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.

Why can we remember the past and not the future? Why does time appear to move in only one direction when the laws of physics have no preferred direction in time? According to one physicist, it might be because we live in a bubble multiverse.

What is time? Newton thought it was absolute, Einstein thought it was relative, and today some people think it doesn't exist at all. This package, which is part of our Science fiction, science fact project brings you articles and podcasts exploring the nature of time.

According to Einstein, the past, present and future have exactly the same character - so why do we feel that there is a particular moment we call "now"? The physicist George Ellis looks for an answer in the curious laws of quantum mechanics.

Looking out to Canary Wharf, to the arch at Wembley Stadium, and down onto the Gherkin, the 700 people working on the construction site of the Heron Tower in London had one of the best views in London. Plus was lucky enough to speak to two engineers involved in building the tower and asked how maths was involved in the construction of such an impressive addition to the London skyline.

The Velodrome, with its striking curved shape, was the first venue to be completed in the London Olympic Park. Plus talks to structural engineers Andrew Weir and Pete Winslow from Expedition Engineering, who were part of the design team for the Velodrome, about how mathematics helped create its iconic shape.

Convex or concave? It's a question we usually answer just by looking at something. It's convex if it bulges outwards, and concave if it bulges inwards. But when it comes to mathematical functions, things aren't that simple. A team of computer scientists from the Massachusetts Institute of Technology have recently shown that deciding whether a mathematical function is convex can be very hard indeed.

The Velodrome, with its striking curved shape, was the first venue to be completed in the London Olympic Park. Plus talks to structural engineers Andrew Weir and Pete Winslow from Expedition Engineering, who were part of the design team for the Velodrome, about how mathematics helped create its iconic shape.

Is it rational to believe in a god? The most famous rational argument in favour of belief was made by Blaise Pascal, but what happens if we apply modern game theory to the question?