Melvyn Bragg and guests discuss the Second Law of Thermodynamics which can be very simply stated like this: "Energy spontaneously tends to flow from being concentrated in one place to becoming diffused and spread out". It was first formulated – derived from ideas first put forward by Lord Kelvin - to explain how a steam engine worked, it can explain why a cup of tea goes cold if you don't drink it and how a pan of water can be heated to boil an egg.But its application has been found to be rather grander than this. The Second Law is now used to explain the big bang, the expansion of the cosmos and even suggests our inexorable passage through time towards the 'heat death' of the universe. It's been called the most fundamental law in all of science, and CP Snow in his Two Cultures wrote: "Not knowing the Second Law of Thermodynamics is like never having read a work of Shakespeare".What is the Second Law? What are its implications for time and energy in the universe, and does it tend to be refuted by the existence of life and the theory of evolution?With John Gribbin, Visiting Fellow in Astronomy at the University of Sussex; Peter Atkins, Professor of Chemistry at Oxford University; Monica Grady, Head of Petrology and Meteoritics at the Natural History Museum.

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