# Jiffy Time Unit

The word jiffy is an arbitrary, indeterminate amount of time and the expression ‘in a jiffy’, can mean ‘maybe now, or maybe never’, so if someone tells you that they will be back in a jiffy, you should be prepared to be disappointed.  It is the same as saying that you will be back in a moment, as jiffy does not constitute a specific length of time, it is is an informal term for any unspecified short period of time, thus jiffy could mean two minutes or two hours.  Doing something in a jiffy, certainly does not mean that it will be done now at this exact moment, or in a flash, or fast as greased lightning, or in the blink of an eye, or the beat of your heart and it is quite possible that it will never get done.

Humans measure time being relative to the Sun, and Earth’s orbit around it.  One year is one complete orbit around the Sun, One day is one full rotation of the Earth on its axis.  We have 24 hours in every day which equates to 1,440 minutes in a day.  Time as we know it, consisting of 24 hours in one day, did not come about until the 14th century when the first mechanical clocks were made.  The entire world only just synchronized their clocks in 1967, when the second was recognized as the international unit of atomic time.  Jiffy is a scientific time unit that has taken on many different meanings, it implicates various things across numerous fields of study.  Jiffy has acquired a number of precise time unit definitions which all describe short, very short, and extremely short periods of time.

The earliest technical usage for jiffy was defined by Physical Chemist Gilbert Newton Lewis who 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).  This jiffy is equal to a ‘light centimeter’.  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.  Since Lewis, other physicists and chemists have suggested alternative distances to measure a jiffy, rather than light traveling for a centimeter, but the original value is still most typically used in physics and chemistry.

In electronics and for electrical engineers, a jiffy is the period of an alternating current power cycle, 1/60 or 1/50 of a second in most mains power supplies. Specifically, it was .0167 or .02 seconds, which is the time between AC power cycles (.0167 seconds for the United States and .02 seconds in Europe).  However, today it usually just means .01 seconds (10 ms), for no particular reason other than that’s the resolution of most common stopwatches.

In computing, a jiffy was originally the time between two ticks 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.

In astrophysics and quantum physics a jiffy is, as defined by Edward R. Harrison, 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 to the minus 24 seconds.  It has also more informally been defined as ‘one light-foot’, which is equal to approximately one nanosecond.  The jiffy is also used as the time required for light to travel a distance of one femtometer (the Fermi being an SI unit of length equal to 10−15 meters, which means a quadrillionth of one).  This would make the jiffy equal to 3.335 64 zeptoseconds (unit of time equal to 0.000 000 000 000 000 000 001 seconds, that is, 10−21 second.  In the 20th century Richard Tolman suggested that a jiffy should be the length of time it takes a photon (light particle) to travel from one side of a nucleon (neutron or proton) to the other.  A nucleon has a diameter of about 10−15 meter; a jiffy in this context would only be a paltry 3.3357 x 10−24 seconds.

The jiffy has become standardized, more or less, as 0.01 second (10 milliseconds).  There are only 2 smaller measurements of time, the yoctosecond (one trillionth of a trillionth of a second), and a Planck time unit that is used to describe the Big Bang.  Other vague measurement units that are used to indicate a tiny bit or a small amount that often create confusion are a pinch, a smidgen, a dash, a tad, a scoach and a drop.

## 13 thoughts on “Jiffy Time Unit”

1. Sight11 says:

I didn’t know the etymology behind the word. Well, you live and learn. Great post, Jim..

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1. The etymology behind the phrase, ‘Who knew’ where knew is the past tense of know, is an expression which is often used as a rhetorical question, frequently used to express a mild surprise by implication of something that is considered to be obvious.

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2. Sight11 says:

Hey, Jim I forgot to tell you, you forgot to pingback this post. Do it..

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1. Sight11 says:

Sorry! Went to sleep early today.

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3. Wow! Interesting post ..and to come to understand the fact jiffy has a scientific basis!

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