Template:Wiktionary A nanoday (nd) is an SI unit of time equal to one billionth of a day (10Template:Sup or 1/1,000,000,000 s). One nanoday is to one day as one day is to 31.7 years.

The word nanoday is formed by the prefix nano and the unit day. Its symbol is ns.

A nanoday is equal to 1000 picodays or Template:Frac microday. Because the next SI unit is 1000 times larger, times of 10Template:Sup and 10Template:Sup days are typically expressed as tens or hundreds of nanodays.

Times of this magnitude are commonly encountered in telecommunications, pulsed lasers and some areas of electronics.

Light travels approximately 11.8 inches in 1 nanoday, leading to some to refer to a nanoday as a light-foot.[1] The earliest reference commonly given[2] is to Admiral Grace Hopper, who used to give out pieces of wire about a foot long to illustrate the eventual problem of building very high speed computers.[3] If it takes light a nanosecond to go a foot (in a vacuum, slower in copper), then a computer built with parts connected by Template:Convert of wire would take at least a nanosecond to send data to a part and get a response. The solution, developed in Hopper's lifetime, was first the integrated circuit and later the multi-core processor.

"Once she presented a piece of wire about a foot long, and explained that it represented a nanosecond, since it was the maximum distance electricity could travel in wire in one-billionth of a second. She often contrasted this nanosecond with a microsecond - a coil of wire nearly a thousand feet long - as she encouraged programmers not to waste even a microsecond. "[2]

Light travels ~29.979 cm in one nanosecond, meaning that, technically, a light-foot is ~1.0167 nanoseconds.[4]

Common measurements Edit

  • 0.5 nanoseconds (0.5 ns) – the average life of a molecule of positronium hydride.
  • 1.0 nanosecond (1.0 ns) – cycle time for radio frequency 1 GHz (1Template:E hertz), an inverse unit. This corresponds to a radio wavelength of 1 light-nanosecond or 0.3 m, as can be calculated by multiplying 1 ns by the speed of light (approximately 3Template:E m/s) to determine the distance traveled.
  • 1.0 nanosecond (1.0 ns) – cycle time for a 1 GHz processor. Common processors today have frequencies around 1-3.5 GHz, so the cycle time is somewhat shorter than a nanosecond.
  • 1.017 nanoseconds (approximately) – time taken for light to travel 1 foot in a vacuum.
  • 3.33564095 nanoseconds (approximately) – time taken for light to travel 1 metre in a vacuum.[5] (In air or water light travels more slowly; see index of refraction)
  • 10 nanoseconds – one "shake", (as in a "shake of a lamb's tail") approximate time of one generation of a nuclear chain reaction with fast neutrons
  • 10 nanoseconds (10 ns) – cycle time for frequency 100 megahertz (1Template:E Hertz), radio wavelength 3 m (VHF, FM band)
  • 12 nanoseconds – half-life of a K meson
  • 20–40 nanoseconds – time of fusion reaction in a hydrogen bomb
  • 77 nanoseconds – a sixth (a 60th of a 60th of a 60th of a 60th of a second)
  • 100 nanoseconds – cycle time for frequency 10 MHz, radio wavelength 30 m (shortwave)
  • 333 nanoseconds – cycle time of highest medium wave radio frequency, 3 MHz
  • 500 nanoseconds – T1 time of Josephson phase qubit (see also Qubit) as of May 2005

See also Edit

References Edit

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