The distance between two points is the length of a straight line segment between them. In the case of two locations on Earth, usually the distance along the surface is meant: either "as the crow flies" (along a great circle) or by road, railroad, etc. Distance is sometimes expressed in terms of the time to cover it, for example walking or by car. Sometimes a distance thus indicated is ambiguous because the means ...

Including:

• Distance - Distance covered
• Distance - Formal definition
• Distance - The distance formula
• Distance - Generalized distance in arbitrary dimensions: Norms
• Distance - Distances in other spaces

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See also:

Euclidean distance, Euclidean distance - Definition, Euclidean distance - One-dimensional distance, Euclidean distance - Two-dimensional distance, Euclidean distance - 2D approximations for computer applications, Euclidean distance - Three-dimensional distance, Euclidean distance - 3D approximations for computer applications

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For two 3D points, and , the distance is computed as: Euclidean distance - 3D approximations for computer applications. As noted in the 2D approximation section, when comparing distances (for which is greatest, not for the actual difference), it isn't necessary to take the square root at all. If distance A is greater than distance B, then A2 will also be greater than ...

See also:

Euclidean distance, Euclidean distance - Definition, Euclidean distance - One-dimensional distance, Euclidean distance - Two-dimensional distance, Euclidean distance - 2D approximations for computer applications, Euclidean distance - Three-dimensional distance, Euclidean distance - 3D approximations for computer applications

Read more here: » Euclidean distance: Encyclopedia II - Euclidean distance - Three-dimensional distance

The absolute value is closely related to the idea of distance. As noted above, the absolute value of a real or complex number is the distance from that number to the origin, along the real number line, for real numbers, or in the complex plane, for complex numbers, and more generally, the absolute value of the difference of two real or complex numbers is the distance between them. The standard Euclidean distance between two points and in Euclidean nSee also:

Absolute value, Absolute value - Real numbers, Absolute value - Complex numbers, Absolute value - Absolute value functions, Absolute value - Ordered rings, Absolute value - Distance, Absolute value - Fields, Absolute value - Vector spaces, Absolute value - Algorithms, Absolute value - Notes

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The distance to the Pleiades has been estimated by many methods, as it is an important step in calibrating distance scales for the whole universe. Accurate knowledge of the distance to the Pleiades allows astronomers to plot a Hertzsprung-Russell Diagram for the cluster, which, when compared to those plotted for clusters whose distance is not known, allows their distances to be estimated. Other methods can then extend the distance scale from open clusters to galaxies and clusters of galaxies ...

See also:

Pleiades star cluster, Pleiades star cluster - History, Pleiades star cluster - Distance, Pleiades star cluster - Composition, Pleiades star cluster - Age and future evolution, Pleiades star cluster - Reflection nebulosity, Pleiades star cluster - Names and technical information, Pleiades star cluster - The Pleiades in folklore

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The length of a marathon was not fixed, since all that was important was that all athletes competed on the same course. The exact length of an Olympic marathon varied depending on the route established for each venue. The choice of distance was somewhat arbitrary. The first Olympics in 1896 had a marathon distance of 40 km. The starting point for the 1908 Olympic marathon in London was modified so that the Royal Family could have a good view and the length happened to be 42.195 km (26 miles 385 yards). For the next Olympics in 1912, t ...

See also:

Marathon sport, Marathon sport - Distance, Marathon sport - History, Marathon sport - World records and world's best, Marathon sport - The Olympic traditions, Marathon sport - Running a marathon, Marathon sport - Glycogen and the wall, Marathon sport - Training, Marathon sport - Before the race, Marathon sport - During the race, Marathon sport - After the marathon, Marathon sport - Marathon races, Marathon sport - Notable marathon runners, Marathon sport - Men, Marathon sport - Women

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A long standing problem in the study of planetary nebulae is that their distances are generally not well known. Many methods for estimating distances to planetary nebulae rely on making general assumptions, which may be very inaccurate for the object concerned. In recent years, however, observations made using the Hubble Space Telescope have allowed a new method of determining distances. All planetary nebulae are expanding, and observations several years apart and with high enough angular resolution will reveal the growth of the nebul ...

See also:

Cat's Eye Nebula, Cat's Eye Nebula - General information, Cat's Eye Nebula - Observations, Cat's Eye Nebula - Infrared observations, Cat's Eye Nebula - Optical and ultraviolet observations, Cat's Eye Nebula - X-ray observations, Cat's Eye Nebula - Distance, Cat's Eye Nebula - Age, Cat's Eye Nebula - Composition, Cat's Eye Nebula - Kinematics and morphology, Cat's Eye Nebula - Open questions

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The distance dG(u, v) between two (not necessary distinct) vertices u and v in a graph G is the length of a shortest path between them. The subscript G is usually dropped when there is no danger of confusion. When u and v are identical, their distance is 0. When u and v are unreachable from each ...

See also:

Glossary of graph theory, Glossary of graph theory - Basics, Glossary of graph theory - Subgraphs, Glossary of graph theory - Paths and walks, Glossary of graph theory - Cycles, Glossary of graph theory - Trees, Glossary of graph theory - Cliques, Glossary of graph theory - Strongly connected component, Glossary of graph theory - Knots, Glossary of graph theory - Minors, Glossary of graph theory - Embedding, Glossary of graph theory - Adjacency and degree, Glossary of graph theory - Independence, Glossary of graph theory - Connectivity, Glossary of graph theory - Distance, Glossary of graph theory - Genus, Glossary of graph theory - Weighted graphs and networks, Glossary of graph theory - Direction, Glossary of graph theory - Various, Glossary of graph theory - To be merged

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The distance from the basket to the three point line varies at different levels of play. For college basketball, the NCAA set the line at 19 feet, 9 inches in 1987. This distance is also used in US high schools, and it is the distance most commonly used on public courts. It is easily identifiable without measurement, as it coincides exactly with the top of the key. In international play (including Olympics), FIBA introduced the three- ...

See also:

Three-point field goal, Three-point field goal - Distance, Three-point field goal - Form, Three-point field goal - History, Three-point field goal - College vs. NBA vs. International, Three-point field goal - Utilization of the three-pointer in gameplay

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A distance between two points P and Q in a metric space is d(P,Q), where d is the distance function that defines the given metric space. We can also define the distance between two sets A and B in a metric space as being the minimum (or infimum) of distances between any two points P in A and Q in B. Alternatively, the distance between sets may indicate "how different they are", by taking the supremum over one set of the distance from a point in that set to the other set, and conversely, and taking the ...

See also:

Distance, Distance - Distance covered, Distance - Formal definition, Distance - The distance formula, Distance - Generalized distance in arbitrary dimensions: Norms, Distance - Distances in other spaces

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Distance education or distance learning is a field of education that focuses on the pedagogy/andragogy, technology, and instructional systems design that is effectively incorporated in delivering education to students who are not physically "on site" to receive their education. Instead, teachers and students may communicate asynchronously (at times of their own choosing) by exchanging printed or electronic media, or through technology that allows them to communicate in real time (synchronously). Distance education courses that require a physical on-site presence for any reason including the taking of examinations i ...

Including:

• Distance education - Major institutions offering distance learning programs
• Distance education - Azerbaijan
• Distance education - Australia
• Distance education - Canada
• Distance education - China
• Distance education - France
• Distance education - Germany
• Distance education - India
• Distance education - Iran
• Distance education - Ireland
• Distance education - Mexico
• Distance education - The Netherlands
• Distance education - Philippines
• Distance education - Portugal
• Distance education - Russia
• Distance education - Singapore
• Distance education - South Africa
• Distance education - Spain
• Distance education - Switzerland
• Distance education - Thailand
• Distance education - United Kingdom
• Distance education - United States
• Distance education - International

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Unicity distance is a term used in cryptography referring to the length of an original ciphertext needed to break the cipher by reducing the number of possible spurious keys to zero in a brute force attack. That is, after trying every possible key, there should be just one decipherment that makes sense. Consider an attack on the ciphertext string "WNAIW" encrypted using a Vigenere cipher with a five letter key. Conceivably, this string could be deciphered into any other string — RIVER and WATER are both possibilities f ...

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In mathematics, the Chebyshev distance between two points p and q in a Euclidean space with standard coordinates pi and qi respectively is maxi( | pi − qi | ). This concept is named after Pafnuty Chebyshev. In chess, the distance between square ...

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The cosmic distance ladder refers to the methods by which astronomers determine the distances to celestial objects. Each rung of the ladder provides information that can be used to determine the distances at the next higher rung. Many of the rungs involve standard candles — objects whose intrinsic brightness is believed known. By comparing the intrinsic brightness with the apparent brightness, one derives a distance. At the base of the ladder are radar observations of Venus, which allow one to determine the distance between the Earth an ...

Including:

• Cosmic distance ladder - Clarification

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For the computer science term, see Action at a distance (computer science). In physics, action at a distance is the interaction of two objects which are separated in space with no known mediator of the interaction. This term was used most often with early theories of gravity and electromagnetism to describe how an object could "know" the mass (in the case o ...

Including:

• Action at a distance physics - Electricity
• Action at a distance physics - Gravity
• Action at a distance physics - Newton
• Action at a distance physics - Einstein
• Action at a distance physics - Quantum mechanics

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On the Sizes and Distances [of the Sun and Moon] is the only extant work written by Aristarchus of Samos, an ancient Greek astronomer who lived circa 310 BC - 230 BC. In this work, he calculates the sizes of the Sun and Moon, as well as their distances from the Earth in Earth radii. Aristarchus On the Sizes and Distances - Symbols. His method relied on several very difficult observations: The angle between the sun and moon when the moon is exactly half lit The apparent size of t ...

Including:

• Aristarchus On the Sizes and Distances - Symbols
• Aristarchus On the Sizes and Distances - Half-lit Moon
• Aristarchus On the Sizes and Distances - Lunar eclipse
• Aristarchus On the Sizes and Distances - Results
• Aristarchus On the Sizes and Distances - Works cited

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edit The comoving distance or conformal distance of two objects in the universe is the distance divided by a time-varying scale factor representing the expansion of the universe. As a result the comoving distances on average are not increasing with time. The scale factor is usually taken to be one at present, so currently the comoving distance is equal to the ordinary distance. Comoving distance - Introduction. Thinking about the shape of the universe in the context of the stand ...

Including:

• Comoving distance - Introduction
• Comoving distance - Comoving coordinates
• Comoving distance - Comoving distance
• Comoving distance - Other useful distances
• Comoving distance - Small — galaxy or galaxy cluster — scales

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Action at a distance is an anti-pattern (a recognized common error) in which behavior in one part of a program varies wildly based on difficult or impossible to identify operations in another part of the program. The way to avoid the problems associated with action at a distance are a proper design which avoids global variables and alters data in a controlled and local manner. The term is based on the physics concept of the same name, where particles may ...

Including:

• Action at a distance computer science - Example
• Action at a distance computer science - Action at a distance across objects

Read more here: » Action at a distance computer science: Encyclopedia - Action at a distance computer science

One of the oldest distance education universities is the University of South Africa, which has been offering DE courses since 1946. The largest distance education university in the United Kingdom is the Open University founded 1969. In Germany the FernUniversität in Hagen was founded 1974. There are now many similar institutions around the world and these are listed below. There are many private and public, non-profit and for-profit institutions offering courses and degree programs through distance education. Levels of accredi ...

See also:

Distance education, Distance education - Origins, Distance education - Major institutions offering distance learning programs, Distance education - Azerbaijan, Distance education - Australia, Distance education - Belgium, Distance education - Brazil, Distance education - Canada, Distance education - China, Distance education - France, Distance education - Germany, Distance education - India, Distance education - Iran, Distance education - Ireland, Distance education - Israel, Distance education - Mexico, Distance education - The Netherlands, Distance education - Philippines, Distance education - Portugal, Distance education - Russia, Distance education - Singapore, Distance education - South Africa, Distance education - Spain, Distance education - Switzerland, Distance education - Thailand, Distance education - United Kingdom, Distance education - United States, Distance education - International, Distance education - Methods, Distance education - Delivery systems

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In Distance Education, students may not be required to be present in a classroom, but that also maybe a question of option. For example in the Open Universities in India, especially in the Indira Gandhi National Open University, week end contact sessions are held. These are optional, but for certain courses which have practical components such as those for computers, attendance to the tune of about 90% is compulsory. The National Open University in India is based on the United Kingdom Open University model (though it is many years since the ...

See also:

Distance education, Distance education - Origins, Distance education - Major institutions offering distance learning programs, Distance education - Azerbaijan, Distance education - Australia, Distance education - Belgium, Distance education - Brazil, Distance education - Canada, Distance education - China, Distance education - France, Distance education - Germany, Distance education - India, Distance education - Iran, Distance education - Ireland, Distance education - Israel, Distance education - Mexico, Distance education - The Netherlands, Distance education - Philippines, Distance education - Portugal, Distance education - Russia, Distance education - Singapore, Distance education - South Africa, Distance education - Spain, Distance education - Switzerland, Distance education - Thailand, Distance education - United Kingdom, Distance education - United States, Distance education - International, Distance education - Methods, Distance education - Delivery systems

Read more here: » Distance education: Encyclopedia II - Distance education - Methods