Speaker 1: The oderon pops up when protons collide and bounce a
Speaker 1: three gluon ghost too quick to announce.
Speaker 2: When microbes invade and our skin begins to swell, the
Speaker 2: immune system calls upon the langerhon cell.
Speaker 1: If our universe sits in a black hole's embrace, do
Speaker 1: our own black holes? Nest makomatrioshka in space.
Speaker 2: Whatever questions keep you up at night, Daniel and Kelly's
Speaker 2: answers will make it right.
Speaker 1: Welcome to Daniel and Kelly's Extraordinary Universe of Listener Questions,
Speaker 1: episode number thirty six.
Speaker 2: Hello. I'm Kelly Wienersmith. I study parasites and space, and
Speaker 2: I think that this was one of our better rhyming
Speaker 2: starts to the show.
Speaker 1: Hi, I'm Daniel. I'm a particle physicist, and my goal
Speaker 1: is to write a rhyme that Zach Weenersmith doesn't skip.
Speaker 2: Well, I mean, I think you're violating the arrow of
Speaker 2: time with that, because you know, he's just he's not
Speaker 2: going to listen to any of them.
Speaker 1: No, he's listening to this part right now, and he's thinking, hmmm,
Speaker 1: maybe I should go back and listen to the rhymes. See.
Speaker 2: Okay, Well, so here he's gonna have to listen because
Speaker 2: here's here's what I was thinking we could do today.
Speaker 2: So I ask chat gpt to write a two line
Speaker 2: poem about each of the topics that we're talking about today.
Speaker 2: And I thought that after we answered each question, we
Speaker 2: could revisit our poem and then compare the chat gpt
Speaker 2: poem and one see we could have people like way
Speaker 2: in on which one they thought was better. Yes, and
Speaker 2: we could see if chat gpt was like accurate at.
Speaker 1: All all part of our to force Zach to listen
Speaker 1: to our terrible poetry.
Speaker 2: That's right, that's right. And you know, if we're going
Speaker 2: to force him, it should be on a day when
Speaker 2: we did like pretty okay.
Speaker 1: So and since you can rewind podcasts, we can break
Speaker 1: the podcast earrow of time.
Speaker 2: We can, right. And for background for anyone who's wondering,
Speaker 2: Zach is my husband who has a degree in literature,
Speaker 2: who cringes whenever Daniel and I make any attempts at poetry.
Speaker 2: So haha, Zach.
Speaker 1: But today we're not just here to needle Kelly's husband.
Speaker 1: We're here to answer your questions because you're curious about
Speaker 1: the universe, from the stuff inside your body to the
Speaker 1: vast celestial bodies that make up our universe. You want
Speaker 1: to understand it, you want to fit it all in
Speaker 1: your mind and make it make sense. But sometimes it
Speaker 1: doesn't play along. There's something that sticks out and doesn't
Speaker 1: click together. And we are here to make it all work.
Speaker 2: Yes, we are putting together the puzzles for you, and
Speaker 2: let's start with the puzzle presented to us by Tammy
Speaker 2: from Denver.
Speaker 3: Hi, Daniel, and Kelly. This is Tammy from Denver. Heard
Speaker 3: about the Odaron particle on another podcast, basically that it
Speaker 3: exists and would love to learn more about it. I
Speaker 3: have just a few questions. How is the ouduran discovered?
Speaker 3: Does it exist naturally or is it created? And if
Speaker 3: it's created, then how is the particle stable or does
Speaker 3: it decay? And if it decays, what is the half life?
Speaker 3: Does the auduron interact with other particles and if so,
Speaker 3: how would it combine with them, repel them or would
Speaker 3: it just ignore them? If combined, would the resulting particle
Speaker 3: be stable? Thank you for answering my questions and I
Speaker 3: really enjoy the show.
Speaker 2: All right, I'll be honest, I have never heard of
Speaker 2: the odoron particle. Oh yeah, there's two d's in it.
Speaker 1: It's an odd name, but it doesn't smell bad. The
Speaker 1: odorons sounds like a really stinky particle.
Speaker 2: We'd have to get a smell expert back on the
Speaker 2: show to talk about the odoron particle. But all right,
Speaker 2: I guess this one is in your wheel, So tell
Speaker 2: us about the oduron particle.
Speaker 1: The auduron particle is not a particle in the sense
Speaker 1: that you are probably thinking. You're imagining. The universe is
Speaker 1: made up of little bits and bobs and they come
Speaker 1: together to build apples and dinosaurs and all sorts of stuff,
Speaker 1: and you can think of them as like tiny little
Speaker 1: marbles or little bits of matter and ask questions like
Speaker 1: how much mass does it have, how long does it live?
Speaker 1: How does it interact? But physicists are very generous with
Speaker 1: the term particle. It can mean lots and lots of
Speaker 1: different things. And here the short answer is that the
Speaker 1: oderon is not a little bit of stuff. It's actually
Speaker 1: just kind of a pattern seen among gluons when protons
Speaker 1: or anti protons collide.
Speaker 2: All right, so what does that mean? What does a
Speaker 2: pattern indicate?
Speaker 1: So to understand what's going on here, we really have
Speaker 1: to understand some crucial details of the strong force, which
Speaker 1: is who's in charge when protons collide. So often we
Speaker 1: smash protons together, right, like at the large hadron collider,
Speaker 1: we have a beam of proton going one way, or
Speaker 1: another being of protons going the other way, we smash
Speaker 1: them into each other. Sometimes they just bounce off each other,
Speaker 1: like the way two billiard balls would. There's no internal
Speaker 1: structure at play there. They just bounce off each other,
Speaker 1: and we call this an elastic collision. Sometimes they smash
Speaker 1: and like what's going on inside the protons interacts and
Speaker 1: we call this an inelastic collision, and then you get
Speaker 1: like new particles, etc. But if the protons are just
Speaker 1: bouncing off of each other in an elastic way, right,
Speaker 1: not breaking open, just being treated as if they were
Speaker 1: their own particles, then how does that interaction happen? Right,
Speaker 1: the protons get close to each other, how do they
Speaker 1: bounce off exactly? Well, they do that by exchanging virtual particles,
Speaker 1: like we can talk about how electrons repel each other
Speaker 1: by exchanging a virtual photon, or if you prefer the
Speaker 1: field picture, by having ripples in the electromagnetic field between them.
Speaker 1: When protons bounce off each other, it's similar except that
Speaker 1: they exchange gluons because gluons are the field that mediates
Speaker 1: the strong force. It's the analogy of the photon for electromagnetism.
Speaker 2: Still with me, I'm still with you. In my head,
Speaker 2: I can imagine what a photon is, but I'm having
Speaker 2: trouble remembering what a gluon is.
Speaker 1: Yeah, so a gluon is just like a photon for
Speaker 1: a different force. Right, Photons we have for light and electromagnetism.
Speaker 1: Gluons are for the strong force. Remember we have sort
Speaker 1: of four fundamental forces. There's the strong force, the weak force, electromagnetism,
Speaker 1: and gravity. Well, the photon is for electromagnetism, the weak
Speaker 1: forces the W and Z particles, and the strong force
Speaker 1: has the gluons. Okay, right, Okay, so we have two
Speaker 1: protons coming together and they're exchanging gluons to bounce off
Speaker 1: of each other. But gluons are really really weird.
Speaker 4: Okay.
Speaker 2: I'm still feeling like you don't get to judge me
Speaker 2: for using Latin names with all the terms that you're
Speaker 2: throwing around now, But I'm still following you. I'm still
Speaker 2: following you.
Speaker 1: Well, Unfortunately, a lot of the terms we use are
Speaker 1: not Latin names. They're just adopted from English, and then
Speaker 1: we give them totally different meanings to be massively confusing.
Speaker 2: Right, which seems even worse than but.
Speaker 1: Totally agree it's even worse. For example, sample we talk
Speaker 1: about gluons as having color, even though it's not like
Speaker 1: you can look at them and see colors. But color
Speaker 1: for gluons is an analogy to charge. For electrons, electrons
Speaker 1: have a negative charge. Protons have a positive charge. That's
Speaker 1: the electromagnetic charge. The strong force has its own charge,
Speaker 1: but we call it color because there are three varieties, red, green,
Speaker 1: and blue. But there's a crucial difference between the strong
Speaker 1: force and electromagnetism. While the photon has no charge, right,
Speaker 1: it interacts with charge particles, but the photon itself is neutral.
Speaker 1: Gluons do have charge, and that's going to turn out
Speaker 1: to be crucial for forming this interaction among gluons that
Speaker 1: we call the odoron. So the gluon itself interacts with
Speaker 1: all particles that have strong charge or color, but it
Speaker 1: also itself has color. It is a colored particle. It's
Speaker 1: like if the photon was positive or negative in charge.
Speaker 2: Okay, so when we say that a gluon has a charge,
Speaker 2: but we call it a color instead. Should I think
Speaker 2: of it as having a charge, but we're just calling
Speaker 2: it a color, But it actually is like has a
Speaker 2: charge that.
Speaker 1: Yeah, you can think of it.
Speaker 2: Why don't we just call it a charge?
Speaker 1: We do sometimes call it a charge if you're thinking
Speaker 1: charge more generally, not just electromagnetic charge. So you can
Speaker 1: think of strong charge. Every time we say the word color,
Speaker 1: you can just think strong charge and that totally works. Okay,
Speaker 1: just realize that it's not electromagnetic charge. You're not talking
Speaker 1: about positives and negatives here.
Speaker 2: Okay, So then, uh, this is going to be a
Speaker 2: real basic Kelly's embarrassed question. So then what does charge
Speaker 2: mean in a much more general sense?
Speaker 1: Oh yeah, I think we have a whole episode about that.
Speaker 1: But charge means that two fields are coupled together. So
Speaker 1: in the electromagnetic charge couples the photon field to any
Speaker 1: other kind of field. So any field that has a
Speaker 1: charge the photon interacts with, really that's a coupling between
Speaker 1: those two fields. It means energy can slosh back and
Speaker 1: forth from the electron field to the photon field, or
Speaker 1: from the gluon field to the quark field. So a
Speaker 1: charge is just like a coupling between two fields, says
Speaker 1: energy can transfer between them.
Speaker 2: Okay, got it.
Speaker 1: All right, So back to the gluon. Why are we
Speaker 1: talking about the gluon having color or having strong charge,
Speaker 1: because it has to in order to form this ouduron.
Speaker 1: And it's really fascinating. I think this is super cool.
Speaker 1: Why the gluon has colors. One more detail we need
Speaker 1: to understand before we get to the oduron, which is
Speaker 1: why you have to have multiple gluons. When two electrons
Speaker 1: come together, they can exchange just a single photon and
Speaker 1: they're done. And that's because the photon doesn't carry any charge. Right,
Speaker 1: So the electron comes in with negative charge, leads with
Speaker 1: negative charge. It's all good. But because the gluon is charged,
Speaker 1: protons cannot just exchange one gluon because protons have to
Speaker 1: have no color charge. Any object that's out there in
Speaker 1: the universe can't have a color charge all by itself.
Speaker 1: And so if a proton comes in emits one gluon,
Speaker 1: because that gluon carries away some color charge, then the
Speaker 1: proton itself would be color charged, and the proton that
Speaker 1: receives the gluon would be color charged, So the protons
Speaker 1: have to exchange two gluons, one going each direction, so
Speaker 1: that the total color charge is canceled out. But they
Speaker 1: can still exchange momentum and bounce off of each other.
Speaker 1: So let's recap. We're talking about what's happening when two
Speaker 1: protons bounce off of each other without destroying each other.
Speaker 1: They're just exchanging some momentum, and they do that by
Speaker 1: exchanging gluons. But because gluons are charged and protons are
Speaker 1: not charged under the strong force, then the gluons have
Speaker 1: to balance in charge, and so you have to have
Speaker 1: one going one way and one going the other way, Okay,
Speaker 1: and that's where the auduron comes in. The oduron is
Speaker 1: like an interaction, a pattern between those two gluons. While
Speaker 1: the gluons are between these two protons, they can also
Speaker 1: interact because they both have color charge. And that's what
Speaker 1: an aduron is. It's like a compound of gluons that
Speaker 1: are sort of bound together very briefly while two protons
Speaker 1: are interacting.
Speaker 2: Okay, so I should think of it as two gluons
Speaker 2: that are bound or they just kind of hang out
Speaker 2: near each other like awkward teenagers.
Speaker 1: Yeah, it's very short lived. It's not stable. It's really
Speaker 1: on the edge of whether you should call this thing
Speaker 1: a particle. It's more like a mathematical observation. And it
Speaker 1: turns out that you can exchange more than two gluons.
Speaker 1: You can exchange three or four or nineteen. And if
Speaker 1: you take all the exchanges which have an odd number
Speaker 1: of gluons three, five, seven, nine, eleven, and you add
Speaker 1: them all together mathematically, then the movement of that thing,
Speaker 1: the way the momentum gets exchanged between the protons is
Speaker 1: exactly as if there was a single particle exchange. So
Speaker 1: take all the odd number of gluon exchanges where these
Speaker 1: gluons are doing weird stuff and interacting along the way,
Speaker 1: add them all together. You get a big, ugly mess
Speaker 1: of mathematics. But then it collapses. It simplifies into a
Speaker 1: very simple equation, the same equation you would write if
Speaker 1: you had a single particle of mediating this exchange. And
Speaker 1: that's what the odderon is. It's like this abstraction of
Speaker 1: all of these common, iplicated interactions which happens to come
Speaker 1: together into a very simple equation. And that's why they
Speaker 1: call it the odd Oran because it's all the odd
Speaker 1: number of gluon exchanges three, five, seven, nine, et cetera.
Speaker 2: I think I don't follow why it has to be
Speaker 2: odd numbers of exchanges.
Speaker 1: This mathematical simplification to take a bunch of terms and
Speaker 1: put it together into one particle works for the odd terms.
Speaker 1: It also works for the even terms. The even term
Speaker 1: has a different name. So we called these the odoran
Speaker 1: and the other ones I think we call the pomeran.
Speaker 2: Oh, come on, they need to be the even rons
Speaker 2: or something. Why are they the potter?
Speaker 1: I was embarrassed to even tell you. I know, it's crazy.
Speaker 1: It's unforgivable the way we've named these things.
Speaker 5: It is.
Speaker 2: I'm upset. I'm getting worked up over here.
Speaker 1: Yeah. So this is a really interesting bit of physics, Tammy,
Speaker 1: and I'm glad you asked about it. Apologies that it
Speaker 1: turned out to be so complicated. There's lots of little
Speaker 1: details that you have to put together here to understand
Speaker 1: what an oduron is. I'll try to recap it again
Speaker 1: one more time, just to make sure it's all coming together.
Speaker 1: When two protons bound off of each other, they have
Speaker 1: to exchange gluons. It has to be more than one gluon,
Speaker 1: because the gluons themselves carry charge, but the protons cannot.
Speaker 1: And they can also do three, five or seven or nineteen,
Speaker 1: And if you add up all the odd terms together,
Speaker 1: it looks mathematically equivalent to exchanging a particle. That doesn't
Speaker 1: mean that particle is there and real and you could
Speaker 1: like look at it and say, oh, there's an oderon.
Speaker 1: It means that we see this pattern in the universe
Speaker 1: and we wonder, h that's cool. Let's treat it as
Speaker 1: if it was a particle. And this is a really
Speaker 1: subtle effect. It was predicted in nineteen seventy three, and
Speaker 1: it took fifty years for us to find evidence of it,
Speaker 1: and we had to compare proton proton collisions with proton
Speaker 1: anti proton collisions because those have a small difference in
Speaker 1: how many odorons would be made. And finally, fifty years
Speaker 1: after its predicted, they saw evidence for this in those collisions.
Speaker 1: So you asked, how is it created and the answer
Speaker 1: is in proton proton interactions. You also asked if it decays, Well,
Speaker 1: it only exists very very briefly. It doesn't exist on
Speaker 1: its own and then turn into other stuff. So in
Speaker 1: that sense, it always the case. It's more like a
Speaker 1: transient exchange object. It's not like a building block that
Speaker 1: you can use to make other stuff with.
Speaker 2: Okay, So that was a great explanation before we hear
Speaker 2: what Tammy thinks, because maybe we can also get Tammy's
Speaker 2: input on the poem. I think we're going to get
Speaker 2: to all right, So here's what chat GPT had to
Speaker 2: say of the oduran. Chat GPT says, in quantum shadows,
Speaker 2: the aduran leaves its subtle trace and a symmetry of
Speaker 2: gluons shaping matters hidden face. So is that is that correct? Daniel?
Speaker 1: It's not wrong. It's a little heavy, vague symbolism.
Speaker 2: Okay, all right, h And then you said the oduran
Speaker 2: pops up when protons collide and bounce a three gluon
Speaker 2: ghost too quick to announce.
Speaker 1: Yeah, So Tammy, let us know what you think of
Speaker 1: the physics explanation and who's poetry you prefer?
Speaker 2: Oh, putting Timmy on the spot, all right, that's what
Speaker 2: we're gonna do to all the listeners today, all right,
Speaker 2: throwing it to Tammy.
Speaker 3: Hi, Daniel and Kelly, thanks for answering my questions and
Speaker 3: correcting the assumption that the odd around is a particle
Speaker 3: and for explaining how it's created. You do a great
Speaker 3: job of explaining complicated concepts in an accessible way, and
Speaker 3: I learned new and interesting facts and concepts from both
Speaker 3: you and Kelly every episode. Thanks so much.
Speaker 1: All Right, we're back and we're answering questions from listeners
Speaker 1: today we are satisfying your curiosity. Up next is a
Speaker 1: fun question from Jude from Washington State.
Speaker 5: Hi, I just tried to lang her hand cell. The
Speaker 5: explanation described very generally what they do, but it didn't
Speaker 5: describe how they work. Can you explain what Langerhans cells
Speaker 5: are and how they work to help the skin respond
Speaker 5: to new stimuli. Thanks for helping us understand the universe.
Speaker 5: Jude from Washington State.
Speaker 2: All right, So after I reread this question, I thought
Speaker 2: to myself, Oh, this is one of those that kind
Speaker 2: of feels like maybe I'm being asked to do someone's homework.
Speaker 2: And then I thought, well, unfortunately for Jude, if that's
Speaker 2: the case, it takes me about three months to answer
Speaker 2: someone's questions, so it's no longer helpful. And also, I'm
Speaker 2: sure Jude is just genuinely curious about Langerhan cells.
Speaker 1: We always assume good fish, that's right.
Speaker 2: And I'm being totally unfair. So langer Han cells. Actually
Speaker 2: I did not know about langer Han cells, so I
Speaker 2: really enjoyed getting a chance to read about them. They
Speaker 2: were first described by Paul langer Hans in eighteen sixty eight.
Speaker 1: Did he name them after himself?
Speaker 2: Oh gosh, I don't know. I know that for a
Speaker 2: while there people were naming things after other people, and
Speaker 2: so this could be somebody being nice and naming something
Speaker 2: after someone else. I don't know. Maybe he did name
Speaker 2: them after you know, I would name something the Wienersmith
Speaker 2: sell if I could, So I can't judge too harshly, frankly.
Speaker 1: So this guy was just looking through a microscope and
Speaker 1: saw something new and weird.
Speaker 2: Yeah yeah, and so actually, as I understand it, he
Speaker 2: thought that it was a projection of a neuron going
Speaker 2: into your skin. So you find these cells in like
Speaker 2: your epidermis, which is the outer layer of skin, and
Speaker 2: they looked you know, when you imagine a neuron in
Speaker 2: your head, they sort of end with like sort of
Speaker 2: like a circle with that then has all of these
Speaker 2: projections sort of coming out from it. Well, it kind
Speaker 2: of looks like that circle with a bunch of projections,
Speaker 2: and so he thought like, oh, this is kind of
Speaker 2: neuron like, and so maybe it's part of the nervous system.
Speaker 2: But then a lot later we realized, no, it's actually
Speaker 2: part of the immune system. And so the Langerhan cells
Speaker 2: are like a line of attack from the immune system
Speaker 2: that is acting in your skin. Okay, And so you
Speaker 2: find them again in your epidermis, and so this is
Speaker 2: the outer layer of skin, and in particular, they're sort
Speaker 2: of like moving around inside of your keratinocytes. Keratinocytes are
Speaker 2: like so if you look at your fingers, you've got
Speaker 2: this like thick layer that is impermeable, and those are
Speaker 2: your keratinocytes. And so I learned about you know, I'm
Speaker 2: going to try to not throw too many words at you.
Speaker 2: I know, I can see Daniel's face already starting to
Speaker 2: roll his eyes, but I didn't know this, and I'm excited, right, Okay.
Speaker 2: So the deeper you go into the top layer of skin, yeah,
Speaker 2: your keratinocytes are alive and they're fed by your blood vessels.
Speaker 2: But the closer you get to your surface of your skin,
Speaker 2: they essentially start suffocating and dying and then getting like
Speaker 2: cemented and smoothed together to produce the like layer that
Speaker 2: protects you. And so I didn't really that like just
Speaker 2: you know, the closer you get, the more like dead
Speaker 2: they are, and over time they kind of like schluff off.
Speaker 2: And that also helps protect you from stuff, because like
Speaker 2: you know, if you've got like a bad microbond there,
Speaker 2: eventually they kind of like fall off with your dead
Speaker 2: skin cells and they're like, no, I was trying to
Speaker 2: get in there and now they're they're gone.
Speaker 1: This gives me the mental impression that our skin is
Speaker 1: like a slow motion waterfall, just sort of like cascading
Speaker 1: off of our pain.
Speaker 2: It was kind of like that, Yeah, I mean, you're
Speaker 2: you're like turning over your skin cells, you know, pretty
Speaker 2: regularly they're getting like sort of sluffed off and waterfalled off.
Speaker 1: Wow.
Speaker 2: Crazy, The waterfalls are more beautiful to think of than
Speaker 2: your skin cells falling off.
Speaker 1: But anyway, and so these laying your hand cells are
Speaker 1: part of these keratinocytes.
Speaker 2: They are living amongst your keratinocytes, and so they're a
Speaker 2: different kind of cell. As I mentioned, they kind of
Speaker 2: look like the end of like neurons. So they've got
Speaker 2: all of these like long projections that are sort of
Speaker 2: weaving amongst the keratinocytes, and so that let's them sort
Speaker 2: of like feel around for invaders. And then their unique
Speaker 2: immune cells and that they do two pretty different jobs.
Speaker 2: So one thing that they do is that their macrophage
Speaker 2: like and macrophage means big eater, and so when they
Speaker 2: encounter an invader, they essentially engulf it and consume it.
Speaker 2: Oh wow, so that it, you know, can't do any damage,
Speaker 2: but what if there's more. The other thing that they
Speaker 2: do is they take it to your lymph nodes so
Speaker 2: that they can present it to other parts of your
Speaker 2: immune system, so other parts of your immune system can
Speaker 2: start mounting a defense in case it turns out that
Speaker 2: there's more and you need to mount a bigger defense.
Speaker 1: So they're moving around, right, I'm imagining these caratinocytes is
Speaker 1: like squishy squares squeeze together, but these Langerhead cells can
Speaker 1: like go between them, like in the alley ways.
Speaker 2: Yeah, so they're again they're not really like squares. They're
Speaker 2: like they're like circles, but out coming out from the
Speaker 2: circles are all of these long filaments. They're think more
Speaker 2: like an octopus, but the arms are sort of like
Speaker 2: weaving amongst the cells, the keratinosites, like the cells in
Speaker 2: your skin, so that they can like explore all around
Speaker 2: to try to find invaders.
Speaker 1: Wow. And so there are security guards, they like attack
Speaker 1: them if they can, and if they and it's too
Speaker 1: much to handle, they like bring them back to the
Speaker 1: lymph node and say book them.
Speaker 2: So they definitely attack them. And then once they've eaten them,
Speaker 2: they can like still take a piece of what they've
Speaker 2: eaten and bring it to your lymph nodes and be like, Okay, guys,
Speaker 2: look what I found. Keep your eye out for this,
Speaker 2: and like maybe get ready to mount an immune response.
Speaker 2: And so in that sense, they're dendritic cells, which is
Speaker 2: another kind of immune cell. So they do two different jobs.
Speaker 2: They eat it and then they alert the immune system
Speaker 2: to the presence of invaders in case a bigger attack
Speaker 2: needs to be mounted.
Speaker 1: Wow. Fascinating.
Speaker 2: Yeah, it's pretty cool. And so they can come from
Speaker 2: bone marrow. So like say you've got a massive infection
Speaker 2: in your finger and it's like you've got a lot
Speaker 2: of inflammation, your langer hand cells will start moving towards
Speaker 2: that inflammation to like, you know, help deal with the invaders,
Speaker 2: to help eat them and sort of figure out what
Speaker 2: needs to go on, and then at that point your
Speaker 2: body might not have a lot of langer hand cells
Speaker 2: to replenish after they've all sort of gone to do
Speaker 2: this job, And so your bone marrow will make more
Speaker 2: langer hand cells and they'll sort of move up into
Speaker 2: the skin to replace the ones that have been lost.
Speaker 2: But during normal periods, your langer hand cells will just
Speaker 2: sort of like divide and replicate on their own. And
Speaker 2: part of how we know that your langer hand cells
Speaker 2: divide and sort of self renew is that when we've
Speaker 2: done human limb transplants, we've looked at langer hand cells
Speaker 2: over time, and the donors langer hand cells are still
Speaker 2: there over long periods of time, so they must be
Speaker 2: replicating on their own as opposed to coming from the
Speaker 2: patient's own bone marrow. Yeah, I thought that was kind
Speaker 2: of interesting that that's how we sort of figured that out.
Speaker 1: So Jude asks how they work to help the skin
Speaker 1: respond to new stimuli, But it sounds like they're more
Speaker 1: involved in the immune response.
Speaker 2: Yeah, that's right. They're not like helping you feel things
Speaker 2: like the if the stimuli is a bacterial invader. The
Speaker 2: way they help you respond is they eat it and
Speaker 2: then they tell the immune system that this is something
Speaker 2: that you need to prepare to attack. Another thing that
Speaker 2: they regularly do, like if you aren't encountering anything bad,
Speaker 2: every once in a while, the langer Hand cells will
Speaker 2: leave and just go to your lymph nodes and be like, hey,
Speaker 2: this is what you look like. And so they've got
Speaker 2: two modes. They've got to, like what's called an activated mode,
Speaker 2: where essentially they're like, I am bringing you something bad,
Speaker 2: I am worked up, I am activated. But they also
Speaker 2: have a mode where they're just like, hey, I'm just
Speaker 2: telling you what you look like. This is something you
Speaker 2: don't need to attack. And so they're just sort of
Speaker 2: like trying to give you a heads up that like,
Speaker 2: here's what you look like. Don't freak out about you.
Speaker 2: And you know, anyone who has an autoimmune disease will
Speaker 2: know it's important not freak out at your own body.
Speaker 2: And so this regular reminder of what you look like
Speaker 2: is important, and so that's another thing that they do. Unfortunately,
Speaker 2: sometimes things go wrong, and when things go wrong with
Speaker 2: these cells, you can get langer hands sell histiocytosis. That
Speaker 2: doesn't sound good, No, it's not good. This is a
Speaker 2: kind of cancer that can be kind of hard to
Speaker 2: diagnose because it can be in your skin, but it
Speaker 2: can also end up in places like your bones, or
Speaker 2: your lungs, or your central nervous system or your lymph nodes. Basically,
Speaker 2: they get like lodged somewhere and they start replicating, and
Speaker 2: we don't really understand very well why this happens, and
Speaker 2: it can give you lots of very different symptoms, so
Speaker 2: sometimes it can be a little bit hard to diagnose.
Speaker 2: And I was listening to a podcast with a pediatric
Speaker 2: oncologist who was saying that this is sort of an
Speaker 2: understudied kind of cancer because we don't understand langer hand
Speaker 2: cells particularly well. And so he was, you know, just
Speaker 2: like every other scientist, arguing that we need more research
Speaker 2: and more money. And this is something you hear Daniel
Speaker 2: and I say all the time anyway. So, yeah, sometimes
Speaker 2: things go wrong with these cells, and this is unfortunately
Speaker 2: another cause of cancer.
Speaker 1: It's also incredible to me that this ever works. I mean,
Speaker 1: this whole system seems so baroke, so complicated, it's so
Speaker 1: easy to break down that I'm amazed that people are
Speaker 1: just like walking around all day with everything going normally.
Speaker 2: The immune system in particular just seems incredibly complicated, and
Speaker 2: the more we study it, the more complicated it seems
Speaker 2: to get. And so yeah, it is kind of amazing
Speaker 2: that we're not all just sort of shambling and falling
Speaker 2: apart every moment of every day.
Speaker 1: So speak for yourselves. I kind of am over here.
Speaker 1: I'm rounding up to one hundred these days. Don't forget.
Speaker 2: Oh I'm not. I'm not. I'm happy with my actual
Speaker 2: age of forty forty. I'm running down.
Speaker 1: Actually, it's also incredible to me that so much in
Speaker 1: biology that someone like you who's been doing biology for
Speaker 1: decades will be like, oh, I don't know anything about this,
Speaker 1: and there's still like so much to learn.
Speaker 2: I know, well, I mean I like, as we've discussed,
Speaker 2: like when I was at UC Davis, they were just
Speaker 2: so many biology departments. Yeah, yeah, there's I could spend
Speaker 2: my whole life, literally my whole life reading biology papers
Speaker 2: and somebody could still be like, oh, hey, have you
Speaker 2: heard about this sell in the human body, And I'd
Speaker 2: be like, Nope, nope, that's new.
Speaker 1: But today I'm learning.
Speaker 2: But yes, and thank you to you know the listener questions.
Speaker 2: One of my favorite things is that quite often it's like, oh,
Speaker 2: haven't heard of that, but today today I will be
Speaker 2: able to explain it, which is awesome. So should we
Speaker 2: go to the chat GPT poem?
Speaker 1: Yes? So what did chat GPT compose about? Langraham cells?
Speaker 2: Sentinels in the skin? They quietly stand guard, laying our hand.
Speaker 2: Cells catch whispers of danger before it hits hard.
Speaker 1: I don't know if it's just your delivery, but I
Speaker 1: think chat GBT is like a little over dramatic on
Speaker 1: the poetry.
Speaker 2: Yeah, yeah, no, I do think they're overdoing it a bit.
Speaker 2: They were super dramatic. I was a bit uh. I mean,
Speaker 2: I guess maybe I was a little over dramatic too,
Speaker 2: but in like a superhero funny way, you know. So
Speaker 2: I said, when microbe's invade and our skin begins to swell,
Speaker 2: the immune system calls upon the Langerhans cell. Langer Hans anyway,
Speaker 2: So I think mine was way more fun.
Speaker 1: All right, Jude, Well, we want you to weigh in.
Speaker 1: Let us know if we answered your question, and also
Speaker 1: which poem you prefer.
Speaker 5: Hi, Kelly, that was great. I'm a librarian, not in school.
Speaker 5: No homework here genuine curiosity. I'd never heard of Langerhans
Speaker 5: cells until they were mentioned in another podcast. The description
Speaker 5: piqued my curiosity. My further reading was either too vague
Speaker 5: or too complicated. Your explanation made sense even to my
Speaker 5: non science spring. As a bonus, I have a better
Speaker 5: understanding for how skin works. I didn't realize that Langerhan
Speaker 5: cells were so adaptive, identifying both friend and foe. Amazing biology,
Speaker 5: which gets to the Kelly versus chat GPT poetry slam.
Speaker 5: Kelly's poem was more apt and vivid. You conveyed the
Speaker 5: superhero in the every day that fits the langerhand cell.
Speaker 1: Thanks all right, We are back and we're answering questions
Speaker 1: from you today. We want to know what you are
Speaker 1: curious about. What part of the universe doesn't make sense.
Speaker 1: Write to us two questions at Danielankelly dot org and
Speaker 1: you'll get an answer. Of Next, we're talking about black
Speaker 1: holes and the universe. Here's a question from Philip.
Speaker 6: Hi Daniel and Kelly. This is Philip from Bucharest with
Speaker 6: the hypothesis of the universe in a black hole doing
Speaker 6: the rounds lately in certain corners of the press, and
Speaker 6: which I might say, you've debanked rather nicely in past episodes.
Speaker 6: I found myself wondering how would such a situation influence
Speaker 6: what we already see around us. For example, it seems
Speaker 6: that we already have black holes in our universe. Is
Speaker 6: physics as we know it. Even allowing for black holes
Speaker 6: inside black holes, would the infinities be compounded or would
Speaker 6: that suggest that a singularities do not actually contain infinities.
Speaker 6: Thank you for the great podcast, and can't wait to
Speaker 6: hear her answer.
Speaker 2: I can't wait to hear chet Chip. It's his poem
Speaker 2: about this. I can imagine black holes within black holes
Speaker 2: is going to give a particularly epic and overblown poem. Also,
Speaker 2: I'll note that I'm you know, I'm always excited when
Speaker 2: we have a listener from another country, Like it still
Speaker 2: kind of amazes me that we have this like technology
Speaker 2: that allows us to reach out to people from all
Speaker 2: over the world. Philip is from Bucharest. That's pretty cool
Speaker 2: to me.
Speaker 1: That is very cool, super fun question. Thank you, Philip.
Speaker 1: Love this first, let's remind people why our universe is
Speaker 1: not a black hole. I mean, you hear this a
Speaker 1: lot in popular science. It's really fun, but it glosses
Speaker 1: over a lot of really important details. So on the surface,
Speaker 1: the universe seems like it has something in common with
Speaker 1: a black hole. I mean, a black hole has an
Speaker 1: event horizon beyond which nothing can emerge. Well, our universe
Speaker 1: has a cosmic horizon. There's a place past which we
Speaker 1: cannot see because the universe has a finite age and
Speaker 1: the light has finite speed. So something that's far enough away,
Speaker 1: an event that happened a long long time ago, far
Speaker 1: far away life from it will not have reached us yet.
Speaker 1: So there's parts of the universe that are just invisible
Speaker 1: to us.
Speaker 2: Teach the controversy.
Speaker 1: So both of those things have the word horizon in them,
Speaker 1: but that's really the end of the similarity. Event horizon
Speaker 1: means nothing will ever escape the cosmic horizon. We will
Speaker 1: eventually see those things if we wait long enough. So
Speaker 1: it's sort of a statement of what we can see
Speaker 1: right now, whereas an event horizon says you will never
Speaker 1: see this stuff. In fact, the definition of an event
Speaker 1: horizon requires you to wait till the end of the
Speaker 1: universe to know for sure that nothing came out. It's
Speaker 1: defined as the place from which nothing ever emerged, even
Speaker 1: at infinite time, so that's really very superficial. The other
Speaker 1: similarity between black holes and our universe is singularities. General
Speaker 1: relativity predicts that black holes have singularities at their heart,
Speaker 1: these points of infinite density. But we know that's not
Speaker 1: real anyway, because quantum mechanics says that can't happen, and
Speaker 1: that's a general relativity only extrapolation, so it's fun to
Speaker 1: think about, but unlikely to be real. In the same way,
Speaker 1: if you wind the universe back in time, it gets
Speaker 1: denser and denser as you reverse the expansion by cranking
Speaker 1: that clock backwards. And if you keep going and again
Speaker 1: ignore quantum mechanics and just use general relativity, then you
Speaker 1: get to a moment when the universe had infinite density.
Speaker 1: So that sounds similar to the black hole singularity, but
Speaker 1: it's really quite different. A black hole singularity is a
Speaker 1: location in space, a point of infinite density, right, whereas
Speaker 1: the Big Bang singularity is a moment in time that
Speaker 1: occurred everywhere. If the universe is infinite, then it always
Speaker 1: was infinite, and then that singularity was everywhere. So they
Speaker 1: both contain the word singularity and have infinities, but they're
Speaker 1: very very different. Kind of beasts.
Speaker 2: Okay, But so here's the thing. I kind of zoned out,
Speaker 2: and what I heard was that both of them have horizons,
Speaker 2: and both of them have singularities, and so I'm pretty convinced. Well,
Speaker 2: I'm kidding, I'm kidding.
Speaker 1: So we're the listeners who've been zoning out. Here's one
Speaker 1: more argument, which is, there's a fascinating coincidence in our universe.
Speaker 1: We can calculate the radius of a black hole's event
Speaker 1: horizon based only on the mass of the black hole
Speaker 1: and also the speed of light and the gravitational constant.
Speaker 1: But the thing that changes from black hole to black
Speaker 1: hole is the mass, and that's what controls the radius.
Speaker 1: Very simple calculation, it's called the short styled radius. Now,
Speaker 1: if you put into that equation the mass of the
Speaker 1: observable universe, you get out a radius. And what does
Speaker 1: that radius mean. It means if you had a black
Speaker 1: hole the mass of the observable universe, what would be
Speaker 1: the radius of the event horizon of that black hole.
Speaker 1: It's fascinating that that turns out to be the same
Speaker 1: size as our cosmic horizon. That means that if you
Speaker 1: had all the mass of the universe in a singularity,
Speaker 1: it would be a black hole who sizes the universe,
Speaker 1: And so that's kind of cool. It sounds like it
Speaker 1: means our universe could be a black hole because anyway,
Speaker 1: it has the mass and radius of a black hole. Right,
Speaker 1: But of course here comes Daniel to ruin that fun party.
Speaker 1: That calculation assumes a hole by stuff. It only works
Speaker 1: in an empty universe where you only have a black hole,
Speaker 1: and there's no expansion in our universe. We don't think
Speaker 1: it is empty past the cosmic horizon, and it is expanding,
Speaker 1: so that calculation does not apply, even though it's a
Speaker 1: fun coincidence, all right, So that's the warm up. As
Speaker 1: Philip says, the universe unlikely to be a black hole,
Speaker 1: even though that would be more fun if it were.
Speaker 1: His question is could you have black holes within black holes?
Speaker 1: Like if the universe was a black hole? Could you
Speaker 1: have a black hole in our universe? Because we see
Speaker 1: one at the center of the galaxy and we've observed
Speaker 1: them in the universe, is it possible if we're in
Speaker 1: a black hole to have black holes? Or more generally,
Speaker 1: can black holes exist within black holes? Super fun question,
Speaker 1: And the first thing you might think about is well,
Speaker 1: merging black holes, Like, what happens when two black holes
Speaker 1: come together? Is there a moment there when you have
Speaker 1: like two singularities within the event horizon, and could you
Speaker 1: call that like a black hole within a black hole?
Speaker 1: Kind of yeah, but it's temporary. What happens here is
Speaker 1: that the black holes approach each other and then they
Speaker 1: form a common horizon from their common energy. So they
Speaker 1: still have their own horizons, right the original event horizon
Speaker 1: you calculate just for that black hole, but because of
Speaker 1: their combined gravitational power, they now have a larger combined horizon.
Speaker 1: So in that sense, they're kind of black holes within
Speaker 1: a common black hole. Though it's not going to last
Speaker 1: because eventually they will radiate energy and they will orbit
Speaker 1: each other and they'll ring down to form one singularity
Speaker 1: within the event horizon, and then you're just going to
Speaker 1: get one bigger black hole. So it eventually becomes one
Speaker 1: event horizon. But temporarily you can have cool stuff like
Speaker 1: two singularities orbiting each other within the event horizon.
Speaker 2: Just to try to remember from a previous episode, but
Speaker 2: when we talked about when black holes get together, it
Speaker 2: is more likely that one throws the other one out right,
Speaker 2: or is it more likely that they merge.
Speaker 1: It depends a lot in the dynamics. If two galaxies merge,
Speaker 1: they and you can get their central black holes merging,
Speaker 1: or you can get one of them kicked out, And
Speaker 1: that definitely has happened. It's a more complicated situation there
Speaker 1: because you have more than two objects. You have like
Speaker 1: the whole galaxy and the black hole, and so three
Speaker 1: body systems are much more chaotic than two body systems,
Speaker 1: got it, And so that seems cool. And then you
Speaker 1: might try to engineer a situation where one black hole
Speaker 1: is much bigger than the other. Like imagine a tiny
Speaker 1: baby black hole being shot into a mega black hole,
Speaker 1: and then you can ask, like, how long can it
Speaker 1: survive within that mega black hole because it feels like
Speaker 1: a little black hole inside a bigger black hole. Right, Well,
Speaker 1: that's basically the same scenario we just talked about. It's
Speaker 1: again the merger of two black holes, except one of
Speaker 1: them is really big and one of them is really
Speaker 1: really small. Same thing's going to happen is they're going
Speaker 1: to form a common horizon. They're going to orbit each other,
Speaker 1: and then they're gonna merge. It's going to look a
Speaker 1: lot more like one eats the other, just because the
Speaker 1: center of gravity is closer to the bigger one. But
Speaker 1: fundamentally it's the same physics, two black holes merging and
Speaker 1: one big one eating the other one of a change
Speaker 1: of reference frame. So so far we have a temporary
Speaker 1: black hole within the other black hole. But if you've
Speaker 1: been listening to the show, we talked last time about
Speaker 1: Caushi horizons and complicated structure inside black holes. So if
Speaker 1: you take your big black hole and you spin it,
Speaker 1: then you have an event horizon still, but now within
Speaker 1: the black hole you have another horizon. It's called the
Speaker 1: Caushi horizon. Outside the Caushi horizon, things fall in just
Speaker 1: like they do in normal black holes. But inside the
Speaker 1: Caushi horizon, the structure of space time is very different,
Speaker 1: and the singularity is no longer inevitable, Like you can
Speaker 1: have stable orbits around the singularity, you don't have to
Speaker 1: fall into it. For gr nerds, the singularity becomes timelike.
Speaker 1: It's no longer true that every path through space leads
Speaker 1: to this singularity, and so it's possible, though it's very,
Speaker 1: very difficult because life inside the Caushi horizon is extraordinarily
Speaker 1: unstable and unpredictable. As we talked about last time, it's
Speaker 1: not actually deterministic because now you have a singularity that
Speaker 1: can appear in your past like cone. But in principle,
Speaker 1: for the purposes of sounding like cool pop scientists, you
Speaker 1: can potentially exist within the caushi horizon of a spinning
Speaker 1: black hole for quite a long time, saying its stables
Speaker 1: maybe a bit much, but in that sense, you can
Speaker 1: have a mini black hole within a bigger spinning black
Speaker 1: hole and have it hanging out there for quite a while.
Speaker 2: So is that a yes to that? What was the
Speaker 2: actual question? Would the infinities be compounded or would that
Speaker 2: suggest that the singularities do not actually contain infinities.
Speaker 1: So the infinities here are densities, right, not masses. Each
Speaker 1: black hole has a finite mass, and that mass controls
Speaker 1: its vent horizon. The singularity is the density, saying that
Speaker 1: that mass has been compacted to essentially zero space. So yes,
Speaker 1: you can add two masses together and you're going to
Speaker 1: get a bigger mass, a larger but still finite mass,
Speaker 1: and it's still going to have an infinite density. Of course,
Speaker 1: all of this is just ignoring quantum mechanics and quantum
Speaker 1: gravity and assuming general relativity is the law of the land,
Speaker 1: which we don't think it is, but you know, for
Speaker 1: the purposes of this question, so yeah, you're going to
Speaker 1: get compounded infinities in that sense.
Speaker 2: Okay, all right, are we ready for the poem?
Speaker 1: Bring on Shakespeare GPT.
Speaker 2: Okay, here we go, a black hole nested where no
Speaker 2: light can ever flee, an abyss with an abyss folding infinity.
Speaker 1: Now it's a little bit tortured. All right.
Speaker 2: Oh, we've got to give him your poem again.
Speaker 1: All right? Do it?
Speaker 2: If our universe sits in a black hole's embrace, do
Speaker 2: our own black holes nest like a Matrushka doll in space.
Speaker 2: I don't know if I said Matrushka correctly, but he knows.
Speaker 2: I'm sure he knows what we're going for.
Speaker 1: Let's hear from Philip if we answered his question, and
Speaker 1: if you like chat GPT's poetry better than mine.
Speaker 4: Hello again, Daniel and Kelly. Wow, it's like they say,
Speaker 4: come for the black horse in science, stay for the poetry.
Speaker 4: Slam with ai. Thank you for the fulful answer to
Speaker 4: my question. I guess it sits firmly in the yes
Speaker 4: but category, along with many other physics topics. So based
Speaker 4: on the fine print of the theory, the singularities could
Speaker 4: technically nest inside one another, but that remains in no
Speaker 4: way relevant to those universe we observe. Imagining that is
Speaker 4: a fascinating thought experiment, but still leaves us no way
Speaker 4: to deduce something about what is really happening inside the
Speaker 4: event horizon. Well, I'll try to do better next time,
Speaker 4: and thank you for now.
Speaker 2: Well, Daniel, I feel like what we've learned today is
Speaker 2: that what we laughed at the fact that chat GPT's
Speaker 2: poems are sort of like a you know, overly emotional
Speaker 2: teenager's poems. To be honest, I'm not sure that that
Speaker 2: much that much worse than ours. And so chat GIPT
Speaker 2: is at like Daniel and Kelly level of poetry right now,
Speaker 2: which is, you know, not Emily Dickinson.
Speaker 1: Maybe we should feed it all of Zach's books to
Speaker 1: ask it to write Zach style poetry.
Speaker 2: I still imagine Zach would do better. But Zach and
Speaker 2: I did have Soonish scraped by AI. Were any of
Speaker 2: your books scraped by AI? And were they part of
Speaker 2: that absolutely part of that big case settlement thing.
Speaker 1: Well, maybe we should get the real Zach to write
Speaker 1: our poetry.
Speaker 2: One week, I asked him, and he politely declines, maybe
Speaker 2: it's better we keep some parts of our lives separate.
Speaker 1: Yeah, that's good. All right. Well, thank you very much
Speaker 1: everybody for listening and for sharing your curiosity. It's your
Speaker 1: desire to understand the universe that powers our podcast.
Speaker 2: Please send your questions to questions at Danielankelly dot org.
Speaker 2: We answer every question and some of the questions end
Speaker 2: up on the show, and we look forward to hearing
Speaker 2: from you.
Speaker 1: We really do Thanks everybody for listening. Please go and
Speaker 1: do us a favor and rate the show on whatever
Speaker 1: podcast app you're using. It really helps people find us.
Speaker 2: Daniel and Kelly's Extraordinary Universe is edited by the amazing
Speaker 2: Matt Kesselman.
Speaker 1: He really is a wizard. You can also find us
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Speaker 1: Come engage with us.
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Speaker 2: We really do want to hear from you, and you.
Speaker 1: Can find our website www dot danieland Kelly dot org,
Speaker 1: where you'll also find an invitation to join our discord,
Speaker 1: where everybody comes and talks about the amazing.
Speaker 2: Universe, and we also have the most amazing moderators. This
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