Jiffy (time)

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This article discusses the word jiffy in the context of measuring time. For other uses of the word, see jiffy.

The term jiffy (or jiffie) is used in different applications for various different short periods of time, usually 1/60 of a second.

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.

1 Use in electronics
2 Use in computing
3 Use in physics
4 External links

[edit] Use in electronics

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

[edit] 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; on early microcomputer systems and on many game consoles (which use televisions as a display device), it is common to 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 2.6.13 release, on the Intel i386 platform, a jiffy is by default 4 ms, or 1/250th of a second. The value for older Linux 2.6 kernels (up to 2.6.12), on same platform, is 1 ms, or 1/1000th of a second. The value on Linux 2.4 and earlier kernels was 10ms, or 1/100th of a second.

[edit] 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

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

A jiffy in astrophysics and quantum physics, as defined by Edward R. Harrison ("The Cosmic Numbers" in Cosmology, The Science of the Universe, 1981 Cambridge Press), is the amount of time it takes for light to travel one fermi (the size of a nucleon). One fermi is about 10^-13 cm, so a jiffy is equal to 10^-23 seconds. In the article, it is noted that the name was suggested for this unit by Richard Tolman.