What is SECOND?

1 1/60 of a minute of time, or 1/86 400 of the mean solar day; once defined as the fraction 1/ 31 556925-9747 of the tropical year for the epoch 1900 January 0 at 12 hr ET. Since 1965 defined, in terms of the resonance vibration of the caesium-133 atom, as the interval occupied by 9192 631770 cycles. This was adopted in 1967 as the SI unit of time-interval. Symbol s. 2 Unit of angular measure, equal to 1/60 of a minute of arc; indicated by the symbol ". Also arcsecond. 3 In duodecimal notation V12 of an inch; indicated by 4 Unit for expressing flow times in capillary viscometers Redwood, Saybolt Universal, or Engler, eg an Engler second is that viscosity which allows 200 cm3 of fluid through an Engler viscometer in one second,


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