Speaker 1: Hey, Daniel, you're often saying that things in space are beautiful. Yeah,
Speaker 1: you know, I never look at a telescope image and
Speaker 1: think yuck. I love the swirls of galaxies, I love
Speaker 1: the explosions of stars. It's all gorgeous. But what makes
Speaker 1: it beautiful? Is it the symmetry? No, I think it's
Speaker 1: beautiful just to see the power of physics and action
Speaker 1: at a grand scale. So would you still think something
Speaker 1: in space was beautiful if it was a little off?
Speaker 1: Why did you do something? Or hey, is there something
Speaker 1: I should know about? I mean, I'm not saying I
Speaker 1: had anything to do with it, but you know, maybe
Speaker 1: just be open minded about the shape of things in space. Fortunately,
Speaker 1: I love galaxies and stars of all shapes and sizes.
Speaker 1: I am more handmade cartoonist and the creator of PhD comics.
Speaker 1: I'm Daniel. I'm a particle physicist, and I do really
Speaker 1: think the universe is beautiful. There's a lot to appreciate
Speaker 1: out there, right. It's big and amazing and quite sparkly
Speaker 1: spaces it is, and it makes me wonder, why do
Speaker 1: we find our universe beautiful? Are we lucky that we
Speaker 1: just ended up in the universe that we find beautiful
Speaker 1: or is it sort of predetermined that any universe we
Speaker 1: would find ourselves in we would appreciate Somehow do you
Speaker 1: think it's there's an evolutionary advantage to finding the universe beautiful?
Speaker 1: Like you know, maybe there were some early humans who
Speaker 1: hated the universe, but you know they didn't make it
Speaker 1: because they got depressed about living in something they didn't like. Yeah,
Speaker 1: I would like to think that there's an evolutionary advantage
Speaker 1: to joy, but I'm not a biologist, so it's too
Speaker 1: far out of my Bailey way. But welcome to our podcast.
Speaker 1: Daniel and Jorge explained the universe in production of I Heartare,
Speaker 1: in which we marvel at the beauty of the universe
Speaker 1: and try to unravel its intermting. We look at everything
Speaker 1: around us and ask why is it that way? Why
Speaker 1: isn't it this other way? What does it mean that
Speaker 1: it swirls this way and bends that way and twist
Speaker 1: this other direction. We look everywhere in the universe and
Speaker 1: we never stop asking why because there is a lot
Speaker 1: out there for us to observe and explore and appreciate.
Speaker 1: And that's a very interesting word, isn't it. Daniel and
Speaker 1: to appreciate the universe and space and everything in it absolutely.
Speaker 1: And one thing I love when we look at like
Speaker 1: Hubble images is seeing the dynamics. I mean, you imagine
Speaker 1: that things out there in space are fixed, their static.
Speaker 1: You're just sort of looking at a picture. But when
Speaker 1: you see these images from Hubble, you see flows. You
Speaker 1: see like explosions, you see gas clouds smashing into each other.
Speaker 1: Of course, it's on the millions of years time scale,
Speaker 1: so you're seeing one image of it. But even just
Speaker 1: from that one image, you can tell there's stuff going on.
Speaker 1: So you're thinking faster, like if you hit the fast
Speaker 1: forward but and you'd be like, wow, now that's beautiful. Well,
Speaker 1: I would like to hit the fastboard button and see
Speaker 1: what happens to the university would answer a lot of
Speaker 1: really fun questions. But I think there's also a lot
Speaker 1: of beauty and taking some process that's dynamic, that's violent,
Speaker 1: and then just freezing it. It's like looking at our
Speaker 1: water drop hitting a surface and seeing those little mini
Speaker 1: droplets in the ring come out. It captures something about
Speaker 1: the physics that's happening in a way that I just
Speaker 1: find beautiful. So lately you've been talking to an artist
Speaker 1: right about this idea of beauty in the universe. Yeah,
Speaker 1: that's right. We have some listeners who are scientists, and
Speaker 1: listeners who are engineers, and also listeners who are rightists
Speaker 1: and artists and cartoonists and of all stripes. And one
Speaker 1: of them called me up recently and asked me what
Speaker 1: I thought about the meaning of life and beauty in
Speaker 1: the universe. And we had a really fascinating conversation. Wow,
Speaker 1: what what do you have to say about the meaning
Speaker 1: of life beauty in the universe? Sounds like a big question.
Speaker 1: And the title of our next movie starting Juda Robbers
Speaker 1: Life Beauty the Universe. Well, I think I said something
Speaker 1: like scientists try to uncover beauty in the universe and
Speaker 1: artists try to create it. Wow, but our artists part
Speaker 1: of the universe. Yeah, and I guess that makes all artists.
Speaker 1: I would agree with that, especially cartoonists. Yes, absolutely. But
Speaker 1: she also asked me a really fascinating question. We were
Speaker 1: like just about to get off the phone, and she said,
Speaker 1: hold on a second, I have a question science question.
Speaker 1: If you have always been curious about do you think
Speaker 1: a lot of people have such a question that they've
Speaker 1: always wanted to ask in case they ever talked to
Speaker 1: a physicist. I don't know, I hope. So I think
Speaker 1: everybody should be prepared. If you end up on an
Speaker 1: airplane flight next to a physicist, you should be ready.
Speaker 1: You should have that question in your pocket. But that
Speaker 1: is a pretty great question. How do we know what
Speaker 1: the shape of the Milky Way? Galaxia, Yeah, that was
Speaker 1: her question. She said, we're inside the Milky Way, so
Speaker 1: how is it that we can see pictures of the
Speaker 1: Milky Way? Or more generally, how do we know the
Speaker 1: shape of the Milky Way if we're stuck in the
Speaker 1: middle of it? Right? Because I yes, we don't have
Speaker 1: the equivalent of a galactic mirror. Right, we can't take
Speaker 1: a selfie. So how do you know, like what your
Speaker 1: nose looks like? Right? If you never had a mirror,
Speaker 1: how would you know what your nose looks like? Yeah,
Speaker 1: we need like a super long selfie stick, you know,
Speaker 1: put a hubble on the edge of a stick that's
Speaker 1: like a hundred thousand light years long to take a
Speaker 1: picture of the Milky Way. That would take for a
Speaker 1: long long time. So today we'll be answering this question
Speaker 1: from one of our listeners. So today on the program,
Speaker 1: we'll be asking the question how do we know the
Speaker 1: shape of the Milky Way? And Daniel, it turns out
Speaker 1: it has a very surprising shape, doesn't It does have
Speaker 1: a weird shape. I think a lot of people have
Speaker 1: an idea for what the Milky Way looks like. But
Speaker 1: I was actually surprised when I dug into this to
Speaker 1: discover it's not quite the shape that everybody expected. You know,
Speaker 1: you just made me realize that most basically any picture
Speaker 1: we've ever seen of the Milky Way was probably an
Speaker 1: artist rendition. Oh I know, don't to even get me
Speaker 1: started on artists renditions in astronomy. It's crazy. The renditions
Speaker 1: are the artists probably both. But almost anytime you see
Speaker 1: a new result in astronomy usually comes with some image,
Speaker 1: and that image is not usually data. It's usually like
Speaker 1: some artist rendition of how this might look, which includes
Speaker 1: huge amounts of like it just invented stuff that's totally speculation,
Speaker 1: and you can disentangle like what we know what it's
Speaker 1: actually real from what like the artists just thought of
Speaker 1: at three am when they were doodling on their computer. Right,
Speaker 1: they should publish the data, right, Like, just show a
Speaker 1: bunch of numbers. Yeah, at the top of the article.
Speaker 1: I'm sure a lot of people would click on that. Well.
Speaker 1: I think the data itself is fascinating. Think about the
Speaker 1: picture of the black hole. That's fascinating to see an
Speaker 1: actual picture of an actual black hole. The zillions of
Speaker 1: artistic images of black holes. But there's only one truth,
Speaker 1: and we want to know the truth, not just like
Speaker 1: what some artists imagined. Imagine if particle physics we just
Speaker 1: like published artists impressions of data from the collision, you know,
Speaker 1: instead of actual data, we would get tossed out of science.
Speaker 1: As like you said, Daniel, that artists do capture truth.
Speaker 1: I think they create beauty. I don't know if it's
Speaker 1: always true. It's not always true. That day succeed all right,
Speaker 1: all right, well, this is an interesting question. How do
Speaker 1: you know what the shape of the Milky Way is
Speaker 1: if you are standing in the middle of it and
Speaker 1: or at least off to a little bit of a
Speaker 1: corner of it. So, as usual, Daniel went out there
Speaker 1: into the wilds of the internet to ask people if
Speaker 1: they knew how we know the shape of the Milky Way?
Speaker 1: And so if you like to participate in future baseless
Speaker 1: speculation with that research on topics of the day. Please
Speaker 1: write to us. And also, if you have a question
Speaker 1: for a physicist you've never had a chance to ask,
Speaker 1: please write to us two questions at Daniel and Jorge
Speaker 1: dot com. We love our listener emails and we really
Speaker 1: do respond to every single one. We should change the
Speaker 1: name of the podcast Daniel to baseless speculation. I think
Speaker 1: that's implied already in physics or in our podcasts Daniel
Speaker 1: and Jorge, so it must include baseless speculation. Yeah, so
Speaker 1: I think about it for a second. Do you know
Speaker 1: how we know the shape of the milk way? What
Speaker 1: would you answer? It's what people had to say. I
Speaker 1: believe our galaxy is relatively flat. So I assume if
Speaker 1: you aim a telescope through the galaxy and then raise
Speaker 1: it above or below the plane of our galaxy, you
Speaker 1: can see there's nothing there. So the natural conclusion is
Speaker 1: that the oxy is rather flat. I would guess that
Speaker 1: the way we moved the shape our galaxy is by
Speaker 1: using all the telescopes that we have, such as Hubble,
Speaker 1: and looking at the whole range of radiation from UV
Speaker 1: to visible lights, two X and gamma rays, and making
Speaker 1: up an image of our galaxy. I think it is
Speaker 1: by scientists and astronomers looking at distant stars in our
Speaker 1: own galaxy and trying to uh map the distance. And
Speaker 1: we also can observe the band of light in the
Speaker 1: in the clear dark sky, which looks like, you know,
Speaker 1: a straight line. And also more importantly, I think we
Speaker 1: have observed distant galaxies and then we can see that
Speaker 1: most galaxies are spiral. I'm assuming that it's mostly just
Speaker 1: from you know, the telescope images and knowing where the
Speaker 1: large sources of mass and our galaxy are, and performing
Speaker 1: models and looking at gravity and to figure out what
Speaker 1: kind of shape that's best. That's a tough one. I'm
Speaker 1: honestly not really a hun percent sure. I do know,
Speaker 1: just like from an energy perspective, I believe the shape
Speaker 1: is um, you know, saddle, and I think it has
Speaker 1: to do with offsetting energy. I don't know many clever
Speaker 1: people fearing out how stars move around the center of
Speaker 1: the galaxy, and that's that gives us a clue of
Speaker 1: how everything is organized around us. All right, people had
Speaker 1: some pretty good ideas here. Nobody said I don't know,
Speaker 1: or that sounds impossible, right, Well, I think people know
Speaker 1: that we've mostly figured it out, and so they imagine
Speaker 1: there must be a way to do it. Oh. Interesting,
Speaker 1: they just assume we figured it out many clever people. Yeah,
Speaker 1: I guess nobody assumed that all this time physicists have
Speaker 1: been making stuff up. It's just been an artist's impression
Speaker 1: this entire time, this entire time. Yeah, Actually, the Milky
Speaker 1: Way looks like a w or x. It's a top hat.
Speaker 1: It looks like a glass of milk. Actually. Yeah, So
Speaker 1: that's an interesting question because we are in the middle
Speaker 1: of the galaxy, right or you know, a little bit
Speaker 1: off to this, but we're not like very far away
Speaker 1: from it, so we don't have a view of it.
Speaker 1: So it's kind of hard to tell. I mean, when
Speaker 1: you look out, you see a cloud of stars. Yeah,
Speaker 1: when you look out, you just see a cloud of stars.
Speaker 1: And that's why it took us actually a long time
Speaker 1: to figure out the shape of the Milky Way. It's
Speaker 1: something we've only recently understood, even like at its broadest scale.
Speaker 1: You know, like people thousands of years ago didn't understand
Speaker 1: the shape of the Milky Way. It's a modern idea
Speaker 1: that the Milky Way is this spiral disk I guess
Speaker 1: it'd be like, you know, trying to guess what the
Speaker 1: shape of the Pacific Ocean is if you're a fish.
Speaker 1: That kind of hard. Do you think fish wonder about that?
Speaker 1: I don't think they want to know, you know. I
Speaker 1: bet fish artists are constantly drawing images of the shape
Speaker 1: of the Pacific Ocean that are just totally baseless speculation
Speaker 1: for their knees articles. Yeah, and I'm sure the fishes
Speaker 1: have a real problem with that, I know on their
Speaker 1: fish casts. Yeah. So, um, it's a pretty interesting question.
Speaker 1: And I guess we figured it out. And so the
Speaker 1: question is how did we figure out out? What is
Speaker 1: the shape of the Milky Way galaxy? So Daniel step
Speaker 1: us through what is kind of a history of this?
Speaker 1: Why did we realize we are in a galaxy? First
Speaker 1: of all, those are two actually fascinating but different questions.
Speaker 1: Like people have looked up in the night sky and
Speaker 1: seeing this band, this thing we call the Milky win
Speaker 1: the night sky, this band of light that looks like
Speaker 1: spilled milk that people have seen obviously for thousands of years.
Speaker 1: For that you only need eyeballs, And people have been
Speaker 1: wondering like what is that, you know, and It was
Speaker 1: only like around the time of Galileo, when we had
Speaker 1: telescopes that people realized it wasn't just some sort of
Speaker 1: gas or some sort of fire in the sky, but
Speaker 1: it was actually made of zillions of tiny little stars.
Speaker 1: So that idea there is only a few hundred years old. Wow,
Speaker 1: So how did Galileo figure it out? I mean, when
Speaker 1: you look at the Milky Way with a telescope, you
Speaker 1: can actually see the individual dots or you just see
Speaker 1: a concentration of dots kind of in that area. Well both.
Speaker 1: I mean, it gets denser in some regions and it's
Speaker 1: dimmer in other regions, but you can look at the
Speaker 1: edges of it and you can see that that cloud
Speaker 1: is really just made up a lot of tiny little dots.
Speaker 1: And of course, the more powerful your telescope, the more
Speaker 1: you can resolve the denser and denser regions. But at
Speaker 1: that time, I'm guessing gilly Little didn't know we were
Speaker 1: in a galaxy or what a galaxy was, right, Like,
Speaker 1: he probably just thought there's a there's a weird concentration
Speaker 1: of stars along this line. Yeah, we didn't even have
Speaker 1: the idea of a galaxy. We just thought, well, there
Speaker 1: was just a universe and it was filled with stars.
Speaker 1: And the whole idea of that stars were clumped into galaxies,
Speaker 1: these little like island universes, they called them, originally came
Speaker 1: about only about a hundred years ago when people started
Speaker 1: measuring the distances to these other faint little smudges, like
Speaker 1: you have the big Milky Way or at this huge
Speaker 1: spilled milk in the sky, and people understood, oh, that's
Speaker 1: just a bunch of stars. But then people also saw
Speaker 1: these little smudges that they couldn't quite resolve that looked
Speaker 1: like distant gas clouds, and they thought, oh, these are
Speaker 1: other just you know, gas clouds that are fairly nearby um.
Speaker 1: And it wasn't until about a hundred years ago that
Speaker 1: they realized that those were entire different galaxies that were
Speaker 1: super far away. And that's sort of the origin of
Speaker 1: this idea that we are a cluster of stars gathered
Speaker 1: together into this little island in space. Right. What year
Speaker 1: was that? That was in about nineteen twenty. That was
Speaker 1: the year of the Great Debate in astronomy, when there
Speaker 1: were folks arguing that the Milky Way basically was the
Speaker 1: whole universe and those little smudges were just gas clouds
Speaker 1: in the Milky Way, and other folks arguing that the
Speaker 1: Milky Way was just a little island and those smudges
Speaker 1: were other distant galaxies. So even in nineteen twenty there
Speaker 1: was a huge debate about that, and that's around the
Speaker 1: time when we started to kind of get a sense
Speaker 1: of the shape of the Milky Way. Right, Yeah, exactly,
Speaker 1: because the whole idea, the basic concept for how you
Speaker 1: build a map for something you're inside of, is that
Speaker 1: you need to measure the distances to the things you're seeing.
Speaker 1: But if you're just looking at the night sky and
Speaker 1: you seeing a bunch of pin pricks, you can't tell
Speaker 1: the difference between lots of different shapes. Is everything far
Speaker 1: away and really bright? Is everything close by and not
Speaker 1: that bright? Are some things far and something's close. It's
Speaker 1: really hard to tell if you don't know the distances.
Speaker 1: So you have to build basically a three D map
Speaker 1: to everything you're seeing from the inside. And that started
Speaker 1: to happen only when we develop better techniques for measuring
Speaker 1: the distances. Two stars, right, because from where we are,
Speaker 1: all stars look like little pinpoints, right, It's not like
Speaker 1: stars that are closer to us actually looked like a circle.
Speaker 1: Everything is so far away that everything looks like a pinpoint. Basically, Yeah,
Speaker 1: the only things that you can actually resolve in the
Speaker 1: telescope are planets and things in our solar system. Everything
Speaker 1: else is so far away that it looks just like
Speaker 1: a point. Remember, the nearest star is more than four
Speaker 1: light years away, so there's no way you're going to
Speaker 1: see the difference between like the left side of the
Speaker 1: star and the right side of the star, and you
Speaker 1: can't resolve it. And even if you could, that wouldn't
Speaker 1: tell you necessarily how far away it was because you
Speaker 1: wouldn't have any recognizable features on it to give you
Speaker 1: a sense of scale, So you still wouldn't know is
Speaker 1: it close by and pretty small or really far away
Speaker 1: and huge. And that was actually the question of about
Speaker 1: these nebula. I mean, with the nebula, you can see
Speaker 1: the left and the right side of it, these smudges,
Speaker 1: and people were wondering are they close by and pretty
Speaker 1: big or really far away and incredibly enormous. And that
Speaker 1: was one argument actually against the idea that these nebula
Speaker 1: other galaxies. People thought, if there are other galaxies, they
Speaker 1: must be just like unfathomily far away and really really big.
Speaker 1: So yeah, you definitely need some sort of system to
Speaker 1: measure the distance to these things, because you can't just
Speaker 1: look at a star and tell how far away it is. Yeah, okay,
Speaker 1: So then how did we start to get a sense
Speaker 1: of the shape of the Milky Way? Did we just
Speaker 1: start looking out into the swirl and gave us somehow
Speaker 1: a sense of the shape of it. Yeah, it dates back,
Speaker 1: you know, more than a hundred years. People just sort
Speaker 1: of started looking at stars and trying to get a map.
Speaker 1: And the way you can tell the distance to nearby stars.
Speaker 1: He's using something called parallax, which means you look at
Speaker 1: the star when we're on one side of the sun,
Speaker 1: and then again when we are on the other side
Speaker 1: of the sun, and that gives you a sense based
Speaker 1: on how much it moves in the sky how far
Speaker 1: away it is. It's sort of like putting your finger
Speaker 1: at arms length and then looking at it through your
Speaker 1: left eye or your right eye. You can see that
Speaker 1: it changes, and then as your finger gets closer and closer,
Speaker 1: it makes a bigger and bigger difference. So by how
Speaker 1: much your view changes as you look from one eye
Speaker 1: to the other you can tell how far away something is.
Speaker 1: It's binocular vision, right, So that was the first idea
Speaker 1: to use parallax to measure the distance to fairly nearby stars. Wow,
Speaker 1: and how well does that work? It works pretty well
Speaker 1: for stars up to you know, ten twenty fifty light
Speaker 1: years maybe, But there's a problem and that it only
Speaker 1: really lets you see pretty nearby stars, stars that are
Speaker 1: bright enough, and stars that can penetrate like the interstellar
Speaker 1: fog of the gas and the dust. So the first
Speaker 1: ideas we had of the shape of the Milky Way
Speaker 1: where oh, it's basically a blob and we're in the
Speaker 1: middle of it, because that's what happens when you're standing
Speaker 1: in a fog. Like imagine you're in a crowd of
Speaker 1: people in a fog. You look around, you think, oh,
Speaker 1: I'm at the center of this crowd, right, But everybody
Speaker 1: thinks that because they have a limited vision, crock could
Speaker 1: look like a hot dog or a top hat. Right.
Speaker 1: You never know, Yeah, you'd never know. And so what
Speaker 1: we have to do is develop a way to see
Speaker 1: further away stars, to see out to the edges of
Speaker 1: the Milky Way, to find something really bright that we
Speaker 1: could calibrate that we could figure out how far away
Speaker 1: it is, and that let us get a sense for
Speaker 1: the shape of the Milky Way. All right, let's get
Speaker 1: into how we finally cracked this method for measuring the
Speaker 1: shape of the galaxy and what the shape actually is.
Speaker 1: But first let's take a quick break. All right, we're
Speaker 1: asking the question how do we know the shape of
Speaker 1: the Milky Way? And Daniel so, so far we have
Speaker 1: one method for telling how far stars are, but it
Speaker 1: doesn't get us far enough. So how do we know
Speaker 1: what the shape of the blob of stars that were
Speaker 1: in looks like? So we take advantage of some really weird,
Speaker 1: really lucky stars. It's almost like somebody has sprinkled these
Speaker 1: stars out there precisely to allow us to measure the
Speaker 1: distance to them. It's amazing how perfectly they work for
Speaker 1: exactly this purpose. So it has to do something with
Speaker 1: a special kind of star. There's a special kind of star. Now,
Speaker 1: a normal star burns at the same brightness all the time,
Speaker 1: and so you can't tell the difference between it being
Speaker 1: really far away and super bright or it being close
Speaker 1: up and fairly dim. But there's another kind of star,
Speaker 1: a variable star whose brightness changes week to week and
Speaker 1: month to month. These are called sephids, and they're first
Speaker 1: discovered by famous female astronomer Henrietta Levitt. And so on
Speaker 1: the time scale like days or months, they get brighter
Speaker 1: and then they get dimmer, and they get brighter and
Speaker 1: then they get dimmer, right, And that tells us a
Speaker 1: little bit about where it is the frequen or is
Speaker 1: it more like we know that these stars are all
Speaker 1: about the same size. They're not all about the same size,
Speaker 1: But there's a really key relationship. There's a connection between
Speaker 1: how quickly they change, like the period between going from
Speaker 1: brightest to dimmest. There's a close connection between that time
Speaker 1: and the brightness of the star, the actual brightness of
Speaker 1: the star. And so while you can't measure how bright
Speaker 1: this star would be if you were standing right next
Speaker 1: to it, you can measure how long it takes to
Speaker 1: go from its brightest to its dimmest. And what they
Speaker 1: discovered when they looked at nearby sephids ones that they
Speaker 1: could measure the distance to using other techniques was that
Speaker 1: there was this incredible relationship, this very clean relationship. So
Speaker 1: if you measured the period, you could extract the luminosity.
Speaker 1: If you knew how long it took to go from
Speaker 1: bright to dim and back, you could then calculate how
Speaker 1: bright it actually was. Oh, I see, that's pretty clever.
Speaker 1: It's like we and I guess we use parallel axes,
Speaker 1: is what they would use to sort of calibrate all this.
Speaker 1: Like we using parallax. We figured out that close by
Speaker 1: sephids are brighter when they blink faster or something like that.
Speaker 1: That's right. We use the close by ones, the ones
Speaker 1: where we could measure their brightness and their actual distance
Speaker 1: using parallax, And we figured out that there's this relationship
Speaker 1: between the period and the luminosity. And if you know
Speaker 1: the actual brightness of a star and you can measure
Speaker 1: the brightness here on Earth, then you can tell how
Speaker 1: far away it is, because everything goes by one over
Speaker 1: our squared, Like the further you are away from the star,
Speaker 1: the dimm or it will be. But that's something that's
Speaker 1: very simple and easy to understand. Twice as far away
Speaker 1: be four times as dim. You're ten times as far away,
Speaker 1: it will be a hundred times as dim. So if
Speaker 1: you know the actual brightness, you know the brightness that
Speaker 1: you measure here you can figure out how far away
Speaker 1: from it you must be, right. That's pretty clever. And
Speaker 1: so that's our main method for getting the shape of
Speaker 1: the galaxy, Like just going by these stars. That's our
Speaker 1: main method. Yea. The sefid stars really are the key,
Speaker 1: and we can see them because they're super duper bright.
Speaker 1: Like some of these stars are like ten thousand times
Speaker 1: brighter than the Sun, so they can penetrate through those
Speaker 1: clouds of gas and dust and you can see them
Speaker 1: even on the other side of the Milky Way. Well,
Speaker 1: sometimes there are ten thousand times brighter, sometimes they're demmer.
Speaker 1: On a good day, they're so bright that you can
Speaker 1: see them in other galaxies. That was the clue that
Speaker 1: Hubble needed to understand that these nebula, these little smudges
Speaker 1: in space, were super duper far away, because he saw
Speaker 1: these sephids varying in other galaxies, like you can see
Speaker 1: sefids in Andromeda. You can see them in other galaxies
Speaker 1: blinking on and off and telling us how far away
Speaker 1: it was. Really. Yeah, like within this mug there would
Speaker 1: be like a little pixel that turned on and off, Yes, exactly.
Speaker 1: And that's the key that told them that these nebula
Speaker 1: were not just pretty big gas clouds inside our galaxies,
Speaker 1: but actually entire other galaxies because his distance measurements put
Speaker 1: them much further away than anything else we saw in
Speaker 1: the sky. It's like if you map the stuff around
Speaker 1: you and you find there's an edge and then there's
Speaker 1: a huge gap, and they see these other dots. That's
Speaker 1: what gives you this like island universe picture of our cosmos.
Speaker 1: It's not just a bunch of stars sprinkled through space
Speaker 1: which with occasional clumping, but that there are these little
Speaker 1: localized blobs which we now called galaxies, these island universes.
Speaker 1: It's almost like somebody on purpose put a bunch of
Speaker 1: light posts all over the universe for us to see
Speaker 1: what the shape and the structures of it are. It's
Speaker 1: really incredible. Without sephids, we would know so much less
Speaker 1: about the nature of the universe. Now recently we've developed
Speaker 1: even more powerful techniques to do sort of the same
Speaker 1: thing on a grander scale. See Deeper into the Universe,
Speaker 1: And we talked to another podcast about the whole structure
Speaker 1: of our cosmos, the large scale structure like where galaxies
Speaker 1: themselves are distributed, and for that we use type one
Speaker 1: a supernova, which is another space object in the same
Speaker 1: kind of category ory where by watching it from far
Speaker 1: away you can tell how bright it actually is and
Speaker 1: then you can figure out how far away it must be.
Speaker 1: But sepids are sort of like the middle ground. Parallax
Speaker 1: is for really close stuff, sefids is for sort of
Speaker 1: intermediate and type one a supernova take you the furthest distance.
Speaker 1: But when it comes to mapping the Milky Way, it's
Speaker 1: really the sefids that are leading the charge, and they're
Speaker 1: sort of amazing, Like you might wonder, like, why is
Speaker 1: the star blinking on and off so regularly? Yeah, it's
Speaker 1: almost like we don't really have a picture of the
Speaker 1: real Milky Way. We just have a picture of sefond
Speaker 1: Milky Way. Have they sort of map out? It's like tracers, right,
Speaker 1: you can tell where the sephids are, and then you
Speaker 1: can assume where the rest of the Milky Way is
Speaker 1: because that's something we can anchor to. Yeah, hopefully the
Speaker 1: sefond galaxy looks like the regular Milky Way galaxy, right, Like,
Speaker 1: hopefully there's nothing weird that makes them a different shape. Yeah. Well,
Speaker 1: if you look at some of the most recent papers
Speaker 1: and we'll talk about these results in a minute. Mapping
Speaker 1: the shape of the Milky Way to great detail, you
Speaker 1: can see that we have the most concentration of sefids nearby,
Speaker 1: because those are the ones that are easiest to see.
Speaker 1: So we know the shape of our side of the
Speaker 1: Milky Way much better than the other side of the
Speaker 1: Milky Way because we haven't seen as many sephids over there.
Speaker 1: That's all right, because we're probably in the good side
Speaker 1: of the galaxy, right Everyone has a good side, and
Speaker 1: if we're on this side, we're probably the better side.
Speaker 1: If we're taking a selfie, we definitely want this profile
Speaker 1: to show up. Yeah, yeah, And and I guess maybe
Speaker 1: a question is why exactly are these seffids blinking so regularly?
Speaker 1: I know it's weird, right because our son just burns,
Speaker 1: and it burns pretty steadily, and you know, it varies
Speaker 1: a little bit, and there's these eleven year cycles, but
Speaker 1: it doesn't just like go up and down on time
Speaker 1: scales of weeks and months. Imagine wou would be like
Speaker 1: to live at a solar system like that where the
Speaker 1: it got substantially brighter and then dimmer and brighter than dimmer.
Speaker 1: But there's some really interesting physics going on inside the star.
Speaker 1: It happens because these stars are mostly burning helium, and
Speaker 1: as they get hot, the helium gets ionized, gets stripped
Speaker 1: away from its electrons, and then it becomes opaque. So
Speaker 1: it's still burning on the inside, but that light is
Speaker 1: no longer leaving the star, so it absorbs its own radiation,
Speaker 1: which makes it really hot, and then it expands, which
Speaker 1: then cools it down, so then it's less ionized and
Speaker 1: less transparent, and so then it sort of collapses again
Speaker 1: until it heats up and gets more opaque and absorbs
Speaker 1: its own radiation, which fluffs it back out again. Since
Speaker 1: incredible cycle, and it's amazing that it's so regular. You know,
Speaker 1: these stars go on and off, on and off on
Speaker 1: the time scale of weeks, for millions of years. It
Speaker 1: sounds like my diet, how much helium re meading these
Speaker 1: days and makes me feel light? Right, Um, that's pretty cool.
Speaker 1: So it's yeah, it's pretty regular. I wonder what it
Speaker 1: would be like to live in a solar system like that, Like,
Speaker 1: you know, you wouldn't just have seasons, you would also
Speaker 1: have potentially you know, like hot sun colt sun season. Yeah,
Speaker 1: amazingly I don't think I've ever read a science fiction
Speaker 1: novel set on a planet orbiting a sethod. That would
Speaker 1: be pretty fascinating. Somebody should write that one, or if
Speaker 1: somebody has written it, please email me and let me
Speaker 1: know because I want to read it. Yeah, and I
Speaker 1: guess you know, we also maybe had a sense of
Speaker 1: what our galaxy could look like by looking at other galaxies. Right,
Speaker 1: Like we saw these mudges, and once we got a
Speaker 1: better view of and we saw that they mostly only
Speaker 1: fall in a couple of shapes, right, Yeah, it's pretty fascinating.
Speaker 1: If you look at the other galaxies, you can see
Speaker 1: a bunch of patterns, like a lot of them are
Speaker 1: spiral galaxies like ours, where you have a heavy blob
Speaker 1: in the middle, sort of like an egg, you know,
Speaker 1: with a yolk, and then a few arms spiraling out
Speaker 1: past it. And that's pretty awesome. Yeah, and what else?
Speaker 1: You also have other kinds of galaxies, like you have
Speaker 1: elliptical galaxies. This is the name we give galaxies that
Speaker 1: don't really have any interesting features like these arms. And
Speaker 1: sometimes these are big and older galaxies with older stars
Speaker 1: in them. They're not making stars as much anymore. But
Speaker 1: you can actually also find smaller elliptical galaxies. And then
Speaker 1: there are the galaxies we call irregular galaxies. These are
Speaker 1: just like smears of stars in space. They're not like
Speaker 1: nicely organized or spinning or tight or compact in any way.
Speaker 1: And I think these are mostly galaxies that have recently
Speaker 1: had some sort of interaction, like two galaxies are colliding,
Speaker 1: and in the meantime it's a bit of a mess
Speaker 1: until gravity sort of reorganizes it back into something nice
Speaker 1: and neat. Right to eat more fiber, maybe that might
Speaker 1: help a little less helium in their diet. And then
Speaker 1: there's another kind of galaxy called a dwarf galaxy. These
Speaker 1: galaxies are much smaller. You can have galaxies of all
Speaker 1: sorts of sizes, you know, from like three thousand to
Speaker 1: three hundred thousand light years, but these dwarf galaxies are like,
Speaker 1: you know, maybe a thousand light years across, contains just
Speaker 1: about like a billion stars. And some of these are
Speaker 1: like satellites of other galaxies, like the Milky Way has
Speaker 1: other little galaxies orbiting it. These little dwarf galaxies sort
Speaker 1: of going around us, right, And how did they form?
Speaker 1: Did they form on their own? Like did they make
Speaker 1: their own stars or did they just kind of grouped
Speaker 1: together and got kicked out of a galaxy. Totally fascinating
Speaker 1: topic of current research. You know, we think that some
Speaker 1: of these formed on their own when the structure of
Speaker 1: the universe came to be, that these pockets of dark
Speaker 1: matter gathered together gas and dust to make galaxies. And
Speaker 1: some of those pockets were bigger and some of them
Speaker 1: were smaller, which is why you have a variation in
Speaker 1: the size of galaxies. But also galaxies are turbulent, and
Speaker 1: sometimes you have collisions, and when you have collisions, you
Speaker 1: have like the main clump sticks together to make a
Speaker 1: big new galaxy, but some bits get tossed off and
Speaker 1: you end up with these little dwarf galaxies. Is sort
Speaker 1: of like the shards of galaxies after collisions. But it's
Speaker 1: not something we totally understand. And dwarf galaxies are a
Speaker 1: really fascinating area of study, especially for dark matter, because
Speaker 1: some of them have a lot of dark matter and
Speaker 1: some of them have, like we're the almost no dark matter,
Speaker 1: So it's something we're still trying to understand. Some of
Speaker 1: them have dwarf matter. Probably all right, let's get into
Speaker 1: well we actually know about the shape of the galaxy.
Speaker 1: We talked about how we can tell what the shape is,
Speaker 1: but let's talk about what it actually looks like. But first,
Speaker 1: let's take another quick break. All right, the shape of
Speaker 1: the galaxy, Daniel, Do we have a shapely milky way
Speaker 1: or do we have a blobby note way? Does they
Speaker 1: need to go on a diet. It definitely has a
Speaker 1: blob in the middle, you know, like many of us
Speaker 1: do these days. But I think it's quite a nice shape.
Speaker 1: I like the bar in the middle and then the
Speaker 1: spirals coming out of it. I think it's really pretty gorgeous. Well,
Speaker 1: let's describe the milky way. What do we know about
Speaker 1: the shape that isn't an artist rendition? What do you
Speaker 1: mean has a bar in the middle? Yeah, so a
Speaker 1: spiral galaxy is not just like a point in the
Speaker 1: middle with spiral arms coming out our galaxy and like
Speaker 1: something like two thirds of spiral galaxies have a bar.
Speaker 1: It's like an elongated blob instead of a circle in
Speaker 1: the middle. And then the spiral arms come out of
Speaker 1: the edges of those bars. Wait, what what do you
Speaker 1: mean it's a bar that's laying flat or it's like
Speaker 1: standing up on the plane of the galaxy. No, it's
Speaker 1: laying flat like a tassel, like a like a stick
Speaker 1: with tassel. Yeah, exactly, it's like a stick with tassels,
Speaker 1: and it's laying flat on the plane of the Milky Way.
Speaker 1: And then the spiral arms started the edge of the
Speaker 1: bar and they spin around. So we just have two arms.
Speaker 1: We actually have multiple arms. We have a four major arms,
Speaker 1: two really big ones and two smaller ones, and then
Speaker 1: other little strands, so you can have multiple tassels. Out
Speaker 1: of the edge of one side of the bar. They
Speaker 1: go off in different directions. Yeah, they leave from sort
Speaker 1: of like different parts of the bar, then spiral out.
Speaker 1: Really gorgeous. You should spend some time looking at the
Speaker 1: images of galaxies. It's beautiful. And something I only recently
Speaker 1: understood about these spirals is that they're not just like
Speaker 1: a bunch of stars clumped together. They're actually a shock
Speaker 1: wave moving through the galaxy. Wait, what it's It's not
Speaker 1: a tassel. It's more like a wave when you move
Speaker 1: your arms through water. Yeah, there's like a shock wave
Speaker 1: of density moving through the galaxy. And as that happens,
Speaker 1: new stars are formed, and so it's like this new
Speaker 1: star forming region is sort of passing through the galaxy.
Speaker 1: I mean, the galaxy is definitely spinning, but these spiral
Speaker 1: arms also spin relative to the galaxy. It's like one
Speaker 1: of those toys with flashing lights, where which light is
Speaker 1: lit up is moving and it gives the impression of motion. Right.
Speaker 1: The spiral arms are something like that. There are these
Speaker 1: shock waves of gas creating new stars as they move,
Speaker 1: and so they rotate relative to the galaxy. Oh wait,
Speaker 1: so the arms of the galaxy are not they're not
Speaker 1: streaming stars. They're not like we were spinning, and you know,
Speaker 1: it's sort of like the trail of a comet. Maybe
Speaker 1: you're saying it's more it's the opposite. It's like they're
Speaker 1: being created by something else. They're being created by this
Speaker 1: shock wave that's passing through the galaxy. It's like the
Speaker 1: shock wave of density that's moving through. You know, like
Speaker 1: if you have traffic, right, somebody slams on the brake
Speaker 1: in traffic, then this shock wave passes through the traffic,
Speaker 1: the shock wave of density where the cars are like
Speaker 1: all closer near to each other. And that's what's happening
Speaker 1: in the galaxy. And that's what these arms are. And
Speaker 1: when that happens, you get many more stars being formed,
Speaker 1: because you know, it's not actually that easy to make
Speaker 1: a star. You have hot gas that's all swirling around.
Speaker 1: It's not easy for gravity to condense that down because
Speaker 1: remember gravity is really weak. Things need to be sort
Speaker 1: of cold and slow moving for gravity to win, and
Speaker 1: so it needs some help. And so these shock waves
Speaker 1: that compress the gas get things started. All right, let's continue,
Speaker 1: And this shock wave is coming from the center of
Speaker 1: the galaxy, like there's some some kind of event or
Speaker 1: what created this shock wave? That's a great question. I
Speaker 1: think it must come from the history of the galaxy formation.
Speaker 1: A lot of these spiral galaxies are formed from the
Speaker 1: collisions of smaller galaxies. So what you're seeing is sort
Speaker 1: of leftover angular momentum from those collisions that's then turned
Speaker 1: into this chocolo. Somebody spilled a lot of milk in
Speaker 1: the Milky Way and they're still crying about it. Alright,
Speaker 1: So then what else do we know? What else have
Speaker 1: we found? And and I guess what's our best measurement
Speaker 1: of the shape of the galaxy. So there's a recent
Speaker 1: couple of papers in the last few years by this
Speaker 1: really awesome project that's been doing a careful job of
Speaker 1: trying to map the shape of the Milky Way. And
Speaker 1: the project actually is a great name. It's called the
Speaker 1: Ogol Project o g l E because hey, you know,
Speaker 1: they're checking out the shape of the Milky Way, so
Speaker 1: they're sort of at the stars exactly, they're creeping the
Speaker 1: stars though. It stands for Optical Gravitational Lensing Experiment, and
Speaker 1: it's a Polish project that's actually based in Chili, and
Speaker 1: they can search for micro lensing like these little events,
Speaker 1: these little gravitational lensing events where some object in our
Speaker 1: galaxy passes in front of something in the background and
Speaker 1: gives a little gravitational blur to it. But they can
Speaker 1: also do a really good job of looking for sethids.
Speaker 1: So they have the largest catalog of sephids anybody's ever collected,
Speaker 1: and they used it to map the shape of the
Speaker 1: Milky Way. Did they also consider calling it the lensing
Speaker 1: Experiment with gravitational and optics, but couldn't couldn't get the copyright.
Speaker 1: They would have been supered by Scandinavia. Can't get l copyright, no, exactly,
Speaker 1: they have to let that go, all right, So it's
Speaker 1: it's maybe our best view of the galaxy because they
Speaker 1: like nobody else has looked at it with this much detail. Yeah,
Speaker 1: they have the biggest collection. So they have twenty four
Speaker 1: hundred sephids and they're scattered all over the galaxy, though
Speaker 1: most of them are on our side of the galaxy
Speaker 1: because it's easier to spot closer by sefids. And they've
Speaker 1: learned something kind of amazing about the shape of the
Speaker 1: Milky Way. They learned the Milky Way is not actually flat.
Speaker 1: What it's not like a like a cooked egg. Yeah,
Speaker 1: it's not like a cooked egg. It's got to warp
Speaker 1: to it, so like you imagine a flat surface and
Speaker 1: there's a blob in the middle. Well, as you move
Speaker 1: away from the edge of the milky Way, the arms
Speaker 1: tilt up, and on the other side the arms sort
Speaker 1: of tilt down. So it makes like a very gentle
Speaker 1: sort of s shape if you look at it from
Speaker 1: the side, or like a what he said, like a tilda,
Speaker 1: like a little squiggles from the side, the galaxy looks
Speaker 1: like a squiggle. Yes, it's sort of cool. So I
Speaker 1: guess you could figure that out. Yeah, if you look
Speaker 1: close enough, you know, you would see that some stars
Speaker 1: are higher or lower at the tips. Yeah, exactly, so
Speaker 1: these tips are bent, we're spinning around. We have these
Speaker 1: cool structure, We have the bar, we have the spirals.
Speaker 1: But then we also have this twist, like this literal
Speaker 1: twist in the story about the shape of the Milky Way,
Speaker 1: this thing we've been trying to understand for hundreds of
Speaker 1: years now has this really interesting wrinkle to it. And
Speaker 1: that shape. Is it rotating with the galaxy or is
Speaker 1: the galaxy kind of like undulating as well as it's spinning.
Speaker 1: It's fascinating, it's actually undulating. Like the galaxy takes two
Speaker 1: hundred twenty million years for a star to go all
Speaker 1: the way around. That's like the length of a galactic year.
Speaker 1: Our son will be back where it is today in
Speaker 1: two hundred twenty million years. But this twist takes like
Speaker 1: six or seven hundred million years to rotate. It's moving
Speaker 1: slower than the actual stars. Wow. So like if you
Speaker 1: spit up a movie of the galaxy, you would see
Speaker 1: it like rippling kind of yes, exactly, And that's what
Speaker 1: I'm talking about that you're seemed as like really long
Speaker 1: term physics, sort of a frozen moment of it in
Speaker 1: time like the galaxy is not just a blob sitting there.
Speaker 1: It's undulating, it's rippling, it's twisting, it's torking, right, But
Speaker 1: we're seeing just a moment of it. These incredible galactic
Speaker 1: forces that operate over like millions and billions of years.
Speaker 1: We can spot it with just these images. That's when
Speaker 1: I find really beautiful about these dynamic astronomical images. Did
Speaker 1: you say torking or torking, say the galaxy twirking? I
Speaker 1: think actually that's what's going on, is that it's twerking
Speaker 1: with some other nearby galaxy. We need the galaxy kid
Speaker 1: party so much. I know, who knew the galaxy was
Speaker 1: not safe for work? Yeah? Alright, so but why is
Speaker 1: it tworking or warping or undulating after all this time?
Speaker 1: Wouldn't it just settle into a nice disc kind of
Speaker 1: like the Solar system? Yeah, you would think so. And
Speaker 1: if this was an ancient effect, then it would settle
Speaker 1: into a fixed shape and it would just rotate in
Speaker 1: that shape. But we think that probably what's going on
Speaker 1: is that this is something more recent, something in the
Speaker 1: last fifty million years, not something ancient that's then been
Speaker 1: ironed out. It's something which is still happening, and so
Speaker 1: we think it's probably not something like intergalactic magnetic fields
Speaker 1: or the shape of dark matter, which are more static
Speaker 1: and not changing as much. We think probably what's going
Speaker 1: on is that it's interacting with some other galaxy. Really
Speaker 1: what that the ripple could be our reaction to another galaxy. Yeah,
Speaker 1: Like there could be some dwarf galaxy that's orbiting the
Speaker 1: Milky Way or that's in the process of being absorbed
Speaker 1: by the Milky Way. Think about what happens when two
Speaker 1: objects like galaxies absorb each other. They don't just smash
Speaker 1: together and form one thing. They passed through each other first,
Speaker 1: slow down, and then come back. They sort of slashed
Speaker 1: back and forth a few times before they coalesced into
Speaker 1: one object. And if you looked at that, just like
Speaker 1: one snapshot, one moment in time, you might see this
Speaker 1: kind of thing that the objects start to distort each
Speaker 1: other before they actually coalesce. So this could be some
Speaker 1: dwarf galaxy nearby, you know, like fifty or a hundred
Speaker 1: thousand light years away, that has already crashed through the
Speaker 1: disc of the galaxy once, creating this kind of ripple,
Speaker 1: and it's slowing down turning around to come back for
Speaker 1: another pass. It's pretty fascinating. Yeah, it seems like the
Speaker 1: galaxy has a much more interesting shape than maybe we
Speaker 1: thought before. Yeah, and that's because it's part of a
Speaker 1: huge dynamical system. These galaxies are all in a dance
Speaker 1: with each other. You know, they're separated by millions of
Speaker 1: light years, but they still tug on each other. And
Speaker 1: remember that our galaxy is not just sprinkled in space
Speaker 1: with other galaxies. There's a bunch of other ones nearby.
Speaker 1: We're all orbiting a common central point. And so each
Speaker 1: g EAXI is like a particle of gas in this
Speaker 1: larger system, you know, and each one has like spin
Speaker 1: and bounce and it's all story and it's you know,
Speaker 1: hit this other one and bounced off this wall and
Speaker 1: crazy stuff. So each one has a real dynamical history.
Speaker 1: They're not just like hanging out in space doing nothing,
Speaker 1: and we are just a tiny little spec in one
Speaker 1: corner of it, right, Yeah, Like we're just a tiny
Speaker 1: speck in a tiny speck in a tiny speck in
Speaker 1: one of its arms, Yeah, exactly. And we're not at
Speaker 1: the center of our milky Way, and we're not out
Speaker 1: at the edge that we are in the center when
Speaker 1: it comes to us sort of the up and down,
Speaker 1: Like we're pretty close to the galactic plane when it
Speaker 1: comes to being off for on the galactic plane, but
Speaker 1: we're not that close to the center or midtwerk or
Speaker 1: mid twerk. Yeah, but it's good that we're not that
Speaker 1: close to the center because there's a huge amount of
Speaker 1: radiation from stuff going on in the center of the galaxy.
Speaker 1: And it's also probably because they were not too far
Speaker 1: out from the center because there are fewer metals out
Speaker 1: there to be harder to have awesome things like steel
Speaker 1: and aluminum and all that kind of stuff we need
Speaker 1: to build our civilization. So we're in a pretty good spot. Yeah,
Speaker 1: you don't want to be too far away from a party,
Speaker 1: but you don't want to be too close to the
Speaker 1: party either, that's right. You want to go to work
Speaker 1: and just the right spot, just like Goldilocks. All right. Well,
Speaker 1: it's overall really amazing that we can get a sense
Speaker 1: of what the shape of the galaxy. I mean, think
Speaker 1: about what a huge problem it is to know what
Speaker 1: the shape of the ocean you're in or the land
Speaker 1: you're on. The fact that we can you know understand
Speaker 1: the universe that much and have these amazing telescopes and
Speaker 1: techniques and engineering and technology. Is pretty incredible that we
Speaker 1: can get a sense of our home in our place
Speaker 1: in the galaxy. Yeah, it really is selfies on a
Speaker 1: cosmic scale. You know, Before we had cameras, people would
Speaker 1: like look in lakes to see their reflection and wonder like,
Speaker 1: what do I look? Likely they knew what all their
Speaker 1: family and friends and everybody around them look like, But
Speaker 1: it's harder to get a picture of your own body,
Speaker 1: your own face. And in the same way, we wonder
Speaker 1: like what does our galaxy look like? It's weirdly more
Speaker 1: challenging to understand the shape of our own galaxy then
Speaker 1: our neighboring galaxy for just the same reasons. So it's
Speaker 1: cool that we've developed all these techniques to get a
Speaker 1: map for like our own home. Yeah, although I think
Speaker 1: I guess technically you should call an ugly maybe not
Speaker 1: a selfie, that's an ugly word for it. Yeah, all right, Well,
Speaker 1: the next time you get to see some stars out
Speaker 1: there in the sky, or maybe even get a glimpse
Speaker 1: of the Milky Way, think about how much we know
Speaker 1: about it and how we know about it and what
Speaker 1: an incredible and maybe beautiful structure it is. That's right.
Speaker 1: And any time you find yourself contemplating the universe and
Speaker 1: there's something about it you just don't quite understand or
Speaker 1: are wondering about, please write to us, suggested as a
Speaker 1: podcast or just ask us a question. We love our
Speaker 1: listener emails, so send them on to Questions at Daniel
Speaker 1: and Jorhey dot com. We hope you enjoyed that, and hey,
Speaker 1: do us a favorite this week? Maybe tell your friends
Speaker 1: about the podcast or follow us on Instagram or Twitter
Speaker 1: so you can learn more about what we're up to.
Speaker 1: Thanks for joining us. Let's see you next time. Thanks
Speaker 1: for listening, and remember that Daniel and Jorge explained the
Speaker 1: Universe is a production of I Heart Radio. For more
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