The video navigates the complexities of quantum mechanics, connecting the theoretical concept of Schrodinger's Cat to practical interpretations of reality and physics. Sean Carroll, a physicist and author, converses with Neil deGrasse Tyson, delving into how quantum physics explains phenomena like entanglement and the existence of particles, suggesting that these principles shape our understanding of the universe.

Sean Carroll elaborates on the historical evolution of quantum theory, acknowledging different interpretations, such as the copenhagen interpretation and many-worlds theory. The narrative highlights the complications and debates surrounding these interpretations, emphasizing the idea that our perception of reality might differ significantly from what scientists uncover. Neil deGrasse Tyson aids in demystifying complex notions, maintaining that the universe operates beyond human intuition yet remains decipherable through science.

Main takeaways from the video:

Please remember to turn on the CC button to view the subtitles.

Key Vocabularies and Common Phrases:

1. entangle [ɛnˈtæŋɡl] - (verb) - To cause something to become twisted together or caught in a tangle. - Synonyms: (intertwine, entwine, mesh)

But the problem with two entangled particles, which we haven't even defined what that means, but you have a very sophisticated audience.

2. superposition [ˈsuːpərpəˈzɪʃən] - (noun) - The action of placing one thing on or above another, especially so that they coincide. - Synonyms: (overlay, layer, pile)

And the cat goes into a superposition of being awake and being asleep.

3. quantum mechanics [ˈkwɒntəm mɪˈkænɪks] - (noun) - Branch of physics dealing with physical phenomena at nanoscopic scales, where action is on the order of the Planck constant. - Synonyms: (quantum physics, wave mechanics, quantum theory)

And through the miracle of quantum mechanics, when you look at those vibrating fields, they appear to us as particles

4. cosmological constant [ˌkɒzməˈlɒdʒɪkəl ˈkɒnstənt] - (noun) - A quantity representing the energy density of empty space in Einstein's field equations of gravitation. - Synonyms: (Einstein's cosmological term, vacuum energy, dark energy)

The cosmological constant, the vacuum energy, which are equivalent.

5. copenhagen interpretation [ˈkoʊpənˌheɪɡən ɪnˌtɜːrprɪˈteɪʃən] - (noun) - A theory about quantum mechanics that holds that quantum mechanics does not provide a description of an objective reality but deals only with probabilities. - Synonyms: (quantum interpretation, probability interpretation, Bohr's interpretation)

Well, you just mentioned in that world, I have some memory that I haven't heard about lately, but that there was the copenhagen interpretation

6. emergence [ɪˈmɜːrdʒəns] - (noun) - The process of becoming visible after being concealed or the process of coming into view or becoming exposed. - Synonyms: (appearance, materialization, development)

emergence. I've seen a lot of that lately.

7. entropy [ˈɛntrəpi] - (noun) - A measure of the amount of disorder or randomness in a system. - Synonyms: (disorder, chaos, randomness)

Can you do something about entropy?

8. hilbert space [ˈhɪlbərt speɪs] - (noun) - An abstract vector space used in quantum mechanics and other physical and mathematical systems. - Synonyms: (vector space, mathematical framework, abstract space)

The state of the universe is a vector in hilbert space.

9. dark energy [dɑːrk ˈɛnərdʒi] - (noun) - A hypothesized form of energy that permeates all of space and tends to accelerate the expansion of the universe. - Synonyms: (vacuum energy, cosmological force, quintessence)

The dark energy is interesting again, I've written papers about different possibilities for that.

10. vector [ˈvɛktər] - (noun) - A quantity having direction as well as magnitude, especially as determining the position of one point in space relative to another. - Synonyms: (direction, quantity, orientation)

The state of the universe is a vector in hilbert space.

Neil deGrasse Tyson and Sean Carroll Discuss Controversies in Quantum Mechanics

Schrodinger's cat. Everything in the box, the air, the light, you know, everything moving around in the background interacts differently with the awake cat running around trying to get out, and the asleep cat just snoring peacefully on the ground. Is there a world where I open the box and I see the awake cat as a different world from the one in which I open the box and it's asleep? There will be two worlds. And it happens long before you open the box, because as soon as the other stuff in the box, as soon as the photons and the atoms and everything become entangled with the cat, boom, there's two worlds. So where are those two worlds? Or is that the wrong question? That's the wrong question. The worlds are not located in space. Space is located in each world. Holy crap. He knows this. I gotta go. I gotta go. I don't believe anything anymore. It's over. There is no God.

Oh, no. This is startalk. Neil degrasse Tyson here, your personal astrophysicist, got with me. Chuck. Nice, Chuck. Hey, Neil. Hey. What's happening? All right. What are you holding in your hand here? Holding a book. Oh, okay. A book that I, you know, that I picked up off of the coffee table. The biggest ideas in the universe. Well, that's what this episode is gonna be about. Yes, but I know some big ideas. Right. But I don't know the biggest ideas. There's a. The. In the front of this title. Right. And quite the qualifier. Yeah. This is written by the one and only Sean Carroll. Sharon, welcome to my office. Thank you so much. New York, your office. These are the best places, most exciting places that I know. We have corresponded and emailed and talked, and we have never been in the same space. No, I think we did in LA once, right? I think so. Was there. I think briefly. Very, very briefly. Okay. But, yeah, many phone calls. Delighted to have a meaningful exchange with you at this point. Right. With microphones in front of us, cameras trained. Cameras trained. Meaningful. Exactly.

Okay, so just before we delve, in which Sean Carroll are you. I'm the physicist. One. The physicist. Sean Carroll. Yes. And the other Sean Carroll is who? My evil twin. He has the beards. You know? Which one is the evil twin? But is it like. Is it a. Is it a. It's not quite as evil. It's more like Bushy Santa Claus. It doesn't really look like. But he's a very accomplished biologist. Also writes books. You should buy those, too. Okay. Very nice. All right. Very good. So, Sean Carroll, let me get your bio going here. The homewood professor of natural philosophy. That's very retro. Yes. Oh, man. Just like Newton. I was trying to say. Yeah, ike had some title like that. Natural philosophy at the Johns Hopkins University down in Baltimore, which is the home of the headquarters of the Hubble space Telescope. The Space Telescope Science Institute. It is right there. Cool. And you're also on the faculty at the Santa Fe Institute, but you're only on a visiting faculty, so they got really cute here. Fractal faculty. Yeah, pretty cute. And you get cuter. Not my. You can't get cuter than that. No, you can. I mean, unless there are a bunch of Sean carrolls who are tinier and look exactly like Sean Carroll. Oh, to continue the fractal. Right, move on in. Sean Carroll. At all scale. Exactly. Frightening.

And your research areas? Quantum physics, spacetime, cosmology, emergence. I love emergence. Maybe we can hit on that. entropy. I've seen a lot of that lately. Can you do something about entropy? If you can't do anything about it, you have nothing for us to increase it. We can do that without you. dark energy, symmetry and origins of the universe. You're all in. You got a podcast. Podcast of your own mindscape. I think I've been on that. Have I been on that podcast? No, not yet. Not yet. Okay, we'll see. It's in my inbox. Maybe. I haven't gotten to it yet. And this latest book, the biggest ideas in the universe, the second in a trilogy. This one, Quanta and Field Quanta. Wouldn't that be the smallest idea in the universe? Oh, smallest thing can be the biggest idea. Oh. Oh, dear. Oh, snap. You gotta put Chuck in his place early. Otherwise he'll just run ranch all over you. Yeah, he got you on that one. Yeah, that's true. That's true. He gotcha.

So this is a trilogy. The first big ideas book was what it was called Space Time in motion, which is like publishers speak for classical, regular, ordinary, armchair physics. Isaac Newton Physics. Yeah, yeah. Isaac Newton Physics. And Albert Einstein for that man. Well, yeah, he was the star. Isn't it funny? At this point, Albert Einstein is the old physics. Classical physics. Now we're going quanta and fields. Two very big ideas. Yeah. And can we get a hint in what you'll be happy to hear? It's complexity and emergence is volume three. That's gonna be. It's basically appetizer, main course, dessert here. The third one's gonna be fun. Okay, very good.

You're an active research scientist. You publish books. You're active on social media. So this is great, just to see kindred soul out there. It's very tiring, isn't it? Why did we do this, bill? Whose idea was this? Let's go out and have a drink. We'll talk about it in service to the universe. We are servants of cosmic curiosity that permeates within us all. We know that the idea of fields as my memory of the history of physics began with Michael Faraday. Is that correct, or does it go farther back than that? That would be fine if you gave it to Faraday. I mean, he certainly played a huge role in figuring out mid 19th century. Mid 19th century electricity, magnetism.

Both had fields associated with them. Technically, no one ever mentions this, but our old friend Pierre Simone Laplace, circa 1800, realized that Isaac Newton had this idea of gravity, the inverse square law. And Newton was very puzzled. Like, you have the earth here, you have the moon over there. There's a gravitational force. How does the moon know what the gravitational force is? There's nothing between them. Nothing between them. Action at a distance. Right. And Laplace figured out you could rewrite Newton's theory of gravity in terms of a gravitational field. So I kind of give him credit. Wow, look at that. So in my high school, I had a friend who, his name was Frank Larisse, and we just learned about some of these great french physicists, mathematicians, Lagrange, Laplace. And over lunch one day, he said, there will be the Larisse equations. This was just a fun little dream state that we all occupied in high school.

Okay, so fields. Why are fields real? Or are they just a convenience? Because, by the way, you are partially in the department of philosophy there. Yeah. So I get to ask you philosophically leaning questions. I'm not allowed to say, that's a philosophy question, and ignore it. I actually have to answer those questions? You actually have to answer it. That's my job. All right. Yeah. So the story that we tell in the book is if you were 1895, right, if you were just before the turn to the 20th century, you would have thought that matter, tables and chairs, was made of particles, stuff we knew about electrons, you knew about atoms, and you would have thought that the forces between the atoms were mediated by fields. The gravitational field, the electric field, the magnetic field. And one of the great triumphs of quantum physics in the twenties and thirties was it said, it's all fields. Electricity, magnetism are fields, but so are electrons and quarks and neutrinos, and they vibrate in different ways. And through the miracle of quantum mechanics, when you look at those vibrating fields, they appear to us as particles. The particles come out of the field.

Is this an early variant of what would later be string theory, where they're saying particles are vibrations in the strings? Well, particles are vibrations in the fields. And that's absolutely accurate in the regimes we're talking about here. Is there something deeper that they could be vibrations of strings, et cetera? That's a speculative idea. Very, very promising. We just don't know. Yeah. Much smaller. Need to know for predicting what's going to come out of the large hadron collide. Okay, so you. So let me ask you a blunt question, which sounds stupid, but I think it's me. It's a meaningful question. Do electrons exist? As. As. As. Now, wait, is that. Is that a science or a philosophical question?

Well. Well, because natural philosophy, as I understand it, we have never measured the size of the electron. It is smaller than the smallest capacity we have ever conjured to measure its size. Okay, I gotta ask you a preliminary question. How truthful do you want me to be? I love it. Okay, give me. Give me what you say. In the back room. In the back room with the cigars. No. First lie to me. Then tell me the truth. The lie is what is real is the electronization field. And little vibrations in those electron fields show up in our detectors as particles. So it's not that we haven't measured the size of the electron, is that there is no such thing as the size of the electron. The electron is a vibration in a field. It can have different vibrational wavelengths, and it shows up as the particle. Yes, that's right. Yeah, that's right. I mean, it comes to the party that way, but otherwise, it's not. It's not. Yeah. Yeah. Okay. That is so trippy. That is so freaky, Mandy. So you and Einstein both were bothered by this? I was very bothered by this. So you cannot measure the electron in its wave state to be a particle, because the act of measuring it turns it into the particle. The way that we usually measure things.

You say, where is it? And you get a little track in your particle detector because you keep asking where it is, and you always get a definite answer to the question, where is it? But when you're not asking that question, it's spread out all over the place. Okay, is that the lie or the truth? That's only a lie. I haven't even gotten to the truth yet. Okay, now give me the truth. Okay. When quantum mechanics came along in the 1920s, we realized that instead of an electronic. Let's celebrate. We are in the centennial. We're very close of the discovery of quantum physics. The centennial decade. The quantum year. Yeah, yeah, yeah. The centennial decade. And that was a watershed decade where Hubble discovers that the Milky Way is not alone among galaxies in the universe, and he discovers the universe is expanding. And I'm just saying, we got to tip our hat to the 1920s here. The roaring twenties. We live in shame that we can't live up to that anymore.

Yeah, it was too bad. Let's be honest. They weren't working with much to start with. Low hanging fruit. You guys are building on top of everything that they've actually discovered. Oh, yeah, absolutely. All right. We're building up to the truth here. So, you realize in the 1920s that you thought the electron was a little particle. In fact, you should describe it in quantum mechanics by a wave function. If you ever took chemistry, if you ever saw those pictures of the orbitals of electrons, etcetera, that's the wave function of the electron. Soon thereafter, you realize, no, actually, you should be doing field theory, quantum field theory. And so there's a field that the electron is a vibration in, and you're asking, what really exists? Well, there's a wave function of that field, so there's, like, fieldiness on top of fieldiness. And finally you say that, okay, what if you have, like, different fields, different particles? Do they each have a wave function? No, there's one wave function for the whole kitten caboodle of them. The wave function of the universe. That's what's real. The wave function of the universe is real.

You know, he's been smoking something. That's crazy. You know, where was he before then? Are you just talking this, or is this hypothesized soon to be experimentally verified? I encourage all of the listeners out there to check out my paper entitled reality. That would be a research paper. Research paper called reality as a vector in hilbert space, okay? That's what reality is. So, look, first, let me explain. Not everyone agrees with the true thing I just said. There's disagreement because of this fact that physicists, it's your personal truth, can't agree on what quantum mechanics really says. So we have this idea that everyone uses in quantum mechanics, hilbert space, which is the space of all possible imaginable quantum states of the universe. And someone like me, who is a purist, an extremist about this, says we have all possible quantum states. The actual universe is one of them, and it changes with time. Other people will say, no, that's not reality. That's just a tool we use to describe predictions, to make predictions for experiments.

Other people will say that's part of reality, but there's other parts as well. We don't have a consensus on this. Okay. I like the absence of consensus. Yeah, exactly. It wakes you up in the morning. The whole thing sounds very political. Oh, yeah. Oh, my God. All right, so how do you square all the successful predictions of quantum physics with any intuitive understanding of what's going on? Because I've said many times, and I'm happy to say it again, the universe is under no obligation to make sense to us. So once you accept that, why try to make sense of it and jump through hoops and brain twists just to say, well, it's got to be this or it's got to be that, but it calculates and it works. Move on. The universe under no obligation to make sense. But remarkably, it keeps making sense once we really let ourselves listen to what the universe is trying to tell us. Universe seems to be intelligible.

It's not deeply, ineffably mysterious, and it's a give and take. It's not like our intuition just maps on to reality. Reality is like, no, your intuition was a little bit off there. Try to update, and if you're open minded about it and you buy the right books, very updatable. You can absolutely get there is what I'm saying. Yeah. Hey, startalk fans, I don't know if you know this, but the audio version of the podcast actually posts a week in advance of the video version. And you can get that in Spotify and Apple Podcast and most other podcast outlets that are out there. Multiple ways to ingest all that is cosmic. On startalk, I'm reminded of the, the charming illustrated book series by George Gamow, Mister Tompkins in, I guess, Wonderland. And what he would do is he's a physicist, famous physicist, mid 20th century. Okay. Lived only. Just died only 20 years ago or so. But he.

Yeah, George Gamow, he was one of the original predictors of the temperature of the universe. Pioneer lever bang theory. Yeah. If the universe began as a. As an explosion with a big bang, could you measure that? And then he was on a paper that. Okay, so what temperature did he get for? It was like he was at a factor of ten. Yeah, no, it was a factor of ten. No, I. Within a factor of ten, they had different. I think it was like five degrees. He said, the universe is five degrees, and the universe turned out to be three degrees. Okay. Okay. So rich gott, okay. Friend of the show has said that's like predicting that a 50 foot flying saucer will land on the White House lawn. But a 30 foot floor saucer, that's pretty wild, right? Yeah. It's not even that the numbers are different. It's that it's a prediction at all that would come true.

But this story you're telling right here is exactly why this crazy talk about Hilbert spaces in quantum fields has some plausibility. Because we have some data in front of us. We try to explain it, we invent an equation that explains it, and then we extrapolate that equation to wild places that it's never been before, and it comes back telling us, yeah, that's what I said. That's what I said was going to happen. And the big bang is an example. Quantum field theory is another example. But Mark Twain did this first. You know the Mark Twainism. Yeah. Yeah. So he had read that there was some research paper about the rate at which the Mississippi river is depositing silt in the delta, and so it's growing in this direction. And then he says, oh, that means 30 million years ago, the Mississippi river ended in Canada. And then he says, the great thing about science, there's such wholesale conclusions drawn from a trifling investment of fact. That's brilliant.

Yeah, that's Mark Twain doing it in Mister Tompkins in Wonderland. What made it entertaining, especially if you're a budding scientist, is he changes the values of the physical constants in an ordinary world. Okay. And then you get to see what happens in an ordinary way. Otherwise, these phenomena are inaccessible to us. So, in one of them, he said, all right, 60 miles an hour is the speed of light. And now you're driving down the street. What do you see? And then another one. I think he changed Planck's constant. Yeah, sure. And so could you just give me a handle on things that would happen if Planck's constant were macroscopic? Like, if I walk through the doorway, I would, like, diffract, right? Wouldn't I? Yeah, you would diffract, and we wouldn't be able to know exactly that you had a position and velocity at the same time.

Right. You know the old joke about Werner Heisenberg being pulled over, and the cop says, you know how fast you were going? And Heisenberg says, no, but I know exactly where I am. Because you can't know, according to the Heisenberg uncertainty principle, both your velocity and position at the same time. Metropolitan rocks at physics, continuous. I was going to say who wrote that? Can I try that out? I don't know. That's the uncertainty principle. No one pin you down in quantum mechanics. You're fundamentally not a set of particles. You're a set of waves. Planck constant, which sort of sets the scale for quantum physics, were much bigger, macroscopic, then we would all be these kind of undulating waves moving through the universe, interfering with each other and becoming entangled and then measuring things. And we don't want to live there. No place to be, really. And so you mentioned entangled. That's been a buzz phrase. Everybody loves it.

Everybody loves it. It's one of the biggest hits hearing about. It's one of the biggest hits right now. Entanglement. Entanglement. One of the goals is, what's the farthest particle that you can entangle on the premise that maybe that'll be useful one day. And from all the news articles I've seen, China leads the world in entangled particle distances. So what do you have to do? I'm sorry, because I'm just losing something right here. I'm missing something. If something is entangled, what difference would it make about the distance? I'm missing that. Who knows? I'm saying, in science, you just push the envelope. If you've never pushed it before. I got you one day. Are they.

We heard in Congress that just. Did you hear in Congress? China is going to land something on the far side of the moon, and Congress wants to know why. How come we're not landing something on the far side of the moon? This is an entire conversation in Congress. Right, right. No, but Chuck is completely right about entanglement. It doesn't matter how far away things are. But the problem with two entangled particles, which we haven't even defined what that means, but you have a very sophisticated audience. So they know what this means, is that as soon as you measure one of them, the entanglement breaks. So it's not that they get further apart, just that as you bring them further apart, the chances that one of them bumps into something gets bigger and bigger. And so, therefore. So that's what makes this distance record meaningful as a record. So, one of them was they entangled particles between orbit and Earth's surface, and another one was they entangled particles inside a fiber optic network, 50 km, which is about city size. And so then the suspicion is, with entangled particles, you might be able to make a secure Internet. Un decodable. Unhackable. Unhackable. You can't. You can't decrypt encryption. Wouldn't make a difference at that point. Right. Because it's. So. Is this. Is this a pipe dream?

Well, it's very hard, because once you get beyond a few particles, it becomes harder and harder and harder to remain, all of them being entangled with each other. And that's ultimately what you need. But that's a technology problem. It's not like you're violating the laws of physics. So we're setting our best engineers on it, trying to build quantum computers, etcetera. Get a bread, engineers. You fixed it. You do that. We've shown it's conceivable. What do you want from us? Yeah, what more do you need? The math works. Yeah. All right. Johnson. There's no law of physics against it. Exactly. You know, the engineers who said, we will never fly faster than sound did not get that from a physicist. That's right. Okay. Because we rifle bolts went faster than sound, and the crack of a whip is faster than sound. We had that. So, back to this. Can you foresee a value to a 50 kilometer quantum entangled network the size of a city?

Mostly, that's just showing off. I think it's much more important technologically to have 1000 or a million quantum entangled things very close to each other. Then you can manipulate them, build a computer, do things. Isn't that what goes on in a quantum chip? Isn't there a lot of entangled like it to be? It's very, very hard because literally any photon that bumps into them messes things up. That's why you need to push it down to absolute zero or very, very close. Oh, I had not fully appreciated that. Yeah. The photos I saw, most of that was just like, refrigerator, the door, the freezer compartment, just to have the little bitty thing in the middle. Otherwise, because, like, you and I, radiating our infrared all over the place, would. Would totally decohere those quantum bits. That would be the opposite of cohere, which is what this conversation makes me feel like. Are you decoherent? I'm decoherent.

Catch us up on entangled particles. Well, this is part of this fact that we said before that there's not a separate quantum wave function for every individual thing in the universe. There's only one wave function for all of them at once. And what the wave function tells us is the probability of observing something. So, if you have two particles and let's say they have positions, you don't know where it is. In fact, literally, when something like the Higgs boson decays, decays into an electron and a positron the anti electron. And you say, well, what direction are they going in? And the answer is, they're both going in all directions. Their wave functions are coming out sort of in a spherical pattern. But then when you observe one of them, that's where it is. That's where it is. And momentum is conserved. So now you know the other one is going in. Exactly. So you know where the other one is without having detected it yet. That's entanglement.

So what entangles them? The rules of physics. Okay, that doesn't. That's not. Stop it. That's just the ending. That's my mother saying. Because I said so. That's what that. Mom, why can't I have ice cream for breakfast? Because I said so. That's why I. What law of physics prescribes this? quantum mechanics. That's the nature of quantum mechanics. This is how science works. You sort of conjecture an idea, then you say, is that right or not? And so, in quantum mechanics, the fundamental way things work is that the state of the universe is a vector in hilbert space, which means that the combined state of every particle in the universe and every field and every. Everything is described by one single mathematical object. And, in fact, I don't like the word entanglement, because it kind of. It makes it hard to update your intuition.

It makes it sound like what really exists are these two particles. And you measure one, then you're like, why did the other one change? If you just accept that what exists is the combined quantum state of everything in the universe, then it's no surprise at all that when you look at a little bit of it, it affects the rest. Okay, but interesting. Can I just take two random particles? Okay, that's. I gotta admit, that makes a lot of sense. Can I take two random particles that were not born together and entangled them? Sure. Okay. Yeah. Entanglement happens whenever you have two objects that are not entangled, but they interact with each other in different ways depending on different parts of their wave function. So let me just give you a down to earth example. Schrodinger's cat. You've heard about this. Schrodinger, who apparently didn't like cats, goes to a great amount of thought experiment, effort to put a cat in a superposition. That's right. That would have never worked with Schrodinger's dog. That would not have flown Schrodinger's daughter. People wouldn't have had it said that he didn't like cats. Right. Okay. This is why he picked the cat.

So it's in a superposition of alive and dead. I'm a cat person. So in my version, they're a superposition of awake and asleep. It's very sweet. You don't have to kill the cat. You don't have to kill it. I didn't know you didn't have to kill the cat is you don't have to kill the cat. But the point is, there are different places in the box, okay? And what that means is that everything in the box, the air, the light, you know, everything moving around in the background, interacts differently with the awake cat running around trying to get out, and the asleep cat just snoring peacefully on the ground. And so the environment, as we say, entangles with the cat right away because it interacts with it, but interacts with it differently depending on different parts of the wave function. I don't know that that's more clear to me. So you're sleep and awake cat. But we declared that without actually sticking sleep and awake cat in the box. I mean, we're just asserting that. Why does that make it let the cat just be drowsy in between? I'm in and out.

This is Schrodinger's whole point. This is why he set up in the experiment. There's a radioactive thought experiment he didn't clear. So radioactivity. And there's a Geiger counter. And the Geiger counter will click when it detects radioactive decay in radioactivity. You have no idea which particle is going to decay, okay? Just statistically, you know very accurately what fraction of them will. But the fact that you don't know creates a brilliant, beautiful random number, in a sense. Yeah. Okay. So if you needed a random thing, you get a decaying set of particles, and you can build. You can draw randomness from that. That is as good a random as we can predict. 100% random, as far as we know. As far as we know. Nothing better. And this is the 1930s, when Schrodinger was very unhappy with the state of quantum mechanics. He was not bragging about quantum mechanics.

He was saying, surely you don't believe this? And he says, when we say this particle has a probability of decaying, what quantum mechanics actually says is there's a wave function for the particle, and it is in a superposition of. I have decayed, and I have not decayed, and the part of it that is decayed sets off the Geiger counter. Now, the Geiger counter is in a superposition of I have clicked, and I have not clicked, and the Geiger counter in the part that clicks, knocks over a hammer, breaks a vial full of sleeping gas, and the cat goes to sleep. So the cat goes into a superposition of being awake and being asleep. That's the whole point of the sort of Rube Goldberg Gizmo that Schrodinger builds in there. But how does that help anything?

Well, Schrodinger's trying to say in the way that we thought of quantum mechanics back then. There was these giant debates between Bohr and Einstein about what quantum mechanics really means. Niels Bohr and Niels Bohr would have said, look, when you open the box and look, the cat suddenly changes from being in a superposition of awake and asleep to being one or the other. And Schrodinger is like, come on, you think that when I look at it, it changes like that? I gotcha, I gotcha. So his thing is that superposition exists at all times, everywhere, no matter what, and it has nothing to do with the fact that I looked at it. It's in that superposition. You just gotta accept that. He should have said that. He blinked. He lost courage at the last second. And it was a decade and a half later, or two decades later, a graduate student at Princeton named Hugh Everett said exactly those words. He said, just believe what the formula is telling you. And what the formula tells you is when you look at it, guess what? You enter into a superposition. There's a part of you that has seen the cat awake and a part of you that has seen the cat asleep. And Hugh Everett says that's because both of those possibilities exist just in two separate worlds, because what we're dealing with is a probability in the first place.

So that always exists. It doesn't change because you observed it, but it's still the scares. Well, you just mentioned in that world, I have some memory that I haven't heard about lately, but that there was the copenhagen interpretation. Yeah, that was Niels Bohr. Niels Bohr is danish. And so they credited, I guess, the city. But it was really a Bohr interpretation, not a Copenhagen. Well, he had his people who would come into his institute and hang around and go out spreading the gospel of Boer. So this was the idea. Heisenberg, Pauli. There's a bunch. There's a bunch. Okay. So can you catch us up on the many worlds interpretation? Right. So the copenhagen interpretation really frustrated people like Einstein and Schrodinger because it seemed to give up on arguably the single most crucial feature of science, which is realism about the physical world. You know, before quantum mechanics came along. You knew there was a real world out there, even if you didn't know exactly what it was doing. And Bohr and his friends seem to be saying that before you open the box and look at the cat, there is no fact of the matter about what the cat is. And Einstein, Schrodinger said, even if you don't know what the fact of the matter is, there should be some.

And so Everett sort of lives up to the dreams of Einstein and Schrodinger and says, yes, there is a reality there. But sadly for you, the reality is there's many different worlds, and they don't interact with each other. So Everett is just saying that in this world of superpositions that quantum mechanics always describes, you should just take them all seriously. They're all actually there. It's not just a mathematical trick. That is really, really tough. I get it. It is rough. You got the sleepy cat, you got the sleep cat, you got the awake cat. Is there a world where I open the box and I see the awake cat as a different world from the one in which I open the box and it's asleep? There is. There are. Well, there will be two worlds, and it happens long before you open the box, because as soon as the other stuff in the box, as soon as the photons and the atoms and everything become entangled with the cat, boom, there's two worlds. So where are those two worlds? Or is that the wrong question? That's the wrong question. I see that you quickly got it as soon as you asked it. You knew. No, I knew.

The worlds are not located in space. Space is located in the world. He knows it. Chuck gets it. He gets it. Chuck, I need you for. No, there is no God. Oh, no. I mean, that's also true, but whole nother podcast. Wow, that is so cool. I mean, that is really, really freaky, trippy cool. And many, many people believe this. Not everyone does. So it's something we don't have a consensus for. The people who don't believe in. Have a better experience. Yeah, I was gonna say, if you don't believe that, then you gotta go back to what we were just talking about, which is the Niels Bohr. Now you're actually. I'm sorry. That sounds more like magic. That doesn't. That sounds like magic to me. Like, I opened it up or I looked at it, or because I looked at the electron, that's when it is where it is and became what it became. Why would that be? Why.

I mean, why would that ever be? I have to clear something up here. Go ahead, please, before. Help me out. Okay. Let me just clear something out. Go ahead. In physics, we talk about the observer, okay? On many levels. And in quantum physics, the observer is not simply some conscious entity looking at it. Right. I understand that. If you want to make a measurement, you have to, like, shine light on it. You have to interact with it in some way. And what happened over the years, over the decades, is like, there was, like, a new age movement that was convinced, after hearing this kind of vocabulary, started saying, oh, it's our consciousness that's affecting the outcome. Look at it. It's your brain energy going into the thing. Yeah, that's like some quantum field of dreams stuff. That's crazy. That's crazy. So you get a lot of this new age look. They're coming back to absolutely respectable physicists who said exactly things like that. No, really? Oh, yeah. No. Wigner Pauli. Yeah, they actually. Oh, yeah. Oh, yeah. Okay. But they're all dead now.

Look, quantum mechanics is forcing you to make some hard decisions about how reality works. And so they're all freaky one way or the other. Either there's many, many worlds, or you bring it into existence by looking at it, or there is no reality. And, you know, none of them are exactly what we grew up thinking. The startalk interview with physicist Sean Carroll had some spillage that didn't fit in what we posted to the general public. It was at that meeting where I met Seth MacFarlane. Oh, cool. If she continues to do what she does, and successfully, so it will ruin Neil's chances of ruining every other movie. Oh, when I saw the Thor movie, I always wondered, how much does that hammer away? We all wonder this, right? Mjolnir forged in the heart of a dying star, and I said, yes, I got this. The heart of a dying star.

If you want to get the rest of that content, either become a Patreon member and that gives you access, or if you're already a Patreon member, go right on in and continue that episode. Quantum physics, you'd agree, is the most successful idea of the universe we've ever had. Yes. Yes. Nothing comes close. So I can exist in my macroscopic state because the quantum averages of me make me a physical object. That's fair, probably, to say, okay, I see what you're saying. I got you. So I can still be described by quantum physics. That's just not as convenient as newtonian physics. And all the light in the room is constantly measuring you and localizing you. Okay, yes, exactly. Exactly. Okay, so now are you here at the moment? You're here right now. Okay. So if all the quantum phenomenon average out into my macroscopic state, is there any quantum manifestation in the large scale universe?

Oh, yeah, sure. Our favorite has to be the microwave background. The cosmic microwave background. Right. Now, we don't know this for sure, but you look at the relic radiation from the big Bang. Okay. Big Bang, 14 billion years ago, was hot and dense and glowing. About 300 and some hundred thousand, 380. I think 1000 years after the big Bang, it became transparent. And so we see the relic radiation from the big bang, and for reasons we don't completely understand, it's super duper smooth. It's almost exactly the same temperature of radiation from place to place, but it's not exactly the same direction. You can look at this direction, every opposite direction, completely opposite direction. Right. And we have the temperature in this office is nowhere near that stable. Right. Right in this corner, it's like two degrees higher. Three, five. And what's it's. You're saying one part in 100,001, part in a hundred thousand difference in temperature from this side of the universe to that side of the universe, and it's that uniform all the way across? Yeah, that's right.

Insane. That's insane. That's insane. And my office can't. Wow. But that really does kind of forces your hand that you know, that all of that, the big bang happened and that it came from this one thing. It had to come from the one thing, because that's the only way as it spreads out that you can get that kind of uniformity, is that it comes from this one thing. That's right. And the best theory that we have for why it's so uniform is called inflation. You might have heard before the universe expands at some super fast rate very, very early on. And it's very much like stretching your sheet on your bed and smoothing it out. Right. It wants to smooth it out, but something gets in the way. quantum mechanics. So quantum mechanics says you're trying to smooth out the universe the best you can, but when you measure it, there'll be little ripples. And we think that those tiny variations in temperature, one part in 100,000, come from the quantum mechanical uncertainty in the state of the universe at early times. And of course, those grow into planets and stars and galaxies.

It has left its paw print in the picture of the early universe. Right. Oh, man. Another way. Am I right to say that had it been completely smooth, it's not clear that we would have made galaxies I was gonna say, would we even be. Exactly. These fluctuations give us the seeds on which you collapse matter. Yeah. All right. That is so nutty. But let me bring up one other important manifestation only if quantum mechanics understand it better. Hopefully, you will not. If it regresses, the chair is solid. That's all because of quantum mechanics. You know, you've seen the picture, the cartoon of an atom, right? Little nucleus in the middle, electrons orbiting around like it's a solar system. That can't be right, because if you get a bunch of atoms together and they're all little solar systems, they would just squish together. It's not right, that picture, because the electrons are not little point particles moving in orbits. They're wave functions that have a size. They take up space. And the reason why the chair can be solid is because the wave functions of electrons in the atoms take up space and don't want to overlap, and therefore, matter has extent in space.

One of my favorite stories was, was it from the book night thoughts of a classical physicist? Oh, yeah, Lewis. Oh, no, that's not Lewis. No, no, maybe. No, I'm misremembering. So, either it was fictionalized in that novel, or I'm remembering it as a. As a memoir from Ernest Rutherford, who first showed how empty the atom is by passing. Was it neutrons or alpha particles? Alpha particles. Okay, so he's got gold, he's got helium nuclei, and he has a very thin sheet of gold, because you can hammer gold. Very, very thin. And so he wants to get, like, the fewest width atoms of gold foil that he can possibly get. And then he starts firing particles through it, and, like, nearly all of them just go straight through, untouched, undiverted, nothing. And then he alone, at that moment, realized how empty matter was. And this is the story where I hear that the next morning he woke up. He was afraid to step on the ground out of fear he would fall through the floor.

Is this just apocryphal, the last part you might have made up? I don't know about that one. But the story you can read about in my new book, Quanta and Fields, where I explained this, the idea that it's empty, I don't like it when people say that, because what Rutherford really figured out, because you're a field guy. Well, the fields, they matter. But what he really figured out is that most of the mass is at the center, in the nucleus. And so it's not just that they mostly pass through that's important. Also, very occasionally, one ricochets right back at you. So it's not just that the gold is sort of spread out and diffuse. There's some oomph there right at the middle in the nucleus of the atom. Just while we're fired up here. What's the latest thinking on dark matter? dark energy. Where should we see future advances? Just looking for a dark matter particle. Are you all in on a particle thing? You got some other exotic.

I'm happy for it to be a particle. I've proposed theories where it's not a particle, but they're not very good, these theories. The dark matter is probably kind of a particle. We haven't found it yet. And I would say that, you know, we had a chance of having found it already. The experiments are pretty good, but it wasn't like a 99% chance. It was like a 50% chance we would have found it already. So the fact that we haven't found it already is not yet cause for concern. Okay. The dark energy is interesting again, I've written papers about different possibilities for that, but the simplest one is the best. Einstein's idea that there's energy in empty space. It's just a fact of the matter. Every cubic centimeter of space as 100,000,000th of an erg of energy inherent in space itself. Erg is a unit of energy pushing the universe apart. And so we don't know. In fact, there was a provocative recent result from the dark energy spectroscopic instrument, which claimed that maybe the dark energy is declining very slowly. That desi dark energy spectrum.

But there's like three different experiments whose digname is desi. So I actually like to use all the words. Okay, this one. That's a different one. Exactly. Yeah, yeah, I. So we don't know. That would be very, very fascinating and exciting that the dark matter field is changing. dark energy field. dark energy field slowly declining with time declining. Now, is that allowed? If the Einstein's cosmological constant, which was our first indication that there might be this thing such as dark energy working opposite gravity, that is identically a constant, the way it comes out. That's right. So if this is true, then the cosmological constant is not the dark energy. The dark energy is something else.

The cosmological constant, the vacuum energy, which are equivalent. That was a candidate. That's one possible thing. The dark energy could be the simplest. Appreciate that. And it's a leading candidate because it comes out of the leading candidate. We're using the equation anyway. And it was already there. That's right. Everything else is a little bit more delicate, a little more fragile, hard to figure out, but post martial constant is pretty easy. Just put it in there. This has been exhausting. One last thing, just as a teaser for your next book. When I think of emergence, I assume you mean it. In the tree of life, there are life forms that have features that cannot be deduced from their biological form. Like flocking birds. Right. You can't analyze anything about a bird that we know of that will tell you that they will flock with other birds.

Right. So you will not be surprised to learn there's a lot of philosophical controversy about these concepts. But basically, yes. The point is, as you said before, we can get through the day talking about people and tables and chairs without knowing that they're made of atoms or quantum fields. So there's different levels of description that all seem to work. They have to be consistent with each other. But you don't need to know about your quantum fields to get through the day or balance your stock portfolio. Just go through. Yeah, emergence. There we are. There you go. Urgent consciousness. Free will. Yeah. All part of that. That's part of emergence. Yeah, yeah.

The more I think about free will, the less I think we have it. It's. It's. I've. I've not reversed in this vector direction. I'm headed about some momentum. Yeah, it makes sense. I mean, what if you stripped away everything? Would you then have free will? So if you don't have free will, then what you're talking about is there has to be an influence put upon you. No, no, I'm gonna take whoever said it. You'll know I don't think we have free will, but what choice do I have? Somebody said that? Who said that? That's funny. I don't know that one. There's, like, a funny one philosopher joke. Like, you know, you walk into the restaurant and they say, what do you want? And say, I'll have whatever the universe says I'm gonna have. Like, I have no choice about what it's gonna be.

But I don't think that's the right way to talk. I think I do have the ability to make choices. Well, I've heard you on other podcasts. Give for me what was most resonant account of free will that I can think of, while others were spouting off all manner of things. So I felt very in your club. All right, I got your back on this one. Good, so we don't have time for that here. But other. Oh, man. You can't leave me hanging like Godfrey. No, let the man. There's another book coming out. We gotta bring it back. How to be good. Bring it back. He used to be in California. He's now just down the street in Baltimore. Excellent, Brett. Yeah. One train wide away. We can totally do that. But are you going to make that trip?

I mean, seriously, I'm literally here right now. Where are you? I was going to say, how would I know his vibrational energy is here? It's a probability. Otherwise, don't know. Sean, delight to have you in my office here at the Hayden Planetarium, the American Museum of Natural History. Thanks for making the trip. You're on a book tour right now, so good luck with that. Sometimes you need a little bit of that and keep the physics coming. I will do that. Absolutely. Thanks for having me on. There's surely an unlimited appetite for the cool stuff. Lots of cool stuff in the universe. All right, Chuck. Always good to have you, man. Always a pleasure. All right. This has been the latest update on the moving frontier of the universe through the lens of theoretical physicist Sean Carroll. I'm Neil degrasse Tyson, your personal astrophysicist. As always. Keep looking up, Sadeena.

Science, Philosophy, Education, Quantum Mechanics, Entanglement, Cosmic Phenomena, Startalk