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A unit of time is any particular time interval, used as a standard way of measuring or expressing duration. The base unit of time in the International System of Units (SI), and by extension most of the Western world , is the second , defined as about 9 billion oscillations of the caesium atom.
Unit system Domain Derivation Unit name Unit symbol Dimension symbol Quantity name Definition In SI base units In other SI units SI: Physics: Basic: second [n 1] s: T: time: The duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom. s: SI ...
Change of acceleration per unit time: the third time derivative of position m/s 3: L T −3: vector Jounce (or snap) s →: Change of jerk per unit time: the fourth time derivative of position m/s 4: L T −4: vector Magnetic field strength: H: Strength of a magnetic field A/m L −1 I: vector field Magnetic flux density: B: Measure for the ...
This category identifies units of time, either general (in Chronology) or for specific scientific and other uses; and some closely related notions. The main article for this category is Unit of time .
The SI system after 1983, but before the 2019 revision: Dependence of base unit definitions on other base units (for example, the metre is defined as the distance travelled by light in a specific fraction of a second), with the constants of nature and artefacts used to define them (such as the mass of the IPK for the kilogram).
In the International System of Units (SI), the unit of time is the second (symbol: s). It has been defined since 1967 as "the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom", and is an SI base unit. [12]
Download QR code; Print/export Download as PDF; ... Pages in category "Names of units of time" The following 5 pages are in this category, out of 5 total. ...
Unit Dimension Notes Name Symbol [nb 1] Name Symbol photon energy: n: 1: count of photons n with energy Q p = h c/λ. [nb 2] photon flux: Φ q: count per second: s −1: T −1: photons per unit time, dn/dt with n = photon number. also called photon power: photon intensity: I: count per steradian per second sr −1 ⋅s −1: T −1: dn/dω ...