Elementary Math Definition of a Sphere
The word sphere comes from the Greek word sphaira meaning "globe" or "ball." It is relatively descriptive of anything round and three-dimensional in shape. Bouncing balls are spheres, and so are moons. The earth is a sphere, as well, and revolves around the sun, which is also a sphere of fire and gases.
Other People Are Reading
-
Hemispheres
-
There are four hemispheres of the earth: the northern hemisphere, the southern hemisphere, the western hemisphere and the eastern hemisphere. Dividing the sphere into thirds or quarters would produce three to four shapes that resemble three to four blocks of cheese . It would also be like sectioning off the four hemispheres of the earth. Dividing a sphere in half would give two half moons.
Flat or Spherical
-
A bicycle wheel or a tire is not a sphere but a circle. A pizza is not a sphere but a circle. Though it can be divided into eight or 12 pieces, a pizza in the shape of a sphere would be difficult to make at a pizza parlor and deliver to your house in a pizza box.
-
Two-Dimensional Circles
-
A circle is round but has no depth like a sphere does. Pictures are flat and two-dimensional. Two-dimensional objects can be measured only in terms of length and width, which is called the area of an object. A circle is two-dimensional.
Since a circle does not really have a bottom or base, the area cannot be determined in the same way that a shape with corners is determined.
Diameter and Radius
-
The distance across the widest part of a circle or sphere through its center is called the diameter, and half of that distance is called the radius.
The area of a circle is determined by calculating π (pi) times the radius squared. Π (pi) is always equal to the value 3.14.
Equations and Formulas
-
The surface area of a sphere is calculated by multiplyng four times π (pi) times the radius squared.
The volume of a sphere is determined by calculating four times π (pi) times the radius cubed and dividing that by three.
-
References
- Photo Credit Image by Flickr.com, courtesy of woodley wonderworks
