Jiffy (time)

Jiffy is an informal term for any unspecified short period of time, as in "I will be back in a jiffy". From this it has acquired a number of more precise applications for short, very short, extremely short, ultra short or hyper short periods of time. First attested in 1785, the word's origin is unclear, though one suggestion is that it was thieves' cant for lightning.[1]

Beginnings in measurement

The earliest technical usage for jiffy was defined by Gilbert Newton Lewis (1875–1946). He proposed a unit of time called the "jiffy" which was equal to the time it takes light to travel one centimeter in a vacuum (approximately 33.3564 picoseconds).[2] It has since been redefined for different measurements depending on the field of study.[3]

Uses

In electronics, a jiffy is the period of an alternating current power cycle,[2] 1/60 or 1/50 of a second in most mains power supplies.

In computing, a jiffy was originally the time between two ticks of the system timer interrupt.[4] It is not an absolute time interval unit, since its duration depends on the clock interrupt frequency of the particular hardware platform.[5]

Early microcomputer systems such as the Commodore 64 and many game consoles (which use televisions as a display device) commonly synchronize the system interrupt timer with the vertical frequency of the local television standard, either 59.94 Hz with NTSC systems, or 50.0 Hz with most PAL systems. Jiffy values for various Linux versions and platforms have typically varied between about 1 ms and 10 ms, with 10 ms reported as an increasingly common standard in the Jargon File.[6]

Stratus VOS uses a jiffy of 1/65,536 second to express date and time (number of jiffies elapsed since 1 January 1980 00:00 Greenwich Mean Time). Stratus also defines the microJiffy, being 1/65,536 of a regular Jiffy.[7]

The term "jiffy" is sometimes used in computer animation as a method of defining playback rate, with the delay interval between individual frames specified in 1/100th-of-a-second (10 ms) jiffies, particularly in Autodesk Animator .FLI sequences (one global frame frequency setting) and animated Compuserve .GIF images (each frame having an individually defined display time measured in 1/100 s).

The speed of light in a vacuum provides a convenient universal relationship between distance and time, so in physics (particularly in quantum physics) and often in chemistry, a jiffy is defined as the time taken for light to travel some specified distance. In astrophysics and quantum physics a jiffy is, as defined by Edward R. Harrison,[8] the time it takes for light to travel one fermi, which is approximately the size of a nucleon. One fermi is 10−15 m, so a jiffy is about 3 × 10−24 seconds. It has also more informally been defined as "one light-foot", which is equal to approximately one nanosecond.[6]

One author has used the word jiffy to denote the Planck time of about 5.4 × 10−44 seconds, which is the time it would take light to travel a Planck length if ordinary geometry were still relevant at that scale.[9]

See also

References

  1. ^ Douglas Harper (November 2001). "jiffy". Online Etymology Dictionary. Retrieved 2008-03-18.
  2. ^ a b Gerard P. Michon (November 2002). "What's a jiffy?". Units of Measurement. Numericana. Retrieved 2008-12-30.
  3. ^ Russ Rowlett (September 2001). "jiffy". How Many? A Dictionary of Units of Measurement. University of North Carolina. Retrieved 2009-08-31.
  4. ^ "Documentation/timers/NO_HZ.txt (3.10)". May 7, 2013.
  5. ^ "time(7) - Linux manual page". man7.org.
  6. ^ a b Entry on jiffy in The Jargon File
  7. ^ ""StrataDOC - Time Intervals". Stratus. Retrieved 2018-11-01.
  8. ^ "The Cosmic Numbers" in Cosmology, The Science of the Universe, 1981 Cambridge Press
  9. ^ Lieu, Richard; Hillman, Lloyd W. (2003-03-10). "The Phase Coherence of Light from Extragalactic Sources: Direct Evidence against First-Order Planck-Scale Fluctuations in Time and Space". The Astrophysical Journal. 585 (2): L77–L80. arXiv:astro-ph/0301184. Bibcode:2003ApJ...585L..77L. doi:10.1086/374350.

External links

Microsecond

A microsecond is an SI unit of time equal to one millionth (0.000001 or 10−6 or ​1⁄1,000,000) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available.

A microsecond is equal to 1000 nanoseconds or ​1⁄1,000 of a millisecond. Because the next SI prefix is 1000 times larger, measurements of 10−5 and 10−4 seconds are typically expressed as tens or hundreds of microseconds.

Nanosecond

A nanosecond (ns) is an SI unit of time equal to one thousand-millionth of a second (or one billionth of a second), that is, 1/1,000,000,000 of a second, or 10−9 seconds.

The term combines the prefix nano- with the basic unit for one-sixtieth of a minute.

A nanosecond is equal to 1000 picoseconds or ​1⁄1000 microsecond. Time units ranging between 10−8 and 10−7 seconds are typically expressed as tens or hundreds of nanoseconds.

Time units of this granularity are commonly encountered in telecommunications, pulsed lasers, and related aspects of electronics.

Picosecond

A picosecond is an SI unit of time equal to 10−12 or 1/1,000,000,000,000 (one trillionth) of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000 001 seconds. A picosecond is to one second as one second is to approximately 31,689 years. Multiple technical approaches achieve imaging within single-digit picoseconds: for example, the streak camera or intensified CCD (ICCD) cameras are able to picture the motion of light.The name is formed by the SI prefix pico and the SI unit second. It is abbreviated as ps.

One picosecond is equal to 1000 femtoseconds, or 1/1000 nanoseconds. Because the next SI unit is 1000 times larger, measurements of 10−11 and 10−10 second are typically expressed as tens or hundreds of picoseconds. Some notable measurements in this range include:

1.0 picoseconds (1.0 ps) – cycle time for electromagnetic frequency 1 terahertz (THz) (1 x 1012 hertz), an inverse unit. This corresponds to a wavelength of 0.3 mm, as can be calculated by multiplying 1 ps by the speed of light (approximately 3 x 108 m/s) to determine the distance traveled. 1 THz is in the Far infrared.

1 picosecond – time taken by light in a vacuum to travel approximately 0.30 mm

1 picosecond – half-life of a bottom quark

~1 picosecond – lifetime of a single H3O+ (hydronium) ion in water at 20 °C

picoseconds to nanoseconds – phenomena observable by dielectric spectroscopy

1.2 picoseconds – switching time of the world's fastest transistor (845 GHz, as of 2006)

1.7 picoseconds - rotational correlation time of water

3.3 picoseconds (approximately) – time taken for light to travel 1 millimeter

10 picoseconds after the Big Bang – electromagnetism separates from the other fundamental forces

10–150 picoseconds – rotational correlation times of a molecule (184 g/mol) from hot to frozen water

108.7827757 picoseconds – transition time between the two hyperfine levels of the ground state of the caesium-133 atom at absolute zero

330 picoseconds (approximately) – the time it takes a common 3.0 GHz computer CPU to complete a processing cycle

International standards
Obsolete standards
Time in physics
Horology
Calendar
Archaeology and geology
Astronomical chronology
Other units of time
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