History of measurementThe earliest recorded systems of weights and measures originate in the 3rd or 4th millennium BC. Even the very earliest civilizations needed measurement for purposes of agriculture, construction and trade. Early standard units might only have applied to a single community or small region, with every area developing its own standards for lengths, areas, volumes and masses. Often such systems were closely tied to one field of use, so that volume measures used, for example, for dry grains were unrelated to those for liquids, with neither bearing any particular relationship to units of length used for measuring cloth or land.
Standard (metrology)In metrology (the science of measurement), a standard (or etalon) is an object, system, or experiment that bears a defined relationship to a unit of measurement of a physical quantity. Standards are the fundamental reference for a system of weights and measures, against which all other measuring devices are compared. Historical standards for length, volume, and mass were defined by many different authorities, which resulted in confusion and inaccuracy of measurements.
Stoney unitsIn physics the Stoney units form a system of units named after the Irish physicist George Johnstone Stoney, who first proposed them in 1881. They are the earliest example of natural units, i.e., a coherent set of units of measurement designed so that chosen physical constants fully define and are included in the set. The constants that Stoney used to define his set of units is the following:[ Astrophysics, clocks and fundamental constants, by Karshenboim and Peik, p.
AbampereThe abampere (abA), also called the biot (Bi) after Jean-Baptiste Biot, is the derived electromagnetic unit of electric current in the emu-cgs system of units (electromagnetic cgs). One abampere corresponds to ten amperes in the SI system of units. An abampere of current in a circular path of one centimeter radius produces a magnetic field of 2π oersteds at the center of the circle. The name abampere was introduced by Kennelly in 1903 as a short name for the long name (absolute) electromagnetic cgs unit of current that was in use since the adoption of the cgs system in 1875.
Unit of lengthA unit of length refers to any arbitrarily chosen and accepted reference standard for measurement of length. The most common units in modern use are the metric units, used in every country globally. In the United States the U.S. customary units are also in use. British Imperial units are still used for some purposes in the United Kingdom and some other countries. The metric system is sub-divided into SI and non-SI units.
Portuguese units of measurementPortuguese units were used in Portugal, Brazil, and other parts of the Portuguese Empire until the adoption of the metric system in the 19th century and have continued in use in certain contexts since. The various systems of weights and measures used in Portugal until the 19th century combine remote Roman influences with medieval influences from northern Europe and Islam. These influences are obvious in the names of the units. The measurement units themselves were, in many cases, inherited from a distant past.
Korean units of measurementKorean units of measurement, called cheokgwan-beop () or cheokgeun-beop () in Korean, is the traditional system of measurement used by the people of the Korean peninsula. It is largely based on the Chinese system, with influence from Japanese standards imposed following its annexation of the Korean Empire in 1910. Both North and South Korea currently employ the metric system. Since 2007, South Korea has criminalized the use of Korean units in commercial contexts but informal use continues, especially of the pyeong as a measure of residential and commercial floorspace.
StatampereThe statampere (statA) is the derived electromagnetic unit of electric current in the CGS-ESU (electrostatic cgs) and Gaussian systems of units.:278 One statampere corresponds to 10/c_cgs ampere ≈ 3.33564e-10ampere in the SI system of units. The name statampere is a shortening of abstatampere, where the idea was that the prefix abstat should stand for absolute electrostatic and mean ‘belonging to the CGS-ESU (electrostatic cgs) absolute system of units’.
League (unit)A league is a unit of length. It was common in Europe and Latin America, but is no longer an official unit in any nation. Derived from an ancient Celtic unit and adopted by the Romans as the leuga, the league became a common unit of measurement throughout western Europe. Since the Middle Ages, many values have been specified in several countries. It may have originally represented, roughly, the distance a person could walk in an hour. Ancient Roman units of measurement The league was used in Ancient Rome, defined as 11⁄2 Roman miles (7,500 Roman feet, modern 2.
