You're unlikely to ever run into a black hole, but here's what it "looks" and "sounds" like when two black holes run into each other. The movie shows a simulation of the gravitational waves generated when two black holes collide and form a third, and the sound file shows what these waves would sound like if you cold hear them.

Most precise experiment to date confirms one of Einstein's predictions

And what are gravitational waves?

Find out with Martin Rees

Are the unchanging features of the Universe really unchanging?

The world's biggest physics experiment is due to start

Over the last few years the words string theory have nudged their way into public consciousness. It's a theory of everything in which everything's made of strings — or something like that. But why strings? What do they do? Where did the idea come from and why do we need such a theory? David Berman has an equation-free introduction for beginners.

What goes up must come down — or does it? Find out how to cheat gravity with Julian Havil.

What is the cosmological constant?

In the last issue Lewis Dartnell explained how chaos on the brain is not only unavoidable but also beneficial. Now he tells us why the same is true for our solar system and sends us on a journey that has been travelled by comets and spacecraft.

Extrasolar planets have been grabbing the headlines

Two people who get on well together can often find their relationship destabilised by the arrival of a third into their orbit.