Why does time only ever move in one direction? We talk to philosophers of physics Jeremy Butterfield and David Wallace, as well as the eminent Roger Penrose about the puzzle time poses to physicists and what it has to do with the Big Bang and the second law of thermodynamics.
On the twelfth day of advent we celebrate Stephen Hawking's contribution to cosmology.
On the sixth day of advent we find out why gravitational waves are so important in revealing the secrets of the Universe.
The cosmic microwave background is the earliest light we can see in the Universe. So important is this baby picture of the Universe, it's been involved in two Nobel Prizes. Why?
Find out what gravitational waves will tell us about the Universe: from understanding its birth to figuring out whether black holes have hairs.