## Articles

Rock and its use for tools and buildings has shaped human civilisation. Here's an introduction to the maths of rocks.

Fully functioning invisibility cloaks are closer to becoming a reality than you might think. Here's a quick look at the maths and science involved in producing them.

Is the proposed ABBA rule for penalty shootouts really fairer than the existing rule? Maths shows that it is, and also suggests another, more subtle rule.

Compound interest is the curse of debt and the blessing of saving. Find out how it works and what it has to do with one of the most important numbers in mathematics.

The great thing about geometry is that you can sometimes prove things using pictures. Enjoy these three great visual proofs of Pythagoras' theorem!

We talk to pioneering mathematician Stephen Cook, who came up with the concept of NP-complete problems, about his work, computer science, and artificial intelligence.

There are problems that are easy to solve in theory, but impossible to solve in practice. Intrigued? Then join us on a journey through the world of complexity, all the way to the famous P versus NP conjecture.

How will the Universe end? In a big crunch? Or a big freeze? It all depends on its shape...