What's a Time Crystal?

Daniel and guest host Katie Goldin talk about the crazy and real science of time crystals

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Episode Transcript

Speaker 1 (00:08):
Hey, Katie, did you know that if you stick any
two science worse 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 alway, Yeah, okay, okay,
what about Alligator Crystal? I love it? Want to see

(00:31):
that one. Let's do time, Pump. I'm calling Netflix and
set up a pitch meeting right now. Hi. I'm Daniel.

(00:54):
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 I Heart Radio in which we take you on

(01:16):
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, Orge isn't with us today, but

(01:38):
instead we have a wonderful guest podcast host, Katie introduce
yourself to everybody. Hi, guys, I am 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

(01:59):
realm of things. I hope I can fill Jorges shoes
a little bit temporarily. Do you know what his shoe sizes.
He's a cartoonist, so he just draws really big, floppy
clown shoes and that'll be perfect for me. Well, you
guys should all check out. Creature Feature is a super
fun podcast, and Katie's a lot of fun, which is
why we invite her here as a guest host. And

(02:22):
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? Katie? 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

(02:43):
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 zooplankton really understands time. I'm gonna say no, that's
a bold, controversial take. But yeah, it's really hard to

(03:05):
get inside of the heads of animals. That's a problem
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
or like I'm two 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.

(03:28):
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,

(03:48):
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

(04:09):
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 twelve o'clock, you know,
we kind of have this concept of time, like is
it not just our human invention or is there actually

(04:32):
a real thing of time outside of our little mickey
mouse watches. Yeah, it's a 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

(04:53):
dig into that later in the podcast about the concept
of time in quantum mechanics. And the concept of time
in general relativity, which turned out to be totally fundamentally
different ideas of what time is. But yeah, we do
think the 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

(05:13):
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

(05:35):
it could be an illusion. It could be the time
is not something deep and fundamental to the universe. It
could be that it's 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 the time isn't fundamental.

(05:56):
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 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. Oh, that
sounds beautiful. What comes into your mind when I said it?

(06:16):
For his 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

(06:39):
on the internet what they thought. That's right. Folks out
there volunteered 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 two questions at Daniel and Jorge
dot com. And so here is what people had to say.

(07:02):
My only thought is that there are these points in
space that maybe our 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.
Um made a whole Rick and Morty episode about those.

(07:25):
I don't know what time crystals are. Well, I know
about Courts is a crystal, and we use courts to
get precision timing and 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 call back to Rick and Morty. They definitely

(07:46):
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 contends that you have to really understand
science to understand the show, and I just think it's
a fun show. Yeah, well, you know, I watch Rick

(08:07):
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 real
stickler for those time travel plot holes that always pop up. Yeah, exactly.

(08:32):
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 risks. How do they
work to tell time? Do you have just a little
crystal man in your watch going like it's about two thirty?

(08:54):
That's exactly how it works. You crack it open, you'll
spot 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

(09:17):
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

(09:39):
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 end up

(10:00):
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.

(10:23):
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

(10:44):
is the same everywhere. It 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 gonna like juggle balls here, then you took
a step sideways, the same rules should apply, the same
juggling should work. A crystal takes that and sort of
breaks that symmetry into something discreet. So now the universe

(11:05):
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 is 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 ponds. Yeah, exactly, take space and break it

(11:28):
up into chessboards, and you can only move one square
or two squares. You can't move one and a half
or two and a half squares. And so that's the
idea of a space crystal, and like do you think
of a crystal is a big shiny thing, But when
you zoom down into it, the reason that it's shiny,
the reason it has those properties that reflect LFE that way,
is because it has this regular structure in space. So

(11:48):
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 and evolutionary biology because they are
surprisingly sometimes used in eyeballs, like in the eyes of
mollusks will have these guanting crystal structures that help them

(12:10):
reflect light. You don't think of organic material as something
you can turn into a crystal, but yeah, you can
take guanting form a guanting crystal form an eyeball. 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 guanting crystals that form in certain eyeballs, like in

(12:31):
the eyes of scalps, will have this characteristic that helps
them reflect light in such a way that gives them
really interesting vision. And 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,

(12:53):
like two hundred of them. Oh my gosh, Well that
makes me feel better. That's why I don't eat scalops
because I don't like crystalline eyeballs. And instead of using
lenses like a human or mammal eye or most animals eyes,
they actually use mirrors inside of their eyes as kind
of a miniature telescope by using that guanting crystal structure. Wow, amazing. Well,

(13:14):
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 as the regularly repeating pattern, but it doesn't
fall apart. It is in its lowest energy state, and
so we can hang out basically for a long time.
It needs to be broken up if you want those

(13:36):
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

(13:58):
very comfortable. That's so interesting. It's something like an ice
cube forms a lot of 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 gonna do a
whole podcast episode about all the different weird kinds of ice.
It's like one that's not transparent black ice, and it's

(14:20):
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. That actually happens.
We think sort of like on the surface of Jupiter,
which rains diamonds into the interior, which might form like

(14:43):
a big liquid diamond ocean. So Jupiter is really rich,
talking about Kardashian levels of rich. Absolutely, absolutely, So now
we understand, like the idea of a crystal, it's like
a regular structure, but that's a crystal structure in space.
So now it's turned 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

(15:06):
do you put time in a crystal? Because time is
not physical matter. You can't arrange it in a lott
of 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?

(15:29):
So a time crystals 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 regularly returns to
the same position. So this is like four dimensional chess

(15:52):
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 it 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

(16:12):
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 of it and comes back,
and then moves out of it and then comes back.
So you wanted 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,

(16:32):
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

(16:54):
the other critical thing is that it has to be stable,
meaning it has to be in its grounds eight. 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

(17:16):
like a perpetual motion, which 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 pieces.
But before we do that, let's take a quick break.

(17:41):
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 emotion forever at a low energy state,
which sounds like perpetual motion to me, which I thought

(18:03):
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 impossible, and
it's only recently that people thought 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

(18:25):
regularly returns to a specific state that's one of the
lattest point and yet is stable. So we could like
do this forever. And this started in about twenty twelve
when a famous physicist named Frank Wilcheck. He's at m
I T and he won the Nobel Prize for understanding
the strong interaction, which is a thing that like binds
quirks together into protons and neutrons. So he's generally a

(18:47):
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 axons to describe that hypothetical particle,
and in 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,

(19:10):
a ring of particles that 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 mind. So is
this something that would happen on the quantum level. Are
we talking about entire like star systems doing this like

(19:34):
time crystal thing, or are we talking about something on
a very small scale. This is something a very small scale.
This would definitely be a quantum effect. It's not the
kind of thing that you can have happened from 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

(19:55):
can never have exactly zero energy, so when you force
them into their howest 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

(20:16):
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 that I
need a new one, But hey, guess what, I got
a little bit more out of that battery. So maybe

(20:38):
it was some quantum time crystals at work there. Or
when your iPhone battery says it's at zero but it's
still running, and you're like, am I using the Casimir
effect to charge my bode? 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.

(21:00):
Like think about a wheel with spokes. As it rotates,
it returns to basically the same configuration. The problem is
that bicycle wheels, a macroscopic object, could never actually spin forever.
And that's also not its ground state. It's not the
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

(21:23):
out of bicycle wheels and water and marbles and so
on and so forth. But Frank will Check 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

(21:46):
mistake in well checked paper tattletale. I know this, 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 want
a Nobel Prize in must be the truth, 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

(22:07):
make mistakes. Ye 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
he won the Nobel Prize, Yeah, you know, I'm as

(22:31):
much a Nobel Prize winner in a field you didn't
study as you are Nobel Prize winner in physics. So they're, yeah,
exactly what was this mistake and how did that change
this whole concept of being able to have these little,
little tiny time crystals. Yeah. So Patrick Bruno showed that
the example that will Check proposed, this idea of a

(22:52):
ring of particles rotating was actually more similar to a
bicycle wheel spinning than we thought that he would only
rotate if it was actually in a more energetic state,
and he showed that the example that will Check 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

(23:13):
out there, then people started working on They thought, 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 like dig into again and ask the question anew,
and then a lot of people will follow and be like, oh,
that's interesting, I wonder if we could actually crack this problem.

(23:33):
And so Frank will Checks 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 of time crystals
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.

(23:55):
Wet blankets trying to make it so that I can't
make a little quantum circus with a little merry go round,
and I'm thinking about 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

(24:16):
make one. You know, sometimes the theorists say that's as 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

(24:37):
is something you were bringing up earlier, like is time
or 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

(25:01):
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 their
being time. Well, it's also really interesting to sort of
dig into it theoretically and ask, like our fundamental picture

(25:24):
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. Have very different opinions about

(25:45):
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 another episode. But the

(26:07):
important thing is that quantum mechanics tells us how those
quantum states evolved, like the Shortinger equation, the most famous equation,
and 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

(26:30):
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 like goes on forever into the future

(26:52):
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

(27:13):
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, or quantum mechanics says space time

(27:37):
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 really closely connected. And if you think

(27:57):
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 denser, and as you
look backwards in time, time doesn't go on forever. It
comes back to some sort of like singularity in the
early universe. And according to general relativity, is very natural,
for example, to have a beginning of time, for time

(28:17):
to have started rum 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, 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

(28:39):
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 some of the parts
and the parts themselves. Yeah, you're absolutely right, And one
of the reasons they disagree is that usually they play

(29:00):
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 are

(29:23):
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,

(29:44):
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 of while I
draw up some little quantum merrigo rounds schematics. We are back.

(30:14):
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,

(30:36):
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

(30:59):
probe thing 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

(31:21):
close connection between space and time, that this thing that
exists in space space crystals can also be made in time,
that 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

(31:41):
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,

(32:02):
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 that the foundation of quantum mechanics. So one of
these theories has to get torn up basically and start again.

(32:23):
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

(32:45):
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 is on both
of them are wrong. And we kind of come up
with a whole new theory that combines the two or
kind of cross checking these two rule books that were

(33:06):
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 where 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

(33:27):
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 job relativity for
a while, and the goal, of course, is to come
up with a single holistic explanation from the whole universe
or how everything fits together, and that requires like trying
to weave these threats together. And in the past we've succeeded,
Like we figured out that electricity and magnetism are really

(33:48):
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

(34:08):
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 this this idea about
the connection between time and energy. Right 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, Nother's theorem that tells

(34:31):
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 ten seconds
or in a million years. And we've talked in the
program before how we're not actually sure whether energy is
conserved because the universe is not actually static in time.

(34:52):
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,

(35:14):
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,

(35:36):
you need really tiny pliers. And usually in physics, when
we're talking about tiny players were 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 zapped them with lasers.
And atoms, you know, have various ways that they can sit.

(35:58):
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

(36:21):
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 the spin up, spin up, spin down,
spin up, whatever, and then you zap them with a laser.

(36:41):
And the laser is basically just photons, right, This is
an oscillating electromagnetic field, and so it 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 cannot oscillate up and flip spins up and then
as laid down and flip spins down. So what we see,

(37:03):
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,
but 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.

(37:24):
You 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

(37:47):
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 started going and it goes for a while
even without you doing the initial thing, but with the

(38:07):
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 like 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's just these atoms and

(38:28):
a laser, then we think it could last essentially forever
if it really is a time crystal. 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,

(38:48):
you 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 qual 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

(39:09):
question of like could you actually build these things? One
of the experimental obstacles to actually making this existing 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. That's so interesting. So this proof
of concept by being able to create these oscillating atoms

(39:31):
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
that time crystals. We think the time crystals are a reality.

(39:53):
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 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.

(40:13):
That doesn't mean that general relativities are right about everything
we know. It breaks down as 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

(40:33):
get along? Community? Right? Community 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. They often like decay

(40:56):
and they don't last very long in the state that
you want. Well, time crystals might be a gray 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

(41:17):
tiny computers for teeny tiny quantum hamsters. So that whole
scene where they're breaking into the quantum mainframe, that's gonna work.
Feeling good about this? Are they powered by tiny little
quantum cotton candies? 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, keeping going.

(41:38):
Or maybe they should eat like scalloped crystal eyeballs. Now
we're getting into a horror movie. Oh yeah, that's right.
That's the Dark TV spinoff that will will sell after
the future. So this team in 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,

(41:59):
and they put a bunch of nitrogen atoms inside that
diamond and then they turned 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.

(42:19):
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 gaps, I think exactly. So it's a really
exciting time sort of theoretically, like is this possible? There
was a lot of discussion. People fought for many years
that this was totally impossible. All the theorem suggested couldn't

(42:42):
be done, and then people found few loopholes, and then
a bunch of experimentalists when out there, said hey, we're
just gonna 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 signs that people
didn't even consider as possible suddenly explode with activity and
ideas and in vation. That's the great thing about sciences.
You're always finding new things. Like you take old information,

(43:08):
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 to Daniel says time can't be eternal. Anyway,

(43:28):
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 asked the right question or had the right
first idea. And so Frank Wilcheck is a little cookie,
but I love that he goes out there and tries
to tackle something that people think is impossible and actually

(43:50):
makes 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 is just 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

(44:13):
to ask a question because you think it will 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

(44:35):
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 My Heart Radio for More podcast for my

(44:59):
Heart Radio at the I Heart Radio app, Apple Podcasts,
or wherever you listen to your favorite shows. H