3. What We'll Never Know

In the third of this year's Reith Lectures, recorded at the Royal Society during its 350th anniversary year, its President Martin Rees continues to explore the challenges facing science in the 21st century. He stresses there are things that will always lie beyond our sphere of comprehension and we should accept these limits to our knowledge. On the other hand, there are things we've never even dreamt of that will one day be ours to explore and understand. The outcome of the quest for alien life will revolutionise our sense of self in the next two decades. But some things -- like travelling back in time -- will never happen.

Lecture 2: 'Surviving the Century'

In the second of this year's Reith Lectures, recorded for the first time in Wales in the National Museum Cardiff, Martin Rees, President of the Royal Society and Astronomer Royal, continues to explore the challenges facing science in the 21st century. Our planet is coming under increasing strain from climate change, population explosion and food shortages. How can we use science to help us solve the crisis that we are moving rapidly towards, as we use up our natural resources ever more quickly?

Lecture 1: ''The Scientific Citizen'

In the first of this year's Reith Lectures, entitled Scientific Horizons, Martin Rees, President of the Royal Society, Master of Trinity College and Astronomer Royal, explores the challenges facing science in the 21st century. We are increasingly turning to government and the media to explain the risks we face. But in the wake of public confusion over issues like climate change, the swine 'flu vaccine and, more recently, Iceland's volcanic ash cloud, Martin Rees calls on scientists to come forward and play a greater role in helping us understand the science that affects us all.

Professor Michael Sandel delivers four lectures about the prospects of a new politics of the common good. The series is presented and chaired by Sue Lawley.

Sandel makes the case for a moral and civic renewal in democratic politics. Recorded at George Washington University in Washington DC, he calls for a new politics of the common good and says that we need to think of ourselves as citizens, not just consumers.

Professor Michael Sandel delivers four lectures about the prospects of a new politics of the common good. The series is presented and chaired by Sue Lawley.

Recorded at the Centre for Life in Newcastle, Sandel considers how we should use our ever-increasing scientific knowledge. New genetic technologies hold great promise for treating and curing disease, but how far we should go in using them to manipulate muscles, moods and gender?

Professor Michael Sandel delivers four lectures about the prospects of a new politics of the common good. The series is presented and chaired by Sue Lawley.

Sandel considers the role of moral argument in politics. He believes that it is often not possible for government to be neutral on moral questions and calls for a more engaged civic debate about issues such as commercial surrogacy and same-sex marriage.

Michael Sandel, Harvard Professor of Government, delivers four lectures about the prospects of a new politics of the common good. The series is presented and chaired by Sue Lawley.

Sandel considers the expansion of markets and how we determine their moral limits. Should immigrants, for example, pay for citizenship? Should we pay schoolchildren for good test results, or even to read a book? He calls for a more robust public debate about such questions, as part of a 'new citizenship'.

Chinese Vistas: Jonathan Spence lectures about China.

Recorded at Lord's cricket ground.

Spence discusses how Chinese ideas of sport and athleticism have slowly evolved over the centuries, from languorous courtship and formalised martial arts to the demanding arenas of team sports and the ultimate Olympic challenges that China will controversially host in August.

Chinese Vistas: Jonathan Spence lectures about China.

Recorded at The Asia Society in New York.

Spence explores the two centuries in which the United States gradually moved from its position as a dominant beacon of freedom and democracy for China, to becoming a more demanding global rival during and since World War II. Is America right to be wary of the emerging superpower or can the two economic and military giants co-exist happily?

Jonathan Spence lectures about China.

Spence examines China's relations with the United Kingdom through three centuries of trade, warfare, unequal treaties and missionary endeavours that shaped their mutual perceptions.