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Encyclopedia > Metric system

The metric system is a decimalised system of measurement. It exists in several variations, with different choices of base units, though the choice of base units does not affect its day-to-day use. Over the last two centuries, different variants have been considered the metric system. Since the 1960s the International System of Units (SI) ("Système International d'Unités" in French, hence "SI") has been the internationally recognised standard metric system. Metric units are widely used around the world for personal, commercial and scientific purposes. A standard set of prefixes in multiples of 10 may be used to derive larger and smaller units. However, the prefixes for multiples of 1000 are the most commonly used. A system of measurement is a set of units which can be used to specify anything which can be measured and were historically important, regulated and defined because of trade and internal commerce. ... The former Weights and Measures office in Middlesex, England. ... “SI” redirects here. ... The word standard has several meanings: Originally, standard referred to a conspicuous object used as a rallying point in battle. ...

Three nations have not officially adopted the International System of Units as their primary or sole system of measurement: Liberia, Myanmar and the United States.
Three nations have not officially adopted the International System of Units as their primary or sole system of measurement: Liberia, Myanmar and the United States.

Contents

Image File history File links Download high-resolution version (1427x628, 47 KB)hey yo jenny. ... Image File history File links Download high-resolution version (1427x628, 47 KB)hey yo jenny. ... Anthem Kaba Ma Kyei Capital Naypyidaw Largest city Yangon Official languages Burmese Demonym Burmese Government Military junta  -  Chairman of the State Peace and Development Council Than Shwe  -  Prime Minister Soe Win  -  Acting Prime Minister Thein Sein Establishment  -  Bagan 849–1287   -  Taungoo Dynasty 1486–1752   -  Konbaung Dynasty 1752–1885   -  Colonial rule...

Overview

One goal of the metric system is to have a single unit for any physical quantity; another important one is not needing conversion factors when making calculations with physical quantities. All lengths and distances, for example, are measured in metres, or thousandths of a metre (millimetres), or thousands of metres (kilometres), and so on. There is no profusion of different units with different conversion factors, such as inches, feet, yards, fathoms, rods, chains, furlongs, miles, nautical miles, leagues, etc. Multiples and submultiples are related to the fundamental unit by factors of powers of ten, so that one can convert by simply moving the decimal place: 1.234 metres is 1234 millimetres, 0.001234 kilometres, etc. The use of fractions, such as 27 of a metre, is not prohibited, but uncommon, as it is generally not necessary. An inch (plural: inches; symbol or abbreviation: in or, sometimes, ″ - a double prime) is the name of a unit of length in a number of different systems, including English units, Imperial units, and United States customary units. ... A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′ – a prime) is a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ... This article is about the unit of measure known as the yard. ... A fathom is the name of a unit of length in the Imperial system (and the derived U.S. customary units). ... A rod is a unit of length, equal to 5. ... As a unit of measurement within the Imperial system, the chain (surveyors chain, Gunters chain) is defined as 22 yards, 66 feet, or four rods. ... ‹ The template below (Unit of length) is being considered for deletion. ... “Miles” redirects here. ... A nautical mile or sea mile is a unit of length. ... For other uses, see league. ... For other uses, see Fraction (disambiguation). ...


The original metric system was intended to be used with the time units of the French Republican Calendar, but these fell into disuse. Today decimal time is not in everyday use. Submultiples of the second (the microsecond for example) are used in scientific work but for lengths of time greater than a second traditional units, with their non-decimal conversion factors, are more often used than decimal multiples of the second. A French Revolutionary Calendar in the Historical Museum of Lausanne. ... French decimal clock from the time of the French Revolution Decimal time is the representation of the time of day using units which are decimally related. ...


In the late 18th century, Louis XVI of France charged a group of experts to develop a unified, natural and universal system of measurement to replace the disparate systems then in use. This group, which included such notables as Lavoisier, produced the metric system, which was then adopted by the revolutionary government of France. In the early metric system, there were several fundamental or base units, the grad or grade for angles, the metre for length, the gram for mass and the litre for capacity. These were derived from each other via the properties of natural objects, mainly the Earth and water: 1 metre was originally defined as 140,000,000 of the polar circumference of the Earth, the kilogram was originally defined as the mass of one litre (or, equivalently, 1 dm³) of water at its melting point (this definition was later revised to specify a temperature of 4 °C). The Celsius temperature scale was derived from the properties of water, with 0 °C being defined as its freezing point and 100 °C being defined as its boiling point under a pressure of one standard atmosphere. Louis XVI Louis XVI (August 23, 1754 - January 21, 1793), was King of France and Navarre from 1774 until 1791, and then King of the French in 1791-1792. ... Antoine-Laurent de Lavoisier (August 26, 1743 - May 8, 1794) was a French nobleman prominent in the histories of chemistry, finance, biology, and economics. ... The grad is a measurement of plane angles of value 1/400 of a full circle, thus dividing a right angle in 100. ... This article is about the unit of length. ... BIC pen cap, about 1 gram. ... The litre or liter (see spelling differences) is a unit of volume. ... This article is about Earth as a planet. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... The circumference is the distance around a closed curve. ... Kg redirects here. ... For other uses, see Celsius (disambiguation). ... Standard atmosphere (symbol: atm) is a unit of pressure. ...


The metre was later redefined as the length of a particular bar of platinum-iridium alloy; then in terms of the wavelength of light emitted by a specified atomic transition; and now is defined as the distance travelled by light in an absolute vacuum during 1299,792,458 of a second. The gram, originally one millionth of the mass of a cubic metre of water, is currently defined by one thousandth of the mass of a specific object that is kept in a vault in France; however there are efforts underway to redefine it in terms of physical quantities that could be reproduced in any laboratory with suitable equipment. The second, originally 186,400 of the mean solar day was redefined in 1967 to be 9,192,631,770 periods of vibration of the radiation emitted at a specific wavelength by an atom of caesium-133. Varying choices have been made for the fourth base unit, that which is needed to incorporate the field of electromagnetics; As of 2006, this is the ampere, being the base unit of electrical current. Other quantities are derived from the base units; for example, the basic unit of speed is metres per second. As each new definition is introduced, it is designed to match the previous definition as precisely as possible, so these changes of definition have not affected most practical applications. (See SI and individual unit articles for full definitions.) This article is about the unit of length. ... General Name, Symbol, Number platinum, Pt, 78 Chemical series transition metals Group, Period, Block 10, 6, d Appearance grayish white Standard atomic weight 195. ... This article is about the chemical element. ... For other uses, see Light (disambiguation). ... The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness.[1] It is the speed of all electromagnetic radiation, including visible light, in a vacuum. ... BIC pen cap, about 1 gram. ... This article is about the unit of time. ... Solar time is based on the idea that, when the sun reaches its highest point in the sky, it is noon. ... For other uses, see Ampere (disambiguation). ... This article does not cite any references or sources. ... Look up si, Si, SI in Wiktionary, the free dictionary. ...


The names of multiples and submultiples are formed with prefixes. They include deca- (ten), hecto- (hundred), kilo- (thousand), mega- (million), and giga- (billion); deci- (tenth), centi- (hundredth), milli- (thousandth), micro- (millionth), and nano- (billionth). The most commonly used prefixes for multiples depend on the application and sometimes tradition. For example, long distances are stated in thousands of kilometres, not megametres. An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. ...


Most everyday users of the metric system measure temperature in degrees Celsius, though the SI unit is the kelvin, a scale whose units have the same "size", but which starts at absolute zero. Zero degrees Celsius equals 273.15 kelvins (the word "degree" is no longer to be used with kelvins since 1967-1968). For other uses, see Temperature (disambiguation). ... For other uses, see Celsius (disambiguation). ... For other uses, see Kelvin (disambiguation). ... For other uses, see Absolute Zero (disambiguation). ...


Angular measurements have been decimalised, but the older non-decimal units of angle are far more widely used. The decimal unit, which is not part of SI, is the gon or grad, equal to one hundredth of a right angle. Subunits are named, rather than prefixed: the gon is divided into 100 decimal minutes, each of 100 decimal seconds. The traditional system, originally Babylonian, has 360 degrees in a circle, 60 minutes of arc (also called arcminutes) in a degree, and 60 seconds of arc (also called arcseconds) in a minute. The clarifier "of arc" is dropped if it is clear from the context that we are not speaking of minutes and seconds of time. Sometimes angles are given as decimal degrees, e.g., 26.4586 degrees, or in other units such as radians (especially in scientific uses other than astronomy) or angular mils. This article is about angles in geometry. ... This article is about angles in geometry. ... This article is about the shape and mathematical concept of circle. ... For the musical group, see Radian (band). ... For other uses, see Astronomy (disambiguation). ... The mil (in full, angular mil) is a unit of angular measure. ...


History

Countries by date of metrication
Countries by date of metrication

In 1586, the Flemish mathematician Simon Stevin published a small pamphlet called De Thiende ("the tenth"). Decimal fractions had been employed for the extraction of square roots some five centuries before his time, but nobody established their daily use before Stevin. He felt that this innovation was so significant that he declared the universal introduction of decimal coinage, measures and weights to be merely a question of time. Image File history File links Download high resolution version (1357x700, 23 KB) Summary World Map showing Metrication, color-coded by year of conversion. ... Image File history File links Download high resolution version (1357x700, 23 KB) Summary World Map showing Metrication, color-coded by year of conversion. ... Metrication or metrification refers to the introduction of the SI metric system as the international standard for physical measurements—a long-term series of independent and systematic conversions from the various separate local systems of weights and measures. ... The term Flemings (Dutch: ) denotes the majority population in Flanders (the northern half of Belgium). ... Simon Stevin Simon Stevin (1548/49 – 1620) was a Flemish mathematician and engineer. ...


The idea of a metric system has been attributed to John Wilkins, first secretary of the Royal Society of London in 1668.[1] The idea did not catch on, and England continued with its existing system of various weights and measures. John Wilkins. ... For other uses, see Royal Society (disambiguation). ...


In 1670 Gabriel Mouton, a French abbot and scientist, proposed a decimal system of measurement based on the circumference of the Earth. His suggestion was a unit, milliare, that was defined as a minute of arc along a meridian. He then suggested a system of sub-units, dividing successively by factors of ten into the centuria, decuria, virga, virgula, decima, centesima, and millesima. Gabriel Mouton (1618 – 28 September 1694) was a French abbot and scientist. ...


His ideas attracted interest at the time, and were supported by Jean Picard as well as Huygens in 1673, and also studied at Royal Society in London. In 1673, Gottfried Leibniz independently made proposals similar to those of Mouton. Leibniz redirects here. ...


The proliferation of disparate measurement systems was one of the most frequent causes of disputes amongst merchants and between citizens and tax collectors. A unified country with a single currency and a countrywide market, as most European countries were becoming by the end of the 18th century, had a very strong economic incentive and was in a position to break with this situation and standardise on a measuring system. The inconsistency problem was not one of different units but one of differing sized units so instead of simply standardising size of the existing units, the leaders of the French revolutionary governments decided that a completely new system should be adopted.

The first official adoption of such a system occurred in France in 1791 after the French Revolution of 1789. The creators of this metric system tried to choose units that were logical and practical. The revolution gave an opportunity for drastic change with an official ideology of "pure reason". It was proposed as a considerable improvement over the inconsistent collection of customary units that existed before, and that it be based on units of ten, because scientists, engineers, and bureaucrats at the time found this more convenient for the complex unit conversion they often must do. Image File history File links This is a lossless scalable vector image. ... The French Revolution (1789–1815) was a period of political and social upheaval in the political history of France and Europe as a whole, during which the French governmental structure, previously an absolute monarchy with feudal privileges for the aristocracy and Catholic clergy, underwent radical change to forms based on...


The adoption of the metric system in France was slow, but its desirability as an international system was advocated by geodesists and others. Since then a number of variations on the system evolved. Their use spread throughout the world, first to the non-English-speaking countries, and more recently to the English-speaking countries. This article or section should include material from Erdmessung. ...


The whole system was derived from the properties of natural objects, namely the size of the Earth and the density of water, and simple relations in between one unit and the other. In order to determine as precisely as possible the size of the Earth, several teams were sent over several years to measure the length of as long a segment of a meridian as feasible. It was decided to measure the meridian spanning Barcelona and Dunkirk which was the longest segment almost fully over land within French territory. It should be noted that even though, during the many years of the measurement, hostilities broke out between France and Spain, the development of such a standard was considered of such value that Spanish troops escorted the French team while in Spanish territory to ensure their safety. On the earth, a meridian is a north-south line between the North Pole and the South Pole. ... On the earth, a meridian is a north-south line between the North Pole and the South Pole. ... Location Coordinates : Time Zone : CET (GMT +1) - summer: CEST (GMT +2) General information Native name Barcelona (Catalan) Spanish name Barcelona Nickname Ciutat Comtal (City of Counts) Postal code 08001–08080 Area code 34 (Spain) + 93 (Barcelona) Website http://www. ... For other uses of Dunkirk or Dunkerque, see Dunkirk (disambiguation). ...


The whole process ended in the proclamation on June 22, 1799 of the metric system with the storage in the Archives of the Republic of the physical embodiments of the standard, the prototype metre and the prototype kilogram, both made in a platinum alloy, witnessed by representatives of the French and several foreign governments and most important natural philosophers of the time. The motto adopted for the metric system was: "for all men, for all time". is the 173rd day of the year (174th in leap years) in the Gregorian calendar. ... 1799 was a common year starting on Tuesday (see link for calendar). ... A scientist, in the broadest sense, refers to any person that engages in a systematic activity to acquire knowledge or an individual that engages in such practices and traditions that are linked to schools of thought or philosophy. ...


In revolutionary France the system was not particularly well accepted, and the old units, now illegal, remained in widespread use. On February 12, 1812, Napoleon, who had other concerns than enforcement of the system, authorised the usage of Mesures usuelles, traditional French measures redefined on the base of Metric System (toise as 2 metres, livre as 500 grams, etc.), and finally in 1816 a law made these Mesures usuelles standards. This law was cancelled in 1825 and the metric system reinstated fully in 1837.[citation needed] It had already been reinstated in 1820 by a somewhat unlikely person, King William I of the neighboring (United) Netherlands. Although he was generally considered more conservative, he was desperate to bring at least some form of unity to his rather disunited kingdom and stimulate the industrial development of the South. Although the imposed system was metric, a number of old local names like 'pond' (pound) and 'ons' (ounce) were substituted for 500 g and 100 g respectively, and although they were officially abolished in the 1870s, they survive to the present day. The king's attempts were in vain in that Belgium claimed its independence from the Netherlands, but the metric system survived and began a slow but steady conquest of the world. By the 1960s, the majority of nations were on the metric system and most that were not had started programmes to fully convert to the metric system (metrication). As of 2007 only three countries, the United States, Liberia, and Myanmar (Burma) had not mandated the metric system upon their populace. is the 43rd day of the year in the Gregorian calendar. ... For the overture by Tchaikovsky, see 1812 Overture; For the wars, see War of 1812 (USA - United Kingdom) or Patriotic War of 1812 (France - Russia) For the Siberia Airlines plane crashed over the Black Sea on October 4, 2001, see Siberia Airlines Flight 1812 1812 was a leap year starting... Mesures usuelles (French for customary measurements) were a system of measurement introduced to act as compromise between metric system and traditional measurements. ... Mesures usuelles (French for customary measurements) were a system of measurement introduced to act as compromise between metric system and traditional measurements. ... Metrication or metrification refers to the introduction of the SI metric system as the international standard for physical measurements—a long-term series of independent and systematic conversions from the various separate local systems of weights and measures. ... Anthem Kaba Ma Kyei Capital Naypyidaw Largest city Yangon Official languages Burmese Demonym Burmese Government Military junta  -  Chairman of the State Peace and Development Council Than Shwe  -  Prime Minister Soe Win  -  Acting Prime Minister Thein Sein Establishment  -  Bagan 849–1287   -  Taungoo Dynasty 1486–1752   -  Konbaung Dynasty 1752–1885   -  Colonial rule...


Later improvements in the measurement of both the size of the Earth and the properties of water revealed discrepancies between the metric standards and their originally intended values. The Industrial Revolution was well under way and the standardisation of mechanical parts, mainly bolts and nuts, was of great importance and they relied on precise measurements. Though these discrepancies would be mostly hidden in the manufacturing tolerances of those days, changing the prototypes to conform to the new and more precise measurements would have been impractical particularly since new and improved instruments would continually change them. A Watt steam engine, the steam engine that propelled the Industrial Revolution in Britain and the world. ...


It was decided to break the linkage between the prototypes and the natural properties they were derived from. The prototypes then became the basis of the system. The use of prototypes, however, is problematic for a number of reasons. There is the potential for loss, damage or destruction. There is also the problem of variance of the standard with the changes that any artifact can be expected to go through, though they be slight. Also whilst there may be copies, there must be only one official prototype which cannot be universally accessible.


The metre had been defined in terms of such a prototype and remained so until 1960. At that time, the metre was defined as a certain number of wavelengths of a particular frequency of light emitted by a certain element. Since 1983 the metre has been defined as the distance light travels in a given fraction of a second in a vacuum. Thus the definition of the metre ultimately regained a linkage with a natural property, this time a property thought immutable in our universe and truly universal. The kilogram is now the only base unit still defined in terms of a prototype. Since 1899, the kilogram has been formally anchored to a single platinum-iridium cylinder in Sèvres, France. Kg redirects here. ...


On May 20, 1875 an international treaty known as the Convention du Mètre (Metre Convention) was signed by 17 states (including the United States). This treaty established the following organisations to conduct international activities relating to a uniform system for measurements: is the 140th day of the year (141st in leap years) in the Gregorian calendar. ... 1875 (MDCCCLXXV) was a common year starting on Friday (see link for calendar). ... The Convention du Mètre of May 20, 1875 is an international treaty that established what is now known as the SI system of units. ...

  1. Conférence générale des poids et mesures (CGPM), an intergovernmental conference of official delegates of member nations and the supreme authority for all actions;
  2. Comité international des poids et mesures (CIPM), consisting of selected scientists and metrologists, which prepares and executes the decisions of the CGPM and is responsible for the supervision of the International Bureau of Weights and Measures;
  3. Bureau international des poids et mesures (BIPM), a permanent laboratory and world centre of scientific metrology, the activities of which include the establishment of the basic standards and scales of the principal physical quantities and maintenance of the international prototype standards.

The metric system is used widely for scientific purposes but there are some exceptions, especially at large and small scales, such as the parsec. It has been adopted for everyday life by most nations through a process called metrication. As of 2006, 95% of the world's population live in metricated countries, although non-metric units are still used for some purposes in some countries. The holdouts to full metrication are the United States and, to a lesser degree, the United Kingdom, where there is public attachment to the traditional units. The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures (CGPM, sometimes written in English Conférence Générale des Poids et Mesures). ... The International Committee for Weights and Measures is the English name of the Comité international des poids et mesures (CIPM, sometimes written in English Comité International des Poids et Mesures). ... The Bureau International des Poids et Mesures (International Bureau of Weights and Measures, or BIPM) is a standards organization, one of the three organizations established to maintain the SI system under the terms of the Metre Convention. ... A parsec is the distance from the Earth to an astronomical object which has a parallax angle of one arcsecond. ... Metrication or metrification refers to the introduction of the SI metric system as the international standard for physical measurements—a long-term series of independent and systematic conversions from the various separate local systems of weights and measures. ...


Goals

The metric system was designed with several goals in mind.


Neutral and universal

The designers of the metric system meant to make it as neutral as possible so that it could be adopted universally.


Replicable

The usual way to establish a standard was to make prototypes of the base units and distribute copies. This would make the new standard reliant on the original prototypes which would be in conflict with the previous goal since all countries would have to refer to the one holding the prototypes.


The designers developed definitions of the base units such that any laboratory equipped with proper instruments should be able to make their own models of them. The original base units of the metric system could be derived from the length of a meridian of the Earth and the weight of a certain volume of pure water. They discarded the use of a pendulum since its period or, inversely, the length of the string holding the bob for the same period changes around the Earth. Likewise, they discarded using the circumference of the Earth over the Equator since not all countries have access to the Equator while all countries have access to a section of a meridian. On the earth, a meridian is a north-south line between the North Pole and the South Pole. ... For other uses, see Pendulum (disambiguation). ...


Decimal multiples

The metric system is decimal, in the sense that all multiples and submultiples of the base units are factors of powers of ten of the unit. Fractions of a unit (e.g. 29/64) are not used formally. The practical benefits of a decimal system are such that it has been used to replace other non-decimal systems outside the metric system of measurements; for example currencies.


The simplicity of decimal prefixes encouraged the adoption of the metric system. Clearly the advantages of decimal prefixes derive from our using base 10 arithmetic, a consequence of our happening to have 10 digits (fingers and thumbs). At most, differences in expressing results are simply a matter of shifting the decimal point or changing an exponent; for example, the speed of light may be expressed as 299 792.458 km/s or 2.99792458×108 m/s. Decimal, or denary, notation is the most common way of writing the base 10 numeral system, which uses various symbols for ten distinct quantities (0, 1, 2, 3, 4, 5, 6, 7, 8 and 9, called digits) together with the decimal point and the sign symbols + (plus) and − (minus) to... The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness.[1] It is the speed of all electromagnetic radiation, including visible light, in a vacuum. ...


Common prefixes

Main article: SI prefix

All derived units would use a common set of prefixes for each multiple. Thus the prefix kilo could be used both for mass (kilogram) or length (kilometre) both indicating a thousand times the base unit. This did not prevent the popular use of names for some derived units such as the tonne which is a megagram while a quintal is accepted as 100 kilograms; both are derived from old customary units and were rounded to metric. An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. ... This article is about the metric tonne. ... The quintal is a historical unit of mass with many different definitions in different countries. ...


The function of the prefix is to multiply or divide the measure by a factor of ten, one hundred or a positive integer power of one thousand.[2] If the prefix is Greek-derived, the measure is multiplied by this factor. If the prefix is Latin-derived, it is divided. The Greek prefix kilo~ and the Latin prefixes centi~ and milli~ are those most familiar from everyday use.

Examples:
metre (common base unit)
decametre = 10 metres (a measure used in naval artillery)
hectometre = 100 metres (not a commonly used measure)
kilometre = 1000 metres
decimetre = 110 of a metre
centimetre = 1100 of a metre
millimetre = 11000 of a metre
litre (common base unit)
decalitre = 10 litres (not a commonly used measure)
hectolitre = 100 litres (used for beer kegs, 1 keg is approx. 12 of a hectolitre)
kilolitre = 1000 litres (not commonly used)
decilitre = 110 of a litre
centilitre = 1100 of a litre
millilitre = 11000 of a litre

A similar application of Greek and Latin prefixes can be made with other metric measurements.


Relation of volume and mass of water

Originally, units for volume and mass were directly related to each, with mass defined in terms of a volume of water. Even though that definition is no longer used, the relation is quite close at room temperature and nearly exact at 4 °C. So as a practical matter, one can fill a container with water and weigh it to get the volume, for example. Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ...

Relations:
1000 litres = 1 cubic metre ≈ 1 tonne of water ("cubic metre" is commonly used instead of "kilolitre")
1 litre = 1 cubic decimetre ≈ 1 kilogram of water
1 millilitre = 1 cubic centimetre ≈ 1 gram of water
1 microlitre = 1 cubic millimetre ≈ 1 milligram of water

Practical

The base units were chosen to be of similar magnitude to customary units. The metre, being close to half a toise (French yard equivalent), became more popular than the failed decimal hour of the Republican Calendar which was 2.4 times the normal hour. A toise (symbol: T) is a unit of measure for length, area and volume originating in pre-revolutionary France. ...


The kilometre was originally defined as the length of an arc spanning a decimal minute of latitude, a similar definition to that of the nautical mile which was the length of an arc of one (non-decimal) minute of latitude. This article is about the geographical term. ... A nautical mile or sea mile is a unit of length. ... This article is about the geographical term. ...


Coincidental similarities to real-life values

Two important values, when they were expressed in the metric system, turned out to be very close to a multiple of 10. The standard acceleration due to gravity on Earth gn has been defined to be 9.80665 m/s² exactly, which is the value at about 45° north or south of the equator. Accordingly the force exerted on a mass of one kilogram in Earth gravity (F = m·a) is about ten newtons (kg-m/s²). This simplified the metrication of many machines such as locomotives, which were simply re-labelled from e.g. "85 tonnes" to "850 kN". A closer approximation is π² m/s², which means a one-metre pendulum has a period of almost exactly two seconds. This article is about the unit of length. ... This article is about the unit of time. ... For other uses, see Force (disambiguation). ... For other uses, see Mass (disambiguation). ... A tonne (also called metric ton) is a non-SI unit of mass, accepted for use with SI, defined as: 1 tonne = 103 kg (= 106 g). ... For other uses, see Pendulum (disambiguation). ...


Also, the standard atmospheric pressure, previously expressed in atmospheres, when given in pascals, is 101.325 kPa. Since the difference between 10 atmospheres and 1 MPa is only 1.3%, many devices were simply re-labeled by dividing the scale by ten, e.g. 1 atm was changed to 0.1 MPa. Atmospheric pressure is the pressure at any given point in the Earths atmosphere. ... Standard atmosphere (symbol: atm) is a unit of pressure. ... For other uses, see Pascal. ...


In addition, the speed of light in a vacuum turns out to be astonishingly close (0.07% error) to 3×108 m/s. The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness.[1] It is the speed of all electromagnetic radiation, including visible light, in a vacuum. ...


A useful conversion used in meteorology is 1 m/s ≈ 2 knots with less than a 3% error, actually 1.94384 knots (to 5 decimal places). The equivalent conversion for distance is not so "rounded", 1 nautical mile = 1.852 km (exactly) = 1 minute of arc Latitude (approximately).[3] A knot is a unit of speed abbreviated kt or kn. ... A nautical mile or sea mile is a unit of length. ... This article is about the geographical term. ...


Metric systems

Original system

The metric system, and metre was first fully described by Englishman John Wilkins in 1668 in a treatise presented to the Royal Society some 120 years before the French adopted the system. It is believed that the system was transmitted to France from England via the likes of Benjamin Franklin (who spent a great deal of time in London), and produced the by-product of the decimalised paper currency system, before finding favour with American revolutionary ally Louis XV.[4]


The original French system continued the tradition of having separate base units for geometrically related dimensions, i.e. metre for lengths, are (100 m²) for areas, stere (1 m³) for dry capacities and litre (1 dm³) for liquid capacities. The hectare, equal to a hundred ares, is the area of a square 100 metres on a side (about 2.5 acres), and is still in use to measure fields. This article is about the unit of length. ... An are (symbol a) is a unit of area, equal to 100 square meters (10 m × 10 m), used for measuring land area. ... The cubic metre (symbol m³) is the SI derived unit of volume. ... The litre or liter (see spelling differences) is a unit of volume. ... A hectare (symbol ha) is a unit of area, equal to 10 000 square metres, commonly used for measuring land area. ... An are (symbol a) is a unit of area, equal to 100 square meters (10 m × 10 m), used for measuring land area. ... This article is about the unit of measurement. ...


The base unit of mass is the kilogram. This is the only base unit that has a prefix, for historical reasons. Originally the kilogram was called the "grave", and the "gramme" was an alternative name for a thousandth of a grave. After the French Revolution, the word "grave" carried negative connotations, as a synonym for the title "count". The grave was renamed the kilogram.[5] This also serves as the prototype in the SI. It included only few prefixes from milli, one thousandth to myria ten thousand. Kg redirects here. ... Look up si, Si, SI in Wiktionary, the free dictionary. ... An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. ... Milli (symbol m) is an SI prefix in the SI system of units denoting a factor of 10-3, or 1/1,000. ...


Several national variants existed thereof with aliases for some common subdivisions. In general this entailed a redefinition of other units in use, e.g. 500-gram pounds or 10-kilometre miles or leagues. An example of these is mesures usuelles. However it is debatable whether such systems are true metric systems. Look up pound in Wiktionary, the free dictionary. ... Mesures usuelles (French for customary measurements) were a system of measurement introduced to act as compromise between metric system and traditional measurements. ...


Centimetre-gram-second systems

Early on in the history of the metric system various centimetre gram second systems of units (CGS) had been in use. These units were particularly convenient in science and technology. For example, in CGS the density of water is approximately 1 gram per cubic centimetre. ...


Metre-kilogram-second systems

Later metric systems were based on the metre, kilogram and second (MKS) to improve the value of the units for practical applications. Metre-kilogram-second-coulomb (MKSC) and metre-kilogram-second-ampere (MKSA) systems are extensions of these. This article is about the unit of length. ... Kg redirects here. ... This article is about the unit of time. ... The coulomb (symbol: C) is the SI unit of electric charge. ... For other uses, see Ampere (disambiguation). ...


The International System of Units (Système international d'unités or SI) is the current international standard metric system and the system most widely used around the world. It is based on the metre, kilogram, second, ampere, kelvin, candela and mole. Look up si, Si, SI in Wiktionary, the free dictionary. ... For other uses, see Kelvin (disambiguation). ... Photopic (black) and scotopic [1] (green) luminosity functions. ... The mole (symbol: mol) is the SI base unit that measures an amount of substance. ...


Metre-tonne-second systems

The metre-tonne-second system of units (MTS) was based on the metre, tonne and second. It was invented in France and mostly used in the Soviet Union from 1933 to 1955. The metre-tonne-second or mts system of units is a system of physical units introduced in the Soviet Union in 1933, but abolished in 1955. ... This article is about the metric tonne. ...


Gravitational systems

Gravitational metric systems use the kilogram-force (kilopond) as a base unit of force, with mass measured in a unit known as the hyl, TME, mug or metric slug. Note these are not part of the International System of Units (SI). In the gravitational metric system(s) the base unit of force is not normalised to one mass unit (gram or kilogram) times one length unit (metre or centimetre) per time unit squared (second) as in the SI, but it depends on a selected or locally measured gravitational constant gn. ... The unit kilogram-force (kgf, often just kg) or kilopond (kp) is defined as the force exerted by one kilogram of mass in standard Earth gravity. ... For other meanings, see Slug (disambiguation) The slug is an English and U.S. customary unit of mass. ... The slug is an English unit of mass. ... “SI” redirects here. ...


Variations in terminology

In keeping with American English spelling, meter, liter, etc. are used in the United States. In addition, the official US spelling for the rarely used SI prefix for ten is deka. In American English the term metric ton is the normal usage whereas in other varieties of English tonne is common. Spelling differences redirects here. ... This article is about the SI prefix. ...


The US government has approved this terminology for official use. In scientific contexts only the symbols are used; since these are universally the same, the differences do not arise in practice in scientific use.


Gram is also sometimes spelled gramme in English-speaking countries other than the United States, though it is an older spelling and its usage is declining.


Conversion and calculation errors

  • Gimli Glider — In 1983 a Boeing 767 jet ran out of fuel in midflight because of two mistakes in figuring the fuel supply of Air Canada's first aircraft to use metric measurements. [6]
  • Mars Climate Orbiter — In 1999 NASA lost a $125 million Mars orbiter because one engineering team used metric units while another used US customary units for a calculation. [7]

Gimli Glider is the nickname of an Air Canada aircraft which was involved in an infamous aviation incident. ... Air Canada (TSX: AC.A, TSX: AC.B) is Canadas largest airline and flag carrier. ... Artists conception of the Mars Climate Orbiter Mars Climate Orbiter during tests The Mars Climate Orbiter (formerly the Mars Surveyor 98 Orbiter) was one of two spacecraft in the Mars Surveyor 98 program, the other being the Mars Polar Lander (formerly the Mars Surveyor 98 Lander). ...

Notes and references

  1. ^ Metric system 'was British' - from the BBC video news
  2. ^ The factor ten thousand was also once used. The corresponding prefixes myria~ (104) and myrio~ (10-4) were both Greek-derived.
  3. ^ Bureau International des Poids et Mesures (March 2006). The International System of Units (SI) (Table 8). 8th ed.. Retrieved on 2007-04-12.
  4. ^ John Wilkins. (1668) Pat Naughtin, transcriber. Real Character and a Philosophical Language. Selected pages republished by Metrication matters. Accessed 2007-08-03.
  5. ^ Nelson, Robert A (February 2000). The International System of Units: Its History and Use in Science and Industry. Applied Technology Institute. Retrieved on 2007-04-12.
  6. ^ "Jet's Fuel Ran Out After Metric Conversion Errors", New York Times, July 30, 1983. Retrieved on 2007-08-21. "Air Canada said yesterday that its Boeing 767 jet ran out of fuel in midflight last week because of two mistakes in figuring the fuel supply of the airline's first aircraft to use metric measurements. After both engines lost their power, the pilots made what is now thought to be the first successful emergency dead stick landing of a commercial jetliner." 
  7. ^ "NASA's metric confusion caused Mars orbiter loss", CNN, September 30, 1999. Retrieved on 2007-08-21. "NASA lost a $125 million Mars orbiter because one engineering team used metric units while another used English units for a key spacecraft operation, according to a review finding released Thursday. For that reason, information failed to transfer between the Mars Climate Orbiter spacecraft team at Lockheed Martin in Colorado and the mission navigation team in California. Lockheed Martin built the spacecraft. "People sometimes make errors," said Edward Weiler, NASA's Associate Administrator for Space Science in a written statement." 

There exist several unit prefixes used like the SI prefixes, but that are not part of the SI system. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 102nd day of the year (103rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 102nd day of the year (103rd in leap years) in the Gregorian calendar. ... The New York Times is an internationally known daily newspaper published in New York City and distributed in the United States and many other nations worldwide. ... is the 211th day of the year (212th in leap years) in the Gregorian calendar. ... For the Jimi Hendrix song, see 1983. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 233rd day of the year (234th in leap years) in the Gregorian calendar. ... The Cable News Network, commonly known as CNN, is a major cable television network founded in 1980 by Ted Turner. ... is the 273rd day of the year (274th in leap years) in the Gregorian calendar. ... Events of 2008: (EMILY) Me Lesley and MIley are going to China! This article is about the year. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 233rd day of the year (234th in leap years) in the Gregorian calendar. ...

See also


  Results from FactBites:
 
Online Conversion - Metric System (0 words)
A metric system is a system of units for measurement developed in late 18th century France with decimal multipliers.
In the early metric system there were two fundamental or base units, the metre and the kilogram, for length and mass.
Later metric systems were based on the metre, kilogram and second (MKS) to improve the value of the units for practical applications.
Metric system - Wikipedia, the free encyclopedia (2966 words)
In the early metric system there were several fundamental or base units, the grad or grade for angles, the metre for length, the gram for mass and the litre for capacity.
The original base units of the metric system could be derived from the length of a meridian of the Earth and the weight of a certain volume of pure water.
The metric system is decimal, in the sense that all multiples and submultiples of the base units are factors of powers of ten of the unit.
  More results at FactBites »

 
 

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