Speaker 1: Hey, Katie, did you know that if you stick any
Speaker 1: two science worse together you get a great science fiction
Speaker 1: movie title. Really? Is it really that easy? Oh yeah,
Speaker 1: just give it a shot. Okay, let's see Quantum Hamster Boom.
Speaker 1: I can see that whole movie in my mind alway, Yeah, okay, okay,
Speaker 1: what about Alligator Crystal? I love it? Want to see
Speaker 1: that one. Let's do time, Pump. I'm calling Netflix and
Speaker 1: set up a pitch meeting right now. Hi. I'm Daniel.
Speaker 1: I'm a particle physicist, and I really would like to
Speaker 1: write a science fiction movie someday. And I am Katie.
Speaker 1: I am a science podcaster, and I am already writing
Speaker 1: dialogue for Quantum Hamster in my head. And Welcome to
Speaker 1: the podcast Daniel and Jorge Explain the Universe, a production
Speaker 1: of I Heart Radio in which we take you on
Speaker 1: a tour of everything that's amazing in the universe, everything
Speaker 1: that's out there doing crazy stuff you couldn't imagine, and
Speaker 1: all the weird quantum stuff happening at the particle level
Speaker 1: and everything in between. But we want you to come
Speaker 1: away from our podcast not just hearing about the crazy
Speaker 1: stuff in the universe, but actually understanding it. And as
Speaker 1: you might have guessed, Orge isn't with us today, but
Speaker 1: instead we have a wonderful guest podcast host, Katie introduce
Speaker 1: yourself to everybody. Hi, guys, I am Katie Golden. I'm
Speaker 1: the host of Creature Feature, a podcast about animal and
Speaker 1: human behavior. I studied psychology and evolutionary biology, so I
Speaker 1: am very excited to take a journey into the physics
Speaker 1: realm of things. I hope I can fill Jorges shoes
Speaker 1: a little bit temporarily. Do you know what his shoe sizes.
Speaker 1: He's a cartoonist, so he just draws really big, floppy
Speaker 1: clown shoes and that'll be perfect for me. Well, you
Speaker 1: guys should all check out. Creature Feature is a super
Speaker 1: fun podcast, and Katie's a lot of fun, which is
Speaker 1: why we invite her here as a guest host. And
Speaker 1: you know, today's episode is all about how we understand
Speaker 1: the universe and how we understand things like time, which
Speaker 1: makes me wonder since you're an expert on creatures and
Speaker 1: evolutionary behavior, do animals understand time? Katie? That's a really
Speaker 1: good question. I'd say it depends on the animal, and
Speaker 1: it depends on what you mean by understand a lot
Speaker 1: of animals can kind of mark the passage of time
Speaker 1: without possibly really understanding it. Like there's a great migration
Speaker 1: of plankton that happens every day with the rising and
Speaker 1: setting of the sun. But could you say that as
Speaker 1: little zooplankton really understands time. I'm gonna say no, that's
Speaker 1: a bold, controversial take. But yeah, it's really hard to
Speaker 1: get inside of the heads of animals. That's a problem
Speaker 1: talk about on my podcast. Well, I wouldn't be surprised
Speaker 1: if animals like crows understood time. There's a group of
Speaker 1: crows that seem to always gather outside my window, right
Speaker 1: or like I'm two o'clock in the afternoon when I
Speaker 1: have a big zoom meeting. Yeah, I think patterns are
Speaker 1: really easy for animals to understand, especially the smart ones crows.
Speaker 1: If you feed them, they'll come back and visit you
Speaker 1: whenever you feed them, so they will learn your patterns,
Speaker 1: much like a cat. You know how your cat wakes
Speaker 1: you up just in time early in the morning for
Speaker 1: you to feed them. They understand patterns. They will memorize
Speaker 1: your rhythms and patterns for the best snacking opportunities. Well,
Speaker 1: you know, I was wondering if you were going to
Speaker 1: ask whether any animal understands time, even humans, because as
Speaker 1: you might know, time is a slippery topic and it's
Speaker 1: something a lot of our listeners ask us to talk
Speaker 1: about because it's not something that even human physicists can
Speaker 1: get our minds around. Why do we remember the past
Speaker 1: and not the future? Why is there now? Is the
Speaker 1: now actually real? Or is time just an illusion? All
Speaker 1: of these really simple basic questions about time haven't yet
Speaker 1: been answered. So wait is time? When we're talking about
Speaker 1: time though, is it just a human invention? Like we
Speaker 1: made clocks, we have one o'clock to twelve o'clock, you know,
Speaker 1: we kind of have this concept of time, like is
Speaker 1: it not just our human invention or is there actually
Speaker 1: a real thing of time outside of our little mickey
Speaker 1: mouse watches. Yeah, it's a great question. There's a lot
Speaker 1: of it that is invented by humanity, like units, you know,
Speaker 1: one second, one minute, that's totally arbitrary, and an alien
Speaker 1: species might invent something totally different. But in our understanding
Speaker 1: of physics, time seems to be real, and we will
Speaker 1: dig into that later in the podcast about the concept
Speaker 1: of time in quantum mechanics. And the concept of time
Speaker 1: in general relativity, which turned out to be totally fundamentally
Speaker 1: different ideas of what time is. But yeah, we do
Speaker 1: think the time is a feature of the universe. We
Speaker 1: think it's something out there and real, but we won't
Speaker 1: really know until we one day get to talk to
Speaker 1: alien physicists and see if they even understand the concept
Speaker 1: of time. That's so interesting. So there is an actual
Speaker 1: cosmic time that is occurring that we sort of view
Speaker 1: through our own little human lens, our sun dials and
Speaker 1: our watches and our appointments, but that may not really
Speaker 1: capture the whole truth about what time is. Yeah, or
Speaker 1: it could be an illusion. It could be the time
Speaker 1: is not something deep and fundamental to the universe. It
Speaker 1: could be that it's sort of emerges that it's like
Speaker 1: a special condition that only happens under certain circumstances, you know,
Speaker 1: the way like ice forms sometimes in the universe, but
Speaker 1: not always. You could have a universe without ice. That's
Speaker 1: not a big deal. It might be the time isn't fundamental.
Speaker 1: But we'll dig into all that on today's podcast. We
Speaker 1: actually want to focus today on something even weirder than
Speaker 1: just the question of time, which is a big puzzle
Speaker 1: for physicist. We want to talk about something which has
Speaker 1: been bopping around the Internet and creating a lot of
Speaker 1: buzz recently. That's this topic of time crystals. Oh, that
Speaker 1: sounds beautiful. What comes into your mind when I said it?
Speaker 1: For his time crystals a bunch of clocks floating around
Speaker 1: in a crystalline structure. All right, And so today on
Speaker 1: the program we'll be asking and hopefully answering the question
Speaker 1: what is a time crystal? So, Daniel, you asked people
Speaker 1: on the internet what they thought. That's right. Folks out
Speaker 1: there volunteered to speculate baselessly on the topic of the day,
Speaker 1: just to give us a sense for what they knew
Speaker 1: and what they didn't know. And so if you would
Speaker 1: like to submit your baseless speculations for future podcast episodes,
Speaker 1: please write to me two questions at Daniel and Jorge
Speaker 1: dot com. And so here is what people had to say.
Speaker 1: My only thought is that there are these points in
Speaker 1: space that maybe our time markers, or there are certain
Speaker 1: blocks of crystals that hold elements or signatures of certain
Speaker 1: time events that you can look back on. That's easy.
Speaker 1: Um made a whole Rick and Morty episode about those.
Speaker 1: I don't know what time crystals are. Well, I know
Speaker 1: about Courts is a crystal, and we use courts to
Speaker 1: get precision timing and watches and things like that. Maybe
Speaker 1: there's other crystals that can do the same thing. So
Speaker 1: what do you think about those answers, Katie? I do
Speaker 1: like the call back to Rick and Morty. They definitely
Speaker 1: have a scientific approach to time with all of their
Speaker 1: time travel episodes, do they? Though? Are you a Rick
Speaker 1: and Morty fan? I like it it's a loaded question
Speaker 1: to ask if you're a Rick and Morty fan, because
Speaker 1: I think that there are some really hardcore fans out
Speaker 1: there who will contends that you have to really understand
Speaker 1: science to understand the show, and I just think it's
Speaker 1: a fun show. Yeah, well, you know, I watch Rick
Speaker 1: and Morty sometimes, but I'm a real stickler for getting
Speaker 1: the science right when you're doing time travel, and that's
Speaker 1: really hard. It's very difficult to have a narrative that
Speaker 1: makes sense if you're also going backwards in time and
Speaker 1: jumping all around, and so that sometimes gets the way
Speaker 1: of me enjoying Rick and Morty. I see, you're real
Speaker 1: stickler for those time travel plot holes that always pop up. Yeah, exactly.
Speaker 1: Speaking of time, the focus of today's episode is this question,
Speaker 1: what is a time crystal? I like some of these answers.
Speaker 1: You know, we do use a crystal in watches sometimes
Speaker 1: to tell time, right, crystals are at the heart of
Speaker 1: a lot of watches on people's risks. How do they
Speaker 1: work to tell time? Do you have just a little
Speaker 1: crystal man in your watch going like it's about two thirty?
Speaker 1: That's exactly how it works. You crack it open, you'll
Speaker 1: spot we're writing a Rick and Morty episode. But that's
Speaker 1: not actually the kind of time crystal that we're talking
Speaker 1: about today. Today's episode is about something totally different. So
Speaker 1: what kind of time crystal are we talking about? If
Speaker 1: it's not a little crystal telling you what time it is.
Speaker 1: The idea of a time crystal basically is an extension
Speaker 1: of the idea of a space crystal. So let's first
Speaker 1: talk about what a space crystal is, remind ourselves about
Speaker 1: like the basic idea there, and then we'll try to
Speaker 1: apply that concept to time crystals. Now, I'm imagining a
Speaker 1: crystal floating through space, but I'm going to guess that's
Speaker 1: probably not what it is. No, exactly that's exactly what
Speaker 1: it is for a space crystal, right, A space crystal
Speaker 1: is what it's just like a regular pattern and a
Speaker 1: crystal like the kind of thing that you see like
Speaker 1: a shiny gem or something else you would call a
Speaker 1: crystal is if you zoom down into it and understood
Speaker 1: it like at the molecular or the atomic level. The
Speaker 1: way it's built is like a bunch of Lincoln logs
Speaker 1: or something. You have regularly spaced atoms all end up
Speaker 1: in like a three dimensional pattern. Right, It's that kind
Speaker 1: of grid like structure. I always think of a sort
Speaker 1: of a wafer kind of treat, maybe just because I'm hungry,
Speaker 1: but it's those layers and layers of interlocking wafer like
Speaker 1: molecular structures. Right, Yeah, exactly. You have wafer and then
Speaker 1: you have caramel, then you have another wafer, then you
Speaker 1: have chocolate. That's exactly the recipe for building your crystal.
Speaker 1: Just making me hungrier, Katie's crystal cookies, I love it. Well.
Speaker 1: Sugar is a crystal. Yes, sugar is a crystal. And
Speaker 1: basically anything that's a crystal that has a regular pattern.
Speaker 1: And that's the core concept that we have to understand
Speaker 1: when we're talking about crystals. Basically, you're building a lattice.
Speaker 1: You're taking a continuous symmetry right like space in itself
Speaker 1: is the same everywhere. It doesn't really matter if you
Speaker 1: take one step forward or a half step forward. The
Speaker 1: same laws of physics reply, everything works the same way.
Speaker 1: If you're gonna like juggle balls here, then you took
Speaker 1: a step sideways, the same rules should apply, the same
Speaker 1: juggling should work. A crystal takes that and sort of
Speaker 1: breaks that symmetry into something discreet. So now the universe
Speaker 1: has a symmetry still, but it's not like smooth. You
Speaker 1: have to take like exactly the right size step in
Speaker 1: order to see the universe the same way. So if
Speaker 1: you're like inside a big crystal is a huge lattice
Speaker 1: and you're sitting on an atom, you have to take
Speaker 1: a step exactly the size of the lattice so that
Speaker 1: you're still sitting on an atom. It's chess rules, except
Speaker 1: you're all ponds. Yeah, exactly, take space and break it
Speaker 1: up into chessboards, and you can only move one square
Speaker 1: or two squares. You can't move one and a half
Speaker 1: or two and a half squares. And so that's the
Speaker 1: idea of a space crystal, and like do you think
Speaker 1: of a crystal is a big shiny thing, But when
Speaker 1: you zoom down into it, the reason that it's shiny,
Speaker 1: the reason it has those properties that reflect LFE that way,
Speaker 1: is because it has this regular structure in space. So
Speaker 1: when we say crystal here, we generally just mean like
Speaker 1: a regular, discrete structure. That's so interesting. I mean, crystal
Speaker 1: structures are really interesting and evolutionary biology because they are
Speaker 1: surprisingly sometimes used in eyeballs, like in the eyes of
Speaker 1: mollusks will have these guanting crystal structures that help them
Speaker 1: reflect light. You don't think of organic material as something
Speaker 1: you can turn into a crystal, but yeah, you can
Speaker 1: take guanting form a guanting crystal form an eyeball. That's fascinating.
Speaker 1: So most eyeballs don't have crystals in them. It's a
Speaker 1: special situation. Yeah, we have lenses in most eyeballs, but
Speaker 1: those guanting crystals that form in certain eyeballs, like in
Speaker 1: the eyes of scalps, will have this characteristic that helps
Speaker 1: them reflect light in such a way that gives them
Speaker 1: really interesting vision. And scallops have eyes, yes they do.
Speaker 1: You wouldn't think so, I'll think about that. Next time
Speaker 1: i'm biting into one, I'm tasting crystalline eyeballs. They're actually
Speaker 1: beautiful blue eyes and they have a whole mess of them,
Speaker 1: like two hundred of them. Oh my gosh, Well that
Speaker 1: makes me feel better. That's why I don't eat scalops
Speaker 1: because I don't like crystalline eyeballs. And instead of using
Speaker 1: lenses like a human or mammal eye or most animals eyes,
Speaker 1: they actually use mirrors inside of their eyes as kind
Speaker 1: of a miniature telescope by using that guanting crystal structure. Wow, amazing. Well,
Speaker 1: the other important thing to understand about these kinds of
Speaker 1: crystals that we're talking about space crystals is that they
Speaker 1: are stable. So like those crystals in the eyes of scallops,
Speaker 1: or that diamond that comes up out of the ground
Speaker 1: is stable as the regularly repeating pattern, but it doesn't
Speaker 1: fall apart. It is in its lowest energy state, and
Speaker 1: so we can hang out basically for a long time.
Speaker 1: It needs to be broken up if you want those
Speaker 1: atoms back. Is that why diamonds are so tough because
Speaker 1: of that crystalline structure. Yeah, because the crystalline structure makes
Speaker 1: them really hard to break. And also that's why they
Speaker 1: last a long time because they're in a stable state.
Speaker 1: Like the atoms, they're very happy to be in that situation.
Speaker 1: They're not going to relax into some other lower ground
Speaker 1: state and then break up into something else energetically. They're
Speaker 1: very comfortable. That's so interesting. It's something like an ice
Speaker 1: cube forms a lot of structure, but it does melt.
Speaker 1: So is that an example of like an unstable crystal structure. Yeah.
Speaker 1: Ice is actually super fascinating because it can form lots
Speaker 1: of different kinds of structures. And we're gonna do a
Speaker 1: whole podcast episode about all the different weird kinds of ice.
Speaker 1: It's like one that's not transparent black ice, and it's
Speaker 1: like nine other kinds of ice. So it can form
Speaker 1: lots of weird crystal structures, but actually is in a
Speaker 1: stable state. The only reason it melts is because you're
Speaker 1: adding energy to it. Right. Melting means you're like heating
Speaker 1: it up from the outside. Same with diamonds. You put
Speaker 1: diamonds in hot enough temperatures, they will melt. That actually happens.
Speaker 1: We think sort of like on the surface of Jupiter,
Speaker 1: which rains diamonds into the interior, which might form like
Speaker 1: a big liquid diamond ocean. So Jupiter is really rich,
Speaker 1: talking about Kardashian levels of rich. Absolutely, absolutely, So now
Speaker 1: we understand, like the idea of a crystal, it's like
Speaker 1: a regular structure, but that's a crystal structure in space.
Speaker 1: So now it's turned to the topic we're trying to
Speaker 1: talk about today, which is time crystals. Right, take that
Speaker 1: same idea and apply it to time. Okay, but how
Speaker 1: do you put time in a crystal? Because time is
Speaker 1: not physical matter. You can't arrange it in a lott
Speaker 1: of structure. So what are you trying to say here?
Speaker 1: So take the same idea you're applying to a lattice
Speaker 1: in space, where you say, all right, the thing looks
Speaker 1: the same if I take one step to the right,
Speaker 1: or one step forward or one step backwards. And now
Speaker 1: say what happens if I take a step forwards in time?
Speaker 1: So a time crystals some kind of object or substance
Speaker 1: which has a regular repeating pattern in time, which means
Speaker 1: like it looks the same now and then in a second,
Speaker 1: and then in two seconds, and then in three seconds
Speaker 1: and in between. It doesn't have to look the same,
Speaker 1: but it's going through some transformation so regularly returns to
Speaker 1: the same position. So this is like four dimensional chess
Speaker 1: where it's like you're playing this chess game where you're
Speaker 1: only allowed to move one space at a time in
Speaker 1: a certain direction, but it through time and not through
Speaker 1: physical space necessarily, Yes, exactly. And so what you want
Speaker 1: is something which returns to the same configuration, but after
Speaker 1: discrete units of time, right, not like it's in that
Speaker 1: same state all the time. That would just be a
Speaker 1: space crystal. You want a time crystal which is in
Speaker 1: a certain configuration, then moves out of it and comes back,
Speaker 1: and then moves out of it and then comes back.
Speaker 1: So you wanted to sort of break this continuous time
Speaker 1: symmetry where things always look the same into a discrete symmetry,
Speaker 1: so that it looks the same and then it doesn't,
Speaker 1: and then it comes back and it looks the same again.
Speaker 1: That's the property you have in a space crystal, right,
Speaker 1: you have this distance between points in space. Now we
Speaker 1: want distance between configurations in time. Kind of sounds like
Speaker 1: a dance to me. You have to do your dance
Speaker 1: movements through not just space, but through time, and it
Speaker 1: has to synchronize in a specific way. Yes, exactly, And
Speaker 1: the other critical thing is that it has to be stable,
Speaker 1: meaning it has to be in its grounds eight. That
Speaker 1: means that basically it's doing this forever. So you need
Speaker 1: something which is both in motion but also in the
Speaker 1: most relaxed, lowest energy state, and that's a really unusual combination.
Speaker 1: You have to imagine something basically moving forever that sounds
Speaker 1: like a perpetual motion, which I didn't realize is something
Speaker 1: you could do. Well, my mind is blown, so I'm
Speaker 1: going to try to recollect my brain back into pieces.
Speaker 1: But before we do that, let's take a quick break.
Speaker 1: And we're back and Daniel is trying to reassemble the
Speaker 1: pieces of my brain that exploded. Because we were talking
Speaker 1: about how there is something where with a time crystal
Speaker 1: you can remain in emotion forever at a low energy state,
Speaker 1: which sounds like perpetual motion to me, which I thought
Speaker 1: was just science fiction. So how could this possibly happen? Yeah,
Speaker 1: it's a really awesome question. And it's for this reason
Speaker 1: that people thought forever like this is a silly idea.
Speaker 1: Nobody should even talk about it. It's obviously impossible, and
Speaker 1: it's only recently that people thought maybe there's a way
Speaker 1: to make this happen. Maybe there's a way to configure
Speaker 1: a system that can be in motion through time where
Speaker 1: regularly returns to a specific state that's one of the
Speaker 1: lattest point and yet is stable. So we could like
Speaker 1: do this forever. And this started in about twenty twelve
Speaker 1: when a famous physicist named Frank Wilcheck. He's at m
Speaker 1: I T and he won the Nobel Prize for understanding
Speaker 1: the strong interaction, which is a thing that like binds
Speaker 1: quirks together into protons and neutrons. So he's generally a
Speaker 1: smart guy, and he's also kind of famous for coming
Speaker 1: out of left field with a crazy idea that turns
Speaker 1: out to be pretty good. He's the guy, for example,
Speaker 1: who coined the term axons to describe that hypothetical particle,
Speaker 1: and in he put out this kind of crazy paper saying,
Speaker 1: you know what, here's a situation where time crystals might
Speaker 1: be possible. He constructed an example of a quantum system,
Speaker 1: a ring of particles that sort of rotates and every
Speaker 1: sort of clock cycle returns to a similar configuration and
Speaker 1: repeats the same pattern in time. So exploded into like
Speaker 1: the community of theoretical physics blowing everybody's mind. So is
Speaker 1: this something that would happen on the quantum level. Are
Speaker 1: we talking about entire like star systems doing this like
Speaker 1: time crystal thing, or are we talking about something on
Speaker 1: a very small scale. This is something a very small scale.
Speaker 1: This would definitely be a quantum effect. It's not the
Speaker 1: kind of thing that you can have happened from macroscopic systems.
Speaker 1: And the reason you can only do it potentially for
Speaker 1: quantum systems is that quantum systems have a really weird
Speaker 1: relationship with zero energy. Right. Things that the quantum scale
Speaker 1: can never have exactly zero energy, so when you force
Speaker 1: them into their howest energy state, it's not actually down
Speaker 1: to zero energy. But a whole fun podcast episode recently
Speaker 1: about zero point energy in the Casimir effect, which basically
Speaker 1: says if you look into empty space, it's actually filled
Speaker 1: with an infinite number of photons because all the fields
Speaker 1: that are out there in space can never really relax
Speaker 1: down to zero energy. So time crystals, if you think
Speaker 1: they're possible, could only be possible for tiny, little microscopic
Speaker 1: quantum particles. This is like when my car battery drained
Speaker 1: down to quote unquote zero and the mechanics that I
Speaker 1: need a new one, But hey, guess what, I got
Speaker 1: a little bit more out of that battery. So maybe
Speaker 1: it was some quantum time crystals at work there. Or
Speaker 1: when your iPhone battery says it's at zero but it's
Speaker 1: still running, and you're like, am I using the Casimir
Speaker 1: effect to charge my bode? And you might also be imagining,
Speaker 1: you know, obvious examples of like larger physical systems, not
Speaker 1: just stars, that seem to have this property that they
Speaker 1: could spin, for example, and return to the same state.
Speaker 1: Like think about a wheel with spokes. As it rotates,
Speaker 1: it returns to basically the same configuration. The problem is
Speaker 1: that bicycle wheels, a macroscopic object, could never actually spin forever.
Speaker 1: And that's also not its ground state. It's not the
Speaker 1: most lowest energy state. Lowest energy state for a bicycle
Speaker 1: wheel is when it's stopped right, And so that's why
Speaker 1: we aren't able to actually make a perpetual motion machine
Speaker 1: out of bicycle wheels and water and marbles and so
Speaker 1: on and so forth. But Frank will Check wrote this
Speaker 1: paper and said, you know what, it might be possible
Speaker 1: for quantum objects, basically like a little quantum wheel. He
Speaker 1: tried to show this thing could spin forever and actually
Speaker 1: be in its ground state. Now. Of course this set
Speaker 1: off like a lot of conversations in the theoretical physics community.
Speaker 1: And there's another theorist, Patrick Bruno, who actually found a
Speaker 1: mistake in well checked paper tattletale. I know this, but
Speaker 1: this is a good lesson, like Nobel Prize winners make mistakes.
Speaker 1: I feel like a lot of times people quote Nobel
Speaker 1: Prize winners and if they said it and they want
Speaker 1: a Nobel Prize in must be the truth, right, But
Speaker 1: like they're just people. You know, Yes, they're smart and
Speaker 1: they got lucky, but they're also people and sometimes they
Speaker 1: make mistakes. Ye take that, you Nobel Prize winning smarty pants.
Speaker 1: I especially love it when they interview a Nobel Prize
Speaker 1: winner on a topic they're like, not an expert in
Speaker 1: you know, you'll hear like a Nobel Prize winning physicist
Speaker 1: commenting on economic policy and you're like, you don't know
Speaker 1: anything more about that than anybody else, Like just because
Speaker 1: he won the Nobel Prize, Yeah, you know, I'm as
Speaker 1: much a Nobel Prize winner in a field you didn't
Speaker 1: study as you are Nobel Prize winner in physics. So they're, yeah,
Speaker 1: exactly what was this mistake and how did that change
Speaker 1: this whole concept of being able to have these little,
Speaker 1: little tiny time crystals. Yeah. So Patrick Bruno showed that
Speaker 1: the example that will Check proposed, this idea of a
Speaker 1: ring of particles rotating was actually more similar to a
Speaker 1: bicycle wheel spinning than we thought that he would only
Speaker 1: rotate if it was actually in a more energetic state,
Speaker 1: and he showed that the example that will Check suggested
Speaker 1: had the possibility to decay into a ground state which
Speaker 1: wouldn't be rotating, and so it wouldn't actually qualify as
Speaker 1: a time crystal. But you know, once the idea is
Speaker 1: out there, then people started working on They thought, that's interesting,
Speaker 1: let's reinvestigate a lot of times you have an area
Speaker 1: in physics where people are like, oh, we already know
Speaker 1: the answer there, that's totally impossible, and it takes one
Speaker 1: brave person like dig into again and ask the question anew,
Speaker 1: and then a lot of people will follow and be like, oh,
Speaker 1: that's interesting, I wonder if we could actually crack this problem.
Speaker 1: And so Frank will Checks credit with like cracking this
Speaker 1: problem open again, and then a huge number of people
Speaker 1: started writing papers, and there were a lot of people
Speaker 1: that said, oh no, it turns out of time crystals
Speaker 1: completely impossible. They wrote all these no go papers that
Speaker 1: proved under various conditions. You could never have a time crystal.
Speaker 1: You can never have a quantum mechanical arrangement of particles
Speaker 1: that repeats in time and is at its ground state.
Speaker 1: Wet blankets trying to make it so that I can't
Speaker 1: make a little quantum circus with a little merry go round,
Speaker 1: and I'm thinking about cork on a unicycle just going
Speaker 1: on forever, and I don't like it. I want to
Speaker 1: hear some optimism. Well, we'll talk about the actual experiments
Speaker 1: in a minute, because this also inspired a bunch of
Speaker 1: folks to say, well, let's go see if we can
Speaker 1: make one. You know, sometimes the theorists say that's as possible,
Speaker 1: this is impossible, but it's up to the universe to
Speaker 1: decide whether it actually happens. And so I like when
Speaker 1: experimentalists sort of don't listen to the theorists and just
Speaker 1: go out there and explore. But it's actually really interesting
Speaker 1: and important question about time crystals because it gets to
Speaker 1: the heart of how we think about time. And this
Speaker 1: is something you were bringing up earlier, like is time
Speaker 1: or real thing? If time crystals are really really would
Speaker 1: tell us something fundamental about the nature of like time
Speaker 1: and the universe. Yeah, because I feel like we don't
Speaker 1: really have a frame of reference outside of our human
Speaker 1: invention of We mark the minutes, we mark the seconds.
Speaker 1: We pick sort of these units of time, probably based
Speaker 1: on our ability to like the time it takes us
Speaker 1: to think about a second, is about how long a
Speaker 1: second is, So you know, it's based very much on
Speaker 1: our human brains. But it's interesting. I guess I've never
Speaker 1: really thought too much about finding empirical evidence for their
Speaker 1: being time. Well, it's also really interesting to sort of
Speaker 1: dig into it theoretically and ask, like our fundamental picture
Speaker 1: of the universe, what does that tell us about time?
Speaker 1: And we have two pictures of the universe the way
Speaker 1: things work sort of at the deepest level in the universe,
Speaker 1: quantum mechanics and general relativity. And as listeners the podcast know,
Speaker 1: these two don't often agree, and that's also the case
Speaker 1: about the nature of time. Have very different opinions about
Speaker 1: what time is, and quantum mechanics says that space and
Speaker 1: time are very different, and according to quantum mechanics, you
Speaker 1: have like a description of the universe. It says like,
Speaker 1: here's your quantum particle, there's your quantum particle, whatever. And
Speaker 1: you know, quantum mechanics tells us what's likely to happen
Speaker 1: to those particles in the future, and all that crazy
Speaker 1: stuff that we can dig into another episode. But the
Speaker 1: important thing is that quantum mechanics tells us how those
Speaker 1: quantum states evolved, like the Shortinger equation, the most famous equation,
Speaker 1: and quantum mechanics, that's what it does. It tells us,
Speaker 1: if you have a quantum state, here's what it's going
Speaker 1: to look like in the future. And also you can
Speaker 1: turn that equation around and you can say, here's how
Speaker 1: you got to now, here's how the past must have
Speaker 1: looked if the present looks this way. And there's a
Speaker 1: concept we often talk about called quantum information, and that's
Speaker 1: what this means. It says that if you know how
Speaker 1: the universe looks now, you can figure out how we
Speaker 1: got here because quantum information is never destroyed. And that's
Speaker 1: a deep and fundamental statement about the nature of the
Speaker 1: universe because it means, according to quantum mechanics, the time
Speaker 1: is eternal time like goes on forever into the future
Speaker 1: and into the past. So that's true of quantum mechanics,
Speaker 1: like in the quantum miniature universe, but like when we
Speaker 1: look at the larger universe, once we scale it up,
Speaker 1: those ideas don't hold true. Yeah, exactly. This is relevant
Speaker 1: to the rules of tiny little particles. But you're right,
Speaker 1: when we scale up to the rest of the universe,
Speaker 1: things do look a little different. And this is when
Speaker 1: general relativity comes in, because when it comes to like
Speaker 1: the shape of the universe and the age of the universe,
Speaker 1: the thing that matters most is gravity, and general relativity
Speaker 1: is the best theory we have that describes how gravity works.
Speaker 1: And the most important concept in general relativity that's relevant
Speaker 1: for today's conversation is this notion that space and time
Speaker 1: are very deeply connected, or quantum mechanics says space time
Speaker 1: are separate. Time is just like the way that things
Speaker 1: in space evolve one step to the other. General relativity says, no, no, no,
Speaker 1: Time is like just one part of this thing we
Speaker 1: call space time, and there's a deep symmetry between space
Speaker 1: and time, and they evolve together and they get twisted
Speaker 1: together and they really closely connected. And if you think
Speaker 1: about what general relativity says about time even more deeply,
Speaker 1: you know, general relativity says that the universe is expanding
Speaker 1: and that it used to be denser, and as you
Speaker 1: look backwards in time, time doesn't go on forever. It
Speaker 1: comes back to some sort of like singularity in the
Speaker 1: early universe. And according to general relativity, is very natural,
Speaker 1: for example, to have a beginning of time, for time
Speaker 1: to have started rum zero in the early universe. So
Speaker 1: quantum mechanics says space and time very different and time
Speaker 1: has lasted forever. General relativity says, no, no no, no, These
Speaker 1: are just two different sides of the same coin. And
Speaker 1: it makes perfect sense for time to have started in
Speaker 1: the early universe. So two very different pictures about this
Speaker 1: very basic piece of the universe. Well, the universe is
Speaker 1: made out of quantum particles, and so the bigger aspects
Speaker 1: of the universe are made up of the quantum aspects
Speaker 1: of the universe. So it's very interesting that you have
Speaker 1: this disagreement ostensibly between basically the some of the parts
Speaker 1: and the parts themselves. Yeah, you're absolutely right, And one
Speaker 1: of the reasons they disagree is that usually they play
Speaker 1: in different fields. When we talk about tiny little particles,
Speaker 1: gravity is so weak that it's basically irrelevant, and we
Speaker 1: can ignore what general relativity says. And then when we
Speaker 1: zoom up to talk about stars and planets, all those
Speaker 1: tiny little particles are so small they get just averaged out.
Speaker 1: All the quantum effects basically disappear. So general relativity is
Speaker 1: dominant for really big heavy stuff, and quantum mechanics are
Speaker 1: dominant for really tiny, very low mass stuff. And it's
Speaker 1: very rare for the two to be important, so we
Speaker 1: can't tell like who wins when they're both important. The
Speaker 1: only way to figure that out is to do things
Speaker 1: like look inside of a black hole, where things are
Speaker 1: so small but so dense that both of them are important.
Speaker 1: And that's not something we've been able to do yet,
Speaker 1: not yet. Maybe in a few years. Well, I want
Speaker 1: to hear about how this disagreement impacts whether or not
Speaker 1: I can have my tiny time crystal Carnival. But maybe
Speaker 1: we should take a quick break first of while I
Speaker 1: draw up some little quantum merrigo rounds schematics. We are back.
Speaker 1: I'm trying to decide whether to sell cotton candy at
Speaker 1: my little quantum Carnival with the time crystal Dance, the
Speaker 1: time crystal Carousel, And so Daniel is going to explain
Speaker 1: to me how quantum mechanics and general relativity, the small
Speaker 1: side of the universe, the quantum side, and the big side,
Speaker 1: the US and stars and everything else can disagree so
Speaker 1: much about time and space. Yeah, well, I wish we
Speaker 1: knew the answer to that. But one way that we
Speaker 1: might be able to probe it is to look inside
Speaker 1: the core of a black hole and understand, you know,
Speaker 1: who's right about the nature of the universe, or go
Speaker 1: back in time to the Big Bang. But you know
Speaker 1: that's kind of inaccessible. So we're excited anytime we can
Speaker 1: probe thing that we think gets near this question that
Speaker 1: lets us like understand around the edges of these questions
Speaker 1: about the fundamental nature of the universe. And that's why
Speaker 1: time crystals are super fascinating because they explore this connection
Speaker 1: between space and time. Like if time crystals can actually
Speaker 1: be made, it's really a strong argument that there's a
Speaker 1: close connection between space and time, that this thing that
Speaker 1: exists in space space crystals can also be made in time,
Speaker 1: that time can be seen sort of like as another
Speaker 1: dimension of space. It adds sort of like a check
Speaker 1: in the column of general relativity. And so that would
Speaker 1: mean that quantum mechanics is actually behaving in a way
Speaker 1: that is following the rules of general relativity. It would
Speaker 1: mean that we need to adapt somehow quantum mechanics to
Speaker 1: play along nicely with this concept that space and time
Speaker 1: are deeply connected. And you know, we know already that
Speaker 1: quantum mechanics can't really be right about time being eternal
Speaker 1: in every direction, like we think the universe had a beginning,
Speaker 1: So it doesn't really make sense to hold tightly to
Speaker 1: this concept that time must be eternal. On the other hand,
Speaker 1: it's a pretty big thing to get rid of, to
Speaker 1: let go of this concept of quantum unitarity, that quantum
Speaker 1: information is not ever lost. That's something we really think
Speaker 1: is that the foundation of quantum mechanics. So one of
Speaker 1: these theories has to get torn up basically and start again.
Speaker 1: And the question is which. And we're hoping that time
Speaker 1: crystals give us like a glimmer of understanding as to
Speaker 1: how to begin that process. But even if we knew
Speaker 1: right for example, that general relativity was correct, doesn't tell
Speaker 1: us exactly how to start on quantum mechanics, and before
Speaker 1: we put too many nails in the coffin of quantum mechanics, like,
Speaker 1: I don't think anybody out there in physics believes general
Speaker 1: relativity is correct. It's got to be wrong because it
Speaker 1: assumes that the universe is smooth and continuous in a
Speaker 1: way that quantum mechanics we know our experiments tell us
Speaker 1: just can't be true. So my money is on both
Speaker 1: of them are wrong. And we kind of come up
Speaker 1: with a whole new theory that combines the two or
Speaker 1: kind of cross checking these two rule books that were
Speaker 1: writing based on the quantum information and then the larger
Speaker 1: scale general relativity information. And it sounds like you physicists
Speaker 1: have to cross check them and figure out where which
Speaker 1: things make sense and then kind of get rid of
Speaker 1: the things that don't as you cross check them, and
Speaker 1: time crystals might help you do that. Yeah, exactly, And
Speaker 1: you're right, we're sort of trying to weave these threads together.
Speaker 1: You know, people have been working on quantum mechanics for
Speaker 1: a while, people have been working on job relativity for
Speaker 1: a while, and the goal, of course, is to come
Speaker 1: up with a single holistic explanation from the whole universe
Speaker 1: or how everything fits together, and that requires like trying
Speaker 1: to weave these threats together. And in the past we've succeeded,
Speaker 1: Like we figured out that electricity and magnetism are really
Speaker 1: just two sides of the same coin, and neither theory
Speaker 1: was wrong. They just sort of fit together in an
Speaker 1: unexpected way. And then we added the weak force, and
Speaker 1: now we have like a theory of the electromagnetic weak forces.
Speaker 1: These three things sort of woven together into one common understanding.
Speaker 1: The goal is to make progress by pulling these things together,
Speaker 1: by getting our understanding from various bits of physics and
Speaker 1: sort of putting it together to make a holistic picture.
Speaker 1: And there's one more part of that thread that we
Speaker 1: might try to pull in, and this this idea about
Speaker 1: the connection between time and energy. Right the time crystal,
Speaker 1: if it exists, is a weird thing because it's in motion,
Speaker 1: but it's also like at its lowest energy state. Well,
Speaker 1: there's another deep theorem about physics, Nother's theorem that tells
Speaker 1: us why we have energy conservation in our universe. It
Speaker 1: says that energy is conserved in our universe because there's
Speaker 1: some symmetry with time that the laws of physics should
Speaker 1: work the same now as they do in ten seconds
Speaker 1: or in a million years. And we've talked in the
Speaker 1: program before how we're not actually sure whether energy is
Speaker 1: conserved because the universe is not actually static in time.
Speaker 1: It's growing with time, it's expanding. So all these questions
Speaker 1: are all mixed up in the very nature of time
Speaker 1: and the meaning of it, and the conservation of energy
Speaker 1: and general relativity versus quantum mechanics, which is why I
Speaker 1: was so excited to see experimental tests of time crystals, Like,
Speaker 1: all right, put the theoretical questions aside, can somebody actually
Speaker 1: make one of these things? Right? How do you? I mean,
Speaker 1: it seems like you need really tiny pliers and a
Speaker 1: really powerful microscope to be able to make a time crystal.
Speaker 1: How do you go about doing those experiments? So the
Speaker 1: original idea of this ring of atoms didn't work because
Speaker 1: people showed that it was not actually in its ground state.
Speaker 1: But then a bunch of smart people got together and
Speaker 1: came up with, you know, other ideas, and you're exactly right,
Speaker 1: you need really tiny pliers. And usually in physics, when
Speaker 1: we're talking about tiny players were talking about photons, we're
Speaker 1: talking about like shooting little beams of light at individual
Speaker 1: atoms to try to make them do something interesting. And
Speaker 1: so that's exactly what they did here. They put a
Speaker 1: bunch of atoms together and then they zapped them with lasers.
Speaker 1: And atoms, you know, have various ways that they can sit.
Speaker 1: These atoms, for example, have a particular quantum spin. They
Speaker 1: can spin up or they can spin down. And remember
Speaker 1: we're not talking about atoms spinning the way like a
Speaker 1: basketball spins on the tip of your finger. This is
Speaker 1: some weird quantum mechanical property. And so it either has
Speaker 1: spin up or it has spin down. It's very difficult
Speaker 1: for it to be sort of in between. So you
Speaker 1: arrange a bunch of these atoms in a row, and
Speaker 1: then the atoms like to either be spin up or
Speaker 1: spin down, and then you zap them with a laser,
Speaker 1: which makes those spins flip. I see, so you're zapping them,
Speaker 1: they have a certain spin preference, and then they start
Speaker 1: to go the other direction. Yeah, So you have them
Speaker 1: in some arrangement like the spin up, spin up, spin down,
Speaker 1: spin up, whatever, and then you zap them with a laser.
Speaker 1: And the laser is basically just photons, right, This is
Speaker 1: an oscillating electromagnetic field, and so it can flip the
Speaker 1: spins because these atoms all have electric charges. So the
Speaker 1: laser comes in and it can flip the spins in
Speaker 1: a certain pattern. Because the laser is an electromagnetic field
Speaker 1: that cannot oscillate up and flip spins up and then
Speaker 1: as laid down and flip spins down. So what we see,
Speaker 1: this is super interesting in these experiments, is that they
Speaker 1: arrange these atoms in a random pattern. The laser comes
Speaker 1: in and it makes these spins flip. They oscillate, right,
Speaker 1: you might think, all right, well, that's no big deal,
Speaker 1: but you're slapping them around exactly, you're slapping them around.
Speaker 1: But then what happens when you turn off the laser.
Speaker 1: You turn off the laser and these atoms keep flipping.
Speaker 1: You keep flipping in exactly the same pattern as when
Speaker 1: you had the laser on. So they remember how they're
Speaker 1: supposed to flip, even after the laser that's been smacking
Speaker 1: them around stops doing that. Exactly, they're in some weird
Speaker 1: stable configuration where they're in motion and they're returning to
Speaker 1: the same state over and over again, and they're not
Speaker 1: just static, right, they're in motion. This is some ground
Speaker 1: state configuration that's above zero, so it has continuous energy.
Speaker 1: So how long do they do this? Because you know,
Speaker 1: someone might think of like that Newton's Cradle office toy
Speaker 1: where you started going and it goes for a while
Speaker 1: even without you doing the initial thing, but with the
Speaker 1: conservation of momentum and eventually breaks down and stops moving.
Speaker 1: So what happens with these atoms? Yeah, that's a great question,
Speaker 1: and this is an experimental issue, right. In order to
Speaker 1: do this, you need to like isolate these atoms, so
Speaker 1: you need to put them in some sort of larger trap,
Speaker 1: like use magnets or something to keep the rest of
Speaker 1: the world from like messing it up. If you were
Speaker 1: in an empty universe where it's just these atoms and
Speaker 1: a laser, then we think it could last essentially forever
Speaker 1: if it really is a time crystal. But it's difficult
Speaker 1: to keep these things sort of isolated forever. People can
Speaker 1: do it for minutes at a time, but that's the
Speaker 1: longest that's been achieved. But we think that's just because
Speaker 1: of this question of like, you know, isolating it from
Speaker 1: the universe. We think that probably if it was totally separated,
Speaker 1: you could just keep going, right, because even in a vacuum,
Speaker 1: there's not nothingness. There's still stuff going on in that vacuum.
Speaker 1: Yeah exactly. It's impossible to separate anything from the rest
Speaker 1: of the universe because there's always like qual fields and
Speaker 1: fluctuations and all this kind of stuff. And so that's
Speaker 1: why it's fun to explore these things at a theoretical level,
Speaker 1: like is this possible? And then it's a totally separate
Speaker 1: question of like could you actually build these things? One
Speaker 1: of the experimental obstacles to actually making this existing reality.
Speaker 1: But there's this team at University of Maryland that put
Speaker 1: this thing together and it kind of looks like they
Speaker 1: did it, you know, it kind of looks like the
Speaker 1: time crystal is real. That's so interesting. So this proof
Speaker 1: of concept by being able to create these oscillating atoms
Speaker 1: that you smack once and they're like all right, I
Speaker 1: get it, I get it. I'll keep doing that, and
Speaker 1: then you can use that information to maybe do more
Speaker 1: work sort of in terms of like theoretical physics. Yeah exactly,
Speaker 1: And that gives us some like understanding of you know,
Speaker 1: what is the nature of time? Now that we know
Speaker 1: that time crystals. We think the time crystals are a reality.
Speaker 1: We can go back and use that to like help
Speaker 1: guide us in building a deeper, more fundamental theory of
Speaker 1: like quantum gravity that has the right respect for time,
Speaker 1: that treats time more like an element of space time.
Speaker 1: We think that the existence of time crystals points in
Speaker 1: the direction that the general relativity concept of time is correct.
Speaker 1: That doesn't mean that general relativities are right about everything
Speaker 1: we know. It breaks down as singularities, but this basic
Speaker 1: concept that space and time are deeply interwoven is more
Speaker 1: likely to be true because time crystals exist. Right, Maybe
Speaker 1: we're seeing a little more agreement between quantum mechanics and
Speaker 1: general relativity than there was before. Can't we all just
Speaker 1: get along? Community? Right? Community is the name of the day,
Speaker 1: And also it's fun experimentally, like this is a really
Speaker 1: important thing that might actually be useful technologically, imagine like
Speaker 1: storing information. One thing that's difficult about building quantum computers
Speaker 1: is that it's hard for them to have memories because
Speaker 1: quantum objects these tiny little particles. They often like decay
Speaker 1: and they don't last very long in the state that
Speaker 1: you want. Well, time crystals might be a gray way
Speaker 1: to build memory circuits for quantum computers because they are
Speaker 1: stable in their lowest state and sort of remember the
Speaker 1: configuration that you put them in. The pattern that you
Speaker 1: put them in lasts through time. This is great for
Speaker 1: our quantum hamster script because now we can get teeny
Speaker 1: tiny computers for teeny tiny quantum hamsters. So that whole
Speaker 1: scene where they're breaking into the quantum mainframe, that's gonna work.
Speaker 1: Feeling good about this? Are they powered by tiny little
Speaker 1: quantum cotton candies? That what gives the quantum hamster its power.
Speaker 1: I mean, they got to keep up their carbs so
Speaker 1: they can run in those tiny quantum wheels, keeping going.
Speaker 1: Or maybe they should eat like scalloped crystal eyeballs. Now
Speaker 1: we're getting into a horror movie. Oh yeah, that's right.
Speaker 1: That's the Dark TV spinoff that will will sell after
Speaker 1: the future. So this team in Maryland did this, and
Speaker 1: then there's a team at Harvard that did something different.
Speaker 1: They took a diamond, right, which is a space crystal,
Speaker 1: and they put a bunch of nitrogen atoms inside that
Speaker 1: diamond and then they turned those nitrogen atoms into a
Speaker 1: time crystal by zapping it with a laser in a
Speaker 1: very similar way. That's truly got to be a girl's
Speaker 1: best friend. A diamond, and inside the diamond is a
Speaker 1: time diamond. Yeah, exactly, a time diamond inside a space diamond.
Speaker 1: That or it's like the taco bell version, you know,
Speaker 1: take a burrito and wrap it in a taco and
Speaker 1: then dip the whole thing in cheese. Either would be
Speaker 1: good engagement gaps, I think exactly. So it's a really
Speaker 1: exciting time sort of theoretically, like is this possible? There
Speaker 1: was a lot of discussion. People fought for many years
Speaker 1: that this was totally impossible. All the theorem suggested couldn't
Speaker 1: be done, and then people found few loopholes, and then
Speaker 1: a bunch of experimentalists when out there, said hey, we're
Speaker 1: just gonna try to make this thing, and it looks
Speaker 1: like they might have. So it's really fun for me
Speaker 1: to see like a whole area of signs that people
Speaker 1: didn't even consider as possible suddenly explode with activity and
Speaker 1: ideas and in vation. That's the great thing about sciences.
Speaker 1: You're always finding new things. Like you take old information,
Speaker 1: you shake it up, and you find new things you
Speaker 1: previously thought was impossible and now when I'm late to
Speaker 1: an appointment, I can say, well, have you heard the
Speaker 1: news about time crystals? Our whole concept of time might
Speaker 1: not be right. That's right. Maybe I'm not late, maybe
Speaker 1: you're late to Daniel says time can't be eternal. Anyway,
Speaker 1: I've got a note from my physicist who says it's okay.
Speaker 1: The larger motivation is that there are still really basic
Speaker 1: questions out there, really big puzzles that haven't been solved
Speaker 1: because nobody asked the right question or had the right
Speaker 1: first idea. And so Frank Wilcheck is a little cookie,
Speaker 1: but I love that he goes out there and tries
Speaker 1: to tackle something that people think is impossible and actually
Speaker 1: makes progress and makes a mistake, but along the way,
Speaker 1: you know, breaks open a whole area of research. And
Speaker 1: so somebody out there listening, hoping to grow up to
Speaker 1: be a is just to make some big discovery. Don't
Speaker 1: think that we figured it all out. We are far
Speaker 1: from understanding the nature of the universe around us. There
Speaker 1: are lots of really basic questions out there for you
Speaker 1: to find the answers to. And if you're too afraid
Speaker 1: to ask a question because you think it will be
Speaker 1: stupid or wrong, you may never open up some really
Speaker 1: interesting research avenues. Yeah, exactly, and remember even Nobel Prize
Speaker 1: winners make mistakes. Take that Nobel Prize winner is not
Speaker 1: so fancy now, are we? Well? Thank you guys so
Speaker 1: much for listening. I hope you enjoyed our little time
Speaker 1: Crystal time, and we will see you next time time
Speaker 1: Crystal or not, we don't know, it's hard to say.
Speaker 1: All right, thanks for listening everyone, Thanks for listening, and
Speaker 1: remember that Daniel and Jorge Explain the Universe is a
Speaker 1: production of My Heart Radio for More podcast for my
Speaker 1: Heart Radio at the I Heart Radio app, Apple Podcasts,
Speaker 1: or wherever you listen to your favorite shows. H