## Articles

**Eugen Jost**is a Swiss artist whose work is strongly influenced by mathematics. He sent us this Postcard from Italy, telling us about his work and the important roles that nature and numbers play in it.

**Jon Walthoe**explains the tricks involved and how great thinkers like Pythagoras, Newton and Gödel tackled the problems.

**Andy Burbanks**explains what Lyapunov Exponents are, what the much misunderstood phenomenon of chaos

*really*is, and how you can iterate functions to produce marvellous images of chaos from simple mathematics.