a thought about your youth, because when you were young, you were a revolutionary. you wanted dramatic change, to destroy the status quo. i just wonder if you've brought that spirit into your physics, into your study of the universe. yes. it was not...notjust me. it was a big chunk of my generation that had this dream of changing the world, right? and then making a world better without wars, without borders. we got disappointed. we sort of thought, well, the rest of the planet, the rest of the people doesn't really want to change the world so much. and i think it's a moment of disappointment that i found something else which was revolutionary, which was modern physics. so i shifted from political revolution to scientific revolution. and what sense can you describe physics as potentially revolutionary? because we have a worldview in which we think we know everything. right? this is up, this is down, the earth is flat, nothing is moving. this is solid, continuous. and then we learn about the universe and we discover actually it's not true. i mean, the earth is not flat, it's round. it's not true we're not moving. the earth is spinning, we're going around the sun. this is plenty of little atoms and voids in between. so there's this continuous challenge to previous knowledge and to grow. for knowledge to grow, you have to abandon something old, notjust physics and biology, etc... but that's a very interesting idea because you talked about the importance of a word you use, unlearning, the importance of unlearning things, ie, not being tied to old assumptions that you inherit and don't question. when you got deep into theoretical physics, astrophysics, did you find that you were being restricted by some of the thinking that was pervasive, that was the convention of the time? yes, absolutely. first of all, by learning the physics that we have, the knowledge we have acquired, notjust physics, biology is the same, when you realise that we are a family with all the rest of the animals and the plants of the planet, we have to unlearn something about ourself, change our view about ourselves with darwin and in physics, this is continuous. einstein discoveries are a way of unlearning something about time. and then somehow through my university studies, i got to the point of realising that there were a lot of open questions as basis for contemporary knowledge. and so with the enthusiasm of the youth who want to solve all the problems, "0h, great, i want to do that!" and so i think we're in the same situation as usual — to learn something better about the universe, we have to figure out what are the aspects of our current knowledge that we have to abandon. now i've got a little book in front of me. i guess your most recent, white holes: inside the horizon. now you talk about challenging the status quo. would you say that this little book, the idea of white holes and the premises that it is based upon is a fundamental challenge to the way theoretical physics has thought about the universe in the last couple of decades? this is a book not about something we have discovered. it's a book in which i tell what it is, a process for discovering. we don't know if white holes exist in the sky for real... just to help everybody, including me, because i'm not going to pretend i come to this with a great depth of knowledge, just tell me in simple terms what your theory of a white hole is. what we have discovered in the last decades, i would say, and was a perhaps beautiful, most surprising discovery about the universe is that it is full of these holes, these black holes. we have pictures of them, we have great evidence of them. and my knowledge of a black hole would be that in essence, it's about the death of a certain kind of star, which creates such immense forces, immense gravity, that in a sense, gravity takes over from everything else. and there is a sort of — i know this is simplistic — but a massive sort of implosion of forces. exactly. and space itself gets holed by this, by this implosion. and one should think inside there is a huge, immense space where things are falling in and we see things that are spiralling around the black holes and going to fall in. that's something we know, thanks to the astronomers, the astrophysicist. we have quite totally convincing, i would say, evidence that these things exist. and we understand them pretty well up to what happened inside. deep inside. the very heart? right. so we're in a very funny situation, right? because the universe is all these little holes here and there and we see things falling in. where does it go? the hypothesis on which we're working with many colleagues is that once everything falls inside, a quantum phenomenon makes a sort of bounce so slowly after everything is going to come out and a black hole becomes a white hole, a white hole being again like a hole. but not where everything can go in, but from which everything can come out. so whatever fell into the black hole, it's going to come out from the white hole. that's hypothesis. this is difficult. this is difficult stuff for people like me to understand. i think the model, you throw things inside and after a while, it comes out. what you then posit is that the universe is full of these little specks of, i mean, you could almost say specks of dust, that are actually these white holes which have emerged from black holes and which are all around us. there could even, in theory, be one in this studio. there could be one passing by here. yes. so what you are positing, therefore, correct me if i'm wrong, is this sort of a universe that is truly infinite, because we used to think that the black hole was sort of the end of everything. but you're saying that even a black hole contains the potentiality for something beyond it? nothing is forever, not even a black hole. a black hole has a finite life. that's what we learned from stephen hawking. and at the end of this finite life, something should happen. one thing that could happen is the end of time. but i don't think it's a convincing story, a more convincing story is that the black hole changes into a white hole and things can come out. you, in developing this theory, you have challenged a lot of scientific thinking, bringing me back to the idea of you as a revolutionary. you've sort of challenged string theory, which was pervasive for a number of years. scientists who oppose you say that your work is riddled with mistakes and is also so speculative that it shouldn't be compared with the work they do, which is much more rooted in the science. oh, this is challenging. that's true. and that's how best science works, right? we explore different opinions, different hypothesis, and we try to compare and see who comes out with something that get confirmed or supported by experiment. now, the majority of the people who are sceptical about this approach, people who also expected some results, that nature has said no. very recently there was a big disappointment in that community, which came from the big experiment in switzerland, in geneva, from lhc, which was everybody expected discovery of supersymmetry. this is the large hadron collider? exactly. and supersymmetry has not been found. so you see, this is how science works. the different communities exploring different ideas. sure. i mean, somebody turns out to be right, somebody turns out to be wrong. that's a huge, tangible experiment which comes out with data and results. i mean, what's fascinating to me about you as one of the world's renowned physicists, is that so much of the way you express and communicate your ideas isn't through calculus. it isn't through pages of mathematical calculation, it's through poetry, it's through analogy. this book is actually, in a sense, driven by your determination to draw an analogy with dante's journey into the inferno. the book is a travelogue. it's a... i tell the story of what would happen if we would go inside the black hole, what we see around us. how would the distortion of space and time be felt by us? go to the centre, go through the centre, come out of the white hole. to be both ridiculous and pedantic, it's an absurd notion because, of course, you know, no being could enter a black hole. i mean, the whole idea is ridiculous. but i understand that you're trying to communicate an idea using your imagination. i just wonder if you are, in a way, trying to marry science with imaginative art, almost. you know, you once said you wanted to be a poet. i mean, it's the poetry of science that you're getting at. yes. and i think there is something in the core of science which is exactly that. einstein, for instance, tells the story of himself wondering what would happen if he could ride a ray of light and he was trying to figure out in his head what would happen. or copernicus, right? he asked, what would the solar system look like if it was on the sun? kepler wrote a fantastic book, which is called the dream, in which he tells the story of him and his mother, or a character representing him and his mother, going to the moon and seeing things from there. i think great science, of course, is based on questions, on mathematics. i mean, my technical papers are full of equations in mathematics, of course, but it's nourished by intuition and by imagination and by the capacity of changing perspective and seeing things from a different point of view. and you embrace uncertainty. i mean, you're very candid when you talk about the possibility that you're wrong. i mean, scientists often steer clear of this, but i'm going to quote you, something you say, because it's so interesting. you said, "even today, i'm still far from convinced "that i have the truth in my pocket. "we fall in love with our own ideas. "we're convinced by them, we defend them tooth and nail. "we cling to them like children to sweets. "but deep in our hearts, doubt is never quelled, "the fear that we are actually deluded." exactly. today you've been expounding on your fascinating white hole theory to me, but would it matter to you? i don't know if there are white holes. monday and tuesday and thursday, i'm sure there are white holes. 0k, friday, doubts, saturday, no, no, no, they don't exist. sunday, i'm depressed. then monday again, i think i'm right. what if in the course of your lifetime it's definitively proven that white holes don't exist and that your entire loop quantum gravity theory doesn't stand up? would that sort of be devastating to you? no, no, no. i would much be happier, of course, if some precise measurement is made before i die, proving that all this is right, i would be very happy, but i don't think it should be devastating. like it shouldn't be devastating for the people studying supersymmetry, the fact that supersymmetry was not found. that's the way we learn, by trial and error. but isn't it odd, then, that science becomes so tribal? you've described the fact that your loop quantum gravity theory, which challenged string theory, has developed this sort of sense of tribes and size. you said it's a bit like, using your italian football metaphor, it's a bit like milan versusjuventus. you take a side and you stick to that side and you cheer when your side scores a sort of rhetorical point, and you hate it when the other side claims the victory and science shouldn't be like that. why is it like that? to the opposite. if you look at history, all the things we have understood came out from different... take the atomic structure of matter, for instance. at the end of the 19th century, there were two big tribes fighting one another, one saying, "there are really "little atoms, molecules here moving around." and the other side saying, "no, no, that's completely "wrong, that's silly." one side turned out to be right, one turned out to be wrong. or take copernicus and ptolemy. huge debate during the renaissance, and so on and so forth. when maxwell wrote his equations, there were other theories, so there were competing theories. what's specific and peculiar about science is that historically, these big debates have been resolved. and that's the fascination of this activity, this funny activity, which is science for humans. we debate, we fight, but then we agree. everybody now agrees that there are atoms. everybody agrees that copernicus is right and ptolemy was wrong. everybody agrees that maxwell's equations are the best description rather than others. so it's this process of debate and discussion and defending opposite ideas actually converge because at the end of the day, we need measurement to say who is right, who is wrong. there is a sort of broad distinction between theoretical science and applied science. you clearly are steeped in the world of theory and you ponder the universe and infinite space and time, the meaning of time and space. many other scientists look very much at applications in what we would call the real world, the material world... that's right. ..as you say, we believe in, just as we believe this desk is here. does applied science not interest you or would you argue that your work actually does lead to implications, as i put it at the beginning, to things that matter to you and me? most of the current applied science is grounded in theoretical, purely theoretical investigations of the past. here in london, faraday had this laboratory and famously he was asked, "what is this useful for?" by a representative of the king. and his answer was, "i have no idea, but i'm sure that "in the future you will put taxes on that." and in fact, he was doing electricity and magnetism. so if we do come to why we, who do not truly understand the depth of your work, should care about your work and that it will matter to us, what would your quick answer be? it would not be because it's going to be applied. it would be for a completely different reason. why do we study history? why do we do art? why do we do poetry? why do we do philosophy? because we are humans who want to think, we have desire of knowledge. what mostly pushes theoretical science is just trying to understand better the world. it's the desire of understanding. i think it's deeply human and it of course has been super useful for then having television, so you and i can talk and many people can listen and all that. but the origin is not that. it'sjust the profound human desire for understanding better what's around us. i want to take you back to the young carlo rovelli, who was the revolutionary, who dabbled with the style of revolutionary politics, which led some to direct action, to violence. didn't take you in that direction. and as you say, you then turned to science to try and change the world in different ways. i just wonder whether you now worry that science is being co—opted to change the world in ways that alarm you. i know not long ago you spoke to christopher nolan, the director of the movie oppenheimer, which showed one way in which amazing scientific achievement was co—opted by governments for very clear military ends. and today we have a long and difficult discussion about how we're going to use artificial intelligence. how worried are you by the way science is being used today? i'm worried about the way everything is being used today. i think science is important for me, but it's not the most important thing. the most important thing is our human life or our social life. and i think that the decisions are taken by politics, by our common discussions. science is a tool. it's a profoundly powerful tool. but it's just that, no more than that. sometimes it itself can influence and have positive and negative effects. and of course, it has both. it's not that science by itself is neutral. it's the other way around. nothing is neutral. i think everything is political. and we, as citizens, i believe, not as scientists, should hold the responsibility of the good and the bad we're doing the world. if you were to look at your field, where would you say that the practical applications might be most exciting? i mean, in one of your flights of fancy... oh, i would be as humble as faraday and say that i have no idea about that. yeah, but you've said, for example, you wish that the human species had not decided some years ago to stop serious investment in space travel, for example. and you fantasised about the degree to which your study of space and time leads you to believe that, you know, in some theoretical future, human beings would be able to travel in time. and i then get confused — how seriously am i to take carlo when he says these things? well, you know, in the �*60s, we kids were all convinced that we would have starships and would go from planet to planet or from stars to star with our... yeah, as kids. as kids. well, but that was the convention of the world, that scientific progress was going in that direction. i was a kid when man went to the moon. it seemed strange to me that to me, growing out, men wouldn't go to mars and then venus. and then, then, then, then. and then didn't happen. i don't think, i... look, i don't believe in technological progress so much. i think that we have discovered great things. we have had a lot of technological progress. we will have more. but i'm not part of this, "oh, my god, the great technology "of the future." no, and in some ways, you are somebody who clearly is somewhat depressed about the state of the world. and again, i'm thinking of your political past, but i'm also thinking of your activist present. you are an advocate of lobbying governments to cut, dramatically cut spending on military hardware. n ot exa ctly. i organised an appeal which was signed by 60 nobel prizes, so it's my community, not to ask our government to cut military spending, which is naive, but ask our government to start negotiating, and collaborating with other governments to cut military spending together. military spending has piled up. and when this happened, there's either a war, a big war coming, ora huge waste of resources. both cases are terrible. i think the problem is, is that we're going toward more and more belligerence instead of toward more and more collaboration. "my political outlook," you said recently, "is as radical as it has always been." ijust wonder, as you get sucked into debates about how much government spends, governments across the world spend on armaments, you get sucked into debates about what should happen in ukraine or the mideast or wherever. how much of your intellectual energy, your thinking energy, is taken up with the state of the world? and how much are you distracted from the enormous thoughts that we began this interview discussing? it's a good question, and i myself struggle with that. i think that i am, first of all, a human being and a citizen of this planet and then a scientist, and not vice versa. so i love when i can shut the door and take my notebook and start writing equations. but i think we all have a responsibility toward humankind that, trying to give our little drop to avoid the disasters of the past. talking of disasters of the past, you say that we may be the first species to knowingly watch our own demise. doesn't suggest to me that for all of your experience and all of your work and all of your challenge posed to all of us to think in different ways, you don't have much faith in our future. i think it's open. it could be that humankind goes ahead well, but it's not granted at all. and it depends on us. you put it this way. humans have been fighting with one another for long. united kingdoms was different kingdoms fighting against one another, and it was not a bad idea to unite and stop fighting, of course, and make it a unitary thing where we don't kill. we disagree. we go to westminster and debate and insult one another. that's fine, but we don't kill one another. i think we should... it's essential at this point, given the nuclear war, given everything, that we do that at the scale of the planet. and i think there's a lot of people who are asking that. i mean, stop trying to resolve the problems by massacring one another. and so i would like, with many others, to, you know, a little drop toward a world where we discuss instead of killing one another. carlo rovelli, we must end there. i thank you very much for being on hardtalk. thank you. thank you very much. hello there. we've seen some strong aurora pictures coming in over recent hours here at the bbc weather centre. this beautiful one was from the aberdeenshire area in northern scotland. but this one is from folkestone. the significance of this is if you can see the northern lights in folkestone here in the uk, you can see it pretty much everywhere. so the aurora is very strong. it's worth taking a look outside. use a camera or a mobile phone to see the best views, because those bits of equipment are more sensitive than our eyes to low levels of light. but you have a chance over the next few hours. now, weather wise, ok, there will be a few showers coming and going, but we'll also see some fairly lengthy, clear spells. so whilst it's dark, you do have a chance of spotting the aurora. on into monday's forecast, and it's a day of sunshine and showers, really. starting off, most of us will have a fine morning with plenty of sunshine around. most of the showers really get going into the afternoon. and there could be some slightly longer spells of rain coming into west scotland and maybe northern counties of northern ireland. our temperatures continue to be a little bit below average for the time of year. now we've got more of those showers to come on tuesday. again, a lot of sunshine, the showers have been most frequent into the northwest of both england and wales. then we get this ridge of high pressure building in during tuesday afternoon. now, that should kill the showers off in northern ireland. central and southern wales and south west england having a fine end to the day as well. now that ridge of high pressure is going to be short lived, pushed out of the way by this next weather system coming in off the atlantic for wednesday. it's going to be a wet day then, with around 20mm to 30mm of rain expected, could bring one or two more issues. we'll have to be careful, i suppose, in northern ireland, where it has been so wet over recent times. the rain does clear through, followed by showers, with the winds picking up later in the day from the west. now, temperatures will start to come down a little bit across northern areas, 8—10 celsius for scotland and for northern ireland. 11—13 celsius for england and wales. but towards the end of the week, this area of low pressure is going to swing through the uk, and as it does so, we'll start to get a chillier flow of air coming in from the northwest. now, temperatures might not change very much on the face of it, but i think those north—westerly winds will start to make the weather feel a little cooler. and there'll be some showers around in the week with more general outbreaks of rain heading in, it looks, for some of us, into next weekend. live from london, this is bbc news. jordan's military has dropped aid into northern gaza by parachute, as gaza experiences some of the most intense air strikes since the start of the conflict. america's top diplomat, antony blinken, is in turkey as he continues to push for humanitarian pauses in the fighting. prince william meets with singapore's leaders ahead of his third annual earthshot prize ceremony. hello. i'm sally bundock. a very warm welcome to the programme. we start with the latest from the israel—gaza conflict. intense fighting has continued through the night in the gaza strip. this is the view from southern israel into northern gaza, where you can see explosions and flares in the sky. israel says it's now split gaza into two parts, north and south. further south, a royal jordanian air force cargo plane has dropped several containers of humanitarian relief supplies over the gaza strip. the update was shared in a tweet by thejordanian king. jordan's state news agency said the consignment was urgent medical aid for thejordanian field hospital in gaza. israeli media reports say the air drop was carried out in co—ordination with the idf. meanwhile, the us has stepped up diplomatic efforts in the region.