Neil Turok interviewed by Alan Macfarlane and Tina Košir 19th February 2008

0:09:07 Born in Johannesburg, South Africa, 1958; grew up in a very political family, always in trouble; police raids; parents very involved with African National Congress and the resistance movement; father [Ben Turok] went to prison when I was three for three and a half years, and mother when I was five for about six months; we left as refugees in 1966 and moved to Kenya, then Tanzania; had a wonderful childhood in Africa and then came to Britain; when mother was in prison I stayed with my grandmother in Durban; she was a Christian Scientist and took me to Sunday school which I loved; by the time I returned home after six months I was praying every night which my two elder brothers found ridiculous and broke me of the habit; used to have debates with them on the existence of God

4:09:15 Father trained as a land surveyor and had an engineering/mathematical leaning; he taught me Pythagoras’s theorem and how make maps; he interested me in the ancient Greeks as he was a keen student of philosophy; he was imprisoned in 1961`and while in prison he studied philosophy and took a degree by correspondence; most interested in the pre-Socratic philosophers, people who had suddenly seen the world with fresh eyes and had a perspective uncluttered by mythology; he was a strong influence on me; his passion for politics and freedom was inspiring; mother was the carer, left to look after three boys on her own when my father went to prison; very difficult because she was also a political activist and under constant harassment from the authorities; under house arrest some of the time; her own family effectively disowned her because she had married my father; tried to encourage her to leave him; she is a brave person and when my father finally got out of prison she helped him to escape across the border; she then got permission to leave with us on condition that we never returned and took us to Kenya where we met up with our father again; she was the backbone of the family and continued to play that role throughout our childhood; father always busy with a hundred schemes and ideas

8:36:17 First went to school in South Africa; I was very precocious and naughty, talked the whole time in class; moved up a year as I got quickly bored with what we were being taught; from the age of three attracted by physics - pouring, measuring and weighing things, loved geometry, fascinated with nature, collected insects, even hail in buckets to experiment with; moved to Kenya at seven and was in a school for six months in Nairobi; don't remember much about it but my father was in the ministry which made maps and remember seeing how they converted aerial photographs into topographical maps and I found that fascinating; in Tanzania I went to an ordinary Government school but had an exceptional teacher; she was a Scottish volunteer who had an identical twin sister who also taught, so did their mother; they all lived together in the school; she was my maths and science teacher, Margaret Carnie, and I am still in touch with her; she now lives in Edinburgh and is in her eighties, an absolutely exceptional person; as a teacher she taught me that I could do whatever I wanted; she gave me books, sent me outside to make a map of the school; I taught myself trigonometry, made measurements and scale drawings of the school; then she gave me books about physics; I learnt Archimedes principle, pulleys, weights, forces, and we did a lot of projects; she didn't instruct me but pointed me in the right direction; she was so convinced that I could do things that she gave me an incredible start; subsequent to that I moved to England aged ten and went to a primary school in Crouch End, London; my father was selling ‘Encyclopaedia Britannica’ as he couldn't get another job; at school they handed out pages of long multiplication, division, addition, and I thought it was a joke; I had done that four years before; once you have learnt the rules of how to multiply numbers you don't need to repeat examples but you use it for real problems; despite the fact that we had moved to England to go to better schools, I found the standard way below what I had had in Africa; however, secondary schools in England were much better; went to William Ellis, a grammar school in Highgate with some outstanding science teachers; bit of a shock moving from Africa to a grey London existence; had a wonderful maths teacher, modest but caring; I was a year ahead of my age group; was concentrating on biology, still collecting beetles, joined the British Entomological and Natural History Society, and elected a committee member of the society when I was thirteen; the amateur collectors whom I met were almost all over sixty but they were preserving the tradition of the animal collectors and classifiers; still believe there is more beauty in a beetle than all of human works of art

19:16:23 Came to Cambridge to do mathematical biology, but after six months, having taken courses in theoretical physics it grabbed my attention as the most powerful, simple, effective part of science that we know of; you can write an equation in one line that will describe a million phenomena with incredible precision and there is nothing like that in biology; I switched over to physics as an undergraduate; [AM asks for an explanation of Dirac's equation] Dirac working like everyone else on the basis of knowledge that had previously been discovered; he knew about relativity, about Schrödinger and Schrödinger's equation; he knew these things were correct because they had already proven themselves; Dirac wanted an equation which satisfied both relativity and quantum theory as described by Schrödinger; he thus had a mathematical puzzle and there is only one equation that satisfies the terms; he was the lucky guy to be in the right place at the right time with the right mathematical tools; he had an extraordinary mathematical mind; he had very little formal training having been trained as an engineer; never liked mathematics for its own sake; just invented it as he went along; his equation now describes ninety of all the particles that we know of, and the remaining thirty are described by Maxwell and successor theories

22:57:10 Coming to Cambridge found the course completely unsystematic; the first lecture course we took was called modern physics and we were lectured by Tony Hewish; it involved hand-waving (Hewish), quantum theory, radio astronomy, a little bit of relativity, a little bit about data and how you make sense of it; no mathematical derivation in the course was over two or three lines but it gave you a glimpse of a lot of exciting science and ideas which was deeply influential; think it was a model of its time as mostly when physics is taught in universities now, and certainly in the U.S., it is taught in a very systematic way where it takes you at least two years before you get to anything modern, which I think is a big mistake because you want to grab people as early as possible; once they are motivated they will learn much faster; thus without that course I might not have gone into physics at all

24:49:11 Although I had done very well at Cambridge I was tired of it; there were things about it that I didn't like; it is an elitist institution although I'm not against intellectual elitism in the best sense, but a lot of the elitism here ends up with having formal dinners where students from middle or lower-middle class backgrounds end up wanting to pretend they are almost aristocrats; becomes almost farcical; [later] was at Downing College, a science college, which I liked, but didn't like to see the students getting increasingly interested in putting on airs and graces, which I didn't fit in with; decided not to stay here to do Part 3 mathematics and went to Imperial College and took their masters in theoretical physics and then a PhD; difficult as life in London is nowhere near as nice for a student as Cambridge; quite a lonely time; tiny student digs; all the students go home in the evening so no real college life, plus working on a PhD which in theoretical physics mostly consists in banging your head against the wall and you have no idea whether you have any talent or whether the problem you a working on makes any sense; I spent two years like that without a clear idea of what I was doing; I worked extremely hard in my first year on a problem I then realized was not an interesting problem; you learn through this but it is not an easy route; I would advise anybody who is learning theoretical physics to be very careful that you are really willing to put up with some very hard times; it is not a subject where you get a quick reward

28:37:00 Father worked for the Open University and was very committed to his work; I used to see them regularly; they lived in Watford; while  I was in Cambridge they moved to Zambia so were not around for long periods; when a graduate student I was lucky enough to find a mistake in a paper by a very famous scientist who later won the Nobel Prize, Frank Wilczek; he came to England for a conference and I saw him and he graciously accepted and withdrew the paper; I wrote a paper with my advisor on that problem and then I got a post-doc. at the  Institute of Theoretical Physics in Santa Barbara which is probably the leading such institute in the world; fantastic place; interdisciplinary; think they had three permanent faculty when I was there and about twenty-five post-docs. so we didn't interact with faculty very much; they had set the tone and the quality but it was left to us to find other post-docs. to work with; as a result I worked in many different fields and looked around to find a niche for myself; there are very few places like that today and even that institute now has a faculty of 10-12 and far fewer post-docs; it was a new institute with a freewheeling atmosphere; every single one of the post-docs. that I was with now has an excellent position in theoretical physics yet there was not planned mentoring or supervision

32:02:10 I lost contact with the teacher (Margaret C) in Tanzania and then I came to Cambridge in 1997, and a couple of years after I did some work with Stephen Hawking and I was on a TV documentary programme which she saw; she wrote me a letter; delighted; went to see her in Edinburgh and she was the same person she always was; have stayed in touch with her since; when I saw her I started to tell her what I worked on; she stopped me and said this was not what interested her; she wanted to know what banged in the big bang; a good question that coincidentally I was working on and have subsequently given as a title to talks and attributed it to her; indeed it is the most important question

34:59:16 [TK Having read 'The Endless Universe' explain what the cyclic model of the universe is all about] The original motivation for the cyclic hypothesis came from string theory and a development of it called M-theory; these are our best current attempts to unify all the laws of physics into a single mathematical framework which is consistent both mathematically, logically and also consistent with everything we know about the world; lot of progress has been made and it does seem to be a single mathematical framework in which all the laws of physics fit - Einstein's theory of gravity, Maxwell's theory of electro-magnetism, Dirac's theory of particles; all these fit together in a single framework now called M-theory; other people had developed this but to me the application of M-theory and the true test of it would be to see whether it would describe cosmology, could it describe the universe; the origin of the cyclic picture goes back to a workshop in 1999 where we invited the leading researchers working on M-theory and leading cosmologists just to see whether anything interesting came out; this was at the Isaac Newton Institute in Cambridge; we had several lectures and during one Paul Steinhardt, my long-time collaborator from Princeton, and I both had the same idea that within M-theory there are these objects called branes (shorthand for membranes) but you can have a one-dimensional brane which is a string, a two-dimensional brane which is the membrane or surface, a three-dimensional brane which is space, or four-dimensional branes and up to ten-dimensional branes which can exist; the world, if we want to picture it in that way, consists of a ten-dimensional brane with other branes of lower dimension imbedded inside it; the intriguing thing is that you can't do this in an arbitrary way; once you have decided you want a theory of ten-dimensions you have to have all the other branes of different dimensions within it, and the rules whereby they interact are unique so there is no adjustment possible in the theory, which makes it attractive

38:33:12 Up until our workshop nobody had seriously tried to apply this to cosmology; at our workshop we were fascinated with the particular picture that had emerged, that the way to get from ten-dimensional M-theory to the real world was to get rid of seven of the dimensions by curling six of them up in a little ball so at every point of this room you should imagine that with a really powerful microscope I could look very closely at each point of space and would actually see an extra little ball of six-dimensions; so every point of three-dimensions would have six curled up; even though it at first sounds shocking it is a very beautiful idea when you look at it more closely; most intriguing to us was that there was a seventh-dimension which was even more bizarre; the seventh-dimension is a gap between two objects which are three-dimensional branes; so you have a picture of the world with the three-dimensional brane we live in, and the particles  we are made of travel around in this brane; light travels in this brane, but just next door to it there is another brane; these two branes are called 'end of the world' branes meaning that they are the end of the seventh-dimension and there is nothing beyond them, they are almost like mirrors; the world is a sandwich with nothing outside it with the seventh-dimension of space in between the two three-dimensional branes we live in; at every point of those three-dimensional branes there are another six-dimensions curled up; our thought was what happens when these two three-dimensional branes collide? Must be a pretty violent event as the whole dimension disappears for a moment; on the other hand the three-dimensional brane we live on does not shrink to a point when they collide, they simply move together; therefore it can't be like the big bang because as we knew that was an event where all of space was at a point; we could see immediately that here was another possibility for a bang which is that the space we live in did not shrink to a point, all that happened was a collision between another world and ours

41:51:12 Subsequently we worked through the mathematics of this and discovered that this event of the brane collisions indeed appears, if you try to describe the set up using Einstein's theory of gravity, just like the big bang; in Einstein's theory there is not a complete description of these branes colliding and when you add that element in you find that indeed space does not shrink to a point at the back, space is extended; now you have the possibility of a physical mechanism which caused the big bang which is describable; if the whole universe came out of a point that would not be mathematically describable; we do not know how to describe the structure of a single point; what we use in physics are differential equations with different points, and can't write such an equation with one point; if you had a picture of the big bang that was an extended bang across space, now you have the possibility of describing a physical mechanism that caused the bang; that is where the cyclic picture emerged in trying to understand how to describe the big bang's singularity; what we realized was that it could be the collision between two of these branes and that meant there was time before the big bang; but if these branes can collide once then they can collide again; quite quickly after we had invented the initial model called the ekpyrotic model (ekpyrotic means out of fire taken from the Ancient Greeks picture that the universe began in a conflagration); when we realize it could happen many times and indefinitely we called it the cyclic model

44:23:10 [TK: You say three-dimensions expand constantly and the only thing that shrinks is that spring-like force between the branes in the fourth-dimension] Exactly, it is essentially like a pump [TK: this gap is really small - 10 to -30 metres - is it possible to imagine where it is?] It is everywhere so every point of our three dimensional world is just 10 to -30 metres away from a corresponding point in the neighbouring world which is, if you like, the mirror world, sitting at the other end of the seventh-dimension; we are only just separated from it by an absolutely immeasurably small distance; it is interesting to ask whether there are any other manifestations of this extra dimension; in fact the origin of the seventh-dimension was that in our world there is a peculiar asymmetry in nature - left-handed objects are not the same as right-handed; when you have neutrinos (certain kinds of elementary particles) they only come left-handed; anti-neutrinos are right-handed; it has always been a puzzle why nature is asymmetrical; the reason why this two brane picture was invented is precisely so that the left-handed guys can be on our brane and the right-handed on the other brane, then mathematically it all works out

47:08:07 [TK: You said that atoms and light exist in one brane] In the other brane there is other stuff [TK: The force of gravity connects them?] Exactly [TK: What does that look like? You mention the dark matter might be the gravity of the other brane] The dark matter  might be the matter on the other brane and the matter on the two branes interacts only through gravity; the way we understand gravity is that it is the curving of space, which is what Einstein understood; the sun bends space and that's what keeps the planets going around in circles around it; in this M-theory picture its really what I call Einstein++ because it says there are not merely three dimensions but ten; then there are all these other objects of different dimension but each of them behaves exactly in the manner that Einstein envisaged; you have the two branes and matter in one deforms the space in between the branes and that is how gravity is transmitted across the gap to the other; that is how the dark matter influences us; this is a neat picture as it does predict dark matter which is visible only through gravity; that is what we see when observing a galaxy; light only moves on our brane; the unfortunate thing about this picture if true is that it is really hard to test; since our only way of interacting with the dark matter is through gravity we can't make dark matter in a laboratory; it is way beyond the energies we can get in current laboratories; its an unpleasant situation that you have a marvellous theory but you don't yet know how to test it; I believe that it is all the more reason that we should focus on the big bang because we know it happened and can measure the outcome in many ways, and can use that to check whether this theory is right

50:14:24 [TK: How can you check? You mention gravitational waves in your book..] Yes, there is surprisingly a remarkably direct way of checking this picture that the big bang was a brane collision with gravitational waves; these are ripples in space which travel at the speed of light; we have never detected them directly because they interact very weakly with matter; even though we believe the universe is full of them we have not been able to measure them yet; they will be measured within the next ten years; when they are this will be a new window on the universe because we will see black holes colliding and all kinds of violent phenomena which emit gravitational waves; because these interact so weakly with matter it is a wonderful thing from the point of view of seeing the big bang because it is just like the universe is transparent to gravitational waves; so when we look out at the sky now we see the microwave radiation from the big bang and that shows us the universe as it was 13.7 billion years ago at about 300,000 years after the big bang because only then had the universe become transparent to light; before that time it was very dense and hot which is opaque to light; using light we can never look back earlier but gravitational waves take us right back to the bang itself; the waves emitted at the bang would just travel straight through the plasma without any interference and straight into our detectors; there are experiments being planned - LISA a set of three satellites which will be put in space in 2013 or so and they will be looking for gravitational waves coming out of the early universe; the way in which you check this theory of the brane collisions is first of all by a negative check; the standard picture of the big bang just accepts that the universe emerged from a point without any explanation; what state would it have had to be in order to end up like it is today? The answer to that question is initially very puzzling as here is a tiny universe springing into existence and how did it get so big and smooth and uniform in all directions as we see it today? That was just seen as a paradox for a long time; puzzles led to a standard picture in cosmology according to which you simply assume a universe jumped into existence, and you assume it was full of inflationary energy which has the property of making space expand exponentially; you can add this energy into Einstein's theory of gravity and it is a repulsive form of energy which blows the universe up and makes it very smooth and uniform; but it is never really explained why the universe started out in this way; to come to gravitational waves, this epoch of inflation has a very dramatic side effect; when you make the universe blow up exponentially it is such a violent process that you generate lots of waves, the ripples in space time which are just there present in the vacuum, even in empty  space; when you start to blow up exponentially this enormous blow up spews out gravitational waves which we should be able to measure; the cyclic model is much gentler; you have these two objects which drift together over periods of billions or even trillions of years before they collide; when they do so all of space is not at a point, it is all spread out; when they collide they simply fill all space with radiation and then it subsequently expands; you do not get the gravitational waves that you would with inflation; if these gravitational waves are seen they will instantly disprove our model so it is testable; even though direct gravitational waves will not be detectable until after 2013, next year something called the Planck satellite will fly and that will have the means of detecting gravitational waves indirectly though their effect on micro-radiation coming from the early universe; Stephen Hawking bet me when we first came up with our model that gravitational waves will be detected by the Planck and our model will be proved wrong; I accepted the bet which he has not yet set; he plans to go into space three or four years from now on Virgin Galactic; I have suggested that, if I am right, I go into space, but he did not accept; it could be that next year our model may be dead; I have worked on theories before that have been proven wrong; I think it is good science and one should be humble in the face of the universe; the best we can do is make the best, most consistent models that we can, and then we have to test them ruthlessly in order to prove them wrong; that is progress as it rules out that avenue