What is a Sphere?
The word sphere has its origin from the Greek word saphaira, which means a ball or a globe. In simple terms, a sphere is a perfect circle in 3-D space. The only difference between a circle and a sphere is their orientation in the space. A circle is 2D, whereas a sphere is 3D. A sphere is a round-shaped object in three dimensions. A sphere has no vertices or edges, unlike other three-dimensional forms. Equidistant from the center are all points on the spherical surface. In other words, the distance between the center of the sphere and any point on the sphere's surface is equal. We observe several real-world things in spherical form around us. Given the three-dimensionality of a sphere, it also has a surface and volume. Our planet Earth is not a perfect sphere but a spheroid. It's almost comparable to that of a sphere and therefore referred to as a spheroid. The sphere shares the same properties as a circle, like a radius, diameter, chord area, etc. Still, due to 3D orientation, it possesses some distinct features like lateral surface area, curved surface area, and volume.
Properties of a Sphere
The following characteristics aid us to easily identify a spherical object. They are listed below:
Area and Formula for the Area of a Sphere
The area of a hollow sphere = 4 x pi x r2, where r is the internal radius of the sphere. Suppose we substitute the value of r as D/2 (D is the diameter of the sphere), the formula changes and becomes pi x D2.
From the equation, it is clear that a sphere’s area is four times to that of a circle with the same radius. The unit of measurement is square units.