October 1, 2020 • 43 mins
Daniel and Jorge talk about a new massive blob of galaxies discovered right around the corner.
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Speaker 1 (00:08):
Hey, or hey, do you know what our cosmic addresses? Yeah,
it's a one universe lane, isn't it. Well, that's where
you can send us all your gifts of presence and bananas.
I mean, that's how the aliens know where to find,
is right, that's true. But I actually don't need a
lot of bananas delivered in the mail, So let's not
encourage people to send us any fresh fruit. No, no,
I think you know what you mean, Like our address
(00:29):
like in the universe, Like if we're here on Earth
around our star about halfway down the Milky Way. Yeah,
that's enough to get your mail delivered to your house.
But like, what about the rest of our cosmic context?
I mean, like what's the equivalent of our city or
zip code? Yeah, And it turns out that we're part
of a cluster called the Local Group sounds local, and
(00:50):
then zooming out a little bit where the suburbs of
an even bigger cluster called Virga, and then part of
a super cluster of a hundred thousand galaxies called Lena Kia.
And then you know, that's actually about as far as
we've mapped. Wait, we don't know where we live exactly
in the universe. We don't know, So if you want
to order alien bananas, you just gotta put a question mark.
(01:12):
Gonna throw up a flare. I am more handy cartoonists
and the creator of PhD comics. Hi, I'm Daniel. I'm
(01:33):
a particle physicist, and I don't like Earth bananas, but
I'd be willing to try alien bananas. Really, how do
you know they're not going to be worse? You don't know.
But that's the joy of exploration. I want to land
on a new planet, to see the new kinds of life,
the new kinds of animals and critters, and taste any
new potentially delicious fruits. Well, you're welcome to be humanity's taste.
(01:55):
I guess to make sure it's all right, somebody's gotta
do it. I'll probably come down with the alien banana flu.
But welcome to our podcast Daniel and Jorge Explain the Universe,
a production of My Heart Radio in which we don't
take any actual trips out into the universe, but a
mental journey through all the amazing questions and discoveries, all
the things science has figured out and the things that
(02:18):
science is still working on. We think that curiosity belongs
to everybody, and that you are questions are as fascinating
and as important as those that scientists are working on
right now. Yeah, because it is a huge universe out there,
with a lot of places to explore and a lot
of things to discover, and a big question is how
do we fit into all of this? What is our
(02:40):
place in the universe? And how do we fit into
this giant cosmic ballet of stars and galaxies and dust.
And it's sort of an extension of exploration that humans
have been doing basically forever, since we wondered what was
over that hill, what's past that mountain, what's over that ocean?
And modern day explorers might wonder like, well, is there
(03:02):
anything left for me to look for? Thanks to Google
Earth and satellite technology, we basically know where all the
mountains are and all the little islands you can name
after your chihuahua. But it turns out there's a lot
of exploration left to do. Yeah, is there an equivalent
of Google Universe? Google? Get on it now. Yet it's
mostly a big question mark. But you can look at
(03:24):
maps of our cosmic neighborhood to see what's around us,
what's nearby? If you just google large scale structures of
the universe. Wow, does it tell you how much each
galaxy is worth? Can you figure out the perse square
light here value? You know, even just our solar system
is worth like a gazillion dollars because of all the
platinum and gold and stuff that you can find in aster.
(03:46):
So it's basically just infinite. Well, we are still learning
about the basics of where we are in the universe
and what's kind of around is and so a big
question is, you know, what can we find? What interesting
things are there in our very own neighborhood here in
the universe, And it's not something that we can easily
explore in person. In the old days of exploration, you
(04:08):
would hop in a ship and you would land on
foreign shores and you would wonder who else was living
there and what kind of fruits did they enjoy. But
these days it's not so easy. The distances are vast,
the technology is still so primitive. But we have other
ways of exploring the universe. You mean, we don't have
those warp drives and teleportation devices yet. Well, you know,
I sent them to the Daniel and Jorge Engineering department.
(04:29):
So I'm just waiting for the prototype to come back
last engineer in our team here. But yeah, you're right,
it is kind of interesting that we have to explore
the universe from here. From Earth using telescopes, we can
actually like go out that far because some of the
things that we can see are hundreds or millions of
light years away, like the pretty much we might never
(04:52):
see them in person. That's right, most of these things
we will never see in person. And most of these
things that we're looking at, they don't exist right now
on the way that we are seeing them, right, we
are seeing old light that comes to us from them.
So what's actually happening now out there is not what
we are seeing. Yeah, So astronomers are out there looking
(05:12):
and exploring and checking out what's around us, and recently
there's been an incredible discovery. Just this past summer, astronomers
discovered a whole new thing pretty close to our corner
of the universe here, and it's huge. It's basically the
biggest thing anybody has ever found, and it's shockingly large
(05:33):
and shockingly close. It's basically a literal mind exploder. So
today on the podcast, we'll be asking the question what
is the South Pole Wall and why did they give
it such a ridiculous name south? But yeah, it's a
little confusing because is it a pole or is it
(05:53):
a wall? Is it a wall of poles? Is it
a wall around the South Pole? I guess it's south,
but south relative to who, Well, you have a very
northern bias, right, You tend to view the earth is up,
north is up, and so you know, maybe that gives
you a clue. I was born in the equator, so, Daniel,
I'm pretty agnasting. I think maybe this time you can
(06:14):
rag on after physicists and how they name things, and
as particle physicists can get a break for a weekend
for once. Yeah, and also, who's paying for this wallt Daniel?
The Aliens are definitely paying for the wall, yeah, with
the tariffs. But yeah, so they discovered something huge and enormous.
I mean, it's like you said, it's the biggest thing
(06:35):
pretty much ever discovered. Is that true. Yeah, it's in
the top five biggest things we know about in the universe,
and of the top five, it's the closest one. So
it's really kind of amazing that we haven't seen this before,
that we didn't even know about it before. It really
it makes me feel like, you know, cartographers in the
fifteen hundreds drawing maps to the Earth and like leaving
(06:58):
out America. You know, like how could to be so
ignorant of like an enormous continent that's honestly not that
far away. It'd be like discovering a whole wall of
poles in your backyard and you're like, where did that
come from? That's right, I didn't order this online. Yeah,
so it's a new discovery. It's huge, it's very close.
(07:18):
But we're wondering how many people out there know about
this south Pole Wall and whether it was discovered recently. So,
as usual, Daniel went out there and ask people on
the internet if they knew what is the south Pole Wall?
So thanks to everybody who volunteered to share their baseless
and uninformed speculation with us for our podcast. And if
(07:39):
you would like to be a victim War Future podcast
to share your unprepared thoughts on difficult questions in physics,
please write to us two questions at Daniel and Jorge
dot com. Think about it for a second. Do you
know what the south Pole Wall is? Here's what people
had to say. Does that have something to do with
flat earther theory, it's all a man made will but
(08:00):
around South Pole to stop animals or in shooters from
coming in as a way to preserve this out pole.
Maybe it's some sort of electromagnetic barrier, not just an
obvious structure, something to do with like a magnetic like
the Earth's magnetic field, some sort of barrier for particles
(08:22):
in the sun from the sun. Maybe it's related somehow
to the like Aurora borealis and southern lights. The South
Pole Wall is a ice fault formation that is incredibly
difficult to traverse on foot or sled or with dogs.
(08:46):
I have no idea. I am guessing that it is
a wall, either physical or metaphorical, located in the South Pole.
The first thing that comes into mind is a big
rule of ice in the South Pole, like the one
phone Game of Thrones. I'm not sure, but I believe
there are some I don't know if they're called caverns
(09:06):
or cliffs or something like that, but I believe there's
some impediment in our way to get to the uh,
to travel freely to the South Pole where the ice
is all right. It sounds like nobody knew well. I
think this is a real commentary on the name of
this thing, right, because everybody keyed in on south Pole
and wall, right, And I like how somebody said it
(09:29):
was like Game of Thrones, although that wall wasn't the North.
That's right, Maybe it's the equivalent. Maybe it's for like
the penguin zombie. Well, we physicists, we do like having
symmetry in the universe. So if there's going to be
a wall in the north, there should be a wall
in the south, because otherwise you gotta ask why what's
special about North? Right? Yeah, winter is coming? Is there
(09:49):
another version of our universe out there in the multiverse
in which summer is coming? Well, technically, if it's a
south Pole wall, it would come in our summer, which
is winter for them. The beauty and power of symmetry
once again displayed. But I guess maybe the takeaway here
is that not a lot of people had heard of it,
which means it didn't make the news that much. Maybe
(10:10):
that's right. Most of our listeners are pretty up on
the cosmic news here. Yeah, I think it just didn't
fall into people's brains. It's an incredible discovery. It's something
that's fascinating and something it tells us about where we
live in the universe, but it doesn't really actually change
your day to day life. So maybe people just heard
about it and filed it away. But honestly, I think
(10:30):
we should pin most of the blame on the name
of this thing. Wow, I can't disagree with you more,
Daniel about the naming of things. Finally we're agreeing about
how the name. All right, let's let's not keep people
in suspense here. So what is the South Pole Wall, Daniel?
And when was it discovered? So? The South Pole Wall
is an incredibly huge and immensely vast, gargantuan wall of galaxies.
(10:56):
I remember that galaxies are not just sprinkled everywhere through space.
Our Earth goes around our Sun, which is the core
of our solar system, which is one of many solar
systems in our galaxy. But those galaxies are not just
everywhere in space, sprinkled randomly. They tend to clump together
into clusters of galaxies, and those clusters of galaxies form
(11:18):
structures we call superclusters. And then those superclusters are not
just sprinkled everywhere. They tend to form these enormous structures,
these walls, these filaments, these sheets that surround incredible voids
in which there are no stars, no galaxies, no planets,
no people, no podcasts. Yeah, it's weird to think of
space being not random, you know what I mean, Like
(11:41):
we're just still looking at the nights guy and seeing
stars kind of sprinkled kind of randomly and evenly. But
actually the universe has a lot of structure, like, it
has a lot of things in it, Like everything's kind
of organized in the way. That's right, Things are organized,
and it's gravity that's doing the organizing. Gravity is very
gently but very gradually pulling things together and clumping them.
(12:04):
And it's kind of incredible that gravity is the thing
doing this job. Because of all the forces we are
aware of, the strong force, the weak force, electromagnetism, gravity,
Gravity is the weakest, and not by a little bit,
but like by tens of orders of magnitude. But it's
also the only one that can't be like balanced out.
(12:25):
Electromagnetism can be neutralized with positive and negative forces, but
gravity always pulls. It can't push, so eventually everything else
gets balanced out. Is just gravity left over to sweep
stuff together into stars and planets and galaxies and superclusters.
And then these incredibly immense voids and walls and filaments.
(12:45):
And that's essentially where the exploration is today, is figuring
out like where is our cluster and our supercluster in
this larger structure, what's around us? Right? Yeah, And what's
kind of cool too is that these giants, you know,
super ginormous structures, they're all kind of evidence of the
quantum fluctuations right at the very beginning of the universe. Right,
(13:08):
there's sort of like the wrinkles or the fingerprints of
quantum randomness and structure that was in the early universe.
That's exactly right. Gravity has essentially just exaggerated initial little
over densities. If you had only gravity in the universe
was totally smooth, you wouldn't get any sort of structure
at all, because gravity would pull equally on everything in
(13:30):
all directions, and you wouldn't get any clumping. You need
some sort of initial clumping to get things started and
form this runaway effect where gravity makes things heavier and
then pulls harder, and then makes things heavier which pulls harder.
And you're right in the very beginning what this comes from,
our little tiny quantum fluctuations in the very first moments
of the universe, and basically everything's been derivative from that.
(13:54):
It's like we had one idea very early on sketch
the doodle, and everything else is just derived from that.
And it's amazing. Do you think that you can go
from like a quantum fluctuation is something that huge sort
of like you know, like a little baby scar that
you had as a baby, you still have it as
an adult. And let's give people a sense for like
how big we're talking about. These structures are like billions
(14:17):
of light years wide. These are not little things. There's
not like one galaxy, two galaxies. Remember each galaxy already
is an incredibly enormous thing. But we're talking about bubbles
and sheets that are billions of light years on a side,
and that all comes from tiny quantum fluctuations expanded rapidly
during inflation. Yeah, because you know, I guess like one
(14:40):
galzi is a hundred thousand light years, and so if
you put like thousands of them together, then it's literally
billions of light years. It's billions of light years, meaning
if you're going at the speed of light, it still
takes you a billion years to go from one side
to the other. And so you can imagine the whole
universe is sort of like a big pile of bubbles,
like a big quantum foam that was inflated from the
(15:01):
early universe to this incredibly vast quantum foam. And we've
recently discovered that we're essentially living on the edge of
one of those bubbles. And we're now looking around us.
We're like, oh, look, there's a bubble over there. There's
a bubble over there. But we're really just beginning to
map the universe to understand what is our cosmic neighborhood.
(15:21):
We're seeing edges of bubbles here and bubbles merging over there,
and so it's like it's early days, you know, we
have only just begun to explore. Yeah, and so tell
me about this wall that we just found. This wall,
the South Pole wall. You said it's a ginormous. When
you say ginormous, is that the technical term or is
there a number associated? The technical term actually is huge jungis.
(15:43):
But this one is a billion and a half light
years wide. Right, So you shoot a photon, you press
the button on your laser on one side of the thing.
You wait a billion and a half years before across
it to the other side. And that's only the part
of it that we've seen so far. It could go
on more. Yeah, astronomers are not even sure that we've
(16:04):
seen all of it. So it's a structure of galaxies basically. Right,
it's not like a row of stars. It's like a
row of galaxies and they're all sort of like sprinkled
in a wall or or what's going on. That's right,
it's actually a row of clusters of galaxies. Clusters of
galaxies are grouped together. They're gravitationally bound. There there's enough
(16:26):
gravity between galaxies to sort of hold them together into objects.
That's why we call them a cluster. We don't just
like artificially draw a line and say this is a cluster,
that's a cluster. We look for things that are holding
themselves together gravitationally. So this is a wall of clusters
of galaxies, and we call it a wall because it's
much wider and longer than it is thick, sort of
(16:47):
like our galaxy. Right, our galaxy is flat, it's like
a hundred thousand light years across and a thousand light
years thick, and these things have sort of similar dimensions.
There are much much wider and longer than they are thick.
So we called them a wall. Now do you call
them Do you group them together because they're close to
each other, or because they're actually kind of gravitationally affecting
(17:09):
each other, or bound together they are gravitationally holding themselves together.
Remember that the whole universe is expanding. Everything is moving
away from everything else. That's because space between objects is
getting bigger. We don't understand it. It's this thing called
dark energy that's just inflating all of space and increasing
the distances between everything. But if stuff is near enough
(17:30):
to each other and has enough mass, it can resist that.
It can be gravitationally bound. Like our solar system. Dark
energy is increasing the space between the Earth and the Sun,
but gravity of the Sun holds the Earth in place
so that distance doesn't change. So our solar system is
gravitationally bound. Our galaxy is gravitationally bound. It's small enough
(17:51):
and compact enough that on that scale, gravity wins. And
that's true also on the scale of clusters, and it's
sort of true on the scale of super clusters. Clusters
of clusters, people argue about whether they're actually gravitationally bound.
Are they going to hold together in the long term
future of the universe, or is dark energy gonna win
and tear on them apartment. That's sort of on the edge, right,
(18:14):
because I guess if expansion is fascin enough or big enough,
it would even rip our solar system. But I guess
we're we're lucky that it's not. That's right, We're lucky
that it's not. But we're living in a fascinating moment
in the universe where gravity has had time to build
galaxies and clusters, and now superclusters have sort of formed
and maybe gravitationally bound, but it's not clear if gravity
(18:35):
will have time to build those together and really hold
them together and then build super duper clusters, or whether
dark energy will tear them apart. So we're living at
this fascinating moment in the history of the universe. That's
why there is a maximum size to an object in
the universe, because any bigger than that, gravity hasn't had
time to sort of pull it together. And so we're
(18:56):
really looking at the biggest things in the universe. It's
sort of incredible, right. So we found this giant wall,
and so a big question I have is how did
we find it and why didn't we see this earlier?
If it's so big? So let's get into that. But
first let's take a quick break. All right, Daniel, we're
(19:24):
talking about the South Pole Wall, which is I guess,
is that where the anti Santa Claus lives? Is that
defense that it put around into health village? That's right,
it's his first line of defense against folks coming to
trying to steal their Christmas presents earlier. He's not as
or she's not as jolly as the North Pole Santa Claus. No,
(19:46):
there's South Pole boiling oil, and there's archery, and it's
all sorts of stuff. Just just leave them alone. But anyways,
they found this summer a giant wall of galaxies called
the South Pole Wall, and it's huge. It's one and
have billion light years wide. And Daniel, this seems like
a big thing that we should have seen earlier, but
we didn't. So I guess what's the history of finding this?
(20:09):
How do we find it? And why didn't we see
it before? We didn't see it before because it's not
easy to spot. We can't actually see it very well
because there's something in the way and that's the rest
of our galaxy. If you look out into the sky,
mostly you're seeing stars, and those stars are other stars
in our galaxy. But remember the galaxy is much wider
(20:31):
than it is thick, So in most directions you're looking
out through a little bit of our galaxy and then
out into deep space where you can see other galaxies
and stuff. But if you look in just the right direction,
then you're looking through the galaxy. And on a really
dark night you can see this. You can see the
Milky Way, which is the plane of the rest of
the galaxy, and it looks much brighter and sort of
(20:52):
more smeared out than individual stars because it's a huge
number of stars that are further away there on the
other side of the Milky Way, and so they sort
of add up to this milky spread. And it's hard
to see things on the other side of this plane
of the Milky Way because there are so many stars
and gas and dust in our way. Yeah, we're in
(21:13):
the way of our view, kind of kind of like
the back of your head. Yeah, the rest of the galaxy.
And so they called it the South Pole Wall because
if you're standing on Earth, it's sort of in the
direction that the South Pole points. That is, the south
pole of Earth sort of points towards the center of
the galaxy. Not exactly, but you know, close enough, close
(21:33):
enough for astronomical naming committees apparently. Yeah. Yeah, it is
pretty amazing to think that we can see the Milky Way, right.
I mean, it looks like a fuzzy cloud, but it
really it's like millions of stars kind of all kind
of joining their light together and causing this glow. Yeah,
it's billions of stars. Right. The Milky Way has more
than a hundred billion stars in it, and the center
(21:55):
of the Milky Ways, where most of them are. There's
also a lot of gas and dust, so it's just
very difficult to see through the center of the Milky Way.
Astronomers called this whole region of the sky the Zone
of Avoidance. It sounds like something from a video game,
but it basically means look somewhere else because this part
is hard. Don't look here, you're not gonna be able
to see much. Yeah, and so we can't actually see
(22:17):
most of the South Pole wall in the visible light.
We can't just like look at and say, oh, there's
a galaxy. There's a galaxy. There's a galaxy, otherwise we
would have spotted it earlier. You know. It was like
in the nineteen eighties people started to understand that we
could make a huge three D map of our universe
and that it had interesting things to look at, and
that's when we discovered the first of these voids and walls,
(22:41):
and so now it's you know, forty years later, we're
finally figuring out one of the biggest structures was hiding
right behind the bulge of the Milky Way. It is
sort of fascinating that, you know, from our little point
on Earth, just sitting in the spherical ball and looking
out at the stars, we can get a three D
D view of things, right, because when you look at
(23:02):
the night sky it looks kind of like two D,
like all the stars are painted on the ceiling. But
somehow we're able to get a three D view of
what's going on out there, to the point where you know,
we can make out these super cluster structures. Yeah, it's incredible,
because of course you're right, we do see it two
D image, right, We can't resolve distance. We don't know
necessarily how far a star is, and this ambiguity there
(23:25):
when you look at one individual star, you don't know
is it's super bright but very far away, or not
that bright and kind of close up. So for a
long time, that was a big puzzle in astronomy, is
how to measure the distance two stars. We had a
whole fun podcast episode just on that topic, and it
turns out that it depends on how far away it is.
(23:46):
If it's really close by, you can use the equivalent
of sort of like opening one eye and closing the
other one and seeing how the image changes to see
how far away it is. As the Earth goes around
the Sun, you get two images of the star, and
if it's further away, you have to rely on these
super clever little stars, these variable stars, whose brightness is
(24:07):
connected to how fast they pulse. And then if they're
really far away, then you have to use type one
a supernova, which is sort of a standard candle. We
know how bright they are because the physics constrains them
to only be a certain brightness, and so we can
tell how far away they are. So we have this
sort of cosmic distance ladder, but that only works for
things we can see. Yeah, so the Milky Way is
(24:28):
kind of standing in the way of a huge part
of our field of view. It's blocking it, but somehow
we were able to see through it is to find
this South Pole wall. So how do we look through
the Milky Way? Well, again, the answer is gravity. Gravity
is like the most important thing astronomically. It basically controls
the whole universe. And in this case, what we did
(24:49):
is we measured how fast some galaxies were moving and
in what direction to make a sort of cosmic map
of the flow of galaxies, and then we use that
to figure out, like, well, where is there stuff? Because
gravity affects how things move. So we started from understanding
how galaxies are flowing, and then we look for sort
(25:10):
of like blobs, like discontinuities, like oh, everything is clustering
over here, there must be something there, or these guys
are flowing fast, and then we expected so they must
be pulled on by something. From the velocity of galaxies,
you can infer where the mass is. But wait, our
galaxies moving that fast, and we as humans and in
(25:31):
such a short period of time, can tell they're moving
because like, if I look at the stars, they don't
look like they're moving. That's right. We are not watching
galaxies move and like clocking them. It's not like Usain Bolt,
where we measure a distance and measure of time and
then use that to measure the velocity. Instead, we're looking
at the light from those stars and we're seeing how
the light from the stars is shifted in frequency because
(25:54):
like the Doppler effect, if something is moving away from you,
then light from it will get shifted to longer wavelengths
so gets stretched out. And something is moving towards you,
light from it will get shifted to shorter wavelengths to
get blue shifted. And so we can measure the light
from these stars and we can see hasn't been shifted
away from what we expect because we we know what
(26:15):
the light from these stars, from these galaxies should look like.
Because stars around the universe are all the same, they
admit from hydrogen and from sodium in various lines. We
can see those lines get shifted, so we can measure
the velocity of all of these galaxies. So we have
this huge catalog of thousands of thousands of galaxies and
we know in which direction they're moving. But wait, I
(26:35):
thought the shifting of light only works if it's moving
away or towards you. How do you tell if it's
moving to the right or to the left, or up
or down. That's true. The red shift and blue shift
measures the velocity along a line from us to them,
and sort of the radial velocity, and so you have
to use other tricks to try to sort of guess
and construct from the motion of all the galaxies nearby
(26:58):
what these sort of three D map is. But you're right,
we don't really know a lot about this sort of
transverse motion of these galaxies. So everything we know is
is just from that velocity towards or away from us,
that's right, and we're we're sort of guessing about everything
else guessing. You can see these things moving over short
periods of time, so you have some idea, but they
(27:18):
are really far away, so it's very difficult to measure
those distances. And also how do we know where they
are how far away they are? Don't we need like
a supernova to happen in them before we know, or
do we have supernova from each of those thousands of galaxies,
we have supernova that go out really, really far. That's
the nice thing about type one A supernova is they're
they're super bright and they're basically in every galaxy, but
(27:41):
we don't have one. We haven't seen one necessarily in
every galaxy. But we have ideas for where other things are,
so we can place them sort of in a ladder,
and we have the most information about the closest things.
And so that's why we're starting to map the structure
of the universe. And we're beginning from the nearby neighborhood.
That's where we can see for examples, to sephids in
some of these galaxies and type of a supernova. We
(28:03):
definitely have the most information about the local neighborhood. All right,
So then step us through, how do we find the
South Pole Wall. Did we, you know, gain some sort
of new trick to look through the milky way or
we just got better at it and suddenly it popped up.
It's just sort of like being careful and finally analyzing
the hard bit of the data. You know, if you're
(28:23):
doing science, you get a bunch of data and the
first thing you do is you eat the ice cream
off the top, right, And I said, well, here's the
easy question to answer, the most exciting one. You do that,
and people have found cool stuff. They found the Sloane
Great Wall, which is as big as the South Pole Wall,
but it's further away and it's easier to spot. So
they found other structures. But then people started to get
(28:45):
more comprehensive about their search, and so they looked through
sort of some gaps, and they noticed there was a
gap in our cosmic neighborhood where we didn't understand what
was going on. That's because it was behind this zone
of avoidance. So they decided to look like, well, what
is there, and they combined data from a bunch of
different surveys slowing Digital Sky Survey and lots of other
(29:06):
surveys to make one sort of mega database of all
the galaxies called cosmic flows. And so they analyzed this
hard bit and they noticed that galaxies between us and
this region, we're moving away from us faster than you
would expect from just dark energy, and the galaxies past
this region we're moving away from us more slowly than
(29:29):
you would expect. And so that's suggest right there that
there's some like big blob of some moving together. There's
some gravity. They're holding it together, pulling on galaxies between
us and this blob and slowing down galaxies that are
past the blob. We saw like this giant, like if
you're looking at it on a on a radar, you
would see like a like a flock of birds kind
(29:51):
of all moving together away from us. Yeah, exactly. So
you put together where all these galaxies are and how
fast they're moving away from us, and the only way
to explore in the velocities of these galaxies. They call
this peculiar velocity, velocity other than the velocity of the
expansion of the universe. The only way to explain this
peculiar velocity, such a quaint term peculiar, is in like local,
(30:13):
you know, like as in our velocity and not somebody else's.
They didn't want to go with weird or or local
velocity or something anyway. The only way to explain this
peculiar velocity is to say, well, there must be something
big there, some new source of gravity. And this is
not the first time that we've used gravity to deduce
the presence of something. Remember our podcast episode about the
(30:36):
Great Attractiveate. That's some other like incredible source of gravity
that's similarly tugging on stuff and changing the peculiar velocities.
So we know that there must be something there, all right,
So we saw something big out there but we can
we see it directly, like can we see the glow
from it, or we can only see the gravity of it.
(30:57):
We can only see the gravity from most bit little
bits of it sort of peek out the sides of
the zone of avoidance. Then you can't spot it. And
then they actually went back through old surveys to say,
shouldn't we have seen this before? And it turns out
that you can see sort of edges of it in
previous astronomical surveys, and so people have been sort of
(31:18):
like known to look for it and and have been paying
more attention. They could have discovered this like ten twenty
years ago. They saw like the edges of it, the
edges of it sort of peek out past the zone
of avoidance. The bulk of it, though, is basically invisible
to us in terms of electromagnetic radiation that we can't
see it via radio waves, are infrared or anything because
(31:39):
it has to pass through the galaxy. So it's only
gravitational information that we have about most of it. But
that's pretty good, Like if you look up this paper,
they're pretty good three D map of the density of
this thing that shows you like where the galaxies are
and where they aren't. It's a fascinating structure. All right,
Let's get into the shape of this South Pole Wall
and why it's important that we found it. But first
(32:00):
let's take another quick break. All right, Daniel, we're talking
about the wall south, the Southern Wall that the first
man built, or the first Aliens built, I guess to
(32:23):
keep out the alien zombies. You know, I'm just kidding.
We found a giant galactic structure, or a structure of
galaxies kind of pointing if you look south of the
Earth towards the South Pole and keep going past the
Milky Way out there in space, and it's huge. It's
one and a half billion light years wide. And what
does it look like, Daniel? Is it like literally a wall,
(32:45):
or like a sheet or just like a giant lump.
This looks like a giant cosmic banana. You're just saying that, Daniel,
just saying that. It really does look like a huge banana.
What do you mean, like like it's curved. If you
look at this thing from the paper, it's sort of
long and narrow, and it even has like a little
thing sticking up at the top that could be like
(33:06):
you know, where it's peeled off the giant cosmic banana
tree man. So are you saying it looks delicious, is
what you're saying. I'm saying you've got to be hungry
to eat this thing as well. It's huge and it
has a lot of potassium, a lot. I'm not joking
that it looks like a banana. But you know, it's
sort of like staring at clouds. You can see whatever
shape you want, and so I guess I just had
(33:27):
bananas on the brain in my mind. It's not as
much of a wall as is sort of like a
vast tube, but it's definitely big, and it's incredible because
it's it's also telling us not just where the stuff
is that we can see where the galaxies and the
stars and maybe the aliens and their bananas are. It's
also a map of the dark matter. What what do
(33:47):
you mean? Well, remember that stuff in the universe is
not sprinkled at randomly, right, It's clumped together based on
the gravitational over densities from the early universe. But most
of the stuff in the universe is not the kind
of stuff that we can see. It's dark matter. There's
five times as much invisible mysterious matter that's affected by gravity.
(34:07):
As the kind of matter that we're familiar with and
the kinds of matter that we can see tend to
line up with the dark matter. Both of them are
affected by gravity and they pull on each other. So actually,
when you look at stars in the sky, they're telling
you where the dark matter is, because dark matter has
created these like gravitational wells for stars and galaxies to
(34:29):
fall into into form. So the light matter, the normal matter,
is sort of like lights showing you where the dark
matter is. I mean, but we think right like, you're
assuming that where there are stars, there is dark matter.
I mean you're assuming like it's the same kind of
concentration or ratio between dark matter and regular matter as
(34:50):
we have. Yes, and that's something that we've seen. We've
measured in lots of different galaxies and we see some
variation there. There are some galaxies with more dark matter
or less dark matter, and we don't full understand that
at all, but roughly we can say that there's a
five to one relationship between dark matter and normal matter,
and certainly on distances this large enormous supercluster sized structures,
(35:12):
we expect the dark matter to have formed these structures
like they just would not have formed without the dark matter.
You run a simulation the universe without the dark matter,
you just don't get structures like this this early in
the universe. I feel like you're almost telling me that
the you know, basically most of the universe is dark matter,
and it's clumping and doing its own thing, and really
the stars the bright stuff. Us, we're really just kind
(35:34):
of like the bling, you know, like we're just here
to tell everyone where the dark matter is. Yeah, we're
like those birds that ride on the back of rhinoceroses
and sort of like pick the worms off of them.
That's us. Yeah, I mean, call us the bling, call
us the worm eating birds. Whatever you like. Where the
frosting on the cupcake. Yeah, kind of right. I mean
when you when you talk about the structure of the universe,
(35:55):
it's really the dark matter structure we're just hanging on. Yeah,
we call it normal matter because we're used to it,
but it's actually pretty unusual in the universe. It's just
five percent of the energy in the universe is devoted
to making me and you and cosmic bananas. So that's
why it's fascinating to sort of use this light matter,
this luminous matter to tell us what's actually going on
(36:17):
in the universe, and gravity is really the key there.
It tells us where the dark matter is. It's also
telling us about the balance between the dark matter holding
stuff together and dark energy trying to tear it apart.
Except that here we can't actually see the galaxies in
the stars in the light right like we can only
see the gravity, which means maybe this whole wall is
(36:38):
just a giant wall of dark matter. We don't really know, right,
that's true, We don't really know. Although on the bits
of it that we do see, the edges of the
banana that stick out past the zone of avoidance, we
can't see luminous stars there. So it would be pretty
weird to find a massive dark matter wall, But that
would be pretty awesome and gives a sense of how
(36:58):
big this thing is, Like how any galaxies are in
this giant wall? Or like how many stars? Do you
have a sense? It's trillions and trillions of stars, you know,
it's thousands and thousands of galaxies, and each galaxy has
billions of stars, and we don't know how big this
thing is. The thing that's incredible to me is that
before we discovered this, we had sort of a gap
(37:19):
in our understanding of the cosmic neighborhood right around this spot, right,
and people like, well, we don't know what's there, probably
nothing interesting. And then they found this great wall and
it's basically completely fills that gap. You know, it's like
it couldn't have been any bigger. You know, there's like
a little spot you haven't checked and you open up
the door and it turns out it's totally full of stuff.
(37:41):
We have this giant gap that looks like a banana,
but we don't know what's inside. Oh wait, it is
a giant banana. The giant banana. And you know, it's
really important that we understand the shape of the universe
around us. It really is telling us about how the
universe was formed, because it tells us about how this
structure has made and it's telling us about the future
(38:01):
of the universe. Is telling us, is dark matter gonna
win and hold this stuff together? Is dark energy gonna
win and tear this stuff apart? You know, we think
about this stuff on really long time scales, billions of years,
but it's really sort of frothing and dynamical. This is
sort of like if you watch froth forming or water boiling,
but you just watch the first like two milliseconds of
(38:23):
the movie. We're basically two milliseconds into the movie of
the universe, of this frothing, bubbling boiler, trying to understand
the forces at play. Wow, you mean, like we don't
know who's gonna win at the end, but we're still
figuring that out looking at the things around us. Yeah, well,
we know that dark energy, if it continues as it
has been, is gonna eventually tear things apart, but we
(38:44):
don't know where those fractures are going to happen exactly.
Like how much will gravity get to clump together to
form structures that will be impervious to dark energy, and
then dark energy will just increase the distance between them.
How big will those objects be? We don't really know.
It depends sort of delicately on how much dark matter
and how much dark energy there is. I mean, like, well,
(39:04):
the universe is expanding, but the stuff in it could
hold together. Potentially, the stuff and it probably will hold together.
Our galaxy will hold together, Our cluster of galaxies probably
will hold together. Will our superclusters survive or be torn apart?
By dark energy. We don't really know will these walls
and filaments be pulled apart. Are they even gravitationally held
together today? Or are they just sort of near each other.
(39:27):
These are the questions we don't know the answer to.
It's like a cosmic battle between the two greatest forces
in the universe, and we're basically right in the middle
of We're just here on the back of the rhinoceros
picking worms, looking at it like eating popcorn, but instead
of popcorn, it's it's worm. That's right. Hey, look this
worm looks like a banana. Al right, Well, it's pretty
(39:48):
amazing that we are still discovering things that are that big.
Like you know, if I look at into the sky,
how big is this giant wall, Daniel? Is it like
like an inch or like a centimeter, or like a
whole foot as a fracture of the night sky? If
you held, I think a banana at arms length. It's
about that big. No, that's too much of a coinci is, Danny.
(40:09):
It goes from the constellation Perseus in the northern hemisphere
to the constellation APUs. I can't pronounce this one in
the far south, so it is really pretty big. And
the incredible thing is that it's twice as close as
the Sloan Great Wall, right, this long great Wall, just
as big discovered decades ago. This thing is twice is close,
which should make it more obvious. But you know, there's
(40:31):
just so much we still don't know about, the pretty local,
large scale structure and sort of the grand scheme of
things in our neighborhood. It's amazing. It's amazing. It's almost
like we're, you know, explorers. Only a thousand years ago.
We didn't know that America was there, or you know,
Australia was there. Probably I know how many incredible opportunities
were there to discover things, you just have to hop
(40:52):
in a boat and sail for a few days. If
you had known where to look, discovery is easy. And
that's the situation we're in today. We're looking around us
and we just don't know what's out there. There could
be incredible, mind blowing surprises if we just look a
little further or look in the places that have been
hard to look at so far. Are definitely surprises out there.
(41:12):
And then remember we've only mapped a tiny little dot
of the universe. When we talked about like our Solar
System being a tiny fraction of the Milky Way, which
is a tiny fraction of our cluster. If you look
out even further, it just goes on and on and on,
and what we've mapped is a tiny fraction of just
the observable universe. So most of it is a huge
(41:33):
cosmic question. It could be maybe an infinite question mark.
It could be an infinite question mark, And it could
be that we just have sort of bubbles and walls
and voids that go on forever. But it could also
be that once you get a sense of those bubbles
and voids, that you see a larger pattern and that
could tell you something about the early universe and this
quantum foam that generated all of this structure. Or it
(41:55):
could be that at that level it's mostly random. We
just don't know the answer. Like that's a pretty big
question to not know the answer to. And maybe once
we figure out our address, we can finally get those
deliveries from the Amazon aliens. That's right, and I want
them in thirty minutes by drone from across the universe,
same century delivery. I'll pay extra for that, all right, Well,
(42:19):
we hope you enjoyed that and you've got a little
bit of a better sense of where we are in
the universe and what's out there for us to discover.
Thanks for listening, See you next time. Thanks for listening,
and remember that Daniel and Jorge Explain the Universe is
(42:40):
a production of I Heart Radio. For more podcast from
My Heart Radio, visit the I Heart Radio Apple Apple Podcasts,
or wherever you listen to your favorite shows. M
Hey, or hey, do you know what our cosmic addresses? Yeah,
it's a one universe lane, isn't it. Well, that's where
you can send us all your gifts of presence and bananas.
I mean, that's how the aliens know where to find,
is right, that's true. But I actually don't need a
lot of bananas delivered in the mail, So let's not
encourage people to send us any fresh fruit. No, no,
I think you know what you mean, Like our address
(00:29):
like in the universe, Like if we're here on Earth
around our star about halfway down the Milky Way. Yeah,
that's enough to get your mail delivered to your house.
But like, what about the rest of our cosmic context?
I mean, like what's the equivalent of our city or
zip code? Yeah, And it turns out that we're part
of a cluster called the Local Group sounds local, and
(00:50):
then zooming out a little bit where the suburbs of
an even bigger cluster called Virga, and then part of
a super cluster of a hundred thousand galaxies called Lena Kia.
And then you know, that's actually about as far as
we've mapped. Wait, we don't know where we live exactly
in the universe. We don't know, So if you want
to order alien bananas, you just gotta put a question mark.
(01:12):
Gonna throw up a flare. I am more handy cartoonists
and the creator of PhD comics. Hi, I'm Daniel. I'm
(01:33):
a particle physicist, and I don't like Earth bananas, but
I'd be willing to try alien bananas. Really, how do
you know they're not going to be worse? You don't know.
But that's the joy of exploration. I want to land
on a new planet, to see the new kinds of life,
the new kinds of animals and critters, and taste any
new potentially delicious fruits. Well, you're welcome to be humanity's taste.
(01:55):
I guess to make sure it's all right, somebody's gotta
do it. I'll probably come down with the alien banana flu.
But welcome to our podcast Daniel and Jorge Explain the Universe,
a production of My Heart Radio in which we don't
take any actual trips out into the universe, but a
mental journey through all the amazing questions and discoveries, all
the things science has figured out and the things that
(02:18):
science is still working on. We think that curiosity belongs
to everybody, and that you are questions are as fascinating
and as important as those that scientists are working on
right now. Yeah, because it is a huge universe out there,
with a lot of places to explore and a lot
of things to discover, and a big question is how
do we fit into all of this? What is our
(02:40):
place in the universe? And how do we fit into
this giant cosmic ballet of stars and galaxies and dust.
And it's sort of an extension of exploration that humans
have been doing basically forever, since we wondered what was
over that hill, what's past that mountain, what's over that ocean?
And modern day explorers might wonder like, well, is there
(03:02):
anything left for me to look for? Thanks to Google
Earth and satellite technology, we basically know where all the
mountains are and all the little islands you can name
after your chihuahua. But it turns out there's a lot
of exploration left to do. Yeah, is there an equivalent
of Google Universe? Google? Get on it now. Yet it's
mostly a big question mark. But you can look at
(03:24):
maps of our cosmic neighborhood to see what's around us,
what's nearby? If you just google large scale structures of
the universe. Wow, does it tell you how much each
galaxy is worth? Can you figure out the perse square
light here value? You know, even just our solar system
is worth like a gazillion dollars because of all the
platinum and gold and stuff that you can find in aster.
(03:46):
So it's basically just infinite. Well, we are still learning
about the basics of where we are in the universe
and what's kind of around is and so a big
question is, you know, what can we find? What interesting
things are there in our very own neighborhood here in
the universe, And it's not something that we can easily
explore in person. In the old days of exploration, you
(04:08):
would hop in a ship and you would land on
foreign shores and you would wonder who else was living
there and what kind of fruits did they enjoy. But
these days it's not so easy. The distances are vast,
the technology is still so primitive. But we have other
ways of exploring the universe. You mean, we don't have
those warp drives and teleportation devices yet. Well, you know,
I sent them to the Daniel and Jorge Engineering department.
(04:29):
So I'm just waiting for the prototype to come back
last engineer in our team here. But yeah, you're right,
it is kind of interesting that we have to explore
the universe from here. From Earth using telescopes, we can
actually like go out that far because some of the
things that we can see are hundreds or millions of
light years away, like the pretty much we might never
(04:52):
see them in person. That's right, most of these things
we will never see in person. And most of these
things that we're looking at, they don't exist right now
on the way that we are seeing them, right, we
are seeing old light that comes to us from them.
So what's actually happening now out there is not what
we are seeing. Yeah, So astronomers are out there looking
(05:12):
and exploring and checking out what's around us, and recently
there's been an incredible discovery. Just this past summer, astronomers
discovered a whole new thing pretty close to our corner
of the universe here, and it's huge. It's basically the
biggest thing anybody has ever found, and it's shockingly large
(05:33):
and shockingly close. It's basically a literal mind exploder. So
today on the podcast, we'll be asking the question what
is the South Pole Wall and why did they give
it such a ridiculous name south? But yeah, it's a
little confusing because is it a pole or is it
(05:53):
a wall? Is it a wall of poles? Is it
a wall around the South Pole? I guess it's south,
but south relative to who, Well, you have a very
northern bias, right, You tend to view the earth is up,
north is up, and so you know, maybe that gives
you a clue. I was born in the equator, so, Daniel,
I'm pretty agnasting. I think maybe this time you can
(06:14):
rag on after physicists and how they name things, and
as particle physicists can get a break for a weekend
for once. Yeah, and also, who's paying for this wallt Daniel?
The Aliens are definitely paying for the wall, yeah, with
the tariffs. But yeah, so they discovered something huge and enormous.
I mean, it's like you said, it's the biggest thing
(06:35):
pretty much ever discovered. Is that true. Yeah, it's in
the top five biggest things we know about in the universe,
and of the top five, it's the closest one. So
it's really kind of amazing that we haven't seen this before,
that we didn't even know about it before. It really
it makes me feel like, you know, cartographers in the
fifteen hundreds drawing maps to the Earth and like leaving
(06:58):
out America. You know, like how could to be so
ignorant of like an enormous continent that's honestly not that
far away. It'd be like discovering a whole wall of
poles in your backyard and you're like, where did that
come from? That's right, I didn't order this online. Yeah,
so it's a new discovery. It's huge, it's very close.
(07:18):
But we're wondering how many people out there know about
this south Pole Wall and whether it was discovered recently. So,
as usual, Daniel went out there and ask people on
the internet if they knew what is the south Pole Wall?
So thanks to everybody who volunteered to share their baseless
and uninformed speculation with us for our podcast. And if
(07:39):
you would like to be a victim War Future podcast
to share your unprepared thoughts on difficult questions in physics,
please write to us two questions at Daniel and Jorge
dot com. Think about it for a second. Do you
know what the south Pole Wall is? Here's what people
had to say. Does that have something to do with
flat earther theory, it's all a man made will but
(08:00):
around South Pole to stop animals or in shooters from
coming in as a way to preserve this out pole.
Maybe it's some sort of electromagnetic barrier, not just an
obvious structure, something to do with like a magnetic like
the Earth's magnetic field, some sort of barrier for particles
(08:22):
in the sun from the sun. Maybe it's related somehow
to the like Aurora borealis and southern lights. The South
Pole Wall is a ice fault formation that is incredibly
difficult to traverse on foot or sled or with dogs.
(08:46):
I have no idea. I am guessing that it is
a wall, either physical or metaphorical, located in the South Pole.
The first thing that comes into mind is a big
rule of ice in the South Pole, like the one
phone Game of Thrones. I'm not sure, but I believe
there are some I don't know if they're called caverns
(09:06):
or cliffs or something like that, but I believe there's
some impediment in our way to get to the uh,
to travel freely to the South Pole where the ice
is all right. It sounds like nobody knew well. I
think this is a real commentary on the name of
this thing, right, because everybody keyed in on south Pole
and wall, right, And I like how somebody said it
(09:29):
was like Game of Thrones, although that wall wasn't the North.
That's right, Maybe it's the equivalent. Maybe it's for like
the penguin zombie. Well, we physicists, we do like having
symmetry in the universe. So if there's going to be
a wall in the north, there should be a wall
in the south, because otherwise you gotta ask why what's
special about North? Right? Yeah, winter is coming? Is there
(09:49):
another version of our universe out there in the multiverse
in which summer is coming? Well, technically, if it's a
south Pole wall, it would come in our summer, which
is winter for them. The beauty and power of symmetry
once again displayed. But I guess maybe the takeaway here
is that not a lot of people had heard of it,
which means it didn't make the news that much. Maybe
(10:10):
that's right. Most of our listeners are pretty up on
the cosmic news here. Yeah, I think it just didn't
fall into people's brains. It's an incredible discovery. It's something
that's fascinating and something it tells us about where we
live in the universe, but it doesn't really actually change
your day to day life. So maybe people just heard
about it and filed it away. But honestly, I think
(10:30):
we should pin most of the blame on the name
of this thing. Wow, I can't disagree with you more,
Daniel about the naming of things. Finally we're agreeing about
how the name. All right, let's let's not keep people
in suspense here. So what is the South Pole Wall, Daniel?
And when was it discovered? So? The South Pole Wall
is an incredibly huge and immensely vast, gargantuan wall of galaxies.
(10:56):
I remember that galaxies are not just sprinkled everywhere through space.
Our Earth goes around our Sun, which is the core
of our solar system, which is one of many solar
systems in our galaxy. But those galaxies are not just
everywhere in space, sprinkled randomly. They tend to clump together
into clusters of galaxies, and those clusters of galaxies form
(11:18):
structures we call superclusters. And then those superclusters are not
just sprinkled everywhere. They tend to form these enormous structures,
these walls, these filaments, these sheets that surround incredible voids
in which there are no stars, no galaxies, no planets,
no people, no podcasts. Yeah, it's weird to think of
space being not random, you know what I mean, Like
(11:41):
we're just still looking at the nights guy and seeing
stars kind of sprinkled kind of randomly and evenly. But
actually the universe has a lot of structure, like, it
has a lot of things in it, Like everything's kind
of organized in the way. That's right, Things are organized,
and it's gravity that's doing the organizing. Gravity is very
gently but very gradually pulling things together and clumping them.
(12:04):
And it's kind of incredible that gravity is the thing
doing this job. Because of all the forces we are
aware of, the strong force, the weak force, electromagnetism, gravity,
Gravity is the weakest, and not by a little bit,
but like by tens of orders of magnitude. But it's
also the only one that can't be like balanced out.
(12:25):
Electromagnetism can be neutralized with positive and negative forces, but
gravity always pulls. It can't push, so eventually everything else
gets balanced out. Is just gravity left over to sweep
stuff together into stars and planets and galaxies and superclusters.
And then these incredibly immense voids and walls and filaments.
(12:45):
And that's essentially where the exploration is today, is figuring
out like where is our cluster and our supercluster in
this larger structure, what's around us? Right? Yeah, And what's
kind of cool too is that these giants, you know,
super ginormous structures, they're all kind of evidence of the
quantum fluctuations right at the very beginning of the universe. Right,
(13:08):
there's sort of like the wrinkles or the fingerprints of
quantum randomness and structure that was in the early universe.
That's exactly right. Gravity has essentially just exaggerated initial little
over densities. If you had only gravity in the universe
was totally smooth, you wouldn't get any sort of structure
at all, because gravity would pull equally on everything in
(13:30):
all directions, and you wouldn't get any clumping. You need
some sort of initial clumping to get things started and
form this runaway effect where gravity makes things heavier and
then pulls harder, and then makes things heavier which pulls harder.
And you're right in the very beginning what this comes from,
our little tiny quantum fluctuations in the very first moments
of the universe, and basically everything's been derivative from that.
(13:54):
It's like we had one idea very early on sketch
the doodle, and everything else is just derived from that.
And it's amazing. Do you think that you can go
from like a quantum fluctuation is something that huge sort
of like you know, like a little baby scar that
you had as a baby, you still have it as
an adult. And let's give people a sense for like
how big we're talking about. These structures are like billions
(14:17):
of light years wide. These are not little things. There's
not like one galaxy, two galaxies. Remember each galaxy already
is an incredibly enormous thing. But we're talking about bubbles
and sheets that are billions of light years on a side,
and that all comes from tiny quantum fluctuations expanded rapidly
during inflation. Yeah, because you know, I guess like one
(14:40):
galzi is a hundred thousand light years, and so if
you put like thousands of them together, then it's literally
billions of light years. It's billions of light years, meaning
if you're going at the speed of light, it still
takes you a billion years to go from one side
to the other. And so you can imagine the whole
universe is sort of like a big pile of bubbles,
like a big quantum foam that was inflated from the
(15:01):
early universe to this incredibly vast quantum foam. And we've
recently discovered that we're essentially living on the edge of
one of those bubbles. And we're now looking around us.
We're like, oh, look, there's a bubble over there. There's
a bubble over there. But we're really just beginning to
map the universe to understand what is our cosmic neighborhood.
(15:21):
We're seeing edges of bubbles here and bubbles merging over there,
and so it's like it's early days, you know, we
have only just begun to explore. Yeah, and so tell
me about this wall that we just found. This wall,
the South Pole wall. You said it's a ginormous. When
you say ginormous, is that the technical term or is
there a number associated? The technical term actually is huge jungis.
(15:43):
But this one is a billion and a half light
years wide. Right, So you shoot a photon, you press
the button on your laser on one side of the thing.
You wait a billion and a half years before across
it to the other side. And that's only the part
of it that we've seen so far. It could go
on more. Yeah, astronomers are not even sure that we've
(16:04):
seen all of it. So it's a structure of galaxies basically. Right,
it's not like a row of stars. It's like a
row of galaxies and they're all sort of like sprinkled
in a wall or or what's going on. That's right,
it's actually a row of clusters of galaxies. Clusters of
galaxies are grouped together. They're gravitationally bound. There there's enough
(16:26):
gravity between galaxies to sort of hold them together into objects.
That's why we call them a cluster. We don't just
like artificially draw a line and say this is a cluster,
that's a cluster. We look for things that are holding
themselves together gravitationally. So this is a wall of clusters
of galaxies, and we call it a wall because it's
much wider and longer than it is thick, sort of
(16:47):
like our galaxy. Right, our galaxy is flat, it's like
a hundred thousand light years across and a thousand light
years thick, and these things have sort of similar dimensions.
There are much much wider and longer than they are thick.
So we called them a wall. Now do you call
them Do you group them together because they're close to
each other, or because they're actually kind of gravitationally affecting
(17:09):
each other, or bound together they are gravitationally holding themselves together.
Remember that the whole universe is expanding. Everything is moving
away from everything else. That's because space between objects is
getting bigger. We don't understand it. It's this thing called
dark energy that's just inflating all of space and increasing
the distances between everything. But if stuff is near enough
(17:30):
to each other and has enough mass, it can resist that.
It can be gravitationally bound. Like our solar system. Dark
energy is increasing the space between the Earth and the Sun,
but gravity of the Sun holds the Earth in place
so that distance doesn't change. So our solar system is
gravitationally bound. Our galaxy is gravitationally bound. It's small enough
(17:51):
and compact enough that on that scale, gravity wins. And
that's true also on the scale of clusters, and it's
sort of true on the scale of super clusters. Clusters
of clusters, people argue about whether they're actually gravitationally bound.
Are they going to hold together in the long term
future of the universe, or is dark energy gonna win
and tear on them apartment. That's sort of on the edge, right,
(18:14):
because I guess if expansion is fascin enough or big enough,
it would even rip our solar system. But I guess
we're we're lucky that it's not. That's right, We're lucky
that it's not. But we're living in a fascinating moment
in the universe where gravity has had time to build
galaxies and clusters, and now superclusters have sort of formed
and maybe gravitationally bound, but it's not clear if gravity
(18:35):
will have time to build those together and really hold
them together and then build super duper clusters, or whether
dark energy will tear them apart. So we're living at
this fascinating moment in the history of the universe. That's
why there is a maximum size to an object in
the universe, because any bigger than that, gravity hasn't had
time to sort of pull it together. And so we're
(18:56):
really looking at the biggest things in the universe. It's
sort of incredible, right. So we found this giant wall,
and so a big question I have is how did
we find it and why didn't we see this earlier?
If it's so big? So let's get into that. But
first let's take a quick break. All right, Daniel, we're
(19:24):
talking about the South Pole Wall, which is I guess,
is that where the anti Santa Claus lives? Is that
defense that it put around into health village? That's right,
it's his first line of defense against folks coming to
trying to steal their Christmas presents earlier. He's not as
or she's not as jolly as the North Pole Santa Claus. No,
(19:46):
there's South Pole boiling oil, and there's archery, and it's
all sorts of stuff. Just just leave them alone. But anyways,
they found this summer a giant wall of galaxies called
the South Pole Wall, and it's huge. It's one and
have billion light years wide. And Daniel, this seems like
a big thing that we should have seen earlier, but
we didn't. So I guess what's the history of finding this?
(20:09):
How do we find it? And why didn't we see
it before? We didn't see it before because it's not
easy to spot. We can't actually see it very well
because there's something in the way and that's the rest
of our galaxy. If you look out into the sky,
mostly you're seeing stars, and those stars are other stars
in our galaxy. But remember the galaxy is much wider
(20:31):
than it is thick, So in most directions you're looking
out through a little bit of our galaxy and then
out into deep space where you can see other galaxies
and stuff. But if you look in just the right direction,
then you're looking through the galaxy. And on a really
dark night you can see this. You can see the
Milky Way, which is the plane of the rest of
the galaxy, and it looks much brighter and sort of
(20:52):
more smeared out than individual stars because it's a huge
number of stars that are further away there on the
other side of the Milky Way, and so they sort
of add up to this milky spread. And it's hard
to see things on the other side of this plane
of the Milky Way because there are so many stars
and gas and dust in our way. Yeah, we're in
(21:13):
the way of our view, kind of kind of like
the back of your head. Yeah, the rest of the galaxy.
And so they called it the South Pole Wall because
if you're standing on Earth, it's sort of in the
direction that the South Pole points. That is, the south
pole of Earth sort of points towards the center of
the galaxy. Not exactly, but you know, close enough, close
(21:33):
enough for astronomical naming committees apparently. Yeah. Yeah, it is
pretty amazing to think that we can see the Milky Way, right.
I mean, it looks like a fuzzy cloud, but it
really it's like millions of stars kind of all kind
of joining their light together and causing this glow. Yeah,
it's billions of stars. Right. The Milky Way has more
than a hundred billion stars in it, and the center
(21:55):
of the Milky Ways, where most of them are. There's
also a lot of gas and dust, so it's just
very difficult to see through the center of the Milky Way.
Astronomers called this whole region of the sky the Zone
of Avoidance. It sounds like something from a video game,
but it basically means look somewhere else because this part
is hard. Don't look here, you're not gonna be able
to see much. Yeah, and so we can't actually see
(22:17):
most of the South Pole wall in the visible light.
We can't just like look at and say, oh, there's
a galaxy. There's a galaxy. There's a galaxy, otherwise we
would have spotted it earlier. You know. It was like
in the nineteen eighties people started to understand that we
could make a huge three D map of our universe
and that it had interesting things to look at, and
that's when we discovered the first of these voids and walls,
(22:41):
and so now it's you know, forty years later, we're
finally figuring out one of the biggest structures was hiding
right behind the bulge of the Milky Way. It is
sort of fascinating that, you know, from our little point
on Earth, just sitting in the spherical ball and looking
out at the stars, we can get a three D
D view of things, right, because when you look at
(23:02):
the night sky it looks kind of like two D,
like all the stars are painted on the ceiling. But
somehow we're able to get a three D view of
what's going on out there, to the point where you know,
we can make out these super cluster structures. Yeah, it's incredible,
because of course you're right, we do see it two
D image, right, We can't resolve distance. We don't know
necessarily how far a star is, and this ambiguity there
(23:25):
when you look at one individual star, you don't know
is it's super bright but very far away, or not
that bright and kind of close up. So for a
long time, that was a big puzzle in astronomy, is
how to measure the distance two stars. We had a
whole fun podcast episode just on that topic, and it
turns out that it depends on how far away it is.
(23:46):
If it's really close by, you can use the equivalent
of sort of like opening one eye and closing the
other one and seeing how the image changes to see
how far away it is. As the Earth goes around
the Sun, you get two images of the star, and
if it's further away, you have to rely on these
super clever little stars, these variable stars, whose brightness is
(24:07):
connected to how fast they pulse. And then if they're
really far away, then you have to use type one
a supernova, which is sort of a standard candle. We
know how bright they are because the physics constrains them
to only be a certain brightness, and so we can
tell how far away they are. So we have this
sort of cosmic distance ladder, but that only works for
things we can see. Yeah, so the Milky Way is
(24:28):
kind of standing in the way of a huge part
of our field of view. It's blocking it, but somehow
we were able to see through it is to find
this South Pole wall. So how do we look through
the Milky Way? Well, again, the answer is gravity. Gravity
is like the most important thing astronomically. It basically controls
the whole universe. And in this case, what we did
(24:49):
is we measured how fast some galaxies were moving and
in what direction to make a sort of cosmic map
of the flow of galaxies, and then we use that
to figure out, like, well, where is there stuff? Because
gravity affects how things move. So we started from understanding
how galaxies are flowing, and then we look for sort
(25:10):
of like blobs, like discontinuities, like oh, everything is clustering
over here, there must be something there, or these guys
are flowing fast, and then we expected so they must
be pulled on by something. From the velocity of galaxies,
you can infer where the mass is. But wait, our
galaxies moving that fast, and we as humans and in
(25:31):
such a short period of time, can tell they're moving
because like, if I look at the stars, they don't
look like they're moving. That's right. We are not watching
galaxies move and like clocking them. It's not like Usain Bolt,
where we measure a distance and measure of time and
then use that to measure the velocity. Instead, we're looking
at the light from those stars and we're seeing how
the light from the stars is shifted in frequency because
(25:54):
like the Doppler effect, if something is moving away from you,
then light from it will get shifted to longer wavelengths
so gets stretched out. And something is moving towards you,
light from it will get shifted to shorter wavelengths to
get blue shifted. And so we can measure the light
from these stars and we can see hasn't been shifted
away from what we expect because we we know what
(26:15):
the light from these stars, from these galaxies should look like.
Because stars around the universe are all the same, they
admit from hydrogen and from sodium in various lines. We
can see those lines get shifted, so we can measure
the velocity of all of these galaxies. So we have
this huge catalog of thousands of thousands of galaxies and
we know in which direction they're moving. But wait, I
(26:35):
thought the shifting of light only works if it's moving
away or towards you. How do you tell if it's
moving to the right or to the left, or up
or down. That's true. The red shift and blue shift
measures the velocity along a line from us to them,
and sort of the radial velocity, and so you have
to use other tricks to try to sort of guess
and construct from the motion of all the galaxies nearby
(26:58):
what these sort of three D map is. But you're right,
we don't really know a lot about this sort of
transverse motion of these galaxies. So everything we know is
is just from that velocity towards or away from us,
that's right, and we're we're sort of guessing about everything
else guessing. You can see these things moving over short
periods of time, so you have some idea, but they
(27:18):
are really far away, so it's very difficult to measure
those distances. And also how do we know where they
are how far away they are? Don't we need like
a supernova to happen in them before we know, or
do we have supernova from each of those thousands of galaxies,
we have supernova that go out really, really far. That's
the nice thing about type one A supernova is they're
they're super bright and they're basically in every galaxy, but
(27:41):
we don't have one. We haven't seen one necessarily in
every galaxy. But we have ideas for where other things are,
so we can place them sort of in a ladder,
and we have the most information about the closest things.
And so that's why we're starting to map the structure
of the universe. And we're beginning from the nearby neighborhood.
That's where we can see for examples, to sephids in
some of these galaxies and type of a supernova. We
(28:03):
definitely have the most information about the local neighborhood. All right,
So then step us through, how do we find the
South Pole Wall. Did we, you know, gain some sort
of new trick to look through the milky way or
we just got better at it and suddenly it popped up.
It's just sort of like being careful and finally analyzing
the hard bit of the data. You know, if you're
(28:23):
doing science, you get a bunch of data and the
first thing you do is you eat the ice cream
off the top, right, And I said, well, here's the
easy question to answer, the most exciting one. You do that,
and people have found cool stuff. They found the Sloane
Great Wall, which is as big as the South Pole Wall,
but it's further away and it's easier to spot. So
they found other structures. But then people started to get
(28:45):
more comprehensive about their search, and so they looked through
sort of some gaps, and they noticed there was a
gap in our cosmic neighborhood where we didn't understand what
was going on. That's because it was behind this zone
of avoidance. So they decided to look like, well, what
is there, and they combined data from a bunch of
different surveys slowing Digital Sky Survey and lots of other
(29:06):
surveys to make one sort of mega database of all
the galaxies called cosmic flows. And so they analyzed this
hard bit and they noticed that galaxies between us and
this region, we're moving away from us faster than you
would expect from just dark energy, and the galaxies past
this region we're moving away from us more slowly than
(29:29):
you would expect. And so that's suggest right there that
there's some like big blob of some moving together. There's
some gravity. They're holding it together, pulling on galaxies between
us and this blob and slowing down galaxies that are
past the blob. We saw like this giant, like if
you're looking at it on a on a radar, you
would see like a like a flock of birds kind
(29:51):
of all moving together away from us. Yeah, exactly. So
you put together where all these galaxies are and how
fast they're moving away from us, and the only way
to explore in the velocities of these galaxies. They call
this peculiar velocity, velocity other than the velocity of the
expansion of the universe. The only way to explain this
peculiar velocity, such a quaint term peculiar, is in like local,
(30:13):
you know, like as in our velocity and not somebody else's.
They didn't want to go with weird or or local
velocity or something anyway. The only way to explain this
peculiar velocity is to say, well, there must be something
big there, some new source of gravity. And this is
not the first time that we've used gravity to deduce
the presence of something. Remember our podcast episode about the
(30:36):
Great Attractiveate. That's some other like incredible source of gravity
that's similarly tugging on stuff and changing the peculiar velocities.
So we know that there must be something there, all right,
So we saw something big out there but we can
we see it directly, like can we see the glow
from it, or we can only see the gravity of it.
(30:57):
We can only see the gravity from most bit little
bits of it sort of peek out the sides of
the zone of avoidance. Then you can't spot it. And
then they actually went back through old surveys to say,
shouldn't we have seen this before? And it turns out
that you can see sort of edges of it in
previous astronomical surveys, and so people have been sort of
(31:18):
like known to look for it and and have been paying
more attention. They could have discovered this like ten twenty
years ago. They saw like the edges of it, the
edges of it sort of peek out past the zone
of avoidance. The bulk of it, though, is basically invisible
to us in terms of electromagnetic radiation that we can't
see it via radio waves, are infrared or anything because
(31:39):
it has to pass through the galaxy. So it's only
gravitational information that we have about most of it. But
that's pretty good, Like if you look up this paper,
they're pretty good three D map of the density of
this thing that shows you like where the galaxies are
and where they aren't. It's a fascinating structure. All right,
Let's get into the shape of this South Pole Wall
and why it's important that we found it. But first
(32:00):
let's take another quick break. All right, Daniel, we're talking
about the wall south, the Southern Wall that the first
man built, or the first Aliens built, I guess to
(32:23):
keep out the alien zombies. You know, I'm just kidding.
We found a giant galactic structure, or a structure of
galaxies kind of pointing if you look south of the
Earth towards the South Pole and keep going past the
Milky Way out there in space, and it's huge. It's
one and a half billion light years wide. And what
does it look like, Daniel? Is it like literally a wall,
(32:45):
or like a sheet or just like a giant lump.
This looks like a giant cosmic banana. You're just saying that, Daniel,
just saying that. It really does look like a huge banana.
What do you mean, like like it's curved. If you
look at this thing from the paper, it's sort of
long and narrow, and it even has like a little
thing sticking up at the top that could be like
(33:06):
you know, where it's peeled off the giant cosmic banana
tree man. So are you saying it looks delicious, is
what you're saying. I'm saying you've got to be hungry
to eat this thing as well. It's huge and it
has a lot of potassium, a lot. I'm not joking
that it looks like a banana. But you know, it's
sort of like staring at clouds. You can see whatever
shape you want, and so I guess I just had
(33:27):
bananas on the brain in my mind. It's not as
much of a wall as is sort of like a
vast tube, but it's definitely big, and it's incredible because
it's it's also telling us not just where the stuff
is that we can see where the galaxies and the
stars and maybe the aliens and their bananas are. It's
also a map of the dark matter. What what do
(33:47):
you mean? Well, remember that stuff in the universe is
not sprinkled at randomly, right, It's clumped together based on
the gravitational over densities from the early universe. But most
of the stuff in the universe is not the kind
of stuff that we can see. It's dark matter. There's
five times as much invisible mysterious matter that's affected by gravity.
(34:07):
As the kind of matter that we're familiar with and
the kinds of matter that we can see tend to
line up with the dark matter. Both of them are
affected by gravity and they pull on each other. So actually,
when you look at stars in the sky, they're telling
you where the dark matter is, because dark matter has
created these like gravitational wells for stars and galaxies to
(34:29):
fall into into form. So the light matter, the normal matter,
is sort of like lights showing you where the dark
matter is. I mean, but we think right like, you're
assuming that where there are stars, there is dark matter.
I mean you're assuming like it's the same kind of
concentration or ratio between dark matter and regular matter as
(34:50):
we have. Yes, and that's something that we've seen. We've
measured in lots of different galaxies and we see some
variation there. There are some galaxies with more dark matter
or less dark matter, and we don't full understand that
at all, but roughly we can say that there's a
five to one relationship between dark matter and normal matter,
and certainly on distances this large enormous supercluster sized structures,
(35:12):
we expect the dark matter to have formed these structures
like they just would not have formed without the dark matter.
You run a simulation the universe without the dark matter,
you just don't get structures like this this early in
the universe. I feel like you're almost telling me that
the you know, basically most of the universe is dark matter,
and it's clumping and doing its own thing, and really
the stars the bright stuff. Us, we're really just kind
(35:34):
of like the bling, you know, like we're just here
to tell everyone where the dark matter is. Yeah, we're
like those birds that ride on the back of rhinoceroses
and sort of like pick the worms off of them.
That's us. Yeah, I mean, call us the bling, call
us the worm eating birds. Whatever you like. Where the
frosting on the cupcake. Yeah, kind of right. I mean
when you when you talk about the structure of the universe,
(35:55):
it's really the dark matter structure we're just hanging on. Yeah,
we call it normal matter because we're used to it,
but it's actually pretty unusual in the universe. It's just
five percent of the energy in the universe is devoted
to making me and you and cosmic bananas. So that's
why it's fascinating to sort of use this light matter,
this luminous matter to tell us what's actually going on
(36:17):
in the universe, and gravity is really the key there.
It tells us where the dark matter is. It's also
telling us about the balance between the dark matter holding
stuff together and dark energy trying to tear it apart.
Except that here we can't actually see the galaxies in
the stars in the light right like we can only
see the gravity, which means maybe this whole wall is
(36:38):
just a giant wall of dark matter. We don't really know, right,
that's true, We don't really know. Although on the bits
of it that we do see, the edges of the
banana that stick out past the zone of avoidance, we
can't see luminous stars there. So it would be pretty
weird to find a massive dark matter wall, But that
would be pretty awesome and gives a sense of how
(36:58):
big this thing is, Like how any galaxies are in
this giant wall? Or like how many stars? Do you
have a sense? It's trillions and trillions of stars, you know,
it's thousands and thousands of galaxies, and each galaxy has
billions of stars, and we don't know how big this
thing is. The thing that's incredible to me is that
before we discovered this, we had sort of a gap
(37:19):
in our understanding of the cosmic neighborhood right around this spot, right,
and people like, well, we don't know what's there, probably
nothing interesting. And then they found this great wall and
it's basically completely fills that gap. You know, it's like
it couldn't have been any bigger. You know, there's like
a little spot you haven't checked and you open up
the door and it turns out it's totally full of stuff.
(37:41):
We have this giant gap that looks like a banana,
but we don't know what's inside. Oh wait, it is
a giant banana. The giant banana. And you know, it's
really important that we understand the shape of the universe
around us. It really is telling us about how the
universe was formed, because it tells us about how this
structure has made and it's telling us about the future
(38:01):
of the universe. Is telling us, is dark matter gonna
win and hold this stuff together? Is dark energy gonna
win and tear this stuff apart? You know, we think
about this stuff on really long time scales, billions of years,
but it's really sort of frothing and dynamical. This is
sort of like if you watch froth forming or water boiling,
but you just watch the first like two milliseconds of
(38:23):
the movie. We're basically two milliseconds into the movie of
the universe, of this frothing, bubbling boiler, trying to understand
the forces at play. Wow, you mean, like we don't
know who's gonna win at the end, but we're still
figuring that out looking at the things around us. Yeah, well,
we know that dark energy, if it continues as it
has been, is gonna eventually tear things apart, but we
(38:44):
don't know where those fractures are going to happen exactly.
Like how much will gravity get to clump together to
form structures that will be impervious to dark energy, and
then dark energy will just increase the distance between them.
How big will those objects be? We don't really know.
It depends sort of delicately on how much dark matter
and how much dark energy there is. I mean, like, well,
(39:04):
the universe is expanding, but the stuff in it could
hold together. Potentially, the stuff and it probably will hold together.
Our galaxy will hold together, Our cluster of galaxies probably
will hold together. Will our superclusters survive or be torn apart?
By dark energy. We don't really know will these walls
and filaments be pulled apart. Are they even gravitationally held
together today? Or are they just sort of near each other.
(39:27):
These are the questions we don't know the answer to.
It's like a cosmic battle between the two greatest forces
in the universe, and we're basically right in the middle
of We're just here on the back of the rhinoceros
picking worms, looking at it like eating popcorn, but instead
of popcorn, it's it's worm. That's right. Hey, look this
worm looks like a banana. Al right, Well, it's pretty
(39:48):
amazing that we are still discovering things that are that big.
Like you know, if I look at into the sky,
how big is this giant wall, Daniel? Is it like
like an inch or like a centimeter, or like a
whole foot as a fracture of the night sky? If
you held, I think a banana at arms length. It's
about that big. No, that's too much of a coinci is, Danny.
(40:09):
It goes from the constellation Perseus in the northern hemisphere
to the constellation APUs. I can't pronounce this one in
the far south, so it is really pretty big. And
the incredible thing is that it's twice as close as
the Sloan Great Wall, right, this long great Wall, just
as big discovered decades ago. This thing is twice is close,
which should make it more obvious. But you know, there's
(40:31):
just so much we still don't know about, the pretty local,
large scale structure and sort of the grand scheme of
things in our neighborhood. It's amazing. It's amazing. It's almost
like we're, you know, explorers. Only a thousand years ago.
We didn't know that America was there, or you know,
Australia was there. Probably I know how many incredible opportunities
were there to discover things, you just have to hop
(40:52):
in a boat and sail for a few days. If
you had known where to look, discovery is easy. And
that's the situation we're in today. We're looking around us
and we just don't know what's out there. There could
be incredible, mind blowing surprises if we just look a
little further or look in the places that have been
hard to look at so far. Are definitely surprises out there.
(41:12):
And then remember we've only mapped a tiny little dot
of the universe. When we talked about like our Solar
System being a tiny fraction of the Milky Way, which
is a tiny fraction of our cluster. If you look
out even further, it just goes on and on and on,
and what we've mapped is a tiny fraction of just
the observable universe. So most of it is a huge
(41:33):
cosmic question. It could be maybe an infinite question mark.
It could be an infinite question mark, And it could
be that we just have sort of bubbles and walls
and voids that go on forever. But it could also
be that once you get a sense of those bubbles
and voids, that you see a larger pattern and that
could tell you something about the early universe and this
quantum foam that generated all of this structure. Or it
(41:55):
could be that at that level it's mostly random. We
just don't know the answer. Like that's a pretty big
question to not know the answer to. And maybe once
we figure out our address, we can finally get those
deliveries from the Amazon aliens. That's right, and I want
them in thirty minutes by drone from across the universe,
same century delivery. I'll pay extra for that, all right, Well,
(42:19):
we hope you enjoyed that and you've got a little
bit of a better sense of where we are in
the universe and what's out there for us to discover.
Thanks for listening, See you next time. Thanks for listening,
and remember that Daniel and Jorge Explain the Universe is
(42:40):
a production of I Heart Radio. For more podcast from
My Heart Radio, visit the I Heart Radio Apple Apple Podcasts,
or wherever you listen to your favorite shows. M
Hosts And Creators
Daniel Whiteson
Kelly Weinersmith
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