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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.
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 each (24 × 60 × 60 = 86400).
May 29, 2019 · Second – Unit of Time. Symbol: s. The second is defined by taking the fixed numerical value of the cesium frequency ∆ν Cs, the unperturbed ground-state hyperfine transition frequency of the cesium-133 atom, to be 9,192,631,770 when expressed in the unit Hz, which is equal to s −1. Learn More.
"The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency, ∆ ν 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 ."
SI Unit of Time. The SI unit of time is the second, which has been further accurately defined as “the time interval equal to 9192631770 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).”
Apr 9, 2019 · Atomic clocks enable us to define the second — the international unit of time — in a precise, measurable way that doesn’t change over time. And they allow us to divide the second into extremely small parts, opening up new applications with each finer subdivision.
The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency ΔνCs, 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.
The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the cesium frequency Δ ν Cs , the unperturbed ground-state hyperfine transition frequency of the cesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s -1 .
Apr 29, 2024 · This represents the sole definition of the second in the International System of Units (SI). Jonathan D. Betts. Home Technology Engineering Mechanical Engineering. millibar. measurement. Written and fact-checked by. The Editors of Encyclopaedia Britannica.
The SI unit of time, the second, symbol s, is easy enough to define, but time itself can only be defined in reference to other quantities. As we will see, time isn't even the steady thing that it seems to be, but can change how quickly or slowly is passes depending on speed and mass.
