Speaker 1: Hey, Jorgey, do you have your antimatter snack yet? I
Speaker 1: had a banana as usual. It's anti slip. Does that count? No?
Speaker 1: But you do know that bananas give off antimatter radiation,
Speaker 1: don't you wait? What that's bananas? Isn't that dangerous. It's
Speaker 1: so little that it doesn't really matter. That's why you're
Speaker 1: so matter of fact about it. That's why it annihilated
Speaker 1: my taste for bananas. Well, the important thing is that
Speaker 1: it annihilates your hunger. That's the whole point of eating food,
Speaker 1: is the antimatter of hunger. Hi am or Handy, cartoonist
Speaker 1: and the creator of PhD comics. Hi, I'm Daniel. I'm
Speaker 1: a particle physicist and a professor at U C Irvine.
Speaker 1: And it really has been years since I had a banana. Years.
Speaker 1: Oh my gosh, I feel sorry for you. Why are
Speaker 1: you depriving yourself and one of life's simplest pleasures. Although
Speaker 1: I recently convinced my daughter to start eating bananas, so
Speaker 1: now we have bananas around the house. Oh my goodness. Wait,
Speaker 1: why are you recommending it to your daughter but not
Speaker 1: having any yourself. You know, it's a very personal question,
Speaker 1: person to person, I mean you brought it up, and
Speaker 1: I'm just asking a fallow up question. I just mean
Speaker 1: that it's subjective. You know, one person can love bananas,
Speaker 1: another person can hate them. To slippery slope, some people
Speaker 1: find them appealing. Welcome to a podcast Daniel and Jorge
Speaker 1: Explained the Universe, a production of Our Heart Radio in
Speaker 1: which we try to explain our subjective, our personal experience
Speaker 1: of the universe the way that it seems to us.
Speaker 1: All this data that we gather with our eyeballs, biological
Speaker 1: and technological, the things that we see out there in
Speaker 1: the universe, we want to understand all of them. We
Speaker 1: want the whole universe to be a story that makes
Speaker 1: sense to the human brain. This is part of course,
Speaker 1: the long journey of science and trying to wrap up
Speaker 1: the mysteries of the cosmos into something we understand. And
Speaker 1: our goal on this podcast is to take you on
Speaker 1: that journey and explain all of it to you. Yeah,
Speaker 1: because it is a very mysterious universe, full of amazing
Speaker 1: things that are happening in it, and a lot of
Speaker 1: things that we don't understand, even things that we take
Speaker 1: for granted on an everyday basis. Yeah, there are so
Speaker 1: many basic questions about the universe that we do not
Speaker 1: have answers to, which means that for you young folks listening,
Speaker 1: you future scientists, there are plenty of discoveries left to
Speaker 1: be made, lots and lots of open questions for you
Speaker 1: to explore. These are big questions about the universe, about
Speaker 1: our very existence, of why we're here and how it
Speaker 1: is that we are here because there is a lot
Speaker 1: of the things in the universe that matter, and also
Speaker 1: a lot of things that antimatter, like bananas. I wasn't
Speaker 1: joking that bananas produced antimatter. That's a real thing. Oh yeah,
Speaker 1: But is an antimatter dangerous? Like if you touch antimatter,
Speaker 1: you explode anti matter. When it hits real matter, it
Speaker 1: will annihilate into photons. But bananas contain potassium, which is unstable.
Speaker 1: It undergoes radioactive decay, emitting positrons, which are anti electrons,
Speaker 1: and when those do hit your body, they will annihilate
Speaker 1: and create a tiny little flash of light. But it's
Speaker 1: such a tiny amount of antimatter that it doesn't really matter. Well,
Speaker 1: that's why I eat bananas, because you know, it makes
Speaker 1: me glow, makes me feel lighter too. There isn't potassium
Speaker 1: in everything. I mean, it's all around us too, right,
Speaker 1: It's not just bananas that have potassium. That's right. It's
Speaker 1: not just bananas that have potassium. And it's all sorts
Speaker 1: of other things that also radioactively decay. So it's actually
Speaker 1: anti matter sort of all around us all the time.
Speaker 1: It's also showering down on us from the atmosphere because
Speaker 1: of cosmic ray impacts. Yeah, there are all kinds of
Speaker 1: amazing things showering us at the moment right now and
Speaker 1: enveloping us, and and for a lot of those things,
Speaker 1: we still have big questions about them, even big things
Speaker 1: like gravity. Anti matter is fascinating. It appears in science fiction,
Speaker 1: but it's also some thing that's real. It's one of
Speaker 1: these interesting hints that the universe is more complex than
Speaker 1: just the stuff that we are made out of, that
Speaker 1: the universe is capable of doing many more things than
Speaker 1: can just be found out of the particles that we
Speaker 1: are made of. There are all sorts of other weird
Speaker 1: possible particles out there, and they all give us hints
Speaker 1: about what the underlying rules are governing the universe itself.
Speaker 1: And you're right, because ant matter is so rare. There
Speaker 1: are basic questions we have about its properties, Yeah, including
Speaker 1: something as basic as gravity, gravity, which you know we
Speaker 1: kind of depend on every day of our lives to
Speaker 1: stay on planet Earth. Without gravity, we'd all be floating
Speaker 1: out there in space. That's not something I ever worry about,
Speaker 1: but maybe I should start to do. We need to
Speaker 1: like look at the gravity prediction every day as well
Speaker 1: as the weather prediction. Well, I know it's a heavy
Speaker 1: burden to be carrying around worrying about gravity, but it
Speaker 1: seems to be pretty reliable. Right. We ever noticed any
Speaker 1: change in your gravity? I mean, I don't want to
Speaker 1: enquire about your weight or anything like that. That's also
Speaker 1: personal information. That definitely explains it. Right, It's not that
Speaker 1: I'm getting heavier and heavier. It's at the gravity of
Speaker 1: the Earth itself is increasing. Sounds like you have an
Speaker 1: amazing experiment in at hand here, But it does raise
Speaker 1: a lot of interesting questions about gravity and antimatter, specifically
Speaker 1: whether or not they are the same for everything in
Speaker 1: the universe. That's right, antimatter seems to be like the
Speaker 1: opposite of matter in so many interesting ways, and so
Speaker 1: people also wonder whether or not antimatter falls down or
Speaker 1: whether it might possibly fall up, like does antimatter fail upwards?
Speaker 1: So today on the program we'll be tackling the question
Speaker 1: does antimatter feel anti gravity? Interesting? Now, are you saying
Speaker 1: it might feel anti gravity or it has anti feelings
Speaker 1: against gravity? We should invite it onto the podcast to
Speaker 1: ask it what its emotional response is to gravity. But
Speaker 1: I think today we're focusing on a more physics question,
Speaker 1: which is just like, when gravity does this thing, where
Speaker 1: does antimatter go? Doesn't like run away from gravity? Is
Speaker 1: that what you mean? Because antimatter is the opposite of
Speaker 1: matter in so many interesting ways, Yet we also really
Speaker 1: don't understand how gravity works for fundamental particles. We think
Speaker 1: about gravity in terms of like boulders or basketballs, or baseballs,
Speaker 1: or even little bits of sand, But once we get
Speaker 1: down to the quantum level, those particles do things that baseball's,
Speaker 1: basketballs and bits of sand can't do, and we don't
Speaker 1: really know how to apply gravity to those situations, which
Speaker 1: opens up all sorts of questions like maybe it does
Speaker 1: the opposite of what it does for normal matter. Do
Speaker 1: you think antimatter minds that we call it antimatter? Like
Speaker 1: maybe it just has a different opinion about the universe.
Speaker 1: You know, maybe it's just pro something else. Yeah, I
Speaker 1: think in the antimatter galaxies that might be out there
Speaker 1: in deep space. On their podcast, they're probably calling us
Speaker 1: the antimatter yeah. Or maybe there's a third opinion, you know,
Speaker 1: why does it have to be so adversarial these politics
Speaker 1: of physics? Stop the polarization of physics exactly, it's all
Speaker 1: just matter. Yeah, it's not helping our society for sure. Well,
Speaker 1: as usual, we were wondering how many people have thought
Speaker 1: about anti matter and whether it feels gravity, or whether
Speaker 1: it feels anti gravity, or whether anti feels gravity. So
Speaker 1: thanks very much to everybody who participates in this segment
Speaker 1: of the podcast. If you would like to try answering
Speaker 1: the question of the day, please feel free to write in.
Speaker 1: We'll set you up and you can hear your voice
Speaker 1: on the podcast. Think about it for a second. Do
Speaker 1: you think antimatter falls down or up? Here's what people
Speaker 1: had to say, pravity, because anti gravity might be things
Speaker 1: pushing each other apart. What do you think gravity or
Speaker 1: anti gravity? I feel like anti matter still has mass.
Speaker 1: It doesn't have like anti mass, so I don't think
Speaker 1: it feels anti gravity. Do we know if there's anti gravity?
Speaker 1: Is their uncle gravity? I think that antimatter feel gravity
Speaker 1: in the same way that normal matter feels gravity, and
Speaker 1: anti gravity, I think is we don't know if that
Speaker 1: even exists. Well, if I remember your lessons on anti matter,
Speaker 1: it should feel gravity because any matter is just regular
Speaker 1: matter with opposite chart. I know that matter feels gravity
Speaker 1: because of the bending of spacetime towards something with mass.
Speaker 1: I don't really know what anti matter is and whether
Speaker 1: it exists in another field or spatial field than mass.
Speaker 1: But I suppose in the field that anti matter exists,
Speaker 1: maybe there's the bending of that field, which would be
Speaker 1: called anti gravity, So I'd say it does feel anti gravity. Alright,
Speaker 1: a lot of very pro and anti pocisitions on this question.
Speaker 1: My emotions go up and down as I was listening
Speaker 1: to those things. I like how people were anti knowing
Speaker 1: an answer. What happens when knowledge collides with anti knowledge.
Speaker 1: You probably get the current state of affairs right now
Speaker 1: in the world. You get a physics podcast about the
Speaker 1: mysteries of the universe. But it is an interesting question
Speaker 1: whether antimatter feels anti gravity, because I guess antimatter feels
Speaker 1: natively about a lot of things. Yeah, antimatter is one
Speaker 1: of my favorite ideas in physics because it shows you
Speaker 1: that our matter isn't the only kind of matter that
Speaker 1: can be out there. There's like the opposite of our
Speaker 1: kind of matter. Though, like what exactly opposite means is
Speaker 1: a bit of a question philosophically, Right, Well, I guess
Speaker 1: maybe start with the basics what is matter for of all?
Speaker 1: Because I know there are matter particles and there are
Speaker 1: force particles, right, I think the basic idea is that
Speaker 1: the universe is filled with quantum fields, and some of
Speaker 1: these are matter quantum fields. Right. Yeah, what we call
Speaker 1: matter is what you and I are made out of.
Speaker 1: We call it matter because it's the first thing we discovered,
Speaker 1: and so we sort of named it the normal stuff.
Speaker 1: And you and I are made of these particles electrons
Speaker 1: and protons and neutrons, which are of course made up
Speaker 1: of core works inside them. And as you say, they
Speaker 1: are all bound together by forces, the electromagnetic force, the
Speaker 1: weak nuclear force, the strong force, which all use particles
Speaker 1: to communicate with each other. So there's like the photon
Speaker 1: for the electromagnetic force and the gluon for the strong
Speaker 1: nuclear force. And so you and I are like this
Speaker 1: big complicated mesh of particles all weaving themselves together to
Speaker 1: make me and you. Right, and we are made out
Speaker 1: of the basic three kinds of matter particles, right, electrons,
Speaker 1: and one type of forks, and another type of cork.
Speaker 1: And wait, a third type of cork. Right, three courts?
Speaker 1: How many quarks are there? There are six quarks that
Speaker 1: we have discovered, the up cork and the down cork.
Speaker 1: Those two are the ones that we find mostly in
Speaker 1: the proton and the neutron, although there is a little
Speaker 1: bit of other kinds of quirks sometimes appearing in the
Speaker 1: proton and neutron, but for the most part, it's up
Speaker 1: quarks and down corks make protons and neutrons, and you
Speaker 1: add electrons to complete the atom. Right, So we're made
Speaker 1: out of those kinds of icles, and most of most
Speaker 1: of the stuff in the universe is made out of
Speaker 1: those three particles, right, Like the planets, the stars, the
Speaker 1: comments out there, the asteroids, the whole galaxies are basically
Speaker 1: those three kinds of particles. Right. Yeah, we think that
Speaker 1: our entire solar system, our entire galaxy, our cluster of
Speaker 1: galaxy is all made out of this same kind of
Speaker 1: basic stuff that these basic building blocks can be put
Speaker 1: together in lots of different ways to make stars and
Speaker 1: lava and weasels and peanut butter and all the stuff
Speaker 1: that we know in the universe. And that's why we
Speaker 1: call it matter. And on a semantic note, I would
Speaker 1: include also the force particles, you know, the gluons and
Speaker 1: the photons and things that tie them together to really
Speaker 1: make them who we are. So we're not just like
Speaker 1: a loose pile of particles as constituting matter in this case.
Speaker 1: I know, sometimes particle physicists distinguished between matter particles and
Speaker 1: force particles, but when we're talking about matter and versus antimatter,
Speaker 1: I think it makes more sense to just lump it
Speaker 1: all together as matter. Okay, shifting definitions here of basic
Speaker 1: things like matter and force. I guess we're all a
Speaker 1: little bit das to that. But also that's the stuff
Speaker 1: that we're made out of. But there's also other stuff
Speaker 1: in the universe in this category of matter, right, there's
Speaker 1: like heavier electrons and heavier courts. Yes, there are other
Speaker 1: versions of these particles. This is one of the really
Speaker 1: fascinating things about particle physics is that the particles we know,
Speaker 1: the electron, the upcork, and the down cork have these reflections.
Speaker 1: That's what I meant earlier about the sort of philosophical
Speaker 1: definition of opposite. Because with the particles we know, there
Speaker 1: are several versions of them. So even before we talk
Speaker 1: about antimatter, as you said, there are heavier versions of
Speaker 1: these particles, so they're sort of reflected in this one
Speaker 1: dimension along mass. So there's like a heavier version of
Speaker 1: the electron it's called a muon, and a heavier version
Speaker 1: of the up cork it's called a charm cork. And
Speaker 1: then there's a second reflection, right, So there's the muan
Speaker 1: and then the towel is the upcork, the charm cork,
Speaker 1: and then the top cork. So each of these basic
Speaker 1: particles of matter that we know, there's two more versions
Speaker 1: of each of them. So it's this weird reflection of
Speaker 1: the kinds of matter that we're familiar with along the
Speaker 1: mass access they're heavier versions of each of these. Well,
Speaker 1: not all the particles, right, the force particles don't have
Speaker 1: heavier cousins, do they. Yeah, that's right. Only the fermions
Speaker 1: have these heavier cousins. We're not aware of any heavier
Speaker 1: version of the photon or the z boson. Okay, but
Speaker 1: there is something called antimatter particles, which is like if
Speaker 1: you take all of those particles you mentioned, the ones
Speaker 1: we're made out of their heavier cousins. And also in
Speaker 1: some ways, if you also take the force particles and
Speaker 1: numpit amount in, there's a whole other version of all
Speaker 1: of those particles that are called antimatter. That's exactly right.
Speaker 1: So all these particles that were aware of, there's another
Speaker 1: way they're reflected, not just like there's a heavier version
Speaker 1: of them, but now there's like this opposite version of
Speaker 1: them where we take all the charges, for example, and
Speaker 1: we flip them, so the electron has charged minus one.
Speaker 1: There's another version of the electron, which we call the
Speaker 1: antimatter version of the electron. Sometimes we call it a positron,
Speaker 1: which has charged plus one. So it's reflected in this
Speaker 1: like different direction. And that's true also for the muan
Speaker 1: and for the up cork, and for the down cork
Speaker 1: and the top cork. All these particles have their antimatter versions.
Speaker 1: So the antimatter versions are when you flip their charges,
Speaker 1: which is related to the kind of force they feel, right,
Speaker 1: Like electrons feel the electromagnetic force, which means they have
Speaker 1: a charge, and that's what you flip to get the
Speaker 1: anti electron exactly. And we're talking here just about the
Speaker 1: electric charge, which is a label that we put on
Speaker 1: particles that feel the electromagnetic force. And a minus charge
Speaker 1: means one thing, and a positive charge means something else.
Speaker 1: And we know, for example that like positive negative charges
Speaker 1: will pull on each other and similar charges will repel
Speaker 1: each other. So that's a label we put on particles
Speaker 1: to describe how they react to electromagnetic fields. And so
Speaker 1: an electron an apostitron are the same, except they react
Speaker 1: oppositely to these fields. The same electromagnetic field which pushes
Speaker 1: an electron up will push a positron down, so it
Speaker 1: has the same mass as an electron, but the opposite
Speaker 1: electric charge. Right. And then other particles like the corks,
Speaker 1: they don't feel the electromagnetic force, right, so they don't
Speaker 1: have electrical charge. Right. Corks do have electromagnetic charge, but
Speaker 1: they're really weird. They're like plus two thirds or minus
Speaker 1: one third, so they definitely feel electromagnetic fields. You just
Speaker 1: don't typically think of them as doing so because they
Speaker 1: also have a charge for a much more powerful force,
Speaker 1: a strong nuclear force. So they have the electric charge
Speaker 1: and they also have this color charge for the strong
Speaker 1: nuclear force. Okay, so of course feel the color charge
Speaker 1: and also the electric charge. Now, then is an anti
Speaker 1: cork something that has both of those things flipped or
Speaker 1: just one of those things flipped. Both of those things
Speaker 1: get flipped for an antiquark exactly. And I guess that's
Speaker 1: true for all the other particles. But what about the
Speaker 1: force particles. That's also true for their antimatter versions, So
Speaker 1: that's really interesting. It actually depends on the force particle.
Speaker 1: So for example, the W boson that actually carries electric charge,
Speaker 1: it's like there's a positive version and a negative version,
Speaker 1: and one is the anti particle of the other. So
Speaker 1: the antiparticle of the W plus is the W minus. Okay. Yeah.
Speaker 1: And then there's some interesting things about certain particles that
Speaker 1: are their own antiparticle, like photons, right, that's right. For photons,
Speaker 1: there is no other particle to serve as the antiparticle.
Speaker 1: They are their own antiparticle, which is sort of weird.
Speaker 1: But the way we think about in particle physics is
Speaker 1: like you take a particle, you apply the antiparticle operator
Speaker 1: to it, and say, what do you get? If you
Speaker 1: start with an electron and you apply the antimatter particle
Speaker 1: operator to it, you get a positron. You start with
Speaker 1: the photon and you apply this operator to it, you
Speaker 1: just get the photon back and sort of like symmetric.
Speaker 1: So the photon serves as its own antiparticle. Because I guess,
Speaker 1: does the photon have a charge. Photon does not have
Speaker 1: an electric charge, right, the photon does not feel electromagnetic fields.
Speaker 1: If a photon is flying through space and this electric
Speaker 1: field there does not bend the path of the photon.
Speaker 1: If you don't have anything to flip, then you can't
Speaker 1: have an antimatter because is that kind of generally the rule.
Speaker 1: That's generally the rule, and that holds also for example,
Speaker 1: for gluons. Luonto the particle that transmit the strong nuclear force,
Speaker 1: and they do carry color, they carry this charge, and
Speaker 1: so you can't have anti gluons. You can take a
Speaker 1: gluon and make the anti version of it as the
Speaker 1: opposite color. All right, So that's matter and antimatter. But
Speaker 1: one thing, I guess all matters seems to have in common,
Speaker 1: whether or not it feels certain forces or not. Is
Speaker 1: that everybody seems to feel gravity? Right, Well, we're not
Speaker 1: exactly sure about what happens with antimatter and gravity, but
Speaker 1: there is something we think that isn't flipped, which is
Speaker 1: the mass. Like an electron we think has the same
Speaker 1: mass as a positron, it's not like that mass then
Speaker 1: goes negative. That suggests they probably have a similar relationship
Speaker 1: to gravity as the original particle, but we just aren't sure. Well, yeah,
Speaker 1: I guess that's what I was trying to get at,
Speaker 1: which is that a lot of most of these particles,
Speaker 1: the matter particles, have mass, right, that's one thing we
Speaker 1: know about them, and almost in a way, that's kind
Speaker 1: of what makes the matter part Yeah, all the fermions
Speaker 1: definitely do have mass. Even the new trinos have mass,
Speaker 1: even though they have a really tiny little bit of it,
Speaker 1: and all of them get mass, we think from the
Speaker 1: same process, which is interacting with the Higgs boson, And
Speaker 1: to interact with the Higgs boson you have to have
Speaker 1: an antimatter particle. Also, the Higgs boson requires particles to
Speaker 1: interact like in pairs. It couldn't give the electron mass
Speaker 1: if the positron didn't exist, for example, right, All right,
Speaker 1: well then, I guess you know, we know that all
Speaker 1: of these matter particles feel gravity, right because we feel gravity,
Speaker 1: and all of the things on Earth feel gravity. And
Speaker 1: we know that the stars and the planets out there,
Speaker 1: and the galaxies and the galaxy clusters all feel gravity
Speaker 1: and they're mostly made out of matter stuff. And so
Speaker 1: the question that is, does antimatter also feel gravity or
Speaker 1: does it feel something else, maybe the opposite of gravity.
Speaker 1: And so let's get into that weighty question. But first
Speaker 1: let's take a quick break. All right, we're anti talking
Speaker 1: about not feeling anti gravity or is this a pro
Speaker 1: gravity podcast? I'm definitely pro gravity. I don't want it
Speaker 1: to pick up and move somewhere else, like I'd like
Speaker 1: for it to stay pretty much where it is. I'm
Speaker 1: relying on it every day. Oh really, I guess I'm
Speaker 1: more morally flexible when it comes to gravity. I mean,
Speaker 1: if I could, like, you know, ignore it for a
Speaker 1: little bit, that'd be pretty cool to fly around, wouldn't
Speaker 1: that be great? It would be nice to be able
Speaker 1: to manipulate gravity, right If we had ways to create
Speaker 1: like anti gravity somehow, it'd be easier to move your
Speaker 1: bed across the room, or to ship stuff across the world,
Speaker 1: or to launch stuff into outer space. That would be
Speaker 1: pretty awesome. We forget other stuff. How about ourselves, we
Speaker 1: could all be flying around. Finally, you get that flying
Speaker 1: car exactly right. It could be an anti car. Well,
Speaker 1: that's one of the exciting things about all of these
Speaker 1: open questions is that once you understand the way the
Speaker 1: universe works, you might discover something really surprising that's could
Speaker 1: give you a handle for creating all sorts of new
Speaker 1: crazy technologies. Yeah. I mean, we've been waiting for these
Speaker 1: anti gravity flying cars for for years. We're still waiting, Daniel,
Speaker 1: what's the hold? Well, you know, antime matter is not
Speaker 1: easy to study. It's sort of all around us in
Speaker 1: very very tiny amounts. It's made when cosmic rays hit
Speaker 1: the atmosphere. Part of the shower of particles that comes
Speaker 1: down to the surface is antimatter. There's like muans and
Speaker 1: anti muans as well, but it doesn't last very long
Speaker 1: because it smashes into stuff and annihilates, and it just
Speaker 1: doesn't seem to be very much of it in the universe,
Speaker 1: which is one of the big mysteries. Right. We talked
Speaker 1: a lot about how matter and antimatter are symmetric. It's
Speaker 1: all the same, just with the flipped number. You might
Speaker 1: wonder like, well, why isn't there more antimatter in the universe.
Speaker 1: Why is the universe matter and not anti matter? What's
Speaker 1: the difference in the end. Yeah, we have a whole
Speaker 1: episode on that, and I think we also have a
Speaker 1: whole episode on the annihilation of matter and antimatter. Right.
Speaker 1: When a matter particle like an electron hits it's antimatter
Speaker 1: version a positron, they like disappear and turn into pure energy, right, Yeah,
Speaker 1: they can turn into a photon, they can turn into
Speaker 1: a z boson, And you're right, they do disappear, right.
Speaker 1: It's not like what comes out as a rearrangement of
Speaker 1: the bits inside the electron and the positron. This really
Speaker 1: is alchemy that we're talking about. You're transforming the energy
Speaker 1: from one quantum field the electron of depositron field, then
Speaker 1: into a photon field, and then into something else. That
Speaker 1: photon can turn into corks or into w's or into
Speaker 1: something else entirely. It really is pretty awesome. This annihilation
Speaker 1: is like a conduit for transforming matter into something else.
Speaker 1: And it's funny that you mentioned that it's all around us, right,
Speaker 1: I mean, well, technically it is all around us, because
Speaker 1: if there's an electron quantum field all around this, there's
Speaker 1: also an anti electron quantum field all around this too. Right.
Speaker 1: Is it a separate field or is it the same
Speaker 1: field as the electron? Oh, good question, It is its
Speaker 1: own field. There's another field there for the anti electron.
Speaker 1: We tend to comple them together sometimes in the calculations,
Speaker 1: although it gets complicated because there's like left handed versions
Speaker 1: of them and right handed versions of them, and the
Speaker 1: weak force treats those differently. Dig into our episode about
Speaker 1: the weak force and symmetry to understand that more in detail.
Speaker 1: But the short answer is, yes, we are surrounded by
Speaker 1: quantum fields for antiparticles. Even if there aren't actually antiparticles
Speaker 1: around us. Their fields are there, like parking spots are
Speaker 1: there even if no cars are in them. Yeah, there's
Speaker 1: negativity all around us these days, it seems. But as
Speaker 1: we're saying, what's interesting about antimatter is that it's like
Speaker 1: regular matter, but it has certain of its properties flipped,
Speaker 1: like the charge of the electromagnetic force and charge and
Speaker 1: also it's a color and things like that. And so
Speaker 1: one thing that regular matter particles we know have is
Speaker 1: something called mass, Like it's a little it's a property
Speaker 1: of regular matter particles, and that's the thing that gives it,
Speaker 1: you know, inertia, and it makes it feel gravity. Right,
Speaker 1: it's kind of a measure of how much it feels
Speaker 1: gravity or how hard it is to push or pull. Yeah,
Speaker 1: mass is one of these amazing things that seems so simple.
Speaker 1: We think we understand it. You have an intuitive stance
Speaker 1: of what mass is, but when you dig into it theoretically,
Speaker 1: it turns out to be kind of complicated. As you
Speaker 1: say this, two different ideas of mass there. One is
Speaker 1: inertial mass, which is like, when you push on something,
Speaker 1: how much does it move? And that's the mass that
Speaker 1: appears in Newton's equation F equals M A. Basically, it
Speaker 1: relates F how hard you're pushing on something to A
Speaker 1: how fast it accelerates when you push on it. And
Speaker 1: Newton tells us that the relationship between those two quantities
Speaker 1: is mass. That's sort of what inertial mass is. Something
Speaker 1: with more inertial mass takes a larger force to get
Speaker 1: the same acceleration. Something with almost no inertial mass. You
Speaker 1: can accelerate pretty easily with a very small force. That's
Speaker 1: conceptionally different from this other concept of mass, gravitational mass.
Speaker 1: That's the mass that appears, and like the gravitational force
Speaker 1: equation g mm over are squared that tells you, like
Speaker 1: how strong gravitational forces between two objects, right, and so,
Speaker 1: regular particles have this property that we call mass. I
Speaker 1: mean we've called it before in this podcast. Like it's
Speaker 1: almost like a label or it's almost like a charge
Speaker 1: for the force of gravity, right, Like the electric charge
Speaker 1: is kind of like it's a measure how much it
Speaker 1: feels electromagnetic force. Mass is kind of like the measure
Speaker 1: of how much it feels gravity and inertiap Right, It's
Speaker 1: almost like it's like a little property of matter. Yeah,
Speaker 1: it's like a little property of matter and you shouldn't
Speaker 1: think of it. It's like how much stuff the electron has,
Speaker 1: or how much stuff the top cork has. In our theory,
Speaker 1: these are all point particles. I have no volume. This
Speaker 1: is just like a property of the particle. If you're
Speaker 1: comfortable assigning like quantum labels to things, like this thing
Speaker 1: has a positive charge, and you don't have to like
Speaker 1: figure out a physical place for that charge to live.
Speaker 1: You should try to do the same thing with the
Speaker 1: mass of the particle. Like the particle just has this mass.
Speaker 1: You don't have to like have room to put enough
Speaker 1: stuff into the top cork to make heavy. It just
Speaker 1: sort of is that massive. There's another interesting level to
Speaker 1: dig into there, which is like, is this mass actually
Speaker 1: a property of the particle itself or is it a
Speaker 1: property of the interaction of that particle with fields, Because
Speaker 1: we think that like in a universe without a Higgs field,
Speaker 1: all these matter particles, the top cork, the electron, they
Speaker 1: would be massless, they would fly around like photons. It's
Speaker 1: only because the Higgs field is there that these particles
Speaker 1: have a mass. So sort of like a cloud of
Speaker 1: Higgs bosons surrounding every particle changing the way it moves
Speaker 1: so that it looks like as if it had mass.
Speaker 1: So if you want to zoom out, you can just think,
Speaker 1: I'm just gonna put a label on these particles. You
Speaker 1: want to zoom in, you could think about, like, well,
Speaker 1: this particle is sort of like a virtual cloud of
Speaker 1: Higgs bosons around it that are changing it, and I'm
Speaker 1: just going to label the whole cloud is having this mass.
Speaker 1: Do you think of it as a kind of a
Speaker 1: label like you said that particles just have just like
Speaker 1: electric charge, And so the question is if antimatter is
Speaker 1: just regular matter with some of the charges flipped, does
Speaker 1: it also flip the label of mass, like does it
Speaker 1: also flip how it feels gravity or how it feels inertia? Right,
Speaker 1: that's the main question we're asking today. Yeah, and it
Speaker 1: really comes down to this basic question about what is
Speaker 1: gravity anyway? Is gravity a force the way the other
Speaker 1: forces are, you know, the electromagnetic force and the strong force,
Speaker 1: who have all their charges flipped for antimatter. If you
Speaker 1: think about it that way, then gravity is just another
Speaker 1: force and the charge for it is mass, as you say,
Speaker 1: And then it would make sense. It would be like
Speaker 1: sementric It would follow the pattern if also mass was
Speaker 1: flipped for antimatter. Or is gravity not a force? If
Speaker 1: gravity is something else? And we've been thinking about it
Speaker 1: as a force because we just don't see the curvature
Speaker 1: of space and time, and so we've created this fictitious
Speaker 1: force to explain the effect of the bending of space
Speaker 1: time on the motion of particles and If that's the case,
Speaker 1: it would make sense for space time to treat everything
Speaker 1: inside of it the same way. Antimatter and matter particles
Speaker 1: are both just little bundles of energy and his energy
Speaker 1: that bends that space, and so then it would make
Speaker 1: sense for matter and antimatter to all have the same
Speaker 1: relationship with gravity instead of the opposite relationship. So this
Speaker 1: question about whether antimatter feels gravity or anti gravity is
Speaker 1: also kind of a question about like what is gravity anyway?
Speaker 1: But I guess the main picture of trying to pain
Speaker 1: is that you know, like if an electron has a
Speaker 1: negative charge, the negative electric charge, and it weighs, you know,
Speaker 1: point zero zero zero zero zero something kilograms, doesn't anti
Speaker 1: electron not just have positive electric charge, but does it
Speaker 1: also maybe way negative through a point zero zeros there
Speaker 1: zero something kilograms? And what would that mean for the
Speaker 1: anti electron? Yeah, that would be super fascinating, right, And
Speaker 1: because we have two different concepts of mass, we have
Speaker 1: to think about them sort of individually. Like if a
Speaker 1: positron had negative inertial mass, what would that mean? It
Speaker 1: would mean that if you push on it in one direction,
Speaker 1: it would accelerate the other direction, right, Remember force equals
Speaker 1: mass times acceleration. These are vectors, So if mass is negative,
Speaker 1: that means that acceleration of force are pointing in different directions.
Speaker 1: So you like give it a shove to the left
Speaker 1: and it moves to the right. That's what having negative
Speaker 1: inertial mass would mean. That's like really counterintuitive. Negative gravitational
Speaker 1: mass would be different. It would allow for gravitational repulsion.
Speaker 1: Gravity attracts things that both have positive mass. But if
Speaker 1: two particles, one with positive gravitational mass and one with
Speaker 1: negative gravitational mass meat, they might repel each other, which
Speaker 1: would be really interesting because that's not something we've ever seen.
Speaker 1: Gravitational repulsion. Yeah, super fascinating. And so let's maybe talk
Speaker 1: more about each of these scenarios one at a time.
Speaker 1: And so, first of all, let's say that antimatter doesn't
Speaker 1: just flip the charges electrical charges of the forces in
Speaker 1: regular matter particles, but let's say it also flips its
Speaker 1: inertial mass, so it has anti inertia. I guess is
Speaker 1: the idea, And like you said, it's kind of kind
Speaker 1: of intuitive where you try to push something but it
Speaker 1: actually moves towards you. That would be weird, right, That
Speaker 1: would be very weird instead of counter through everything we've
Speaker 1: understood and everything we've experienced in the universe, that would
Speaker 1: be a very strange experience for us to shove somebody
Speaker 1: and then have them slam into you. But I guess
Speaker 1: maybe it does make sense if you just think about
Speaker 1: it as it being antimatter, and where you think you're
Speaker 1: pushing it, you're actually pulling it because it feels you're
Speaker 1: pushing force the opposite way, So it's almost like you're
Speaker 1: just pulling on something, right, Like an electron attracts a
Speaker 1: positively charged particle, right, so it doesn't push it when
Speaker 1: it gets near it, it actually pulls it. So couldn't
Speaker 1: that just be the same for anti mass? It could be,
Speaker 1: although it's a bit more general than that. We're talking about.
Speaker 1: Any force applied to a positron would then move it
Speaker 1: in the opposite direction of that force, whether it's a
Speaker 1: gravitational force or electromagnetic force, or the weak force, which
Speaker 1: positrons also feel. It's a little bit deeper than just
Speaker 1: saying electromagnetism can attract and repel, so what's the big deal.
Speaker 1: Now it's applied to every force on this positron, it
Speaker 1: would be pretty strange. Yeah, but I mean if you
Speaker 1: think about it, like an electron repels another electron, right,
Speaker 1: because they have both have negative charge. Now, if you
Speaker 1: have an electron and a positron, they would normally attract
Speaker 1: each other because they have opposite charges. But then if
Speaker 1: it has negative inertial mass, then it actually maybe flips
Speaker 1: that force and it does repel. Yeah. I think what
Speaker 1: happens there is even weirder because the positron is repelled
Speaker 1: from the electron, but the electron is still attracted to
Speaker 1: the positron, right, It's still attracted to that positive charge,
Speaker 1: and so they sort of like chase each other. Like
Speaker 1: the positron gets pushed away from the electron, but the
Speaker 1: electron gets pulled along with the positron, So you get
Speaker 1: this sort of like weird runaway effect. Yeah. I guess
Speaker 1: when that is kind of a way to prove that
Speaker 1: antimatter doesn't have anti inertial mass is that, you know,
Speaker 1: if you have an electron, it gets attracted to an
Speaker 1: anti electron, which means that it doesn't have anti inertia. Yeah,
Speaker 1: anti inertia would be really weird. Negative inertial mass particles
Speaker 1: would behave very strangely, and this is something we would
Speaker 1: have seen because we do see positrons in the world.
Speaker 1: We see them in cosmic rays, we can bend them
Speaker 1: with magnets. We don't see them doing this sort of
Speaker 1: weird behavior of being pushed in the opposite direction of
Speaker 1: the force. So negative inertial mass is not something anybody
Speaker 1: really considers seriously. When it comes to antimatter. It would
Speaker 1: be really bizarre. We haven't seen it, but I wonder
Speaker 1: if it's possible, Like could you have maybe a third
Speaker 1: version of an electron, not just a positron, with something
Speaker 1: that has its opposite charge, but also has negative inertia,
Speaker 1: which would act just like another electron to an electron,
Speaker 1: Like you would think it was an electron, but really
Speaker 1: it's an antimatter electron with a flip inertial mass. Yeah,
Speaker 1: negative mass electron. It's certainly possible that there are other
Speaker 1: reflect actions of the particles that we're not aware of.
Speaker 1: Our we're not limited to just matter and antimatter or
Speaker 1: heavier versions. You know, there are theories about like supersymmetric
Speaker 1: versions of each of these particles, and so it's totally
Speaker 1: possible to come up with another idea like a particle
Speaker 1: that it's just like the electron, but with negative inertial mass,
Speaker 1: and say maybe it could exist in the universe. Then
Speaker 1: you have to answer questions like, well, why was made
Speaker 1: in the Big Bang? Where are these? If they do exist,
Speaker 1: why haven't we seen them? And if you haven't seen them,
Speaker 1: they have to come up with an explanation for why
Speaker 1: they don't seem to appear in our universe. But it
Speaker 1: doesn't mean that it couldn't possibly exist in the universe.
Speaker 1: But I guess you're saying that the antimatter that we
Speaker 1: have seen so far, like the anti electrons that we've seen,
Speaker 1: seem to have regular inertial mass. Yeah, and this is
Speaker 1: not so challenging to observe because we can apply pretty
Speaker 1: powerful forces like electromagnetic forces to antimatter particles, which are
Speaker 1: rare but not impossible to make into manipulated and we
Speaker 1: can see their behavior. So, for example, the discovery of
Speaker 1: antimatter was seeing a positron moved through a magnetic field
Speaker 1: and bending in a way that an electron doesn't. So
Speaker 1: we're pretty sure that antimatter has inertial mass the same
Speaker 1: way that normal matter does. All right, Well, now let's
Speaker 1: tackle this idea of having anti gravitational mass. Now, is
Speaker 1: there such a thing as gravitational mass? I thought gravity
Speaker 1: wasn't really a force, It was really kind of a
Speaker 1: bending of space. This idea has some interesting history. Newton
Speaker 1: considered these things separate. He said, things have inertial mass
Speaker 1: and they have gravitational mass. These are different ideas. If
Speaker 1: you're on an empty space where there's no gravity, and
Speaker 1: objects still had inertia, right, and the force of gravity,
Speaker 1: the mass that appears in there didn't necessarily have to
Speaker 1: be the same as the mass in F equals m A.
Speaker 1: People measured it, and they always found these two things
Speaker 1: to be the same. The mass that appears in those
Speaker 1: equations were the same, and so people thought, well, that's weird,
Speaker 1: what a crazy coincidence of these things really are separate
Speaker 1: concepts and yet always managed to be exactly the same.
Speaker 1: So that was sort of an unexplained mystery for a
Speaker 1: long time. Einstein, when he developed his theory of relativity,
Speaker 1: he said, well, let's just assume that these things are
Speaker 1: the same. He baked that in to his theory of relativity.
Speaker 1: That's not a proof that they are, that's just an
Speaker 1: assumption of the foundation of general relativity. He said that
Speaker 1: gravity and inertia are basically the same thing. Okay, and
Speaker 1: so then what does that mean for having negative gravitational
Speaker 1: mass or anti gravitational mass. Well, it means that general
Speaker 1: relativity makes a very strong prediction that anything with energy
Speaker 1: bends space the same way. And so we think that
Speaker 1: antimatter probably feels gravity the same way that matter does.
Speaker 1: So Einstein and general relativity say antimatterer should feel gravity,
Speaker 1: it shouldn't feel anti gravity, and that's a strong prediction
Speaker 1: from general relativity. Well, that's a strong you're saying assumption
Speaker 1: about general relativity, right, But it is it possible for
Speaker 1: something to have negative gravitational mass, so that if I
Speaker 1: throw it at a black hole, it's actually going to
Speaker 1: run away from the black hole and not towards the
Speaker 1: black hole. I mean, it's possible in the sense that
Speaker 1: like anything is possible in the universe, and we don't
Speaker 1: know if general relativity accurately describes everything in the universe,
Speaker 1: and specifically, we don't know how to apply general relativity
Speaker 1: to particles. So it's possible that antimatter breaks general relativity
Speaker 1: and that quantum gravity allows for other weird forces on
Speaker 1: antimatter particles like anti gravity. But if you just say
Speaker 1: we believe in general relativity, then it's not possible for
Speaker 1: antimatter to have anti gravity. I see, So if something
Speaker 1: could have negative gravitational mass, it would mean Einstein was wrong,
Speaker 1: or that general grotivity needs to be maybe expanded. Doesn't
Speaker 1: necessarily mean it's wrong, or would you just need to
Speaker 1: like add something to Einstein's theory. Well, that's an interesting
Speaker 1: philosophical question. I mean, we're pretty sure that Einstein is wrong,
Speaker 1: not in the sense that any of his predictions have
Speaker 1: been proven wrong, but we don't know how to extend
Speaker 1: his theory to quantum particles. It definitely needs some sort
Speaker 1: of adaptation, and that might mean that it needs to
Speaker 1: be like tossed out and completely replaced with the theory
Speaker 1: of quantum gravity. That's a completely different picture of how
Speaker 1: space gets bent using like quantum gravitons. Or it might
Speaker 1: be that we take Einstein's theory and we quantize it
Speaker 1: that we like say, space itself is made of quantum
Speaker 1: bits that are woven together, and general relativity emerges from that.
Speaker 1: We really don't know whether we need to build on
Speaker 1: top of Einstein's theory or whether we need to like
Speaker 1: re examine the very foundations of it. But we do
Speaker 1: know that can't work in the quantum realm, so it
Speaker 1: needs some sort of update. It might be that we
Speaker 1: discovered failing only when we see inside black holes, or
Speaker 1: it might be that we discovered failing when we examine
Speaker 1: the gravitational properties of antimatter. Well, I guess I'm not
Speaker 1: quite sure what you're saying. Are you saying that? Okay?
Speaker 1: So eince science theory assumes that gravitational mass and inertial
Speaker 1: mass are the same, which means that you can't have
Speaker 1: negative rotational mass anti gravitational mass, or that you still
Speaker 1: could or like, if you have negative inertial math anti
Speaker 1: inertial mass, then that would also mean you have anti
Speaker 1: gravity irrotational mass. Einstein's theory says you can't have negative
Speaker 1: gravitational mass, that that just can't happen because of the
Speaker 1: equip into principle. But we don't know that that's true, right,
Speaker 1: We don't know what the universe actually does. So if
Speaker 1: we discover antimatter with negative gravitational mass, that means general
Speaker 1: relativity is wrong in some important way. But maybe wouldn't
Speaker 1: that just mean that it has negative inertial mass. Like,
Speaker 1: if something has a negative inertial in them mass, then
Speaker 1: in in Einstein's formulation, they would also have negative gravitational mass. Yeah,
Speaker 1: that's a really cool thought. You're right that general relativity
Speaker 1: just requires that they have the same inertial and gravitational mass,
Speaker 1: which I suppose would allow for them to both be negative.
Speaker 1: But again, we haven't seen particles with negative inertial mass.
Speaker 1: So the antimatter we know and we are familiar with
Speaker 1: doesn't have negative inertial mass, so then general relativity would
Speaker 1: predict that it also has positive gravitational mass M. So
Speaker 1: it's then it is possible to have a particle out
Speaker 1: there that if you throw at a black hole, it's
Speaker 1: going to run away from the black hole. But if
Speaker 1: it has both negative and gravitational mass, it would have
Speaker 1: the opposite force on it, and then that worse would
Speaker 1: push it in the opposite direction, and two opposites resulted
Speaker 1: in going the same way. WHOA, So it would still
Speaker 1: go towards the black hole. It would still go towards
Speaker 1: the black hole, Yes, because they would cancel each other out. Yeah, exactly.
Speaker 1: Black hole's force would technically be away from it, and
Speaker 1: that would result in a particle moving towards it. So
Speaker 1: double bonkers unless um, somehow Einstein's theory is wrong and
Speaker 1: they're sort of not the same thing, right exactly, the
Speaker 1: possibility that Einstein is wrong and that antimatter particles have
Speaker 1: positive inertial mass and negative gravitational mass. All right, well,
Speaker 1: it seems like, um, it is possible maybe to have
Speaker 1: anti gravity from being an antimatter particle, to have an
Speaker 1: anti inertial or anti gravitational mass seems possible. But I
Speaker 1: guess then the question is does it actually happen? What
Speaker 1: are some experiments we've done to try to find the
Speaker 1: answer to this question. So let's get into that, But
Speaker 1: first let's take another quick break. All right, we are
Speaker 1: feeling a lot of anti emotions here talking about antimatter,
Speaker 1: anti gravity, anti mass, anti everything. It's a very contrary episode.
Speaker 1: We're going up, we're going down. We're going anti up
Speaker 1: and anti down all at the same time. Can you
Speaker 1: go anti anti? Those would be your double negative mass particles, right,
Speaker 1: be anti anti attracted to a black hole? What would
Speaker 1: you call the antimatter version of your parents, sister, your
Speaker 1: anti anti These are tough questions we're asking today, assuming
Speaker 1: people are still listening or the left in an anti huff.
Speaker 1: All right, we're talking about whether or not antimatter feels
Speaker 1: anti gravity, which is kind of turned out to be
Speaker 1: a pretty complicated question because, first of all, you have
Speaker 1: to think about whether antimatter has anti inertia mass or
Speaker 1: anti gravitational mass, and whether or not if they're the
Speaker 1: same thing according to Einstein, or maybe they're not. I
Speaker 1: don't know. I don't know. I feel like from all
Speaker 1: this theoretical discussion, it seems like you're saying that it's
Speaker 1: not possible to have anti gravity. I think it's very
Speaker 1: unlikely that antimatter has anti gravity just because general relativity
Speaker 1: is so successful. The YadA YadA YadA, dot dot dot.
Speaker 1: On the other hand, why do we do experiments. We
Speaker 1: don't do experiments just to like yawn and check the
Speaker 1: boxes off of theoretical predictions. We do experiments because we
Speaker 1: want to explore the universe. We want to find crazy,
Speaker 1: shocking things that we can't explain that let us pull
Speaker 1: the rug out of everything we thought we knew and
Speaker 1: build up new ideas about the universe. So this is
Speaker 1: definitely something we should check. We should go and see
Speaker 1: whether antimatter follows our expectations or anti follows them. I
Speaker 1: think I see what you're saying. You're saying you're anti
Speaker 1: anti gravity, but you're pro the government giving you more
Speaker 1: money to run experiments. Is that kind of what I'm
Speaker 1: sensing here. I it's a little um contradictory position here.
Speaker 1: I think it's just exciting to go out and ask
Speaker 1: basic questions, like, hey, does antimatter of f all up
Speaker 1: or down? And it's incredible to me that almost a
Speaker 1: hundred years after we've discovered anti matter, we still don't
Speaker 1: really know the answer to that. Like, experimentally, it turned
Speaker 1: out to be surprisingly tricky to do experiments with antimatter, right,
Speaker 1: And specifically, you're talking about measuring I guess, the gravity
Speaker 1: of a particle, right, I mean, you can measure the
Speaker 1: gravity of a planet, of a person, of a banana,
Speaker 1: but it's hard to kind of talk about the gravity
Speaker 1: of tiny little particles because they feel very little gravity.
Speaker 1: It's hard to even measure the gravity of a banana.
Speaker 1: Like you can measure the weight of a banana, you
Speaker 1: put it on a scale, but there you're measuring the
Speaker 1: gravity of the Earth. Right. The Earth is pulling on
Speaker 1: the banana. If you have two bananas in the room
Speaker 1: next to you, it's pretty hard to measure their attraction
Speaker 1: between themselves because gravity is so weak. It's like ten
Speaker 1: to the thirty times as weak as electromagnetism, So it's
Speaker 1: something we typically ignore. Right, you have two bananas on
Speaker 1: your table, you don't expect to see them like creep
Speaker 1: towards each other if you leave them alone. But they
Speaker 1: would in space, Right, that's the idea. If you were
Speaker 1: floating out there in space and you have two bananas,
Speaker 1: eventually they would become a bi banana. Banana na na. Yeah.
Speaker 1: But even doing that experiment in space would be hard
Speaker 1: because the gravity is so weak that it might get
Speaker 1: swamped by other stuff like the solar wind would probably
Speaker 1: blow on those bananas, pushing on them harder than the
Speaker 1: force of gravity between the bananas. Or if the bananas
Speaker 1: have like a little bit of residual positive and negative charge,
Speaker 1: like you rubbed one on your pants accidentally and giving
Speaker 1: it some static electricity, then those forces, even a few
Speaker 1: electrons on the surface of each one, would be more
Speaker 1: powerful than gravity. So gravity is super hard to measure
Speaker 1: for small things because it's so weak, it's swamped by
Speaker 1: everything else. It's like trying to listen to a whisper
Speaker 1: during a really loud concert. But I guess if you
Speaker 1: said the experiment the right way and make sure everything
Speaker 1: doesn't have a charge, the two bananas would come together eventually,
Speaker 1: because that is what happens out there in space, right,
Speaker 1: That's how planets get formed and asteroids and the sun. Right. Yeah,
Speaker 1: we think that's the basic process for forming all of
Speaker 1: the structure in the universe. And we've done some really
Speaker 1: pretty awesome virtuoso experiments measuring the gravity of like little things,
Speaker 1: things about the size of a centimeter and involves isolating
Speaker 1: them from everything else and seeing very very small motion,
Speaker 1: which people observe by like attaching a mirror to the
Speaker 1: object and shining a laser on the mirror and seeing
Speaker 1: the laser spot like move a tiny little bit so
Speaker 1: that you see that the object has moved. These are
Speaker 1: really super precise experiments, very very difficult to do, but
Speaker 1: still there. With macroscopic objects, we're talking about like things
Speaker 1: the size of a millimeter or centimeter, not individual particles,
Speaker 1: so we can measure the mass of tiny, regular matter
Speaker 1: of things. But I guess it's hard to do it
Speaker 1: with antimatter, right, because that's really the question we're asking
Speaker 1: today is like, if you have something made out of
Speaker 1: or a whole bunch of antimatter in one spot, would
Speaker 1: it feel anti gravity? That's the experiment. That's also hard
Speaker 1: to do it because it's hard to put together a
Speaker 1: lot of antimatter. It is. We can make antimatter at CERN,
Speaker 1: for example, we smash matter into targets and the whole
Speaker 1: spray of stuff comes out, including some antimatter, and we
Speaker 1: can filter it out and do experiments with it, and
Speaker 1: we do that kind of thing. But we make like
Speaker 1: pico grams of antimatter every year it's CERN. So you
Speaker 1: want to make like a bananas amount of antimatter, it
Speaker 1: would cost zillions of dollars and take years and years
Speaker 1: and years. So instead of making really big objects out
Speaker 1: of antimatter, we try to do really precision experiments with
Speaker 1: much smaller amounts of antimatter. Also, would be super dangerous
Speaker 1: to come to make like a even a piece size
Speaker 1: or raisin size amount of antimatter, because then if it
Speaker 1: touches regular matter, it's it's going to destroy the Earth basically, right,
Speaker 1: It's one of the most efficient ways to release the
Speaker 1: energy inside matter, which is a huge amount, right equals
Speaker 1: mc squared. C is a really big number. The speed
Speaker 1: of light C squared is a really big number. Is squared.
Speaker 1: So as you say, like a raisin's worth of antimatter
Speaker 1: combined with the reason but have as much energy is
Speaker 1: like a nuclear detonation. So yes, if you are making
Speaker 1: antimatter in your kitchen, be very careful. Yeah, we're very
Speaker 1: anti that kitchen. A recipe there, But I think what
Speaker 1: you're saying is that you can make antimatter in your
Speaker 1: colliders and certain, but you haven't made enough to really
Speaker 1: do gravitational experiments to see whether antimatter feels anti gravity.
Speaker 1: We actually have done a few experiments with antimatter that
Speaker 1: do ask this question about the effects of gravity on
Speaker 1: these particles, but they're very, very difficult to do and
Speaker 1: not as sensitive as we'd like yet. What I mean,
Speaker 1: so you did the experiments but didn't reach a conclusion
Speaker 1: or what couldn't get the data. So they've done the experiments.
Speaker 1: They take anti protons and they combine them with anti
Speaker 1: electrons to make anti hydrogen. And the reason they do
Speaker 1: that is you need neutral antimatter. You don't want any
Speaker 1: electric or magnetic fields affecting your antimatter. You want to
Speaker 1: measure only the gravitational force on these objects. So they
Speaker 1: make neutral anti hydrogen, which is super awesome anyway, because
Speaker 1: then they can do things like study the spectral properties
Speaker 1: of it and see if anti hydrogen behaves the same
Speaker 1: way as hydrogen, which this whole other really fascinating field
Speaker 1: of science to try to figure out what is the
Speaker 1: difference between matter and antimatter. But because they have a
Speaker 1: collection of these anti hydrogen atoms, they can also see
Speaker 1: like what happens when they float there, Like do they
Speaker 1: drift down or do they drift up? Well, I guess,
Speaker 1: first of all, how do you hold a bunch of
Speaker 1: anti hydrogen? So you create this I guess by bringing
Speaker 1: together anti electrons and anti protons, and then they make
Speaker 1: answer hydrogen and then you get a little cloud of
Speaker 1: anti hygen. What do you do with that? Do you
Speaker 1: keep it inside of a bottle? It's really challenging to contain.
Speaker 1: You're absolutely right. What we do is we keep it
Speaker 1: in a magnetic bottle. It doesn't work very well. A
Speaker 1: magnetic bottle is good at holding charged particles. Because magnetic
Speaker 1: fields bend the path of charged particles. So, for example,
Speaker 1: the beams and the large hadron collider are kept moving
Speaker 1: in a circle because of very powerful magnets or plasma,
Speaker 1: and a fusion reactor is kept in a magnetic bottle
Speaker 1: to keep it from escaping because it's filled with charge particles.
Speaker 1: It doesn't work very well all on neutral particles, but
Speaker 1: even anti hydrogen has a magnetic moment because the spins
Speaker 1: the particles, they do feel magnetic fields a little bit,
Speaker 1: so we can keep them in like a very very
Speaker 1: bad magnetic bottle, and it works best if those anti
Speaker 1: hydrogen atoms are slow, if they're cold, they're not like
Speaker 1: flying around with high velocity, then this very weak bottle
Speaker 1: tends to contain them. But that's a challenge because making
Speaker 1: anti hydrogen that's moving slowly is hard because you have
Speaker 1: to combine the positrons and the anti protons which come
Speaker 1: in in beams, so you have to have like slow beams,
Speaker 1: like gases of these things like merge together. The whole
Speaker 1: thing is experimentally very tricky. Yeah, it sounds pretty hard,
Speaker 1: but they have done this kind of and what did
Speaker 1: they find. Did they find that it falls at the
Speaker 1: bottom of this bad bottle, or does it flow it
Speaker 1: up to the top of the bad bottle. So there's
Speaker 1: a very cool experiment at CERN. It's called the Alpha experiment,
Speaker 1: which stands for anti hydrogen laser physics apparatus. Is a
Speaker 1: terrible acronym or really awesome experiment. And they do not
Speaker 1: see anti matter falling upwards very fast. I mean, some
Speaker 1: of these hydrogen atoms do float up and some of
Speaker 1: them do float down. And because the difficulty of measuring gravity,
Speaker 1: it's not a very precise measurement. What they can do
Speaker 1: is they can say that anti hydrogen doesn't have a
Speaker 1: negative gravitational mass of sixty five times the inertial mass.
Speaker 1: So if anti hydrogen had a negative gravitational mass of
Speaker 1: like a hundred or a million times the inertial mass,
Speaker 1: they would have seen it because they would have flown
Speaker 1: upwards really fast. They don't see them flying upwards really fast,
Speaker 1: so they can say if it does have a negative
Speaker 1: gravitational mass, it's not that big. So it's like very imprecise.
Speaker 1: So far, if they had a lot more anti hydrogen
Speaker 1: or more time, they can make more precise measurements. They
Speaker 1: could sort of narrow this down statistically, all they can
Speaker 1: do right now is like rule out a really crazy
Speaker 1: result where anti hydrogen has a negative gravitational mass that's
Speaker 1: also much bigger in magnitude in the inertial mass. But
Speaker 1: could it have a varying different gravitational mass in magnitude
Speaker 1: than than it's inertial mass. I mean, we're exploring the
Speaker 1: bonkers universe theory out here, so maybe right. And this
Speaker 1: is also sort of like just the way that they
Speaker 1: can express their results. Even if the theoretical options are well,
Speaker 1: it either has a positive gravitational mass or negative one
Speaker 1: times the inertial mass. We can't tell the difference between
Speaker 1: those two. Experimentally, all we can do is tell the
Speaker 1: difference between negative sixty five and positive one. So we
Speaker 1: can rule out negative sixty five, we can't yet rule
Speaker 1: out negative one. M I see. So they done the
Speaker 1: experiment and they don't have a clear result, but it's
Speaker 1: not an anti result either. It's not. And they're just
Speaker 1: getting started, right, and so they're going to make more
Speaker 1: anti hydrogen and they're gonna do more precise experiments. There
Speaker 1: are other experiments coming online at CERN to measure this
Speaker 1: in other ways and so in the next few years
Speaker 1: we hope to get more precise measurements of the gravitational
Speaker 1: properties of antimatter. All right, Besides cern are there other
Speaker 1: experiment is that we've done or are going to do
Speaker 1: to measure the gravity of antimatter. These kind of particle
Speaker 1: physics experiments are really the most direct way to probe this.
Speaker 1: You can also do other sort of thought experiments to
Speaker 1: think about the effects of antimatter. For example, like the
Speaker 1: protons that are inside me and you, we talked earlier
Speaker 1: about how they have quarks inside them, Well, they also
Speaker 1: have antimatter inside them. Like the gluons that are inside
Speaker 1: the protons, they sometimes turn into cork anti cork pairs
Speaker 1: like very briefly before going back to being a gluon
Speaker 1: the way like a photon will turn into a particle
Speaker 1: antiparticle pair briefly and go back to being a photon.
Speaker 1: So that means that like you and I are partially
Speaker 1: made of anti matter. If antimatter had anti gravity in
Speaker 1: some weird way, then we would see the effect of
Speaker 1: that on protons. And we don't see any weird behavior
Speaker 1: of protons. They don't seem to have any sort of
Speaker 1: like deviation between their inertial and gravitational mass. So that's
Speaker 1: a strong hint that antimatter probably has normal. Yeah, we
Speaker 1: all have a little bit of negativity inside of us,
Speaker 1: a little bit of a contrarian inside of us. But
Speaker 1: I think you're saying that we all are made a
Speaker 1: little bit of antimatter and it doesn't seem to be
Speaker 1: affecting the regular matter. But at the same time, it's
Speaker 1: a very tiny amount, isn't Isn't it like super duper
Speaker 1: negligible the amount of antimatter inside of us? Yeah, so
Speaker 1: it would be pretty negligible. All right. Well, maybe to
Speaker 1: wrap up here, I think we've sort of maybe a
Speaker 1: little bit debunked the idea of anti gravity for antimatter particles.
Speaker 1: I mean, theoretically, it seems like it's not really possible,
Speaker 1: or I mean it's possible, but we would mean we
Speaker 1: would see a very different universe. And also these experiments
Speaker 1: that you describe kind of rule it out as well.
Speaker 1: So if that's true, then if you can't have anti gravity,
Speaker 1: what does that mean about our theories of the universe.
Speaker 1: I think I agree mostly with what you say, but
Speaker 1: I always hold out a little bit of hope for
Speaker 1: the crazy result. You know, even if the theory very
Speaker 1: strongly says that can't happen, that just makes me more
Speaker 1: excited to go and discover it that way, because it
Speaker 1: means undermining that whole theory and starting from scratch, and
Speaker 1: to me, those are the most exciting moments in science.
Speaker 1: So I think you're right that the theory very strongly
Speaker 1: suggests that antimatter doesn't have anti gravity, But that still
Speaker 1: makes me hopeful. Wait, what makes you hopeful that maybe
Speaker 1: one of these experiments will get a shocking result and
Speaker 1: discover antimatter fluting up in a gravitational field and give
Speaker 1: us a clue about the next direction we should take
Speaker 1: for gravity, for understanding whether it is a quantum field
Speaker 1: or whether space itself is quantized, and how to get
Speaker 1: to quantum gravity. All right, well, I think what you're
Speaker 1: trying to say is keep giving you money to run
Speaker 1: these experiments just to make sure that the universe is
Speaker 1: not actually crazy. I'd say, we never know where the
Speaker 1: next surprise, where the great big learning moment about the universe,
Speaker 1: will come, and so it makes a lot of sense
Speaker 1: to go out there and do careful experiments and see
Speaker 1: if the universe is the way we expect or not?
Speaker 1: Where is to the anti way we expect? All right,
Speaker 1: we'll stay tuned, as I guess we keep exploring this
Speaker 1: idea of antimatter and what gravity actually is. I guess
Speaker 1: it's hard to prove that there's such a thing as
Speaker 1: anti gravity if we don't actually kind of know what
Speaker 1: gravity is. That's a good point. We anti know gravity,
Speaker 1: right like, It's still kind of up for the babe
Speaker 1: whether general relativity, which is Einstein's theory, is right or not,
Speaker 1: and how it matches up with quantum mechanics. It's one
Speaker 1: of the deepest questions at the heart of modern physics,
Speaker 1: how to unify these two pillars of our understanding of
Speaker 1: the universe. All right, well, I guess we'll keep waiting
Speaker 1: for news from the fringes of physics. We'll keep funding
Speaker 1: those experiments. You mean it's above my pay grade? All right? Well,
Speaker 1: we hope you enjoyed that or anti enjoyed that. Thanks
Speaker 1: for joining us, See you next time. Thanks for listening,
Speaker 1: and remember that. Daniel and Jorge Explain the Universe is
Speaker 1: a production of I Heart Radio. For more podcast from
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