Melvyn Bragg and guests discuss the planet Venus which is both the morning star and the evening star, rotates backwards at walking speed and has a day which is longer than its year. It has long been called Earth’s twin, yet the differences are more striking than the similarities. Once imagined covered with steaming jungles and oceans, we now know the surface of Venus is 450 degrees celsius, and the pressure there is 90 times greater than on Earth, enough to crush an astronaut. The more we learn of it, though, the more we learn of our own planet, such as whether Earth could become more like Venus in some ways, over time. WithCarolin Crawford Public Astronomer at the Institute of Astronomy and Fellow of Emmanuel College, University of CambridgeColin Wilson Senior Research Fellow in Planetary Science at the University of OxfordAnd Andrew Coates Professor of Physics at Mullard Space Science Laboratory, University College LondonProduced by: Simon Tillotson and Julia Johnson

Melvyn Bragg and guests discuss the properties of atoms or molecules with a single unpaired electron, which tend to be more reactive, keen to seize an electron to make it a pair. In the atmosphere, they are linked to reactions such as rusting. Free radicals came to prominence in the 1950s with the discovery that radiation poisoning operates through free radicals, as it splits water molecules and produces a very reactive hydroxyl radical which damages DNA and other molecules in the cell. There is also an argument that free radicals are a byproduct of normal respiration and over time they cause an accumulation of damage that is effectively the process of ageing. For all their negative associations, free radicals play an important role in signalling and are also linked with driving cell division, both cancer and normal cell division, even if they tend to become damaging when there are too many of them.With Nick Lane Professor of Evolutionary Biochemistry at University College LondonAnna Croft Associate Professor at the Department of Chemical and Environmental Engineering at the University of NottinghamAnd Mike Murphy Professor of Mitochondrial Redox Biology at Cambridge UniversityProducer: Simon Tillotson

Melvyn Bragg and guests discuss the history of real and imagined machines that appear to be living, and the questions they raise about life and creation. Even in myth they are made by humans, not born. The classical Greeks built some and designed others, but the knowledge of how to make automata and the principles behind them was lost in the Latin Christian West, remaining in the Greek-speaking and Arabic-speaking world. Western travellers to those regions struggled to explain what they saw, attributing magical powers. The advance of clockwork raised further questions about what was distinctly human, prompting Hobbes to argue that humans were sophisticated machines, an argument explored in the Enlightenment and beyond.The image above is Jacques de Vaucanson's mechanical duck (1739), which picked up grain, digested and expelled it. If it looks like a duck...with Simon Schaffer Professor of History of Science at Cambridge UniversityElly Truitt Associate Professor of Medieval History at Bryn Mawr CollegeAnd Franziska Kohlt Doctoral Researcher in English Literature and the History of Science at the University of OxfordProducer: Simon Tillotson

Bats and dolphins use echolocation to navigate and find prey. Early natural historians doubted this ability. Bats produce high-frequency sounds with special muscles to prevent deafness. Prey have evolved ways to detect bat sounds, and fish can hear dolphin sounds. Also discusses how technology is being inspired by echolocation for assisting visual impairments.

Melvyn Bragg and guests discuss the discovery and growing understanding of the Proton, formed from three quarks close to the Big Bang and found in the nuclei of all elements. The positive charges they emit means they attract the fundamental particles of negatively charged electrons, an attraction that leads to the creation of atoms which in turn leads to chemistry, biology and life itself. The Sun (in common with other stars) is a fusion engine that turn protons by a series of processes into helium, emitting energy in the process, with about half of the Sun's protons captured so far. Hydrogen atoms, stripped of electrons, are single protons which can be accelerated to smash other nuclei and have applications in proton therapy. Many questions remain, such as why are electrical charges for protons and electrons so perfectly balanced?WithFrank Close Professor Emeritus of Physics at the University of OxfordHelen Heath Reader in Physics at the University of BristolAndSimon Jolly Lecturer in High Energy Physics at University College LondonProducer: Simon Tillotson.

In a programme first broadcast on April 12th 2018, Melvyn Bragg and guests discuss the contribution of George Stephenson (1781-1848) and his son Robert (1803-59) to the development of the railways in C19th. George became known as The Father of Railways and yet arguably Robert's contribution was even greater, with his engineering work going far beyond their collaboration. Robert is credited with the main role in the design of their locomotives. George had worked on stationary colliery steam engines and, with Robert, developed the moving steam engine Locomotion No1 for the Stockton and Darlington Railway in 1825. They produced the Rocket for the Rainhill Trials on the Liverpool and Manchester Railway in 1829. From there, the success of their designs and engineering led to the expansion of railways across Britain and around the world. with Dr Michael Bailey Railway historian and editor of the most recent biography of Robert StephensonJulia Elton Past President of the Newcomen Society for the History of Engineering and TechnologyandColin Divall Professor Emeritus of Railway Studies at the University of YorkProducer: Simon Tillotson. This programme is a repeat

Melvyn Bragg and guests discuss the pioneering scientist Rosalind Franklin (1920 - 1958). During her distinguished career, Franklin carried out ground-breaking research into coal and viruses but she is perhaps best remembered for her investigations in the field of DNA. In 1952 her research generated a famous image that became known as Photograph 51. When the Cambridge scientists Francis Crick and James Watson saw this image, it enabled them the following year to work out that DNA has a double-helix structure, one of the most important discoveries of modern science. Watson, Crick and Franklin's colleague Maurice Wilkins received a Nobel Prize in 1962 for this achievement but Franklin did not and today many people believe that Franklin has not received enough recognition for her work. With:Patricia Fara President of the British Society for the History of ScienceJim Naismith Interim lead of the Rosalind Franklin Institute, Director of the Research Complex at Harwell and Professor at the University of OxfordJudith Howard Professor of Chemistry at Durham UniversityProducer: Victoria Brignell.

Melvyn Bragg and guests discuss fungi. These organisms are not plants or animals but a kingdom of their own. Millions of species of fungi live on the Earth and they play a crucial role in ecosystems, enabling plants to obtain nutrients and causing material to decay. Without fungi, life as we know it simply would not exist. They are also a significant part of our daily life, making possible the production of bread, wine and certain antibiotics. Although fungi brought about the colonisation of the planet by plants about 450 million years ago, some species can kill humans and devastate trees. With:Lynne Boddy Professor of Fungal Ecology at Cardiff UniversitySarah Gurr Professor of Food Security in the Biosciences Department at the University of ExeterDavid Johnson N8 Chair in Microbial Ecology at the University of ManchesterProducer: Victoria Brignell.

The octopus, the squid, the nautilus and the cuttlefish are some of the most extraordinary creatures on this planet, intelligent and yet apparently unlike other life forms. They are cephalopods and are part of the mollusc family like snails and clams, and they have some characteristics in common with those. What sets them apart is the way members of their group can change colour, camouflage themselves, recognise people, solve problems, squirt ink, power themselves with jet propulsion and survive both on land, briefly, and in the deepest, coldest oceans. And, without bones or shells, they grow so rapidly they can outstrip their rivals when habitats change, making them the great survivors and adaptors of the animal world.WithLouise Allcock Lecturer in Zoology at the National University of Ireland, GalwayPaul Rodhouse Emeritus Fellow of the British Antarctic SurveyandJonathan Ablett Senior Curator of Molluscs at the Natural History MuseumProducer: Simon Tillotson.

In a programme first broadcast in 2017, Melvyn Bragg and guests discuss Gauss (1777-1855), widely viewed as one of the greatest mathematicians of all time. He was a child prodigy, correcting his father's accounts before he was 3, dumbfounding his teachers with the speed of his mental arithmetic, and gaining a wealthy patron who supported his education. He wrote on number theory when he was 21, with his Disquisitiones Arithmeticae, which has influenced developments since. Among his achievements, he was the first to work out how to make a 17-sided polygon, he predicted the orbit of the minor planet Ceres, rediscovering it, he found a way of sending signals along a wire, using electromagnetism, the first electromagnetic telegraph, and he advanced the understanding of parallel lines on curved surfaces. With Marcus du Sautoy Professor of Mathematics and Simonyi Professor for the Public Understanding of Science at the University of OxfordColva Roney-Dougal Reader in Pure Mathematics at the University of St AndrewsAnd Nick Evans Professor of Theoretical Physics at the University of SouthamptonProducer: Simon Tillotson.