Measurement is the assignment of a number to a characteristic of an object or event, which can be compared with other objects or events. The scope and application of measurement are dependent on the discipline. In the natural sciences and engineering, measurements do not apply to nominal properties of objects or events, consistent with the guidelines of the International vocabulary of metrology published by the International Bureau of Weights and Measures. However, in other fields such as statistics as well as the social and behavioral sciences, measurements can have multiple levels, which would include nominal, ordinal and ratio scales. Measurement is a cornerstone of trade, science and quantitative research in many disciplines. Many measurement systems existed for the varied fields of human existence to facilitate comparisons in these fields; these were achieved by local agreements between trading partners or collaborators. Since the 18th century, developments progressed towards unifying accepted standards that resulted in the modern International System of Units.
This system reduces all physical measurements to a mathematical combination of seven base units. The science of measurement is pursued in the field of metrology; the measurement of a property may be categorized by the following criteria: type, magnitude and uncertainty. They enable unambiguous comparisons between measurements; the level of measurement is a taxonomy for the methodological character of a comparison. For example, two states of a property may be compared by difference, or ordinal preference; the type is not explicitly expressed, but implicit in the definition of a measurement procedure. The magnitude is the numerical value of the characterization obtained with a suitably chosen measuring instrument. A unit assigns a mathematical weighting factor to the magnitude, derived as a ratio to the property of an artifact used as standard or a natural physical quantity. An uncertainty represents the systemic errors of the measurement procedure. Errors are evaluated by methodically repeating measurements and considering the accuracy and precision of the measuring instrument.
Measurements most use the International System of Units as a comparison framework. The system defines seven fundamental units: kilogram, candela, ampere and mole. Six of these units are defined without reference to a particular physical object which serves as a standard, while the kilogram is still embodied in an artifact which rests at the headquarters of the International Bureau of Weights and Measures in Sèvres near Paris. Artifact-free definitions fix measurements at an exact value related to a physical constant or other invariable phenomena in nature, in contrast to standard artifacts which are subject to deterioration or destruction. Instead, the measurement unit can only change through increased accuracy in determining the value of the constant it is tied to; the first proposal to tie an SI base unit to an experimental standard independent of fiat was by Charles Sanders Peirce, who proposed to define the metre in terms of the wavelength of a spectral line. This directly influenced the Michelson–Morley experiment.
With the exception of a few fundamental quantum constants, units of measurement are derived from historical agreements. Nothing inherent in nature dictates that an inch has to be a certain length, nor that a mile is a better measure of distance than a kilometre. Over the course of human history, first for convenience and for necessity, standards of measurement evolved so that communities would have certain common benchmarks. Laws regulating measurement were developed to prevent fraud in commerce. Units of measurement are defined on a scientific basis, overseen by governmental or independent agencies, established in international treaties, pre-eminent of, the General Conference on Weights and Measures, established in 1875 by the Metre Convention, overseeing the International System of Units and having custody of the International Prototype Kilogram; the metre, for example, was redefined in 1983 by the CGPM in terms of light speed, while in 1960 the international yard was defined by the governments of the United States, United Kingdom and South Africa as being 0.9144 metres.
In the United States, the National Institute of Standards and Technology, a division of the United States Department of Commerce, regulates commercial measurements. In the United Kingdom, the role is performed by the National Physical Laboratory, in Australia by the National Measurement Institute, in South Africa by the Council for Scientific and Industrial Research and in India the National Physical Laboratory of India. Before SI units were adopted around the world, the British systems of English units and imperial units were used in Britain, the Commonwealth and the United States; the system came to be known as U. S. is still in use there and in a few Caribbean countries. These various systems of measurement have at times been called foot-pound-second systems after the Imperial units for length and time though the tons, hundredweights and nautical miles, for example, are different for the U. S. units. Many Imperial units remain in use in Britain, which has switched to the SI system—with a few exceptions such as road signs, which are still in miles.
Draught beer and cider must be sold by the imperial pint, milk in returnable bottles can be sold by the imperial pint. Many people meas
Standardization or standardisation is the process of implementing and developing technical standards based on the consensus of different parties that include firms, interest groups, standards organizations and governments Standardization can help to maximize compatibility, safety, repeatability, or quality. It can facilitate commoditization of custom processes. In social sciences, including economics, the idea of standardization is close to the solution for a coordination problem, a situation in which all parties can realize mutual gains, but only by making mutually consistent decisions; this view includes the case of "spontaneous standardization processes", to produce de facto standards. Standard weights and measures were developed by the Indus Valley Civilization; the centralized weight and measure system served the commercial interest of Indus merchants as smaller weight measures were used to measure luxury goods while larger weights were employed for buying bulkier items, such as food grains etc.
Weights existed in categories. Technical standardisation enabled gauging devices to be used in angular measurement and measurement for construction. Uniform units of length were used in the planning of towns such as Lothal, Kalibangan, Dolavira and Mohenjo-daro; the weights and measures of the Indus civilization reached Persia and Central Asia, where they were further modified. Shigeo Iwata describes the excavated weights unearthed from the Indus civilization: A total of 558 weights were excavated from Mohenjodaro and Chanhu-daro, not including defective weights, they did not find statistically significant differences between weights that were excavated from five different layers, each measuring about 1.5 m in depth. This was evidence; the 13.7-g weight seems to be one of the units used in the Indus valley. The notation was based on decimal systems. 83% of the weights which were excavated from the above three cities were cubic, 68% were made of chert. The implementation of standards in industry and commerce became important with the onset of the Industrial Revolution and the need for high-precision machine tools and interchangeable parts.
Henry Maudslay developed the first industrially practical screw-cutting lathe in 1800. This allowed for the standardisation of screw thread sizes for the first time and paved the way for the practical application of interchangeability to nuts and bolts. Before this, screw threads were made by chipping and filing. Nuts were rare. Metal bolts passing through wood framing to a metal fastening on the other side were fastened in non-threaded ways. Maudslay standardized the screw threads used in his workshop and produced sets of taps and dies that would make nuts and bolts to those standards, so that any bolt of the appropriate size would fit any nut of the same size; this was a major advance in workshop technology. Maudslay's work, as well as the contributions of other engineers, accomplished a modest amount of industry standardization. Joseph Whitworth's screw thread measurements were adopted as the first national standard by companies around the country in 1841, it came to be known as the British Standard Whitworth, was adopted in other countries.
This new standard specified a 55° thread angle and a thread depth of 0.640327p and a radius of 0.137329p, where p is the pitch. The thread pitch increased with diameter in steps specified on a chart. An example of the use of the Whitworth thread is the Royal Navy's Crimean War gunboats; these were the first instance of "mass-production" techniques being applied to marine engineering. With the adoption of BSW by British railway lines, many of which had used their own standard both for threads and for bolt head and nut profiles, improving manufacturing techniques, it came to dominate British manufacturing. American Unified Coarse was based on the same imperial fractions; the Unified thread angle has flattened crests. Thread pitch is the same in both systems except that the thread pitch for the 1⁄2 in bolt is 12 threads per inch in BSW versus 13 tpi in the UNC. By the end of the 19th century, differences in standards between companies, was making trade difficult and strained. For instance, an iron and steel dealer recorded his displeasure in The Times: "Architects and engineers specify such unnecessarily diverse types of sectional material or given work that anything like economical and continuous manufacture becomes impossible.
In this country no two professional men are agreed upon the size and weight of a girder to employ for given work." The Engineering Standards Committee was established in London in 1901 as the world's first national standards body. It subsequently extended its standardization work and became the British Engineering Standards Association in 1918, adopting the name British Standards Institution in 1931 after receiving its Royal Charter in 1929; the national standards were adopted universally throughout the country, enabled the markets to act more rationally and efficiently, with an increased level of cooperation. After the First World War, similar national bodies were established in other countries; the Deutsches Institut für Normung was set up in Germany in 1917, followed by its counterparts, the American National Standard Institute and the French Commissi
The kilogram or kilogramme is the base unit of mass in the International System of Units. Until 20 May 2019, it remains defined by a platinum alloy cylinder, the International Prototype Kilogram, manufactured in 1889, stored in Saint-Cloud, a suburb of Paris. After 20 May, it will be defined in terms of fundamental physical constants; the kilogram was defined as the mass of a litre of water. That was an inconvenient quantity to replicate, so in 1799 a platinum artefact was fashioned to define the kilogram; that artefact, the IPK, have been the standard of the unit of mass for the metric system since. In spite of best efforts to maintain it, the IPK has diverged from its replicas by 50 micrograms since their manufacture late in the 19th century; this led to efforts to develop measurement technology precise enough to allow replacing the kilogram artifact with a definition based directly on physical phenomena, now scheduled to take place in 2019. The new definition is based on invariant constants of nature, in particular the Planck constant, which will change to being defined rather than measured, thereby fixing the value of the kilogram in terms of the second and the metre, eliminating the need for the IPK.
The new definition was approved by the General Conference on Weights and Measures on 16 November 2018. The Planck constant relates a light particle's energy, hence mass, to its frequency; the new definition only became possible when instruments were devised to measure the Planck constant with sufficient accuracy based on the IPK definition of the kilogram. The gram, 1/1000 of a kilogram, was provisionally defined in 1795 as the mass of one cubic centimetre of water at the melting point of ice; the final kilogram, manufactured as a prototype in 1799 and from which the International Prototype Kilogram was derived in 1875, had a mass equal to the mass of 1 dm3 of water under atmospheric pressure and at the temperature of its maximum density, 4 °C. The kilogram is the only named SI unit with an SI prefix as part of its name; until the 2019 redefinition of SI base units, it was the last SI unit, still directly defined by an artefact rather than a fundamental physical property that could be independently reproduced in different laboratories.
Three other base units and 17 derived units in the SI system are defined in relation to the kilogram, thus its stability is important. The definitions of only eight other named SI units do not depend on the kilogram: those of temperature and frequency, angle; the IPK is used or handled. Copies of the IPK kept by national metrology laboratories around the world were compared with the IPK in 1889, 1948, 1989 to provide traceability of measurements of mass anywhere in the world back to the IPK; the International Prototype Kilogram was commissioned by the General Conference on Weights and Measures under the authority of the Metre Convention, in the custody of the International Bureau of Weights and Measures who hold it on behalf of the CGPM. After the International Prototype Kilogram had been found to vary in mass over time relative to its reproductions, the International Committee for Weights and Measures recommended in 2005 that the kilogram be redefined in terms of a fundamental constant of nature.
At its 2011 meeting, the CGPM agreed in principle that the kilogram should be redefined in terms of the Planck constant, h. The decision was deferred until 2014. CIPM has proposed revised definitions of the SI base units, for consideration at the 26th CGPM; the formal vote, which took place on 16 November 2018, approved the change, with the new definitions coming into force on 20 May 2019. The accepted redefinition defines the Planck constant as 6.62607015×10−34 kg⋅m2⋅s−1, thereby defining the kilogram in terms of the second and the metre. Since the second and metre are defined in terms of physical constants, the kilogram is defined in terms of physical constants only; the avoirdupois pound, used in both the imperial and US customary systems, is now defined in terms of the kilogram. Other traditional units of weight and mass around the world are now defined in terms of the kilogram, making the kilogram the primary standard for all units of mass on Earth; the word kilogramme or kilogram is derived from the French kilogramme, which itself was a learned coinage, prefixing the Greek stem of χίλιοι khilioi "a thousand" to gramma, a Late Latin term for "a small weight", itself from Greek γράμμα.
The word kilogramme was written into French law in 1795, in the Decree of 18 Germinal, which revised the older system of units introduced by the French National Convention in 1793, where the gravet had been defined as weight of a cubic centimetre of water, equal to 1/1000 of a grave. In the decree of 1795, the term gramme thus replaced gravet, kilogramme replaced grave; the French spelling was adopted in Great Britain when the word was used for the first time in English in 1795, with the spelling kilogram being adopted in the United States. In the United Kingdom both spellings are used, with "kilogram" having become by far the more common. UK law regulating the units to be used when trading by weight or measure does not prevent the use of either spelling. In the 19th century the French word kilo, a shortening of kilogramme, was imported into the English language where it has been used to mean both kilogram and kilometre. While kilo is acceptable in many generalist texts
India known as the Republic of India, is a country in South Asia. It is the seventh largest country by area and with more than 1.3 billion people, it is the second most populous country as well as the most populous democracy in the world. Bounded by the Indian Ocean on the south, the Arabian Sea on the southwest, the Bay of Bengal on the southeast, it shares land borders with Pakistan to the west. In the Indian Ocean, India is in the vicinity of Sri Lanka and the Maldives, while its Andaman and Nicobar Islands share a maritime border with Thailand and Indonesia; the Indian subcontinent was home to the urban Indus Valley Civilisation of the 3rd millennium BCE. In the following millennium, the oldest scriptures associated with Hinduism began to be composed. Social stratification, based on caste, emerged in the first millennium BCE, Buddhism and Jainism arose. Early political consolidations took place under the Gupta empires. In the medieval era, Zoroastrianism and Islam arrived, Sikhism emerged, all adding to the region's diverse culture.
Much of the north fell to the Delhi Sultanate. The economy expanded in the 17th century in the Mughal Empire. In the mid-18th century, the subcontinent came under British East India Company rule, in the mid-19th under British Crown rule. A nationalist movement emerged in the late 19th century, which under Mahatma Gandhi, was noted for nonviolent resistance and led to India's independence in 1947. In 2017, the Indian economy was the world's sixth largest by nominal GDP and third largest by purchasing power parity. Following market-based economic reforms in 1991, India became one of the fastest-growing major economies and is considered a newly industrialised country. However, it continues to face the challenges of poverty, corruption and inadequate public healthcare. A nuclear weapons state and regional power, it has the second largest standing army in the world and ranks fifth in military expenditure among nations. India is a federal republic governed under a parliamentary system and consists of 29 states and 7 union territories.
A pluralistic and multi-ethnic society, it is home to a diversity of wildlife in a variety of protected habitats. The name India is derived from Indus, which originates from the Old Persian word Hindush, equivalent to the Sanskrit word Sindhu, the historical local appellation for the Indus River; the ancient Greeks referred to the Indians as Indoi, which translates as "The people of the Indus". The geographical term Bharat, recognised by the Constitution of India as an official name for the country, is used by many Indian languages in its variations, it is a modernisation of the historical name Bharatavarsha, which traditionally referred to the Indian subcontinent and gained increasing currency from the mid-19th century as a native name for India. Hindustan is a Middle Persian name for India, it was introduced into India by the Mughals and used since then. Its meaning varied, referring to a region that encompassed northern India and Pakistan or India in its entirety; the name may refer to either the northern part of India or the entire country.
The earliest known human remains in South Asia date to about 30,000 years ago. Nearly contemporaneous human rock art sites have been found in many parts of the Indian subcontinent, including at the Bhimbetka rock shelters in Madhya Pradesh. After 6500 BCE, evidence for domestication of food crops and animals, construction of permanent structures, storage of agricultural surplus, appeared in Mehrgarh and other sites in what is now Balochistan; these developed into the Indus Valley Civilisation, the first urban culture in South Asia, which flourished during 2500–1900 BCE in what is now Pakistan and western India. Centred around cities such as Mohenjo-daro, Harappa and Kalibangan, relying on varied forms of subsistence, the civilization engaged robustly in crafts production and wide-ranging trade. During the period 2000–500 BCE, many regions of the subcontinent transitioned from the Chalcolithic cultures to the Iron Age ones; the Vedas, the oldest scriptures associated with Hinduism, were composed during this period, historians have analysed these to posit a Vedic culture in the Punjab region and the upper Gangetic Plain.
Most historians consider this period to have encompassed several waves of Indo-Aryan migration into the subcontinent from the north-west. The caste system, which created a hierarchy of priests and free peasants, but which excluded indigenous peoples by labeling their occupations impure, arose during this period. On the Deccan Plateau, archaeological evidence from this period suggests the existence of a chiefdom stage of political organisation. In South India, a progression to sedentary life is indicated by the large number of megalithic monuments dating from this period, as well as by nearby traces of agriculture, irrigation tanks, craft traditions. In the late Vedic period, around the 6th century BCE, the small states and chiefdoms of the Ganges Plain and the north-western regions had consolidated into 16 major oligarchies and monarchies that were known as the mahajanapadas; the emerging urbanisation gave rise to non-Vedic religious movements, two of which became independent religions. Jainism came into prominence during the life of Mahavira.
Buddhism, based on the teachings of Gautama Buddha, attracted followers from all social classes excepting the middle