Speaker 1: There are so many amazing, colossal mysteries out there, so
Speaker 1: many parts of the universe that are hidden from us
Speaker 1: that still need to be explained. I mean, you've got
Speaker 1: dark matter, you got anti matter, you've got dark energy,
Speaker 1: you got exotic matter, you got why anybody ever lives
Speaker 1: in Virginia. So many things to figure out. And I've
Speaker 1: noticed that lots of people out there, especially those folks
Speaker 1: of you who write into me, are drawn to the
Speaker 1: idea that some of these mysteries could be connected, that
Speaker 1: maybe you could like solve two of them at the
Speaker 1: same time. And I totally get why that's appealing, But
Speaker 1: usually it doesn't work. Could anti matter be the dark matter? No?
Speaker 1: Could dark matter explain dark energy? No? Is dark matter
Speaker 1: the reason people live in Virginia? Probably? Also?
Speaker 2: No?
Speaker 1: But sometimes, very rarely there is a chance to connect
Speaker 1: two things to help solve a mystery. And that's what
Speaker 1: we're gonna do today on the show when we answer
Speaker 1: the question could and I matter help us find dark matter?
Speaker 1: Welcome to Daniel and Kelly's Extraordinary Universe.
Speaker 3: Hello, I'm Kelly Wiener Smith, and I'm a biologist, and
Speaker 3: I'm feeling superior today because at least we know what
Speaker 3: parasites are made of.
Speaker 1: Hi, I'm Daniel. I'm a particle physicist, and I'm hoping
Speaker 1: that dark matter is somehow made of parasites. So I
Speaker 1: can blame Kelly for not figuring it out sooner.
Speaker 3: Oh, we've got to figured out.
Speaker 1: Man.
Speaker 3: If it ends up in our wheelhouse, dark matter will
Speaker 3: be solved in no time.
Speaker 1: What about biological dark matter? If you figured all that out?
Speaker 3: Are you talking about poop?
Speaker 1: And there we are, folks, record time from zero to
Speaker 1: poop for biologists.
Speaker 3: You know, I'm surprised I made it this long with
Speaker 3: the biologist in the room. You do what you can.
Speaker 1: But yes, there's an enormous amount about how our bodies
Speaker 1: work and how it makes poop that we don't understand.
Speaker 1: So there's dark matter in every field.
Speaker 4: You know.
Speaker 3: I would say we understand it, probably much better than
Speaker 3: the dark matter in physics. But I guess your wife
Speaker 3: does a lot of biology dark matter experiments, and do
Speaker 3: you might say there's a lot we don't know.
Speaker 1: Yes, and she has written grand proposals making that exact
Speaker 1: pun as a veiled Pooh reference.
Speaker 3: So I can only imagine how much fun it must
Speaker 3: be to study feces. There's a lot of opportunities for jokes.
Speaker 1: That's right. We try to avoid crappy humor, but you
Speaker 1: know you can't escape it.
Speaker 3: Oh, it's so great sometimes you need it. All right,
Speaker 3: all right, we'll talk about physics dark matter today. How
Speaker 3: long do you think before we have that figured out?
Speaker 1: Wow? When are we going to figure out dark matter?
Speaker 1: You know, it's incredible because it's been decades that we've
Speaker 1: known this is a thing and not understood it. And
Speaker 1: the discovery could be any moment. We have lots of
Speaker 1: ways we're looking for it that could suddenly reveal something
Speaker 1: about dark matter. We could find a dark photon that
Speaker 1: communicates the whole new sector of particles. One of the
Speaker 1: experiments could actually see a signal, So it could be
Speaker 1: any moment. It's really impossible to predict. Or we could
Speaker 1: keep looking fruitlessly for a century. The possibilities are really
Speaker 1: almost endless. It's impossible to predict. I hope you figured
Speaker 1: it out soon before I retire. Perspire and expire.
Speaker 3: Don't exercise too hard, Daniel.
Speaker 1: Perspiration prevents expiration, is my understanding.
Speaker 3: No, that's true, that's true. It's good to perspire subtimes well, today,
Speaker 3: we're gonna be talking about a path that might help
Speaker 3: us understand dark matter. This is something I had never
Speaker 3: thought about before today, which is you know often true
Speaker 3: when you send me an outline for our discussions. And
Speaker 3: so today you're gonna tell us if antimatter can help
Speaker 3: us find dark matter exactly.
Speaker 1: We are going to fall in the chop of trying
Speaker 1: to connect two huge mysteries of the universe together, which
Speaker 1: is something you see in pop science all the time,
Speaker 1: and I get lots of emails from folks trying to
Speaker 1: make connections between two different mysteries we presented on the show,
Speaker 1: which I love. It means that they're thinking deeply about
Speaker 1: the universe and they're trying to put the clues together.
Speaker 1: And it's very tempting to imagine that you could like
Speaker 1: solve two huge mysteries at once, but it doesn't always
Speaker 1: work that way.
Speaker 3: Are there physicists that are working on trying to solve
Speaker 3: two mysteries at once or it's just like everyone admits,
Speaker 3: it's just not going to be that easy. You know,
Speaker 3: when we were talking to Hamas van Reet, I think
Speaker 3: he was saying that when you work on string theory,
Speaker 3: it pops out other solutions. But I guess that's different
Speaker 3: than thinking that two things are connected. It's when you
Speaker 3: study one thing and it turns out it explains multiple things.
Speaker 3: That's sort of the opposite direction.
Speaker 1: No, that's exactly the right example. That's the feeling you
Speaker 1: get when you think, oh, wow, maybe we've uncovered some
Speaker 1: corner of the truth because we're working on problem one,
Speaker 1: it automatically solves this other problem we weren't even trying
Speaker 1: to solve. It tells you that you're making deep connections. So, yeah,
Speaker 1: everybody wants that experience because we have this feeling like
Speaker 1: there is a true explanation for the universe and if
Speaker 1: you just dig deep enough, we'll uncover it and it'll
Speaker 1: bring everything together into this glorious moment of insight. But
Speaker 1: you know, getting there involves chiseling away patiently at the
Speaker 1: rock face of truth and hoping something falls into your lap.
Speaker 1: And so what we're going to talk about today is
Speaker 1: like one strategy people are using, and I think it's
Speaker 1: really cool because it highlights how physicists are doing everything
Speaker 1: they can to look for dark matter. We're looking for
Speaker 1: it up the wazoo, out the wazoo, to the left
Speaker 1: of the wazoo, like really everything we can imagine we
Speaker 1: are doing to look for dark matter.
Speaker 3: You've got that wazoo cover.
Speaker 1: Oh yeah, if it's in the wazoo, we'll find it.
Speaker 3: I think it's possible you're looking at the wrong spot,
Speaker 3: but I hope that you find it. So anti matter
Speaker 3: and dark matter, these are two concepts that I think
Speaker 3: most people don't understand at all. So let's see what
Speaker 3: our audience thinks about anti matter helping us understand dark matter.
Speaker 3: What did they have to say about what insights we
Speaker 3: might be covering today and if you would like to
Speaker 3: share your insights with us, email us at questions at
Speaker 3: Daniel and Kelly dot org.
Speaker 1: So I wrote to people and I asked them can
Speaker 1: antimatter help us find dark matter? Here's what people had
Speaker 1: to say. As far as I know, dark matter only
Speaker 1: interacts with gravitational and with antimatter and matter. Both interacting
Speaker 1: with gravitation will force the same. As far as we
Speaker 1: can tell, dark matter we don't think interacts with matter,
Speaker 1: so it should not interact with antimatter.
Speaker 2: Since we don't really understand much about dark matter, the
Speaker 2: only thing we could observe is gravity, so perhaps we
Speaker 2: can't detect antimatter, but gravity would be the same for
Speaker 2: matter versus antimatter. Maybe that could be an explanation is
Speaker 2: why we can't see it.
Speaker 4: Since antimatter tends to annihilate when it interacts with other matter,
Speaker 4: then maybe any sort of photon urse might represent interacting
Speaker 4: with dark matter if we don't think that there's any
Speaker 4: major amounts of regular matter in that area.
Speaker 3: So I was happy to see that most of the
Speaker 3: answers pretty much matched what I thought, which was I
Speaker 3: don't see how, but you are going to shine that
Speaker 3: light for us.
Speaker 1: I am going to make a connection between dark matter
Speaker 1: and antimatter. And these are great answers, by the way,
Speaker 1: and they're right. Matter and antimatter annihilate, but that is
Speaker 1: not helpful for dark matter. Dark matter might only interact gravitationally,
Speaker 1: so it'd be difficult to find dark matter doesn't interact
Speaker 1: with antimatter any differently than it interacts with matter. So
Speaker 1: these are great answers and right on the money.
Speaker 3: Definitely great answers, and I should say it expressed a
Speaker 3: lot more physics knowledge than I have. Most of those answers.
Speaker 3: So let's start with what do we know about what
Speaker 3: dark matter is. You just gave us some hints about
Speaker 3: what it is and what it isn't, But let's pretend
Speaker 3: you didn't say any of that. Start from the beginning
Speaker 3: for the neophyts of us, the dark matter neophyts.
Speaker 1: So dark matter is amazing because we simultaneously know an
Speaker 1: annoys amount about it and yet we know very little
Speaker 1: about it. It's sort of paradoxical, like we cannot see
Speaker 1: dark matter. It's something that's in the universe. It's not
Speaker 1: actually dark. It's invisible. So the name already is confusing.
Speaker 1: Like when you see dark matter on TV shows, you know,
Speaker 1: spaceship is flying through a cloud of dark matter. They
Speaker 1: show it as dark like black, like it's obscuring your view.
Speaker 1: But in reality, dark matter is there, but it's invisible.
Speaker 1: It's transparent, and that's because light passes through It doesn't
Speaker 1: interact with it the way light passes through glass, but
Speaker 1: even less so, like glass will refract light, but dark
Speaker 1: matter doesn't refract light, though it actually can bend it
Speaker 1: and lends it a little bit. We'll talk about that
Speaker 1: in a minute. But dark matter is more than just invisible.
Speaker 1: It's also intangible, like if you were in a cloud
Speaker 1: of dark matter you wouldn't even notice you like pass
Speaker 1: right through it. Dark matter can like phase through walls
Speaker 1: without interacting at all. So it's this mysterious but sort
Speaker 1: of omnipresent substance that it's also overwhelmingly dominant form of
Speaker 1: matter in the universe. Like eighty percent of the matter
Speaker 1: in the universe is dark matter. It's not weird or rare.
Speaker 1: In fact, we are the weird and rare kind of
Speaker 1: matter in the universe.
Speaker 3: Okay, so it's the dominant matter in the universe, but
Speaker 3: we can't see it or measure it, So how do
Speaker 3: we know that it exists at all?
Speaker 1: Yeah, so very mysterious. We don't know what it's made
Speaker 1: out of. We only learned about it recently, and yet
Speaker 1: we know a lot about it because we have detected
Speaker 1: its contributions to the gravity of our universe in many ways.
Speaker 1: And this is something I really want to underscore carefully,
Speaker 1: because a lot of people think dark matter is like
Speaker 1: a fudge factor, just something we add to the equations
Speaker 1: and don't understand just because things aren't working out. But
Speaker 1: dark matter is much more like this suspect in a
Speaker 1: mystery novel. Do we know a lot about but we
Speaker 1: haven't yet fingered. We know somebody slipped the knife into
Speaker 1: the corpse at some point. We see the footprints, we
Speaker 1: see the broken window. We have fingerprints, you know, we
Speaker 1: have DNA samples. We just haven't found the suspect yet.
Speaker 1: And so dark matter is like that.
Speaker 3: I'm not a big fan of dark matter after that description.
Speaker 3: It doesn't seem like a nice thing. But it helps
Speaker 3: by holding everything together. Is that right? So I shouldn't
Speaker 3: be so negative.
Speaker 1: Yeah, No, dark matter is much more helpful than a murderer.
Speaker 3: That's good. That's good. I mean it's a low bar,
Speaker 3: but that's good.
Speaker 1: So let's talk about how we know that dark matter
Speaker 1: is there and what we know about it, because it
Speaker 1: paints a very comprehensive picture of dark matter. So classically
Speaker 1: we know about dark matter originally because of how galaxies rotate.
Speaker 1: Galaxies are a bunch of stars, but they're also spinning,
Speaker 1: and when things spin, they tend to lose stuff. Like
Speaker 1: if you put a bunch of ping pong balls on
Speaker 1: a Merry go round and you spin it, you don't
Speaker 1: keep all the ping pong balls. They fly out. Because
Speaker 1: things tend to move in straight lines unless they're being
Speaker 1: bent into a curve, Like the reason the Moon stays
Speaker 1: in orbit around the Earth is because gravity is holding
Speaker 1: it in. So you can do this calculation and ask, well,
Speaker 1: is there enough gravity in the galaxy to hold all
Speaker 1: those stars in as we spin around at this crazy
Speaker 1: high speed. You add up all the mass from all
Speaker 1: the stars and the answer is no, and not even
Speaker 1: close by the way, galaxies are spending way too fast
Speaker 1: to hold the stars in, and yet they're not throwing
Speaker 1: stars out into interstellar space. Very often it does happen.
Speaker 1: But to provide enough gravity to hold the galaxy together,
Speaker 1: you have to take all the mass of all the
Speaker 1: visible stuff and multiply it by four or five. So
Speaker 1: there's a huge amount of unaccounted for gravity. Right. The
Speaker 1: gravity is there, it's holding the stars together. We don't
Speaker 1: know what's providing it. That's the original evidence we have
Speaker 1: for dark matter, and that's the one that makes people
Speaker 1: feel like, oh, it's just a fudge factor. You're just
Speaker 1: adding in a number to describe what you're seeing. You
Speaker 1: don't really understand it because that's just one piece of evidence.
Speaker 1: But we have like many more pieces of evidence as well.
Speaker 3: And also I feel like if it was just a
Speaker 3: fudge factor. Then it wouldn't be like times four. Yeah,
Speaker 3: it would be like you know.
Speaker 1: Plus five exactly. It's not a little tweak, right, it's
Speaker 1: a total revolution in our understanding of what the universe
Speaker 1: is made out of.
Speaker 3: Yeah. So, like you're saying, even if we discovered another
Speaker 3: Jupiter in our solar system, that still wouldn't explain.
Speaker 1: No, you've got to discover five more hidden stars in
Speaker 1: our solar system to multiply the mass of our solar
Speaker 1: system by five. Jupiter is nothing in our solar system.
Speaker 3: Yeah, okay, got it, all right, So you've told us
Speaker 3: about one piece of evidence. You're assuring us that there's more.
Speaker 3: What have been our most promising routes of research to
Speaker 3: try to discover what it is that have failed so far.
Speaker 1: Well, we've looked for dark matter in several ways. Essentially,
Speaker 1: we assume dark matter is some kind of particle and
Speaker 1: we look to see if it interacts with our kind
Speaker 1: of matter in any way. So, for example, we have
Speaker 1: huge underground tanks of stuff like liquid xenon, and liquid
Speaker 1: xenon is very quiet, it doesn't like to interact. This
Speaker 1: stuff is underground, so no cosmic rays get to it. Basically,
Speaker 1: you have a big tank of liquid xenon and cameras
Speaker 1: in there. You say, do you ever see a flash
Speaker 1: of light? I mean, you shouldn't see any flashes of light.
Speaker 1: But if dark matter, which could penetrate through all of
Speaker 1: the Earth and make it to your tank of xenon,
Speaker 1: occasionally does bump into your xenon and give it a push,
Speaker 1: you'll see a flash of light as that xenon relaxes.
Speaker 1: So you have your cameras underground on liquid xenon and
Speaker 1: look for flashes of light. It's a crazy experiment, but
Speaker 1: nobody's ever seen anything beyond what you expect from like
Speaker 1: background radiation from the rocks and all this sort of stuff.
Speaker 1: So quiet experiments looking for dark matter bumps haven't seen anything.
Speaker 1: We've tried to make dark matter in the laboratory at
Speaker 1: the large had Drunk collider. We can smash particles together
Speaker 1: and make new kinds of stuff. If dark matter has
Speaker 1: any kind of interaction with protons at all beyond gravity, right,
Speaker 1: this should require some non gravitational interaction. We should be
Speaker 1: able to make it at the large a dron collider,
Speaker 1: and then it would appear as invisible particles. We can
Speaker 1: tell when we made invisible particles with the Large Hadron
Speaker 1: Collider because there's like something on one side of the
Speaker 1: detector and nothing on the other side, so there's an imbalance.
Speaker 1: But we've never seen an unexplained imbalance of particles.
Speaker 3: Did we expect that we would when we started the
Speaker 3: large Head Droun Collider.
Speaker 1: We hoped, so. I was actually one of the people
Speaker 1: really working deeply on this topic. A lot of my
Speaker 1: grattudents have like a written phddcs on searching for dark
Speaker 1: matter with the Large Hyde Drunk Colider. I was really
Speaker 1: hopeful because colliders are so powerful you don't have to
Speaker 1: know what you're looking for, how to make it very
Speaker 1: general search for like what the universe can do. But
Speaker 1: we didn't see anything, and you know, hey, that's research, it's.
Speaker 3: Exploration, not the right wazoo.
Speaker 1: Yeah exactly. And there's one other avenue for looking for
Speaker 1: dark matter, but let's save that related because that's our
Speaker 1: antimatter connection, Okay. And I want to remind people about
Speaker 1: how else we know that dark matter is really a thing,
Speaker 1: and not just like, hey, let's multiply gravity by four
Speaker 1: and we see its effects all over the place, not
Speaker 1: just within galaxies, but between galaxies. Like dark matter is
Speaker 1: not as clumpy as normal matter. It feels gravity, but
Speaker 1: it's not sticky, so it doesn't stick together. Like two
Speaker 1: blobs of dark matter, if they run into each other,
Speaker 1: they just pass right through each other, whereas two blobs
Speaker 1: of normal matter tend to stick together. So you get
Speaker 1: like asteroids and planets forming out of matter, but you
Speaker 1: don't get planetary structures forming out of dark matter. It's
Speaker 1: like a big foamy fluff that fills the universe. It
Speaker 1: has places where it's denser in places where it's less dense,
Speaker 1: but it's much less clumpy than normal matter. So it
Speaker 1: extends out between the galaxies, for example, and it helps
Speaker 1: hold galaxy clusters together. Like we cannot explain using just
Speaker 1: stars in their gravity why galaxies orbit each other the
Speaker 1: way they do, and why galaxy clusters form. You need
Speaker 1: dark matter to explain that too.
Speaker 3: And you can tell that dark matter is clumpy based
Speaker 3: on the activity of galaxies. Is that right?
Speaker 1: Oh, great question. Yeah, we can tell where the dark
Speaker 1: matter is based on the gravitational motion within a galaxy
Speaker 1: and also between galaxies. Like we don't just take matter
Speaker 1: and multiply by four. We can tell where in the galaxy.
Speaker 1: That matter is based on the speed of the stars
Speaker 1: at different distances from the center of the galaxy. Like
Speaker 1: if you put all the dark matter at the very
Speaker 1: center of the galaxy, then all the stars would be
Speaker 1: feeling more gravity and it'd all be going really really fast.
Speaker 1: If you take some of the dark man, you spread
Speaker 1: it out, then it doesn't speed up the stars that
Speaker 1: are closer into the galaxy. So by seeing how the
Speaker 1: velocity of stars varies from the center to the edge
Speaker 1: of the galaxy, you can tell where in the galaxy
Speaker 1: it is, and the same thing applies for between the galaxies.
Speaker 1: By seeing velocities of all these galaxies, you can make
Speaker 1: a map of where the dark matter is between the galaxies.
Speaker 1: And you can also see where the dark matter is
Speaker 1: because of its lensing. I said earlier that dark matter
Speaker 1: is kind of light glass, but it doesn't refract light,
Speaker 1: but it does bend light because dark matter is matter,
Speaker 1: and matter curves space, and curved space will curve the
Speaker 1: path of photons. So if you have a huge blob
Speaker 1: of dark matter between us and some other galaxy, it's
Speaker 1: gonna lens that light, just like as if there was
Speaker 1: some huge lens in space, and we see this in
Speaker 1: the night sky, like we see sometimes two copies of
Speaker 1: a single galaxy because it's light which shot out in
Speaker 1: two different directions got then focused by some dark matter
Speaker 1: lens back towards the Earth, so it looks like the
Speaker 1: same galaxy, but it's not. It's a duplication. It's an
Speaker 1: optical effect. And you can use this to map out
Speaker 1: where the dark matter is in the universe by seeing
Speaker 1: how the much lensing there is in various locations, So
Speaker 1: we can tell where the dark matter is.
Speaker 3: What kind of shape does it take? Does it say like,
Speaker 3: oh got you physicists.
Speaker 1: It's a big middle finger, that's right.
Speaker 3: Yeah, it's just lumpy and kind of amorphis it's a.
Speaker 1: Big cosmic poop. Basically, it's a big lump of no.
Speaker 1: We can make a map and it's really fascinating, maybe
Speaker 1: not surprising. The map of where the dark matter is
Speaker 1: in the universe closely follows the map of where matter
Speaker 1: is in the universe. It's kind of like luminous matter
Speaker 1: stars are a tracer that tell you where the dark
Speaker 1: matter is. And it's not a coincidence the luminous matter
Speaker 1: the stars, the galaxies are there because the dark matter
Speaker 1: is there. So origin of the universe, things are pretty
Speaker 1: spread out, but there's little spots that are denser and
Speaker 1: little spots that are less dense quantum fluctuations, and so
Speaker 1: dark matter where it is denser, it started to gather together.
Speaker 1: A little bit doesn't stick, but still it gathers together
Speaker 1: a little bit and orbits itself and makes these big swirls,
Speaker 1: and that makes it like a gravitational well. And the
Speaker 1: other matter, gas and dust, normal matter falls into that
Speaker 1: well and gets trapped and forms galaxies and forms stars.
Speaker 1: And you can run simulations. If you run the universe
Speaker 1: without any dark matter, you don't get galaxies ten billion
Speaker 1: or twelve or fourteen billion years after the Big Bang,
Speaker 1: You just don't. It takes much much longer. So the
Speaker 1: only reason we have galaxies today is because dark matter
Speaker 1: has gathered together the gas in the dust and forced
Speaker 1: it to make stars and all this kind of stuff.
Speaker 1: So we know that dark matter has played a huge
Speaker 1: role in the evolution of what we call large scale
Speaker 1: structure in the universe. Basically, the reason the universe looks
Speaker 1: the way it is is because of.
Speaker 3: Dark matter, and that interaction doesn't work both ways, right,
Speaker 3: Like dark matter can pull objects towards it. But like
Speaker 3: the Sun isn't pulling dark matter in because dark matter
Speaker 3: doesn't respond to stuff.
Speaker 1: The Sun is pulling dark matter in because dark matter
Speaker 1: does feel gravity. But what happens when the Sun pulls
Speaker 1: dark matter in? You're a blob of dark matter. You
Speaker 1: get pulled towards the sun. Cool gravity is pulling you in.
Speaker 1: You're going faster and faster and faster. Now, if you're
Speaker 1: a comet, you hit the Sun, you vaporize, you interact electromagnetically, hadronically,
Speaker 1: all the other kinds of interactions, like you become part
Speaker 1: of the Sun. If you're a blob of dark matter,
Speaker 1: you're a dark matter comet. What happens when you hit
Speaker 1: the Sun? Nothing? You go right through it the same
Speaker 1: way like if you dropped a ball through a hole
Speaker 1: a tunnel that went all the way through the Earth,
Speaker 1: what would happen. It would go all the way through
Speaker 1: the center and come out the other side the same way.
Speaker 1: Dark matter doesn't stick to the Sun. It passes right
Speaker 1: through the Sun and goes out the other side. That's
Speaker 1: why dark matter doesn't clump the way that normal matter does.
Speaker 1: But it definitely does feel gravity. We have lots of
Speaker 1: other reasons to believe that dark matter is there. Like,
Speaker 1: we can tackle the problem from the other direction. Some
Speaker 1: people are like, well, maybe you're just missing some of
Speaker 1: the matter, Like are there just like big blobs of
Speaker 1: matter out there you're not seeing, you know, could you
Speaker 1: see a huge rock out in the middle between galaxies?
Speaker 1: And so people have tackled the problem in this super
Speaker 1: amazing way. From that direction, we're able to calculate how
Speaker 1: much normal matter there is in the universe based on
Speaker 1: what happened in the first few minutes of the Big Bang.
Speaker 3: Wow.
Speaker 1: Yeah, it's really incredible. We look at the distribution of
Speaker 1: elements in the universe, how much hydrogen, how much helium,
Speaker 1: how much lithium, et cetera, And those amounts are really
Speaker 1: sensitive to the density of normal matter in the early universe.
Speaker 1: Like the denser it was, the more you're going to
Speaker 1: get fusion in the early universe to make those heavier elements,
Speaker 1: and the less dense it was, the less likely you are.
Speaker 1: So it's very sensitive, Like we can measure exactly what
Speaker 1: the density of quarks and protons and all those kind
Speaker 1: of normal matter bits were in the early universe by
Speaker 1: measuring how much lithium is out there in space, and
Speaker 1: so we can tell how much stuff there was very precisely,
Speaker 1: and it very well matches the normal matter we see
Speaker 1: in the universe. So that tells us like, yeah, there
Speaker 1: could be a rock in the middle of space that
Speaker 1: we didn't see, even like one the size of Jupiter
Speaker 1: or a star, but there's definitely not a huge amount,
Speaker 1: not four times the amount of normal matter missing. So
Speaker 1: we sort of like accounted for this problem in two
Speaker 1: different directions and it all adds up. And then the
Speaker 1: sort of coup de grad the thing that like really
Speaker 1: links it together is we can look at the very
Speaker 1: very early universe. We see ripples from the plasma of
Speaker 1: the very early universe. This it's called the cosmic microwave
Speaker 1: background radiation.
Speaker 3: Is this the thing that we thought was pigeon poop?
Speaker 1: I'm that's really important exactly. Okay, This is discovered in
Speaker 1: the sixties and it's evidence that the universe was once
Speaker 1: much more dense. It was this hot, frothing plasma that
Speaker 1: filled the whole universe, and it glowed, and there was
Speaker 1: a moment when that plasma cooled and suddenly became transparent,
Speaker 1: so that glow instead of getting constantly reabsorbed by itself,
Speaker 1: the way like light inside the sun is getting absorbed
Speaker 1: by the sun and we're only seeing light from the surface.
Speaker 1: That plasma in the early universe became transparent, and so
Speaker 1: that glow stuck and we can see that glow and
Speaker 1: we can tell stuff about that plasma, and most importantly,
Speaker 1: we see ripples in that plasma. It's not just like
Speaker 1: a constant glow. It's like brighter here and darker there,
Speaker 1: and those ripples depend on how that plasma is sloshing around,
Speaker 1: and how the plasma slashes around depends on like, well,
Speaker 1: how much dark matter is there holding stuff together with
Speaker 1: its gravity, how many photons are there pushing things apart
Speaker 1: because of the glow, how much normal matter is there
Speaker 1: which feels the photons and the gravity. It's like this
Speaker 1: complex dance of all the different ingredients of the universe
Speaker 1: at that time, and those very specifically control all of
Speaker 1: those wiggles. So by measuring those wiggles, we can nail
Speaker 1: down exactly how much matter was there, how much dark
Speaker 1: matter was there, how many photons were there, and it
Speaker 1: all aligns up with our other calculations. So we have
Speaker 1: like all these different pieces of evidence that tell us
Speaker 1: how much of the universe is normal matter, how much
Speaker 1: of the universe is this weird, unexplained gravitationally feeling otherwise
Speaker 1: totally intangible kind of matter we call dark matter. So like, yeah,
Speaker 1: we got a lot of clues, you just haven't yet
Speaker 1: found the murderer.
Speaker 3: So we've tried to see if it's a particle. No
Speaker 3: evidence for that yet. We don't know if it could
Speaker 3: do anything other than like gravitate and pull things in
Speaker 3: towards it or respond to the gravity of other things.
Speaker 3: But when we get back from the break, you're going
Speaker 3: to bring us to the next big unknown, which is
Speaker 3: anti matter, and we'll talk about what we don't know
Speaker 3: about that, all right, So in the last segment, you
Speaker 3: convinced me that dark matter is probably not just because
Speaker 3: someone forgot to carry a five or something like that.
Speaker 3: So now let's move on to anti matter, which is
Speaker 3: the other thing that we need to understand to answer
Speaker 3: the question what can antimatter tell us about dark matter?
Speaker 1: Right, so forget everything we said about dark matter for now,
Speaker 1: we're gonna talk about a completely separate topic in particle physics,
Speaker 1: which is the mystery of anti matter. And then later
Speaker 1: on we're going to connect these. But antimatter is amazing
Speaker 1: and wonderful and real. It's like something we see, something
Speaker 1: we make, something we study. It's like very pedestrian. In
Speaker 1: the collider I used to work on before the Large
Speaker 1: Hatener Collider, we collided matter and antimatter. We made protons
Speaker 1: and we made anti protons. We smashed them together many
Speaker 1: many times a second. So antimatter is not nearly as
Speaker 1: mysterious as dark matter. We know what it is, we
Speaker 1: know it's a particle. We can make it, we can
Speaker 1: play with it, we build stuff out of it. It's
Speaker 1: amazing in science fiction y, but it's much less theoretical
Speaker 1: than dark matter.
Speaker 3: Okay, you sounded a little bit defensive when we said
Speaker 3: antimatter is real, but I guess you were just trying
Speaker 3: to clarify that we've actually seen them.
Speaker 1: Was I protesting too much? Well, I think some people
Speaker 1: are confused because they read about it in science fiction.
Speaker 1: It seems sort of like bizarre and mystical, but it's
Speaker 1: actually something we play with all the time in real physics.
Speaker 1: It's also just kind of a name we give things
Speaker 1: that reveals something deep about the universe, which is that
Speaker 1: the universe has these beautiful symmetries. Like basically, antimatter is
Speaker 1: a statement that every particle out there has a partner.
Speaker 1: So you have an electron, it's a particle, it has
Speaker 1: negative charge. There's another version of that particle, the positively
Speaker 1: charged version. You have a muon it's negatively charged. There's
Speaker 1: a positively charged version of that. You have a quirk
Speaker 1: with charge two thirds. There's a negative two thirds charged
Speaker 1: version of that. Whatever the universe can do when it
Speaker 1: makes a charged particle, it can also do something very
Speaker 1: similar with the opposite charge. So it's actually this kind
Speaker 1: of beautiful symmetry in the matter that we see out
Speaker 1: there in the universe.
Speaker 3: I'm kind of feeling like we should have saved this
Speaker 3: topic for the Valentine's Day. It feels a little loveyw
Speaker 3: but okay, all right, good to note the universe has symmetry.
Speaker 1: Well, they have a very explosive relationship, because what happens
Speaker 1: when an electron and positiron meet is they don't live
Speaker 1: happily ever after they annihilate. And popular science tells you
Speaker 1: that annihilating into pure energy. Really what happens is they
Speaker 1: annihilate into a photon, which and a photon is nothing
Speaker 1: but energy, that's true, but it's not this like abstract
Speaker 1: form of energy. It's like it's another kind of field
Speaker 1: that's rippling and making us a particle.
Speaker 3: All right, Well, it's just some parasites get divorced too.
Speaker 3: So I'm seeing connections here, and.
Speaker 1: This is just an example of the kinds of symmetries
Speaker 1: we see in the universe. We notice that it's not
Speaker 1: just like forty two different particles and they're all different.
Speaker 1: There are relationships between them, There are patterns between them,
Speaker 1: and often the patterns work in just this way. There's
Speaker 1: like several versions of the same particle. So there's an
Speaker 1: electron and there's the positron, which is just like the
Speaker 1: opposite version of the electron. Don't think of them as
Speaker 1: separate particles. Think of them as two halves of the
Speaker 1: same coin. But the electron is also one half of
Speaker 1: other kinds of coins. For example, the electron has another version,
Speaker 1: the muon. The muon is the same as the electron,
Speaker 1: just heavier. The tao is just the same as the muon,
Speaker 1: and the electron even heavier.
Speaker 3: I feel like the coin analogy is breaking down. Yes,
Speaker 3: we're talking about dungeons and dragons, dice or something.
Speaker 1: And we think that the electron participates in even other symmetries.
Speaker 1: This this whole theory called supersymmetry, which says that every
Speaker 1: particle has this weird partner particle. So the electron would
Speaker 1: have the selectron, and quirks would have the squarks, and
Speaker 1: we haven't discovered those. We don't know if it's true,
Speaker 1: but it's sort of a theme in particle physics that
Speaker 1: every particle has reflections, other copies of itself.
Speaker 3: This might be the first time where I've thought, oh,
Speaker 3: physicists are doing a good job with naming something though,
Speaker 3: because like the squirks, that's both cute and it sort
Speaker 3: of tells you what it is, you know.
Speaker 1: Yeah, yeah, I like the supersymmetric names. And it's also
Speaker 1: kind of arbitrary, like what is matter and what is antimatter? Well,
Speaker 1: the universe is very symmetric. The laws of physics are
Speaker 1: almost the same for matter and antimatter, so they are
Speaker 1: opposite each other in the sense they have opposite charges.
Speaker 1: But it's not like antimatter is like against building stuff.
Speaker 1: You could build a universe out of antimatter.
Speaker 3: We think, but antimatter is the rare thing that we
Speaker 3: don't see a lot of, right, and so what causes
Speaker 3: that asymmetry? There?
Speaker 1: Boy? Do I wish I had the answer to that question,
Speaker 1: because I would be talking to the King of Sweden,
Speaker 1: shaking their hand and getting a million dollars. Nobody knows.
Speaker 3: Would you still podcast if you got the Nobel Prize?
Speaker 1: Of course, absolutely, I podcast more often. Absolutely nice.
Speaker 3: You'd remember the little people.
Speaker 1: Oh, you're the little people right as you sit in
Speaker 1: front of your shelf of awards over there.
Speaker 3: The shelf is out of the screen.
Speaker 1: Huh. If you won the Nobel Prize, your biggest problem
Speaker 1: would be like where to put it on your shelf
Speaker 1: otherwise crowded with prizes.
Speaker 3: Oh you're making me feel really nice, but that's definitely
Speaker 3: over selling. But thank you.
Speaker 1: But you're right. It is a big mystery because if
Speaker 1: it's true that the universe treats matter and anti matter
Speaker 1: the same way, why are we made of matter? Why
Speaker 1: is the Earth made of matter? The galaxy made of matter?
Speaker 1: We think most of the galaxies near us are made
Speaker 1: of matter. That's an asymmetry, and that doesn't seem to
Speaker 1: add up because if the universe made the same amount
Speaker 1: of matter and antimatter in the very beginning, when it
Speaker 1: was filled with frothing energy which is then cooled into
Speaker 1: these fields. Then that matter and antimatter would annihilate. And
Speaker 1: that's mostly what happened when we made matter in antimatter
Speaker 1: in the early universe. In annihilated and the universe was
Speaker 1: mostly filled with photons for a little while, which must
Speaker 1: have been brilliant. But there was a little bit left
Speaker 1: over because there wasn't a perfect symmetry between the matter
Speaker 1: and antimatter, and we don't know why. We don't know
Speaker 1: was there more matter made in the early universe or
Speaker 1: is there some process in the universe that produces matter
Speaker 1: more than antimatter. There's definitely some asymmetry there because, as
Speaker 1: you say, there's more matter and less antimatter. But I
Speaker 1: also just want to emphasize like antimatter, we name it
Speaker 1: antimatter because it's the one that's not made as often,
Speaker 1: not because it's against anything.
Speaker 3: You said that we don't know of universes that are
Speaker 3: made of antimatter. Could there be universes of antimatter or
Speaker 3: like a chunk of antimatter out in the galaxies or
Speaker 3: whatever that we haven't seen yet.
Speaker 1: Yeah, it's tempting to say, oh, let's look up at
Speaker 1: the night sky. We see galaxies out there. How do
Speaker 1: we know they're not made of antimatter because antimatter would
Speaker 1: produce photons a way it matter does. And that's true.
Speaker 1: But we can tell if some of those galaxies are
Speaker 1: made of matter and antimatter, because galaxies don't just produce photons,
Speaker 1: they also produce charged particles, like the Sun produces lots
Speaker 1: of photons you can see it, but also lots of
Speaker 1: protons and electrons, and so antimatter is much rarer. In
Speaker 1: our solar wind we are shooting matter out into the universe.
Speaker 1: And if a neighboring galaxy was shooting antimatter out into
Speaker 1: the universe the same way as you would expect, then
Speaker 1: between them there would be this like ribbon of collisions,
Speaker 1: this like interface where our solar or galactic winds were
Speaker 1: hitting their solar galactic winds and annihilating and making these
Speaker 1: bright flashes.
Speaker 3: I bet that would look awesome.
Speaker 1: It would be amazing. I hope it's real when we've
Speaker 1: looked for that and we haven't seen it, which means
Speaker 1: either the whole universe is just matter, or if there
Speaker 1: are anti matter galaxies, they're too far away for us
Speaker 1: to see. Now, that doesn't rule out that, like we
Speaker 1: live in a vast pocket of matter ninety billion light
Speaker 1: years across and be on the edge of the observable universe,
Speaker 1: there are vast pockets of antimatter. Maybe even most of
Speaker 1: the universe is antimatter for all we know. But in
Speaker 1: the region we can see, we can't spot any antimatter galaxies,
Speaker 1: and we can't spot any interface between matter and antimatter.
Speaker 1: So as far as we know, the universe is mostly matter.
Speaker 1: And we've been studying anti matter for a long time,
Speaker 1: and so we have some ideas for like what might
Speaker 1: explain this asymmetry. We found some ways that the universe
Speaker 1: prefers to make matter over antimatter. There's some like little
Speaker 1: particle physics processes which if you run them forward in time,
Speaker 1: will make more matter than antimatter, but they're very small effects.
Speaker 1: They go under the name of CP violation. We can
Speaker 1: dig into that in another episode maybe, And so we
Speaker 1: have found some ways that the universe is not symmetric
Speaker 1: and prefers matter, but it doesn't explain it, Like if
Speaker 1: we run our models and you start from a perfectly
Speaker 1: symmetric universe, you don't get the huge asymmetry that we
Speaker 1: see today. You just can explain a little bit. So
Speaker 1: there's definitely a big mystery out there that remains. We
Speaker 1: cannot figure out yet why the universe seems to be
Speaker 1: filled with matter and not antimatter. And you know, there
Speaker 1: are some intriguing clues out there, like some particles don't
Speaker 1: have antiparticles, Like you know, the electron has the antiparticle,
Speaker 1: the positron, what's the antiparticle of the photon. The photon
Speaker 1: doesn't have a charge, so you flip its charge, you
Speaker 1: just get a photon. So some people say the photon
Speaker 1: is its own antimatter, or another way to say that
Speaker 1: is that there is no antiparticle.
Speaker 3: Is that the only particle we know of that doesn't
Speaker 3: have an antiparticle.
Speaker 1: No, there's a few, like the z boson, which is
Speaker 1: the equivalent of the photon, but for the weak force
Speaker 1: that doesn't have an antiparticle. It's also doesn't have a charge.
Speaker 1: The Higgs boson has no electric charge. There's no anti
Speaker 1: Higgs boson. And something we still don't know is whether
Speaker 1: neutrinos are their own antiparticle or not. Neutrinos have no
Speaker 1: electric charge, but they do have a weak charge. We
Speaker 1: talked about that recently on the podcast and you can
Speaker 1: flip those. We don't even know if anti neutrinos are
Speaker 1: actually different or if they're just neutrinos. We still have
Speaker 1: to figure that out. Neutrinos are so difficult to do
Speaker 1: experiments with that it's very tricky to understand their behavior,
Speaker 1: and so there's a lot we still have to learn
Speaker 1: about what antimatter is. But we can make it in
Speaker 1: the lab. We have these amazing experiments we've done at
Speaker 1: CERN where we've built like anti hydrogen, where you have
Speaker 1: an anti proton and an anti electron you get them
Speaker 1: to bind together to make hydrogen and to emit light,
Speaker 1: and so we can study in detail does antimatter actually
Speaker 1: follow the same laws of physics so far it does.
Speaker 1: They did this incredible experiment recently to try to answer
Speaker 1: what sounds like a dumb question but turns out to
Speaker 1: be a really deep question, which is does antimatter fall
Speaker 1: up or down in a gravitational field? Yeah, I see
Speaker 1: you going, oh oh, wait a second, I don't know
Speaker 1: the answer to that because On one hand, you think, oh,
Speaker 1: it's a kind of matter. Matter falls down in a
Speaker 1: gravitational field. It attracts, right, But that's assuming that it
Speaker 1: feels gravity the same way. And gravity is not something
Speaker 1: we fundamentally understand. According to Einstein, it shouldn't matter. But
Speaker 1: we think Einstein's probably wrong when it comes to the
Speaker 1: gravity of particles. And wouldn't it be amazing if antimatter
Speaker 1: fell up? Yeah, and it might be amazing to you
Speaker 1: that we don't know the answer to this question already.
Speaker 1: And the reason is that gravity is super duper weak
Speaker 1: and antimatter we can make it, but it's hard to
Speaker 1: make large quantities of it, and you really need like
Speaker 1: a large quantity of something in order to study its gravity.
Speaker 1: We've never measured the gravity of a single particle. The
Speaker 1: smallest thing we've ever measured the gravity of is like milligrams,
Speaker 1: which is huge number of particles. So they're doing these
Speaker 1: experiments to try to isolate every other kind of force
Speaker 1: on these anti hydrogen molecules to see can we see
Speaker 1: them falling up or can we see them falling down?
Speaker 1: And initial bindings suggests that antimatter falls down, which is
Speaker 1: kind of a bummer. Because boy, wouldn't that be cool?
Speaker 1: And then we could make our hoverboards finally, and all
Speaker 1: sorts of stuff. I know, I know, I've been promising
Speaker 1: kids hoverboards for years and have not delivered. Terrible physicists.
Speaker 3: Wouldn't a hoverboard made of antimatter just like vaporize or
Speaker 3: explosively combust when you jump on it.
Speaker 1: No, you need to isolate the anti matter underneath somehow
Speaker 1: to provide that levitation in a magnetic bottle. I mean,
Speaker 1: there's some engineering details that other people would figure out
Speaker 1: once we have the essential bits understood.
Speaker 3: We've got a symmetry question for you. So some particles
Speaker 3: have a symmetric partner in some dome. If tomorrow someone
Speaker 3: was to say, Okay, have this new particle that we've
Speaker 3: never heard of before, could you predict if it would
Speaker 3: have a partner or not? Do we understand when you
Speaker 3: get partners or not?
Speaker 1: I would say, if it has a charge, then it's
Speaker 1: going to have a partner, because that's an inherent property
Speaker 1: of a quantum field. Like the reason the electron has
Speaker 1: the partner is because the electrons field can wiggle in
Speaker 1: a way to make an electron and the things that
Speaker 1: allow it to do that wiggle also allowed to do
Speaker 1: the opposite wiggle to make the anti electron. So electrons
Speaker 1: and anti electrons are wiggles in the same field. So
Speaker 1: if you discover the Kelly on, Okay, now there's a
Speaker 1: Kelly field in the universe. If it can make a Kelly,
Speaker 1: then it can make an anti Kelly.
Speaker 3: I think we should name it Wienersmith because that's more
Speaker 3: distinctive and funnier. But anyway, I like where you're going
Speaker 3: with this.
Speaker 1: But another question is if you discover a new field
Speaker 1: with two particles one's positive and one's negative, which one
Speaker 1: do you call the matter and which one do you
Speaker 1: call the antimatter? That's kind of arbitrary. There's nothing mattery
Speaker 1: about one or the other except do you find more
Speaker 1: of it in the universe. Right, So, like you could
Speaker 1: flip those definitions, and you can flip them arbitrarily. You
Speaker 1: could keep the electron as matter and the anti electrons antimatter.
Speaker 1: You could say, well, from you ons, we're gonna call
Speaker 1: the anti muon matter now, and it makes no difference. Right,
Speaker 1: So there's sort of arbitrary labels. So whether the Wienersmith
Speaker 1: boson or the anti Wiennersmith boson, is the matter or
Speaker 1: antimatter it matters?
Speaker 3: Not? Oh man, We've had wazoos and dark matter and
Speaker 3: Wienersmith bosons. This is maybe the best episode we've ever done.
Speaker 3: And on that note, let's take a break and when
Speaker 3: we get back we will answer the question can anti
Speaker 3: matter help us find dark matter? All right, we're back.
Speaker 3: So this is an episode of Daniel and Kelly's Extraordinary Universe.
Speaker 3: So I'm guessing the answer to can anti matter help
Speaker 3: us find dark matter? Is going to be something like maybe?
Speaker 3: But I love that as an answer. It's at least
Speaker 3: informative and honest. So let's see what is the answer
Speaker 3: going to be today? Where do we start with this? Daniel?
Speaker 1: Yeah, the answer is maybe. And it's an example of like, hey,
Speaker 1: physicists trying to be clever and finding any possible way
Speaker 1: to observe dark matter, and everything we're doing to find
Speaker 1: dark matter particles to understand like is dark matter made
Speaker 1: out of a particle and what is that particle rests
Speaker 1: on a really big assumption that we can't actually justify,
Speaker 1: which is maybe dark matter feels something other than gravity,
Speaker 1: Like we know it feels gravity. We invented the idea
Speaker 1: to explain gravity we couldn't otherwise explain, and it's really
Speaker 1: important to do that. But none of those explanations require
Speaker 1: that it ever feels any other kind of force. It's
Speaker 1: possible that dark matter is some particle out there that
Speaker 1: only feels gravity and has no other charges. That's a
Speaker 1: possibility that would be really frustrating because gravity is very
Speaker 1: hard to use on particles, it's so weak. We might
Speaker 1: never understand the particle nature of dark matter in that scenario.
Speaker 1: So we hope, we pray. We assume that dark matter
Speaker 1: has some other kind of interaction, maybe some force we
Speaker 1: haven't figured out yet, and that would allow us to
Speaker 1: interact with it on a particle level more powerfully than gravity.
Speaker 1: And we need to make that assumption in order to
Speaker 1: see it. Basically, So we make that assumption and we
Speaker 1: move on. It could be totally wrong, and that might
Speaker 1: be the reason we've never seen dark matter, but we
Speaker 1: kind of got to do it.
Speaker 3: I mean, like, if you guys finally figured out gravity,
Speaker 3: would that help or would that not solve the problem?
Speaker 3: You wouldn't need to hope anymore.
Speaker 1: I love the tone there, like, if you guys finally
Speaker 1: figured out gravity. It's like, have you finally shoveled the walk?
Speaker 1: Did you finally take out the trash?
Speaker 3: That's right, have you cleaned your room? Daniel?
Speaker 1: It might be you know, if we understood quantum gravity,
Speaker 1: we might figure out a way to enhance it, or
Speaker 1: to manipulate it in such a way that it was
Speaker 1: more powerful for particles. Like if it turns out that
Speaker 1: there are extra dimensions to the universe and gravity appears
Speaker 1: to be weak because most of the gravity's leaking out
Speaker 1: into those other dimensions, then we might be able to
Speaker 1: manipulate it and make it more powerful. For example, people
Speaker 1: hope that exactly that is happening. When you smash particles
Speaker 1: together at the Large Hadron Collider, you're overcoming that extra
Speaker 1: dimensional reduction in the power of gravity to make miniature
Speaker 1: black holes, which would reveal the nature of quantum gravity. So, yeah,
Speaker 1: it's possible if we got off our butts and figured
Speaker 1: out quantum gravity, that would help us find dark matter.
Speaker 3: I never know where conversations are going to go with you.
Speaker 3: I didn't expect it to be like, well, if there's
Speaker 3: another dimension, like whoa, whoa, Now we've got extra dimensions.
Speaker 3: While we're trying to answer this question. But anyway, Okay, let's.
Speaker 1: Put that aside for now. And so we're assuming that
Speaker 1: dark matter feels some other kind of force that matter
Speaker 1: also feels, because that what allow us to see it,
Speaker 1: Like those big tanks of liquid xenon underground. They're assuming
Speaker 1: there's some kind of force that dark matter feels and
Speaker 1: xenon feels. So when dark matter flies to xenon, they
Speaker 1: can bump on each other because otherwise it's hopeless. So
Speaker 1: if you make that assumption, you also are allowed to
Speaker 1: assume that sometimes dark matter can bump into its anti
Speaker 1: dark matter and annihilate and turn into something which can
Speaker 1: then turn into normal matter. Right, So if there is
Speaker 1: some new kind of force, it's got a particle called
Speaker 1: it the dark photon. So now maybe sometimes dark matter
Speaker 1: annihilates with anti dark matter into a dark photon, which
Speaker 1: then turns into normal matter like an electron and an
Speaker 1: anti electron, or a muon and an anti muon.
Speaker 3: Okay, so we've got dark matter which we can't see.
Speaker 3: Now we need to find anti dark matter, which we
Speaker 3: probably have all or not. That's direct, And then what
Speaker 3: would a dark photon look like? It would annihilate a
Speaker 3: real photon, right, is that how you know it existed?
Speaker 4: No?
Speaker 1: No, No, dark photons and real photons wouldn't interact. You're thinking
Speaker 1: of an antiphoton, which also doesn't exist. So there's two
Speaker 1: directions to think about here, antimatter and dark matter, which
Speaker 1: are two separate concepts, right, but now we're combining them.
Speaker 1: We're imagining what if there's anti dark matter that can
Speaker 1: annihilate with the dark matter produce some new kind of
Speaker 1: weird version of the photon, a dark photon, dark matter's
Speaker 1: equivalent of a photon, and that dark photon can then
Speaker 1: turn into normal matter. So if that's possible, which is
Speaker 1: big assumption, no justification. We're only assuming it because otherwise
Speaker 1: this whole line of research doesn't work.
Speaker 3: I can't believe you guys get grants funded, but you
Speaker 3: go ahead. My parasites have to exist before I get
Speaker 3: to study them.
Speaker 1: Being brutally honest about this because I don't want to
Speaker 1: mislead people, and otherwise people will write it and be like,
Speaker 1: but how do you know? And I want to be
Speaker 1: straight up like, we don't know.
Speaker 3: I appreciate that, yeah.
Speaker 1: And so if that's happening, then what you can do
Speaker 1: is say, well, where is dark matter DNSE in the universe? Okay,
Speaker 1: centers of galaxies. We think a lot of it is
Speaker 1: collected there. Let's look in the center of galaxies and
Speaker 1: see if dark matter is smashing into its antimatter and
Speaker 1: producing unexplained pairs of particles like an electron and an
Speaker 1: anti electron, or muon an anti muon, and here's the
Speaker 1: antimatter angle. It's rare to see antimatter in the universe.
Speaker 1: So if there's an unexplained source of antimatter, it might
Speaker 1: be due to dark matter annihilating and turning into matter
Speaker 1: and antimatter. So we look out there in the universe
Speaker 1: for unexplained sources of antimatter, which might be due to
Speaker 1: dark matter annihilating with its own kind of antimatter and
Speaker 1: turning into normal matter and normal antimatter.
Speaker 3: Okay, that's exciting. Have we failed that.
Speaker 1: We actually do have some really tantalizing signals of that.
Speaker 1: People have looked out into space for all kinds of antimatter.
Speaker 1: We look for positrons, which are rare but not super rare,
Speaker 1: and there are some things out there in the universe
Speaker 1: that make them. Like pulsars. We look for antiproton, which
Speaker 1: are more rare than anti electrons. We look for anti deuterium.
Speaker 1: We also look for anti helium or anti helium three,
Speaker 1: which is even rarer in the universe. So the bigger stuff,
Speaker 1: the bigger fat or juicier anti matter particles are rarer,
Speaker 1: which makes them a clearer signal. So we have a
Speaker 1: bunch of fun experiments looking for antimatter in space, basically
Speaker 1: as a hope that if you see it, it might
Speaker 1: be an indication of dark matter. And there's an experiment
Speaker 1: on the space station. It's called AMS, which stands for
Speaker 1: the Alpha Magnetic Spectrometer. Basically, it's a big particle detector
Speaker 1: and a magnet in space. The mag that shows you
Speaker 1: the particles bending, which tells you they're charge, so you
Speaker 1: can tell whether they're matter or antimatter. And it's just
Speaker 1: basically like this particle experiment that's stuck on the space station.
Speaker 1: It's run by Sam Ting, who has already a Nobel Prize,
Speaker 1: And they see a bunch of positrons anti electrons that
Speaker 1: they can't explain, that nobody can explain. So they see
Speaker 1: all these weird particles, these anti particles actually in space
Speaker 1: that nobody can explain, and people have long wondered, like,
Speaker 1: is this a signal of dark matter? Are we seeing
Speaker 1: dark matter? And it's exciting, but it's also very indirect, like, yeah,
Speaker 1: you're seeing antimatter, and antimatter is rarer in the universe
Speaker 1: than matter, but it's not that rare, especially anti electrons
Speaker 1: like pulsars do make a lot of anti electrons and
Speaker 1: fling them out into space and are famously hard to understand,
Speaker 1: So it's possible that the signal they're seeing is just
Speaker 1: pulsars or something else weird out there in the universe
Speaker 1: that makes antimatter, right, antimatter again weird, but not weird
Speaker 1: enough that the only way to make it is dark matter.
Speaker 1: So it's like, if you see it, it's kind of indirect.
Speaker 3: So it'd be helpful if we understood more about how
Speaker 3: antimatter is made.
Speaker 1: Yes, absolutely, the biggest challenge in astronomy is that most
Speaker 1: of the universe is doing weird, funky stuff we don't understand.
Speaker 1: So when you see something you don't understand, you're like, well,
Speaker 1: is this the thing I was looking for or something
Speaker 1: totally weird and new that we didn't understand anyway, looking
Speaker 1: for signals from the center of the galaxy, and you
Speaker 1: might ask, well, do we understand the rest of the
Speaker 1: center of the galaxy, what's going on in there and
Speaker 1: all the other signals we might see. The answer is
Speaker 1: definitely not. Like there's a huge amount of stuff going
Speaker 1: on in the center of the galaxy. We don't know
Speaker 1: what's in there, what it's doing, how it's interacting. It's
Speaker 1: hidden by gas and dust. It's a big question mark.
Speaker 1: So we're looking for a little weird signal on top
Speaker 1: of a big weird thing we don't understand. It's like
Speaker 1: listening for a whisper inside a rave in a language
Speaker 1: you don't understand. We're doing the best we can.
Speaker 3: That's a daunting task. As someone who doesn't like areas
Speaker 3: with lots of people, that also sounds very overwhelming. Okay,
Speaker 3: so we've got an experiment on the space station. Are
Speaker 3: we trying to collect data on this in any other way?
Speaker 1: We are, absolutely. There's a bunch of people looking for
Speaker 1: cosmic ray anti matter. One of the really exciting experiments
Speaker 1: is called GAPS. This is a huge balloon experiment that's
Speaker 1: going to fly over Antarctica. They like build a particle detector,
Speaker 1: then they attach it to a weather balloon and they
Speaker 1: just fill it with helium and then just let it
Speaker 1: float up and circulate according to the winds around Antarctica,
Speaker 1: and it'll be up there for days, weeks, months, depending
Speaker 1: on the experiment. And like these are really nerve racking
Speaker 1: experiments because sometimes they crash. You know, it's weather and
Speaker 1: its winds and their storms, and they lose it. And
Speaker 1: so imagine you're a graduate student. You spent like four
Speaker 1: years building this very delicate piece of equipment. Now you
Speaker 1: just send it up into the skies and the hope
Speaker 1: that it doesn't just like get obliterated. And so this
Speaker 1: would be a really cool experiment because it's very sensitive
Speaker 1: to antimatter. It's hoping to trap anti particles, so like
Speaker 1: slow them down and trap them inside the experiment so
Speaker 1: that they form an exotic atom bound between like matter
Speaker 1: and antimatter. So imagine you have like anti deuterium or
Speaker 1: anti helium three comes into your experiment, gets slowed down
Speaker 1: and then like bonds with some silicon atoms, and you
Speaker 1: have this weird atom that's like two kind of nuclei
Speaker 1: bound together, one matter, one antimatter, and they're gonna admit
Speaker 1: a bunch of weird light as they relax down and
Speaker 1: then eventually annihilate and make a big flash, and by
Speaker 1: the pattern of those annihilations they can tell exactly what
Speaker 1: kind of antimatter it was. So this is a future
Speaker 1: experiment they're working on. Somebody's out there right now, like
Speaker 1: building this thing and preparing it for launch over Antarctica.
Speaker 1: They've been saying for years it's like about to go,
Speaker 1: and the last I heard, it's gonna fly in twenty
Speaker 1: twenty five. So this might tell us something about antimatter,
Speaker 1: cosmic rays, antimatter from space, which might be a clue
Speaker 1: about where the dark matter is and if there's anti
Speaker 1: dark matter annihilating with the dark matter to send us
Speaker 1: messages about what it's doing.
Speaker 3: And do you know if that was part of the
Speaker 3: justification for getting this project funded or was this more
Speaker 3: a question about antimatter.
Speaker 1: Now, this is definitely one of the motivations for this
Speaker 1: experiment directly. It's like understanding antimatter cosmic rays. Cosmic ray
Speaker 1: is an enduring mystery anyway, like we don't understand what's
Speaker 1: making them, and especially the very highest so gaps can
Speaker 1: do lots of different kind of physics not just look
Speaker 1: for dark matter signals, but I think the signal from
Speaker 1: AMS is very tantalizing, and it inspires lots of follow
Speaker 1: up experiments. And you know, when you see something you
Speaker 1: don't understand, you try to explain it, and then you
Speaker 1: do follow up experiments say well, if that's true, then
Speaker 1: we should also see it over here, and let's do
Speaker 1: a different kind of experiments that also spots it. Because,
Speaker 1: like with dark matter, what you want is a coherent story.
Speaker 1: You don't just want one unexplained data that you can
Speaker 1: fudge away with some factor. You want a total story that,
Speaker 1: when you poke at it from lots of different directions,
Speaker 1: is always telling you the same story. And that's the
Speaker 1: thing about dark matter. No matter how we study it,
Speaker 1: we can tell its matter. It's there, it has gravity,
Speaker 1: and so what we want is to complete that story
Speaker 1: by understanding its interactions with normal matter and maybe with
Speaker 1: anti dark matter. And so that's why GAPS is like
Speaker 1: a very different kind of experiment from AMS, not just
Speaker 1: like a repeat of it, to hope to get like
Speaker 1: a different angle on the mystery, and maybe it'll see
Speaker 1: something and confirm it, and then we'll all can be
Speaker 1: convinced that we're seeing antiparticles from dark matter, or maybe
Speaker 1: they'll see nothing, or maybe it'll see something else totally
Speaker 1: weird that we didn't expect the way astronomy often does.
Speaker 3: So if they could afford it, and I know this
Speaker 3: would be a much more expensive experiment, would it be
Speaker 3: better to put that detector outside of Earth's magnetosphere because
Speaker 3: some of those galactic cosmic rays sort of get stopped
Speaker 3: or are you at Antarctica because they get shuttled to
Speaker 3: the poles.
Speaker 1: Yeah, great question. There's sort of just different traditions and
Speaker 1: physics ways people figure it out to make physics work,
Speaker 1: and definitely launching stuff into space is one of them.
Speaker 1: But wow, that's expensive and slow, and then you've got
Speaker 1: to get in line and you can cancel it any
Speaker 1: minute after ten years of work, and so sort of
Speaker 1: an intermediate approach is like, hey, we just need a
Speaker 1: big balloon. We don't have to go all the way
Speaker 1: into space. We can just go like go to the
Speaker 1: top of the atmosphere. And the winds around Antarctica actually
Speaker 1: tend to propel things in a circle, so you can
Speaker 1: sort of like float in circles and do these loops
Speaker 1: around Antarctica. So there's a long tradition of these balloon
Speaker 1: experiments around anti Arctica. Really amazing science and really brave,
Speaker 1: you know, Like, I'm so impressed by these people who
Speaker 1: risk everything for these balloon experiments and have to go
Speaker 1: to Antarctica to launch them and recover them. I mean,
Speaker 1: for some people they get to go to Antarctica, it's
Speaker 1: like really exciting for them. But for me, I'm like, yikes.
Speaker 3: I agreed. Yes, I have a friend who's excited because
Speaker 3: he got to go to Antarctica, But for me it
Speaker 3: would be I have to go to the Antarctica, but I
Speaker 3: don't love being cold. We got four inches of snow
Speaker 3: and that is the right amount and it'll melt next
Speaker 3: week and that's perfect exactly.
Speaker 1: And that's one of the things I love about science.
Speaker 1: You know, it takes all kinds. It takes normal people
Speaker 1: who don't want to go to Antarctica and crazy people
Speaker 1: who do want to go to Antarctica, and we're all
Speaker 1: grateful for them.
Speaker 3: Something for everyone exactly. All right, Well, so what do
Speaker 3: you think, Daniel when the results of the GAPS experiment
Speaker 3: come in or are we going to have an episode
Speaker 3: just about what they found? Unless it crashes, let's do it.
Speaker 1: I definitely want to know the answer, and I want
Speaker 1: to share the answer with everybody. And I'm just really
Speaker 1: hoping that dark matter is interesting and complicated and has
Speaker 1: some kind of interactions. You know, that would make sense
Speaker 1: because our kind of matter does. It's not just like gravitational.
Speaker 1: It interacts in all sorts of complicated ways, and we
Speaker 1: have lots of different kinds of normal matter, all these
Speaker 1: different particles. It would be really weird if dark matter,
Speaker 1: which is most of the universe, was also really simple,
Speaker 1: like just one kind of particle and one kind of
Speaker 1: interaction gravity. It would be unusual. But then, you know,
Speaker 1: the universe is not afraid to surprise us and confuse us.
Speaker 1: So it could be that dark matter is kind of
Speaker 1: sterile and boring. But I suspect that it's not. I
Speaker 1: suspect there's lots of different dark matter particles and they're
Speaker 1: all doing some weird, funky dance out there. It's certainly
Speaker 1: possible that that's the case, and that's the universe I
Speaker 1: hope we live in, because it would be much more
Speaker 1: discoverable if dark matter is just gravitational. It could be
Speaker 1: a long long time or ever before we figure it out.
Speaker 3: Well, let's hope we have the answer before we retire, perspire,
Speaker 3: or expire. I'm keeping my fingers cross.
Speaker 1: For you, all right. Thanks he everyone, And so sometimes
Speaker 1: you see there are connections between the mysteries of the universe.
Speaker 1: Dark matter and antimatter might dance together to make themselves explainable.
Speaker 3: Here's hoping. Until next time. Daniel and Kelly's Extraordinary Universe
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