## geometry

*unless*the lines are parallel. This annoying exception is constantly inserting itself into otherwise simple mathematical statements.

**Burkard Polster**and

**Marty Ross**explain how to get around the problem.

**Nicholas Mee**discovers, that would be far too simple. In fact, the length of a day varies throughout the year. If you plot the position of the Sun in the sky at the same time every day, you get a strange figure of eight which has provided one artist with a source for inspiration.

**Liz Newton**takes you on a journey of origami, maths and science.

**Josefina Alvarez**and

**Cesar L. Garcia**investigate.

**Gábor Domokos**, one of their discoverers, reckons that in some sense they barely exists at all. So what are Gömböcs and what makes them special?

**Phil Dench**tells

*Plus*how he uses mathematics to help bring these models to life.