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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.
An order of magnitude of time is usually a decimal prefix or decimal order-of-magnitude quantity together with a base unit of time, like a microsecond or a million years. In some cases, the order of magnitude may be implied (usually 1), like a "second" or "year". In other cases, the quantity name implies the base unit, like "century". In most ...
The earliest technical usage for jiffy was defined by Gilbert Newton Lewis (1875–1946). He proposed in 1926 a unit of time called the "jiffy" which was equal to the time it takes light to travel one centimeter in vacuum (approximately 33.3564 picoseconds). [5]
Speed has the dimensions of distance divided by time. The SI unit of speed is the metre per second (m/s), but the most common unit of speed in everyday usage is the kilometre per hour (km/h) or, in the US and the UK, miles per hour (mph). For air and marine travel, the knot is commonly used.
A millisecond (from milli-and second; symbol: ms) is a unit of time in the International System of Units equal to one thousandth (0.001 or 10 −3 or 1 / 1000) of a second [1] [2] or 1000 microseconds.
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 top speed of the world's fastest roller coaster, Formula Rossa. 90: 320: 200: 3 × 10 −7: Typical speed of a modern high-speed train (e.g. latest generation of production TGV); a diving peregrine falcon—fastest bird; 320 km/h or 200 mph is a parameter sometimes used in defining a supercar. [15] 91: 328: 204: 3.04 × 10 −7
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.