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In Our Time: Absolute Zero

Friday 8 March 2013, 10:56

Melvyn Bragg Melvyn Bragg

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Editor's note: In Thursday's programme Melvyn Bragg and his guests discussed Absolute Zero. As always the programme is available to listen to online or to download and keep.

Absolute Zero Absolute Zero

I'm sorry that we didn't have enough time to talk about the rabbit that came out of the hat in the last half minute: the creation of temperatures lower than absolute zero. I'm sure that acutely informed listeners will understand Nicola's accurate and elliptical explanation, but it was one of those cases where I kept it back and kept it back for a bit too long.

It's a very odd world, isn't it, the world of serious, advanced, abstract science. There's a deep under-the-ocean feeling about it, an uttermost edge of the known world feeling. I must say, I was - I know I've said this so often before - bowled over by the contributions of Nicola and Stephen particularly, because it was their first time on the programme. Simon is a rock, as well as being the sort of rock you tap and out pours pure knowledge.

I was up in the Lake District last weekend for the opening few days of the Words by the Water Literary Festival. Keswick was made for a literary festival. The theatre which houses it stands at the foot of what Wordsworth called the jewel of the Lakes - Derwentwater, on which there is an island, on which once lived a saint called Herbert who asked God to let him die at the same time as St Cuthbert. His prayer was granted.

Listening to the effortless erudition and wit of Michael Frayn, the passionate knowledge of Dickens by Claire Tomalin, and that was just the beginning of a fortnight which will include the Poet Laureate, Jack Straw, Chris Mullin, Ruth Rendell ... These literary festivals are a marvel. Simon Hoggart was there. He keeps threatening to write a book about literary festivals and I ventured the Wigton literary festival, which must be the smallest in the world as we had one event last year and we will have one event this year.

Then back to London and into work on Absolute Zero, and I'm putting together the South Bank Show Awards which is a mighty task, getting together about sixty or seventy artists who are nominated for the awards, as well as those who want to come and enjoy presentations on every category, from opera through popular music, to painting, to television comedy and so on, along the spectrum of the current British arts scene which is, despite cuts, still thriving. 

Grabbed a morning off to have a walk on Hampstead Heath with one of my daughters who'd just come back from America. The beginnings of budding on the trees – how do they know? – and a lunch with one of my oldest friends at a restaurant in the West End, in the most magnificent dining room in all London with, miraculously, the lowest prices.

And pounding through London. It's now become a landscape on its own, with newspaper vendors recognised and the probably eternal contrast between beggars in the street and grandees sweeping through the streets. Sometimes I wonder how the whole thing keeps together, don't you?

The pal I had lunch with brought me a copy of Charles Dickens' Night Walks. He had a period of intense insomnia and the only way to cure it, he discovered, was to go to bed, lie in bed for a few minutes, get up instantly and walk for five or six hours through the night through London. Exhilarating stuff. You keep wondering why he wasn't attacked, or murdered, or assailed, or assaulted. Perhaps we exaggerate the violence of the London of that time.


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  • rate this

    Comment number 1.

    See also 'Quantum fridge' gets close to absolute zero:


  • rate this

    Comment number 2.

    I think if the program had gone on a bit longer, it would have emerged that temperatures can be “lower” than zero temperature in a numerical sense but not in a physical sense. Temperatures lower than zero (negative temperatures) can only apply to certain systems, eg a two-level system. As an analogy to get the idea, think of people who live either in a valley or on a nearby mountain. If they are all in the valley, their energy is as low as possible and their “temperature” is zero. Give them some energy and some will climb the mountain so their “temperature” increases. When equal numbers occupy the valley and the mountain, the temperature turns out to be (positive) infinity. Give them some more energy and the number on the mountain will exceed the number in the valley - this corresponds (in the relevant equations) to a negative temperature. When all the people are on the mountain, the temperature is minus infinity. So bodies with temperatures below zero (ie negative temperatures) are actually hotter than bodies at zero temperature (and heat will flow from the former to the latter if they are in contact). This may sound as if physicists are playing around with words but it makes a bit more sense if you take entropy into account.

  • rate this

    Comment number 3.

    I apologise for an error in the last comment. The third and fourth last sentences should read: "Give them some more energy and the number on the mountain will exceed the number in the valley - this corresponds (in the relevant equations) to a large negative temperature. When all the people are on the mountain, the temperature is small and negative."

    So as you add heat, the initial (positive) temperature increases eventually to very large positive numbers, goes through positive infinity to negative infinity and then further increases to become a small negative number. [It's important to note this only applies when one can talk about the temperature of one part of the total energy of a physical system because it has become decoupled from the other parts of the total energy.]

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    Comment number 4.

    "Physicist Ulrich Schneider from the Ludwig Maximilian University in Munich, Germany, and some of his colleagues reached sub-absolute-zero temperatures working in the laboratory with a quantum gas made up of potassium atoms, according to nature.com"

    It was only a few billonths K, and seems the logical consequence of quantum theory.


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