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The amount of time light takes to travel one Planck length. quectosecond: 10 −30 s: One nonillionth of a second. rontosecond: 10 −27 s: One octillionth of a second. yoctosecond: 10 −24 s: One septillionth of a second. jiffy (physics) 3 × 10 −24 s: The amount of time light takes to travel one fermi (about the size of a nucleon) in a ...
"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 ...
The mass of one litre of water at the temperature of melting ice. A litre is one thousandth of a cubic metre. M second: s time "The second is 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." 13th CGPM (1967/68, Resolution 1; CR, 103)
The International System of Units, internationally known by the abbreviation SI (from French Système international d'unités), is the modern form of the metric system and the world's most widely used system of measurement. It is the only system of measurement with official status in nearly every country in the world, employed in science ...
An attosecond (abbreviated as as) is a unit of time in the International System of Units (SI) equal to 10 −18 or 1 ⁄ 1 000 000 000 000 000 000 (one quintillionth) of a second. [1] An attosecond is to a second, as a second is to approximately 31.69 billion years. [2]
The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency, Δν Cs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s −1.
Conversions between units in the metric system are defined by their prefixes (for example, 1 kilogram = 1000 grams, 1 milligram = 0.001 grams) and are thus not listed in this article. Exceptions are made if the unit is commonly known by another name (for example, 1 micron = 10 −6 metre).
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 ...