Summary
Melvyn Bragg and his guests discuss the photon, one of the most enigmatic objects in the Universe. Generations of scientists have struggled to understand the nature of light. In the late nineteenth century it seemed clear that light was an electromagnetic wave. But the work of physicists including Planck and Einstein shed doubt on this theory. Today scientists accept that light can behave both as a wave and a particle, the latter known as the photon. Understanding light in terms of photons has enabled the development of some of the most important technology of the last fifty years.
With:
Frank Close Professor Emeritus of Physics at the University of Oxford
Wendy Flavell Professor of Surface Physics at the University of Manchester
Susan Cartwright Senior Lecturer in Physics and Astronomy at the University of Sheffield.
Producer: Thomas Morris.
Transcript
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| 0:00.0 | Just before this BBC podcast gets underway, here's something you may not know. |
| 0:04.7 | My name's Linda Davies and I Commission Podcasts for BBC Sounds. |
| 0:08.5 | As you'd expect, at the BBC we make podcasts of the very highest quality featuring the most knowledgeable experts and genuinely engaging voices. |
| 0:18.0 | What you may not know is that the BBC makes podcasts about all kinds of things like pop stars, |
| 0:24.6 | poltergeist, cricket, and conspiracy theories and that's just a few examples. |
| 0:29.7 | If you'd like to discover something a little bit unexpected, find your next podcast over at BBC Sounds. |
| 0:36.0 | Thank you for downloading this episode of In Our Time. |
| 0:38.7 | For more details about in our time and for our terms of use please go to BBC.co. UK slash radio for I hope you enjoy |
| 0:45.9 | the program. Hello what is light this is a question which is perplexed the greatest |
| 0:51.2 | thinkers for hundreds of years. |
| 0:53.1 | In the late 19th century, scientists thought they'd finally solved the problem. |
| 0:56.8 | Light they thought was an electronic electromagnetic wave, a form of radiation closely |
| 1:02.1 | related to electricity and magnetism. |
| 1:05.0 | But in 1905 Albert Einstein showed that it can also be thought of as a stream of tiny particles, |
| 1:10.6 | later named photons. Photons are all around us. Every second the light bulb |
| 1:15.2 | above my head is producing a million times more photons than there are cells in |
| 1:19.1 | my body. Fotons are radiating in that trillions from the BBC transmitters to bring you this radio program. |
| 1:25.2 | An x-ray machines and microwave ovens are both clever ways of making use of them. |
| 1:30.0 | But the photons still remains mysterious. |
| 1:32.4 | Towards the end of his life, Einstein said that after 50 years of thought, |
| 1:35.6 | he still didn't understand what a photon was. |
| 1:38.6 | Of course, today he said, every rascal thinks he knows the answer, |
... |
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