Physics and Cosmology

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 Cambridge

Stephen Blundell
Professor of Physics at the University of Oxford

Nicola Wilkin
Lecturer in Theoretical Physics at the University of Birmingham

Producer: Thomas Morris

http://www.bbc.co.uk/programmes/b01r113g

Duration: 43 minutes
First broadcast: Thursday 16 May 2013

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.

http://www.bbc.co.uk/programmes/b01sdnkg