In Our Time: Science

Melvyn Bragg and his guests discuss exoplanets. Astronomers have speculated about the existence of planets beyond our solar system for centuries. Although strenuous efforts were made to find such planets orbiting distant stars, it was not until the 1990s that instruments became sophisticated enough to detect such remote objects. In 1992 Dale Frail and Aleksander Wolszczan discovered the first confirmed exoplanets: two planets orbiting the pulsar PSR B1257+12. Since then, astronomers have discovered more than 900 exoplanets, and are able to reach increasingly sophisticated conclusions about what they look like - and whether they might be able to support life. Recent data from experiments such as NASA's space telescope Kepler indicates that such planets may be far more common than previously suspected.With:Carolin Crawford Gresham Professor of Astronomy and a member of the Institute of Astronomy at the University of CambridgeDon Pollacco Professor of Astronomy at the University of WarwickSuzanne Aigrain Lecturer in Astrophysics at the University of Oxford and a Fellow of All Souls College.Producer: Thomas Morris.

Melvyn Bragg and his guests begin a new series of the programme with a discussion of the French polymath Blaise Pascal. Born in 1623, Pascal was a brilliant mathematician and scientist, inventing one of the first mechanical calculators and making important discoveries about fluids and vacuums while still a young man. In his thirties he experienced a religious conversion, after which he devoted most of his attention to philosophy and theology. Although he died in his late thirties, Pascal left a formidable legacy as a scientist and pioneer of probability theory, and as one of seventeenth century Europe's greatest writers. With:David Wootton Anniversary Professor of History at the University of YorkMichael Moriarty Drapers Professor of French at the University of CambridgeMichela Massimi Senior Lecturer in the Philosophy of Science at the University of Edinburgh.Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the invention of radio. In the early 1860s the Scottish physicist James Clerk Maxwell derived four equations which together describe the behaviour of electricity and magnetism. They predicted the existence of a previously unknown phenomenon: electromagnetic waves. These waves were first observed in the early 1880s, and over the next two decades a succession of scientists and engineers built increasingly elaborate devices to produce and detect them. Eventually this gave birth to a new technology: radio. The Italian Guglielmo Marconi is commonly described as the father of radio - but many other figures were involved in its development, and it was not him but a Canadian, Reginald Fessenden, who first succeeded in transmitting speech over the airwaves.With:Simon Schaffer Professor of the History of Science at the University of CambridgeElizabeth Bruton Postdoctoral Researcher at the University of LeedsJohn Liffen Curator of Communications at the Science Museum, LondonProducer: Thomas Morris.

Experts discuss the revolutionary nature and impact of Albert Einstein's theories of relativity on our understanding of space, time, energy, and gravity. Topics include the concept of space-time, time dilation, visualizing space-time, the equation e=mc², creativity in science, the mathematics of relativity, and the development of general relativity.

Melvyn Bragg and his guests discuss cosmic rays. In 1912 the physicist Victor Hess discovered that the Earth is under constant bombardment from radiation coming from outside our atmosphere. These so-called cosmic rays have been known to cause damage to satellites and electronic devices on Earth, but most are absorbed by our atmosphere. The study of cosmic rays and their effects has led to major breakthroughs in particle physics. But today physicists are still trying to establish where these highly energetic subatomic particles come from.With:Carolin Crawford Gresham Professor of Astronomy and a member of the Institute of Astronomy at the University of Cambridge Alan Watson Emeritus Professor of Physics at the University of Leeds Tim Greenshaw Professor of Physics at the University of Liverpool.Producer: Thomas Morris.

Explore the history and unique characteristics of water, including its composition discovered by Lavoisier. Learn about water's ability to store energy, its unusual behavior when cooled, and its importance for organic chemistry. Discover the role of water in biological processes and the mysteries of ice's structure.

In a programme first broadcast in 2013, Melvyn Bragg and his guests discuss absolute zero, the lowest conceivable temperature.  In the early eighteenth century the French physicist Guillaume Amontons suggested that temperature had a lower limit.  The subject of low temperature became a fertile field of research in the nineteenth century, and today we know that this limit - known as absolute zero - is approximately minus 273 degrees Celsius.  It is impossible to produce a temperature exactly equal to absolute zero, but today scientists have come to within a billionth of a degree.  At such low temperatures physicists have discovered a number of strange new phenomena including superfluids, liquids capable of climbing a vertical surface.With:Simon Schaffer Professor of the History of Science at the University of CambridgeStephen Blundell Professor of Physics at the University of OxfordNicola Wilkin Lecturer in Theoretical Physics at the University of BirminghamProducer: Thomas Morris

Melvyn Bragg and his guests discuss the life and work of the Victorian anthropologist and archaeologist Augustus Pitt-Rivers. Over many years he amassed thousands of ethnographic and archaeological objects, some of which formed the founding collection of the Pitt Rivers Museum at Oxford University. Inspired by the work of Charles Darwin, Pitt-Rivers believed that human technology evolved in the same way as living organisms, and devoted much of his life to exploring this theory. He was also a pioneering archaeologist whose meticulous records of major excavations provided a model for later scholars. With:Adam Kuper Visiting Professor of Anthropology at Boston UniversityRichard Bradley Professor in Archaeology at the University of ReadingDan Hicks University Lecturer & Curator of Archaeology at the Pitt Rivers Museum at the University of Oxford.Producer: Thomas Morris.

Melvyn Bragg and his guests discuss comets, the 'dirty snowballs' of the Solar System. In the early 18th century the Astronomer Royal Sir Edmond Halley compiled a list of appearances of comets, bright objects like stars with long tails which are occasionally visible in the night sky. He concluded that many of these apparitions were in fact the same comet, which returns to our skies around every 75 years, and whose reappearance he correctly predicted. Halley's Comet is today the best known example of a comet, a body of ice and dust which orbits the Sun. Since they contain materials from the time when the Solar System was formed, comets are regarded by scientists as frozen time capsules, with the potential to reveal important information about the early history of our planet and others.With:Monica Grady Professor of Planetary and Space Sciences at the Open UniversityPaul Murdin Senior Fellow at the Institute of Astronomy at the University of CambridgeDon Pollacco Professor of Astronomy at the University of WarwickProducer: Thomas Morris.

Melvyn Bragg and his guests discuss the history of crystallography, the study of crystals and their structure. The discovery in the early 20th century that X-rays could be diffracted by a crystal revolutionised our knowledge of materials. This crystal technology has touched most people's lives, thanks to the vital role it plays in diverse scientific disciplines - from physics and chemistry, to molecular biology and mineralogy. To date, 28 Nobel Prizes have been awarded to scientists working with X-ray crystallography, an indication of its crucial importance. The history of crystallography began with the work of Johannes Kepler in the 17th century, but perhaps the most crucial leap in understanding came with the work of the father-and-son team the Braggs in 1912. They built on the work of the German physicist Max von Laue who had proved that X-rays are a form of light waves and that it was possible to scatter these rays using a crystal. The Braggs undertook seminal experiments which transformed our perception of crystals and their atomic arrangements, and led to some of the most significant scientific findings of the last century - such as revealing the structure of DNA. With:Judith Howard Director of the Biophysical Sciences Institute and Professor of Chemistry at the University of DurhamChris Hammond Life Fellow in Material Science at the University of LeedsMike Glazer Emeritus Professor of Physics at the University of Oxford and Visiting Professor of Physics at the University of WarwickProducer: Natalia Fernandez.