Daniel and Jorge Explain the UniverseDaniel and Jorge talk about what is revealed if you empty space of all possible particles.
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Hey Daniel, do you enjoy doing housework?
There's something satisfying about it compared to the abstraction of research. You know, you start doing dishes and then the dishes are done.
Yeah, that's a cost and effect, right, basic law of the universe. If you wash dishes, they will presumably be clean.
I wish that same thing applied to physics research. You know, you do the physics research and the mysteries are unraveled. Doesn't know what's happened that way?
Well, there's no guarantee in science.
How about you. Are you a fan of housework?
Uh? No? And yet I'm the person who does all the dishes in my house. Well, actually the dishwasher doesn't, but I assist the dishwasher. I'm the assistant dishwasher.
And are you a fan of vacuuming?
I'm not a huge fan.
No.
I mean, I think my vacuum has a big fan, but I am not a fan of vacuuming.
I agree vacuuming totally sucks.
Hi.
I'm Horium, my cartoonist and the author of all ours great big universe.
Hi.
I'm Daniel. I'm a particle physicist and a professor at U SEE Irvine, And sometimes I feel like my head contains a perfect vacuum.
You mean, like a perfect vacuuming machine or a perfect lack of pressure.
You know how sometimes you reach back into your mind for a good idea and you just find nothing. On the other hand, you know, maybe that means you're ready to suck in a bunch of new information.
M I thought you were saying your brain sucks.
The creative process is a mystery to me.
You know.
Sometimes you reach back there and you find gold, and other times you are just left empty handed.
It is pretty dusty inside of my head as well. But anyways, welcome to our podcast, Daniel and Jorge Explained Universe, a production of iHeartRadio.
In which we try to take the whole universe and squeeze it into your brain, hoping that there's enough space to contain all of its mysteries, all of its majesty, all of its marvelous contents, including quantum particles, including black holes, including neutron stars, including photons, and everything else that makes this universe a wonderful, delicious and bizarre place to live.
That's right. It is science's job to dig down into the dusty corners of the universe and polish off our knowledge about how things work and why things are the way they are.
And when scientists think about dust, we're not always just thinking it as an annoyance, something to get rid of. Instead, we want to take the universe apart into its smallest pieces, and so dust provides a very useful clue. What is dust made out of? What happens when we break dust open into smaller bits? Why is the universe so dusty? Anyway?
So we are actually technically all made out of star dust, right, isn't that what the famous saying from Carl Sagan?
That is the famous saying, And you know it's mostly true. All the heavier elements we were made of, at least were composed in the hearts of stars out there, fusing together the primordial hydrogen and helium created during the Big Bang. But since a large part of our bodies are made of hydrogen, part of us are actually Big Bang dust, not just star dust.
I guess maybe since atoms are all made of the same things technically, like, it's just more and more dust, kind of compounded dust that we're made out.
Of Jorges dusty theory of the universe.
Now, does that mean that bunnies are also made out of dust bunny?
Or are dust bunnies made out of bunnies?
How about people named dusty? Would they also be made out of star dust?
Star dust and bang dust? And while it's fun to make these jokes, it's also really a fascinating mystery, like what is all of this stuff? What is its fundamental nature? Deep down? And that question is sitting inside a deeper, broader, maybe even emptier question, which is like, what is all of this stuff sitting in? What happens to the universe if you get rid of all the dust, you finally suck it all away and reveal the nothingness? What is all of that nothingness?
That's right? What is nothing? Is it nothing? Or is nothing something?
Do we have nothing to say about it? And can we anyway spin it into a forty five minute podcast?
No, let's just create an audio vacuum right now for forty five minutes.
Ready, go, that's actually a great analogy for today's podcast because even in that quiet, pun free moment, there was not nothing. There was something.
So today on the podcast will be asking the question what is a vacuum?
Now?
I imagine, Daniel, you mean like a space vacuum, not like a household vacuum.
I do love digging into the physics of everyday objects because it turns out there's always a surprising amount of complicated physics that goes into like what is a mirror? Or how does glass work? This kind of stuff is super fun. But no, today I want to talk about the nothingness of the universe. What happens if you use a vacuum to suck up all this stuff? What is that vacuum? And philosophically, what does that mean about the nature of reality?
Yeah, and I guess more fundamentally, does a vacuum exist? Is it possible to actually have nothing in the universe?
Or is it possible to have multiple different vacuums or vacuu a.
Or maybe more a trippy is a vacuum something?
Or if a vacuum is something, maybe that's just what we define as nothing as the most vacuum eist something.
Okay, now I'm getting nothing out of this.
I just invented a word vacuumist. Vacuumist, though it sounds more like somebody who operates a vacuum. Maybe it's not the best choice.
Well, that would be a vacuumer, wouldn't it be?
Not an expert in naming things?
Are here very clearly, But anyways, as usual, we were wondering how many people out there had thought about this fundamental question what is a vacuum and if they have any ideas about whether it is something or nothing.
So thanks very much to everybody out there who answers these questions for the podcast. And if you've been listening for a while or even just a few weeks and you'd like to throw your hat into the ring, everybody's welcome, please write to me two questions at Danielandjorge dot com.
So think about it for a second. What do you think a vacuum is? Here's what people have to say.
It sounds like the inside of my head when you ask this question, But if I were to think of it, vacuum is like a whiteboard with infinite possibilities, And when something comes along, like a whiteboard marker, you can either draw stuff on it, or you can just raise stuff on it.
It's just everything.
The vacuum would be space without any stuff in it, like no atmosphere, but I think space always has some stuff in it, so it's not really a true vacuum. That's really all I know.
Pretty sure the vacuum is like space with all its quantum fields, like at its resting state.
I can guess by what it says the vacuum is not a vacuum cleaner, but the vacuum of space. What causes it is actually a good question. I don't know. Maybe it's something related to a dark energy and expansion.
But probably not.
I think vacuum is the definition, the theoretical definition of the absence of matter in a given space.
I think vacuum quite literally means emptiness or absence of stuff.
Now, if you have a bottle, you remove everything from it, then you have a vacuum, but I think that's pretty ideal.
I don't think you can actually remove everything from a bottle.
Vacuum is the absence of matter, but I know that it doesn't mean it's empty, and there are lots of quantum craziness going around in what we traditionally call vacuum. So I'm looking forward for you guys to explain it all.
Right, a lot of interesting answers here. Someone got kind of technical talking about fields and resting states, the absence of matter.
Lots of really cool answers here that explore really the wide spectrum of possibilities for what nothing is.
Yeah, I guess you could define it in several ways, right, like absence of matter or absence of energy, or absence of quantum field maybe.
Yeah, And we will tear all of that apart on the podcast today.
Well, it's dig into it, Daniel. How does physicists define what a vacuum is?
So, the definition of a vacuum from the point of view and especially quantum field theory, is space with no particles in it. Essentially space as empty as possible from energy. If you can stuck all the energy out, including the matter, and relax space down to its lowest energy state, that's what we consider a vacuum.
Now, how is it different than the concept of space itself, Like, is space the vacuum or can space be a vacuum?
Well, there's the difference between space and sort of empty space. Space itself doesn't have to be a vacuum like at the heart of the Sun, there's space. Right. There's all sorts of particles bouncing around, whizzing around, incredible density, very high temperature, lots of matter, lots of energy. All of that sits within space. Right, The Sun is in space. Even the heart of the Sun has space within it. It's not empty space. It's very high energy, very dense space. As you move away from the Sun, of course, that space gets lower and lower energy, fewer particles. Everywhere in the universe we think has space in it.
You mean everywhere in space has space in it.
Yeah. As soon as you use the word where, you're assuming a location, and location requires space. You can't really have locations without space. Space represents the relationships between points, right, And that's really what space is.
I guess. Can you have the universe without space or space without the universe?
You might be able to have the universe without space because we don't fundamentally know what space itself is. We don't know if it's a necessary, fundamental part of the universe, meaning that like it has to exist, or if it's an emergent property of something deeper, you know, something that just sort of gets woven together out of the fundamental bits of the universe that might not require space. If you're not familiar with the concept of like fundamental versus emergent, fundamental just means it's required, it's essential, whereas emergent means it's not. That sometimes it happens and sometimes it doesn't. Like ice cream and pies, we think are emergent properties or something the universe can do, they can't exist. But it's possible to have a universe without ice cream and pause. So we think it might be possible to have a universe without space, though that's not something we understand. There are various theories out there, but that's an open question in physics. So far, we're operating under the assumption that space is essential for the universe.
Well, I don't know about physics, but ice cream is pretty essential to my life. I mean, a universe without ice cream it's not a universe I want to live in.
And yet the vast majority of the history of the universe had exactly zero ice cream in it, unless, of course, there are ancient alien civilizations who also enjoyed cold custards.
We don't know. So you're saying you don't know if aliens have ice cream or not. It's still an open question.
I can make no definitive statement about alien ice cream that is exactly true.
Yes, Also, I think in a vacuum, no one can hear you ice cream. You're like, I don't even know where to go with that joke.
That was the perfect joke. There's no possible response to it. A vacuum is the only possible response to that joke.
That's right. It's a micdrop moment.
Boom, Exactly, I just dropped my ice cream over here. It's an ice cream drop moment.
Put anaze back to our discussion. So you're saying a vacuum is space with no matter in it, no particles in it.
Yeah, that's exactly right. Whereas the minimum energy which includes particles. Right, if you're talking about what space is, space is fundamentally something we don't understand, but it has inside of it the possibility to contain all sorts of energy and matter. You can have protons in space, you can have photons in space. Photons are not technically matter, they fall into the radiation category. Right, So you can all sorts of different kinds of energy inside of space, and we have a huge variety of energy density in space right around us on Earth is an incredible number of particles. You take a cubic meter of air just in front of you here on Earth, and there's like ten to the twenty five mongules in that cubic meter of air swarming with particles.
Well, I guess you know, for me traditional Newtonian kind of high school physics, or you know, kind of as we grow up kind of way. A particle are bits of stuff that can fly around or float around, and so it's kind of easy to imagine just a chunk of space, a Cuba space with no little bits in it. Right, that would be a vacuum in a traditional sense.
In a traditional sense, depending on whether you're including radiation also, right, To really get a vacuum, you want to minimize the overall energy, not just the total matter. So yeah, you want to apply your vacuum and suck out all the bits, but then you also want to prevent photons and other kinds of non matter radiation from entering that cube of space to get the best of vacuum you can get.
Well, radiation is also particles, right, Like a photon is a particle.
A photon is a particle, but it's not matter in the same sense. These are like silly overlapping definitions. So yeah, if you suck out all the particles, that would include photons. So yes, that would be all the radiation.
I guess it's complicated because now we know that a particle is really just like a little blip in a quantum field. Right.
So there are sort of two different philosophical pictures about how this all works, and one that we talk about in the podcast a lot is what you just described, which is to imagine particles themselves as emergent properties. They're not fundamental things in the universe. They're just wiggles in these fields that fill all of space. And in that picture, fields are the most fundamental thing that when you have space, it contains these fields, and these fields are like places that energy can be. They're like, you know, how you can stack energy up and if you wiggle them in just the right way, then we call that a particle. So that's sort of one picture of the structure of space, time, and matter. There's another picture which says fields are nonsense. Really everything is made of particles, and the way particles communicate with each other and exchange momentum and stuff is by exchanging other particles. So the sort of the fields picture, which I think is more popus maybe more intuitive, But there is also this other picture that says that particles are the most fundamental thing in fields are nonsense, because remember, we never actually see fields themselves. Fields are sort of a unobserved story. We tell ourselves to explain what we do see in the universe, but we never actually see them. We only see their effect on particles.
Fields are sort of like the potential for particles to happen.
Yeah, they're sort of like the parking lot into which you can put cars, right, but again, we can't ever see them directly, like even electric field which don't seem controversial as a topic, like do electric fields exist? Well, how do you see an electric field? You put an electron in it and you see it move. What you're really seeing is the electron moving, not the field itself, So it's sort of a little bit indirect.
Well, maybe we're getting a little bit ahead of ourselves. I think what you're saying is that the idea that a vacuum is just a chunk of space without particles in it is still our energy is still pretty good.
Yeah, that's a pretty good concept of a vacuum is though it's surprisingly rare in the universe and hard to achieve.
Well, I guess maybe the first question or listeners might have is is space out there really a vacuum.
It's hard for me to say that anywhere in the universe is actually a true vacuum. If you go like near the surface of the Earth where space officially starts, which is like one hundred kilometers above the surface of the Earth, although the United States calls you an astronaut, if you've been above eighty kilometers, then that's where space officially starts. But there's a lot of stuff out there still. You know, the Earth's atmosphere doesn't end. It's not like there's a pane of glass there that's holding the atmosphere and it should drifts off gradually. So there's still a lot of atmosphere up there. And if you fly your satellite at that orbit, you'll be dragged by that atmosphere and eventually you deorbit back to the Earth's surface. So we know that there's definitely a lot of stuff out there still.
Just above the Earth or just outside of the Earth. It's kind of you say, it's kind of hard to find a true vacuum.
And so you go further, right, like, Okay, I'm going to leave Earth entirely, I'm gonna go into interplanetary space halfway between Earth and Mars. Well, then there's still a lot of stuff out there. You know, the Sun pumps out not just photons, which we consider energy and particles and so it disrupts your vacuum, but also matter particles, electrons, protons, alpha particles, very very high speed particles moving on like hundreds of kilometers per second. And there's not a tiny number of them. There's like millions of protons per cubic meter out there in interplanetary space.
Whoa coming from the Sun, right.
Yeah, this is the solar wind. And you know that's a tiny number compared to the density of air here on Earth. It's like ten to the nineteen times less dense. So it feels like a vacuum if somebody chucks you out the air lock. But it's not even really close to a vacuum because you still have millions of particles per cubic meter.
Well, what if you go out further into space, can you find a true vacuum out there?
If you like, leave the solar system and go into interstellar space still inside the galaxy, then you're still surrounded by what we call the interstellar medium, which is mostly and a little bit of dust some cosmic rays. And here it's much more sparse and it's highly variable. You can get from like ten to the minus four up to ten to the six molecules per cubic meter, so it's still really not close to empty. And don't forget that's just the kind of matter we know about, right, protons and electrons. There's still also the dark matter which is filling the galaxy. Inside the galaxy where inside the dark matter halo, which is five times as much matter as the normal matter. So inside the galaxy you can't really ever say you have a vacuum.
What about like the far reaches of space, Like if you go deep out there in the middle of nowhere, really in the middle of nowhere between galaxies.
So take a point, for example, between the Milky Way and Andromeda. You're far outside of the galaxy. There's still something there. There's the intergalactic medium. This is a rarefied plasmi. It's mostly protons and it's not zero. There's like one to ten atoms per cubic meter, and there's actually kind of a lot of stuff out there, this plasma that's between galaxies. This number sort of shocks me. Is about half of the ordinary matter in the universe. Like you look up at the night sky and you see stars, and you think about galaxies, and you know, there's a lot of dark matter out there that we can't see. But you imagine probably we're seeing all the normal matter. But something like half fifty percent of all the normal matter in the universe is between galaxies, in these sort of filaments of plasma that connects them together.
Yeah, because these filaments are huge, right, like the space between galaxies and clusters of galaxies. It's a lot. So even if you only have one to ten atoms per cubic meter, it adds up to as you're saying, half of the stuff in the universe.
Yeah, it's really a lot of stuff. But you can get more sparse. Right, You're like, let's not hang out between the galaxies. Let's leave the galactic cluster, or let's find one of these supervoids that are between the superclusters. Right and out there is the closest you can get to a vacuum, you know, the number density of particles, the particles per cubic meter drops to almost zero. There's almost no photons out there either. It's like as close to zero as you can get.
Wait, isn't that weird? Like how can you have no photons? Like you'd be there and you would look out around you and you wouldn't see anything.
It'll never actually get too zero. Right, You'll be as distant as possible from all of those galaxies, and so you'll have the dimmest view of all of them. But you're right, they'll never actually get to zero, Right, It's not like you look around you and you see total blackness. So the number of photons will never actually get to zero. Even inside those supervoids. It's like the furthest you can get from all the light sources. It's like if you're trying to find a dark spot in your city to look at the night sky, and you get as far away as possible from all the street lights, you're still gonna have some light there.
Are you trying to say that there is no perfect vacuum in the universe, naturally occurring perfect vacuum in the universe, Like it's not possible to find a perfect vacuum.
It's probably impossible for all of those reasons. I think every chunk of space problems has at least one photon in it from some distant galaxy that threw that particle in that direction.
But that's kind of an average though, right, Like maybe when you're out there you see a photon every once in a while, but in between the times that you see a photon, you would be sort of in a perfect vacuum potentially.
And here's where we run up against the technical question, because every chunk of space also contains dark energy, right. Dark energy not something we understand, but every chunk of space has some of it. So the technical definition of a vacuum is not space with no energy in it. It's spaced with a minimum amount of energy. So you can be in a chunk of space that has some energy in it and still call that a vacuum if you're convinced that that's the most relaxed possible state of space.
Hmm.
It sounds like maybe there's a concept of a perfect vacuum, and then there's a concept of like what's the minimum vacuum that the universe naturally has out there? You know, kind of like temperature, right like, there's absolute zero, and then there's what actually actually seen the universe.
There's what space theoretically could accomplish in terms of relaxation, and then there's this sort of most relaxed space that actually exists in the universe, and those could be different.
M all right, So let's get into what would actually happen if you create a perfect vacuum in the universe. What would that mean, Is it possible? And would it be as tidy as we want it to be? So let's dig into that. But first, let's take out quick break.
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All right, we're talking about vacuuming the universe. It sounds like the universe has a lot of space that you need to suck up.
It's a big chore to clean up the whole universe.
Now, is the universe more of like a shag carpet or you think it's more of a wooden floors kind of situation.
I think it'd be pretty hard to totally thoroughly cleanse the universe, So yeah, it's definitely shag carpeting out there.
Or maybe right like, we don't know if maybe the universe encompasses all of the matter in the universe, or maybe there's a bunch of universe out there that is truly empty.
It's possible, though. Cosmologists prefer the assumption that the universe is essentially the same everywhere. It's not a totally solid experimental point, but it's sort of the simplest idea that there's no special place in the universe. And so when you zoom out really really far on cosmic scales, we see so far the universe has the same density of stuff basically everywhere, again massively zooming out on the scale of superclusters of galaxies. So that would suggest that there isn't any place in space that's like really truly specially empty, different from the part of the universe that we find ourselves in. So that's just an assumption, right, which is extrapolating from what we see out to infinity, which is always dangerous.
Yeah. I think sometimes people talk about the analogy with like fish in the water, right, Like you could be a fish at the bottom of the ocean and think, oh, the whole universe is filled with water, right, because as far as I can see, there's water.
Yeah, that's right. I think that's Max tech Mark's analogy, which is really wonderful because it gives you a sense of your naivete and how you might not know what you don't know. And there could, of course be boundaries to the kind of universe that you imagine. We could be living in a bubble where these laws of physics apply and everything seems to make sense to us, but there could be an edge to it out past which the universe is in another phase, you know, crazy densities where quantum gravity applies, or maybe the Inflanton field hasn't decayed yet, or other crazy notions, so it's always possible.
Or maybe we're living inside of a vacuum of someone cleaning up their universe in a super mega.
Universe, man, that would totally suck so well.
As you were saying earlier, it's kind of hard to find a naturally occurring perfect vacuum because even if you're out there in the depth of space in between galactic clusters, there's stills kind of stuff in it. There might be some a little bit of light or an atom here or there, or maybe even dark energy or dark matter.
Right, Yeah, that's right. It's hard to find a chunk of space that really has no particles in it because the universe is buzzing with stuff and that's flying everywhere and filling everything up.
So then I guess the next question that we can ask is is the perfect vacuum possible? And what would it look like like? Can you have a chunk of space without any particle, matter or energy in it? What's left if you have none of that?
Yeah, So imagine that you were able to somehow rid chunk of space of all the particles. Maybe you built a box that blocked all photons another matter from entering, and you sucked everything out of it. What would be in there? Right? What is sort of the nature of nothing. What is the minimum thing that exists in the universe, or like, what is reality when there's nothing in it? And you know, we don't know the answer to that question at the deepest level, but we do have a theory that describes it. Right, We call that thing space, and space still has a structure to it even if you suck all the stuff out of it. Right, this is what we were talking about earlier, that there's a possibility for things to exist, and that possibility are the fields. We think of these as part of space itself, That these fields exist even when there's nothing in them, that the possibility for things to exist is part of the structure of space itself.
I guess, as you were saying, it kind of depends on whether you consider fields to be a thing or not. Like, if you consider them to be a thing, then fields kind of take up all of space in the universe, Right, you can't have a space without fields. But if fields are just kind of a made up concept, then it is possible to have empty space.
If you consider field to be the most fundamental, then yes, they are the bedrock. They are contained as part of space. They're a fundamental aspect of the universe, and we can talk in a minute about like what is the lowest energy those fields can occupy, What would that vacuum mean, et cetera, et cetera. If you reject fields and say, look, I can't ever see fields. I don't think that those really are the way particles push on each other, then you have another picture, which is virtual particles. Particles push on each other by exchanging these virtual particles, you know, in two electrons whiz by each other, They're not using their fields to push on each other. They're exchanging virtual photons. So if you use that picture, you don't just delete the field to replace it with nothing else. You delete the fields and you replace it with an infinite number of virtual particles. So in neither picture of the universe is really truly empty, even when you have no real matter in it.
Well, is it possible to have space without fields?
Right?
Because field kind of have come and gone in our history of the universe, And also I think mathematically it's sort of possible to just not have a field and still have space. Right.
What do you mean fields have come and gone? You mean it's a scientific concept or in the cosmological history of the universe, I.
Mean, like in the cosmological history, right, like you know, the Big Bang, we didn't have some of the fields we have.
Right Our description of the history of the universe goes back really really far to what we think is like a few tiny moments in time after maybe the universe was created, But it really goes back only as far as we can describe with our current laws of physics, and those laws always include fields. So it might be that before a certain point there weren't fields, but that's because the universe is like in a different phase where fields are no longer a good description of what's happening, and so we use fields as a way to describe the universe we're in right now. We don't know if fields are fundamental or when the universe changes conditions to a point where these laws of physics are no longer relevant that some other description is useful. Going back to your fish analogy, sort of imagining that the universe currently is in a certain phase, like the way the fish are swimming through water, and that water is a certain phase, and they develop laws of physics that describe, you know, the fluid dynamics of that water. If the water was to boil then the water's in a new phase and their laws don't work anymore. In the same way, there's a moment before which we don't think fields probably describe the phase of the universe. We don't know how to describe it requires quantum gravity. But from that moment and forward, we think fields are a good description of the whole universe. So in that sense, yeah, fields haven't always existed, but only because this phase of the universe hasn't always existed.
Well, I guess what I mean is like, if it is a phase, it kind of seems optional, kind of like the water in the ocean, right, Like, you know, you can imagine a universe existing without the muon field for example, or the towel field, or the you know, certain quarks or whatever, and you would still maybe have a functioning universe, which means maybe they're optional, in which case maybe you can have universe without fields.
We don't know the answer to that question, right What is the physics of other phases of the universe where our laws of physics do not apply? That's a question of like what is quantum gravity? You know, what happens when things get super duper dense and very very hot, where gravity is important, and quantum mechanics is important. We just don't have a theory that describes that. Some candidate theories do include fields, right, There's still are fields in some of those theories, and so it might be that there are still fields back before that moment in time when our current theories break down. We just don't know. So from that point of view, you don't always have fields. But if we're talking about, like what is a vacuum, I think that's sort of in the context of our current kind of space, the current phase of the universe that we're in, you can still say what is a vacuum in that context.
So then I'm trying to figure out what you're trying to say. Are you saying that you cannot have a vacuum, a true vacuum, or are you saying that you can't have a vacuum where there's not even fields in it? Or does your definition of a vacuum just includes the fields as a base kind of layer of existence.
It's that last one. What we consider a vacuum is space at its most relaxed, which is what is the least energy possible to exist in space? And because our concept of space includes these built in fields. They will always contain fields, So a vacuum is not perfect zeroness, complete emptiness. It's a most relaxed state of space, which will always include these fields.
But I guess, is it theoretically possible to have zero energy space?
It is not theoretically possible because all these fields are quantum fields. They're not classical fields like Maxwell's theory of electromagnetism, which has like electric and magnetic fields oscillating which makes light. Those fields could be absolute zero. You could have them at zero energy. You could have zero electric field and zero magnetic field. Our modern view is that these fields are quantum fields, which means they oscillate differently instead of whiggling like a string where they can take any value. There are only certain solutions that are allowed. They're like discretized. They're quantized, and the mathematics don't work for zero energy, like the solution of the quantum field equations don't allow a zero energy solutions. It's like a minimum energy required for any quantum fields. They have to be like bubbling and frothing at some tiny little level at the very minimum.
I guess maybe what I'm asking it at a fundamental level is can you have a universe with no fields?
Are you asking whether we could have a universe with fields that are at zero or a universe where space literally does not have the capacity for fields.
Can you have a universe where there are no fields in it?
That? We don't know? Right? Our current definition of space has these fields built in. Is it possible to have another kind of space without fields where you wouldn't even have the possibility to have matter in it? We don't know. We don't even know what that would mean, right, because you can't have things in it? What does distance really mean? If space is by definition empty? Distance is sort of defined to be between two locations, right, So be like a whole new kind of space, one that doesn't even have the capacity to have stuff in it.
But that does a math allow for it? Or does a math not only exist like the math we have only exists or is defined in a universe with fields in it?
You could create a conceptual space with no fields in it. Sure it's trivial, right, Like there's no math for it, there's nothing in it, right, So it's just like it's like writing nothing on a sheet of paper. That's your theory?
Well, yeah, I mean kind of right. Well, there's a paper, right, the paper exists, you're just not putting an equation in it, or you're writing zero in it.
Yeah, zero, Right, But what is zero like is that you have a field whose value is zero. If you're talking about like really true empty of any theoretical content that can exist, theoretically, it doesn't describe anything in our universe. Right. All these concept has to make contact with reality. So our best description of reality as we see it out there is space that always has fields in it. In those fee fields are never at zero energy. We've never discovered any evidence for fieldless space. Theoretically you can make that concept, sure, but we don't think it describes reality.
I see. So I think what you're saying is that the universe that we see out there has fields in it, and therefore there's no such thing as perfect nothingness because everything we see has fields in it.
Yeah. If perfect nothingness as things without fields, then we don't think that exists. In the universe. Every chunk of space has those fields, and those fields have some zero point energy, some minimum fuzziness, some oscillation to them. For example, the Higgs field feels all of space and the Higgs field is sort of weirdly stuck at high energy. So it's not a trivial amount of energy that's in space even when there's no matter in it.
But I think what you mean by like everywhere there has this little bit of energy to it, you don't mean like there's actually energy there. I think what you mean is that there's kind of like the potential for there to be things in it, or like the universe leans towards stuff being there.
No, I mean there's literally energy in space. The Higgs field, for example, filled space, and it has a high potential energy. Even if there are no particles there, there is energy in the configuration of the field itself.
That's what I mean. I think, as you said, it has the potential to do stuff. It's a potential energy. It's not like a little photon floating out there in space.
That's right, it's potential energy exactly. It's like if you mentioned a guitar string. Somebody has pulled the guitar string away from its relaxed state and it's taught, so it's storing energy in that. It's not moving. There's no kinetic energy right now. It's not oscillating, but it's held in a configuration that has energy. If somebody was to release it, it would vibrate and make a noise. Right. The Higgs field is just like that. It's held in some configuration that stores a lot of energy, and that's potential energy. But every field has some energy, not even just the Higgs field. Like the electromagnetic field that fills space is held in a non zero value, and that's not just potential energy. That's like actually thrumming with kinetic.
Energy, throwing in a quantum set. I think what you mean is like there's like quantum particles popping in and out of existence. Is that what you mean?
Not enough energy to make a real particle, But the field itself has energy, it is vibrating. You can think of these fields as having kinetic energy and potential energy, just like a string, right, which slides back and forth between having kinetic and potential energy as it oscillates. So these fields have actual energy, not enough to make a particle. Right. The lowest energy state of these things is not one particle. It's zero particles, but not zero energy.
All right, So then what does that mean for the idea of a vacuum? Means that in our universe, you can have a perfect vacuum.
In our universe. We define sort of theoretical concept is the most relaxed state of all the fields. That's sort of like how we define a vacuum. We don't define it to be like the theoretical minimum where all the fields are a zero, because that's not theoretically possible. We consider this sort of state of space as we understand it and try to imagine what would be the most relaxed configuration that all the field could get into. And we now know that that's not at zero. But what's interesting is that there might be multiple ways for the field to relax. There might be a few stable configurations. One of those would be the true vacuum, the actual lowest possible state. The other ones would be false vacua, like places that space gets stuck as it's trying to relax down to zero and it ends up in a stable configuration that's not actually the lowest energy state.
I think what you're saying is that, like even if you go out there in the middle of space, or even if you create one, like you make a box where nothing can get in it and there's no particles, you see no particles in it. There is still a little bit of like thrumbing or a little bit of a vibration of the fields in that space not creating fully particles, Like there's not enough there to actually pop out a particle that you can see and interact with, but there's like, you know, half a particle forming in then it's gone, and there's a quarter of a particle Thereah, but it's gone. Kind of situation, right.
Yeah, And you just intuited your way from the field description to the particles cold description, like what the energy of this field mean if it's not enough to have an actual particle there, Well, it's sort of like you know the particles exist, and that they don't they pop in and out of existence. That's replacing the idea of a field with these virtual particles that have some weird energy from space itself and not enough to really exist in the sense of like you could hang out and you could leave the electron there and come back a billion years later it would still be there. These are virtual particles. That's sort of intuitive way to think about what a virtual particle is, just like another way to think about a field when the field doesn't have enough energy to make real particles, it might have enough to make virtual particles.
All right, Well, let's get into the idea of what it would mean if you actually created a real vacuum, and it has to do with this concept of fields relaxing. How relax can you make a field? What sort of medication do you need to give it in order for it to finally relax. We'll dig into that, but first let's take another quick break.
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All right, we're talking about nothing today. This is the episode about nothing.
This is the Seinfeld of podcast.
That's right. I'll be Kramer and you be which one of us is Kramer, which one of them visits George Consent.
I think you're definitely more Kramer, and I'm more George for sure. I always wanted to be an architect.
Yeah, I thought I was a comedian. Wait a minute. We were talking about nothing and the idea of nothing and whether it's possible to have nothing in the universe, and it sounds like that's not really possible. In the universe that we see and experience, there are things called quantum fields and so which occupied all of space and which has kind of inherent energy to it. So there's really no trunk of space out there that has zero energy in it.
Yeah, that's right. Space has these fields and they're always wiggling at least a little bit. And so instead of thinking about true zeroness of space, which we think is impossible, physicists like to think about the minimum energy state of space. That's what we call the vacuum, what happens when space relaxes as much as it's theoretically allowed.
Okay, so then I guess we're this more like maximum vacuum of the universe. Maybe not the perfect vacuum, but the most vacuuminness that the universe can get.
Yeah, the vacuumist. But I like that phrase maximum vacuum. That sounds cool like an eighties band starring Max Headroom.
Yeah with long long hair. Yeah, that might be out of our age.
And to understand what's actually achievable, like how you can really relax space itself, you have to understand like how the fields wiggle and how they interact with each other, how energy slashes back and forth. It's sort of like you know when you lie down to take a nap and you feel like, Okay, I'm totally relaxed. Then you discover, oh no, I'm actually holding this muscle tot and then you learn to relax that and relax that, and you only really ever fall asleep when all of your muscles are fully relaxed in their lowest energy state.
Well, I guess maybe a question is there are fields that have zero energy to them or not? Or do all quantum fields have some inherent energy to them?
No quantum fields can have zero energy in them. It's just an inherent property of any quantum object that cannot have zero energy.
Why not?
There's the mathematical approach, which is like you look at the shorter your equation you try to solve it, the minimum energy solution is not at zero. The intuitive way to think about it is the Heisenmber uncertainty principle. Right. If you accept that things have a minimum uncertainty to them, then having zero energy would perfectly define its momentum and its location. At the same time, you would know too much about it. So in order to maintain the fuzziness of the universe, these quantum fields have to be buzzing a little bit.
WHOA. That seems to get really philosophical.
Every time you try to understand quantum mechanics intuitively, you got to reach for philosophy. That's really all we have. You know, quantum mechanics has the beautiful mathematics which gives you answers. But you want like intuitive understanding, then it's all philosophy.
But what do you mean, Like, you can't have uncertainty with a perfect vacuum, Like couldn't you have a field that has zero average energy but it kind of like has a negative state of being. I don't know, I don't know what I'm talking about, But why can't you have fuzziness and a zero average.
The value of the field is zero on average, but the energy is not zero. The same way that like when a string vibrates on the guitar. If you took pictures of where the string was and you average its location, its average location is at the most relaxed state at a straight string. You took any point on that string and asks like, where is it on average? On average, it's at its relaxed state. It's at the middle point where the string is straight, but it's oscillating still, right, it's still moving. So these fields can have energy while their average value is still at zero.
And so what would happen if a string had no energy.
Well, a classical string can have no energy, right, And that means you know exactly its location and exactly it's momentum. It's zero momentum. But a quantum object can't do that. You can't know both of those things simultaneously about a quantum object. And it's not just that we can't know it. Then information does not exist, cannot exist. It's not noah bowl, it's not determined.
Would wouldn't be a quantum object?
Oh yeah, sure. If you want to overthrow quantum mechanics, then yes, you can have objects with zero energy. So classical fields definitely can. But all evidence suggests that all the fields we know about other than gravity at least are quantum fields. They have quantum properties.
Wait are you saying gravity is a non quantum field.
Well, our theory of gravity is a classical one, right, and suggests that space can have zero curvature to it and all sorts of stuff. We don't have a quantum theory of gravity, so yeah, we have an only classical understanding of gravity. We're not successfully quantized gravity. We don't even know if gravity is a field or if it's just like the curvature of space. So that's not something we understand at all. But all the fields that we have been able to probe and understand, electromagnetism and the weak force, a strong force, these are definitely all quantum fields, and so they definitely cannot have zero energy. Same with the Higgs field, also definitely a quantum field.
So wait, then, are you saying that if gravity is not a quantum field, then you can have a non quantum field.
It's possible that gravity is a non quantum field. Yeah, we just don't really understand gravity. I remember that Einstein's theory of gravity was developed basically at the same time as quantum mechanics, and so he wrote it as a classical theory. It makes all sorts of assumptions about the universe. You know that you can have smooth, continuous paths that you can know precisely the velocity and location of things that we don't think are true about the universe. He built those into his theory, and yet it works in every location where we can test it. So it's a deep question in modern physics, like how do we reconcile general relativity with quantum mechanics. But yeah, it's possible that gravity is a field that's a classical field that could relax down to zero.
I'm just trying to dig into what you say.
I mean.
So when you say it's not possible, what you actually mean is like it's not allowed under or the quantum view of the universe, which may or may not be true.
Yeah, that's true. It might be that the final unification and understanding of the bigger picture of physics involves an overthrowing of quantum mechanics rather than general relativity. Maybe generativity is right and space is a classical backdrop in some way, but in our current understanding of space. At least it contains these quantum fields which can't go down to zero. But yeah, that could be all wrong.
Okay, Well, let's get back to our discussion vacuums. So you're saying that maybe what we can talk about is maximum vacuum of the universe, which is when these fields relax down to the lowest level. And you're saying that there's kind of different ways for these fields to relax, Like there's meditation, there's drinking chamma meal tea.
Meditation and medication exactly. Well, you know, this sort of story of the universe is relaxation. The universe is expanding, which means it's getting more dilute, which means it's getting lower temperature. Right, it's cooling down. As the universe expands, the matter gets more and more sparse, and so the energy in those fields is going down, down, down, down down. So we think about the whole universe as relaxing. All the common fields are sort of chill and out heading towards zero.
Wait, what does that mean? Does that mean like an field can have a lot of energy and it can have a little bit of energy.
Yeah, fields in the center of the sun have a lot of energy. Fields out in intergalactic space have much less energy.
No, But I mean like like as a concept of a field, right.
Like, well, having multiple particles just means that field is wiggling more Like the field wiggles, that's one particle. The field wiggles more, that's two particles. Field wiggles even more, that's a billion particles.
I guess I was referring to this idea that maybe there's a chunk in space out there with nothing in it that has fields in it that are vibrating and have energy to it. Can that energy be different values?
So it depends on how space cools, right, It's sort of like making it too flea. You've got to get it to that special configuration. So the universe is cooling, time is going on, space is relaxing, And then I think the question you're asking is like could it relax into different values? Could you have like one state of energy over here, another state of lower energy over there?
Yeah, Like can the electron feel when it relaxes down to its minimum? Can it relax down to point one or point three or point four? Or when it relaxes There's just one possible relaxation meta.
So almost all the fields relax in a very simple way, which is heading towards zero and hitting that minimum, so that their average value is zero and they have the minimum energy, and that should be the same everywhere in the universe. But one field, the Higgs field, has some weird wiggles in it, and it gets stuck as it cools. So the whole universe is cooling down. Everything is settling down, sort of rolling towards the bottom of a valley. But the Higgs field gets stuck in this false vacuum as a large amount of energy stuck in it high potential energy configuration. While everything else like rolled to the bottom of a canyon. It got stuck sort of like on a shelf on the canyon wall. So the Higgs field is different from all the other fields. It's harder for it to relax because the shape of its potential energy.
I think what you mean is like if each field is like the string and a guitar. All of the fields kind of settled down to kind of a minimum vibration, but the Higgs field is kind of stuck in this kind of high vibration state.
It's not actually vibrating and it has high potential energy. So while everything else settled down to like the lowest possible vibration, it got like stuck in this configuration where somebody's pulling it really hard and it's taught. It's not vibrating, there's not a lot of kinetic energy, has a lot of potential energy. So the Higgs field sort of like got stuck on a bump on the side of your guitar and is pulled sideways and taught and stuck.
There, like there's a certain curve to the string. Maybe I don't know.
And so one question is like, is that the true vacuum or is that a false vacuum. Is it possible for the Higgs field to relax to a lower state, And we've talked about that several times, like if the Higgs field would collapse to a lower potential energy configuration, that would change the nature of physics in our universe, and you know, all of our atoms would explode at the speed of light and all sorts of crazy stuff. But we think that probably there are multiple possible vacuum states, and the Higgs field is stuck in sort of a false vacuum, and the true vacuum is a lower energy configuration that it can't quite get to. It's sort of stuck in this vacuum.
M like the Higgs field can relax to maybe lower, but for some reason it's not.
Yeah, somebody's holding on to that string.
It's the finger of God or God's pick.
Maybe God's just in a dad band and that defines the nature of the universe.
Yeah, there you go. That's right. And as Dan is.
Called maximum vacuum.
Maximum vacuum, that's right. Now, does God play all the instruments or is he like a one man Dad. It's like the Holy Quick Quintet, you know.
But then all members are actually part of the one right. I don't have enough theological background to comment on that without offending.
People anyways, So you were saying that maybe, like we're not in the most vacuumus of vacuums that the universe can be in. And thankfully all.
Space out there probably has some particles in it. Even if you were able to remove particles from space, you would have space in a sort of Higgs field that's stuck at a high potential energy. And so yeah, probably nothing out there currently is even capable of getting to the maximum vacuum state that our kind of space is technically capable of achieving.
And thankfully right, because if we ever flip to that a lower or more vacuum e vacuum, then we're all toast like our universe would kind of get upturned and really suck.
Absolutely. We have a whole episode about what would happen if the Higgs field did go to zero, and yeah, it would ruin your life.
On the plus that you wouldn't have to vacuum your house anymore.
It would be automatically vacuumed and.
Just rumba our way to a more blissful existence. All right, Well, I think the answer to our question of the episode is that a vacuum, it would be a spot with nothing in it, not even energy. And as far as we know, our universe kind of has something in it everywhere, and so a perfect vacuum it's not possible, and we have to settle for the eighties Coverman maximum vacuum.
And when physicists talk about vacuums, that's what they mean. They mean a chunk of space with no particles in it, relaxed to its maximum possible state, which is not zero energy.
I feel like physicists are settling then, though, shouldn't they be striving for perfection.
No, we're just defining our achievements as success.
I see you're lowering standards.
We're redefining success.
Everyone gets a trophy exactly, participation vacuum. All right, Well, I guess the next time you look at into the space, think about the idea that there is nothing out there that is truly nothing. There's always something out there in the universe.
And nothingness has a lot of something to think.
About that's not nothing. Well, we hope you enjoyed that. Thanks for joining us, See you next time.
Thanks for listening, and remember that. Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact. But the people in the dairy industry are. That's why they're working hard every day to find new ways to reduce waste, conserve natural resources, and drive down greenhouse gas emissions. House US dairy tackling greenhouse gases many farms use anaerobic digesters to turn the methane from manure into renewable energy that can power farms, towns, and electric cars. Visit you as Dairy dot COM's Last Sustainability to learn more.
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