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Jiffy (time)


The term jiffy (or jiffie) is used in different applications for various different short periods of time.

In general parlance, the term means any unspecified short period of time, or a moment, and is often used in the sense of the time taken to complete a task, as in, "I"ll be done in a jiffy." Records of the term date to 1785. Its ultimate origin is unknown, but it is believed to have been thieves" cant for lightning.

Use in electronicsIn electronics, a jiffy is the time between alternating current power cycles (1/60 or 1/50 of a second) — see alternating current.


Use in computing

In computing, a jiffy is the duration of one tick of the system timer interrupt. It is not an absolute time interval unit, since its duration depends on the clock interrupt frequency of the particular hardware platform.

Typically, this time is 0.01 seconds. Early microcomputer systems such as the Commodore 64 and many game consoles (which use televisions as a display device) commonly synchronize the system clock with the vertical frequency of the local television standard, either 59.94 Hz with NTSC systems, or 50.0 Hz with most PAL systems. Within the Linux 2.6 operating system kernel, since release 2.6.13, on the Intel i386 platform a jiffy is by default 4 ms, or 1/250th of a second. The jiffy value for other Linux versions and platforms have typically varied between about 1 ms and 10 ms.


Use in physics

In physics (particularly in quantum physics and often in chemistry), a jiffy is the time taken for light to travel the radius of an electron.

A jiffy in astrophysics and quantum physics, as defined by Edward R. Harrison, is the amount of time it takes for light to travel one fermi (the size of a nucleon). One fermi is 10–15 m, so a jiffy is about 3 × 10–24 seconds. In the article, it is noted that the name was suggested for this unit by Richard Tolman.

Sometimes a jiffy is defined as the time taken for light to travel one foot, or sometimes the width of a nucleon in a vacuum — see speed of light.

Sometimes a jiffy is also defined as the time it takes light, the fastest possible thing, to traverse the smallest possible length, the Planck length. So a jiffy, in this definition, is the shortest possible time period, or "tick", of time. Nothing exists smaller than a Planck length and nothing exists between the Jiffy "ticks". This is the smallest possible "piece" of reality obtainable. It is also known as the Planck time and worth 5.4 × 10–44 seconds.


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