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Hello this week we're discussing the speed of light the medium most of you are listening to through radio waves

Travels at the speed of light those of you closer to the radio transmitter will hear in-artime

Fractionally before someone further away

Scientists and philosophers have been fascinated with light for millennia Aristotle

wrongly contended that the speed of light is infinite

It was the 17th century before serious attempts were made to measure its actual velocity

We now know it's about 186,000 miles per second

Then in 1905 Einstein's special theory of relativity predicted that nothing can travel faster than the speed of light

This had dramatic effect dramatic effects on the study of the nature of space and time

It's also been thought that the speed of light is a constant in nature a kind of cosmic speed limit now the scientists aren't so sure

Join me to discuss this a John Barrow professor of mathematical sciences and Gresham professor of astronomy at Cambridge University

Jocelyn Belm-Bernel visiting professor of astrophysics at Oxford University and you and Morris senior lecturer in the history of science at the University of Wales

Aberystwyth John Barrow festival. What is light? What's it made of?

Well, it's always a bad question to ask scientists what something is

We tend not really to know what things really are, but just what they do and what their effects are

And we look upon light as a way in which energy

Is transmitted from one place to another in the universe in a wave-like fashion

We're familiar with light being

Having many possible wavelengths now not just the visible forms of light that

We've known about ever since there are human beings with eyes, but we know that light spectrum stretches into the infrared and

...