Melvyn Bragg and guests discuss how scientists sought to understand the properties of gases and the relationship between pressure and volume, and what that search unlocked. Newton theorised that there were static particles in gases that pushed against each other all the harder when volume decreased, hence the increase in pressure. Those who argued that molecules moved, and hit each other, were discredited until James Maxwell and Ludwig Boltzmann used statistics to support this kinetic theory. Ideas about atoms developed in tandem with this, and it came as a surprise to scientists in C20th that the molecules underpinning the theory actually existed and were not simply thought experiments. The image above is of Ludwig Boltzmann from a lithograph by Rudolf Fenzl, 1898With Steven Bramwell Professor of Physics at University College LondonIsobel Falconer Reader in History of Mathematics at the University of St Andrewsand Ted Forgan Emeritus Professor of Physics at the University of BirminghamProducer: Simon Tillotson

Melvyn Bragg and guests discuss the French philosopher Henri Bergson (1859-1941) and his ideas about human experience of time passing and how that differs from a scientific measurement of time, set out in his thesis on 'Time and Free Will' in 1889. He became famous in France and abroad for decades, rivalled only by Einstein and, in the years after the Dreyfus Affair, was the first ever Jewish member of the Académie Française. It's thought his work influenced Proust and Woolf, and the Cubists. He died in 1941 from a cold which, reputedly, he caught while queuing to register as a Jew, refusing the Vichy government's offer of exemption.WithKeith Ansell-Pearson Professor of Philosophy at the University of WarwickEmily Thomas Assistant Professor in Philosophy at Durham UniversityAnd Mark Sinclair Reader in Philosophy at the University of RoehamptonProducer: Simon Tillotson

Melvyn Bragg and guests discuss the most destructive riots in London's history, which reached their peak on 7th June 1780 as troops fired on the crowd outside the Bank of England. The leader was Lord George Gordon, head of the Protestant Association, who objected to the relaxing of laws against Catholics. At first the protest outside Parliament was peaceful but, when Gordon's petition failed to persuade the Commons, rioting continued for days until the military started to shoot suspects in the street. It came as Britain was losing the war to hold on to colonies in North America.The image above shows a crowd setting fire to Newgate Prison and freeing prisoners by the authority of 'His Majesty, King Mob.'WithIan Haywood Professor of English at the University of RoehamptonCatriona Kennedy Senior Lecturer in Modern British and Irish History and Director of the Centre for Eighteenth Century Studies at the University of Yorkand Mark Knights Professor of History at the University of WarwickProducer: Simon Tillotson

Explore the life of Nero, the infamous ruler of the Roman Empire known for his alleged murders, fires, and persecution of Christians. Delve into his rise to power, the political influence of women in his life, his alleged musical performance during the burning of Rome, his extravagant lifestyle, and the aftermath of a destructive fire in ancient Rome.

Melvyn Bragg and guests discuss one of Shakespeare's most popular works, written c1595 in the last years of Elizabeth I. It is a comedy of love and desire and their many complications as well as their simplicity, and a reflection on society's expectations and limits. It is also a quiet critique of Elizabeth and her vulnerability and on the politics of the time, and an exploration of the power of imagination.With Helen Hackett Professor of English Literature and Leverhulme Research Fellow at University College LondonTom Healy Professor of Renaissance Studies at the University of Sussexand Alison Findlay Professor of Renaissance Drama at Lancaster University and Chair of the British Shakespeare AssociationProducer: Simon Tillotson

Melvyn Bragg and guests discuss theories about the origins of teeth in vertebrates, and what we can learn from sharks in particular and their ancestors. Great white sharks can produce up to 100,000 teeth in their lifetimes. For humans, it is closer to a mere 50 and most of those have to last from childhood. Looking back half a billion years, though, the ancestors of sharks and humans had no teeth in their mouths at all, nor jaws. They were armoured fish, sucking in their food. The theory is that either their tooth-like scales began to appear in mouths as teeth, or some of their taste buds became harder. If we knew more about that, and why sharks can regenerate their teeth, then we might learn how humans could grow new teeth in later lives. With Gareth Fraser Assistant Professor in Biology at the University of FloridaZerina Johanson Merit Researcher in the Department of Earth Sciences at the Natural History Museumand Philip Donoghue Professor of Palaeobiology at the University of BristolProducer: Simon Tillotson

Melvyn Bragg and guests discuss why the potato crop failures in the 1840s had such a catastrophic impact in Ireland. It is estimated that one million people died from disease or starvation after the blight and another two million left the country within the decade. There had been famines before, but not on this scale. What was it about the laws, attitudes and responses that made this one so devastating?The image above is from The Illustrated London News, Dec. 29, 1849, showing a scalp or shelter, "a hole, surrounded by pools, and three sides of the scalp were dripping with water, which ran in small streams over the floor and out by the entrance. The poor inhabitants said they would be thankful if the landlord would leave them there, and the Almighty would spare their lives. Its principal tenant is Margaret Vaughan."With Cormac O'Grada Professor Emeritus in the School of Economics at University College DublinNiamh Gallagher University Lecturer in Modern British and Irish History at the University of CambridgeAnd Enda Delaney Professor of Modern History and School Director of Research at the University of EdinburghProducer: Simon Tillotson

Explore the origins and impact of the Danelaw, a Viking rule period in England. The podcast discusses the division of English and Danish territories, the influence on trade and cities, the composition of Viking armies, and the offensive military campaigns. It also covers the transition to the Danelaw, the reign of King Canute, the influence on language and place names, and archaeological evidence of Christian influences.

Melvyn Bragg and guests discuss the life and works of Hopkins (1844-89), a Jesuit priest who at times burned his poems and at others insisted they should not be published. His main themes are how he, nature and God relate to each other. His friend Robert Bridges preserved Hopkins' poetry and, once printed in 1918, works such as The Windhover, Pied Beauty and As Kingfishers Catch Fire were celebrated for their inventiveness and he was seen as a major poet, perhaps the greatest of the Victorian age. WithCatherine Phillips R J Owens Fellow in English at Downing College, University of CambridgeJane Wright Senior Lecturer in English Literature at the University of Bristoland Martin Dubois Assistant Professor in Nineteenth Century Literature at Durham UniversityProducer: Simon Tillotson

Melvyn Bragg and guests discuss what it means to be oneself, a question explored by philosophers from Aristotle to the present day, including St Augustine, Kierkegaard, Heidegger and Sartre. In Hamlet, Polonius said 'To thine own self be true', but what is the self, and what does it mean to be true to it, and why should you be true? To Polonius, if you are true to yourself, ‘thou canst not be false to any man’ - but with the rise of the individual, authenticity became a goal in itself, regardless of how that affected others. Is authenticity about creating yourself throughout your life, or fulfilling the potential with which you were born, connecting with your inner child, or something else entirely? What are the risks to society if people value authenticity more than morality - that is, if the two are incompatible? The image above is of Sartre, aged 8 months, perhaps still connected to his inner child.With Sarah Richmond Associate Professor in Philosophy at University College LondonDenis McManus Professor of Philosophy at the University of Southamptonand Irene McMullin Senior Lecturer in Philosophy at the University of EssexProducer: Simon Tillotson