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Hello, since the end of the 19th century, and especially since the dropping of the atomic bomb

in 1945, the word radiation has carried a fearful resonance. But in physics, it doesn't just

be in the emissions of radioactive material. Radiation is any process by which your body

emits energy, travels through a medium or no medium, and is absorbed by another body.

So the history of the discovery of radiation is the story of a process of uncovering the ways

that are apparently quite different forces of nature like electricity, magnetism and light are

connected. And how they in turn are linked to quite new discoveries like X-rays and radioactivity

and radio waves. Along the way, the discovery of radiation has allowed us to identify new chemical

elements and to work out what the stars are made of. And this is a story of pure science and how

it led to enormous social military and economic projects. We would need to discuss the history of

the discovery of radiation, a Jim Alcalili, professor of theoretical physics, and chair in the

public engagement in science at the University of Surrey, Frank Close, professor of physics at Exeter

College University of Oxford, and Frank James, professor of the history of science at the Royal

Institution. Jim Alcalili, can you just give us a headline of what for this discussion,

radiation and radioactivity will mean? Yes, you described it well in your introduction that people

when they hear the word radiation, they immediately assume it's a bad thing, radiation poisoning,

exposure to radiation, because they do tend to confuse it with radioactivity. But radiation,

as you say, is just any emanation of energy from an object. So light, sunlight is radiation,

heat is radiation, and radioactivity is quite specific. I guess we'll come to that later on in

the program. When we talk about radiation and most of radiation that we'll be discussing today,

...