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, which is in two dimensions, a sphere is the set of points which are all the same distance r from a given point in space. This distance r is known as the "radius" of the sphere, and the given point is known as the center of the sphere. The maximum straight distance through the sphere is known as the "diameter". It passes through the center and is thus twice the radius.
In mathematics, a careful distinction is made between the sphere (a two-dimensional surface embedded in three-dimensional Euclidean space) and the ball (the interior of the three-dimensional sphere).
Read more about Sphere: Volume of A Sphere, Surface Area of A Sphere, Equations in R3, Terminology, Hemisphere, Generalization To Other Dimensions, Generalization To Metric Spaces, Topology, Spherical Geometry, Eleven Properties of The Sphere, Cubes in Relation To Spheres
Famous quotes containing the word sphere:
“If today there is a proper American “sphere of influence” it is this fragile sphere called earth upon which all men live and share a common fate—a sphere where our influence must be for peace and justice.”
—Hubert H. Humphrey (1911–1978)
“For my part, I have no hesitation in saying that although the American woman never leaves her domestic sphere and is in some respects very dependent within it, nowhere does she enjoy a higher station . . . if anyone asks me what I think the chief cause of the extraordinary prosperity and growing power of this nation, I should answer that it is due to the superiority of their woman.”
—Alexis de Tocqueville (1805–1859)
“Wherever the State touches the personal life of the infant, the child, the youth, or the aged, helpless, defective in mind, body or moral nature, there the State enters “woman’s peculiar sphere,” her sphere of motherly succor and training, her sphere of sympathetic and self-sacrificing ministration to individual lives.”
—Anna Garlin Spencer (1851–1931)