Metric time
Encyclopedia
Metric time is the measure of time interval using the metric system
, which defines the second
as the base unit of time, and multiple and submultiple units formed with metric prefixes
, such as kiloseconds and milliseconds. It does not define the time of day, as this is defined by various time scales, which may be based upon the metric definition of the second. Other units of time, the minute
, hour
, and day
, are accepted for use with the modern metric system
, but are not part of it.
in 1795, it included units for length, area, dry volume, liquid capacity, weight or mass, and even currency, but not for time. Decimal time
of day had been introduced in France two years earlier, but was set aside at the same time the metric system was inaugurated, and did not follow the metric pattern of a base unit and prefixed units. James Clerk Maxwell
and Elihu Thomson
(through the British Association for the Advancement of Science
- BAAS) introduced the Centimetre gram second system of units
(cgs) in 1874, in order to derive electric and magnetic metric units, following the recommendation of Carl Friedrich Gauss
in 1832.
The ephemeris second (defined as 1/86400 of a mean solar day) was made one of the original base units of the modern metric system, or International System of Units (SI
), at the 10th General Conference on Weights and Measures (CGPM) in 1954. The SI second was later redefined more precisely as
the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium
-133 atom.
, Joseph Louis Lagrange
, proposed in a report to the commission the names déci-jour and centi-jour (deci
day and centi
day in English). Base units equivalent to decimal divisions of the day, such as 1/10, 1/100, 1/1000, or 1/100,000 day, or other divisions of the day, such as 1/20 or 1/40 day, have also been proposed, with names such as tick, meck, chi, chron, moment, etc., and multiple and submultiple units formed with metric prefixes. Such alternative units have not gained any notable acceptance, however, mostly from sheer lack of acquaintance and familiarity.
A modified second = 1/100 000 of a day = 0.864 s could be a viable alternative. Any redefinition of the second, however, creates conflicts with anything based on its precise current definition. Another unit for time, more familiar than some other suggestions, could be 14.4 minutes, i.e. a shorter quarter of an hour, or a centiday, as proposed by Lagrange. The centiday was used in China
(called ke
in Chinese
) for thousands of years.
In the 19th century, M.J. de Rey-Pailhade proposed using the centiday, abbreviated cé, divided into 10 decicés, 100 centicés, 1000 millicés. and 10000 dimicés.
In 1897, the Commission de décimalisation du temps was created by the French Bureau of Longitude, with the mathematician Henri Poincaré
as secretary. The commission proposed making the standard hour
the base unit of metric time, but the proposal did not gain acceptance and was eventually abandoned.
. Metric time properly refers to measurement of time interval, while decimal time refers to the time of day. Standard time of day is defined by various time scales, such as UTC, which are now usually based upon the metric base unit of time, the second. Some proposals for alternative units of metric time are accompanied by decimal time scales for telling the time of day based upon these alternative units. Other proposals called "metric time" refer only to decimal time, and therefore are not truly metric.
French
decimal time is sometimes called "metric time" because it was introduced around the same time as the metric system and both were decimal, but it was not part of the decree creating the original metric system and its units were named for the hour
, minute
and second
, instead of using metric prefixes. Other decimal time standards, such as Swatch Internet Time
, are not considered metric time.
gives date and time as the number of seconds since January 1, 1970, and Microsoft's FILETIME as multiples of 100ns since January 1, 1601. VAX/VMS uses the number of 100ns since November 17, 1858 and RISC OS
the number of centiseconds since January 1, 1900.
None of these systems are strictly linear, as they have discontinuities at leap second
s.
has only developed prefixes
regarding 10 units exponentially
in both the multiple and submultiple directions. The first three multiples would be viable for use within a metric time system; they are:
However, the SI Units’ fourth value is:
This makes for relatively nonviable units with which to measure human time/life.
To make this system of prefixes work for metric time, standard units and prefixes would need to be developed or revived for the 4th and 5th exponents to make metric time viable to human life. Historically, the metric system included a myria- prefix to represent 104, but the SI disposed of it. Historically, 100 000 m were equal to one grade.
writing on occasion. In the novel A Deepness in the Sky
by Vernor Vinge
, the spacefaring Qeng Ho culture is depicted as using metric units such as the kilosecond
and megasecond for all time interval measurements.
The novels Accelerando and Glasshouse
by Charles Stross
have several uses of metric time, including kiloseconds, megaseconds, and megayears. In the second case, humans are living in habitats circling brown dwarfs, with no lingering connection to the Solar System that gave birth to the earlier time scale. In Glasshouse
characters use kiloseconds, "megs" etc. to refer to different periods of time, any earlier use of megayears has been dropped.
The Risen Empire
by Scott Westerfeld
uses metric time to measure time within an empire that extends over many star systems.
In television, the Simpsons
episode "They Saved Lisa's Brain
" has Principal Skinner saying that, thanks to the city being under Mensa's
control, that the city's trains are not only running on time, but they are running on metric time, while looking at an analog clock with numbers 1–10 (which indicates decimal time
).
An opening scene of Fritz Lang
's 1927 film Metropolis shows a metric clock with ten numbers instead of twelve, illustrating the improved efficiency of future industrial society.
A song off of the 2000 album Veni Vidi Vicious
by the Swedish band The Hives
is titled "The Hives - Introduce the Metric System in Time".
Metric system
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...
, which defines the second
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
as the base unit of time, and multiple and submultiple units formed with metric prefixes
SI prefix
The International System of Units specifies a set of unit prefixes known as SI prefixes or metric prefixes. An SI prefix is a name that precedes a basic unit of measure to indicate a decadic multiple or fraction of the unit. Each prefix has a unique symbol that is prepended to the unit symbol...
, such as kiloseconds and milliseconds. It does not define the time of day, as this is defined by various time scales, which may be based upon the metric definition of the second. Other units of time, the minute
Minute
A minute is a unit of measurement of time or of angle. The minute is a unit of time equal to 1/60th of an hour or 60 seconds. In the UTC time scale, a minute on rare occasions has 59 or 61 seconds; see leap second. The minute is not an SI unit; however, it is accepted for use with SI units...
, hour
Hour
The hour is a unit of measurement of time. In modern usage, an hour comprises 60 minutes, or 3,600 seconds...
, and day
Day
A day is a unit of time, commonly defined as an interval equal to 24 hours. It also can mean that portion of the full day during which a location is illuminated by the light of the sun...
, are accepted for use with the modern metric system
Si
Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...
, but are not part of it.
History
When the metric system was introduced in FranceFrance
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
in 1795, it included units for length, area, dry volume, liquid capacity, weight or mass, and even currency, but not for time. Decimal time
Decimal time
Decimal time is the representation of the time of day using units which are decimally related. This term is often used to refer specifically to French Revolutionary Time, which divides the day into 10 decimal hours, each decimal hour into 100 decimal minutes and each decimal minute into 100 decimal...
of day had been introduced in France two years earlier, but was set aside at the same time the metric system was inaugurated, and did not follow the metric pattern of a base unit and prefixed units. James Clerk Maxwell
James Clerk Maxwell
James Clerk Maxwell of Glenlair was a Scottish physicist and mathematician. His most prominent achievement was formulating classical electromagnetic theory. This united all previously unrelated observations, experiments and equations of electricity, magnetism and optics into a consistent theory...
and Elihu Thomson
Elihu Thomson
Elihu Thomson was an American engineer and inventor who was instrumental in the founding of major electrical companies in the United States, the United Kingdom and France.-Early life:...
(through the British Association for the Advancement of Science
British Association for the Advancement of Science
frame|right|"The BA" logoThe British Association for the Advancement of Science or the British Science Association, formerly known as the BA, is a learned society with the object of promoting science, directing general attention to scientific matters, and facilitating interaction between...
- BAAS) introduced the Centimetre gram second system of units
Centimetre gram second system of units
The centimetre–gram–second system is a metric system of physical units based on centimetre as the unit of length, gram as a unit of mass, and second as a unit of time...
(cgs) in 1874, in order to derive electric and magnetic metric units, following the recommendation of Carl Friedrich Gauss
Carl Friedrich Gauss
Johann Carl Friedrich Gauss was a German mathematician and scientist who contributed significantly to many fields, including number theory, statistics, analysis, differential geometry, geodesy, geophysics, electrostatics, astronomy and optics.Sometimes referred to as the Princeps mathematicorum...
in 1832.
The ephemeris second (defined as 1/86400 of a mean solar day) was made one of the original base units of the modern metric system, or International System of Units (SI
Si
Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...
), at the 10th General Conference on Weights and Measures (CGPM) in 1954. The SI second was later redefined more precisely as
the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium
Caesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...
-133 atom.
Alternative units
Numerous proposals have been made for alternative base units of metric time. On March 28, 1794, the president of the commission which developed the metric systemMetric system
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...
, Joseph Louis Lagrange
Joseph Louis Lagrange
Joseph-Louis Lagrange , born Giuseppe Lodovico Lagrangia, was a mathematician and astronomer, who was born in Turin, Piedmont, lived part of his life in Prussia and part in France, making significant contributions to all fields of analysis, to number theory, and to classical and celestial mechanics...
, proposed in a report to the commission the names déci-jour and centi-jour (deci
Deci
Deci is a prefix in the metric system denoting a factor of one tenth. Adopted in 1795, the prefix comes from the Latin decimus, meaning tenth. Its most frequent use is in the non-SI unit, the decibel, used to measure sound intensity and many other ratios....
day and centi
Centi
Centi is a prefix in the metric system denoting a factor of one hundredth. Adopted in 1795, the prefix comes from the Latin centum, meaning hundred. It is mainly used with the metre to express lengths in centimetres, a common unit of length....
day in English). Base units equivalent to decimal divisions of the day, such as 1/10, 1/100, 1/1000, or 1/100,000 day, or other divisions of the day, such as 1/20 or 1/40 day, have also been proposed, with names such as tick, meck, chi, chron, moment, etc., and multiple and submultiple units formed with metric prefixes. Such alternative units have not gained any notable acceptance, however, mostly from sheer lack of acquaintance and familiarity.
A modified second = 1/100 000 of a day = 0.864 s could be a viable alternative. Any redefinition of the second, however, creates conflicts with anything based on its precise current definition. Another unit for time, more familiar than some other suggestions, could be 14.4 minutes, i.e. a shorter quarter of an hour, or a centiday, as proposed by Lagrange. The centiday was used in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
(called ke
Ke (unit)
The ke is a traditional Chinese unit of decimal time lasting approximately a quarter of a western hour. Traditionally the ke divides a day into 100 equal intervals of 14.4 minutes . The ke is equivalent to the centiday , a non-SI prefixed unit...
in Chinese
Chinese language
The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...
) for thousands of years.
In the 19th century, M.J. de Rey-Pailhade proposed using the centiday, abbreviated cé, divided into 10 decicés, 100 centicés, 1000 millicés. and 10000 dimicés.
In 1897, the Commission de décimalisation du temps was created by the French Bureau of Longitude, with the mathematician Henri Poincaré
Henri Poincaré
Jules Henri Poincaré was a French mathematician, theoretical physicist, engineer, and a philosopher of science...
as secretary. The commission proposed making the standard hour
Hour
The hour is a unit of measurement of time. In modern usage, an hour comprises 60 minutes, or 3,600 seconds...
the base unit of metric time, but the proposal did not gain acceptance and was eventually abandoned.
Alternative meaning
Metric time is sometimes used to mean decimal timeDecimal time
Decimal time is the representation of the time of day using units which are decimally related. This term is often used to refer specifically to French Revolutionary Time, which divides the day into 10 decimal hours, each decimal hour into 100 decimal minutes and each decimal minute into 100 decimal...
. Metric time properly refers to measurement of time interval, while decimal time refers to the time of day. Standard time of day is defined by various time scales, such as UTC, which are now usually based upon the metric base unit of time, the second. Some proposals for alternative units of metric time are accompanied by decimal time scales for telling the time of day based upon these alternative units. Other proposals called "metric time" refer only to decimal time, and therefore are not truly metric.
French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
decimal time is sometimes called "metric time" because it was introduced around the same time as the metric system and both were decimal, but it was not part of the decree creating the original metric system and its units were named for the hour
Hour
The hour is a unit of measurement of time. In modern usage, an hour comprises 60 minutes, or 3,600 seconds...
, minute
Minute
A minute is a unit of measurement of time or of angle. The minute is a unit of time equal to 1/60th of an hour or 60 seconds. In the UTC time scale, a minute on rare occasions has 59 or 61 seconds; see leap second. The minute is not an SI unit; however, it is accepted for use with SI units...
and second
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
, instead of using metric prefixes. Other decimal time standards, such as Swatch Internet Time
Swatch Internet Time
Swatch Internet Time is a decimal time concept introduced in 1998 and marketed by the Swatch corporation as an alternative, decimal measure of time...
, are not considered metric time.
In computing
In computing, at least internally, metric time gained widespread use for ease of computation. Unix timeUnix time
Unix time, or POSIX time, is a system for describing instants in time, defined as the number of seconds elapsed since midnight Coordinated Universal Time of Thursday, January 1, 1970 , not counting leap seconds, which are declared by the International Earth Rotation and Reference Systems Service...
gives date and time as the number of seconds since January 1, 1970, and Microsoft's FILETIME as multiples of 100ns since January 1, 1601. VAX/VMS uses the number of 100ns since November 17, 1858 and RISC OS
RISC OS
RISC OS is a computer operating system originally developed by Acorn Computers Ltd in Cambridge, England for their range of desktop computers, based on their own ARM architecture. First released in 1987, under the name Arthur, the subsequent iteration was renamed as in 1988...
the number of centiseconds since January 1, 1900.
None of these systems are strictly linear, as they have discontinuities at leap second
Leap second
A leap second is a positive or negative one-second adjustment to the Coordinated Universal Time time scale that keeps it close to mean solar time. UTC, which is used as the basis for official time-of-day radio broadcasts for civil time, is maintained using extremely precise atomic clocks...
s.
Fractions of a second
While larger metric prefixes of a second are rarely used, subdivision prefixes are well established within science and technology. Milliseconds, microseconds and smaller units (but not centiseconds) are well established.Problems
The main problem of metric time lies in the units. The International System of UnitsInternational System of Units
The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...
has only developed prefixes
SI prefix
The International System of Units specifies a set of unit prefixes known as SI prefixes or metric prefixes. An SI prefix is a name that precedes a basic unit of measure to indicate a decadic multiple or fraction of the unit. Each prefix has a unique symbol that is prepended to the unit symbol...
regarding 10 units exponentially
Exponentiation
Exponentiation is a mathematical operation, written as an, involving two numbers, the base a and the exponent n...
in both the multiple and submultiple directions. The first three multiples would be viable for use within a metric time system; they are:
| Multiple | Name of Unit | Seconds | Minutes |
|---|---|---|---|
| 101 | decasecond | 10 | |
| 102 | hectosecond | 100 | 1.666 |
| 103 | kilosecond | 1 000 | 16.666 |
However, the SI Units’ fourth value is:
| Multiple | Name of Unit | Seconds | Minutes | Hours | Days | Years |
|---|---|---|---|---|---|---|
| 106 | megasecond | 1 000 000 | 16 666.666 | 277.777 | 11.574 | |
| 109 | gigasecond | 1 000 000 000 | 16 666 666.666 | 277 777.777 | 11 574.074 | 31.689 |
This makes for relatively nonviable units with which to measure human time/life.
To make this system of prefixes work for metric time, standard units and prefixes would need to be developed or revived for the 4th and 5th exponents to make metric time viable to human life. Historically, the metric system included a myria- prefix to represent 104, but the SI disposed of it. Historically, 100 000 m were equal to one grade.
| Multiple | Name of Unit | Seconds | Minutes | Hours | Days |
|---|---|---|---|---|---|
| 104 | myriasecond | 10 000 | 166.6 | 2.777 | |
| 105 | gradasecond | 100 000 | 1 666.6 | 27.77 | 1.157 |
In popular culture
Metric time appears in science fictionScience fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...
writing on occasion. In the novel A Deepness in the Sky
A Deepness in the Sky
A Deepness in the Sky is a Hugo Award–winning science fiction novel by Vernor Vinge. Published in 1999, the novel is a loose prequel to his earlier novel A Fire Upon the Deep...
by Vernor Vinge
Vernor Vinge
Vernor Steffen Vinge is a retired San Diego State University Professor of Mathematics, computer scientist, and science fiction author. He is best known for his Hugo Award-winning novels and novellas A Fire Upon the Deep , A Deepness in the Sky , Rainbows End , Fast Times at Fairmont High ...
, the spacefaring Qeng Ho culture is depicted as using metric units such as the kilosecond
Kilosecond
A kilosecond is 1000 seconds , so there are 86.4 kiloseconds in a 24 hour day, and 604.8 kiloseconds in a week. The second is the International System of Units base unit of time, combine with the prefix kilo- which means 1000, results in the definition of a kilosecond...
and megasecond for all time interval measurements.
The novels Accelerando and Glasshouse
Glasshouse (novel)
Glasshouse is a science fiction novel by British author Charles Stross, first published in 2006. The novel is set in the twenty seventh century aboard a spacecraft adrift in interstellar space. Robin, the protagonist, has recently had his memory erased...
by Charles Stross
Charles Stross
Charles David George "Charlie" Stross is a British writer of science fiction, Lovecraftian horror and fantasy. He was born in Leeds.Stross specialises in hard science fiction and space opera...
have several uses of metric time, including kiloseconds, megaseconds, and megayears. In the second case, humans are living in habitats circling brown dwarfs, with no lingering connection to the Solar System that gave birth to the earlier time scale. In Glasshouse
Glasshouse (novel)
Glasshouse is a science fiction novel by British author Charles Stross, first published in 2006. The novel is set in the twenty seventh century aboard a spacecraft adrift in interstellar space. Robin, the protagonist, has recently had his memory erased...
characters use kiloseconds, "megs" etc. to refer to different periods of time, any earlier use of megayears has been dropped.
The Risen Empire
The Risen Empire
The Risen Empire is a science fiction novel by Scott Westerfeld.-Setting and plot:The novel is set in an undefined distant future , in which there is a galactic empire spanning eighty worlds, amongst other human civilizations...
by Scott Westerfeld
Scott Westerfeld
Scott Westerfeld is an American author of science fiction. He was born in Texas and now divides his time between Sydney, Australia and New York City, USA.-Books:...
uses metric time to measure time within an empire that extends over many star systems.
In television, the Simpsons
The Simpsons
The Simpsons is an American animated sitcom created by Matt Groening for the Fox Broadcasting Company. The series is a satirical parody of a middle class American lifestyle epitomized by its family of the same name, which consists of Homer, Marge, Bart, Lisa and Maggie...
episode "They Saved Lisa's Brain
They Saved Lisa's Brain
"They Saved Lisa's Brain" is the twenty-second episode of The Simpsons tenth season. It first aired on the Fox network in the United States on May 9, 1999. After writing a thoughtful letter to the Springfield Shopper, Lisa is invited to join the Springfield chapter of Mensa...
" has Principal Skinner saying that, thanks to the city being under Mensa's
Mensa International
Mensa is the largest and oldest high-IQ society in the world. It is a non-profit organization open to people who score at the 98th percentile or higher on a standardised, supervised IQ or other approved intelligence test...
control, that the city's trains are not only running on time, but they are running on metric time, while looking at an analog clock with numbers 1–10 (which indicates decimal time
Decimal time
Decimal time is the representation of the time of day using units which are decimally related. This term is often used to refer specifically to French Revolutionary Time, which divides the day into 10 decimal hours, each decimal hour into 100 decimal minutes and each decimal minute into 100 decimal...
).
An opening scene of Fritz Lang
Fritz Lang
Friedrich Christian Anton "Fritz" Lang was an Austrian-American filmmaker, screenwriter, and occasional film producer and actor. One of the best known émigrés from Germany's school of Expressionism, he was dubbed the "Master of Darkness" by the British Film Institute...
's 1927 film Metropolis shows a metric clock with ten numbers instead of twelve, illustrating the improved efficiency of future industrial society.
A song off of the 2000 album Veni Vidi Vicious
Veni Vidi Vicious
Veni Vidi Vicious is the second album by Swedish garage punk band The Hives, released in April 2000. It was released through Burning Heart Records and distributed through Warner Music Group...
by the Swedish band The Hives
The Hives
The Hives are a Swedish garage rock band that first garnered attention in the early 2000s as a prominent group of the garage rock revival. Their mainstream success came with the release of the "greatest hits" album Your New Favourite Band, featuring their most well-known song "Hate to Say I Told...
is titled "The Hives - Introduce the Metric System in Time".
External links
- Metric unit of time (second) Official text of SI brochure from International Bureau of Weights and Measures
- Metric Time? University of Illinois Physics Department
- Decimal Time - Metric Time explains the difference between decimal time and metric time (broken link)
- c# Metric Time Open Source Project
- Metric Time clock in JavaScript