Multimedia

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

http://www.bbc.co.uk/programmes/p003c1cn

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.

http://www.bbc.co.uk/programmes/p003k9kh

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

http://www.bbc.co.uk/programmes/p003k9ks

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.

http://www.bbc.co.uk/programmes/p003k9g5

Duration: 45 minutes
First broadcast: Thursday 18 November 2004

Melvyn Bragg and guests discuss the Higgs Boson particle. One weekend in 1964 the Scottish scientist Peter Higgs was walking in the Cairngorm Mountains. On his return to his laboratory in Edinburgh the following Monday, he declared to his colleagues that he had just experienced his ‘one big idea’ and now had an answer to the mystery of how matter in the universe got its mass. That big idea took many years of refining, but it has now generated so much international interest and has such an important place in physics that well over one billion pounds is being spent in the hope that he was right. It’s the biggest science project on Earth; the quest to find the ‘Higgs Boson’, a fundamental constituent of nature that – if it does exist – has such a central role in defining the universe that it’s also known as the God Particle.

What is the Higgs Boson? Why is it so important to scientists and how are they planning to find it?

With Jim Al-Khalili, Senior Lecturer in Physics at the University of Surrey; David Wark, Professor of Experimental Physics at Imperial College London and the Rutherford Appleton Laboratory; Professor Roger Cashmore, former Research Director at CERN and now Principal of Brasenose College, Oxford.

http://www.bbc.co.uk/programmes/p004y2b7

Duration: 45 minutes
First broadcast: Thursday 27 May 2004

Melvyn Bragg and guests discuss our knowledge of the planets in both our and other solar systems. Tucked away in the outer Western Spiral arm of the Milky Way is a middle aged star, with nine, or possibly ten orbiting planets of hugely varying sizes. Roughly ninety-two million miles and third in line from that central star is our own planet Earth, in thrall to our Sun, just one of the several thousand million stars that make up the Galaxy.

Ever since Galileo and Copernicus gave us a scientific model of our own solar system, we have assumed that somewhere amongst the myriad stars there must be other orbiting planets, but it took until 1995 to find one. ‘51 Pegasus A’ was discovered in the Pegasus constellation and was far bigger and far closer to its sun than any of our existing theories could have predicted. Since then 121 new planets have been found. And now it is thought there may be more planets in the skies than there are stars.

What causes a planet to form? How do you track one down? And how likely is there to be another one out there with properties like the Earth’s?

With Paul Murdin, Senior Fellow at the Institute of Astronomy in Cambridge; Hugh Jones, planet hunter and Reader in Astrophysics at Liverpool John Moores University; Carolin Crawford, Royal Society Research Fellow at the Institute of Astronomy in Cambridge

http://www.bbc.co.uk/programmes/p004y25b

Duration: 45 minutes
First broadcast: Thursday 25 March 2004

Melvyn Bragg and guests discuss the 30 year search to solve all the biggest questions in physics. At the end of the last century, brave voices were predicting that all the big questions of physics were on the verge of being answered by a Theory of Everything. The disparity between the physics of the very small would finally be reconciled with the very large, and the four forces of nature would finally be united with a single set of equations. It was suggested that with such a theory we might solve the riddle of black holes, unlock the secrets of the Big Bang, probe other universes and even uncover the mystery of travelling through time. But Stephen Hawking, who once said that with a Theory of Everything “we would know the m mind of God”, has changed his mind and now says that it may not be possible after all.

So what are the prospects for a Theory of Everything? Why do we need one? How do we get one? And what would it mean if we did?

With Brian Greene, Professor of Physics and Mathematics at Columbia University and author of The Fabric of the Cosmos; John Barrow, Professor of Mathematical Sciences at the University of Cambridge and author of The Constants of Nature; Dr Val Gibson, particle physicist from the Cavendish Laboratory and Fellow of Trinity College, Cambridge

http://www.bbc.co.uk/programmes/p004y24b