In Our Time: Science

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 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 how members of the same species send each other invisible chemical signals to influence the way they behave. Pheromones are used by species across the animal kingdom in a variety of ways, such as laying trails to be followed, to raise the alarm, to scatter from predators, to signal dominance and to enhance attractiveness and, in honey bees, even direct development into queen or worker. The image above is of male and female ladybirds that have clustered together in response to pheromones. With Tristram Wyatt Senior Research Fellow at the Department of Zoology at the University of OxfordJane Hurst William Prescott Professor of Animal Science at the University of Liverpooland Francis Ratnieks Professor of Apiculture and Head of the Laboratory of Apiculture and Social Insects at the University of SussexProducer: Simon Tillotson

Melvyn Bragg and guests discuss the remarkable achievement of Aristotle (384-322BC) in the realm of biological investigation, for which he has been called the originator of the scientific study of life. Known mainly as a philosopher and the tutor for Alexander the Great, who reportedly sent him animal specimens from his conquests, Aristotle examined a wide range of life forms while by the Sea of Marmara and then on the island of Lesbos. Some ideas, such as the the spontaneous generation of flies, did not survive later scrutiny, yet his influence was extraordinary and his work was unequalled until the early modern period.The image above is of the egg and embryo of a dogfish, one of the animals Aristotle described accurately as he recorded their development.WithArmand Leroi Professor of Evolutionary Development Biology at Imperial College LondonMyrto Hatzimichali Lecturer in Classics at the University of CambridgeAndSophia Connell Lecturer in Philosophy at Birkbeck, University of LondonProducer: Simon Tillotson

Explore the life of Emmy Noether, a renowned mathematician of the 20th century. Learn about her groundbreaking contributions to subatomic physics and her connection between conservation laws and symmetry. Discover her impact on the understanding of physics and mathematics, and her resilient legacy in teaching and theoretical physics.

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.