Melvyn Bragg and guests Steve Jones, Bill Amos and Eleanor Weston discuss the evolutionary history of the whale. The ancestor of all whales alive today was a small, land-based mammal with cloven hoofs, perhaps like a pig or a big mole. How this creature developed into the celebrated leviathan of the deep is one of the more extraordinary stories in the canon of evolution. The whale has undergone vast changes in size, has moved from land to water, lost its legs and developed specialised features such as filter feeding and echo location. How it achieved this is an exemplar of how evolution works and how natural selection can impose extreme changes on the body shape and abilities of living things. How the story of the whales was pieced together also reveals the various forms of evidence - from fossils to molecules - that we now use to understand the ancestry of life on Earth.Steve Jones is Professor of Genetics at University College London; Eleanor Weston is a mammalian palaeontologist at the Natural History Museum, London; Bill Amos is Professor of Evolutionary Genetics at Cambridge University.

Melvyn Bragg and guests Frank Close, Jocelyn Bell Burnell and Ruth Gregory discuss the Vacuum of Space. The idea that there is a nothingness at the heart of nature has exercised philosophers and scientists for millennia, from Thales's belief that all matter was water to Newton's concept of the Ether and Einstein's idea of Space-Time. Recently, physicists have realised that the vacuum is not as empty as we thought and that the various vacuums of nature vibrate with forces and energies, waves and particles and the mysterious phenomena of the Higgs field and dark energy.

Patricia Fara, Stephen Pumfrey and Rhodri Lewis join Melvyn Bragg to discuss the Jacobean lawyer, political fixer and alleged founder of modern science Francis Bacon.In the introduction to Thomas Spratt's History of the Royal Society, there is a poem about man called Francis Bacon which declares 'Bacon, like Moses, led us forth at last, The barren wilderness he past, Did on the very border stand Of the blest promis'd land, And from the mountain's top of his exalted wit, Saw it himself, and shew'd us it'.Francis Bacon was a lawyer and political schemer who climbed the greasy pole of Jacobean politics and then fell down it again. But he is most famous for developing an idea of how science should be done - a method that he hoped would slough off the husk of ancient thinking and usher in a new age. It is called Baconian Method and it has influenced and inspired scientists from Bacon's own time to the present day.

Melvyn Bragg and guests discuss the Library at Alexandria. Founded by King Ptolemy in the 3rd century BC the library was the first attempt to collect all the knowledge of the ancient world in one place. Scholars including Archimedes and Euclid came to study its grand array of papyri. the legacy of the library is with us today, not just in the ideas it stored and the ideas it seeded but also in the way it organised knowledge and the tools developed for dealing with it. It still influences the things we know and the way we know them to this day.With Simon Goldhill, Professor of Greek at the University of Cambridge; Matthew Nicholls, Lecturer in Classics at the University of Reading; Serafina Cuomo, Reader in Roman History at Birkbeck College, University of London.

Melvyn Bragg and guests discuss one of the deepest problems in contemporary physics. It’s called the measurement problem and it emerged from the flurry of activity in the early 20th century that gave rise to Quantum Mechanics. If the most famous fruit in physics is an apple, the most famous animal in physics is a cat. Schrödinger’s cat is named after Edwin Schrödinger, a theoretical physicist who in the early 20th century helped to develop the radical theories of Quantum Mechanics. The cat does not actually exist – it is the subject of a thought experiment – in which the rules of quantum mechanics make it appear both dead and alive at the same time.The problem of a cat that is both dead and alive illustrates the challenges of quantum physics and at the heart of this apparent absurdity is a thing called the measurement problem.The measurement problem arises because we don’t really understand how the atoms that constitute our world behave. They are fundamentally mysterious to us, even shocking, and they defy our attempts to measure and make sense of them. Possible solutions range from the existence of multiple realities to the rather more mundane possibility of an error in our mathematics - but a solution, if found, could transform our understanding of reality. With Basil Hiley, Emeritus Professor of Physics at Birkbeck, University of London, Simon Saunders, Reader in Philosophy of Physics and University Lecturer in Philosophy of Science at the University of Oxford; Roger Penrose, Emeritus Rouse Ball Professor of Mathematics at the University of Oxford

Melvyn Bragg and guests discuss the Observatory in Jaipur with its vast and beautiful instruments built to make astronomical measurements of the stars. Commissioned in the early 18th century by the Rajput prince and child prodigy, Jai Singh, it was at the centre of attempts to marry hundreds of years of Indian and Persian astronomical tradition. The Observatory was also at the very centre of the city which was laid out according to astrological principles. Jai Singh’s observatory was the cutting edge of Indian astronomy but also a repository for aeons of Hindu and Islamic intellectual life. The instruments were extraordinarily accurate for the time but used no lenses and were built of masonry, not metal. They helped to develop astrological tables, immensely important in Hindu Society, and come down to us as a record of Indian astronomy on the cusp of colonialism. With Chandrika Kaul, Lecturer in Modern History at the University of St Andrews; David Arnold, Professor of Asian and Global History at the University of Warwick; Chris Minkowski, Professor in Sanskrit at the University of Oxford

To celebrate the 200th anniversary of the birth of Charles Darwin in 2009 and the 150th anniversary of the publication of On the Origin of Species, Melvyn Bragg presents a series about Darwin's life and work.Melvyn visits Darwin's home at Down House in Kent. Despite ill health and the demands of his family, Darwin continued researching and publishing until his death in April 1882.Featuring contributions from Darwin biographer Jim Moore, geneticist at University College London Steve Jones, Darwin expert Alison Pearn of the Darwin Correspondence Project and former garden curator at Down House Nick Biddle.

To celebrate the 200th anniversary of the birth of Charles Darwin and the 150th anniversary of the publication of On the Origin of Species, Melvyn Bragg presents a series about Darwin's life and work.How Darwin was eventually persuaded to publish On the Origin of Species in November 1859 and the book's impact on fellow scientists and the general public.Featuring contributions from Darwin biographer Jim Moore, Steve Jones, geneticist at University College London, Jim Secord of the Darwin Correspondence Project and Johannes Vogel, Sandy Knapp and Judith Magee, all of the National History Museum.

To celebrate the 200th anniversary of the birth of Charles Darwin and the 150th anniversary of the publication of On the Origin of Species, Melvyn Bragg presents a series about Darwin's life and work.Darwin's expedition aboard the Beagle in December 1831 and how his work during the voyage influenced and provided evidence for his theories.Featuring contributions from Darwin biographer Jim Moore, Steve Jones, geneticist at University College London, David Norman, Fellow of Christ's College Cambridge and Jenny Clack, curator of the University.

To celebrate the 200th anniversary of the birth of Charles Darwin in 2009 and the 150th anniversary of the publication of On the Origin of Species, Melvyn Bragg presents a series about Darwin's life and work.Melvyn tells the story of Darwin's early life in Shropshire and discusses the significance of the three years he spent at Cambridge, where his interests shifted from religion to natural science.Featuring contributions from Darwin biographer Jim Moore, geneticist at University College London Steve Jones, fellow of Christ's College Cambridge David Norman and assistant librarian at Christ's College Cambridge Colin Higgins.