Melvyn Bragg and guests discuss the speed of light. Scientists and thinkers have been fascinated with the speed of light for millennia. Aristotle wrongly contended that the speed of light was infinite, but it was the 17th Century before serious attempts were made to measure its actual velocity – we now know that it’s 186,000 miles per second. Then in 1905 Einstein’s Special Theory of Relativity predicted that nothing can travel faster than the speed of light. This then has dramatic effects on the nature of space and time. It’s been thought the speed of light is a constant in Nature, a kind of cosmic speed limit, now the scientists aren’t so sure. With John Barrow, Professor of Mathematical Sciences and Gresham Professor of Astronomy at Cambridge University; Iwan Morus, Senior Lecturer in the History of Science at The University of Wales, Aberystwyth; Jocelyn Bell Burnell, Visiting Professor of Astrophysics at Oxford University.

Melvyn Bragg and guests discuss the Poincaré Conjecture. The great French mathematician Henri Poincaré declared: “The scientist does not study mathematics because it is useful; he studies it because he delights in it, and he delights in it because it is beautiful. If nature were not beautiful, it would not be worth knowing and life would not be worth living. And it is because simplicity, because grandeur, is beautiful that we preferably seek simple facts, sublime facts, and that we delight now to follow the majestic course of the stars.” Poincaré’s ground-breaking work in the 19th and early 20th century has indeed led us to the stars and the consideration of the shape of the universe itself. He is known as the father of topology – the study of the properties of shapes and how they can be deformed. His famous Conjecture in this field has been causing mathematicians sleepless nights ever since. He is also credited as the Father of Chaos Theory.So how did this great polymath change the way we understand the world and indeed the universe? Why did his conjecture remain unproved for almost a century? And has it finally been cracked?With June Barrow-Green, Lecturer in the History of Mathematics at the Open University; Ian Stewart, Professor of Mathematics at the University of Warwick; Marcus du Sautoy, Professor of Mathematics at the University of Oxford.

Melvyn Bragg and guests discuss the Needham Question; why Europe and not China developed modern technology. What do these things have in common? Fireworks, wood-block printing, canal lock-gates, kites, the wheelbarrow, chain suspension bridges and the magnetic compass. The answer is that they were all invented in China, a country that, right through the Middle Ages, maintained a cultural and technological sophistication that made foreign dignitaries flock to its imperial courts for trade and favour. But then, around 1700, the flow of ingenuity began to dry up and even reverse as Europe bore the fruits of the scientific revolution back across the globe. Why did Modern Science develop in Europe when China seemed so much better placed to achieve it? This is called the Needham Question, after Joseph Needham, the 20th century British Sinologist who did more, perhaps, than anyone else to try and explain it.But did Joseph Needham give a satisfactory answer to the question that bears his name? Why did China’s early technological brilliance not lead to the development of modern science and how did momentous inventions like gunpowder and printing enter Chinese society with barely a ripple and yet revolutionise the warring states of Europe? With Chris Cullen, Director of the Needham Research Institute in Cambridge; Tim Barrett, Professor of East Asian History at SOAS; Frances Wood, Head of Chinese Collections at the British Library.

Melvyn Bragg and guests discuss the Prussian naturalist and explorer Alexander Von Humboldt. He was possibly the greatest and certainly one of the most famous scientists of the 19th century. Darwin described him as 'the greatest scientific traveller who ever lived'. Goethe declared that one learned more from an hour in his company than eight days of studying books and even Napoleon was reputed to be envious of his celebrity.A friend of Goethe and an influence on Coleridge and Shelly, when Darwin went voyaging on the Beagle it was Humboldt's works he took for inspiration and guidance. At the time of his death in 1859, the year Darwin published On the Origin of Species, Humboldt was probably the most famous scientist in Europe. Add to this shipwrecks, homosexuality and Spanish American revolutionary politics and you have the ingredients for one of the more extraordinary lives lived in Europe (and elsewhere) in the 18th and 19th centuries. But what is Humboldt's true position in the history of science? How did he lose the fame and celebrity he once enjoyed and why is he now, perhaps, more important than he has ever been? With Jason Wilson, Professor of Latin American Literature at University College London, Patricia Fara, Affiliated Lecturer in the Department of History and Philosophy of Science at the University of Cambridge, Jim Secord, Professor in the Department of History and Philosophy of Science at the University of Cambridge and Director of the Darwin Correspondence Project.

Melvyn Bragg and guests discuss the galaxies. Spread out across the voids of space like spun sugar, but harbouring in their centres super-massive black holes. Our galaxy is about 100,000 light years across, is shaped like a fried egg and we travel inside it at approximately 220 kilometres per second. The nearest one to us is much smaller and is nicknamed the Sagittarius Dwarf. But the one down the road, called Andromeda, is just as large as ours and, in 10 billion years, we'll probably crash into it. Galaxies - the vast islands in space of staggering beauty and even more staggering dimension. But galaxies are not simply there to adorn the universe; they house much of its visible matter and maintain the stars in a constant cycle of creation and destruction. But why do galaxies exist, how have they evolved and what lies at the centre of a galaxy to make the stars dance round it at such colossal speeds? With John Gribbin, Visiting Fellow in Astronomy at the University of Sussex; Carolin Crawford, Royal Society University Research Fellow at the Institute of Astronomy at Cambridge; Robert Kennicutt, Plumian Professor of Astronomy and Experimental Philosophy at the University of Cambridge.

Melvyn Bragg and guests discuss Carbon. It forms the basis of all organic life and has the amazing ability to bond with itself and a wide range of other elements, forming nearly 10 million known compounds. It is in the food we eat, the clothes we wear, the shampoo we use and the petrol that fuels our cars. Because carbon has the largest range of subtle bonding capabilities, 95% of everything that exists in the universe is made up of carbon atoms that are stuck together. It is an extraordinary element for many reasons: the carbon-nitrogen cycle provides some of the energy produced by the Sun and the stars; it has the highest melting point of all the elements; and its different forms include one of the softest and one of the hardest substances known. What gives carbon its great ability to bond with other atoms? What is the significance of the recent discovery of a new carbon molecule - the C60? What role does carbon play in the modern chemistry of nanotechnology? And how should we address the problem of our diminishing carbon energy sources? With Harry Kroto, Professor of Chemistry at Florida State University; Monica Grady, Professor of Planetary and Space Sciences at the Open University; Ken Teo, Royal Academy of Engineering Research Fellow at Cambridge University.

Melvyn Bragg and guests discuss the heart. Aristotle considered the heart to be the seat of thought, reason and emotion. The Roman physician Galen located the seat of the passions in the liver, the seat of reason in the brain, and considered the heart to be the seat of the emotions. It was not until the 17th century that the physician William Harvey wrote in the preface to his thesis On the Motion of the Heart and Blood in Animals, a letter addressed to King Charles I. 'The heart of animals is the foundation of their life, the sovereign of everything within them...from which all power proceeds. The King, in like manner, is the foundation of his kingdom, the sun of the world around him, the heart of the republic, the foundation whence all power, all grace doth flow'. Harvey was probably wise to address the King in this manner, for what he laid out in his groundbreaking text challenged scientific wisdom that had gone unquestioned for centuries about the true function of the heart. Organs had been seen in a hierarchical structure with the heart as the pinnacle. But Harvey transformed the metaphor into something quite different: the heart as a mechanistic pumping device. How had the Ancient Greeks and Islamic physicians understood the heart? What role did the bodily humours play in this understanding? Why has the heart always been seen as the seat of emotion and passion? And why was it that despite Harvey's discoveries about the heart and its function, this had limited implications for medical therapy and advancement? With David Wootton, Anniversary Professor of History at the University of York; Fay Bound Alberti, Research Fellow at the Wellcome Unit for the History of Medicine at the University of Manchester; Jonathan Sawday, Professor of English Studies at the University of Strathclyde.

Melvyn Bragg and guests discuss the relationship between astronomy and the British Empire. The 18th century explorer and astronomer James Cook wrote: 'Ambition leads me not only farther than any other man has been before me, but as far as I think it possible for man to go'. Cook's ambition took him to the far reaches of the Pacific and led to astronomical observations which measured the distance of Venus to the Sun with unprecedented accuracy. Cook's ambition was not just personal and astronomical. It represented the colonial ambition of the British Empire which was linked inextricably with science and trade. The discoveries about the Transit of Venus, made on Cook's voyage to Tahiti, marked the beginning of a period of expansion by the British which relied on maritime navigation based on astronomical knowledge. With Simon Schaffer, Professor in History and Philosophy of Science at the University of Cambridge; Kristen Lippincott, former Director of the Royal Observatory, Greenwich; Allan Chapman, Historian of Science at the History Faculty at Oxford University.

Melvyn Bragg and guests discuss the search for immunisation. In 1717, Lady Mary Wortley Montagu, the wife of the British Ambassador to the Ottoman Empire, wrote a letter to her friend describing how she had witnessed the practice of smallpox inoculation in Constantinople. This involved the transfer of material from a smallpox postule into multiple cuts made in a vein. Lady Montagu had lost her brother to smallpox and was amazed that the Middle Eastern practice of inoculation rendered the fatal disease harmless. In Britain, the practice was unknown. Inoculation was an early attempt at creating immunity to disease, but was later dismissed when Edward Jenner pioneered immunisation through vaccination in 1796. Vaccination was hailed a huge success. Napoleon described it as the greatest gift to mankind, but when the British government introduced the compulsory Vaccination Act in 1853, targeted at the poor and the working class, it sparked a mass opposition movement.How did a Gloucestershire country surgeon become known as the father of vaccination? Why did the British government introduce compulsory smallpox vaccination in 1853? What were the consequences of those who opposed it? And how was the disease finally eradicated? With Nadja Durbach, Associate Professor of History at the University of Utah, Chris Dye, Co-ordinator of the World Health Organisation's work on tuberculosis epidemiology, Sanjoy Bhattacharya, Lecturer in the Wellcome Trust Centre for the History of Medicine at UCL

Melvyn Bragg and guests discuss the formation of the Royal Society. In the 17th century the natural philosopher Francis Bacon heralded the new age of science. The frontispiece to his 1620 edition of the Instauratio Magna depicted a galleon travelling between the metaphorical Pillars of Hercules thought to lie at the Strait of Gibraltar and believed to mark the end of the known world. The image encapsulated Bacon's desire to sail beyond the limits set by Aristotle and the curriculum of the Ancient universities towards the new continent of science. Bacon imagined practical scientists engaged in a collaborative effort to expand knowledge of the natural world. But it was not until the turbulence of the Civil War and Commonwealth years had passed that such a group of scientists would gather together in London for this purpose, and form the Royal Society. Amongst its members were Robert Boyle, Robert Hooke, Christopher Wren and Isaac Newton, who explicitly rejected dogma and insisted on practical experimentation and observation. How was the Royal Society formed against a backdrop of religious and political strife? What was it about the way this group of men worked that allowed each individual to flourish in his own field? How successful was the Royal Society in disseminating the benefits of experimental science and what is its enduring legacy? With Stephen Pumfrey, Senior Lecturer in the History of Science at the University of Lancaster; Lisa Jardine, Professor of Renaissance Studies at Queen Mary, University of London; Michael Hunter, Professor of History at Birkbeck, University of London.