What is friction?

CrowdScience listener David was playing snooker in Thailand when he started thinking how such a smooth ball was dependent on the rough green baize of the table to bring it to a stop. Would it be possible to play snooker at all in a completely frictionless universe? Sometimes friction produces heat. Could we ever control it completely? We try to reduce friction in some cases by using lubricants, whilst at other times like braking at a traffic junction we depend upon friction entirely. Anand Jagatia heads to Edinburgh in Scotland, UK, to meet some true masters of this mysterious entity: players of the winter sport Curling. What exactly is friction, and does thinking about it tell us something deeper about the universe? Taking part: Jennifer Dodds, Team GB Olympic Gold medallist Dave Lieth, Head of performance services, British Curling Susan Perkin, Professor of Physical Chemistry, University of Oxford Roger Lewis, Professor of Mechanical Engineering, University of Sheffield Presented by Anand Jagatia Produced by Alex Mansfield With thanks to David for his question. [Image: curling. Credit: Getty Images]