Sphere
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| :''[[Spheres (Peter Sloterdijk)]]'' | :''[[Spheres (Peter Sloterdijk)]]'' | ||
| - | # A regular three-dimensional object in which every [[cross-section]] is a [[circle]]; the figure described by the revolution of a semi-circle about its diameter. | + | A '''sphere''' (from [[Greek language|Greek]] ''σφαῖρα''—''sphaira'', "globe, ball") is a perfectly round [[geometrical]] object in [[solid geometry|three-dimensional space]], such as the shape of a round [[ball]]. Like a [[circle]] in two dimensions, a perfect sphere is completely [[symmetrical]] around its center, with all points on the surface lying the same distance ''r'' from the center point. This distance ''r'' is known as the '''[[radius]]''' of the sphere. The maximum straight distance through the sphere is known as the '''[[diameter]]''' of the sphere. It passes through the center and is thus twice the radius. |
| - | # A spherical object; a [[globe]] or [[ball]]. | + | |
| - | # The apparent outer limit of space, the edge of the heavens, imagined as a hollow globe within which celestial bodies appear to be embedded. | + | In higher mathematics, a careful distinction is made between the sphere (a two-dimensional spherical surface [[embedding|embedded]] in three-dimensional [[Euclidean space]]) and the [[Ball (mathematics)|ball]] (the three-dimensional shape consisting of a sphere and its interior). |
| - | # Any of the concentric hollow transparent globes formerly believed to rotate around the [[Earth]], and which carried the heavenly bodies; there were originally believed to be eight, and later nine and ten; friction between them was thought to cause a harmonious sound (the ''[[music of the spheres]]''). | + | |
| - | #* '''1603''', John Florio, translating Michel de Montaigne, ''Essays'', vol. 1 p. 153: | + | ==See also== |
| - | #*: It is more simplicitie to teach our children [...] [t]he knowledge of the starres, and the motion of the eighth '''spheare''', before their owne. | + | *[[3-sphere]] |
| - | # An area of activity for a planet; or by extension, an area of influence for a [[god]], [[hero]] etc. | + | *[[Affine sphere]] |
| - | # The region in which something or someone is active; one's [[province]], [[domain]]. | + | *[[Alexander horned sphere]] |
| + | *[[Ball (mathematics)]] | ||
| + | *[[Banach–Tarski paradox]] | ||
| + | *[[Cube]] | ||
| + | *[[Cuboid]] | ||
| + | *[[Curvature]] | ||
| + | *[[Directional statistics]] | ||
| + | *[[Dome (mathematics)]] | ||
| + | *[[Dyson sphere]] | ||
| + | *[[Hoberman sphere]] | ||
| + | *[[Homology sphere]] | ||
| + | *[[Homotopy groups of spheres]] | ||
| + | *[[Homotopy sphere]] | ||
| + | *[[Hypersphere]] | ||
| + | *[[Metric space]] | ||
| + | *[[Napkin ring problem]] | ||
| + | *[[Pseudosphere]] | ||
| + | *[[Riemann sphere]] | ||
| + | *[[Smale's paradox]] | ||
| + | *[[Solid angle]] | ||
| + | *[[Sphere packing]] | ||
| + | *[[Spherical cap]] | ||
| + | *[[Spherical helix]] | ||
| + | *[[Spherical sector]] | ||
| + | *[[Spherical segment]] | ||
| + | *[[Spherical shell]] | ||
| + | *[[Spherical wedge]] | ||
| + | *[[Spherical zone]] | ||
| + | *[[Spherical coordinates]] | ||
| + | *[[Spherical Earth]] | ||
| + | *[[Zoll surface|Zoll sphere]] | ||
| - | ====Synonyms==== | ||
| - | * (''object''): [[ball]], [[globe]], [[orb]] | ||
| - | * (''region of activity''): [[area]], [[domain]], [[field]], [[orbit]], [[sector]] | ||
| {{GFDL}} | {{GFDL}} | ||
Revision as of 12:38, 3 December 2011
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A sphere (from Greek σφαῖρα—sphaira, "globe, ball") is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point. This distance r is known as the radius of the sphere. The maximum straight distance through the sphere is known as the diameter of the sphere. It passes through the center and is thus twice the radius.
In higher mathematics, a careful distinction is made between the sphere (a two-dimensional spherical surface embedded in three-dimensional Euclidean space) and the ball (the three-dimensional shape consisting of a sphere and its interior).
See also
- 3-sphere
- Affine sphere
- Alexander horned sphere
- Ball (mathematics)
- Banach–Tarski paradox
- Cube
- Cuboid
- Curvature
- Directional statistics
- Dome (mathematics)
- Dyson sphere
- Hoberman sphere
- Homology sphere
- Homotopy groups of spheres
- Homotopy sphere
- Hypersphere
- Metric space
- Napkin ring problem
- Pseudosphere
- Riemann sphere
- Smale's paradox
- Solid angle
- Sphere packing
- Spherical cap
- Spherical helix
- Spherical sector
- Spherical segment
- Spherical shell
- Spherical wedge
- Spherical zone
- Spherical coordinates
- Spherical Earth
- Zoll sphere
Unless indicated otherwise, the text in this article is either based on Wikipedia article "Sphere" or another language Wikipedia page thereof used under the terms of the GNU Free Documentation License; or on research by Jahsonic and friends. See Art and Popular Culture's copyright notice.
