October 29, 2025 • 19 mins
Black Hole is a podcast series exploring the most extreme and fascinating phenomena in our universe. Hosted by Felix Mercer, each episode delivers deep dives into cosmic mysteries including supermassive black holes, neutron stars, the cosmic web's vast architecture, and the relativity of time itself. Through accessible explanations and compelling narratives, the series examines how gravity shapes reality, how dead stars create the elements necessary for life, and why time passes differently depending on motion and gravity. Without interviews or guest segments, Felix guides listeners through twenty-five-minute journeys into the heart of astrophysics, making complex concepts understandable and awe-inspiring.
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This content was created in partnership and with the help of Artificial Intelligence AI
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Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:00):
Welcome back to black Hole. I'm Felix Mercer, your AI host.
Over our last four episodes, we've examined super massive black holes,
explored their complete anatomy, revealed gravity's ultimate power, and investigated
neutron stars at the edge of physical possibility. But today
we're pulling back, we're zooming out. We're going to look
(00:21):
at the universe not as individual objects, not as stars
or galaxies or even clusters of galaxies, but as a whole.
And when you do that, when you step back far
enough to see the entire cosmos at once, something extraordinary
reveals itself. The universe has a structure, It has an architecture,
and that architecture looks remarkably, almost disturbingly like something biological.
(00:47):
Zoom out far enough past our solar system, past our galaxy,
past our local group of galaxies, past even our supercluster,
and the universe begins to look like a vast neural network,
like the interconnected neurons in the human brain. Galaxies aren't
scattered randomly through space like dust in the wind. They're organized,
(01:08):
they're connected. They form filaments, strands of matter stretching across
hundreds of millions of light years. Connecting at nodes where
massive clusters of galaxies gather, all surrounding vast empty regions
called voids. This is the cosmic web, the largest structure
in the universe, and understanding it means understanding how the
(01:28):
universe itself is organized, how it formed, and ultimately where
we fit within this grand architecture. For most of human history,
we assumed the universe was more or less uniform. Sure
they were stars and galaxies, but we thought they were
distributed randomly, spread evenly throughout space, like grains of sand
on a beach. The first hints that this wasn't true
(01:50):
came in the early twentieth century, when astronomers began cataloging
galaxies and noticed they seemed to cluster together. But the
full picture didn't emerge until much late, until we had
the technology to map large volumes of space and see
the patterns hiding in the distribution of galaxies. The revelation
came gradually, then all at once. In nineteen eighty nine,
(02:12):
a team of astronomers led by Margaret Geller and John
Hookra published results from their survey of galaxy positions, and
the astronomical community was stunned. They had discovered what they
called the Great War, a structure composed of galaxy stretching
across more than five hundred million light years of space.
This wasn't a cluster. This was something fundamentally different, a
(02:35):
sheet like structure, a cosmic filament on a scale that
challenged our understanding of how structure could even form in
the universe. But the Great War was just the beginning.
As galaxy surveys became more comprehensive, as telescopes became more powerful,
and we could map larger and larger volumes of space,
the pattern became undeniable. The Sloane Digital Sky SIR, which
(03:00):
began in two thousand Zeril zero, mapped millions of galaxies,
and when astronomers potted their positions in three dimensions, the
cosmotic web revealed itself in all its glory. Galaxies were
arranged in filaments, long tendrils of matter connecting at nodes,
like intersections on a highway system. Between these filaments lay voids,
(03:24):
vast empty regions containing very few galaxies. The universe wasn't
uniform at all. It was organized into the largest structure
that exists, a web spanning billions of light years, encompassing
everything we can observe. The scale is difficult to comprehend.
Individual filaments in the cosmic web can stretch for hundreds
(03:46):
of millions of light years. The voids between them can
be equally large, regions of space larger than the distance
from the Milky Way to the Virgo cluster, containing almost nothing.
When you maply observable universe by perhaps ninety percent of
its volume is composed of these voids. The remaining ten
percent everything we can see, all the galaxies and stars
(04:08):
and matter, is concentrated into the filaments and nodes of
the web. The question, of course, is why why does
the universe organize itself this way? Why filaments invoids rather
than uniform distribution. The answer lies in something we cannot see,
something that makes up roughly eighty five percent of all
matter in the universe. The answer is dark matter, and
(04:31):
understanding the cosmic web means understanding dark matter's role as
the universe's invisible architect. Dark matter doesn't emit light, it
doesn't absorb light. It doesn't interact with electromagnetic radiation at all,
which is why we call it dark. We know it
exists because we can see its gravitational effects on visible
(04:52):
matter on the motion of galaxies, on the bending of
light from distant objects. But more than just existing dark
mans matter dominates the universe's matter content. For every kilogram
of normal matter the atoms that make up stars, in
planets and people, there are roughly five and a half
kilograms of dark matter. This invisible substance outweighs everything we
(05:14):
can see by more than five to one, and it
was dark matter that built the cosmic web. Here's how
it happened. In the early universe. Just after the Big Bang,
matter was distributed almost uniformly throughout space, not perfectly uniform.
There were tiny fluctuations quantum variations in density from place
to place, but the differences were minuscule, less than one
(05:37):
part in one hundred thousand. Yet those tiny variations were
enough In regions that were even slightly denser than average,
gravity was slightly stronger, and gravity, given enough time, amplifies
even the smallest differences. Dark matter, because it doesn't interact
with radiation, was free to begin collapsing under its own
gravity almost immediately. Normal matter, by contrast, were still coupled
(06:01):
to photons held in place by radiation pressure from the
incredibly hot plasma that filled the early universe, so dark
matter got a head start. It began collapsing, first, forming
gravitational wells regions of higher density that would eventually pull
in everything around them. Over hundreds of millions of years,
dark matter continued collapsing, forming structures that grew larger and larger.
(06:26):
But here's the key insight. The collapse wasn't unifor the
initial fluctuations. Those quantum variations from the early universe had structure.
They had patterns. Some regions were slightly denser along particular directions,
forming elongated over densities. As these collapsed under gravity, they
formed filaments, long threads of dark matter stretching across space.
(06:50):
Where multiple filaments intersected, the density became even higher, creating
nodes and between the filaments. Regions that started slightly less
dense than average became even emptier as gravity pulled matter
away from them and toward the denser filaments. These became
the voids, vast under dense regions from which matter evacuated
(07:11):
over cosmic time. Eventually, about three hundred and eighty thousand
years after the Big Bang, the universe cooled enough that
normal matter decoupled from radiation suddenly freed from radiation pressure,
atoms began falling into the gravitational wells that dark matter
had already carved out. Normal matter followed dark matter's template,
(07:34):
flowing along the filaments, accumulating at the nodes draining from
the voids. The cosmic web that dark matter had built
became populated with the material we can actually see. This
process has been beautifully confirmed through computer simulations. The Millennium simulation,
running two thousand and five, tracked the evolution of more
(07:54):
than ten billion particles representing dark matter across a cubic
volume of space over two billion light years on a side.
Starting from initial conditions based on observations of the early Universe,
the simulation evolved the particles forward in time using nothing
but gravity. What emerged was a cosmic web virtually indistinguishable
(08:16):
from what we observe in real galaxy surveys. Filaments, nodes, voids,
all arising naturally from gravity acting on those tiny initial
fluctuations over cosmic time. Think of the filaments as cosmic highways.
They're the paths along which matter flows, the roots by
which galaxies move and interact. Matter in the voids doesn't
(08:38):
stay there, it gets pulled toward the filaments, flowing down
the gravitational gradients like water finding its way downhill. Once
in a filament, matter is channeled toward the nodes, the
intersections where multiple filaments meet. These nodes are where the
largest structures in the universe form the galaxy clusters and
superclusters that represent the most massive gravitationally bound systems we know,
(09:03):
and the voids, far from being empty, are actually crucial
to understanding the overall structure. The voids are where dark
energy's influence is most apparent. Dark energy, that mysterious force
causing the universe's expansion to accelerate, pushes most strongly in
regions where matter density is lowest. In the voids, with
(09:24):
very little matter to provide gravitational attraction, dark energy dominates,
and these regions expand faster than average, becoming even emptier
over time. The cosmic web is not just shaped by
gravity pulling matter together. It's also shaped by dark energy
pushing matter apart in the voids, creating the contrast between
(09:45):
the dense filaments and the empty spaces between them. So
where do we live in all of this? What's our
cosmic address? Let's start small and zoom out. You're on Earth,
which orbits the Sun, which is located in the U
Ryan arm of the Milky Way galaxy. The Milky Way
is part of the Local Group, a small cluster of
(10:06):
about fifty galaxies dominated by two large spirals, the Milky
Way and Andrometera. The Local Group, in turn, is located
on the outskirts of the Virgo Supercluster, a large concentration
of galaxies centered on the Virgo Cluster about fifty million
light years from us. But that's not the end of
the story. In twenty fourteen, astronomers mapped the motions of
(10:29):
galaxies in our cosmic neighborhood and discovered that the Virgo
Supercluster itself is just a lobe of an even larger structure,
which they named Laniakia Hawaiian for immense Heaven. Laniakia is
a supercluster of superclusters containing roughly one hundred thousand galaxies
spread across five hundred million light years, and Laniakia is
(10:52):
a node in the cosmic web, one intersection point in
the vast network of filaments that spans the universe. But
we can trace our location even more specifically. The Local
Group lies within a filament sometimes called the local sheet,
a flattened structure connecting the Virgo supercluster to the Coma supercluster.
(11:13):
We're not at a node, not in one of the
major intersections. We're out on a filament, in a relatively
quiet neighborhood of the cosmic web, far from the massive
galaxy clusters that mark the web's most active intersections. There's
something philosophically profound about this realization. We're not central, we're
not in a special location. We're on a thread in
(11:34):
the cosmic tapestry, at no particularly distinguished position. Yet that
thread connects us to everything else, to the nodes where
thousands of galaxies gather, to other filaments stretching away toward
the observable universe's edge, to the architecture that encompasses all
of existence. And this architecture is dynamic. Galaxies aren't stationary
(11:56):
on the web. They're moving, flowing along the filaments to
toward the nodes. Our local group, for instance, is moving
at about six hundred kilometres per second relative to the
cosmic microwave background, pooled by the gravitational attraction of over
dense regions and pushed by the expansion of under dense regions.
For decades, astronomers referred to this mysterious source of gravity
(12:20):
as the Great Attractor, a region of space toward which
our local galaxies are falling. We now understand the Great
Attractor is part of the larger flow pattern toward Lanniacre's center.
But there's a complication to mapping our cosmic neighborhood. We
live inside a galaxy, and that galaxy has a disc,
and that disc contains dust and gas that blocks our
(12:41):
view in certain directions. There's a region called the zone
of avoidance, a banned roughly twenty degrees tall, running around
the sky where we simply cannot see distant galaxies because
the Milky Way itself is in the way. About ten
to twenty percent of the sky is obscured this way.
It's like trying to map a city when you can't
(13:02):
look out the windows on one side of your building.
We can infer what's there based on gravitational effects and
on observations at wavelengths that penetrate the dust better than
visible light, but there's a fundamental limit to how well
we can map the cosmic web in those directions. Despite
this limitation, the mapping continues growing more detailed year by year.
(13:23):
We now have three dimensional maps showing the positions of
millions of galaxies, revealing the cosmic Web's intricate structure in
ever finer detail. And these maps don't just show where
galaxies are now, because light takes time to travel. Looking
at distant galaxies means looking back in time. The farther
we look, the younger the universe we see. This means
(13:46):
we can actually watch the cosmic web forming, see how
it evolved from the nearly uniform early universe to the
highly structured cosmos we inhabit today. The story of that
evolution is written in the Observations Tree. Hundred and eighty
thousand years after the Big Bang, the cosmic microwave background
radiation shows us a universe with only tiny density fluctuations.
(14:09):
By a few hundred million years later, the first stars
and galaxies were forming, concentrated in the denser regions that
would become filaments and nodes. By one to two billion
years after the Big Bang, the basic structure of the
cosmic web was in place, though it was less pronounced
than today. Over the subsequent billions of years, the structure
(14:30):
became more defined. Matter continued flowing from voids into filaments,
from filaments into nodes. Galaxy costers grew more massive, voids
expanded and became emptier, and the process hasn't stopped. The
cosmic web is still evolving today, still developing, Galaxies still
flowing along filaments, clusters, still growing more massive. We're living
(14:52):
in a dynamic universe, a universe that's changing on time
scales far longer than human lifetimes, but nonetheless not static,
not frozen, not complete. But evolution has a direction, and
in the cosmos Web's case, that direction is determined by
dark energy. We know the universe's expansion is accelerating, but
galaxies are moving apart from each other at an ever
(15:15):
increasing rate. This acceleration is driven by dark energy, and
it has profound implications for the cosmosic Web's future. Currently,
structures on the scale of galaxy clusters and smaller are
gravitationally bound. They're held together by their own gravity, strong
enough to resist the expansion of space. But the cosmosic
(15:36):
Web's larger structures, the filaments themselves, the conections between superclusters,
these are not gravitationally bound. They are being stretched by
the expanding space. Between them. As the inverse ages and
dark energy's influence grows stronger, this stretching will accelerate. In
the distant future. Tens of billions of years from now,
(15:57):
the cosmos Web will begin to dissolve. The filaments will break,
superclusters will become isolated from each other as the space
between them expands faster than light can travel across it. Eventually,
even galaxy clusters may be torn apart if dark energy's
strength increases over time, though this depends on dark energy's
precise nature, something we still don't fully understand. The ultimate
(16:20):
fate is isolation. Each gravitationally bound structure will become its
own island universe, cut off from all others by the
exponentially expanding space between them. An observer in some distant
galaxy trillions of years from now will look out and
see almost nothing beyond their own local group. The cosmic
web will have been erased by expansion, and with it,
(16:42):
any direct evidence that there ever was a larger universe.
This has led some physicists to wonder whether something similar
has already happened, whether we're missing evidence of structures even
larger than the cosmic web because they've already been stretched
beyond our observable horizon, but that's a concern for the
far few. Today. The cosmos web surrounds us, connects us,
(17:04):
defines the large scale structure of everything we can observe.
It's a testament to how the universe organizes itself, how
gravity and dark matter and dark energy and the initial
quantum fluctuations from the Big Bang all work together to
create order from near uniformity. There's something deeply satisfying about
discovering that the universe has structure, that it's not random chaos,
(17:28):
but organized architecture. The cosmic web tells us that even
on the larger scales, there are patterns, there are connections,
there are rules governing how matter distributes itself. Every galaxy
we see is part of this web, following its dictates,
moving along its highways, gathering at its intersections. And every
(17:48):
atom in your body traveled along these cosmic highways to
get here. The matter that makes up Earth, that makes
up you, was once part of the cosmic web, structure,
flowing along filaments pled by gravity toward what would eventually
become our soul and neighborhood. You are quite literally made
of the cosmic web assembled from material that followed its
(18:10):
architecture across billions of light years and billions of years
to wind up precisely here, precisely now. The cosmic web
is our cosmic context, the largest structure we inhabit, the
architecture within which everything else exists. Understanding it means understanding
our place in the universe, not as isolated observers, but
(18:34):
as participants in a vast, connected, organized system that spans
all of observable space. We're part of something larger, something structured,
something that reveals the universe is far more organized than
we ever imagined when we first looked up at the
scattered stars in the night sky. Thank you for listening
to this episode of Black Hole. If you enjoyed exploring
(18:56):
the architecture of the universe, please subscribe to stay updated
on future episodes. This episode was brought to you by
Quiet Please Podcast Networks. For more content like this, please
go to Quiet Please dot ai, Quiet, please dot Ai
hear what matters
Welcome back to black Hole. I'm Felix Mercer, your AI host.
Over our last four episodes, we've examined super massive black holes,
explored their complete anatomy, revealed gravity's ultimate power, and investigated
neutron stars at the edge of physical possibility. But today
we're pulling back, we're zooming out. We're going to look
(00:21):
at the universe not as individual objects, not as stars
or galaxies or even clusters of galaxies, but as a whole.
And when you do that, when you step back far
enough to see the entire cosmos at once, something extraordinary
reveals itself. The universe has a structure, It has an architecture,
and that architecture looks remarkably, almost disturbingly like something biological.
(00:47):
Zoom out far enough past our solar system, past our galaxy,
past our local group of galaxies, past even our supercluster,
and the universe begins to look like a vast neural network,
like the interconnected neurons in the human brain. Galaxies aren't
scattered randomly through space like dust in the wind. They're organized,
(01:08):
they're connected. They form filaments, strands of matter stretching across
hundreds of millions of light years. Connecting at nodes where
massive clusters of galaxies gather, all surrounding vast empty regions
called voids. This is the cosmic web, the largest structure
in the universe, and understanding it means understanding how the
(01:28):
universe itself is organized, how it formed, and ultimately where
we fit within this grand architecture. For most of human history,
we assumed the universe was more or less uniform. Sure
they were stars and galaxies, but we thought they were
distributed randomly, spread evenly throughout space, like grains of sand
on a beach. The first hints that this wasn't true
(01:50):
came in the early twentieth century, when astronomers began cataloging
galaxies and noticed they seemed to cluster together. But the
full picture didn't emerge until much late, until we had
the technology to map large volumes of space and see
the patterns hiding in the distribution of galaxies. The revelation
came gradually, then all at once. In nineteen eighty nine,
(02:12):
a team of astronomers led by Margaret Geller and John
Hookra published results from their survey of galaxy positions, and
the astronomical community was stunned. They had discovered what they
called the Great War, a structure composed of galaxy stretching
across more than five hundred million light years of space.
This wasn't a cluster. This was something fundamentally different, a
(02:35):
sheet like structure, a cosmic filament on a scale that
challenged our understanding of how structure could even form in
the universe. But the Great War was just the beginning.
As galaxy surveys became more comprehensive, as telescopes became more powerful,
and we could map larger and larger volumes of space,
the pattern became undeniable. The Sloane Digital Sky SIR, which
(03:00):
began in two thousand Zeril zero, mapped millions of galaxies,
and when astronomers potted their positions in three dimensions, the
cosmotic web revealed itself in all its glory. Galaxies were
arranged in filaments, long tendrils of matter connecting at nodes,
like intersections on a highway system. Between these filaments lay voids,
(03:24):
vast empty regions containing very few galaxies. The universe wasn't
uniform at all. It was organized into the largest structure
that exists, a web spanning billions of light years, encompassing
everything we can observe. The scale is difficult to comprehend.
Individual filaments in the cosmic web can stretch for hundreds
(03:46):
of millions of light years. The voids between them can
be equally large, regions of space larger than the distance
from the Milky Way to the Virgo cluster, containing almost nothing.
When you maply observable universe by perhaps ninety percent of
its volume is composed of these voids. The remaining ten
percent everything we can see, all the galaxies and stars
(04:08):
and matter, is concentrated into the filaments and nodes of
the web. The question, of course, is why why does
the universe organize itself this way? Why filaments invoids rather
than uniform distribution. The answer lies in something we cannot see,
something that makes up roughly eighty five percent of all
matter in the universe. The answer is dark matter, and
(04:31):
understanding the cosmic web means understanding dark matter's role as
the universe's invisible architect. Dark matter doesn't emit light, it
doesn't absorb light. It doesn't interact with electromagnetic radiation at all,
which is why we call it dark. We know it
exists because we can see its gravitational effects on visible
(04:52):
matter on the motion of galaxies, on the bending of
light from distant objects. But more than just existing dark
mans matter dominates the universe's matter content. For every kilogram
of normal matter the atoms that make up stars, in
planets and people, there are roughly five and a half
kilograms of dark matter. This invisible substance outweighs everything we
(05:14):
can see by more than five to one, and it
was dark matter that built the cosmic web. Here's how
it happened. In the early universe. Just after the Big Bang,
matter was distributed almost uniformly throughout space, not perfectly uniform.
There were tiny fluctuations quantum variations in density from place
to place, but the differences were minuscule, less than one
(05:37):
part in one hundred thousand. Yet those tiny variations were
enough In regions that were even slightly denser than average,
gravity was slightly stronger, and gravity, given enough time, amplifies
even the smallest differences. Dark matter, because it doesn't interact
with radiation, was free to begin collapsing under its own
gravity almost immediately. Normal matter, by contrast, were still coupled
(06:01):
to photons held in place by radiation pressure from the
incredibly hot plasma that filled the early universe, so dark
matter got a head start. It began collapsing, first, forming
gravitational wells regions of higher density that would eventually pull
in everything around them. Over hundreds of millions of years,
dark matter continued collapsing, forming structures that grew larger and larger.
(06:26):
But here's the key insight. The collapse wasn't unifor the
initial fluctuations. Those quantum variations from the early universe had structure.
They had patterns. Some regions were slightly denser along particular directions,
forming elongated over densities. As these collapsed under gravity, they
formed filaments, long threads of dark matter stretching across space.
(06:50):
Where multiple filaments intersected, the density became even higher, creating
nodes and between the filaments. Regions that started slightly less
dense than average became even emptier as gravity pulled matter
away from them and toward the denser filaments. These became
the voids, vast under dense regions from which matter evacuated
(07:11):
over cosmic time. Eventually, about three hundred and eighty thousand
years after the Big Bang, the universe cooled enough that
normal matter decoupled from radiation suddenly freed from radiation pressure,
atoms began falling into the gravitational wells that dark matter
had already carved out. Normal matter followed dark matter's template,
(07:34):
flowing along the filaments, accumulating at the nodes draining from
the voids. The cosmic web that dark matter had built
became populated with the material we can actually see. This
process has been beautifully confirmed through computer simulations. The Millennium simulation,
running two thousand and five, tracked the evolution of more
(07:54):
than ten billion particles representing dark matter across a cubic
volume of space over two billion light years on a side.
Starting from initial conditions based on observations of the early Universe,
the simulation evolved the particles forward in time using nothing
but gravity. What emerged was a cosmic web virtually indistinguishable
(08:16):
from what we observe in real galaxy surveys. Filaments, nodes, voids,
all arising naturally from gravity acting on those tiny initial
fluctuations over cosmic time. Think of the filaments as cosmic highways.
They're the paths along which matter flows, the roots by
which galaxies move and interact. Matter in the voids doesn't
(08:38):
stay there, it gets pulled toward the filaments, flowing down
the gravitational gradients like water finding its way downhill. Once
in a filament, matter is channeled toward the nodes, the
intersections where multiple filaments meet. These nodes are where the
largest structures in the universe form the galaxy clusters and
superclusters that represent the most massive gravitationally bound systems we know,
(09:03):
and the voids, far from being empty, are actually crucial
to understanding the overall structure. The voids are where dark
energy's influence is most apparent. Dark energy, that mysterious force
causing the universe's expansion to accelerate, pushes most strongly in
regions where matter density is lowest. In the voids, with
(09:24):
very little matter to provide gravitational attraction, dark energy dominates,
and these regions expand faster than average, becoming even emptier
over time. The cosmic web is not just shaped by
gravity pulling matter together. It's also shaped by dark energy
pushing matter apart in the voids, creating the contrast between
(09:45):
the dense filaments and the empty spaces between them. So
where do we live in all of this? What's our
cosmic address? Let's start small and zoom out. You're on Earth,
which orbits the Sun, which is located in the U
Ryan arm of the Milky Way galaxy. The Milky Way
is part of the Local Group, a small cluster of
(10:06):
about fifty galaxies dominated by two large spirals, the Milky
Way and Andrometera. The Local Group, in turn, is located
on the outskirts of the Virgo Supercluster, a large concentration
of galaxies centered on the Virgo Cluster about fifty million
light years from us. But that's not the end of
the story. In twenty fourteen, astronomers mapped the motions of
(10:29):
galaxies in our cosmic neighborhood and discovered that the Virgo
Supercluster itself is just a lobe of an even larger structure,
which they named Laniakia Hawaiian for immense Heaven. Laniakia is
a supercluster of superclusters containing roughly one hundred thousand galaxies
spread across five hundred million light years, and Laniakia is
(10:52):
a node in the cosmic web, one intersection point in
the vast network of filaments that spans the universe. But
we can trace our location even more specifically. The Local
Group lies within a filament sometimes called the local sheet,
a flattened structure connecting the Virgo supercluster to the Coma supercluster.
(11:13):
We're not at a node, not in one of the
major intersections. We're out on a filament, in a relatively
quiet neighborhood of the cosmic web, far from the massive
galaxy clusters that mark the web's most active intersections. There's
something philosophically profound about this realization. We're not central, we're
not in a special location. We're on a thread in
(11:34):
the cosmic tapestry, at no particularly distinguished position. Yet that
thread connects us to everything else, to the nodes where
thousands of galaxies gather, to other filaments stretching away toward
the observable universe's edge, to the architecture that encompasses all
of existence. And this architecture is dynamic. Galaxies aren't stationary
(11:56):
on the web. They're moving, flowing along the filaments to
toward the nodes. Our local group, for instance, is moving
at about six hundred kilometres per second relative to the
cosmic microwave background, pooled by the gravitational attraction of over
dense regions and pushed by the expansion of under dense regions.
For decades, astronomers referred to this mysterious source of gravity
(12:20):
as the Great Attractor, a region of space toward which
our local galaxies are falling. We now understand the Great
Attractor is part of the larger flow pattern toward Lanniacre's center.
But there's a complication to mapping our cosmic neighborhood. We
live inside a galaxy, and that galaxy has a disc,
and that disc contains dust and gas that blocks our
(12:41):
view in certain directions. There's a region called the zone
of avoidance, a banned roughly twenty degrees tall, running around
the sky where we simply cannot see distant galaxies because
the Milky Way itself is in the way. About ten
to twenty percent of the sky is obscured this way.
It's like trying to map a city when you can't
(13:02):
look out the windows on one side of your building.
We can infer what's there based on gravitational effects and
on observations at wavelengths that penetrate the dust better than
visible light, but there's a fundamental limit to how well
we can map the cosmic web in those directions. Despite
this limitation, the mapping continues growing more detailed year by year.
(13:23):
We now have three dimensional maps showing the positions of
millions of galaxies, revealing the cosmic Web's intricate structure in
ever finer detail. And these maps don't just show where
galaxies are now, because light takes time to travel. Looking
at distant galaxies means looking back in time. The farther
we look, the younger the universe we see. This means
(13:46):
we can actually watch the cosmic web forming, see how
it evolved from the nearly uniform early universe to the
highly structured cosmos we inhabit today. The story of that
evolution is written in the Observations Tree. Hundred and eighty
thousand years after the Big Bang, the cosmic microwave background
radiation shows us a universe with only tiny density fluctuations.
(14:09):
By a few hundred million years later, the first stars
and galaxies were forming, concentrated in the denser regions that
would become filaments and nodes. By one to two billion
years after the Big Bang, the basic structure of the
cosmic web was in place, though it was less pronounced
than today. Over the subsequent billions of years, the structure
(14:30):
became more defined. Matter continued flowing from voids into filaments,
from filaments into nodes. Galaxy costers grew more massive, voids
expanded and became emptier, and the process hasn't stopped. The
cosmic web is still evolving today, still developing, Galaxies still
flowing along filaments, clusters, still growing more massive. We're living
(14:52):
in a dynamic universe, a universe that's changing on time
scales far longer than human lifetimes, but nonetheless not static,
not frozen, not complete. But evolution has a direction, and
in the cosmos Web's case, that direction is determined by
dark energy. We know the universe's expansion is accelerating, but
galaxies are moving apart from each other at an ever
(15:15):
increasing rate. This acceleration is driven by dark energy, and
it has profound implications for the cosmosic Web's future. Currently,
structures on the scale of galaxy clusters and smaller are
gravitationally bound. They're held together by their own gravity, strong
enough to resist the expansion of space. But the cosmosic
(15:36):
Web's larger structures, the filaments themselves, the conections between superclusters,
these are not gravitationally bound. They are being stretched by
the expanding space. Between them. As the inverse ages and
dark energy's influence grows stronger, this stretching will accelerate. In
the distant future. Tens of billions of years from now,
(15:57):
the cosmos Web will begin to dissolve. The filaments will break,
superclusters will become isolated from each other as the space
between them expands faster than light can travel across it. Eventually,
even galaxy clusters may be torn apart if dark energy's
strength increases over time, though this depends on dark energy's
precise nature, something we still don't fully understand. The ultimate
(16:20):
fate is isolation. Each gravitationally bound structure will become its
own island universe, cut off from all others by the
exponentially expanding space between them. An observer in some distant
galaxy trillions of years from now will look out and
see almost nothing beyond their own local group. The cosmic
web will have been erased by expansion, and with it,
(16:42):
any direct evidence that there ever was a larger universe.
This has led some physicists to wonder whether something similar
has already happened, whether we're missing evidence of structures even
larger than the cosmic web because they've already been stretched
beyond our observable horizon, but that's a concern for the
far few. Today. The cosmos web surrounds us, connects us,
(17:04):
defines the large scale structure of everything we can observe.
It's a testament to how the universe organizes itself, how
gravity and dark matter and dark energy and the initial
quantum fluctuations from the Big Bang all work together to
create order from near uniformity. There's something deeply satisfying about
discovering that the universe has structure, that it's not random chaos,
(17:28):
but organized architecture. The cosmic web tells us that even
on the larger scales, there are patterns, there are connections,
there are rules governing how matter distributes itself. Every galaxy
we see is part of this web, following its dictates,
moving along its highways, gathering at its intersections. And every
(17:48):
atom in your body traveled along these cosmic highways to
get here. The matter that makes up Earth, that makes
up you, was once part of the cosmic web, structure,
flowing along filaments pled by gravity toward what would eventually
become our soul and neighborhood. You are quite literally made
of the cosmic web assembled from material that followed its
(18:10):
architecture across billions of light years and billions of years
to wind up precisely here, precisely now. The cosmic web
is our cosmic context, the largest structure we inhabit, the
architecture within which everything else exists. Understanding it means understanding
our place in the universe, not as isolated observers, but
(18:34):
as participants in a vast, connected, organized system that spans
all of observable space. We're part of something larger, something structured,
something that reveals the universe is far more organized than
we ever imagined when we first looked up at the
scattered stars in the night sky. Thank you for listening
to this episode of Black Hole. If you enjoyed exploring
(18:56):
the architecture of the universe, please subscribe to stay updated
on future episodes. This episode was brought to you by
Quiet Please Podcast Networks. For more content like this, please
go to Quiet Please dot ai, Quiet, please dot Ai
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