Speaker 1: Hey, extraordinaries. Quick note for today's episode, I want to
Speaker 1: let you know about my new book, To Aliens Speak Physics.
Speaker 1: It's all about whether or not we can use physics
Speaker 1: as a universal language to communicate with aliens, or whether
Speaker 1: physics is more human than many people imagine. And the
Speaker 1: book features cute cartoons of aliens from my friend Andy Warner.
Speaker 1: If you've enjoyed my science outreach and wondered how you
Speaker 1: could support me, this is how The book is out
Speaker 1: in November fourth. Look for the link on the book
Speaker 1: website www dot alienspeakphysics dot com. Okay, on to today's episode.
Speaker 1: Whenever we look out into the universe, we see something
Speaker 1: new that astonishes us, something beyond our wildest imaginings of
Speaker 1: what the universe could do. It's a rich tapestry of
Speaker 1: extreme physics, and yet all of it is described by
Speaker 1: physics deep down. The mechanisms that create black holes, or
Speaker 1: collide galaxies or explode stars are rooted in the basic
Speaker 1: principles of physics, and so far we've been able to
Speaker 1: come up with explanations for how these incredible events occur
Speaker 1: and how the universe is vast and beautiful cosmos is shaped. Today,
Speaker 1: we're going to dig into the physics that underlies one
Speaker 1: of the most dramatic and literally brilliant phenomena in space,
Speaker 1: astrophysical jets. Welcome to Daniel and Kelly's extraordinary, brilliant universe.
Speaker 2: Hello.
Speaker 3: I'm Kelly Waidersmith.
Speaker 4: I study parasites and space, and before looking at today's outline,
Speaker 4: I didn't know that astrophysical jets was a phrase that's
Speaker 4: worth it.
Speaker 1: Hi, I'm Daniel. I'm a particle physicist, and if I
Speaker 1: had a baseball team, I might call them the astrophysical Jets.
Speaker 4: Oh, is that because your brain is fixating on the
Speaker 4: astros part?
Speaker 1: It just sounds like a team that would score a
Speaker 1: lot of runs.
Speaker 3: Yeah, yeah, no and throw their balls really fast. I think.
Speaker 4: So, when I was looking through the outline today, it
Speaker 4: occurred to me that this doesn't feel like it's in
Speaker 4: your main area of research, and so I was wondering
Speaker 4: if you could tell us, like, when you are researching
Speaker 4: something that you don't have knowledge of, like right at
Speaker 4: your fingertips, what is your process like for preparing our outline?
Speaker 1: Yeah, well, that's fascinating because this actually is sort of
Speaker 1: right on the edge of my area of research. I'm
Speaker 1: sort of card carrying particle physicists, which means that most
Speaker 1: of my career is like, smash particles together at the
Speaker 1: large had drunk collider, see what new kind of stuff
Speaker 1: comes out. But it's always been super interested in space,
Speaker 1: and like many people, I got into it because of astronomy.
Speaker 1: But then I kind of discovered like astronomy is mostly
Speaker 1: standing around in the cold looking at fuzzy things through
Speaker 1: a telescope, and that wasn't as exciting to me. Apologies
Speaker 1: to us. I mean, there's out there who love that
Speaker 1: and thank you for doing it, but it wasn't for me.
Speaker 1: But later in my career I got reinterested in astrophysics,
Speaker 1: which isn't looking through a telescope, but it's like trying
Speaker 1: to understand the physics behind what's going on out there,
Speaker 1: like how does the star work, et cetera. So the
Speaker 1: last few years I've actually written some papers on the
Speaker 1: centers of galaxies and neutron stars and supernova and stuff
Speaker 1: like this, but it is a little bit far from
Speaker 1: my core area of expertise. So it means reading a
Speaker 1: lot of.
Speaker 3: Papers, got it. How many are you reading.
Speaker 1: All of the papers all of them.
Speaker 3: Wow.
Speaker 1: I mean what I try to do is find a
Speaker 1: review in that area, like, find somebody who knows the fields,
Speaker 1: who's written like a broad perspective, read that really carefully,
Speaker 1: and then read a bunch of the papers it references
Speaker 1: to make sure I know what's being summarized and what's
Speaker 1: actually going on, and what's the sort of the lore
Speaker 1: all this kind of stuff. But it's a lot of
Speaker 1: work to try to really understand a new field well
Speaker 1: enough to try to contribute something to it. And you know,
Speaker 1: I think you were asking though about like if you
Speaker 1: want to talk about something on the podcast, not necessarily
Speaker 1: like write a bunch of papers about it. But I
Speaker 1: finally it's kind of similar to talk about something on
Speaker 1: the podcast. You got to understand it really well because
Speaker 1: my co host is really smart and asks hard questions,
Speaker 1: and if I want to explain things correctly in a
Speaker 1: way that actually clicks in people's minds, I got to
Speaker 1: have it all up in my brain. So yeah, it
Speaker 1: means reading a lot of papers when it's not my area.
Speaker 1: Is that your experience? Also?
Speaker 2: Yeah?
Speaker 4: Yeah, when I'm working on my outline, I'm always asking
Speaker 4: myself wwda, which is what will Daniel ask, trying to
Speaker 4: figure out, like what other things do I need to
Speaker 4: research that I am prepared for whatever?
Speaker 1: Daniel asks, Yeah, I feel like everybody in my life
Speaker 1: who I get to know, I have sort of like
Speaker 1: a mini version of them in my head, like a
Speaker 1: little model of them which constantly gets you know, improved
Speaker 1: and updated and of course the most interesting people, it's
Speaker 1: never actually correct, which is why they can wonderfully surprise me.
Speaker 1: But I feel like that's a big part of understanding
Speaker 1: who's somebody is. It's like comparing them to like the
Speaker 1: little model you have of who they are and what
Speaker 1: they might say and how they might react. It's super fun.
Speaker 4: Do the models in here, and then we should change
Speaker 4: subjects back to what we meant to talk about today.
Speaker 3: But do the models in your head?
Speaker 4: Like, are they like miniature people that you see or
Speaker 4: are you just imagining their personalities without their bodies?
Speaker 3: Like what do you imagine?
Speaker 1: Are they in the room with me right now?
Speaker 2: Right?
Speaker 5: So?
Speaker 1: I'm not schizophrenic, I'm pretty sure. No, it's just like you,
Speaker 1: I just asked myself, you know, what would my kids
Speaker 1: say in this situation? Or how would my wife react
Speaker 1: to having this for dinner? Or what would Kelly ask
Speaker 1: me if I said X y Z. You know, I
Speaker 1: think they're just useful for trying to understand who somebody is.
Speaker 1: But I also think it's helpful for understanding yourself because
Speaker 1: you end up building also a model of yourself and
Speaker 1: turning the inwards and anyway, I have my own Bonker's
Speaker 1: theory of consciousness, but that's not what today's episode is about.
Speaker 4: So when you sent me the outline for relativistic beaming,
Speaker 4: I was like, I just have zero clue what this means.
Speaker 4: We'll give us, like some background what we should expect
Speaker 4: in this episode.
Speaker 1: Yeah, this episode is about how the universe is constantly
Speaker 1: surprising us. How every time we look out into space
Speaker 1: we see something new and weird, something that doesn't quite
Speaker 1: make sense. And yet if we apply our knowledge of physics,
Speaker 1: it turns out we can crack it. We can make
Speaker 1: sense that we can explain why it's happening, and often
Speaker 1: it gives us an incredible view of what's going on
Speaker 1: in extreme situations, you know, the cores of galaxies, when
Speaker 1: things are really hot and dense and fast. But it
Speaker 1: requires us to put together a lot of little pieces
Speaker 1: of physics. Gravity electromagnetism, even special relativity, in order to
Speaker 1: explain what we see out there in the universe. And
Speaker 1: so today's episode is a story of like several decades,
Speaker 1: almost a century, of trying to understand some stuff we
Speaker 1: see out in space and finally putting it together. And
Speaker 1: the last piece of that is a process called relativistic beaming.
Speaker 1: And I had a bunch of listeners write to me
Speaker 1: and ask me about these astrophysical jets that are omitted
Speaker 1: from the centers of galaxies, and so I thought, let's
Speaker 1: do a deep dive into all the physics that makes
Speaker 1: those happen, especially that last bit, which I've never heard
Speaker 1: anybody cover with a popular treatment. So that was the
Speaker 1: motivation for today's episode.
Speaker 3: Awesome.
Speaker 4: I'm excited about today's episode because I love those moments where, like,
Speaker 4: you've studied a bunch of different topics that don't necessarily
Speaker 4: seem connected, but they turn out to be the building
Speaker 4: blocks that you need to understand something completely different that
Speaker 4: you probably wouldn't have been able to understand if you
Speaker 4: hadn't done all of that background sort of foundational work
Speaker 4: ahead of time.
Speaker 3: Exactly, So let's learn, all.
Speaker 1: Right, And so relativistic beaming is the last piece of it,
Speaker 1: but maybe the least well known. So I decided to
Speaker 1: go out there and ask our audience if they knew
Speaker 1: anything about relativistic beaming to help us calibrate. If you
Speaker 1: would like to participate for our future episodes, please don't
Speaker 1: be shy. Write to us questions at Danielankelly dot org.
Speaker 1: In the meantime, ask yourself, do you know what relativistic
Speaker 1: beaming is? Here's what our listeners had to say.
Speaker 5: Relativistic beaming.
Speaker 2: I think that's when Chapman from the Yankees beams you
Speaker 2: in the head by accident, and if that happens with
Speaker 2: one of his fastballs, and then when that happens, time
Speaker 2: will definitely go slower for you.
Speaker 5: So relativistic relativistic beaming, well.
Speaker 6: I can't remember off the top of my head. I
Speaker 6: think it was to do with synchotrons. When electrons are
Speaker 6: going near the speed of light and go around a corner.
Speaker 6: The radiation they release very is in a very tightly
Speaker 6: controlled spatial beam because of relativistic effects.
Speaker 5: Relativistic beaming is the ability of a thought to enter
Speaker 5: my mind and then instantly disappear as soon as I
Speaker 5: try to act on it. But in physics, maybe it's
Speaker 5: something to do with moving near massless particles near the
Speaker 5: speed of light and taking advantage of some of the
Speaker 5: relativistic changes that occur as a result.
Speaker 4: I think my favorite answer, I mean, they were all great,
Speaker 4: but was how a thought enters my mind and then
Speaker 4: it's disappears. Relativistic beaming in that sense happens to me
Speaker 4: like fifty times a day lately.
Speaker 1: You have that experience where you have an idea and
Speaker 1: then you try to write it down before it leaves
Speaker 1: your brain, and sometimes it's like no pencil or paper,
Speaker 1: you can't get to your phone, and you're like, oh, no,
Speaker 1: it's gonna go away.
Speaker 4: Yeah, it does, it go away, because it does for
Speaker 4: me a lot of the time. Or are you just scared?
Speaker 3: But it stays?
Speaker 1: We does, okay, No, And then sometimes I have like
Speaker 1: the remnants of the idea. I'm like, I remember feeling
Speaker 1: this way about it and it was something about that
Speaker 1: and what was it?
Speaker 4: And man, yep, no, I all think to myself, don't
Speaker 4: get distracted, don't get distracted while I'm looking for the pencil,
Speaker 4: and then I always think about, like, oh, did we
Speaker 4: make it as lunch this morning? And then it's gone
Speaker 4: and anyway, Okay, so the thought that we do not
Speaker 4: want to forget is what is relativistic beaming.
Speaker 1: That's right. And the story starts with the things shooting
Speaker 1: out of the centers of galaxies. These things called astrophysical jets.
Speaker 1: And if you have a mental image of a galaxy,
Speaker 1: you're probably imagining something like a disc. You've got a
Speaker 1: bunch of stars a swirl together, and that's what the
Speaker 1: Milky Way looks like, and that's what Andromeda looks like.
Speaker 1: But there's another really important feature of galaxies that's not
Speaker 1: always visible to the naked eye, and these are the
Speaker 1: jets that shoot up and down from the poles of
Speaker 1: the galaxy, out of the center. So instead of just
Speaker 1: imagining a disk, imagine a huge beam of light beaming
Speaker 1: up and down relative to the plane of the disk.
Speaker 1: These are astrophysical jets.
Speaker 3: Okay.
Speaker 4: And so the jet is made of light. And just
Speaker 4: so I make sure i'm picturing thing because you said photons, right.
Speaker 1: Well, the jet has light in it. They are bright,
Speaker 1: but they're actually not just made of light. They're mostly
Speaker 1: plasma so they're like high speed particles. There's electrons, there's protons,
Speaker 1: and there are photons as well.
Speaker 4: Wow, okay, so I just want to make sure that
Speaker 4: I've got my image of a galaxy correct. So at
Speaker 4: the center of our solar system there's the Sun, but
Speaker 4: at the center of a galaxy there isn't necessarily some
Speaker 4: big thing. It's just what is at the center of
Speaker 4: a galaxy. We talked about it maybe being a black hole,
Speaker 4: but we don't really know right well.
Speaker 1: There are lot of questions about what's at the center
Speaker 1: of the galaxy because it's hard to see it's so
Speaker 1: dense there. You know, I think a lot of people
Speaker 1: have the image of a galaxy as like just a
Speaker 1: bunch of stars sprinkled around, But there's a big density variation,
Speaker 1: Like the center of the galaxy is much denser than
Speaker 1: the outskirts. It's sort of like, you know, there's Manhattan
Speaker 1: and then there's the suburbs, and then there's the excerbs,
Speaker 1: and we live kind of in the suburbs. It's not
Speaker 1: very dense, but it's not as rural as it is
Speaker 1: further out in the galaxy. But near the center there's
Speaker 1: a lot of stars and there's a lot of gas
Speaker 1: and dust, so it is difficult to study the center
Speaker 1: of the galaxy. But we do know a lot about
Speaker 1: the centers of the galaxies also by looking at other galaxies,
Speaker 1: and so far, every galaxy we've studied has a super
Speaker 1: massive black hole at its center, with a couple of
Speaker 1: exceptions in cases where we're like pretty sure the super
Speaker 1: massive black hole has been ejected by like a recent
Speaker 1: collision or something.
Speaker 3: You can eject a super massive black hole.
Speaker 4: We've probably talked about this on a prior episode and
Speaker 4: my bad memory is why life is so endlessly surprising
Speaker 4: to me?
Speaker 1: But whoa yeah, yeah, Well, when galaxies merge, what happens
Speaker 1: is the center's merge. It takes a long long time
Speaker 1: and then the black holes merge, but not always. And
Speaker 1: if you have like three galaxies merging at the same time,
Speaker 1: two of them can work together and eject the third one.
Speaker 1: And so yeah, gravitational kicks can eject the super massive
Speaker 1: black hole from the core. It's not something we understand
Speaker 1: super well. We do think that there are super massive
Speaker 1: black holes at the cores of these galaxies. So imagine
Speaker 1: a very very dense center of the galaxy and then
Speaker 1: fewer stars as you move away from the center, and
Speaker 1: then from the center shooting up and down. Are these
Speaker 1: massive astrophysical jets. They can go for like hundreds of
Speaker 1: thousands of light years.
Speaker 3: Wow.
Speaker 4: But they're not necessarily coming from the super massive black hole,
Speaker 4: but just from like the general center.
Speaker 1: We're going to dig into that later in the episode.
Speaker 1: But we think they are connected. Yes, And this was
Speaker 1: one of the central puzzles of astrophysical jets and continues
Speaker 1: to be like what exactly is powering them? It's a
Speaker 1: really fun question.
Speaker 4: Okay, so stuff is shooting out, is it just kind
Speaker 4: of like trickling out or is it moving really fast?
Speaker 1: These are some of the fastest things in the universe. Like,
Speaker 1: these jets are shooting particles out, often very close to
Speaker 1: the speed of light. Like the energy of particles in
Speaker 1: these jets is often much higher than energy of particles
Speaker 1: in our experiments here on Earth, like the Large Hadron Collider,
Speaker 1: we accelerate particles to have an energy of like around
Speaker 1: five to seven tarra electron volts. That's trillions of electron volts.
Speaker 1: But these galactic centers can accelerate particles to much higher energies,
Speaker 1: which connects to lots of fascinating mysteries, like we see
Speaker 1: super high energy particles arriving on Earth and we don't
Speaker 1: understand where they come from. And one theory is that
Speaker 1: they're being kicked to super high energy by these galactic accelerators.
Speaker 1: Essentially that these centers of galaxies are like enormous guns
Speaker 1: shooting out particles at super high energies.
Speaker 3: But then you so you shoot the particles out, and
Speaker 3: then where do they go? What happens to them?
Speaker 1: Well, if you believe that it's natural, right, and there's
Speaker 1: really fun theories out there about how like maybe aliens
Speaker 1: have megastructures and they're engineering the centers of galaxies to
Speaker 1: do particle physics experiments. That would be awesome two galaxies
Speaker 1: pointing at each other. But in general, they just shoot
Speaker 1: out into the universe. And you can see these astrophysical
Speaker 1: jets if you look at it in the right spectrum,
Speaker 1: really beautiful. You should google these images. They're spectacular. Often
Speaker 1: these things are bigger than the galaxies themselves. They just
Speaker 1: shoot out into the universe and then you know there
Speaker 1: are magnetic fields out there in the universe, and these
Speaker 1: are mostly charged particles and so they bend and they
Speaker 1: fly around. And one reason why we like to study
Speaker 1: the cosmic rays, the super high energy cosmic raise is
Speaker 1: that they are less bent than the other particles. So
Speaker 1: you want to know where something came from. If it's
Speaker 1: like gotten bent and zipped around and changed direction one
Speaker 1: hundred times, it's hard to tell. But if it's come
Speaker 1: mostly straight at you, and high energy particles get less
Speaker 1: bent by magnetic fields, then it's easier to sort of
Speaker 1: point back in the sky and say where it came from.
Speaker 1: Reason why we look for the super high energy particles
Speaker 1: because they tend to point back to their source more
Speaker 1: than lower energy particles. Yeah, very cool.
Speaker 3: Okay, so they're going really fast. It's a lot of
Speaker 3: different stuff.
Speaker 4: Is this like a narrow beam or is this like
Speaker 4: pretty wide and spread out.
Speaker 1: It's pretty narrow like when they were first discovered, And
Speaker 1: we'll dig into that. These are little sources like in
Speaker 1: the sky. They're pretty small, which is one reason why
Speaker 1: it was such a puzzle. And it's sort of amazing.
Speaker 1: And you know, you have these galaxies and they're emitting
Speaker 1: these things up and down the north and south pole
Speaker 1: from the center and it's fascinating because it's not shot
Speaker 1: out by the super massive black hole itself. Obviously, black
Speaker 1: holes do not emit photons. It's not like, you know,
Speaker 1: black holes are shooting particles out into space or anything
Speaker 1: like that. But the environment the black hole creates, and
Speaker 1: in general, the environment of the galaxy might be the
Speaker 1: thing that's powering these particles and creating these beams.
Speaker 3: Awesome.
Speaker 4: So we've gotten to the what, and now we're going
Speaker 4: to take a break, and then we'll get to the why.
Speaker 4: Why do you get astrophysical jets? Not the baseball team?
Speaker 4: All right, we're back. We've described astrophysical jets, and now
Speaker 4: Daniel's going to help us understand why you get these
Speaker 4: bursts of loads of different kinds of things coming out
Speaker 4: of the center of galaxies.
Speaker 1: Yeah, and I think a fun way to attack this
Speaker 1: is to take us through the history in the last
Speaker 1: century of people trying to understand them and putting together
Speaker 1: lots of different things simultaneously. Because astrophysical jets are connected
Speaker 1: to something else we've probably heard about, which are quasars.
Speaker 1: Let's put astrophysical jets in our pocket for a minute
Speaker 1: and talk about the history of quasars, why they were confusing,
Speaker 1: how we understand them, and then how they come back
Speaker 1: together to help us understand astrophysical jets.
Speaker 3: Let's get into the quasar question.
Speaker 1: So quasars are fun because, like the word itself is
Speaker 1: like sounds super cool and science fiction. And they're name
Speaker 1: because we didn't understand what they were, right. So quasars
Speaker 1: are short for quasi stellar objects. And they were first
Speaker 1: found back in the nineteen fifties when we didn't really
Speaker 1: understand a lot about the galaxy. Oh it's only like
Speaker 1: twenty or thirty years since we understood that there were
Speaker 1: other galaxies out there in the universe, and we started
Speaker 1: studying these things they called nebula that turned out to
Speaker 1: be other distant galaxies. And then in parallel, we had
Speaker 1: the birth of radio astronomy. You know, astronomy used to
Speaker 1: be just in the optical like you look through a
Speaker 1: telescope and you see, what do I see out there?
Speaker 1: And let's make a map? But radio and World War
Speaker 1: two led to the advent of radio telescopes. People listening
Speaker 1: to the sky in the radio and what they found
Speaker 1: were these radio sources in the nineteen fifties where they
Speaker 1: couldn't find any optical objects as well. They were like hmm,
Speaker 1: there's something out there that's emitting in the radio, but
Speaker 1: the telescopes at the time couldn't see anything there in
Speaker 1: the visible so they're like, what are these things?
Speaker 4: So then are they quasi objects because they're like, maybe
Speaker 4: that's from space. I don't know, maybe we messed something up,
Speaker 4: like why, yeah, why the quasi part?
Speaker 1: Yeah exactly. They didn't understand what they were, so they're like,
Speaker 1: maybe there's something like stars because they're sort of localized,
Speaker 1: but there's no visible object there initially, so it was
Speaker 1: a real mystery at first, which is why I think
Speaker 1: they went for like, let's give this kind of a
Speaker 1: fuzzy name so we don't know, we don't paint ourselves
Speaker 1: in the corner, which hey, maybe that was wise.
Speaker 4: Oh yeah, so maybe after they figured out what it was,
Speaker 4: they should have called it like straight up stellar objects,
Speaker 4: like we're totally sure about this.
Speaker 1: But they're not stars, right, they're not stars, So it
Speaker 1: was good that they left.
Speaker 3: That fuzz Oh so stellar means star, not just like spacey.
Speaker 1: Yes, exactly, like a star.
Speaker 3: Yeah, yeah, Kelly is really good with words.
Speaker 1: All right, Moving on, and they knew it was that
Speaker 1: they had a very small angular size, right, like they
Speaker 1: could tune the radio telescopes in a certain direction and
Speaker 1: see it and then turn it a little further away
Speaker 1: and not see it right, and so you could tell
Speaker 1: that this thing was coming from a localized spot in
Speaker 1: the sky. And by the sixties there were like hundreds
Speaker 1: of these things had been cataloged, and so people started
Speaker 1: a dedicated search for like, let's look to see if
Speaker 1: we can find something that corresponds to them. And then
Speaker 1: in the early sixties they finally found one. They found
Speaker 1: like a what looked like a faint star right at
Speaker 1: the location of the radio source, but the spectrum of
Speaker 1: it didn't really make sense. It was very confusing to understand,
Speaker 1: like what this object was.
Speaker 3: What was it? It was a quasar? Then what is
Speaker 3: a quasar?
Speaker 1: And what is a quasar? That was the question, right,
Speaker 1: So first thing they just look at the spectrum and
Speaker 1: they noticed, like the spectrum implies that it's really really
Speaker 1: really red shifted, meaning that it's really really far away.
Speaker 1: Because remember, as we look out into space, we're not
Speaker 1: just looking back in time. We're looking at things moving
Speaker 1: away from us. Hubble's big discovery was that the further
Speaker 1: away something is the faster it seems to be moving
Speaker 1: away from us. And so if you find something which
Speaker 1: is super red shifted, meaning it's moving away from us
Speaker 1: very fast, that also means it's super distant. And that
Speaker 1: was one of the early puzzles. It's like, Okay, we're
Speaker 1: seeing this star. It's not super bright, but it's crazy
Speaker 1: far away, which means that at its source it's got
Speaker 1: to be like insanely bright for us to see it.
Speaker 1: These things were apparently like most of the way across
Speaker 1: the universe, and yet somehow we were still seeing them.
Speaker 1: So people were like, wow, what this doesn't make sense
Speaker 1: if our calculations are correct. There's an incredible source of
Speaker 1: energy being shot at us from across the universe. How
Speaker 1: can that be right?
Speaker 3: Yeah? How can that be right? It's like a murder mystery.
Speaker 3: I'm waiting for the end.
Speaker 1: Yeah, exactly. And so you have this combination of like
Speaker 1: extreme velocity and distance, yet we're able to see it.
Speaker 1: And this implies some intense source of power, right, you
Speaker 1: need something in order to generate something to make these
Speaker 1: things brighter. Essentially, it would have to be like a
Speaker 1: thousand times brighter than the entire Milky Way for us
Speaker 1: to see it across the universe, so we're talking like
Speaker 1: three billion light years away, and so the early explanation
Speaker 1: was that you have an active galactic nuclei. So the
Speaker 1: centers of the galaxies are not just like here's a
Speaker 1: bunch of stars all swirling around and they're just sort
Speaker 1: of denser than they are out here, but that there's
Speaker 1: something else going on. And this is essentially at the
Speaker 1: same time as we're starting to understand, hey, are black
Speaker 1: holes are real thing. They're not just like a calculation
Speaker 1: that Einstein and his friends did, are like an actual
Speaker 1: thing out there in the universe. And so this all
Speaker 1: came together into this cohesive explanation that the center of
Speaker 1: the galaxy is very dense gravitationally, and you have these
Speaker 1: super massive black holes at their cores, and the gravity
Speaker 1: of that super massive black hole combined with its magnetic field,
Speaker 1: is generating these astrophysical jets.
Speaker 4: Okay, so a quasar is the center of a galaxy
Speaker 4: where you have a black hole and all of that
Speaker 4: denseness and stuff is shooting out.
Speaker 1: Yes, exactly as seen from Earth. So like you could
Speaker 1: describe it in several ways. You could say you have
Speaker 1: an active galactic nucleus, which is generating these jets from Earth.
Speaker 1: If you see it, you call it a quasar, and
Speaker 1: so it's sort of the union of these things as
Speaker 1: seen from different angles.
Speaker 3: So does every galaxy have a quasar?
Speaker 1: No, every galaxy does not necessarily have a quasar. It's fascinating.
Speaker 1: Not every galaxy has an active nucleus, right, It's really interesting.
Speaker 4: And is that because not every galaxy has a black
Speaker 4: hole at its center? Maybe, or this is a different reason.
Speaker 1: We don't know. It's a real mystery. It seems like
Speaker 1: the universe made a lot of quasars about ten billion
Speaker 1: years ago, and since then it hasn't been making very
Speaker 1: many of them. So like that's why most of them
Speaker 1: are far away, Like there aren't quasars that are like
Speaker 1: quasaring right now nearby, Like the Andromeda doesn't have a quake,
Speaker 1: so Heart doesn't have massive bright pulls of plasma shooting
Speaker 1: out from both sides of it. You have to look
Speaker 1: further away, which implies it was in the past. So
Speaker 1: there was something in the conditions of the universe ten
Speaker 1: billion years ago which was really quasari, and it's no longer.
Speaker 1: Is the universe very quasari.
Speaker 4: It's like the fashion of the universe, like neon leggings
Speaker 4: were big in the eighties and quasars were big at someway,
Speaker 4: but both went out of style. Yeah exactly, but the
Speaker 4: leggings are coming back. Maybe quasars come.
Speaker 1: There nostalgia for the early universe. I don't know. These
Speaker 1: things are dangerous, right, so it's crazy. The oldest quasar
Speaker 1: we've seen comes from a galaxy we visualized six hundred
Speaker 1: and ninety million years after the Big Bang, so that's
Speaker 1: less than a billion years after you know, the first
Speaker 1: atoms are formed, and then finally stars are formed, and
Speaker 1: then galaxies come together, and already you have the conditions
Speaker 1: necessary to create a quasar. And this is one of
Speaker 1: the bigger puzzles in the early universe recently, is like
Speaker 1: how things got so big so fast? You know, how
Speaker 1: did you get super massive black holes at the centers
Speaker 1: of galaxies so quickly after the beginning of the universe.
Speaker 1: Our simulations can't explain that. James Webspace Telescope, which looks
Speaker 1: in their infrared, can see super distant, super old stuff
Speaker 1: and it's visualized galactic formation that nobody understands either. Like
Speaker 1: very early in the universe, you have galaxies that are
Speaker 1: much bigger than anything we can understand. So this is
Speaker 1: a core question, and it's like, how does stuff come
Speaker 1: together and form structure in the early universe so quickly.
Speaker 1: There's definitely an element there that we don't understand in
Speaker 1: Quasars are a big part of that. Why did they
Speaker 1: come up in the early universe? Why aren't they making
Speaker 1: them anymore?
Speaker 4: Why did they go out of style like the fashion
Speaker 4: in the eighties, which I would say was a really
Speaker 4: good era. So okay, so the jets are different than
Speaker 4: the quasars. The jets come out of the quasars, and
Speaker 4: so why are the quasars making the jets?
Speaker 1: Yeah, I would say quasars are the thing we see
Speaker 1: from Earth, right, Okay, the jets are the sort of
Speaker 1: underlying physical process says that generates our observation of the quasar.
Speaker 1: But you're right, it's a good question. What is making
Speaker 1: these jets. They're super bright, they're super intense. We think
Speaker 1: they're powered by this active galactic nuclei and fundamentally the
Speaker 1: black holes at their cores. Right, these are super massive
Speaker 1: black holes. And remember black holes come in two categories.
Speaker 1: There's like there's a star that burned up all of
Speaker 1: its fuel, and the fusion is no longer providing pressure
Speaker 1: to keep that star puffed up, and so the gravity
Speaker 1: eventually wins and it collapses and you get a black
Speaker 1: hole that's going to give you a black hole up
Speaker 1: to like fifty eighty maybe one hundred times the mass
Speaker 1: of our Sun. But the black holes are the centers
Speaker 1: of galaxies. These things are like millions or billions of
Speaker 1: times the mass of the Sun. So definitely not the
Speaker 1: collapse of an individual star, and again a big mystery
Speaker 1: as to how they form. But they're enormously massive, and
Speaker 1: they're at the centers of these galaxies, and we think
Speaker 1: that the gravitational energy of these black holes, as well
Speaker 1: as their spin, is what's powering these astrophysical jets.
Speaker 4: All right, So as a biologist, yeah, it's counterintuitive to
Speaker 4: me because I feel like the main thing I know
Speaker 4: about black holes is that they like suck things in
Speaker 4: if it gets close enough.
Speaker 3: Yeah, and so now we're talking.
Speaker 4: About stuff getting seemingly spit out of black holes.
Speaker 3: So what bridge the gap there for me?
Speaker 1: Yeah, it's a good question. And remember that black holes
Speaker 1: are super gravitational and powerful, but they're not magical right there,
Speaker 1: just like suck everything in. You can, for example, orbit
Speaker 1: a black hole the way you can orbit the Sun,
Speaker 1: because a gravity from a black hole is just gravity.
Speaker 1: So if you're at the right velocity and at the
Speaker 1: right radius, you can orbit a black hole forever. It's
Speaker 1: not going to magically suck you in. So let's think
Speaker 1: about how black holes are the centers of galaxies work. Well,
Speaker 1: you have the black hole, then you have stuff swirling
Speaker 1: around it, right, so that stuff could in principle stay
Speaker 1: in orbit forever. So just because it's near the black
Speaker 1: hole doesn't mean it's going to get sucked in necessarily.
Speaker 1: And that's why you have like this accretion disc. If
Speaker 1: you think about your image of a black hole, it's
Speaker 1: not just like a black sphere. It's like a disc
Speaker 1: of stuff that's orbiting around it. That's the stuff that's
Speaker 1: like on deck for going into the black hole. Hasn't
Speaker 1: fallen in yet, all right, So why does it actually
Speaker 1: fall in. It falls in because there's friction. Like if
Speaker 1: you're just orbiting a black hole or a star, you
Speaker 1: could do that forever. But if you and ten trillion
Speaker 1: of your friends are all orbiting a star, you're gonna
Speaker 1: bump into each other, and occasionally somebody's gonna get nudged
Speaker 1: into the center right out of orbit. That's what an
Speaker 1: accretion disk is. It's like a huge cloud of gas
Speaker 1: and dust and little bits, and there's friction between them.
Speaker 1: They bump into each other, they pull on each other gravitationally,
Speaker 1: so some of the stuff falls in. All right, So
Speaker 1: particles are now falling in towards the black hole. But
Speaker 1: black holes also have magnetic fields. They're not just gravitational objects.
Speaker 1: And what do magnetic fields do? They bend the path
Speaker 1: of charge particles. Think about particles coming from the Sun
Speaker 1: towards the Earth. What happens to them? They don't just
Speaker 1: hit us down here on the Earth. They get deflected
Speaker 1: by the magnetic field, and they get deflected towards the
Speaker 1: North pole and towards the South pole, and some of them,
Speaker 1: because the magnetic field is different at the north pole,
Speaker 1: go in at the atmosphere there, which is what causes
Speaker 1: the Northern lights or the Southern lights. Those are super
Speaker 1: high energy particles from space hitting the atmosphere and then
Speaker 1: glowing gorgeous. Yeah, and so just like the Earth has
Speaker 1: gravity but also has a magnetic field. Particles falling into
Speaker 1: the blank hole will get deflected up towards the north
Speaker 1: pole or the south pole because of the super intense
Speaker 1: magnetic field, and so they get sped up by the
Speaker 1: gravitational field and then they get bent by the magnetic
Speaker 1: field and then shot up or down the poles.
Speaker 3: Ah.
Speaker 4: Okay, so everything that's getting shot out then has some charge.
Speaker 1: Yes, almost everything here is going to be charged, because
Speaker 1: it's very hard to stay neutral. Like if you have
Speaker 1: protons and electrons and they're in hydrogen atom, the energy
Speaker 1: of that bond is tiny compared to the energy of
Speaker 1: these particles, and so they're just going to blow apart. Right,
Speaker 1: So basically everything is plasma here. Everything is charged, and
Speaker 1: so you get plasma. They gets sho up and down
Speaker 1: the north and south poles, and plasma itself glows. So
Speaker 1: where do the photons come from? Right? Photons come from
Speaker 1: these particles getting bent by the magnetic fields. Because how
Speaker 1: does a charge particle change direction? Every time a charge
Speaker 1: particle change direction, it emits a photon. That's the only
Speaker 1: way you can do it. Can't just be like I'm
Speaker 1: going this way, now I'm going that way. And the
Speaker 1: way it does it is by emitting a photon. It's
Speaker 1: like I'm going straight, I'm gonna go right. I'm going
Speaker 1: to admit a photon for the left. Therefore I'm going
Speaker 1: to recoil against it to the right. Just like if
Speaker 1: you're flying through space and you want to change direction,
Speaker 1: what do you do? You fire your rockets and you
Speaker 1: shoot some stuff out in the opposite direction that you
Speaker 1: want to go. Charge particles have to do that also,
Speaker 1: and they shoot out photons. They have like an infinite
Speaker 1: supply of photons inside of them. You can imagine. They
Speaker 1: don't literally have all those photons. They just you know,
Speaker 1: dump some of their energy into the electromagnetic field with
Speaker 1: momentum the opposite direction that they need to go, and
Speaker 1: so then they go that way. And there's nobody like
Speaker 1: driving these particles. I'm making them sound like they're making
Speaker 1: these decisions, but this is just the process anyway. So
Speaker 1: stuff falls in towards the center gets routed towards the
Speaker 1: poles using a magnetic field, and that's how you get
Speaker 1: these jets. And the power comes from the gravitational energy
Speaker 1: of the black hole.
Speaker 4: So the centers of galaxies that have astrophysical jets are
Speaker 4: only the centers of galaxies that have a black hole
Speaker 4: in the middle. Is that fair to say because you
Speaker 4: need the black hole's magnetic field.
Speaker 1: Yeah, exactly, And that's because almost every single galaxy has
Speaker 1: a super massive black hole at its heart. OK, So
Speaker 1: that's pretty safe to say anyway.
Speaker 3: And do all black holes make these jets?
Speaker 1: Yeah, that's a great question. And so some of these
Speaker 1: active galactic nuclei have all the conditions we think for
Speaker 1: making a jet, but they don't have jets. Right, there's
Speaker 1: a big, powerful black hole there, there's a swirling mass
Speaker 1: of gas and dust and particles, but there's no jet.
Speaker 1: And so, as you said earlier, this is not something
Speaker 1: we currently understand, and there's a lot of current research
Speaker 1: on like understanding the magnetic environment around a black hole,
Speaker 1: because it's fun to even think about, Like, well, why
Speaker 1: do black holes have magnetic fields? Anyway? Aren't they gravitational objects?
Speaker 3: Yeah?
Speaker 2: Why?
Speaker 1: Black holes are really weird things. And there's only three
Speaker 1: things that they can have. They can have a mass, right,
Speaker 1: you can put stuff into a black hole and it grows,
Speaker 1: so it's mass increases. But they can also have an
Speaker 1: electric charge, right, Like what happens if you have a
Speaker 1: black hole and it's neutral. And you drop an electron
Speaker 1: into a black hole, well, now it has a charge.
Speaker 1: Because the universe serves electric charge. It can't just eat
Speaker 1: the electric charge and then boom, it's gone. You've deleted
Speaker 1: it from the universe. The universe conserves electric charge. So
Speaker 1: if you drop an electron into a black hole, we
Speaker 1: don't know what happens to the electron. Is it's still
Speaker 1: an electron, whatever, is it something else? But we do
Speaker 1: know that that charge is now added to the event horizon.
Speaker 1: So we don't know what's going on inside the black hole,
Speaker 1: but you can think of the event horizon itself now
Speaker 1: as charged.
Speaker 4: So do most black holes have a negative or a
Speaker 4: positive charge? Or is it like split fifty to fifty?
Speaker 4: What is the predominant charge of black holes?
Speaker 1: Yeah, great question. Most black holes have either a positive
Speaker 1: or a negative charge. It's about split fifty to fifty.
Speaker 1: We think we haven't measured this in detail for any
Speaker 1: black holes. But you know, imagine that you randomly throw
Speaker 1: in positive and negative particles and you do it a
Speaker 1: billion times. In order for the black hole to be neutral,
Speaker 1: those would have to be exactly equal. It's like flipping
Speaker 1: a coin a trillion times and getting exactly half of
Speaker 1: them to be heads and exactly half of them to
Speaker 1: be tailed very very unlikely. So we think there probably
Speaker 1: are no electrically neutral black holes in the universe. Probably
Speaker 1: every black hole out there has some charge because it's
Speaker 1: eaten positives and negatives, and the chances that they add
Speaker 1: up exactly to zero basically zero. So now you have
Speaker 1: a black hole has gravity, has mass, and it has
Speaker 1: electric charge. There's one more thing black holes can have,
Speaker 1: which is spin, because the universe also conserve angular momentum. Right,
Speaker 1: momentum is just like if you're moving through space. Newton
Speaker 1: tells us that you can't just move without something pushing
Speaker 1: you or this conservation of momentum. Well, spin is also conserved.
Speaker 1: If you like set something spinning in space, it'll spin forever.
Speaker 1: The only way to stop is to come with some
Speaker 1: external torque. Same thing is true if you drop something
Speaker 1: into a black hole instead of just dropping an object
Speaker 1: straight in imagine if you drop an object so it
Speaker 1: hits the black hole like sort of near the edge,
Speaker 1: sort of like spinning a bicycle wheel right, pushing on
Speaker 1: the edge to make it spin rather than poking it
Speaker 1: in the center. Same thing. If you drop an object
Speaker 1: into a black hole, you can make it spin, and
Speaker 1: it conserves that spin. The universe can't just get rid
Speaker 1: of angular momentum. So now you have an object which
Speaker 1: has an electric charge and it has to spin. What
Speaker 1: happens with that?
Speaker 3: You've got a magnetic field.
Speaker 1: Boom, Oh my gosh, congratulations exactly. And because magnetic fields
Speaker 1: are not generated by magnetic charges, we don't know if
Speaker 1: monopoles exist in the universe. Right, the only way to
Speaker 1: make a magnetic field in our universe is to combine
Speaker 1: electric charges and motion. So currents generated magnetic fields. Spinning
Speaker 1: objects generated magnetic fields. So black holes have magnetic fields.
Speaker 1: And this is fun to think about. The way I
Speaker 1: visualize it is that I put the charge and spin
Speaker 1: on the event horizon. We don't know what's going on inside,
Speaker 1: so you don't have to worry about like, how is
Speaker 1: the information getting from inside the black hole to the outside.
Speaker 1: Just imagine a spinning sphere of charge and that generates
Speaker 1: a magnetic field. The event horizon is conceptually similar to that.
Speaker 4: Okay, so all black holes. It sounds like all black
Speaker 4: holes should have magnetic fields, because probably none of them
Speaker 4: are neutral. Exactly, but they don't all make the jets.
Speaker 4: Is that because some of them have stronger magnetic fields
Speaker 4: than others or we really don't know.
Speaker 1: We really don't know. Yeah, it's a mystery active galactic
Speaker 1: nuclei hot area of research and definitely not something we understand.
Speaker 1: You know, when they do this, it's really dramatic. One
Speaker 1: other way to study these things is not to look
Speaker 1: for the active galactic nuclei, but to try to study
Speaker 1: the black holes and their magnetic fields in more detail.
Speaker 1: And so, for example, we have image black holes, a
Speaker 1: couple of them, right, Remember these pictures that look like
Speaker 1: a Crispy Kreme donut of the accretion disk around a
Speaker 1: black hole. Super awesome from the event Horizon telescope. That's
Speaker 1: the stuff that's swirling around the black hole, waiting on
Speaker 1: deck maybe to go in. Well, a few years after
Speaker 1: they released that image, they released a follow up image
Speaker 1: where they studied the magnetic field lines near the black hole.
Speaker 1: By looking at the polarization of the photons that come
Speaker 1: from different parts of the accretion disc, they can understand
Speaker 1: the magnetic fields and polarization of photons is kind of weird.
Speaker 1: It's because photons are vector objects. They're not just like
Speaker 1: a location in space. They also have like a direction,
Speaker 1: and so they can essentially spin as they move. And
Speaker 1: so photons have like this little vector extra vector that
Speaker 1: you can measure. We don't have to dick into the
Speaker 1: details now, but we are studying the polarization of these
Speaker 1: photons that come from the vicinity of black holes and
Speaker 1: trying to understand which models of magnetic fields in the
Speaker 1: vicinity of black holes make the most sense best agree
Speaker 1: with the data with what we see out there in
Speaker 1: the universe.
Speaker 4: Cool, all right, So let's take a break. And we've
Speaker 4: talked about astrophysical jets, and I realized that in my head,
Speaker 4: I've decided that that is what relativistic beaming means.
Speaker 3: But maybe that's not actually true. So let Daniel shake
Speaker 3: in his head.
Speaker 4: No, so let's clear up Kelly's misconceptions after the break.
Speaker 4: All right, So, astro physical jets are those things that
Speaker 4: get shot out of quasars that have black holes, but
Speaker 4: not all of them.
Speaker 3: And I thought that.
Speaker 4: This resulted in relativistic beaming, like the beam that comes
Speaker 4: out of the center is But no, you.
Speaker 3: Shook your head. No, So what is relativistic beaming Daniel.
Speaker 1: Yes, so we have these astrophysical jets. We understand something
Speaker 1: about how they're made. They're extraordinarily powerful. We used to
Speaker 1: call them quasars when we saw them in the sky,
Speaker 1: and we see them all over the universe. There's lots
Speaker 1: of them that we spotted. We've I think identified seven
Speaker 1: hundred and fifty thousand different quasars in the umbers, which
Speaker 1: is a lot. Most of them are not pointed at
Speaker 1: us right, so we can see them even if they're
Speaker 1: not pointed at us. And the most dramatic pictures you'll
Speaker 1: see online are ones we see sort of from the side.
Speaker 1: We can see them from the side because they emit photons.
Speaker 1: Also from the side, they hit each other and they glow,
Speaker 1: et cetera, et cetera. But the brightest ones are the
Speaker 1: ones pointed right at us. Like if there's a galaxy
Speaker 1: out there that's oriented perfectly, so we're looking exactly at
Speaker 1: the plane of the galaxy and the core of the
Speaker 1: nuclei is pointed like directly at the Earth, then those
Speaker 1: particles are shooting exactly towards us when they're emitted from
Speaker 1: the galaxy, and then they benefit from a super awesome
Speaker 1: extra special boost that makes that galactic core even brighter
Speaker 1: than it otherwise would be. And that's relativistic beaming.
Speaker 4: Ah, okay, So it's not brighter just because it's pointing
Speaker 4: at us, making it easier to see.
Speaker 3: It's brighter for some other reason.
Speaker 1: That's right. It is brighter because it's pointing at us,
Speaker 1: and that makes it easier to see. But plus it
Speaker 1: gets souped up because of this relativistic effect, which you
Speaker 1: could also consider to just be like the relativistic version
Speaker 1: of the Doppler effect. Right, anything that's moving towards you
Speaker 1: is going to get blue shifted. Anything moving away from
Speaker 1: you is going to get red shifted. And it's easy
Speaker 1: to understand that. It's something we experience every day. If
Speaker 1: you hear a police car drive by you, you hear
Speaker 1: the sound that its siren makes changes as it passes you. Right,
Speaker 1: when it's approaching, it's a higher sound. When it's moving away,
Speaker 1: it's a lower sound. Why is that. It's because the
Speaker 1: wavelength gets shifted to longer wavelengths when it's moving away
Speaker 1: from you. Right. If you just imagine, like a source
Speaker 1: moving away from you, it's going to draw out longer
Speaker 1: wavelengths than a source moving towards you, and so each
Speaker 1: wavelength is a little bit shorter. That's a generic Doppler effect.
Speaker 1: Things moving away from us are red shifted, which is
Speaker 1: also how we can infer distance because there's a relationship
Speaker 1: between red shift and distance. In the universe, things moving
Speaker 1: towards us are blue shifted, and we see this in
Speaker 1: the sky like not everything in the sky is moving
Speaker 1: away from us, Andrameda, for example, is overcoming the expansion
Speaker 1: of the universe and local gravity is pulling it towards us.
Speaker 1: So Andromeda in the sky is blue shifted, not red shifted. Okay,
Speaker 1: so that's the Doppler effect, which is something fairly well known.
Speaker 1: But special relativity changes everything. Right, normal Doppler effect is
Speaker 1: what happens when things are pretty slow and not moving
Speaker 1: super fast, like the way I move here on Earth. Right,
Speaker 1: especially now that I'm fifty years old.
Speaker 3: You're a spry fifty Daniel.
Speaker 1: Thank you. Astro Physically speaking, I'm quite yes, these quasars
Speaker 1: make me feel like a spring chicken. But when relativity
Speaker 1: comes into play, things change, and astrophysical jets are moving
Speaker 1: near the speed of light relative to us, and so
Speaker 1: they benefit from the relativistic Doppler effect, which super enhances
Speaker 1: the brightness in the direction of motion the energy of
Speaker 1: these things in the direction of motion. For two reasons.
Speaker 7: Reason one and reason number one is our old friend,
Speaker 7: length contraction, and the rule of thumb for length contraction
Speaker 7: is moving objects seem shorter.
Speaker 1: So if you're just like looking at a ruler and
Speaker 1: it's sitting next to you, you measure it's a meter long.
Speaker 1: If instead it's zooming towards you at nine tenths the
Speaker 1: speed of light, and then you measure it, you're not
Speaker 1: going to measure it to be a meter long. You're
Speaker 1: going to measure it to be less than a meter.
Speaker 1: Moving objects are shorter, and that's a super fun and
Speaker 1: mind bending consequence special relativity which I love thinking about.
Speaker 1: And people often ask me like, well, why is it shorter?
Speaker 1: And you know, I think that's a really revealing question
Speaker 1: because the answer is it only actually makes sense for
Speaker 1: it to be shorter in the universe, where the speed
Speaker 1: of light is fixed for all observers, it has to
Speaker 1: be shorter. It wouldn't actually make sense to measure that
Speaker 1: meter stick as a meter if it's moving. But our
Speaker 1: intuition is that speed shouldn't change the length of things.
Speaker 1: Kelly thinks, Oh, and my daughter's running across the yard.
Speaker 1: She's the same person, in the same size as she
Speaker 1: was when she was standing still, and mostly she is
Speaker 1: almost she is you can't tell, which is what gives
Speaker 1: us this intuitive feeling that length shouldn't depend on velocity.
Speaker 1: But we're wrong. It actually does. There's no good reason
Speaker 1: why length shouldn't depend on velocity. So this question, like
Speaker 1: why does length depend on velocity, reveals again just our
Speaker 1: bias towards things we find intuitive. If I told you, oh,
Speaker 1: the length doesn't depend on velocity, you wouldn't ask me why.
Speaker 1: You should just be like, yeah, yeah, cool. Anyway, that's
Speaker 1: a digression on the special relativity. But in this case,
Speaker 1: what's happening is the thing is shooting right at us,
Speaker 1: moving very very high speeds. Right. So from the point
Speaker 1: of view of that object, the distance between it and
Speaker 1: the Earth is contracted, right because it sees the Earth
Speaker 1: moving towards it at really high speeds, right, So we're
Speaker 1: seeing it as if it was closer, right. So relativity
Speaker 1: is like shrinking the distance between us and the center
Speaker 1: of this galaxy. This furnace where the black hole is
Speaker 1: shooting bullets at us at super high speed.
Speaker 3: It's bringing us closer to that, and that's what makes
Speaker 3: it brighter.
Speaker 1: That's one of the things that makes it brighter. It's
Speaker 1: reason number one. And that's why it's called relativistic beaming
Speaker 1: because it's like, the relativistic Doppler effect is making this
Speaker 1: much brighter if it's pointed at you.
Speaker 4: That's amazing that we figured that out, because you'd look
Speaker 4: out at the sky and you'd be like, some quasers
Speaker 4: are brighter than the other.
Speaker 3: But like to account for that anyway, go.
Speaker 1: Humans, And that's why I started this episode with, like,
Speaker 1: to understand this, you got to understand gravity of black holes,
Speaker 1: you got to understand magnetism of the bending, and then
Speaker 1: you've got to bring in the relativity to show why
Speaker 1: these things are so bright.
Speaker 3: So many blocks, all right? Reason two.
Speaker 1: Reason number two is the other fun bit of special relativity,
Speaker 1: which is time dilation. Right, So special relativity tells us
Speaker 1: that moving objects look shorter, but also that moving clocks
Speaker 1: run more slowly. Right, And so what's happening when you
Speaker 1: look at Equasar is relativity changes the frequency of these things. Right,
Speaker 1: We talked about how you go from red shift or
Speaker 1: blue shift depending on the velocity. Well, changing the color,
Speaker 1: changing the frequency also changes the energy, right, And so
Speaker 1: if these things are blue shifted, that makes them more energetic.
Speaker 1: So the particles are not just pointed at us, the
Speaker 1: moving at us at very high speed, and relativity boosts
Speaker 1: that to make them have more energy in our frame.
Speaker 1: And that's a confusing thing to think about, like how
Speaker 1: does relativity give something more energy? Remember that energy is
Speaker 1: conserved in a static universe. It's not actually conserved in
Speaker 1: our expanding universe, but it's not invariant, meaning like I
Speaker 1: can measure the energy of something and you can measure
Speaker 1: the energy to be different. If your daughter is running
Speaker 1: past you on the lawn, you measured her to have
Speaker 1: a certain velocity a certain kinetic energy. If your husband
Speaker 1: is running next to her, he says, no, she's not
Speaker 1: moving at all. She has no energy. So you two
Speaker 1: can disagree on how much energy she has. Because energy
Speaker 1: is frame dependent, we think it's conserved in a static universe,
Speaker 1: but it's not invariant, which often leads to confusion. So
Speaker 1: you and I can disagree about how much energy something has,
Speaker 1: and the energy of these astrophysical jest depends on the
Speaker 1: observer because energy is frame dependent. It's relative, it's not
Speaker 1: an absolute quantity.
Speaker 4: Okay, Okay, So while you were describing this, I realize that.
Speaker 4: So we're talking about charged particles moving super fast towards us.
Speaker 4: Is this s galactic cosmic radiation? Is this what the
Speaker 4: astronauts have to worry about?
Speaker 1: This is one source of that. Absolutely. Yeah. And when
Speaker 1: you're out there in space near the ISS, for example,
Speaker 1: this is one of those elements. You're absolutely right. It's
Speaker 1: a dangerous environment. And that partially comes from the Sun,
Speaker 1: and partially comes from inside our galaxy, and partially comes
Speaker 1: from other galaxies. We think the highest energy ones come
Speaker 1: from the centers of other galaxies.
Speaker 4: WHOA, Okay, so I should be saying that galactic cosmic
Speaker 4: radiation comes from quasars.
Speaker 3: No from astrophysical.
Speaker 1: Jets or quasars. Yeah, either one works, okay.
Speaker 3: And they're super bright because of relativistic beaming.
Speaker 1: Yes, absolutely, they're super bright even without the relativistic beaming.
Speaker 1: But then they're super double extra bright because of the
Speaker 1: relativistic beaming. The ones that are pointed right at us
Speaker 1: gets super enhanced because of these relativistic effects. So it's
Speaker 1: this incredible dance of all these pieces of physics, and
Speaker 1: it took us decades to put this all together, and
Speaker 1: so many different branches of physics and so many different
Speaker 1: historical traditions came together for us to like start to
Speaker 1: understand a coherent picture of what's going on inside galaxies
Speaker 1: and such an important thread in science, you know, is
Speaker 1: understanding things from different perspectives and like making sure the
Speaker 1: story you're telling is coherent when you come at it
Speaker 1: from different angles, and that's often how we unravel mysteries. Right,
Speaker 1: We're like, well, this seems to work, but wait, what
Speaker 1: about this piece? If I measure differently or if I
Speaker 1: come out from this angle, it's not making sense. Because
Speaker 1: we think, we hope the universe does make sense and
Speaker 1: that there is a story out there that we can
Speaker 1: unravel no matter how you look at it.
Speaker 4: And I really love human story, So let me tell
Speaker 4: an astronaut story really quick. So when I was reading
Speaker 4: astronaut memoirs, there's a lot of times where they'll talk
Speaker 4: about like being in space and then like a flash
Speaker 4: of light, it's like it passes through their eyeballs and
Speaker 4: they were kind of not sure what it was. It's
Speaker 4: probably kind of a scary experience. And I think that
Speaker 4: the main hypothesis to explain what's happening is that galactic
Speaker 4: cosmic radiation is passing through your eyeballs and it like
Speaker 4: lights up, you know, the receptors in your eye, and
Speaker 4: that's what you see. It's kind of scary and yeah,
Speaker 4: one super scary too. Kind of amazing though, to think that.
Speaker 3: Your vision is being impacted by something happening in a
Speaker 3: quasar and a distant galaxy.
Speaker 4: Anyway, What a crazy universe we live in. Also, I
Speaker 4: like it down here on Earth.
Speaker 1: I know it is nice to live here beneath the
Speaker 1: shelter of our magnetic field and our atmosphere, yeah, where
Speaker 1: our eyeballs are not getting pelted by bullets shot out
Speaker 1: by black holes from other very distinct galaxies.
Speaker 3: Thank you magnetic fields protecting our Earth.
Speaker 1: Thank you our fragile environment. And thanks to everybody out
Speaker 1: there for being curious about how the universe works and
Speaker 1: listening to this explanation for how the centers of distant
Speaker 1: galaxies combined gravity, electromagnetism, and relativity to shoot particles at you.
Speaker 3: See, y'all, next time.
Speaker 4: Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio.
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