Symmetry is not always an easy thing to explain to our students. Yet every human culture finds symmetry so attractive, perhaps because we humans are basically symmetrical, with the axis of symmetry travelling from our head to our toes.
An object has mirror symmetry if you can divide it into two matching pieces, like looking at a reflection in a mirror. We use the term “reflection” to describe the matching image. This is also call a “flip” in more colloquial language. An object has rotational symmetry if it can be rotated about a fixed point and parts match the new position exactly. For example, you can trace the outline of a shape on paper then rotate this shape around the centre point of the paper image. If this new position matches the original shape on the paper then this shape has rotational symmetry. It may match more than one time as it turns a full circle.
Not all things have symmetry. It is important to talk about what is NOT symmetrical too,so that your students build a clearer image, remove any blockages.
When I worked at The LEGO Centre in Drummoyne many years ago, we had over 70 000 children visit our LEGO play area. There we were able to observe that almost all the spontaneous LEGO constructions were symmetrical. Without anyone directing the children, they appeared to want their construction to be shape symmetrical, although colours did not always match.
This collection of photographs enables you to discuss a wide variety of objects and images with a special focus on symmetry. Where is the line of symmetry? Is there more than one axis? Are real-life objects always exactly symmetrcal? Do we call something symmetrical even though not every single piece matches exactly?