Everyone knows what time is. We can practically feel it ticking away, marching on in the same direction with horrifying regularity. Time has enslaved the Western world and become our most precious commodity. Turn it over to the physicists however, and it begins to morph, twist and even crumble away. So what is time exactly?

This podcast featuring Paul Davies, a theoretical physicist and cosmologist at Arizona State University and Director of BEYOND: Centre for Fundamental Concepts in Science, explores this difficult question and accompanies our What is time article.

Astronomers have explained a strange effect observed in the vicinity of black holes.

Why too many bodies present a problem.

A closer look at the power of symmetry in physics.

Finally we can be sure — black holes, those gravitational monsters that gobble up everything that gets too close to them, do exist.

Does light have weight? Newton thought so. His laws predicted that gravity would bend light, two centuries before Einstein's revolution.

Why (some) physicists want to modify Einstein's general theory of relativity.

How to catch those elusive gravitational waves.

Space is the stage on which physics happens. It's unaffected by what happens in it and it would still be there if everything in it disappeared. This is how we learn to think about space at school. But the idea is as novel as it is out-dated.