperature possible, is defined as being exactly 0 K and −273.15 °C. Until 19 May 2019, the temperature of the triple point of water was defined as exactly 273.16 ...
Newton then determined the "degrees of heat" of these samples based on the solidification times, and tied this scale to the linseed one by measuring the melting point of tin in both systems. This second system of measurement led Newton to derive his law of convective heat transfer, also known as Newton's law of cooling.