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Why Do We Have Stars? · Daniel and Kelly’s Extraordinary Universe

• 0:07
  Speaker 1: So I was outside the other night with my son
• 0:09
  Speaker 1: looking up at the sky, and we were having a
• 0:11
  Speaker 1: great time, and he turned to me and he asked
• 0:12
  Speaker 1: me a question. He said, Hey, Dad, why are there stars?
• 0:17
  Speaker 1: You mean like movie stars? No, No, why astronomical stars?
• 0:22
  Speaker 1: He wanted to know. Wow, what did you say? Well?
• 0:24
  Speaker 1: I thought he was asking me, like, why do stars exist?
• 0:27
  Speaker 1: You know, why do we have bright stars in the sky.
• 0:29
  Speaker 1: So of course I give him a long physics explanation
• 0:31
  Speaker 1: for you know, how funion works and all this kind
• 0:33
  Speaker 1: of stuff. I wonder what it's like to have your
• 0:35
  Speaker 1: dad be a physics professor. It's awesome. It's awesome. I
• 0:41
  Speaker 1: wonder how many times he's just like dad. I just
• 0:42
  Speaker 1: wanted a one sentence answer. I once heard him explaining
• 0:48
  Speaker 1: to his friends about black holes, and I thought, Hey,
• 0:52
  Speaker 1: that dude is cool because of me. I think cool
• 0:57
  Speaker 1: as might not be the appropriate adjective here. But what's
• 1:01
  Speaker 1: the What's he satisfied with your explanation? No? Not at all.
• 1:04
  Speaker 1: In fact, it turns out I totally misunderstood his question.
• 1:07
  Speaker 1: When he asked why are their stars? He didn't mean
• 1:10
  Speaker 1: like why does the star burn? He meant like, why
• 1:12
  Speaker 1: are their stars? Plural, like why don't we just have
• 1:15
  Speaker 1: one star? Right? Or like why isn't everything just spread
• 1:18
  Speaker 1: out smoothly in the universe? Why does things clump together
• 1:21
  Speaker 1: to make planets and stars and all that stuff? WHOA,
• 1:24
  Speaker 1: That is a good question. Yeah, it's a great question.
• 1:27
  Speaker 1: It's a kind of question kids ask, right, the kind
• 1:29
  Speaker 1: of question you don't necessarily think to ask. It's such
• 1:32
  Speaker 1: a basic, simple question. That's a question I have. And
• 1:34
  Speaker 1: I'm I'm definitely not five years old. Ye I am
• 1:55
  Speaker 1: Morhan and I'm Daniel, and welcome to our podcast, Daniel
• 1:59
  Speaker 1: and Jorgey Wayne the Universe, in which we try to
• 2:01
  Speaker 1: take everything or anything in the universe, even the obvious
• 2:05
  Speaker 1: stuff like stars, and explain it to you. Why is
• 2:07
  Speaker 1: it there? How does it work? Do I have to
• 2:09
  Speaker 1: worry about it? Can I buy one online? We try
• 2:12
  Speaker 1: to answer the smooth questions and also the lumpy questions.
• 2:16
  Speaker 1: And today is going to be a bit of a
• 2:18
  Speaker 1: lumpy episode. Today on the program, we're asking the question
• 2:26
  Speaker 1: why are there stars? The universe has a really strange
• 2:30
  Speaker 1: kind of shape. I mean, it's huge, but it's mostly empty, right,
• 2:34
  Speaker 1: Like there's vast distances between stars and even vaster ones
• 2:38
  Speaker 1: between galaxies. But then you have these hot little points, right,
• 2:42
  Speaker 1: all this matter concentrated in these little dots. It's a
• 2:45
  Speaker 1: really weird arrangement. Why is it concentrating these little pin points?
• 2:49
  Speaker 1: Why isn't more diffuse or why don't all those pin
• 2:53
  Speaker 1: points just clumped together? Yeah? Why don't we have just
• 2:55
  Speaker 1: one mega star or like a big pudding of delute
• 3:00
  Speaker 1: gas everywhere? Right? Why is the universe the way it
• 3:03
  Speaker 1: is and not any of those other ways? It could
• 3:05
  Speaker 1: have been those ways in some alternate multiverse. It probably
• 3:08
  Speaker 1: is those ways, but in those multiverses they don't have
• 3:10
  Speaker 1: awesome podcasts to ask this question. Yeah. Yeah, because you
• 3:14
  Speaker 1: look at the night sky and it's beautiful, right, I
• 3:16
  Speaker 1: mean it's it's like this black void with little white pinpoints.
• 3:20
  Speaker 1: But you gotta wonder why does it look that way? Okay,
• 3:23
  Speaker 1: so I have to take a digression here an artistic
• 3:25
  Speaker 1: question for you or here, which is why do you
• 3:28
  Speaker 1: think we find the night sky beautiful? I mean, I agree,
• 3:32
  Speaker 1: it's gorgeous. This is the best view in the universe, right,
• 3:34
  Speaker 1: But is it necessary do we find it beautiful to
• 3:36
  Speaker 1: be evolved to find it beautiful? Is it just chance? Like?
• 3:39
  Speaker 1: Could we have evolved in a way. We look up
• 3:41
  Speaker 1: at the night stine, We're like, yuck, that's gross. M h. Well,
• 3:45
  Speaker 1: I think we have a innate appreciation for sparkly things, right,
• 3:50
  Speaker 1: we like we'll all pyromaniacs. Yeah, no, I mean evolved
• 3:55
  Speaker 1: evolved from liking water maybe or being attracted to water
• 3:59
  Speaker 1: or spark the water. I don't know, sparkling water. They
• 4:02
  Speaker 1: had ivan then caved mondays right, Yeah, I think people
• 4:07
  Speaker 1: used to carbonate their own water back in cave men days.
• 4:09
  Speaker 1: I'm pretty sure that we should have asked that question
• 4:12
  Speaker 1: Ryan North when we had him on the podcast. When
• 4:13
  Speaker 1: did they invent sparkling water? The greatest invention all time?
• 4:18
  Speaker 1: Sparkling water. That's a great question is why are there
• 4:24
  Speaker 1: stars and planets as opposed to just having a monotonous,
• 4:30
  Speaker 1: monogamous no homogeneous, monochronous, monochromatic Yeah, I mean like a
• 4:39
  Speaker 1: plane universe. I guess why do we have stars and
• 4:41
  Speaker 1: planets and objects and spark the objects and things rather
• 4:46
  Speaker 1: than we're just living in a giant gas cloud. That's right. Yeah,
• 4:50
  Speaker 1: So that's the question we're gonna try to tackle today,
• 4:53
  Speaker 1: give you a solid answer for it. And so as
• 4:56
  Speaker 1: usual before we answer the question we I went out
• 4:59
  Speaker 1: and I asked bunch of unsuspecting you see, Irvine students,
• 5:02
  Speaker 1: off the top of their head. I asked them that question.
• 5:05
  Speaker 1: So think about it at home or wherever you're listening.
• 5:07
  Speaker 1: Why do you think there are stars and planets and
• 5:10
  Speaker 1: not just a smooth universe? Here's what people had to say.
• 5:14
  Speaker 1: Why is the universe so lumpy like? Why doesn't matter
• 5:17
  Speaker 1: just spread out totally smoothly and evenly through the universe.
• 5:20
  Speaker 1: I want to say gravity, because there's like a certain
• 5:23
  Speaker 1: kind of gravity putting things in place. And I have
• 5:28
  Speaker 1: no idea. Okay, gravity, it's a result of the big bank.
• 5:32
  Speaker 1: You had matter and antimatter, and they made clumps and
• 5:36
  Speaker 1: they kept expanding, and that's just how it occurred. At
• 5:40
  Speaker 1: least that's the model that I've heard. There were at
• 5:45
  Speaker 1: some point areas where there was a slight greater density,
• 5:49
  Speaker 1: and you know, in the matter in the universevity works,
• 5:52
  Speaker 1: a greater density will kind of collapse in the greater
• 5:55
  Speaker 1: and greater and greater density to you have a galaxy,
• 5:57
  Speaker 1: your plans or whatever the ions. Okay, all right, so
• 6:01
  Speaker 1: that's pretty interesting. I feel like you should maybe stop
• 6:03
  Speaker 1: advertising that they're U s Irvine students because I don't
• 6:07
  Speaker 1: know if you're helping the marketing there. I think it's
• 6:10
  Speaker 1: wonderful all these U see Irvine students are willing to
• 6:13
  Speaker 1: stop and think about a random question from a randy,
• 6:16
  Speaker 1: random scruffy looking dude and think about the universe. Likecent
• 6:21
  Speaker 1: of people answer these questions. To me, they get full
• 6:23
  Speaker 1: credit even just for trying, for thinking about it, for
• 6:26
  Speaker 1: engaging right. To me, that's wonderful. When we first started
• 6:29
  Speaker 1: this project, I was sure I was going to get
• 6:31
  Speaker 1: one percent answers. So the fact that they don't know
• 6:34
  Speaker 1: not a big deal. The fact that they try to answer,
• 6:36
  Speaker 1: that's wonderful. I think you should try it down the
• 6:38
  Speaker 1: streets of New York next and see what kind of
• 6:40
  Speaker 1: reaction you get get out of here. Yeah, well, as
• 6:43
  Speaker 1: you were suggesting, maybe I should go up to cal
• 6:45
  Speaker 1: Tech and see see if they get them more precise answers.
• 6:48
  Speaker 1: But everyone seems to say gravity as the answer to
• 6:51
  Speaker 1: the question. Yeah, everybody says gravity, And I think that
• 6:55
  Speaker 1: comes from everybody's feeling correctly that gravity plays a big role, right.
• 6:59
  Speaker 1: Gravity is the thing that made these structures. Gravity is
• 7:02
  Speaker 1: which responsible for holding a start together. Gravity controls the
• 7:06
  Speaker 1: shape of the galaxy. Gravity certainly plays a big role,
• 7:09
  Speaker 1: but I guess the twist is that it's not the
• 7:13
  Speaker 1: only thing you need to make stars. Right. Gravity only
• 7:15
  Speaker 1: clumps links together if you if you already have small
• 7:19
  Speaker 1: clumps to begin with, right, that's right, Gravity is not
• 7:22
  Speaker 1: the complete answer. If you had a universe that was
• 7:25
  Speaker 1: totally smooth, right, completely smooth, then gravity couldn't do anything
• 7:30
  Speaker 1: because each particle in the universe would be pulled both
• 7:33
  Speaker 1: left and right with equal force because it would be
• 7:36
  Speaker 1: equal amounts of stuff on both sides of it, And
• 7:39
  Speaker 1: so every object would be sort of like pinned down
• 7:42
  Speaker 1: by gravity. But it couldn't form any structures, right, So
• 7:45
  Speaker 1: gravity can't make lumps. It can only exaggerate lumps. Once
• 7:49
  Speaker 1: you've gotten a little bit started, we paint that picture
• 7:52
  Speaker 1: a little bit more for me. So let's imagine a
• 7:54
  Speaker 1: perfectly smooth universe, meaning that all the particles in the
• 7:59
  Speaker 1: universe are kind of at the same distance from each
• 8:02
  Speaker 1: other as every other particle in the universe exactly. So imagine,
• 8:06
  Speaker 1: you know, every particle is on a grid, right, and
• 8:09
  Speaker 1: they have one particle every centimeter or something. Right, So
• 8:12
  Speaker 1: take a perfectly exact grid. Everyone. Every particle is one
• 8:15
  Speaker 1: centimeter apart from the next particle exactly. And if you're
• 8:18
  Speaker 1: thinking this is strange and artificial, it's actually very simple, right,
• 8:22
  Speaker 1: And it's very natural. The opposite idea that there's one
• 8:25
  Speaker 1: place where there's particles are closer together, or they're denser
• 8:28
  Speaker 1: and they're denser, or something that's strange, that's unusual, that
• 8:32
  Speaker 1: would be like, well, why they're not here. So having
• 8:34
  Speaker 1: a perfectly smooth, symmetric universe as a as a starting
• 8:38
  Speaker 1: point actually makes the most sense. It's the most natural concept,
• 8:42
  Speaker 1: like a perfect jelly or like a perfect crystal exactly,
• 8:46
  Speaker 1: like a perfectly smooth chocolate pudding with new lumps in it. Right.
• 8:49
  Speaker 1: So if and and if the universe is infinite, you're
• 8:53
  Speaker 1: saying that cloud of perfectly ordered particles would not clump
• 8:58
  Speaker 1: together exactly. So take one random particle, right, And it
• 9:01
  Speaker 1: doesn't matter which one you choose, because we set this
• 9:03
  Speaker 1: up so that all the particles are exactly the same.
• 9:06
  Speaker 1: So pick one random particle. Now, that particle is going
• 9:09
  Speaker 1: to get pulled on by all the other particles in
• 9:12
  Speaker 1: the universe due to gravity and other forces. But let's
• 9:14
  Speaker 1: just think about gravity right now. Now, Um, there's an
• 9:18
  Speaker 1: infinite number of particles pulling it to the left, and
• 9:20
  Speaker 1: an infinite number of particles pulling it to the right,
• 9:22
  Speaker 1: and up and down to right exactly, and in any
• 9:25
  Speaker 1: any way you slice it, you get the same answer. Right. Um,
• 9:28
  Speaker 1: you divide the universe into two halves around this particle,
• 9:31
  Speaker 1: and one half of the universe is pulling it one way,
• 9:33
  Speaker 1: the other half is pulling it the other way. It
• 9:35
  Speaker 1: exactly balances out. It cancels perfectly. Right. It's like if
• 9:39
  Speaker 1: you have two kids and each one is pulling on
• 9:41
  Speaker 1: one arm, You're not going anywhere. Right. Does that happen
• 9:44
  Speaker 1: to you often? That's a random hypothetical I just invented.
• 9:47
  Speaker 1: It's not that I have two kids who often have
• 9:49
  Speaker 1: totally different ideas about what we should do or um,
• 9:53
  Speaker 1: where they want to go or where they want to eat.
• 9:55
  Speaker 1: That's right, um. And so in this scenario, every particle
• 9:59
  Speaker 1: is an equilibrium. Right. There's no way to begin lumpiness
• 10:03
  Speaker 1: because everything is being tugged equally left and right or
• 10:07
  Speaker 1: up and down, or you know, back and forth. So
• 10:10
  Speaker 1: you would the universe would just sit there, It would
• 10:13
  Speaker 1: just stay static. It would it wouldn't wouldn't move right, like,
• 10:17
  Speaker 1: we would just stay there forever, because every particle would
• 10:19
  Speaker 1: just be perfectly bounds where it is. Exactly. It's like
• 10:22
  Speaker 1: if you put a ball in the bottom of a bowl, right,
• 10:25
  Speaker 1: it's just gonna sit there. It's not gonna go anywhere, right,
• 10:28
  Speaker 1: And that's exactly the situation of each of those particles.
• 10:30
  Speaker 1: They're sitting in the bottom of a bowl. That bowl
• 10:33
  Speaker 1: is the gravitational well made by all the other particles
• 10:35
  Speaker 1: in the universe. And so if the universe is infinite,
• 10:39
  Speaker 1: then you can apply the same argument to every particle, right.
• 10:42
  Speaker 1: And so if you start out with an infinite, smooth universe,
• 10:46
  Speaker 1: then you can't get any structure. You can't start to
• 10:50
  Speaker 1: build anything. Hold on, you said that if that's only
• 10:52
  Speaker 1: if the universe is infinite, But what happens if we
• 10:54
  Speaker 1: have this perfect jelly and the universe is finite, meaning
• 10:58
  Speaker 1: that at some point ends. Yeah, well, then this argument
• 11:01
  Speaker 1: doesn't apply because there's some point um Because then this
• 11:05
  Speaker 1: argument only applies to the very center of the universe. Right. Then,
• 11:08
  Speaker 1: if the universe is finite, that means that it has
• 11:11
  Speaker 1: a center, right, that there's someplace where there's an equal
• 11:14
  Speaker 1: amount of stuff to the left and to the right
• 11:16
  Speaker 1: and up and down right, and this argument would only
• 11:19
  Speaker 1: apply right there, or if you go to the edge
• 11:21
  Speaker 1: of all that stuff right. This is again assuming the
• 11:24
  Speaker 1: universe is finite. If you go to the edge of
• 11:26
  Speaker 1: all that stuff, the argument doesn't hold anymore. You have
• 11:28
  Speaker 1: more stuff on one side than on the other. So
• 11:31
  Speaker 1: in the scenario of a finite universe, everything would be
• 11:34
  Speaker 1: attracted towards the center. Everything would be attracted towards the center.
• 11:37
  Speaker 1: All everyone, all the particles would just go towards the center.
• 11:40
  Speaker 1: And then what would happen? Man, I think it would
• 11:42
  Speaker 1: get like a huge star or a massive black hole,
• 11:45
  Speaker 1: or it would be a pretty crazy party, So the
• 11:48
  Speaker 1: universe would be just one star or one black hole.
• 11:51
  Speaker 1: I'm because I would be pretty complicated, but I think, yeah,
• 11:55
  Speaker 1: you would end up with one really big blob of matter, um,
• 11:58
  Speaker 1: and it would be you know, it wouldn't be compally
• 12:00
  Speaker 1: compressed into a point because matter resists being compressed and
• 12:03
  Speaker 1: and if it was spinning right then that keeps it
• 12:06
  Speaker 1: from being compressed further. Um. I don't know if anybody's
• 12:09
  Speaker 1: really studied what would happen if you just like had
• 12:11
  Speaker 1: a huge universized blob of finite matter and then let
• 12:15
  Speaker 1: it collapse. That would be fascinating. So it would be
• 12:19
  Speaker 1: kind of this one just one, not two, not three,
• 12:22
  Speaker 1: just one giant lump of stuff. That's right. And even
• 12:25
  Speaker 1: in that scenario where the universe is perfectly smooth but finite, right,
• 12:29
  Speaker 1: you can't get any asymmetries. Everything has to be perfectly
• 12:33
  Speaker 1: balanced in every direction. Right. Yes, you have a center,
• 12:35
  Speaker 1: so everything's attracted towards the center, but you can't like
• 12:39
  Speaker 1: make stars clumping along the way as they're getting dragged
• 12:42
  Speaker 1: towards the center. Still has to be perfectly smooth because
• 12:44
  Speaker 1: it's the same in every direction, right, In order to
• 12:47
  Speaker 1: get the kind of structure that we see when we
• 12:49
  Speaker 1: look at the night sky, you have like a star
• 12:50
  Speaker 1: here and no star there, and or galaxy here and
• 12:53
  Speaker 1: galaxy there. That's and those are asymmetry. So right, that's
• 12:57
  Speaker 1: a structure, that's a lump. Yeah, it's a in the
• 13:00
  Speaker 1: universe exactly. So that's obviously not the universe we're in.
• 13:03
  Speaker 1: We're not in a perfectly smooth, jelly universe, and we're
• 13:06
  Speaker 1: not living in one giant, singular super cluster of stuff.
• 13:12
  Speaker 1: We live in this kind of a stranger universe, right,
• 13:15
  Speaker 1: and thank god we do, right. I mean, it would
• 13:17
  Speaker 1: be pretty boring to live in an infinitely smooth pudding
• 13:20
  Speaker 1: or even just have like one big star living in
• 13:22
  Speaker 1: a perfect jelly. Seems pretty pretty peaceful to me. Again,
• 13:26
  Speaker 1: I think you should have a snack before we do
• 13:28
  Speaker 1: this podcast. Okay, although, as you tell you tend towards
• 13:31
  Speaker 1: these food analogies that I think it just reflects what
• 13:33
  Speaker 1: you're feeling rather than what you're thinking. Well, let's let's
• 13:37
  Speaker 1: get into how lumpy the universe is and how it
• 13:39
  Speaker 1: got that way. But first let's take a quick break.
• 13:54
  Speaker 1: All right, So we don't live in a perfectly smooth universe,
• 13:57
  Speaker 1: and we don't live in a universe such as one
• 13:59
  Speaker 1: giant cluster, black hole, slash star. That's not the universe
• 14:04
  Speaker 1: we'll live in, right, We are actually in a very
• 14:06
  Speaker 1: lumpy universe. Yeah, And the universe, the structure universe is
• 14:09
  Speaker 1: really fascinating. We should dig into it really deeply in
• 14:12
  Speaker 1: another podcast episode and talk about it and why it
• 14:14
  Speaker 1: is this way in that way. Um, but let's just
• 14:16
  Speaker 1: review briefly sort of where we are in the universe,
• 14:20
  Speaker 1: the the status of the lumps, the level of lumpiness
• 14:23
  Speaker 1: of the universe. Yeah, so we we are sitting here
• 14:26
  Speaker 1: on Earth presumably, that's right. We are two lumps on
• 14:29
  Speaker 1: a rock. Yeah. Um, presumably most of our listeners are
• 14:32
  Speaker 1: on Earth. And if you're not, by the way, if
• 14:34
  Speaker 1: you're listening to this podcast and you're not on Earth,
• 14:36
  Speaker 1: we really want to hear from you. Yeah. Absolutely, But
• 14:40
  Speaker 1: we are in a big rock around rock, going around
• 14:43
  Speaker 1: a sun, a star, and that's our solar system, right,
• 14:47
  Speaker 1: and even that is super lumpy. I mean from the
• 14:49
  Speaker 1: point of view of like how smooth this stuff distributed.
• 14:53
  Speaker 1: You know, people are probably familiar with how far away
• 14:55
  Speaker 1: the Sun is. It's you know, it takes a time
• 14:57
  Speaker 1: for light to even get there. It's minutes and minute,
• 15:00
  Speaker 1: it's in minutes, right, And the Sun itself is a
• 15:02
  Speaker 1: huge blov of matter, but it's super far away. You know.
• 15:05
  Speaker 1: The size of the Earth is enormous and the size
• 15:08
  Speaker 1: of the Sun is enormous, but the size of the
• 15:09
  Speaker 1: distance between them dwarfs both of them. Right, So even
• 15:14
  Speaker 1: just the solar system is really really lumpy in that
• 15:16
  Speaker 1: sense that the matter is concentrated and not spread out.
• 15:19
  Speaker 1: And then our solarcism is inside of a galaxy. Right,
• 15:23
  Speaker 1: and that's even lumpier from that point of view, right,
• 15:26
  Speaker 1: Like the distance between stars is huge compared to the
• 15:29
  Speaker 1: size of the stars. And it had some sort of structure, right,
• 15:32
  Speaker 1: Like the galaxy has spirals and it's kind of thicker
• 15:36
  Speaker 1: and more dense in the middle. Right, there's no structure
• 15:39
  Speaker 1: at that scale too. Yeah, the galaxy told me it
• 15:42
  Speaker 1: doesn't like when you talk about it's thickening waistline rhead.
• 15:45
  Speaker 1: But it's true. It sparkly. I'm talking about its sparkliness.
• 15:51
  Speaker 1: It's beautiful. It's beautiful, the milky way. Um, yeah, exactly.
• 15:55
  Speaker 1: We got all these stars, hundred billions of stars, but
• 15:56
  Speaker 1: they're not just a blob, right, They're not just distributed
• 15:59
  Speaker 1: evenly all THEO. For a long time people thought that's
• 16:01
  Speaker 1: what happened, But now we know that they're arranged in
• 16:03
  Speaker 1: this amazing swirl pattern right or the center of the galaxy.
• 16:07
  Speaker 1: And then we have these arms that come out and
• 16:09
  Speaker 1: because it's rotating, those arms sort of dragged behind it,
• 16:13
  Speaker 1: and uh, and you get this amazing swirl and then
• 16:15
  Speaker 1: you can keep going like the galaxy is part of
• 16:17
  Speaker 1: a supercluster of galaxies and that's super. No, you missed one?
• 16:21
  Speaker 1: What you missed one? The galaxy is part of a
• 16:23
  Speaker 1: cluster of galaxies, right, And when we talk about a cluster,
• 16:27
  Speaker 1: we mean things that are gravitationally bound to each other,
• 16:29
  Speaker 1: that essentially are orbiting each other over billions and billions
• 16:33
  Speaker 1: of years. So we and ours is called the local group,
• 16:36
  Speaker 1: right Like our cluster of galaxies is very imaginatively called
• 16:40
  Speaker 1: the local group. I know that sounds like a temporary
• 16:43
  Speaker 1: name somebody came up with, like, oh, I need to
• 16:45
  Speaker 1: call this something and talk to my advisor, and then
• 16:47
  Speaker 1: it just stuck and they're like, dang, and I should
• 16:49
  Speaker 1: have named it after my dog. What's the opposite of local?
• 16:53
  Speaker 1: Like basically, just here, it means the galaxies near us, right,
• 16:58
  Speaker 1: It's pretty lame name. Um yeah, so that's the cluster.
• 17:03
  Speaker 1: You know, our galaxy cluster is green and you know
• 17:06
  Speaker 1: local sources locally, that's right. I don't think it's vegan,
• 17:12
  Speaker 1: but at least it's local, right. Um yeah, exactly. Our
• 17:22
  Speaker 1: galaxy is part of a structure of of other with
• 17:25
  Speaker 1: other galaxies. Even that cluster is part of another structure
• 17:29
  Speaker 1: in the universe, right. Yeah. They call those superclusters, and
• 17:33
  Speaker 1: these are basically clusters of clusters another imaginative name. Huh.
• 17:37
  Speaker 1: And again you might ask, like, are these totally arbitrary?
• 17:39
  Speaker 1: Is just making this up? Could you have organized it differently?
• 17:42
  Speaker 1: The answers, No, there's some science behind it. We think
• 17:44
  Speaker 1: about how these groups operate, you know, And essentially a
• 17:48
  Speaker 1: supercluster is not just a really really big cluster, it's
• 17:52
  Speaker 1: a cluster of clusters, meaning that the each cluster inside
• 17:56
  Speaker 1: a supercluster is gravitationally bound to itself, and then those
• 17:59
  Speaker 1: things themselves are gravitationally bound to each other, and that's
• 18:02
  Speaker 1: what makes the super clustered. They're sort of trapped in
• 18:05
  Speaker 1: a sort of gravitational bubble almost. Yeah, the way like
• 18:08
  Speaker 1: you know, the Earth and the Moon are a gravitational system, right,
• 18:11
  Speaker 1: which is embedded inside the Solar System, which is embedded
• 18:13
  Speaker 1: inside the galaxy. Right, you might say it's arbitrary to
• 18:17
  Speaker 1: define whether or not the Moon is part of the
• 18:18
  Speaker 1: Earth system, of the Solar System, whatever. Really makes much
• 18:20
  Speaker 1: more sense to consider the Earth to be part of
• 18:22
  Speaker 1: our system, and then the Solar System may be part
• 18:25
  Speaker 1: of the galaxy, rather than just say like, oh, it's
• 18:27
  Speaker 1: all one big galaxy. So that's why we get these hierarchies,
• 18:30
  Speaker 1: and it's amazing that we have these hierarchies, you know,
• 18:32
  Speaker 1: and like also because you can zoom down right and
• 18:34
  Speaker 1: you get like down to the atom and things are
• 18:36
  Speaker 1: orbiting and stuff. So we have this over incredible the
• 18:40
  Speaker 1: different distances from microscopic to what megascopic we have similar
• 18:45
  Speaker 1: structures of things orbiting each other and right on these
• 18:47
  Speaker 1: on these large scales, like an infinite Russian doll, you
• 18:51
  Speaker 1: can stack them up almost infinitely, seems yeah, but infinite,
• 18:54
  Speaker 1: we don't know, right, We talked about that another time,
• 18:56
  Speaker 1: Like we think the universe probably has the smallest scale,
• 19:00
  Speaker 1: and when we talk about the structure of the galaxy
• 19:02
  Speaker 1: as the structure of the the universe, and another podcast episode
• 19:04
  Speaker 1: we'll talk about the biggest structures in the university is
• 19:07
  Speaker 1: a whole other fascinating topic. You can keep going in.
• 19:09
  Speaker 1: There are bigger, bigger structures, right. Well, there's a point
• 19:12
  Speaker 1: where they stop. Yeah, at some point they stop. At
• 19:15
  Speaker 1: some point they stop. There's an end to the Russian doll,
• 19:19
  Speaker 1: as far as we know, there is. There's the largest
• 19:21
  Speaker 1: Russian doll. Yeah. Um, anyway, but that's the topic for
• 19:24
  Speaker 1: another another day. Let's talk about why why we have structure. Yeah,
• 19:28
  Speaker 1: the point is that there is structure, right, Like, we're
• 19:30
  Speaker 1: not in a smooth universe and we're not just one
• 19:32
  Speaker 1: giant lump. There is like texture to the universe, right,
• 19:36
  Speaker 1: there's features, there's things to look at, there's good stuff
• 19:40
  Speaker 1: to see exactly, and as our you see I question
• 19:45
  Speaker 1: answers earlier said gravity is responsible for forming those things.
• 19:49
  Speaker 1: But gravity couldn't start those structures, right, That was the
• 19:52
  Speaker 1: point we were making earlier. So the point is that
• 19:54
  Speaker 1: gravity can't make lumps. When you start a lump, gravity
• 19:57
  Speaker 1: will accelerate like a chain reaction. Right, when you have
• 20:00
  Speaker 1: one point that's denser than everything else, it will have
• 20:03
  Speaker 1: a stronger gravitational pull and it'll start to attract stuff
• 20:06
  Speaker 1: and then look at heavier and have a stronger gravitational pull,
• 20:09
  Speaker 1: and it will feed on itself. But if everything is smooth,
• 20:12
  Speaker 1: then you can't. So the question is, so gravity can
• 20:14
  Speaker 1: make lumps bigger, but the question really comes down to
• 20:17
  Speaker 1: where did the first lumps come from. It's kind of
• 20:20
  Speaker 1: like gravity can roll a snowball down the hill, but
• 20:23
  Speaker 1: it can't sort of start the snowball rolling, Yeah, exactly, exactly,
• 20:28
  Speaker 1: Like once it's rolling, it gets bigger and lump here.
• 20:30
  Speaker 1: But you need some sort of something to get that
• 20:33
  Speaker 1: snowball going. Yeah, you have to knock it out of
• 20:35
  Speaker 1: equilibrium to get it to get things snowballing exactly. Okay,
• 20:44
  Speaker 1: all right, So how did the universe key head lumps?
• 20:47
  Speaker 1: How is it not perfectly smooth or one giant? So
• 20:50
  Speaker 1: that was a big mystery for a long time, right,
• 20:52
  Speaker 1: because it's very natural to think that the universe started symmetrically.
• 20:56
  Speaker 1: I think probably the most popular model for how the
• 20:58
  Speaker 1: universe started is the universe versus infinite and that has
• 21:01
  Speaker 1: infinite amount of matter in it, and that was created
• 21:03
  Speaker 1: in the first moments, right that we don't understand at all.
• 21:07
  Speaker 1: But not understanding it means we want to start with
• 21:09
  Speaker 1: the simplest idea. Okay, And it's not very simple to
• 21:12
  Speaker 1: imagine the creation of an infinite universe with an infinite
• 21:14
  Speaker 1: amount of stuff in it. But if you're gonna go there,
• 21:17
  Speaker 1: it makes more sense to say that the universe starts
• 21:19
  Speaker 1: out smooth. That's where this idea of smoothness comes right, right,
• 21:22
  Speaker 1: like simplicity, because the opposite like, oh, that the universe
• 21:26
  Speaker 1: was created with some initial lumpiness, that's weird. Because then
• 21:28
  Speaker 1: you have to ask why this lumpingness, Why not that lumpiness?
• 21:31
  Speaker 1: Who made that choice? Right? And uh so it was
• 21:34
  Speaker 1: a big puzzle for a long time. Um, And there's
• 21:37
  Speaker 1: really only one way that we know of that you
• 21:40
  Speaker 1: can make lumpiness out of smoothness. There's only one thing
• 21:44
  Speaker 1: in physics that's capable of doing that, Meaning there's only
• 21:47
  Speaker 1: one thing they can add features to something that should
• 21:51
  Speaker 1: be perfectly plain. That's right, what you need there's something
• 21:55
  Speaker 1: that's not deterministic, something which has a random element to it, right,
• 22:00
  Speaker 1: because if every particle universe starts in the same situation,
• 22:03
  Speaker 1: then they should all have the same future. Which you
• 22:05
  Speaker 1: need is to distinguish them somehow, for this one have
• 22:07
  Speaker 1: a different future than that one, for this one, have
• 22:09
  Speaker 1: a different experience somehow. The only thing we know they
• 22:12
  Speaker 1: can do that that can break determinism is quantum mechanics.
• 22:15
  Speaker 1: Because quantum mechanics has real randomness in it. Is that
• 22:20
  Speaker 1: the source then of randomness in the universe. Like without
• 22:23
  Speaker 1: quantum mechanics, we would all be perfectly smooth. Yeah, exactly,
• 22:27
  Speaker 1: But there was still another puzzle, right, So quantum mechanics
• 22:30
  Speaker 1: gives you randomness, but you know, quantum mechanics does not
• 22:32
  Speaker 1: something you notice. You don't like drive around and notice
• 22:35
  Speaker 1: random stuff happening from quantum mechannicals, Like if my phone
• 22:38
  Speaker 1: is here, it's not here and there, that's right. I mean,
• 22:41
  Speaker 1: maybe your bank accounts seems to fluctuate randomly, but there
• 22:44
  Speaker 1: actually is an explanation. My bank account could use more physics,
• 22:48
  Speaker 1: for sure. I am a quantum mechanic accountant, quantom accountant
• 22:54
  Speaker 1: um exactly. And that's why quantum mechanics took such a
• 22:57
  Speaker 1: long time to discover, because people thought the universe was deterministic.
• 23:00
  Speaker 1: I thought two particles in the same situation would always
• 23:02
  Speaker 1: have the same future. I see, there's no reason for
• 23:05
  Speaker 1: them to be different. Like if you create a universe
• 23:08
  Speaker 1: without quantum mechanics, there's no reason for all the particles
• 23:11
  Speaker 1: to be different. There's nothing that gives it that initial
• 23:14
  Speaker 1: randomness exactly. The problem is that quantum mechanics is a
• 23:19
  Speaker 1: tiny amount of randomness, right, it's at the particle scale.
• 23:22
  Speaker 1: It's super duper small, right, these tiny little fluctuations, And
• 23:26
  Speaker 1: what are we talking about concretely, we're talking about like
• 23:28
  Speaker 1: particles being created out of the vacuum. Quantum mechanics can
• 23:31
  Speaker 1: do that. It can take energy and just turn it
• 23:33
  Speaker 1: into particles and then they can turn back into energy.
• 23:36
  Speaker 1: Or you know, this particle can have a chance to
• 23:38
  Speaker 1: go left or right, and you know, maybe this one
• 23:40
  Speaker 1: goes left and another one goes right. This kind of stuff,
• 23:43
  Speaker 1: it's really really tiny effects, not really enough to get
• 23:46
  Speaker 1: gravity going because gravity is super duper weak, right, Gravity
• 23:50
  Speaker 1: needs more than the tiniest little discrepancy. I mean, if
• 23:54
  Speaker 1: you've given billions of years. But the kicker is that
• 23:56
  Speaker 1: the universe used to be small, right, that's the twist.
• 23:59
  Speaker 1: Ending is that the universe used to be really tiny
• 24:01
  Speaker 1: and small. That's right, And so the very first moments
• 24:04
  Speaker 1: of the universe were super dramatic. What happened in the
• 24:07
  Speaker 1: first first moments of the universe was inflation. Inflation is
• 24:11
  Speaker 1: this idea that the universe used to be much denser
• 24:14
  Speaker 1: and then it got stretched out, it got inflated, right,
• 24:17
  Speaker 1: And that's just not stuff moving through space. This is
• 24:19
  Speaker 1: the actual expansion of space itself, meaning things got stretched right,
• 24:24
  Speaker 1: more space was made everything I'm blown and inflated and
• 24:27
  Speaker 1: blown up. What that means is that the microscopic became macroscopic.
• 24:32
  Speaker 1: We'll step us through this. So you're saying, this is
• 24:34
  Speaker 1: all this all goes back to the Big Bang, right,
• 24:37
  Speaker 1: Everything goes back to the Big Bang in the end.
• 24:39
  Speaker 1: You can blame everything in the Big Bang technically, I
• 24:41
  Speaker 1: guess yeah, um officer, I was speeding because the Big
• 24:46
  Speaker 1: Bang dot dot dot dot dot. I blame the universe. YadA, YadA, YadA,
• 24:51
  Speaker 1: I was speeding quantum mechanics. That gets me out of
• 24:56
  Speaker 1: every ticket, trust me. Before we keep going, let's take
• 24:58
  Speaker 1: a short break. Yeah, so the universe used to be very,
• 25:14
  Speaker 1: very small, and that's where these that's where quantum mechanics
• 25:17
  Speaker 1: played a big role, right, Yeah, And be careful when
• 25:19
  Speaker 1: you say the universe used to be very small, because
• 25:20
  Speaker 1: we're still saying the universe was infinite, right, and an
• 25:23
  Speaker 1: infinite amount of stuff in it, but it was denser, right.
• 25:26
  Speaker 1: It used to be more squished when it was created,
• 25:29
  Speaker 1: and then it was and then all that stuff was
• 25:31
  Speaker 1: stretched out due to inflation. Oh. I see, So it's
• 25:34
  Speaker 1: like an infinite ruler getting stretched. It's still infinite, right,
• 25:37
  Speaker 1: I see. So you're saying that the features we've see
• 25:40
  Speaker 1: in the universe today are really just the quantum features
• 25:45
  Speaker 1: that we used to have when we were denser, not smaller.
• 25:49
  Speaker 1: But now when inflation happened at the Big Bang, everything
• 25:52
  Speaker 1: all these small fluctuations got way way bigger. Yeah, it's
• 25:56
  Speaker 1: like an ant man right where he can. He can
• 25:59
  Speaker 1: make things much much of it. Right, ants can be enormous,
• 26:01
  Speaker 1: and then they can do construction projects and you can
• 26:04
  Speaker 1: ride in the back of a butterfly and cool stuff.
• 26:06
  Speaker 1: Take the microscopic and make it macroscopic. Right, So the
• 26:10
  Speaker 1: timeline is the universe is created perfectly smooth, right, little
• 26:15
  Speaker 1: quantum fluctuations happen a little bit this, one particle moves
• 26:19
  Speaker 1: a little bit this way, one particle moves a little
• 26:20
  Speaker 1: bit that way. Then inflation takes over and blows that
• 26:24
  Speaker 1: up right and inflates. It makes those tiny little fluctuations
• 26:29
  Speaker 1: into bigger fluctuations enough to see gravity, and then gravity
• 26:33
  Speaker 1: takes over for the next fourteen billion years. YadA, YadA, YadA.
• 26:36
  Speaker 1: I was speeding officer. I'm telling you that story works
• 26:43
  Speaker 1: every time. Yeah, they probably fall asleep before you finish.
• 26:48
  Speaker 1: Another physics professor, you just let him go. So you're saying,
• 26:55
  Speaker 1: the universe used to be small or denser, and and
• 26:58
  Speaker 1: everything was smoother at that scale, except that if we
• 27:02
  Speaker 1: didn't have quantum mechanics, but we still had inflation. Then
• 27:05
  Speaker 1: we would have exploded the universe or expanded universe, and
• 27:09
  Speaker 1: it would remain smooth. Yes, exactly, it would remain smooth
• 27:13
  Speaker 1: because we had those quantum fluctuations that a little bit
• 27:15
  Speaker 1: of random this at the beginning gave the universe texture exactly.
• 27:19
  Speaker 1: And those little fluctuations were random, right, and they could
• 27:22
  Speaker 1: have been different, different random throws of the universe dice,
• 27:26
  Speaker 1: and we would have a completely different structure. I mean,
• 27:28
  Speaker 1: I think the kinds of structures we would have would
• 27:31
  Speaker 1: still be the same. We would still have galaxies and stars, whatever,
• 27:33
  Speaker 1: but they would be arranged differently. So you might ask,
• 27:36
  Speaker 1: why do we have a galaxy here and not there?
• 27:39
  Speaker 1: And you can trace the answer that all the way
• 27:41
  Speaker 1: back to one little particle fluctuating my millibil of seconds
• 27:46
  Speaker 1: after the Big Bang. If it fluctuated this way, we
• 27:48
  Speaker 1: get this galaxy. We fluctuated that way, we get a
• 27:51
  Speaker 1: different galaxy, or in the same galaxy in a different place.
• 27:54
  Speaker 1: That you said that that provided the seeds for the structure,
• 27:58
  Speaker 1: meaning it would have and it expanded, it would have
• 28:01
  Speaker 1: been smooth, but it had these kind of slightly small
• 28:04
  Speaker 1: shades of a texture, and those those shades became exaggerated
• 28:09
  Speaker 1: by gravity, and then things started to clump around those
• 28:11
  Speaker 1: little shades of texture exactly. And we can see this.
• 28:14
  Speaker 1: We can look back in time and we can see
• 28:16
  Speaker 1: this progression happening. Like if you look back deep, deep
• 28:20
  Speaker 1: into the history of the universe, you see the first
• 28:22
  Speaker 1: light that we can see, which comes from about three
• 28:25
  Speaker 1: eighty thousand years after the Big Bang. It's the cosmic
• 28:27
  Speaker 1: microwave background. We've talked about a few times. This light
• 28:30
  Speaker 1: is really really smooth. It's almost the same no matter
• 28:33
  Speaker 1: where you look at it. It's like the same color,
• 28:34
  Speaker 1: the same temperature, whatever. But if you measure it really
• 28:38
  Speaker 1: carefully that you can see little variations, tiny little fractions
• 28:43
  Speaker 1: of colder and hotter spots. Those that took four hundred
• 28:46
  Speaker 1: thousand years just to get that far right, those are
• 28:49
  Speaker 1: the seeds of from this quantum fluctuations exaggerated by gravity
• 28:54
  Speaker 1: for four hundred thousand years, then propagated forward in time.
• 28:56
  Speaker 1: Give gravity another few billion years, and you start to
• 28:59
  Speaker 1: get things like stars and galaxies and all that stuff. Right,
• 29:02
  Speaker 1: But we can see these quantum fluctuations from the early universe.
• 29:05
  Speaker 1: It's like the pattern that made our our cosmos was
• 29:10
  Speaker 1: totally random. It was totally random, exactly. And we think
• 29:13
  Speaker 1: quantum mechanics is truly random, right, not like there's some
• 29:17
  Speaker 1: hidden process that's controlling it that we don't understand. We
• 29:20
  Speaker 1: think it's really truly random. As mind blowing as it
• 29:22
  Speaker 1: is for anything in the universe to be honestly truly random,
• 29:26
  Speaker 1: it is, and it affects our universe is structure at
• 29:29
  Speaker 1: the deepest level. Right. Wow, it's amazing to think that
• 29:32
  Speaker 1: the reason you and I are here, or the whole
• 29:34
  Speaker 1: Earth this year, or the whole Sun and our solericism,
• 29:37
  Speaker 1: or even maybe even our galaxies here is just the
• 29:40
  Speaker 1: the random fluctuation of one little tiny particle way back
• 29:43
  Speaker 1: in the Big Bang. Yeah, it's the truth, man, The
• 29:46
  Speaker 1: truth is stranger than fiction. That's why. That's why I'm
• 29:49
  Speaker 1: a physicist, because you know, the universe will always alarm you.
• 29:53
  Speaker 1: The universe is like weirder and hotter and nastier and
• 29:56
  Speaker 1: crazier and stranger than anything human could or invent. Right, Well,
• 30:01
  Speaker 1: depends on how crazy and weird you are. But how
• 30:04
  Speaker 1: hot and where you are that's a whole different podcast.
• 30:15
  Speaker 1: So um, I'll have to play this podcast for my son,
• 30:18
  Speaker 1: But that basically answers this question, right, like why do
• 30:20
  Speaker 1: we have stars and not to the smooth distribution of matter,
• 30:23
  Speaker 1: you need two elements. You need quantum mechanics to give
• 30:26
  Speaker 1: you any fluctuation to avoid the smoothness, to break the
• 30:30
  Speaker 1: balance exactly, to break the balance, and then you need
• 30:32
  Speaker 1: inflation to blow it up so that it matters, and
• 30:35
  Speaker 1: that gravity can then take over. So it's a complicated
• 30:38
  Speaker 1: dance to Gravity takes these small fluctuations and basically exacerbates them, right,
• 30:43
  Speaker 1: it makes them, yeah, lumpier and clumpier than than it started. Yeah,
• 30:48
  Speaker 1: but remember gravity can only take little lumps and make
• 30:50
  Speaker 1: them into bigger lumps, right, It can't make lumps if
• 30:53
  Speaker 1: something is totally smooth. All right. Thanks to everyone for
• 30:58
  Speaker 1: listening to this lumpy episode and for listening to my
• 31:01
  Speaker 1: long explanation to my son's short question. Yeah, and whether
• 31:05
  Speaker 1: you're a movie star like Tom Cruise or just a
• 31:09
  Speaker 1: scruffy physicists, if you have any question or lumpy or
• 31:12
  Speaker 1: smooth or why or why do you have to be
• 31:15
  Speaker 1: a movie star or a scruffy physicist? Are you saying
• 31:17
  Speaker 1: you can't be both? That that no you can totally
• 31:23
  Speaker 1: be both. Totally. Yeah, don't ask me for a counterexample.
• 31:27
  Speaker 1: I can't think of one. Maybe maybe in another random
• 31:29
  Speaker 1: role of the universe. That's right. Why are you not
• 31:32
  Speaker 1: a movie star? Dad? Quantum mechanics, So whether you are
• 31:39
  Speaker 1: any of these things, if you have any questions, but
• 31:41
  Speaker 1: you can write us at feedback at Daniel and Jorge
• 31:45
  Speaker 1: dot com. We love getting your email, We love answering
• 31:47
  Speaker 1: questions on Twitter, so get in touch, send us your thoughts.
• 31:51
  Speaker 1: And so the next time you look out into the
• 31:53
  Speaker 1: night sky and you see all those sparkly stars, just
• 31:55
  Speaker 1: think everything is there. You are there because the one
• 32:00
  Speaker 1: and them part of them. But you still have to
• 32:02
  Speaker 1: pay your taxes and your speeding tickets unless you can
• 32:05
  Speaker 1: talk your way out of them. If you still have
• 32:16
  Speaker 1: a question after listening to all these explanations, please drop
• 32:20
  Speaker 1: us a line. We'd love to hear from you. You
• 32:22
  Speaker 1: can find us at Facebook, Twitter, and Instagram at Daniel
• 32:26
  Speaker 1: and Jorge That's one word, or email us at feedback
• 32:29
  Speaker 1: at Daniel and Orge dot com.