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Word of the Week (133): SVEDBERG (probability 25579), by David Sutton

A SVEDBERG is a unit of time used to measure sedimentation velocity; it takes its name from the Swedish chemist, Theo Svedberg.

This is just one of the many somewhat esoteric units that figure in the scientific armoury along with the more familiar elements of the metric system. Most of them are named in honour of a particular scientist. The DALTON (from Sir Francis Dalton) is a unit of atomic mass, also known as the AMU. The ERLANG (from AK Erlang, Danish mathematician) is a unit of traffic intensity in a telephone system. The MORGAN (from Thomas Hunt Morgan, US biologist) is a unit of distance between genes on a chromosome. The RUTHERFORD (from the physicist Ernest Rutherford) is a unit of radioactive decay equal to 1 million disintegrations per second. The SIEMENS (from Ernst Werner von Siemens, German engineer) is a unit of electrical conductance equivalent to one ampere per volt. The SIEVERT (from RM Sievert, Swedish physicist) is the SI unit of radiation dose. The TROLAND (from L. T. Troland, US physicist and psychologist) is a unit of measurement of retinal response to light. The MAXWELL (from the physicist James Clerk Maxwell) is a unit of magnetic flux. And I probably don't need to tell you about the JANSKY, the HERTZ, the OERSTED, the NEWTON and the FARADAY.

Finally a couple not named for scientists. The CANDELA is a unit of luminous intensity; I don't know how this relates to the STILB, the unit of intrinsic brightness, or to the LAMBERT, a unit of brightness, the brightness of surface radiating one lumen per square centimetre. And the OSMOL or OSMOLE is a unit of osmotic pressure.

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