Daniel and Kelly’s Extraordinary Universe - What's a Time Crystal?

Episode Date: February 9, 2021

Daniel and guest host Katie Goldin talk about the crazy and real science of time crystals Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

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Oh, yeah. We'll talk about all that's viral and transnational. with a little bit of chisement and a whole lot of laughs. And of course, the great bevras you've come to expect. Listen to the new season of Dacias Come Again on the IHeartRadio app, Apple Podcasts, or wherever you get your podcast. Hey, Katie, did you know that if you stick any two science words together, you get a great science fiction movie title? Really? Is it really that easy? Oh, yeah, just give it a shot.

Okay, let's see. Quantum Hamster. Boom, I can see that whole movie in my mind all right. Oh, yeah. Okay, okay, what about alligator crystal? I love it. Want to see that one. Oh, let's do time pump.

I am calling Netflix and set up a pitch meeting right now. Hi, I'm Daniel. I'm a particle physicist, and I really would like to write a science fiction movie someday. And I am Katie. I am a science podcaster, and I am already writing dialogue for quantum hamster in my head. And welcome to the podcast, Daniel and Jorge, Explain the Universe, a production of IHeart Radio. in which we take you on a tour of everything that's amazing in the universe, everything that's out there doing crazy stuff you couldn't imagine

and all the weird quantum stuff happening at the particle level and everything in between. But we want you to come away from our podcast, not just hearing about the crazy stuff in the universe, but actually understanding it. And as you might have guessed, Jorge isn't with us today, but instead we have a wonderful guest podcast host. Katie, introduce yourself to everybody.

Hi, guys. I'm Katie Golden. I'm the host of Creature Feature, a podcast about animal and human behavior. I studied psychology and evolutionary biology. So I am very excited to take a journey into the physics realm of things. I hope I can fill Jorge's shoes a little bit temporarily. Do you know what his shoe size is? He's a cartoonist, so he just draws really big floppy clown shoes, I think.

That'll be perfect for me. well you guys should all check out creature feature it's a super fun podcast and katie's a lot of fun which is why we invited her here as a guest host and you know today's episode is all about how we understand the universe and how we understand things like time which makes me wonder since you're an expert on creatures and evolutionary behavior do animals understand time katy that's a really good question i'd say it depends on the animal and it depends on what you mean by understand. A lot of animals can kind of mark the passage of time without possibly really understanding it. Like there's a great migration of plankton that happens every day with the

rising and setting of the sun. But could you say that as little zoo plankton really understands time? I'm going to say no. That's a bold, controversial take. But yeah, it's really hard to get inside of the heads of animals. That's a problem we talk about on my podcast. Well, I wouldn't be surprised if animals like crows understood time. There's a group of crows that seem to always gather outside my window right around like 2 o'clock in the afternoon when I have a big Zoom meeting. Yeah, I think patterns are really easy for animals to understand, especially the smart ones. Crows, if you feed them, they'll come back and visit you whenever you feed them so they will learn your patterns, much like a cat. You know how your cat wakes you up just in time early in the morning for you to

feed them. They understand patterns. They will memorize your rhythms and patterns for the best snacking opportunities. Well, you know, I was wondering if you were going to ask whether any animal understands time, even humans, because as you might know, time is a slippery topic. And it's something a lot of our listeners ask us to talk about because it's not something that even human physicists can get our minds around. Why do we remember the past and not the future? Why is there now? Is the now actually real or is time just an illusion? All of these really simple, basic questions about time haven't yet been answered. So wait, is time, when we're talking about time, though, is it just a human invention? Like, we made clocks. We have one o'clock to 12 o'clock. You know,

we kind of have this concept of time. Like, is it not just our human invention or is there actually a real thing of time outside of our little Mickey Mouse watches? Yeah, it's a great. great question. There's a lot of it that is invented by humanity like units, you know, one second, one minute. That's totally arbitrary and an alien species might invent something totally different. But in our understanding of physics, time seems to be real. And we will dig into that later in the podcast about the concept of time in quantum mechanics and the concept of time in general relativity, which turn out to be totally fundamentally different ideas of what time is. But yeah, we do think that time is a feature of the universe. We think it's something out there and real, but we won't

really know until we one day get to talk to alien physicists and see if they even understand the concept of time. That's so interesting. So there is an actual cosmic time that is occurring that we sort of view through our own little human lens, our sun dials and our watches and our appointments, but that may not really capture the whole truth about what time is. Yeah, or it could be and illusion. It could be that time is not something deep and fundamental to the universe. It could be that it sort of emerges, that it's like a special condition that only happens under certain circumstances, you know, the way like ice forms sometimes in the universe, but not always. You could have a universe without ice. That's not a big deal. It might be that

time isn't fundamental. But we'll dig into all that on today's podcast. We actually want to focus today on something even weirder than just the question of time, which is a big puzzle for a physicist. we want to talk about something which has been bopping around the internet and creating a lot of buzz recently. That's this topic of time crystals. Ooh, that sounds beautiful. What comes into your mind when I say the phrase time crystals? A bunch of clocks floating around in a crystalline structure. All right.

And so today on the program, we'll be asking and hopefully answering the question. What is? a time crystal. So Daniel, you asked people on the internet what they thought. That's right. Folks out there volunteer to speculate baselessly on the topic of the day just to give us a sense for what they knew and what they didn't know. And so if you would like to submit your baseless speculations for future podcast episodes, please write to me to questions at danielanhorpe.com. And so here is what people had to say. My only thought is that, There are these points in space that maybe are time markers or there are certain blocks of crystals that hold elements

or signatures of certain time events that you can look back on. That's easy to make a whole Rick and Morty episode about those. I don't know what time crystals are. Well, I know that quartz is a crystal, and we use quartz to get precision timing in watches. and things like that. Maybe there's other crystals that can do the same thing. So what do you think about those answers, Katie?

I do like the callback to Rick and Morty. They definitely have a scientific approach to time with all of their time travel episodes. Do they, though? Are you a Rick and Morty fan? I like it. It's a loaded question to ask if you're a Rick and Morty fan because I think that there are some really hardcore fans out there who will contend that you have to really understand science

to understand the show. I just think it's a fun show. Yeah. Well, you know, I watch Rick and Morty sometimes, but I'm a real stickler for getting the science right when you're doing time travel. And that's really hard. It's very difficult to have a narrative that makes sense if you're also going backwards in time and jumping all around.

And so that sometimes gets the way of me enjoying Rick and Morty. I see. You're a real stickler for those time travel plot holes that always pop up. Yeah, exactly. Speaking of time, the focus of today's episode is this question. What is a time crystal? I like some of these answers. You know, we do use a crystal in watches sometimes to tell time, right?

Crystals are at the heart of a lot of watches on people's wrists. How do they work to tell time? Do you have just a little crystal man in your watch going like, eh, it's about 2.30? That's exactly how it works. You crack it open, you'll spot him. Now we're writing a Rick and Morty episode. But that's not actually the kind of time crystal that we're talking about today. Today's episode is about something totally different.

So what kind of time crystal are we talking about if it's not a little crystal telling you what time it is? The idea of a time crystal basically is an extension of the idea of a space crystal. So let's first talk about what a space crystal is, remind ourselves about like the basic idea there. And then we'll try to apply that concept to time crystals. Now I'm imagining a crystal floating through space. but I'm going to guess that's probably not what it is. No, exactly. That's exactly what it is for a space crystal, right?

A space crystal is what? It's just like a regular pattern. And a crystal, like the kind of thing that you see, like a shiny gem or something else you would call a crystal, is if you zoom down into it and understood it like at the molecular or the atomic level, the way it's built is like a bunch of Lincoln logs or something. You have regularly spaced atoms all lined up in like a three-dimensional pattern. Right. It's that kind of grid-like structure. I always think of a sort of a wafer kind of treat. Maybe just because

I'm hungry, but it's those layers and layers of interlocking wafer-like molecular structures, right? Yeah, exactly. You have wafer, and then you have caramel, then you have another wafer, then you have chocolate. That's exactly the recipe for building your crystal. Just making me hungrier. Katie's crystal cookies. I love it. Well, sugar is a crystal. Yes, sugar is a crystal. And basically, anything that's a crystal that has a regular pattern. And that's the core concept that we have to understand when we're talking about crystals. Basically, you're building a lattice. You're taking a continuous symmetry, right? Like space in itself is the same everywhere. Doesn't really matter if you take one step forward or a half step forward. The same laws of physics reply. Everything works the same

way. If you're going to like juggle balls here, then you took a step sideways, the same rules should apply, same juggling should work. A crystal takes that and sort of breaks that symmetry into something discrete. So now the universe has a symmetry still, but it's not like smooth. You have to take like exactly the right size step in order to see the universe the same way. So if you're like inside a big crystal, it's a huge lattice and you're sitting on an atom, you have to take a step exactly the size of the lattice so that you're still sitting on an atom. It's chess rules, except you're all pawns. Yeah, exactly. Take a little. space and break it up into chess boards and you can only move one square or two squares. You can't move

one and a half or two and a half squares. Right. And so that's the idea of a space crystal. And like you do think of a crystal as a big shiny thing. But when you zoom it down into it, the reason that it's shiny, the reason it has those properties that reflect light that way is because it has this regular structure in space. So when we say crystal here, we generally just mean like a regular discrete structure. That's so interesting. I mean, crystal structures are really interesting. in evolutionary biology because they are surprisingly sometimes used in eyeballs, like in the eyes of mollusks will have these guanning crystal structures that help them reflect light. You don't think of organic material as something you can turn into a crystal, but yeah, you can take guanin, form a guanin

crystal form an eyeball. Wow, that's fascinating. So most eyeballs don't have crystals in them. It's a special situation? Yeah. We have lenses in most eyeballs, but those guanine crystals that form in certain eyeballs, like in the eyes of scallops will have this characteristic that helps them reflect light in such a way that gives them really interesting vision. Wait, hold on a second. Scallops have eyes? Yes, they do. You wouldn't think so. I'll think about that next time I'm biting into one. I'm tasting crystalline eyeballs. They're actually beautiful blue eyes and they have a whole mess of them, like 200 of them. Oh my gosh.

Wow. Well, that makes me feel better. That's why I don't eat scallops because I don't like crystalline eyeballs. Yeah. And instead of using lenses like a human or mammal eye or most animal's eyes, they actually use mirrors inside of their eyes as kind of a miniature telescope by using that guanine crystal structure. Wow.

Amazing. Well, the other important thing to understand about these kinds of crystals that we're talking about space crystals is that they are stable. So like those crystals in the eyes of scallops or that diamond that comes up out of the ground is stable. It's a regular repeating pattern, but it doesn't fall apart. It's in its lowest energy state. And so it can hang out basically for a long time. It needs to be broken up if you want those atoms back.

Is that why diamonds are so tough because of that crystalline structure? Yeah, because the crystalline structure makes them really hard to break. And also, that's why they last a long time because they're in a stable state. Like the atoms, they're very happy to be in that situation. They're not going to relax into some other lower ground state and then break up into something else. Energetically, they're very comfortable. That's so interesting.

But something like an ice cube forms a lattice structure, but it does melt. So is that an example of like an unstable crystal structure? Yeah, ice is actually super fascinating because it can form lots of different kinds of structures. And we're going to do a whole podcast episode about all the different weird kinds of ice. It's like one that's not transatlantic. transparent black ice and it's like nine other kinds of ice. So it can form lots of weird crystal structures but actually is in a stable state. The only reason it melts is because you're adding

energy to it, right? Melting means you're like heating it up from the outside. Same with diamonds. You put diamonds in hot enough temperatures. They will melt. Wow. That actually happens we think sort of like on the surface of Jupiter which rains diamonds into the interior which might form like a big liquid diamond ocean. So Jupiter is really rich. We're talking about Kardashian. levels of rich. Absolutely. Absolutely. So now we understand like the idea of a crystal. It's like a regular structure. That's a crystal structure in space. So now let's turn to the topic we're trying to talk about today, which is time crystals, right? Take that same idea and apply it to time. Okay. But how do you put time in a crystal? Because time is not physical matter. You can't arrange it in a lattice structure. So

what are you trying to say here? So take the same idea you're applying to a lattice in space. where you say, all right, the thing looks the same if I take one step to the right or one step forward or one step backwards and now say, what happens if I take a step forwards in time? So a time crystal, some kind of object or substance, which has a regular repeating pattern in time, which means like it looks the same now and then in a second and then in two seconds and then in three seconds. And in between, it doesn't have to look the same, but it's going through some transformation so that it regularly returns to the same position. Hmm. So this is like four-dimensional chess where it's like you're playing this chess game where you're only allowed to move one space at a time in a certain direction, but through time and not through physical space necessarily. Yes, exactly. And so what you want is something which returns to the same configuration, but after discrete units of time, right? Not like it's in that same state all the time. That would just be a space crystal. You want a time crystal, which is in a certain configuration, then moves out. out of it and comes back and then moves out of it and then comes back. So you want it to sort of break this continuous time symmetry where things always look the same into a discrete symmetry so that

it looks the same and then it doesn't and then it comes back and it looks the same again. That's the property you have in a space crystal, right? You have this distance between points in space. Now we want distance between configurations in time. Kind of sounds like a dance to me. You have to do your dance movements through not just space but through time and it has to synchronize in a specific way. Yes, exactly. And the other critical thing is that it has to be stable, meaning it has to be in its ground state. That means that basically it's doing this forever. So you need something which is both in motion, but also in the most relaxed lowest energy state. And that's a really unusual combination. You have to

imagine something basically moving forever. That sounds like a perpetual motion, which I I didn't realize is something you could do. Well, my mind is blown, so I'm going to try to recollect my brain back into the pieces, but before we do that, let's take a quick break. Imagine that you're on an airplane, and all of a sudden you hear this. Attention passengers. The pilot is having an emergency, and we need someone, anyone, to land this plane. Think you could do it?

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Get your tickets today. AXS.com. And we're back, and Daniel is trying to reassemble the pieces of my brain that exploded because we were talking about how there is something where with a time crystal, you can remain in motion forever at a low energy state, which sounds like perpetual motion to me, which I thought was just science fiction. So how could this possibly happen? Yeah, it's a really awesome question. And it's for this reason that people thought forever, like, this is a silly idea. Nobody should even talk about it. It's obviously the impossible. And it's only recently that people thought, hmm, maybe there's a way to make

this happen. Maybe there's a way to configure a system that can be in motion through time where it regularly returns to a specific state. That's sort of the lattice point. And yet is stable. So it could like do this forever. And this started in about 2012 when a famous physicist named Frank Wilczek, he's at MIT and he won the Nobel Prize for understanding the strong interaction, which is a thing like binds corks together into protons and neutrons. So he's generally a smart guy and he's also kind of famous for coming out of left field with a crazy idea that turns out to be pretty good. He's the guy, for example, who coined the term axions to describe that hypothetical particle. And in 2012, he put out this kind of crazy paper saying,

you know what? Here's a situation where time crystals might be possible. He constructed an example of a quantum system, a ring of particles, a sort of rotates and every sort of clock cycle returns to a similar configuration and repeats the same pattern in time. So exploded into like the community of theoretical physics blowing everybody's minds. So is this something that would happen on the quantum level? Are we talking about entire like star systems doing this like time crystal thing? Or are we talking about something on a very small scale? This is something in a very small scale. This would definitely be a quantum effect. It's not the kind of thing that you can have happen for macroscopic systems.

And the reason you can only do it potentially for quantum systems is that quantum systems have a really weird relationship with zero energy, right? Things that the quantum scale can never have exactly zero energy. So when you force them into their lowest energy state, it's not actually down to zero energy. But a whole fun podcast episode recently about zero point energy in the Casimir effect, which basically says if you look into empty space, It's actually filled with an infinite number of photons because all the fields that are out there in space can never really relax down to zero energy. So time crystals, if you think they're possible, could only be possible for tiny little microscopic quantum particles. This is like when my car battery drained down to quote unquote zero and the mechanics said I'd need a new one.

But hey, guess what? I got a little bit more out of that battery. So maybe it was some quantum time crystals at work there. Yeah, or when your iPhone battery says it's at zero, but it's still running. And you're like, hmm, am I using the Casimir effect to charge my phone? And you might also be imagining, you know, obvious examples of like larger physical systems, not just stars, that seem to have this property that they could spin, for example, and return to the same state. Like, think about a wheel with spokes. As it rotates, it returns to basically the same configuration. The problem is that a bicycle wheel is a macroscopic object could never actually spin forever.

And that's also not its ground state. It's not its most lowest energy state. Lowest energy state for a bicycle wheel is when it's stopped. Right. And so that's why we aren't able to actually make a perpetual motion machine out of bicycle wheels and water and marbles and so on and so forth. But Frank Wilczek wrote this paper and said, you know what, it might be possible for quantum objects. Basically like a little quantum wheel, he tried to show this thing. could spin forever and actually be in its ground state.

Now, of course, this set off like a lot of conversations in the theoretical physics community. And there's another theorist, Patrick Bruno, who actually found a mistake in Welchek's paper. Tattletail. I know. But this is a good lesson. Like, Nobel Prize winners make mistakes. I feel like a lot of times people quote Nobel Prize winners. And if they said it and they won a Nobel Prize, it must be the truth, right?

Right. But like, they're just people, you know. Yes, they're smart. and they got lucky, but they're also people, and sometimes they make mistakes. Yeah, take that, you Nobel Prize winning smarty pants. I especially love it when they interview a Nobel Prize winner. On a topic, they're like not an expert in. You know, you'll hear like a Nobel Prize winning physicist commenting on economic policy.

And you're like, you don't know anything more about that than anybody else. Like, just because you won the Nobel Prize. Yeah, you know, I'm as much a Nobel Prize winner in a field you didn't study. as you are Nobel Prize winner in physics. So there. Yeah, exactly. But what was this mistake and how did that change this whole concept of being able to have these little tiny time crystals?

Yeah, so Patrick Bruno showed that the example that Wilcheck proposed, this idea of a ring of particles rotating was actually more similar to a bicycle wheel spinning than we thought that it would only rotate if it was actually in a more energetic state. And he showed that the example that Willcheck suggested, had the possibility to decay into a ground state, which wouldn't be rotating. And so it wouldn't actually qualify as a time crystal. But, you know, once the idea is out there, then people started working on. They thought, hmm, that's interesting.

Let's reinvestigate. A lot of times you have an area in physics where people are like, oh, we already know the answer there. That's totally impossible. And it takes one brave person to dig into again and ask the question anew. And then a lot of people will follow. It would be like, oh, that's interesting. I wonder if we could actually crack this problem.

And so Frank Wilczek's credit with, like, cracking this problem open again. And then a huge number of people started writing papers. And there were a lot of people that said, oh, no, it turns out a time crystal is completely impossible. They wrote all these no-go papers that proved under various conditions, you could never have a time crystal. You can never have a quantum mechanical arrangement of particles that repeats in time and is at its ground state. Wet blanket's trying to make it so that I can't make a little quantum circus with a little merigo round. And I'm thinking of a cork on a unicycle just going on forever. And I don't like it.

I want to hear some optimism. Well, we'll talk about the actual experiments in a minute because this also inspired a bunch of folks to say, well, let's go see if we can make one. You know, sometimes the theorists say, that's possible. This is impossible. But it's up to the universe to decide whether it actually happens. And so I like when experimentalists sort of don't listen to the theorists and just go out there and explore. but it's actually really interesting and important question about time crystals because it gets to the heart of how we think about time.

And this is something you were bringing up earlier, like, is time a real thing? If time crystals are really, really would tell us something fundamental about the nature of like time and the universe. Yeah, because I feel like we don't really have a frame of reference outside of our human invention of we mark the minutes, we mark the seconds, we pick sort of these units of time, probably based on our ability to, like the time it takes us to think about a second is about how long a second is. So, you know, it's based very much on our human brains, but it's interesting. I guess I've never really thought too much about finding empirical evidence for

there being time. Well, it's also really interesting to sort of dig into it theoretically and ask like our fundamental picture of the universe, what does that tell us about time? And we have two pictures of the universe, the way things work sort of at the deepest level in the universe, quantum mechanics and general relativity. And as listeners, the podcast know, these two don't often agree. And that's also the case about the nature of time. They have very different opinions about what time is. And quantum mechanics says that space and time are very different. And according to quantum mechanics, you have like a description of the universe. It says like, here's your quantum particle, there's your quantum particle, whatever. And you know, quantum mechanics tells us what's likely

to happen to those particles in the future and all that crazy stuff that we can dig into on another episode. But the important thing is that quantum mechanics tells us how those quantum states evolve, like the Schrodinger equation, the most famous equation in quantum mechanics, that's what it does. It tells us, if you have a quantum state, here's what it's going to look like in the future. And also, you can turn that equation around. And you can say, here's how you got to now. Here's how the past must have looked if the present looks this way. And there's a concept we often talk about called quantum information. And that's what this means. It says that if you know how the universe looks now, you can figure out how we got here because quantum information is never destroyed. And that's a deep

and fundamental statement about the nature of the universe because it means, according to quantum mechanics, the time is eternal. Time light goes on forever into the future and into the past. So that's true of quantum mechanics, like in the quantum miniature universe, but like when we look at the larger universe, once we scale it up, those ideas don't hold true. Yeah, exactly. This is relevant to the rules of tiny little particles, but you're right, when we scale up to the rest of the universe, things do look a little different. And this is when general relativity comes in, because when it comes to like the shape of the universe and the age of the universe, the thing that matters most is gravity. And general relativity is the best theory we have that describes how gravity works. And the most important concept in general relativity that's relevant for today's conversation is this notion that space and time are very deeply connected. Our quantum mechanics says space time are separate. Time is just like the way that things in space evolve one step to the other. General relativity says, no, no, no, time is like just one part of this thing we call space time. And there's a deep symmetry between space and time and they evolve together and they get twisted together and they're really closely connected.

And if you think about what general relativity says about time even more deeply, you know, general relativity says that the universe is expanding and that it used to be done. denser. And as you look backwards in time, time doesn't go on forever. It comes back to some sort of singularity in the early universe. And according to general relativity, it's very natural, for example, to have a beginning of time for time to have started from zero in the early universe. So quantum mechanics says space and time very different and time has lasted forever. General relativity says, no, no, no, these are just two different sides of the same coin and it makes perfect sense for time to have started in the early universe. So two very different pictures about this very basic piece of the universe. Well, the universe is made out of quantum

particles. And so the bigger aspects of the universe are made up of the quantum aspects of the universe. So it's very interesting that you have this disagreement ostensibly between basically the sum of the parts and the parts themselves. Yeah, you're absolutely right. And one of the reasons they disagree is that usually they play in different fields. When we talk about tiny little particles, gravity is so weak that it's basically irrelevant and we can ignore what general relativity says. And then when we zoom up to talk about stars and planets, all those tiny little particles are so small, they get just averaged out. All the quantum effects basically disappear. So general relativity is dominant for really big, heavy stuff and quantum mechanics is

dominant for really tiny, very low mass stuff. And it's very rare for the two to be important. So we can't tell like who wins when they're both important. The only way to figure that out is to do things like look inside of a black hole where things are so small but so dense that both of them are important. And that's not something we've been able to do yet. Not yet, maybe in a few years. Well, I want to hear about how this disagreement impacts whether or not I can have my tiny time crystal carnival. But maybe we should take a quick break first while I draw up some little quantum merry-go-round schematics. Imagine that you're on an airplane and all of a sudden you hear this.

Attention passengers. The pilot is having an emergency and we need someone, anyone, to land this plane. Think you could do it? It turns out that nearly 50% of men think that they could land the plane with the help of air traffic control. And they're saying like, okay, pull this, do this, pull that, turn this. It's just... I can do my eyes closed.

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Listen to the new season of Grasas Has Come Again as part of My Cultura Podcast Network on the IHartRadio app, Apple Podcasts, or wherever you get your podcast. We are back. I'm trying to decide whether to sell cotton candy at my little quantum carnival with the time crystal dance, the time crystal carousel. And so Daniel is going to explain to me how quantum mechanics and general relativity, the small side of the universe, the quantum side and the big side, the us and stars and everything else, can disagree so much about time and space. Yeah, well, I wish we knew the answer to that. But one way that we might be able to probe it is to look inside the core

of a black hole and understand, you know, who's right about the nature of the universe or go back in time to the Big Bang. But, you know, that's kind of inaccessible. So we're excited anytime we can probe something that we think gets near this question that lets us like understand around the edges of these questions about the fundamental nature of the universe. And that's why time crystals are super fascinating because they explore this connection between space and time. Like if time crystals can actually be made, it's really a strong argument that there's a close connection between space and time, that this thing that exists in space, space crystals, can also be made in time. The time can be seen sort of like as another dimension of space. It adds sort of like a check

in the column of general relativity. And so that would mean that quantum mechanics is actually behaving in a way that is following the rules of general relativity. It would mean that we need to adapt somehow quantum mechanics to play along nicely with this concept that space and time are deeply connected. And you know, we know already that quantum mechanics can't really be right about time being eternal in every direction. Like we think the universe had a beginning. So it doesn't really make sense to hold tightly to this concept that time must be eternal. On the other hand, it's a pretty big thing to get rid of, to let go of this concept of quantum unitarity, that quantum information is not ever lost. That's something we really think is at the foundation of quantum mechanics.

So one of these theories has to get torn up, basically, and start again. And the question is which. And we're hoping that time crystals give us like a glimmer of understanding as to how to begin that process. But even if we knew, right, for example, that general relativity was correct, doesn't tell us exactly how to start on quantum mechanics. And before we put too many nails in the coffin of quantum mechanics, like, I don't think anybody out there in physics believes general relativity is correct. It's got to be wrong because it assumes that the universe is smooth and continuous in a way that quantum mechanics, we know our experiments tell us just can't be true. So my money's on both of them are wrong and we've got to come up with a whole new theory that

combines the two. Well, we're kind of cross-checking these two rule books that were writing based on the quantum information and then the larger scale general relativity information. And it sounds like you physicists have to cross-check them and figure out which things make sense and then kind of get rid of the things that don't as you cross-check them. And time crystals might help you do that. Yeah, exactly. And you're right. We're sort of trying to weave these threads together. You know, people have been working on quantum mechanics for a while. People have been working on general relativity for a while. And the goal, of course, is to come up with a single holistic explanation for the whole universe for how everything fits together. And that requires like trying to weave these

threads together. And in the past, we've succeeded, like we figured out that electricity and magnetism are really just two sides of the same coin, and neither theory was wrong. They just sort of fit together in an unexpected way. And then we added the weak force, and now we have like a theory of the electromagnetic weak forces. These three things sort of woven together into one common understanding. The goal is to make progress by pulling these things together, by getting our understanding from various bits of physics and sort of putting it together to make a holistic picture. And there's one more part of that thread that we might try to pull in. And there's this idea about the connection between time and energy. The time crystal, if it exists, is a weird thing because it's in motion, but it's

also like at its lowest energy state. Well, there's another deep theorem about physics, Nuther's theorem, that tells us why we have energy conservation in our universe. It says that energy is conserved in our universe because there's some symmetry with time, that the laws of physics should work the same now as they do in 10 seconds or in a million years. And we've talked in the program before how we're not actually sure whether energy is concerned because the universe is not actually static in time. It's growing with time. It's expanding. So all these questions are all mixed up in the very nature of time and the meaning of it and the conservation of energy and general relativity versus quantum mechanics, which is why I was so excited to see experimental tests of time crystals.

like, all right, put the theoretical questions aside, can somebody actually make one of these things? Right. How do you, I mean, it seems like you need really tiny pliers and a really powerful microscope to be able to make a time crystal. How do you go about doing those experiments? So the original idea of this ring of atoms didn't work because people showed that it was not actually in its ground state. But then a bunch of smart people got together and came up with, you know, other ideas. And you're exactly right. You need really tiny pliers. And usually in physics, when we're talking about tiny pliers, we're talking about photons. We're talking about like shooting little beams of light at individual atoms to try to make them do something interesting.

And so that's exactly what they did here. They put a bunch of atoms together and then they zap them with lasers. And atoms, you know, have various ways that they can sit. These atoms, for example, have a particular quantum spin. They can spin up or they can spin down. And remember, we're not talking about atoms spinning the way like a basketball. spins on the tip of your finger, this is some weird quantum mechanical property. And so it either has spin up or it has spin down. It's very difficult for it to be sort of in between. So you

arrange a bunch of these atoms in a row and then the atoms like to either be spin up or spin down and then you zap them with a laser, which makes those spins flip. I see. So you're zapping them, they have a certain spin preference and then they start to go the other direction? Yeah. So you have them in some arrangement, like they spin up, spin up, spin down, spin up, whatever. Then you zap them with a laser, and the laser is basically just photons, right? This is an oscillating electromagnetic field, and so we can flip the spins because these atoms all have electric charges. So the laser comes in, and it can flip the spins in a certain pattern, because the laser

is an electromagnetic field that can, like, oscillate up, and flip spins up, and then oscillate down, and flip spins down. So what we see, this is super interesting in these experiments, is that they arrange these atoms in a random pattern. The laser comes in and it makes these spins flip. They oscillate, right? You might think, all right, well, that's no big deal. Right, you're slapping them around.

Exactly. You're slapping them around. But then what happens when you turn off the laser? You turn off the laser and these atoms keep flipping. Oh, wow. And they keep flipping in exactly the same pattern as when you had the laser on. So they remember how they're supposed to flip even after the laser that's been smacking them around stops doing that. Exactly. They're in some weird, stable configuration where they're

in motion and they're returning to the same state over and over again. And they're not just static, right? They're in motion. This is some ground state configuration that's above zero. So it has continuous energy. So how long do they do this? Because, you know, someone might think of like that Newton's cradle office toy where you start it going and it goes for a while even without you doing the initial thing but with the conservation of momentum and eventually breaks down and stops moving. So what happens with these atoms? Yeah, that's a great question. And this is an experimental issue, right? In order to do this, you need to isolate these atoms. So you need to put them in some sort of larger trap, like use magnets or something to keep the rest of the world from like messing

it up. If you were in an empty universe where it was just these atoms and a laser, then we think it could last essentially forever if it really is a time crystal. Wow. But it's difficult to keep these things sort of isolated forever, people can do it for minutes at a time, but that's the longest that's been achieved. But we think that's just because of this question of like, you know, isolating it from the universe. We think that probably if it was totally separated, it could just keep going. Right. Because even in a vacuum, there's not nothingness. There's still stuff going on in that vacuum. Yeah, exactly. It's impossible to separate anything from the rest of the universe because there's always like quantum fields and fluctuations and all this kind of stuff. And so that's why it's

fun to explore these things at a theoretical level like, is this possible? And then it's a totally separate question of like, could you actually build these things? What are the experimental obstacles to actually making this exist in reality? But there's this team at University of Maryland that put this thing together and it kind of looks like they did it. You know, it kind of looks like the time crystal is real. Oh, that's so interesting. So this proof of concept by being able to create these oscillating atoms that you smack once and they're like, all right, I get it. I get it. I'll keep doing that. And then you can use that information to maybe do more work sort of in terms of like theoretical physics. Yeah, exactly. And that gives us some like understanding of,

you know, what is the nature of time? Now that we know the time crystals or we think that time crystals are a reality, we can go back and use that to like help guide us in building a deeper, more fundamental theory of like quantum gravity that has the right respect for time that treats time. That treats time. more like an element of space time. We think that the existence of time crystals points in the direction that the general relativity concept of time is correct. That doesn't mean that general relativity is right about everything. We know it breaks down to singularities, but this basic concept that space and time are

deeply interwoven is more likely to be true because time crystals exist. Right. Maybe we're seeing a little more agreement between quantum mechanics and general relativity than there was before. Can't we all just get along? Unity, right? Unity is the name of the day. And also, it's fun experimentally.

Like, this is a really important thing that might actually be useful technologically. Imagine, like, storing information. One thing that's difficult about building quantum computers is that it's hard for them to have memories because quantum objects, these tiny little particles. Yeah. They often like decay and they don't last very long in the state that you want. Well, time crystals might be a great way to build memory. circuits for quantum computers because they are stable in their lowest state and sort of remember

the configuration that you put them in the pattern that you put them in lasts through time. This is great for our quantum hamster script because now we can get teeny tiny computers for our teeny tiny quantum hamsters. So that whole scene where they're breaking into the quantum mainframe, that's going to work. Feeling good about this. Are they powered by tiny little quantum cotton candy? Is that what gives the quantum hamster its power? I mean, they got to keep up their carbs so they can run in those tiny quantum wheels, keep them going.

Or maybe they should eat like scalloped crystal eyeballs. Now we're getting into a horror movie. Yeah, that's right. That's the dark TV spin-off that will sell after the feature. So this team at Maryland did this, and then there's a team at Harvard that did something different. They took a diamond, right, which is a space crystal, and they put a bunch of nitrogen atoms inside that diamond, and then they turn those nitrogen atoms into a time crystal by zapping it with a laser in a very similar way. That's truly got to be a girl's best friend. A diamond,

and inside the diamond is a time diamond. Yeah, exactly. A time diamond inside a space diamond. That or it's like the Taco Bell version, you know, take a burrito and wrap it in a taco and then dip the whole thing in cheese. Either would be good engagement gifts, I think. Exactly. So it's a really exciting time sort of theoretically. Like, is this possible? There was a lot of discussion. People thought for many years that this was totally impossible. All the theorem suggested couldn't be done. And then people found few loopholes. And then a bunch of experimentalists went out there and said, hey, we're just going to try to make this thing. And it looks like they might have. So it's really fun for me to see like a whole area of science that people didn't even consider it was possible suddenly explode with activity and ideas and innovation. That's the great thing about sciences. You're always finding new things. Like you take old information, you shake it up and you find new things you previously thought was impossible. And now when I'm late to an appointment, I can say, well, have you heard the news about time crystals?

Our whole concept of time might not be right. That's right. Maybe I'm not late. Maybe you're late. Right. It's no way to know. There's no way to know. Daniel says time can't be eternal anyway.

I've got a note from my physicist. who says it's okay? The larger motivation is that there are still really basic questions out there, really big puzzles that haven't been solved because nobody has the right question or had the right first idea. And so Frank Welchek is a little kooky, but I love that he goes out there and tries to tackle something that people think is impossible and actually make progress and makes a mistake, but along the way, you know, breaks open a whole area of research.

And so somebody out there listening, hoping to grow up to be a physicist, to make some big discovery. Don't think that we figured it all out. We are far from understanding the nature of the universe around us. There are lots of really basic questions out there for you to find the answers to. And if you're too afraid to ask a question because you think it'll be stupid or wrong, you may never open up some really interesting research avenues. Yeah, exactly.

And remember, even Nobel Prize winners make mistakes. Take that Nobel Prize winner is not so fancy now, are we? Well, thank you guys so much for listening. I hope you enjoyed our little time crystal time, and we will see you next time. Time Crystal. Or not. We don't know. It's hard to say.

All right. Thanks for listening, everyone. Thanks for listening. And remember that Daniel and Jorge Explain the Universe is a production of IHeart Radio. For more podcasts from IHeart Radio, visit the. iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. Why are TSA rules so confusing? You got a hoot of you.

I'm Manny. I'm Noah. This is Devin. And we're best friends and journalists with a new podcast called No Such Thing, where we get to the bottom of. of questions like that. Why are you screaming? I can't expect what to do. Now, if the rule was the same, go off on me. I deserve it. You know, lock him up. Listen to no such thing on the IHeart radio app, Apple podcasts, or wherever you get your podcast. No such thing. From tips for healthy living

to the latest medical breakthroughs, WebMD's Health Discovered podcast keeps you up to date on today's most important health issues through in-depth conversations with experts from across the community, WebMD reveals how today's health news will impact your life tomorrow. It's not that people don't know that exercise is healthy, it's just that people don't know why it's healthy and we're struggling to try to help people

help themselves and each other. Listen to WebMD Health Discovered on the IHeart Radio app or wherever you get your podcasts. Hi, it's Honey German and I'm back with season two of my podcast. Grazias, come again. We got you when it comes to the latest in music and entertainment with interviews with some of your favorite Latin

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