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| A '''system of measurement''' is a set of units which can be used to specify anything which can be ] and were historically important, regulated and defined because of ] and internal ]. |
A '''system of measurement''' is a set of units which can be used to specify anything which can be ] and were historically important, regulated and defined as early as the Letter of Nanse c 1785 BC because of ] and internal ]. | ||
| ==History== | ==History== | ||
| Measures define property and thus have been resistant to change for thousands of years. International commerce between Mesopotamia and Egypt eventually was expanded by the Empires of the Hittites, Parthians, Greeks, Romans, Persians to cover most of Europe, Asia and Africa, in Modern times reaching the Americas and Oceanaisia. Even in European and Asian cities which adopted the Metric system centuries ago, units such as the English System of Feet and Pounds survive because people are comfortable with them. In ancient as in modern systems of measurement, some quantities are designated as fundamental units, meaning ''all other needed units can be derived from them''. In early and most historic eras, some units could be given by fiat, by the authority of a guild setting cloth yards or board measure or by a king setting taxes or by some religious authority or other strong leader setting tithes. One cause of the French Revolution was science beginning to have the authority to regulate the standards of measure and reducing the French Kings ability to increase his revenues by changing the definities of property he could tax. In 1593 Queen Elizabeth 1 decreed a change to the Mile and Furlong such that the old Roman Myle of 8 furlongs of 625 fote and 1000 passus became 660 feet and a mile of 5280 feet. This arrangement allowed there to be twice as many seconds in a century as there were inches in the circumference of the Earth at the equator and made navigation by the use of seconds pendulums and chronometers easier. (see ) | |||
| {{main|History of measurement}} | {{main|History of measurement}} | ||
| There still exists the idea that mathematics and science to include standards of measure began with the Greeks and Romans. | |||
| <blockquote> | <blockquote> | ||
| ''Although we might suggest that the Egyptians had discovered the art of measurement, it is only with the Greeks that the science of measurement begins to appear. The Greek's knowledge of geometry, and their early experimentation with weights and measures, soon began to place their measurement system on a more scientific basis. By comparison, Roman science, which came later, was not as advanced...''<ref>Quoted from the </ref> | ''Although we might suggest that the Egyptians had discovered the art of measurement, it is only with the Greeks that the science of measurement begins to appear. The Greek's knowledge of geometry, and their early experimentation with weights and measures, soon began to place their measurement system on a more scientific basis. By comparison, Roman science, which came later, was not as advanced...''<ref>Quoted from the </ref> | ||
| </blockquote> | </blockquote> | ||
| From the first beginnings of civilization, contracts for international commerce, the ownership of lands used for agriculture, and building lots intended for public works involving architecture and engineering depended on fixed standards of measure. The size of ships used to carry bulk cargo's were designed around things like board measure. If a contract specified timbers of a given length that length was to some extent determined by whose vessel was going to carry them and whether they would all fit. The same was true of cloth measure and definitions of wine barrels and amphorae. Fields were designed to be of a size that could be plowed and harvested by a yoke of oxen and contain enough grain for their fodder. When horses began to plow fields they could plow enough both for the crop and their fodder plus a section to be left fallow and the size of the fields increased. The first systematic measures were body measures of fingers, palms, hands, spans, cubits, remen, and ells. Agricultural measures expanded feet into yards, paces, rods, perch, and stadions, while the amount of time it took to get someplace by a road or a course of navigation became defined as a rivers journey, a minute of march, a days sail, miles, knots, stadia and degrees. All of that occurred in the pre dynastic chalcolithic and was a full blown international system by the third dynasty of Egypt. Cannons of architectural proportion standardized measures for building materials such as wood and stone in the pyramid age, partly for structural concerns. A given sized timber of a given type of wood had certain expectations for what load it could carry over a given span and the same was true for stone. People building ships had the same sort of concerns when specifying the wood for masts and the means of fastening planking. | |||
| The ] gave rise to acceptance of the ], and this has spread around the world, replacing most customary units of measure. In most systems, ] (distance), ], and ] are ''fundamental quantities''; or as has been now accepted as better in science, the substitution of ] for ], as a better more basic ]. Some systems have changed to recognize the improved relationship, notably the 1824 legal changes to the ]. | The ] gave rise to acceptance of the ], and this has spread around the world, replacing most customary units of measure. In most systems, ] (distance), ], and ] are ''fundamental quantities''; or as has been now accepted as better in science, the substitution of ] for ], as a better more basic ]. Some systems have changed to recognize the improved relationship, notably the 1824 legal changes to the ]. | ||
Revision as of 12:54, 10 December 2013
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 as early as the Letter of Nanse c 1785 BC because of trade and internal commerce.
History
Measures define property and thus have been resistant to change for thousands of years. International commerce between Mesopotamia and Egypt eventually was expanded by the Empires of the Hittites, Parthians, Greeks, Romans, Persians to cover most of Europe, Asia and Africa, in Modern times reaching the Americas and Oceanaisia. Even in European and Asian cities which adopted the Metric system centuries ago, units such as the English System of Feet and Pounds survive because people are comfortable with them. In ancient as in modern systems of measurement, some quantities are designated as fundamental units, meaning all other needed units can be derived from them. In early and most historic eras, some units could be given by fiat, by the authority of a guild setting cloth yards or board measure or by a king setting taxes or by some religious authority or other strong leader setting tithes. One cause of the French Revolution was science beginning to have the authority to regulate the standards of measure and reducing the French Kings ability to increase his revenues by changing the definities of property he could tax. In 1593 Queen Elizabeth 1 decreed a change to the Mile and Furlong such that the old Roman Myle of 8 furlongs of 625 fote and 1000 passus became 660 feet and a mile of 5280 feet. This arrangement allowed there to be twice as many seconds in a century as there were inches in the circumference of the Earth at the equator and made navigation by the use of seconds pendulums and chronometers easier. (see statutory law)
Main article: History of measurementThere still exists the idea that mathematics and science to include standards of measure began with the Greeks and Romans.
Although we might suggest that the Egyptians had discovered the art of measurement, it is only with the Greeks that the science of measurement begins to appear. The Greek's knowledge of geometry, and their early experimentation with weights and measures, soon began to place their measurement system on a more scientific basis. By comparison, Roman science, which came later, was not as advanced...
From the first beginnings of civilization, contracts for international commerce, the ownership of lands used for agriculture, and building lots intended for public works involving architecture and engineering depended on fixed standards of measure. The size of ships used to carry bulk cargo's were designed around things like board measure. If a contract specified timbers of a given length that length was to some extent determined by whose vessel was going to carry them and whether they would all fit. The same was true of cloth measure and definitions of wine barrels and amphorae. Fields were designed to be of a size that could be plowed and harvested by a yoke of oxen and contain enough grain for their fodder. When horses began to plow fields they could plow enough both for the crop and their fodder plus a section to be left fallow and the size of the fields increased. The first systematic measures were body measures of fingers, palms, hands, spans, cubits, remen, and ells. Agricultural measures expanded feet into yards, paces, rods, perch, and stadions, while the amount of time it took to get someplace by a road or a course of navigation became defined as a rivers journey, a minute of march, a days sail, miles, knots, stadia and degrees. All of that occurred in the pre dynastic chalcolithic and was a full blown international system by the third dynasty of Egypt. Cannons of architectural proportion standardized measures for building materials such as wood and stone in the pyramid age, partly for structural concerns. A given sized timber of a given type of wood had certain expectations for what load it could carry over a given span and the same was true for stone. People building ships had the same sort of concerns when specifying the wood for masts and the means of fastening planking.
The French Revolution gave rise to acceptance of the metric system, and this has spread around the world, replacing most customary units of measure. In most systems, length (distance), weight, and time are fundamental quantities; or as has been now accepted as better in science, the substitution of mass for weight, as a better more basic parameter. Some systems have changed to recognize the improved relationship, notably the 1824 legal changes to the imperial system.
Later science developments showed that either electric charge or electric current may be added to complete a minimum set of fundamental quantities by which all other metrological units may be defined. (However, electrical units are not necessary for a minimum set. Gaussian units, for example, have only length, mass, and time as fundamental quantities.) Other quantities, such as power, speed, etc. are derived from the fundamental set; for example, speed is distance per unit time. Historically a wide range of units was used for the same quantity, in several cultural settings, length was measured in inches, feet, yards, fathoms, rods, chains, furlongs, miles, nautical miles, stadia, leagues, with conversion factors which were not simple powers of ten or even simple fractions within a given customary system. yes were they necessarily the same units (or equal units) between different members of similar cultural backgrounds. It must be understood by the modern reader that historically, measurement systems were perfectly adequate within their own cultural milieu, and the understanding that a better more universal system (based on more rationale and fundamental units) only gradually spread with the maturation and appreciation of the rigor characteristic of Newtonian physics. Moreover, changing a measurement system has real fiscal and cultural costs as well as the advantages that accrue from replacing one measuring system with a better one.
Once the analysis tools within that field were appreciated and came into widespread use in the emerging sciences, especially in the applied sciences like civil and mechanical engineering, pressure built up for conversion to a common basis of measurement. As people increasingly appreciated these needs and the difficulties of converting between numerous national customary systems became more widely recognised there was an obvious justification for an international effort to standardise measurements. The French Revolutionary spirit took the first significant and radical step down that road.
In antiquity, systems of measurement were defined locally, the different units were defined independently according to the length of a king's thumb or the size of his foot, the length of stride, the length of arm or per custom like the weight of water in a keg of specific size, perhaps itself defined in hands and knuckles. The unifying characteristic is that there was some definition based on some standard, however egocentric or amusing it may now seem viewed with eyes used to modern precision. Eventually cubits and strides gave way under need and demand from merchants and evolved to customary units.
In the metric system and other recent systems, a single basic unit is used for each fundamental quantity. Often secondary units (multiples and submultiples) are used which convert to the basic units by multiplying by powers of ten, i.e., by simply moving the decimal point. Thus the basic metric unit of length is the metre; a distance of 1.234 m is 1234.0 millimetres, or 0.001234 kilometres.
Current practice
Main article: MetricationMetrication is complete or nearly complete in almost all countries of the world. US customary units are heavily used in the United States and to some degree Liberia. Traditional Burmese units of measurement are used in Burma. U.S. units are used in limited contexts in Canada due to a high degree of trade; additionally there is considerable use of Imperial weights and measures, despite de jure Canadian conversion to metric.
A number of other jurisdictions have laws mandating or permitting other systems of measurement in some or all contexts, such as the United Kingdom – where for example its road signage legislation only allows distance signs displaying imperial units (miles or yards) – or Hong Kong.
In the United States, metric units are used almost universally in science, widely in the military, and partially in industry, but customary units predominate in household use. At retail stores, the liter is a commonly used unit for volume, especially on bottles of beverages, and milligrams are used to denominate the amounts of medications, rather than grains. Also, other standardized measuring systems other than metric are still in universal international use, such as nautical miles and knots in international aviation and shipping.
Metric system
Main articles: Metric system and International System of Units
Metric systems of units have evolved since the adoption of the first well-defined system in France in 1795. During this evolution the use of these systems has spread throughout the world, first to non-English-speaking countries, and then to English speaking countries.
Multiples and submultiples of metric units are related by powers of ten and their names are formed with prefixes. This relationship is compatible with the decimal system of numbers and it contributes greatly to the convenience of metric units.
In the early metric system there were two fundamental or base units, the metre for length and the gram for mass. The other units of length and mass, and all units of area, volume, and compound units such as density were derived from these two fundamental units.
Mesures usuelles (French for customary measurements) were a system of measurement introduced to act as a compromise between the metric system and traditional measurements. It was used in France from 1812 to 1839.
A number of variations on the metric system have been in use. These include gravitational systems, the centimetre–gram–second systems (cgs) useful in science, the metre–tonne–second system (mts) once used in the USSR and the metre–kilogram–second system (mks).
The current international standard metric system is the International System of Units (Système international d'unités or SI) It is an mks system based on the metre, kilogram and second as well as the kelvin, ampere, candela, and mole.
The SI includes two classes of units which are defined and agreed internationally. The first of these classes are the seven SI base units for length, mass, time, temperature, electric current, luminous intensity and amount of substance. The second of these are the SI derived units. These derived units are defined in terms of the seven base units. All other quantities (e.g. work, force, power) are expressed in terms of SI derived units.
Imperial and US customary units
Main articles: Imperial and US customary measurement systems, Imperial units, and US customary unitsBoth imperial units and US customary units derive from earlier English units. Imperial units were mostly used in the British Commonwealth and the former British Empire but in most Commonwealth countries they have been largely supplanted by the metric system. They are still used for some applications in the United Kingdom but have been mostly replaced by the metric system in commercial, scientific, and industrial applications. US customary units, however, are still the main system of measurement in the United States. While some steps towards metrication have been made (mainly in the late 1960s and early 1970s), the customary units have a strong hold due to the vast industrial infrastructure and commercial development.
While imperial and US customary systems are closely related, there are a number of differences between them. Units of length and area (the inch, foot, yard, mile etc.) are identical except for surveying purposes. The Avoirdupois units of mass and weight differ for units larger than a pound (lb.). The imperial system uses a stone of 14 lb., a long hundredweight of 112 lb. and a long ton of 2240 lb. The stone is not used in the US and the hundredweights and tons are short being 100 lb. and 2000 lb. respectively.
Where these systems most notably differ is in their units of volume. A US fluid ounce (fl oz) c. 29.6 millilitres (ml) is slightly larger than the imperial fluid ounce (28.4 ml). However, as there are 16 US fl oz to a US pint and 20 imp fl oz per imperial pint, these imperial pint is about 20% larger. The same is true of quarts, gallons, etc. Six US gallons are a little less than five imperial gallons.
The Avoirdupois system served as the general system of mass and weight. In addition to this there are the Troy and the Apothecaries' systems. Troy weight was customarily used for precious metals, black powder and gemstones. The troy ounce is the only unit of the system in current use; it is used for precious metals. Although the troy ounce is larger than its Avoirdupois equivalent, the pound is smaller. The obsolete troy pound was divided into twelve ounces opposed to the sixteen ounces per pound of the Avoirdupois system. The Apothecaries' system; traditionally used in pharmacology, now replaced by the metric system; shares the same pound and ounce as the troy system but with different further subdivisions.
Natural units
Natural units are physical units of measurement defined in terms of universal physical constants in such a manner that some chosen physical constants take on the numerical value of one when expressed in terms of a particular set of natural units. Natural units are natural because the origin of their definition comes only from properties of nature and not from any human construct. Various systems of natural units are possible. Below are listed some examples.
- Geometric unit systems are useful in relativistic physics. In these systems the base physical units are chosen so that the speed of light and the gravitational constant are set equal to unity.
- Planck units are a form of geometric units obtained by also setting Boltzmann's constant, the Coulomb force constant and the reduced Planck constant to unity. They might be considered unique in that they are based only on properties of free space rather than any prototype, object or particle.
- Stoney units are similar to Planck units but set the elementary charge to unity and allow Planck's constant to float.
- "Schrödinger" units are also similar to Planck units and set the elementary charge to unity too but allow the speed of light to float.
- Atomic units (au) are a convenient system of units of measurement used in atomic physics, particularly for describing the properties of electrons. The atomic units have been chosen such that the fundamental electron properties are all equal to one atomic unit. They are similar to "Schrödinger" units but set the electron mass to unity and allow the gravitational constant to float. The unit energy in this system is the total energy of the electron in the Bohr atom and called the Hartree energy. The unit length is the Bohr radius.
- Electronic units are similar to Stoney units but set the electron mass to unity and allow the gravitational constant to float. They are also similar to Atomic units but set the speed of light to unity and allow Planck's constant to float.
- Quantum electrodynamical units are similar to the electronic system of units except that the proton mass is normalised rather than the electron mass.
Non-standard units
Non-standard measurement units, sometimes found in books, newspapers etc., include:
Area
- The American football field, which has a playing area 100 yards (91.4 m) long by 160 feet (48.8 m) wide. This is often used by the American public media for the sizes of large buildings or parks: easily walkable but non-trivial distances. Note that it is used both as a unit of length (100 yd or 91.4 m, the length of the playing field excluding goal areas) and as a unit of area (57,600 sq ft or 5,350 m), about 1.32 acres (0.53 ha).
- British media also frequently uses the football pitch for equivalent purposes, although soccer pitches are not of a fixed size, but instead can vary within defined limits (100–130 yd or 91.4–118.9 m long, and 50–100 yd or 45.7–91.4 m wide, giving an area of 5,000 to 13,000 sq yd or 4,181 to 10,870 m). However the UEFA Champions League field must be exactly 105 by 68 m (114.83 by 74.37 yd) giving an area of 7,140 m (0.714 ha) or 8,539 sq yd (1.764 acres). Example: HSS vessels are aluminium catamarans about the size of a football pitch... - Belfast Telegraph 23 June 2007
Energy
- A ton of TNT equivalent, and its multiples the kiloton, the megaton, and the gigaton. Often used in stating the power of very energetic events such as explosions and volcanic events and earthquakes and asteroid impacts. A gram of TNT as a unit of energy has been defined as 1000 thermochemical calories (1,000 cal or 4,184 J).
- The atom bomb dropped on Hiroshima. Its force is often used in the public media and popular books as a unit of energy. (Its yield was roughly 13 kilotons, or 60 TJ.)
- One stick of dynamite
Units of currency
A unit of measurement that applies to money is called a unit of account. This is normally a currency issued by a country or a fraction thereof; for instance, the US dollar and US cent (1⁄100 of a dollar), or the euro and euro cent.
ISO 4217 is the international standard describing three letter codes (also known as the currency code) to define the names of currencies established by the International Organization for Standardization (IOS).
Historical systems of measurement
Main article: History of measurementThroughout history, many official systems of measurement have been used. While no longer in official use, some of these customary systems are occasionally used in day to day life, for instance in cooking.
Afroasia
- Arabic
- Egyptian
- Hebrew (Biblical and Talmudic)
- Maltese
- Mesopotamian
Asia
See also: history of measurement systems in IndiaEurope
See also
Conversion tables
Notes and references
- Quoted from the Canada Science and Technology Museum website
- "Statutory Instrument 2002 No. 3113 The Traffic Signs Regulations and General Directions 2002". Her Majesty's Stationery Office (HMSO). 2002. Retrieved 18 March 2010.
- HK Weights and Measures Ordinance
- M. Ismail Marcinkowski, Measures and Weights in the Islamic World. An English Translation of Professor Walther Hinz's Handbook “Islamische Maße und Gewichte“, with a foreword by Professor Bosworth, F.B.A. Kuala Lumpur, ISTAC, 2002, ISBN 983-9379-27-5. This work is an annotated translation of a work in German by the late German orientalist Walther Hinz, published in the Handbuch der Orientalistik, erste Abteilung, Ergänzungsband I, Heft 1, Leiden, The Netherlands: E. J. Brill, 1970.
Bibliography
- Tavernor, Robert (2007), Smoot's Ear: The Measure of Humanity, ISBN 0-300-12492-9
External links
- CLDR - Unicode localization of currency, date, time, numbers
- A Dictionary of Units of Measurement
- Old units of measure
- Measures from Antiquity and the Bible Antiquity and the Bible
- Reasonover's Land Measures A Reference to Spanish and French land measures (and their English equivalents with conversion tables) used in North America
- The Unified Code for Units of Measure
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