In Our Time With Melvyn Bragg Folgen

Melvyn Bragg and guests discuss the rise of the idea of perpetual motion and its decline, in the 19th Century, with the Laws of Thermodynamics. For hundreds of years, some of the greatest names in science thought there might be machines that could power themselves endlessly. Leonardo Da Vinci tested the idea of a constantly-spinning wheel and Robert Boyle tried to recirculate water from a draining flask. Gottfried Leibniz supported a friend, Orffyreus, who claimed he had built an ever-rotating wheel. An increasing number of scientists voiced their doubts about perpetual motion, from the time of Galileo, but none could prove it was impossible. For scientists, the designs were a way of exploring the laws of nature. Others claimed their inventions actually worked, and promised a limitless supply of energy. It was not until the 19th Century that the picture became clearer, with the experiments of James Joule and Robert Mayer on the links between heat and work, and the establishment of the First and Second Laws of Thermodynamics.With Ruth Gregory Professor of Mathematics and Physics at Durham UniversityFrank Close Professor Emeritus of Physics at the University of OxfordandSteven Bramwell Professor of Physics and former Professor of Chemistry at University College LondonProducer: Simon Tillotson.

Born near Mexico City in 1907, Frida Kahlo is considered one of Mexico's greatest artists. She took up painting after a bus accident left her severely injured, was a Communist, married Diego Rivera, a celebrated muralist, became friends with Trotsky and developed an iconic series of self-portraits. Her work brings together elements such as surrealism, pop culture, Aztec and Indian mythology and commentary on Mexican culture. In 1938, artist and poet Andre Breton organised an exhibition of her work in New York, writing in the catalogue, "The Art of Frida Kahlo is a ribbon around a bomb." She was not as widely appreciated during her lifetime as she has since become, but is now one of the most recognised artists of the 20th century. WithPatience Schell Chair in Hispanic Studies at the University of AberdeenValerie Fraser Emeritus Professor of Latin American Art at the University of EssexAndAlan Knight Emeritus Professor of the History of Latin America at the University of OxfordProducer: Simon Tillotson.

Frederick the Great ruled Prussia from 1740 until his death in 1786. Born in 1712, he increased the power of the state, he made Prussia the leading military power in Europe and his bold campaigns had great implications for the European political landscape. An absolute monarch in the age of enlightenment, he was a prolific writer, attracted figures such as Voltaire to his court, fostered education and put Berlin firmly on the cultural map. He was much admired by Napoleon and was often romanticised by German historians, becoming a hero for many in united Germany in the 19th and 20th centuries. Others, however, vilified him for aspects such as his militarism and the partition of Poland. With Tim Blanning Emeritus Professor of Modern European History at the University of CambridgeKatrin Kohl Professor of German Literature at the University of Oxford and a Fellow of Jesus CollegeAnd Thomas Biskup Lecturer in Early Modern History at the University of HullProducer: Simon Tillotson.