Part 4! What are the basic lessons of quantum mechanics? What does quantum mechanics teach us about the nature of reality? How does a quantum worldview differ from a classical one? I discuss these questions and more in today’s Ask a Spaceman!

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EPISODE TRANSCRIPTION (AUTO-GENERATED)

Welcome back, folks. We are now on part four of a total mumble mumble episodes on the theory of quantum mechanics. In the interpretations of that theory, I'm almost done writing it. I. I saw one more episode left to write as I am sitting here recording Episode four. I hope it all ties together. Well, if you're a fan of jumping into the middle of things without really understanding what's going on, hello. If not, I suggest you start at the beginning, which is helpfully labeled Part one. Where are we? We've seen over the past three episodes, the place that quantum mechanics holds in the larger world of physics. It is a physical theory of the subatomic world of the small and the slow in the universe, and that's what it does. And that's what it does really, really well, we've dug into the basic postulates the bare bones statements that we take as assumptions to get our theory started. These are very general, very broad and very abstract statements that are the totality of quantum theory.

This is the theory. This is how it starts everything else that flows from quantum mechanics, from entanglement to quantum computers to to Everything starts with that handful of basic statements, and we've explored how the early pioneers of the theory went from classical to quantum physics. They went from Mozart to death metal without really wanting to and without really knowing what the heck they were doing. But they were forced to by experiment. They were realizing the wave particle, dual duality, nature of light and eventually matter. They were trying to understand quantum phenomena. They were trying to understand atomic spectra and scattering experiments they were trying to see without being able to directly see the the subatomic world. I feel like we're in a really good spot, but I have to warn you that there's trouble ahead. If quantum mechanics were just like any other physical theory, this would be a relatively short series like the one I did about Newton or the one about general relativity or electromagnetism.

I would say, Here's the math. Here's the explanation. And here's how you can construct a worldview that incorporates that explanation. Here's how to build some intuition so that even without the math, you can wrap your hand around it, et cetera, et cetera. You know the usual ask a spaceman stuff. I've been teasing it for a few more episodes, and I'm gonna tease it just one more. But quantum mechanics starts getting really angry the moment you jump from the Here's the math part to the Here's the explanation part, and the interpretations of quantum mechanics are going to occupy the entire rest of the series. In fact, we've already had a taste of it in the Heisenberg versus Schrodinger solutions to Quantum mechanics and, most importantly, the philosophies behind them, where Schroedinger said, Hey, let's investigate the wave nature of matter and try to take what we know from classical physics and use it to paint a picture of the subatomic world and develop a successful theory. And he did so And then there was the Heisenberg approach, which was The subatomic world has absolutely no connection to the classical world.

Why should we use our intuition to guide us in this completely new realm? Instead, let's build a new intuition, using new mathematics that don't really concern themselves with quote what's actually happening. You don't build a picture from there, you just get results. And he did it and both approaches were successful, which caused a lot of problems. When we start talking about the interpretations of quantum mechanics, it's going to be all super abstract mental stuff that is going to be absolutely delightful and a blast to talk about, Trust me, but it is going to be about the philosophy behind quantum mechanics. It's going to be about the interpretation, the meaning of quantum mechanics, which I know is the the title of this series. But I needed three or four episodes to lay the groundwork of what quantum theory actually is before we talk about what it means. We needed to talk about the math and the physics before we talk about the philosophy. And Heisenberg and Schroedinger had very, very different philosophies in approaching the quantum world and the debates.

They had, the arguments they had, the differences they had are going to continue and continue to, uh, continue to the present day. So I thought we could use a little pause. It's been a heavy few episodes. We've talked about mathematical postulates, the the nature of physical theory, uh, observables in states, we've talked about wave particle duality, uh, and and photoelectric effect. They've been heavy, so let's have a little stop on our way to Quantum, though I want to spend this episode talking about the realities of quantum mechanics. I know in the last episode we talked about some of the major experimental results that led to quantum mechanics. But let's broaden our horizons because that was quantum mechanics of 100 years ago. Let's talk about quantum mechanics in the 21st century. Quantum mechanics isn't just about a bunch of physics nerd experiments done a century ago. Quantum mechanics is about the real world. Quantum mechanics isn't just an abstract theory with nothing to connect it to reality string theory.

It's an accurate description of real phenomena in the real world, and it's perhaps the most well tested theory in all of physics. It's time to put away classical thinking and look at the world like a quantum mechanic. So put away your violence. Put away your cellos in your brass and get out the electric guitar because it's time for some death metal. We now have at this point in the story in 1925 in the history of quantum mechanics, and in this series episode number four, we have a fully developed theory of subatomic particles. The postulate that I described the Schrodinger solution, the Heisenberg solution, the direct solution, which did not get enough air time as it deserved. Eventually, the von Neumann synthesis of everything into the modern day postulate the modern day formulation. When you crack open your textbook on quantum mechanics, it begins with those postulates.

Here is the basic theory of quantum mechanics, and then with the Heisenberg and Schrodinger pictures and the Von Norman approach and all that we have those postulate given life. The postulates say this is how we believe the subatomic world works. Probabilities matter. You don't know the answer until you get it. Measurement changes the thing that you're observing and so on. But then, once you cast that in mathematical language and you develop an equation that you can use to make predictions well, you get to learn more stuff. You get to go beyond the postulate. That's a cool thing about mathematics. Like special relativity starts with. The postulate of the speed of light is constant. There's a lot more you learn from special relativity. Once you start fleshing that out, you learn about equals. MC squared. You learn about length and time dilation. We have our basic postulates and what they teach us about the world and at least the subatomic world. But now that we have the extraordinary equation, the he Heisenberg Matrix mechanics now that we have a theory of quantum mechanics, let's see how the weirdness is manifested.

Let's lay out all our cards on the table. Ladies and gentlemen, this is quantum mechanics. The most important things you need to know. Number one. Everything is made of waves and particles at the same time. In the classical world, there was this distinction. Particles are localized, they are tiny of their little bullets. You can point to a particle and say the particle is right there, and when it hits you, you feel it in one little spot and and waves are spread out. You can't just point with your finger and say, there's a wave. You have to gesture vaguely and say The wave is over here. And when the wave hit you, you don't feel it in one spot. It sloshes up against you, and these seemed like very distinct and different phenomenon. It turns out that everything has properties of both. When I look at an electron. It doesn't just have particle nature as wave nature. When I look at a photon or light, it doesn't just have wave nature. It also has particle nature. When I look at you, you have a little bit of wave nature to you.

Quantum mechanics takes this choice between waves and particles and says, I'll have a little bit of both. It turns out that this distinction between particles and waves was a false distinction. It was a fake. We were wrong to think that. And that distinction only applies in the classical world. When you go down into the subatomic world, that distinction, it becomes meaningless objects, subatomic objects. I know. I use the word particles a lot in this show. I should say subatomic objects, they just are who they are and their label. Your labels do not apply to them. The wave nature, however, only comes out in certain situations. It depends on how much energy you have, how big you are compared to your built in wavelength. If you're walking down the street, I can calculate your debro wavelength. It's incredibly tiny, and you are so much bigger than your wavelength that your wave. Nature doesn't really manifest. It doesn't really come out.

And that's why we didn't see this wave particle nature until we started looking at tiny stuff where their wavelengths were large compared to what they were. In retrospect, it was there all along because we've been trying to understand light for centuries, if not millennia. And light has always exhibited wave natures and particle nature, depending on the experiment. And we were trying to force it into a box like Dang it light. Are you a wave or are you a particle? It turns out it's both or really, it turns out it's its own thing that sometimes acts like a particle and sometimes acts like a wave. And if we had made that realization earlier, if we had turned off that binary thinking a little earlier, we may have arrived at quantum mechanics sooner. This wave particle duality that manifests itself at subatomic scales and does not manifest itself in macroscopic scales that boundary is not well understood. I've talked about the correspondence principle, which guides us in mapping from quantum mechanics to classical mechanics, it says.

On one end of the spectrum, you're in full quantum world And then now you have a mapping so that the complete other end of the spec you're in total classical world. In the quantum world, you got to care about wave, particle nature and duality. In the classical world, it's just gonna be one or the other. Electron is just gonna act like a particle light is just gonna act like a wave. But somewhere in between is this fuzzy boundary that we don't fully understand which many experiments are currently trying to probe. Like, uh, can we bring out the wave nature of a virus? That would be cool. There are experiments underway trying to do that. Now a word from our sponsor better help. One of my favorite things about being a physicist is that the training I've received in physics is training to solve problems. It's training to look at difficult, complex, mind bending problems and find a simple solutions to to take baby steps to find approximations and problem.

Solving itself is a great skill that I found that physics has helped me with it. And you know what else can help with that? It's therapy, I. I regularly speak with a therapist I've known and trusted this. The therapist for years, who is this person has guided me through very difficult points in my life and and moments of of easy sailing and just it's there someone who is close, a confidant and who also understands people, which was not a part of my physics training. If you're thinking of giving therapy a try, I want you to try better help. It's convenient, accessible, affordable, entirely online. Seriously, give it a shot. I. I can't advocate for mental health anymore. When you want to be a better problem solver therapy can get you there. Visit better help dot com slash spaceman today to get 10% off your first month. That's better. HE LP dot com slash spaceman Most important thing to think like a quantum mechanic.

Number two. Some things, but not everything come in indivisible chunks. This is the quantum and quantum mechanics. Some things are quantized could have had a different name if history played out differently. I'm sure the aliens call it something else over in Andromeda Galaxy. But this was the first part of the subatomic world that really flew in the face of conventional thinking, and it was a huge shock. It was so much of a shock that when Max Plank himself introduced the idea of quantization that maybe light is emitted in chunks notice, he did not say that light is chunks that was Einstein. A few years later, Plank said, maybe light is emitted in chunks. He himself didn't believe it. He said, Look, I'm just introducing a weird, nasty hack. Yeah, it works. I don't know why it works, and I'm sure we'll figure something better out soon. We have yet to figure out something better because it looks like that's the way it is. Not everything is discrete. Not everything comes in indivisible chunks, especially patreon.

That's patreon dot com slash PM Sutter P MS U TT ER It is how you keep this show going truly. If you want to know what is the number one way to help support the show. Patreon dot com slash PM Sutter. I truly appreciate every single dollar that keeps this show going. Not everything is discrete. Some things we study in the subatomic world are continuous. The the position of an electron can be wherever it wants, but the energy level of an electron inside of an atom can't be anything it wants. We have rules to guide us about when things are gonna be discrete and when they're gonna be continuous, when they're gonna be smooth and when they're gonna be chunky. But we really only know that from experiment like, OK, this list of things, this is discrete. This is chunky. This is it comes in in individual indivisible chunks. And this doesn't the realization that electrons exist in quantized energy levels inside of an atom, unlocked all of spectroscopy and all of chemistry.

The realization that light is quantized unlocked the wave particle nature of light and eventually matter. But not everything is quantized Uh, uh like linear momentum. You moving in a straight line That's not quantized. You can have any amount of linear momentum you want angular. Momentum is quantized. When you're sitting there in a in a like an office wheelie chair and you're spinning, you have a certain amount of angular momentum. There is a minimum amount of angular momentum that you can possibly have in the universe, and that is equal to Plank's constant. You cannot have angular momentum. Less than that, you can have zero if you want. But if you have any amount of angular momentum, you must have at least that. And then every amount of angular momentum that any object has in the entire universe is some multiple, some whole number multiple of planks, constant. You know, in the case of you spending in the chair, it's like 11 bajillion times, planks constant. But it's not a bajillion 0.5 times planks constant.

Your angular momentum is quantized, but your linear momentum moving in a straight line is not. Number three probabilities are in charge. This one is just straight up uncomfortable. We are forced by experiment and well tested theory quantum mechanics to acknowledge that we can't know everything we want to know about the universe. Heisenberg was perhaps the first one to really come to terms with it. You know, Einstein touched on this when he explained the photoelectric effect. He needed to include probabilities in his analysis. But it was really Heisenberg who really saw this for what it was and was able to claim. And that's why we have the Heisenberg uncertainty principle. Like if you're trying to study a subatomic particle position and momentum, you won't be able to get both to as high degree precision simultaneously. You can have one or the other, or you can balance a little bit. You can be a little bit fuzzy on both. You can be sharp on position, but not momentum.

You can be sharp on momentum, but loose on position or a little bit 50 50. But you can't be sharp on both. The Heisenberg uncertainty principle started as a thought experiment but grew to encompass many aspects of the quantum world. The nature of probabilities comes up all the time. I'm shooting electrons through a strong magnetic field. Sometimes they go up, sometimes they go down. I cannot tell you if you point to an electron and you say, what is it gonna do? I say, I don't know. 50 50. I can't tell you if it's gonna go up or go down. I have to run the experiment and then it will choose on average give with a lot of electrons, I can say yeah, half of them are gonna go up and half of them are gonna go down. But I can't tell you which ones are gonna go up and which ones are gonna go down probabilities are a thing. Max Bone realized that the wave in the Schrodinger equation that the wave you are wave nature when I say you have a wave nature walking down the street. What does that wave? Max Bourne interpreted that as a wave of probability.

A wave of where you might be the next time I go looking for you. Where the waves are high have a high amplitude. Those are places where I am likely to see you where the waves have a low amplitude. That is where I am unlikely to see you. If I put an electron in a box, it has this fuzzy probability cloud associated with it. That cloud technically extends throughout the universe, and a decent amount of it extends beyond the box. So just the next time I go looking for the electron, it can be just outside the box. It doesn't care. This is the phenomenon of quantum tunneling, which is the basis of modern micro circuitry of computers. Every time you turn your computer on, every time you turn your smartphone on, you are testing quantum mechanics. We'll get to that. I think at the end of the series, I'll talk about the real life applications. I think someone remind me every particle, every object has a way of nature.

And that way of nature tells us that probabilities are in charge. This really hurts as a physicist, because the entire program of classical physics was getting better and better about determining, like the ultimate fate of the universe. If I give you a starting scenario, then I will tell you exactly how it will play out. Not so in quantum mechanics. I can only tell you how it might play out, and you actually have to make the observation to to see what happens. Number four non locality is probably a thing. I haven't really talked about non locality yet because it doesn't appear in the postulates. But it once you start working with the postulates and fleshing out your theory, it shows up and it will play a major role in the debates over the interpretation of quantum KICs to come up. So now is as good a time as any. That in this non locality thing can depend on your interpretation. But, uh, as far as I'm aware, all modern interpretations of quantum mechanics do acknowledge the reality of non locality, and now locality is based on entanglement.

If I have a quantum object, an electron, it has a wave and a particle nature. The wave tells me where I might find it the next time I go looking for it. If I take in another electron, it has its own wave particle nature. It has its own fuzzy cloud of probabilities, of where it might be the next time I go looking for it. If I put these electrons close to each other or let them bounce off of each other, their fuzzy clouds of probability intersect and mingle. And then there's not two fuzzy clouds of probability. There's only one fuzzy cloud of probability. And then when I pull these electrons away from each other, the fuzzy cloud of probability that they share doesn't go away. They become entangled. They're quantum states over a lap where there isn't a separate quantum description of this particle and a separate quantum description of that particle. There's only a single quantum description of both particles. Simultaneously. I'm gonna dig into this a lot, a lot, a lot in a couple episodes, because this is, well, I I'll give it away.

Einstein had a lot of problems with quantum mechanics, even though he helped found it and he had a lot of arguments, and he ended up going along with the uncertainty principle. He ended up going along with probabilities, but he couldn't get over entanglement because it meant or implied that quantum mechanics is non local. Because if I take these two particles where they're quantum fuzziness probability, you can insert the wa Word wave function here if you want, uh, overlap, and then I move them far away from each other. They still technically overlap, and they can influence each other and possibly influence each other faster than the speed of light. That seems like a problem, but it also appears as after a century of studying it, that it's a real thing. No, we've discovered that this doesn't violate the speed of light because this can't be used for communication. No information is transmitted, but they do influence each other. One particle on one side of the universe does affect, in a quantum way another particle on the other side of the universe, and this just flies against everything we understand about physics.

I'll really dig into this in the episode on Einstein's reaction to quantum mechanics. But it appears to be a thing, and you just have to deal with it. Thankfully, Number five quantum mechanics is about mostly the very small quantum mechanics really is a revolution. It completely rewrote the books on how to understand the natural world. We had centuries of physics knowledge that we had assumed. Once we discovered atoms and electrons and nuclear and all that we assumed we could just take our knowledge of classical physics and make it tiny, and it would work. Except it didn't everything we tried in classical physics. Newton's laws, electromagnetism, thermodynamics, everything we tried wouldn't work. Really. The only thing that worked was our understanding of waves, which Schroedinger took and applied. And that works, but not in the way that he intended more on that. In the next episode, we had to throw out classical physics to understand the quantum world, but thankfully, we don't have to think about it often.

Sure, it's responsible for large parts of the modern world, like atomic power and semiconductors, but most of the time we don't have to think about it. Like I said before, I am not entangled with my neighbor. I do not exist in a superposition of multiple states. If I'm going somewhere and you see me, you know where I am. In the macroscopic world, the rules of classical physics do apply. This is the turf. The domain of classical physics is up here in the microscopic world. We only have to think this way when we go into the subatomic world. So, thankfully, on the day to day, we don't have to think about quantum physics much. But when we do think about it, it's a pain. We have the math, but we don't know what the math means. We have ways, techniques, tools for making predictions, I can tell you, based on the postulates of quantum mechanics and the theories developed by Heisenberg, Schrodinger and Moore, I can tell you what the atomic spectrum of say oxygen is, and I can tell you exactly what it is and why it is.

Why is the spectrum Why is the radiation emitted from oxygen? That pattern, I can tell you you can shoot electrons at a screen, a metal screen, and I can tell you exactly how they'll behave. I can shine light on a metal bar, and I can tell you exactly what will happen. I can use the tools of quantum mechanics to tell me that in so much more. But the math is so weird and so outlandish and flies in the face of intuition like we saw with the postulates like we saw with the history we And in this episode that how probabilities are in charge and objects have both wave and particle natures. It doesn't make any sense. We don't know what the math means. How are we supposed to talk about the math in a way that fits in to the way we talk about literally everything else in the universe? And that is the next story we have? Thank you so much for listening. I have so many people to thank. So thanks to E on email at Charman on Twitter. Massimiliano S on Facebook.

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Thank you so much to everyone. It really is a delight to create these episodes for you. I have so much fun, I really do, and I can't wait for more. Send me more questions. Ask us spaceman at gmail dot com. Hashtag Ask the spaceman. Ask the spaceman dot com There's a website hit me up on Social at Palma on all channels, and I'll see you next time for more complete knowledge of time and space, the It's always the right time deal. Hey, you wanna go to Mickey D's for lunch? Oh, let's go now, But it's not lunchtime yet.

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