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The [[metric system]] is a system of measurement developed during the [[French Revolution]]'s anti-religious [[The Cult of Reason|Cult of Reason]]<ref>However, according to researcher Pat Norton, the system was described a century earlier by Englishman John Wilkins.  [http://abc.net.au/news/stories/2007/07/15/1978802.htm Australian Broadcasting Corporation], 15 July 2007 (retrieved 15 July 2007.)</ref> and based on permanent natural standards rather than on royal decrees. [[Joseph-Louis Lagrange]] headed the Revolutionary weights-and-measures committee that developed it and set its initial definitions.

The '''metric system''' is a system of measurement developed during the [[French Revolution]]'s anti-religious [[The Cult of Reason|Cult of Reason]]<ref>However, according to researcher Pat Norton, the system was described a century earlier by Englishman John Wilkins.  [http://abc.net.au/news/stories/2007/07/15/1978802.htm Australian Broadcasting Corporation], 15 July 2007 (retrieved 15 July 2007.)</ref> and based on permanent natural standards rather than on royal decrees. [[Joseph-Louis Lagrange]] headed the Revolutionary weights-and-measures committee that developed it and set its initial definitions.

Traditional systems of measurement all used standard lengths of parts of the human body, or standard distances that a human might walk. The metric system, by contrast, initially used the [[Earth]] itself as the ultimate standard.

Traditional systems of measurement all used standard lengths of parts of the human body, or standard distances that a human might walk. The metric system, by contrast, initially used the [[Earth]] itself as the ultimate standard.

| yocto-

| yocto-

| y

| y

| 10^-24

| 10⁻²⁴

|-

|-

| zepto-

| zepto-

| z

| z

| 10^-21

| 10⁻²¹

|-

|-

| atto-

| atto-

| a

| a

| 10^-18

| 10⁻¹⁸

|-

|-

| femto-

| femto-

| f

| f

| 10^-15

| 10⁻¹⁵

|-

|-

| pico-

| pico-

| p

| p

| 10^-12

| 10⁻¹²

|-

|-

| nano-

| nano-

| n

| n

| 10^-9

| 10⁻⁹

|-

|-

| micro- ([[Greek language|Greek]] ''small'')

| micro- ([[Greek language|Greek]] ''small'')

| μ

| μ

| 10^-6

| 10⁻⁶

|-

|-

| milli- ([[Latin]] ''one thousand'')

| milli- ([[Latin]] ''one thousand'')

| m

| m

| 10^-3

| 10⁻³

|-

|-

| centi- (Latin ''one hundred'')

| centi- (Latin ''one hundred'')

| c

| c

| 10^-2

| 10⁻²

|-

|-

| deci- (Latin ''ten'')

| deci- (Latin ''ten'')

| d

| d

| 10^-1

| 10⁻¹

|-

|-

| deka- (Greek ''ten'')

| deka- (Greek ''ten'')

The base unit of length, and originally the unit from which all other definitions flowed, is the [[meter]]. The original definition was "one ten-millionth the distance from the equator to the north pole." Lagrange's surveyors computed this distance (probably using a variation on Eratosthenes' tropical-shadow experiment) and inscribed it on a metal bar that they kept at the weights-and-measures headquarters building in Sèvres, [[France]].

The base unit of length, and originally the unit from which all other definitions flowed, is the [[meter]]. The original definition was "one ten-millionth the distance from the equator to the north pole." Lagrange's surveyors computed this distance (probably using a variation on Eratosthenes' tropical-shadow experiment) and inscribed it on a metal bar that they kept at the weights-and-measures headquarters building in Sèvres, [[France]].

But this artifact, being made of metal, tended to expand and contract. Centuries later, when the scientific community realized what had happened, the task of re-standardizing all meter sticks to the equator-to-pole-times-10^-7 definition was judged too onerous. Therefore the meter was redefined. At first it was defined as 1,650,763.73 wavelengths of the orange-red line in the excitation spectrum of [[krypton]]-86. Today it is defined as 1⁄299,792,458th of a light-second.

But this artifact, being made of metal, tended to expand and contract. Centuries later, when the scientific community realized what had happened, the task of re-standardizing all meter sticks to the equator-to-pole-times-10⁻⁷ definition was judged too onerous. Therefore the meter was redefined. At first it was defined as 1,650,763.73 wavelengths of the orange-red line in the excitation spectrum of [[krypton]]-86. Today it is defined as 1⁄299,792,458th of a light-second.

The meter in all its multiples replaces all other units of measurement, long and short. Long distance is measured in the meter multiplied by a thousand--the kilometer. Short distances are measured in centimeters--or millimeters, or micrometers, or however small one needs to measure them.

The meter in all its multiples replaces all other units of measurement, long and short. Long distance is measured in the meter multiplied by a thousand—the kilometer. Short distances are measured in centimeters—or millimeters, or micrometers, or however small one needs to measure them.

=== Volume ===

=== Volume ===

The base unit of volume is derived from the meter: it's the ''cubic meter'' [m³]. Traditionally, the ''liter''<ref>http://www.bipm.org/en/si/si_brochure/chapter4/table6.html</ref> is used. 1 liter is defined as 10^-3 m³ = 1 dm³. '''Capacity''', traditionally measured in liters, refers to the volume occupied by a liquid.  Today, one liter is defined as the volume of one kilogram of water at four degrees [[Celsius]].

The base unit of volume is derived from the meter: it's the ''cubic meter'' [m³]. Traditionally, the ''liter''<ref>http://www.bipm.org/en/si/si_brochure/chapter4/table6.html</ref> is used. 1 liter is defined as 10⁻³ m³ = 1 dm³. '''Capacity''', traditionally measured in liters, refers to the volume occupied by a liquid.  Today, one liter is defined as the volume of one kilogram of water at four degrees [[Celsius]].

=== Mass ===

=== Mass ===

The base unit of mass is the ''gram''. Originally a gram was the mass of one cubic centimeter (see above), then called a ''milliliter'', of [[water]]. The Lagrange committee fashioned an artifact exactly one thousand times as heavy as this--the volume, in short, of one liter of water--and stored this permanently at Sèvres.

The base unit of mass is the ''gram''. Originally a gram was the mass of one cubic centimeter (see above), then called a ''milliliter'', of [[water]]. The Lagrange committee fashioned an artifact exactly one thousand times as heavy as this—the volume, in short, of one liter of water—and stored this permanently at Sèvres.

[[Joseph Lagrange|Lagrange]]'s committee also proposed a unit of mass called the ''grave'', to be equal to one thousand grams. But the [[French Revolution|Revolutionary]] government rejected this name as sounding too much like the [[German]] word ''graf'', translated as ''comte'' or [[count]] in French. Therefore, the artifact at Sèvres would be called a kilogram instead--and that artifact has that name to this day.

[[Joseph Lagrange|Lagrange]]'s committee also proposed a unit of mass called the ''grave'', to be equal to one thousand grams. But the [[French Revolution|Revolutionary]] government rejected this name as sounding too much like the [[German]] word ''graf'', translated as ''comte'' or [[count]] in French. Therefore, the artifact at Sèvres would be called a kilogram instead—and that artifact has that name to this day.

Mass never changes. But in addition to the prototype meter changing its length over time, scientists later realized that water has different densities at different [[temperature|temperatures]].

Mass never changes. But in addition to the prototype meter changing its length over time, scientists later realized that water has different densities at different [[temperature]]s.

Today, the standard [[kilogram]] is kept at the International Bureau of Standards headquarters in Sèvres. It remains today the only generally accepted unit of measurement based on an artifact.

Today, the standard [[kilogram]] is kept at the International Bureau of Standards headquarters in Sèvres. It remains today the only generally accepted unit of measurement based on an artifact.

== Relation to other systems of measurement ==

== Relation to other systems of measurement ==

The [[International System of Units]] borrows some definitions and concepts from the metric system--most notably the meter and the kilogram--and adds other definitions of other quantities, most notably [[time]], [[force]], [[amount of substance]], plane [[angle]], solid angle, and [[luminous intensity]]. The liter ''is not'' the unit of volume in that system, however, but liter is accepted for use with the SI.

The [[International System of Units]] borrows some definitions and concepts from the metric system—most notably the meter and the kilogram—and adds other definitions of other quantities, most notably [[time]], [[force]], [[amount of substance]], plane [[angle]], solid angle, and [[luminous intensity]]. The liter ''is not'' the unit of volume in that system, however, but liter is accepted for use with the SI.

In addition to the International System (or in French, ''Système International'', or SI for short), scientists have invented other systems of measurement that include units of time, force, [[energy]], and electric charge. The most popular are the meter-kilogram-second and centimeter-gram-second systems.

In addition to the International System (or in French, ''Système International'', or SI for short), scientists have invented other systems of measurement that include units of time, force, [[energy]], and electric charge. The most popular are the meter-kilogram-second and centimeter-gram-second systems.

==Usage worldwide==

==Usage worldwide==

According to [[CIA]]'s World Factbook<ref>[https://www.cia.gov/library/publications/the-world-factbook/appendix/appendix-g.html CIA World Factbook, Appendix G]</ref>, the SI system has been officially adopted in all countries of the world, with an exception of [[Burma]], [[Liberia]] and [[the United States of America]].  The inertia of the United States, unfortunate though it may be, is rooted in an enormous amount of existing industrial equipment and usage.  Companies that do any international business have to do a lot of conversion work in order to make their products compatible with the rest of the world.  This is slowly leading to more widespread adoption of the SI system in the United States, but progress is very slow.

According to [[CIA]]'s World Factbook,<ref>[https://www.cia.gov/library/publications/the-world-factbook/appendix/appendix-g.html CIA World Factbook, Appendix G]</ref> the SI system has been officially adopted in all countries of the world, with an exception of [[Burma]], [[Liberia]] and [[the United States of America]].  The inertia of the United States, unfortunate though it may be, is rooted in an enormous amount of existing industrial equipment and usage.  Companies that do any international business have to do a lot of conversion work in order to make their products compatible with the rest of the world.  This is slowly leading to more widespread adoption of the SI system in the United States, but progress is very slow.

Some space missions have failed because of unit incompatibility in guidance software between US and SI measurements.

Some space missions have failed because of unit incompatibility in guidance software between US and SI measurements.

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== See Also ==

== See also ==

* [http://creationwiki.org/Metric_system Metric system] by [[CreationWiki]] (Creationists accept it too.)

* [http://creationwiki.org/Metric_system Metric system] by [[CreationWiki]] (Creationists accept it too.)

* [http://www.essex1.com/people/speer/metric.html Metric system] by Essex1.com

* [http://www.essex1.com/people/speer/metric.html Metric system] by Essex1.com