The Photon

In Our Time: Science

BBC

History

4.5 • 1.4K Ratings

🗓️ 12 February 2015

⏱️ 45 minutes

🔗️ Recording | iTunes | RSS

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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	Thank you for downloading this episode of In Our Time, for more details about in our time, and for our terms of use, please go to BBC.co.uk.
0:09.0	I hope you enjoy the program.
0:11.0	Hello, what is Light? This is a question which is perplexed the greatest thinkers for hundreds of years.
0:16.0	In the late 19th century, scientists thought they'd finally solved the problem.
0:20.0	Light they thought was an electronic electromagnetic wave a form of
0:24.9	radiation closely related to electricity and magnetism. But in 1905
0:29.7	Albert Einstein showed that it can also be thought of as a stream of tiny particles, later named
0:35.2	photons. Fotons are all around us. Every second the light bulb above my head is
0:39.7	producing a million times more photons than there are cells in my body.
0:44.3	Photons are radiating in that trillions from the BBC transmitters to bring you this
0:47.8	radio program.
0:48.8	An x-ray machines and microwave ovens are both clever ways of making use of them. But the
0:54.3	photon still remains mysterious. Towards the end of his life,
0:57.0	Einstein said that after 50 years of thought he still didn't understand what
1:01.2	a photon was. Of course course today he said every rascal
1:04.5	thinks he knows the answer but he is deluding himself.
1:07.2	We'd me to discuss the photo now Frank Close, Professor Emeritus of Physics at
1:12.2	the University of Oxford, Wendy Fluevall, Professor of Surface Physics
1:15.9	at the University of Manchester and Susan Cartwright, Senior Lecture in Physics and Astronomy
1:20.7	at the University of Sheffield. Frank Close, I started this program by saying,
1:26.0	what is light, could you begin to tell us how a scientist in the 19th century
1:30.0	might have answered that question?
	...

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