Melvyn Bragg discusses Jean-Baptiste Lamarck, the 18th century French scientist.Charles Darwin defined Natural Selection in On the Origin of Species, “Variations, however slight and from whatever cause proceeding, if they be in any degree profitable to the individuals of a species… will tend to the preservation of such individuals, and will generally be inherited by the offspring”. It was a simple idea that had instant recognition, “How extremely stupid not to have thought of that!” said T H Huxley. However, Darwin did not invent the idea of evolution and not everyone saw his ideas as original. The great geologist Charles Lyell repeatedly referred to “Lamarck’s theory as modified by Darwin”, Darwin complained to him, “I believe this way of putting the case is very injurious to its acceptance”. He desperately wanted to escape the shadow of this genuine scientific precursor and what has become known as the ‘Lamarckian Heresy’ has maintained a ghostly presence on the fringes of biology to this day.Who was Lamarck? How did Natural Selection escape from his shadow and gain acceptance from the scientific establishment? And has any evidence emerged that might challenge the elegant simplicity of Darwin’s big idea?With Sandy Knapp, Senior Botanist at the Natural History Museum, Steve Jones, Professor of Genetics in the Galton Laboratory at University College London and author of Almost Like a Whale: The Origin of Species Updated; Simon Conway Morris, Professor of Evolutionary Paleobiology at Cambridge University.

Melvyn Bragg and guests discuss the age of the Earth. It was once thought that the world began in 4004 BC. Lord Kelvin calculated the cooling temperature of a rock the size of our planet and came up with a figure of 20 million years for the age of the Earth. Now, the history of our planet is divided into four great Eons: the Hadean, the Archaen, the Proterozoic and the Phanerozoic. Together, they are taken to encompass an incredible four and a half billion years. How can we begin to make sense of such a huge swathe of time? And can we be sure that we have got the Earth's age right? Geologists use Eras, Periods and Epochs to further punctuate what's known as 'Deep Time', but can we be sure that the classifications we use don't obscure more than they reveal? With Richard Corfield, Research Associate in the Department of Earth Sciences at Oxford University; Hazel Rymer, Senior Lecturer in the Department of Earth Sciences at the Open University; Henry Gee, Senior Editor at Nature.

Melvyn Bragg and guests discuss the nature and existence of mathematical infinity. Jonathan Swift encapsulated the counter-intuitive character of infinity with insouciant style:“So, naturalists observe, a fleaHath smaller fleas on him that preyAnd these hath smaller fleas to bite ‘emAnd so proceed ad infinitum.”Alas, the developing utility mathematicians put to the idea of infinity did not find the English philosopher Thomas Hobbes quite so relaxed. When confronted with a diagram depicting an infinite solid whose volume was finite, he wrote, “To understand this for sense, it is not required that a man should be a geometrician or logician, but that he should be mad”. Yet philosophers and mathematicians have continued to grapple with the unending, and it is a core concept in modern maths.So, what is mathematical infinity? Are some infinities bigger than others? And does infinity exist in nature?With Ian Stewart, Professor of Mathematics at the University of Warwick; Robert Kaplan, co-founder of The Math Circle at Harvard University and author of The Art of the Infinite: Our Lost Language of Numbers; Sarah Rees, Reader in Pure Mathematics at the University of Newcastle.

Melvyn Bragg and guests discusses the life and ideas of James Clerk Maxwell whose work is not widely known, but whose genius and contribution to the age in which we live is enormous.He took the first colour photograph, defined the nature of gases and with a few mathematical equations expressed all the fundamental laws of light, electricity and magnetism - and in doing so he provided the tools to create the technological age, from radar to radio and televisions to mobile phones. He is credited with fundamentally changing our view of reality, so much so that Albert Einstein said, “One scientific epoch ended and another began with James Clerk Maxwell”. But who was James Clerk Maxwell? What were his ideas, and does this nineteenth century ‘natural philosopher’ deserve a place alongside Newton and Einstein in the pantheon of science? With Simon Schaffer, Reader in History and Philosophy of Science at the University of Cambridge; Peter Harman, Professor of the History of Science at Lancaster University and editor of The Scientific Letters and Papers of James Clerk Maxwell; Joanna Haigh, Professor of Atmospheric Physics at Imperial College London.

Melvyn Bragg and guests discuss the attempt to define humanity’s part in the natural world. In Childe Harold’s Pilgrimage Lord Byron wrote:“There is a pleasure in the pathless woods, There is a rapture on the lonely shore,There is society where none intrudes,By the deep Sea, and music in its roar:I love not man the less, but Nature more.” In the Bible’s book of Genesis, ‘nature’ was the paradise of Eden, but for the philosopher Thomas Hobbes it was a place of perpetual war, where the life of man was “solitary, poore, nasty, brutish and short”. The defining of Nature, whether “red in tooth and claw” or as the fount of all innocence, is an attempt to define man’s origins and purpose and humanity’s part in the natural world. With Jonathan Bate, Professor of English Literature at the University of Warwick; Roger Scruton, Professor of Philosophy at the University of Buckingham; Karen Edwards, Lecturer in English at the University of Exeter.

Melvyn Bragg and guests discuss the formation of volcanoes. In 79AD Mount Vesuvius erupted on the Bay of Naples, buried Pompeii in ash and drowned nearby Herculaneum in lava. The great letter writer Pliny the Younger was staying with his uncle in Misenum and was a witness to the cataclysm. He described it to the historian Tacitus, It seemed as though the sea was being sucked backwards, as if it were being pushed back by the shaking of the land. Certainly the shoreline moved outwards, and many sea creatures were left on dry sand. Behind us were frightening dark clouds, rent by lightning twisted and hurled, opening to reveal huge figures of flame. These were like lightning but bigger. This eruption, which claimed the life of Pliny's uncle, is one of about 500 volcanoes to have erupted in the last two thousand years, some of which are now categorised by vulcanologists as Plinian, after Pliny's famous description.What causes volcanoes? What role do they play in the formation and maintenance of our planet? And is it ever possible to predict when and where they are about to erupt?With Hilary Downes, Professor of Geochemistry at Birkbeck, University of London; Steve Self, Professor of Vulcanology at the Open University; Bill McGuire, Benfield Professor of Geophysical Hazards at University College London.

Melvyn Bragg and guests discuss the Lunar Society. In the late 18th century, with the ascendant British Empire centred on London, a small group of friends met at a house on the crossroads outside Birmingham and applied their minds to the problems of the age. Between them they managed to launch the Industrial Revolution, discover oxygen, harness the power of steam and pioneer the theory of evolution. They were the Lunar Society, a gathering of free and fertile minds centred on the remarkable quartet of Matthew Boulton, James Watt, Joseph Priestly and Erasmus Darwin. The potter Josiah Wedgwood, another member, summed up the ethos of this group when he said that they were ‘living in an age of miracles in which anything could be achieved’.But how did the Lunar Society operate? What was the blend of religious dissent, entrepreneurial spirit and intellectual adventure that proved so fertile and how did their discoveries permanently change the shape and character of this country?With Simon Schaffer, Reader in History and Philosophy of Science at the University of Cambridge; Jenny Uglow, Honorary Visiting Professor at the University of Warwick and author of The Lunar Men: The Friends who Made the Future; Peter Jones, Professor of French History at the University of Birmingham.

Melvyn Bragg and guests discuss the function and significance of memory. The great writer of remembrance, Marcel Proust, declared “We are able to find everything in our memory, which is like a dispensary or chemical laboratory in which chance steers our hand, sometimes to a soothing drug and sometimes to a dangerous poison”. The memory is vital to life and without it we could not be the people we are, but can it really contain the sum of all our experience? Is it a repository constantly mounting events waiting to be plucked to consciousness, or if not, then under what criteria are memories turfed out?With Martin Conway, Professor of Psychology at Durham University; Mike Kopelman, Professor of Neuropsychiatry at King's College London and St Thomas’ Hospital; Kim Graham, Senior Scientist at the Medical Research Council’s Cognition and Brain Sciences Unit.

Melvyn Bragg and guests discuss blood. For more than 1500 years popular imagination, western science and the Christian Church colluded in a belief that blood was the link between the human and the divine. The Greek physician, Galen, declared that it was blood that contained the force of life and linked the body to the soul, the Christian Church established The Eucharist – the taking of the body and blood of Christ. In our blood was our individuality, it was thought, our essence and our blood lines were special. Transfusion threatened all that and now itself is being questioned.Why is it that blood was used to define both man and messiah? And how has the tradition of blood in religious thought been affected by the progress of medicine?With Miri Rubin, Professor of European History at Queen Mary, University of London; Dr Anne Hardy, Reader in the History of Medicine at the Wellcome Trust Centre for the History of Medicine at University College London; Jonathan Sawday, Professor of English Studies at the University of Strathclyde.

Melvyn Bragg and guests discuss the life cycle of stars. In his poem Bright Star John Keats wrote, "Bright Star, would I were steadfast as thou art". For Keats the stars were symbols of eternity- they were beautiful and ordered and unchanging - but modern astronomy tells a very different story. Stars, like everything else in the universe, are subject to change. They are born among vast swirls of gas and dust and they die in the stunning explosions we call supernovae. They create black holes and neutron stars and, in the very beginning of the universe, they forged the elements from which all life is made. But how do stars keep burning for millions of years, why do they self-destruct with such ferocity and what will happen to the universe when they all go out?With Paul Murdin, Senior Fellow at the Institute of Astronomy, Cambridge; Janna Levin, Advanced Fellow in Theoretical Physics in the Department of Applied Mathematics & Theoretical Physics at the University of Cambridge; Phil Charles, Professor of Astronomy at Southampton University.