Are there parallel universes? Universes in which, rather than reading this article, you are still asleep; in which you are happier, unhappier, richer, poorer, or even dead? The answer is "possibly". It's a controversial claim but one that has won more and more followers over the last few decades.

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.

Most of us know what we mean when we say that something has happened. For theoretical physicists, however, this isn't an easy question. Sean Carroll of the California Institute of Technology explains why it's hard to define events and what to do about it.

Most of us know what we mean when we say that something has happened. Theoretical physicists, however, struggle with the concept of an event. Why?

Imagine if your body weight depended on the colour of your underwear. Strangely, something quite similar happens when you make measurements in quantum mechanics. Discover more about contextuality in this video interview with Jeremy Butterfield, philosopher of physics.

Quantum mechanics seems to suggest that passive observation is impossible: the very act of looking at something can change what's being looked at. In this video interview, we talk to David Wallace and Adrian Kent to find out more.

Imagine your weight depended on the colour of your underwear! Something quite similar happens with measurements in quantum physics. Find out more here...

What does contextually mean for real-life measurements and what does it have to do with religious questions?

Imagine your weight depended on the colour of your underwear! Something quite similar may be happening when you are measuring things in quantum physics. Find out more here...