Shake (unit)

Source: Wikipedia, the free encyclopedia.

A shake is an informal

metric unit of time equal to 10 nanoseconds, or 10−8 seconds.[1] It was originally coined for use in nuclear physics
, helping to conveniently express the timing of various events in a nuclear reaction.

Etymology

Like many informal units having to do with nuclear physics, it arose from

idiomatic expression "in two shakes of a lamb's tail"
, which indicates a very short time interval.

Lexicographers have discussed at length that the oldest documented usage of the phrase "two shakes of a lamb's tail" found first (so far) in the works of Richard Barham c. 1800;[2] however, the phrase almost certainly was part of vernacular language long before then.[3]

Nuclear physics

For nuclear-bomb designers, the term was a convenient name for the short interval, rounded to 10 nanoseconds, which was frequently seen in their measurements and calculations: The typical time required for one step in a chain reaction (i.e. the typical time for each neutron to cause a fission event, which releases more neutrons) is of the order of 1 shake, and a chain reaction is typically complete by 50 to 100 shakes.[4]

Integrated circuitry

Shakes are also applicable to circuits. Since signal progression in

IC chips is very rapid, on the order of nanoseconds, a shake is a good measure of how quickly a signal can progress through an integrated circuit
(IC).

See also

  • ‘Barn’ a companion unit of cross-sectional area created by the same people, for the same general purposes, at the same time (the measured value of nuclear-reaction cross section was larger than expected, hence deemed “as big as a barn”).
  • List of humorous units of measurement

References

  1. ^ Rowlett, Russ (ed.). "[Letter] S". How many? A dictionary of units of measurement. Chapel Hill, NC: University of North Carolina. Archived from the original on 2007-06-29.
  2. Barham, R.H. (1840). The Ingoldsby Legends
    .
  3. ^ "Two shakes of a lamb's tail". idiomation.wordpress.com. Archived from the original on 2 May 2012. Retrieved 28 June 2012.
  4. ^ Cochran, Thomas B. (10 April 1994). "Hydronuclear Testing or a Comprehensive Test Ban?" (PDF). Washington, DC: Natural Resources Defense Council. p. 4. Archived from the original (PDF) on 2008-12-06. The period, 10−8 seconds, turns out to be a convenient unit of time, and it was defined during the Manhattan Project as one 'shake'.
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