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Metric time is the measure of time intervals using the metric system. The modern SI system defines the second as the base unit of time, and forms multiples and submultiples with metric prefixes such as kiloseconds and milliseconds. Other units of time – minute, hour, and day – are accepted for use with SI, but are not part of it
One billionth of a second. Time for molecules to fluoresce. shake: 10 −8 s: 10 nanoseconds, also a casual term for a short period of time. microsecond: 10 −6 s: One millionth of a second. Symbol is μs millisecond: 10 −3 s: One thousandth of a second. Shortest time unit used on stopwatches. jiffy (electronics) ~ 10 −3 s
One billionth of one second 1 ns: The time needed to execute one machine cycle by a 1 GHz microprocessor 1 ns: The time light takes to travel 30 cm (11.811 in) 10 −6: microsecond: μs One millionth of one second 1 μs: The time needed to execute one machine cycle by an Intel 80186 microprocessor 2.2 μs: The lifetime of a muon
One hour of time is divided into 60 minutes, and one minute is divided into 60 seconds. Thus, a measurement of time such as 3:23:17 (3 hours, 23 minutes, and 17 seconds) can be interpreted as a whole sexagesimal number (no sexagesimal point), meaning 3 × 60 2 + 23 × 60 1 + 17 × 60 0 seconds .
Occasionally, these units can be found in technical literature, but traditional units like minutes, hours, days and years are much more common, and are accepted for use with SI. It is possible to specify the time of day as the number of kiloseconds of elapsed time since midnight. Thus, instead of saying 3:45 p.m. one could say (time of day) 56. ...
The day is divided into 24 hours, and each hour into 4 puncta, 10 minuta, or 40 momenta. Similarly, the week is divided into seven days, and each day into 96 puncta , 240 minuta , or 960 momenta . A moment ( momentum ) is a medieval unit of time .
Its hours are a secondary unit computed as precisely 3,600 seconds. [23] However, an hour of Coordinated Universal Time (UTC), used as the basis of most civil time, has lasted 3,601 seconds 27 times since 1972 in order to keep it within 0.9 seconds of universal time, which is based on measurements of the mean solar day at 0° longitude.
The invention in 1955 of the caesium atomic clock has led to the replacement of older and purely astronomical time standards, for most practical purposes, by newer time standards based wholly or partly on atomic time. Various types of second and day are used as the basic time interval for most time scales. Other intervals of time (minutes ...