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  2. Unit of time - Wikipedia

    en.wikipedia.org/wiki/Unit_of_time

    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.

  3. Demore Barnes - Wikipedia

    en.wikipedia.org/wiki/Demore_Barnes

    Demore Barnes (born February 26, 1976) is a Canadian actor. Barnes is best known for his roles as Sergeant First Class Hector Williams in the CBS military action television series The Unit, the archangel Raphael in Supernatural and Deputy Chief Christian Garland in Law & Order: Special Victims Unit.

  4. Time in physics - Wikipedia

    en.wikipedia.org/wiki/Time_in_physics

    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]

  5. 2019 revision of the SI - Wikipedia

    en.wikipedia.org/wiki/2019_revision_of_the_SI

    The SI system after the 2019 definition: Base units as defined in terms of physical constants and other base units. Here, means is used in the definition of . The SI system after 1983, but before the 2019 redefinition: Base unit definitions in terms of 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 ...

  6. SI base unit - Wikipedia

    en.wikipedia.org/wiki/SI_base_unit

    "The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 × 10 −34 when expressed in the unit J s, which is equal to kg m 2 s −1, where the metre and the second are defined in terms of c and ∆ν Cs." [1] The mass of one litre of water at the temperature ...

  7. Planck units - Wikipedia

    en.wikipedia.org/wiki/Planck_units

    Some authors define the base Planck units to be those of mass, length and time, regarding an additional unit for temperature to be redundant. [ note 1 ] Other tabulations add, in addition to a unit for temperature, a unit for electric charge, so that either the Coulomb constant k e {\displaystyle k_{\text{e}}} [ 12 ] [ 13 ] [ 14 ] or the vacuum ...

  8. List of physical quantities - Wikipedia

    en.wikipedia.org/wiki/List_of_physical_quantities

    Absorbed dose received per unit of time Gy/s L 2 T −3: Action: S: Momentum of particle multiplied by distance travelled J/Hz L 2 M T −1: scalar Angular acceleration: ω a: Change in angular velocity per unit time rad/s 2: T −2: Area: A: Extent of a surface m 2: L 2: extensive, bivector or scalar Area density: ρ A: Mass per unit area kg ...

  9. Natural units - Wikipedia

    en.wikipedia.org/wiki/Natural_units

    In physics, natural unit systems are measurement systems for which selected physical constants have been set to 1 through nondimensionalization of physical units.For example, the speed of light c may be set to 1, and it may then be omitted, equating mass and energy directly E = m rather than using c as a conversion factor in the typical mass–energy equivalence equation E = mc 2.