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What shapes can galaxies take? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Daniel, you like dark chocolate, right, and you hate
• 0:11
  Speaker 1: white chocolate.
• 0:12
  Speaker 2: It's more than just liking it, It's a way of life.
• 0:15
  Speaker 3: Man.
• 0:16
  Speaker 1: WHOA, that's a lot writing on a flavor. But I
• 0:20
  Speaker 1: wonder does the shape of a chocolate matter to you?
• 0:23
  Speaker 2: Hmm? You mean, like if it's a chocolate chip or
• 0:25
  Speaker 2: a chocolate bar or something else.
• 0:27
  Speaker 1: Yeah, I'm trying to figure out how picky you are.
• 0:29
  Speaker 2: Well, you know, it is really fun to make chocolate
• 0:31
  Speaker 2: have all sorts of weird shapes, but I think it
• 0:33
  Speaker 2: all tastes the same. What if it's pear shape, as
• 0:36
  Speaker 2: long as it's not a disaster fruit and chocolate is
• 0:38
  Speaker 2: a delicious combination.
• 0:39
  Speaker 1: What if it's shaped like white chocolate.
• 0:42
  Speaker 2: Like, chocolate isn't the shape, man?
• 0:45
  Speaker 1: What if it's shaped like a galaxy?
• 0:46
  Speaker 2: Ooh, that sounds delicious.
• 0:48
  Speaker 1: Or what if it's the size of a galaxy?
• 0:50
  Speaker 2: Sounds like I have my work cut out from it.
• 1:07
  Speaker 1: Hi am Hore, my cartoonist and the author of Oliver's
• 1:10
  Speaker 1: Great Big Universe.
• 1:11
  Speaker 2: Hi. I'm Daniel. I'm a particle physicist and a professor
• 1:14
  Speaker 2: at UC Irvine, and I've never run out of my
• 1:17
  Speaker 2: taste for dark chocolate.
• 1:18
  Speaker 1: I wonder if your dislike of white chocolate is just
• 1:21
  Speaker 1: context based.
• 1:22
  Speaker 2: You mean, like it's a bad childhood memory.
• 1:24
  Speaker 1: Yeah, No, well I mean more like situational. You know, like,
• 1:26
  Speaker 1: what if you're in a dessert not a dessert, Well,
• 1:28
  Speaker 1: maybe it could be a desert island. But what if
• 1:30
  Speaker 1: it's also deserted, but the only dessert available or anything
• 1:35
  Speaker 1: to eat is white chocolate? Would you starve or would
• 1:37
  Speaker 1: you eat it?
• 1:39
  Speaker 2: I would eat it, but as I did, I would
• 1:41
  Speaker 2: understand how much better it would have been if it
• 1:44
  Speaker 2: was dark chocolate.
• 1:46
  Speaker 1: I see, you'd be complaining the whole time.
• 1:48
  Speaker 2: He I'd be the only one there, So who's to
• 1:50
  Speaker 2: complain to?
• 1:51
  Speaker 1: Hey, you could complain to the white chocolate. I guess
• 1:53
  Speaker 1: could paint a face on it, kind of like.
• 1:55
  Speaker 2: Wilson, complaining makes everything better.
• 1:58
  Speaker 1: That it does. But anyways, welcome to our pot. Daniel
• 2:00
  Speaker 1: and Jorge explain the Universe, a production of iHeartRadio.
• 2:03
  Speaker 2: In which we do our best to enjoy all of
• 2:05
  Speaker 2: the flavors of the universe. The electronic, the muonic, the
• 2:08
  Speaker 2: tawonic flavors, the ups, the downs, the charms, the bottoms,
• 2:12
  Speaker 2: the tops, everything in the universe that has a flavor
• 2:14
  Speaker 2: and everything that can be explained. We take a bite
• 2:18
  Speaker 2: out of all of it and explain everything to you.
• 2:21
  Speaker 1: Wait wait, wait, you just said you take a bite
• 2:22
  Speaker 1: out of white chocolate and enjoy it.
• 2:25
  Speaker 2: I'm confused on adviceive Council. I'm going to pass on
• 2:28
  Speaker 2: answering that question.
• 2:29
  Speaker 1: But aren't you curious what makes white chocolate different than
• 2:32
  Speaker 1: dark chocolate?
• 2:32
  Speaker 2: Yeah, it's the lack of chocolate.
• 2:35
  Speaker 1: No, it has chocolate as coco butter.
• 2:38
  Speaker 2: Coco butter is chocolate the way like butter by itself
• 2:41
  Speaker 2: is a whole meal. You know, it's there to accentuate
• 2:43
  Speaker 2: the flavors.
• 2:45
  Speaker 1: Obviously, you haven't been to Texas with the eat of
• 2:48
  Speaker 1: fright butter, which is where I am right now.
• 2:50
  Speaker 2: Yeah, exactly so. Not a big fan of deep fried
• 2:53
  Speaker 2: butter or white chocolate. To put those two things in
• 2:55
  Speaker 2: the same category.
• 2:57
  Speaker 1: They probably have the same number of calories.
• 3:00
  Speaker 2: To be honest, have you tried deep fried white chocolate?
• 3:03
  Speaker 1: Ooh, that might be a different state. Sounds like more
• 3:07
  Speaker 1: of an Arkansas thing.
• 3:08
  Speaker 2: Maybe keep traveling and report back.
• 3:11
  Speaker 1: That's right, I'm going a mission to try all the
• 3:14
  Speaker 1: freight of fats. But anyways, we do like to wet
• 3:17
  Speaker 1: our appetite and satisfy our appetite for the universe, our
• 3:20
  Speaker 1: curiosity for how things work out there in the cosmos.
• 3:23
  Speaker 1: Why are things the way they are, why are they
• 3:24
  Speaker 1: shaped like the way they are, and why do they
• 3:27
  Speaker 1: taste the way they do?
• 3:28
  Speaker 2: Because it's more than just the colors in the night sky,
• 3:31
  Speaker 2: the bright twinkling lights, the reds, the greens, everything else
• 3:34
  Speaker 2: that's up there. It's also the structure in the night
• 3:37
  Speaker 2: sky that tells us a story about the history of
• 3:40
  Speaker 2: the universe and where the universe is headed.
• 3:42
  Speaker 1: It's right because things in the universe aren't all the same.
• 3:46
  Speaker 1: Some things are shaped differently than others. They look different,
• 3:49
  Speaker 1: they have a different form, and it all reflects back
• 3:53
  Speaker 1: on how it all came together.
• 3:55
  Speaker 2: All the structure in the universe was inevitably put together
• 3:58
  Speaker 2: by gravity as it pulls things together in battles, angular momentum,
• 4:02
  Speaker 2: and other forces, and the shapes that we end up
• 4:04
  Speaker 2: with and how they change over time tell us about
• 4:07
  Speaker 2: how those forces work together and what the history of
• 4:09
  Speaker 2: the universe is. If you peer out in the night
• 4:12
  Speaker 2: sky beyond the stars, you see all these little smudges.
• 4:15
  Speaker 2: Those smudges are distant galaxies and each one has its
• 4:19
  Speaker 2: own shape that tells a story about how it got there.
• 4:22
  Speaker 1: And so the podcast will we tackling the question what
• 4:29
  Speaker 1: are the possible shapes of galaxies? Now, Daniel, is this
• 4:33
  Speaker 1: like the shape? What it looks like? Or how much
• 4:35
  Speaker 1: do galaxies exercise? Like? Are you a fit galaxy? Are
• 4:39
  Speaker 1: you a buff galaxy? Are you a little flabby around
• 4:43
  Speaker 1: the edges?
• 4:44
  Speaker 2: I'm not selling a galaxy workout video, and this is
• 4:47
  Speaker 2: not some sort of cosmic drift. No, we are not
• 4:50
  Speaker 2: judging the shapes. We are just observing and trying to
• 4:52
  Speaker 2: understand how they got there.
• 4:54
  Speaker 1: Doing Galaxies have names like p X thirty nine. Isn't
• 4:57
  Speaker 1: that also the name of some workout.
• 4:59
  Speaker 2: Program it is? Now, yeah, we're panding that and we're
• 5:04
  Speaker 2: making a cosmic workout program exactly.
• 5:07
  Speaker 1: That's right. Yes, it's the milky way.
• 5:10
  Speaker 2: You gets fit, like the whirlpool galaxy. I don't know
• 5:13
  Speaker 2: how that works.
• 5:13
  Speaker 1: Does it depend on how much dark chocolate the galaxy
• 5:16
  Speaker 1: has eaten?
• 5:17
  Speaker 2: Collapsing into a huge bar of dark chocolate is the
• 5:20
  Speaker 2: eventual end of every galaxy.
• 5:22
  Speaker 1: The dream state for all physicists.
• 5:25
  Speaker 2: But it is fascinating to look up at the night
• 5:27
  Speaker 2: sky and to see all these different shapes. Some of
• 5:29
  Speaker 2: them are ellipses, some of them are blobs, some of
• 5:31
  Speaker 2: them are stretched out. There's even one that looks like
• 5:33
  Speaker 2: a question mark. Almost every possible shape you can imagine
• 5:37
  Speaker 2: is up there somewhere in the night sky. And there
• 5:40
  Speaker 2: are so many galaxies in the universe that it makes
• 5:43
  Speaker 2: astronomers wonder how they all got that way. It makes
• 5:45
  Speaker 2: them want to invent crazy illogical names for the various categories.
• 5:50
  Speaker 2: There's a lot of rich signs to do in the
• 5:51
  Speaker 2: shapes of galaxies.
• 5:53
  Speaker 1: Well, that's kind of a new concept, maybe for a
• 5:56
  Speaker 1: lot of people, because you know, we all grew up
• 5:57
  Speaker 1: looking at pictures of galaxies and they all kind of
• 6:00
  Speaker 1: the same, right, they look like little swirls.
• 6:02
  Speaker 2: I mean, if you've only looked at a few pictures,
• 6:04
  Speaker 2: they might all look the same. But as soon as
• 6:06
  Speaker 2: you look at a handful or a dozen or so,
• 6:07
  Speaker 2: you start to notice there's a lot of weird shapes
• 6:10
  Speaker 2: out there. Some of them have more arms, fewer arms,
• 6:12
  Speaker 2: some of them have no arms at all. There's a
• 6:15
  Speaker 2: lot of weird stuff in the universe.
• 6:16
  Speaker 1: M Is it sort of like cloud watching, Like you
• 6:19
  Speaker 1: look out into the sky and you look at the
• 6:21
  Speaker 1: clouds and they're all different shapes, like pie shaped or
• 6:24
  Speaker 1: you know, a butterfly shape.
• 6:26
  Speaker 2: Yeah, exactly. And if you understand the dynamics of water
• 6:29
  Speaker 2: droplet formation and air currents, you can understand why certain
• 6:32
  Speaker 2: clouds look the way they do. They tell you a
• 6:34
  Speaker 2: story about what's happening up there, what the forces are
• 6:37
  Speaker 2: that are doing battle. And it's the same for galaxies.
• 6:40
  Speaker 2: There's enormous cosmic forces pushing on these things and pulling
• 6:43
  Speaker 2: on these things, and the shapes reveal exactly what happened.
• 6:47
  Speaker 1: How much dark chocolate it eight.
• 6:50
  Speaker 2: How much it's been subscribing toges new workout video.
• 6:53
  Speaker 1: That's right, how many spins it's been doing well? As usual,
• 6:56
  Speaker 1: we were wondering how many people out there had thought
• 6:58
  Speaker 1: about this question of what shape galaxies can be, and
• 7:01
  Speaker 1: so as usual, Daniel went out there into the internet
• 7:03
  Speaker 1: to ask people what are the possible shapes galaxies can take.
• 7:07
  Speaker 2: I'm grateful as always to our group of volunteers, and
• 7:11
  Speaker 2: if you would like to join them to contribute your
• 7:13
  Speaker 2: voice to the podcast, please don't be shy right to
• 7:15
  Speaker 2: us to questions at Danielanjorge dot com. Everybody's welcome.
• 7:19
  Speaker 1: So think about it for a second. What kinds of
• 7:21
  Speaker 1: shapes have you seen in galaxies? Here's what people had
• 7:24
  Speaker 1: to say.
• 7:25
  Speaker 4: There's spiral galaxies or barred spirals like ours. I don't know,
• 7:31
  Speaker 4: maybe there's just bars. There's irregular ones that were disturbed
• 7:34
  Speaker 4: by gliding with other galaxies haven't settled down yet. I
• 7:39
  Speaker 4: think there's blobs or spherical shape galaxies, and I hope
• 7:43
  Speaker 4: there's a galaxy shape like Mickey.
• 7:44
  Speaker 2: Mouse somewhere out there.
• 7:46
  Speaker 5: I think they're most often some kind of circular shape,
• 7:48
  Speaker 5: given that they're rotating around the black hole that's usually
• 7:51
  Speaker 5: at the center of the galaxy. I think the Milky
• 7:53
  Speaker 5: Way is considered a spiral galaxy, but I would guess
• 7:56
  Speaker 5: he can probably have most any shape that's possible that
• 7:58
  Speaker 5: could form around a center of man No.
• 8:00
  Speaker 3: I did used to take part in Zooniverse, so I
• 8:04
  Speaker 3: know that you can have spiral shape galaxies, and they
• 8:07
  Speaker 3: can have different numbers of arms, and they can also
• 8:09
  Speaker 3: have a bar feature or not across the center. Then
• 8:13
  Speaker 3: you also get s elliptical galaxies, which when they're sort
• 8:17
  Speaker 3: of close to the plane it's called lenticular galaxies. And
• 8:24
  Speaker 3: then you can have globular clusters. Now may be other
• 8:27
  Speaker 3: galaxy shapes as well, but they're the main types that
• 8:30
  Speaker 3: I remember.
• 8:31
  Speaker 1: All right. I feel like they quickly spiral out of control.
• 8:36
  Speaker 2: There are a lot of ellipses there. As people were.
• 8:38
  Speaker 1: Thinking, Yeah, they just kept going around and around in circles.
• 8:44
  Speaker 2: I don't know if there is a Mickey mouse shaped galaxy,
• 8:46
  Speaker 2: but if the universe is infinite, then I guess somewhere
• 8:49
  Speaker 2: there has to be one.
• 8:50
  Speaker 1: Well, I wonder if there are like three galaxies kind
• 8:52
  Speaker 1: of crashing into each other right before they do, they
• 8:55
  Speaker 1: do look like a maybe a Mickey mouse shape.
• 8:57
  Speaker 2: Well, you know, if you google Mickey mouse galaxy, you
• 9:00
  Speaker 2: don't get mostly scientific images.
• 9:02
  Speaker 1: Yeah. Or I wonder if you look far enough or
• 9:04
  Speaker 1: long enough at galaxy shapes, if you'll eventually run into
• 9:07
  Speaker 1: one that's inappropriate. We're not safe for work.
• 9:10
  Speaker 2: Not safe for the universe, safe for astronomy. Probably. It's
• 9:17
  Speaker 2: sort of like looking at clouds. You can stare at
• 9:19
  Speaker 2: a galaxy and imagine a creative interpretation.
• 9:22
  Speaker 1: Interesting, I see what you're saying. Maybe it reveals more
• 9:24
  Speaker 1: about your inner space than outer space.
• 9:26
  Speaker 2: Yeah, exactly, It's like a roar shark test.
• 9:28
  Speaker 1: Yeah, if you have a dark mind or a white
• 9:30
  Speaker 1: chocolate mind.
• 9:33
  Speaker 2: A white chocolate mind is like a brain that's been
• 9:35
  Speaker 2: battered and fried.
• 9:37
  Speaker 1: Oh my gosh. Well, anyways, maybe we should start at
• 9:42
  Speaker 1: the beginning here, you know, if we're going to talk
• 9:44
  Speaker 1: about the shape of galaxies, like how do galaxies form
• 9:46
  Speaker 1: in the first place, and what might determine their shape?
• 9:49
  Speaker 2: Yeah. I think people usually think about the universe in
• 9:52
  Speaker 2: terms of stars, but to me, it's much more natural
• 9:54
  Speaker 2: to think about the universe in terms of galaxies. It's
• 9:57
  Speaker 2: like the basic building block of the universe. You look
• 9:59
  Speaker 2: at into deep space and it's mostly filled with galaxies
• 10:02
  Speaker 2: scattered everywhere. You can argue about whether those galaxies come
• 10:05
  Speaker 2: together to make larger structure and whether the internal structure
• 10:08
  Speaker 2: of those galaxies is more important, But to me, galaxies
• 10:11
  Speaker 2: are like the basic building block of the universe. So yeah,
• 10:14
  Speaker 2: it's important to figure out like why do we have galaxies,
• 10:17
  Speaker 2: Why are they typically this size? Why does the universe
• 10:20
  Speaker 2: do this kind of thing?
• 10:21
  Speaker 1: I see, Galaxies are sort of like maybe the atom
• 10:24
  Speaker 1: for you, Like, you know, it's made out of things
• 10:26
  Speaker 1: that are smaller, but you know, to understand most of
• 10:30
  Speaker 1: what we see around us in chemistry and materials and
• 10:32
  Speaker 1: things like that, you can just sort of think about
• 10:34
  Speaker 1: the atomic structure.
• 10:36
  Speaker 2: Yeah, to me, it's always really fascinating the size of
• 10:39
  Speaker 2: things that emerge. You know, we don't know if there's
• 10:41
  Speaker 2: the smallest thing in the universe, but it's fascinating that,
• 10:43
  Speaker 2: Like the atom is a certain size, right, and planets
• 10:47
  Speaker 2: are a certain size, and stars are a certain size.
• 10:49
  Speaker 2: Galaxies also are a certain size, and if you poke
• 10:52
  Speaker 2: into the physics behind them, how they came together, and
• 10:55
  Speaker 2: then you learn something about what the universe likes to do,
• 10:58
  Speaker 2: which somehow maybe bubbles up from the tiniest particles, though
• 11:01
  Speaker 2: that's not a process that we understand.
• 11:03
  Speaker 1: You mean, like galaxies don't vary that much in size, right,
• 11:06
  Speaker 1: Like you don't see a tiny, tiny galaxy and humongas
• 11:10
  Speaker 1: you know, superstructure spanning galaxies. They mostly all fall within
• 11:14
  Speaker 1: a certain range, just like planets all sort of fall
• 11:17
  Speaker 1: within a certain range.
• 11:18
  Speaker 2: Yeah, there is a very wide range of size of galaxies,
• 11:21
  Speaker 2: but it doesn't extend down to like the size of cats.
• 11:23
  Speaker 2: You don't have like galaxies the size of cats, and
• 11:25
  Speaker 2: you don't have galaxies the size of superclusters exactly. So
• 11:28
  Speaker 2: there's a certain like size of galaxy that the universe
• 11:31
  Speaker 2: likes to make and not much much much bigger and
• 11:33
  Speaker 2: not much much much smaller, And that tells you something
• 11:36
  Speaker 2: about the balance of the forces.
• 11:38
  Speaker 1: Sort of like planets too. I guess you can have
• 11:40
  Speaker 1: small planets, but you can't have like a Solar system
• 11:42
  Speaker 1: sized planet.
• 11:43
  Speaker 2: Yeah, if you had something like that, it would just
• 11:44
  Speaker 2: collapse into a star, right. And in the end, it
• 11:47
  Speaker 2: all comes back to the same original story of like,
• 11:49
  Speaker 2: why do we have any structure at all? Why is
• 11:52
  Speaker 2: in the universe just like smoothly filled with particles. Why
• 11:56
  Speaker 2: do things clump together? And that dates back all the
• 11:59
  Speaker 2: way to the very beginning of little patches where things
• 12:02
  Speaker 2: were denser and little patches where things were less dense.
• 12:04
  Speaker 2: We think there were quantum fluctuations in the early universe
• 12:07
  Speaker 2: as particles formed out of this pre particle goo, this
• 12:10
  Speaker 2: very hot and dense stuff that we don't understand very well.
• 12:13
  Speaker 2: You've got little fluctuations that were more dense here and
• 12:15
  Speaker 2: less dense there, and those were the seeds that gravity
• 12:18
  Speaker 2: latched onto that started pulling things together to make things
• 12:22
  Speaker 2: more and more dense. Because the denser you are, the
• 12:24
  Speaker 2: more you have gravity and then you can pull on things,
• 12:27
  Speaker 2: which leads to a runaway effect where things get more
• 12:29
  Speaker 2: and more dense.
• 12:30
  Speaker 1: So I guess you need these fluctuations to even start something, right,
• 12:33
  Speaker 1: because if everything in the universe was evenly spaced, then
• 12:36
  Speaker 1: you would feel the same pool of gravity in all
• 12:38
  Speaker 1: directions and nothing would ever clump together exactly.
• 12:41
  Speaker 2: So the quantum fluctuations get you started, and then they
• 12:43
  Speaker 2: get blown up by inflation. Right, the universe expanded super
• 12:47
  Speaker 2: duper rapidly in the first few moments that we understand,
• 12:50
  Speaker 2: and those grew these little fluctuations from quantum size something
• 12:54
  Speaker 2: you could never see to macroscopic fluctuations, things big enough
• 12:58
  Speaker 2: for like gravity to really grab a hold of and
• 13:00
  Speaker 2: start to seed structure. And you have these fluctuations in
• 13:03
  Speaker 2: the dark matter as well as in the normal matter.
• 13:06
  Speaker 2: And it's really these fluctuations that determine everything. These quantum fluctuations,
• 13:10
  Speaker 2: blown up to a specific size, create pols of dark matter,
• 13:14
  Speaker 2: which then create galaxies.
• 13:16
  Speaker 1: Now, these quantum fluctuations, these are quantum fluctuations of what
• 13:20
  Speaker 1: the matter or the space itself.
• 13:22
  Speaker 2: I think most fundamentally they are quantum fluctuations in the fields. Right,
• 13:25
  Speaker 2: we don't really know what happens before we have fields.
• 13:29
  Speaker 2: But you can think about the fields before you can
• 13:31
  Speaker 2: think about the particles, because as the fields are cooling,
• 13:34
  Speaker 2: it starts to make sense to talk about individual particles.
• 13:37
  Speaker 2: Before that, it's more like you're talking about waves in
• 13:39
  Speaker 2: the ocean rather than droplets. But as things cool down
• 13:42
  Speaker 2: and get less dense than you get particles. So it's
• 13:44
  Speaker 2: those quantum fluctuations in those initial fields that give you
• 13:47
  Speaker 2: a little bit more energy here, a little bit less
• 13:49
  Speaker 2: energy there, and that eventually turns into more particles here
• 13:52
  Speaker 2: and fewer particles there.
• 13:54
  Speaker 1: Because I guess the fields don't scale with the growth
• 13:57
  Speaker 1: of the universe, do they. They kind of stay at
• 13:59
  Speaker 1: the same sea scale. So when the universe was a
• 14:01
  Speaker 1: lot smaller, the fluctuations in those fields were huge in
• 14:05
  Speaker 1: comparison to the size of the universe.
• 14:06
  Speaker 2: Mm hmm exactly. And then as the universe expands, that
• 14:10
  Speaker 2: energy just gets dilute, right, Everything gets colder and less dense.
• 14:13
  Speaker 1: And smaller by comparison, I guess.
• 14:15
  Speaker 2: Right, yeah, and smaller by comparison. And we talked in
• 14:17
  Speaker 2: a recent episode about how different slices of the universe
• 14:20
  Speaker 2: pie evolve over time. You have the radiation slice, which
• 14:24
  Speaker 2: gets more dilute but also gets red shifted, so its
• 14:27
  Speaker 2: energy actually goes away faster. As the universe expands, you
• 14:30
  Speaker 2: have the matter portion, where the energy is constant, but
• 14:33
  Speaker 2: because space is expanding, it gets more and more dilute.
• 14:36
  Speaker 2: Then you have the dark energy fraction, which doesn't get
• 14:38
  Speaker 2: diluted as the universe expands, and so its overall energy
• 14:42
  Speaker 2: fraction increases.
• 14:43
  Speaker 1: But I guess getting back to galaxies, So how did
• 14:45
  Speaker 1: these quantum fluctuations then result in galaxies?
• 14:49
  Speaker 2: So these quantum fluctuations give you a little bit more
• 14:51
  Speaker 2: matter here and a little bit less matter there. And
• 14:53
  Speaker 2: in the very early universe, you had dark matter and
• 14:56
  Speaker 2: you had normal matter, and you had photons, and these
• 14:59
  Speaker 2: things are all sort of sloshing around, and the photons
• 15:02
  Speaker 2: are pressing on the normal matter, the dark matter is
• 15:04
  Speaker 2: pulling things back in, and you had this actual ringing
• 15:07
  Speaker 2: of the early universe. It would be called these baryon
• 15:10
  Speaker 2: acoustic oscillations, sort of like the sound of the early universe.
• 15:14
  Speaker 2: The pressure waves in that initial plasma was slashing around,
• 15:17
  Speaker 2: and a big component of that is the dark matter
• 15:20
  Speaker 2: that's pulling things together. At some moment that the universe
• 15:23
  Speaker 2: expands enough and cools enough that that goes from being
• 15:26
  Speaker 2: a plasma to being a neutral gas. Like the protons
• 15:29
  Speaker 2: and the electrons find each other so they can no
• 15:31
  Speaker 2: longer be pushed by the photons, so that sort of
• 15:34
  Speaker 2: freezes the structure into place, and you get places where
• 15:36
  Speaker 2: you had more dark matter and more normal matter, and
• 15:39
  Speaker 2: that's where you ended up with galaxies today.
• 15:41
  Speaker 1: In the spots that had more dark matter and regular matter.
• 15:44
  Speaker 2: So some of those spots have more dark matter, some
• 15:46
  Speaker 2: of the spots have less dark matter but more normal
• 15:48
  Speaker 2: matter because they got pushed by the photons. And if
• 15:51
  Speaker 2: you look out into the universe, you can actually see
• 15:53
  Speaker 2: these spots. We have clusters of galaxies that formed where
• 15:56
  Speaker 2: the dark matter was denser, and then you have these
• 15:58
  Speaker 2: rings of galaxies that formed where the normal matter was denser.
• 16:02
  Speaker 2: Actually see these bubbles from the early universe. It's sort
• 16:05
  Speaker 2: of incredible. But basically, you had places with more matter
• 16:08
  Speaker 2: and that means more gravity and that pulls all the
• 16:10
  Speaker 2: gas together and that's what allows you to create stars.
• 16:13
  Speaker 2: And galaxies are basically just huge pools of gas with
• 16:16
  Speaker 2: stars forming inside them.
• 16:18
  Speaker 1: So that's kind of what a galaxy is, or was
• 16:20
  Speaker 1: initially was just a cloud of gas, and at the beginning,
• 16:23
  Speaker 1: I imagine it was just kind of a homogeneous, you know,
• 16:26
  Speaker 1: blobby kind of cloud of gas, no structure or shape
• 16:29
  Speaker 1: at all, or maybe just kind of like a blobby shape.
• 16:32
  Speaker 2: A big blob of gas that's pulling together and collapsing.
• 16:35
  Speaker 2: And initially it's almost all hydrogen. It's like a tiny
• 16:38
  Speaker 2: little bit of helium also made in the Big Bang,
• 16:41
  Speaker 2: but almost all hydrogen. And then you get these things
• 16:43
  Speaker 2: collapsing into stars, and those groups of stars then form galaxies.
• 16:48
  Speaker 2: But you still have also lots of gas in there,
• 16:50
  Speaker 2: so you have stars embedded in huge clouds of gas,
• 16:53
  Speaker 2: and together those things have formed galaxies.
• 16:56
  Speaker 1: All right. That sounds like when galaxies start to get
• 16:59
  Speaker 1: into shape and started to become something. And so let's
• 17:02
  Speaker 1: dig deeper into that. What are some of the new
• 17:05
  Speaker 1: and old ideas about how galaxies form? And then let's
• 17:08
  Speaker 1: figure out if they've been exercising. First, let's take a
• 17:11
  Speaker 1: quick break. All right, we're talking about the shapes of galaxies.
• 17:27
  Speaker 1: What shapes can they be? Can they be square? Can
• 17:30
  Speaker 1: they look like a cube? Can they look like Mickey mouse?
• 17:34
  Speaker 1: Inquiring minds one to know?
• 17:38
  Speaker 2: Well, one thing we can see initially is that there
• 17:40
  Speaker 2: are different sizes of galaxies. There are smaller galaxies out there,
• 17:44
  Speaker 2: there are bigger galaxies out there. You know, our galaxy
• 17:47
  Speaker 2: has a few one hundred billion stars, but there are
• 17:49
  Speaker 2: galaxies out there with trillions of stars and dwarf galaxies
• 17:53
  Speaker 2: with only like tens of thousands or hundreds of thousands
• 17:56
  Speaker 2: of stars. So there's a pretty big range of galaxies.
• 18:00
  Speaker 1: But then I guess what determined these sizes the size
• 18:03
  Speaker 1: of the galaxy. Is it just like how much gas
• 18:06
  Speaker 1: happened to pull together because of these quantum fluctuations. Isn't
• 18:09
  Speaker 1: there like a limit to what these quantum fluctuations look like.
• 18:13
  Speaker 2: That was sort of the original idea that big galaxies
• 18:15
  Speaker 2: were born big and little galaxies were born little, and
• 18:18
  Speaker 2: it just depended on like the scoop of stuff that
• 18:20
  Speaker 2: you got. And in that scenario, like large galaxies would
• 18:24
  Speaker 2: form all at once. You know, you have this huge collapse,
• 18:27
  Speaker 2: this monolithic collapse of the gas down into huge galaxy
• 18:31
  Speaker 2: making stars until it was all used up. But these days,
• 18:33
  Speaker 2: the newer idea is that galaxies don't vary that much
• 18:36
  Speaker 2: in size when they're formed. That basically only makes small
• 18:39
  Speaker 2: galaxies initially, and then the bigger galaxies are made from
• 18:42
  Speaker 2: mergers of other galaxies.
• 18:44
  Speaker 1: That's the new idea of how galaxies form. It's like
• 18:46
  Speaker 1: they were all made a kind of like lego blocks,
• 18:48
  Speaker 1: and then the lego blocks started to assemble into bigger
• 18:51
  Speaker 1: galaxies exactly.
• 18:53
  Speaker 2: And this newer idea comes from seeing more examples. You know,
• 18:56
  Speaker 2: initially we could basically only see either nearby galaxy or
• 19:01
  Speaker 2: very bright older galaxies that were further away. But now
• 19:04
  Speaker 2: that we have new exceptional tools like James Webb and
• 19:07
  Speaker 2: even Hubble, we can see further back in time and
• 19:10
  Speaker 2: we can see more examples of smaller galaxies that were
• 19:13
  Speaker 2: further away. So we can see those small galaxies forming.
• 19:16
  Speaker 1: But isn't it kind of a mystery how you go
• 19:17
  Speaker 1: from the smaller galaxies to the bigger galaxies or is
• 19:20
  Speaker 1: it all just like random collisions out there in space.
• 19:24
  Speaker 2: I think there are definitely still open questions, but there's
• 19:26
  Speaker 2: also a lot of it that we do understand. Basically,
• 19:29
  Speaker 2: it's gravity you form these little galaxies, and then those
• 19:31
  Speaker 2: galaxies come together because if they're close enough together, gravity
• 19:35
  Speaker 2: will pull them together. Space is expanding between them. Dark
• 19:39
  Speaker 2: energy is fighting it, but gravity wins at small distances
• 19:42
  Speaker 2: and eventually will pull those things together, the way the
• 19:44
  Speaker 2: Milky Way and Andromeda are getting pulled together overcoming the
• 19:48
  Speaker 2: power of dark energy.
• 19:49
  Speaker 1: So then I guess as we look out into space
• 19:52
  Speaker 1: and back into time, that's basically the movie that plays
• 19:55
  Speaker 1: out for you. As you look out into the cosmos,
• 19:57
  Speaker 1: you see a bunch of little galaxies, and as you
• 20:00
  Speaker 1: fast forward in time, they you can sort of see
• 20:02
  Speaker 1: them merge together to form the galaxies that are closer
• 20:06
  Speaker 1: to us, which are more recent.
• 20:08
  Speaker 2: Exactly, And even our galaxy is the product of many,
• 20:11
  Speaker 2: many mergers. We think that our galaxy is the combination
• 20:14
  Speaker 2: of lots and lots of smaller galaxies which came together
• 20:17
  Speaker 2: to make the Milky Way, sort of like Voltron or
• 20:21
  Speaker 2: Power Rangers or whatever.
• 20:23
  Speaker 1: I don't think power Rangers merge there, Daniel, Oh.
• 20:26
  Speaker 2: No, they don't come together and make one super power Ranger.
• 20:29
  Speaker 1: No, I don't think.
• 20:30
  Speaker 2: So what is that Pokemon or am I thinking.
• 20:32
  Speaker 1: Of I think you're thinking of Voltron?
• 20:34
  Speaker 2: Yes, not even know what Vultron is, so I couldn't
• 20:36
  Speaker 2: be thinking of Voltron. Is it teenage mutan? Ninja? Turtles?
• 20:40
  Speaker 2: Did they come together?
• 20:41
  Speaker 1: It's g I Joe, it's what it is Ji Barbie.
• 20:44
  Speaker 1: My t Ijo emerged with Barbie, and that's how you
• 20:47
  Speaker 1: get the Milky Way.
• 20:49
  Speaker 2: Now you're just spreading misinformation about pop culture and about science.
• 20:54
  Speaker 2: You giving me too much work to do here, man.
• 20:56
  Speaker 1: Yes, that's how we lost the election. But anyways, as
• 21:01
  Speaker 1: getting back to the original question, which is about the
• 21:04
  Speaker 1: shape of galaxies, You've given us kind of a general
• 21:06
  Speaker 1: picture of where galaxies come from. But what the term
• 21:09
  Speaker 1: is their shape, like, what the term is whether they're
• 21:12
  Speaker 1: spiral or blobby or mickey mouse shape.
• 21:15
  Speaker 2: So let's start with the spiral ones because those are
• 21:17
  Speaker 2: sort of the most natural and the simplest ones. And
• 21:20
  Speaker 2: when small galaxies form, they tend to be spiral galaxies.
• 21:23
  Speaker 2: And that's why spiral galaxies are the most common type
• 21:26
  Speaker 2: of galaxy in the universe. And the reason you get
• 21:28
  Speaker 2: a spiral is that this initial blob of gas is spinning, right,
• 21:33
  Speaker 2: Everything in the universe is spinning, and that spin can't
• 21:36
  Speaker 2: go away. We can serve angular momentum in the universe,
• 21:39
  Speaker 2: which means if something is spinning, then to stop it
• 21:41
  Speaker 2: spinning you have to apply some torque to it. You
• 21:43
  Speaker 2: if you like spin it the other direction. But an
• 21:45
  Speaker 2: isolated object like in space you started spinning, is just
• 21:48
  Speaker 2: going to spin forever. Something else from the outside would
• 21:51
  Speaker 2: have to come and push on it in order for
• 21:53
  Speaker 2: it to stop spinning.
• 21:54
  Speaker 1: I wonder if, maybe for listeners we should explain that
• 21:57
  Speaker 1: this idea of just a generic blob of guys out
• 22:00
  Speaker 1: there in space, that it has actually a spin direction,
• 22:03
  Speaker 1: because you might imagine like something that big and that
• 22:06
  Speaker 1: sort of random, it like all the particles are actually
• 22:09
  Speaker 1: kind of flying all directions all the time, not necessarily
• 22:13
  Speaker 1: in a particular direction, but overall it sort of has
• 22:16
  Speaker 1: to have a preference for a general spin direction, right.
• 22:20
  Speaker 2: Yeah, And this can be a little tricky to get
• 22:22
  Speaker 2: your mind around. You might think, well, there's lots of
• 22:24
  Speaker 2: particles out there, why don't they all just average out
• 22:26
  Speaker 2: to no spin? And so think about it in terms
• 22:29
  Speaker 2: of like every individual particle, you know, draw a line
• 22:32
  Speaker 2: through like the center of mass of a bunch of particles.
• 22:35
  Speaker 2: Each particle is contributing to the spin of the overall
• 22:38
  Speaker 2: object in some way. If it's flying to the left,
• 22:40
  Speaker 2: then effectively it's spinning it one way. If it's flying
• 22:42
  Speaker 2: to the right, it's effectively spinning it. The other way. So,
• 22:45
  Speaker 2: now add up all those little pushes basically from all
• 22:48
  Speaker 2: those particles, and ask yourself, does it add up to zero? Well,
• 22:51
  Speaker 2: what are the chances that adds up to exactly zero?
• 22:55
  Speaker 2: That's like saying I'm going to flip a coin a
• 22:57
  Speaker 2: billion times? What are the odds I'm going to get
• 22:59
  Speaker 2: exactly half a billion heads and exactly half a billion tails.
• 23:02
  Speaker 2: Basically that's impossible. So while it's possible for some object
• 23:07
  Speaker 2: out there to have zero total spin, it's very unlikely.
• 23:10
  Speaker 2: The most common thing is for it to have some
• 23:13
  Speaker 2: small amount of overall spin.
• 23:15
  Speaker 1: It's sort of like I wonder if like you can
• 23:17
  Speaker 1: think about the shape of the blob, like it would
• 23:19
  Speaker 1: be almost impossible for this blob of gas to be
• 23:22
  Speaker 1: like perfectly spherical, like most likely it has a little
• 23:26
  Speaker 1: bit of an oblongness in one direction, and so that
• 23:29
  Speaker 1: maybe tells you that the galaxy leans wider in this direction.
• 23:33
  Speaker 1: I think maybe you can think about the spinning of
• 23:35
  Speaker 1: it is the same way. It's like that all the
• 23:37
  Speaker 1: particles are moving in all directions, but overall it's seat
• 23:40
  Speaker 1: of maybe spinning a little bit more in a particular direction.
• 23:44
  Speaker 2: Yeah, the distance from the center plays a big role
• 23:46
  Speaker 2: because the anc momentum varies with distance, So you're right.
• 23:49
  Speaker 2: The fact that it's randomly distributed in distance is also
• 23:52
  Speaker 2: makes it pretty hard to imagine that they would be
• 23:54
  Speaker 2: perfectly balanced. So you just like carve out a random
• 23:57
  Speaker 2: chunk of gas from the early universe. Overall, it's very
• 24:00
  Speaker 2: unlikely for it to be perfectly balanced in spin, so
• 24:04
  Speaker 2: that means it has some overall spin even if it's tiny. Now,
• 24:07
  Speaker 2: collapse that gas with gravity, and that tiny overall spin
• 24:11
  Speaker 2: becomes a pretty fast spin. The way if you're like
• 24:13
  Speaker 2: figure skating and you pull your arms in, you spin
• 24:16
  Speaker 2: faster and faster because the same angular momentum over shorter
• 24:19
  Speaker 2: distances requires a higher velocity of spin. So now this big,
• 24:24
  Speaker 2: slowly spinning blob of gas has become a denser, more
• 24:28
  Speaker 2: quickly spinning blob of gas.
• 24:30
  Speaker 1: Right, It's sort of like when you flush the toilet.
• 24:32
  Speaker 1: Initially things are spinning slowly, but then as they flush
• 24:35
  Speaker 1: down the center it, things are spinning really fast.
• 24:38
  Speaker 2: I love how you always go for the toilet analogy.
• 24:40
  Speaker 2: That really crystallizes it in my mind.
• 24:42
  Speaker 1: I'm all about the dark humor. So then it's spinning.
• 24:45
  Speaker 1: You have this big cloud of gas. It's collapsing because
• 24:48
  Speaker 1: of gravity. Maybe it's kind of squeezes into a pancake first, right,
• 24:51
  Speaker 1: because the gravity that not in the direction of the
• 24:55
  Speaker 1: spin tends to just flatten this big cloud first, right.
• 25:00
  Speaker 2: Exactly, The spin makes it collapse into a pancake instead
• 25:03
  Speaker 2: of just into a point right along the plane of
• 25:06
  Speaker 2: the spin. Basically, angular momentum needs to stick around and
• 25:09
  Speaker 2: so the same way that like the Earth doesn't collapse
• 25:11
  Speaker 2: into the Sun because of our orbital angular momentum around
• 25:15
  Speaker 2: the Sun, the gas turns into a big swirling orbit
• 25:18
  Speaker 2: around the center of the galaxy, the same way like
• 25:20
  Speaker 2: a black hole has an accretion disk around it for
• 25:23
  Speaker 2: all the same reasons. So it sort of collapses into
• 25:26
  Speaker 2: a disc, and that's when the stars start to form.
• 25:28
  Speaker 2: When the gas gets dense enough, stars begin to form.
• 25:31
  Speaker 2: So it's not like you have a bunch of gas
• 25:33
  Speaker 2: which forms stars and then the stars collapse into a disc.
• 25:37
  Speaker 2: It's the gas collapsing into a disc that allows the
• 25:40
  Speaker 2: stars to form. They form in that disk.
• 25:43
  Speaker 1: Okay, So now is that why most galaxies are flat
• 25:48
  Speaker 1: sort of like a you know, and you don't get
• 25:50
  Speaker 1: spherical galaxies or do you get spherical galaxies.
• 25:54
  Speaker 2: You can get elliptical galaxies which include some spheres, and
• 25:57
  Speaker 2: there are also globular clusters out there. But these galaxies,
• 26:00
  Speaker 2: the spiral galaxies, that's why they are flat. They're flat
• 26:03
  Speaker 2: because the stars form in that disc which is shaped
• 26:06
  Speaker 2: by gravity and anglar momentum sort of playing against each other.
• 26:10
  Speaker 2: So here you can see two totally different things in
• 26:12
  Speaker 2: the universe, gravity and angular momentum fighting each other on
• 26:16
  Speaker 2: these vast cosmic scales and determining the structure of most
• 26:19
  Speaker 2: of these galaxies. All these spiral galaxies are basically a
• 26:23
  Speaker 2: balance between these two things, angler momentum and gravity.
• 26:26
  Speaker 1: Okay, so we had a cloud. It's flattened to a pancake,
• 26:29
  Speaker 1: and now what to turn into a spiral? Who flushed
• 26:32
  Speaker 1: the toilet?
• 26:34
  Speaker 2: So it's still spinning. It's got to keep spinning. That's
• 26:37
  Speaker 2: why it's a pancake. And then you get these arms
• 26:39
  Speaker 2: that form. And a lot of people imagine that galactic
• 26:41
  Speaker 2: arms are like your arms that you spinning around. Your
• 26:45
  Speaker 2: arms are like a collection of mass, and as your
• 26:47
  Speaker 2: arms spin, that mass moves. But in the case of galaxies,
• 26:51
  Speaker 2: these arms are not structural. It's not the same stars
• 26:53
  Speaker 2: in the arm and the whole time, the arms are
• 26:56
  Speaker 2: actually density waves in this pancake. So some star get
• 27:00
  Speaker 2: closer together and then further apart, and closer together and
• 27:02
  Speaker 2: further apart. It's more like a wave passing through a stadium.
• 27:05
  Speaker 2: Those people aren't running in a wave. It's just a
• 27:08
  Speaker 2: wave moving through the stationary crowd.
• 27:10
  Speaker 1: Yeah, we had a whole episode about that. I remember.
• 27:13
  Speaker 1: It's sort of like a wave in traffic, Like you
• 27:15
  Speaker 1: were stuck in the highway. There's sort of these ways
• 27:17
  Speaker 1: that go from the back to the front or the
• 27:19
  Speaker 1: front to the back, where you get these cars kind
• 27:22
  Speaker 1: of clustering together for a while, but then they spread
• 27:24
  Speaker 1: out after a while, right, sort of like a traffic
• 27:27
  Speaker 1: jam almost.
• 27:28
  Speaker 2: Yeah, it's sort of like a traffic jam. And it
• 27:30
  Speaker 2: explains why galaxies aren't like really really tightly wound. If
• 27:34
  Speaker 2: you stick your arms out and then you spin, your
• 27:36
  Speaker 2: arms tend to sort of like lag behind you. Or
• 27:39
  Speaker 2: if you had like a ribbon and you were spinning,
• 27:41
  Speaker 2: you would end up winding it around yourself. And so
• 27:44
  Speaker 2: people wondered for a while when they thought that these
• 27:47
  Speaker 2: arms really were structural, why galaxies weren't all like wound
• 27:51
  Speaker 2: up like a ball of yarn. So this explains why
• 27:53
  Speaker 2: they aren't because they're actually just density waves. But you
• 27:56
  Speaker 2: do see a big range of tightness, like you see
• 27:59
  Speaker 2: some with looser wines and some with tighter wines. It's
• 28:02
  Speaker 2: really interesting to see like the variety.
• 28:04
  Speaker 1: By one, you mean, like the spiral. Some spirals are
• 28:07
  Speaker 1: more spirally than others.
• 28:09
  Speaker 2: Yes, some are looser and some are tighter. They're all spirals,
• 28:12
  Speaker 2: but some are looser and some are tighter. And sometimes
• 28:14
  Speaker 2: you see multiple arms, right, But a listener question about
• 28:16
  Speaker 2: a galaxy with like three arms and why you sometimes
• 28:19
  Speaker 2: have four arms or two arms. These are density waves
• 28:22
  Speaker 2: that come out of the perturbations of the initial gas
• 28:24
  Speaker 2: cloud as it's spinning, and so you can get different
• 28:27
  Speaker 2: numbers of arms. You also typically get like a big
• 28:29
  Speaker 2: central bulge. So that's the shape of these spiral galaxies.
• 28:33
  Speaker 2: And they spin for a long time. And they think
• 28:35
  Speaker 2: that eventually spiral galaxies will merge with other spiral galaxies.
• 28:39
  Speaker 2: But they don't have to write. Sometimes the spiral galaxy
• 28:41
  Speaker 2: is happy by itself and they can just sort of
• 28:43
  Speaker 2: live out its life. And the future of these spiral
• 28:46
  Speaker 2: galaxies is that eventually these density waves dissipate and you
• 28:49
  Speaker 2: get just sort of like a smooth pancake galaxy.
• 28:51
  Speaker 1: Wait, what so it starts out smooth, then you get
• 28:55
  Speaker 1: these density waves and give give it a spiral shape,
• 28:58
  Speaker 1: and then eventually after why all the spirals flatten out too.
• 29:02
  Speaker 2: Yeah. I wouldn't say that it starts out smooth. I
• 29:04
  Speaker 2: mean the density waves come from something in that galaxy
• 29:07
  Speaker 2: that was clumpy that seeds the density wave. But eventually
• 29:11
  Speaker 2: interaction between these stars, the pushes and the pulls and
• 29:13
  Speaker 2: the friction, et cetera, will smooth these things out and
• 29:16
  Speaker 2: they will dissipate. You get these things called lenticular galaxies,
• 29:20
  Speaker 2: which have no relationship to lentils at all. To my
• 29:22
  Speaker 2: wife's great disappointment, It just means that they're basically smooth.
• 29:27
  Speaker 1: But I guess maybe we're just saying, is that maybe
• 29:29
  Speaker 1: we've been imagining this original cloud of gas that started
• 29:33
  Speaker 1: the galaxy as being perfectly smooth, but maybe it wasn't right.
• 29:35
  Speaker 1: Like maybe this cloud of gas was lopsided, or maybe
• 29:39
  Speaker 1: it was denser in one direction, and then those weird
• 29:42
  Speaker 1: shapes of the gas then gave you these weird arms distributions.
• 29:47
  Speaker 2: Yeah, it definitely was not smooth, right, The reason this
• 29:50
  Speaker 2: cloud of gas formed in on some other cloud is
• 29:52
  Speaker 2: because it was denser. It formed around some core that
• 29:55
  Speaker 2: was a little bit denser that pulled it together, and
• 29:58
  Speaker 2: there were other sort of like mini cores within it,
• 30:00
  Speaker 2: you know, other little seeds of gravity. So it definitely
• 30:02
  Speaker 2: didn't start out as a perfectly smooth structure at all,
• 30:06
  Speaker 2: and so that plays out and forms these density waves.
• 30:08
  Speaker 2: But because the interaction, things eventually spread out and it
• 30:12
  Speaker 2: gets smoothed out.
• 30:13
  Speaker 1: So that's the future of the bilky Way galaxy too. Eventually,
• 30:15
  Speaker 1: we're just going to We're just going to be a
• 30:17
  Speaker 1: pancake if we.
• 30:19
  Speaker 2: Were left to our own devices. But because Andromeda is
• 30:21
  Speaker 2: going to slam into us, that's going to change our shape.
• 30:24
  Speaker 2: And whether we form a new spiral galaxy as a
• 30:27
  Speaker 2: merger or whether we end up an elliptical galaxy depends
• 30:30
  Speaker 2: a little bit on how much gas we have left
• 30:32
  Speaker 2: when it.
• 30:33
  Speaker 1: Happens, all right. So that's how spiral galaxies get formed.
• 30:36
  Speaker 1: And so they talk about some of the other shapes
• 30:38
  Speaker 1: that galaxies can take, including Daniel's minky mouse galaxy. So
• 30:42
  Speaker 1: let's talk about that. But first let's take another quick break,
• 30:57
  Speaker 1: all right, we're talking about the shape of galaxy sees
• 31:00
  Speaker 1: sponsored by Disney. No, the check didn't come through, sponsored
• 31:07
  Speaker 1: by Warner Brothers. Let's talk about bugs, bunny shape galaxies.
• 31:11
  Speaker 2: You want all these children's entertainment companies to be responsible
• 31:14
  Speaker 2: for the not safer astronomy shapes of galaxies.
• 31:17
  Speaker 1: Well, I'm sure we can censor those out now.
• 31:22
  Speaker 2: We are censoring the nice sky.
• 31:23
  Speaker 1: Oh my gosh, I feel like the nice sky sensors itself.
• 31:28
  Speaker 1: Why is it so hard to see?
• 31:30
  Speaker 2: I know most of the universe has already censored. Maybe
• 31:32
  Speaker 2: dark matter is hidden for us for a reason.
• 31:34
  Speaker 1: That's right. It's it's like the universe using a black marker.
• 31:38
  Speaker 2: It's not dark matter, it's bleeved matter.
• 31:40
  Speaker 1: That's right. Maybe it's not safe for humans.
• 31:42
  Speaker 2: It's redacted matter.
• 31:44
  Speaker 1: Yeah, we can't be trusted with its secrets.
• 31:49
  Speaker 2: If you only knew what the universe was hiding.
• 31:51
  Speaker 1: Oh my goodness. You know you can get in trouble
• 31:53
  Speaker 1: for divology classified information. Have you heard?
• 31:58
  Speaker 2: I have not.
• 31:59
  Speaker 1: I want to watch out for that. All right, So
• 32:00
  Speaker 1: let's talk about some of the other shapes that galaxies
• 32:03
  Speaker 1: can be. We talked about spiral shapes. That's kind of
• 32:05
  Speaker 1: maybe the traditional shape of a galaxy that most people
• 32:08
  Speaker 1: think about, but galaxies can have other shapes.
• 32:10
  Speaker 2: Yeah, spiral galaxies are the most common in the universe,
• 32:12
  Speaker 2: but the biggest galaxies are elliptical galaxies. These are often
• 32:17
  Speaker 2: found in like the rich central regions of galaxy clusters,
• 32:21
  Speaker 2: and they are usually the result of lots of spiral
• 32:23
  Speaker 2: galaxies merging. And these elliptical galaxies are not nearly as
• 32:27
  Speaker 2: pretty to look at. Like a spiral has features, you
• 32:29
  Speaker 2: can see it. It's like a disc, there's arms in it.
• 32:32
  Speaker 2: Sometimes elliptical galaxies basically just a big blob. You know,
• 32:36
  Speaker 2: it's smooth, there's almost no features in it. It's just
• 32:39
  Speaker 2: a bunch of stars.
• 32:40
  Speaker 1: Well maybe that's pretty to some people.
• 32:43
  Speaker 2: I'm not saying it's not esthetic, but it's just a
• 32:45
  Speaker 2: bit of a blob.
• 32:46
  Speaker 1: Are you trying to shape shame some galaxies out there?
• 32:51
  Speaker 2: I'm just creating categories, man, that's all I'm doing. An
• 32:55
  Speaker 2: important feature of elliptical galaxies is that they don't have
• 32:57
  Speaker 2: a lot of star formation going on, and so why
• 33:00
  Speaker 2: they're elliptical galaxies?
• 33:02
  Speaker 1: Now, hold on, what do you mean by elliptical, Like
• 33:04
  Speaker 1: it's shaped like an ellipses, but Is it flat or
• 33:06
  Speaker 1: is it Are you saying it's more shaped like a football?
• 33:09
  Speaker 1: What is this shape? Exactly?
• 33:10
  Speaker 2: It's more like a big watermelon, you know. And an
• 33:12
  Speaker 2: ellipse in general includes spheres, right, It's just sort of
• 33:15
  Speaker 2: like a more general phrase the same way that like
• 33:18
  Speaker 2: a circle technically is an ellipse. It just has its
• 33:20
  Speaker 2: two axes equal. So an elliptical galaxy is just like
• 33:24
  Speaker 2: a big watermelon shaped galaxy. It might be longer in
• 33:26
  Speaker 2: one direction or another.
• 33:28
  Speaker 1: So it's like a blob, like a submarine shape.
• 33:30
  Speaker 2: Blob, Yeah, exactly, like it's a big submarine floating through space.
• 33:33
  Speaker 2: It's not flat like a pancake.
• 33:35
  Speaker 1: And that's the overall shape of it. Is it like
• 33:37
  Speaker 1: denser in the middle? Is it just all all the
• 33:39
  Speaker 1: stars evenly distributed? Does it have like a shell? Paint
• 33:43
  Speaker 1: the picture for us?
• 33:44
  Speaker 2: So, elliptical galaxies definitely do have a core where things
• 33:47
  Speaker 2: are denser, and then they peter out near the edge.
• 33:50
  Speaker 2: But essentially there's not that much else to talk about.
• 33:52
  Speaker 2: They're roughly ellipsoidal, and they have a bunch of stars
• 33:55
  Speaker 2: in them, and I think maybe the other most interesting
• 33:57
  Speaker 2: thing about them is that they don't have a lot
• 33:58
  Speaker 2: of gas basically mostly stars, which means that you're not
• 34:03
  Speaker 2: having a lot more stars being formed. Right. It's the
• 34:06
  Speaker 2: gas that forms the stars, and in a lot of
• 34:08
  Speaker 2: galaxies you continuously have more stars being formed, But elliptical
• 34:12
  Speaker 2: galaxies are almost always quenched, which means no new stars
• 34:16
  Speaker 2: are being formed.
• 34:18
  Speaker 1: And are the stars in them also really old?
• 34:21
  Speaker 2: Right?
• 34:21
  Speaker 1: If it's not forming new stars in all of its
• 34:23
  Speaker 1: stars must.
• 34:24
  Speaker 2: Be old exactly, which affects the color of the galaxies
• 34:26
  Speaker 2: as well. Because stars that are really big turn out
• 34:29
  Speaker 2: to be really hot, which makes them blue, and those
• 34:31
  Speaker 2: kinds of stars don't burn for very long. The colder stars,
• 34:34
  Speaker 2: the smaller stars, are redder, and those tend to be
• 34:37
  Speaker 2: the ones that burn for billions and billions of years.
• 34:40
  Speaker 2: So if you look at a galaxy and you see
• 34:42
  Speaker 2: only red stars, that means there are no new stars
• 34:45
  Speaker 2: being formed there. There's only the long lived short people
• 34:48
  Speaker 2: who are left. And so these elliptical galaxies don't have
• 34:51
  Speaker 2: new stars being formed, which makes them redder than other galaxies.
• 34:55
  Speaker 1: So all the blue stars basically burn themselves out and
• 34:57
  Speaker 1: are maybe just floating there but you can't see them.
• 35:00
  Speaker 2: Yeah, exactly, they have their stellar remnants, but they're no
• 35:03
  Speaker 2: longer burning. And that's basically why this is an elliptical galaxy.
• 35:07
  Speaker 2: I mean, imagine two spiral galaxies forming. If they don't
• 35:10
  Speaker 2: have a lot of gas left, then what happens. They're
• 35:12
  Speaker 2: mostly just stars. And then those two spiral galaxies merge,
• 35:16
  Speaker 2: and now you have two planes. You have one plane
• 35:18
  Speaker 2: of rotation from each galaxy, and now they've mixed, so
• 35:22
  Speaker 2: you have some stars moving along one plane, some stars
• 35:24
  Speaker 2: moving along another plane. Now throw in another spiral galaxy,
• 35:27
  Speaker 2: and another and another. Eventually you have lots of different
• 35:31
  Speaker 2: planes of rotation, and what do you get. You get
• 35:33
  Speaker 2: an ellipse. So you add a bunch of spiral galaxies
• 35:36
  Speaker 2: together without a whole lot of gas to make new stars,
• 35:39
  Speaker 2: then you just get a big ellipse.
• 35:40
  Speaker 1: It's like you're just joining different pancakes at different angles,
• 35:44
  Speaker 1: and then you push it all together and you just
• 35:46
  Speaker 1: get a giant cloud of stars exactly.
• 35:48
  Speaker 2: And that might make you think, well, then every single
• 35:51
  Speaker 2: galaxy that's merged should be an ellipse, right, because you
• 35:54
  Speaker 2: get these spirals, and then you add spirals together, you
• 35:56
  Speaker 2: should get ellipses. How can you still have really big
• 35:59
  Speaker 2: spiral galaxies? Like the Milky Way or Andromeda. And the
• 36:02
  Speaker 2: answer is the gas. When the two spiral galaxies merge,
• 36:05
  Speaker 2: if there's still a lot of gas in the original spirals,
• 36:08
  Speaker 2: then that gas interacts and collapses again, forming a new spiral.
• 36:13
  Speaker 2: And that's how you get a big spiral galaxy. The
• 36:15
  Speaker 2: gas from the original ones smashes into each other, forming
• 36:19
  Speaker 2: new stars in a new disk.
• 36:21
  Speaker 1: Right. But I guess maybe the question is like, why
• 36:23
  Speaker 1: don't elliptical galaxies eventually collapse into a pancake too? Like,
• 36:27
  Speaker 1: wouldn't they also have, you know, an overall spin, even
• 36:31
  Speaker 1: if you're adding different mini galaxies, but didn't it all
• 36:33
  Speaker 1: have an overall spin? Wouldn't over time it also collapse
• 36:36
  Speaker 1: into a pancake and then maybe also into a spiral.
• 36:39
  Speaker 2: It might eventually, but because there's very little gas in
• 36:42
  Speaker 2: those galaxies, is almost no friction, and so it's really
• 36:44
  Speaker 2: hard for those stars to interact with each other. You know,
• 36:47
  Speaker 2: they're basically really isolated from each other except for gravity.
• 36:50
  Speaker 1: What do you mean by let low friction? How does
• 36:52
  Speaker 1: that plan into a cloud of gas form into a pancake.
• 36:55
  Speaker 2: It's very hard for these stars to exchange energy in
• 36:58
  Speaker 2: any way. Think about how things can come things collapse
• 37:01
  Speaker 2: because they bounce off each other. If everything just stayed
• 37:03
  Speaker 2: in its original orbit, nothing would ever collapse. Your gas
• 37:06
  Speaker 2: cloud never would have formed a pancake. In order to
• 37:09
  Speaker 2: collapse down to a pancake, they have to somehow bounce
• 37:11
  Speaker 2: off each other and exchange energy. That's why, for example,
• 37:15
  Speaker 2: dark matter doesn't collapse into a pancake because it has
• 37:17
  Speaker 2: no interactions other than gravity. It just stays in a
• 37:20
  Speaker 2: big spherical halo.
• 37:22
  Speaker 1: So even though it's drawn to the center, when they
• 37:24
  Speaker 1: get to the center, they just miss each other and
• 37:26
  Speaker 1: keep going.
• 37:26
  Speaker 2: Yeah, exactly. But if there's some gas there to sort
• 37:29
  Speaker 2: of slow the stars down and exchange energy, then things
• 37:33
  Speaker 2: can collapse. But elliptical galaxies have almost no gas, and
• 37:36
  Speaker 2: so the stars basically ignore each other unless they come
• 37:39
  Speaker 2: really close and some gravitational interaction can slow them down.
• 37:42
  Speaker 2: So I think like eventually elliptical galaxies will flatten out
• 37:47
  Speaker 2: for all the same reasons we've been talking about, but
• 37:49
  Speaker 2: because gravity is so weak compared to the other forces,
• 37:52
  Speaker 2: it's going to take much much longer then if you
• 37:53
  Speaker 2: actually have a lot of gas in there to facilitate
• 37:56
  Speaker 2: that kind of interaction.
• 37:58
  Speaker 1: But as we're looking back into time with like the
• 38:01
  Speaker 1: James Web telescope gig do we see evidence of that
• 38:04
  Speaker 1: like in the distant past? Is it mostly all pancakes
• 38:09
  Speaker 1: or are there still a lot of elliptical galaxy.
• 38:11
  Speaker 2: In the distant past? We can see that these pancakes
• 38:14
  Speaker 2: are the ones that are formed. Like, you don't form
• 38:15
  Speaker 2: elliptical galaxies initially, you form little spirals, and then if
• 38:18
  Speaker 2: those spirals use up most of their gas and have
• 38:21
  Speaker 2: quenched and then merge, then you see ellipticals being formed.
• 38:25
  Speaker 2: So the only way to make an elliptical galaxy is
• 38:27
  Speaker 2: to basically use up the gas in the spiral galaxies
• 38:29
  Speaker 2: initially and then merge them, and then they're sort of
• 38:32
  Speaker 2: frozen in their original planes.
• 38:34
  Speaker 1: So I guess maybe what you're saying, is it not
• 38:36
  Speaker 1: enough time has passed made for these elliptical galaxies to
• 38:40
  Speaker 1: flatten out, to basically see everything flatten out.
• 38:43
  Speaker 2: Exactly in the far far future. Elliptical galaxies, if left
• 38:46
  Speaker 2: to their own devices, will eventually flatten out because of gravity.
• 38:49
  Speaker 2: But spiral galaxies are flattened because the gas, because the
• 38:52
  Speaker 2: gas has a lot more interactions than the stars.
• 38:54
  Speaker 1: All right, So then that's the elliptical galaxies, what other
• 38:57
  Speaker 1: shapes can galaxies be?
• 38:59
  Speaker 2: So there's another category called irregular galaxies, and these are
• 39:02
  Speaker 2: ones that are basically not elliptical and not spiral. So
• 39:05
  Speaker 2: astronomers are like, hmmm, let's make a bucket for other stuff.
• 39:09
  Speaker 2: And irregular galaxies can be like almost any shape. You
• 39:11
  Speaker 2: see stuff long and thin, you see stuff spread out,
• 39:14
  Speaker 2: you see stuff in a question mark shape. There's a
• 39:17
  Speaker 2: huge number of these also, but almost every single time
• 39:20
  Speaker 2: it's a transient shape. It's because something has been like perturbed.
• 39:24
  Speaker 2: Two galaxies have smashed into each other or passed really
• 39:26
  Speaker 2: close to each other and torn themselves apart and haven't
• 39:29
  Speaker 2: yet settled into some new stable shape, probably elliptical or spiral.
• 39:34
  Speaker 2: So it's sort of like an intermediate state for galaxies
• 39:37
  Speaker 2: that are interacting.
• 39:39
  Speaker 1: I thought you mean a regular like a toilet reference.
• 39:41
  Speaker 2: Again, these should have more fiber of these galaxies, I mean,
• 39:45
  Speaker 2: really take care of yourselves.
• 39:46
  Speaker 1: Yeah, puts a men abuse with that dark chocolate.
• 39:50
  Speaker 2: Maybe dark matter is the fiber of the universe that
• 39:52
  Speaker 2: really is making things.
• 39:53
  Speaker 1: Regular, all right, So you're saying that in paint the
• 39:57
  Speaker 1: picture for us. Again, these are just like we shapes
• 40:00
  Speaker 1: out there of galaxies like they look like an L
• 40:02
  Speaker 1: shaped or like a maybe like a Mickey mouse.
• 40:05
  Speaker 2: Yeah, if you just google like irregular galaxies, you can
• 40:08
  Speaker 2: see all sorts of crazy stuff and it's basically the
• 40:10
  Speaker 2: results of collisions, so it can be a mess. Just
• 40:13
  Speaker 2: like if you look at simulations of what's gonna happen
• 40:15
  Speaker 2: when Andromeda in the Milky Way collide. In the beginning,
• 40:18
  Speaker 2: it doesn't really have any shape at all. It's just
• 40:20
  Speaker 2: like a huge spray stars this way and stars that way,
• 40:23
  Speaker 2: and then eventually it settles down into a new shape.
• 40:27
  Speaker 2: But in the intermediate shape, it just depends on the
• 40:29
  Speaker 2: angles and the sizes and how they hit. You can
• 40:31
  Speaker 2: get basically any shape you like.
• 40:33
  Speaker 1: And you say, most of these irregular galaxies are because
• 40:36
  Speaker 1: of collisions of other galaxies, But can you form an
• 40:39
  Speaker 1: irregular shape galaxy from scratch?
• 40:42
  Speaker 2: Cool question. I think the answer is no, because you
• 40:45
  Speaker 2: don't get star formation in a spiral galaxy until the
• 40:48
  Speaker 2: gas collapses, right, So it's not like you can form
• 40:51
  Speaker 2: a bunch of stars in a random place. The stars
• 40:53
  Speaker 2: don't really form until the gas is already collapsed into
• 40:56
  Speaker 2: a disc. Really, and so I don't think you can
• 40:59
  Speaker 2: form in a regular galaxy from scratch. I think it's
• 41:02
  Speaker 2: the combination of other galaxies coming together sort of chaotically.
• 41:06
  Speaker 1: All right, So then does that cover all the shapes
• 41:08
  Speaker 1: galaxies can be.
• 41:09
  Speaker 2: It doesn't. There's one really cool, very strange, spectacular shape
• 41:13
  Speaker 2: of galaxy that's very very rare. It's called a ring galaxy.
• 41:17
  Speaker 1: WHOA, Like it's shaped like a hoop.
• 41:20
  Speaker 2: It's really cool. It has like a central core, like
• 41:22
  Speaker 2: a blob in the middle, and then there's a big gap,
• 41:25
  Speaker 2: and then surrounding it is a whole ring of stars.
• 41:29
  Speaker 1: So it's flat.
• 41:29
  Speaker 2: It's flat, yeah, exactly, So it's flat pancake, but instead
• 41:33
  Speaker 2: of being like a full disc, it's got a core
• 41:35
  Speaker 2: and then like a ring, so it's sort of like
• 41:37
  Speaker 2: a bicycle wheel. You have like the tire and then
• 41:39
  Speaker 2: you have the central hub and there's a huge gap
• 41:42
  Speaker 2: in between.
• 41:43
  Speaker 1: Sort of like a Saturn galaxy.
• 41:45
  Speaker 2: Yeah, exactly, like a Saturn galaxy. And these are really fascinating.
• 41:50
  Speaker 2: The center is red, so like they're older stars, and
• 41:53
  Speaker 2: the ring tends to be blue, so they're really beautiful
• 41:56
  Speaker 2: to look at. WHOA and patriotic, Yeah, I guess they're French.
• 42:02
  Speaker 2: They're Dutch and they're American red.
• 42:05
  Speaker 1: Right that all of that. Yes, it's multinational. How do
• 42:09
  Speaker 1: these galaxies form?
• 42:10
  Speaker 2: So this was a real mystery for a long time.
• 42:12
  Speaker 2: We didn't even see one of these until like nineteen fifty.
• 42:15
  Speaker 2: They're so rare, and I think that these things are
• 42:18
  Speaker 2: formed in a really lucky, spectacular collision. Basically, when one
• 42:22
  Speaker 2: galaxy passes right through the center of the other one,
• 42:27
  Speaker 2: it creates this ring from the shock wave of dense
• 42:29
  Speaker 2: gas that's rushing out of that collision.
• 42:32
  Speaker 1: You mean like two spiral galaxies or two elliptical galaxies
• 42:35
  Speaker 1: just totally just head on crash into each other.
• 42:39
  Speaker 2: Yeah, exactly. You have like some galaxy punched right through
• 42:42
  Speaker 2: the exact center of another gas rich spiral galaxy. It'll
• 42:47
  Speaker 2: create this shock wave in that gas which will create stars.
• 42:51
  Speaker 2: And that's why the ring tends to be blue, because
• 42:54
  Speaker 2: it tends to be big, fat, young hot stars that
• 42:58
  Speaker 2: tend to burn bright. Whoa no judgment?
• 43:01
  Speaker 1: Is it's safe for work? Does it safe for work?
• 43:04
  Speaker 1: The broadcast?
• 43:05
  Speaker 2: I mean hot in a technical temperature sense.
• 43:07
  Speaker 1: Right, Well, you just got really excited there.
• 43:12
  Speaker 2: I'm excited to see star formation, right. Star formation is
• 43:14
  Speaker 2: so exciting. It's like the thing that makes the universe bright.
• 43:17
  Speaker 2: It's the reason we can see things in the universe
• 43:19
  Speaker 2: is because stars form. It's kind of a miracle almost,
• 43:22
  Speaker 2: And so these collisions create a whole ring of new
• 43:26
  Speaker 2: stars that are sort of moving out away from the galaxy.
• 43:29
  Speaker 1: So that the main stars crash into each other and
• 43:32
  Speaker 1: the collision kind of exploded all the gas to the
• 43:35
  Speaker 1: outer edge and that's where these new stars are forming.
• 43:38
  Speaker 1: But why did it stay in a flat shape?
• 43:41
  Speaker 2: Well, the original disc essentially was flat, right, and so
• 43:43
  Speaker 2: what happened was created a pressure wave in that flat disc.
• 43:47
  Speaker 2: There isn't gas in those other directions to compress. It's
• 43:50
  Speaker 2: sort of the same reason that like a ripple moves
• 43:52
  Speaker 2: along the surface of the water, you slap the water
• 43:55
  Speaker 2: and you get rings on the surface. You don't get
• 43:57
  Speaker 2: rings of water like moving up also, and that's sort
• 44:00
  Speaker 2: of where the gas is.
• 44:01
  Speaker 1: I see. It's like you had a giant disc flat
• 44:05
  Speaker 1: pancake and you sort of poked the middle of it
• 44:07
  Speaker 1: and it sent the ripple along the pancake exactly.
• 44:11
  Speaker 2: And that's what we're seeing. We're like in the middle
• 44:13
  Speaker 2: of watching this. So this is a pretty spectacular hypothesis.
• 44:16
  Speaker 2: And people thought well, if this is true, then we
• 44:18
  Speaker 2: should see like galaxies literally on top of each other,
• 44:22
  Speaker 2: and also we should be able to like identify the
• 44:24
  Speaker 2: galaxy that caused that ripple. And now we've seen enough
• 44:26
  Speaker 2: of these things that you can actually spot that we
• 44:28
  Speaker 2: have pictures of ring galaxies where you can tell which
• 44:32
  Speaker 2: galaxy has just passed through it, like you know, recently
• 44:35
  Speaker 2: on galactic timescales, and we've even seen one where the
• 44:39
  Speaker 2: galaxy is in the process of punching right through the
• 44:41
  Speaker 2: middle of the other galaxy.
• 44:43
  Speaker 1: Well, it's interesting that this is happening not just in
• 44:46
  Speaker 1: one place, but like all over the universe.
• 44:48
  Speaker 2: Yeah, everywhere. And it turns out that's what the question
• 44:51
  Speaker 2: mark galaxy is. It looks kind of like a question
• 44:53
  Speaker 2: mark because we're seeing one galaxy which is a spiral,
• 44:56
  Speaker 2: and then there's another galaxy which is on edge so
• 44:58
  Speaker 2: it looks like a line, and it's passing right through
• 45:01
  Speaker 2: the middle of it. So you get this combination of
• 45:03
  Speaker 2: two galaxies forming a question mark, and in a million
• 45:06
  Speaker 2: years or so, the one that's being hit is going
• 45:09
  Speaker 2: to turn into a ring galaxy.
• 45:10
  Speaker 1: Wait, wait, how does how does a question mark form.
• 45:12
  Speaker 2: Save one which is a disc and you can sort
• 45:14
  Speaker 2: of see the arms of it, and that's sort of
• 45:16
  Speaker 2: the round part of the question mark. This is so
• 45:19
  Speaker 2: difficult to do over audio. And then the line part
• 45:21
  Speaker 2: of the question mark is another galaxy, but we're only
• 45:23
  Speaker 2: seeing it on edge, so it looks like a line
• 45:26
  Speaker 2: instead of a circle. So instead of looking like a
• 45:28
  Speaker 2: figure eight, it looks like a figure eight, but one
• 45:30
  Speaker 2: of them has been twisted down, so it's like a
• 45:32
  Speaker 2: circle and a line combined.
• 45:35
  Speaker 1: Complicated, Yes, it's complicated. I think we're a galaxy question mark.
• 45:42
  Speaker 2: I think we're supposed to merge into something question mark.
• 45:45
  Speaker 1: I don't know. Yeah, maybe it just.
• 45:47
  Speaker 2: Goes to show you there's questions everywhere in the universe
• 45:49
  Speaker 2: literally literally.
• 45:51
  Speaker 1: Yeah, all right, Well, what does this all tell us about,
• 45:55
  Speaker 1: like the Bilky Way and why we're here and is
• 45:58
  Speaker 1: it weird that we're here or are we a pretty
• 46:00
  Speaker 1: typical galaxy?
• 46:02
  Speaker 2: So we're a pretty typical galaxy. We're not one of
• 46:04
  Speaker 2: the biggest galaxies, we're not one of the smallest galaxies.
• 46:06
  Speaker 2: We have one of the most common types of galaxies
• 46:08
  Speaker 2: in the universe. But it also tells us that we
• 46:11
  Speaker 2: contain multitudes. You know that the Milky Way has lots
• 46:14
  Speaker 2: of little baby galaxies inside of it. Some of the
• 46:17
  Speaker 2: reasons we have stars that are not in the disc
• 46:20
  Speaker 2: that like orbit above the disc or whatever, are from
• 46:22
  Speaker 2: those collisions, stars that survive those collisions of galaxies and
• 46:26
  Speaker 2: are still hanging out orbiting in their original galactic plane.
• 46:30
  Speaker 2: And when we look at the distribution of galaxies, all
• 46:33
  Speaker 2: the different shapes, it forces us to tell this story,
• 46:35
  Speaker 2: to explain everything we see, and to play detective and
• 46:38
  Speaker 2: to understand, like what happened in the early universe, how
• 46:41
  Speaker 2: did we get here from the big blob of gas
• 46:44
  Speaker 2: from the Big Bang? And it helps us unravel, you know,
• 46:46
  Speaker 2: the whole history of the universe and also to think
• 46:49
  Speaker 2: about its future.
• 46:50
  Speaker 1: But it sort of seems like in terms of shape,
• 46:52
  Speaker 1: there's really only one shape, which is the sort of
• 46:55
  Speaker 1: like the spiral, and then the other shapes you get
• 46:57
  Speaker 1: them by combining spirals together, so it's more like a
• 47:00
  Speaker 1: sequential category of galaxies.
• 47:02
  Speaker 2: Yeah, to use your analogy, it's like the spirals are
• 47:05
  Speaker 2: atoms and everything else is like a molecule built out
• 47:07
  Speaker 2: of those atoms.
• 47:09
  Speaker 1: And those other shapes only sort of happen if two galaxies.
• 47:11
  Speaker 2: Collide, exactly a cloud of gas will form a spiral
• 47:14
  Speaker 2: galaxy if left on its own, and the other ones
• 47:16
  Speaker 2: need combinations of spiral galaxies.
• 47:19
  Speaker 1: And it also sounds sort of like the future is
• 47:21
  Speaker 1: a little bit unknown, right, like we're maybe not sure
• 47:23
  Speaker 1: what eventual shape things are going to take in the future.
• 47:27
  Speaker 2: Yeah, our galaxy and will collide with Andromeda, and whether
• 47:30
  Speaker 2: we form a new spiral galaxy along that plane depends
• 47:33
  Speaker 2: how much gas is left. We know that Andromeda is
• 47:36
  Speaker 2: already starting to quench, and we think that the Milky
• 47:38
  Speaker 2: Way is quenching, which might mean that we don't have
• 47:41
  Speaker 2: enough gas to make a new spiral galaxy. It might
• 47:43
  Speaker 2: mean we end up with a big elliptical blob.
• 47:46
  Speaker 1: Or we win end up with a galaxy.
• 47:49
  Speaker 2: Maybe from some point of view, just before Andromeda plummets
• 47:54
  Speaker 2: into the heart of the Milky Way, you might be
• 47:56
  Speaker 2: able to make us do a question.
• 47:58
  Speaker 1: Mark. Well, here's the question, Daniel. If our galls she's
• 48:00
  Speaker 1: called the Milky Way and there's chocolate in our galaxy,
• 48:03
  Speaker 1: isn't all chocolate then milk chocolate?
• 48:05
  Speaker 2: No, you're ruining chocolate for me, man, I'm going to
• 48:11
  Speaker 2: have to look forward to importing chocolate from Andromeda.
• 48:13
  Speaker 1: There you go. Should have just said no way man.
• 48:16
  Speaker 1: All right, well, an interesting view into the cosmos and
• 48:20
  Speaker 1: all the different things that can happen out there, and
• 48:23
  Speaker 1: another interesting reminder that the universe is still evolving, still changing.
• 48:27
  Speaker 1: Things are colliding, things are changing shapes, things are asking
• 48:30
  Speaker 1: questions of themselves. It's an ever changing universe.
• 48:33
  Speaker 2: And the past is contained in the present. If we
• 48:35
  Speaker 2: can dig into it deep enough and think hard about
• 48:38
  Speaker 2: the rules at play, we can figure out what happened
• 48:41
  Speaker 2: in the universe.
• 48:42
  Speaker 1: That's right, sort of like how the white chocolate contains
• 48:44
  Speaker 1: cocoa butter, which is technically makes.
• 48:47
  Speaker 2: It chocolate and you should only eat it at state
• 48:50
  Speaker 2: fairs deep.
• 48:51
  Speaker 1: Fried, that's right, or in a desert island.
• 48:55
  Speaker 2: Only crack open in case of emergency.
• 48:57
  Speaker 1: All right, well, we hope you enjoyed that. Thanks for
• 48:59
  Speaker 1: joining us. See you next time.
• 49:05
  Speaker 2: For more science and curiosity, come find us on social
• 49:08
  Speaker 2: media where we answer questions and post videos. We're on Twitter,
• 49:12
  Speaker 2: disc Word, Insta, and now TikTok. Thanks for listening, and
• 49:16
  Speaker 2: remember that Daniel and Jorge Explain the Universe is a
• 49:18
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• 49:27
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