## Articles

**paper folding**.

**number 23**.

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

**Klein bottle**.

**Isaac Newton**and David Gregory - took place on the campus of Cambridge University. The discussion concerned the

**kissing problem**, but it was to be another 260 years before the problem was finally solved.

**data compression**.

**Golden Ratio**, and ever since people have been fascinated by its extraordinary properties. Find out if beauty is in the eye of the beholder, and how the Golden Ratio crosses from mathematics to the arts.

**Medical statistics**can help us to decide what treatment to look for when we are ill, and to estimate our chances of recovery.

*Plus*meets mathematician, author and broadcaster

**Simon Singh**to find out about the science of secrecy.