Many things make a noise when you hit them, but not many are commonly used to play music — why is that? Jim Woodhouse looks at harmonic and not so harmonic frequencies and at how percussion instruments are tuned.

As an electronic musician Oli Freke has always been fascinated by sine waves, so much so that he's created a song based on them for the Geekpop festival, which is currently taking place on the Web. In this article he explores his song, touching on ancient Greek mythology, strange piano tunings and Johann Sebastian Bach.

Frances Elwell looks at the eddies and currents, from the pungent problem of sewage outflow to the search for bodies of people who have fallen into rivers, explaining that fluid mechanics lies behind it all.

On 11th August 1999 a total eclipse of the Sun will be visible from parts of the UK. It will provide a spectacular display, but why is the Sun so interesting? Helen Mason explains.