Daniel and Kelly’s Extraordinary Universe - What is Quantum Tunneling?

Episode Date: July 2, 2019

Hint: It's not tunnels in switzerland. Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

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On the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want or gone. Hold up. Isn't that against school policy? That seems inappropriate.

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Hey, Jorge, are you any good at bowling by any chance? I am either the world's best or worst bowler. All right, but when you go bowling, Do you ever get any, like, gutter balls? I can't deny that I get gutter balls? All right, but are you so off the mark that sometimes your bowling ball ends up, like, in the next lane? I also can't deny that that's ever happened to me. Oh, man.

Well, in that case, you might have a special physics distinction. Oh, how's that? You might be the world's first quantum bowler. Is that another TV show, like Quantum Leap, but about quantum bowling? That's right. It's the Big Lobowski meets quantum bowler. Quantum Leap. It's my new pitch. Hi, I'm Jorge. I'm a cartoonist and the creator of PhD comics.

And I'm Daniel. I'm a particle physicist, a terrible bowler, and the co-author of a book with Jorge called We Have No Idea about all the mystic. of the universe. So welcome to our podcast, Daniel and Jorge Explain the Universe, a production of I-Hard Radio. That's right, in which we take things around us in the universe that we find amazing or crazy or wet and sticky or just weird and interesting, and we try to explain them to you. That's right, all the strikes, all the gutter balls, and all the spares out there in the universe. That's right, even the splits. We'll roll it right down the middle for you and into your brain. Sometimes there's even a spin on the ball, right?

I have no idea how to do spin on a ball. I see people do that. I've tried to do that. It's failed miserably. I'm all about the straight grandma role. Spin actually helps you. You think as a particle physicist, I'd be all pro spinning balls and all that stuff,

but I found it impossible. My wrist almost breaks every time I try to do it. Well, on the program, we usually talk about topics that people have questions about or people are really curious about, about the universe, about physics, about how the world and how reality really works. And so today we're tackling a pretty interesting topic, right, Daniel? That's right. This is a topic people wrote in and asked us to explain.

And I think it's because they hear talked about it in physics podcasts and you read about it in physics books. And there's a bunch of online videos talking about it. But frankly, there are very few actually satisfying explanations. And I think people wanted us to dig into it and see if we could explain to them what's going on. It's definitely one of those topics that sound cool, for sure. Like just those two words put together. Well, anything after quantum sounds cool, right? Quantum banana. Quantum bowling. Even that sounds interesting.

An evening of quantum bowling with Daniel and Jorge, that sounds like an event you'd pay 20 bucks to go to, right? Well, today on the program, we'll be tackling a subject that almost seems like magic maybe and that a lot of people associate with perhaps teleportation. The idea that maybe you can move from one spot to another spot kind of instantly or through a wall or something like that. on the podcast we'll be talking about quantum tunneling. Quantum tunneling is one of my favorite topics because it's one of those really weird effects you see in quantum mechanics. You know, when you zoom in on the world and you discover it's microscopic nature, you try to understand it in terms of things we know and understand

and your brain is trying to use particles and waves and all this stuff. This is one of those effects that really just stumps us when we try to explain it in terms. of macroscopic things. We try to get an intuitive handle on it. And so it just shows us that the world is so different from the world that we actually understand. I guess my question, Daniel,

is, am I going to spend this episode complaining about the naming of this effect? Like, is this really like a tunnel? Like every other episode. Like every other episode of this podcast? Probably, yes, probably. We'll spend most of the time you complaining about the name

and me trying to argue that the physics version is different from the cultural version or whatever. There's poetry and physics. There is some poetry and physics. There's also plenty of clumsiness. Now, this is a fascinating topic because it's the kind of thing that's really impossible to explain in terms of classical analogs.

You know, things that you have intuition for, particles and waves and bowling balls. It's just something that those things can't do. And so it opens the door in our minds. It says the universe is weirder than you will ever understand, right? And that's the kind of thing that got me into physics, you know, the review. revealing that the universe operates under rules, but rules that are weird and in some ways alien to the world that we know. So, yeah, it's got two cool words, quantum and tunneling. And so, I don't know, that makes me think of like something that drills deep down into the quantum realm or, you know, something that lets me, like, travel to the quantum realm or something.

What is the quantum realm? Where is it? How do you get there? That's a whole other podcast episode. It's on the Admen movies, obviously. All right, well, we'll have to have Paul Rudd on as a guest and Michael Douglas, since he's Professor Pim. I mean, they can explain to us all about the PIM particles in the quantum realm. But you're right, quantum tunneling does have a really cool sound to it.

And so as usual, I was wondering, like, what do people know about quantum tunneling? Do people, does everybody already understand this? We don't need to explain it, or is it a huge mystery? Do people have misconceptions? And so I walked around campus at UC Irvine and it costed friendly strangers to ask them. So before you listen to these answers, think about it for a second. If somebody asked you randomly on the street and didn't give you the option of Googling it, would you know what quantum tunneling is?

That's right. No Googling allowed. Here's what people had to say. Do you know what quantum tunneling is? No. I don't know. It makes me think of like mountains in Switzerland and how they have to like build tunnels underneath them. And then that's where Surin is. So there's probably some quantum tunneling down there. I have. Can you explain it? No.

I have not. No. Not really. No. Probably not. I've heard of it, but I'm not sure what the concept is. I don't know. What's that meaning?

No, I have not. I have not heard of that. I have not. Something has to do with light and how electrons flow around. Something like that. All right. Not a popular or familiar topic, about half the people that had never heard of it. That's right.

People were pretty clueless, though. Some people were pretty creative. I love the answer about tunnels near CERN. That was very creative. Yeah, they said that it made them think of the tunnels underneath the mountains of Switzerland because Switzerland has tunnels and they do physics experiments. So therefore, two and two together, obviously that's what a quantum tunnel is. It's not a terrible answer.

Like, you know, what kind of tunnel do you need to build a large Hadron Collider? You know, hey, a quantum tunnel, right? A tunnel in which you do quantum experiments, that's not a terrible answer. Maybe that's more of a quantuming tunnel. And the truth is the Swiss are awesome in building tunnels. They sort of have to be because they're surrounded by mountains, but they really are world class in building these tunneling machines. And so it's no surprise that the Large Hadron Collider is in Switzerland

because that really is the best place to build tunnels for your quantum experiments. Yeah, they have to dig all those tunnels to burial that money that they keep for rich people. All that illicitly gotten gold, you know. Hey, what do I mean? I have a Swiss bank account in my dreams. Well, you know, true story. I discovered by opening her mail that my wife has a. Swiss bank account. She has a retirement plan in Switzerland.

All right. What other secrets have you discovered by opening her mail, Daniel? Oh, no. The best part of the story is that she didn't know she had a Swiss bank account until I told her. Feels like a born movie here. No, it has actually a pretty mundane explanation. When we were in Switzerland, so I could work on the Large Hajon Collider, she had a job working in research in Switzerland.

And unbeknownst to her, they opened an account in her name. and deposited some retirement funds there and then we discovered it later and like, oh my gosh, look, Katrina has a Swiss bank account with money in it. That's how banking works in Switzerland. They just give it away. Yeah, exactly.

So, yeah, she has a Swiss bank account, but I don't. Well, anyway, so people were not very familiar with quantum tunneling, which means that, hey, we can talk about it on that podcast. That's right. It's an awesome topic to demystify. First, we'll explain what it is, and then we'll explain how it works

and how it's not teleportation. Right. That's my big question, is, Is it like teleportation? Is it associated with teleportation? Can we teleport with quantum tunneling? All right, start us off, Daniel. How would you describe what quantum tunneling is?

So I think the best place to start is to sort of warm up our intuition. Like, let's think about this problem using things we're familiar with. And then we can make the analogy to the quantum version. We can understand where that breaks down, like where our intuition goes wrong. So let's start with our intuition. And the kind of problem we're trying to describe is sort of like, playing with a bowling ball inside an empty swimming pool. Let's just go for the bowling ball and swimming pool.

Yeah. I mean, isn't that a familiar thing? When you see a empty swimming pool, don't you think, I wonder what would happen if I threw a bowling wall in there? Well, let's give our listeners just a quick idea of what we're talking about. So quantum tunneling is kind of this idea that a particle, or in the usual case, it's an electron, it can sort of be on one side of a barrier in one moment,

And then the next moment, it's on the other side of the barrier, right? The general idea of quantum tunneling is that it's really hard to keep electrons in a little trap or in a little hole. That they really, they're hard to pin down. And people are probably familiar with that because the Heisenberg uncertainty principle, like, you know, you can't really isolate a quantum particle in one little spot in space very long. But, you know, if you try to do it, then, you know, eventually it's going to leak out. And the point of quantum tunneling is that electrons can build these tunnels or burrow through. these barriers to, you know, adjacent little holes or adjacent little wells. So that's the idea is that it's like you have a particle and there's a barrier in front of it.

And at some point, it just moves to the other side of the barrier. Yeah, exactly. You can see it on one side of the barrier. And even if it doesn't have enough energy to get over the barrier, sometimes you see it on the other side. And then you have to ask like, how did it get here, right? Right. Like spontaneously, it just appears on the other side or what? Yeah, well, sometimes on one side and then it's on the other side and then it goes back, right?

And there's a lot of interesting stuff there about like, you know, if the particle was here and then later it's there, how did it get from one place, from the first place to the next place, right? In your mind, you're used to things. If it's in one spot and then later it's in another spot, you imagine it took a path from one spot to the other spot, right? That's the way classical things work, baseballs, hamsters, whatever. But that's not true for quantum objects. Quantum objects are here and then later they're there. And there is not necessarily any path between those places. is that the particle took. It didn't move. It just was here and then it was there. Yeah. It's frustrating because quantum particles don't have this underlying hidden truth, right? It's not like there is a true story about where the particle was at every moment and we just don't know it. It doesn't have that story.

That story doesn't exist. You know, it's in a location only when you ask, where is it? And then it's in a location later when you ask, where is it? You're saying particles don't really have a here or there. it's like they're around here well they have a here like at some moment you can say it's here and another moment you can say it's there but you can't connect the dots

right you can't say that there must be a line between those two dots and the particle took that line or there doesn't have to necessarily be a line it's just here and then later it's there it's you know it's like frames in a movie but without the intervening

connections like if you're watching a movie you know the person would be standing here and then suddenly they'd be standing over there and then they'd be studying this other part of the frame, right? Almost like they were teleporting between spots.

I was just going to say that. That's not teleportation, right? When you're watching a movie and you know and you watch this frame by frame, you don't imagine they're teleporting from frame to frame, right? You're just saying, well, I know he's here at this frame and it was there at that frame, right? That's not teleportation.

You're saying a quantum particle doesn't have a path between these two things. If you ask it where it is, it'll just kind of pop around all over the place. Yeah, you can ask the particle where it is and it will answer, right? And then later you can ask it where it is and it will answer, but you don't necessarily know anything about where it is in the intervening time and you can't assume that there's some classical path. You know, if you ask, where's my baseball and what's its velocity, right? Then you can actually predict exactly where it's going to go at any moment. And so it has this thing we call the classical

path. It's position and velocity at any point in time. And when you're looking at it, you're just sort of sampling that, right? But for a quantum particle, that doesn't exist. You can ask where is it, and you can ask where is it later, right? But you can't connect the dots between those two and assume that there's a path that it's following. Well, this is a perfect point to take a break. kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently, the explosion actually impelled metal, glass.

The injured were being loaded into ambulances. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and Order Criminal Justice System is back. In season two, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts.

My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Oh, wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor, and they're the same age.

And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. I'm Dr. Joy Harden Bradford. And in session 421 of therapy for black girls, I sit down with Dr. Othia and Billy Shaka to explore how our hair connects to our identity, mental health, and the ways we heal.

Because I think hair is a complex language system, right? In terms of it can tell how old you are, your marital status, where you're from, you're a spiritual belief. But I think with social media, there's like a hyperfixation and observation of our hair, right? That this is sometimes the first thing someone sees when we make a post or a reel is how our hair is styled. You talk about the important role hairstylists play in our community, the pressure to always look put together, and how breaking up with perfection can actually free us. Plus, if you're someone who gets anxious about flying, don't miss Session 418 with Dr. Angela Neil Barnett,

where we dive into managing flight anxiety. Listen to therapy for black girls on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Okay, so then the idea. of quantum tunneling is that a particle is on one side of a wall or a barrier, and then the next instant it's in the other side of the barrier. And so what we want to do here today is sort of explain how that happens and why it's not teleportation. Yeah, exactly. How does that happen? And what does it mean and why it's not teleportation? And so you think a great way to think

to get into this topic is to think about bowling balls and pools. Yeah. Well, I mean, what is a barrier after all, right? Like I think people think about electrons as tiny little balls. So I was thinking about let's use a bowling ball because that's macroscopic and what is really a barrier right i mean people might be thinking like what kind of barriers are we talking about and so let's imagine a macroscopic barrier like a familiar one right you're at the bottom of swimming pool with a bowling ball by the way this is this amazing video of a guy this one inspired me is this amazing video online of a guy with the bowling ball in his swimming pool and he can do these hilarious tricks where he puts like the pins behind him and he rolls the bowling ball and it does these crazy moves and he knocks off all the

pins. Anyway, so you're at the bottom of the swimming pool with a bowling ball, right? And what happens is you just put it down? Let's make it clear. The pool is empty. I'm not drowning here. That's right. I'm not... Empty swimming pool, yes. I'm not holding it onto a heavy ball and sitting in the ball. I'm wearing scuba gear. No, let's not make this any more complicated. Yeah, it's an empty swimming pool with a bowling ball. But let's also make it clear. It's one of these swimming pools that has a curved floor, right? Like a bowl-shaped floor, right? Like if it's a swimming pool with straight edges at the bottom, this is not going to work. That's right. Also, there's no like chainsaws or, you know, traps or, you know, rabbit hamsters or anything else in the swimming pool.

Just, you know, to be clear. Just the bowling ball in an empty curved pool. You know, or if it's easier for you imagine a grape in the bottom of a bowl or whatever. But the point is, what happens when you put the bowling ball at the bottom of the swimming pool? It just sits there, right? It doesn't leave. You're never going to find it in your neighbor's empty swimming pool, right? It's always going to be in that pool. And the barrier in this case is the edge of the swimming pool. You mean like if you don't touch it, if you don't push it, if the wind doesn't blow, it's just going to stay there. That's right, exactly.

And you expect it to stay there. You don't expect to come by one day and find it in your neighbor's swimming pool, right? The idea is that if something does disturb it, like a raccoon comes by and pushes it, it's just going to roll back down to the bottom of the pool again, right? That's kind of the idea. That's right, exactly, because the walls of the pool are the barrier, right? That's what we talk about. It's a potential barrier.

And if a raccoon comes and pushes it, you know, and he pushes it, you know, as hard as a raccoon can, then it's going to roll up and then it's going to roll back down. And it might roll back up the other side, but it's never going to roll higher than it went originally, right? It's just going to eventually relax down to the bottom of the swimming pool. And so if you don't give it enough energy to go over the lip, then it's trapped in the pool, right? It's never going to get out of the pool unless it has enough energy to go up and over the edge of the swimming pool, right? And so that's the barrier.

Like, that's the wall. Yeah, exactly. And your intuition says it's trapped, right? If you don't give enough energy, it's never, ever, ever, ever, ever, ever, going to end up in your neighbor's swimming pool, right? That's where your intuition says, right? Unless there are some really strong raccoons,

but that's a different... I don't know what kind of neighborhood this is with all these empty swimming pools and, like, tough gangs of raccoons pushing bowling balls. But we're sketching out quite the science fiction dystopia here. But, yeah, you don't expect it to ever

be able to get out of the pool by itself. That's right, exactly. That barrier you can consider it to be perfect, right? The only way to the next swimming pool is to go over the barrier, right? You can never go through the barrier. These raccoons are not tough enough to throw the bowling ball, like, and crush

the ground and get through it, right? Wait, what if they're Swiss raccoons and they dig a tunnel? Yeah, or they're like superhero raccoons, like in one of those Marvel movies, is some, isn't there some super raccoon, or is he just look like a raccoon, and he's not actually a raccoon? Technically, a genetically modified raccoon.

Aliens that look like human, like Earth raccoons. I never quite figured that one out. But we digress. We do. We do digress. That's the analogy, right? Now, instead of the bowling ball, think of an electron. And instead, when we talk about barriers, we're talking about, you know, barriers to that electron. So maybe made by other particles, you know, protons or something.

that would repel it, right? Something that you would build to try to keep the electron localized, like a little trap. Like a little magnetic field maybe, keeping it trapped or something. Yeah, yeah, a little magnetic field or electrostatic potential or something. Anything you can do to trap an electron. And people do this, right? They want to study individual electrons or individual ions. They build atom traps.

They're pretty cool. And so people actually do this. But it's also a good case study for quantum mechanics because it helps us think about how these things work and don't work. So it's a very popular sort of junior level quantum mechanics problem in college. So what happens? You put the electron in this little well, right? And it's like a bear. It's like a swimming pool. And you think if the electron doesn't have enough energy to go over the edge, then it's trapped, right? Just like the bowling ball. If it doesn't have enough energy, how could it ever get into the neighboring swimming pool? Well, the thing you find is that even though it doesn't have enough

energy, sometimes it appears in your neighbor's swimming pool. Like it gets through that barrier. It appears in the adjacent well. Like if you have a series of these potential wells, you know, these little traps made for electrons, and you put it in one, you can come back the next day and find it in the next one, even though it didn't have enough energy to go over that barrier. Even though it was trapped by a magnetic field, it somehow slipped out. Yes, exactly. And so that's what we call quantum tunneling, right? How did it get through the barrier? In principle, the barrier should bar it, right? That's what barriers do.

It should bar it from passing. Just the way the ground does, the end of the swimming pool does. So the question is, why does an electron not get stuck? Right, because if it tried to move, the field would push it back into the trap, but somehow it's able to slip out

or create a tunnel. Exactly, exactly. And your instinct might be to say, well, maybe it like momentarily goes over the barrier. Like, you know, I don't know, Heisenberg uncertainty, blah, blah, maybe it borrows a little energy momentarily gets over the barrier, right?

That's tempting because you want to think of the barrier as working. And so you want to think that if it's going to go to the other well, it somehow has to go over. But it doesn't, right? It can't. It's a conservation of energy. So that explanation doesn't work. The electron doesn't get more energy momentarily, magically.

It's just on one side of the barrier and then it's on the next. Like Zeus didn't come down and touch the bowling ball and push it into the other swing pool that's impossible. That's right. We're assuming that there's no other source of energy, right? And it never has enough energy to go over the edge of the swimming pool and into the next one.

So the only way to the other swimming pool is to tunnel, is to go through the barrier. And then once it's out and on the other side of the barrier, does it stay there or does it sometimes pop back in? Or does it fly off at that point? It pops back in. Yeah, it can pop back in and it can go to the next one, right? The point is that you can never really trap an electron. And the reason is not that it goes over the edge. And the reason is not really teleportation, right?

The reason is that these barriers at a quantum level are just different than the barriers we have here at the macroscopic level. And electrons are different from bowling balls. We like to think of them that way because it's useful, because the way we understand the unknown is to do it in terms of the known. But in the end, these things can do things. quantum mechanical things can do things that the classical things, the macroscopic things that we're familiar with just can't do. And one of those things is the electron, it has a chance to just ignore the barrier.

It's like every time it goes up against the barrier, a dye is rolled. And if it comes up, you know, all sixes, it's like, ha-ha barrier, I get to ignore you. You said every time it goes up against the barrier, meaning is it like it's always pushing against the barrier, or is it like a continual roll of the die or what? No, that's a good point. the way I was speaking about it was wrong because I was talking about it like having a classical path like it has a position and a velocity at every moment. In reality, its motion is governed by

this wave equation, right, the wave function that we use to describe where it is. And that tells us where it's more likely to be and where it's less likely to be. And we know that for it to get from one side of the barrier to the other, it has to go through the barrier. We know this because it can be inside the barrier. Like in principle, that should be impossible. Right? Like how can you be inside the barrier? You're not breaking the barrier. The bearer's not destroyed. But it can sort of like defy the barrier. It can sort of ignore the barrier. It has a probability to just sort of like shrug off the barrier the way a teenager shrugs off a curfew, you know. So the trap, the magnetic field that is trapping the electron doesn't affect the probability of where the electron can be or it does. Doesn't it? Doesn't it like squeeze the probability cloud of the electron or something like that? It totally does. It affects it, but it can't trap it completely.

It's just impossible to trap it completely unless the barrier is infinitely high. If the barrier is infinitely strong, then the electron is totally trapped. But as long as the barrier is not infinite, right? Imagine the swimming pool that's infinitely deep. Then the quantum mechanical bowling ball can't get out. But even if it's super high, if it's a billion miles high but not infinite, then the quantum mechanical one can get to the other side. It just has a chance.

But you're right, it does affect it. It squeezes those probabilities. The probabilities are shaped by the barrier. But you're saying there's still a little tiny probability that it's going to jump over. Not jump over, but go through, right? And the probability is smaller as the barrier gets wider, and it's smaller as the barrier gets taller. So that all makes sense. The thing that's confusing is like, how do you explain what it's doing in the barrier?

Is it just like ignoring the barrier? Does it just have a chance to avoid the barrier? it's hard to come up with a sort of like an intuitive understanding of what it's doing there. You know, it's like it's in the no man's land. It's in a place where nothing should be, but there it is. Right. Is it because the bowling ball is not really a bowling ball, right? It's more like a cloud, kind of like a fog.

And you're saying sometimes the fog can sort of extend and kind of appear on the other side of the swing pool. If you measure an electron, you say, okay, it's in my trap. And then you ask, where is my electron likely to be? in one second, then most likely it's to be, it's going to be in the trap. There's a little bit of probability it's going to be in the barrier, and there's a little bit of probability it's going to be in the next one, right? It's going to be in the next trap. So, you know, after you know where an electron is, it doesn't tell you where it is necessarily a second later. It's just, you have a probability distribution of where you're going to find it. And we can calculate those

probabilities using the Schrodinger equation, but that's, again, that's just a description of what we have observed. The Schrodinger's equation itself is not an explanation. It's just like a mathematical formulation that successfully describes what we've observed. Oh, I see. It's the probability of where it's going to be if you measure it. So if you measure it, there's a tiny little probability you're going to measure it in your neighbor's pool. Yes, exactly. And it's tempting to think, oh, well, that's just particles, right? Particles are here and then particles are there, right? That's not the property that allows the electron to quantum tunnel, right? You can have that property in an infinitely deep swimming pool where electrons can't tunnel, right?

In an infinitely deep potential well, right, the electrons can't get out. It's the only one that can completely hold them. But in that well, electrons can still be here and then later be over there and then later be over here, as long as you're still within the well. But if the wall is not infinitely high, then there is a probability that randomly it's going to ignore or jump over the barrier and be on the other side if you measure. That's right. Not jump over, but go through, right? Jumping over means Why not jump over? Well, jumping over means... Because you don't really know, right? You do know.

Like he was here inside and then it was outside and you don't know, you don't really know the path it took to get outside, right? Well, to get over, it would need to have enough energy to go over the barrier, right? And that energy has to come from somewhere. And we have energy conservation in our universe. And so it can't go over the barrier, right? It's like the raccoon pushing the bowling ball. If it doesn't have enough energy to push it over the lip, it's just never going to go over the lip. And the reason this works, we can do the calculations, and the reason it works is because the electron is in the barrier. Like quantum barriers are just different from classical barriers.

They're sort of optional. You just always have a chance to ignore them. You know, it's like speed traps. Sometimes the cop sees you and sometimes he doesn't. But if you find it inside the barrier, doesn't it mean it gained a whole bunch of energy? No, it can be inside the barrier, meaning that it doesn't have a lot of energy. enough energy to be there, but it's there anyway. Where does the probability come

from? Do you know what I mean? Like, for it to be probable, it needs to have some sort of physical explanation, doesn't it? Yeah, and the explanation is that the bowling ball analogy is wrong, because this is not a bowling ball, and these are not a swimming pool. It's a weird,

blobby, wavy, fuzzy thing that can do this thing that no bowling ball or swimming pool can do. And the barrier also is a little fuzzy, right? You can't build, it perfectly strong barrier unless it's infinitely high. In quantum mechanics, barriers are not the same as swimming pools, right? They're different.

And so the analogy breaks down. And these things can do things that the things we're familiar with can't do. And one of them is that sometimes they sort of ignore each other. With that, let's take a break. We'll be back in just a short minute. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal.

Apparently the explosion actually impelled metal glass. The injured were being loaded into ambulances, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and Order Criminal Justice System is back. In Season 2, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts.

My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Well, wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up.

Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor. and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him

because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the Iheart radio app, Apple Podcasts, or wherever you get your podcast. I'm Dr. Joy Harden Bradford. And in session 421 of Therapy for Black Girls, I sit down with Dr. Othia and Billy Shaka to explore how our hair connects to our identity, mental health, and the ways we heal. Because I think hair is a complex language system, right, in terms of it can tell how old you are,

your marital status, where you're from, you're a spiritual belief. But I think with social media, there's like a hyper fixation and observation of our hair, right? That this is sometimes the first thing someone sees when we make a post or a reel is how our hair is styled. You talk about the important role hairstylist play in our hair. community, the pressure to always look put together, and how breaking up with perfection can actually free us. Plus, if you're someone who gets anxious about flying, don't miss session 418 with Dr. Angela Neil Barnett, where we dive into managing flight anxiety. Listen to therapy for black girls on the iHeartRadio app, Apple Podcasts, or wherever you get your podcast.

but um and the interesting thing is that it's not just electrons right like this you're talking about all particles oh yeah electrons are just the simplest case but any quantum mechanical particle any particle that's motion is primarily described by like the schrodinger equation so single particles or ions or nuclei or whatever these things can do this also we see it all over the place it's actually an important part of lots of physical processes that we know and love. Well, I think it's interesting to think about the idea that, you know, these walls in the room that I'm in are sort of just barriers too, right? Like what's preventing my hand from going through the wall is not just my inner piece,

but it's like the electromagnetic forces between my hand and the wall. Exactly. And that, as you say, is a quantum mechanical barrier. Like the very tip of your finger, imagine that's an electron. When it approaches the wall, it meets a barrier, a barrier made by the electrons in the wall. And that's what's doing the repulsion. And so you're right, there's a tiny chance that first electron is just going to go right through the barrier instead of bouncing off of it. And I might lose that one electron from my finger.

You might. Or there's an even tinier chance that the next set of particles will quantum tunnel through. And an even tinier chance that also the next ones will. So there's some non-zero chance that you'll put your hand. through the wall without breaking the wall. That's crazy. It's a non-zero chance that I can walk through, or do I walk through the wall or appear on the other side or both?

I know this would be a Jorge quantum tunneling through the wall. Yeah, there's totally a non-zero chance. Now, you could stand there all day, your whole life, walking into walls and not successfully go through it, and I'm pretty sure that would be your experience, because the probabilities we're talking about are ridiculously tiny. Like, these barriers are pretty tall, and there's lots of particles.

It has to happen for all of them. And so it's basically impossible, but not technically exactly zero. So there is a possibility, Daniel, that you sitting right there where you are will suddenly find yourself on the other side of the wall that's in front of you, right? Exactly. There is a possibility. I could quantum tunnel into the bathroom or whatever. Let's say it happens right now.

Poof. Would you say you teleport it to the bathroom? I mean, what's the difference between that and actually teleporting? Well, we did a whole episode about teleportation, remember, and we decided that teleportation is impossible while this is possible. And, you know, it's really tempting to connect this, this idea of tunneling with the concept that quantum particles can sort of skip their way through life, right? They don't need to exist at every moment. So they're here and then they're there and the other thing. And so if you want to call this teleportation, then every particle is teleporting all the time.

So that's my problem with it. It's like, this is a natural thing that particles are all. always doing, even without barriers. Like, even a particle in an infinite box is doing this sort of skipping thing because it doesn't exist between the moments you're observing it. So if this is teleportation, then that's teleportation also. And everything is constantly teleporting. You're saying that we, you don't want to call it teleportation, not because it's not

teleportation, which I would argue maybe it is experientially. But it's just that if you call a teleportation, it would sort of dilute or break the definition of teleportation. Yeah. If this is teleportation, then we're all teleporting all the time. So if everyone is nice, then nobody's nice. It's kind of what you're saying. It's the teleporter's quantum dilemma, exactly.

All right. So that makes a bit more sense. And quantum tunneling is really important, like it happens in the sun. If you want nuclear fusion to happen, the kind of thing that powers the sun, that generates all that light that, you know, makes you look so nice and tan and grows all that food that you eat, then you need these particles to be able to quantum tunnel through some of the potential barriers that they face. You know, particles in fusion don't like to touch each other, right?

Because nuclei are both positively charged because of all the protons. So to get them to fuse, you have to push them together and they're repelling each other. And that's a barrier. So you've got to get them sometimes through that barrier in order to do the fusion. And you're saying sometimes they tunnel to that. But mostly, do they mostly get pushed together

or do they actually tunneled together? I think it's some of both. I mean, the center of the sun is so hot, so dense, that these particles can just sort of overcome the Kulam barrier, like they have enough energy. But definitely tunneling is an important part of it. Like fusion wouldn't be the fusion we know and love without quantum tunneling.

If everything's fusion, then nothing is fusion, that's what you're saying. That's right. That's the theme today, right? Label everything. And there are other effects like, you know, back to electrons, electrons don't like to stay in little traps. But if you're building chips for computers,

then you'd like your electrons to be in certain places. You want to know, like, hey, this transistor is on or this transistor is off or whatever. And it gets harder and harder to make transistors be reliable as they get smaller and smaller because you get dominated by these quantum effects and these little traps get smaller and smaller and electrons like to jump out of them.

And you don't want your ones in your computer to suddenly switch into zeros. And so this actually is a big, big effect in miniaturizing transistors or does a big effect in speeding up your iPhone. At some point, if you make electronic small enough, the quantum effects are going to totally mess everything up. Yeah, exactly. Quantum mechanics messes it up again.

Bummer. Why can't they just be electric? Strikes out. Quantum mechanics strikes out again. Why can't we just use little bowling balls and tiny little swimming pools instead of electrons? Sorry, and bowling striking is good. So it wins. That's right. Yeah, strikes out exactly. You brought it full circle there. Very nice.

All right. So that's pretty much quantum tunneling. It's this idea that particles are all quantum. And as such, they have these weird, fuzzy location, right? They're not in any particular place. And so it's impossible to trap a particle because it's fuzzy and it might slip out. That's right. Quantum barriers are just different from the ones you're familiar with. They work under different rules. and those rules have little random exceptions to them. So sometimes they can just be ignored. And it's weird and it's confusing and your intuition breaks down. But it's also wonderful because it shows you how the world works at a smaller level, right?

It reveals to you where your intuition is wrong. And that means that it's showing you the truth of the universe. Yeah. And the truth is bowling. Yeah, exactly. The truth is quantum bowling. This episode brought to you by the American Bowling Association. That's right. Yeah, exactly.

But that's what happens at the microscopic level, but on the larger level, we can't do that because, you know, there's a lot of electrons in my hand. And the chance that all of them are going to quantum tunnel at the same time is just almost zero. Yeah, exactly. Like, if there's a chance for you to roll a one million-sided die and get zero, you know, that can happen. But if you have to do that for a million die all at once and get the same answer, then it's basically improm. very improbable, almost impossible. So the macroscopic stuff sort of gets averaged out.

But still possible. It's still possible. Absolutely, you could quantum tunnel through the walls and not counted as teleportation. All right. It's just what quantum stuff does. Yeah.

Yeah. Drives physicist crazy. No, it excites us. It's wonderful. We're always looking for weird quantum effects that show us how the universe works. It's, you know, it's what we live for, these little moments. All right.

Well, we hope you enjoyed that discussion and hope that answered all of the questions that listeners had about, what is quantum tunneling? Thanks for sending in your questions. They're inspiring. And if you have questions about things you'd like to see explain, please send them to us at questions at daniel and Jorge.com. We love your messages. That's right.

And if you are Swiss and we'd like to tunnel some money over to us, we are also available at feedback at Daniel and Jorge. Or just dump it right into Katrina's bank account if that's more convenient. There you go. All right, thanks for listening. If you still have a question after listening to all these explanations, please drop us a line. We'd love to hear from you. You can find us at Facebook, Twitter, and Instagram at Daniel and Jorge, that's one word,

or email us at Feedback at Daniel and Jorge.com. Thanks for listening and remember that Daniel and Jorge Explain the Universe is a production of IHeartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. Ninth, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, everything changed. There's been a bombing at the TWA terminal. Just a chaotic, chaotic scene.

In its wake, a new kind of enemy emerged, terrorism. Listen to the new season of Law and Order Criminal Justice System. On the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her.

Now he's insisting we get to know each other, but I just want her gone. Hold up. Isn't that against school policy? That seems inappropriate. Maybe. Find out how to end. by listening to the OK Storytime podcast and the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Have you ever wished for a change but weren't sure how to make it?

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