A short introduction to symmetry and groups
This is a part
of maths that I've always liked a lot. It is beautiful and satisfying
in itself and it also has very many important applications in areas
such as crystallography and particle physics.
I'm going just far enough for you to see some examples of how
symmetry can be described by groups.
You won't need any previous maths
for this, but I will introduce some mathematical terms to make
describing things simpler.
This will then make a good jumpingoff
point for anyone who wants to dig deeper in the mathematical theory.
I've divided up what I've written into the following parts:
 Some thoughts on symmetry
 Looking at some particular symmetries
 The symmetry transformations of a square
 How do its reflections fit together?

How do all the symmetries of a square fit together? . . . the rules
for a group.

Fitting together the symmetry transformations for some other shapes

A new group
 Finding this new group in more places
 Some examples of infinite groups
 When does multiplying give groups?
 And finally ...
I've written these parts as separate linked webpages
to make it easier for you to think
how things will work out before looking at the answer.
You just need to click on the potatohead to move to the next section.
next
or home