Summary
Melvyn Bragg and guests discuss how scientists sought to understand the properties of gases and the relationship between pressure and volume, and what that search unlocked. Newton theorised that there were static particles in gases that pushed against each other all the harder when volume decreased, hence the increase in pressure. Those who argued that molecules moved, and hit each other, were discredited until James Maxwell and Ludwig Boltzmann used statistics to support this kinetic theory. Ideas about atoms developed in tandem with this, and it came as a surprise to scientists in C20th that the molecules underpinning the theory actually existed and were not simply thought experiments.
The image above is of Ludwig Boltzmann from a lithograph by Rudolf Fenzl, 1898
With
Steven Bramwell Professor of Physics at University College London
Isobel Falconer Reader in History of Mathematics at the University of St Andrews
and
Ted Forgan Emeritus Professor of Physics at the University of Birmingham
Producer: Simon Tillotson
Transcript
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| 0:00.0 | BBC Sounds, Music, Radio, Podcasts. |
| 0:04.9 | Thanks for downloading this episode of In Our Time. |
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| 0:14.8 | I hope you enjoyed the programs. |
| 0:16.8 | Hello, in 1662, Robert Boyle observed that when the volume of a gas goes up, the pressure |
| 0:22.2 | goes down and when the volume goes down, the pressure goes up. |
| 0:26.3 | The most popular explanation for that endorsed by Newton was that there were tiny static particles |
| 0:31.5 | in the gas, pushing each other apart and the more they were squeezed, the higher the pressure. |
| 0:36.7 | What though, if the atoms were not static but moving quickly, what would flow from that? |
| 0:41.7 | A lot, it's turned out, and those who developed this moving kinetic theory of gases helped |
| 0:46.5 | unlock much of modern physics, including temperature, the workings of the sun and quantum theory. |
| 0:52.3 | I'd like to discuss kinetic theory of Isabel Faulkner, read her in the history of mathematics |
| 0:56.7 | at the University of St Andrews, Ted Faulkner, emeritus professor at physics at the University |
| 1:01.4 | of Birmingham and Seymour Bramble, professor at physics at University College London. |
| 1:05.8 | Steve Bramble, can you summarize what the kinetic theory of gases is and why it matters? |
| 1:12.5 | Yes, so the kinetic theory of gases is a very simple model for a gas. |
| 1:18.0 | The idea that a gas consists of atoms or molecules that fly around in empty space in the vacuum, |
| 1:24.6 | they bump into each other, they bump into other objects. |
| 1:27.9 | The idea is that using Newton's Laws of Motion, you can then calculate all the properties |
| 1:34.7 | of a gas from that picture. |
| 1:38.2 | The picture to have in mind is a billiard ball, bouncing around on the table, but there |
... |
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