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:

“Thought dissolves the material universe by carrying the mind up into a *sphere* where all is plastic.”

—Ralph Waldo Emerson (1803–1882)

“In the new science of the twenty-first century, not physical force but spiritual force will lead the way. Mental and spiritual gifts will be more in demand than gifts of a physical nature. Extrasensory perception will take precedence over sensory perception. And in this *sphere* woman will again predominate.”

—Elizabeth Gould Davis (b. 1910)

“It is in the nature of allegory, as opposed to symbolism, to beg the question of absolute reality. The allegorist avails himself of a formal correspondence between “ideas” and “things,” both of which he assumes as given; he need not inquire whether either *sphere* is “real” or whether, in the final analysis, reality consists in their interaction.”

—Charles, Jr. Feidelson, U.S. educator, critic. Symbolism and American Literature, ch. 1, University of Chicago Press (1953)