In Our Time


Duration: 45 minutes
First broadcast: Thursday 19 April 2007

Melvyn Bragg and guests discuss symmetry. Found in Nature – from snowflakes to butterflies – and in art in the music of Bach and the poems of Pushkin, symmetry is both aesthetically pleasing and an essential tool to understanding our physical world. The Greek philosopher Aristotle described symmetry as one of the greatest forms of beauty to be found in the mathematical sciences, while the French poet Paul Valery went further, declaring; “The universe is built on a plan, the profound symmetry of which is somehow present in the inner structure of our intellect”.

The story of symmetry tracks an extraordinary shift from its role as an aesthetic model – found in the tiles in the Alhambra and Bach’s compositions – to becoming a key tool to understanding how the physical world works. It provides a major breakthrough in mathematics with the development of group theory in the 19th century. And it is the unexpected breakdown of symmetry at sub-atomic level that is so tantalising for contemporary quantum physicists.

So why is symmetry so prevalent and appealing in both art and nature? How does symmetry enable us to grapple with monstrous numbers? And how might symmetry contribute to the elusive Theory of Everything?

With Fay Dowker, Reader in Theoretical Physics at Imperial College, London;
Marcus du Sautoy, Professor of Mathematics at the University of Oxford;
Ian Stewart, Professor of Mathematics at the University of Warwick


Duration: 45 minutes
First broadcast: Thursday 08 February 2007

Melvyn Bragg and guests discuss one of the most important philosophers of the 20th century, Karl Popper whose ideas about science and politics robustly challenged the accepted ideas of the day. He strongly resisted the prevailing empiricist consensus that scientists’ theories could be proved true.

Popper wrote: “The more we learn about the world and the deeper our learning, the more conscious, specific and articulate will be our knowledge of what we do not know, our knowledge of our ignorance”. He believed that even when a scientific principle had been successfully and repeatedly tested, it was not necessarily true. Instead it had simply not proved false, yet! This became known as the theory of falsification.

He called for a clear demarcation between good science, in which theories are constantly challenged, and what he called “pseudo sciences” which couldn’t be tested. His debunking of such ideologies led some to describe him as the “murderer of Freud and Marx”.

He went on to apply his ideas to politics, advocating an Open Society. His ideas influenced a wide range of politicians, from those close to Margaret Thatcher, to thinkers in the Eastern Communist bloc and South America.

So how did Karl Popper change our approach to the philosophy of science? How have scientists and philosophers made use of his ideas? And how are his theories viewed today? Are we any closer to proving scientific principles are “true”?

With John Worrall, Professor of Philosophy of Science at the London School of Economics; Anthony O’Hear, Weston Professor of Philosophy at Buckingham University; Nancy Cartwright, Professor of Philosophy at the LSE and the University of California

Indian Mathematics

Duration: 45 minutes
First broadcast: Thursday 14 December 2006

Melvyn Bragg and guests discuss the contribution Indian mathematicians have made to our understanding of the subject. Mathematics from the Indian subcontinent has provided foundations for much of our modern thinking on the subject. They were thought to be the first to use zero as a number. Our modern numerals have their roots there too. And mathematicians in the area that is now India, Pakistan and Bangladesh were grappling with concepts such as infinity centuries before Europe got to grips with it. There’s even a suggestion that Indian mathematicians discovered Pythagoras’ theorem before Pythagoras.

Some of these advances have their basis in early religious texts which describe the geometry necessary for building falcon-shaped altars of precise dimensions. Astronomical calculations used to decide the dates of religious festivals also encouraged these mathematical developments.

So how were these advances passed on to the rest of the world? And why was the contribution of mathematicians from this area ignored by Europe for centuries?

With George Gheverghese Joseph, Honorary Reader in Mathematics Education at Manchester University; Colva Roney-Dougal, Lecturer in Pure Mathematics at the University of St Andrews; Dennis Almeida, Lecturer in Mathematics Education at Exeter University and the Open University

The Speed of Light

Duration: 45 minutes
First broadcast: Thursday 30 November 2006

Melvyn Bragg and guests discuss the speed of light. Scientists and thinkers have been fascinated with the speed of light for millennia. Aristotle wrongly contended that the speed of light was infinite, but it was the 17th Century before serious attempts were made to measure its actual velocity – we now know that it’s 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 then has dramatic effects on the nature of space and time. It’s been thought the speed of light is a constant in Nature, a kind of cosmic speed limit, now the scientists aren’t so sure.

With John Barrow, Professor of Mathematical Sciences and Gresham Professor of Astronomy at Cambridge University; Iwan Morus, Senior Lecturer in the History of Science at The University of Wales, Aberystwyth; Jocelyn Bell Burnell, Visiting Professor of Astrophysics at Oxford University

The Poincaré Conjecture

Duration: 45 minutes
First broadcast: Thursday 02 November 2006

Melvyn Bragg and guests discuss the Poincaré Conjecture. The great French mathematician Henri Poincaré declared: “The scientist does not study mathematics because it is useful; he studies it because he delights in it, and he delights in it because it is beautiful. If nature were not beautiful, it would not be worth knowing and life would not be worth living. And it is because simplicity, because grandeur, is beautiful that we preferably seek simple facts, sublime facts, and that we delight now to follow the majestic course of the stars.”

Poincaré’s ground-breaking work in the 19th and early 20th century has indeed led us to the stars and the consideration of the shape of the universe itself. He is known as the father of topology – the study of the properties of shapes and how they can be deformed. His famous Conjecture in this field has been causing mathematicians sleepless nights ever since. He is also credited as the Father of Chaos Theory.

So how did this great polymath change the way we understand the world and indeed the universe? Why did his conjecture remain unproved for almost a century? And has it finally been cracked?

With June Barrow-Green, Lecturer in the History of Mathematics at the Open University; Ian Stewart, Professor of Mathematics at the University of Warwick; Marcus du Sautoy, Professor of Mathematics at the University of Oxford.


Duration: 45 minutes
First broadcast: Thursday 29 June 2006

Melvyn Bragg and guests discuss the galaxies. Spread out across the voids of space like spun sugar, but harbouring in their centres super-massive black holes.

Our galaxy is about 100,000 light years across, is shaped like a fried egg and we travel inside it at approximately 220 kilometres per second. The nearest one to us is much smaller and is nicknamed the Sagittarius Dwarf. But the one down the road, called Andromeda, is just as large as ours and, in 10 billion years, we’ll probably crash into it.

Galaxies – the vast islands in space of staggering beauty and even more staggering dimension. But galaxies are not simply there to adorn the universe; they house much of its visible matter and maintain the stars in a constant cycle of creation and destruction.

But why do galaxies exist, how have they evolved and what lies at the centre of a galaxy to make the stars dance round it at such colossal speeds?

With John Gribbin, Visiting Fellow in Astronomy at the University of Sussex; Carolin Crawford, Royal Society University Research Fellow at the Institute of Astronomy at Cambridge; Robert Kennicutt, Plumian Professor of Astronomy and Experimental Philosophy at the University of Cambridge


Duration: 45 minutes
First broadcast: Thursday 03 November 2005

Melvyn Bragg and guests discuss the unique properties of asteroids. They used to be regarded as the ‘vermin of the solar system’, irritating rubble that got in the way of astronomers trying to study more interesting phenomena. It was difficult or even impossible for an observer of asteroids to book time using the world’s best telescopes, because they were regarded as unspectacular objects that could tell us little about the origins of the universe.

However, that has all changed. It is now thought that asteroids are the unused building blocks of planets, ‘pristine material’ that has remained chemically unchanged since the creation of the solar system; a snapshot of matter at the beginning of time. At the moment the Japanese probe Hayabusa is 180 million miles away, pinned to the back of the asteroid Itokawa, attempting to gain our first samples of the chemical composition of an asteroid.

Why did asteroids fail to form planets? How do they differ from their celestial cousins, the comets? And are either of them likely to create another impact on planet Earth?

With Monica Grady, Professor of Planetary and Space Sciences, Open University; Carolin Crawford, Royal Society Research Fellow, University of Cambridge; John Zarnecki, Professor of Space Science, Open University.

The Graviton

Duration: 45 minutes
First broadcast: Thursday 24 November 2005

Melvyn Bragg and guests discuss the search for the Graviton particle. Albert Einstein said “I know why there are so many people who love chopping wood. In this activity one immediately sees the results”. Einstein spent the last thirty years of his life trying to find a theory that would unify electromagnetism with gravity, but success eluded him.

The search is still on for a unifying theory of gravitational force and hopes are pinned on the location of the graviton – a hypothetical elementary particle that transmits the force of gravity. But the graviton is proving hard to find. Indeed, the Large Hadron Collider at CERN still won’t allow us to detect gravitons per se, but might be able to prove their existence in other ways.

The idea of the graviton particle first emerged in the middle of the 20th century, when the notion that particles as mediators of force was taken seriously. Physicists believed that it could be applicable to gravity and by the late 20th century the hunt was truly on for the ultimate theory, a theory of quantum gravity.

So why is the search for the graviton the major goal of theoretical physics? How will the measurement of gravitation waves help prove its existence? And how might the graviton unite the seemingly incompatible theories of general relativity and quantum mechanics?

With Roger Cashmore, Former Research Director at CERN and Principal of Brasenose College, Oxford; Jim Al-Khalili, Professor of Physics at the University of Surrey; Sheila Rowan, Reader in Physics in the Department of Physics and Astronomy at the University of Glasgow

Dark Energy

Duration: 45 minutes
First broadcast: Thursday 17 March 2005

Melvyn Bragg and guests discuss ‘dark energy’. Only 5% of our universe is composed of visible matter, stars, planets and people; something called ‘dark matter’ makes up about 25% and an enormous 70% of the universe is pervaded with the mysteriously named ‘dark energy’. It is a recent discovery and may be only a conjecture, but it has been invoked to explain an abiding riddle of the cosmos: if the expansion of the universe is powered by the energy of the Big Bang, then why isn’t the expansion slowing down over time as the initial energy runs down and the attractive force of gravity asserts itself? Scientists had predicted a Big Crunch as the logical opposite of the Big Bang, but far from retracting, the expansion of the universe is actually accelerating…it’s running away with itself.

How do we know that the universe is behaving like this and what’s causing it? If dark energy is the culprit, then what is this elusive, though omnipresent entity?

With Sir Martin Rees, Astronomer Royal and Professor of Cosmology and Astrophysics, Cambridge University; Carolin Crawford, Royal Society University Research Fellow at the Institute of Astronomy, University of Cambridge; Sir Roger Penrose, Emeritus Rouse Ball Professor of Maths at Oxford University.

The Second Law of Thermodynamics

Duration: 45 minutes
First broadcast: Thursday 16 December 2004

Melvyn Bragg and guests discuss the Second Law of Thermodynamics which can be very simply stated like this: “Energy spontaneously tends to flow from being concentrated in one place to becoming diffused and spread out”. It was first formulated – derived from ideas first put forward by Lord Kelvin – to explain how a steam engine worked, it can explain why a cup of tea goes cold if you don’t drink it and how a pan of water can be heated to boil an egg.

But its application has been found to be rather grander than this. The Second Law is now used to explain the big bang, the expansion of the cosmos and even suggests our inexorable passage through time towards the ‘heat death’ of the universe. It’s been called the most fundamental law in all of science, and CP Snow in his Two Cultures wrote: “Not knowing the Second Law of Thermodynamics is like never having read a work of Shakespeare”.

What is the Second Law? What are its implications for time and energy in the universe, and does it tend to be refuted by the existence of life and the theory of evolution?

With John Gribbin, Visiting Fellow in Astronomy at the University of Sussex; Peter Atkins, Professor of Chemistry at Oxford University; Monica Grady, Head of Petrology and Meteoritics at the Natural History Museum