Ian Hutchinson: Nuclear Fusion, Plasma Physics, and Religion | Lex Fridman Podcast #112

The following is a conversation with Ian Hutchinson, a nuclear engineer and plasma physicist at mit. He has made a number of important contributions in plasma physics, including the magnetic confinement of plasmas seeking to enable fusion reactions, which happens to be the energy source of the stars, to be used for practical energy production. Current nuclear reactors, by the way, are based on fission. As we discuss, Ian has also written on the philosophy of science and the relationship between science and religion, arguing in particular against scientism, which is a negative description of the overreach of the scientific method to questions not amenable to it. On this latter topic, I recommend two of his books, his new one Can a Scientist Believe in Miracles? Where he ANSWERS More than 200 questions on all aspects of God and science, and and his earlier book on scientism called Monopolizing Knowledge. As you may have seen already, I work hard on having an open mind, always questioning my assumptions and in general marvel at the immense mystery of everything around us and the limitations of at least my mind. I'm not religious myself in that I don't go to the synagogue, a church or mosque, but I see the beautiful bond in the community that religion at its best can create. I also see both in scientists and religious leaders, signs of arrogance, hypocrisy, greed and a will to power. We're human, whether Buddhist, Christian, Hindu, Jewish, Muslim, agnostic or atheist. This podcast is my humble attempt to explore a complicated human nature, what Stanislav Lem in his book Solaris called our own labyrinth of dark passages and secret chambers. I ask that you try to keep an open mind as well and be patient with the limitations of mind. Quick summary of the ads two new amazing sponsors, SunBasket and Power. Please consider supporting this podcast by going to sunbasket.com lex and use code lex at checkout and go into powerdot.com lex and use code Lex at checkout as well. Click the links, Buy the stuff if you like. Just visiting the site and considering the purchase is really the best way to support this podcast. It's how they know I sent you and based on that, that might sponsor the podcast in the future. If you enjoy this thing, subscribe on YouTube, review it with five stars on Apple, podcast support on Patreon, or connect with me on Twitter at Lex Friedman as usual, I'll do a few minutes of ads now and never any ads in the middle that can break the flow of the conversation. This show sponsored by Sunbasket, visit sunbasket.com lex and use code lex to get 35 bucks off your order and to support this podcast Sunbasket delivers fresh, healthy, delicious meals straight to your door. As you may know, my diet is pretty minimalist, so it's nice to get some healthy variety into the mix. They make it super easy. With everything pre portioned and ready to prep and cook, you can enjoy a delicious, healthy dinner in as little as 15 minutes. I just ordered my first set of meals. Haven't gotten them yet, but I can't wait. I just finished the 6 mile run 1000 body weight reps and I'm starving. But let me risk listing the actual menu items that I ordered because they sound delicious. Italian Sausages and vegetable skewers with two Romescos I don't actually know what romescos are, but the pictures looked awesome. And pork fried cauliflower rice with carrots and peas. By the way, cauliflower rice is one of my favorite things ever. Right now Sambaska is offering $35 off your order when you go right now to some basket.com lex they told me to say right now with urgency. So pause this podcast and go to the website and make the purchase or just go to the website and check it out. Enter promo code LEX at checkout this show is also sponsored by power dot. Get it@powerdot.com lex and use code lex at checkout to get 20% off and to support this podcast. This thing is amazing. It's an ESTIM electrical stimulation device that I've been using a lot for muscle recovery recently, mostly for my shoulders and legs as I've been doing the 1,000 body weight reps and six miles every day as I just finished. They call it the Smart Muscle Stimulator, which is true since the app that goes with it is amazing. It has 15 programs for different body parts and guides you through everything you need to do. I take recovery really seriously these days and Power Dot has been a powerful addition to the whole regime of stretching, ice massage and sleep and diet that I do. It's used by professional athletes and by slightly insane but mostly normal people like me. It's portable so you can throw it in a bag and bring it anywhere. Get it@powerdot.com lex and use code lex at checkout to get 20% off on top of the 30 day free trial and to support this podcast and now here's my conversation with Ian Hutchinson.

Maybe it'd be nice to draw a distinction between nuclear physics and plasma physics. What is the distinction?

Nuclear physics is about the physics of the nucleus and my department, Department of Nuclear Science and Engineering at MIT is very concerned about all the Interactions and reactions and consequences of things that go on in the nucleus, including nuclear energy, fission energy, which is the nuclear energy that we have already, and fusion energy, which is the energy source of the sun and stars, which we don't quite know how to turn into practical energy for humankind at the moment. That's what my research has mostly been aimed at. But plasmas are essentially the fourth state of matter. So if you think about solid, liquid, gas, Plasma is the fourth of those states of matter. And it's actually the state of matter which one reaches if one raises the temperature. So cold things, you know, like ice are solid. Liquids are hotter water. And if you heat water beyond 100 degrees Celsius, it becomes gas. Well, that's true of most substances. And plasma is a state of matter in which the electrons are unbound from the nuclei, so they become separated from the nuclei and can move separately. So we have positively charged nuclei, and we have negatively charged electrons. The net is still electrically neutral. But a plasma conducts electricity, has all sorts of important properties that are associated with that separation. And that's what plasmas are all about. And the reason why my department is interested in plasma physics very strongly Is because most things. Well, for one thing, most things in the universe are plasma. The vast majority of matter in the universe is plasma. But most particularly stars and the sun are plasmas because they're very hot. And it's only in very hot states that nuclear fusion reactions take place. And we want to understand how to implement those kind of phenomena on Earth.

Maybe another distinction we want to try to get at is difference between fission and fusion. So you mentioned fusion is the kind of reaction happening in the sun. So what's fission and what's fusion?

Sure. Well, fission is taking heavy elements like uranium and breaking them up. And it turns out that that process of breaking up heavy elements releases energy.

What does it mean to be a heavy element?

It means that there are many nuclear particles in the nucleus itself, Neutrons and protons in the nucleus itself. So that in the case of uranium, there are 92 protons in each nucleus and even more neutrons, so that the total number of nucleons in the nucleus, nucleons is short for either a proton or a neutron. The total number might be 235. That's U235. Or it might be 238. That's U238. So those are heavy elements. Light elements, by contrast, have very few nucleons, protons or neutrons in the nucleus. Hydrogen is the lightest nucleus. It has one proton. There are actually slightly heavier forms of hydrogen isotopes. Deuterium has a proton and a neutron, and tritium has a proton and two neutrons. So it has total of three nucleons in the neutron in the nucleus. Well, taking light elements like isotopes of hydrogen and not breaking them up, but actually fusing them together, reacting them together to produce heavier elements, typically helium. Okay, which is helium is a nucleus which has two protons and two neutrons. That also releases energy. And that and that or reactions like that. Making heavier elements from lighter elements is what mostly powers the sun and stars. Both fusion and fission release approximately a million times more energy per unit mass than chemical reactions. So a chemical reaction means take hydrogen, take oxygen, react them together, let's say, and get water. That releases energy. The energy released in a chemical reaction like that, or the burning of coal or an oil or whatever else is about a million times less per unit mass than what is released in nuclear reactions.

So. But it's hard to do.

It requires very high energy of impact. And actually it's very easy to understand why. And that is that those two nuclei, if they're both, let's say hydrogen nuclei, one is, let's say deuterium and the other is, let's say tritium, they're both electrically charged and they're positively charged. So they, like charges, repel. Everyone knows that. Right. So basically, to get them close enough together to react, you have to overcome the repulsion, the electric repulsion of the two nuclei from one another. And you have to get them extremely close to one another in order for the nuclear forces to overtake the electrical forces and actually form a new nucleus. And so one requires very high energies of impact in order for reactions to take place. And those high energies of impact correspond to very high temperatures of random motion.

So that's why you can do something like that in the sun. So we can build the sun. That's one way to do it. But on earth, how do you create a fusion reaction?

Yeah, well, nature engineering, Nature's fusion reactors are indeed the stars. And they are very hot in the. In the center, and. And they reach the point where they release more energy from those reactions than they lose by radiation and transport to the surface and so forth. And that's a state of ignition. And that's what we have to achieve to give net energy. It's like lighting a fire. If you have a bundle of sticks and you hold a match up to it and you see smoke coming from the sticks, but you take the match away and the sticks just fizzle out. The reason they did it fizzled out, is that, yes, they were burning, there was smoke coming from them, but they were not ignited. But if you are able to take the match away and they keep burning and they are generating enough heat to keep themselves hot and hence keep the reactions going, that's chemical ignition. But what we need to do, what the stars do in order to generate nuclear fusion energy is they are ignited, they, they are generated enough energy to keep themselves hot. And that's what we've got to do on Earth if we're going to make fusion work on Earth. But it's much harder to do on Earth than it is, you know, in a star, because, you know, we need temperatures of order tens of millions of degrees Celsius in order for the reactions to go fast enough to generate enough electricity to keep it or enough energy to keep it going. And so if you've got something that's tens of millions of degrees Celsius and you want to keep it all together and keep the heat in long enough to have enough reactions taking place, you can't just put it in a bottle, plastic or glass, it would be gone in milliseconds. So you have to have some non material mechanism of confining the plasma. In the case of stars, that non material force is gravity. So gravity is what holds a star together, it's what holds the plasma in long enough for it to react and sustain itself by the fusion reactions. But on Earth, gravity is extremely weak. I mean, I don't mean to say we don't fall. Yes, we fall, but the mutual gravitational attraction of small objects is very weak compared with the electrical repulsion or any other force that you can think about on Earth. And so we need a stronger force to keep the plasma together, to confine it. And the, the predominant attempt at making fusion work on Earth is to use magnetic fields to confine the plasma. And that's what I've worked on for essentially most of my career, is to understand how we can, and how best we can confine these incredibly hot gases, plasmas, using magnetic fields, with the ultimate objective of releasing fusion energy on Earth and, you know, generating electricity with it and powering our society with it.

Dumb question. So on top of the magnetic fields, do you also need the plastic water bottle walls or is it purely magnetic fields?

Well, actually we do need walls. Those walls must be kept away from the plasma because otherwise they'd be melted or the plasma must be kept away from them, inside of them. But the main purpose of the Walls is not to keep the plasma in. It's to keep the atmosphere out. So if we want to do it on Earth, where there's air, we want the plasma to consist of hydrogen isotopes or other things, the things we're trying to react. And by the way, the density of those plasmas, at least in magnetic confinement fusion, is very low. It's maybe a million times less than the density of air in this room. So in order for a fusion reactor like that to work, you have to keep all of the air out and just keep the plasma in. So, yes, there are other things, but those are things that are relatively easy. I mean, making a vacuum these days is technologically quite straightforward. We know how to do that. Okay. What we don't quite know how to do is to make a confinement device that's isolates the plasma well enough so that it's able to keep itself burning with its own reactions.

So maybe. Can you talk about what a tokamak is?

The Russian acronym from which the word tokamak is built just means toroidal magnetic chamber. So it's a toroidal chamber, a torus is a geometric shape which is like a doughnut with a hole down the middle, okay? And so it's the meat of the doughnut, okay? That's the torus, and it's got a magnetic field. So that's really all tokamak means. But the particular configuration that is very widespread and is the sort of best prospect in the least in the near term for making fusion energy work is one in which there's a very strong magnetic field the long way around the doughnut, around the torus. So you've got to imagine that there's this doughnut shape with an embedded magnetic field just going round and round the long way. The big advantage of that is that plasma particles, when they're in the presence of a magnetic field, feel strong forces from the magnetic field. And those forces make the particles gyrate around the direction of the magnetic field line. So basically, the particles follow helical orbits, following, like, a spring that's directed along the magnetic field. Well, if you make the magnetic field go inside this toroidal chamber and just simply go round and round the chamber, then because of this helical orbit, the particles can't move fast across the magnetic field, but they can move very quickly along the magnetic field. And if you have a magnetic field that doesn't leave the chamber, it doesn't matter if they move along the magnetic field. It doesn't mean they're going to exit the chamber. But if you just had a straight magnetic field, for example, coming from a Helmholtz coil or a bar magnetic, then you'd have to have ends. It would come, would come to the ends of the chamber somewhere, and the particles would hit the ends and they would lose their energy. So that's why it's toroidal, and that's why we have a strong magnetic field. It's providing a confinement against motion in the direction that would lead the particles to leave the chamber. It turns out that here we're getting a little bit technical, but it turns out that a toroidal field alone is not enough. And so you need more fields to produce true, true confinement of plasma. And we get those by passing a current as well through the plasma itself.

To make sure it stays on track.

Well, what that does is makes the field lines themselves into much bigger helices. And that, for reasons that are too complicated to explain, that clinches the confinement of the particles, at least in terms of their single particle orbit, so they don't leave the chamber.

So when the particles are flying along this donut, the inside of the donut, where's the generation of the energy coming from? Are they smashing into each other?

Yeah, eventually. I mean, in a fusion reactor, there will be deuterons and tritons and they will be smashing in. They will be very hot. They'll be 100 million degrees Celsius or something. So they're moving thermally with very large thermal energies in random directions. And they will collide with one another and have fusion reactions. When those fusion reactions take place, energy is released. Large amounts of energy is released in the form of particles. One of the particles that's released is an alpha particle, which is also charged and it's also confined. And that alpha particle stays in the doughnut and heats the other particles that are in that donut. So it transfers its energy to those and it keeps them hot. There is. There's some leaking of heat all the time. Radiation, some transport and so forth. There's also a neutron released from that reaction. The neutron carries out four fifths of the fusion energy. And that will have to be captured in a blanket that surrounds the chamber in which we take the energy, drive some kind of electrical generator from, you know, thermal thermal engine, gas turbine or something like that, and power, the power you got energy.

So where do we stand, where do we stand on getting this thing to be something that actually works? It generates energy?

Yeah. Well, there have been experiments that have generated net nuclear energies or nuclear powers in the vicinity of, you know, a Few tens of megawatts for a few seconds. So that's, you know, 10 megajoules, that's not much energy. It's a few donuts worth of energy.

Okay, yeah, literal donuts, that's right.

But, but we have studied how well tokamaks confined plasmas, and so we now understand in rather great detail the way they work. And we're able to predict what is going to be required in order to build a tokamak that becomes self sustaining, that becomes essentially ignited, or very, so close to ignited that it doesn't matter. And at the moment, at least if you use the modest magnetic field values, still very strong, but, but limited, limited magnetic field values, you have to build a very big device. And so we are at the moment at Worldwide Fusion Research, is at the moment in the process of building a very big experiment that's located in the south of France. It's called ITER I T E R, which means the way, or just means the International Tokamak Experimental Reactor, if you like. And that experiment is designed to reach this burning plasma state and to generate about 500 megawatts of fusion power for hundreds of seconds at a time. It'll still only be an experiment. It won't put electricity on the grid or anything like that. It's to figure out what, whether it works and what the remaining engineering challenges are. It's a scientific experiment. It won't be engineered to run round the clock and so on and so forth, which ultimately one needs to do in order to make something that's practical for generating electricity. But it will be the first demonstration on Earth of a controlled fusion reaction for long time. Time period.

Is that exciting to you?

It's been an objective that is in many ways motivated my entire career and the career of many people like me in the field. I have to admit though that one of the problems with ITER is that it's an extremely big and expensive and long time to build experiment. And so it won't even come into operation until about 2025, even though it's been being built 10 years and it's been, it was designed for 30 years before that. And so that's actually one of the big disappointments of my career in a certain sense, which is that we won't get to burning fusion reaction until well past the first operation of iter. And whether I'm alive or not, I don't know, but I certainly will be well and truly retired by the time that happens. And so when I realized maybe some years ago that that was going to be the case. It was a discouragement to me, let's put it like that.

But if we can try to look, maybe in a ridiculous kind of way, look into 100 years from now, 200 years, 500 years from now, and we, you know, there's folks like Elon Musk trying to travel outside the solar system. I mean, the amount of energy we need for some of the exciting things we want to do in this world, if we look again 100 years from now, seems to be a very large amount. So do you think fusion energy will eventually, sometime into your retirement, will be basically behind most of the things we do?

Look, I absolutely think that fusion research is completely justified. In fact, we should be spending more time and effort on it than we currently do. But it isn't going to be a magic bullet that somehow solves all the problems of energy. By the way, that's a generic statement you could make about any energy source, in my view. I think it's a grave mistake to think that science of any sort is suddenly going to find a magic bullet for meeting all the energy needs of society or any of the other needs of society, by the way. And we can talk about that later.

Okay, definitely.

But, but, but fusion is very worthwhile and we should be doing it. And so my disappointment that I just expressed was, in a certain sense, a personal disappointment. I do think that fusion energy is a terrific challenge. It's very difficult to bring the energy source of the sun and stars down to earth. This does contrast in a certain sense with fission energy. By contrast, fission energy. To build a fission reactor proved to be amazingly easy. You know, we did it within a few years of discovering nuclear fission, people had figured out how to build a reactor and did so, you know, during the Second World War, which is, by.

The way, fission is how the current nuclear power plants work.

Yeah. And so we have nuclear energy today because fission reactors are relatively easy to build. You've got to have what's hard is getting the materials okay. And that's just as well, because if everyone could get those materials, you know, there would be weapons, proliferation and so forth. But it wasn't all that long after even the discovery of nuclear fission that fission reactors were built. And fission reactors, of course, operated before we had weapons. So I think nuclear power is obviously important to meet the energy challenges of our age. It is completely, intrinsically, completely CO2 emissions free. And in fact, the wastes that come from nuclear power, whether it's fission or fusion for that matter, are so moderate in quantity that we shouldn't really be worried about them. I mean, yes, fission products are highly radioactive and we need to keep them away from people, but there's so little of them. It's that keeping them away from people is not particularly difficult. And so while people complain a lot about the drawbacks of fission energy, I think most of those complaints are ill informed. We can talk about the challenges and the disasters, if you like, of fission reactors, but I think fission in the near term offers a terrific opportunity for environmentally friendly energy, which in the world as a whole is rapidly being taken advantage of. China and India and places like that are rapidly building fission plants. We're not rapidly building fission plants in the U.S. although we are actually building two at the moment, two new ones. But we do still get 20% of our electricity from fission energy and we could get a lot more.

So it's clean energy.

So it's clean energy.

Now again, the concern is there's a very popular HBO show just came out on Chernobyl. There's the Three Mile island, there's Fukushima. That's the most recent disaster. So there's a kind of a concern of. Yeah, I mean, nuclear disasters is that, what do you make of that kind of concern, especially if we look into the future of fission energy based reactors?

Well, first of all, let me say one or two words about the contrast between fission and fusion and then we'll come on to the question of the disasters and so forth. Fission does have some drawbacks and they're, and they're largely to do with four, four main areas. One is do we have enough uranium or other fissile fuels to supply our energy needs for a long time. The answer to that is we know we have enough uranium to support fission energy worldwide for thousands of years, but maybe not for millions of years. Okay, so that's resources. Secondly, there are issues to do with wastes. Fission wastes are highly radioactive and some of them are volatile. And so for example, in Fukushima, the problem was that some fraction of the fission waste were volatilized and went out as a cloud and polluted areas with cesium 137, strontium 90 and things like that. So that's a challenge of fission. There's a problem of safety beyond that, and that is that in fission it's hard to turn the reactor off. When you turn, when you stop the nuclear reactions, there is still a lot of heat being liberated from the fission products. And that is actually what the problem was at Fukushima. The Fukushima reactors were shut down the moment that the earthquake took place and they were shut down safely. What then happened after that? Fukushima was, you know, there was this enormous tidal wave many tens of meters high that came through and destroyed the electricity grid feed to the Fukushima reactors. And their cooling was then turned off. And it was the after heat of the turned off reactors that eventually caused the problems that led to release. And so that, so that is, that's a safety concern. And then, and then finally there's a problem of proliferation and that is that fission reactors need fissile fuel and the technologies for producing the, and enriching and so forth. The fuels can be used, can be by bad actors to generate the materials needed for a nuclear weapon. And that's a very serious concern. So those are the four problems. Fusion has major advantages in respect of all of those problems. It has more longer term fuel resources. It has far more benign waste issues. The radioactivity from fusion reactions is at least 100 times less than it is from fission reactions. It has essentially none of this after heat problem because it doesn't produce fission products that are highly radioactive and generating their own heat when it's turned off. In fact, the hard part of fusion is turning it on, not turning it off. And finally, you don't need the same fission technology to make fusion work. And so it's got terrific advantages from the point of view of proliferation control. So those are four main issues which make fusion seem attractive technologically because they address some of the problems of fission energy. I don't mean to say that fission energy is, is overwhelmingly problematic, but clearly there have been catastrophes associated with fission reactors. Fukushima actually is, I think in many ways often overstated as a disaster because after all, nobody was killed by the reactors. Essentially zero. And that's in the context of a disaster, a tsunami that killed between 15 and, and 20,000 people more or less instantaneously. So in the scale of risks, one should take the view that in my estimation that fission energy came out of that looking pretty good. Okay. Of course that's not the popular conception. Okay.

Yeah. With a lot of things that threaten our well being. We seem to be very bad users of data. We seem to be very scared of shark attacks and not at all scared of car accidents and this kind of miscalculation. And I think from everything I understand, nuclear energy, efficient based energy goes into that category. It's one of the safest, one of the cleanest forms of energy. And yet the priority, whoever does the PR for nuclear energy has a hard job ahead of them at the moment.

Well, I think part of that is their association with nuclear weapons. Because when you say the word nuclear, people don't instantly think about nuclear energy. They think about nuclear weapons. And so there is perhaps a natural tendency to do that. But yes, I agree with you. People are very poor at estimating risks, and they react emotionally, not rationally in most of these situations.

Can we talk about nuclear weapons just for a little bit? So fission is the kind of reaction that's central to the nuclear weapons we have today.

That's what sets them off.

That's what sets them off. So if we look at the hydrogen bomb, maybe you can say how these different weapons work.

So the earliest nuclear weapons, the nuclear bombs that were dropped on Japan, et cetera, et cetera, were pure fission weapons. They used enriched uranium or plutonium. And their energy is essentially entirely derived from fission reactions. But it was early realized that more energy was available if one could somehow combine a fission bomb with fusion reactions. Because the fusion reactions give more energy per unit mass than fission reactions. And this was called the super. You might have heard of the expression the super, or more simply hydrogen bombs, okay? Bombs which use isotopes of hydrogen and fusion reactions associated with the them.

So like you said, it's hard to turn on.

It's hard to turn on because you need very high temperatures and you need confinement of that long enough for the reactions to take place. And so a bomb, actually a thermonuclear bomb or a hydrogen bomb, has essentially a chemical implosion which then sets off a fission explosion, which then sets off and compresses hydrogen isotopes and other things which I don't know because I don't. I've never had a security clearance, okay? So I. So I can't betray any secrets about weapons because I've never been party to them. But because I know a lot about this problem, I can guess, okay, and sets off fusion reactions in the middle, okay? So that's basically. It's that sequence of things which produce these enormous, you know, multi megaton bombs that have very large yields. And so fusion alone can't get. Can't get you there. It is actually possible to set off or to try to set off little fusion bombs alone without the surrounding fission explosion. And that is what is called laser fusion. So another approach to fusion, which actually is mostly researched in the weapons complex, the national labs and so forth, because it's more associated with the technologies of weapons, is inertial fusion. So if you decide, instead of trying to make your plasma, just sit there in this Torus in the tokamak be controlled steady state with a magnetic field. If you're willing to accept that, I'll just set off an explosion. Okay. And then I'll gather the energy from that somehow. I don't quite know how, but let's not ask that question too much then. It is possible to imagine generating fusion alone explosions. And the way you do it is you take some small amount of deuterium tritium fuel, you bombard it with energy from all sides. And this is what the lasers are used for. Extremely powerful lasers, which compresses the pellet of fusion and heats it. It compresses it to such a high density and temperature that the reactions take place very, very quickly. And in fact, they can take place so quickly that it's all over with before the thing flies apart.

Wow.

And that is heated up really fast.

That is inertial fusion. Okay.

Is that useful for energy generation for outside?

Not yet. I mean, there are those people who think it will be, but you may have heard of the big experiment called the National Ignition Facility, which was built at Livermore starting in the late 1990s and has been in operation since around about 2010. It was designed in with the claim that it would reach ignition, fusion ignition in this pulsed form where the reactions are got over with so quickly before the thing whole thing flies apart. It didn't actually reach ignition and it doesn't look as if it will, although, you know, we never know. Maybe people figure out how to make it work better. But the answer is, in principle, it seems possible to reach ignition in this way. Maybe not with that particular laser facility.

Are you surprised that we humans haven't destroyed ourselves given that we've invented such powerful tools of destruction? Like, what do you make of the fact that for many decades we've had nuclear weapons. Now, speaking about estimating risk, at least to me it's exceptionally surprising. I was born in the Soviet Union that big egos of the big leaders, when rubbing up against each other, have not created the kind of destruction everybody was afraid of for decades.

Well, I must say I'm extremely thankful that it hasn't. I don't know whether I'm surprised about it. I've never thought about it from the point of view of is it surprising that we've avoided it? I'm just very thankful that we have. I think that there's is a sense in which cooler heads have prevailed at crucial moments. I think there is also a sense in which mutually assured destruction has in fact worked as a policy to restrain the great powers from going to war, and in fact, the fact that we haven't had a world war, you know, since the 1940s, is perhaps even attributable to nuclear weapons in a kind of strange and peculiar way. But I think humans are deeply flawed and sinful people. And I certainly don't feel that we're guaranteed that it's going to go on like this.

And we'll talk about the sort of the biggest picture view of it all. But let me just ask in terms of your worries, if we look 100 years from now, we're in the middle of what is now a natural pandemic that from the looks of it, fortunately is not as bad as it could possibly been. If you look at the Spanish flu, if you look at the history of pandemics, if you look at all the possible pandemics that could have been that folks like Bill Gates are exceptionally terrified.

About.

I know many people are suffering, but it's better than it could have been. So now we're talking about nuclear weapons. In terms of existential threats to us sinful humans, what worries you the most? Is it nuclear weapons? Is it natural pandemics? Engineered pandemics? Nanotechnology? In my field of artificial intelligence, some people are afraid of killer robots and robots, yeah. Do you think in those existential terms, do any of those things worry you?

I am certainly not confident that my children and grandchildren will experience the benefits of civilization that I have enjoyed. I think it's possible for our civilizations to break down catastrophically. I also think that it's possible for our civilizations to break down progressively, and I think they will if we continue to have the explosion of population on the planet that we currently have. I mean, it's quite wrong to think of our problems as mostly being CO2. If we can just solve CO2, then we can go on having this continually expanding economy everywhere in the world. Of course you can't do that. I mean, there is a finite bearing capacity of our planet on the resources of our planet, on the resources of our planet, and we can't continue to do that. So I think there are lots of technical reasons why a continually expanding economy and civilization is impossible. And therefore, actually, I'm as much nervous about the fact that our population is 8 billion or something right now worldwide as I am about the fact that a few million people would be killed by COVID 19. I mean, I don't know want to be callous about this, but from the big picture, it seems like that's much more of a problem Overpopulation, people not dying is ultimately more of a problem than people dying. So that probably sounds incredibly callous to your listeners, but I think it's simply a sober assessment of the situation.

Is there ways from the way those 8 billion or 7 billion or whatever the number is live that could make it sustainable? You know, because you've kind of implied there's a kind of, we have, especially in the west, this kind of capitalist view of really consuming a lot of resources. Is there a way to, like, if you could change one thing or a few things, what would you change to make this life, make it more likely that your grandchildren have a better life than you?

Well, okay, so let's talk a bit about energy because that's something I know a lot, a lot about, having thought about it most of my career. In order to reach a steady state CO2 level, okay, that's acceptable in terms of global climate change and so on and so forth, we need to reduce our carbon emissions by at least a factor of 10 worldwide. Okay. What's more, the average energy consumption and hence CO2 emission of people in the world is less than a tenth of what we per capita than what we have in the west, in America and Europe and so forth. So if you have in mind some utopia in the future where we've reached a sustainable use of energy and we've also reached a situation in which there's far less inequity in the world in the sense that people have share the energy resources more uniformly then what that is equivalent to would be to reduce the CO2 emissions in Western economies not by a factor of 10, but by a factor of 100. In other words, has to go down to 1% of what it is now. Okay, so you know, when people talk about, you know, let's use natural gas because, you know, maybe it only uses 60% of the energy of coal, it's complete nonsense. That's not even scratching the surface of what we would need to do. So is that going to be feasible? I very much doubt it. And therefore I actually doubt that we can reach a level of energy of fossil energy use that is 1% of the current use in the west without totally dramatic changes either in our society, our use of energy and so forth, which actually of course much of that energy is used for producing food and so on and so forth. So it's actually not so obvious that we can, we can get, we can cut down our energy usage by that factor or we've got to reduce the human population, population.

So you run up against that number that's increasing still. And you don't think there could be depressing? No, it's not. It's not. It's not. It's not depressing. It's. It's difficult. Like many truths are. Do you have a hope that there could be a technological solution?

In short, no. There is no technological solution to, for example, for population control. I mean, we have the technology to prevent ourselves bearing children. That's not a problem. Technology's in. Okay, solved. The challenges, society, the challenges, human choices. The challenge is almost entirely human and sociological. Not technology. Not technology. And when people talk about energy, they think that there's some kind of technological magic bullet for this, but there isn't, okay? And there isn't for the reasons I just mentioned, not because it's obvious there isn't, but actually there isn't. And in any case, that it's true of energy, it's true of pollution, it's true of human population, it's true of. Most of the big challenges in our society are not scientific or technological challenges. They're human sociological challenges. And that's why I think it's a terrible mistake, even for folks like me who work at, well, the highest.