Speaker 1: Welcome to Stuff from the Science Lab from how stuff
Speaker 1: works dot com. Hey guys, and welcome to the podcast.
Speaker 1: This is Alice Madam, science how stuff works dot com.
Speaker 1: And this is Robert Lamb, science writer at how stuff
Speaker 1: works dot com. Today we're doing the third podcast in
Speaker 1: our very first recurring series, and that series has been
Speaker 1: looking at how different celestial bodies get their start. Today
Speaker 1: we're talking about galaxies. If I had to listen to
Speaker 1: the series, I would start with galaxies, then go to stars,
Speaker 1: and then listen to planets, just for heads up if
Speaker 1: you haven't heard any of them. Okay, but not because
Speaker 1: of preference, right, because no, just because because one thing
Speaker 1: that occurred to me when I was actually writing our
Speaker 1: article about that galaxy formation is that this one, I
Speaker 1: think is often overlooked because like the formation of the universe,
Speaker 1: like that, like the Big Bang, like that's so huge
Speaker 1: and mind boggling that you instantly think of that, and
Speaker 1: then things like the formation of a planet or the
Speaker 1: solar system that's a lot closer to home and you
Speaker 1: can relate to that a little better. But a galaxy
Speaker 1: that's just kind of somewhere in between. It's not Yeah,
Speaker 1: I mean, it's enormous. It's on such an enormous scale,
Speaker 1: but not on such a just mind boggling cosmic scale
Speaker 1: that people set around and I think, ponderate unless you're
Speaker 1: you know, like actually a cosmologist or after physicist. So
Speaker 1: we have to back up to the Big Bang. But
Speaker 1: we're not going to get into the Big Bang. Um.
Speaker 1: So it is a galaxy. A galaxy, Well, it is
Speaker 1: the largest structure in the universe, and it binds billions
Speaker 1: or even trillions of stars together in a big gravitational yoke.
Speaker 1: What else is in galaxies besides stars? Well, you've got
Speaker 1: planets yep, yeah, cats, dog, Well that's on the smaller scale.
Speaker 1: But no, you've got cosmic dust, vast clouds of gas, um,
Speaker 1: you know, comets, like every thing really if you can
Speaker 1: name it, it's in the galaxy, including dark matter, yes,
Speaker 1: dark matter, dark energy, all that good stuff. So let's
Speaker 1: rewind roughly fourteen billion years ago, two win galaxies got
Speaker 1: their start. Yeah, back to the Big Bang, which is
Speaker 1: our best theory about how all this came about. And
Speaker 1: I like to think of and this is a this
Speaker 1: is a very basic analogy, but I like to think
Speaker 1: that this way. Imagine you have a map of the
Speaker 1: universe right spread out on a table. Yes, now, no, now,
Speaker 1: imagine the entire map like wadded up into a single
Speaker 1: ball of paper. But a ball of paper like just
Speaker 1: microscopic and size, you know, just ridiculously small. Yeah. I've
Speaker 1: come across a different a few different estimations of how
Speaker 1: big or how small via that singularity was. Some people
Speaker 1: say it's about the size of a dime. Other people
Speaker 1: say it's smaller than an electron. Yeah, yeah, you see it.
Speaker 1: See size estimation is bearing. But whatever the exact size,
Speaker 1: a whole lot, like everything, the entire universe crunched down
Speaker 1: to one unimaginably small because whether we're talking about the
Speaker 1: size of a quarter or the size of a basketball
Speaker 1: or the size of an atom. Um that's a lot
Speaker 1: of universe packed into one god stopper. And then it
Speaker 1: then it expands and yeah, and you have hot matter,
Speaker 1: it ends up cooling. But but nothing has there's not
Speaker 1: really any structure. It's not like wham, now we have
Speaker 1: you know, galaxies and planets, etcetera. You just have a
Speaker 1: lot of like it's like raw uncooked galaxy. No not,
Speaker 1: I mean raw uncooked universe out there. Yeah, you have
Speaker 1: the ingredients. You just have a lot of gas, a
Speaker 1: lot of dust just floating out there. So how those
Speaker 1: ingredients evolve in somewhere than a hundred billion galaxies. Well,
Speaker 1: there are two bodies of theories according to NASA about
Speaker 1: how this came about, all right. There are bottom up
Speaker 1: theories and they're top down theories, and this sort of
Speaker 1: sounds like what they are. Yeah, you know, it's it's
Speaker 1: kind of like in a bottom up theory, the gas,
Speaker 1: all this gas and dust collapses and compresses into a
Speaker 1: clump about the size of a million sons. And that's
Speaker 1: that's starting small for something that's gonna become, you know, galaxies.
Speaker 1: All right. These clumps then merge to build galaxies. All right.
Speaker 1: Again bottom up, and as we touched onto some previous podcasts,
Speaker 1: this is acretion. This is the process of little particles
Speaker 1: coming together forming slightly larger particles which then have a
Speaker 1: gravitational pull on other particles. It's like a snowball going
Speaker 1: down a hill. Right. If you're listening to these podcasts,
Speaker 1: there's definitely a theme of acretion running through all of them. Yeah.
Speaker 1: So yeah, this one is just that the gas collapse
Speaker 1: into enormous but cosmically small clumps which then end up
Speaker 1: forming larger clumps which become galaxies. And then you have
Speaker 1: your top down theories, which of course start big. And
Speaker 1: the school of thought is going to argue that the
Speaker 1: resulting clumps were each of us of multiple galaxies, and
Speaker 1: then the size got too big to manage, and they
Speaker 1: broke down into our individual galaxy, like the Milky Way galaxy.
Speaker 1: And if you follow this train of thought, then you
Speaker 1: get an understanding of why galaxies occur in clusters, but
Speaker 1: either way bottom up, top down. The resulting clumps then
Speaker 1: collapsed into proto galaxies, which consisted of dark matter and
Speaker 1: hydrogen gas. Yeah, and then the hydrogen then falls to
Speaker 1: the center of the proto galaxy, wanted the dark matter
Speaker 1: remains as an outer halo surrounding everything. You know. When
Speaker 1: we're researching this podcast, it came across another interesting theory,
Speaker 1: that of hierarchical formation, in which merging of established galaxies
Speaker 1: occurs too, And so the story on it was this.
Speaker 1: Researchers from University of Switzerland saw some merging galaxies in
Speaker 1: a group dubed s g oh Dash one two, which
Speaker 1: is a very sexy name for those galaxies. Right, and
Speaker 1: roughly four billion light years away, and they reported their
Speaker 1: findings in the August two thousand eight issue of the
Speaker 1: Astrophysical Journal Letters. Have you read that, lady, Robert so Um,
Speaker 1: they were saying that smaller galaxies were destined for one
Speaker 1: another courtesy of the mutual gravitational attraction, and then they
Speaker 1: formed these massive galaxies. Okay, so that was that was
Speaker 1: their take on it, and their theory also stipulated that
Speaker 1: star formation would primarily occur when galaxies were small, but
Speaker 1: they would gather all their mass during the mergers. But
Speaker 1: we'll get to star formation in the second. So astronomers
Speaker 1: recognized to basic shapes for galaxies. There's elliptical and then
Speaker 1: their spiral and we're spiral galaxies, but we're technically a
Speaker 1: spiral bar galaxy. Yeah right, a lot of them are
Speaker 1: actually yeah, well the spiral galaxies are essentially we're spiral galaxy.
Speaker 1: And you also have you disorganized galaxies, which are kind
Speaker 1: of my favorite. Which, um, if you think about two
Speaker 1: galaxies merging, um, maybe when they first merged, they they're
Speaker 1: disorganized and then they sort themselves out into their neat
Speaker 1: spiral shape for their elliptical shape, but who knows, they're
Speaker 1: not sure of that. And then there's a third type
Speaker 1: of galaxy, UM, the disorganized galaxy, which you have to
Speaker 1: kind of identify with this kind of galaxy, right, um,
Speaker 1: that disorganized but no, no, no no, that was not a
Speaker 1: personal rabbert. Although are you disorganized? No, just I'm organized,
Speaker 1: but in a disorganized fashion at times. Depends on what
Speaker 1: I'm doing. Well, they say, the people who have very
Speaker 1: organized deaths have too much time in their hands, right yeah.
Speaker 1: And then some people don't don't decorate their offices at all,
Speaker 1: or their cubicles. That's just I don't know if that's
Speaker 1: not being if that's being really organized, or that's just
Speaker 1: being lame. I know somebody at work who had decorated
Speaker 1: their cubicle and then took it down in protest when
Speaker 1: she had a bad day one day, and she never
Speaker 1: put it back up. I don't think it's an odd
Speaker 1: form of protests. It didn't convey anything to me. Attachment detachment.
Speaker 1: I think say these UM, so you have your your spirals,
Speaker 1: you have your ellipticals, and then UM, at least initially,
Speaker 1: emerged galaxies might not like these two main shapes. They
Speaker 1: might be disorganized, but eventually astronomers believe that the merge
Speaker 1: galaxies result in an elliptical galaxy. As such, our Milky
Speaker 1: Way has probably never emerged with another galaxy, because again
Speaker 1: it's that's hard spiral shape. But the massive elliptical galaxies
Speaker 1: found at the center of galaxy clusters are probably the
Speaker 1: result of some serious cosmic mashups. Yeah, it's just it's
Speaker 1: almost it's kind of like accretion on a huge scale,
Speaker 1: with just galaxies running into each other, just becoming this big,
Speaker 1: enormous thing. But the interesting thing that I was reading
Speaker 1: about is just because two galaxies passed close by, they
Speaker 1: don't have to merge, they don't have to make this
Speaker 1: one big galactic family. Rapidly moving ones I read can
Speaker 1: pass through one another, sort of like ghosts almost, but
Speaker 1: the slower moving ones seemed to be likely to get
Speaker 1: all up in each other's business and merge. Something to
Speaker 1: keep in mind when we went eventually merged with Andromeda. Right, indeed,
Speaker 1: so let's about star formation and the elliptical and spiral galaxies. Okay,
Speaker 1: how does that figure in? All? Right? Well, stars develop
Speaker 1: inside a proto galaxy when the cloud, when the clouds
Speaker 1: of gas mix and collide, so of all the stars
Speaker 1: in a proto galaxy form at once, and the mature
Speaker 1: galaxy essentially retains the roundest shape of the proto galaxy
Speaker 1: and becomes an elliptical galaxy. Spiral galaxies, however, occur when
Speaker 1: the stars inside the proto galaxy or as at different intervals,
Speaker 1: so you know, they're not popping up all at once,
Speaker 1: They're happening at different times, and the gas between the
Speaker 1: developing stars continues to collapse, and the resulting gravitational differences
Speaker 1: manhandle the proto galaxy stars, the dust, and the gas.
Speaker 1: What do you know? This motion starts to force everything
Speaker 1: into a rotating disk, and additional differences in gravity result
Speaker 1: in the spiral arms. It's kind of like when I
Speaker 1: was trying to make sense of this, I thought of
Speaker 1: it in terms of, like imagine like with an elliptical galaxy,
Speaker 1: Like imagine a town where everybody's the same age, you know,
Speaker 1: only like everybody's like thirty five, so you only have
Speaker 1: the kind of places thirty five year olds hang out,
Speaker 1: like no, you know, no place where like teenagers roll
Speaker 1: or where it's one of those over fifty communities. That's
Speaker 1: what it is. Yeah, Yeah, that kind of thing whereas
Speaker 1: elliptical has would like an elliptical galaxy is like a
Speaker 1: town where you have guys of all ages with his
Speaker 1: diversity and conflict spinning everything around, so much more interesting
Speaker 1: place to live if you're into that. Yeah, so that's
Speaker 1: my convoluted analogy of the day. Did you know that
Speaker 1: the Milky Way galaxy is rotating and will complete a
Speaker 1: revolution in two fifty million years, like a galactic year?
Speaker 1: That would be okay, Yeah, it's a lot longer than
Speaker 1: one of those restaurants that rotates at the top of
Speaker 1: the hotel will market on the calendar. Put them in
Speaker 1: Google calendar alert. Galactic year just finished. Well, said Robert.
Speaker 1: So that was kind of a light intro to galaxy formation.
Speaker 1: If you guys want to hear more about the mechanics
Speaker 1: of galaxy formation or get deeper into the topic, send
Speaker 1: us an email at science Stuff at hows to first
Speaker 1: dot com and we'll see what we can do. For instance,
Speaker 1: like bottom up theories, there are a number of bottom
Speaker 1: up theories. There are a number of top down theories,
Speaker 1: but they're a number of steps. Yeah, and but these
Speaker 1: are the basics, and obviously there's a lot of formation
Speaker 1: that continues um, you know at lower levels within the galaxy,
Speaker 1: which we've touched down on in uh in other podcasts. Yeah,
Speaker 1: as always, you can take galaxies into the search part
Speaker 1: on how Stuff Works homepage and see what good stuff
Speaker 1: that brings up. They're gonna see how galaxies work. Maybe
Speaker 1: whether space has a shape? This is a good one.
Speaker 1: Is there a hole in space? That's another one that
Speaker 1: we have, Yeah, or the big bank very written by Strickland.
Speaker 1: But I think you did a good job. Hey, and
Speaker 1: we also have a Facebook and a Twitter account now,
Speaker 1: so um you can check those out. Just to search
Speaker 1: for stuff in the science lab or lab stuff on
Speaker 1: Twitter on Twitter or Facebook and then lead you right
Speaker 1: to us, and uh we update that thing pretty pretty regularly.
Speaker 1: Come see what science the topics we're thinking about this week.
Speaker 1: So that's all the galactic goodness we have for you
Speaker 1: guys today. Thanks for listening. For more on this and
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