b'thermometers. His value of -273 was derived from 0.00366, which was the accepted expansion coeffi-cient of gas per degree Celsius rela- This is the third in a series of articles about the metric system.tive to the ice point. The inverse ofCTE-MAY 2020-CGTech-PRINT.pdf 1 3/26/2020 9:35:41 AM-0.00366 is -10.00366 = -273.22Lord Kelvin (1824-1907) was anheat, the mathematical analysis of C. This value is very close to the trueIrish Scottish mathematician andelectricity and magnetism, ideas for value of -273.15 C. physicist. His contributions to sci- the electromagnetic theory of light On Oct. 16, 1967, the 13th CGPMence included the absolute temper- and fundamental work in hydrody-meeting decided that: ature scale, the dynamic theory ofnamics.CTE Theunitofthermodynamic temperature would be denoted by the name kelvin and the symbol K.The same name and symbol would be used to express a tem-perature interval.A temperature interval also could be expressed in degrees Celsius.Instead of degrees, temperatures on the Kelvin scale are called kel-vins. Absolute zero, or 0 K, is the coldest temperature theoretically possible, but it cannot be reached by artificial or natural means. At ab-solute zero, all molecular motion does not cease, yet it lacks sufficient energy for transference to other sys-tems. Therefore, it is correct to say molecular energy is minimal at 0 K.CThe following are some interest-Ming facts: YHelium melts at 0.95 K (-272.2 C or -458 F). CMMYThe average temperature of the universe is approximately 2.73 K CY(-270.4 C or -454.8 F).CMYThe mean surface temperature Kon Earth is 287 K (13.9 C or 56.9 F).The surface temperature of the sun is 5,778 K (5,504.9 C or 9,940.7 F).about the author Edmund Isakov, Ph.D., is a consultant, a CTE contributor and the author of International System of Units (SI): How the World Measures Almost Everything, and the People Who Made It Possible, which is available at https://books.industrialpress.com. Contact him at 561-369-4063 or [email protected]/cteguide.com25MetricMatters-2.indd 25 4/16/20 12:27 PM'