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Speaker 1: Hey, Daniel, you like dark chocolate, right, and you hate

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Speaker 1: white chocolate.

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Speaker 2: It's more than just liking it, It's a way of life.

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Speaker 3: Man.

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Speaker 1: WHOA, that's a lot writing on a flavor. But I

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Speaker 1: wonder does the shape of a chocolate matter to you?

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Speaker 2: Hmm? You mean, like if it's a chocolate chip or

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Speaker 2: a chocolate bar or something else.

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Speaker 1: Yeah, I'm trying to figure out how picky you are.

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Speaker 2: Well, you know, it is really fun to make chocolate

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Speaker 2: have all sorts of weird shapes, but I think it

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Speaker 2: all tastes the same. What if it's pear shape, as

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Speaker 2: long as it's not a disaster fruit and chocolate is

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Speaker 2: a delicious combination.

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Speaker 1: What if it's shaped like white chocolate.

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Speaker 2: Like, chocolate isn't the shape, man?

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Speaker 1: What if it's shaped like a galaxy?

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Speaker 2: Ooh, that sounds delicious.

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Speaker 1: Or what if it's the size of a galaxy?

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Speaker 2: Sounds like I have my work cut out from it.

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Speaker 1: Hi am Hore, my cartoonist and the author of Oliver's

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Speaker 1: Great Big Universe.

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Speaker 2: Hi. I'm Daniel. I'm a particle physicist and a professor

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Speaker 2: at UC Irvine, and I've never run out of my

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Speaker 2: taste for dark chocolate.

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Speaker 1: I wonder if your dislike of white chocolate is just

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Speaker 1: context based.

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Speaker 2: You mean, like it's a bad childhood memory.

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Speaker 1: Yeah, No, well I mean more like situational. You know, like,

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Speaker 1: what if you're in a dessert not a dessert, Well,

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Speaker 1: maybe it could be a desert island. But what if

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Speaker 1: it's also deserted, but the only dessert available or anything

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Speaker 1: to eat is white chocolate? Would you starve or would

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Speaker 1: you eat it?

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Speaker 2: I would eat it, but as I did, I would

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Speaker 2: understand how much better it would have been if it

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Speaker 2: was dark chocolate.

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Speaker 1: I see, you'd be complaining the whole time.

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Speaker 2: He I'd be the only one there, So who's to

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Speaker 2: complain to?

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Speaker 1: Hey, you could complain to the white chocolate. I guess

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Speaker 1: could paint a face on it, kind of like.

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Speaker 2: Wilson, complaining makes everything better.

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Speaker 1: That it does. But anyways, welcome to our pot. Daniel

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Speaker 1: and Jorge explain the Universe, a production of iHeartRadio.

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Speaker 2: In which we do our best to enjoy all of

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Speaker 2: the flavors of the universe. The electronic, the muonic, the

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Speaker 2: tawonic flavors, the ups, the downs, the charms, the bottoms,

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Speaker 2: the tops, everything in the universe that has a flavor

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Speaker 2: and everything that can be explained. We take a bite

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Speaker 2: out of all of it and explain everything to you.

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Speaker 1: Wait wait, wait, you just said you take a bite

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Speaker 1: out of white chocolate and enjoy it.

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Speaker 2: I'm confused on adviceive Council. I'm going to pass on

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Speaker 2: answering that question.

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Speaker 1: But aren't you curious what makes white chocolate different than

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Speaker 1: dark chocolate?

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Speaker 2: Yeah, it's the lack of chocolate.

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Speaker 1: No, it has chocolate as coco butter.

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Speaker 2: Coco butter is chocolate the way like butter by itself

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Speaker 2: is a whole meal. You know, it's there to accentuate

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Speaker 2: the flavors.

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Speaker 1: Obviously, you haven't been to Texas with the eat of

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Speaker 1: fright butter, which is where I am right now.

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Speaker 2: Yeah, exactly so. Not a big fan of deep fried

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Speaker 2: butter or white chocolate. To put those two things in

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Speaker 2: the same category.

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Speaker 1: They probably have the same number of calories.

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Speaker 2: To be honest, have you tried deep fried white chocolate?

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Speaker 1: Ooh, that might be a different state. Sounds like more

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Speaker 1: of an Arkansas thing.

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Speaker 2: Maybe keep traveling and report back.

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Speaker 1: That's right, I'm going a mission to try all the

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Speaker 1: freight of fats. But anyways, we do like to wet

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Speaker 1: our appetite and satisfy our appetite for the universe, our

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Speaker 1: curiosity for how things work out there in the cosmos.

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Speaker 1: Why are things the way they are, why are they

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Speaker 1: shaped like the way they are, and why do they

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Speaker 1: taste the way they do?

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Speaker 2: Because it's more than just the colors in the night sky,

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Speaker 2: the bright twinkling lights, the reds, the greens, everything else

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Speaker 2: that's up there. It's also the structure in the night

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Speaker 2: sky that tells us a story about the history of

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Speaker 2: the universe and where the universe is headed.

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Speaker 1: It's right because things in the universe aren't all the same.

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Speaker 1: Some things are shaped differently than others. They look different,

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Speaker 1: they have a different form, and it all reflects back

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Speaker 1: on how it all came together.

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Speaker 2: All the structure in the universe was inevitably put together

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Speaker 2: by gravity as it pulls things together in battles, angular momentum,

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Speaker 2: and other forces, and the shapes that we end up

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Speaker 2: with and how they change over time tell us about

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Speaker 2: how those forces work together and what the history of

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Speaker 2: the universe is. If you peer out in the night

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Speaker 2: sky beyond the stars, you see all these little smudges.

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Speaker 2: Those smudges are distant galaxies and each one has its

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Speaker 2: own shape that tells a story about how it got there.

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Speaker 1: And so the podcast will we tackling the question what

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Speaker 1: are the possible shapes of galaxies? Now, Daniel, is this

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Speaker 1: like the shape? What it looks like? Or how much

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Speaker 1: do galaxies exercise? Like? Are you a fit galaxy? Are

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Speaker 1: you a buff galaxy? Are you a little flabby around

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Speaker 1: the edges?

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Speaker 2: I'm not selling a galaxy workout video, and this is

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Speaker 2: not some sort of cosmic drift. No, we are not

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Speaker 2: judging the shapes. We are just observing and trying to

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Speaker 2: understand how they got there.

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Speaker 1: Doing Galaxies have names like p X thirty nine. Isn't

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Speaker 1: that also the name of some workout.

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Speaker 2: Program it is? Now, yeah, we're panding that and we're

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Speaker 2: making a cosmic workout program exactly.

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Speaker 1: That's right. Yes, it's the milky way.

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Speaker 2: You gets fit, like the whirlpool galaxy. I don't know

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Speaker 2: how that works.

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Speaker 1: Does it depend on how much dark chocolate the galaxy

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Speaker 1: has eaten?

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Speaker 2: Collapsing into a huge bar of dark chocolate is the

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Speaker 2: eventual end of every galaxy.

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Speaker 1: The dream state for all physicists.

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Speaker 2: But it is fascinating to look up at the night

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Speaker 2: sky and to see all these different shapes. Some of

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Speaker 2: them are ellipses, some of them are blobs, some of

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Speaker 2: them are stretched out. There's even one that looks like

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Speaker 2: a question mark. Almost every possible shape you can imagine

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Speaker 2: is up there somewhere in the night sky. And there

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Speaker 2: are so many galaxies in the universe that it makes

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Speaker 2: astronomers wonder how they all got that way. It makes

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Speaker 2: them want to invent crazy illogical names for the various categories.

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Speaker 2: There's a lot of rich signs to do in the

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Speaker 2: shapes of galaxies.

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Speaker 1: Well, that's kind of a new concept, maybe for a

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Speaker 1: lot of people, because you know, we all grew up

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Speaker 1: looking at pictures of galaxies and they all kind of

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Speaker 1: the same, right, they look like little swirls.

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Speaker 2: I mean, if you've only looked at a few pictures,

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Speaker 2: they might all look the same. But as soon as

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Speaker 2: you look at a handful or a dozen or so,

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Speaker 2: you start to notice there's a lot of weird shapes

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Speaker 2: out there. Some of them have more arms, fewer arms,

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Speaker 2: some of them have no arms at all. There's a

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Speaker 2: lot of weird stuff in the universe.

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Speaker 1: M Is it sort of like cloud watching, Like you

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Speaker 1: look out into the sky and you look at the

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Speaker 1: clouds and they're all different shapes, like pie shaped or

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Speaker 1: you know, a butterfly shape.

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Speaker 2: Yeah, exactly. And if you understand the dynamics of water

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Speaker 2: droplet formation and air currents, you can understand why certain

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Speaker 2: clouds look the way they do. They tell you a

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Speaker 2: story about what's happening up there, what the forces are

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Speaker 2: that are doing battle. And it's the same for galaxies.

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Speaker 2: There's enormous cosmic forces pushing on these things and pulling

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Speaker 2: on these things, and the shapes reveal exactly what happened.

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Speaker 1: How much dark chocolate it eight.

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Speaker 2: How much it's been subscribing toges new workout video.

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Speaker 1: That's right, how many spins it's been doing well? As usual,

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Speaker 1: we were wondering how many people out there had thought

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Speaker 1: about this question of what shape galaxies can be, and

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Speaker 1: so as usual, Daniel went out there into the internet

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Speaker 1: to ask people what are the possible shapes galaxies can take.

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Speaker 2: I'm grateful as always to our group of volunteers, and

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Speaker 2: if you would like to join them to contribute your

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Speaker 2: voice to the podcast, please don't be shy right to

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Speaker 2: us to questions at Danielanjorge dot com. Everybody's welcome.

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Speaker 1: So think about it for a second. What kinds of

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Speaker 1: shapes have you seen in galaxies? Here's what people had

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Speaker 1: to say.

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Speaker 4: There's spiral galaxies or barred spirals like ours. I don't know,

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Speaker 4: maybe there's just bars. There's irregular ones that were disturbed

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Speaker 4: by gliding with other galaxies haven't settled down yet. I

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Speaker 4: think there's blobs or spherical shape galaxies, and I hope

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Speaker 4: there's a galaxy shape like Mickey.

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Speaker 2: Mouse somewhere out there.

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Speaker 5: I think they're most often some kind of circular shape,

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Speaker 5: given that they're rotating around the black hole that's usually

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Speaker 5: at the center of the galaxy. I think the Milky

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Speaker 5: Way is considered a spiral galaxy, but I would guess

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Speaker 5: he can probably have most any shape that's possible that

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Speaker 5: could form around a center of man No.

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Speaker 3: I did used to take part in Zooniverse, so I

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Speaker 3: know that you can have spiral shape galaxies, and they

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Speaker 3: can have different numbers of arms, and they can also

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Speaker 3: have a bar feature or not across the center. Then

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Speaker 3: you also get s elliptical galaxies, which when they're sort

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Speaker 3: of close to the plane it's called lenticular galaxies. And

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Speaker 3: then you can have globular clusters. Now may be other

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Speaker 3: galaxy shapes as well, but they're the main types that

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Speaker 3: I remember.

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Speaker 1: All right. I feel like they quickly spiral out of control.

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Speaker 2: There are a lot of ellipses there. As people were.

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Speaker 1: Thinking, Yeah, they just kept going around and around in circles.

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Speaker 2: I don't know if there is a Mickey mouse shaped galaxy,

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Speaker 2: but if the universe is infinite, then I guess somewhere

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Speaker 2: there has to be one.

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Speaker 1: Well, I wonder if there are like three galaxies kind

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Speaker 1: of crashing into each other right before they do, they

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Speaker 1: do look like a maybe a Mickey mouse shape.

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Speaker 2: Well, you know, if you google Mickey mouse galaxy, you

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Speaker 2: don't get mostly scientific images.

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Speaker 1: Yeah. Or I wonder if you look far enough or

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Speaker 1: long enough at galaxy shapes, if you'll eventually run into

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Speaker 1: one that's inappropriate. We're not safe for work.

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Speaker 2: Not safe for the universe, safe for astronomy. Probably. It's

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Speaker 2: sort of like looking at clouds. You can stare at

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Speaker 2: a galaxy and imagine a creative interpretation.

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Speaker 1: Interesting, I see what you're saying. Maybe it reveals more

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Speaker 1: about your inner space than outer space.

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Speaker 2: Yeah, exactly, It's like a roar shark test.

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Speaker 1: Yeah, if you have a dark mind or a white

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Speaker 1: chocolate mind.

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Speaker 2: A white chocolate mind is like a brain that's been

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Speaker 2: battered and fried.

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Speaker 1: Oh my gosh. Well, anyways, maybe we should start at

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Speaker 1: the beginning here, you know, if we're going to talk

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Speaker 1: about the shape of galaxies, like how do galaxies form

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Speaker 1: in the first place, and what might determine their shape?

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Speaker 2: Yeah. I think people usually think about the universe in

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Speaker 2: terms of stars, but to me, it's much more natural

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Speaker 2: to think about the universe in terms of galaxies. It's

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Speaker 2: like the basic building block of the universe. You look

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Speaker 2: at into deep space and it's mostly filled with galaxies

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Speaker 2: scattered everywhere. You can argue about whether those galaxies come

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Speaker 2: together to make larger structure and whether the internal structure

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Speaker 2: of those galaxies is more important, But to me, galaxies

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Speaker 2: are like the basic building block of the universe. So yeah,

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Speaker 2: it's important to figure out like why do we have galaxies,

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Speaker 2: Why are they typically this size? Why does the universe

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Speaker 2: do this kind of thing?

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Speaker 1: I see, Galaxies are sort of like maybe the atom

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Speaker 1: for you, Like, you know, it's made out of things

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Speaker 1: that are smaller, but you know, to understand most of

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Speaker 1: what we see around us in chemistry and materials and

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Speaker 1: things like that, you can just sort of think about

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Speaker 1: the atomic structure.

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Speaker 2: Yeah, to me, it's always really fascinating the size of

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Speaker 2: things that emerge. You know, we don't know if there's

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Speaker 2: the smallest thing in the universe, but it's fascinating that,

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Speaker 2: Like the atom is a certain size, right, and planets

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Speaker 2: are a certain size, and stars are a certain size.

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Speaker 2: Galaxies also are a certain size, and if you poke

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Speaker 2: into the physics behind them, how they came together, and

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Speaker 2: then you learn something about what the universe likes to do,

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Speaker 2: which somehow maybe bubbles up from the tiniest particles, though

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Speaker 2: that's not a process that we understand.

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Speaker 1: You mean, like galaxies don't vary that much in size, right,

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Speaker 1: Like you don't see a tiny, tiny galaxy and humongas

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Speaker 1: you know, superstructure spanning galaxies. They mostly all fall within

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Speaker 1: a certain range, just like planets all sort of fall

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Speaker 1: within a certain range.

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Speaker 2: Yeah, there is a very wide range of size of galaxies,

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Speaker 2: but it doesn't extend down to like the size of cats.

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Speaker 2: You don't have like galaxies the size of cats, and

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Speaker 2: you don't have galaxies the size of superclusters exactly. So

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Speaker 2: there's a certain like size of galaxy that the universe

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Speaker 2: likes to make and not much much much bigger and

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Speaker 2: not much much much smaller, And that tells you something

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Speaker 2: about the balance of the forces.

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Speaker 1: Sort of like planets too. I guess you can have

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Speaker 1: small planets, but you can't have like a Solar system

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Speaker 1: sized planet.

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Speaker 2: Yeah, if you had something like that, it would just

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Speaker 2: collapse into a star, right. And in the end, it

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Speaker 2: all comes back to the same original story of like,

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Speaker 2: why do we have any structure at all? Why is

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Speaker 2: in the universe just like smoothly filled with particles. Why

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Speaker 2: do things clump together? And that dates back all the

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Speaker 2: way to the very beginning of little patches where things

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Speaker 2: were denser and little patches where things were less dense.

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Speaker 2: We think there were quantum fluctuations in the early universe

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Speaker 2: as particles formed out of this pre particle goo, this

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Speaker 2: very hot and dense stuff that we don't understand very well.

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Speaker 2: You've got little fluctuations that were more dense here and

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Speaker 2: less dense there, and those were the seeds that gravity

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Speaker 2: latched onto that started pulling things together to make things

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Speaker 2: more and more dense. Because the denser you are, the

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Speaker 2: more you have gravity and then you can pull on things,

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Speaker 2: which leads to a runaway effect where things get more

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Speaker 2: and more dense.

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Speaker 1: So I guess you need these fluctuations to even start something, right,

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Speaker 1: because if everything in the universe was evenly spaced, then

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Speaker 1: you would feel the same pool of gravity in all

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Speaker 1: directions and nothing would ever clump together exactly.

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Speaker 2: So the quantum fluctuations get you started, and then they

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Speaker 2: get blown up by inflation. Right, the universe expanded super

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Speaker 2: duper rapidly in the first few moments that we understand,

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Speaker 2: and those grew these little fluctuations from quantum size something

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Speaker 2: you could never see to macroscopic fluctuations, things big enough

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Speaker 2: for like gravity to really grab a hold of and

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Speaker 2: start to seed structure. And you have these fluctuations in

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Speaker 2: the dark matter as well as in the normal matter.

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Speaker 2: And it's really these fluctuations that determine everything. These quantum fluctuations,

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Speaker 2: blown up to a specific size, create pols of dark matter,

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Speaker 2: which then create galaxies.

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Speaker 1: Now, these quantum fluctuations, these are quantum fluctuations of what

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Speaker 1: the matter or the space itself.

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Speaker 2: I think most fundamentally they are quantum fluctuations in the fields. Right,

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Speaker 2: we don't really know what happens before we have fields.

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Speaker 2: But you can think about the fields before you can

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Speaker 2: think about the particles, because as the fields are cooling,

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Speaker 2: it starts to make sense to talk about individual particles.

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Speaker 2: Before that, it's more like you're talking about waves in

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Speaker 2: the ocean rather than droplets. But as things cool down

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Speaker 2: and get less dense than you get particles. So it's

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Speaker 2: those quantum fluctuations in those initial fields that give you

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Speaker 2: a little bit more energy here, a little bit less

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Speaker 2: energy there, and that eventually turns into more particles here

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Speaker 2: and fewer particles there.

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Speaker 1: Because I guess the fields don't scale with the growth

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Speaker 1: of the universe, do they. They kind of stay at

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Speaker 1: the same sea scale. So when the universe was a

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Speaker 1: lot smaller, the fluctuations in those fields were huge in

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Speaker 1: comparison to the size of the universe.

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Speaker 2: Mm hmm exactly. And then as the universe expands, that

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Speaker 2: energy just gets dilute, right, Everything gets colder and less dense.

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Speaker 1: And smaller by comparison, I guess.

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Speaker 2: Right, yeah, and smaller by comparison. And we talked in

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Speaker 2: a recent episode about how different slices of the universe

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Speaker 2: pie evolve over time. You have the radiation slice, which

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Speaker 2: gets more dilute but also gets red shifted, so its

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Speaker 2: energy actually goes away faster. As the universe expands, you

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Speaker 2: have the matter portion, where the energy is constant, but

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Speaker 2: because space is expanding, it gets more and more dilute.

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Speaker 2: Then you have the dark energy fraction, which doesn't get

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Speaker 2: diluted as the universe expands, and so its overall energy

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Speaker 2: fraction increases.

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Speaker 1: But I guess getting back to galaxies, So how did

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Speaker 1: these quantum fluctuations then result in galaxies?

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Speaker 2: So these quantum fluctuations give you a little bit more

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Speaker 2: matter here and a little bit less matter there. And

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Speaker 2: in the very early universe, you had dark matter and

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Speaker 2: you had normal matter, and you had photons, and these

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Speaker 2: things are all sort of sloshing around, and the photons

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Speaker 2: are pressing on the normal matter, the dark matter is

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Speaker 2: pulling things back in, and you had this actual ringing

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Speaker 2: of the early universe. It would be called these baryon

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Speaker 2: acoustic oscillations, sort of like the sound of the early universe.

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Speaker 2: The pressure waves in that initial plasma was slashing around,

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Speaker 2: and a big component of that is the dark matter

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Speaker 2: that's pulling things together. At some moment that the universe

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Speaker 2: expands enough and cools enough that that goes from being

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Speaker 2: a plasma to being a neutral gas. Like the protons

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Speaker 2: and the electrons find each other so they can no

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Speaker 2: longer be pushed by the photons, so that sort of

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Speaker 2: freezes the structure into place, and you get places where

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Speaker 2: you had more dark matter and more normal matter, and

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Speaker 2: that's where you ended up with galaxies today.

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Speaker 1: In the spots that had more dark matter and regular matter.

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Speaker 2: So some of those spots have more dark matter, some

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Speaker 2: of the spots have less dark matter but more normal

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Speaker 2: matter because they got pushed by the photons. And if

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Speaker 2: you look out into the universe, you can actually see

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Speaker 2: these spots. We have clusters of galaxies that formed where

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Speaker 2: the dark matter was denser, and then you have these

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Speaker 2: rings of galaxies that formed where the normal matter was denser.

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Speaker 2: Actually see these bubbles from the early universe. It's sort

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Speaker 2: of incredible. But basically, you had places with more matter

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Speaker 2: and that means more gravity and that pulls all the

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Speaker 2: gas together and that's what allows you to create stars.

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Speaker 2: And galaxies are basically just huge pools of gas with

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Speaker 2: stars forming inside them.

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Speaker 1: So that's kind of what a galaxy is, or was

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Speaker 1: initially was just a cloud of gas, and at the beginning,

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Speaker 1: I imagine it was just kind of a homogeneous, you know,

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Speaker 1: blobby kind of cloud of gas, no structure or shape

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Speaker 1: at all, or maybe just kind of like a blobby shape.

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Speaker 2: A big blob of gas that's pulling together and collapsing.

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Speaker 2: And initially it's almost all hydrogen. It's like a tiny

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Speaker 2: little bit of helium also made in the Big Bang,

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Speaker 2: but almost all hydrogen. And then you get these things

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Speaker 2: collapsing into stars, and those groups of stars then form galaxies.

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Speaker 2: But you still have also lots of gas in there,

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Speaker 2: so you have stars embedded in huge clouds of gas,

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Speaker 2: and together those things have formed galaxies.

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Speaker 1: All right. That sounds like when galaxies start to get

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Speaker 1: into shape and started to become something. And so let's

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Speaker 1: dig deeper into that. What are some of the new

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Speaker 1: and old ideas about how galaxies form? And then let's

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Speaker 1: figure out if they've been exercising. First, let's take a

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Speaker 1: quick break. All right, we're talking about the shapes of galaxies.

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Speaker 1: What shapes can they be? Can they be square? Can

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Speaker 1: they look like a cube? Can they look like Mickey mouse?

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Speaker 1: Inquiring minds one to know?

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Speaker 2: Well, one thing we can see initially is that there

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Speaker 2: are different sizes of galaxies. There are smaller galaxies out there,

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Speaker 2: there are bigger galaxies out there. You know, our galaxy

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Speaker 2: has a few one hundred billion stars, but there are

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Speaker 2: galaxies out there with trillions of stars and dwarf galaxies

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Speaker 2: with only like tens of thousands or hundreds of thousands

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Speaker 2: of stars. So there's a pretty big range of galaxies.

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Speaker 1: But then I guess what determined these sizes the size

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Speaker 1: of the galaxy. Is it just like how much gas

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Speaker 1: happened to pull together because of these quantum fluctuations. Isn't

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Speaker 1: there like a limit to what these quantum fluctuations look like.

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Speaker 2: That was sort of the original idea that big galaxies

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Speaker 2: were born big and little galaxies were born little, and

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Speaker 2: it just depended on like the scoop of stuff that

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Speaker 2: you got. And in that scenario, like large galaxies would

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Speaker 2: form all at once. You know, you have this huge collapse,

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Speaker 2: this monolithic collapse of the gas down into huge galaxy

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Speaker 2: making stars until it was all used up. But these days,

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Speaker 2: the newer idea is that galaxies don't vary that much

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Speaker 2: in size when they're formed. That basically only makes small

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Speaker 2: galaxies initially, and then the bigger galaxies are made from

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Speaker 2: mergers of other galaxies.

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Speaker 1: That's the new idea of how galaxies form. It's like

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Speaker 1: they were all made a kind of like lego blocks,

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Speaker 1: and then the lego blocks started to assemble into bigger

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Speaker 1: galaxies exactly.

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Speaker 2: And this newer idea comes from seeing more examples. You know,

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Speaker 2: initially we could basically only see either nearby galaxy or

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Speaker 2: very bright older galaxies that were further away. But now

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Speaker 2: that we have new exceptional tools like James Webb and

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Speaker 2: even Hubble, we can see further back in time and

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Speaker 2: we can see more examples of smaller galaxies that were

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Speaker 2: further away. So we can see those small galaxies forming.

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Speaker 1: But isn't it kind of a mystery how you go

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Speaker 1: from the smaller galaxies to the bigger galaxies or is

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Speaker 1: it all just like random collisions out there in space.

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Speaker 2: I think there are definitely still open questions, but there's

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Speaker 2: also a lot of it that we do understand. Basically,

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Speaker 2: it's gravity you form these little galaxies, and then those

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Speaker 2: galaxies come together because if they're close enough together, gravity

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Speaker 2: will pull them together. Space is expanding between them. Dark

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Speaker 2: energy is fighting it, but gravity wins at small distances

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Speaker 2: and eventually will pull those things together, the way the

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Speaker 2: Milky Way and Andromeda are getting pulled together overcoming the

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Speaker 2: power of dark energy.

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Speaker 1: So then I guess as we look out into space

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Speaker 1: and back into time, that's basically the movie that plays

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Speaker 1: out for you. As you look out into the cosmos,

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Speaker 1: you see a bunch of little galaxies, and as you

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Speaker 1: fast forward in time, they you can sort of see

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Speaker 1: them merge together to form the galaxies that are closer

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Speaker 1: to us, which are more recent.

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Speaker 2: Exactly, And even our galaxy is the product of many,

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Speaker 2: many mergers. We think that our galaxy is the combination

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Speaker 2: of lots and lots of smaller galaxies which came together

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Speaker 2: to make the Milky Way, sort of like Voltron or

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Speaker 2: Power Rangers or whatever.

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Speaker 1: I don't think power Rangers merge there, Daniel, Oh.

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Speaker 2: No, they don't come together and make one super power Ranger.

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Speaker 1: No, I don't think.

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Speaker 2: So what is that Pokemon or am I thinking.

443
00:20:32,600 --> 00:20:34,080
Speaker 1: Of I think you're thinking of Voltron?

444
00:20:34,200 --> 00:20:36,479
Speaker 2: Yes, not even know what Vultron is, so I couldn't

445
00:20:36,480 --> 00:20:40,760
Speaker 2: be thinking of Voltron. Is it teenage mutan? Ninja? Turtles?

446
00:20:40,760 --> 00:20:41,480
Speaker 2: Did they come together?

447
00:20:41,600 --> 00:20:44,720
Speaker 1: It's g I Joe, it's what it is Ji Barbie.

448
00:20:44,880 --> 00:20:46,960
Speaker 1: My t Ijo emerged with Barbie, and that's how you

449
00:20:47,000 --> 00:20:47,680
Speaker 1: get the Milky Way.

450
00:20:49,760 --> 00:20:53,320
Speaker 2: Now you're just spreading misinformation about pop culture and about science.

451
00:20:54,520 --> 00:20:56,440
Speaker 2: You giving me too much work to do here, man.

452
00:20:56,359 --> 00:21:01,200
Speaker 1: Yes, that's how we lost the election. But anyways, as

453
00:21:01,320 --> 00:21:04,080
Speaker 1: getting back to the original question, which is about the

454
00:21:04,119 --> 00:21:06,760
Speaker 1: shape of galaxies, You've given us kind of a general

455
00:21:06,800 --> 00:21:09,880
Speaker 1: picture of where galaxies come from. But what the term

456
00:21:09,960 --> 00:21:12,040
Speaker 1: is their shape, like, what the term is whether they're

457
00:21:12,080 --> 00:21:15,560
Speaker 1: spiral or blobby or mickey mouse shape.

458
00:21:15,680 --> 00:21:17,840
Speaker 2: So let's start with the spiral ones because those are

459
00:21:17,880 --> 00:21:20,240
Speaker 2: sort of the most natural and the simplest ones. And

460
00:21:20,320 --> 00:21:23,360
Speaker 2: when small galaxies form, they tend to be spiral galaxies.

461
00:21:23,359 --> 00:21:26,040
Speaker 2: And that's why spiral galaxies are the most common type

462
00:21:26,080 --> 00:21:28,800
Speaker 2: of galaxy in the universe. And the reason you get

463
00:21:28,800 --> 00:21:33,040
Speaker 2: a spiral is that this initial blob of gas is spinning, right,

464
00:21:33,080 --> 00:21:36,080
Speaker 2: Everything in the universe is spinning, and that spin can't

465
00:21:36,119 --> 00:21:38,959
Speaker 2: go away. We can serve angular momentum in the universe,

466
00:21:39,000 --> 00:21:41,200
Speaker 2: which means if something is spinning, then to stop it

467
00:21:41,359 --> 00:21:43,320
Speaker 2: spinning you have to apply some torque to it. You

468
00:21:43,320 --> 00:21:45,600
Speaker 2: if you like spin it the other direction. But an

469
00:21:45,680 --> 00:21:48,720
Speaker 2: isolated object like in space you started spinning, is just

470
00:21:48,760 --> 00:21:51,359
Speaker 2: going to spin forever. Something else from the outside would

471
00:21:51,359 --> 00:21:53,000
Speaker 2: have to come and push on it in order for

472
00:21:53,080 --> 00:21:53,959
Speaker 2: it to stop spinning.

473
00:21:54,200 --> 00:21:57,040
Speaker 1: I wonder if, maybe for listeners we should explain that

474
00:21:57,119 --> 00:22:00,320
Speaker 1: this idea of just a generic blob of guys out

475
00:22:00,320 --> 00:22:02,719
Speaker 1: there in space, that it has actually a spin direction,

476
00:22:03,280 --> 00:22:06,280
Speaker 1: because you might imagine like something that big and that

477
00:22:06,440 --> 00:22:09,800
Speaker 1: sort of random, it like all the particles are actually

478
00:22:09,880 --> 00:22:13,080
Speaker 1: kind of flying all directions all the time, not necessarily

479
00:22:13,119 --> 00:22:16,800
Speaker 1: in a particular direction, but overall it sort of has

480
00:22:16,880 --> 00:22:20,080
Speaker 1: to have a preference for a general spin direction, right.

481
00:22:20,280 --> 00:22:22,160
Speaker 2: Yeah, And this can be a little tricky to get

482
00:22:22,200 --> 00:22:24,439
Speaker 2: your mind around. You might think, well, there's lots of

483
00:22:24,440 --> 00:22:26,800
Speaker 2: particles out there, why don't they all just average out

484
00:22:26,840 --> 00:22:29,600
Speaker 2: to no spin? And so think about it in terms

485
00:22:29,640 --> 00:22:32,520
Speaker 2: of like every individual particle, you know, draw a line

486
00:22:32,520 --> 00:22:34,960
Speaker 2: through like the center of mass of a bunch of particles.

487
00:22:35,359 --> 00:22:38,320
Speaker 2: Each particle is contributing to the spin of the overall

488
00:22:38,320 --> 00:22:40,680
Speaker 2: object in some way. If it's flying to the left,

489
00:22:40,720 --> 00:22:42,639
Speaker 2: then effectively it's spinning it one way. If it's flying

490
00:22:42,680 --> 00:22:45,399
Speaker 2: to the right, it's effectively spinning it. The other way. So,

491
00:22:45,480 --> 00:22:48,399
Speaker 2: now add up all those little pushes basically from all

492
00:22:48,400 --> 00:22:51,880
Speaker 2: those particles, and ask yourself, does it add up to zero? Well,

493
00:22:51,920 --> 00:22:54,720
Speaker 2: what are the chances that adds up to exactly zero?

494
00:22:55,359 --> 00:22:57,199
Speaker 2: That's like saying I'm going to flip a coin a

495
00:22:57,240 --> 00:22:59,640
Speaker 2: billion times? What are the odds I'm going to get

496
00:22:59,640 --> 00:23:02,840
Speaker 2: exactly half a billion heads and exactly half a billion tails.

497
00:23:02,920 --> 00:23:07,280
Speaker 2: Basically that's impossible. So while it's possible for some object

498
00:23:07,320 --> 00:23:10,440
Speaker 2: out there to have zero total spin, it's very unlikely.

499
00:23:10,480 --> 00:23:12,960
Speaker 2: The most common thing is for it to have some

500
00:23:13,119 --> 00:23:14,840
Speaker 2: small amount of overall spin.

501
00:23:15,640 --> 00:23:17,640
Speaker 1: It's sort of like I wonder if like you can

502
00:23:17,640 --> 00:23:19,880
Speaker 1: think about the shape of the blob, like it would

503
00:23:19,880 --> 00:23:22,520
Speaker 1: be almost impossible for this blob of gas to be

504
00:23:22,680 --> 00:23:26,440
Speaker 1: like perfectly spherical, like most likely it has a little

505
00:23:26,440 --> 00:23:29,040
Speaker 1: bit of an oblongness in one direction, and so that

506
00:23:29,240 --> 00:23:33,000
Speaker 1: maybe tells you that the galaxy leans wider in this direction.

507
00:23:33,760 --> 00:23:35,720
Speaker 1: I think maybe you can think about the spinning of

508
00:23:35,760 --> 00:23:37,760
Speaker 1: it is the same way. It's like that all the

509
00:23:37,800 --> 00:23:40,920
Speaker 1: particles are moving in all directions, but overall it's seat

510
00:23:40,920 --> 00:23:43,720
Speaker 1: of maybe spinning a little bit more in a particular direction.

511
00:23:44,000 --> 00:23:46,480
Speaker 2: Yeah, the distance from the center plays a big role

512
00:23:46,520 --> 00:23:49,679
Speaker 2: because the anc momentum varies with distance, So you're right.

513
00:23:49,720 --> 00:23:52,120
Speaker 2: The fact that it's randomly distributed in distance is also

514
00:23:52,400 --> 00:23:54,080
Speaker 2: makes it pretty hard to imagine that they would be

515
00:23:54,160 --> 00:23:57,160
Speaker 2: perfectly balanced. So you just like carve out a random

516
00:23:57,240 --> 00:24:00,359
Speaker 2: chunk of gas from the early universe. Overall, it's very

517
00:24:00,440 --> 00:24:03,959
Speaker 2: unlikely for it to be perfectly balanced in spin, so

518
00:24:04,000 --> 00:24:07,200
Speaker 2: that means it has some overall spin even if it's tiny. Now,

519
00:24:07,240 --> 00:24:10,920
Speaker 2: collapse that gas with gravity, and that tiny overall spin

520
00:24:11,040 --> 00:24:13,639
Speaker 2: becomes a pretty fast spin. The way if you're like

521
00:24:13,640 --> 00:24:15,920
Speaker 2: figure skating and you pull your arms in, you spin

522
00:24:16,040 --> 00:24:19,399
Speaker 2: faster and faster because the same angular momentum over shorter

523
00:24:19,480 --> 00:24:23,879
Speaker 2: distances requires a higher velocity of spin. So now this big,

524
00:24:24,080 --> 00:24:28,120
Speaker 2: slowly spinning blob of gas has become a denser, more

525
00:24:28,240 --> 00:24:29,879
Speaker 2: quickly spinning blob of gas.

526
00:24:30,280 --> 00:24:32,240
Speaker 1: Right, It's sort of like when you flush the toilet.

527
00:24:32,400 --> 00:24:35,840
Speaker 1: Initially things are spinning slowly, but then as they flush

528
00:24:35,880 --> 00:24:38,119
Speaker 1: down the center it, things are spinning really fast.

529
00:24:38,320 --> 00:24:40,040
Speaker 2: I love how you always go for the toilet analogy.

530
00:24:40,040 --> 00:24:41,600
Speaker 2: That really crystallizes it in my mind.

531
00:24:42,320 --> 00:24:45,560
Speaker 1: I'm all about the dark humor. So then it's spinning.

532
00:24:45,600 --> 00:24:48,440
Speaker 1: You have this big cloud of gas. It's collapsing because

533
00:24:48,440 --> 00:24:51,880
Speaker 1: of gravity. Maybe it's kind of squeezes into a pancake first, right,

534
00:24:51,960 --> 00:24:55,960
Speaker 1: because the gravity that not in the direction of the

535
00:24:55,960 --> 00:25:00,160
Speaker 1: spin tends to just flatten this big cloud first, right.

536
00:25:00,200 --> 00:25:03,639
Speaker 2: Exactly, The spin makes it collapse into a pancake instead

537
00:25:03,640 --> 00:25:06,480
Speaker 2: of just into a point right along the plane of

538
00:25:06,520 --> 00:25:09,639
Speaker 2: the spin. Basically, angular momentum needs to stick around and

539
00:25:09,680 --> 00:25:11,920
Speaker 2: so the same way that like the Earth doesn't collapse

540
00:25:11,920 --> 00:25:15,199
Speaker 2: into the Sun because of our orbital angular momentum around

541
00:25:15,240 --> 00:25:18,200
Speaker 2: the Sun, the gas turns into a big swirling orbit

542
00:25:18,359 --> 00:25:20,639
Speaker 2: around the center of the galaxy, the same way like

543
00:25:20,680 --> 00:25:23,560
Speaker 2: a black hole has an accretion disk around it for

544
00:25:23,640 --> 00:25:26,080
Speaker 2: all the same reasons. So it sort of collapses into

545
00:25:26,119 --> 00:25:28,320
Speaker 2: a disc, and that's when the stars start to form.

546
00:25:28,359 --> 00:25:31,440
Speaker 2: When the gas gets dense enough, stars begin to form.

547
00:25:31,640 --> 00:25:33,480
Speaker 2: So it's not like you have a bunch of gas

548
00:25:33,480 --> 00:25:37,040
Speaker 2: which forms stars and then the stars collapse into a disc.

549
00:25:37,359 --> 00:25:40,119
Speaker 2: It's the gas collapsing into a disc that allows the

550
00:25:40,160 --> 00:25:42,600
Speaker 2: stars to form. They form in that disk.

551
00:25:43,440 --> 00:25:47,840
Speaker 1: Okay, So now is that why most galaxies are flat

552
00:25:48,400 --> 00:25:50,880
Speaker 1: sort of like a you know, and you don't get

553
00:25:50,960 --> 00:25:53,919
Speaker 1: spherical galaxies or do you get spherical galaxies.

554
00:25:54,119 --> 00:25:57,480
Speaker 2: You can get elliptical galaxies which include some spheres, and

555
00:25:57,480 --> 00:26:00,440
Speaker 2: there are also globular clusters out there. But these galaxies,

556
00:26:00,480 --> 00:26:03,480
Speaker 2: the spiral galaxies, that's why they are flat. They're flat

557
00:26:03,560 --> 00:26:06,399
Speaker 2: because the stars form in that disc which is shaped

558
00:26:06,440 --> 00:26:10,080
Speaker 2: by gravity and anglar momentum sort of playing against each other.

559
00:26:10,119 --> 00:26:12,879
Speaker 2: So here you can see two totally different things in

560
00:26:12,920 --> 00:26:16,240
Speaker 2: the universe, gravity and angular momentum fighting each other on

561
00:26:16,280 --> 00:26:19,800
Speaker 2: these vast cosmic scales and determining the structure of most

562
00:26:19,840 --> 00:26:22,960
Speaker 2: of these galaxies. All these spiral galaxies are basically a

563
00:26:23,000 --> 00:26:26,359
Speaker 2: balance between these two things, angler momentum and gravity.

564
00:26:26,960 --> 00:26:29,160
Speaker 1: Okay, so we had a cloud. It's flattened to a pancake,

565
00:26:29,240 --> 00:26:32,639
Speaker 1: and now what to turn into a spiral? Who flushed

566
00:26:32,680 --> 00:26:33,119
Speaker 1: the toilet?

567
00:26:34,760 --> 00:26:37,080
Speaker 2: So it's still spinning. It's got to keep spinning. That's

568
00:26:37,080 --> 00:26:39,439
Speaker 2: why it's a pancake. And then you get these arms

569
00:26:39,480 --> 00:26:41,800
Speaker 2: that form. And a lot of people imagine that galactic

570
00:26:41,880 --> 00:26:45,119
Speaker 2: arms are like your arms that you spinning around. Your

571
00:26:45,240 --> 00:26:47,639
Speaker 2: arms are like a collection of mass, and as your

572
00:26:47,720 --> 00:26:51,240
Speaker 2: arms spin, that mass moves. But in the case of galaxies,

573
00:26:51,400 --> 00:26:53,840
Speaker 2: these arms are not structural. It's not the same stars

574
00:26:53,880 --> 00:26:56,000
Speaker 2: in the arm and the whole time, the arms are

575
00:26:56,000 --> 00:27:00,280
Speaker 2: actually density waves in this pancake. So some star get

576
00:27:00,320 --> 00:27:02,760
Speaker 2: closer together and then further apart, and closer together and

577
00:27:02,760 --> 00:27:05,440
Speaker 2: further apart. It's more like a wave passing through a stadium.

578
00:27:05,480 --> 00:27:08,000
Speaker 2: Those people aren't running in a wave. It's just a

579
00:27:08,040 --> 00:27:10,320
Speaker 2: wave moving through the stationary crowd.

580
00:27:10,760 --> 00:27:12,760
Speaker 1: Yeah, we had a whole episode about that. I remember.

581
00:27:13,000 --> 00:27:15,080
Speaker 1: It's sort of like a wave in traffic, Like you

582
00:27:15,160 --> 00:27:17,320
Speaker 1: were stuck in the highway. There's sort of these ways

583
00:27:17,800 --> 00:27:19,800
Speaker 1: that go from the back to the front or the

584
00:27:19,840 --> 00:27:22,040
Speaker 1: front to the back, where you get these cars kind

585
00:27:22,040 --> 00:27:24,399
Speaker 1: of clustering together for a while, but then they spread

586
00:27:24,400 --> 00:27:26,960
Speaker 1: out after a while, right, sort of like a traffic

587
00:27:27,040 --> 00:27:27,680
Speaker 1: jam almost.

588
00:27:28,320 --> 00:27:30,480
Speaker 2: Yeah, it's sort of like a traffic jam. And it

589
00:27:30,560 --> 00:27:34,520
Speaker 2: explains why galaxies aren't like really really tightly wound. If

590
00:27:34,560 --> 00:27:36,800
Speaker 2: you stick your arms out and then you spin, your

591
00:27:36,880 --> 00:27:39,800
Speaker 2: arms tend to sort of like lag behind you. Or

592
00:27:39,840 --> 00:27:41,760
Speaker 2: if you had like a ribbon and you were spinning,

593
00:27:41,880 --> 00:27:44,560
Speaker 2: you would end up winding it around yourself. And so

594
00:27:44,640 --> 00:27:47,080
Speaker 2: people wondered for a while when they thought that these

595
00:27:47,160 --> 00:27:50,920
Speaker 2: arms really were structural, why galaxies weren't all like wound

596
00:27:51,000 --> 00:27:53,760
Speaker 2: up like a ball of yarn. So this explains why

597
00:27:53,800 --> 00:27:56,879
Speaker 2: they aren't because they're actually just density waves. But you

598
00:27:56,920 --> 00:27:59,640
Speaker 2: do see a big range of tightness, like you see

599
00:27:59,640 --> 00:28:02,480
Speaker 2: some with looser wines and some with tighter wines. It's

600
00:28:02,560 --> 00:28:04,959
Speaker 2: really interesting to see like the variety.

601
00:28:04,560 --> 00:28:07,080
Speaker 1: By one, you mean, like the spiral. Some spirals are

602
00:28:07,400 --> 00:28:08,640
Speaker 1: more spirally than others.

603
00:28:09,520 --> 00:28:12,560
Speaker 2: Yes, some are looser and some are tighter. They're all spirals,

604
00:28:12,720 --> 00:28:14,479
Speaker 2: but some are looser and some are tighter. And sometimes

605
00:28:14,480 --> 00:28:16,880
Speaker 2: you see multiple arms, right, But a listener question about

606
00:28:16,880 --> 00:28:19,480
Speaker 2: a galaxy with like three arms and why you sometimes

607
00:28:19,480 --> 00:28:22,240
Speaker 2: have four arms or two arms. These are density waves

608
00:28:22,280 --> 00:28:24,520
Speaker 2: that come out of the perturbations of the initial gas

609
00:28:24,560 --> 00:28:27,119
Speaker 2: cloud as it's spinning, and so you can get different

610
00:28:27,200 --> 00:28:29,880
Speaker 2: numbers of arms. You also typically get like a big

611
00:28:29,960 --> 00:28:33,639
Speaker 2: central bulge. So that's the shape of these spiral galaxies.

612
00:28:33,880 --> 00:28:35,880
Speaker 2: And they spin for a long time. And they think

613
00:28:35,920 --> 00:28:39,480
Speaker 2: that eventually spiral galaxies will merge with other spiral galaxies.

614
00:28:39,520 --> 00:28:41,760
Speaker 2: But they don't have to write. Sometimes the spiral galaxy

615
00:28:41,840 --> 00:28:43,440
Speaker 2: is happy by itself and they can just sort of

616
00:28:43,440 --> 00:28:46,200
Speaker 2: live out its life. And the future of these spiral

617
00:28:46,240 --> 00:28:49,600
Speaker 2: galaxies is that eventually these density waves dissipate and you

618
00:28:49,640 --> 00:28:51,720
Speaker 2: get just sort of like a smooth pancake galaxy.

619
00:28:51,880 --> 00:28:55,240
Speaker 1: Wait, what so it starts out smooth, then you get

620
00:28:55,280 --> 00:28:58,200
Speaker 1: these density waves and give give it a spiral shape,

621
00:28:58,240 --> 00:29:02,120
Speaker 1: and then eventually after why all the spirals flatten out too.

622
00:29:02,240 --> 00:29:04,400
Speaker 2: Yeah. I wouldn't say that it starts out smooth. I

623
00:29:04,440 --> 00:29:07,760
Speaker 2: mean the density waves come from something in that galaxy

624
00:29:07,760 --> 00:29:11,080
Speaker 2: that was clumpy that seeds the density wave. But eventually

625
00:29:11,360 --> 00:29:13,920
Speaker 2: interaction between these stars, the pushes and the pulls and

626
00:29:13,960 --> 00:29:16,720
Speaker 2: the friction, et cetera, will smooth these things out and

627
00:29:16,720 --> 00:29:20,240
Speaker 2: they will dissipate. You get these things called lenticular galaxies,

628
00:29:20,400 --> 00:29:22,760
Speaker 2: which have no relationship to lentils at all. To my

629
00:29:22,800 --> 00:29:26,120
Speaker 2: wife's great disappointment, It just means that they're basically smooth.

630
00:29:27,000 --> 00:29:29,480
Speaker 1: But I guess maybe we're just saying, is that maybe

631
00:29:29,680 --> 00:29:33,200
Speaker 1: we've been imagining this original cloud of gas that started

632
00:29:33,200 --> 00:29:35,880
Speaker 1: the galaxy as being perfectly smooth, but maybe it wasn't right.

633
00:29:35,960 --> 00:29:39,280
Speaker 1: Like maybe this cloud of gas was lopsided, or maybe

634
00:29:39,280 --> 00:29:42,360
Speaker 1: it was denser in one direction, and then those weird

635
00:29:42,440 --> 00:29:47,560
Speaker 1: shapes of the gas then gave you these weird arms distributions.

636
00:29:47,800 --> 00:29:50,640
Speaker 2: Yeah, it definitely was not smooth, right, The reason this

637
00:29:50,720 --> 00:29:52,920
Speaker 2: cloud of gas formed in on some other cloud is

638
00:29:52,960 --> 00:29:55,640
Speaker 2: because it was denser. It formed around some core that

639
00:29:55,840 --> 00:29:58,120
Speaker 2: was a little bit denser that pulled it together, and

640
00:29:58,160 --> 00:29:59,920
Speaker 2: there were other sort of like mini cores within it,

641
00:30:00,160 --> 00:30:02,920
Speaker 2: you know, other little seeds of gravity. So it definitely

642
00:30:02,960 --> 00:30:05,600
Speaker 2: didn't start out as a perfectly smooth structure at all,

643
00:30:06,040 --> 00:30:08,560
Speaker 2: and so that plays out and forms these density waves.

644
00:30:08,720 --> 00:30:11,960
Speaker 2: But because the interaction, things eventually spread out and it

645
00:30:12,000 --> 00:30:12,840
Speaker 2: gets smoothed out.

646
00:30:13,360 --> 00:30:15,920
Speaker 1: So that's the future of the bilky Way galaxy too. Eventually,

647
00:30:15,960 --> 00:30:17,560
Speaker 1: we're just going to We're just going to be a

648
00:30:17,560 --> 00:30:19,240
Speaker 1: pancake if we.

649
00:30:19,120 --> 00:30:21,560
Speaker 2: Were left to our own devices. But because Andromeda is

650
00:30:21,560 --> 00:30:24,280
Speaker 2: going to slam into us, that's going to change our shape.

651
00:30:24,560 --> 00:30:27,400
Speaker 2: And whether we form a new spiral galaxy as a

652
00:30:27,440 --> 00:30:30,560
Speaker 2: merger or whether we end up an elliptical galaxy depends

653
00:30:30,560 --> 00:30:32,720
Speaker 2: a little bit on how much gas we have left

654
00:30:32,720 --> 00:30:33,080
Speaker 2: when it.

655
00:30:33,040 --> 00:30:36,440
Speaker 1: Happens, all right. So that's how spiral galaxies get formed.

656
00:30:36,440 --> 00:30:38,240
Speaker 1: And so they talk about some of the other shapes

657
00:30:38,280 --> 00:30:42,600
Speaker 1: that galaxies can take, including Daniel's minky mouse galaxy. So

658
00:30:42,680 --> 00:30:45,320
Speaker 1: let's talk about that. But first let's take another quick break,

659
00:30:57,880 --> 00:31:00,400
Speaker 1: all right, we're talking about the shape of galaxy sees

660
00:31:00,880 --> 00:31:07,280
Speaker 1: sponsored by Disney. No, the check didn't come through, sponsored

661
00:31:07,320 --> 00:31:10,480
Speaker 1: by Warner Brothers. Let's talk about bugs, bunny shape galaxies.

662
00:31:11,600 --> 00:31:14,440
Speaker 2: You want all these children's entertainment companies to be responsible

663
00:31:14,480 --> 00:31:17,280
Speaker 2: for the not safer astronomy shapes of galaxies.

664
00:31:17,800 --> 00:31:22,000
Speaker 1: Well, I'm sure we can censor those out now.

665
00:31:22,040 --> 00:31:23,480
Speaker 2: We are censoring the nice sky.

666
00:31:23,600 --> 00:31:27,800
Speaker 1: Oh my gosh, I feel like the nice sky sensors itself.

667
00:31:28,720 --> 00:31:29,959
Speaker 1: Why is it so hard to see?

668
00:31:30,160 --> 00:31:32,400
Speaker 2: I know most of the universe has already censored. Maybe

669
00:31:32,480 --> 00:31:34,240
Speaker 2: dark matter is hidden for us for a reason.

670
00:31:34,400 --> 00:31:37,440
Speaker 1: That's right. It's it's like the universe using a black marker.

671
00:31:38,440 --> 00:31:40,400
Speaker 2: It's not dark matter, it's bleeved matter.

672
00:31:40,640 --> 00:31:42,920
Speaker 1: That's right. Maybe it's not safe for humans.

673
00:31:42,760 --> 00:31:43,840
Speaker 2: It's redacted matter.

674
00:31:44,840 --> 00:31:47,520
Speaker 1: Yeah, we can't be trusted with its secrets.

675
00:31:49,240 --> 00:31:51,479
Speaker 2: If you only knew what the universe was hiding.

676
00:31:51,800 --> 00:31:53,400
Speaker 1: Oh my goodness. You know you can get in trouble

677
00:31:53,440 --> 00:31:56,160
Speaker 1: for divology classified information. Have you heard?

678
00:31:58,360 --> 00:31:58,840
Speaker 2: I have not.

679
00:31:59,080 --> 00:32:00,520
Speaker 1: I want to watch out for that. All right, So

680
00:32:00,560 --> 00:32:03,040
Speaker 1: let's talk about some of the other shapes that galaxies

681
00:32:03,080 --> 00:32:05,360
Speaker 1: can be. We talked about spiral shapes. That's kind of

682
00:32:05,360 --> 00:32:08,400
Speaker 1: maybe the traditional shape of a galaxy that most people

683
00:32:08,440 --> 00:32:10,320
Speaker 1: think about, but galaxies can have other shapes.

684
00:32:10,400 --> 00:32:12,920
Speaker 2: Yeah, spiral galaxies are the most common in the universe,

685
00:32:12,960 --> 00:32:17,480
Speaker 2: but the biggest galaxies are elliptical galaxies. These are often

686
00:32:17,520 --> 00:32:20,880
Speaker 2: found in like the rich central regions of galaxy clusters,

687
00:32:21,280 --> 00:32:23,720
Speaker 2: and they are usually the result of lots of spiral

688
00:32:23,760 --> 00:32:27,320
Speaker 2: galaxies merging. And these elliptical galaxies are not nearly as

689
00:32:27,360 --> 00:32:29,800
Speaker 2: pretty to look at. Like a spiral has features, you

690
00:32:29,800 --> 00:32:32,120
Speaker 2: can see it. It's like a disc, there's arms in it.

691
00:32:32,160 --> 00:32:36,200
Speaker 2: Sometimes elliptical galaxies basically just a big blob. You know,

692
00:32:36,240 --> 00:32:39,360
Speaker 2: it's smooth, there's almost no features in it. It's just

693
00:32:39,400 --> 00:32:40,400
Speaker 2: a bunch of stars.

694
00:32:40,880 --> 00:32:42,560
Speaker 1: Well maybe that's pretty to some people.

695
00:32:43,840 --> 00:32:45,840
Speaker 2: I'm not saying it's not esthetic, but it's just a

696
00:32:45,840 --> 00:32:46,600
Speaker 2: bit of a blob.

697
00:32:46,760 --> 00:32:50,840
Speaker 1: Are you trying to shape shame some galaxies out there?

698
00:32:51,800 --> 00:32:55,000
Speaker 2: I'm just creating categories, man, that's all I'm doing. An

699
00:32:55,040 --> 00:32:57,640
Speaker 2: important feature of elliptical galaxies is that they don't have

700
00:32:57,680 --> 00:33:00,480
Speaker 2: a lot of star formation going on, and so why

701
00:33:00,600 --> 00:33:02,160
Speaker 2: they're elliptical galaxies?

702
00:33:02,360 --> 00:33:04,520
Speaker 1: Now, hold on, what do you mean by elliptical, Like

703
00:33:04,560 --> 00:33:06,920
Speaker 1: it's shaped like an ellipses, but Is it flat or

704
00:33:06,960 --> 00:33:08,880
Speaker 1: is it Are you saying it's more shaped like a football?

705
00:33:09,040 --> 00:33:10,360
Speaker 1: What is this shape? Exactly?

706
00:33:10,440 --> 00:33:12,760
Speaker 2: It's more like a big watermelon, you know. And an

707
00:33:12,760 --> 00:33:15,920
Speaker 2: ellipse in general includes spheres, right, It's just sort of

708
00:33:15,920 --> 00:33:18,200
Speaker 2: like a more general phrase the same way that like

709
00:33:18,200 --> 00:33:20,880
Speaker 2: a circle technically is an ellipse. It just has its

710
00:33:20,880 --> 00:33:23,960
Speaker 2: two axes equal. So an elliptical galaxy is just like

711
00:33:24,000 --> 00:33:26,840
Speaker 2: a big watermelon shaped galaxy. It might be longer in

712
00:33:26,880 --> 00:33:28,560
Speaker 2: one direction or another.

713
00:33:28,360 --> 00:33:30,320
Speaker 1: So it's like a blob, like a submarine shape.

714
00:33:30,360 --> 00:33:33,680
Speaker 2: Blob, Yeah, exactly, like it's a big submarine floating through space.

715
00:33:33,680 --> 00:33:35,200
Speaker 2: It's not flat like a pancake.

716
00:33:35,320 --> 00:33:37,400
Speaker 1: And that's the overall shape of it. Is it like

717
00:33:37,560 --> 00:33:39,840
Speaker 1: denser in the middle? Is it just all all the

718
00:33:39,880 --> 00:33:43,200
Speaker 1: stars evenly distributed? Does it have like a shell? Paint

719
00:33:43,240 --> 00:33:43,920
Speaker 1: the picture for us?

720
00:33:44,000 --> 00:33:46,960
Speaker 2: So, elliptical galaxies definitely do have a core where things

721
00:33:47,040 --> 00:33:49,800
Speaker 2: are denser, and then they peter out near the edge.

722
00:33:50,040 --> 00:33:52,600
Speaker 2: But essentially there's not that much else to talk about.

723
00:33:52,640 --> 00:33:55,120
Speaker 2: They're roughly ellipsoidal, and they have a bunch of stars

724
00:33:55,120 --> 00:33:57,200
Speaker 2: in them, and I think maybe the other most interesting

725
00:33:57,240 --> 00:33:58,920
Speaker 2: thing about them is that they don't have a lot

726
00:33:58,960 --> 00:34:02,959
Speaker 2: of gas basically mostly stars, which means that you're not

727
00:34:03,040 --> 00:34:06,040
Speaker 2: having a lot more stars being formed. Right. It's the

728
00:34:06,080 --> 00:34:08,160
Speaker 2: gas that forms the stars, and in a lot of

729
00:34:08,200 --> 00:34:12,719
Speaker 2: galaxies you continuously have more stars being formed, But elliptical

730
00:34:12,760 --> 00:34:16,360
Speaker 2: galaxies are almost always quenched, which means no new stars

731
00:34:16,360 --> 00:34:17,280
Speaker 2: are being formed.

732
00:34:18,640 --> 00:34:20,960
Speaker 1: And are the stars in them also really old?

733
00:34:21,280 --> 00:34:21,400
Speaker 2: Right?

734
00:34:21,400 --> 00:34:23,439
Speaker 1: If it's not forming new stars in all of its

735
00:34:23,560 --> 00:34:24,360
Speaker 1: stars must.

736
00:34:24,160 --> 00:34:26,880
Speaker 2: Be old exactly, which affects the color of the galaxies

737
00:34:26,920 --> 00:34:29,359
Speaker 2: as well. Because stars that are really big turn out

738
00:34:29,360 --> 00:34:31,719
Speaker 2: to be really hot, which makes them blue, and those

739
00:34:31,800 --> 00:34:34,920
Speaker 2: kinds of stars don't burn for very long. The colder stars,

740
00:34:34,920 --> 00:34:37,239
Speaker 2: the smaller stars, are redder, and those tend to be

741
00:34:37,280 --> 00:34:39,840
Speaker 2: the ones that burn for billions and billions of years.

742
00:34:40,280 --> 00:34:42,040
Speaker 2: So if you look at a galaxy and you see

743
00:34:42,120 --> 00:34:45,520
Speaker 2: only red stars, that means there are no new stars

744
00:34:45,560 --> 00:34:47,880
Speaker 2: being formed there. There's only the long lived short people

745
00:34:48,040 --> 00:34:51,400
Speaker 2: who are left. And so these elliptical galaxies don't have

746
00:34:51,520 --> 00:34:55,040
Speaker 2: new stars being formed, which makes them redder than other galaxies.

747
00:34:55,280 --> 00:34:57,840
Speaker 1: So all the blue stars basically burn themselves out and

748
00:34:57,880 --> 00:35:00,759
Speaker 1: are maybe just floating there but you can't see them.

749
00:35:00,840 --> 00:35:03,319
Speaker 2: Yeah, exactly, they have their stellar remnants, but they're no

750
00:35:03,400 --> 00:35:07,040
Speaker 2: longer burning. And that's basically why this is an elliptical galaxy.

751
00:35:07,040 --> 00:35:10,439
Speaker 2: I mean, imagine two spiral galaxies forming. If they don't

752
00:35:10,440 --> 00:35:12,879
Speaker 2: have a lot of gas left, then what happens. They're

753
00:35:12,880 --> 00:35:16,680
Speaker 2: mostly just stars. And then those two spiral galaxies merge,

754
00:35:16,800 --> 00:35:18,960
Speaker 2: and now you have two planes. You have one plane

755
00:35:18,960 --> 00:35:22,239
Speaker 2: of rotation from each galaxy, and now they've mixed, so

756
00:35:22,280 --> 00:35:24,600
Speaker 2: you have some stars moving along one plane, some stars

757
00:35:24,640 --> 00:35:27,720
Speaker 2: moving along another plane. Now throw in another spiral galaxy,

758
00:35:27,760 --> 00:35:31,040
Speaker 2: and another and another. Eventually you have lots of different

759
00:35:31,080 --> 00:35:33,160
Speaker 2: planes of rotation, and what do you get. You get

760
00:35:33,160 --> 00:35:36,240
Speaker 2: an ellipse. So you add a bunch of spiral galaxies

761
00:35:36,280 --> 00:35:38,840
Speaker 2: together without a whole lot of gas to make new stars,

762
00:35:39,160 --> 00:35:40,560
Speaker 2: then you just get a big ellipse.

763
00:35:40,760 --> 00:35:44,360
Speaker 1: It's like you're just joining different pancakes at different angles,

764
00:35:44,440 --> 00:35:46,040
Speaker 1: and then you push it all together and you just

765
00:35:46,040 --> 00:35:48,320
Speaker 1: get a giant cloud of stars exactly.

766
00:35:48,440 --> 00:35:51,080
Speaker 2: And that might make you think, well, then every single

767
00:35:51,120 --> 00:35:53,799
Speaker 2: galaxy that's merged should be an ellipse, right, because you

768
00:35:54,080 --> 00:35:56,200
Speaker 2: get these spirals, and then you add spirals together, you

769
00:35:56,200 --> 00:35:59,000
Speaker 2: should get ellipses. How can you still have really big

770
00:35:59,040 --> 00:36:02,000
Speaker 2: spiral galaxies? Like the Milky Way or Andromeda. And the

771
00:36:02,040 --> 00:36:05,280
Speaker 2: answer is the gas. When the two spiral galaxies merge,

772
00:36:05,280 --> 00:36:08,319
Speaker 2: if there's still a lot of gas in the original spirals,

773
00:36:08,400 --> 00:36:13,040
Speaker 2: then that gas interacts and collapses again, forming a new spiral.

774
00:36:13,200 --> 00:36:15,840
Speaker 2: And that's how you get a big spiral galaxy. The

775
00:36:15,920 --> 00:36:19,280
Speaker 2: gas from the original ones smashes into each other, forming

776
00:36:19,400 --> 00:36:21,000
Speaker 2: new stars in a new disk.

777
00:36:21,239 --> 00:36:23,120
Speaker 1: Right. But I guess maybe the question is like, why

778
00:36:23,160 --> 00:36:27,759
Speaker 1: don't elliptical galaxies eventually collapse into a pancake too? Like,

779
00:36:27,800 --> 00:36:31,239
Speaker 1: wouldn't they also have, you know, an overall spin, even

780
00:36:31,280 --> 00:36:33,560
Speaker 1: if you're adding different mini galaxies, but didn't it all

781
00:36:33,600 --> 00:36:36,520
Speaker 1: have an overall spin? Wouldn't over time it also collapse

782
00:36:36,560 --> 00:36:39,480
Speaker 1: into a pancake and then maybe also into a spiral.

783
00:36:39,719 --> 00:36:42,200
Speaker 2: It might eventually, but because there's very little gas in

784
00:36:42,239 --> 00:36:44,719
Speaker 2: those galaxies, is almost no friction, and so it's really

785
00:36:44,719 --> 00:36:47,320
Speaker 2: hard for those stars to interact with each other. You know,

786
00:36:47,360 --> 00:36:50,480
Speaker 2: they're basically really isolated from each other except for gravity.

787
00:36:50,680 --> 00:36:52,560
Speaker 1: What do you mean by let low friction? How does

788
00:36:52,600 --> 00:36:55,480
Speaker 1: that plan into a cloud of gas form into a pancake.

789
00:36:55,600 --> 00:36:58,080
Speaker 2: It's very hard for these stars to exchange energy in

790
00:36:58,160 --> 00:37:00,960
Speaker 2: any way. Think about how things can come things collapse

791
00:37:01,000 --> 00:37:03,480
Speaker 2: because they bounce off each other. If everything just stayed

792
00:37:03,480 --> 00:37:06,880
Speaker 2: in its original orbit, nothing would ever collapse. Your gas

793
00:37:06,880 --> 00:37:09,640
Speaker 2: cloud never would have formed a pancake. In order to

794
00:37:09,680 --> 00:37:11,920
Speaker 2: collapse down to a pancake, they have to somehow bounce

795
00:37:11,960 --> 00:37:15,000
Speaker 2: off each other and exchange energy. That's why, for example,

796
00:37:15,120 --> 00:37:17,799
Speaker 2: dark matter doesn't collapse into a pancake because it has

797
00:37:17,880 --> 00:37:20,799
Speaker 2: no interactions other than gravity. It just stays in a

798
00:37:20,800 --> 00:37:22,040
Speaker 2: big spherical halo.

799
00:37:22,239 --> 00:37:24,319
Speaker 1: So even though it's drawn to the center, when they

800
00:37:24,320 --> 00:37:26,080
Speaker 1: get to the center, they just miss each other and

801
00:37:26,160 --> 00:37:26,600
Speaker 1: keep going.

802
00:37:26,800 --> 00:37:29,960
Speaker 2: Yeah, exactly. But if there's some gas there to sort

803
00:37:29,960 --> 00:37:33,080
Speaker 2: of slow the stars down and exchange energy, then things

804
00:37:33,080 --> 00:37:36,080
Speaker 2: can collapse. But elliptical galaxies have almost no gas, and

805
00:37:36,080 --> 00:37:39,319
Speaker 2: so the stars basically ignore each other unless they come

806
00:37:39,400 --> 00:37:42,399
Speaker 2: really close and some gravitational interaction can slow them down.

807
00:37:42,480 --> 00:37:47,120
Speaker 2: So I think like eventually elliptical galaxies will flatten out

808
00:37:47,200 --> 00:37:49,480
Speaker 2: for all the same reasons we've been talking about, but

809
00:37:49,560 --> 00:37:52,280
Speaker 2: because gravity is so weak compared to the other forces,

810
00:37:52,320 --> 00:37:53,880
Speaker 2: it's going to take much much longer then if you

811
00:37:53,920 --> 00:37:56,480
Speaker 2: actually have a lot of gas in there to facilitate

812
00:37:56,520 --> 00:37:57,320
Speaker 2: that kind of interaction.

813
00:37:58,040 --> 00:38:01,080
Speaker 1: But as we're looking back into time with like the

814
00:38:01,160 --> 00:38:03,799
Speaker 1: James Web telescope gig do we see evidence of that

815
00:38:04,640 --> 00:38:08,920
Speaker 1: like in the distant past? Is it mostly all pancakes

816
00:38:09,040 --> 00:38:12,200
Speaker 1: or are there still a lot of elliptical galaxy.

817
00:38:11,840 --> 00:38:14,000
Speaker 2: In the distant past? We can see that these pancakes

818
00:38:14,000 --> 00:38:15,520
Speaker 2: are the ones that are formed. Like, you don't form

819
00:38:15,560 --> 00:38:18,560
Speaker 2: elliptical galaxies initially, you form little spirals, and then if

820
00:38:18,600 --> 00:38:21,000
Speaker 2: those spirals use up most of their gas and have

821
00:38:21,120 --> 00:38:24,920
Speaker 2: quenched and then merge, then you see ellipticals being formed.

822
00:38:25,160 --> 00:38:27,080
Speaker 2: So the only way to make an elliptical galaxy is

823
00:38:27,080 --> 00:38:29,800
Speaker 2: to basically use up the gas in the spiral galaxies

824
00:38:29,840 --> 00:38:32,360
Speaker 2: initially and then merge them, and then they're sort of

825
00:38:32,440 --> 00:38:34,120
Speaker 2: frozen in their original planes.

826
00:38:34,520 --> 00:38:36,239
Speaker 1: So I guess maybe what you're saying, is it not

827
00:38:36,400 --> 00:38:40,200
Speaker 1: enough time has passed made for these elliptical galaxies to

828
00:38:40,280 --> 00:38:43,800
Speaker 1: flatten out, to basically see everything flatten out.

829
00:38:43,760 --> 00:38:46,520
Speaker 2: Exactly in the far far future. Elliptical galaxies, if left

830
00:38:46,560 --> 00:38:49,640
Speaker 2: to their own devices, will eventually flatten out because of gravity.

831
00:38:49,840 --> 00:38:52,560
Speaker 2: But spiral galaxies are flattened because the gas, because the

832
00:38:52,600 --> 00:38:54,680
Speaker 2: gas has a lot more interactions than the stars.

833
00:38:54,920 --> 00:38:57,600
Speaker 1: All right, So then that's the elliptical galaxies, what other

834
00:38:57,680 --> 00:38:58,799
Speaker 1: shapes can galaxies be?

835
00:38:59,000 --> 00:39:02,440
Speaker 2: So there's another category called irregular galaxies, and these are

836
00:39:02,480 --> 00:39:05,560
Speaker 2: ones that are basically not elliptical and not spiral. So

837
00:39:05,640 --> 00:39:09,000
Speaker 2: astronomers are like, hmmm, let's make a bucket for other stuff.

838
00:39:09,080 --> 00:39:11,920
Speaker 2: And irregular galaxies can be like almost any shape. You

839
00:39:11,960 --> 00:39:14,520
Speaker 2: see stuff long and thin, you see stuff spread out,

840
00:39:14,600 --> 00:39:17,239
Speaker 2: you see stuff in a question mark shape. There's a

841
00:39:17,280 --> 00:39:19,920
Speaker 2: huge number of these also, but almost every single time

842
00:39:20,120 --> 00:39:23,839
Speaker 2: it's a transient shape. It's because something has been like perturbed.

843
00:39:24,080 --> 00:39:26,759
Speaker 2: Two galaxies have smashed into each other or passed really

844
00:39:26,800 --> 00:39:29,480
Speaker 2: close to each other and torn themselves apart and haven't

845
00:39:29,560 --> 00:39:34,360
Speaker 2: yet settled into some new stable shape, probably elliptical or spiral.

846
00:39:34,719 --> 00:39:37,320
Speaker 2: So it's sort of like an intermediate state for galaxies

847
00:39:37,360 --> 00:39:38,160
Speaker 2: that are interacting.

848
00:39:39,120 --> 00:39:41,280
Speaker 1: I thought you mean a regular like a toilet reference.

849
00:39:41,280 --> 00:39:45,000
Speaker 2: Again, these should have more fiber of these galaxies, I mean,

850
00:39:45,080 --> 00:39:46,360
Speaker 2: really take care of yourselves.

851
00:39:46,880 --> 00:39:48,960
Speaker 1: Yeah, puts a men abuse with that dark chocolate.

852
00:39:50,280 --> 00:39:52,600
Speaker 2: Maybe dark matter is the fiber of the universe that

853
00:39:52,719 --> 00:39:54,000
Speaker 2: really is making things.

854
00:39:53,800 --> 00:39:57,320
Speaker 1: Regular, all right, So you're saying that in paint the

855
00:39:57,320 --> 00:40:00,560
Speaker 1: picture for us. Again, these are just like we shapes

856
00:40:00,600 --> 00:40:02,520
Speaker 1: out there of galaxies like they look like an L

857
00:40:02,560 --> 00:40:05,320
Speaker 1: shaped or like a maybe like a Mickey mouse.

858
00:40:05,400 --> 00:40:08,040
Speaker 2: Yeah, if you just google like irregular galaxies, you can

859
00:40:08,040 --> 00:40:10,440
Speaker 2: see all sorts of crazy stuff and it's basically the

860
00:40:10,480 --> 00:40:13,040
Speaker 2: results of collisions, so it can be a mess. Just

861
00:40:13,040 --> 00:40:15,600
Speaker 2: like if you look at simulations of what's gonna happen

862
00:40:15,600 --> 00:40:18,320
Speaker 2: when Andromeda in the Milky Way collide. In the beginning,

863
00:40:18,520 --> 00:40:20,480
Speaker 2: it doesn't really have any shape at all. It's just

864
00:40:20,480 --> 00:40:23,879
Speaker 2: like a huge spray stars this way and stars that way,

865
00:40:23,920 --> 00:40:27,120
Speaker 2: and then eventually it settles down into a new shape.

866
00:40:27,160 --> 00:40:29,239
Speaker 2: But in the intermediate shape, it just depends on the

867
00:40:29,280 --> 00:40:31,040
Speaker 2: angles and the sizes and how they hit. You can

868
00:40:31,080 --> 00:40:32,480
Speaker 2: get basically any shape you like.

869
00:40:33,160 --> 00:40:35,959
Speaker 1: And you say, most of these irregular galaxies are because

870
00:40:36,000 --> 00:40:39,520
Speaker 1: of collisions of other galaxies, But can you form an

871
00:40:39,520 --> 00:40:41,920
Speaker 1: irregular shape galaxy from scratch?

872
00:40:42,360 --> 00:40:45,440
Speaker 2: Cool question. I think the answer is no, because you

873
00:40:45,480 --> 00:40:48,360
Speaker 2: don't get star formation in a spiral galaxy until the

874
00:40:48,400 --> 00:40:51,319
Speaker 2: gas collapses, right, So it's not like you can form

875
00:40:51,360 --> 00:40:53,880
Speaker 2: a bunch of stars in a random place. The stars

876
00:40:53,920 --> 00:40:56,640
Speaker 2: don't really form until the gas is already collapsed into

877
00:40:56,680 --> 00:40:59,319
Speaker 2: a disc. Really, and so I don't think you can

878
00:40:59,320 --> 00:41:02,120
Speaker 2: form in a regular galaxy from scratch. I think it's

879
00:41:02,160 --> 00:41:05,920
Speaker 2: the combination of other galaxies coming together sort of chaotically.

880
00:41:06,120 --> 00:41:07,960
Speaker 1: All right, So then does that cover all the shapes

881
00:41:08,040 --> 00:41:08,799
Speaker 1: galaxies can be.

882
00:41:09,040 --> 00:41:13,360
Speaker 2: It doesn't. There's one really cool, very strange, spectacular shape

883
00:41:13,360 --> 00:41:17,239
Speaker 2: of galaxy that's very very rare. It's called a ring galaxy.

884
00:41:17,560 --> 00:41:19,440
Speaker 1: WHOA, Like it's shaped like a hoop.

885
00:41:20,320 --> 00:41:22,840
Speaker 2: It's really cool. It has like a central core, like

886
00:41:22,880 --> 00:41:25,440
Speaker 2: a blob in the middle, and then there's a big gap,

887
00:41:25,480 --> 00:41:28,680
Speaker 2: and then surrounding it is a whole ring of stars.

888
00:41:29,080 --> 00:41:29,720
Speaker 1: So it's flat.

889
00:41:29,840 --> 00:41:33,120
Speaker 2: It's flat, yeah, exactly, So it's flat pancake, but instead

890
00:41:33,160 --> 00:41:35,200
Speaker 2: of being like a full disc, it's got a core

891
00:41:35,520 --> 00:41:37,120
Speaker 2: and then like a ring, so it's sort of like

892
00:41:37,160 --> 00:41:39,920
Speaker 2: a bicycle wheel. You have like the tire and then

893
00:41:39,960 --> 00:41:42,920
Speaker 2: you have the central hub and there's a huge gap

894
00:41:42,960 --> 00:41:43,920
Speaker 2: in between.

895
00:41:43,840 --> 00:41:45,600
Speaker 1: Sort of like a Saturn galaxy.

896
00:41:45,680 --> 00:41:50,279
Speaker 2: Yeah, exactly, like a Saturn galaxy. And these are really fascinating.

897
00:41:50,320 --> 00:41:53,239
Speaker 2: The center is red, so like they're older stars, and

898
00:41:53,280 --> 00:41:56,160
Speaker 2: the ring tends to be blue, so they're really beautiful

899
00:41:56,239 --> 00:42:02,440
Speaker 2: to look at. WHOA and patriotic, Yeah, I guess they're French.

900
00:42:02,719 --> 00:42:05,280
Speaker 2: They're Dutch and they're American red.

901
00:42:05,640 --> 00:42:09,160
Speaker 1: Right that all of that. Yes, it's multinational. How do

902
00:42:09,239 --> 00:42:10,200
Speaker 1: these galaxies form?

903
00:42:10,560 --> 00:42:12,560
Speaker 2: So this was a real mystery for a long time.

904
00:42:12,719 --> 00:42:15,720
Speaker 2: We didn't even see one of these until like nineteen fifty.

905
00:42:15,719 --> 00:42:18,160
Speaker 2: They're so rare, and I think that these things are

906
00:42:18,200 --> 00:42:22,640
Speaker 2: formed in a really lucky, spectacular collision. Basically, when one

907
00:42:22,680 --> 00:42:26,680
Speaker 2: galaxy passes right through the center of the other one,

908
00:42:27,200 --> 00:42:29,920
Speaker 2: it creates this ring from the shock wave of dense

909
00:42:29,960 --> 00:42:32,560
Speaker 2: gas that's rushing out of that collision.

910
00:42:32,800 --> 00:42:35,719
Speaker 1: You mean like two spiral galaxies or two elliptical galaxies

911
00:42:35,880 --> 00:42:38,759
Speaker 1: just totally just head on crash into each other.

912
00:42:39,120 --> 00:42:42,719
Speaker 2: Yeah, exactly. You have like some galaxy punched right through

913
00:42:42,760 --> 00:42:47,680
Speaker 2: the exact center of another gas rich spiral galaxy. It'll

914
00:42:47,719 --> 00:42:51,600
Speaker 2: create this shock wave in that gas which will create stars.

915
00:42:51,760 --> 00:42:54,040
Speaker 2: And that's why the ring tends to be blue, because

916
00:42:54,040 --> 00:42:58,160
Speaker 2: it tends to be big, fat, young hot stars that

917
00:42:58,200 --> 00:43:01,600
Speaker 2: tend to burn bright. Whoa no judgment?

918
00:43:01,680 --> 00:43:03,319
Speaker 1: Is it's safe for work? Does it safe for work?

919
00:43:04,120 --> 00:43:04,760
Speaker 1: The broadcast?

920
00:43:05,200 --> 00:43:07,720
Speaker 2: I mean hot in a technical temperature sense.

921
00:43:07,880 --> 00:43:09,839
Speaker 1: Right, Well, you just got really excited there.

922
00:43:12,120 --> 00:43:14,759
Speaker 2: I'm excited to see star formation, right. Star formation is

923
00:43:14,800 --> 00:43:17,279
Speaker 2: so exciting. It's like the thing that makes the universe bright.

924
00:43:17,360 --> 00:43:19,480
Speaker 2: It's the reason we can see things in the universe

925
00:43:19,600 --> 00:43:22,759
Speaker 2: is because stars form. It's kind of a miracle almost,

926
00:43:22,920 --> 00:43:25,919
Speaker 2: And so these collisions create a whole ring of new

927
00:43:26,000 --> 00:43:29,880
Speaker 2: stars that are sort of moving out away from the galaxy.

928
00:43:29,640 --> 00:43:32,239
Speaker 1: So that the main stars crash into each other and

929
00:43:32,600 --> 00:43:35,400
Speaker 1: the collision kind of exploded all the gas to the

930
00:43:35,440 --> 00:43:38,920
Speaker 1: outer edge and that's where these new stars are forming.

931
00:43:38,960 --> 00:43:41,000
Speaker 1: But why did it stay in a flat shape?

932
00:43:41,120 --> 00:43:43,799
Speaker 2: Well, the original disc essentially was flat, right, and so

933
00:43:43,840 --> 00:43:47,280
Speaker 2: what happened was created a pressure wave in that flat disc.

934
00:43:47,760 --> 00:43:50,440
Speaker 2: There isn't gas in those other directions to compress. It's

935
00:43:50,440 --> 00:43:52,120
Speaker 2: sort of the same reason that like a ripple moves

936
00:43:52,120 --> 00:43:55,040
Speaker 2: along the surface of the water, you slap the water

937
00:43:55,280 --> 00:43:57,359
Speaker 2: and you get rings on the surface. You don't get

938
00:43:57,440 --> 00:44:00,279
Speaker 2: rings of water like moving up also, and that's sort

939
00:44:00,280 --> 00:44:01,319
Speaker 2: of where the gas is.

940
00:44:01,840 --> 00:44:05,000
Speaker 1: I see. It's like you had a giant disc flat

941
00:44:05,040 --> 00:44:07,560
Speaker 1: pancake and you sort of poked the middle of it

942
00:44:07,600 --> 00:44:10,960
Speaker 1: and it sent the ripple along the pancake exactly.

943
00:44:11,040 --> 00:44:13,200
Speaker 2: And that's what we're seeing. We're like in the middle

944
00:44:13,200 --> 00:44:16,480
Speaker 2: of watching this. So this is a pretty spectacular hypothesis.

945
00:44:16,520 --> 00:44:18,600
Speaker 2: And people thought well, if this is true, then we

946
00:44:18,640 --> 00:44:22,040
Speaker 2: should see like galaxies literally on top of each other,

947
00:44:22,239 --> 00:44:24,160
Speaker 2: and also we should be able to like identify the

948
00:44:24,200 --> 00:44:26,759
Speaker 2: galaxy that caused that ripple. And now we've seen enough

949
00:44:26,760 --> 00:44:28,719
Speaker 2: of these things that you can actually spot that we

950
00:44:28,800 --> 00:44:32,080
Speaker 2: have pictures of ring galaxies where you can tell which

951
00:44:32,080 --> 00:44:35,400
Speaker 2: galaxy has just passed through it, like you know, recently

952
00:44:35,680 --> 00:44:39,000
Speaker 2: on galactic timescales, and we've even seen one where the

953
00:44:39,000 --> 00:44:41,920
Speaker 2: galaxy is in the process of punching right through the

954
00:44:41,920 --> 00:44:43,280
Speaker 2: middle of the other galaxy.

955
00:44:43,600 --> 00:44:46,520
Speaker 1: Well, it's interesting that this is happening not just in

956
00:44:46,560 --> 00:44:48,840
Speaker 1: one place, but like all over the universe.

957
00:44:48,640 --> 00:44:51,520
Speaker 2: Yeah, everywhere. And it turns out that's what the question

958
00:44:51,640 --> 00:44:53,720
Speaker 2: mark galaxy is. It looks kind of like a question

959
00:44:53,800 --> 00:44:56,120
Speaker 2: mark because we're seeing one galaxy which is a spiral,

960
00:44:56,160 --> 00:44:58,400
Speaker 2: and then there's another galaxy which is on edge so

961
00:44:58,400 --> 00:45:01,040
Speaker 2: it looks like a line, and it's passing right through

962
00:45:01,080 --> 00:45:03,239
Speaker 2: the middle of it. So you get this combination of

963
00:45:03,280 --> 00:45:06,320
Speaker 2: two galaxies forming a question mark, and in a million

964
00:45:06,440 --> 00:45:09,040
Speaker 2: years or so, the one that's being hit is going

965
00:45:09,080 --> 00:45:10,600
Speaker 2: to turn into a ring galaxy.

966
00:45:10,800 --> 00:45:13,040
Speaker 1: Wait, wait, how does how does a question mark form.

967
00:45:12,920 --> 00:45:14,560
Speaker 2: Save one which is a disc and you can sort

968
00:45:14,560 --> 00:45:16,480
Speaker 2: of see the arms of it, and that's sort of

969
00:45:16,560 --> 00:45:19,160
Speaker 2: the round part of the question mark. This is so

970
00:45:19,239 --> 00:45:21,400
Speaker 2: difficult to do over audio. And then the line part

971
00:45:21,440 --> 00:45:23,919
Speaker 2: of the question mark is another galaxy, but we're only

972
00:45:23,920 --> 00:45:26,000
Speaker 2: seeing it on edge, so it looks like a line

973
00:45:26,080 --> 00:45:28,520
Speaker 2: instead of a circle. So instead of looking like a

974
00:45:28,560 --> 00:45:30,839
Speaker 2: figure eight, it looks like a figure eight, but one

975
00:45:30,840 --> 00:45:32,840
Speaker 2: of them has been twisted down, so it's like a

976
00:45:32,880 --> 00:45:34,480
Speaker 2: circle and a line combined.

977
00:45:35,480 --> 00:45:40,319
Speaker 1: Complicated, Yes, it's complicated. I think we're a galaxy question mark.

978
00:45:42,440 --> 00:45:44,959
Speaker 2: I think we're supposed to merge into something question mark.

979
00:45:45,000 --> 00:45:47,200
Speaker 1: I don't know. Yeah, maybe it just.

980
00:45:47,080 --> 00:45:49,480
Speaker 2: Goes to show you there's questions everywhere in the universe

981
00:45:49,760 --> 00:45:51,360
Speaker 2: literally literally.

982
00:45:51,719 --> 00:45:55,120
Speaker 1: Yeah, all right, Well, what does this all tell us about,

983
00:45:55,920 --> 00:45:58,040
Speaker 1: like the Bilky Way and why we're here and is

984
00:45:58,080 --> 00:46:00,800
Speaker 1: it weird that we're here or are we a pretty

985
00:46:00,840 --> 00:46:01,760
Speaker 1: typical galaxy?

986
00:46:02,000 --> 00:46:04,279
Speaker 2: So we're a pretty typical galaxy. We're not one of

987
00:46:04,280 --> 00:46:06,600
Speaker 2: the biggest galaxies, we're not one of the smallest galaxies.

988
00:46:06,640 --> 00:46:08,920
Speaker 2: We have one of the most common types of galaxies

989
00:46:08,920 --> 00:46:11,440
Speaker 2: in the universe. But it also tells us that we

990
00:46:11,520 --> 00:46:14,840
Speaker 2: contain multitudes. You know that the Milky Way has lots

991
00:46:14,840 --> 00:46:17,640
Speaker 2: of little baby galaxies inside of it. Some of the

992
00:46:17,719 --> 00:46:19,880
Speaker 2: reasons we have stars that are not in the disc

993
00:46:20,120 --> 00:46:22,560
Speaker 2: that like orbit above the disc or whatever, are from

994
00:46:22,600 --> 00:46:26,600
Speaker 2: those collisions, stars that survive those collisions of galaxies and

995
00:46:26,640 --> 00:46:30,480
Speaker 2: are still hanging out orbiting in their original galactic plane.

996
00:46:30,640 --> 00:46:33,040
Speaker 2: And when we look at the distribution of galaxies, all

997
00:46:33,040 --> 00:46:35,720
Speaker 2: the different shapes, it forces us to tell this story,

998
00:46:35,719 --> 00:46:38,400
Speaker 2: to explain everything we see, and to play detective and

999
00:46:38,400 --> 00:46:41,040
Speaker 2: to understand, like what happened in the early universe, how

1000
00:46:41,080 --> 00:46:43,840
Speaker 2: did we get here from the big blob of gas

1001
00:46:44,000 --> 00:46:46,680
Speaker 2: from the Big Bang? And it helps us unravel, you know,

1002
00:46:46,719 --> 00:46:49,480
Speaker 2: the whole history of the universe and also to think

1003
00:46:49,520 --> 00:46:50,280
Speaker 2: about its future.

1004
00:46:50,760 --> 00:46:52,399
Speaker 1: But it sort of seems like in terms of shape,

1005
00:46:52,400 --> 00:46:55,279
Speaker 1: there's really only one shape, which is the sort of

1006
00:46:55,320 --> 00:46:57,239
Speaker 1: like the spiral, and then the other shapes you get

1007
00:46:57,280 --> 00:46:59,920
Speaker 1: them by combining spirals together, so it's more like a

1008
00:47:00,120 --> 00:47:02,759
Speaker 1: sequential category of galaxies.

1009
00:47:02,920 --> 00:47:05,400
Speaker 2: Yeah, to use your analogy, it's like the spirals are

1010
00:47:05,440 --> 00:47:07,839
Speaker 2: atoms and everything else is like a molecule built out

1011
00:47:07,880 --> 00:47:09,200
Speaker 2: of those atoms.

1012
00:47:09,120 --> 00:47:12,279
Speaker 1: And those other shapes only sort of happen if two galaxies.

1013
00:47:11,760 --> 00:47:14,320
Speaker 2: Collide, exactly a cloud of gas will form a spiral

1014
00:47:14,360 --> 00:47:16,560
Speaker 2: galaxy if left on its own, and the other ones

1015
00:47:16,680 --> 00:47:18,840
Speaker 2: need combinations of spiral galaxies.

1016
00:47:19,000 --> 00:47:21,040
Speaker 1: And it also sounds sort of like the future is

1017
00:47:21,040 --> 00:47:23,640
Speaker 1: a little bit unknown, right, like we're maybe not sure

1018
00:47:23,840 --> 00:47:27,440
Speaker 1: what eventual shape things are going to take in the future.

1019
00:47:27,560 --> 00:47:30,520
Speaker 2: Yeah, our galaxy and will collide with Andromeda, and whether

1020
00:47:30,560 --> 00:47:33,760
Speaker 2: we form a new spiral galaxy along that plane depends

1021
00:47:33,800 --> 00:47:36,360
Speaker 2: how much gas is left. We know that Andromeda is

1022
00:47:36,400 --> 00:47:38,600
Speaker 2: already starting to quench, and we think that the Milky

1023
00:47:38,600 --> 00:47:40,960
Speaker 2: Way is quenching, which might mean that we don't have

1024
00:47:41,120 --> 00:47:43,839
Speaker 2: enough gas to make a new spiral galaxy. It might

1025
00:47:43,880 --> 00:47:46,359
Speaker 2: mean we end up with a big elliptical blob.

1026
00:47:46,280 --> 00:47:48,040
Speaker 1: Or we win end up with a galaxy.

1027
00:47:49,719 --> 00:47:54,720
Speaker 2: Maybe from some point of view, just before Andromeda plummets

1028
00:47:54,760 --> 00:47:56,640
Speaker 2: into the heart of the Milky Way, you might be

1029
00:47:56,680 --> 00:47:57,919
Speaker 2: able to make us do a question.

1030
00:47:58,000 --> 00:48:00,279
Speaker 1: Mark. Well, here's the question, Daniel. If our galls she's

1031
00:48:00,280 --> 00:48:03,320
Speaker 1: called the Milky Way and there's chocolate in our galaxy,

1032
00:48:03,440 --> 00:48:05,120
Speaker 1: isn't all chocolate then milk chocolate?

1033
00:48:05,800 --> 00:48:11,480
Speaker 2: No, you're ruining chocolate for me, man, I'm going to

1034
00:48:11,560 --> 00:48:13,799
Speaker 2: have to look forward to importing chocolate from Andromeda.

1035
00:48:13,880 --> 00:48:16,440
Speaker 1: There you go. Should have just said no way man.

1036
00:48:16,840 --> 00:48:19,960
Speaker 1: All right, well, an interesting view into the cosmos and

1037
00:48:20,000 --> 00:48:22,200
Speaker 1: all the different things that can happen out there, and

1038
00:48:23,040 --> 00:48:27,320
Speaker 1: another interesting reminder that the universe is still evolving, still changing.

1039
00:48:27,320 --> 00:48:30,680
Speaker 1: Things are colliding, things are changing shapes, things are asking

1040
00:48:30,800 --> 00:48:33,920
Speaker 1: questions of themselves. It's an ever changing universe.

1041
00:48:33,560 --> 00:48:35,880
Speaker 2: And the past is contained in the present. If we

1042
00:48:35,920 --> 00:48:38,680
Speaker 2: can dig into it deep enough and think hard about

1043
00:48:38,880 --> 00:48:41,280
Speaker 2: the rules at play, we can figure out what happened

1044
00:48:41,320 --> 00:48:42,000
Speaker 2: in the universe.

1045
00:48:42,400 --> 00:48:44,640
Speaker 1: That's right, sort of like how the white chocolate contains

1046
00:48:44,680 --> 00:48:47,560
Speaker 1: cocoa butter, which is technically makes.

1047
00:48:47,400 --> 00:48:50,360
Speaker 2: It chocolate and you should only eat it at state

1048
00:48:50,400 --> 00:48:51,600
Speaker 2: fairs deep.

1049
00:48:51,320 --> 00:48:53,960
Speaker 1: Fried, that's right, or in a desert island.

1050
00:48:55,280 --> 00:48:57,080
Speaker 2: Only crack open in case of emergency.

1051
00:48:57,160 --> 00:48:59,080
Speaker 1: All right, well, we hope you enjoyed that. Thanks for

1052
00:48:59,160 --> 00:49:01,000
Speaker 1: joining us. See you next time.

1053
00:49:05,800 --> 00:49:08,680
Speaker 2: For more science and curiosity, come find us on social

1054
00:49:08,719 --> 00:49:12,640
Speaker 2: media where we answer questions and post videos. We're on Twitter,

1055
00:49:12,760 --> 00:49:16,120
Speaker 2: disc Word, Insta, and now TikTok. Thanks for listening, and

1056
00:49:16,160 --> 00:49:18,880
Speaker 2: remember that Daniel and Jorge Explain the Universe is a

1057
00:49:18,920 --> 00:49:23,480
Speaker 2: production of iHeartRadio. For more podcasts from iHeartRadio, visit the

1058
00:49:23,600 --> 00:49:27,719
Speaker 2: iHeartRadio app Apple podcasts, or wherever you listen to your

1059
00:49:27,800 --> 00:49:28,560
Speaker 2: favorite shows.