A sphere (from Greek —
sphaira, "globe, ball") is a perfectly round geometrical
object in threedimensional 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 surface of a sphere (referred to as a
“sphere”), and the inside of a sphere (referred to as a
“ball”). Thus, a sphere in three dimensions is
considered to be a twodimensional spherical surface
embedded in threedimensional Euclidean space, while a
ball is a solid figure bounded by a sphere.
This article deals with the mathematical concept of a
sphere. In physics, a sphere is an object (usually
idealized for the sake of simplicity) capable of
colliding or stacking with other objects which occupy
space.
Volume
In 3 dimensions, the volume inside a sphere is given by the
formula
where r is the radius of
the sphere, d = 2r is the diameter of the sphere and π
is the constant pi.
Surface
area of a sphere
The surface area of a sphere is
given by the formula
