In Our Time: Science Folgen

Melvyn Bragg and guests discuss plasma, the fourth state of matter after solid, liquid and gas. As over ninety-nine percent of all observable matter in the Universe is plasma, planets like ours, with so little plasma and so much solid, liquid and gas, appear all the more remarkable. On the grand scale, plasma is what the Sun is made from and, when we look into the night sky, almost everything we can see with the naked eye is made of plasma. On the smallest scale, here on Earth, scientists make plasma to etch the microchips on which we rely for so much. Plasma is in the fluorescent light bulbs above our heads and, in laboratories around the world, it is the subject of tests to create, one day, an inexhaustible and clean source of energy from nuclear fusion.With Justin Wark Professor of Physics and Fellow of Trinity College at the University of OxfordKate Lancaster Research Fellow for Innovation and Impact at the York Plasma Institute at the University of Yorkand Bill Graham Professor of Physics at Queens University, BelfastProducer: Simon Tillotson.

In a programme first broadcast in 2016, Melvyn Bragg and guests discuss Zeno of Elea, a pre-Socratic philosopher from c490-430 BC whose paradoxes were described by Bertrand Russell as "immeasurably subtle and profound." The best known argue against motion, such as that of an arrow in flight which is at a series of different points but moving at none of them, or that of Achilles who, despite being the faster runner, will never catch up with a tortoise with a head start. Aristotle and Aquinas engaged with these, as did Russell, yet it is still debatable whether Zeno's Paradoxes have been resolved.With Marcus du Sautoy Professor of Mathematics and Simonyi Professor for the Public Understanding of Science at the University of OxfordBarbara Sattler Lecturer in Philosophy at the University of St Andrewsand James Warren Reader in Ancient Philosophy at the University of CambridgeProducer: Simon Tillotson

Melvyn Bragg and guests discuss the development of photography in the 1830s, when techniques for 'drawing with light' evolved to the stage where, in 1839, both Louis Daguerre and William Henry Fox Talbot made claims for its invention. These followed the development of the camera obscura, and experiments by such as Thomas Wedgwood and Nicéphore Niépce, and led to rapid changes in the 1840s as more people captured images with the daguerreotype and calotype. These new techniques changed the aesthetics of the age and, before long, inspired claims that painting was now dead.WithSimon Schaffer Professor of the History of Science at the University of CambridgeElizabeth Edwards Emeritus Professor of Photographic History at De Montfort UniversityAndAlison Morrison-Low, Research Associate at National Museums ScotlandProducer: Simon Tillotson.