Second part

0:09:07 [TK: What is dark matter and what role does it play in the cyclic model?] Dark energy is nothing but the tension of these branes; when Einstein first developed the theory of general relativity he realized that space could have tension and he called it the cosmological constant; reason it was cosmological is that the tension has a very peculiar effect when combined with gravity; normally used to thinking of the tension as causing something to shrink but if you put the tension into Einstein's equations it does the opposite and causes the world to expand; Einstein used this to make a static universe model; he assumed the world was a three-dimensional sphere and then the gravity of ordinary matter would make it tend to collapse, and balanced tension and gravity against each other to make a static universe; unfortunately it was unstable and his model didn't make much sense so he abandoned it; ten years later it was found that the universe is expanding and he should have predicted that; though he abandoned the cosmological constant we always knew it could be there and the surprise has always been why it is not bigger than it is, why is the tension of space not huge; even if you have space with no tension and start adding particles and fields to the universe each one of those particles contributes something to the tension; to end up with very small tension is really difficult; in the late 1990's quite strong evidence emerged that the tension is not zero but actually positive and that we call the dark energy; so it appears that apparently empty space is actually full of energy and energy associated with the tension of three-dimensional space; the surprise is why is it so tiny at 10 to the power -120; though ridiculously tiny nevertheless it matters in the universe today otherwise we would not have seen it; very important for the future of the universe as it causes it to expand faster; we are currently 13.7 billion years old and  at another 13.7 billion years in the future this stuff will have really taken hold and begun to dilute away the galaxies exponentially; further billions of years on almost all the galaxies we know now will have disappeared from view and we will be alone in an empty universe surrounded perhaps by our nearest neighbour galaxies but nothing else; people in the future will be very puzzled by the apparently empty universe; they won't see the radiation left over from the big bang because it will have been diluted away; faced with a universe which started from a big bang which ended up dominated by dark energy we thought we would try to see things from a different point of view and that is how the cyclic model arose; we had this picture that the bang could be a collision between branes, that the branes would separate and possibly they would collide again; with regard to dark energy we discovered that when the branes separate if they do have some dark energy that causes them to expand and become very flat and parallel with each other; the dark energy can actually decay and can be the force that brings the branes together to produce another big bang; the dark energy makes the universe empty, smooth, vacuous and ready for another big bang which will produce another universe which is very big and smooth and will be emptied out again by the dark energy; so the dark energy is like a stabilizer; without it the branes would collide and the wrinkles and deformations they had acquired in one cycle of evolution would be magnified the next time and the whole universe would become more contorted and violent; without dark energy our model does not work whereas in the conventional picture of cosmology it is not necessary; on the puzzle of why is it so small? People working in the conventional framework have given up saying we can never explain why, at the big bang, whatever produced the bang somehow made the choice to fill the universe with radiation, matter, huge densities and energies and then add in 10 to the -120 of dark energy; instead they resort to the anthropic principle which says that maybe all kinds of universes emerge but we are not there in most of them so that if the dark energy was much greater in magnitude then it would have killed us; an appealing argument in some ways but does not have any predictive power; in our case if you have a picture of a very old universe, much older than 13.7 billion years, in previous epochs the dark energy played a huge and even controlling influence, then you have a huge amount of time for this dark energy to relax and its values can change; in theories like M-theory everything can change and all the laws of physics are dynamic; maybe what has happened is that dark energy has settled down to a value which is just right to keep the universe cycling in a stable fashion; given that the universe is able to have long cycles its entirely conceivable that dark energy has settled; we have published some papers on this idea and it is a radical alternative to the standard view; what we have shown is that technically we can construct mechanisms to make a model which will self-adjust the cosmological constant to the small values like the ones we see today; its only a model and not clearly true but the dark energy has made us really rethink our concept of cosmology and the big bang whereas people had seen it as a one-off intervention

12:20:09 [TK: You also write that no form of energy in the past ever goes out of existence and when cosmologists study dark energy today they are also studying the same type of energy that dominated in the distant past and will dominate in the far future. Could there be any information stored in the dark energy about the past and the future?] Yes, definitely; in the cyclic model as the universe passes through one of these violent events it happens that any signals or radio waves left over from the previous cycle are preserved; you will need very sensitive detectors to read it but its there in principle; it is an exciting thought that we could possibly communicate our discoveries about science to future generations in future cycles; what actually happens near one of these events is that all the particles we are made of lose their mass as the branes collide and move at the speed of light ; it would be a very unfamiliar world where we would be blown apart in a burst of radiation and immediately after be reconstituted into material objects

14:34:08 [TK: Is the big crunch just another name for the big bang?]

Yes. [TK: Maybe something more about extra dimensions] According to our current understanding of the laws of fundamental physics and unified theories, the laws of physics we see are largely determined by the size and shape of the extra dimensions; so at every point in this room there are another six-dimensions of space curled up in a rather complicated little ball which we can study mathematically; the detailed configurations of the extra dimensions actually fixes the physical laws we see - electro-magnetism, the strong force, the weak force, the different spectrum of particles; at one level we have not solved these problems in physics but converted it to another problem which is - Why are the extra dimensions the way they are? But that is progress as you have taken an apparently insoluble problem and converted it into another which may or may not be solvable; from my point of view what makes it interesting is that we have learnt from this framework that not only do the laws of physics govern the universe but the universe governs the laws; if we understand cosmology then we understand the laws of physics; this structure was determined at the big bang so when the bang  happens you should not only study the gap between the branes which causes them to collide, but the other six-dimensions are doing something in this process at the same time and it better be mathematically consistent; maybe in involves changes in their configuration and once we have understood the whole process in the big bang maybe we will understand why the whole universe emerged; then you will have understood all of physics; the one question will be what banged

18:01:24 [TK: Do you think the universe is a cosmos that can be explained rather than a chaos that cannot?] I don't know if there are limits to knowledge; some people in the last years have become rather pessimistic and have resorted to the anthropic principle and similar arguments to say that this is the end of the road for physics; I know that if we take this attitude we will get nowhere [TK: But you say that this is the best time to be a cosmologist, why?] Because the last ten years have seen unimaginable amounts of data collected from the universe; I was a cosmologist in 1992, before the Kobe satellite mapped the universe for the first time, when I was seriously considering giving up because most of the discussion was based on prejudice as there was no good data; 1992 suddenly gave us a clean picture of the big bang and for last ten years we have had a stream of high quality data and we now have the prospect of measurements of gravitational waves looking right back to the bang; it is an unique period in human history; not only are we speculating on the origin of the world but we have the data to test these theories; I think to be pessimistic now is really ridiculous

20:41:15 [TK: Are there any ethical problems connected with the cyclic  model?] I shall give you an example of an ethical problem which is that according to the cyclic model the basic motivation is to try to understand what happened at the bang and to make mathematical models; our first statement is that it is interesting to try to make a consistent mathematical model of the big bang itself; some people don't want to even consider this saying it is beyond science, religious territory; it is an ethical statement in my view to say a subject like this is legitimate science; not only can we do mathematics but experimental test observations, and we should; I think it leads to a better appreciation of the universe; even if you have got a model that is wrong you are trying to understand the universe; some people are arguing even within physics that we have reached the end of the road and that there are some problems too hard for us to understand; I think it is our ethical responsibility to keep going and to encourage young people who may have better ideas than we do; for me it is a very deep belief that even if science is going to be much more difficult from now on it is something that we have to do and our children will never forgive us for giving up; what we have learnt from physics is that nature is remarkably simple once you see through all the details and it is one of the treasures of humanity that we have this picture; interest in pure science and honest thinking about the universe is an activity which is common to all of humanity, should be cultivated and worked on, and if the next leap takes 10,000 years, fine, we will wait

26:12:10 [TK: If the cyclic model proves to be right would it be possible to abuse that knowledge in some way?] Very likely, all knowledge can be abused and it is up to people to use it wisely; I don't think there are any intrinsic ethics in science but they have to be added; having said that, I am not worried by any applications at the moment as its very far in the future that people may be able to manipulate these energies; at the moment laboratory energies we can reach are about 10 to the power of 15 times too small to probe any of the physics of the bang itself; I think probably our descendants will figure out how to do it one day but I'm not too worried about it

27:59:14 Probably the single greatest breakthrough of the last ten years has been the realization that gravity is describable in a way without using gravity; gravity is the curving of space according to Einstein, but in the late 1990's a young Argentinean physicist called Juan Maldacena made an exciting conjecture for which now there is a huge amount of evidence; the conjecture was that in certain situations you can take a chunk of space which is dynamical but bounded and that you could describe everything that happened in the interior purely by what was on the  boundary; called a holographic principle and has been used to explain black holes, for example; in the last few months we have been using this to understand cosmology so what we do it to map a dynamical universe called a bulk onto a boundary and we follow the system as it goes towards a big bang, a singularity; what we have shown is that on the boundary you can describe how the system goes through; essentially you take the bulk which has gravity in it, map it onto the rigid boundary, follow it until it hits a singularity, follow it through the singularity, come out on the other side and map it back into the bulk where it is again described by gravity; we have constructed the first complete model of passage through a singularity and it appears that not only can the world go though a singularity and survive but also in the process of heading towards the singularity it turns out that the variations in the density of the stuff on the boundary are created; these variations in density are of exactly the form we need to explain variations in density in the real universe called scale invariance; scale invariance is also a reflection of an underlying symmetry; what happened is that Maldacena's picture whereby gravity maps the matter on the boundary, that picture is automatically scale-invariant; we have written a couple of papers about this though there are many aspects still to be completed; if this picture turns out to be correct it will easily be the most elegant explanation of the origin of the density variations as it really all comes from symmetry principles

33:58:02 Martin Rees and Stephen Hawking are polar opposites; Martin's great strength is keeping abreast of the latest observational discoveries and facts about the universe and trying to piece them together in a coherent picture; think his contributions to cosmology have been on the phenomenological side; Stephen's contributions have been the opposite, in fundamental theory; from his point of view mathematical consistency and elegance is primary; its in the tradition of Einstein who wasn't too worried about data; Stephen's work has always tried to employ the most advanced mathematical techniques to address theoretical puzzles and problems so he would be much more interested in a fundamental theoretical paradox than he would in the very latest observations, although he has huge respect for them and should they become definitive he might even believe them; there is also a cultural difference between astro-physicists and theoretical physicists and the former are often quick to jump on a new measurement, star or galaxy, whereas the latter take a longer-term view; neither necessarily right and Martin and Stephen represent those two cultures

37:25:12 Cambridge has been fantastic for me mainly for two reasons, one was the amazing collegiate atmosphere; I was working in Princeton before I came here, an excellent department, possibly the best physics department in the world, but much more aggressive and self-promoting; what is so enjoyable here is that colleagues are very willing to spend time to discuss, share ideas or knowledge, without any agenda; the second thing that is great about Cambridge is the flexibility of the institution, that providing you fulfil a certain number of basic duties which are pretty modest compared with other universities, you can do what you want; coming to Cambridge I had the freedom to set up an institute in Cape Town, to raise money for it and bring in all sorts of allies and partners; I don't believe there is any other university in the world where I would have had that freedom; Cambridge provides an open space which is not too controlled which is very valuable; I was at Downing College for three years when I returned but have resigned; I think the college concept is in severe need of renewal and is no longer a community of scholars; too established, less ambitious and too many dinners

40:59:14 When my daughter was five I wanted to take her to Cape Town to spend some time with her grandparents; Herbert Huppert as chairman of the faculty board allowed me to take a sabbatical there to talk about possible collaboration with the University of Cape Town; my daughter went to school there and I was working on the ekpyrotic universe in peace; went to the university in order to fulfil the requirement to establish a link with Cambridge and asked what I could do; they said they needed maths as South Africa and had a strategic problem as they didn't have enough students coming through with high-level maths skills; idea emerged to set up a centre in South Africa for good maths students from throughout Africa and bring the best international lecturers in the world and create some mathematical stars; told my father and next day there was a rugby match on TV and I said I would come to his house to see it with him which he agreed to, with the proviso that I spend an hour in his office and produce a page on the proposed African Institute of Mathematical Sciences; next thing I knew was that he had faxed it to all the people he knew in higher education in South Africa and then I had to do it; when I came back to Cambridge he called me with news of a fantastic building for sale in Muizenberg, an 80 room hotel near the beach and told me to buy it; we did buy it for £65,000 using an inheritance that my brothers and I had; I brought the three deans of science from the local universities to the hotel and told them that this was where we were going to set up the best maths institute in Africa; one of the deans got very excited and he is now the director of the institute; we converted the hotel and through a lot of work and good luck it has become the most amazing institute

46:49:00 [TK: How is it doing now?] AIMS is in its fifth year and we've graduated about 160 students so far; they come from everywhere in Africa and currently there are 53 students from twenty countries, including 20 women; we designed it to be innovative with programme geared towards problem solving and encouraging people to think for themselves; the students have been incredibly successful and last year we had about 48 graduates of which 45 are now on masters and PhD programmes in top institutions, one is a lecturer, one is doing and MBA and another is working in an IT company; these students are the most highly motivated I have ever come across and given nine months at AIMS which they use to the maximum, they work 16 hours a day, learn computing and modelling, learn how to write and give presentations; through necessity we stumbled on a model of education which is extremely effective, getting people from many different backgrounds but all intelligent; the best teachers in the world are all willing to come to teach the best students in Africa; they all live in this hotel so it is a 24 hour learning environment with impromptu discussions and tutorial at any time so a terrifically intense atmosphere; after nine months these students are ready to go into any field of science; in an old institution like Cambridge it develops layers of bureaucracy, rules and curricula which are almost fixed in stone, whereas a new institution can jump to the cutting edge; at AIMS there is almost total freedom to create able people who can go into any technical field and contribute to it; doing it in Africa means that you get students with very high motivation levels as this is the chance of a lifetime for them; you might have thought Africa was the last place to develop a model for post-graduate education, in fact it has been the best place to do it; experience of a student from the Congo; my conception of AIMS went from it being a necessary step in solving a strategic problem, the lack of highly skilled people in Africa, more towards the conception that this will benefit science in the long run; believe that these people from different cultures bring a new energy and freshness into science, and very likely some new ways of looking at things; this year we have five students from AIMS in the maths department [in Cambridge] and previously you would almost never see a black African there, and the ones you saw were very isolated and felt second-rate; these students are having a fantastic time and I am hopeful that one of them will come at or near the top in the financial maths course here, a very brilliant student; it is now our culture at AIMS that we are going to prove something to the world that black Africans are every bit as good as whites at science; ridiculous statement by Jim Watson after which his genome was sequenced and found to be 16% black African used to encourage students; our dream is that the next Einstein will be an African

55:51:16 [TK: Winning the TAD prize means winning $100,000 but more importantly you are granted a wish. Can you tell us what your wish will be?] The wish has two parts and the first is that the next Einstein will be an African and that may sound surprising, but Einstein was a Jew and Jews didn't get into science until c1880 and were actually prohibited from going into universities in many countries in Europe; some Jews went into medicine but very few went into hard science; once they got into it they flourished so that over a quarter of Nobel prizes in physics were won by Jews and a quarter of Fields medallists similarly; I do not believe that this is something innate to Jews though some element of Jewish culture may be helpful - great respect for the written word, for study - but more importantly, they were out to prove something; the Jews were suppressed and persecuted but when they got half a chance they wanted to prove something about themselves; look at Africa, culturally one of the richest continents - music, art, design -  and ingenious mechanics; there are geniuses all over Africa; anecdote from when teaching in Lesotho; second part of the dream is a plan which is to replicate AIMS all over Africa; looking for major donors - Bob Geldof may do so - and at TED this is what I will be asking for; looking for three donors to give $50,000,000 each to set up an endowment fund for student scholarships; we have the support of the African Union who have commissioned us to prepare this plan; we have sites in Nigeria, Ghana, Uganda, Sudan, Madagascar which we have visited and have business plans; when it is done we will have a network of AIMS and will be producing 50 graduates a year from fifteen centres in five years; we think these graduates could have a major impact in African development