Speaker 1: Hey, Daniel, are you glad our universe has antimatter?
Speaker 2: No, I'm definitely pro our universe. So I guess I'm
Speaker 2: not anti antimatter.
Speaker 1: That means your pro matter. But I guess the question is,
Speaker 1: would you miss antimatter if we didn't have it?
Speaker 2: I mean, I like things the way they are, so
Speaker 2: if we lost antimatter, the universe would be pretty different
Speaker 2: and maybe worse. But what if it's better, or maybe
Speaker 2: it couldn't exist without antimatter and it would disappear in
Speaker 2: a puff of mathematical contradictions.
Speaker 1: Okay, then I would be anti antimatter. I would not
Speaker 1: be pro antimatter.
Speaker 2: I'm just saying it matters. Hi.
Speaker 1: I'm Boria mccartoonist and the creator of PhD Comics.
Speaker 2: Hi. I'm Daniel. I'm a particle physicist and a professor
Speaker 2: at UC Irvine, and I love all the kinds of
Speaker 2: matter out there, the matter and the antimatter and the
Speaker 2: pro matter.
Speaker 1: What about the meh matter? Not pro, not anti, It's
Speaker 1: it's just kind of there.
Speaker 2: You know. I will admit that there are some particles
Speaker 2: I think they're exciting. In other particles, I'm like, yeah,
Speaker 2: that's just a mess.
Speaker 1: About your favorite kind of matter is chocolate matters certainly
Speaker 1: better than vanilla matter, karp matter, But anyways, welcome to
Speaker 1: our podcast, Daniel and Jorge Explain the Universe, a production
Speaker 1: of iHeartRadio.
Speaker 2: In which we dig deep into all kinds of matter
Speaker 2: out there that matters. We talk about the things that
Speaker 2: make you up. We talk about the things that make
Speaker 2: nothing up, and things that seem to exist for which
Speaker 2: we do not yet understand. The whole universe is like
Speaker 2: a jigsaw puzzle with lots of weirdly shaped pieces, and
Speaker 2: our goal is to find all those pieces, fit them
Speaker 2: together to tell the whole story of our universe. And
Speaker 2: on this podcast we'd like to do that and try
Speaker 2: to explain all of it to you.
Speaker 1: That's right. It is a vast and complicated universe, full
Speaker 1: of all kinds of crazy and interesting kinds of matter
Speaker 1: and energy and concepts and mathematics that we like to
Speaker 1: explore as human beings and ask questions about and then
Speaker 1: explain it to you, or at least ask you the question,
Speaker 1: what's the matter with you?
Speaker 2: We study all of these particles, we try to understand them,
Speaker 2: and sometimes we even taste them to see if they're delicious.
Speaker 2: But I wasn't joking when I said that some of
Speaker 2: the particles out there are a little crazier and harder
Speaker 2: to think about than others. I mean, there are so
Speaker 2: many particles discovered in the era of the particle Zoo
Speaker 2: that we almost ran out of silly Greek letters to
Speaker 2: use to name all of them.
Speaker 1: Oh boy, what happens when you run out of Greek letters?
Speaker 2: Then you start using Hebrew letters? Okay, like the Gimmel
Speaker 2: particle on the aleph particle. H interesting, But we've discovered
Speaker 2: so many weird masons and baryons that we had to
Speaker 2: use some of those weird Greek letters that nobody even
Speaker 2: really knows how to write down.
Speaker 1: I guess we have done a pretty good job of
Speaker 1: kind of looking out into the universe and basically talent
Speaker 1: up all the different kinds of matter, all the different
Speaker 1: kinds of particles that can't exist out there, because there
Speaker 1: are a lot. As you're saying, there are.
Speaker 2: A lot, and it's sort of a two step process
Speaker 2: to understand the universe. Like number one, just look out
Speaker 2: and see what's there. Gather together all the puzzle pieces.
Speaker 2: Number two, try to click them together to tell the
Speaker 2: whole story. Are there pieces missing, do they fit together
Speaker 2: into a puzzle or is it just a weird, disjointed
Speaker 2: pile of confusion.
Speaker 1: Yeah, And I guess the history of it is that
Speaker 1: we used to think that we knew what the building
Speaker 1: blocks of the universe was, right. We thought the elements
Speaker 1: of the periodic table were like the basic lego pieces
Speaker 1: of the universe. But actually those turned to be made
Speaker 1: of other things. And then those some of those things
Speaker 1: turn to be made of other things.
Speaker 2: That's right. We revealed this sort of hierarchical structure of matter,
Speaker 2: things made of smaller things, made of smaller things, but
Speaker 2: the path to understand them in the history of science
Speaker 2: was not so straightforward. We sort of like drilled down
Speaker 2: and then got wider and weirder, and then drilled down
Speaker 2: again and got wider and weirder. For example, when we
Speaker 2: wanted to understand the nucleus, when we wanted to understand
Speaker 2: protons and neutrons and what's inside them, we'd build bigger
Speaker 2: atom smashers and higher energy colliders, but we didn't immediately
Speaker 2: find out what was inside the proton. Instead, first we
Speaker 2: discovered all sorts of weird other kinds of particles that
Speaker 2: don't exist inside the atom, chaons and pions and rope
Speaker 2: particles and omega particles and all sorts of other Greek letters.
Speaker 2: I don't even know how to pronounce. Things got weird
Speaker 2: before they got clearer.
Speaker 1: Yeah, no, I understand. It's all Greek to me.
Speaker 2: In the same way that we want to understand what's
Speaker 2: inside the quarks that make up the proton, but first
Speaker 2: we found more quarks along the way. Instead of figuring
Speaker 2: out what's inside the upcork and the down cork, we
Speaker 2: found the charm and the strange, and the top and
Speaker 2: the bottom. So the universe gives us a big pile
Speaker 2: of clues before it reveals its deepest secrets.
Speaker 1: Yeah, it is a weird universe full of surprises. And
Speaker 1: one of the weirdest things about matter in the universe
Speaker 1: is that it seems to have an opposite to it.
Speaker 1: There seems to be a lot of antimatter in the universe.
Speaker 2: Every particle out there seems to have its weird twin.
Speaker 2: And we don't know if this is a detour in
Speaker 2: our path to finally understanding what is the fundamental nature
Speaker 2: of matter, or if it's a crucial side quest to
Speaker 2: get a clue that will help us unlock the deepest mystery.
Speaker 2: We don't know if and of matter is necessary, we
Speaker 2: don't know what role it plays, We don't really know
Speaker 2: what clue it's giving us about the nature of the universe.
Speaker 1: And so to the other podcast, we'll be asking the
Speaker 1: question why do we have anti particles? Feel like that's
Speaker 1: a weird double negative question, like why don't we have particles?
Speaker 1: Or why do we have anti particles? What's the correct
Speaker 1: grammar here or is it in Greek?
Speaker 2: I think why do we have anti particles? Is the
Speaker 2: deep question? You know, every time we see something in
Speaker 2: the universe, we wonder like, hmmm, did it have to
Speaker 2: be this way? Is this necessary? Is this a clue
Speaker 2: as to the fundamental nature of the universe or just
Speaker 2: sort of like a random accident.
Speaker 1: Well, so, as usual, we were wondering how many people
Speaker 1: out there had thought about this question or have any
Speaker 1: ideas about why we have anti particles.
Speaker 2: So thank you very much to everybody who answers these
Speaker 2: questions for this fun segment of our podcast. If you
Speaker 2: would like to play along next time, please don't be shy.
Speaker 2: Write to me two questions at Danielandjorge dot Com.
Speaker 1: So think about it for a second. Why do you
Speaker 1: think we have anti particles? Here's what people had to say.
Speaker 3: In general, antiparticles exist because particles exist and there's some
Speaker 3: sort of balance that was broken at.
Speaker 1: The Big Bang.
Speaker 4: I don't know, but the universe seems to like symmetry,
Speaker 4: and somehow antiparticles had to exist for some kind of
Speaker 4: symmetry to be to be fulfilled. But I don't know.
Speaker 4: It's kind of crazy.
Speaker 1: I think anti particles exist for the same reason you
Speaker 1: don't get monopole magnets.
Speaker 2: But I'm got clear, so we'll say with me, well
Speaker 2: maybe not.
Speaker 3: I feel like you need the antiparticles like cancel it out,
Speaker 3: because you can't have like something from nothing. You need
Speaker 3: to have something and then the opposite of it, so
Speaker 3: that like overall nothing has changed.
Speaker 5: Any particles are probably like the ying and yang. For
Speaker 5: every particle, there has to exist an anti particle in
Speaker 5: order to balance the forces in the universe, similar to
Speaker 5: matter and anti matter.
Speaker 6: I think the reason why antiparticles exist is because everything
Speaker 6: in nature and physics seems to be balanced. So if
Speaker 6: you sum up everything, it comes off like zero. But yeah,
Speaker 6: for everything that exists, there needs to be an anti
Speaker 6: thing Somemari like Ying and Young.
Speaker 1: All right, some very philosophical answers here, some of them
Speaker 1: kind of zen.
Speaker 2: Yeah, there's a lot of philosophy in these questions, you know,
Speaker 2: wondering whether the universe could have multiple explanations or just
Speaker 2: one explanation, or whether it has any explanation at all,
Speaker 2: whether it makes sense, and whether it's sensible to human minds.
Speaker 2: All that stuff is tied up in this quest to
Speaker 2: understand the universe.
Speaker 1: Do you think maybe there are anti particle scientists out
Speaker 1: there and or cartoonists we're wondering why do we have particles?
Speaker 1: What is this weird stuff?
Speaker 2: I don't know, but humans are capable of developing science
Speaker 2: as well as antiscience. More recently, I'm.
Speaker 1: Just antiphysics, I like all the other sciences.
Speaker 2: Are you antiphysics or are you anti physicists?
Speaker 1: I'm anti answering that question and that's an answer to
Speaker 1: that a position there. Well, let's dig into it, Daniel Water,
Speaker 1: anti particles is it like antimatter exactly?
Speaker 2: Anti particles are what make up anti matter. So matter
Speaker 2: is the stuff that we find around us that you
Speaker 2: were made of. That I am made out of everything
Speaker 2: you have ever eaten is made out of particles that
Speaker 2: we call matter particles. So you and I are made
Speaker 2: out of protons, neutrons, and electrons, and those protons and
Speaker 2: neutrons are made up of quarks. Anti matter is made
Speaker 2: up of anti particles, so you could have, for example,
Speaker 2: anti hydrogen is made of an anti proton and an
Speaker 2: anti electron, where the anti proton is then made of
Speaker 2: anti quarks. So there's a close connection, of course between
Speaker 2: anti matter and anti particles.
Speaker 1: I see. So particles are the little things that we're
Speaker 1: all made out of, and some of them have anti
Speaker 1: versions of them. Do all particles have anti versions or
Speaker 1: only some of them? Like do the force particles have
Speaker 1: anti force particles?
Speaker 2: Great question, sort of yes and no. All the particles
Speaker 2: have anti particles, but some of them are their own
Speaker 2: anti particles, so I'm not sure if that counts as
Speaker 2: having an anti particle. So, for example, the electron has
Speaker 2: an antiparticle the positron, and the muon has an anti
Speaker 2: particle the anti muon, and the quarks have antiparticles the
Speaker 2: anti quarks. Those are different particles, or you could think
Speaker 2: of them as two parts of the same pair. But
Speaker 2: they are distinct states. But then particles, like you said,
Speaker 2: the force carrying particles like the photon, the photon is
Speaker 2: its own anti particle, and so you might also say
Speaker 2: it doesn't have an anti particle. But I'd like to
Speaker 2: think about it as one particle playing two roles.
Speaker 1: What about some of the other force particles, do they
Speaker 1: have anti versions?
Speaker 2: Well, there are two w bosons, and they are each
Speaker 2: other's antiparticles. So you have the W plus and the
Speaker 2: W minus for example. So those two force particles are
Speaker 2: each other's anti particles, which is why we have two
Speaker 2: of them. The Z boson is its own antiparticle, and
Speaker 2: the gluon is actually eight gluons, all of different colors,
Speaker 2: and some of them are each other's antiparticles. So you
Speaker 2: can have like a red anti green gluon, which is
Speaker 2: the antiparticle to the anti red green gluon. It gets
Speaker 2: really colorful with gluons.
Speaker 1: Well, I feel bad for those particles that are their
Speaker 1: own anti versions of themselves. It's like they're their own
Speaker 1: worst enemies.
Speaker 2: Or maybe they're lonely. Right, one is the loneliest number.
Speaker 1: After all, this should hang out together.
Speaker 2: Some people confuse anti matter with dark matter, And there's
Speaker 2: lots of mysteries in particle physics, right, lots of things
Speaker 2: that we don't understand about the universe, But those are
Speaker 2: two separate mysteries. Dark matter is the invisible matter that's
Speaker 2: out there in the universe that we know is holding
Speaker 2: galaxies together and shaping the whole development of the large
Speaker 2: scale structure of the universe. We don't know what it is,
Speaker 2: and if it's made of particles, that's a different idea
Speaker 2: from antimatter. Antimatter is a real thing that we can make,
Speaker 2: that we can study. We've seen it in our detectors.
Speaker 2: We know for sure that it exists and it's made
Speaker 2: of anti particles.
Speaker 1: Well, I guess maybe the question now is how do
Speaker 1: you make antimatter? Can you make it or does it
Speaker 1: exist in nature or is it just a matter of
Speaker 1: like flipping the sign on some quantum property of regular particles.
Speaker 2: So sort of all of the above. Antimatter isn't very common.
Speaker 2: The universe is almost entirely made of matter, meaning it's
Speaker 2: made of particles instead of anti particles, but sometimes antimatter
Speaker 2: is produced, though it doesn't last very long because it
Speaker 2: runs into normal particles and annihilates but for example, the
Speaker 2: discovery of anti I mapps, which led to the nineteen
Speaker 2: thirty three Nobel Prize, was from naturally produced antimatter. So
Speaker 2: a positron the opposite particle to an electron produced in
Speaker 2: cosmic rays, meaning high energy collisions of particles from space
Speaker 2: hitting the upper atmosphere and creating antimatter which then showered
Speaker 2: down to the surface of the Earth.
Speaker 1: So when was this When was the first time we
Speaker 1: saw antimatter?
Speaker 2: So it was first observed in the late nineteen twenties.
Speaker 2: It was predicted by Paul Durack, the quantum physicist, who
Speaker 2: saw the mathematical need for them in his equations, and
Speaker 2: he said, hm, my equations predict there should be electrons
Speaker 2: and should also be another particle with the opposite charge
Speaker 2: as the electron. So he predicted it, and then Carl
Speaker 2: Anderson saw it. We have a whole fun podcast episode
Speaker 2: about the discovery of antimatter and the twists and turns
Speaker 2: and the egos involved. It's a really fun story. Check
Speaker 2: that out. We've known about it for almost one hundred
Speaker 2: years now.
Speaker 1: It sort of involves cloud chambers, right, which is something
Speaker 1: you can usually find in most science museums.
Speaker 2: Yeah, early particle physics didn't have fancy digital electronics and
Speaker 2: the complicated detectors we have now. They had to use
Speaker 2: techniques to observe the paths of these particles with the
Speaker 2: technology they had. And one thing you can do to
Speaker 2: illuminate what particles are flying through the air around you
Speaker 2: is to create clouds of water vapor. If you have
Speaker 2: air that's super saturated with water, meaning it actually has
Speaker 2: more water in it than it likes to have, then
Speaker 2: it's very easy to knock that water out of the air,
Speaker 2: and a passing charge particle will do just that and
Speaker 2: will create a string of droplets in the air. You
Speaker 2: can actually create cloud chambers at home. Check out lots
Speaker 2: of YouTube videos for how to do this. You can
Speaker 2: build one in your garage. You can see them at
Speaker 2: science museums and so you can see high energy particles
Speaker 2: streaming through the air around you, muons and all sorts
Speaker 2: of stuff. Carl Anderson proved that a fraction of these
Speaker 2: are actually anti matter particles, and he did that by
Speaker 2: showing how they curve differently in magnetic fields. Because magnetic
Speaker 2: fields will change the path of a charge particle depending
Speaker 2: on the charge. A positive charge will be in it
Speaker 2: one way. A negative charge will bend it the other way.
Speaker 2: So he saw particles that had the same mass as electrons,
Speaker 2: but bend in the other.
Speaker 1: Direction like a positively charged electron. Is that basically what
Speaker 1: an anti electron is, Just an electron with a charge flip.
Speaker 2: Yeah, that's what antiparticles are. They're just like their particle counterparts,
Speaker 2: but they have the opposite charges, so the opposite electric charge,
Speaker 2: the opposite weak charges, and the opposite color charges. So
Speaker 2: in the case of the electron, it's basically a positively
Speaker 2: charged electron.
Speaker 1: Right, because I guess an electron doesn't have the weak
Speaker 1: charge and it doesn't have the strong charge.
Speaker 2: Right, Electrons do have the weak charge. Actually, remember, the
Speaker 2: weak force is actually unified with electromagnetism into one force
Speaker 2: we call electro week, and electrons can interact via the
Speaker 2: weak force. They can emit w's for example, that's how
Speaker 2: beta decay happens. So electrons interact with the weak force.
Speaker 2: In fact, every particle we've ever seen interacts with a
Speaker 2: weak force, which is fascinating because the other forces are
Speaker 2: not so democratic. The strong force only interacts with quarks
Speaker 2: and not at all with electrons or neutrinos, and electromagnetism
Speaker 2: doesn't interact with neutrinos. But we've never found a particle
Speaker 2: that doesn't have any kind of weak charge. Every particle
Speaker 2: out there so far we discovered interacts with the weak force.
Speaker 1: Wait, what's the name of the week charge? If you
Speaker 1: have a week charge, what is that called?
Speaker 2: Well, there's actually two different week charges. One of them
Speaker 2: is called weak isospin and the other one is called
Speaker 2: weak hypercharge. But you can combine them actually to make
Speaker 2: electromagnetic charge. So there's two different charges for the electro
Speaker 2: weak force, but one of them is really from electromagnetism.
Speaker 1: I'll pretend I totally understood that. But I guess when
Speaker 1: you're trying to make an anti electron, which one do
Speaker 1: you flip? Do you flip the electromagnetic charge like the
Speaker 1: you know, plus and minds that we're all familiar with,
Speaker 1: or do you flip one of these other sub charges?
Speaker 1: And if you do, do I mean there are several
Speaker 1: versions of an anti electron.
Speaker 2: Now you flip all the charges. So there's only one
Speaker 2: version of a positron, and it has a positive electric charge.
Speaker 2: It also has both of its weak charges flipped.
Speaker 1: But what if you flip one and the other you
Speaker 1: can't do that, man, don't do that. They'll tell you
Speaker 1: why not to do, tell you why I can't do it.
Speaker 1: Then I can choose whether or not I can't.
Speaker 2: I will do it. It's not me, man, it's the
Speaker 2: laws of the universe. No, we do not see particles
Speaker 2: where only one charge is flipped and the other one
Speaker 2: is not.
Speaker 1: Why not.
Speaker 2: Yeah, that's a very cool question, imagining particles that are
Speaker 2: particles according to one force and anti particles according to
Speaker 2: another force. Remember, we recently answered a question about whether
Speaker 2: it even matters whether you're calling something matter or antimatter,
Speaker 2: and turns out that's totally an arbitrary distinction. So it
Speaker 2: doesn't really matter if one force considers a particle matter
Speaker 2: and the other one considers a particle the anti matter.
Speaker 2: But the forces do have to be consistent, and in
Speaker 2: the case of the weak force and electromagnetism, for example,
Speaker 2: they are tightly linked, so you can't just flip one
Speaker 2: and not the other. The charges of the two forces
Speaker 2: really are connected by the structure of the theory.
Speaker 1: I think what you're what you're saying, is this matter
Speaker 1: anti matter distinction is really kind of arbitrary kind of right,
Speaker 1: Like it's not as clear cut, like maybe there are
Speaker 1: shades of gray or shades of antiness.
Speaker 2: Yeah, we definitely don't claim to understand everything there is
Speaker 2: to know about antimatter. But I think you're right A
Speaker 2: lot of this comes down to just like what do
Speaker 2: you call matter and what do you call antimatter. A
Speaker 2: crucial idea is that there are these symmetries that you
Speaker 2: can flip these charges and the equations still work, that
Speaker 2: the universe can do both of these things, and so
Speaker 2: it does in some cases. We have like multiple ways
Speaker 2: to categorize what is matter and what is antimatter.
Speaker 1: Well, I think the thing that most people probably remember
Speaker 1: about antimatter, and that maybe is relevant here, is that
Speaker 1: like a matter particle and it's antimatter particle, if they touch,
Speaker 1: then they annihilate. They become pure energy. Right, We've talked
Speaker 1: about that before they explode. That's one of the things
Speaker 1: about antimatter.
Speaker 2: Particles and their antiparticles can annihilate into a force particle.
Speaker 2: So for example, an electron and a positron can come
Speaker 2: together to make a photon or a z boson and
Speaker 2: a and an anti quark can come together to make
Speaker 2: a glue on, and the opposite can happen. Also, a
Speaker 2: photon can turn into a matter antimatter pair, or a
Speaker 2: z boson can decay into a muon and its anti particle.
Speaker 1: But then I guess if anti nus is kind of
Speaker 1: relative or there's a gray area there, or how does
Speaker 1: that affect the annihilation? Like if I take a cork
Speaker 1: and an antiquark, but I flip some other other signs,
Speaker 1: do they still annihilate?
Speaker 2: They can annihilate if there is a particle that carries
Speaker 2: their combined charges. So for example, an electron and a
Speaker 2: positron can annihilate because in total they have zero electric
Speaker 2: charge and the photon has zero electric charge. That's why
Speaker 2: an electron cannot annihilate with another electron, because then you'd
Speaker 2: have to have a particle with a minus two charge
Speaker 2: in order to conserve electric charge. So the same thing
Speaker 2: goes for the other charges.
Speaker 1: So like if I have a green cork and an
Speaker 1: anti green cork, but a given different you know, regular charges,
Speaker 1: what's gonna happen? Are they going to annihilate or repel
Speaker 1: each other? Or what I'm just trying to get at,
Speaker 1: Like what it means to be anti mime. Is it
Speaker 1: depending on this annihilation thing or is it kind of random.
Speaker 2: It's a little bit more complicated for the color charge
Speaker 2: because gluons themselves are colored. You know, the photons don't
Speaker 2: have any charge for example, right, so it's simple plus
Speaker 2: and minus annihilate to zero charge photons. In the case
Speaker 2: of gluons, gluons do carry color. In fact, they carry
Speaker 2: two colors, which is even more confusing. So for example,
Speaker 2: a red anti green quark can combine to make red
Speaker 2: anti green gluon. The glue on itself carries two of
Speaker 2: those colors, but the gluons don't carry electric charge, so
Speaker 2: this can only happen for quarks that have opposite electric
Speaker 2: charges that can balance out to zero electric charge. So
Speaker 2: one way to think about how to pair particles and
Speaker 2: antiparticles is whether they can annihilate into these force particles.
Speaker 1: I see, So maybe one particle can have multiple anti
Speaker 1: versions of itself.
Speaker 2: There are definitely multiple different versions of quarks that an
Speaker 2: individual quark can annihilate with to create a gluon. Because
Speaker 2: there are so many different kinds of gluons, they always
Speaker 2: have to have opposite electric charges. Because the gluons don't
Speaker 2: have electric charge, So yeah, it gets really complicated when
Speaker 2: you're talking about the color charges because there's multiple different
Speaker 2: color charges and the gluons carry them themselves, and so
Speaker 2: the whole thing is a big mess.
Speaker 1: Is that how you end every physics paper? YadA YadA,
Speaker 1: YadA YadA, And it's all a big mess.
Speaker 2: It's a big mess, and it's a glorious puzzle and
Speaker 2: we're still working to try to figure it out. Yeah.
Speaker 1: Cool, Well, I guess the big question is still why
Speaker 1: do we have anti particles at all? Why do they
Speaker 1: exist in the universe? And so let's dig into that
Speaker 1: question and some of the other open questions about antimatter.
Speaker 1: But first let's take a quick break. All right, we're
Speaker 1: talking about antimatter antiparticles and why do we need them
Speaker 1: at all? Which sounds like a very insensitive question.
Speaker 2: What the deepest question we ask when we see something
Speaker 2: in the universe, We ask like, why is it this
Speaker 2: way and not some other way? Does it have to
Speaker 2: be this way? Is the universe parsimonious, like it only
Speaker 2: contains things that have to happen? Or is it sort
Speaker 2: of like baroque that has all sorts of flourishes that
Speaker 2: it doesn't really need, and it's just sort of beautiful.
Speaker 2: We tend to think of the universe as parsimonious. We
Speaker 2: try to take every piece that we find and fit
Speaker 2: it into the puzzle to explain why the universe works
Speaker 2: this way.
Speaker 1: Well, I guess one of the reasons we as we
Speaker 1: talked about last time, that we call some things matter
Speaker 1: and something's antimatter, is that we mostly see matter out
Speaker 1: there in the universe, at least as far as we know.
Speaker 1: Our planet, our Solar System, our galaxy is made out
Speaker 1: of regular matter, and there's a big mystery about why
Speaker 1: there isn't as much antimatter in the universe. But maybe
Speaker 1: one question that you can ask is, like, is matter
Speaker 1: and antimatter made at the same rate in the universe.
Speaker 1: Like if you run a particle collision experiment and you
Speaker 1: create some energy and some particles spill out to matter,
Speaker 1: particles get made as much as antimatter particles.
Speaker 2: A little bit on what you start from. I mean,
Speaker 2: if you start from particles of matter, then you're going
Speaker 2: to get more matter particles than antimatter particles. If you
Speaker 2: start from antimatter particles, then you're going to get more antimatter,
Speaker 2: and we actually ran a whole collider that smashed matter
Speaker 2: versus antimatter. Now, was the collider outside Chicago, the Tevatron,
Speaker 2: collided protons with anti protons, and so there we got
Speaker 2: even splits of matter and antimatter. Whereas the collider at Cerne,
Speaker 2: the Large Hadron Collider, smashes protons with protons because antimatter
Speaker 2: was such a big headache to produce for the other collider,
Speaker 2: And so there we get more matter produced than antimatter
Speaker 2: because we're starting from matter. But most of these processes
Speaker 2: are symmetric.
Speaker 4: Right.
Speaker 2: If you just have a big pile of photons and
Speaker 2: you wait for them to decay, they will produce an
Speaker 2: equal number of positrons and electrons.
Speaker 1: I see. So I guess the big mystery is that
Speaker 1: it sounds kind of like the universe is able to
Speaker 1: make equal amounts of both kinds of matter, but what
Speaker 1: we see in the universe is mostly only one kind
Speaker 1: of matter.
Speaker 2: Yeah, we suspect that the very early universe, matter and
Speaker 2: antimatter were created at the same rates that as the
Speaker 2: universe cooled down from the frothing pile of quantum fields
Speaker 2: and things got cold and isolated enough that you could
Speaker 2: call things particles, that the particles and anti particles existed
Speaker 2: at basically the same level. Then there was a huge
Speaker 2: amount of annihilation, as you can imagine, and most of
Speaker 2: the matter and antimatter went away and turned into radiation.
Speaker 2: But a little bit more matter is left over than antimatter,
Speaker 2: and we don't understand the source of that discrepancy, even
Speaker 2: though it's the reason why we have matter galaxies and matter,
Speaker 2: stars and matter, people and matter chocolate and not anti matter.
Speaker 2: The universe seems to have some preference for matter over antimatter.
Speaker 1: Which makes me ask the question, is anti chocolate vanilla
Speaker 1: or white chocolate or is it a case of having
Speaker 1: multiple antiversities?
Speaker 2: I hope so, because neither of those things should be
Speaker 2: categorized with chocolate.
Speaker 1: You're just pro chocolate. You just anti everything that's.
Speaker 2: I'm just anti calling things chocolate that aren't chocolate. Even
Speaker 2: calling them anti chocolate somehow groups them to get they're
Speaker 2: in that chocolate category where they don't belong.
Speaker 1: What about vegan chocolate, not chocolate.
Speaker 2: No, totally chocolate. It comes from the cocoa bean.
Speaker 1: Yeah, absolutely, all right, Well, the big question is why
Speaker 1: does it exist? At all. Why do we have antimatter,
Speaker 1: Like is it something that the equations of the universe
Speaker 1: requires or is it just something that seems to happen.
Speaker 1: That's the big question, right.
Speaker 2: That's the question, and the short answer is we don't know.
Speaker 2: But what's really fascinating is that without antimatter, some of
Speaker 2: our basic theories of physics don't work very well together.
Speaker 2: Like we have relativity and we have quantum mechanics, both
Speaker 2: things that we think make sense in the universe, but
Speaker 2: when we try to bring them together, we get some conflicts.
Speaker 2: And it turns out that antimatter resolves those conflicts and
Speaker 2: lets us bring special relativity and quantum mechanics together into
Speaker 2: one theory.
Speaker 1: Wait, I thought those two things didn't like each other.
Speaker 2: So we have two different theories of relativity, special relativity,
Speaker 2: which tells us about what happens and things move really
Speaker 2: really fast near the speed of light, and then general relativity,
Speaker 2: which tells us how space bends in the presence of mass.
Speaker 2: General relativity and quantum mechanics we do not know how
Speaker 2: to combine into a theory of quantum gravity. That's something
Speaker 2: for a future physicist, maybe one of our listeners, to
Speaker 2: figure out, but special relativity and quantum mechanics we do
Speaker 2: know how to combine, and we've had that for many,
Speaker 2: many decades. So that's basically relativistic quantum mechanics, and that
Speaker 2: is something that we know how to do thinking about
Speaker 2: quantum particles and moving near the speed of light, and
Speaker 2: we do that all the time in our particle colliders, right,
Speaker 2: it happens all the time that we have high speed particles.
Speaker 2: So relativistic quantum mechanics we can do bend space, curved space.
Speaker 2: Quantum mechanics we don't know how to do.
Speaker 1: Interesting. Okay, So you're saying somehow antimatter and antiparticles somehow
Speaker 1: make quantum mechanics and special relativity work together. What does
Speaker 1: that mean?
Speaker 2: So it all has to do with preserving causality, and
Speaker 2: special relativity makes it really hard to think about causality,
Speaker 2: to think about the order that things happen in the universe,
Speaker 2: because it forces us to think about the order of
Speaker 2: events in a very different way than like Newton thought
Speaker 2: about things, and the way that we intuitively think about things.
Speaker 2: You probably think about the universe happening as if there's
Speaker 2: like a giant clock and the whole universe like ticks
Speaker 2: forward and then the next thing happens, and the universe
Speaker 2: ticks forward and the next thing happens. But you can
Speaker 2: think of the whole universe as having like one clock,
Speaker 2: so you can tell like one story about what happened
Speaker 2: in the universe. Special relativity tells us that that's not
Speaker 2: actually true, that there's lots of different clocks in the universe,
Speaker 2: and how fast they tick depends on where you are
Speaker 2: and how fast they're moving relative to you, So you
Speaker 2: can actually tell lots of different stories about what happened
Speaker 2: in the universe, even stories that conflict with each other,
Speaker 2: that contradict each other about the order in which events happen.
Speaker 1: Yeah, I know. We've talked about this before and include
Speaker 1: it in our book. It's kind of this idea that
Speaker 1: if two people run a race, you think that whoever
Speaker 1: wins would be clear, but it sort of depends on
Speaker 1: how fast they're moving and how fast the judges moving,
Speaker 1: or how fast you're moving as an observer.
Speaker 2: Right, Imagine two people running a race, but instead of
Speaker 2: running alongside each other on a track the way people
Speaker 2: typically do, imagine them starting in the same place but
Speaker 2: running opposite directions. This makes it easier to think about
Speaker 2: because they end up far apart from each other. If
Speaker 2: you're standing at the starting line and you're not moving
Speaker 2: relative to the starting line, imagine these two runners run
Speaker 2: at the same speed relative to you. You call it
Speaker 2: a tie. But if somebody else is flying along in
Speaker 2: a spaceship alongside one of these runners, they see the
Speaker 2: two runners moving at different speeds relative to them, and
Speaker 2: moving clocks run slow, which means they see one of
Speaker 2: these runners in slow motion relative to the other one,
Speaker 2: So they'll think one of the runners wins the race
Speaker 2: and the other one is slower. But another judge going
Speaker 2: the opposite direction sees the same thing, but flipped. He
Speaker 2: sees the first runner's clock running slow, so he thinks
Speaker 2: the second runner wins the race. So who you think
Speaker 2: wins the race depends on the speed you're going relative
Speaker 2: to the runners. Like people can honestly disagree about the
Speaker 2: order of events, did the first runner reach the finish
Speaker 2: line first or did the second runner reach the finish
Speaker 2: line first. This is not a case of like people
Speaker 2: being confused or mistaken or getting things wrong. It means
Speaker 2: that there are multiple true stories about what happened. In
Speaker 2: the universe that conflict with each other.
Speaker 1: Well, there's sort of one story, right, It's just when
Speaker 1: you transform it between points of views, the order of
Speaker 1: events changes.
Speaker 2: Yeah. That sounds to me like multiple stories. But you're
Speaker 2: right that we can link them together. Special relativity tells
Speaker 2: us how to predict what any observer will see. And
Speaker 2: what special relativity says is that different observers will see
Speaker 2: the order in different events. The laws of physics are
Speaker 2: consistent from frame to frame, and they predict the observers
Speaker 2: tell different stories. Yeah, so you can think about that
Speaker 2: as like one coherent understanding.
Speaker 1: Yeah, that's what I mean. It's not like there's two realities.
Speaker 1: Nobody can ever figure this out. It's more like, you know,
Speaker 1: everyone has to agree on which observer they're measuring your
Speaker 1: race by.
Speaker 2: Right, that's right. It means that the order of events
Speaker 2: is not universal, right, that it's dependent on the observer.
Speaker 1: Well, or it is universal, as you said, it changes
Speaker 1: depending on what you ask.
Speaker 2: Yeah, it depends on the observer. Right, It's not something
Speaker 2: everybody agrees on will happen from their point of view. Right,
Speaker 2: Different points of view will see a different order of events,
Speaker 2: and that's very confusing when you think about causality because
Speaker 2: you think, like you know, there should be an order
Speaker 2: two events, Like you can't finish the race before you
Speaker 2: start it, you can't receive a message before you send it.
Speaker 2: You can't die before you're born. There are some things
Speaker 2: send in the universe where there's a causal link between them, right,
Speaker 2: and so they have to happen in a certain order.
Speaker 1: All right, Well, what does that mean for causality and antimatter?
Speaker 2: Then well, you might think that this makes the universe nonsense,
Speaker 2: because if different people can see events order different ways,
Speaker 2: does not just break causality. Does that mean you can
Speaker 2: eat an apple before it's grown? Does that mean you
Speaker 2: can get a message before it's sent? This kind of stuff, Well,
Speaker 2: special relativity has some protection built in for that, right,
Speaker 2: It says this can only happen for things that are really,
Speaker 2: really far apart, things that are so far apart that
Speaker 2: light can't pass between them. We call these space like
Speaker 2: events instead of timelike events. And so you can reorder
Speaker 2: events that are really really far apart because they're already
Speaker 2: not causally connected. If two things are so far apart
Speaker 2: that light couldn't pass between them, then there's no way
Speaker 2: for them to have a causal connection. You can't like
Speaker 2: send a message from one to the other. And so
Speaker 2: things that are already causally not connected. Those things you
Speaker 2: can reorder by traveling at some crazy speed. Things that
Speaker 2: are causally connected, Like if you turn on a flashlight
Speaker 2: and then the beam arrive somewhere else, there's enough time
Speaker 2: for light to get from one to the other. You
Speaker 2: can't reorder those events just by going faster or.
Speaker 1: Slower, all right, So then how does that figure into antimatter?
Speaker 2: So these events that you can't reorder, those are things
Speaker 2: we call inside our light cone. Light cone are things
Speaker 2: that we can affect in our future, and there's things
Speaker 2: that affected us from the past. So that special relativity,
Speaker 2: and it has this nice causal connection for things inside
Speaker 2: your light cone. Things outside your light cone, they can
Speaker 2: get reordered by things going fast or slow. Quantum mechanics, however,
Speaker 2: doesn't naturally obey this rule. Quantum mechanics has weird limitations
Speaker 2: on how much you can know about objects momentums, and velocities. So,
Speaker 2: for example, you measure a particle really really specifically. The
Speaker 2: Heisenbergen certainty principle tells you you can't know anything about
Speaker 2: its velocity, how fast it's going. So in principle, quantum
Speaker 2: mechanics allows things to go faster than the speed of light.
Speaker 2: That allows particles to move from one place to another
Speaker 2: outside the light cone because they could be going faster
Speaker 2: than the speed of light. Quantum mechanics doesn't have the
Speaker 2: speed of light built into it naturally, it allows particles
Speaker 2: to violate this speed limit. WHOA well.
Speaker 1: On they think quantum mechanics can break the speed of light.
Speaker 1: That sounds a little bit too much, Daniel. I think
Speaker 1: you mean maybe, like our math allows it to, but
Speaker 1: we don't know if in reality it can go faster
Speaker 1: than light. Doing If you just.
Speaker 2: Start from sort of low speed quantum mechanics, the original
Speaker 2: quantum mechanics that was developed right, non relativistic quantum mechanics
Speaker 2: for slow moving particles, then that theory with the Heisenberg
Speaker 2: uncertainty principle doesn't respect the speed limit of the universe.
Speaker 2: It's only when you try to bring quantum mechanics and
Speaker 2: special relativity together to make a theory of relativistic high
Speaker 2: speed particles that you have to answer this question like, uh, oh,
Speaker 2: what happens if particles that quantum mechanics predicts can go
Speaker 2: faster than the speed of light. What does special relativity
Speaker 2: say about that? So it's you know, in trying to
Speaker 2: bring the mathematics in harmony with the universe, that we
Speaker 2: run into this problem. We're like, hold on a second.
Speaker 2: Quantum mechanics has this problem with causality. It allows things
Speaker 2: to move outside your light cone. What's going on and between?
Speaker 2: You bring these two things together, that antiparticles save the
Speaker 2: day and allow you to bring quantum mechanics and special
Speaker 2: relativity together in a way that makes perfect sense.
Speaker 1: I think maybe what you mean is that antimatter says
Speaker 1: physicism because their original theory made no sense.
Speaker 2: Yeah, you cannot bring quantum mechanics and special relativity together
Speaker 2: without anti particles.
Speaker 1: Right, It's like the limitations of the theory would allow
Speaker 1: things to move faster than light, but probably in reality
Speaker 1: they don't.
Speaker 2: That's right. We think special relativity is the law of
Speaker 2: the universe. Nothing moves faster than light. Original old school
Speaker 2: quantum mechanics has this problem that allows things to move
Speaker 2: faster than the speed of light, potentially breaking causality. And
Speaker 2: you're right, we don't think that happens in reality, So
Speaker 2: we need to patch up the theory, and it turns
Speaker 2: out that we need antimatter in order to do that.
Speaker 1: All right, well, let's dig into how antimatter saves the day.
Speaker 1: It's sort of like a plot to is the villain
Speaker 1: actually turns out to be the good guy. So let's
Speaker 1: dig into that, and what does it mean about our
Speaker 1: understanding of matter, antimatter and all kinds of matters or
Speaker 1: in the universe. But first, let's take another quick break.
Speaker 1: All right, we're talking about antimatter antiparticles. Why do we
Speaker 1: have them? Why do we need them? It turns out
Speaker 1: that they're useful in making our theories work, which is
Speaker 1: not really I guess an answer to the question.
Speaker 4: Is it?
Speaker 2: Well, it's sort of an answer to the question. You know.
Speaker 2: It says that the universe needs this to be consistent,
Speaker 2: or our theories need this in order to be consistent
Speaker 2: description of the universe.
Speaker 1: Okay, so then you're saying that it somehow helps reconcile
Speaker 1: special relativity and quantum mechanics. How does it do that?
Speaker 2: So let's think about how quantum mechanics breaks causality. Right,
Speaker 2: Imagine you have like a particle that you emit right
Speaker 2: here at this moment, and quantum mechanics predicts that it
Speaker 2: has a probability to end up like in Andromeda ten
Speaker 2: seconds from now. That would break causality because if be
Speaker 2: outside your leg cone, it would be like getting to
Speaker 2: Andromeda faster than the speed of light. Nothing that we
Speaker 2: do right now should be able to affect Andromeda until
Speaker 2: millions of years into the future, because Andromeda is millions
Speaker 2: of light years away.
Speaker 1: I think you're saying, the quantum mechanics, we have a
Speaker 1: description of a particle here, and because there's uncertainty about
Speaker 1: where it can be, there's a certain probability that in
Speaker 1: the next second it can be right where it is now,
Speaker 1: or it can be a meter away or two meters away.
Speaker 1: And there's a very very very small possibility that in
Speaker 1: the next two seconds, according to the quantum mechanics, it
Speaker 1: can then be in Andromeda. That's kind of how you
Speaker 1: would describe it.
Speaker 2: Yeah, exactly if you have a lot of uncertainty on
Speaker 2: its momentum, because you've narrowed down its position super duper well,
Speaker 2: and Heisenbergen certainty principle tells you can't know both things
Speaker 2: at the same time. So if you know the position
Speaker 2: really really well, you don't know the momentum, and therefore
Speaker 2: there's a possibility that it has some crazy high momentum
Speaker 2: would be faster than the speed of light, getting it
Speaker 2: too Andrama in just ten seconds instead of the millions
Speaker 2: of years it should take. And this would be a
Speaker 2: problem for causality because those two events are spacelike. It's
Speaker 2: outside of our light cone, which means that somebody flying
Speaker 2: by in a spaceship could see them happen. In the
Speaker 2: other order, could see this particle arrive in Andromeda before
Speaker 2: it leaves our galaxy, which is nonsense. Right, So anything
Speaker 2: that moves faster than the speed of light breaks causality.
Speaker 2: That's one reason why we don't think things can move
Speaker 2: faster than the speed of light, because it would allow
Speaker 2: you to reorder events that are causally linked. Right, so
Speaker 2: make the universe nonsense.
Speaker 1: Well, it sort of sounds like quantum mechanics just breaks
Speaker 1: causality anyways, right. Quantum mechanics say that particles can just
Speaker 1: pop out of nowhere without any cause, So like quantum
Speaker 1: mechanics says that a particle can suddenly disappear here and
Speaker 1: appear in Andromeda.
Speaker 2: Why not now, I wouldn't say that quantum mechanics necessarily
Speaker 2: breaks causality. It makes a different description of the universe.
Speaker 2: It makes the universe probabilistic instead of deterministic. It says
Speaker 2: weird things can happen, like a photon can turn into
Speaker 2: an electron and a positron, or it could do something else.
Speaker 2: It says that the laws of the universe only predict
Speaker 2: what might happen instead of what does actually happen. But
Speaker 2: there is still causality, Like in quantum mechanics, the wave
Speaker 2: function right now is determined by the wave function in
Speaker 2: the past. Right The wave function itself doesn't specify exactly
Speaker 2: what will happen, only to probabilities, but the wave function
Speaker 2: is still determined by the past wave function, so there
Speaker 2: should still be logic in quantum mechanics.
Speaker 1: I guess that's weird because if you're saying that anything
Speaker 1: might happen, I.
Speaker 2: Would say anything might happen, you know quantum mechanics, as
Speaker 2: is the probability for things to happen. Some things are
Speaker 2: impossible even in quantum mechanics, like you can't violate conservation
Speaker 2: of electric charge right, Electrons have no probability to turn
Speaker 2: into positrons directly, because I would violate conservation of electric charge,
Speaker 2: which is built into our quantum mechanical theories.
Speaker 1: But haven't we talked about how like, according to quantum mechanics,
Speaker 1: a pink elephant could certainly you're out of nowhere outside
Speaker 1: of the Earth's orbit, right in space.
Speaker 2: Yeah, that's not impossible. That doesn't break any of the rules.
Speaker 1: But then we have no cause would it.
Speaker 2: Well, the cause would be that there's a distribution of
Speaker 2: probabilities for what those particles in the vacuum could do.
Speaker 2: They could sit there and do nothing. They could create
Speaker 2: one electron, they could create ten electrons, they could create
Speaker 2: forty two trillion electrons. They could create a Boltzmann brain,
Speaker 2: they could create a pink elephant. Those things are probabilities.
Speaker 2: What does our universe choose one particular probability and not another?
Speaker 2: What does it choose one that's like really unlikely, like
Speaker 2: a pink elephant in space, and not another that's more
Speaker 2: likely that we don't understand. That's like a deep question
Speaker 2: in quantum philosophy, whether all of them happen at once
Speaker 2: in different universes, whether the universe collapses these wave functions
Speaker 2: to choose one. Whether it even is truly random, That
Speaker 2: is definitely not something we know. But I wouldn't say
Speaker 2: there's no cause there's still like a distribution of probabilities
Speaker 2: for what might happen.
Speaker 1: Well, let's get back to the antimatter particle. How does
Speaker 1: that antimatter particle fit into this scenario.
Speaker 2: Then it turns out if you do these calculations, and
Speaker 2: you calculate like, okay, what's the probability for my particle
Speaker 2: to appear in and Drama in ten seconds from now,
Speaker 2: and you include antimatter, then those probabilities vanish. Because the
Speaker 2: probability for you to see a particle go to Andrama
Speaker 2: in ten seconds, there's another probability for a particle to
Speaker 2: go from Andromeda to here in ten seconds, for an
Speaker 2: antimatter particle to come the opposite direction. And because matter
Speaker 2: and antimatter have all the opposite properties, those two things
Speaker 2: quantum mechanically cancel each other out. So the antimatter nonsense
Speaker 2: cancels out the matter nonsense to make no nonsense. Whoa, whoa, whoa.
Speaker 1: Wait, we had this scenario of having one particle here
Speaker 1: that suddenly appears in Andromeda in ten seconds. You're saying,
Speaker 1: there's a different scenario in which an anti particle the
Speaker 1: exact antiparticle of my particle is where my particle would appear.
Speaker 1: That one disappears and appears where my current particle is
Speaker 1: at the same time, and somehow that cancels it out.
Speaker 1: But what are the chances that there's an antiparticle exactly
Speaker 1: where my particle would go.
Speaker 2: Well, all of this stuff is very unlikely. But when
Speaker 2: you do a quantum mechanical calculation, you sum over all
Speaker 2: the possibilities, and these equations are wave equations, so you
Speaker 2: can get like constructive interference and destructive interference and things
Speaker 2: where the probabilities cancel out, those things just don't happen.
Speaker 2: Like in the Devil's Slight experiment. You see interference places
Speaker 2: where lots of particles and places with no particles, the
Speaker 2: places where no particles land, and the interference on the
Speaker 2: screen is because there's been destructive interference among the probabilities.
Speaker 2: So when the probabilities cancel out, those things just don't
Speaker 2: happen in the universe, And so the probability for a
Speaker 2: particle to break special relativity and appear in Andromeda is
Speaker 2: canceled out by the probability for an antiparticle to do
Speaker 2: the opposite.
Speaker 1: Well, I guess what does it mean to cancel out
Speaker 1: the probability? That means that it's never going to happen.
Speaker 2: It means that it's never going to happen. And so
Speaker 2: if you bring quantum mechanics and special relativity together, you
Speaker 2: include anti particles, then it all clicks together perfectly and
Speaker 2: you get no violations of causality.
Speaker 1: But wait, the wouldn't that also cancel all movements like
Speaker 1: even a meter distance?
Speaker 2: Yeah, great question. It doesn't happen for things inside the
Speaker 2: light cone because things inside the light cone everybody agrees
Speaker 2: on the order, whereas things outside the light cone you
Speaker 2: can reorder them. So, for example, if I say, well, look,
Speaker 2: my particle left here and ended up in a drama
Speaker 2: in ten seconds, that's outside my light cone. So somebody
Speaker 2: else flying by in a spaceship might see them happen
Speaker 2: in the opposite order. Right. Seeing it happen in the
Speaker 2: opposite order is like seeing a particle go backwards in time,
Speaker 2: which is equivalent to the anti matter particle. Right, So
Speaker 2: both probabilities exist, the particle and anti particle version, because
Speaker 2: you can reorder them because they are outside your light cone.
Speaker 2: Things inside your light cone, you can't reorder them. Their
Speaker 2: order is fixed. Only things outside the light cone where
Speaker 2: you could reorder them, where somebody could see it as
Speaker 2: a part article and the other person could see it
Speaker 2: as an anti particle. Only those things cancel out.
Speaker 1: It feels a little convenient, like maybe saying like, oh,
Speaker 1: my theory breaks down after this limit. Let's just come
Speaker 1: up with something totally different and ex sort it only
Speaker 1: applies outside of this limit where my thing breaks.
Speaker 2: Yeah. Well, it's sort of convenient and sort of spooky, right.
Speaker 2: It's sort of like if you didn't know antiparticles existed
Speaker 2: and you were trying to bring quantum mechanics and relativity
Speaker 2: together into relativistic quantum mechanics, You're like, huh, this is
Speaker 2: a problem. This could be solved if, for example, there
Speaker 2: were the existence of antimatter hmm, and then you went
Speaker 2: out in the universe and you found it, You'd be like, wow,
Speaker 2: that was pretty cool. Here it's sort of works the
Speaker 2: opposite direction. We're like, no antimatter exists, and we can
Speaker 2: use it to help bring these two theories together. It
Speaker 2: is very convenient, but that's sort of like a glorious
Speaker 2: moment when you're like, oh wow, look these things. They
Speaker 2: sort of need to exist for the universe to be
Speaker 2: self consistent.
Speaker 1: Now, you said something earlier that was kind of interesting.
Speaker 1: You said, anti particles kind of go back in time.
Speaker 1: What does that mean?
Speaker 2: Well, mathematically you can look at it a particle moving
Speaker 2: forwards in time, and it's equivalent to an antimatter particle
Speaker 2: moving backwards in time. And you can sort of see
Speaker 2: that in this example we're talking about, where like, my
Speaker 2: particle goes from here to Andromeda, and it does it
Speaker 2: faster than the speed of light. Right. If it does
Speaker 2: it faster than the speed of light, that means that
Speaker 2: somebody else going by in a spaceship they could see
Speaker 2: it happen in the opposite order. They could see it
Speaker 2: arrive in Andromeda before it leaves my house in the
Speaker 2: milky way, right, which means that it's started in Andromeda.
Speaker 2: The first event is in Andromeda. So I could say, look,
Speaker 2: this is a particle going forwards in time faster than
Speaker 2: the speed of light. Somebody else could say, no, it
Speaker 2: goes the other direction. They could say, no, it's going
Speaker 2: from your future to your past. But I see it
Speaker 2: as an antimatter particle because they could reorder the events,
Speaker 2: and so they see it going from Andromeda to the
Speaker 2: Milky Way, and they see it moving as an antimatter particle.
Speaker 1: But I guess maybe in order to measure my particle
Speaker 1: here and there, don't I need to measure the particle,
Speaker 1: wouldn't they collapse the wave function and make this all
Speaker 1: kind of not really applicable.
Speaker 2: You would need to collapse the wave function absolutely, and
Speaker 2: of course it wouldn't really happen, right. That probability is
Speaker 2: actually zero. You can't collapse the wave function and make
Speaker 2: this happen. What we're talking about really is just a
Speaker 2: partial probability. There's another part to that calculation, the antimatter part,
Speaker 2: that cancels it out. So you can't actually do this right.
Speaker 2: You can't see a particle appear in Andromeda in ten seconds.
Speaker 2: It would take millions of years to get there, and
Speaker 2: the probability for that to happen is canceled out by
Speaker 2: the anti matter version, So that's why it just doesn't happen.
Speaker 1: Is this sort of like one of those virtual particle
Speaker 1: scenarios where like just a matter of fact that something
Speaker 1: else can happen, actually in a way happens canceling out
Speaker 1: other effects that are happening.
Speaker 2: Yeah, you can think about this the way other quantum
Speaker 2: mechanical weirdness happens, where like particles can interfere with themselves.
Speaker 2: Right again, like in the double slit experiment, if you
Speaker 2: don't know which slit the particle went through, has a
Speaker 2: probability to go through both, and those probabilities can actually
Speaker 2: interfere with themselves, So single particle interferes with itself. This
Speaker 2: is sort of the same deal. Like this single particle
Speaker 2: that goes from here to Andromeda, you could also be
Speaker 2: seen as an antimatter particle going the other direction, and
Speaker 2: those two probabilities cancel, which is why it never actually happens.
Speaker 1: All right, Well, then what is the I guess main
Speaker 1: takeaway is it that quantum mechanics does work with special activity,
Speaker 1: and it's because antimatter particles exist or are a possibility
Speaker 1: in the universe.
Speaker 2: That's exactly right. You need antimatter to bring quantum mechanics
Speaker 2: and special relativity together and not break causality. If we
Speaker 2: think the universe is causal, meaning that like there's a
Speaker 2: logical flow to things, that the past influences the future
Speaker 2: and not the deep past. Then you need antimatter in
Speaker 2: order to have special relativity and quantum mechanics. We just
Speaker 2: don't know how to do it without antimatter.
Speaker 1: Cool. All right, well, you've commissed me. I'm pro antimatter
Speaker 1: or I'm not anti antimatter.
Speaker 2: Does that mean that you're pro anti vanilla, which means
Speaker 2: you're willing to try some chocolate.
Speaker 1: I am pro anything with the word vanilla in it.
Speaker 2: Right, I'm part of the vanilla eradication project. How do
Speaker 2: you feel?
Speaker 1: Oh my god? And that is how this podcast got canceled. Daniel.
Speaker 1: Thank you, it's been a nice run. We're done.
Speaker 2: No, I love vanilla. Vanilla is wonderful.
Speaker 1: We've gone the way of Scott Adams and Dilbert.
Speaker 2: I'm not a flavorist. Okay, I'm definitely pro vanilla.
Speaker 1: I'm just more we think they're flavorists.
Speaker 2: Daniel, I need to go for some flavor sensitivity training.
Speaker 1: It sounds like, thank you, maybe you should examine those
Speaker 1: anti FeAs.
Speaker 2: All right, well, between this and the next episode, I
Speaker 2: will do a deep dive into my own internal flavor preferences.
Speaker 1: There you go examine your own anti matter. All right, Well,
Speaker 1: another interesting bit of how we're trying to figure out
Speaker 1: how the universe works, and how sometimes it's interesting how
Speaker 1: our theories of the universe actually kind of turn out
Speaker 1: to be true, which is kind of surprising, right.
Speaker 2: It is surprising sometimes, and that crazy little human brains
Speaker 2: can come up with mathematical stories that do seem to
Speaker 2: describe the universe, even in ways we didn't anticipate.
Speaker 1: All right, Well, thanks for joining us. We hope you
Speaker 1: enjoyed that. See you next time.
Speaker 2: Hey, everyone, I want to take a moment and share
Speaker 2: a personal message with you. When I record these podcasts,
Speaker 2: there's no live audience here, and so I have no
Speaker 2: idea really how they're going to be received. So I
Speaker 2: love hearing that they have an impact on people's lives,
Speaker 2: maybe inspiring you to think about the universe, or talk
Speaker 2: to your kids about physics, or even just keep your
Speaker 2: brain going on long drive or a boring shift at work.
Speaker 2: That's what gives me the energy to keep making these
Speaker 2: to put them out twice a week without fail for
Speaker 2: five years now. So it really heartens me to hear
Speaker 2: from you. But I realize that you all don't get
Speaker 2: to know each other as much to hear about these experiences.
Speaker 2: So I want to share a little bit with you,
Speaker 2: including an example that made me smile and one that
Speaker 2: frankly brought some tears to my eyes. First, a happy one,
Speaker 2: someone writes and says, I don't have a question but
Speaker 2: a compliment. Just wanted to let both of you know
Speaker 2: that I greatly appreciate the way you both explain physics.
Speaker 2: As a person who has no science background and barely
Speaker 2: passed college algebra, it's refreshing to hear people explain things
Speaker 2: without talking down to the listener. That's wonderful and it's
Speaker 2: exactly what we're trying to do, make physics more accessible
Speaker 2: to everybody without dumbing it down at all. But some
Speaker 2: of the messages we get are a little bit harder
Speaker 2: to hear. A woman wrote in that her brother is
Speaker 2: a listener and an ultrarunner, but that at thirty nine
Speaker 2: he had a massive stroke and faces a long recovery.
Speaker 2: She writes that quote each night he makes sure his
Speaker 2: phone is charged and loaded with enough Daniel and Jorgey
Speaker 2: to get him through the night. It's without drama that
Speaker 2: I say that your show is one of his lifelines,
Speaker 2: right now, you guys are his intellectual support above all,
Speaker 2: on behalf of our family. I want to thank you
Speaker 2: for your podcast and being a comfort to him in
Speaker 2: this season. Wow, it's hard to overstate how deeply that
Speaker 2: touches me, and I want to send him our encouragement
Speaker 2: on his road to recovery. I'm so glad that we
Speaker 2: can be there to help in this small way, and
Speaker 2: I want to say thank you to everyone out there,
Speaker 2: those of you who are listening and writing back or
Speaker 2: just enjoying silently. You're all the reason that I do this.
Speaker 2: Thanks for listening, and remember that Daniel and Jorge explain
Speaker 2: the Universe is a production of iHeartRadio. For more podcasts
Speaker 2: from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever
Speaker 2: you listen to your favorite shows.