Can the Universe exist without space?

Daniel and Jorge break down the Universe to its most basic level and ask if space is necessary

Learn more about your ad-choices at https://www.iheartpodcastnetwork.com

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:08):
Hey, Jorge, are you a hoarder or do you like
to throw things away? We keep everything, we have, every drawing,
my kids ever made. Man, not me. I value space
more than stuff. I love to throw things away. Wow,
what does your family give you for your birthday? Then?
Empty space? Actually, my wife rent a dumpster and says

(00:30):
I can throw out anything I want. It's like a
negative present. Hey, space is precious. You know you can't
have too much of it. You can't have too much
nothing said nobody never, Nothing is better than nothing. This
is the best nothing I ever got. Hi more handmade

(01:00):
cartoonists and the creator of PhD comics. Hi. I'm Daniel,
I'm a particle physicist and I really do love space.
And Welcome to our podcast. Daniel and Jorge explain the
university production of I Heart Radio, in which we explore
all the stuff in space, empty space, not so empty space,
space builled with really crazy bonk, or stuff that's hard

(01:20):
to understand, and sometimes even the very nature of space.
We talk about all of these things in this podcast,
and we break them down, and our goal is to
deliver them to you in a way that actually makes sense,
so you go away thinking, huh, I get it, or
at least I get it as much as scientists get it,
which sometimes isn't that much. And sometimes it feels like
we're talking about a whole lot of nothing, and sometimes

(01:43):
we are literally talking about nothing, and sometimes we're trying
to figure out what is nothing exactly right. Yeah, deep questions, now, Daniel,
when you say you love space, do you mean like
you love, you know, just space travel, like where the
planets are, or did you just like, you know, having
the idea of space in your life. I love all
of it. I love outer space, I love deep space.

(02:04):
I live near space. I also love having space in
my living room, Like it's not unusual for me to
toss out a piece of furniture and go, you know what,
the room is just better with nothing there. You like
everything about space. There's nothing negative about space for you.
I'm pretty pro space. Yeah. Absolutely, you would live in
an empty box if you could, exactly. I'm like a
cat that way. Are you looking forward and to your

(02:26):
children leaving the house then, because that's just more space,
is more space. I'm not looking for to them leaving,
but if they do, I'm looking forward to throwing all
their stuff away. Oh man, that's going to come back
to want you. They're like, why did you throw away
my comic book collection that's worth three million dollars? Now, yeah, exactly,
but this space is priceless, right, Well, we like to

(02:48):
talk about space in this podcast and also about what
it represents, what it means, because it's kind of a
topic that businesses don't have a super clear idea about.
That's right. It's one of these really fun quite in
physics because only recently did we figure out that it's
a question that sort of has an answer. It's a
question that's worth asking. It's one of these questions that's

(03:08):
so basic that we just sort of assumed we knew
the answer. You know, space is space. It's the nothing,
it's the emptiness. And only recently have we realized, Wow,
space could be much more than that, and it really
deserves our attention. Right. Even more important is this sort
of idea that maybe we don't need space, Like maybe
it's just sort of like an add on to the universe. Yeah,

(03:30):
is it at the foundation of reality or is it
just something that fills up something else? You know, imagine
what it would have been like to be a person
ten thousand years ago. You never would have experienced reality
without air, for example, So the concept of like a vacuum,
a place where there was no air would have been
totally alien to you. So now, of course we know
that that's possible. It seems obvious that air is not

(03:51):
a fundamental property of the universe. But we're at the
next level and wondering, like, well, is space fundamental? Could
you take it apart? Do you really need it? Yeah?
In fact, so the universe, it doesn't have any air
in it, right, most of the universe is pretty empty. Yeah,
from that point of view, exactly, we were dealing with
a very unrepresentative example. And we do this all the

(04:11):
time in science. We assume that the things we experience
our universal and we can generalize from these examples to
the whole universe. We're doing this all the time, left
and right without even realizing it. So now we're asking
a similar question about space. You know, our our assumptions
about space valid. Can we break it apart? Do we
even need it? Is it possible for it to have

(04:32):
bubbled up from something else? Yeah, it's a space topic.
But space is pretty empty. I think we have a
whole podcast episode about that, right, Like, what's the average
density of the universe or like how much stuff is
there really on a like cubic foot Yeah, we do
have a whole podcast about how empty spaces and we
take you on a journey from the top of the
atmosphere into the Solar System and then out into interstellar

(04:54):
space and then finally into intergalactic space. And mostly space
is intergalactic space, right, Like there are these huge streams
of galactic clusters of galaxies swinging around each other, but
between them there are these vast bubbles and voids that
don't have galaxies in them. So most of the universe
sort of by volume, is this intergalactic space, which is

(05:17):
not totally empty. There's still stuff in there. That's a
little bit of dark matter, there's definitely dark energy. But
it's most of the universe and it's pretty empty, but
not down to zero. Yeah, and there's a lot of
it space, I mean, in the universe, there's a whole
bunch of it. Like if you are going at the
speed of light, it would still take you as far
as we know right now, you know, tens of billions

(05:37):
of years just to go from one side to the other.
That's a lot of time. Absolutely, And remember the speed
of light is like mind boggling lee fast, right, It's
incredibly fast. And yet these distances, even inside our Solar
System are incredible, Like it takes minutes for light to
get from here just to Mars, which is our neighbor,
and hours to get out to the outer Solar system.

(05:59):
You know, when we communicate with probes and rovers and
stuff on other planets, the reason you can't drive them
is because they are so far away. You can't do
real time driving because the lag is too long. And
that's just inside our Solar system. So the distances to
other galaxies millions of light years and deeper into space
billions of light years, they're hard for us to get

(06:19):
our mind around. So, yeah, space is pretty spacious. I
guess I hadn't thought about it before. Like if even
if you're Superman or Superwoman and you're traveling, you can
you're able to fly at the speed of light, it
would still take you like a billion years just to
you know, go to the other galaxies out there in
the universe. Yeah, well that's an interesting question. Does Superman
have to travel at the speed of light? Can he
be superluminal? I mean, how far away is his home

(06:41):
planet anyway, I don't know you're the physicist. I just
read the comic books. I don't dissect them scientifically. I'll
go find out exactly where his home planet is and
figure out if he broke the law on the way here,
and if so, I'll issue him a physics ticket. Well,
he can just bring it up with his heat visioned Daniel.
And also, how are you going to arrest him? Good
luck with that, citizens arrest Mr Superman. But yeah, there's

(07:04):
a lot of space out there. It's definitely not a
small part of the universe. But I guess the question
is it a necessary part of the universe. So today
on the podcast, we'll be asking the question can the
universe exist without space? Space? Space? Space space? That question

(07:27):
is so profound it needs an echo. It echoes through
the vacuum of infinity, through the vacuum of our understanding
of the universe. Absolutely, through the empty space in my head.
But it's a fun question, and it sort of mirrors
the way I treat furniture. You know, I look around
my house and I asked myself, do we need that chair?
Nobody ever sits there and we get rid of it.
We're like, ah, it's better off. And now we're cycling

(07:49):
through modern physics and we're like, m, do we really
need the whole concept of space? Like is it really
have to be included in the sort of fundamental list
of things you need to build a universe or is
it like you know, ice cubes or atoms or hurricanes,
something that you know comes from your more basic ingredients.
I would hate to be a furniture in your house.
I feel like I would live in constant fear. Yes, absolutely,

(08:12):
you must constantly justify your existence in my house, or
you're on the trashy. It's like huff Post reporters. You know,
hopefully that's just for your furniture, not your family as well.
Or pets. Absolutely, living creatures definitely belong to the family.
Chairs not so much so if you could have a
bigger house, would you have a bigger house? No? No,
I don't need a bigger house. In fact, I had

(08:34):
some friends who once moved to a bigger house and
I almost ruin their marriage because they ended up shouting
each other from different rooms across the house. And they
did better when they had to, you know, share a
small apartment. Yeah, we talked about this and I offered
the better solution of just getting an intercom system. You
are going to engineer everybody's marriage. Huh. I'm gonna go
to your your couple's counseling. There's a solution for everything

(08:54):
in engineering, marital engineering. Wow, that's a better name for therapist.
But anyways, Yeah, it's a big question whether or not
we need space in the universe. It seems pretty fundamental,
you know, like, how can you have a universe without space? Like,
isn't space the universe? Yeah, but just because it's hard
to imagine doesn't mean it's not reality. Right. A lot
of what reality is was difficult for us to wrap

(09:16):
our minds around. So when you do this kind of exploration,
you got to sort of be willing to give up
something you thought was fundamental, something you assumed was inherent,
and ask your question whether it can come from something else.
All right, Well, as usual, we were wondering how many
people out there have thought about this spacious question, whether
or not we need space. So Daniel went out there

(09:37):
into the well to the internet to ask people is
it possible to have a universe without space. Here's what
they had to say. Oh, that's a good question. I
don't think, so okay, why, Well, I don't know. I
don't know. I don't know. I don't know why. I
just know I think space is only one of the dimensions, right,

(10:00):
you can probably have a universe. It's just time and
maybe not space. I'm gonna say yes. Well, my understanding
is that, yeah, I guess you can. Um. I mean,
was this space when the Big Bang occurred in the
moments after that, or was it all dense metal with
zero space? But my understanding is that if you have

(10:22):
a different universe that could operate off a completely different
set of physical laws. So I guess never say never
in that regard. You can have a universe without space.
Our situation with matter having out competed antimatter, I think
is actually pretty unique. Um there, and I would I

(10:49):
think they're a little universe blips all over where universe
pops into existence and annihilates and no spaces created. I
guess you can have universe with out just this dimension space,
and you can have all the other dimensions possible, but

(11:09):
it will be crowded. I guess it would mean what
you mean by universe, because before the Big Bang all
the universe was there. It was just compressed and to
my knowledge, there was no space. So if you can't
that just the universe then yeah, all right, some mixed
reactions here. Some people could live without it, some people

(11:29):
could really want it. Yeah. It basically wraps up the
whole question of what spaces and where it comes from
and all these answers I see echoes of general relativity
and quantum mechanical perspectives on this question. So good job listeners,
And to those of you who would like to participate
in future rounds of answer random questions for the podcast,
please write to us two questions at Daniel and Jorge

(11:51):
dot com. There's a lot of reference here and the
answers to the Big Bang to write that's something I
hadn't thought about before. Was their space before the Big Bang?
At the Big Bang? Or was space created at some
point in the history of the universe? Yeah, space and time? Right,
all right, Well, let's dig into it, Daniel. Let's start
with maybe the basic stuff, like what is space? How

(12:11):
do physicists think about what space is? Yeah, this is
a great question, and we have sort of two answers
for what space is based on whether you're thinking about
it from the point of view of like quantum mechanics
or whether you're thinking about it from the point of
view of general relativity. And remember that these are the
two pillars of thinking in modern physics, too great ways

(12:33):
to describe parts of the experiments we've done. Quantum Mechanics
describes basically everything that has to do with little particles
at small scales and all the forces that were familiar
with except for gravity, and general relativity talks about how
space is curved and it's bent, and that's really what
gravity is. And so the answer to the question what
is space sort of depends on whose perspective you want

(12:55):
to take first? What do you mean, how can something
depend on your perspective? Aren't you looking for like one answer?
We are absolutely looking for one answer, but we don't
have one answer. We have two theories, quantum mechanics and
general relativity. They treat space very differently and we haven't
been able to unify them. So the short answer is
we don't know what space is because we don't have
a single coherent theory for the whole universe, and the

(13:18):
two theories we do have disagree about what space is,
all right, So what are the two theories about space?
And is there enough space between them to tell the difference. Well,
you know, let's start with quantum mechanics. Quantum mechanics is
the theory that tells us how electromagnetism works, how the
weak force works, you know, how photons move, and it
tells us that space is fundamental. It assumes that space

(13:41):
exists and it adds stuff to it. So if you're
gonna build a universe using at least our current theory
of quantum mechanics, then you start from space. You say,
let's assume there's a space, and then at every point
in that space, I'm gonna say whether or not there's
a quantum field and how much energy it has. But
it's sort of like at the bedrock of the whole theory,
just like assuming that space and time are things that

(14:03):
you can put fields in them, right, because that's kind
of baked into the definition of a field, right, Like
you can't have a field without space, like a field
is by definition like how things vary in a space.
That's right exactly. And we'll talk later about whether you
can generalize that to like abstract spaces rather than physical
spaces and what that means. But you're right for the

(14:24):
physical fields that we're talking about, you know, like the
photon field. It's just a value all through space. But
as you say, space is fundamental to that. You need
to know like there's a certain value of field here
and over there at a different location in space, it
has a different value. And for example, the shrouding your
equation tells us how a wave function exists across space,

(14:46):
and how that wave function evolves through time it spreads
out through space, for example. So it's pretty deeply baked in.
So quantum field theory sort of the modern version of it,
as we think about it, doesn't really have an answer
to the question of what is space. It just sort
of like assumes it exists and starts from there. It's
like the basical list of ingredients. Would you say then

(15:06):
that maybe quantum fields defined space or do you think
space could exist without quantum fields. Well, that's a great question.
In our current theory, you can't have space without quantum fields,
Like quantum fields filled the entire universe. There's no sense
in which you could have space without them. That's just
sort of according to the theory. But do they define space?

(15:27):
I think they're deeply coupled to it. Yeah, absolutely, so
I think it's definitely part of the inherent nature of
space in quantum field theory that you have these fields
that live on top of it. But remember that quantum
field theory can also have stuff in it that doesn't
sort of come into the very beginning, right, Like we
can talk about the very basic ingredients of the universe,

(15:47):
space and quantum fields, but we don't add to that
things like you know the atom, right, The atom is
not a required element of the definition of the universe.
It comes from that other stuff. So the ad and
we think it exists, but it's not like fundamental. And
remember the goal of physics, as you say, is to
come to one theory, one explanation, one most basic list

(16:09):
of ingredients and the rules for combining them that then
explains everything else. So we're constantly trying to throw stuff
out on purpose so we can get like the minimal
list of fundamental things that can then explain everything else.
As emergent. We want to explain ice cream and atoms
and hurricanes in terms of the simpler, more basic elements.
Do you guys want the dumpster then too, so you

(16:30):
can throw out theories. I definitely want to throw space
out on the physics dumpster. I would love to explain
space in terms of something more basic and fundamental and say, man,
remember when we had space criming in here and we
had no space because we had so much space. But
then if there's no space, then there's no space in
the dumpster either, Daniel, where would you throw it out? Oh? Man,

(16:53):
I'll get a bigger dumpster, all right, So then that's
quantum mechanics. But then general relativity has a different view
of space. Yeah, General relativity tells us that space is
not something which is just like inherent and that you
can assume. General relativity tells us that space is really different.
It's dynamical. It's not like the backdrop for everything. Instead,

(17:14):
it's in this dance with matter. Right. When you have
matter and energy around, space bends and it curves, and
it can do weird things like it can ripple, right,
and it can expand. And this is the things that
we see, like we see ripples in space. We know
that this general relativity picture is at least approximately correct.
It might not be the fundamental theory of the universe,

(17:35):
but it's really accurate. It predicts these gravitational waves and
we see them. It can accommodate at least the accelerated
expansion of the universe in terms of a cosmological constant.
We don't understand why that's there, what's happening, etcetera, but
it can be accommodated in general relativity. So it's very
successful description of how matter and space interact. And it

(17:56):
suggests that space is not fundamental, that it sort of
states at the same level as matter our energy, because
the too sort of have this feedback loop between each other.
Basically says that space is a thing, right like, it's
not static, it doesn't exist, it doesn't ignore matter, you know,
like it responds to matter, and you know, it's not
independent of matter exactly. And you can do these weird

(18:16):
things that we never imagined that it could do, which
means it might be able to do other weird things
we also hadn't yet had the imagination to do. Anytime,
we're limited by our imagination. I'm always skeptical that we've
thought of everything. I know, the theorists are very smart,
and even our science fiction authors are always pushing the
boundaries of creativity when it comes to like, you know,
intellectual concepts. But there's always the possibility that there's always

(18:40):
something else out there we just haven't thought of that
could be happening in our universe. So space could have
really weird properties that we never imagined. Imagine, for example,
being a scientist that's a fish swimming through water all
the time and not realizing, you know, that space could end,
or that your water wasn't actually fundamental, and they could
do other weird things like boil and turn into a gas.

(19:01):
You know, space like that could have other phases, other
weird properties we just haven't observed yet, and so we
assume are impossible because I guess, once you can get
space to bend or ripple or expand then who knows
what you can make it do? Who knows what you
can make it do exactly? And the solutions to general
relativity are so complicated and difficult, and that it's not
possible to conceive of all the possible configurations that are

(19:23):
consistent with it. Those are the two views of space.
One says that it's something that you know, can't touch
or that you live on top of, and the other
one says that it's something that it's more of a thing,
like it's dynamic and you can manipulate it and it
can change, So that those are the two basic views
about space, right, But it doesn't sort of explain what
space is. It's just sort of like how you regard space. Yeah,

(19:45):
but that's sort of what space is. You know, space
is how we treat it. Some people might say space
is just like a mathematical construct in our minds. You know,
that's not actually something that's physical. For example, in quantum mechanics,
we never deal with space itself directly, right, All we
ever do is deal with the fields in space. We
never like interact with space itself, and so it's sort

(20:07):
of like just an abstraction. It's just like a way
of thinking about organizing these fields. Whereas in general relativity,
like spaces the thing. It's the thing that's keeping us
on the Earth. It explains gravity, which is pretty important.
So you know, how we represent them in our theories
goes a long way to telling you what we think
they are. All right, Well, I think that sets the
space for a deeper discussion about space and whether or

(20:30):
not Daniel can through it in the dumpster or not.
Please please please, please, please please please. I would be
so offended if I was space right now, I would
limit your space Daniel. But let's get into that question
and also whether or not we will ever be able
to know what the answer is. But first, let's take
a quick break. All right, we're talking about space and

(21:05):
whether or not we can just toss it out, Daniel,
I feel like that's so unappreciative. How can you just
throw the thing out that you know you grew up in. Well,
you know, let's make a distinction here. We are, of
course searching to explain space, to figure out whether it's
the basic ingredient of the universe or whether it emerges
from something else. But that's not to say the things

(21:25):
that emerge are uninteresting or unimportant. Right, Like, the entire
field of biology is emergent in the sense that you could,
in principle, calculated all from fundamental particles. But that's not
like a smart way to do biology. Nobody would anybody
does do biology from the particle perspective. I just want
to make sure people don't think that we're being negative

(21:46):
about emergent phenomena. They're fascinating, they're amazing, they're incredible. We
are emergent phenomena. It's just, you know, part of this
question of getting down, drilling down to the deepest nature
of reality is to ask what's fundamental and what's emergent,
not necessarily to judge them. You just want to add
your bets and not offend your spouse's biologist. I have
the deepest of respects for my spouse and also for biology,

(22:07):
which is not your furniture. Just not my furniture, absolutely
all right. So there are two perspectives about space. It
seems like quantum mechanics doesn't say anything about space other
than it's there and you can't mess with it, and
general relativity says that it's something that you can sort
of mess with and change and bend. And I guess
the question is are those two things incompatible or is

(22:29):
there a sort of a fundamental conflict about them? Like
couldn't you have quantum mechanics sit on top of general relativity? Yeah, exactly,
And people are working on exactly that, trying to unify
general relativity and quantum mechanics in several different ways, and
in doing so, they're giving us hints about answers to
this question about whether space is fundamental or not. Like

(22:50):
when they put these two things together, they basically have
to make a decision like, well, do we have spaces
the list of fundamental ingredients in our new theory of
quantum gravity or not. And there's a couple of different approaches.
One is sort of like make gravity a quantum theory,
thinking about it as like just another quantum force that
exchanges particles the gravitons in order to make gravity happen,

(23:12):
and sort of making quantum mechanics primary. And the other
is to try to quantize gravity itself, you know, either
make the universe into little pixels or take the gravitational
field and make a discreet and so that would make
a general relativity sort of at the primary foundational level
of these new theories of quantum gravity, and which direction
you go sort of dictates the fate of the idea

(23:33):
of space and whether it's fundamental or emergent. I guess
maybe one difference is that like in general relativity, if
you have a speck of dust, it's technically bending the
space around it. But in quantum mechanics, if you have
like a proton or an electron, it's not really bending
space around it. Right, In quantum mechanics, we have no
description of the curvature of space that works, right, So yeah, absolutely,

(23:55):
we don't have a quantum mechanical description of gravity or
the bending of space, so we can't describe how space
has bent around of dust particle. We know that it
is though, right we think that that's true. One of
the difficulties is that we can't test these things very
well because particles have very very small amounts of gravity.
Member gravity so much weaker than all the other forces,

(24:17):
like ten to the thirty times weaker. So we can't
really test these things because all the other forces dominate.
Two protons, for example, coming together, the large Hage and
collider feel almost no gravity in comparison to the strong
and the weak and the electromagnetic forces, So it's very
hard to do an experiment at the particle level that
tests gravity. I guess maybe then to get back to

(24:37):
our question, then what do these two theories say about
the idea of having no space? Like could you have
no space in plantum mechanics or general relativity or is
that impossible according to the theories. So there are now
really fun ideas about how space might not be fundamental,
how you could have a universe without space in quantum mechanics.

(24:59):
And I think these ideas are really cool because they
make us think about quantum mechanics sort of at a
more basic level. You know, we think about the wave function.
For example. Wave function is like this basic element of
quantum mechanics. It tells you what's going to happen to
a particle, or for example, where a particle might be.
If you have a question about the outcome of your experiment,

(25:19):
the wave function tells you this outcome has a certain probability,
and that outcome has another probability. And typically we think
about the wave function as distributed across space, like is
the electron here or is the electron there, But in
principle it can be distributed across abstract states also, you know,
like the electron spin or the outcome of your experiment,

(25:40):
or all sorts of other kinds of things. And so
it's not hard for us to sort of augment the
current concept of space with these like abstract spaces. We
call them Hilbert spaces in which the wave function lives.
And it might be that those Hilbert spaces are the
actual primary thing that we can sort of let go
of these concepts of position and based the whole existence

(26:02):
of the universe just on those sort of abstract spaces
than the ones that are not physical, that don't represent
actual locations, that are not anywhere. I think what you're
saying is that, like maybe space, according to the theory,
is not like a physical thing or physical space, but
it's rather just sort of like a mathematical concept or
set of relationships. Is that what you mean. Yeah, we

(26:23):
know that it's a set of relationships. As we said earlier,
in quantum mechanics, we never actually interact with space. All
we do is we see sort of the propagation of
information through fields as that information moves through space. But
really that information is moving through the field, and so
you can think about it in terms of like pieces
of space that are sort of woven together. So it's

(26:45):
like the relationships between different elements of the field, and
the space itself is really just like the relationship between
those elements. So this one is far away from that one,
or this one is close to that one. So you
don't have to have those bits of the field like
hanging in an absolute, actually existing space. It might just
be that they have those relationships in another way and

(27:07):
woven together that gives the same effect as if they
were actually in a space. I wonder if it's sort
of like the concept of money. You know, like something
is worth more or has a bigger price on it
just because it doesn't mean that it has more energy
to it or more matter to it, or you know,
sits closer to you, or you can do more things
with it. It's just so happens that this thing has

(27:29):
a labeled with a big price on it, and that
that one has a labeled with a lower price on it.
Is that kind of what you mean, Like, maybe space
is really just like the economy of the yeah, exactly.
And you can also think about it in terms of
like your networks. Think about your relationships with your family.
Who are you close to We even use that word close, right,
Even if you're physically far away from somebody else, you

(27:50):
have a network of people that you interact with who
know you very well, and then people who are distant,
and then people who are basically super impossibly far away. Well,
it might be that that sort of like the fundamental
definition of who you are and what your spaces rather
than like where you actually are sitting in your bedroom
or in Los Angeles or in Germany or wherever. Maybe

(28:10):
space is just an emotional space, you know what I mean?
Like space is really just the emotional currency of your relationships. Yeah,
and these are just analogies we're using to try to
get your mind away from this primacy of space that
we've been assuming and thinking about the universe as built
out of things that don't hang in space but still
have relationships with each other, and then those relationships are

(28:33):
what space emerges from. And we can actually do this
not just by doing analogies to social media, but actually mathematically,
and people have taken the way function of the universe.
For example, think about, like what is a quantum mechanical
description of the whole universe? Can you describe everything in
the universe and you don't have to necessarily put them
in a location, you know, just say there's a probability

(28:54):
for this particle and probably for that particle, and then
link them together and say, well, this one is entangled
that one. This concept of quantum entanglement of particles having
like their fates connected to each other because they have
a common past. This entanglement might provide that weave, It
might provide the connection between like the bits of the
universe that when you weave them together, some things are

(29:16):
more entangled than others, and so they seem closer together,
and other things are less entangled, and so they seem
more distant. It might be that this quantum entanglement are
those same relationships that connect these bits of the wave
function that make it seem as if it is hanging
in some space. And this sort of set of relationships
or currency or valuations, that's what you call these Hilbert

(29:37):
spaces or is that different? The Hilbert space is the
set of possible wave functions that you can have, and
then the relationships between the different wave functions that are disconnected,
those are the entanglements. Those come together to make this
sort of like grand weave that we call space. And
if this is true, it doesn't mean that space is
not like real. It just means that it comes from

(29:57):
something else, you know, that it bubbles up from something
more primary, just like air is real, even if it's
not fundamental to the universe. You can still breathe it.
It's still very nice on a nice, fresh windy day
in Los Angeles. Come on, never happens. But I guess
maybe a question is what's the difference? You know, like
the word Hilbert space still has the word space in it,

(30:19):
So like what would be the difference between a Hilbert
space or these abstract connection space and maybe a more
regular definition of space. Well, our four dimensional space has
certain properties. You know, information transforms through it in a
certain way. It follows the speed of light. There are
four dimensions, including time. An abstract Hilbert space is much

(30:40):
broader and more general, like it can be infinite dimensional.
You can have complex values, you know, imaginary numbers, all
sorts of things. So this is sort of like a
subset of all the possible Hilbert spaces. It's like it
turns out that the relationship between all these quantum wave
functions can be described in this sort of simpler subspace,
this four dimensional subspace, in which all that information can

(31:03):
be mapped onto the whole hill of beans. It's the
whole hill of beans. But it also means other interesting things.
If this is true. It means that, for example, you
could have different spaces inside this, like larger Hilbert space.
You can have like our chunk of space which is
all woven together, and you could have another one somewhere
else was also emerged and is totally disconnected from ours,

(31:24):
and you could have maybe parts of it without these relationships, right,
Like you could have a whole bunch of people with
no friends on Facebook exactly, or even parts of the
world where there is no Facebook. Hard to imagine, right,
but it might be true. And so if this picture
is accurate, then the answer is absolutely you can have
the universe without space. It's not necessarily clear that you

(31:46):
need space to have the universe. And you can have
parts of the universe with space, parts of the universe
without space, and other parts of the universe you know
that have different kinds of spaces. And you might be thinking,
hold on, he's saying the word parts. What does he
mean if there's no space, what parts is he talking about?
And again, you know, these parts don't necessarily have like
a spatial relationship. You can't say this one is here

(32:08):
and that one is there in the sense of like
where is your family? You know, you guys might be
physically somewhere, but the actual relationships between you, those connections
that tie you together, like where is that It isn't
really anywhere, It just sort of in your emotional space. Yes,
if you can't find your family, that's a whole different
problem there, and a whole different type of podcast. There's

(32:28):
the whole genre for that. But that's sort of the
quantum mechanical view. If you say quantum mechanics is primary
and the way function for the universe is the most
basic thing, then can you build up a universe without spaces?
Space necessary? That's the quantum mechanical path, right, And it
sounds like the answer is sort of yes, Like if
quantum mechanics is all there is, then it might be
possible to see how you could not have space absolutely.

(32:51):
And there's some really fun recent ideas things called like
condensate cosmology, where space condenses in these like steam like
droplets from these weird fun spin networks that are more fundamental,
but we're gonna do a whole podcast about that sometime
in the future. Well all right, well then, and now,
what does general relativity say about not having any space?
Is that possible? According to that view, general relativity really

(33:14):
has no problem with space not existing because in our
general relativistic understanding of the universe, think about what happens
in the history, Right, we have the current universe. We
look back in time and we see the universe getting
more and more compact, and we propagate back and further
and further and further and approaches this special moment, this singularity,

(33:36):
this time before which space does not exist. And you know,
there are various ideas for how to tackle that and
what that means and if it's a breakdown of the
theory and if it needs to be replaced by something else.
But in our current albeit imperfect, non quantum mechanical general relativity,
there is this concept that there is no space before
the Big Bang, there's no space or it was just

(33:59):
super compressed. It's super compressed in the very first moments
of the universe, but before that, before the singularity itself, right,
this moment of infinite density, that space did not exist.
That it doesn't make sense to ask where is something
or when is something because the whole notion of space
and time came into existence then, like there is no

(34:20):
space and time before then. And this is not something
that's very easy to think about because we don't think
about space and definitely not time beginning right, But a
whole other podcast episode about whether you need time and
if time is an emergent phenomena. It's a whole even
more difficult question to grapple with because you have to
think about, like, could there be a time before which
there was no time. But putting that aside for the

(34:42):
time being, at least, it's hard still to think about
a universe existing without space. But if you can still
have time, right, if you say time exists, but maybe
space is not fundamental, it might make sense to you
to think about like space itself is this weird thing
we talked about, this weird do that does stuff, and
it can bubble and it can expand. It's being created
right now. If it's being created, then you know, maybe

(35:04):
there was a moment before it was created, or you know,
you can think about what is there when it's not
being created right and there's there's no space, if there's
no space being created exactly, and it might be that
you can have a universe before space is created. Might
be the time existed before the Big Bang, but just
not space. And there's some like conditions required for space

(35:26):
to be created for it to expand. Like you might
think it's a weird concept for space to be created,
but remember that it's happening right now. You know, the
expansion of the universe is not the motion of stuff
through the universe. It's the creation of new space between
us and other galaxies, between you and your couch between
everything and everything else. So it's happening right now. And

(35:49):
it's just that we have only recently realized that space
is this bizarre fabric that can do these things like
be created spontaneously everywhere simultaneously, that we've come to ask
these quests, and so we just really don't have a
notion and understanding of what space is even in general relativity.
But it's certainly is possible that it can be created.
And so yeah, you can imagine there being a pre

(36:10):
Big Bang moment when there was a universe but just
no space. All right, Well, it sounds like both theories
are pretty cool with the idea of not having space.
They can both take it or leave it. Yeah, absolutely,
variations of quantum mechanics can accommodate space not being fundamental
even though our current quantum field theory sort of assumes
that it's there. You can build these extensions that sort

(36:32):
of make it possible for space to be emergent, for
it to bubble up, rather than just being an assumed
property of the universe. Alright, so space, take it or
leave it? Leave it? All right, Let's get into how
we would ever know if space is or not disposable
or dispensable. But speaking of time, it's time to take
another quick break, all right, Daniel. It sounds like physicists

(37:08):
could take space or leave it. It sounds like both
theories about the universe would be okay. They wouldn't break
down if you suddenly got rid of space. Yeah. And
I think if you took a survey of physicists right
now and you ask them if space was fundamental or emergent,
if it came from something else more fundamental, I bet
you get like saying that it's an emergent, that it's

(37:29):
not fundamental, that it's comes up from something else, which
means that you could have a universe without it, or
portions of the universe without it. I think that's the
current mainstream thinking. And as we all know, the universe
works democratically, so whatever the majority says must be true. No,
we're definitely capable of being misled and having the wrong idea.
But I think it's sort of exciting that it's widespread.

(37:50):
It means that lots of people are working on it,
People are developing new ways of thinking about these really
really basic questions, and people out there also should be
excited it means that, like we're just the beginning of
asking questions about the universe and tackling them. If you
are excited about questions like you know, what is the
universe and where did they come from? And what's it
really made out of? Remember that there are huge tracts

(38:12):
of questions that are just really being explored by This
is just now, and so there's plenty of room to
make like really fundamental Einstein level discoveries about the nature
of the universe. Right. I think what you're saying is
that there's an electoral college in the universe, and who knows,
who knows what the rules are for that? That's right. Fortunately,
physics is easier to calculate than the electoral college. All right,

(38:35):
I guess maybe now the big question is how would
we know or not whether space is fundamental or whether
or not it's like an add on or like an
optional preference in the universe you could live in. Is
there a way for us to test it because we
live in this space that we're trying to test. Is
it possible to I don't know, create an experiment where

(38:56):
you have no space? Yeah, there's really two steps to that. First,
is we gotta make more theoretical progress and then we
got to do some experiments. So on the theoretical side,
what we really need is a unification of quantum mechanics
and general relativity. We need a theory of quantum gravity
that tells us how the universe works, so that we
can think about, like what is space, and this theory

(39:19):
if it all hangs together and like does everything it
has to do, meaning it can describe everything that gravity
can do, and they can describe all the tiny fundamental
particles and it brings those together in a way that
makes sense that you know, they don't disagree with each
other like the current quantum mechanics and general relativity do.
Then we can ask questions of that theory. So first
we've got to make progress. Theoretically, we need like an

(39:41):
actual theory that totally works. Before the break, we talked
about a few possibilities like directions people are going. These
are like half formed ideas. People are like building scaffolding.
You can see the outlines of a structure of people
are trying to make work, but nobody has an actual
functioning theory of quantum gravity where we can ask these
kind of questions and get answers. I guess you need

(40:01):
some sort of theory first, right, Like, you can't just
take out space and measure it and not measure it.
How do you measure not space? Well, we have done
a lot of really cool experiments about space, right, Like
seeing gravitational waves is incredible. It tells us that space
really is sort of fungible and dynamic. And measuring the
expansion of the universe that's also kind of an experiment

(40:22):
that tells us what's going on with space. And a
lot of times experiment informs us. Remember that we didn't
expect the universe to be expanding in an accelerating manner
until we saw it, and it totally shocked us and
surprised us. So sometimes experiments can inform us. I think
in this case, we really need theory to tell us,
like how we can do experiments to answer this question,

(40:43):
because currently the only experiments I can think of are
ones that are like at the center of a black
hole or requires super colliders the size of a solar system,
not things we can get done tomorrow. No, exactly, because
for example, general relativity and quantum mechanics they disagree about
what's at the center of a black hole. You know,
general relativity says, oh, there's a singularity there, but quantum

(41:05):
mechanics says, you can't have a singularity because that's too
much information isolated in one little spot and it violates
the Heisenberg uncertainty principle. And so if you could see
what was going on inside the black hole, you can
get great clues as to how to build your theory
of quantum gravity. Or if you could somehow do tests
of particles feeling gravitational forces by building a super huge

(41:26):
collider and smashing those particles together at crazy high energies
enough energy where like gravity is as powerful as the
other forces, that maybe you could get a clue as
to how to build your theory of quantum gravity. But
we can't do either of those experiments today, And so
I think what we need is some inside from the
theory to tell us, well, look, here's how the universe
is put together. Here's our theory of what spaces, and

(41:48):
this theory gives us a clue about how to look
for evidence that the theory is correct. You know, there's
some like wrinkles, some experiment we can predict the outcome
of that can tell you whether or not this is right.
It's like if only you can break the loss of
physics so that you could figure out the laws of exactly.
And there's maybe one more hint of something that we
can do, which is that we can look for more

(42:11):
evidence of this creation of space. We can look for
evidence of those first moments just after the Big Bang
and trying to find some gravitational radiation from the Big
Bang itself. But what do you mean, like a shock wave,
or like actual radiation, or like gravitons. Yes, exactly all
of those things. You know that we have microwave background

(42:31):
radiation from about four hundred thousand years after the Big Bang,
when this hot plasma cooled and became transparent. We see
those photons, and people often say that that radiation is
like from the Big Bang itself. It's not quite as
from you know, four hundred thousand years after the Big Bang,
when the universe became transparent and that light is now
still propagating around. We'd love to see earlier. We'd have

(42:54):
to look further back to the actual creation of the universe,
whatever happened there, And so it might be Passe will
do that by looking for gravitational waves that were created
in those very first moments when the universe was expanding
so rapidly, we think that gravitational waves were made. So
there's another kind of radiation called the cosmic gravitational background

(43:15):
that might have clues as to what the nature of
spaces and whether it was created in those first moments,
if we could see it like the echoes of the
creation of space, yes, exactly, and so we have theories
about what that might look like under various configurations. And
you might remember several years ago people didn't experiment where
they thought they measured those waves. It was called BICEP two.

(43:36):
But then it turns out that they were mistaken and
they were actually just measuring dust between galaxies. So that
was disappointing, But it might still be possible with a
better round of experiments, more precision and control of that dust,
to see the actual radiation from the early universe and
get a glimmour as to whether space was created or
whether it had always been there. And there's another possibility
right us to whether or not we can confirm this

(43:58):
existence or the tendency of space, and that is that
maybe in the future there might not be any space.
Right exactly, are we going to run out of space
or are we just gonna, you know, get a victim
from our house. No, you're absolutely right. And some of
these theories of loop quantum gravity, for example, they predict

(44:18):
that the universe's expansion will stop and it will turn
around and it will compactify, so that space is like
being destroyed instead of being created, and we'll have like
a reverse big bang, this big crunch, And it's not
clear what would happen after that. Would we get another
big bang? Would we just have no space for a while?
But does time even exist anymore? We don't know. So yeah,

(44:39):
stick around another few trillion years and the question might
just answer itself. Yeah, things might get a little bit
more crowded or were space and cluttered? All right? Well,
it sounds like it is possible for the universe to
not have any space, But we may not find out
any time, you know, unless we observe something incredible or
we make a breakthrough in one of these theories that
let us look or you know, kinks that we can

(45:02):
use this evidence that space cannot exist. Yes, and I
think that there will be theoretical progress. People are working
really hard on this stuff. Black hole information paradox is
giving us some clues. So there's a lot of really
smart people working really hard on these questions, and I
think in the next five or ten years we'll see
some really clever, fascinating, mind blowing theories coming out to
explain our bunkers universe. They just need a little space,

(45:25):
you know, no pressure. All right, Well, we hope you
enjoyed that discussion. Thanks for joining us, see you next time.
Thanks for listening, and remember that Daniel and Jorge Explain
the Universe is a production of I Heart Radio or

(45:46):
more podcast from my heart Radio visit the I heart
Radio app, Apple Podcasts, or wherever you listen to your
favorite shows.