Speaker 1: Hey, Daniel, what's the best question anyone has ever asked
Speaker 1: you about dark matter? Well, it's tough to pick. There's
Speaker 1: so many good ones. But I remember a nine year
Speaker 1: old who read our book once and emailed me to
Speaker 1: ask is dark matter bad matter? It must be a
Speaker 1: Star Wars fan. You know the dark side doesn't sound
Speaker 1: very friendly. Yeah, dark matter sounds world of unfriendly and mean.
Speaker 1: It's doesn't never a really good pr team. Well, you know,
Speaker 1: if there are dark matter physicists out there that we
Speaker 1: can't see or touch, what do you think they would
Speaker 1: call us? M I guess they'll probably call us dork matter.
Speaker 1: We wouldn't seem dark to them and insidious. No, actually
Speaker 1: we would. I mean if they have their own dark photons,
Speaker 1: they wouldn't see ours, so we would be dark to them. Man,
Speaker 1: I can just imagine the conferences. You know, you just
Speaker 1: spent the whole day saying you're a dark matter. No,
Speaker 1: you're a dark matter. That's probably actually true. That's exactly
Speaker 1: what would happen. I am, forhand, a cartoonist and the
Speaker 1: creator of PhD comments. Hi, I'm Daniel Whitson, I'm a
Speaker 1: particle physicist, and I'm mostly made out of dork particles. Particles,
Speaker 1: dark dork particles. That's the worst. Well, mostly in the
Speaker 1: summer right now. I'm not going outside very much, so
Speaker 1: pale dark. My dork particles are not very dark. But
Speaker 1: welcome to our podcast Daniel and Jorge Explain the Universe,
Speaker 1: a production of I Heart Radio, in which we take
Speaker 1: you on a mental tour of the universe, zooming down
Speaker 1: to see what the universe is made out of, what
Speaker 1: it looks like at its largest scale, what crazy weird
Speaker 1: stuff we encounter in it, and how we can all
Speaker 1: understand it because humanity is on a journey, a journey
Speaker 1: to understand this universe. We started out really kind of
Speaker 1: clueless about the way things work, and we slowly put
Speaker 1: together little pieces of the picture. But we're here to
Speaker 1: give you a tour of what we have figured out
Speaker 1: and what still remains unknown. Yeah, and it turns out
Speaker 1: we haven't even left the garage, it seems, Daniel, in
Speaker 1: our journey of discovery, because a huge percentage of the
Speaker 1: universe is made out of stuff that we have no
Speaker 1: idea about. You know, twenty five percent of the universe
Speaker 1: is made out of something we call dark matter, which
Speaker 1: is a huge mystery. Right, that's right, And that might
Speaker 1: seem a bit deflating to you, like, wow, we haven't
Speaker 1: figured anything out, But to me that's exciting, Like, wow,
Speaker 1: we haven't figured anything out, which means more discoveries are
Speaker 1: to come, which means mind blowing revelations about the true
Speaker 1: nature of the universe are in our future. You know,
Speaker 1: if you haven't left the garage, that means you can
Speaker 1: still go back inside. If you forget something that's positive,
Speaker 1: that's right, Like you forgot to pack your banana. How
Speaker 1: can you even take a journey of discovery without banana?
Speaker 1: About these days, who can go anywhere? Yeah, we're talking
Speaker 1: about dark matter today and it's a huge mystery and
Speaker 1: it's out there. But a big question is what is
Speaker 1: it made out of? What is it? Is it a fluid,
Speaker 1: is it a an energy? Or is it made out
Speaker 1: of particles or something totally different. That's right, Everything we've
Speaker 1: ever experienced, everything you've ever eaten or touched or tasted,
Speaker 1: are made out of quarks and electrons and stuff like that,
Speaker 1: and so we wonder does the same thing hold for
Speaker 1: dark matter. But it's a pretty big extrapolation. I mean,
Speaker 1: the kind of matter that we're made out of that's
Speaker 1: very familiar, is unusual in the universe, and so it
Speaker 1: seems kind of odd to extrapolate from this tiny little
Speaker 1: corner to a huge fraction of the universe. And so
Speaker 1: particle physicists think maybe it's made of particles, but I
Speaker 1: like to think, hey, maybe it's made of something totally
Speaker 1: weird and new. Yeah, we really have no idea. And
Speaker 1: it's there's five times more dark matter in the universe
Speaker 1: than there is of the stuff that we are made
Speaker 1: out of. And it really could be anything like it
Speaker 1: could be something that's not even a particle. That's right,
Speaker 1: we've never seen matter that's not made of particles. Everything
Speaker 1: we've ever experienced can be broken down into these units.
Speaker 1: But that doesn't mean that everything is like that, Right.
Speaker 1: We have to be very careful about generalizing. We've seen
Speaker 1: so many times in physics when we've learned something we thought, oh,
Speaker 1: this must be the way everything works, and then we
Speaker 1: discover it's not. Actually and there are bigger stories, is
Speaker 1: a larger context, and that's the goal of science, is
Speaker 1: to reveal the actual truth, not just confirm our expectations. Yeah,
Speaker 1: and so one thing we know about dark matter is
Speaker 1: that we know that it feels gravity, because that's how
Speaker 1: we know that it's there. I mean, we can't see it,
Speaker 1: it's dark, but we know it's there because of gravity.
Speaker 1: It's keeping the gaxies together, it's pulling things together, and
Speaker 1: it's you know, affecting the trajectories of galaxies and stars.
Speaker 1: So we know it feels gravity. We certainly do. It's
Speaker 1: basically an invention to explain missing gravity. It's like a
Speaker 1: gravity fudge factor. Yeah. We see things in the universe
Speaker 1: that gravity has done, and we don't see the source
Speaker 1: of that gravity. We're like, what's this invisible thing that's
Speaker 1: making this gravity? And so dark matter is basically an
Speaker 1: explanation for this gravity that we do observe, and so
Speaker 1: it has to feel gravity otherwise it doesn't fit the
Speaker 1: bill at all. But then the question is what else
Speaker 1: does it do? Does it feel anything else? Does it
Speaker 1: feel lonely? Does it feel resentful that we call it
Speaker 1: dark matter? Yeah, we know that it feels gravity, and
Speaker 1: so the question is does it feel any other forces?
Speaker 1: And I think more interestingly about this question is does
Speaker 1: it feel itself like canna bump into itself? Yeah, And
Speaker 1: we got a really interesting question from a listener. Here's
Speaker 1: an email I god from Joe from China, who I
Speaker 1: think really put his finger on the question. He says,
Speaker 1: if you were to take two particles of dark matter
Speaker 1: and let them go in a vacuum, the gravity would
Speaker 1: attract the two particles together. But then would they pass
Speaker 1: right through each other and keep moving? Eventually would they
Speaker 1: settle down and be able to share the same point
Speaker 1: in space like overlapping? Can too dark matter particles? But
Speaker 1: I guess bump into each other or occupy the same space? Yeah?
Speaker 1: Do they not into each other and push back? Do
Speaker 1: they pass right through each other? Can they sit right
Speaker 1: on top of each other. It's a really fascinating question,
Speaker 1: and it goes right to the heart of the sort
Speaker 1: of the science matter of whether dark matter feels itself?
Speaker 1: This question blow your mind a little bit? Yeah, I
Speaker 1: did blow my mind a little bit. I just love
Speaker 1: when somebody asks a new question, a question I haven't
Speaker 1: heard before, or asks it in a new way. So
Speaker 1: I haven't really thought about whether dark matter feels itself? Okay,
Speaker 1: so it's kind of a funny question. Does dark matter
Speaker 1: feel itself? That means that you know it feels itself. Gravitationally, right,
Speaker 1: if you have one bit of dark matter here and
Speaker 1: a bit of dark matter, they're they're gonna be They're
Speaker 1: going to feel each other. They're gonna be attracted to
Speaker 1: each other by gravity. But the question is, you know
Speaker 1: what happens after they feel attracted by gravity. You know,
Speaker 1: they they're moving towards each other. Are they gonna bump
Speaker 1: against and and repel it themselves or are they going
Speaker 1: to pass through each other? Or are they going to
Speaker 1: stick together? Yeah, it's a great question. I mean, if
Speaker 1: you and I have gravitational attraction, if we were out
Speaker 1: in the middle of space, then gravity would very slowly
Speaker 1: pulls together and we would bump into each other. I
Speaker 1: wouldn't phase through each other. You woul get uncomfortable really fast.
Speaker 1: What you're saying more awkward than in space. No one
Speaker 1: can hear you say, hey, I need more space, Daniel,
Speaker 1: get off me. But you couldn't write. You'd be stuck together.
Speaker 1: That's right, we need some other kind of force. But
Speaker 1: you and I do have other kind of forces, right,
Speaker 1: the electromagnetic force who keep us from passing through each other.
Speaker 1: So it's a good way to ask the questions. Yeah,
Speaker 1: so the question is does dark matter feel itself? And so,
Speaker 1: as usual, we went out into the world, and in
Speaker 1: this case, the Internet, to see how many people felt
Speaker 1: that they knew the answer to this question. That's right,
Speaker 1: So thank you to everybody who volunteered to answer random
Speaker 1: Internet physics questions. If you'd like to volunteer right to
Speaker 1: us at questions at Daniel and Jorge dot com. Yeah,
Speaker 1: you can ask us questions or get questions from us.
Speaker 1: Questions in and questions out. It's an eternal flux of questions, right.
Speaker 1: But think about it for a second. If you were
Speaker 1: to try to answer the question does dark matter feel itself?
Speaker 1: What would you answer? And no googling, no googling? What?
Speaker 1: How about? Wikipedia? Also not allowed? About calling my physicist friend?
Speaker 1: Totally allowed, totally allowed. All right, Well, here's what people
Speaker 1: on the Internet had to say. I guess I'm really
Speaker 1: not sure. I know that some scientists hypothesize the dark
Speaker 1: matter is comprised of filaments, and if there were these
Speaker 1: filaments in the dark matter, one would think that they
Speaker 1: would interact in some way. I really don't think so.
Speaker 1: I remember it interacting with something visible. That's a good one.
Speaker 1: The interaction between light matter and dark matter is for
Speaker 1: obviously still figuring that out, but I would think that
Speaker 1: it does interact with itself. I don't think that turn
Speaker 1: dark matter interacts with itself. Um. I think whether discussed
Speaker 1: two galaxies colliding with each other, but there wasn't an
Speaker 1: evidence or the details, so not itself. I would guess
Speaker 1: that dark matter would interact with itself because I know
Speaker 1: that one guess of what dark matter is is the
Speaker 1: dark matter particle axion. And it's kind of hard to
Speaker 1: visualize how a particle can pass through another particle. I
Speaker 1: don't know. I've never thought about it. Okay, Um, dark
Speaker 1: matter and dark energy confuse me a little bit. I
Speaker 1: thought that dark matter was just a theory, and so
Speaker 1: it's like we've we've seen something out there, and the
Speaker 1: theory is that this dark matter, but we don't really know.
Speaker 1: I don't think it can interact with normal matter. I
Speaker 1: surely if it could pass through itself, we would be
Speaker 1: able to see it. It might be a dark force,
Speaker 1: which helps them incorrect. I know it doesn't interact with
Speaker 1: regular matter. I think we don't know whether how it
Speaker 1: interacts with itself. It is matter, so it has maths
Speaker 1: al must interact gravitationally. I don't know. Well, I think
Speaker 1: it does on some level. I don't know whether there
Speaker 1: would be quantum or molecular, but I think it's got
Speaker 1: to interact with itself enough to come together and blobs
Speaker 1: big enough to cause gravitational lensing that we can see
Speaker 1: here from Earth. I guess it's interact with yourself, since
Speaker 1: it's i've gravity. All right, pretty thoughtful answers, you know,
Speaker 1: people sort of thoughts through it. Yeah, there's some good
Speaker 1: stuff in here. People are really thinking about what it
Speaker 1: means to interact and whether gravity counts, and whether gravity
Speaker 1: would make something bump or not? Does gravity count? Does
Speaker 1: the Earth feel USh? Yeah? But also some people getting
Speaker 1: confused about dark energy versus dark matter. That's another rabbit
Speaker 1: hole there. Does dark energy feel? What is dark energy? Anyway?
Speaker 1: We have no idea, all right, So the question is
Speaker 1: that does dark matter feel? And so Daniel Um maybe
Speaker 1: step us through what we know about dark matter and
Speaker 1: it's it's not very sensitive. Unfortunately, you know, we wish
Speaker 1: you would react more. Oh good, that's a good thing,
Speaker 1: right as a thick skin. Well, perhaps know if you
Speaker 1: want to get along with your dark matter roommate. But
Speaker 1: if you want to do experiments to reveal the nature
Speaker 1: of dark matter, you'd like it to respond sometimes, and
Speaker 1: dark matter turns out to be very difficult to probe
Speaker 1: because the only way we've been able to interact with
Speaker 1: dark matter so far at all is with gravity. Like
Speaker 1: we said, we've discovered dark matter because we looked at
Speaker 1: how galaxies spin, and we notice that to spin as
Speaker 1: fast as they do and hold all the stars in place,
Speaker 1: you need a lot more gravity than is generated by
Speaker 1: the stars we see, which means there must be something
Speaker 1: else they're making that gravity. And we see blobs of
Speaker 1: dark matter in the sky. We don't see them. We
Speaker 1: deduce blobs of dark matter in the sky because they're
Speaker 1: bending the light that passes through them. That's a gravitational effect.
Speaker 1: So we have very concrete evidence that dark matter feels gravity.
Speaker 1: That's why we call it matter, not just like dark
Speaker 1: mysterious thing in the space right because it has gravity.
Speaker 1: I see. It's sort of like the probervial elephant in
Speaker 1: the room. You know it's there, everyone knows it's there,
Speaker 1: but it's, uh, it's nobody's talking about. Sort of. It's
Speaker 1: also sort of like the opposite of that, because the
Speaker 1: elf in the room. Everybody is ignoring it, right though
Speaker 1: you can all see it. In this case, we're all
Speaker 1: desperately searching for it, but nobody can find it. It's
Speaker 1: like you're right or right, except you're not. Well. You know,
Speaker 1: sometimes being exactly the opposite direction is also a way
Speaker 1: of being right. Yeah, yeah, you know up bean staff
Speaker 1: yes times minus one. Alright, So we know it feels gravity,
Speaker 1: but there are other forces that we know about in
Speaker 1: the universe, and as far as we know, the dark
Speaker 1: matter doesn't feel them. That's right. And so for example,
Speaker 1: electromagnetism is a very powerful force and when that we
Speaker 1: experience every day. The reason that your hand doesn't go
Speaker 1: through the wall when you're trying to touch it is
Speaker 1: that the wall has particles that are bound together with
Speaker 1: electromagnetic forces, and so it does your hand and so
Speaker 1: you think of them like a chain link fence trying
Speaker 1: to pass through another chain link fence. That's what prevents
Speaker 1: you from passing through another object. It's Electromagnetism is also
Speaker 1: responsible for why things glow right, why we can see things,
Speaker 1: or why they reflect light. To write like, it's light
Speaker 1: hits it and then it interacts and it comes back out.
Speaker 1: That's right. Even blobs of rock that don't glow on
Speaker 1: their own, we can see them in the sky because
Speaker 1: they reflect the sun's light, like the moon or like asteroids.
Speaker 1: And so we know dark matter isn't like that because
Speaker 1: it doesn't give off light, doesn't reflect light. Light passes
Speaker 1: right through it. So right through it, yeah, exactly. And
Speaker 1: I see this all the time in science fiction television,
Speaker 1: that they encounter dark matter and it obscures their view. Right. Oh,
Speaker 1: we can't get out of this cloud of dark matter
Speaker 1: and we can't see where we are. What show are
Speaker 1: you watching and seen that one? I don't remember the
Speaker 1: name of it right now. I watched too much science fiction,
Speaker 1: But you know that, to me, that sounds like a
Speaker 1: fantastic situation, like, oh my gosh, look we found dark matter.
Speaker 1: That's right home. We win the Nobel Prize. It's not like,
Speaker 1: get out of my picture, my photo. It's like I
Speaker 1: got a photo of dark matter. Exactly. We've been trying
Speaker 1: to spot dark matter forever and you just figured it
Speaker 1: out and now it seems like a hassled you. But
Speaker 1: if you were in a cloud of dark matter, you
Speaker 1: couldn't tell because it's invisible right. In fact, we think
Speaker 1: we are in a cloud of dark matter. We think
Speaker 1: the Earth is surrounded by dark matter, but we can't
Speaker 1: see it because it doesn't reflect light. It doesn't feel
Speaker 1: any electromagnetic forces at all. Yeah, we're swimming in dark
Speaker 1: matter right, Like everyone who's listening to this podcast right
Speaker 1: now is probably swimming in dark matter. Like right in
Speaker 1: front of their eyes, is dark matter passing through or
Speaker 1: sitting there? That's right. Dark matter, we think is spread
Speaker 1: out through the galaxy. It's fairly dilute, so it's there's
Speaker 1: a lot of it. There's a lot more dark matter
Speaker 1: than normal matter, but it's much more spread out we
Speaker 1: think the normal matter, which tends to cluster into planets
Speaker 1: and stars and stuff. So we think there's like one
Speaker 1: squirrel's worth of dark matter in the volume of the Earth.
Speaker 1: But it's there, it's out there. Wait, what one squirrels worth?
Speaker 1: One squirrel? Yeah, well it's a standard international unit of mass.
Speaker 1: One squirrel. Are you not familiar with squirrels? I don't.
Speaker 1: I didn't usually baked with squirrels. All my favorite recipes
Speaker 1: are in units of squirrels. You know, a third of
Speaker 1: a squirrel of oats and you know, half a squirrel
Speaker 1: of sugar man. That's that's the pandemic for you. It's
Speaker 1: forcing us into a more primitive Yeah, come over to
Speaker 1: my house sometime. We'll have a squirrel roast. So wait,
Speaker 1: the Earth you're saying is in a pool of dark
Speaker 1: matter that has the same amount of mass as a squirrel.
Speaker 1: That's what it means. That's right, And there's more dark
Speaker 1: matter than this normal matter, but the dark matter is
Speaker 1: more diffuse, it's more spread out, and so out there
Speaker 1: in empty space is about as much dark matter as
Speaker 1: there is here in our solar system. You just made
Speaker 1: me think of a giant squirrel the size of the
Speaker 1: Earth that a dark matter. You're a very visual person,
Speaker 1: so I'd love to see a drawing of that of
Speaker 1: a squirrel attacking the Earth and earth size squirrel attacking us. Finally,
Speaker 1: the aliens have come and they're just giants space squirrels.
Speaker 1: You did it again. Just because it's a dark matter squirrel,
Speaker 1: you assume it was bad, Daniel. Yeah, maybe it's a
Speaker 1: friendly planet sized space squirrel. Yeah, you're right. Now, so
Speaker 1: we we know that it doesn't feel electromagnetism, and that's
Speaker 1: principally because it's dark, we can't see it. But there
Speaker 1: are other forces out there, right, we talk about the
Speaker 1: weak nuclear force. That's a very very non powerful force.
Speaker 1: It's a weak force between particles. Neutrinos feel this force,
Speaker 1: Leptons feel this force. All the particles we know feel
Speaker 1: this force, but it's not very powerful. Like neutrinos pass
Speaker 1: through a light year of lead and have a fifty
Speaker 1: percent chance of feeling anything using the weak force. Our
Speaker 1: particles also feeling, like the particles in my body that
Speaker 1: they feel the weak force. Yeah, all the particles in
Speaker 1: your body, on the electrons and the corks, they all
Speaker 1: feel this force. It's responsible, for example, for a beta decay.
Speaker 1: So one of the corks in a neutron can turn
Speaker 1: into another kind of quirk which turns your neutron into
Speaker 1: a proton. That happens through the weak force, and that's
Speaker 1: why a little neutrinos emitted along with the electron that's created.
Speaker 1: So all the particles in your body are sensitive to
Speaker 1: the weak force. Neutrinos that pass through you can interact
Speaker 1: with you. It's just very very un likely, like there's
Speaker 1: a hundred billion newtrinos passing through your fingernail every second,
Speaker 1: and you don't feel them well, and we know that
Speaker 1: the dark matter doesn't feel it. We suspect that dark
Speaker 1: matter doesn't feel it because we've looked very very carefully.
Speaker 1: We've set up these big underground experiments filled with very quiet,
Speaker 1: heavy liquids, and we have a lot of those atoms
Speaker 1: in there, and we hope that a dark matter particle
Speaker 1: would come by and bump into one of those xenon atoms,
Speaker 1: for example, and we could spot it. And this is
Speaker 1: similar to how newtrinos were first discovered with vast tanks
Speaker 1: of underground liquid waiting for a little recoil from one
Speaker 1: of those atoms. So we have a similar in spirit
Speaker 1: kind of experiment done underground to look for passing dark
Speaker 1: matter particles. All right, So, and there's also the strong force,
Speaker 1: right which that one is pretty important, but dark matter
Speaker 1: doesn't feel that one either. That's right. The strong force
Speaker 1: is very powerful and so unlike the weak force, which
Speaker 1: you know, if dark matter felt it, it would be
Speaker 1: difficult but possible to detect in large underground experiments. If
Speaker 1: dark matter felt the strong force, we would notice that
Speaker 1: right way. I mean, it's very powerful. It wouldn't take
Speaker 1: a very big experiment. If dark matter felt the strong force,
Speaker 1: then it would react to almost every particle in your
Speaker 1: body and every particle in the Earth. It wouldn't be
Speaker 1: hard to notice. It would break up particles all the time.
Speaker 1: It would be a very powerful force. All right. So
Speaker 1: then those are the four main forces that we know about,
Speaker 1: and as far as we know, dark matter only feels gravity.
Speaker 1: And so the question is what what happens to dark matter? Then?
Speaker 1: Does it bump into itself or does it ignore it
Speaker 1: even itself? And so let's get into the question of
Speaker 1: does dark matter feel itself? But first let's take a
Speaker 1: quick break right there. We're talking about dark matter and
Speaker 1: whether it can feel itself, and so we know it
Speaker 1: feels gravity, and we know it doesn't feel the other forces.
Speaker 1: So I guess the question is, you know what happens
Speaker 1: when too dark matter? Part of goals if they are
Speaker 1: particles get attracted to each other, what's going to happen
Speaker 1: and are they gonna bump into each other or just
Speaker 1: totally ignore each other. It's a really fun sort of
Speaker 1: thought experiment. This is exactly what Joe is asking. And
Speaker 1: so you know, let's assume for the dark matter only
Speaker 1: feels gravity, that no other forces we don't know about
Speaker 1: that are involved, that it's just a gravitational thing. And
Speaker 1: you know, that is totally possible. It's possible for a
Speaker 1: particle to have mass and no other interactions. It's sort
Speaker 1: of incredible, but it would be something that we've never
Speaker 1: seen before. But hey, this physics is full of surprises. Well,
Speaker 1: because we know about neutrinos, right, Neutrinos are also sort
Speaker 1: of selective about which forces it feels. Yeah, we don't
Speaker 1: understand that at all, Like why do neutrinos only feel
Speaker 1: the weak force? You know, why don't they feel the
Speaker 1: strong force? Why don't electrons feel the strong force. It's
Speaker 1: just sort of like a thing we observe. We notice
Speaker 1: these things. All the corks feel the strong force. None
Speaker 1: of the electrons or neutrinos or muans or towels, those
Speaker 1: particles feel it. Why not? I mean, we don't know.
Speaker 1: We know that neutrinos don't feel elect a magnetism because
Speaker 1: they don't have a charge. Only things with electric charge
Speaker 1: can feel that. But we don't understand this. It's just
Speaker 1: it's something we observe, something that we hope one day
Speaker 1: to explain From the bottoms of principle. But at this
Speaker 1: point we're pretty clueless. All right, So then what happens,
Speaker 1: Like Joe put it, What if I take two particles
Speaker 1: of dark matter in an empty universe, said I'm a
Speaker 1: meter apart, and then I let go. Well, they attract
Speaker 1: each other, right, gravity pulls them together. But then now
Speaker 1: imagine what happens when sort of their edges meet, right,
Speaker 1: what happens that one blob versus the other blob. Now,
Speaker 1: if this was normal matter, when their edges meet, then
Speaker 1: they would repel each other. They would bump, literally, because
Speaker 1: they have forces to push against each other with. But
Speaker 1: if all you have is gravity, gravity can't push. Gravity
Speaker 1: only pulls. Right, you have two objects with positive mass,
Speaker 1: they only pull on each other unless you have negative
Speaker 1: mass particles. And we have a whole other podcast episode
Speaker 1: about that. Gravity can only attract. So there's no way
Speaker 1: for gravity to put ish, which means these particles just
Speaker 1: get closer and closer. There's no repelling force, and eventually
Speaker 1: they pass through each other. Right, Because there I guess
Speaker 1: point particles right, Well, we don't know if they're made
Speaker 1: of particles, right, but imagine they are mative particles. So
Speaker 1: I think these arguments hold even if they're made of
Speaker 1: some weird other kind of thing that you know isn't
Speaker 1: divided up into little particles. But they can basically cohabitate
Speaker 1: the same space. Right. The only thing that prevents things
Speaker 1: from overlapping are the forces. Right. The reason that one
Speaker 1: proton doesn't want to be next to another proton isn't
Speaker 1: because the stuff in them is like you're crowding me
Speaker 1: or something. It's all about the forces. As you said,
Speaker 1: if you imagined that their point particles, they have zero volume.
Speaker 1: So the only thing that gives distance to things are
Speaker 1: forces that repel, and gravity can't do that. Well. I
Speaker 1: think what's interesting to think about is that you know
Speaker 1: they wouldn't share the same space for very long, right,
Speaker 1: because if you set them a meter apart, they're gonna
Speaker 1: ask some velocity by the time that you get to
Speaker 1: the center, and so they'll just keep going. Yeah, they
Speaker 1: pass through each other, but then gravity will slow them down,
Speaker 1: stop them, turn them around, and they'll come through each
Speaker 1: other again. So like slash back and forth forever and
Speaker 1: right forever, right, because there's nothing, nothing would be making
Speaker 1: you lose energy. Yeah, in your hypothetical universe where there
Speaker 1: is nothing else, then they would slash back and forth forever.
Speaker 1: If they had some other way to lose energy. There's
Speaker 1: like larger blobs of dark matter that are sort of
Speaker 1: you know, equilibrating them or something. Then eventually they would
Speaker 1: slow down and then stop and sit right in the
Speaker 1: same place. But maybe not dark matter what you're saying.
Speaker 1: In in the real universe, that would it is possible
Speaker 1: out there that dark matter has settled. Yeah, it is possible.
Speaker 1: In fact, we think that dark matter is not moving
Speaker 1: very much. There's two theories of dark matter. There's warm
Speaker 1: dark matter and cold dark matter. And warm dark matter
Speaker 1: just means that the dark matter sort of zipping around everywhere.
Speaker 1: It's like has high velocity, and cold dark matter means
Speaker 1: it's mostly sitting around. It's like sluggist chilling and not
Speaker 1: moving very fast. It's chilling matter exactly, chill dark matter.
Speaker 1: That's for a statement of its feelings. Man. Yeah, so
Speaker 1: we think the dark matter is cold. It's cold dark matter,
Speaker 1: and so it's not moving very much. But yeah, if
Speaker 1: you imagine so, like a gravitational well constructed by something else,
Speaker 1: some larger object than two pieces of dark matter in
Speaker 1: that well would fall together to the bottom of it,
Speaker 1: and then they could just sit on top of each other.
Speaker 1: And I guess the same would happen with dark matter
Speaker 1: and regular matter, right, they would technically, like we only
Speaker 1: interact with gravity with dark matter, and so therefore we
Speaker 1: would just pass through us back and forth. Oh that's
Speaker 1: a good point. Yeah, And I think you're right, And
Speaker 1: I think dark matter is passing through us right now,
Speaker 1: or we're passing through dark matter in the same way
Speaker 1: that like neutrinos passed through us. But if there literally
Speaker 1: is no interaction other than gravity, then you're right. Dark
Speaker 1: matter can be in you and you can be in
Speaker 1: dark matter. Oh man, I feel like now we're getting
Speaker 1: ethereal here about dark matter and spiritual It's in you,
Speaker 1: in all of us, and it's not just a hypothetical question.
Speaker 1: We sort of did this experiment on a massive cause,
Speaker 1: a logical scale. Oh yeah, we did it. Oh we
Speaker 1: didn't sort of do what I mean, as much as
Speaker 1: astronomers do anything. They just sort of watched the universe
Speaker 1: do stuff. You say, astronomers don't do anything, Well, they
Speaker 1: don't construct experiments, right, They don't go like, let's build
Speaker 1: a sun that has these properties and distribute these planets
Speaker 1: around it and let it go. Right. They don't do
Speaker 1: that except in simulations, but they just look around and
Speaker 1: find that situation because the universe is so vast and
Speaker 1: so varied that they can usually find whatever they're looking for.
Speaker 1: The shoppers, not doers. I love astronomers. Nothing I say
Speaker 1: should be construed as negative towards astronomy or astronomers. But yeah,
Speaker 1: they're mostly observers, right, And what they found was these
Speaker 1: two clusters of galaxies that had slammed into each other. Yeah,
Speaker 1: it's called the Bullet cluster. Right, it's called the Bullet cluster.
Speaker 1: And this is a collision that happened a long long
Speaker 1: time ago. And by galaxy cluster, we just mean literally
Speaker 1: a group of galaxies, because galaxies orbit each other and
Speaker 1: are sort of grouped to either the same way that
Speaker 1: like stars are grouped together into a galaxy, galaxies themselves
Speaker 1: are grouped together into clusters of galaxies, and sometimes these
Speaker 1: things collide. Right. Dark energy is pushing the whole universe apart,
Speaker 1: creating spaces between things, but there are still forces and
Speaker 1: still directions that can pull things together. And so gravity
Speaker 1: pulled these two clusters together and they slammed into each other,
Speaker 1: and so we basically got to see this experiment happened. Yeah,
Speaker 1: you can look it up online if you google bullet cluster,
Speaker 1: and they're pretty spectacular images. Like, imagine a cluster of
Speaker 1: galaxies slamming into another cluster of galaxies. It's like a
Speaker 1: special effects bonanza. It's like a large hadron collider on
Speaker 1: the biggest scale possible, the largest, the large gaxy collider collider. Yeah,
Speaker 1: and of course you can't see it happen in real time.
Speaker 1: The whole collision took, you know, hundreds of millions of years.
Speaker 1: What we're looking at when we see it in the sky,
Speaker 1: it's just the after effects, and we can reconstruct what
Speaker 1: we think happened from what we're seeing now. And so,
Speaker 1: you know, the clusters are made of sort of three
Speaker 1: basic constituents. You have the stars, of course, so the
Speaker 1: things that are visible in the galaxy, and then between
Speaker 1: the stars you have gas, the things that make the stars.
Speaker 1: And then of course each one has dark matter, these
Speaker 1: huge blobs of dark matter. Remember that most of the
Speaker 1: things that are out there in the sky, the visible galaxies,
Speaker 1: have these halos of dark matter around them. So wherever
Speaker 1: you see stuff in the sky is probably where the
Speaker 1: dark matter is. They tend to follow each other. We've
Speaker 1: never seen or have we seen dark matter by itself.
Speaker 1: We have noticed some clumps, like that's what gravitational lensing is,
Speaker 1: so it is distributed. It goes out further past the
Speaker 1: edge of the galaxy, Like each galaxy has a halo
Speaker 1: that's longer and wider and larger than the galaxy itself.
Speaker 1: And we have seen blobs of dark matter in the
Speaker 1: universe by themselves. They do this gravitational lensing, but for
Speaker 1: the most part, the structure they follow each other. And
Speaker 1: that's not an accident. That's because of gravity. The structure
Speaker 1: of dark matter created the structure of normal matter, like
Speaker 1: created these gravitational wells for normal matter to fall into.
Speaker 1: That's why we have galaxies and stars and planets and squirrels.
Speaker 1: It's like, which came first, the dark matter or the galaxies,
Speaker 1: And the answer is the dark matter. Yeah, well, all
Speaker 1: the matter was created, i think at the same time,
Speaker 1: but dark matter there's more of it, and so it
Speaker 1: has a huge influence on the shape of the universe.
Speaker 1: So we saw this collision happen and we looked at it,
Speaker 1: and what we noticed is that when these two galaxy
Speaker 1: clusters passed through each other, the gas reacted like you
Speaker 1: would expect what to happen when two huge piles of
Speaker 1: stuff hit each other, right, big special effects, explosions, lots
Speaker 1: of friction and radiation at the edges and all that
Speaker 1: kind of stuff. And so you could see the gas
Speaker 1: not just kind of mixing with itself but actually like
Speaker 1: violently reacting. Oh yeah, these things are moving really fast. Absolutely,
Speaker 1: like if you shoot gas really fast and another cloud
Speaker 1: of gas, then things would happen. Things will happen, and
Speaker 1: they slow down, right, And so that energy had to
Speaker 1: go somewhere, and that energy went to heating up the
Speaker 1: gas and then it radiates, and you have all this
Speaker 1: friction between these two colliding clouds of gas. But the
Speaker 1: dark matter in these clusters got stripped way. It passed
Speaker 1: right through. It went right through the clouds of gas
Speaker 1: and right through the clouds of dark matter from the
Speaker 1: other galaxy and passed through to the other side like
Speaker 1: it went through the windshield or you know, thinking maybe
Speaker 1: like in the matrix, remember when they're fighting those ghosts
Speaker 1: and they're in the car and they slammed the brakes
Speaker 1: and the ghosts just keep going. Yeah, kind of like that,
Speaker 1: or like you're walking down the sidewalk with your kid
Speaker 1: and they notice something interesting and they stop and you
Speaker 1: just on your phone, and so you don't even pay
Speaker 1: attention to a block later, you're like, wait a second,
Speaker 1: where's my kid? I mean, that's never happened to me.
Speaker 1: They're reacting with some gas or is it running to
Speaker 1: another kid that you didn't spot? Right, there's the analogy,
Speaker 1: and the two parents just keep going looking at their phone.
Speaker 1: We're really modeling responsible parenting. I know, we're really talking
Speaker 1: about our feelings. And so we can see the dark
Speaker 1: matter came at the other side because we use gravitational lensing,
Speaker 1: we can see it distorting the light from background galaxies.
Speaker 1: So dark matter passed right through normal matter, gas, etcetera.
Speaker 1: Collided and so they got separated. So we really can't
Speaker 1: see in that case, this is a you know, collidab
Speaker 1: lab of dark matter with another lav of dark matter.
Speaker 1: What happens, Well, they massed right through nothing exactly, nothing happens.
Speaker 1: It just it just passes right through at least exciting collision. Ever, Well,
Speaker 1: I'm sure if it's exciting for them to lose their
Speaker 1: kids A few blocks back. All right. So we know
Speaker 1: then for sure through observational experiments that dark matter doesn't
Speaker 1: seem to feel itself, at least not in the way
Speaker 1: that we know about or with any forces that we
Speaker 1: know about. And so the question is, is there maybe
Speaker 1: another way that dark matter can feel itself that we
Speaker 1: don't know about? And so let's get into that. But
Speaker 1: first let's take a quick break. All right, Daniel, have
Speaker 1: you have you find your child yet? I've got your
Speaker 1: child and still looking for mine. Oh well no, wait,
Speaker 1: this one looks like, oh man, what take mishap here? Yeah,
Speaker 1: it's like parent trapped galaxy style. All right. So we're
Speaker 1: talking about dark matter and whether or not it can
Speaker 1: feel itself. And we know you can feel itself with gravity,
Speaker 1: but gravity doesn't help you really, you know, permanently feel
Speaker 1: or clump or things like that. And so the question
Speaker 1: is it could there be maybe another way that dark
Speaker 1: matter interacts with itself that we don't know? There absolutely
Speaker 1: could be, I mean, the existence of dark matter and
Speaker 1: the existence of dark energy, and our sheer ignorance about
Speaker 1: how the universe works, how it begins, and what controls
Speaker 1: its largest dynamics tells us that there's a lot to
Speaker 1: learn about the universe, and so there's certainly could be
Speaker 1: a whole other force out there, some force we've never discovered,
Speaker 1: some force that only dark matter feels and feels with
Speaker 1: other dark matter, and that might be the reason we've
Speaker 1: never seen it, the dark side of the force. Yeah,
Speaker 1: there's nothing preventing another kind of force from existing. It's
Speaker 1: not like we have any idea as to the number
Speaker 1: of forces that there could be, or is any limit
Speaker 1: to how many forces there are. It's just sort of
Speaker 1: like a list of stuff we've seen so far in
Speaker 1: our attempt to understand it. And so that's it. That
Speaker 1: list is almost certainly incomplete, the way our list of
Speaker 1: particles is incomplete, or the list of Beatles is incomplete. Right,
Speaker 1: Like every year he's scovered like a a thousand new kinds
Speaker 1: of Beatle. It's amazing. Yeah, Ringo, Paul Bob Robert And
Speaker 1: that was such a bad joke. I'm sorry. I did
Speaker 1: learn about a new Beatle last week. Actually, I discovered
Speaker 1: that they brought Ringo in, that they fired the original drummer,
Speaker 1: and he's still kind of better about the fifth One
Speaker 1: of the fifth Beatles is usually refers to their producer.
Speaker 1: But yeah, that the Ringo was not the original drummer. Yeah,
Speaker 1: not a music podcast, So let's stick to our strengths
Speaker 1: here matters. Yeah, well, this is a really interesting idea.
Speaker 1: I think that the you know, because it's it's like
Speaker 1: totally possible for there to be a whole another universe
Speaker 1: on top of us, right, Like there could be a
Speaker 1: whole set of other particles to feel, a whole other
Speaker 1: set of forces, but we just can't see them or
Speaker 1: feeling or touch them. Yeah, there's a whole party going on,
Speaker 1: and we weren't invited, and even if we had been invited,
Speaker 1: we couldn't even really attend because it just ignores us completely, right,
Speaker 1: And we know that there's a lot going out there
Speaker 1: that we can't see. Right, what we see in the
Speaker 1: universe is a tiny fraction what's actually happening, even just
Speaker 1: here on Earth with your eyeballs. Your eyeballs see a
Speaker 1: little sliver of all the electromagnetic radiation that's out there.
Speaker 1: There's a lot of stuff going on you can't see.
Speaker 1: And imagine if you could see, you know, cell phone
Speaker 1: signals and television signals and radio waves, the world would
Speaker 1: be a much different looking place. And so we see
Speaker 1: a little fraction of what's actually happening. Wow, and good
Speaker 1: thing to write like it be overwhelmed me. I mean,
Speaker 1: you can get Netflix in the Hulu for free, but
Speaker 1: you know, cloud based delivery would be a different kind
Speaker 1: of thing. All right, So there could be another force
Speaker 1: out there, and it's im possible the dark matter feels
Speaker 1: it then when we see it in these collisions, that
Speaker 1: was interacting with itself in another way. Yeah. So there's
Speaker 1: sort of two different categories of ideas. One is, could
Speaker 1: there be another force that dark matter feels and uses
Speaker 1: to interact with our kind of matter, some new kind
Speaker 1: of force we've never seen before that mediates the interaction
Speaker 1: between those two kinds of particles and that we're looking
Speaker 1: for and we haven't ever seen, and we're looking for
Speaker 1: that in the same way we're looking for like its
Speaker 1: interaction via the weak force. We have these big tanks
Speaker 1: of underground normal matter particles and we wait for dark
Speaker 1: matter to bump into It doesn't matter if it's the
Speaker 1: weak force or some other new kind of force. Like
Speaker 1: would it be really hard to, for example, to take
Speaker 1: one squirrel that's flying through the earth. Yes, And now
Speaker 1: you're talking about one squirrel particle and it's flying through
Speaker 1: like a ton of liquid zenon. These are very difficult experiments,
Speaker 1: and they're done underground, like a kilometer underground to keep
Speaker 1: them cold and isolated from all of the sources of background.
Speaker 1: They're very hard experiments, and they haven't seen anything so far. Right,
Speaker 1: But can you say it conclusively, like there's a pink
Speaker 1: squirrel out there with the purple polka dots, but we
Speaker 1: haven't found it on Earth, so therefore it must not exist.
Speaker 1: You're right. We can't say it does not exist. We
Speaker 1: can say it's less common than one squirrel per cubic
Speaker 1: volume per year. Right, We can just say how likely
Speaker 1: it is to exist at a certain level, and so
Speaker 1: it could still be there. And people are still running
Speaker 1: these experiments, and the longer we run them, the more
Speaker 1: we can push those limits. We can say, if this
Speaker 1: force does exist between standard model A matter and dark matter,
Speaker 1: that it must be even weaker than this limit, than
Speaker 1: this limit, than this lem We keep pushing that down.
Speaker 1: But there's a whole other category, which is like maybe
Speaker 1: dark matter just feel stuff with itself, not with our experiments,
Speaker 1: not with our bodies, but just between itself, like is
Speaker 1: it possible that dark matter bumps into itself and feels
Speaker 1: something right or repels each other with because you're telling
Speaker 1: me that this idea that it only feels gravity is
Speaker 1: sort of on thin nice like maybe there's evidence that
Speaker 1: maybe it does feel something else. Yeah, And this is
Speaker 1: really hard to probe because you can't do experiments using
Speaker 1: normal matter material to probe dark matters interactions with itself.
Speaker 1: You need to like build your experiment out of dark matter, right,
Speaker 1: So all we can do is look at how the
Speaker 1: dark matter is laid out in the universe, like where
Speaker 1: did it end up, and then try to see is
Speaker 1: that consistent with how it should end up if it
Speaker 1: only feels gravity, because if it is bumping into itself,
Speaker 1: that will change the way it's laid out, just like
Speaker 1: if it's hot or cold, if it's fast or slow,
Speaker 1: will also change the distribution of dark matter. So we
Speaker 1: look at the distribution and try to ask is it
Speaker 1: consistent with gravity only or do we need another piece
Speaker 1: of the puzzle aid And what do we see do
Speaker 1: we see out there in the universe that maybe it
Speaker 1: does feel another force? We see that mostly gets things
Speaker 1: right sort of on the scale of galaxies, and larger
Speaker 1: like the distribution of galaxies and how they cluster together
Speaker 1: and superclusters. That all seems right, and you run a
Speaker 1: simulation of the universe with dark matter and normal matter
Speaker 1: and dark matter is only gravity, it mostly gets that right.
Speaker 1: But then if you zoom in, like on the smaller
Speaker 1: scale here, smaller scales like less than a galaxy siza,
Speaker 1: then sub galaxy, then it's not quite right. It doesn't
Speaker 1: predict things the way we see them. For example, we
Speaker 1: know that we have a big blob of dark matter
Speaker 1: in our galaxy, and we know it's the densest at
Speaker 1: the center just because of gravity, But the exact shape
Speaker 1: of that blob is not something that we understand, like
Speaker 1: dark matter with only gravity predicts it sort of like
Speaker 1: peaked right at the center, that the center is like
Speaker 1: a hot spot for dark matter. But we go out
Speaker 1: and measure it, we see it's much more spread out
Speaker 1: than that. It's like much more of a rod core,
Speaker 1: not so much like peaked like a cusp, and so
Speaker 1: that's not something we understand. Fuzzier than what you would expect.
Speaker 1: You would expect it to sort of cluster more, but
Speaker 1: it's actually kind of fuzzy it's like a big fuzzy squirrel,
Speaker 1: not a little tiny intense squirrel. Yeah, it's a hedgehog
Speaker 1: or or something like that rather than a tiny little squirrel.
Speaker 1: And if you change your simulations and you add a
Speaker 1: little bit of bumping this like a little bit like
Speaker 1: maybe sometimes dark matter does bump into itself, that describes
Speaker 1: what we see better, meaning like a little bit of
Speaker 1: a repulsive force with itself. You just add in a
Speaker 1: made up force. You're like, we don't know, but let's
Speaker 1: see if it describes a situation, just like we made
Speaker 1: up dark matter to describe this gravity we were seeing.
Speaker 1: We're like, all right, well, now let's give another force
Speaker 1: to these particles that are creating the gravity, so that
Speaker 1: the distribution of gravity is the way we are seeing it.
Speaker 1: Let's make something up about something that we've made up.
Speaker 1: You're talking about all the physics, now, man, we'll come
Speaker 1: to science. What if that thing we made up for
Speaker 1: the thing we made up, that's something else we make up. Yeah,
Speaker 1: and so this is sort of the state of the art.
Speaker 1: Now we're like looking really carefully trying to understand where
Speaker 1: is the dark matter? Does it agree with what we
Speaker 1: predict and it turns out it doesn't quite agree, and
Speaker 1: there are other little details that the gravity only theory
Speaker 1: is getting wrong, so that they're sort of strong maybe
Speaker 1: or at least a hint of an indication that maybe
Speaker 1: dark matter does feel a whole new force or could
Speaker 1: it be one of the old force. It couldn't be
Speaker 1: one of the old forces. It would have to be
Speaker 1: some sort of self interaction. So this theory is called
Speaker 1: self interacting dark matter, and it solves some of these
Speaker 1: nagging problems that we've had in the gravity only theory
Speaker 1: of dark matter. So that makes it compelling. It's not
Speaker 1: proof at all that this is happening, but it's like, huh,
Speaker 1: we've had this problem. We add this new idea. It
Speaker 1: gives a better explanation. That's cool. And you always have
Speaker 1: to be careful when you're adding more stuff to your theory. Right,
Speaker 1: you'd like the simplest possible explanation, but if that doesn't work,
Speaker 1: then you have to add a little widget to your theory,
Speaker 1: like maybe what if there are two kinds of squirrels matter? Yeah,
Speaker 1: and and that's a whole other idea, right, Like if
Speaker 1: dark matter made of particles, is it one kind of particles?
Speaker 1: Is it two or is it ten? Didn't they decay
Speaker 1: from one kind particle to the other? Do only some
Speaker 1: of them have self interactions? I mean, look at the
Speaker 1: particles that make up our kind of matter. There's all
Speaker 1: sorts of complicated interactions with weird rules we don't understand.
Speaker 1: Why would we imagine dark matter would be like simpler.
Speaker 1: It could be different shades of dark matter, the darkest
Speaker 1: matters squirrels and cats. And and then then you wonder, like,
Speaker 1: all right, well, maybe dark matter could feel itself and
Speaker 1: that would explain like the weird distribution of gravity that
Speaker 1: we're seeing. But what about the bullet cluster? Right? Didn't
Speaker 1: we do this experiment because the two clouds of dark
Speaker 1: matter didn't repel each other. They didn't repel each other.
Speaker 1: But people went back and looked at that again, and
Speaker 1: they said, all right, well, can we explain this and
Speaker 1: have some amount of interaction in there, because it's not
Speaker 1: easy to tell exactly where all the dark matter is
Speaker 1: very precisely, like maybe some of it did interact and
Speaker 1: got sort of stuck in the middle. Most of it didn't,
Speaker 1: but maybe some of it did. You know. It's like
Speaker 1: we made it up in the first place when we
Speaker 1: just you know, it's like there's a first pass and
Speaker 1: there's a more precise test, right, you know, first you
Speaker 1: try to understand the broad strokes. Then you really dig
Speaker 1: in and see if it gets the details right. And
Speaker 1: the other thing is it turns out that this is
Speaker 1: not a great dark matter collider. It's too big dark matter. Well,
Speaker 1: dark matter is very dilute, and so if you throw
Speaker 1: a huge, very dilute cloud of dark matter at another one,
Speaker 1: most of it's just going to pass through anyway. Like,
Speaker 1: dark matter is not as dense as these gas clouds.
Speaker 1: It's sort of like like the stars. Like if you
Speaker 1: have two galaxies that pass through each other, mostly the
Speaker 1: stars don't collide because the stars are embedded in huge,
Speaker 1: vast empty spaces, and so they don't really collide with
Speaker 1: each other head to head. So you were saying, like,
Speaker 1: if I take two dark matter squirrels and I throw
Speaker 1: them at each other, they might repel one against the other.
Speaker 1: But if I take a whole cloud of squirrels that
Speaker 1: are really far apart, they might just pass through each
Speaker 1: other like we've seen in the cluster. Yeah, and they
Speaker 1: would mostly miss, just like the large Hadron collider what
Speaker 1: we do is we collide to clouds of protons against
Speaker 1: each other, because one proton will never hit another proton,
Speaker 1: they're too small. So we have like ten to the
Speaker 1: ten protons and one cloud and ten to the ten
Speaker 1: to the other, and we get you know, ten or
Speaker 1: twenty or fifty collisions. And so it's not that easy
Speaker 1: to make things collide. And so it turns out the
Speaker 1: bullet cluster is actually also consistent with dark matter feeling
Speaker 1: itself at sort of a low level of tweak how
Speaker 1: you look at it. Yeah, and so you know, the
Speaker 1: game here is come up with a theory um model
Speaker 1: that explains everything that we do see all the same time.
Speaker 1: And so you have to add some of this stuff
Speaker 1: to explain the distribution of dark matter and the core
Speaker 1: versus cup effect to the center of the galaxy, but
Speaker 1: not too much that you mess up the description of
Speaker 1: the bullet cluster. So you sort of hemmed in on
Speaker 1: both sides there. Interesting, But I guess maybe the takeaways
Speaker 1: that the answer is, yes, maybe dark matter does feel itself.
Speaker 1: It's totally possible, and there might be some indication out
Speaker 1: there that it does. Yeah, it's a new idea and
Speaker 1: it's gaining traction in the community self interacting dark matter.
Speaker 1: So it's possible that yes, dark matter could feel itself
Speaker 1: and there could be multiple forces that it feels all right,
Speaker 1: So maybe dark matter does have feelings, Daniel, It might
Speaker 1: have a lot more feelings than we could ever understand.
Speaker 1: Shades and shades of nuance. Well, I think it's all again,
Speaker 1: just all of this is just an interesting example of
Speaker 1: how there are things in the universe happening that we
Speaker 1: don't really know about or see or feel or effective.
Speaker 1: We're only seeing a tiny fraction of this grand play
Speaker 1: of the universe, and we're making huge, broad conclusions about
Speaker 1: how the universe works from this tiny little corner of
Speaker 1: the stage. And there's a lot going on that we
Speaker 1: haven't ever observed. And at least we know now. We
Speaker 1: know that we're ignorant, so we know to be humble
Speaker 1: and we know not to over generalize our ideas. But
Speaker 1: it also is tantalizing because you hope that one day
Speaker 1: we will see the rest of the action, We will
Speaker 1: get a glimpse for what's really happening. We might all
Speaker 1: be swimming in a giant squirrel up mr. I like
Speaker 1: to think of myself as a physics raccoon, because it's
Speaker 1: sneaking late at night to steal other people's garbage with
Speaker 1: dark circles on your eyes. That makes sense eating garbage.
Speaker 1: All right, Well that's pretty interesting and cool and or
Speaker 1: chill um, and so we hope you enjoyed that discussion.
Speaker 1: Thanks Joe for writing with your question. And if you
Speaker 1: have a question you'd like us to explore on the podcast,
Speaker 1: please write to us. We love your questions. Two questions
Speaker 1: at Daniel and Jorge dot com. A bit mysterious. See
Speaker 1: you next time. Thanks for listening, and remember that Daniel
Speaker 1: and Jorge Explain the Universe is a production of I
Speaker 1: Heart Radio. For more podcast from my Heart Radio, visit
Speaker 1: the I Heart Radio Apple Podcasts, or wherever you listen
Speaker 1: to your favorite shows.