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MatematikaRia.com

# Sphere

Sphere Facts
Notice these interesting things:
It is perfectly symmetrical
It has no edges or vertices
It is not a polyhedron
All points on the surface are the same distance from the center

And for reference:
Surface Area = 4 × π × r2
Volume = (4/3) × π × r3

Glass Sphere
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Balls and marbles are shaped like spheres.

## Largest Volume for Smallest Surface

Of all the shapes, a sphere has the smallest surface area for a volume. Or put another way it can contain the greatest volume for a fixed surface area.

Example: if you blow up a balloon it naturally forms a sphere because it is trying to hold as much air as possible with as small a surface as possible. Press the Play button to see.

### In Nature

The sphere appears in nature whenever a surface wants to be as small as possible. Examples include bubbles and water drops, can you think of more?

## The Earth

The Planet Earth, our home, is nearly a sphere, except that it is squashed a little at the poles.

It is a spheroid, which means it just misses out on being a sphere because it isn't perfect in one direction (in the Earth's case: North-South)