What's a multiverse? What's the future for intelligent life? And what happened 380,000 after the Big Bang. Find out in these interviews with the physicists David Spergel and Raphael Bousso, who we spoke to during Stephen Hawking's 70th birthday conference.

This is one of our podcasts from Stephen Hawking's 70th birthday conference, which took place in January 2012 in Cambridge. Rachel Thomas talks to Renata Kallosh from Stanford University about a theory that promises to unite the physics of the very small — quantum physics — and the physics of the very large — Einstein's theory of gravity.

"Astronomers are used to large numbers, but few are as large as the odds I'd have given this celebration today," is how Astronomer Royal Martin Rees started his presentation at Stephen Hawking's birthday symposium yesterday. He was talking about the 1960s when he first met Hawking who was then already suffering motor neurone disease. But Rees' prediction has been proved wrong. Hawking turned 70 yesterday and since the time of their first meeting he has made enormous contributions to cosmology and physics.

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.


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.

Last month leading researchers in sports technology met at the Royal Academy of Engineering in London to demonstrate just how far their field has come over recent years. The changes they make to athletes' equipment and clothes may only make a tiny difference to their performance, but once they're added up they can mean the difference between gold and silver. In this podcast we talk to some leading sport engineers.

Some have suggested that the changes that are needed to meet the climate challenge are similar in scale to the Industrial Revolution of the 19th century. And since the built environment is responsible for over half of our energy consumption, most of the changes will need to be made here. For this podcast we talked to engineer Alison Cooke, who manages a project called Energy Efficiency in the Built Environment, and two PhD students at the Centre for sustainable Development in Cambridge, and find out how engineers work with Government, business and other groups to help ensure a sustainable future.

The words quantum physics are usually associated with the weirder end of physics, including strange phenomena like superposition or quantum entanglement, the "spooky action at a distance" as Einstein called it. But it turns out that quantum mechanical processes occur in living systems too. Some species of birds use quantum mechanics to navigate and studying how they do it might actually help us with building quantum computers.