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Agrarianism | Serbia | Serbia
In Serbia, Nikola Pašić (1845–1926) and his People's Radical Party dominated Serbian politics after 1903. The party also monopolized power in Yugoslavia from 1918 to 1929. During the dictatorship of the 1930s, the prime minister was from that party. |
Agrarianism | Ukraine | Ukraine
In Ukraine, the Radical Party of Oleh Lyashko has promised to purify the country of oligarchs "with a pitchfork". The party advocates a number of traditional left-wing positions (a progressive tax structure, a ban on agricultural land sale and eliminating the illegal land market, a tenfold increase in budget spending on health, setting up primary health centres in every village)The Communist Party May Be on Its Last Legs, But Social Populism is Still Alive, The Ukrainian Week (23 October 2014) and mixes them with strong nationalist sentiments. |
Agrarianism | United Kingdom | United Kingdom
In land law the heyday of English, Irish (and thus Welsh) agrarianism was to 1603, led by the Tudor royal advisors, who sought to maintain a broad pool of agricultural commoners from which to draw military men, against the interests of larger landowners who sought enclosure (meaning complete private control of common land, over which by custom and common law lords of the manor always enjoyed minor rights). The heyday was eroded by hundreds of Acts of Parliament to expressly permit enclosure, chiefly from 1650 to the 1810s. Politicians standing strongly as reactionaries to this included the Levellers, those anti-industrialists (Luddites) going beyond opposing new weaving technology and, later, radicals such as William Cobbett.
A high level of net national or local self-sufficiency has a strong base in campaigns and movements. In the 19th century such empowered advocates included Peelites and most Conservatives. The 20th century saw the growth or start of influential non-governmental organisations, such as the National Farmers' Union of England and Wales, Campaign for Rural England, Friends of the Earth (EWNI) and of the England Wales, Scottish and Northern Irish political parties prefixed by and focussed on Green politics. The 21st century has seen decarbonisation already in electricity markets. Following protests and charitable lobbying local food has seen growing market share, sometimes backed by wording in public policy papers and manifestos. The UK has many sustainability-prioritising businesses, green charity campaigns, events and lobby groups ranging from espousing allotment gardens (hobby community farming) through to a clear policy of local food and/or self-sustainability models. |
Agrarianism | Oceania | Oceania |
Agrarianism | Australia | Australia
Historian F.K. Crowley finds that:
The National Party of Australia (formerly called the Country Party), from the 1920s to the 1970s, promulgated its version of agrarianism, which it called "countrymindedness". The goal was to enhance the status of the graziers (operators of big sheep stations) and small farmers and justified subsidies for them.Rae Wear, "Countrymindedness Revisited," (Australian Political Science Association, 1990) online edition |
Agrarianism | New Zealand | New Zealand
The New Zealand Liberal Party aggressively promoted agrarianism in its heyday (1891–1912). The landed gentry and aristocracy ruled Britain at this time. New Zealand never had an aristocracy but its wealthy landowners largely controlled politics before 1891. The Liberal Party set out to change that by a policy it called "populism." Richard Seddon had proclaimed the goal as early as 1884: "It is the rich and the poor; it is the wealthy and the landowners against the middle and labouring classes. That, Sir, shows the real political position of New Zealand." The Liberal strategy was to create a large class of small landowning farmers who supported Liberal ideals. The Liberal government also established the basis of the later welfare state such as old age pensions and developed a system for settling industrial disputes, which was accepted by both employers and trade unions. In 1893, it extended voting rights to women, making New Zealand the first country in the world to do so.
To obtain land for farmers, the Liberal government from 1891 to 1911 purchased of Maori land. The government also purchased from large estate holders for subdivision and closer settlement by small farmers. The Advances to Settlers Act (1894) provided low-interest mortgages, and the agriculture department disseminated information on the best farming methods. The Liberals proclaimed success in forging an egalitarian, anti-monopoly land policy. The policy built up support for the Liberal Party in rural North Island electorates. By 1903, the Liberals were so dominant that there was no longer an organized opposition in Parliament.James Belich, Paradise Reforged: A history of the New Zealanders (2001) pp. 39–46Tom Brooking, "'Busting Up' the Greatest Estate of All: Liberal Maori Land Policy, 1891–1911," New Zealand Journal of History (1992) 26#1 pp. 78–98 online |
Agrarianism | North America | North America
The United States and Canada both saw a rise of Agrarian-oriented parties in the early twentieth century as economic troubles motivated farming communities to become politically active. It has been proposed that different responses to agrarian protest largely determined the course of power generated by these newly energized rural factions. According to Sociologist Barry Eidlin:"In the United States, Democrats adopted a co-optive response to farmer and labor protest, incorporating these constituencies into the New Deal coalition. In Canada, both mainstream parties adopted a coercive response, leaving these constituencies politically excluded and available for an independent left coalition."These reactions may have helped determine the outcome of agrarian power and political associations in the US and Canada. |
Agrarianism | United States of America | United States of America |
Agrarianism | Kansas | Kansas
Economic desperation experienced by farmers across the state of Kansas in the nineteenth century spurred the creation of The People's Party in 1890, and soon-after would gain control of the governor's office in 1892. This party, consisting of a mix of Democrats, Socialists, Populists, and Fusionists, would find itself buckling from internal conflict regarding the unlimited coinage of silver. The Populists permanently lost power in 1898. |
Agrarianism | Oklahoma | Oklahoma
Oklahoma farmers considered their political activity during the early twentieth century due to the outbreak of war, depressed crop prices, and an inhibited sense of progression towards owning their own farms. Tenancy had been reportedly as high as 55% in Oklahoma by 1910. These pressures saw agrarian counties in Oklahoma supporting Socialist policies and politics, with the Socialist platform proposing a deeply agrarian-radical platform:...the platform proposed a "Renters and Farmer's Program" which was strongly agrarian radical in its insistence upon various measures to put land into "The hands of the actual tillers of the soil." Although it did not propose to nationalize privately owned land, it did offer numerous plans to enlarge the state's public domain, from which land would be rented at prevailing share rents to tenants until they had paid rent equal to the land's value. The tenant and his children would have the right of occupancy and use, but the 'title' would remind in the 'commonwealth', an arrangement that might be aptly termed 'Socialist fee simple'. They proposed to exempt from taxation all farm dwellings, animals, and improvements up to the value of $1,000. The State Board of Agriculture would encourage 'co-operative societies' of farmers to make plans for the purchase of land, seed, tools, and for preparing and selling produce. In order to give farmers essential services at cost, the Socialists called for the creation of state banks and mortgage agencies, crop insurance, elevators, and warehouses.This agrarian-backed Socialist party would win numerous offices, causing a panic within the local Democratic party. This agrarian-Socialist movement would be inhibited by voter suppression laws aimed at reducing the participation of voters of color, as well as national wartime policies intended to disrupt political elements considered subversive. This party would peak in power in 1914. |
Agrarianism | Back-to-the-land movement | Back-to-the-land movement
Agrarianism is similar to but not identical with the back-to-the-land movement. Agrarianism concentrates on the fundamental goods of the earth, on communities of more limited economic and political scale than in modern society, and on simple living, even when the shift involves questioning the "progressive" character of some recent social and economic developments. Thus, agrarianism is not industrial farming, with its specialization on products and industrial scale.Jeffrey Carl Jacob, New Pioneers: The Back-to-the-Land Movement and the Search for a Sustainable Future (Penn State University Press. 1997) |
Agrarianism | See also | See also
Agrarian socialism
Farmer–Labor Party, USA early 20th century
Jeffersonian democracy
Labour-Farmer Party, Japan 1920s
Minnesota Farmer–Labor Party, USA early 20th century
United Farmers of Canada, Canada early 20th century
Progressive Party of Canada, Canada early 20th century
Social Credit Party of Canada, Canada early to mid 20th century
Co-operative Commonwealth Federation, Canada early to mid 20th century
Nordic agrarian parties
Yeoman, English farmers |
Agrarianism | References | References |
Agrarianism | Further reading | Further reading |
Agrarianism | Agrarian values | Agrarian values
Brass, Tom. Peasants, Populism and Postmodernism: The Return of the Agrarian Myth (2000)
Marx, Leo. The Machine in the Garden: Technology and the Pastoral Ideal in America (1964).
Murphy, Paul V. The Rebuke of History: The Southern Agrarians and American Conservative Thought (2000)
Parrington, Vernon. Main Currents in American Thought (1927), 3-vol online
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Agrarianism | Primary sources | Primary sources
Sorokin, Pitirim A. et al., eds. A Systematic Source Book in Rural Sociology (3 vol. 1930) vol 1 pp. 1–146 covers many major thinkers down to 1800 |
Agrarianism | Europe | Europe
Bell, John D. Peasants in Power: Alexander Stamboliski and the Bulgarian Agrarian National Union, 1899–1923(1923)
Donnelly, James S. Captain Rock: The Irish Agrarian Rebellion of 1821–1824 (2009)
Donnelly, James S. Irish Agrarian Rebellion, 1760–1800 (2006)
Gross, Feliks, ed. European Ideologies: A Survey of 20th Century Political Ideas (1948) pp. 391–481 online edition , on Russia and Bulgaria
Kubricht, Andrew Paul. "The Czech Agrarian Party, 1899–1914: a study of national and economic agitation in the Habsburg monarchy" (PhD thesis, Ohio State University Press, 1974)
Oren, Nissan. Revolution Administered: Agrarianism and Communism in Bulgaria (1973), focus is post 1945
Stefanov, Kristian. Between Ideological Loyalty and Political Adaptation: 'The Agrarian Question' in the Development of Bulgarian Social Democracy, 1891–1912, East European Politics, Societies and Cultures, Is. 4, 2023.
Roberts, Henry L. Rumania: Political Problems of an Agrarian State (1951).
North America
Goodwyn, Lawrence. The Populist Moment: A Short History of the Agrarian Revolt in America (1978), 1880s and 1890s in U.S.
Lipset, Seymour Martin. Agrarian socialism: the Coöperative Commonwealth Federation in Saskatchewan (1950), 1930s–1940s
McConnell, Grant. The decline of agrarian democracy(1953), 20th century U.S.
Mark, Irving. Agrarian conflicts in colonial New York, 1711–1775 (1940)
Robison, Dan Merritt. Bob Taylor and the agrarian revolt in Tennessee (1935)
Stine, Harold E. The agrarian revolt in South Carolina;: Ben Tillman and the Farmers' Alliance (1974)
Szatmary, David P. Shays' Rebellion: The Making of an Agrarian Insurrection (1984), 1787 in Massachusetts
Woodward, C. Vann. Tom Watson: Agrarian Rebel (1938) online edition
Global South
Handy, Jim. Revolution in the Countryside: Rural Conflict and Agrarian Reform in Guatemala, 1944–1954 (1994)
Paige, Jeffery M. Agrarian revolution: social movements and export agriculture in the underdeveloped world (1978) 435 pages excerpt and text search
Sanderson, Steven E. Agrarian populism and the Mexican state: the struggle for land in Sonora'' (1981)
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Agrarianism | External links | External links
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Agrarianism | Table of Content | Short description, Philosophy, History, Types of agrarianism, Physiocracy, Jeffersonian democracy, Agrarian socialism, Zapatismo, Maoism, Notable agrarian parties, Europe, Bulgaria, Czechoslovakia, France, Hungary, Ireland, Kazakhstan, Latvia, Lithuania, Nordic countries, Poland, Romania, Serbia, Ukraine, United Kingdom, Oceania, Australia, New Zealand, North America, United States of America, Kansas, Oklahoma, Back-to-the-land movement, See also, References, Further reading, Agrarian values, Primary sources, Europe, External links |
Atomic | wiktionary | Atomic may refer to:
Of or relating to the atom, the smallest particle of a chemical element that retains its chemical properties
Atomic physics, the study of the atom
Atomic Age, also known as the "Atomic Era"
Atomic scale, distances comparable to the dimensions of an atom
Atom (order theory), in mathematics
Atomic (coffee machine), a 1950s stovetop coffee machine
Atomic (cocktail), a champagne cocktail
Atomic (magazine), an Australian computing and technology magazine
Atomic Skis, an Austrian ski producer |
Atomic | Music | Music
Atomic (band), a Norwegian jazz quintet
Atomic (Lit album), 2001
Atomic (Mogwai album), 2016
Atomic, an album by Rockets, 1982
Atomic (EP), by , 2013
"Atomic" (song), by Blondie, 1979
"Atomic", a song by Tiger Army from Tiger Army III: Ghost Tigers Rise |
Atomic | See also | See also
Atom (disambiguation)
Atomicity (database systems)
Atomism, philosophy about the basic building blocks of reality
Atomic City (disambiguation)
Atomic formula, a formula without subformulas
Atomic number, the number of protons found in the nucleus of an atom
Atomic chess, a chess variant
Atomic operation, in computer science
Atomic TV, a channel launched in 1997 in Poland
History of atomic theory
Nuclear power
Nuclear weapon
Nuclear (disambiguation) |
Atomic | Table of Content | wiktionary, Music, See also |
Angle | Short description | alt=two line bent at a point|thumb|upright=1.25|A green angle formed by two red rays on the Cartesian coordinate system
In Euclidean geometry, an angle or plane angle is the figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex of the angle.
Two intersecting curves may also define an angle, which is the angle of the rays lying tangent to the respective curves at their point of intersection. Angles are also formed by the intersection of two planes; these are called dihedral angles.
In any case, the resulting angle lies in a plane (spanned by the two rays or perpendicular to the line of plane-plane intersection).
The magnitude of an angle is called an angular measure or simply "angle". This measure, for an ordinary angle, is often visualized or defined using the arc of a circle centered at the vertex and lying between the sides. Two different angles may have the same measure, as in an isosceles triangle. "Angle" also denotes the angular sector, the infinite region of the plane bounded by the sides of an angle.
Angle of rotation is a measure conventionally defined as the ratio of a circular arc length to its radius, and may be a negative number; the arc is centered at the center of the rotation and delimited by any other point and its image after the rotation. |
Angle | History and etymology | History and etymology
The word angle comes from the Latin word , meaning "corner". Cognate words include the Greek () meaning "crooked, curved" and the English word "ankle". Both are connected with the Proto-Indo-European root *ank-, meaning "to bend" or "bow".
Euclid defines a plane angle as the inclination to each other, in a plane, of two lines that meet each other and do not lie straight with respect to each other. According to the Neoplatonic metaphysician Proclus, an angle must be either a quality, a quantity, or a relationship. The first concept, angle as quality, was used by Eudemus of Rhodes, who regarded an angle as a deviation from a straight line; the second, angle as quantity, by Carpus of Antioch, who regarded it as the interval or space between the intersecting lines; Euclid adopted the third: angle as a relationship.; |
Angle | Identifying angles | Identifying angles
In mathematical expressions, it is common to use Greek letters (α, β, γ, θ, φ, . . . ) as variables denoting the size of some angle (the symbol is typically not used for this purpose to avoid confusion with the constant denoted by that symbol). Lower case Roman letters (a, b, c, . . . ) are also used. In contexts where this is not confusing, an angle may be denoted by the upper case Roman letter denoting its vertex. See the figures in this article for examples.
The three defining points may also identify angles in geometric figures. For example, the angle with vertex A formed by the rays AB and AC (that is, the half-lines from point A through points B and C) is denoted or . Where there is no risk of confusion, the angle may sometimes be referred to by a single vertex alone (in this case, "angle A").
In other ways, an angle denoted as, say, might refer to any of four angles: the clockwise angle from B to C about A, the anticlockwise angle from B to C about A, the clockwise angle from C to B about A, or the anticlockwise angle from C to B about A, where the direction in which the angle is measured determines its sign (see ). However, in many geometrical situations, it is evident from the context that the positive angle less than or equal to 180 degrees is meant, and in these cases, no ambiguity arises. Otherwise, to avoid ambiguity, specific conventions may be adopted so that, for instance, always refers to the anticlockwise (positive) angle from B to C about A and the anticlockwise (positive) angle from C to B about A. |
Angle | Types{{anchor | Types |
Angle | Individual angles | Individual angles
There is some common terminology for angles, whose measure is always non-negative (see ):
An angle equal to 0° or not turned is called a zero angle.
An angle smaller than a right angle (less than 90°) is called an acute angle ("acute" meaning "sharp").
An angle equal to turn (90° or radians) is called a right angle. Two lines that form a right angle are said to be normal, orthogonal, or perpendicular.
An angle larger than a right angle and smaller than a straight angle (between 90° and 180°) is called an obtuse angle ("obtuse" meaning "blunt").
An angle equal to turn (180° or radians) is called a straight angle.
An angle larger than a straight angle but less than 1 turn (between 180° and 360°) is called a reflex angle.
An angle equal to 1 turn (360° or 2 radians) is called a full angle, complete angle, round angle or perigon.
An angle that is not a multiple of a right angle is called an oblique angle.
The names, intervals, and measuring units are shown in the table below:
Name zero angle acute angle right angle obtuse angle straight angle reflex angle perigon Unit Interval turn radian degree 0° (0, 90)° 90° (90, 180)° 180° (180, 360)° 360° gon 0g (0, 100)g 100g (100, 200)g 200g (200, 400)g 400g |
Angle | Vertical and {{vanchor | Vertical and angle pairs
thumb|150px|right|Angles A and B are a pair of vertical angles; angles C and D are a pair of vertical angles. Hatch marks are used here to show angle equality.
When two straight lines intersect at a point, four angles are formed. Pairwise, these angles are named according to their location relative to each other.
A transversal is a line that intersects a pair of (often parallel) lines and is associated with exterior angles, interior angles, alternate exterior angles, alternate interior angles, corresponding angles, and consecutive interior angles. |
Angle | Combining angle pairs | Combining angle pairs
The angle addition postulate states that if B is in the interior of angle AOC, then
I.e., the measure of the angle AOC is the sum of the measure of angle AOB and the measure of angle BOC.
Three special angle pairs involve the summation of angles:
thumb|150px|The complementary angles a and b (b is the complement of a, and a is the complement of b.) |
Angle | Polygon-related angles | Polygon-related angles
thumb|300px|right|Internal and external angles
An angle that is part of a simple polygon is called an interior angle if it lies on the inside of that simple polygon. A simple concave polygon has at least one interior angle, that is, a reflex angle. In Euclidean geometry, the measures of the interior angles of a triangle add up to radians, 180°, or turn; the measures of the interior angles of a simple convex quadrilateral add up to 2 radians, 360°, or 1 turn. In general, the measures of the interior angles of a simple convex polygon with n sides add up to (n − 2) radians, or (n − 2)180 degrees, (n − 2)2 right angles, or (n − 2) turn.
The supplement of an interior angle is called an exterior angle; that is, an interior angle and an exterior angle form a linear pair of angles. There are two exterior angles at each vertex of the polygon, each determined by extending one of the two sides of the polygon that meet at the vertex; these two angles are vertical and hence are equal. An exterior angle measures the amount of rotation one must make at a vertex to trace the polygon. If the corresponding interior angle is a reflex angle, the exterior angle should be considered negative. Even in a non-simple polygon, it may be possible to define the exterior angle. Still, one will have to pick an orientation of the plane (or surface) to decide the sign of the exterior angle measure. In Euclidean geometry, the sum of the exterior angles of a simple convex polygon, if only one of the two exterior angles is assumed at each vertex, will be one full turn (360°). The exterior angle here could be called a supplementary exterior angle. Exterior angles are commonly used in Logo Turtle programs when drawing regular polygons.
In a triangle, the bisectors of two exterior angles and the bisector of the other interior angle are concurrent (meet at a single point).Johnson, Roger A. Advanced Euclidean Geometry, Dover Publications, 2007.
In a triangle, three intersection points, each of an external angle bisector with the opposite extended side, are collinear.
In a triangle, three intersection points, two between an interior angle bisector and the opposite side, and the third between the other exterior angle bisector and the opposite side extended are collinear.
Some authors use the name exterior angle of a simple polygon to mean the explement exterior angle (not supplement!) of the interior angle. as cited in This conflicts with the above usage. |
Angle | Plane-related angles | Plane-related angles
The angle between two planes (such as two adjacent faces of a polyhedron) is called a dihedral angle. It may be defined as the acute angle between two lines normal to the planes.
The angle between a plane and an intersecting straight line is complementary to the angle between the intersecting line and the normal to the plane. |
Angle | Measuring angles{{anchor | Measuring angles
Measurement of angles is intrinsically linked with circles and rotation. The angle is first considered as within a circle of given size, centred at the vertex, and from that arrangement a ratio of certain lengths can be used quantify the angle size. As there are a number of valid measurement approaches, some have argued it useful to consider angle size as being proportional to these ratios, rather than defined by or equal to them.
The usual characterization is to consider the smallest rotation of one of the rays about the vertex that maps it onto the other. The length of the arc, s, traced along the circle as the ray is rotated is said to be the arc length that is subtended by (or equivalently, subtends) the angle. However as s is dependent on the arbitrary choice of circle size, the ratio of length s to either the radius or circumference of the circle gives a general measure of angle size.
The ratio of the length s by the radius r is the number of radians in the angle, while the ratio of length s by the circumference C is the number of turns:
right|thumb|The measure of angle is .
The value of thus defined is independent of the size of the circle: if the length of the radius is changed, then the arc length changes in the same proportion, so the ratio s/r is unaltered.
Conventionally, in mathematics and the SI, the radian is treated as being equal to the dimensionless unit 1, thus being normally omitted.
Other angular units are typically based on subdivisions of the turn and may then be obtained by multiplying the angle by a suitable conversion constant of the form , where k is the measure of a complete turn expressed in the chosen unit (for example, for degrees or 400 grad for gradians):
Angles of the same size are said to be equal congruent or equal in measure.
In some contexts, such as identifying a point on a circle or describing the orientation of an object in two dimensions relative to a reference orientation, angles that differ by an exact multiple of a full turn are effectively equivalent. In other contexts, such as identifying a point on a spiral curve or describing an object's cumulative rotation in two dimensions relative to a reference orientation, angles that differ by a non-zero multiple of a full turn are not equivalent. |
Angle | Units | Units
right|thumb|150 px|Definition of 1 radian
Throughout history, angles have been measured in various units. These are known as angular units, with the most contemporary units being the degree ( ° ), the radian (rad), and the gradian (grad), though many others have been used throughout history.
In the International System of Quantities, an angle is defined as a dimensionless quantity, and in particular, the radian unit is dimensionless. This convention impacts how angles are treated in dimensional analysis.
The following table lists some units used to represent angles.
Name Number in one turnIn degrees Descriptionradian≈57°17′45″The radian is determined by the circumference of a circle that is equal in length to the radius of the circle (n = 2 = 6.283...). It is the angle subtended by an arc of a circle that has the same length as the circle's radius. The symbol for radian is rad. One turn is 2 radians, and one radian is , or about 57.2958 degrees. Often, particularly in mathematical texts, one radian is assumed to equal one, resulting in the unit rad being omitted. The radian is used in virtually all mathematical work beyond simple, practical geometry due, for example, to the pleasing and "natural" properties that the trigonometric functions display when their arguments are in radians. The radian is the (derived) unit of angular measurement in the SI.degree 360 1° The degree, denoted by a small superscript circle (°), is 1/360 of a turn, so one turn is 360°. One advantage of this old sexagesimal subunit is that many angles common in simple geometry are measured as a whole number of degrees. Fractions of a degree may be written in normal decimal notation (e.g., 3.5° for three and a half degrees), but the "minute" and "second" sexagesimal subunits of the "degree–minute–second" system (discussed next) are also in use, especially for geographical coordinates and in astronomy and ballistics (n = 360) arcminute21,600 0°1′ The minute of arc (or MOA, arcminute, or just minute) is of a degree = turn. It is denoted by a single prime ( ′ ). For example, 3° 30′ is equal to 3 × 60 + 30 = 210 minutes or 3 + = 3.5 degrees. A mixed format with decimal fractions is sometimes used, e.g., 3° 5.72′ = 3 + degrees. A nautical mile was historically defined as an arcminute along a great circle of the Earth. (n = 21,600). arcsecond1,296,000 0°0′1″The second of arc (or arcsecond, or just second) is of a minute of arc and of a degree (n = 1,296,000). It is denoted by a double prime ( ″ ). For example, 3° 7′ 30″ is equal to 3 + + degrees, or 3.125 degrees. The arcsecond is the angle used to measure a parsec grad400 0°54′ The grad, also called grade, gradian, or gon. It is a decimal subunit of the quadrant. A right angle is 100 grads. A kilometre was historically defined as a centi-grad of arc along a meridian of the Earth, so the kilometer is the decimal analog to the sexagesimal nautical mile (n = 400). The grad is used mostly in triangulation and continental surveying.turn1360° The turn is the angle subtended by the circumference of a circle at its centre. A turn is equal to 2 or (tau) radians. hour angle 24 15° The astronomical hour angle is turn. As this system is amenable to measuring objects that cycle once per day (such as the relative position of stars), the sexagesimal subunits are called minute of time and second of time. These are distinct from, and 15 times larger than, minutes and seconds of arc. 1 hour = 15° = rad = quad = turn = grad. (compass) point 32 11°15′ The point or wind, used in navigation, is of a turn. 1 point = of a right angle = 11.25° = 12.5 grad. Each point is subdivided into four quarter points, so one turn equals 128. milliradian ≈0.057° The true milliradian is defined as a thousandth of a radian, which means that a rotation of one turn would equal exactly 2000π mrad (or approximately 6283.185 mrad). Almost all scope sights for firearms are calibrated to this definition. In addition, three other related definitions are used for artillery and navigation, often called a 'mil', which are approximately equal to a milliradian. Under these three other definitions, one turn makes up for exactly 6000, 6300, or 6400 mils, spanning the range from 0.05625 to 0.06 degrees (3.375 to 3.6 minutes). In comparison, the milliradian is approximately 0.05729578 degrees (3.43775 minutes). One "NATO mil" is defined as of a turn. Just like with the milliradian, each of the other definitions approximates the milliradian's useful property of subtensions, i.e. that the value of one milliradian approximately equals the angle subtended by a width of 1 meter as seen from 1 km away ( = 0.0009817... ≈ ).binary degree 2561°33′45″ The binary degree, also known as the binary radian or brad or binary angular measurement (BAM). The binary degree is used in computing so that an angle can be efficiently represented in a single byte (albeit to limited precision). Other measures of the angle used in computing may be based on dividing one whole turn into 2n equal parts for other values of n.
It is of a turn. radian2180° The multiples of radians (MUL) unit is implemented in the RPN scientific calculator WP 43S. See also: IEEE 754 recommended operationsquadrant490°One quadrant is a turn and also known as a right angle. The quadrant is the unit in Euclid's Elements. In German, the symbol ∟ has been used to denote a quadrant. 1 quad = 90° = rad = turn = 100 grad.sextant660°The sextant was the unit used by the Babylonians, The degree, minute of arc and second of arc are sexagesimal subunits of the Babylonian unit. It is straightforward to construct with ruler and compasses. It is the angle of the equilateral triangle or is turn. 1 Babylonian unit = 60° = /3 rad ≈ 1.047197551 rad. hexacontade60 6°The hexacontade is a unit used by Eratosthenes. It equals 6°, so a whole turn was divided into 60 hexacontades. pechus 144 to 180 2° to 2°30′ The pechus was a Babylonian unit equal to about 2° or °. diameter part ≈376.991 ≈0.95493° The diameter part (occasionally used in Islamic mathematics) is radian. One "diameter part" is approximately 0.95493°. There are about 376.991 diameter parts per turn. zam 224 ≈1.607° In old Arabia, a turn was subdivided into 32 Akhnam, and each akhnam was subdivided into 7 zam so that a turn is 224 zam. |
Angle | Dimensional analysis | Dimensional analysis |
Angle | Signed angles <span class="anchor" id="Sign"></span><span class="anchor" id="Positive and negative angles"></span> | Signed angles
right|thumb|Measuring from the x-axis, angles on the unit circle count as positive in the counterclockwise direction, and negative in the clockwise direction.
It is frequently helpful to impose a convention that allows positive and negative angular values to represent orientations and/or rotations in opposite directions or "sense" relative to some reference.
In a two-dimensional Cartesian coordinate system, an angle is typically defined by its two sides, with its vertex at the origin. The initial side is on the positive x-axis, while the other side or terminal side is defined by the measure from the initial side in radians, degrees, or turns, with positive angles representing rotations toward the positive y-axis and negative angles representing rotations toward the negative y-axis. When Cartesian coordinates are represented by standard position, defined by the x-axis rightward and the y-axis upward, positive rotations are anticlockwise, and negative cycles are clockwise.
In many contexts, an angle of −θ is effectively equivalent to an angle of "one full turn minus θ". For example, an orientation represented as −45° is effectively equal to an orientation defined as 360° − 45° or 315°. Although the final position is the same, a physical rotation (movement) of −45° is not the same as a rotation of 315° (for example, the rotation of a person holding a broom resting on a dusty floor would leave visually different traces of swept regions on the floor).
In three-dimensional geometry, "clockwise" and "anticlockwise" have no absolute meaning, so the direction of positive and negative angles must be defined in terms of an orientation, which is typically determined by a normal vector passing through the angle's vertex and perpendicular to the plane in which the rays of the angle lie.
In navigation, bearings or azimuth are measured relative to north. By convention, viewed from above, bearing angles are positive clockwise, so a bearing of 45° corresponds to a north-east orientation. Negative bearings are not used in navigation, so a north-west orientation corresponds to a bearing of 315°. |
Angle | Equivalent angles | Equivalent angles
Angles that have the same measure (i.e., the same magnitude) are said to be equal or congruent. An angle is defined by its measure and is not dependent upon the lengths of the sides of the angle (e.g., all right angles are equal in measure).
Two angles that share terminal sides, but differ in size by an integer multiple of a turn, are called coterminal angles.
The reference angle (sometimes called related angle) for any angle θ in standard position is the positive acute angle between the terminal side of θ and the x-axis (positive or negative). Procedurally, the magnitude of the reference angle for a given angle may determined by taking the angle's magnitude modulo turn, 180°, or radians, then stopping if the angle is acute, otherwise taking the supplementary angle, 180° minus the reduced magnitude. For example, an angle of 30 degrees is already a reference angle, and an angle of 150 degrees also has a reference angle of 30 degrees (180° − 150°). Angles of 210° and 510° correspond to a reference angle of 30 degrees as well (210° mod 180° = 30°, 510° mod 180° = 150° whose supplementary angle is 30°). |
Angle | Related quantities | Related quantities
For an angular unit, it is definitional that the angle addition postulate holds. Some quantities related to angles where the angle addition postulate does not hold include:
The slope or gradient is equal to the tangent of the angle; a gradient is often expressed as a percentage. For very small values (less than 5%), the slope of a line is approximately the measure in radians of its angle with the horizontal direction.
The spread between two lines is defined in rational geometry as the square of the sine of the angle between the lines. As the sine of an angle and the sine of its supplementary angle are the same, any angle of rotation that maps one of the lines into the other leads to the same value for the spread between the lines.
Although done rarely, one can report the direct results of trigonometric functions, such as the sine of the angle. |
Angle | Angles between curves | Angles between curves
thumb|right|The angle between the two curves at P is defined as the angle between the tangents A and B at P.
The angle between a line and a curve (mixed angle) or between two intersecting curves (curvilinear angle) is defined to be the angle between the tangents at the point of intersection. Various names (now rarely, if ever, used) have been given to particular cases:—amphicyrtic (Gr. , on both sides, κυρτός, convex) or cissoidal (Gr. κισσός, ivy), biconvex; xystroidal or sistroidal (Gr. ξυστρίς, a tool for scraping), concavo-convex; amphicoelic (Gr. κοίλη, a hollow) or angulus lunularis, biconcave.; |
Angle | Bisecting and trisecting angles | Bisecting and trisecting angles
The ancient Greek mathematicians knew how to bisect an angle (divide it into two angles of equal measure) using only a compass and straightedge but could only trisect certain angles. In 1837, Pierre Wantzel showed that this construction could not be performed for most angles. |
Angle | Dot product and generalisations{{anchor | Dot product and generalisations
In the Euclidean space, the angle θ between two Euclidean vectors u and v is related to their dot product and their lengths by the formula
This formula supplies an easy method to find the angle between two planes (or curved surfaces) from their normal vectors and between skew lines from their vector equations. |
Angle | Inner product | Inner product
To define angles in an abstract real inner product space, we replace the Euclidean dot product ( · ) by the inner product , i.e.
In a complex inner product space, the expression for the cosine above may give non-real values, so it is replaced with
or, more commonly, using the absolute value, with
The latter definition ignores the direction of the vectors. It thus describes the angle between one-dimensional subspaces and spanned by the vectors and correspondingly. |
Angle | Angles between subspaces | Angles between subspaces
The definition of the angle between one-dimensional subspaces and given by
in a Hilbert space can be extended to subspaces of finite dimensions. Given two subspaces , with , this leads to a definition of angles called canonical or principal angles between subspaces. |
Angle | Angles in Riemannian geometry | Angles in Riemannian geometry
In Riemannian geometry, the metric tensor is used to define the angle between two tangents. Where U and V are tangent vectors and gij are the components of the metric tensor G, |
Angle | Hyperbolic angle | Hyperbolic angle
A hyperbolic angle is an argument of a hyperbolic function just as the circular angle is the argument of a circular function. The comparison can be visualized as the size of the openings of a hyperbolic sector and a circular sector since the areas of these sectors correspond to the angle magnitudes in each case.Robert Baldwin Hayward (1892) The Algebra of Coplanar Vectors and Trigonometry, chapter six Unlike the circular angle, the hyperbolic angle is unbounded. When the circular and hyperbolic functions are viewed as infinite series in their angle argument, the circular ones are just alternating series forms of the hyperbolic functions. This comparison of the two series corresponding to functions of angles was described by Leonhard Euler in Introduction to the Analysis of the Infinite (1748). |
Angle | Angles in geography and astronomy | Angles in geography and astronomy
In geography, the location of any point on the Earth can be identified using a geographic coordinate system. This system specifies the latitude and longitude of any location in terms of angles subtended at the center of the Earth, using the equator and (usually) the Greenwich meridian as references.
In astronomy, a given point on the celestial sphere (that is, the apparent position of an astronomical object) can be identified using any of several astronomical coordinate systems, where the references vary according to the particular system. Astronomers measure the angular separation of two stars by imagining two lines through the center of the Earth, each intersecting one of the stars. The angle between those lines and the angular separation between the two stars can be measured.
In both geography and astronomy, a sighting direction can be specified in terms of a vertical angle such as altitude /elevation with respect to the horizon as well as the azimuth with respect to north.
Astronomers also measure objects' apparent size as an angular diameter. For example, the full moon has an angular diameter of approximately 0.5° when viewed from Earth. One could say, "The Moon's diameter subtends an angle of half a degree." The small-angle formula can convert such an angular measurement into a distance/size ratio.
Other astronomical approximations include:
0.5° is the approximate diameter of the Sun and of the Moon as viewed from Earth.
1° is the approximate width of the little finger at arm's length.
10° is the approximate width of a closed fist at arm's length.
20° is the approximate width of a handspan at arm's length.
These measurements depend on the individual subject, and the above should be treated as rough rule of thumb approximations only.
In astronomy, right ascension and declination are usually measured in angular units, expressed in terms of time, based on a 24-hour day.
Unit Symbol Degrees Radians Turns Other Hour h 15° rad turn Minute m 0°15′ rad turn hour Second s 0°0′15″ rad turn minute |
Angle | See also | See also
Angle measuring instrument
Angles between flats
Angular statistics (mean, standard deviation)
Angle bisector
Angular acceleration
Angular diameter
Angular velocity
Argument (complex analysis)
Astrological aspect
Central angle
Clock angle problem
Decimal degrees
Dihedral angle
Exterior angle theorem
Golden angle
Great circle distance
Horn angle
Inscribed angle
Irrational angle
Phase (waves)
Protractor
Solid angle
Spherical angle
Subtended angle
Tangential angle
Transcendent angle
Trisection
Zenith angle |
Angle | Notes | Notes |
Angle | References | References |
Angle | Bibliography | Bibliography
.
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Angle | External links | External links
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Angle | Table of Content | Short description, History and etymology, Identifying angles, Types{{anchor, Individual angles, Vertical and {{vanchor, Combining angle pairs, Polygon-related angles, Plane-related angles, Measuring angles{{anchor, Units, Dimensional analysis, Signed angles <span class="anchor" id="Sign"></span><span class="anchor" id="Positive and negative angles"></span>, Equivalent angles, Related quantities, Angles between curves, Bisecting and trisecting angles, Dot product and generalisations{{anchor, Inner product, Angles between subspaces, Angles in Riemannian geometry, Hyperbolic angle, Angles in geography and astronomy, See also, Notes, References, Bibliography, External links |
Asa | wiktionary | Asa may refer to: |
Asa | People and fictional characters | People and fictional characters
Asa (given name), a given name, including a list of people and fictional characters so named
Asa people, an ethnic group based in Tanzania
Aṣa, Nigerian-French singer, songwriter, and recording artist Bukola Elemide (born 1982)
Asa (rapper), Finnish rapper Matti Salo (born 1980) |
Asa | Biblical and mythological figures | Biblical and mythological figures
Asa of Judah, third king of the Kingdom of Judah and the fifth king of the House of David
Ása or Æsir, Norse gods |
Asa | Places | Places
Asa, Hardoi Uttar Pradesh, India, a village
Asu, South Khorasan, Iran, also spelled Asa, a village
Asa, Kwara State, Nigeria, a local government area
Asa River (Japan), a tributary of the Tama River in Tokyo, Japan
Asa (Kazakhstan), a river
Asa River (Venezuela), a river in Venezuela |
Asa | Other uses | Other uses
Acrylonitrile styrene acrylate, acrylic styrene acrylonitrile, an amorphous thermoplastic
Asa (album), the sixth studio album by the German Viking metal band Falkenbach
Asa (raga), a peculiar musical raga in Gurmat Sangeet tradition
ASA carriage control characters, simple printing command characters used to control the movement of paper through line printers
Asa language, spoken by the Asa people of Tanzania
Asa Station, a railway station in San'yō-Onoda, Yamaguchi, Japan
Asa (railway station), Jambyl Region, Kazakhstan
Naboot, also called asa, a quarterstaff constructed of palm wood or rattan
Asha, romanized as aṣ̌a, a Zoroastrian concept
"Asa", a song by Kitt Wakeley featuring Starr Parodi from An Adoption Story, 2022
“Asa”, 2024 single by Snazzy the Optimist |
Asa | See also | See also
ASA (disambiguation)
Åsa (disambiguation)
Aasa (disambiguation)
Asia (disambiguation)
Aza (disambiguation) |
Asa | Table of Content | wiktionary, People and fictional characters, Biblical and mythological figures, Places, Other uses, See also |
Acoustics | short description | thumb|alt=Lindsay's Wheel of acoustics|upright=1.75|Lindsay's Wheel of Acoustics, which shows fields within acoustics
Acoustics is a branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics technology may be called an acoustical engineer. The application of acoustics is present in almost all aspects of modern society with the most obvious being the audio and noise control industries.
Hearing is one of the most crucial means of survival in the animal world and speech is one of the most distinctive characteristics of human development and culture. Accordingly, the science of acoustics spreads across many facets of human society—music, medicine, architecture, industrial production, warfare and more. Likewise, animal species such as songbirds and frogs use sound and hearing as a key element of mating rituals or for marking territories. Art, craft, science and technology have provoked one another to advance the whole, as in many other fields of knowledge. Robert Bruce Lindsay's "Wheel of Acoustics" is a well-accepted overview of the various fields in acoustics. |
Acoustics | History | History |
Acoustics | Etymology | Etymology
The word "acoustic" is derived from the Greek word ἀκουστικός (akoustikos), meaning "of or for hearing, ready to hear"Akoustikos Henry George Liddell, Robert Scott, A Greek-English Lexicon, at Perseus and that from ἀκουστός (akoustos), "heard, audible",Akoustos Henry George Liddell, Robert Scott, A Greek-English Lexicon, at Perseus which in turn derives from the verb ἀκούω(akouo), "I hear".Akouo Henry George Liddell, Robert Scott, A Greek-English Lexicon, at Perseus
The Latin synonym is "sonic", after which the term sonics used to be a synonym for acoustics and later a branch of acoustics. Frequencies above and below the audible range are called "ultrasonic" and "infrasonic", respectively. |
Acoustics | Early research in acoustics | Early research in acoustics
thumb|The fundamental and the first 6 overtones of a vibrating string. The earliest records of the study of this phenomenon are attributed to the philosopher Pythagoras in the 6th century BC.
In the 6th century BC, the ancient Greek philosopher Pythagoras wanted to know why some combinations of musical sounds seemed more beautiful than others, and he found answers in terms of numerical ratios representing the harmonic overtone series on a string. He is reputed to have observed that when the lengths of vibrating strings are expressible as ratios of integers (e.g. 2 to 3, 3 to 4), the tones produced will be harmonious, and the smaller the integers the more harmonious the sounds. For example, a string of a certain length would sound particularly harmonious with a string of twice the length (other factors being equal). In modern parlance, if a string sounds the note C when plucked, a string twice as long will sound a C an octave lower. In one system of musical tuning, the tones in between are then given by 16:9 for D, 8:5 for E, 3:2 for F, 4:3 for G, 6:5 for A, and 16:15 for B, in ascending order.C. Boyer and U. Merzbach. A History of Mathematics. Wiley 1991, p. 55.
Aristotle (384–322 BC) understood that sound consisted of compressions and rarefactions of air which "falls upon and strikes the air which is next to it...", (quoting from Aristotle's Treatise on Sound and Hearing) a very good expression of the nature of wave motion. On Things Heard, generally ascribed to Strato of Lampsacus, states that the pitch is related to the frequency of vibrations of the air and to the speed of sound.
In about 20 BC, the Roman architect and engineer Vitruvius wrote a treatise on the acoustic properties of theaters including discussion of interference, echoes, and reverberation—the beginnings of architectural acoustics.ACOUSTICS, Bruce Lindsay, Dowden – Hutchingon Books Publishers, Chapter 3 In Book V of his (The Ten Books of Architecture) Vitruvius describes sound as a wave comparable to a water wave extended to three dimensions, which, when interrupted by obstructions, would flow back and break up following waves. He described the ascending seats in ancient theaters as designed to prevent this deterioration of sound and also recommended bronze vessels (echea) of appropriate sizes be placed in theaters to resonate with the fourth, fifth and so on, up to the double octave, in order to resonate with the more desirable, harmonious notes.Vitruvius Pollio, Vitruvius, the Ten Books on Architecture (1914) Tr. Morris Hickey Morgan BookV, Sec.6–8Vitruvius article @WikiquoteErnst Mach, Introduction to The Science of Mechanics: A Critical and Historical Account of its Development (1893, 1960) Tr. Thomas J. McCormack
During the Islamic golden age, Abū Rayhān al-Bīrūnī (973–1048) is believed to have postulated that the speed of sound was much slower than the speed of light.
thumb|left|Principles of acoustics have been applied since ancient times: a Roman theatre in the city of Amman
The physical understanding of acoustical processes advanced rapidly during and after the Scientific Revolution. Mainly Galileo Galilei (1564–1642) but also Marin Mersenne (1588–1648), independently, discovered the complete laws of vibrating strings (completing what Pythagoras and Pythagoreans had started 2000 years earlier). Galileo wrote "Waves are produced by the vibrations of a sonorous body, which spread through the air, bringing to the tympanum of the ear a stimulus which the mind interprets as sound", a remarkable statement that points to the beginnings of physiological and psychological acoustics. Experimental measurements of the speed of sound in air were carried out successfully between 1630 and 1680 by a number of investigators, prominently Mersenne. Inspired by Mersenne's Harmonie universelle (Universal Harmony) or 1634, the Rome-based Jesuit scholar Athanasius Kircher undertook research in acoustics.P. Findlen, Athanasius Kircher: The Last Man who Knew Everything, Routledge, 2004, p. 8 and p. 23. Kircher published two major books on acoustics: the Musurgia universalis (Universal Music-Making) in 1650Athanasius Kircher, Musurgia universalis sive Ars magna consoni et dissoni, Romae, typis Ludovici Grignani, 1650 and the Phonurgia nova (New Sound-Making) in 1673.Athanasius Kircher, Phonurgia nova, sive conjugium mechanico-physicum artis & natvrae paranympha phonosophia concinnatum, Campidonae: Rudolphum Dreherr, 1673. Meanwhile, Newton (1642–1727) derived the relationship for wave velocity in solids, a cornerstone of physical acoustics (Principia, 1687). |
Acoustics | Age of Enlightenment and onward | Age of Enlightenment and onward
Substantial progress in acoustics, resting on firmer mathematical and physical concepts, was made during the eighteenth century by Euler (1707–1783), Lagrange (1736–1813), and d'Alembert (1717–1783). During this era, continuum physics, or field theory, began to receive a definite mathematical structure. The wave equation emerged in a number of contexts, including the propagation of sound in air.
In the nineteenth century the major figures of mathematical acoustics were Helmholtz in Germany, who consolidated the field of physiological acoustics, and Lord Rayleigh in England, who combined the previous knowledge with his own copious contributions to the field in his monumental work The Theory of Sound (1877). Also in the 19th century, Wheatstone, Ohm, and Henry developed the analogy between electricity and acoustics.
The twentieth century saw a burgeoning of technological applications of the large body of scientific knowledge that was by then in place. The first such application was Sabine's groundbreaking work in architectural acoustics, and many others followed. Underwater acoustics was used for detecting submarines in the first World War. Sound recording and the telephone played important roles in a global transformation of society. Sound measurement and analysis reached new levels of accuracy and sophistication through the use of electronics and computing. The ultrasonic frequency range enabled wholly new kinds of application in medicine and industry. New kinds of transducers (generators and receivers of acoustic energy) were invented and put to use. |
Acoustics | Definition | Definition
Acoustics is defined by ANSI/ASA S1.1-2013 as "(a) Science of sound, including its production, transmission, and effects, including biological and psychological effects. (b) Those qualities of a room that, together, determine its character with respect to auditory effects."
The study of acoustics revolves around the generation, propagation and reception of mechanical waves and vibrations.
The fundamental acoustical process
The steps shown in the above diagram can be found in any acoustical event or process. There are many kinds of cause, both natural and volitional. There are many kinds of transduction process that convert energy from some other form into sonic energy, producing a sound wave. There is one fundamental equation that describes sound wave propagation, the acoustic wave equation, but the phenomena that emerge from it are varied and often complex. The wave carries energy throughout the propagating medium. Eventually this energy is transduced again into other forms, in ways that again may be natural and/or volitionally contrived. The final effect may be purely physical or it may reach far into the biological or volitional domains. The five basic steps are found equally well whether we are talking about an earthquake, a submarine using sonar to locate its foe, or a band playing in a rock concert.
The central stage in the acoustical process is wave propagation. This falls within the domain of physical acoustics. In fluids, sound propagates primarily as a pressure wave. In solids, mechanical waves can take many forms including longitudinal waves, transverse waves and surface waves.
Acoustics looks first at the pressure levels and frequencies in the sound wave and how the wave interacts with the environment. This interaction can be described as either a diffraction, interference or a reflection or a mix of the three. If several media are present, a refraction can also occur. Transduction processes are also of special importance to acoustics. |
Acoustics | Fundamental concepts | Fundamental concepts |
Acoustics | Wave propagation: pressure levels | Wave propagation: pressure levels
thumb|Spectrogram of a young girl saying "oh, no"
In fluids such as air and water, sound waves propagate as disturbances in the ambient pressure level. While this disturbance is usually small, it is still noticeable to the human ear. The smallest sound that a person can hear, known as the threshold of hearing, is nine orders of magnitude smaller than the ambient pressure. The loudness of these disturbances is related to the sound pressure level (SPL) which is measured on a logarithmic scale in decibels. |
Acoustics | Wave propagation: frequency | Wave propagation: frequency
Physicists and acoustic engineers tend to discuss sound pressure levels in terms of frequencies, partly because this is how our ears interpret sound. What we experience as "higher pitched" or "lower pitched" sounds are pressure vibrations having a higher or lower number of cycles per second. In a common technique of acoustic measurement, acoustic signals are sampled in time, and then presented in more meaningful forms such as octave bands or time frequency plots. Both of these popular methods are used to analyze sound and better understand the acoustic phenomenon.
The entire spectrum can be divided into three sections: audio, ultrasonic, and infrasonic. The audio range falls between 20 Hz and 20,000 Hz. This range is important because its frequencies can be detected by the human ear. This range has a number of applications, including speech communication and music. The ultrasonic range refers to the very high frequencies: 20,000 Hz and higher. This range has shorter wavelengths which allow better resolution in imaging technologies. Medical applications such as ultrasonography and elastography rely on the ultrasonic frequency range. On the other end of the spectrum, the lowest frequencies are known as the infrasonic range. These frequencies can be used to study geological phenomena such as earthquakes.
Analytic instruments such as the spectrum analyzer facilitate visualization and measurement of acoustic signals and their properties. The spectrogram produced by such an instrument is a graphical display of the time varying pressure level and frequency profiles which give a specific acoustic signal its defining character. |
Acoustics | Transduction in acoustics | Transduction in acoustics
thumb|An inexpensive low fidelity 3.5 inch driver, typically found in small radios
A transducer is a device for converting one form of energy into another. In an electroacoustic context, this means converting sound energy into electrical energy (or vice versa). Electroacoustic transducers include loudspeakers, microphones, particle velocity sensors, hydrophones and sonar projectors. These devices convert a sound wave to or from an electric signal. The most widely used transduction principles are electromagnetism, electrostatics and piezoelectricity.
The transducers in most common loudspeakers (e.g. woofers and tweeters), are electromagnetic devices that generate waves using a suspended diaphragm driven by an electromagnetic voice coil, sending off pressure waves. Electret microphones and condenser microphones employ electrostatics—as the sound wave strikes the microphone's diaphragm, it moves and induces a voltage change. The ultrasonic systems used in medical ultrasonography employ piezoelectric transducers. These are made from special ceramics in which mechanical vibrations and electrical fields are interlinked through a property of the material itself. |
Acoustics | Acoustician | Acoustician
An acoustician is an expert in the science of sound. |
Acoustics | Education | Education
There are many types of acoustician, but they usually have a Bachelor's degree or higher qualification. Some possess a degree in acoustics, while others enter the discipline via studies in fields such as physics or engineering. Much work in acoustics requires a good grounding in Mathematics and science. Many acoustic scientists work in research and development. Some conduct basic research to advance our knowledge of the perception (e.g. hearing, psychoacoustics or neurophysiology) of speech, music and noise. Other acoustic scientists advance understanding of how sound is affected as it moves through environments, e.g. underwater acoustics, architectural acoustics or structural acoustics. Other areas of work are listed under subdisciplines below. Acoustic scientists work in government, university and private industry laboratories. Many go on to work in Acoustical Engineering. Some positions, such as Faculty (academic staff) require a Doctor of Philosophy. |
Acoustics | Subdisciplines | Subdisciplines |
Acoustics | Archaeoacoustics | Archaeoacoustics
thumb|St. Michael's Cave
Archaeoacoustics, also known as the archaeology of sound, is one of the only ways to experience the past with senses other than our eyes. Archaeoacoustics is studied by testing the acoustic properties of prehistoric sites, including caves. Iegor Rezkinoff, a sound archaeologist, studies the acoustic properties of caves through natural sounds like humming and whistling. Archaeological theories of acoustics are focused around ritualistic purposes as well as a way of echolocation in the caves. In archaeology, acoustic sounds and rituals directly correlate as specific sounds were meant to bring ritual participants closer to a spiritual awakening. Parallels can also be drawn between cave wall paintings and the acoustic properties of the cave; they are both dynamic. Because archaeoacoustics is a fairly new archaeological subject, acoustic sound is still being tested in these prehistoric sites today. |
Acoustics | Aeroacoustics | Aeroacoustics
Aeroacoustics is the study of noise generated by air movement, for instance via turbulence, and the movement of sound through the fluid air. This knowledge was applied in the 1920s and '30s to detect aircraft before radar was invented and is applied in acoustical engineering to study how to quieten aircraft. Aeroacoustics is important for understanding how wind musical instruments work. |
Acoustics | Acoustic signal processing | Acoustic signal processing
Acoustic signal processing is the electronic manipulation of acoustic signals. Applications include: active noise control; design for hearing aids or cochlear implants; echo cancellation; music information retrieval, and perceptual coding (e.g. MP3 or Opus). |
Acoustics | Architectural acoustics | Architectural acoustics
thumb|right|Symphony Hall, Boston, where auditorium acoustics began
Architectural acoustics (also known as building acoustics) involves the scientific understanding of how to achieve good sound within a building. It typically involves the study of speech intelligibility, speech privacy, music quality, and vibration reduction in the built environment. Commonly studied environments are hospitals, classrooms, dwellings, performance venues, recording and broadcasting studios. Focus considerations include room acoustics, airborne and impact transmission in building structures, airborne and structure-borne noise control, noise control of building systems and electroacoustic systems. |
Acoustics | Bioacoustics | Bioacoustics
Bioacoustics is the scientific study of the hearing and calls of animal calls, as well as how animals are affected by the acoustic and sounds of their habitat. |
Acoustics | Electroacoustics | Electroacoustics
This subdiscipline is concerned with the recording, manipulation and reproduction of audio using electronics. This might include products such as mobile phones, large scale public address systems or virtual reality systems in research laboratories. |
Acoustics | Environmental noise and soundscapes | Environmental noise and soundscapes
Environmental acoustics is the study of noise and vibrations, and their impact on structures, objects, humans, and animals.
The main aim of these studies is to reduce levels of environmental noise and vibration. Typical work and research within environmental acoustics concerns the development of models used in simulations, measurement techniques, noise mitigation strategies, and the development of standards and regulations. Research work now also has a focus on the positive use of sound in urban environments: soundscapes and tranquility.
Examples of noise and vibration sources include railways, road traffic, aircraft, industrial equipment and recreational activities. |
Acoustics | Musical acoustics | Musical acoustics
thumb|The primary auditory cortex, one of the main areas associated with superior pitch resolution
Musical acoustics is the study of the physics of acoustic instruments; the audio signal processing used in electronic music; the computer analysis of music and composition, and the perception and cognitive neuroscience of music. |
Acoustics | Psychoacoustics | Psychoacoustics
Many studies have been conducted to identify the relationship between acoustics and cognition, or more commonly known as psychoacoustics, in which what one hears is a combination of perception and biological aspects. The information intercepted by the passage of sound waves through the ear is understood and interpreted through the brain, emphasizing the connection between the mind and acoustics. Psychological changes have been seen as brain waves slow down or speed up as a result of varying auditory stimulus which can in turn affect the way one thinks, feels, or even behaves. This correlation can be viewed in normal, everyday situations in which listening to an upbeat or uptempo song can cause one's foot to start tapping or a slower song can leave one feeling calm and serene. In a deeper biological look at the phenomenon of psychoacoustics, it was discovered that the central nervous system is activated by basic acoustical characteristics of music. By observing how the central nervous system, which includes the brain and spine, is influenced by acoustics, the pathway in which acoustic affects the mind, and essentially the body, is evident. |
Acoustics | Speech | Speech
Acousticians study the production, processing and perception of speech. Speech recognition and Speech synthesis are two important areas of speech processing using computers. The subject also overlaps with the disciplines of physics, physiology, psychology, and linguistics. |
Acoustics | Structural Vibration and Dynamics | Structural Vibration and Dynamics
Structural acoustics is the study of motions and interactions of mechanical systems with their environments and the methods of their measurement, analysis, and control. There are several sub-disciplines found within this regime:
Modal Analysis
Material characterization
Structural health monitoring
Acoustic Metamaterials
Friction Acoustics
Applications might include: ground vibrations from railways; vibration isolation to reduce vibration in operating theatres; studying how vibration can damage health (vibration white finger); vibration control to protect a building from earthquakes, or measuring how structure-borne sound moves through buildings. |
Acoustics | Ultrasonics | Ultrasonics
thumb|Ultrasound image of a fetus in the womb, viewed at 12 weeks of pregnancy (bidimensional-scan)
Ultrasonics deals with sounds at frequencies too high to be heard by humans. Specialisms include medical ultrasonics (including medical ultrasonography), sonochemistry, ultrasonic testing, material characterisation and underwater acoustics (sonar). |
Acoustics | Underwater acoustics | Underwater acoustics
Underwater acoustics is the scientific study of natural and man-made sounds underwater. Applications include sonar to locate submarines, underwater communication by whales, climate change monitoring by measuring sea temperatures acoustically, sonic weapons, and marine bioacoustics. |
Acoustics | Research | Research |
Acoustics | Professional societies | Professional societies
The Acoustical Society of America (ASA)
Australian Acoustical Society (AAS)
The European Acoustics Association (EAA)
Institute of Electrical and Electronics Engineers (IEEE)
Institute of Acoustics (IoA UK)
The Audio Engineering Society (AES)
American Society of Mechanical Engineers, Noise Control and Acoustics Division (ASME-NCAD)
International Commission for Acoustics (ICA)
American Institute of Aeronautics and Astronautics, Aeroacoustics (AIAA)
International Computer Music Association (ICMA) |
Acoustics | Academic journals | Academic journals
Acoustics | An Open Access Journal from MDPI
Acoustics Today
Acta Acustica united with Acustica
Advances in Acoustics and Vibration
Applied Acoustics
Building Acoustics
IEEE Transacions on Ultrasonics, Ferroelectrics, and Frequency Control
Journal of the Acoustical Society of America (JASA)
Journal of the Acoustical Society of America, Express Letters (JASA-EL)
Journal of the Audio Engineering Society
Journal of Sound and Vibration (JSV)
Journal of Vibration and Acoustics American Society of Mechanical Engineers
MDPI Acoustics
Noise Control Engineering Journal
SAE International Journal of Vehicle Dynamics, Stability and NVH
Ultrasonics (journal)
Ultrasonics Sonochemistry
Wave Motion |
Acoustics | Conferences | Conferences
InterNoise
NoiseCon
Forum Acousticum
SAE Noise and Vibration Conference and Exhibition |
Acoustics | See also | See also
Outline of acoustics
Acoustic attenuation
Acoustic emission
Acoustic engineering
Acoustic impedance
Acoustic levitation
Acoustic location
Acoustic phonetics
Acoustic streaming
Acoustic tags
Acoustic theory
Acoustic thermometry
Acoustic wave
Audiology
Auditory illusion
Diffraction
Doppler effect
Fisheries acoustics
Friction acoustics
Helioseismology
Lamb wave
Linear elasticity
The Little Red Book of Acoustics (in the UK)
Longitudinal wave
Musicology
Music therapy
Noise pollution
Phonon
Picosecond ultrasonics
Rayleigh wave
Shock wave
Seismology
Sonification
Sonochemistry
Soundproofing
Soundscape
Sonic boom
Sonoluminescence
Surface acoustic wave
Thermoacoustics
Transverse wave
Wave equation |
Acoustics | References | References |
Acoustics | Further reading | Further reading
|
Acoustics | External links | External links
International Commission for Acoustics
European Acoustics Association
Acoustical Society of America
Institute of Noise Control Engineers
National Council of Acoustical Consultants
Institute of Acoustic in UK
Australian Acoustical Society (AAS)
Category:Sound |
Acoustics | Table of Content | short description, History, Etymology, Early research in acoustics, Age of Enlightenment and onward, Definition, Fundamental concepts, Wave propagation: pressure levels, Wave propagation: frequency, Transduction in acoustics, Acoustician, Education, Subdisciplines, Archaeoacoustics, Aeroacoustics, Acoustic signal processing, Architectural acoustics, Bioacoustics, Electroacoustics, Environmental noise and soundscapes, Musical acoustics, Psychoacoustics, Speech, Structural Vibration and Dynamics, Ultrasonics, Underwater acoustics, Research, Professional societies, Academic journals, Conferences, See also, References, Further reading, External links |
Atomic physics | Short description | Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. Atomic physics typically refers to the study of atomic structure and the interaction between atoms. It is primarily concerned with the way in which electrons are arranged around the nucleus and
the processes by which these arrangements change. This comprises ions, neutral atoms and, unless otherwise stated, it can be assumed that the term atom includes ions.
The term atomic physics can be associated with nuclear power and nuclear weapons, due to the synonymous use of atomic and nuclear in standard English. Physicists distinguish between atomic physics—which deals with the atom as a system consisting of a nucleus and electrons—and nuclear physics, which studies nuclear reactions and special properties of atomic nuclei.
As with many scientific fields, strict delineation can be highly contrived and atomic physics is often considered in the wider context of atomic, molecular, and optical physics. Physics research groups are usually so classified. |
Atomic physics | Isolated atoms | Isolated atoms
Atomic physics primarily considers atoms in isolation. Atomic models will consist of a single nucleus that may be surrounded by one or more bound electrons. It is not concerned with the formation of molecules (although much of the physics is identical), nor does it examine atoms in a solid state as condensed matter. It is concerned with processes such as ionization and excitation by photons or collisions with atomic particles.
While modelling atoms in isolation may not seem realistic, if one considers atoms in a gas or plasma then the time-scales for atom-atom interactions are huge in comparison to the atomic processes that are generally considered. This means that the individual atoms can be treated as if each were in isolation, as the vast majority of the time they are. By this consideration, atomic physics provides the underlying theory in plasma physics and atmospheric physics, even though both deal with very large numbers of atoms. |
Atomic physics | Electronic configuration | Electronic configuration
Electrons form notional shells around the nucleus. These are normally in a ground state but can be excited by the absorption of energy from light (photons), magnetic fields, or interaction with a colliding particle (typically ions or other electrons).
thumb|In the Bohr model, the transition of an electron with n=3 to the shell n=2 is shown, where a photon is emitted. An electron from shell (n=2) must have been removed beforehand by ionization Electrons that populate a shell are said to be in a bound state. The energy necessary to remove an electron from its shell (taking it to infinity) is called the binding energy. Any quantity of energy absorbed by the electron in excess of this amount is converted to kinetic energy according to the conservation of energy. The atom is said to have undergone the process of ionization.
If the electron absorbs a quantity of energy less than the binding energy, it will be transferred to an excited state. After a certain time, the electron in an excited state will "jump" (undergo a transition) to a lower state. In a neutral atom, the system will emit a photon of the difference in energy, since energy is conserved.
If an inner electron has absorbed more than the binding energy (so that the atom ionizes), then a more outer electron may undergo a transition to fill the inner orbital. In this case, a visible photon or a characteristic X-ray is emitted, or a phenomenon known as the Auger effect may take place, where the released energy is transferred to another bound electron, causing it to go into the continuum. The Auger effect allows one to multiply ionize an atom with a single photon.
There are rather strict selection rules as to the electronic configurations that can be reached by excitation by light — however, there are no such rules for excitation by collision processes. |
Atomic physics | Bohr Model of the Atom | Bohr Model of the Atom
The Bohr model, proposed by Niels Bohr in 1913, is a revolutionary theory describing the structure of the hydrogen atom. It introduced the idea of quantized orbits for electrons, combining classical and quantum physics.
Key Postulates of the Bohr Model
1. Electrons Move in Circular Orbits:
• Electrons revolve around the nucleus in fixed, circular paths called orbits or energy levels.
• These orbits are stable and do not radiate energy.
2. Quantization of Angular Momentum:
• The angular momentum of an electron is quantized and given by:
where:
• Mass of the electron.
• Velocity of the electron.
• Radius of the orbit.
• Reduced Planck's constant ().
• Principal quantum number, representing the orbit.
3. Energy Levels:
• Each orbit has a specific energy. The total energy of an electron in the th orbit is:
where is the ground-state energy of the hydrogen atom.
4. Emission or Absorption of Energy:
• Electrons can transition between orbits by absorbing or emitting energy equal to the difference between the energy levels:
where:
• Planck's constant.
• Frequency of emitted/absorbed radiation.
• Final and initial energy levels. |
Atomic physics | History and developments | History and developments
One of the earliest steps towards atomic physics was the recognition that matter was composed
of atoms. It forms a part of the texts written in 6th century BC to 2nd century BC, such as those of Democritus or written by . This theory was later developed in the modern sense of the basic unit of a chemical element by the British chemist and physicist John Dalton in the 18th century. At this stage, it was not clear what atoms were, although they could be described and classified by their properties (in bulk). The invention of the periodic system of elements by Dmitri Mendeleev was another great step forward.
The true beginning of atomic physics is marked by the discovery of spectral lines and attempts to describe the phenomenon, most notably by Joseph von Fraunhofer. The study of these lines led to the Bohr atom model and to the birth of quantum mechanics. In seeking to explain atomic spectra, an entirely new mathematical model of matter was revealed. As far as atoms and their electron shells were concerned, not only did this yield a better overall description, i.e. the atomic orbital model, but it also provided a new theoretical basis for chemistry
(quantum chemistry) and spectroscopy.
Since the Second World War, both theoretical and experimental fields have advanced at a rapid pace. This can be attributed to progress in computing technology, which has allowed larger and more sophisticated models of atomic structure and associated collision processes. Similar technological advances in accelerators, detectors, magnetic field generation and lasers have greatly assisted experimental work.
Beyond the well-known phenomena which can be describe with regular quantum mechanics chaotic processes can occur which need different descriptions. |
Atomic physics | Significant atomic physicists | Significant atomic physicists |
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