## Articles

**number 23**.

*Plus*takes an illustrated tour of an extraordinary geometric construction: the

**Klein bottle**.

**chaos**.

- Plus looks different! - Redesigning the website
- Beauty is truth, truth beauty - The aesthetics of mathematics
- Readers' corner - Rolling with money revisited: The Pyramid Puzzle

**John D. Barrow**challenges readers to estimate the errors that aren't found from the errors that are.

**Freeman Dyson**, tells

*Plus*why he is an optimist, what makes life interesting and why old-fashioned maths is what you need for physics.