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For more details about In Our Time and for our terms of use, please go to BBC.co. UK forward slash radio for. I hope

you enjoy the program. Hello when contemplating the vacuum of space in the

17th century the physicist Blais Pascal claimed, the eternal silence of these infinite spaces fills

me with dread.

But we're here round today Pascal's anguish might have been assuaged for the vacuum of space,

whilst certainly silent and possibly infinite, is by no means empty.

It's a seething mass of particles, of interactions, forces and energy. To study it undermines the distinction between something

and nothing. But by examining the nature of the vacuum, we get closer to understanding

the fabric of reality and the expansion of the universe.

With me to discuss the vacuum of space at Jocelyn Bell-Burnell,

visiting professor in astrophysics at Oxford University,

Ruth Gregory, Professor of Theoretical Physics at Durham University, and

Frank Close, Professor of Physics at Exeter College University of Oxford.

Frank Close, the idea of nothing was something which preoccupied the Greeks.

Yes, Aristotle, I think, decided that there was no such thing as nothing, and the idea that

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