What's the risk of passive smoking? Or climate change? How big is the terrorist threat? And should we trust league tables? These issues concern all of us, but it's not always easy to make sense of the barrage of media information. **David Spiegelhalter**, Winton Professor for the Public Understanding of Risk, gives *Plus* his take on uncertainty.

How did we evolve our capacity for maths? Does maths piggy-back on our ability for language, or is it a completely separate faculty? Is it dependent on culture? *Plus* spoke to the cognitive psychologist **Rosemary Varley** to find some answers.

**Phil Wilson** continues our series on the life and work of Leonhard Euler, who would have turned 300 this year. This article looks at the calculus of variations and a mysterious law of nature that has caused some scientists to reach out for god.

John Napier was a clever man indeed. Besides inventing the logarithm, he developed ingenious calculating devices that fully exploit the power of the positional system. In this article **Chris Sangwin** tells you how to make your own set of *Napier's bones* and perform mathemagic with an interactive checker board.

Former *Plus* editor **Helen Joyce** explains how *Plus* made it big as a part of our series to celebrate *Plus's* tenth anniversary.

Penguin eggs are not something you'd normally associate with maths, but they are right there on the archives of the Smith Institute, an organisation helping businesses use maths to solve their problems. **Claudia Centazzo** tells us about her role at the institute, selling maths to unsuspecting business people.

The flocking behaviour of birds, the spread of diseases and the Cuban missile crisis — all of these and much more can be modelled mathematically. In our second teacher package we bring together all *Plus* articles on mathematical modelling, ready for use in classroom discussions or students projects.