What is quantum spacetime foam?

Learn about quantum spacetime foam with Daniel and Jorge

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, Daniel, I've noticed that people just add quantum the
word quantum to things to make them sound cool. Oh man,
I hate when they do that. Yeah, like quantum combs,
quantum um cereal. I mean it''s like they put it
on everything just to make it sound awesome. Yep. I
was seeing quantum dog food recently, and I'm pretty sure

(00:30):
that's not a real fact. Your dog both loves it
and hates it at the same time. But does that
mean to just all of quantum mechanics is like a scam,
not all of it, Like, there really is some physics
in quantum mechanics, but I'd say most things that are
called quantum are probably bologny. Hi am Jorge. I'm a

(01:07):
cartoonists and the creator of PhD Comics. Hi I'm Daniel.
I'm a quantum physicist and that is not bologny. Oh well,
it just happens. I'm a cartoon bologny cartoonists. So all
brings it together and welcome to our podcast, Daniel and
Jorge Explain the Universe, a production of I Heart Radio
in which we explore everything that's crazy and amazing about

(01:31):
the universe, from classical physics to quantum mechanics and explain
it to you in a way that you can explain
to your friends and sound super smart. Yeah, in ways
that we do explain it and don't explain it at
the same time. We're sort of like a quantum podcast
in a way. We download individual, discretized units of explanation
into your brain. We spin it up and spin it

(01:53):
down for you guys. But quantum mechanics is one of
my favorite topics because it is so hard for people
to understand usually, but there are ways to look at
quantum mechanics and get a new sense of the world,
to reveal the reality that underlies everything. Yeah, it's your
favorite because people don't understand it. It's my favorite because

(02:13):
it's a great example of how in physics we can
learn that the world is really quite different from the
world we expected it to be. The world we grew
up in is not the way the world works. That
to really understand the universe, we have to remove our blinders,
and quantum mechanics is a great example of that because
it requires basically tossing out your entire intuition for how
the world works and accepting something very different. Yeah, I

(02:37):
feel like that every day that I wake up and
read the news, like, what is this universe we're living in?
What quantum politics is that you're talking about? It's just
the quantum news will say, it's just the quantumy. It
makes sense and doesn't make sense at the same time.
It's about a dead cat and in a life cat
at the same time. I feel like quantum mechanics is
something a lot of people are fascinated by. They've heard

(02:59):
about it, they hear people use words to explain it
that don't quite make sense to them, and so people
are thirsty for a real, honest to god understandable explanation
for some of this bizarre quantum phenomena. Yeah, and it
sort of seems, like you said, it almost seems like
two different universes. You know. There's like the universe that
you grew up and as a kid and feel you

(03:20):
understand where you take a ball and you bounce it
and comes back and you can throw a baseball and
it lands where you think it's gonna land. And then
there's there's the kind of the quantum universe you learned
later on in life, where like none of those things
you learned as a kid seem to apply precisely because
your brain develops all these ideas for how things move
based on what you've experienced. Things seem to move through

(03:42):
the universe, it seems like they have a smooth path,
and so later to grow up and learn that things
don't actually move. They just have these snapshots and then
those later snapshots in your brain is filling in the
in between slices to make like a movie of the universe.
Is quite shocking. I wonder if we had evolved to
be much much smaller, if we would have sort of
a quantum intuition, if we like had everyday experiences of

(04:04):
quantum objects. You mean, like if it's taught at the
preschool level, if we try to teach kids quantum physics,
I don't think we should be doing short in your
equation um one plus one, spin up, spin down, you know,
just the basics that you need to deal with this
crazy world we're living in. That's one approach, but I

(04:27):
think that people would still struggle because they don't have
any actual experience with it. I'm talking about really experiencing
quantum mechanics, Like what if they were quantum effects that
were macroscopic, you know, things that were the sizes of
baseballs operated under quantum rules. It's pretty hard to reveal
that the universe is quantum mechanical. It took us thousands
of years before we figure that out. What if it

(04:49):
wasn't so subtle, what if it was more obvious and
so people actually had an intuition for this, they're like, oh, electrons, Yeah,
those moves just like these other quantum basketballs or whatever
that I was playing in within my kindergarten playground. Yeah. Yeah,
maybe that's the next wave of physics education, is we
need to develop some sort of technology that operates like

(05:10):
quantum objects so kids can play with like quantum balls. Yeah. Well, um,
it does seem like it's kind of a separate and
new universe, and it feels like there's a quantum version
of almost anything. Like for anything that we have in
our world, there seems to be like a quantum version
of it. Like you know, I know I can spin

(05:31):
here in my chair, and there's also something called quantum spin,
and you know, my battery has charged at it, but
there's also something called quantum charge and so on and
so on. Yeah, there's even quantum flavor. Yeah, you think
in kindergarten that there's only sweet and salty and sour,
but there's also quantum flavor, and we have quantum color.
We had a whole podcast episodes about all these. Yeah,

(05:55):
so you can go to quantum Kindergarten too and learn
quantum sharing and quantum And in some cases these things
are metaphors, like quantum flavor. These particles don't actually taste
like anything, but we're trying to make an analogy. We're
trying to extrapolate from something we know, which is flavor,
and give you a sense for this weird new quantum thing.

(06:18):
But in other cases it really does make sense, like
quantum spin. Those particles are not spinning in the same way,
but they really do have angular momentum, so spin really
makes sense. So in some cases the words are you know,
really a stretch. In some cases they really are applicable, right, Yeah,
that was a pretty good way to you just sput
it there, right, so obvious and clear. But but yeah,

(06:44):
but sometimes you know, I wonder, sometimes I wonder if
it are pushing it a little bit too much. And
so today on the podcast, we have a great question
from a listener that we're going to try to answer.
And this is a question from Dale from Dublin. We
had a very interesting question and about another strange sounding
quantum thing. Here's Dale Dale from Toblin oiland here I

(07:08):
heard about a thing called quantum phone or spacetime phone.
Could you talk about that for a bit and let
us know what it is? Chairs Well, I love so
many things about this. First of all, I love Dale's
accent awesome, and I love the Dale wrote in. This
is just an email he sent me saying, hey, can
you explain this? And I asked him to send us
a recording so we could talk about it on air

(07:28):
because I thought a lot of people might be interested
in the answer to this question. So thank you Dale
for writing in, and thank you to everybody who writes
in with their questions. Right, and just as a reminder,
we are on Instagram and Twitter at Daniel and Jorge
and if you want uh Daniel to answer back, try
Twitter or the email because Instagram will not answer your question.

(07:51):
I don't do quantum social media. Yeah, so if you
have a question, send it on into questions at Daniel
and Jorge dot com or engage with us on Twitter
at Daniel in Jorge. Yeah, so this is an interesting question.
Quantum foam. It's sort of sounds like one of these
products that you sell in late night television that will
totally clean your bathroom at the molecular level. I think

(08:14):
a lot of times in marketing, quantum is just used
to describe something to make a sound more modern or technological.
You know, like like quantum dog food. That really is
a thing. I mean, it's your mechanical No, Google, quantum
dog food. There is a product they really do sell
dog Foodn't call it quantum. I think what they mean
by that is new fancy, you know, savvy to the

(08:37):
quantum mechanical world somehow new fancy. Yeah, well that's kind
of what you guys do in physics as well, isn't it. Oh,
this is a charge, but it's kind of new and fancy.
We'll call it quantum quantum. Wait, no, but it actually
is new and fancy. Sometimes we do discover stuff in physics.
It's new and fancy. All the quantum mechanics is new
and fancy. It really does happen. It's not just marketing.

(08:59):
Sometimes dog food is new and fancy. Why not and
coming districted little chunks? That's true? Yeah, alright, so I
should order that product and I should evaluate it before
I give my opinion on it. You're totally right and
content doct food. Please give us a call. We are
opening for sponsorship. In this podcast, I was wondering if

(09:20):
Dale from Dublin was the only person thinking about spacetime foam,
and so I walked around and I asked people what
they thought about space time folm, had they heard of it?
Did they know what Dale was talking about? Did they
have any idea what it was? And these questions again
didn't happen to e c Irvine. This happened at a
local coffee shop because I was trying to get a
sense for the broader public and their understanding of this topic. Yeah,

(09:41):
so before you listen to these answers, think about it
for a second. If a physicist approached you at a
coffee shop, would you be able to answer the question,
what is spacetime foam? Here's what people had to say,
upper layer to spacetime that kind of bubbles up or something.
If that makes sense, Well, I'm no idea. I have
no idea spacetime phone, no spacetime phone, no spacetime phone

(10:09):
for space. I guess, but I don't um space. I'm
not all right. I feel like people were answering and
they were just about to call the police on you.
On these you can sort of hear that in responses.
They're like, I am so regretting answering this questions. What

(10:30):
are you talking about? I think, yeah, I mean people
go to a coffee shop to wake up, and you're
asking them physics questions over their cappuccimo phone. Well, you know,
I specifically tried to choose people that looked like they
were studying, like they had a book open and they
were reading something, because I was hoping to find people
who were, you know, like had their brains on or intellection,

(10:52):
engaged in something, or maybe curious about this kind of thing.
I didn't interrupt, like couples that were smooching, or if
they looked like they were listening to a podcast, You're like,
that person probably knows everything already, right. I try to
avoid people who already have their earbuds in, because I
feel like in public, earbuds mean don't talk to me. Well,
this is kind of an interesting question. Quantum foam and

(11:14):
I I had never heard of it. If you have
approached me at a coffee shop, I would have just
said no, please, go on, please please asked me an
easier question. You would have been like, you look like
this other physicist I know, and I definitely ignore him
in public. So I'm not talking to you as a
blanket policy. That's my decision on physicists. All right, So
this is an interesting question because it's it's like you're

(11:35):
marrying two words that are very common space time and foam,
but that together really don't make any sense. Yes, And
that happens so much in quantum mechanics. People say things
that use words together and you understand the individual words,
but you don't really know what it means when you
put it together. So we'll get into what spacetime foam

(11:56):
is and what we know about it and how we
might be able to find it in in this frothy
little universe we live in. But first let's take a
quick break, all right, Dannel, we're talking about spacetime foam,

(12:21):
and it's not a weird product that you sell on
late night television. It's an actual physical theory in science,
and so let's get into that a little bit. And
I guess let's start with the first two words to
set us up for the foamy part um. So let's
talk a little bit about spacetime, because in this case,
I think Dale from Dublin used the word as one word,

(12:46):
like spacetime, not space common time. He called it spacetime.
So let's maybe refresh for our listeners what it means
to say spacetime. Yeah, it's like you take two words
you put them together. They mean something special, like green
and house. Greenhouse is not just a greenhouse, right, has
its own meaning. So in the same way space time
is sort of a special word in physics, and of

(13:08):
course you know it's spaces. Space is just the three
dimensions of movement. You know, you have X, y, and Z.
And we have a whole other episode about like what
makes up space? Is it a thing because it can
wiggle and dance and jiggle and expand and all this stuff.
But for our purposes today, let's just think about it
as sort of as the directions you can move in X, Y,
and Z. So that's what space means, like the space

(13:30):
we're in, like where we move around in. Yeah, precisely,
nothing special there. And time is just time, right, time
flows forwards, and you can think of time in analogy
to space. You can think of us as moving through
time the way you can move through space. And we
have a whole podcast episode digging into how time is
connected to space and how time is different from space.

(13:52):
But Einstein is the guy who put these two things together.
He's the first one to construct this idea of space
time by taking three dimensions of space that you can
move in and adding the time dimension to it is
sort of a fourth dimension. So together space time is
this four dimensional idea X y Z and then time. Right,
I feel like you just said something profound though you

(14:13):
just said time is time. That man, time is so fascinating.
I could talk endlessly about time. We could spend all
of our time talking about time. But maybe it's not
time to do that. That one phrases made me think
about my whole life and where I'm going with it.
And well, can I sell you my new product. It's
called quantum time the There you go, alright, quantum quantum

(14:35):
watch to keep track of the inevitability of time. It's
new and fancy and has to be charged every fifteen minutes.
There you go, alright. So spacetime is this idea that um,
space and time are not separate, like maybe if you
think about them altogether in one package, one four dimensional bundle.

(14:57):
Then it's more appropriate somehow like uh like the related
like one of them affects the other, so therefore you
should keep track of them all at the same time precisely.
And it was Einstein's theory of special relativity that showed
us exactly how space and time are affected by each other. Specifically,
how time flows depends on where you are and how

(15:18):
fast you are going relative to something else, and so
in order to understand time, you can't just have time
by itself. Time is not universal. Time is local. Time
depends on where you are in space, and so it
makes much more sense to combine these two things together.
It's like having the weather, right. The weather is not
the same everywhere, so you want to talk about the

(15:38):
weather where you are in Buffalo, or in New Delhi
or in Barcelona, and so you pair the weather with
the location because that makes more sense. It's called the
space time weather continuum, which you hear listen to my
new quantum weather reports. It's a new Toppler quantum three
thousand that probably is a real thing. I mean, you're joking,

(15:58):
but there's probably some will station out there with quantum weather.
Dobbler some local weatherman in the middle of Barcelona. And
Geinstein was not crazy, right, Like, he didn't just make
this up and it didn't work. It actually works, Like
bundling space and time together does tell you something about
the universe, and it's there's been theories and experiments done

(16:21):
to prove that this is all for real. Oh, yes,
Einstein was right about this. That doesn't mean Einstein wasn't crazy.
I mean, you dig into that guy's personal life. He
was more than a little bit across. What do you mean.
He was also right about spacetime, all right, So that spacetime.
And now the question from Dale was what is spacetime foam?
And I have to say, I've never heard of this before.

(16:41):
Is this a new thing? Is this something that's only
been around for a couple of years, or is this
like a fringe theory or French theory? I don't know
either one. What is what is going on with spacetime phoam? Well,
I can't endorse your casual slander of entire culture there,
but it is a bit of a fringe in theory.
It's one of these things. It's like it's an idea

(17:03):
that took hold in some people's minds, but then not
a lot of progress was made, so so HA just
been hanging out there, bubbling up in people's brains without
really turning into anything concrete. So it's been around for
a while, but it's not really part of the mainstream physics.
It's just been foaming up in people's research dockets. And
so I know that you keep abreast of all the
latest topics in physics and you read all the physics journals,

(17:25):
and that's probably why you haven't heard about this recently. Right, Well,
at first I thought it was maybe an acronym, like
maybe fo a M stands for something. It's the first
of a multiverse, which is a new theory by Jorge
Cham about how we're the most awesome of all the multiverses.
And somehow Dale from Dublin knew about your theory before

(17:47):
you even thought about it and thought to ask in advance. Wow,
good job, Dale. Yeah, well, in other multiverses he didn't,
but this one, because it's the best he did, all right,
So let's let's talk about this. So there is something
called spacetime foam that physicists think might be real and
might actually kind of describe what the universe is like,

(18:09):
so take us through it, Daniel, what does it mean
to put the word spacetime and foam together? The idea
here is to try to resolve the conflict between our
two great theories of physics. We talked about space time
in terms of relativity, and that all makes sense. And
relativity has been tested out the wazoo and up the
wazoo and in the wazoo in every way around the wazoo.

(18:30):
Because is that it's a great theory. Is that another
physics experiment acronym the wazoo, the wazoo, I'm not sure
what it means collider in Italy apparently, but special relativity
has been extensively tested, and so has general relativity. But
we don't know if it really holds universally. That we

(18:53):
have suspicions that it probably doesn't work on really really
tiny distances. So general relativity said is that space is
sort of smooth, that you can chop it up into
tinier and tinier bits and you'll never sort of run
out of ways to cut it in half. That like
in Zeno's paradox, you could take smaller and smaller steps forever.
That's what general relativity says. It predicts it, or it

(19:16):
assumes it. It assumes that it it uses that as
its essential description of what space is. That you could
have a particle or an object located at any point.
You know, if you have an infinite number of locations
between me and you, that a particle could be at
any of those locations. Oh, I see. It's kind of
like Newtonian physics, right almost in a way, like it
assumes that space is smooth, and it doesn't assume anything

(19:39):
that's that anything is quantized. That's right, And you look
at the universe around you, and the universe seems smooth, right,
It seems like you could sit anywhere. It seems like
if you took a ruler, you could cut it in
an infinite number of ways. Whatever that there's an infinite
number of ways. But just like the screen on your
iPhone looks really crisp and smooth, but if you zoom in,

(20:02):
you discover that there are pixels there. And so general
relativity tells us that the universe is smooth. That's space
is infinitely sliceable. But that's in conflict with quantum mechanics.
Quantum mechanics says that you can't have infinitely sliceable space. Yeah,
that at the fundamental level, it's pixelated, kind of like
my iPhone screen. Although my iPhone screen these days looks

(20:26):
kind of blurry because as I've said before, I need
reading glasses. Now I'm not sure that's a problem with
your iPhone screen, but well it's a it's a problem
for my new quantum reading glasses. Yeah. And so quantum
mechanics has this impact on lots of things that we measure.
Things that at large scales seem smooth turn out to
be discretized, turned out to be sliced up into chunks.
Like a flashlight beam is not a smooth, continuous beam

(20:50):
of light. It's a stream of tiny little packets called photons.
The same way your bowl of ice cream is not
infinitely chopped herble into smaller and smaller spoonful. There are
atoms in there. It's made out of these tiny little
lego pieces. So the same concept can be applied to
lots of things, and quantum mechanics says that probably it
also applies to space. So we have this conflict between

(21:12):
these two great theories of physics, relativity and quantum mechanics,
and the conflict lies in a place that's really hard
to spot where things are super duper small, so meaning
that general relativity doesn't know that there's something called quantum
physics and quantum mechanics. Quantum physics sort of we don't.

(21:33):
Do we know that quantum mechanics takes into account general
relativity or is there such a thing as bending a
space and quantum mechanics. So that's a great question. People
have tried to say, let's take Einstein's theory of general
relativity and let's make a quantum version of it. Can
we make a version of general relativity where space is
pixelated or we know quantum mechanics comes into account, and

(21:56):
currently we have no great functioning theory like these. Reason um,
you can make a theory of general relativity that is quantized,
but it doesn't work when space is really intense, like
inside a black hole. When the gravity gets really really strong,
then the theory breaks down and predicts things that don't
make sense. It gives you like infinities and all sorts
of crazy numbers. So we don't currently have a working

(22:19):
theory of what's called quantum gravity that tries to marry
all the best things from general relativity and quantum mechanics.
So does that mean that quantum mechanics operates kind of
in a Newtonian or like perfect kind of pre Einstein universe.
Quantum mechanics operates often in if what we call a

(22:39):
flat space, you know, space that's not bent by mass.
You can do quantum mechanics in curved space, where if
you're like near the Sun or near a black hole
and space is curved, you can do that quantum mechanics.
But if you try to do it when space is
too curved, when the gravity gets really really strong, then
it just doesn't work. We just don't even have a theory.
We can't like even come up with a theory that

(23:00):
makes sensible predictions, not to mention check those predictions against
actual experiments. All right, So it sounds like general relativity
is good for kind of big distances and tells us
how the universe works at large scales, and quantum mechanics
tells us how it works in really really tiny scales.
But there are situations where the two theories just don't.

(23:22):
Neither of them work. Yeah, and what we need to
do is get inside a black hole and see what
happens when you have both small distances. So quantum mechanics
is relevant and really intends gravity, so general relativity is relevant. Unfortunately,
all the people we've sent into black holes have not
been coming. Yeah, I was gonna say that you're using
the word we they're pretty broadly. There any volunteers out

(23:45):
there who wants to be the first person to die
at a black hole. And this is where the idea
of space time foam comes from. It comes from an
attempt to try to reconcile these two theories. I see.
It's a it's another one of these unifying theories, like
theories of everything. Precisely. There's one theory that says maybe

(24:07):
the universe is made out of tiny little loops. That's
called loop quantum gravity. Another one says maybe everything is
just a tiny vibrating string at string theory. There's even
one called spin foam, where everything is like this weird
spinning kind of foam. But spacetime foam is a particular
theory that tries to unify quantum mechanics and general relativity,

(24:31):
and it imagines space is being made of these tiny
little pixels, but these pixels would be quantum mechanical and
so like bubbles and a frothing foam they might like
pop in and out of existence. All right, let's get
people in the loop of this and get a little
bit more into what quantum foam or spacelime foam is

(24:51):
and how we know about it and what we might
discover if we poke around in the universe. But first,
let's take another quick break. Yeah, all right, Daniel. So

(25:13):
quantum foam is kind of like quantum dog food, and
that you know, you're trying to make something that your
dog will both eat and enjoy at the same time.
We're trying to make something that explains both general relativity
and quantum mechanics all and that your dog will like,
I guess, also um at the same time. And so

(25:35):
and that's hard because, as you said, they're sort of
based on two very different views of the universe, that's right.
And you know, for relativity to work, what we need
is a new imagining of it. We need to start
from a different conception of what space is. Einstein assumed
that space was smooth and continuous, and he built his
theory upon that assumption. So we need to start from
a different assumption and say, actually, spaces made of these

(25:57):
tiny grains or these little bubbles and under stand the
nature of those and then build a theory on top
of that. And I don't know this is true. It's
not clear that spacetime boom is a real description of space.
You know. It might be the pixels are a better description,
or loops or little strings, or we really just don't know,
but we need a new idea. And so theorists are

(26:17):
just sort of being creative and smoking banana peals and saying, well,
maybe it's more like this, and you know, you look
around the macroscopic universe to get inspiration, you know, and
maybe some physicist was smoking a banan appeal and looking
at soap bubbles and thinking, huh, maybe space is just
like that. Well it's it's interesting because I feel like,

(26:38):
you know, there's these two theories and it's not like
you're saying like, oh, maybe quantum mechanics is wrong, and
really we just need to extend general relativity, or you're
not saying, oh general relativity is wrong, we just need
to extend quantum mechanics. I feel like you're saying that
we we need to throw both of these into the
garbage and kind of come up with one theory, start over,

(27:00):
re imagine the universe and come up with one theory
that you know, it sort of looks like one and
looks at the other, but actually kind of works continuously
across the whole universe. Yeah, well, we don't know what
the necessary process will be. It might be that we
can take what we have from general relativity and from
quantum mechanics and marry them um. Or it might be that, yeah,

(27:21):
we have to toss it out and start all over again.
The process of science is iterative, right. It's like a
writer writing a draft of a screenplay or something. You
just keep trying to make it better and better until
it fits, and then at some point you realize, you
know what, this is hot mess of garbage, and you've
got to toss it out and start all over again.
So we don't know. We don't know if you know,
we're one more draft away from something we can publish,

(27:43):
or if you've got to toss it all out and
start on the next book, right, Or maybe the studio
head goes, well, it's too late, let's just make this
bad movie and can you make it funnier? And we
live in that universe that should never have been made
where the plant is It don't make any sense? And
the acting is stiffid best. That's even better than do

(28:05):
we live in a simulation? Is? Do we live in
a poorly written sim simulation? Like that? I got notes
for you simulation authors. Okay, here's how you should have
done the simulation. Here's what rotten Tomato says about your
universe business ratings on on universe simulations. I like it.

(28:25):
There you go. Quantum Rotten Tomatoes is the name of
my new website. Check it out. Alright, So step us through.
What is quantum foam? Then? Is it? What does it
poe mean? Why is it phone? It have bubbles in it?
Is it like a froth? Why is it called quantum phone? Yeah?
The idea is that quantum mechanical things fluctuate. They come
in and out of existence. If you zoom into particles

(28:48):
at the smallest scale, you can't follow them along the
way you would follow a baseball. They sort of pop
into existence and pop out of existence. They turn into
other particles. It's like a constant mess, right, and so
lots of things are happening like it's bubbling at the surface,
kind of like foam. Those are the things in space
and times. This is saying that space, time itself is
like a phone, right, And so if space itself is quantized,

(29:10):
it's made out of these pixels, and these pixels are
quantum mechanical, then it's possible that the pixels themselves are
sort of bubbling in and out of existence. It's one
step to go from space is smooth to space is
discrete r it's made of pixels. It's another to say,
maybe those pixels themselves are not like permanent, they're like temporary,
you know, they're ephemeral. They're coming in and out of

(29:32):
existence because in the end, a lot of quantum mechanical
things are Space itself is coming into and out of existence,
like yeah, like this bit of space run in front
of my eyes here precisely the you know, the object
in front of you, for example, whatever it is, it's
in front of you right now. It's a banana, or
it's an apple or whatever, that's made of quantum mechanical particles.
Now it seems solid, it seems like it's really there.

(29:53):
But if you zoomed in on the little particles, the
particles that make it up are popping in and out
of existence. They're turning into energy, they're turning back the
particles that changing into other particles and then coming back
you don't even notice, right, So that phone or whatever
in front of you is a frothing mess, but you
just don't notice it frothing because the frothing is so tiny.
So if it's hard for you to imagine, like that
space itself could also be frothing. Remember everything around you

(30:16):
is kind of frothing. Oh wait, so this would be
like under the quantum particles. Like you could have a
quantum particle and it's really tiny, but the space it
is sitting on could be bubbling underneath it. Is that
what you're saying precisely, And remember that in modern quantum mechanics,
we don't even really think of particles as like the
basic element of stuff in the universe. Particles are just

(30:38):
excited states of quantum fields. And quantum fields they had
a whole episode on, are a property of space itself.
So you can't really separate the matter and the space
because matter is just an excited state of quantum fields,
which are a part of space, but is the spacetime
foam on the same scale as the particles like um

(30:59):
you know what mean? Like what if there's a particle
that just happens to be sitting on a spacetime bubble
and that bubble pops. Does that particle just disappear or
is it like riding on top of a whole bunch
of little spacetime bubbles. Yeah, I think you have to
think of particles as part of space, because particles are
again excited states of these fields, and the fields themselves

(31:20):
are part of space. And so I thinks it takes
a whole new way of thinking about like the nature
of the universe at the smallest scale. It's not like
particles are sort of filling in slots in space. They're
like excited space. Oh and you're saying that this space
is actually more like foam, meaning that it's just a
whole bunch of little pockets of it kind of pressed together,

(31:43):
and each one of these pockets is a quantum of
space time. That's right. And we don't know the size
of these bubbles. If these bubbles exist, and we don't
know that they do, the question is how big would
they be? And we suspect if they do exist, they'd
be super duper duper duper tiny. But you have the
idea is that you know you have a localization of
energy that energy is an excited state of all the

(32:05):
quantum fields in that space, and that localization of energy
you could extend across multiple bubbles of quantum space, perhaps
for example, like a photon, and that you know, it
could be made of these little frothing bubbles. They're smaller
than that packet of energy. And so what am I
doing when I'm moving through space? Am I moving from
bubble to bubble? Or do I take like each one

(32:27):
of my particles might be in this bobble, bubble or
that bubble. Well, you are those bubbles. You're not in
those bubbles. You are those bubbles and the spacetime foam.
You are the spacetime boam, and so am I. We
are all one with the spacetime foam. Remember, you are
just an excited state of the space that you are occupying.
And when you move that information, then that energy then moves,

(32:50):
you know, it excites another part of the quantum space.
It's like you are the wave on the string. Right.
If I'm holding a string and I wiggle it, you
can say, like where does that wiggle? It moves along
the string the same way you are wiggling the quantum
fields where you are now and then when you travel
somewhere for Thanksgiving, you're gonna wiggle those quantum fields. So
don't think about it as you are particles in space somewhere,

(33:12):
but you are excited wiggling of space. Oh, I see,
I'm just an excitation from one bubble to the next bubble, precisely.
And the idea of spacetime foam is that maybe space
is discretized and those little discrete blobs are popping in
and out of existence. They're like not long lasting, They're

(33:32):
not eternal or permanent. They're sort of frothing, oh, coming
in and out. But what if I get stuck in
one that pops, I wouldn't recommend that. Does that mean
I'm no longer in existence? Then you don't have to
buy quantum pet food for your quantum dog because the
quantum out of existence. You know, these things are at
a very very small scale. So unless you're a particle
on the size of quantum foam, you don't have to

(33:53):
worry about it. But also energy is conserved. So if
space is frothing somewhere and energetic, and there's an excitation
enough space here, that energy is going to go somewhere,
maybe into the next bubble with the next bubble, So
the bubble itself might pop out of existence, but the
energy that is represented by that excitation is not going
to go away. Oh, it's just gonna move on to
another bubble. Yeah, that's what you do. When you move

(34:15):
from place to place. You are exciting those fields, and
now you're exciting these fields over here, all right. And
so there's a theory that says that the universe at
the very core level is like a foam, But that's
just one competing theory about what it looks like down there.
How are we going to find out which one it is?
How do we know if the universe is foaming or
if it's well, we need lots of money to build

(34:40):
a huge particle collecit That's my answer to everything, right right, Money,
It just solves everything for you, doesn't it any It
sort of does you know? If you want to answer
questions about high energy or heavy particles or tiny distances,
which you need is a microscope to look at the
really really small And the only thing that prevents us
from looking at really really small spaces is having enough

(35:01):
money to build a big enough microscope. We know how
to do. It is just really expensive, so we could
probe these distances. We think the distances involved or something
like ten to the minus thirty five meters, which is
ridunculously tiny. Like if you had a microscope with not
just like a ten x hundred eggs, but like tend
to the thirty five x, we might be able to

(35:24):
see these phone bubbles and time. Yeah, we had a
whole episode about how you see tiny things and microscopes
and electron microscopes and particle colliders, so people should dig
into that if they want more information. But basically we
can see down to tend to the minus twenty right now,
which is pretty impressive. We think these bubbles are tend
to the minus thirty five, so fifteen orders of magnitude

(35:45):
is is actually still a lot. You know, there's a
we're far away from being able to see these pixels.
So that's one way is to build a really big collider.
Another is to try to use like really long distances
in space ah to use as base itself like a microscope.
The idea is if space is bubbling and frothing, then

(36:05):
you know it's sort of constantly changing. That means that
like the distance that light has to travel from point
A to point B is not necessarily fixed. So they
do these crazy experiments where they look at something really
really far away and they try to see it in
two different ways. They try to understand, like, you know,
let's look at two photons that left that really bright
source of light maybe a quasar, at the same moment,

(36:27):
and see if they arrived here on Earth at the
same time. If there's a difference, then maybe that's because
there was more quantum foam bubbling up for one photon
then for the other. Oh, I see, because it's foamy.
That means the path you take through this foam is
sort of random. And so like one photon could have
hit a really foamy patch I guess, and and gone

(36:52):
through a little bit of extra space more than the
other particle who just happened to go through a part
of space it wasn't as foamy, and so that would
tell you like, oh, space is not consistent, it's kind
of frothy. That's the idea. I have to say that.
I'm skeptical because you know, on long distance scales, so
you would think that these things would average out, like
you're going for a billion years, then the number of

(37:12):
random tosses of a coin are gonna be pretty close
to So two photons flying through incredible distances in the universe,
you know we're going to have pretty even odds to
go roughly the same distance. Anyway, they look at these photons,
they don't see anything, no surprise, and so they haven't
discovered quantum foam. All right, Well, do you think we'll
ever discover whether the universe is made out of quantum

(37:35):
foam or not? I think we will. I think it
will require some really clever mathematics to come up with
like how these theories might actually work. Because remember, we
don't have a functioning theory. We don't have a theory
we can actually go test the theory. If we ask
you questions, it gives us gibberish. And so we need
to come up with a good theory, and then we
need to be really clever about how to test it.
And I think maybe some time far in the future,

(37:57):
when we can get closer to black holes, will be
able to test some of these theories in environments with
really intense gravity. But it's pretty far off in the future.
So we need clever ideas and we need awesome new experiments, right,
I guess all of that is just to say, San Daniel,
more money is the entire takeaway. Who needs sponsorship from
quantum dog food when you can just have a whole

(38:19):
podcast to ask people for money. That's right. Email me
your quantum dollars to contributions at Daniel and Jorge dot com.
Oh yeah, that does feel like my bank account. It's
both there and not there. It's constantly fluctuated. Yeah, it's
poemy have phoney money, not phony money, phony money. All right, Well,

(38:42):
thank you Dale from Doubling. We hope that answered your
question about what quantum foam or spacetime foam is, and
I guess the answer is stay tuned. Yeah, it's a
really fun idea. It's fun to speculate about what the
universe might be like at the smallest scales. It's fun
to take ideas from our everyday world and see if
they apply at the quantum scale. But today we don't

(39:04):
really know if quantum bom is a thing or just
an idea bubbling up in the mind of physicists. So
keep on looking and keep us sending us your questions.
We're happy to answer them. All right. We hope you enjoyed. Dad.
Thank you for joining us see you next time. Before

(39:25):
you still have a question after listening to all these explanations,
please drop us a line. We'd love to hear from you.
You can find us on Facebook, Twitter, and Instagram at
Daniel and Jorge That's one Word, or email us at
Feedback at Daniel and Jorge dot com. Thanks for listening
and remember that Daniel and Jorge Explain the Universe is
a production of I Heart Radio. For more podcast from

(39:48):
my heart Radio, visit the i heart Radio app, Apple Podcasts,
or wherever you listen to your favorite shows.