A shake is an informal
metric unit
The metric system is a system of measurement that succeeded the decimalised system based on the metre that had been introduced in France in the 1790s. The historical development of these systems culminated in the definition of the Internati ...
of
time
Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to ...
equal to 10
nanosecond
A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, of a second, or 10 seconds.
The term combines the SI prefix ''nano-'' indicating a 1 billionth submultiple of an SI unit ( ...
s, or 10
−8 second
The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds ...
s. It was originally coined for use in
nuclear physics
Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter.
Nuclear physics should not be confused with atomic physics, which studies the ...
, helping to conveniently express the timing of various events in a nuclear reaction, especially neutron reactions.
Etymology
Like many informal units having to do with nuclear physics, it arose from
top secret
Classified information is material that a government body deems to be sensitive information that must be protected. Access is restricted by law or regulation to particular groups of people with the necessary security clearance and need to know, ...
operations of the
Manhattan Project
The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project w ...
during
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
. The word "shake" was taken from the
idiomatic expression
An idiom is a phrase or expression that typically presents a figurative, non-literal meaning attached to the phrase; but some phrases become figurative idioms while retaining the literal meaning of the phrase. Categorized as formulaic language, ...
"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
Richard Harris Barham (6 December 1788 – 17 June 1845) was an English cleric of the Church of England, a novelist and a humorous poet. He was known generally by his pseudonym Thomas Ingoldsby and as the author of ''The Ingoldsby Legends''.
...
; however, the phrase almost certainly was part of vernacular language long before then.
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.
Integrated circuitry
Shakes are also applicable to circuits. Since signal progression in
IC chip
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny M ...
s is very rapid, on the order of nanoseconds, a shake is good measure of how quickly a signal can progress through an
integrated circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
(IC).
See also
* ‘
Barn
A barn is an agricultural building usually on farms and used for various purposes. In North America, a barn refers to structures that house livestock, including cattle and horses, as well as equipment and fodder, and often grain.Allen G. ...
’ 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
Many people have made use of, or invented, units of measurement intended primarily for their humor
Humour (Commonwealth English) or humor (American English) is the tendency of experiences to provoke laughter and provide amusement. The ...
References
{{Time measurement and standards
Units of time