The following is a conversation with lisa and out a theoretical, physicists and cause molly just at harvard who work involves improving our understanding of particle physics, super symmetry burial, genesis, cause malagigi inflation and dark matter, and now a quickie second mention of sponsor check them out in the description is the best way to support spock ass. We got babel well for learning, new languages, notion for note and team collaboration, simply save for keeping your home safe element for keeping your body feeling good with deliciousness an inside track of forgetting biological data and giving you life advice choose wisely. My friends also, if you want to work with our team, were always hiring good unless women that car such hiring or get in touch with me by going lex friedman, dot com, such contact.

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but there's a lot of it in the universe. You also, and what are you books with their bills? Song quote gotta be good. Looking ass, he so hard to see what is dark matter. How should we think about it, given that we can see how should we visualize in our minds, I I think one of the really important thing said physics teaches you is just our limitations, but also our abilities. So the fact that we can do the existence of something that we don't directly c is really a tribute to people that we can do that, but so? Also something that tells you you can't overly rely on your direct sensors if you just relied on just what you see directly you and miss so much of what is happening in the world and we can generalizers, but we're just for now to focus and dark matter it something we know is there and it's not just one way. We know it

or in my book dark matter and the dinosaurs. I talk about the many different ways, dinos, eight or nine- that we we deduce not just the existence of dark matter, but how much? How much is there and they all agree now? How do we know it's there because of it's gravitational force and individually, a particle doesn't have such a big gravitational force. In fact, gravity is an extremely weak for us compared to other forces. We know about a nature, but there's a lot of dark matter out there. It carries a lot of energy five times the amount of energy as the matter we know in in etc. So you can ask: how should we think about it, while it's just just another form, a matter that doesn't interact with light, or at least as far as we know, so it interacts gravitationally clumps forms galaxies, but it doesn't interact with light, which means we just don't see it most of our detection. Before gravitational waves detectors we only.

I saw things because of their interactions with light at some sense, so in theory it it behaves just like any other matter. Just it just doesn't attract light. So when we say in interacts just like any other form of matter, we have to be careful because gravitationally interacts like other forms of matter, but it doesn't experience electromagnetism, which is why it has the different distribution. So in our galaxy it's roughly spherical an unless it has it's own interactions. That's the story, but we we know that it's roughly spherical, whereas ordinary matter can radiate and clumps into a desk, and that's why we see the milky way does so on large scale, some sense. Yes, the the matter is similar in some sense effect. Dark matter is in some sense more important because it can collapse, moreover, willie than ordinary matter

Ordinary matter has has radiated forces which makes it hard to collapse and small skills. So actually it's dark matter. The surf drives in galaxy formation and then ordinary matter kind of comes along with it and there's also just more of it, because it's more of it, it can start collapsing sooner, that is to say the energy density, and matter dominates over radiation earlier and then you would, if you just had an ordinary matter. this part of the story of the origin of a galaxy part of the story of the end of the galaxy and part of the story of the interactions. Exactly I mean in my book, I make kind of sort of jokes about you know it's like when we think about a building. We think about the architect. We think about. You, know the high level where we forget about all the workers that did all the grunt. Work and a fact dark matter was really important in the formation of our universe. Then we forget that sometimes that's a metaphor. On top of a metaphor: ok

if the the the unheard voices that do the actual work. Okay, that exactly no! But it is a metaphor, but it also captures something because the fact is, we don't directly see it. So we forget it's there or we don't understand it's there. We think it's not the fact that we don't see it makes it no less legitimate. It just means that we have challenges in order to find exactly what it is, but things who cannot see that nevertheless have grown initial interaction with the things we can seize. At the layman. Level is just my blowing. You know it is, and it isn't because I think what is teaching us is that, where human universe is what it is and we are trying to interact with that universe and discover where disputes is discovered, amazing things

In fact, I would say it's more surprising that that mount the matter that we know about is constitutes as big a fraction of the universe as it does, I mean who were limited, we're human and the fact that we see five percent of the energy density of the universe. I get about one because of the energy density of matter, that's kind of remarkable, I mean. Why should that be? There could be anything or anything could be out there. Yet the universe that we see is the significant fracture and yet, but a lot of our intuition, I think, operates using. Visuals nations. In the mind an absolute true and it certainly raining books. I realized also how many of our words are based on how we see the world and that's true and that's actually one of the fantastic things about physics. Is that it's you is you have to go beyond your median intuition ticket develop intuitions that apply different distances, different scales, different ways of thinking about things.

yeah how'd, you anthropomorphized dark matter. Had I just did. I think I made it the groundwork workers Oh yeah, that's good! That's where he get paid. The big bucks with a the great books. so you also write a book about matter having to do something with the extinction events, thanks, sure the dinosaurs, which is kind of a fascinating. Presentation of, however, things connected, so I guess the disturbances from the dark matter. they create gravitational disturbances in or cloud at the edge of our soldiers and then that increases

Weight of asteroids hitting earth, so I want to be really clear. This was the speculative theory, though I mean- and I liked it to end on- and we still don't know for sure, but we can what we light about it. So let me take a step back, so we usually assume that dark matter is what weeping physicists there's just one thing: it's basically non interacting it aside from gravity or very weakly interacting matter, but again we have to get outside this mindset of just humans and ask what else could be there and so what we suggested.

Is that there is a fraction of dark matter, not all the dark matter, but some of the dark matter may be. It has interactions of it's own just the same way in in our universe. We have lots of different types of matter. We have nuclei, we have electrons, we immune, they have forces and we have lots of its. It's not a simple model, the standard model, but but does have some basic ingredients, so maybe dark matter also has some interesting structure to it. So maybe there's some small fraction, and the interesting thing is that if some of the dark matter does radiate- and you know I like to call it dark light- because it's light that we don't see but dark matter- would see, it could radiate that and then it could perhaps collapse into a disk. The same way, ordinary matter clapped and mixed into the milky way dusk. So it's not all the dark matter, it's a fraction, but it could conceivably be a very thin disc of dark matter of thin, dense disk of dark.

better, and so then the question is: do these exist and people have done studies now to think about whether they can find them amidst an interesting target? It's something you can measure by measuring the positions and velocities of stars. You can find out what the structure of the of the milky way is, and but the fun proposal was that the solar system orbits around the galaxy and as it does so it goes a little bit up and down. like horses on a car so and the suggestion was every time it goes through. You have an enhanced probability that you would dislodge something from the edge of the solar system is something called the oars cloud. So the idea was that at those times, your more likely to have these, cosmic events such as the amazing one that actually caused the last extinction, that we know for sure it wasn't so amazing for the dinosaurs or for two thirds of the species on the planet, but I guess from africa

as be. What really is amazing? I mean I I do I mean I talk about this document documenting the doses. I it's just an amazing scientific story, because it really is one of the real stories that combined together different fields of science, geologists at the time or you know, people thought that things happen slowly and this would be a cataclysmic event and also, I have to say you know if you, if you think about it, sounds like a story like a five year old would make up. Maybe the dinosaurs were killed by some big rock that can hit the earth, but then there really was a scientific story behind it, and that's also, why, like the darkness, because there's a scientific story behind it so as far fetched as it might You could actually go and look for the experimental consequences, so the observational consequences to test whether it's true I wish you could know like high resolution, details of where that asteroid came from. were ignored cloud, why it happened,

Is it in fact, because the dark matter signal for tracing back to the origin, the errors that humans seem to be somewhat special, but just seem like so many fascinating events at all scales. All scales of physics had to happen for so I'm really really glad you mentioned that because actually, that was one of the main points of my book, dark matter and the dinosaurs. one of the reasons I wrote it was because I really think we are abusing the planet were changing the planet way too quickly and just like anything else, when you alter things, it's good to think about the history of what it took to get here and it and, as you point out it took many.

It operations on many different scales and we had to have the formation of of structure or the formation of galaxies the formation of the solar system, the formation of our planet, the formation humans. I mean this so many steps that go into this and humans in some part, were the result of the fact that this big object hit the earth made the dinosaurs go extinct, mammals, developed, I mean it is an incredible story, and yes, something else may come of it, but it won't be us. if we must with it too much. But it is on a grand scale. Earth is a pretty resilient system. Can you just clarify just fascinating of the shape of, things. So the shape of the milk ways of the observable stuff is mostly lad and he said dogma tests to be spherical, but a subsidy that may be our flag disk. So you want to hear about the shape of things

If a space so structure formed early on and now their structure that we live in is so we know about the milky way galaxy. So the milky way galaxy has that desk. You can see in a dry. Dark place. That's where stars and light is, but you can also measure in some ways the dark matter, and we believe that dark matter is more or less vertically distributed. and, like we said, there's a lot of it, not necessarily in the desk, but just because it's a sphere, this a lot of it sitting there and the reason it doesnt collapse, as far as we know, is that it doesn't really can't radiate the same way so because it can radiate ordinary matter collapses in this actually because

conservation of angular momentum, it because it stays the desk and it doesn't just collapse to the center. So our suggestion was that maybe there are some components of dark matter that also rate it, like I said, that's far from prevent people have such protests to see some evidence of some deaths of certain densities. But I say these are all questions that are worth asking. Basically, if we can figure it out from existing measurements, why not try? Because there's not all dark matter made the same as well. That's a possibility. We actually don't know what dark matter is in the first place. We don't know most of it is we don't know what a fraction is? I mean it's hard to measure. Why is it hard to measure for exactly the reason you said earlier? We don't see it, so we want to think of possibilities for what it can be, if especially if those give rise to some of observational consequences. I mean it's, it's a tough game, because it's not something that's just there for the taking. You have to think about what it can be and how you might find up and the way you detect it

is gravitational effects on things we can see. That would be the way you detect the type of dark matter. I've been talking about. People have suggestions for other forms of dark matter. They could be particles called axons, they could be other types of particles and then there are different ways of protecting me, the most popular candidate for dark matter, probably until pretty recently, because they found it as something called wimps: weekly, interacting massa particles and particles that have mass about the same as the higgs, both on mass and turns out. Then you would get a report, the right density of dark matter, but then be people really like that, of course, because it is connected to the standard model. The particles tat we know about, and if it's connected to that, we have better chance of actually see

it fortunately or unfortunately, it's also a better chance. You can rule it out because you can look for it and so far no one has found it. We're still looking for him is that one of the hopes of the large hadron collider that was originally one of the hopes of large hadron, collider I'd say at this point. It would be very unlikely given what they ve already accomplished. But there are these underground detectors, seen on detectors that look for dark matter coming in and they they are going to try to achieve a much stronger bound then exist today. Just take their tangent. Looking back now, what's the big? Do you inside to humanity that the alleged sea has been able to provide its interesting its both from a major victory they expose on was prefers fifty years ago, and it was discussed.

The higgs mechanism seem to be the only way to expand homage particle masses, and it was right so, on the one hand, was a major victory on the other hand, I've been in physics, long enough to know was also a cautionary tale in some sense because them at the time I start out of his ex. We had some proposed something in the united states called the superconducting super collider alot of physicists are safe, quickly in europe, but I say artifices, we're saying when that the large hadron collider would have the energy reach necessary to discover what underlies the standards We don't want it just discovers term. Only wonder what the next step is, and I think here on people are more cautious that they want to have a more comprehensive search. They could get to higher energies, a more vents so that we could. You know we can really more definitively rule it out, but in that case many people thought they knew would be there. It happened to be a theory, call super symmetry soul.

physicists thought it would be super cemetery am is one of the many factors I think that went into the fact that the large hadron It became the only machine in town and I m the superconducting super collider would have just been a much if it really had achieved what it was poster would have been much more robust tested of the space, some so I'd say for human needs, both a tribute to the ability of discovery and is built, if really believe, and things that they have the confidence to go. Look for them, but it's also a cautionary tale that you don't want to lose. You know assume things before they ve been actually found, so you want to do so. And you you want to believe in your theories, but you also want to question them at the same time. They are more likely to discover the truth, but also an illustration of grand engineering africa, humanity can take on and Maybe a lesson that you could go

and bigger, and I am really glad you said that, though too, because that that's absolutely true I mean it's. It really is an impressive. It's! It's impressive in so many ways, it's impressive, technologically, as in precedent engineering level. It's also impressive that so many countries work together to to do this. It wasn't just one country and how it was. It was also impressive in that it was a long term project that people committed to and made it happen. So it is a demonstration that, when people set their mind, two things and they commit to it that they can do something amazing, but also in the united states may be a lesson that bureaucracy can slow things down to work. chrissy and and politics politics an economics, many many things can make them faster and make them slower? Size is the way to make progress. Politics is the way,

the slow that progress down and now you're. Well, I don't want to oversee that, because without politics, the only way that neither salem, but he may directly. but sometimes I do think what I mean You'Re- not asking this question, but sometimes I do think when I you know think about some of these complex. You know, sometimes it's just good to have a project that people work on together and there were some efforts to do that with not in science to to have palestinians israelis work together. Project called sesame and I think it's not a bad idea when you can do that when you can get. You know a sort of free, forget the politics and just focus on some particular project. Sometimes that can work some kind of forcing function, some kind of deadline that gives pupils in a room together and you're working. A thing, but as part that you realise the car humanity, the

I'll have the same concerns. The same hopes, the same fears, the same that you are all human, another and side effect of working together. On a thing, I that's absolutely true, and it's one of the reasons stern was formed. Actually it was post world war. Two and love european physicists had actually left europe and they want to see europeans work together and answers rebuilt and- and it worked, I mean they they did and it's true and I often think that the in of one of the major problems is we just don't meet enough people so that everyone thinks seems like when they seem, like the other, it's more easy to forget their humanity, so I think it is We want to have these connections, given the complexity of cosmical scales involved here that led to the extension of dinosaurs. When you look out at the future of earth, Do you worry about future extinction events? I do think

we might be in the middle of an extinction right now, if you d find it by the number of species that are getting killed off and its subtle. But you know it's a complex system. The way things respond to events is sometimes things of off. Sometimes animals just moved to another place and the way we ve developed the earth. It's very hard for species, just move somewhere else and we're seeing that with people. Now too, I mean I know, people are worried just about ai taking over and that's a totally different story. We just don't think about the future re much. We think about what we're doing now and we certainly don't Think enough about all the animals that were destroying all the things that are precursors to humans, that we sort of rely on essentially just to think whether the the the things that threaten us the stuff we see that happening gradually or the stuff you don't really

he's gonna happen all of a sudden as unfair as I think about what is what should be more weight. well. It seems like the asteroids, a nuclear war, it could be stuff that just happened. One day, where's it one day meeting over a span of a few days or a few months, but none the scale of decades. In centuries sometimes mostly talk about stuff. That's happening gradually. You can be really surprised. It's actually. interesting, and that was actually one of the reasons it took a while to determine what it was that it caused elastic sanction, because people did think at the time of many people thought that things were more gradual and the idea of extinction was a very was actually a novel concept at some point at noon I mean these aren't predictable events, necessarily there only predictable on a grand scale, but sometimes that sometimes they are in

am. I think people were pretty aware that nuclear weapons were dangerous, a much or people Is it aware now, as they were, you say twenty or thirty years ago, and that certainly worries me? I have it was not as worried about as other people, but now I understand- and it's not- I mean it's more- that as soon as you create things that we lose control over it's scary, and the other thing that were learning from the events today is. That is that it takes a few bad actress who takes everyone to sort of make things work. Well, it takes not that many things to make things go wrong

it's the it's the issue with disease. You know we can find out what causes a disease but to make things better is not necessarily that simple. Sometimes it is, but for things to be healthy, a lot of things have to work for things to go wrong. Only one thing has to go wrong, and so it's amazing that we do- and the same is true for democracy, for democracy to work. A lot of people have to believe in it a few bad actors can destroy things sometimes. So a lot of the things that we really rely on are delicate equilibrium sit with someone you know in there is some robustness and the systems we try to build him robustness, but a few extreme events can sometimes alter things and I think that's what people are scared of today in many ways: they're scared of effort, democracy, they're scared of it for peace, they're scared of it for ai. I think they're not as scared as they should be about nuclear weapons, to be honest and I think, that's at more serious danger than people realize.

I think people are a little bit more scared about pandemics than they were before, but I still say, they're not super scared about it. So you're right. There are these major events that can happen and we are setting things up so that they might happen, and we should be thinking about them. The question is: who should be thinking about them? How should we be thinking about them? How do you make things happen on it? Global scale cassettes wearily. What we mean it certainly should be. A social division should be a source of grand club Duration probably went up in it as one or would it be like it to be a dinosaur It must have been beautiful to like look at that asteroid just enter. The atmosphere until I everything just what there. What eight they'll be one of the things I will travel back in time to You know it's just that is also one of the things that I think you probably could do virtual reality. I dont the gap to be there and get extent has just explained,

I think there is something you know it's an event you just watching, you're, not doing anything you're just looking at it. So maybe a desperate created, actually that is their nuclear weapon explosion, except hence in virtual reality, that's good to remind you about Why do I feel I have to say it out, so I got it. I got the word there is even nuclear history and technology in the southwest, and I went to visit the museum which turned out to be mostly museum of nuclear weapons, and the scary thing is that they will

really cool. You know it's true that you have that. Yes, this is scary, but you also have this. Is this cool feeling and I think we have to get around that because yeah, I kind of think that, yes, you can be in that, but I'm not sure that's going to make people scared. Has it have they actually asked afterwards? Are you more or less scary? It's good. It's really good point. I mean that's a good summary of just humanity in general, where attracted to creating cool stuff. Even those can be danger- and I say that was the really interesting thing about this ain't: a museum. Actually, I was very nice beside a tour from people who have been working there on the cold war, and I shoot one or two people from and how to project. That was a very quarter and you just realise just how just the thing itself gets you so excited. I think that something that sometimes these movies met just the thing itself. You not thinking about the the open

consequences it was kind of like in some ways, it was like the early silicon valley in a people were just think it like what, if we did this, what if we did that- and you know not take you keeping track of like what the full consequences are an You definitely see that happening with ay I now I mean I think that was the moral of the battle that just happen. That is just full speed ahead. which gives me a really great trend- in addition to an another quote, a book see you you write about the experience of facing the sublime in physics, and you quote Reiner, ok, cool for beauty is nothing but the beginning of terror, which were still just able to, door and were so odd because it serenely. Disdains to less has pretty intense is, I think, the nuclear nuclear weapons, but it also, I mean Adam more mundane, perhaps level I think it applies.

Is is really interesting. One of the things I found whenever these books is seen as some people love certainty. Scientists many revel in uncertainty. It said that you want to be in and you want to solve it, but you're at this edwards really frustrating, because you don't really want. It not know the answer, but if question you knew the answer, though, there have been done so you're, always at this edge were this you're trying to sort things out and there is something scary- you don't know what you don't know. If there's going to be a solution, you don't know if you're going to find it. So it's not something that can destroy the earth. It's just something that If you do and you're an individual level, but then, of course, there are much bigger things like the ones you're talking about where they could actually be dangerous. The stuff I do. I just want to be clear, I'm doing theoretical physics, not very dangerous, but sometimes things end up having better consequences than you think. Yeah

but the dangerous and a very pragmatic sense, but, as is still in part, terrifying when you think of her just the size things like a size of dark matter. The power of this thing in terms of its growth potential gravitational facts just cause much globs, jackson, a black hole at the center of our galaxy. This may be where it, why I'm a physicist or why it differ from other people, because I'm not such a big fan of humanity in some ways, some ways I am, but the idea that we were everything would be really boring to me. I loved the idea that so much more out there, that there is a bigger universe and this lots to discover and that where not all there is one to be disappointed if we were all there is yeah and the full diversity of other stuff is prevention

in it. We have no idea how matters we we know. I will see what we can observe suffer. So the idea that this other stuff out there that we have yet to have to figure out its exciting or may ask you out there question. Ok, So, if you think of like humans on earth life on earth, has this pocket of complexity that emerged the initial budget conditions. It came to be in theirs darwinian evolution However, life originated is possible there, some pockets of complexity of that sort inside dark matter is that possible, I chemistry in biology evolving in different ways, and that's when the reasons we suggest. I mean it's, not the reason, but it would be true if there were the type of interactions

I suggest I mean it would need more complex ones, and we don't know- and I will say that the conditions that give rise to life and complexity, they're, complex they're, unlikely, and so it's not like great odds. That would happen, but there's no reason to know that it doesn't happiness worth investigating. Are there other forces that exist in the dark matter sector the successfully, so dark matter sector doesn't have all the forces of the centre model physics ray. for as we know it doesn't have any it might have it at some, level, but it could have its own forces just like the dark matter might not experience our light. Maybe it has its light that

We don't experience. So there could be other kinds of forces. I mean there could be other kinds of forces, even within our sector that are too weak for us to have discovered so far. Are that exists at different scales that we know about? I mean we detect what interact strongly enough without detectors to detect. So it's worth asking and that's one of the reasons we built big sliders to see. Are there other forces, other particles, tat exist, say at higher energies are shorter distant scale, so we ve exports over. So it's not just in the dark matter. Even in our sector, there could be a whole bunch of stuff. We don't ya, know so

maybe it's the man looked at the stand, a model for a particle physics. How does tat matter fit into fish are what is it going to explain what the standard model is so the standard model, a particle physics is basically tells us about natures, most basic elements and their interactions. And so it's the substructure as far as we understand it. So, if you look at Adams, we know they have nuclei and electrons nuclear. I have proteins and new turns in them. Protests in neutrons have particles called corks that are held together by something called the strong force they interact through the strong force, strong nuclear force, some caught the weak nuclear for assent, electromagnetism,

So basically all those particles and their interactions described many many things. We understand. That's the standard model. We now know about the higgs bosun, which is associated with how elementary particles get their master. That piece of the puzzle has also been completed we also know that there are kind of weird array of masses of elementary particles, there's not just the up and down court, but their heavier versions of the up and down cork. Chairman strange top and bottom there's, not just the electron there, some un in a towel. There are particles called neutrinos which are under intense study now, which are partnered with the leptons. The weak interactions. So we really do know these basic elements and we know the forces we know I mean what we're doing particle physics, experiments can usually even ignore gravity, except in exceptional cases that we can talk about. So those are the basic elements in their interactions. Dark matters stands outside that. It's not interacting

those forces. So when we look at the world around us, we don t usually see the effects of dark matter. It's because there's so much of it that we do, and it doesn't have those forces that we know about that. The stand among his work, spectacularly wireless pinch tested to a high degree of precision, people are still testing it and one of the things we do as physicists is we actually wanted to break down at some of what we're looking for the precision measurement or the energy or whatever it will take where those were the senate. is no longer working like not that it's not working approximately we're looking for the deviations in those deviations are critical because they can tell us what underlies denmark, which is what we really want to see next working final, the places where the stem model breaks like what were the place. You could see those tiny little deviations, so we don't know yet, but we know the kinds of things you wouldn't want to look for so one obvious place to look is at higher energy, for it,

here, the large hadron collider, but we'd love to go beyond that. Higher energies means shorter distances, and it means things that we just couldn't produced before I mean equals empty score so you have a heavy particle. You don't have enough energy to make it you'll, never see it. So that's one place the other places. Precision measurements if you enter the standard ma has been tested, exquisitely so evinced. If it's been tested, one percent, you want to look at a tenth of a percent and there are some processes that we know shouldn't even happen at all in the standard model or happen at various press level, and those are other things that we look for. So all of those things could indicate there's something beyond what we know about which of course, will be very exciting. when you just stepped back and look at the standard model, the quirks and all the different particles and neutrinos. Isn't it? Why,

AL, how the cycle system came came to being quits is underpins everything we see absolutely and that's why we'd like to understand it better we want to know: is that part of some bigger sector? Why are these particles? Why did they have the mass as they do? Why is the higgs boson so light compared to the master could have had which we might have even expected, based on the principles of special, two in quantum mechanics. So that's a really big question: why are they what they are in and they originate? Does like some mechanism that created the whole thing? That's one of the things were trying to study Why is it what it is? I even the mechanism that creates stuff like the way a human being is created from a single sell tickets. Joseph the holding like, but you build up this thing. All of this whole thing comes to be from, like her, but I'm you let it is interact with the environment,

right, where it is not its right to work with us over. The question is how much of his the environment is it just the environment, acting on a set of constraints, like how much of it is just the information, the dna or any information. How much is it initial conditions of the universe as the some other thing, acting on. It is a big questions. These are big questions and pretty much every field in a week for the universe, do consider it. You know its everything. There is by definition, but people's now think about. Is it one of many universities in, of course, is a misnomer, but could there be other places where there are self contained gravitational systems that we don't even interact so but those who are really important questions and the only way we can answer them. As we know we go back as far as we can. We try to think theoretically and we try to think about observational consequences. It's all we can do what

anyway, to explore. The are models to look at year are fun nuanced. Disagreement with carlo? Rarely when you talk about him writing in his book, electrons, don't always exist. They exist when they interact the materialize in a place when they collide with something else, and you wrote that, while just read the whole thing cause, this is kind of interesting stocks, may not chief, precise value until they are traded. doesn't mean we can't approximate they're worth until they change hands. Somali electrons may not have definite properties, but they do exist is true that the electron doesn't exist as a classical object with definite position until the position is measured, but something was there which physics Just use a wave function to describe it's a fascinating new as disagreement, so do electrons always exist or not. Does the tree fall in the forest if nobody's there to see it

so I like to think of the universe, is being out there. Whether or not I mean it will be weird. If the only time things came into existence was when I saw them or I measured them, was a lot of eight hours. I mean- I could believe that the middle east doesn't exist because I'm not there now I mean that would be kind of ridiculous. Think we would all agree on that. So I think this only so much that we can contribute to our own powers of seeing so and the system doesn't come into being because on measuring them, and so what is we're? and this isn't even discriminate the standard model. So do to remember how you interpret quantum mechanics. I mean I would say that those wave functions are real. I mean one of the things that don't forget that particle physics does that quantum field theory says is that electrons can be created, destroyed. Is that it's not that every electron has to be near a similar can be me, that's what happens at gliders particles get created and destroyed

that doesn't mean that have have electron in an atom. It's not there, it certainly there. We know about its its charges there, the physics of the kind of way to see the world. So what what with it at the bottom was the bottom turtle What do a sense? It there's a bottom reality. There were trying to approximate with physics I think we always have an our heads. Maybe that we'd like to find that, but I have to I mean I might seem sober I think, I'm kind of more humble, that a lot of visits, I'm not sure that we're ever going to get to that bottom level, but I do think we're going to keep penetrating different layers and get further. I just wonder how far away While we are you, we all wonder that incitement, but even the measure of how far away we are I mean one way you can measure it is just by our everyday lives. In terms are everyday lives, we measured everything in terms of what lies. It there's a lot more to see and so part of it has to do with how far we think we can go.

I mean it might be that the nature of reality changes so much that even these terms, which are different, maybe we'll measure this. The notion of distance itself might break down at some point, But also to push back on, though we've measured, everything, maybe there's stuff we haven't even consider- is measurable, for example, consciousness or that there's there may be stuff just like you said, forces unseen undetected. So it's an interesting thing so when- and this is often a when that happens, so this sort of the fundamental stuff underlying it and then there's sort of the higher low. but you know what will collagen effective theory at some level, you know so. Not always working. I mean when I A ball. I dont tell you where every atom, as I tell you this of all, and so there might be, different layers of reality that are built on terms on terms of matter that we know about in the stuff. We know about that and when I, so we ve been measured everything I say that with the grain of salt I mean I missed,

of course not everything, a cinema. So citizens. lots of phenomena that we don't know stand that we, but often their complex phenomena that will be given in terms of the fundamental issues instead we know about, but that is an interesting question because yes, phenomena there at the higher level of that emerge? But me maybe I could cautiousness. There is far out people that I think that consciousness pants. I guessed right that it's that is that there is going to be almost like fundamental force of physics. That's cautiousness that promise, I mean usually when you have an a crazy sorry, okay, when you have a far out theory. Yes, the thing you do. Is you test all the possibilities within the constructs that exist, so you don't just I'm cheetah most for a possible em. You can't do that, but then to see if it's true I have to find evidence of it or you have to show that it is not possible without that. We're very far from that. I think one of the

Criticisms of your theory on the dinosaurs was that it requires, if I remember correctly, for darkness it'd be weirder than it already is his then I think you had a clever response. That can you? Can you remind him necessarily but brace at them, but I mean we have no idea how weird dark matter is. I mean it's based on the from unthinking. They know a dark matter is and remains so You're too, then already is that we did not already anything. We don't know what it is no normalization here that so dark matter. Do we know that if dark matter varies in density, it definitely does in uterus. Just like I mean so, for example, there's more dark matter in galaxies there there's between Sharon Alex's, so it it a clumps. I mean it's, so it's it's matter if it's distributed, like matter, this matter that it does clump, but the the or the full details of how it clumps and again, by city of the clumping, it's understood of pretty well people do simulations are made where

People are always looking for things, including us. This particle physics is sort of its small scales. Are the deviations on small scale so that in hitting other interactions or other processes or enter since with baryons does say normal matter that we don't understand, but a large scale. We have a pretty good understanding of dark matter. Distribution you are part of our recent debate on quote concerned. and cover reality. Let me ask you this question then what do you? The limits of science, I'm smart enough No. I have no idea, and also its name and clear with science means right, because there's the signs that we do, which is particle physics, we try to find fundamental things in figure what their effects are, this science like biology, where you know it's an edit a higher level. The kind of questions you ask are different: the kinds of measurements are different and the kind of science is going to Then, in the serve more numerical age I mean- or even I like what

I mean to answer a question: does it mean that we can predict, it doesn't mean we can reproduce it? So I think we're coming up against serve the definition of what we mean by science as human beings. So in terms the signs that we can do it. I don't want no, and until we get there, you know we're trying to solve our problems, and you know we ve made progress? I if you think of how much science has advanced in the last century a century and a half, it's incredible in a way that, even though the universe was expanded at the beginning of the twentieth century, didn't know about quantum mechanics at the beginning of the century. We didn't know about special relativity. That's a lot in a relatively short time, and depending on how you think of time. So I think it would be premature to say we know limitations at various points out that history with those out everything or declared the earliest.

As people with various people declared. That would have solved everything, as did the sauce a good place to maybe could you describe the different scene top down and bottom up approaches to theoretical physics that you talked to on the book, so you could try to jump in and say I have a theory that I think is so perfect and that I can protect everything from it or at least protect some salient features from it. The sub down that would be a top down. Bottom up is more like you don't like the questions we just ass, a wire masses. What they are we measure things we want to put them together, Usually a good approach is to combine the two. If you ask a very specific question, but combine it with the methods of knowing that there could be a fundamental their underlying him? Sometimes you make progress and summed know the community tends to get segmented or fragmented into people who do one or the other, but there are definite times I move. So my best collaborations are women.

People who were more top down than I am so out become offers interesting ideas that we want a thought of this either. One of us is working individually, you say, the truly big leaves happen top down like einstein. I stand was not a top down person and beginning he was them especially activity was very much in thinking about. You know they were thought experiments, but he was very much you. They ritual theory about relativity is something like on the nature of electromagnetism. He was trying to understand how maxwell's laws could make sense when they were in a seem to have different cemeteries them. We had thought so he was very much a bottom up process. In fact he resisted top down for a long time. Then, when you try to do the theory of John, to be the general theory of relativity. Whatever you want to call, it incorporates grew body into the system. Where you need some feedback, then he was by a mathematician who were developed some different. geometry and helped him figure out how to write down

and after that he thought top down was the way to go, but he actually didn't make them much progress but turn. So I think it's you know I have to think it was just one or the other. In fact, a lot of people who made real progress were rooted in actual measurements, while speaking of mathematicians, what to use a difference It had a bit of foreign, both between physics, mathematics in the way it helps us to understand the world. What is it to be There's a lot more overlap in physics. Amanda hit them has been, I mean well, maybe not more But there is certainly a lot, but I think again, the kinds of questions your asking are usually different. Mathematicians, like the structure itself, physicists, are trying to concentrate on to some extent on the consequences for the world. I am, but there is a lot of overlap as string theory is an example. There are certain theories where that there's a a certain. mathematical, beauty to it, there's also

you know, there's also some really cool ideas that you get in particle physics where you can describe. What's going on and connected to other ideas, that's also really beautiful. You know, I think I think basically, insights can be beautiful, amps you, they might seems well, but sometime, and sometimes they generally are, and sometimes there are built on a whole system that you have to understand before If you actually saw, I sense equations written out a components queuing things so beautiful you right in a compact way. It looks. Nice What do you think about the successes and failures of string theory to a degree, do think it succeeded to degrees. It not succeeded yet or has failed. I think to talk about any science in terms of success and failure often misses the point because there's not some absolute thing, and I think I do think that stricter as work

at overly ambitious, not overly ambitious but a little bit overly arrogant in the beginning thinking they could solve many problems that they weren't going to solve. That's not to say the methods and advances in in theory, tone exist, and but they certainly work able to immediately solve all the problems they thought they could solve, but it has given us tools. It has given us some insights, but it becomes almost a sociological question of like how much it should be one or the other. I do think that you can get caught up in the problems themselves and, and sometimes you can get caught up in the methods and just of two other examples. So the real physics instead It's often come from people who are thinking of physics as well as as math, because you mentioned, I is their hope. That I may be able to help find a mentioning insights and then another question. Another would ask this question is how special humans they were able to

discover novel insights about the world. That's a great question and it depends what inside someone we're going to find out. I mean you know it because it's hard to think about something that doesnt quite exist. Yet I mean. I could just think about something. Take a step back. In its look like to cent three to four dimensions. You go back to treatment. So soon to go to something you can imagine, so you can sort of save a lot of the things in a very different level about the internet. You casino has the internet, help do things, and you know a definite took on a life of its own, some sense, but is also something that we are able to team. I know that I myself would have been able to write books of the internet into first, because I went to have the time to grow library and look everything up annum.

I'd help me enormously. In some sense, I could be that in a very nice world it could be a tool that helps us go a step further than we would a lot more efficiently, and it's already done that to some extent or it could be like the parts of the internet that we can control the running. Politics are women. So there is certainly a lot of indications. It can do that, Then there are even bigger things that people speculate about about. I want to do something, but in terms of actually figuring things out, in a word in the early stages, in several directions here. One is like on the theorem prover size of wolfram alpha where everything's much more precise and we have large language model type of stuff. One of the limitations of those is. It seems to come up with convincing looking things which we don't know, if it's true or not another big problem for us,

so largely removed are more or less like generalizations of stuff we have so the question is so they still breaks. is an eye waiting to happen it maybe they are happening and maybe a big maybe not, but that that's not quite the same I mean, maybe just some in some cases it's just pattern, recognition that leads to important things, but sometimes it could be something more insightful in that that I can't even my finger on. So it forces us to me. We don't really understand how smart we are. We don't understand how we think about things all that well actually, but one thing true, though, where a lot more efficient right now than computer in coming up with things we require a lot less energy do so if Here's figure out how to do that. Then it's going to be football game so and so there the kinds of connections that we don't know how we're making, but we are making them, and so that's going to be interesting, so

and I say we're in early stages, but this is changing very rapidly, but right now I dont think that it's actually knew Rediscovered, like new laws of physics but could in the future, maybe I can it will raise big questions about what is special about human rights that we dont quite appreciate your would. They could be things that are like that leap of insight that happens truly novel ideas that could potentially be very difficult to do so. There are of abstract questions like that. There's also questions of how is it we can address to some extent. You know how will I be used in the context of the world we live in, which is based on?

our country's countries based on capitalism and a certain political system, and how will global politics deal with it? How will our capitalist system deals with what will be the things that we focus on doing with it? How much will researchers get control of it to be able to ass, different sorts of questions I mean you know, while it was starting out, people were doing these kind of toy problems, but what will it should be applied to and what will be optimize to do this. There is a lot of stands out there that it's really important, restart addressing. What do? You is the most beautiful and solve the problem in physics and gas market, What is really exciting free can lock the mystery of in the next few decades? I'm so is it what's the most beautiful and fell from or what is most beautiful and felt problem, I think we can make progress

Oh boy goes on in the next few centuries. This is this most of the questions. The big questions have to do with what underlies things how things started was at the base of it. There's also just basic questions like how like that you asked earlier. How far will science take us? How much can we understand? There are questions like how we got here and what underlies it. Are there but also, I mean there's really deep questions like in what fraction of are we actually seeing or if there are these other forces? If there is another way of seeing the world is, are there garlic? You know versus beyond their own that if this so a different. How do we even comprehend them? I mean how do we detect like what would we even think about them, so this a lot about trying to get beyond

It's always just getting beyond our limited vision and limited experience and try to see what underlies it, both small skills and at large skills. We just don't know the answers. I mean I'd like to think that we understand more about dark matter about dark energy about are their extra dimensions thinks that we actually work on this play a lot but we work on that's yet to be discovered. The understanding, the extra dimensions peace will be really interesting. Totally. if it is how the universe went from higher dimensions, to what we see it or do the inner are the extremely his present everywhere, I mean the really interesting piece of physics we did that talk about my first book war prejudices finding out that there can be a higher dimension, but only locally. Do think this the gravity of a lower dimension, so it could be like only locally to resign We live in three dimensions that could be hired. Merchants is different. This not

the gravity we're, but it does us it's a phenomena that might be out there that we don't know about all sorts of evolution. Things time depends that we don't know about and of course, that's from the point of view of particle physics. From the point of view, other kinds of physics were just beginning. So who knows you have to exchanges throughout this is not homogeneous throughout the universe. That's that'll be weird enough for the observable universe. It's the same, but beyond. observable universe. Who knows what advice would you give you ve had an exception career? What devices you give to young people? Maybe I college, and how to have a career can be proud of and a life that can be proud of. I think the weird thing about being a scientist or an academic journals You have to believe really strongly what you do while questioning it all the time you can't you know and that's that's a hard balance to have. Sometimes it helps to collaborate with people but to really believe

that you could have good ideas at the same time, knowing they could all be wrong. That's that's! That's a tough tightrope to walk sometimes, but to really test them out and the other thing is sometimes you know if you get too far buried, you look out and you think oh there's so much out there, and sometimes it's just good to bring it back home and just think. Okay can I have as good ideas the person next to me, rather than in of the greatest physicist who ever lived, but right now, like you said, I think, there's lots of big issues out there and his and it's hard to balance it, and sometimes it's hard to forget the role of of physics, but I think you know wilson said it really well when he said you know when they were building fermilab. It was like this phone and the country but it'll make it worth defending. You know, there's just The idea that you ve been all this chaos. It's still in full and that we still make progress in these things, and sometimes you know when major world events are happening. It's easy to forget that, and I think those are

weren't. You dont want to forget those, but to try to keep that balance, because we don't want to lose what it is that makes human special, the big picture and you also lose yourself and the simple joy of puzzles me yeah yeah. I mean that we are like that. Sobbing puzzles And actually one of the things that drives me and my research is the inconsistencies when things don't make sense, it really bugs me and it just won't, go in to you know different directions to see how could these things fit together to bugs you, but that motivates you yeah tell until doesn't, because I think it is because I have this underline belief that it should make sense of the world was that you in many ways and tells you nothing should make sense, but if you believe that it makes sense- and you look for underlying logic- and I think that's just good advice for everything- to try to find the widest the way it is, I think it in a a way tat. I talk about effective, my second second, but none have historic up. You know it's sort of rather than asked the big question. Sometimes we just ass the question

about the immediate things that we can measure and we can like. I said we can sometimes tell one that will fail, but we can have these effective theories, and sometimes I think you know when we hit precious big questions. It's good to do for effective theory. Point Why do I find this as my ways the world we have the way we think things are beautiful there, we live in, I mean you know, sure if we had different senses are different ways of looking at things we witnessed, they find a beautiful, but I have to say it is kind of testing that, no matter how many times I see a sunset, I will always find a beautiful. It's like I don't know, every citizen's: whatever is just all beautiful. You always are so there's there are things ass humans yo clearly resonate with a spoon here. We were maybe about that way. That's about us, but comes of figure out the universe. It's kind of amazing how far we ve got it in a way

have discovered many many wonderful things, but there's a lot more out there and I hope I have the upturn to keep going and with effective theories once more. Step at a time, just keep on rattling and also having a mind the big questions, but doing one small step at a time exactly they are looking out to the stars. He said the sunset for me: it's the sunset, the sunrise and just looking at the stars as wondering: what's out there and having a lot of hope that he was all figured it out right. They like it, they said, but thank you for me one of the humans in the world be here for a that are pushing it forward and figuring out this beautiful puzzle of ours, and thank you for talking days is amazing. Thank you.

For listening to this conversation release right down to support this by gas. We shook otter sponsors in the description and now let me leave you with some words from albert einstein. The important thing is to not stop questioning curiosity has its own reason for existence. Thank you for listening and hope to see you next time.