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:

“Men are rewarded for learning the practice of violence in virtually any *sphere* of activity by money, admiration, recognition, respect, and the genuflection of others honoring their sacred and proven masculinity. In male culture, police are heroic and so are outlaws; males who enforce standards are heroic and so are those who violate them.”

—Andrea Dworkin (b. 1946)

“O sun,

Burn the great *sphere* thou mov’st in! darkling stand

The varying shore o’ th’ world!”

—William Shakespeare (1564–1616)

“A man should not go where he cannot carry his whole *sphere* or society with him,Mnot bodily, the whole circle of his friends, but atmospherically. He should preserve in a new company the same attitude of mind and reality of relation, which his daily associates draw him to, else he is shorn of his best beams, and will be an orphan in the merriest club.”

—Ralph Waldo Emerson (1803–1882)