Daniel and Jorge Explain the UniverseIt's not anti-matter, or supersymmetric matter, but yet another way our familiar particles might be reflected, and could explain a deep mystery of the Universe.
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Hey Daniel, I have a question. Do particles have families?
Oh? Yeah, actually each particle has a whole set of relatives.
Really, So who is the electron's closest cousin?
Well, the positron is kind of like the electrons.
Evil twin Didy have like a twirly mustache, or it's gotta go to Where's where's the opposite color clothes?
Yeah, and then it's got the muon, which is like it's heavier cousin, it's more massive cousin.
M Like it's more fit, like it's bulky or does it just sit around and eat bananas?
Nobody knows. Nobody knows. And then the electron even has like hypothetical.
Relatives what you mean, like long lost relatives.
Yeah, like there might be a super symmetric version of the electron. We call it the selectron.
That sounds like a great superpower. I'd love to select my own relatives. I am more handmade cartoonists and the creator of PhD comics.
Hi. I'm Daniel. I'm a particle physicist, and there is no super symmetric version of me.
Is there an asymmetrical version of you?
I don't know, but if there was a super symmetric version, it would be the Daniel or.
The Daniel Leno, the Daniel Tron.
I'm sure you would come up with an awesome name for that version of Daniel.
Welcome to our podcast Daniel and Jorge Explain the Universe, a production of iHeartRadio.
In which we take you on a mental tour of everything that's amazing, that's wonderful, that inspires your curiosity, everything that makes you wonder how does that work? Why is it like that? Why isn't it some other way? We'd take the whole universe and try to break it down into tiny little pieces and explain them.
To you, and we try to take you in a tour of all the things that are out there, all the amazing and incredible types of objects like black holes, and neutron stars and all of the incredible and mysterious particles that are out there and then might be out there.
That's right, because part of the journey of understanding the universe is thinking about what's there and what might be there. What would make more sense if the universe had it in it. What do we need to add to our vision of the universe to make it make more sense? What puzzle pieces are we missing?
Because that's how scientists explore, right, I know, that's how we kind of probe the unknown. As we sit around and we think, well, well, I guess you guys sit around on and with some coffee and you try to think of what would be what could be out there, what would make sense in terms of the what the equations predict and what the data suggests, and try to think about what we can discover out there in the universe.
Yeah, there's sort of two ways to make big discoveries in physics. One is like try to anticipate them, to look at the pattern of what we know and say, what's missing. Would this make more sense if we had another piece? Like if you were doing a puzzle and you fill the whole thing in it is one piece missing, You're going to go out and look for that one piece, and you know sort of what to look for. You have expected it. The other way to make discoveries just to like go out there as an explore and see what you'll find, and maybe you're run into something amazing you didn't expect. That's also fun. But there's a lot of time that we can't just do that. We don't have necessarily the way to explore us. We have to think about it in advance and try to figure out in advance what is it we should be looking for.
I usually find my puzzle pieces in between my couch cushions, or or under the or on the table.
I borrowed a bunch of puzzles from some friends, and I put the first one together, and it was missing a piece, and it had an extra piece from another one of the puzzles.
What, yeah, I think your friends are trying to drive you crazy.
I think so, because then the next puzzle was the same. So by the time I wanted the next puzzle, I had this like two extra random pieces and two puzzles each missing a piece.
And it wasn't symmetric, like one piece just missing from the other one.
No, it was like a cycle. It was like you have to finish all six to finish any of them, it was torture.
I think they're trying to gaslight you in the puzzle version of gaslighting, trying to puzzle light you.
Then, yeah, exactly, But you know, I have to take issue with what you said earlier that physicists, when we try to have ideas, we sit around and think about stuff. Why is it you think about it? It's just like sitting around these days, going to try to do my thinking while I'm active. I'm going for a walk to think about stuff, doing jumping jacks to think up new theories.
Oh, I thought you were going to complain that you actually lie down when you think for physics.
Is that how you get your creative ideas? Curl up under the desk or something.
My best ideas come when I have my feet up.
For sure. Posture definitely leads to creativity.
Yeah. So we know a lot about the universe, and we know a lot of the particles that are out there that make up matter, that might make up matter, and that make up other things that maybe are not as useful to the universe. But there are also a lot of missing pieces in the universe. There's a lot of empty places in our ideas of particles and matter that could be filled by new particles.
That's right, because when we look at the particles, we don't just want to make a list and say, here are all the particles in the universe were done. We want to understand that. We want to fit them together into patterns, because those patterns our clues, clues that will lead us to be able to pull back a layer of reality and see what's underneath those particles, what are the tiny, even smaller particles that make them up all the way down to the smallest bits of the universe. So the way to do that is to organize our knowledge and look for holes. For example, before we discovered the top cork, we had five quarks and they fit together in two pairs plus one lonely bottom cork, and we thought, where's the partner for the bottom cork. It must be out there, and we went and looked for it and found it. So this strategy of organizing our knowledge and looking for holes and gaps and symmetries is a really productive way to find new things.
And so today end the program, we'll be talking about one such set of holy particles that might exist and that might answer a lot of questions about our understanding of d universe. So we'll be asking the question what is mirror matter.
And why it's so hard to say?
It is a little hard to say. I feel a little tongue tied to saying mirror matter.
Well, you know, there's an whole sociological question we'll dig into later about why mirror matter is not so popular among theoretical physicists, But one answer might be that it's just kind of hard to say.
Do you think that matters?
It's more fun to say dark matter, anti matter than mirror matter.
Don't, don't. Don't use alliteration when you when you discover something new and amazing in physics.
So what you're saying and ours ours are just hard to say. They're horror horror, There are horror choice exactly?
Is that why particle physics has some problems there?
Yeah?
I think so, all right, So, as usual, Daniel went out there into the wiles of the Internet to ask if people were familiar with this idea of mirror matter.
So thanks to everybody who sent in their speculations about what mirror matter might be. If you'd like to speculate on a future top of one of our podcast episodes, please write to us two questions at dangel and Jorge dot com. We'd love to have you participate.
So think about it for a second before you listen to these answers. If someone asks you what is mirror matter, or as you how to pronounce it? For that matter, what would you say is what people had to say, something that reflected like a positive trium versus you know, it's kind of the opposite of each of the particles that we have.
I can only guess by the name. Probably it's the matter that imitates the matter that comes close to or gets in contact with.
I have no idea, So there are two things that come to my mind immedately. The first one is antimeter but I think that this answer is to straightforward, so I don't think this is the right answer to your question. So the second thing that comes to my mind, that's supersymmetry.
I assume that mirror matter talks about particle physics, and I don't know a whole lot about it, but from what I know, I think mirror matter wants to kind of explain why the weak force is the only one that does not respect the mirror reflection symmetry.
That sounds made up, sounds like something i'd hear on Star Trek, but I'm going to go with it relates to supersymmetry.
Those are words I've heard before.
I would guess that mirror matter is matter with the opposite handedness. Mirror matter is maybe matter with particles of opposite spin in charge.
I'm immediately thinking of anti matter, but I'm presuming it's something.
Different, all right. I like the star Trek reference. We should be writing for Star Trek, Daniel.
Star Trek is just stealing from reality. You know, reality is so weird that inspires hilarious fiction.
But people seem to have sort of the idea that it's like matter, but it's somehow their mirror image. So I guess it is a pretty good name. Kind of like there's some kind of idea about symmetry and handedness and spin mm hmm.
And there seems to be a general understanding that there are these symmetries that everything we know could be reflected. There could be a whole other set of stuff in exactly the way that the area is antimatter. Now, now we'll talk in a moment about what mirror matter is. It's not the same thing as antimatter, but it does share that thing in common that it's a reflection of the particles we know. It tells us something about the symmetries that are built into the universe. And the idea is that there's potentially more than one of these reflections. You have the reflection of all the matter particles into antimatter particles, and you can also have the reflection potentially of matter particles into these mirror matter particles. So it's in the same sort of family of ideas, but it's just a different kind of reflection.
Man, I feel like we were living in a house of mirrors or a universe of mirrors.
It's crazy and it's amazing, and it blows my mind how many of these reflections there are, because you know, we talk about antimatter, and we will talk about mirror matter, but then there are also these particle families, Like the electron is not just reflected into the muon, it's reflected into the muon and the tao, and so the whole structure that we understand of the universe of particle physics is really built around all these symmetries and reflections. I mean, that's what we're trying to do, is like organize these things into patterns. And the look of the patterns and say, what does that pattern mean about the universe?
Means that maybe you shouldn't have decorated your old universe with mirrors.
Perhaps you know who did, right, who put up all these mirrors?
Right?
This place is like a crazy funhouse. Why is it so hard to understand? No, it's fascinating, you know, just like you can ask the question, you know, why is there no antimatter left in the universe? You can ask the question like, well, why do we have antimatter at all? Right? Why is there this symmetry? And what does it mean about the universe that there seems to be this balance in the list of particles but not in their actual you know existence, right?
And some people also mentioned the idea of supersymmetry, But mirror matter is not related to supersymmetry, right.
That's right. Supersymmetry is yet another hypothetical reflection and that looks to try to build a symmetry into the universe. It says we have some particles called fermions that make a matter particles and other particles called bosons that make up forces like photons and z bosons. What if each of those has a corresponding particle on the other side, every fermion has some boson that corresponds to it. So the electron has a selectron, and the muon has a s muon, and then every boson like the photon, has a fermion partner. So the photon would have a photino and the W particle would have a we know, for example. And so that again just reflects the whole set of standard model particles over into a new set of hypothetical particles that we have not yet discovered and are not the same as antimatter and not the same as mirror matter. It's just another kind of reflection that tells you about how we're always looking for symmetries in the universe.
But this one seems to claim the mantle of mirror matter, Like it just grabs that word and says, I'm the mirror type of matter.
Yeah, exactly, And it's mostly championed by like one guy in Australia.
What ya wait?
Wait, this is a major physics theory that has a support of exactly one physicist.
Not exactly one physicist. But you know, not that many physicists believe in mirror matter. Although other people have ideas that are very similar to mirror matter, they just don't call it that. So maybe it's just the naming issue. People are like, we hate that name. We're gonna come up with a similar idea and call it something else.
Yeah, you were telling me that this idea also has other names, like alice matters or shadow matter.
Yeah, it's all the same one idea with several different potential names. So I guess, you know, the community around mirror matter was trying out a few things to see what would stick, and I guess mirror matter is the most popular. I kind of like alice matter because it has the like literary reference to it.
I like shadow matter sounds like something out of Dungeons and Dragons.
You're gonna roll a die and try to use your shadow matter sword.
Yeah, the shadow mage uses a shadow matter sword.
Of course. I think it's too similar to dark matter, you know, because then people are like, well, if you put matter in the shadows just to become dark matter, you know, it's very confusing.
All right, Well, let's jump right into it. Daniel, what let's answer the question what is mirror matter. I'm guessing it has to do it's sort of like supersymmetric matter. But maybe you're saying it's a different kind of mirror.
Yeah, it's a different kind of mirror. So whenever we create a new set of hypothetical particles to balance the particles we have, it's because we see an imbalance, we see something asymmetric, and we wonder, why do we have positive charge particles and not negative for example, Or you know, why do we have fermion matter and boson forces not the opposite. So in this case, we've created a whole new set of particles, the mirror particles, to try to balance the parity. A symmetry of the universe, the symmetry about being reflected in the mirror? Does the universe look the same when you reflect it in the mirror? And we've talked on the podcast several times about how our universe seems to be weirdly left handed, like some parts of the standard model, the forces that are involved like to only talk to particles that are left handed and not right handed, and that's weird.
I guess it all sort of goes back to the concept of particles in matter having like properties or values of things like charge or color or what's the other one? Spin spin, ye, favor, spin favorite. They have all these properties and so and really in the math you can just flip them and such a particle could still exist. Like mathematically, you can flip these things, even though you may not necessarily see them in nature. Right, that's kind of the idea, is that particles have these properties and you can flip some of them, and sometimes you see particles that have them, and sometimes you don't see particles that have them.
Yeah, that's exactly right. We look at the structure of our theory and we wonder if it's symmetric. We're like, well, what happens if you flip all these things? You know, if you flip the charges from positive to negative, or you flip everything from the minus z axis to the positive z axis, or you run time backwards in all these things. We wonder like, is our theory symmetric? And so as you say, you can take this set of particles and you can say, well, do we have the opposite set in this sense or in this other sense, or in this third sense? Do we have the opposite set? You know, do they exist? And if not, then why not? Because that tells you something about the universe, right, like why do we only have negatively charged electrons and not positively charged electrons, you know, positrons. And so it's interesting because you feel like there must be a reason. We like to think that the universe should be symmetric because that makes sense because if it's asymmetric, then like who made that choice? Right? Why matter or non antimatter? Did somebody flip a coin? Is it totally random? And we don't like that. In physics, we don't like things that don't have explanations, So we'd like things to be symmetric because then they don't need explanations. So we take our theory, we look for all the things that are asymmetric, and then we try to fill in those holes.
But I guess you know, why do physicists have a preference for symmetry, Like couldn't you ask the same question like who made the universe symmetric? Like if the universe was symmetric, wouldn't you ask the same question?
That's a great question, and that really goes to philosophy, and it's a question of what's simple. You know, when we look at a physics theory, we have questions about it, and when we compare two different physics theories, we want the one that's simpler, that needs like less explanation and fewer ideas. And that's sort of you know, we don't know why the universe is that way, but it does seem to work that way. That simpler ideas seem to work best, and so I would just ask fewer questions about a theory that was symmetric than a theory that was asymmetric, because a theory that's symmetric, You're right, there's no reason why the universe has to be symmetric, but it just seems to make more sense intuitively or esthetically. But you know, that's not a scientific feeling at all. That's sort of like a philosophical or personal aesthetic feeling.
Yeah, that's what I mean. It's like if one of your kids was really well behaved on the other one was a lot of trouble, you'd be like, yep, that makes sense in the universal cosmic balance sense.
I think there is something there, though, because if the universe is asymmetric, there are lots of ways that could be asymmetric, but there's only really one way to be symmetric, and so if you're asymmetric, and you're asymmetric in one particular way, then you have to wonder, why are we living in a multiverse where every choice for that asymmetry is made. Are there other universes out there that are antimatter instead of matter, for example, or are we living in a simulation where this was decided by the people who ran the simulation. It's just sort of unsatisfying to not have an explanation if there are lots of options, whereas if there's only one option, then you know that's just the option. You can ask like why is there only that option? And that's a deeper question.
Like if both your kids are well behaved, you'd be suspicious.
I'd give my wife credit if that was the case, but fortunately we don't live in that universe.
All right, Well, okay, So mirror matter, then, is a matter that also breaks one of these symmetries in nature that you have, and it's sort of related to the weak force, right mm hmm.
I find it a little confusing to think about parody because it's hard to think about whether it matters if you're reflected in the mirror whether the universe prefers right handed or left handed. Now it's the same basic concept, but I think it's easier to think about whether it matters if you rotate your experiment, whether the universe has a preferred direction, which seems obviously crazy. Matchine, you throw a ball and it follows some law of physics, right, parabola goes up and it comes down. Now you watch that same ball toss, but now you're standing on your head. It looks a little different, right, because you've rotated yourself, But the same laws apply, Like you can still apply the laws of physics to the ball. Moving shouldn't matter if you're standing on your head.
Right, except that now down means up and up means down.
Yeah, exactly, you have to put some minus signs in there, but the same laws do apply. Now you don't see exactly the same thing, Like it looks different if you're standing on your head, but the same rules apply. And so parody is sort of like that, like if you reflect something into the mirror, do the same rules apply or not? And people for a long time thought, well, of course, like just because you're doing it in the mirror, the same rules should apply, Like it would be nonsense. If our universe was somehow left handed and it looked different in the mirror, and like the mirror was right handed, it would be weird. It would be weird. And people just assumed for like, you know, as long as people had this idea, until about fifty years ago, people assumed the universe was symmetric in the mirror, that if you didn't experiment, it would look the same in the mirror. That you know, that the mirrors that the in the mirror world, the same laws of physics would apply. Now we can't actually go to the mirror world. We can't do the mirror experiment, right. The idea is, we do experiments in our universe and then we think about what they would look like in the mirror world. We try to we imagine that all the experiments we do in our universe would look the same in the mirror world.
But but the universe is a little bit weirder than that.
Niverse is super duper weird in fact, And it was about fifty years ago that people realized, you know, we never actually checked to see if this is true for all the different kinds of interactions. They had checked for the strong force, they had checked for electromagnetism, and parody was preserved like everything made perfect sense, but nobody had actually checked for the weak interaction. And then one summer people wrote this paper realizing, wow, nobody's ever checked this one thing. Somebody should do it, and the paper came out, and then over Christmas vacation, a scientist at Columbia, the famous professor cs WU, she did the experiment, and she set up a system that would look different in the mirror.
So they broke the mirror. And that was seven years of seven decades of bad physics. Luck is that kind of what happened?
Yeah, exactly?
All right. Let jump into the details here the week fource and symmetry and left and right handedness. But first let's take a quick break.
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All right, we're talking about mirror matter. And this is not related to how I look like in the morning when I look in the mirror. Danny, that's right, But this is no physics could explain it. This relates to how particles look in the mirror. Because particles, as weird as they are, they have this bizarre property that they're either left handed or right handed. And of course particles don't have hands right, but they do have a property which gets inverted in the mirror sort of the way that left handedness and right handedness does. And that's when you compare the direction they spin with the direction they're moving. And because clockwise spin in the mirror still looks clockwise, whereas moving in the mirror can get flipped in the other direction. So a left handed particle looks like a right handed particle in the mirror, and a right handed particle in our universe looks like a left handed particle in the mirror. Right, It's kind of like the mnemonic, you know, like when you use your hand, like you point your thumb one way and then you curl your fingers, and that that sort of like a handedness kind of thing for particles. Right, like the thumb could be pointing to where it's going, and the curl of your finger points to how it's spinning. So when you look in the mirror, that looks not the same.
That's right, and that tells you if a particle is left handed or right handed. Is it moving in the same direction as its spin vector is pointing, or is it moving in the opposite direction. And in a mirror, left handed particles turned into a right handed particle. Now, the weird thing is that the weak force, the weak nuclear force, only interacts with left handed particles. It totally ignores right handed particles.
That's the big asymmetry that the force ignores these other particles.
It doesn't interact with them at all. You know how some forces interact with some particles and not others, Like the strong nuclear force doesn't interact with electrons. Electrons just totally ignore the strong force.
Oh, I see, it just doesn't apply to that.
It just doesn't apply. So there are actually two kinds of electrons. There's the left handed electron or the right hand electron. The weak force only interacts with left handed electrons. It doesn't interact with right handed electrons at all.
And that right handed electron exist, are there? Are they out there right ing around ignoring the weak.
Force absolutely all the time there are left hand right handed electrons, and only left handed electrons interact with the weak force. And that's what causes this parity asymmetry. In the mirror, the weak force interacts with right handed electrons, but in our universe it only talks to left handed particles neutrino's electrons and quarks. That is so bizarre, it's really weird. It's a huge asymmetry. And it's not like a little asymmetry like it talks to left handed particles more than right handed particles. It's complete asymmetry. It only ever talks to left handed particles, never too right handed particles.
What so if I threw a right handed electron, like nothing would stop it in terms of the strong force.
In terms of the weak force force, Yeah, that's right, but you don't really notice that because the weak force is super weak and right handed electrons still feel electromagnetism right the photons and.
It's biased, but it's a weak.
But that's right. And so most of the interactions work with both of them. But the weak force only talks to the left handed particles. And that's why, for example, we've never seen a right handed neutrino, because neutrinos only feel the weak force, and so the only way to talk to neutrinos is through the weak force. But the weak force doesn't talk to right handed particles, and so we've never seen a right handed neutrino.
Wow, it's not just that it has a bias against the electron being right handed, has a bias against any particle being right handed.
That's right. There are two kinds of every particle that it's a left handed kind and the right handed kind. And the weak force only talks to left handed quarks. To what left handed electrons, left handed muons, left handed neutrinos, It never talks to right handed anybody.
Kind of makes me wonder if there's a right handed weak force. Have you guys thought about that? Like, is there are? Maybe there are two forces.
And that's the genesis of the idea for mirror matter.
This kind of case me, it's me and the guy from Australia.
No, but that's exactly this kind of a symmetry makes you wonder is there something out there to balance it? Right? That was exactly the thought you just had live right here on the program. And that's the whole motivation for this entire program of physics is can we find something else out there to balance it? You didn't like that asymmetry, and you're like, let's fill in that gap, let's balance the universe. And that's exactly what we're trying to do with mirror matter.
Yeah, because I believe in cosmic justice.
And so there's sort of two different sets of ideas there. One is a minimal idea and say well, can we restore the balance by saying, well, maybe there is a right handed neutrino out there. We've just never seen it because we can't interact with it with our weak force. So maybe there's a right handed neutrino. And then like some other version of the weak force that's biased in the other way, like a w prime boson and is the prime boson. And that's a cool idea, and that would restore some balance. I mean it would mean that the universe is sort of cracked in half, right, It's not really some is sort of like cracked in half. And we have two different pieces, and we happen to be on the left handed part of it. But mirror matter takes a step further and it says, instead of just adding a right handed neutrino and a new force to talk to it, let's copy all of the particles. So let's take the electron and make a mirror electron. And let's take the quarks and make mirror quarks, and let's have a whole new set of forces, a mirror strong force, a mirror weak force, a mirror electric force. And in that whole mirror then parity is violated in the opposite direction. So rather than just adding the minimal pieces to our standard model to balance parity, reflect the whole thing and just have the whole thing be balanced in the other direction.
Well, wait, I thought that right handed electrons did exist.
Right hand electrons do exist. Yeah, And so this idea would say, well, let's make mirror electrons and you'll have both left and right handed mirror electrons. Right, and we have left handed neutrinos, so this would make right handed mirror neutrinos.
Oh, I see, it's like a whole different it's like a whole new set of two hands.
Yeah, exactly. It's like you got one family, you know, where everything is balanced, except the neutrino is only left handed, and instead of just inviting one more neutrino that's right handed, invite a whole other family right if they have a right handed nutrino.
It's more like in our family, we only like the kids that are right hand and left handed, and instead of making up because we have kids that are left handed right now, we have kids that are right handed, we just don't like them. And so to balance it out, maybe there's another family out there down the street that has right and left handed kids, but they have a different, different preference, different they.
Make different parenting mistakes. That balance is parenting mistakes and.
A whole the terrible in a whole mirror symmetric way.
That's right. The universe doesn't care if you make parenting mistakes as long as somebody else is making the opposite one. That's the physics approach to symmetry is restored and all is good.
Oh man, love to see it. I maybe you wouldn't love to see how things work in your house.
With you, But there's some fascinating twists there, Like one of them is gravity is not mirrored. If there is a graviton this particle that transmits gravity in a quantum theory of gravity, it would not be mirrored. There would not be like a mirror graviton.
It's like it sits at the edge of the mirror or something. Yeah, because it's at the mirror line.
Yeah, because gravity is how we bend space, and there's only one space. We think that our particles and the mirror particles live in the same space. If they have their own graviton, that have to have their own space, and that would be weird. And so yeah, it sits on the mirror itself.
Okay. So the idea of mirror matter then is that there's a whole set of matter particles that are mirrored somehow in this bias that the weak force has, and there's a whole different weak force that has it's a different bias.
Yeah. If you build that parody violation experiment, that doctor Wu's experiment out of mirror matter and did the experiment, you would get the opposite result.
I guess my question is where does this Where's where's all this mirror matter?
Like?
Is it on top of us? Is it next to us? Is it kind of like a parallel universe kind of thing.
Well, we don't know if it exists, first of all, and if it does exist, it be very hard to see. And so in that respects it's sort of similar to dark matter, because we suspect we might only have gravitational interactions with it that we'll talk in a moment about other ways we might probe it, And so it could be right here on top of us without us interacting with it. Right Remember that the universe is filled with all sorts of invisible stuff that you cannot sense, like all the new trinos that are flying through you right now. You don't interact with all the dark matter that surrounds the Earth and fills your room. You can't see or touch or interact with. So it's possible to share space physically overlap with other kinds of matter that you if you do not interact with them. And mirror matter, if it exists, we may only interact with it gravitationally, which is very very weak, which means essentially we wouldn't sense it. And so if there is mirror matter could be right here on top of us, but it could also be out there in the universe. Separated from us.
Well, yeah, I guess, Yeah, I guess like dark matter and the trenius, they're all sitting on top of us, but we don't feel them. Maybe there's a whole bunch of right handed laws and right handed matter that's sitting on top of us too.
Yeah, there could be a right handed whohe doing a right handed podcast right.
Now, doing it the right way, and we feeling left.
And we'd feel left out exactly.
Wow. All right, So I guess my question is like, why why wouldn't our weak force with the left handed bias interact with the left handed mirror matter? Do you know what I mean? Like if in my house, I only like my left handed kids, wouldn't I like the right handed kids in the other house.
Well, first of all, I hope that either all your kids are left handed or they don't listen to this podcast. But you're right, But our forces don't interact with those particles at all. So those particles don't carry like electric charge, They carry mirror electric charge, and they interact with like the mirror photon with mirror electromagnetism, And so yeah, you might ask like why do you need to create all this all these particles, Why don't you just add a right handed neutrino. And I think that's one of the biggest sort of theoretical criticisms of this idea is that it's too much. You don't need all this extra stuff. It just seems like too much of a copy. But the reason to do it, remember, is to try to restore symmetry, is to try to say, well, let's have balance in the universe. And then you might ask, but you know, we're not really balanced. We have like two pieces cracked in half that sort of compliment each other, but we're living on one half of it, right, It's not like the universe has this symmetry. It's sort of broken. And we see that a lot in particle physics that we see se trees that have been broken, and we think that these symmetries are fundamental, that they like existed in the early parts of the universe when everything was hotter, when the universe, when different effective laws of physics were taking place, and then as the universe cooled, it sort of like cracked the way you know ice can crack as it freezes, or where things can crack as a change phase.
Or like we everything fell to one side of the mirror kind of or got trapped inside.
Yeah, and we ended up trapped in one side of the mirror, and that there's other particles that got trapped on the other side. And so these are what we call broken symmetries. We think that they do reflect something deep that's happening in the universe, but that they got broken, and we actually see examples of those, like the Higgs boson is a broken symmetry. Like the Higgs boson unifies the weak force and electromagnetism, and it says that the photon is actually part of the electroweak force. It should go along with the W bosons and the Z boson, But when the universe was cooling, the Higgs sort of got stuck in a weird spot and it gave all this mass to the W and Z and none to the photon. It broke that symmetry. And so in the same way, symmetries that existed in the early hot universe can be broken as sort of the phase of the universe changes. You know, universe doesn't go from like liquid to gas, but as it cools, different physics sort of takes over. And so we think that that might have broken.
So that's another explanation for the asymmetry that wouldn't require this whole new universe sitting on top of us that we can see your touch.
That would explain why this symmetry exists. Sort of at a higher level. It's like, you know, yeah, we still have an asymmetry here today, but we think that maybe there was a symmetry early in the universe that the other half exists. That it explains why the symmetry was broken at some point.
All right, so it sounds like a pretty amazing and incredible concept. I guess the question now is how do we verify if it's true? How do we know it's real? And how do we look for these mirror particles? I guess we can't just look in the mirror.
Danny, my god, nobody thought of that. I'm gonna go do that right now.
Hold on, Nobel prize right here, mirror?
What's the mirror? A Nobel prize is the Loben Prize?
Little yeah? Do you have to pay a million dollars for that one?
That's why nobody accepts it.
All right, let's get into how we look for a mirror matter. But first, let's take a quick break.
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All right, Daniel, sir, there might be a whole mirror universe of mirror electrons and quarks and particles and also forces. There might be a whole universe of mirror forces, like the opposite electromagnetic force and opposite strung force sitting right on top of us right now, acting and ignoring us basically.
Yeah, and they might even have like better snacks than we have.
Yeah, all the bananas would be curved the other way.
They would actually be tasty, but you would still hate it though, mirror Daniel probably would hate it.
Yeah, yeah, yeah, all right, I guess down out of the question is how do we look for a mirror matter if it does exist? And how could we ever, you know, confirm the existence of something we can't see or touch.
It's pretty tough in the sort of cleanest version of the idea. We can only interact with mirror matter through gravity, and so in that sense, we can only look for its effects on a gravitational scale, which means like looking for it the way we look for dark matter.
Because gravity is kind of like the one thing in common we have with mirror matter, Like it's like a two Van diagram to touch at a point.
Yeah, it's the only way that we can interact with it, and so to discover something, to prove that it exists, to understand it, we need to be able to interact with it. There could be all sorts of crazy stuff happening right here on top of us, but if it doesn't interact with us, then we could never discover it. But we think that gravity is sort of universal. Everything that has mass feels gravity. That's like another way that gravity is super weird and amazing. But so we might have to just use gravity to study it. And then there's the natural questions like, well, if there's all this weird stuff out there that we can't see and gives us extra gravity, maybe it's not like dark matter. Maybe it is dark matter.
That's what I was about to ask Daniel. It feels like the perfect conspiracy theory, bump bump bomb, But this guy in Australia has cracked.
People always write in and try to connect the mystery of dark matter with other mysteries. You know, is dark matter like anti matter? Is dark matter? This is dark matter that And it's super fun and it's fascinating because wouldn't it be awesome to like crack two mysteries simultaneously, right, to solve two big questions of physics at once.
This seems really tantalizing, right, because you just told me that there might be a whole universe of matter out there that we can't see a touch, but that influences us gravitationally, and that sounds like exactly like dark matter.
Yeah. Well, do you want the good news first or the bad news?
I want the news that gives me the Noble Prize.
Okay, Well, then here's the good news, and you should go off on your trip to get the Nobel Prize before you hear the bad news. In this case, the good news is that you can use dark matter detectors to look for this kind of stuff, and that there is a detector out there. It's called the Dama experiment. It's in Italy. And it's actually he had a very strong signal for dark matter for like more than ten years. We're gonna do a whole episode on why nobody believes that DAMA detected dark matter despite their amazing evidence for a dark matter and nobody's been believing their signal. They have this very clear signal that looks like it should be dark matter, but nobody else sees it, like other dark matter experiments don't see the same thing, and they should. But this guy in Australia has this explanation. He's like, oh, well, maybe that's because those dark other dark matter experiments are only sensitive to heavier versions of mirror matter, and this one experiment in Italy is different from all the other ways and in such a way that makes it sensitive to mirror matter. So he thinks that this DAMA experiment might actually be a signal of dark matter and a signal that dark matter is mirror matter.
Is this one of the ones that has like a huge vat of some noble gas sitting around waiting for things to ping ping it.
Yeah, it's sort of similar. It's a slightly different setup, which is why it's a little bit different. And we'll dig into the details on another episode. But they have this signature that most of the people in the community think probably isn't dark matter, but you know, they believe it, and their experiment is different from other experiments, and so they try to find like a reason why only they would see this thing that other experiments don't see, and.
They're saying it could also be mirror matter, meaning that they're both the same thing.
Yeah, and so Bob Foot in Australia he wrote this paper saying, haha, maybe this explains why Doma is seeing this weird signal and it's a discovery of mirror matter. So that was pretty exciting for a few minutes.
But but somebody found an error.
Well, it's a little bit unlikely because we know that dark matter, if it exists, is cold, right, it's not fast moving. It tends to poke around the universe, it doesn't zip around, whereas mirror matter, if it's real and it really is a mirror of everything we know, should have similar properties to our matter. It should there should be real saivistic elements of it. And so already we think like, well, mirror matter doesn't really fit the same profile as dark matter. What we know about dark matter doesn't really mimic everything we know about the standard model. It seems like it should be heavier and slower.
Mirror matter is too hot for.
Dark matter, exactly. Everybody looks better in the mirror, right.
Everyone looks hotter. Yeah. Well, but I guess, I mean, are you saying that dark matter is significantly colder in general than we are?
Yes? Absolutely, m I see. Yeah. And then the other thing is that was fifteen years ago, and since then there's been a lot more experiments looking for dark matter and cross checking the DOMA experiment, and if mirror matter was making a signal in the domain experiment, we would have seen it in some of these other experiments CDMs and xenon.
And it's not as special anymore.
Yeah. So there was a brief window, you know, when the experiments looked like they might support this crazy idea and that it was exciting for a few minutes, but it sort of fell apart, all.
Right, So not a lot of support experimentally for this idea. Are there any other ways that we could find mirror matter?
Well, the other things we could do gravitationally are trying to look for its effects, you know, astronomically, because it might be that mirror matter isn't like diffuse and spread out the way dark matter is. It really does have interactions that can form interesting structures. Like there could be mirror stars out there. There could be mirror galaxies and mirror planets, right, and so that could be exciting.
Would we be able to see them? Could they still spit out, you know, photons or do they spit out mirror.
Photos They spit out mirror photons only for the mirror astronomers to write mirror papers about it and win mirror Nobel Prizes. But of course we might be able to see their effects gravitationally. But you know, these are not studies where you're like looking for individual particles of mirror matter, but you're like looking for distortions in cosmic gravitational fields. You know, we talked on the podcast for about weird gravitational anomalies in the universe, like the Great Attractor, a strange source of localized gravity somewhere beyond the Milky Way that we can't explain in terms of the stuff that we see. So that's the kind of thing that you might try to explain using like mirror galaxies.
Oh, but I guess at the mirror at the galaxy level, it's sort of maybe indistinguishable from dark matter.
Maybe, yeah, except that dark matter tends to clump with normal matter. Dark matter normal matter tend to overlay each other. In fact, the reason you have normal matter where it is is because there's dark matter there, like pulling it together.
So then are you saying that there could be a mirror planet like right now in our Solar system spinner and around our Sun. We just can't see it, but we might feel it gravitationally. Is that kind of the idea.
That's kind of the idea. I mean, I never thought about it in terms of like a whole mirror planet in our Solar system. That's pretty awesome. And I'm right now writing that down for an idea for a science fiction novel which somebody should write. That's pretty cool. I was more thinking about like entire mirror galaxies separated from ours. But no, you're right. I mean, if our matter feels gravity, it could pull on this stuff, and so our sun could have a mirror planet surrounding it. And in fact, Bob Foot from Melbourne claims that some weird things in the Solar System support the existence of mirror.
Matter, huh, like that there could be mirror asteroids kind of in the in how all of the things in our solar system move around.
Yeah, and he's looked at some like craters on some things in the Solar system and claimed that they can't be explained using normal impacts from normal asteroids. You would need a mirror asteroid to explain it. And I'm pretty.
Skeptical about and glass everywhere, and they're like, like, it has to be a mirror collision.
I'm pretty skeptical of that because you know, mirror objects wouldn't collide with normal objects the normal way, right, They don't feel electromagnetism or the strong force, so they would mostly just pass through each other and affect each other just gravity nationally, So you can't really have like impact sites or collisions in that same way. You can only feel a gravitational tug. So that would be pretty spectacular. But I'm not sure I buy that argument all.
Right, But it sounds like a pretty interesting idea, And again, I think it really taps into again this whole feeling that maybe there's a whole universe out there that's kind of on top of us, but maybe unreachable. You know, all these ideas are fascinating.
Yeah, that reason and this idea may be wrong or maybe right, but it's definitely true that there is stuff out there that we don't understand. That there's a whole invisible universe of stuff going on that if we could tap into it and figure it out, would give us a sense of context, you know, like where which part of the puzzle are we in. It's like when you're doing a puzzle and you're just working on a time a little bit and you don't even really know like where does this go? Is this part of that foot or is this part of the person's face. That's where we are in physics, and we have no idea where our little piece fits in. We know that the puzzle is huge and we've only tapped into a little bit of it, and so this is temptation will be like, well maybe this fits on over here, maybe this is other part over there. And so it's definitely a good idea to look for weirdnesses in what we see and try to reflect it into the larger context. I think that's definitely a good way forward. I'm not sure about this particular theory, but you know, I'm definitely a fan of this kind of idea.
I like what you did there, Daniel, you said, reflected.
I reflected on that joke for a while.
All right, Well, hopefully that will get everyone to think a little bit about all of these amazing symmetries we have and all of the amazing asymmetries that we have in our universe, because you know, there has to be kind of a reason for these weird, unexplained patterns in our universe.
That's right, and anybody out there could be the person who figures it out. We joke around a little bit about how this's just one guy in Australia, but you know, it only takes one person to have an idea and to change the world, and for that to be correct. Einstein was just one guy, you know, Maxwell was just one guy. All these people who can try red to science they had an idea and they propagated it forward. And so that could be bob Foot in Australia, or it could be you, or it could be your kids. So everybody out there should be thinking deeply about the universe and trying to understand the whole context of our lives.
Yeah, so all of you thinking about physics. Look in the mirror and raise your right hand or your left hand and help us figure all this stuff out.
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 iHeart Radio, 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. How is 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 asdairy dot COM's Last Sustainability to learn more.
We're just days away from our twenty twenty four iHeartRadio Music Festival, preceded by Capital.
W The biggest headliners in live music will be taking over to mobile Arena, Las.
Vegas lost some special surprises of moments you are not going to want to miss.
Stream only on Hulu the iHeartRadio Music Festival and listen on iHeartRadio the most anticipated live music events of the year.
This Friday and Saturday, starting at ten thirty pm Eastern seven thirty fift Hi.
I'm David Eagleman from the podcast Inner Cosmos, which recently hit the number one science podcast in America. I'm a neuroscientists at Stanford and I've spent my career exploring the three pound universe in our heads. Join me weekly to explore the relationship between your brain and your life, because the more we know about what's running under the hood, better we can steer our lives. Listen to Inner Cosmos with David Eagleman on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.
