philosophy
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. 
Is the Universe finite or infinite? Is there infinity inside a black hole? Is space infinitely divisible or is there a shortest length? We talk to philosophers and physicists to find out. 
How understanding why something is impossible can often lead to deeper understanding, contemplations of philosophy and even new mathematics. 

There's no doubt that maths is very good at describing the world around us. Could this be because the Universe we live in is itself a mathematical structure? We talk to Max Tegmark. 
In this podcast we talk to Max Tegmark about his hypothesis that the Universe we live in is a mathematical structure. 
Are number, space and time features of the outside world or a result of the brain circuitry we have developed to live in it? Some interesting parallels between modern neuroscience and the mathematics of 19th century mathematician Bernard Riemann. 
Mathematics does incredibly well at describing the world we live in. Could that be because the Universe itself is a mathematical structure? It's a suggestion that has been put forward by the cosmologist Max Tegmark. We talked to him to find out more. 