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Hello, the second law of thermodynamics can be simply stated thus. Energy spontaneously tends to flow from being concentrated in one place to becoming diffused and spread out.

It was first formulated 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 panor 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 and his two cultures wrote not knowing the second law of thermodynamics is like never having read a work of Shakespeare.

So what is the second law? What are its implications for time and energy in the universe, and does it appear to be refuted by the existence of life and the theory of evolution?

With me to discuss the second law of thermodynamics is John Gribin visiting fellow in astronomy at the University of Sussex and author of Deep Simplicity. Peter Atkins, professor of chemistry at Oxford University and author of Galileo's Finger, and Monica Grady had a meteorite at the Natural History Museum.

John Gribin, before we are going to detail of the second law, can you give us an indication of how a law which began concerning steam locomotives came to have such a broad application?

Can you give us an overview?

But it's because, as you said, it deals with heat. It deals with the flow of heat from one place to another. That's one manifestation of the second law.

And of course that was hugely important in the 19th century as Britain in particular industrialized and the rest of the world followed suit.

If you could understand how heat works, you could build more efficient steam engines, putting it very simply, and so your industry would be more efficient.

But it goes hand in hand with developing technology. As you learn to develop better technology and better steam engines, then you learn more about the second law as well.

So these things always in silence, sort of go hand in hand in a ratcheting process.

And it goes back even a bit further than that to earlier in the 19th century. There was a guy called Count Rumpford who started life as Benjamin Thompson.

And he was involved in boring cannon to make cannon for warfare. And he realized that the process of boring out the cannon generated heat in an inexhaustible fashion, which is the important thing.

Before then people had had the idea that heat was a kind of a fluid called caloric, which was existed in something. And if you heated it by friction, you'd rub it all out. And it'd all be used up.

And he discovered that no matter how long you kept riding away at the lumps of iron to make cannon, you kept producing heat.

So there's this realization that heat was a form of energy. It became understood as a form of energy. And energy, of course, is what drives the whole universe and keeps us going. So it's absolutely fundamental.

Can you tell us just because the listeners would be clamoring to hear this. What's the first law for Madonna?

The first law is very simple. It's a kind of sort of throat clearing which says that the total amount of energy in the universe always stays the same.

And it's been paraphrased as saying you can't get something for nothing. And the second law in a similar vein has been paraphrased as saying things wear out.

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