# The Galaxy’s Own Gravity Could Be Mimicking the Effects of Dark Matter

An episode of [Bedtime Astronomy](https://invisiblenetwork.ai/podcast/1736397134), 7 Sep 2026, 33 min.

Audio: https://dts.podtrac.com/redirect.mp3/api.spreaker.com/download/episode/74753839/darkmilkyp.mp3

Could the Milky Way itself be creating clues that look like dark matter? A new study suggests that gaps and distortions in stellar streams may sometimes arise from the galaxy's own complex gravitational structure. The findings could force astronomers to rethink how they search for the hidden fingerprints of dark matter. Thank you for listening to Bedtime Astronomy — your guide to the cosmos. New episodes on space exploration, NASA missions & the latest astronomy breakthroughs. This episode includes AI-generated content.

## Transcript

[0:03] Speaker 1: Welcome to Bedtime Astronomy. Explore the wonders of the cosmos
[0:07] Speaker 1: with our soothing Bedtime Astronomy podcast. Each episode offers a
[0:12] Speaker 1: gentle journey through the stars, planets, and beyond, perfect for
[0:16] Speaker 1: unwinding after a long day. Let's travel through the mysteries
[0:20] Speaker 1: of the universe as you drift off into a peaceful
[0:22] Speaker 1: slumber under the night sky.
[0:26] Speaker 2: So, imagine you're standing far, far outside our galaxy. just,
[0:31] Speaker 2: you know, looking at it from a massive distance.
[0:33] Speaker 3: Right, way out in the void.
[0:34] Speaker 2: Yeah, exactly. And if you're like most people, you probably
[0:37] Speaker 2: picture the Milky Way as this neat, flat, glowing disk, right?
[0:41] Speaker 2: Just spinning gracefully in the dark vacuum of space.
[0:44] Speaker 3: A majestic pinwheel.
[0:46] Speaker 2: Right, this very orderly pinwheel. But if you were actually
[0:50] Speaker 2: out there floating in the dark and you looked at
[0:51] Speaker 2: the space immediately surrounding that flat plane, you wouldn't see
[0:55] Speaker 2: an empty expanse at all.
[0:57] Speaker 3: No, not even close.
[0:58] Speaker 2: You'd see this chaotic... turbulent graveyard.
[1:01] Speaker 3: It is, yeah. It's a completely mangled, violent frontier out there.
[1:05] Speaker 2: Yeah.
[1:05] Speaker 3: Because the space extending high above and far below those
[1:09] Speaker 3: familiar spiral arms of the Milky Way, it's just littered
[1:12] Speaker 3: with the ruins of shredded, torn apart star clusters.
[1:16] Speaker 2: Oh, wow. So just debris everywhere.
[1:18] Speaker 3: Exactly. We're talking about entire dwarf galaxies and ancient globular
[1:21] Speaker 3: clusters that, well, they strayed just a bit too close
[1:24] Speaker 3: to our galaxy and got completely ripped to pieces by
[1:26] Speaker 3: its gravity.
[1:27] Speaker 2: Ripped to pieces. And for a long time, Astrophysicists have
[1:31] Speaker 2: looked at these ruins, right, floating in this galactic graveyard,
[1:34] Speaker 2: and they believe these shreds actually held the ultimate key
[1:37] Speaker 2: to understanding the invisible scaffolding of the entire universe.
[1:42] Speaker 3: Yeah, that was the big hope.
[1:43] Speaker 2: Because the assumption was, like, the way these stars were
[1:46] Speaker 2: torn apart, that could help us map out the dark
[1:49] Speaker 2: matter surrounding our galaxy.
[1:51] Speaker 3: And honestly, it has driven one of the most profound
[1:54] Speaker 3: observational hunts in modern astrophysics. I mean, it was the
[1:58] Speaker 3: gold standard idea.
[1:59] Speaker 2: Mm-hmm.
[1:59] Speaker 3: But we are really starting to realize that the universe
[2:03] Speaker 3: might be playing this massive, elaborate trick on us.
[2:06] Speaker 2: Which is terrifying, right?
[2:07] Speaker 3: It is, because our own Milky Way is actively deceiving
[2:10] Speaker 3: us in this hunt. So we are looking at this
[2:12] Speaker 3: fundamental crisis, but also, you know, massive opportunity in how
[2:16] Speaker 3: we understand the basic building blocks of reality.
[2:18] Speaker 2: And this all stems from this recent simulation that forced
[2:21] Speaker 2: us to completely rethink what a galactic graveyard actually looks like.
[2:25] Speaker 3: Exactly. It upended everything.
[2:27] Speaker 2: To really understand this deception, we kind of have to
[2:29] Speaker 2: understand the anatomy of our galactic neighborhood first. Let's look
[2:33] Speaker 2: at the sheer scale of the Milky Way's flat plane
[2:36] Speaker 2: versus its outer halo.
[2:38] Speaker 3: Right.
[2:38] Speaker 2: Because the vast majority of the stars we know, you know,
[2:42] Speaker 2: the ones we actually see in the night sky, they
[2:43] Speaker 2: sit nicely on that flat disk. But then you have
[2:45] Speaker 2: this chaotic halo surrounding the whole thing. Yeah.
[2:48] Speaker 3: And the contrast between those two environments, it really comes
[2:51] Speaker 3: down to this concept of the conservation of angular momentum. Okay.
[2:55] Speaker 2: Untack that a bit.
[2:56] Speaker 1: Sure.
[2:57] Speaker 3: So when a galaxy forms from a massive primordial cloud
[3:01] Speaker 3: of gas and dust, it naturally has some slight rotation
[3:05] Speaker 3: to it, right? Just a little bit of a spin.
[3:07] Speaker 2: Like water going down a drain.
[3:09] Speaker 3: Kind of, yeah. And as gravity causes that massive cloud
[3:13] Speaker 3: to collapse inward, the rotation starts to speed up. Think
[3:16] Speaker 3: of a figure skater pulling their arms out.
[3:18] Speaker 2: Right, they spin faster.
[3:19] Speaker 3: Exactly. And because the gas and dust particles are constantly
[3:23] Speaker 3: colliding with one another in this dense cloud, They lose
[3:26] Speaker 3: energy in the up and down directions. So all that
[3:28] Speaker 3: material is forced to settle into this flat spinning disk.
[3:31] Speaker 2: So the physics of the spinning system basically forces the
[3:35] Speaker 2: gas and dust to organize into a flat plane over, what,
[3:39] Speaker 2: billions of years?
[3:40] Speaker 3: Yeah, billions of years of just flattening out.
[3:43] Speaker 2: But the outskirts, what you call the galactic halo, those
[3:45] Speaker 2: are different, right? Because the objects out there didn't form
[3:48] Speaker 2: in that same orderly flat collapse.
[3:52] Speaker 3: Right, they didn't. The halo is populated by objects that, well,
[3:55] Speaker 3: they fill in much later. Or they're objects like older
[3:58] Speaker 3: star clusters that just don't experience those same fluid-like collisions.
[4:02] Speaker 2: Because they're already formed stars, not just loose gas.
[4:05] Speaker 3: Exactly. Without the friction that flattened the gas disk, these
[4:09] Speaker 3: clusters in the halo just keep buzzing around in completely random,
[4:13] Speaker 3: highly elliptical orbits.
[4:14] Speaker 2: So they're just flying everywhere.
[4:16] Speaker 3: Oh, totally. They plunge right through the disk. They arc.
[4:19] Speaker 3: hundreds of thousands of light years high above it, and
[4:21] Speaker 3: they just loop around the galactic core in these wild,
[4:25] Speaker 3: unpredictable trajectories.
[4:27] Speaker 2: I always like to think of it, it's kind of
[4:28] Speaker 2: like the Milky Way is a neatly organized dinner plate, right?
[4:31] Speaker 2: Just sitting there in the middle of a chaotic, swirling
[4:33] Speaker 2: washing machine.
[4:34] Speaker 3: That is a remarkably accurate way to picture it, actually.
[4:38] Speaker 2: And out in this chaotic frontier, this washing machine, we
[4:41] Speaker 2: find what we call stellar streams.
[4:43] Speaker 3: Yes. The rogue bands of stars.
[4:46] Speaker 2: Right. They aren't sitting in the flat disks or... Zipping
[4:49] Speaker 2: through the halo and these long cosmic rivers. I mean,
[4:52] Speaker 2: we are talking about ribbons of stars that can stretch
[4:56] Speaker 2: for hundreds of thousands of light years across the sky.
[4:59] Speaker 3: It's a scale that's almost impossible to truly visualize.
[5:02] Speaker 2: It really is. It makes you wonder, you know, what
[5:04] Speaker 2: the night sky would actually look like if you lived
[5:06] Speaker 2: on a planet that was orbiting a star inside one
[5:09] Speaker 2: of these rogue chaotic bands.
[5:12] Speaker 3: Oh, it would be spectacular. Right.
[5:14] Speaker 2: Because if you were inside a stellar stream rather than
[5:17] Speaker 2: inside the flat plane of the Milky Way looking out
[5:19] Speaker 2: like we do, the view would be completely alien.
[5:22] Speaker 3: Completely. Because, well, you wouldn't be surrounded by a dense
[5:26] Speaker 3: spherical neighborhood of stars in all directions like we are.
[5:29] Speaker 2: Right.
[5:30] Speaker 3: Since your star cluster has been stretched out, your local
[5:32] Speaker 3: stars would appear arranged in this thin glowing line ahead
[5:36] Speaker 3: of you and behind you.
[5:37] Speaker 2: Like a massive illuminated highway stretching across the dark sky.
[5:41] Speaker 3: Yeah, an endless highway of stars. And when you look
[5:44] Speaker 3: toward the Milky Way itself, you wouldn't just see a
[5:46] Speaker 3: band of light cutting across the horizon.
[5:49] Speaker 2: Because you wouldn't be inside it.
[5:50] Speaker 3: Exactly. If your stream carries you high above the galactic plane,
[5:54] Speaker 3: you'd look down and see the entire face of the
[5:56] Speaker 3: spiral galaxy. Wow. You'd just see this massive swirling disk
[6:00] Speaker 3: of fire dominating your entire sky and But you'd know
[6:04] Speaker 3: you weren't truly a part of it.
[6:05] Speaker 2: You're just like the debris circling it.
[6:07] Speaker 3: Just a ghost riding on the outskirts.
[6:10] Speaker 2: But, you know, I do want to challenge a common
[6:13] Speaker 2: description I often hear regarding how these streams actually move.
[6:16] Speaker 3: Sure, go for it.
[6:17] Speaker 2: So a frequent analogy I see is that stellar streams
[6:22] Speaker 2: orbit the Milky Way, much like planets in our solar
[6:25] Speaker 2: system orbit the sun. Right.
[6:27] Speaker 3: You see that a lot.
[6:28] Speaker 2: But I want to push back on that because how
[6:29] Speaker 2: can a massive river of individual stars spread out over
[6:34] Speaker 2: hundreds of thousands of light years behave like a single
[6:38] Speaker 2: solid planet?
[6:39] Speaker 3: That is a great point. And it's where the analogy
[6:41] Speaker 3: kind of breaks down. The idea of planets orbiting a
[6:45] Speaker 3: star is strictly limited to the trajectory. It has nothing
[6:48] Speaker 3: to do with the physical structure of the stream.
[6:50] Speaker 2: Because a planet is a gravitationally bound solid sphere.
[6:54] Speaker 3: Exactly. Yeah. And a stellar stream It's definitely not solid.
[6:58] Speaker 3: I mean, it's essentially the ghost of a former cluster
[7:02] Speaker 3: of stars. The individual stars in the stream, they are
[7:05] Speaker 3: no longer tightly bound to one another by their own gravity.
[7:08] Speaker 2: So they're not holding hams, so to speak.
[7:10] Speaker 3: No, not at all. They are just following the exact
[7:13] Speaker 3: same path through space. Think of a flock of birds
[7:17] Speaker 3: that have been stretched out into a single file line
[7:20] Speaker 3: over miles. Okay, yeah. They're all flying in the same direction.
[7:23] Speaker 3: They're tracing the same path around a mountain. but they
[7:25] Speaker 3: aren't physically attached to one another.
[7:27] Speaker 2: They're just individual objects doomed to walk the exact same
[7:31] Speaker 2: gravitational path.
[7:32] Speaker 3: Precisely.
[7:33] Speaker 2: Which is fascinating. But to really understand how these rivers
[7:36] Speaker 2: end up on that path in the first place and
[7:38] Speaker 2: why they stretch out like that flock of birds, we
[7:40] Speaker 2: kind of have to look at the incredibly violent way
[7:43] Speaker 2: they're actually born.
[7:45] Speaker 3: Yeah, it's a rough origin story. So a stellar stream
[7:49] Speaker 3: forms when a tightly packed group of stars, so like
[7:53] Speaker 3: a globular cluster of or a small dwarf galaxy, crashes
[7:57] Speaker 3: into a larger host galaxy.
[7:58] Speaker 2: And gets ensnared by its gravity. Right.
[8:00] Speaker 3: And over time, that really dense cluster is just stretched
[8:04] Speaker 3: into a long, thin filament.
[8:05] Speaker 2: See, when I hear the word crash in the context
[8:08] Speaker 2: of galaxies, my mind immediately jumps to, you know, a
[8:12] Speaker 2: fiery explosion.
[8:13] Speaker 3: A dark crash.
[8:14] Speaker 2: Exactly. Two dense objects slamming into each other. But physical
[8:18] Speaker 2: star-to-star collisions are actually incredibly rare, right? Because space is
[8:22] Speaker 2: just so overwhelmingly vast. Right.
[8:24] Speaker 3: It's mostly empty space. So what's actually crashing together are
[8:28] Speaker 3: the gravitational fields. Okay.
[8:29] Speaker 2: So it's not a fiery explosion. No.
[8:31] Speaker 3: The violence here is a slow, agonizing gravitational stretching that
[8:35] Speaker 3: plays out over millions or even billions of years.
[8:38] Speaker 2: Yeah.
[8:39] Speaker 3: We were dealing with tidal forces on a massive galactic scale.
[8:43] Speaker 2: I usually visualize this tidal force like a ball of
[8:45] Speaker 2: taffy getting pulled apart.
[8:46] Speaker 3: Oh, that's a good one.
[8:48] Speaker 2: Right. So you have a nice, round, gravitationally bound cluster
[8:51] Speaker 2: of stars. That's our taffy ball. And as it gets
[8:55] Speaker 2: close to the Milky Way, the gravity of the Milky
[8:57] Speaker 2: Way acts like this invisible taffy pulling machine.
[9:00] Speaker 1: Yeah.
[9:01] Speaker 2: Because the strength of gravity gets weaker the further away
[9:04] Speaker 2: you are, right? So the part of the star cluster
[9:06] Speaker 2: that is closest to the Milky Way gets pulled significantly
[9:09] Speaker 2: harder than the part of the cluster that's further away.
[9:12] Speaker 3: That's exactly it. The mechanics of that taffy machine, they
[9:16] Speaker 3: come down to what we call differential gravity.
[9:19] Speaker 2: Differential gravity. Right.
[9:20] Speaker 3: The gravitational pull on the near side of the star
[9:23] Speaker 3: cluster is literally stronger than the internal gravity that's holding
[9:27] Speaker 3: the cluster together.
[9:28] Speaker 2: Oh, so it just overpowers it completely. Yeah.
[9:30] Speaker 3: And simultaneously, the far side of the cluster is experiencing
[9:33] Speaker 3: a weaker pull from the Milky Way. So the front
[9:36] Speaker 3: of the cluster accelerates and pulls away from the center
[9:39] Speaker 3: while the back of the cluster lags behind.
[9:41] Speaker 2: And over millions of years... That differential gravity just draws
[9:46] Speaker 2: that tight ball of stars out into a long string.
[9:49] Speaker 3: Into a river.
[9:50] Speaker 2: And this isn't just some quirky feature of our specific galaxy, right?
[9:55] Speaker 2: Because most galaxies host stellar streams.
[9:57] Speaker 3: Oh, absolutely. Well, the Milky Way is are obviously the
[10:02] Speaker 3: most visible to us just because of our proximity observational
[10:05] Speaker 3: astronomy shows evidence of these streams everywhere.
[10:09] Speaker 2: Which implies something pretty dark, honestly. It means every galaxy
[10:12] Speaker 2: is in a constant state of cannibalizing smaller star clusters.
[10:16] Speaker 3: It's a rough universe out there.
[10:17] Speaker 2: The entire universe is governed by these slow motion gravitational accumulations.
[10:22] Speaker 2: I mean, our own Milky Way has consumed dozens, maybe
[10:26] Speaker 2: hundreds of smaller galaxies to reach its current mass. Yeah.
[10:29] Speaker 3: And the stellar streams are literally the visible scars of
[10:33] Speaker 3: that long history of consumption.
[10:34] Speaker 2: The visible scars. I love that phrasing. And for years,
[10:37] Speaker 2: astronomers have viewed these beautiful, stretched out scars as the
[10:41] Speaker 2: ultimate tool for solving, like, the greatest who-do-nit in modern physics,
[10:45] Speaker 2: which is mapping dark matter.
[10:47] Speaker 3: Yes, the Holy Grail.
[10:49] Speaker 2: Because we already know dark matter exerts this massive gravitational pull, right?
[10:53] Speaker 2: And it makes up the vast majority of the mass
[10:55] Speaker 2: in the universe. It's the invisible scaffolding. Right.
[10:57] Speaker 3: Without it, galaxies would literally fly apart.
[11:00] Speaker 2: Yeah, we know it doesn't interact with light or normal matter,
[11:03] Speaker 2: except through gravity. Without it, the visible matter in the
[11:07] Speaker 2: Milky Way just wouldn't have enough gravity to hold itself
[11:09] Speaker 2: together while spinning at the speeds we observe.
[11:11] Speaker 3: Exactly. It's the glue.
[11:13] Speaker 2: But the core of the dark matter mystery, especially when
[11:15] Speaker 2: it comes to stellar streams, focuses on the specific concept
[11:20] Speaker 2: of subhalos.
[11:22] Speaker 3: Right, subhalos. So different theoretical models of particle physics predict
[11:27] Speaker 3: different behaviors for dark matter.
[11:29] Speaker 1: Okay.
[11:30] Speaker 3: If dark matter is what we call cold, meaning the
[11:32] Speaker 3: particles move pretty sluggishly compared to the speed of light,
[11:36] Speaker 3: gravity would cause it to clump together tightly over billions
[11:39] Speaker 3: of years.
[11:40] Speaker 2: Clumping up. Right.
[11:41] Speaker 3: But if it is warm, it would form looser, more
[11:44] Speaker 3: diffuse structures. But these clumps, regardless of how dense they are,
[11:49] Speaker 3: they are called subhalos.
[11:51] Speaker 2: Okay, so subhalos are just localized clumps of dark matter.
[11:53] Speaker 3: Exactly. They're these dense knots of dark matter scattered throughout
[11:57] Speaker 3: the larger universe. diffuse dark matter halo that envelops the
[12:00] Speaker 3: entire galaxy.
[12:01] Speaker 2: But wait, let me push back on this for a second.
[12:03] Speaker 2: If dark matter is literally the scaffolding of the universe
[12:07] Speaker 2: and it's everywhere, why are we looking for small clumps
[12:10] Speaker 2: of it? Shouldn't it just be this smooth, uniform cloud everywhere?
[12:14] Speaker 3: That's a really common point of confusion. So the overarching
[12:18] Speaker 3: halo is everywhere, but matter, even invisible matter, naturally wants
[12:23] Speaker 3: to clump under its own gravity. Just like regular matter
[12:27] Speaker 3: forms dense stars and empty space, dark matter forms this large,
[12:31] Speaker 3: diffuse cloud, but with smaller, incredibly dense nodes inside it. Oh,
[12:36] Speaker 3: I see.
[12:36] Speaker 2: So there are dense pockets.
[12:38] Speaker 3: Yeah, subhalos. And so we have these invisible clumps, these
[12:41] Speaker 3: subhalos orbiting through the galactic halo.
[12:43] Speaker 2: Along with the stellar streams.
[12:45] Speaker 3: Right. The streams are also orbiting through the halo. So
[12:47] Speaker 3: astronomers realized that a stellar stream is just a ball
[12:50] Speaker 3: of stars stretched out by the host galaxy's gravity. It
[12:53] Speaker 3: should logically look like a relatively smooth, uniform smear of stars.
[12:57] Speaker 2: Like a pristine ribbon.
[12:58] Speaker 3: Exactly. A perfectly straight, smooth highway. But when we actually
[13:02] Speaker 3: look at the streams in our galaxy, they are highly irregular.
[13:05] Speaker 2: They aren't smooth at all.
[13:06] Speaker 3: No, they have gaps. They have these sharp kinks. I mean,
[13:09] Speaker 3: they just look battered.
[13:10] Speaker 2: And so the leading theory proposed that these irregularities were
[13:14] Speaker 2: the direct signature of those dark matter subhilos.
[13:17] Speaker 3: Exactly. The idea was that a massive, invisible clump of
[13:21] Speaker 3: dark matter... Plows through the middle of a smooth, stellar stream.
[13:25] Speaker 2: Just crashes right through it. Yeah.
[13:27] Speaker 3: And we can't see the dark matter clump itself, but
[13:29] Speaker 3: its dense gravitational field violently scatters the visible stars in
[13:33] Speaker 3: the stream, and it leaves behind a gap or a
[13:36] Speaker 3: severe kink.
[13:37] Speaker 2: It's the classic analogy, right? It's like trying to prove
[13:40] Speaker 2: the existence of an invisible bowling ball by watching how
[13:42] Speaker 2: it violently scatters visible bowling pins.
[13:45] Speaker 3: That is exactly what they were doing.
[13:46] Speaker 2: Because we don't need to see the ball if we
[13:48] Speaker 2: can perfectly map the trajectory of the flying pins. If
[13:52] Speaker 2: this theory holds true, studying the specific shapes and sizes
[13:55] Speaker 2: of those gaps and kinks in the stellar streams could
[13:58] Speaker 2: finally teach us about the actual fundamental composition of dark matter.
[14:03] Speaker 3: The stakes here were just incredibly high. Because by analyzing
[14:07] Speaker 3: the physical dimensions of the scars left on the stellar streams,
[14:11] Speaker 3: astrophysicists believe they could essentially reverse engineer the mass, the velocity,
[14:17] Speaker 3: and the density of that invisible bowling ball that caused it.
[14:21] Speaker 1: Wow.
[14:21] Speaker 2: So they could read the scars to find the weapon.
[14:23] Speaker 3: Exactly. And this would allow us to constrain our models
[14:26] Speaker 3: of particle physics and finally determine whether dark matter is cold, warm, or,
[14:32] Speaker 3: you know, something else entirely.
[14:34] Speaker 2: It's a way to essentially see the invisible by looking
[14:37] Speaker 2: at the damage it leaves behind.
[14:38] Speaker 3: It was widely considered the most promising direct method to
[14:42] Speaker 3: hunt for these invisible subolos in our immediate cosmic neighborhood.
[14:46] Speaker 2: It's just such an incredibly elegant theory. You find the
[14:49] Speaker 2: mangled streams, you map the kinks, you calculate the mass
[14:52] Speaker 2: of the dark matter clumps, and boom, you inch closer
[14:54] Speaker 2: to understanding the fundamental nature of the universe.
[14:57] Speaker 3: Very elegant.
[14:58] Speaker 2: But as we know, an elegant theory is really only
[14:59] Speaker 2: good until someone decides to put it to the ultimate extreme.
[15:02] Speaker 2: virtual tests.
[15:03] Speaker 3: And that is exactly what happened.
[15:05] Speaker 2: Right. A team at the University of Washington decided to
[15:08] Speaker 2: rigorously test that foundational assumption underlying this entire methodology. Let's
[15:14] Speaker 2: get into the study.
[15:15] Speaker 3: Yeah. So this study was published in the Astrophysical Journal
[15:18] Speaker 3: on August 27th, 2026. It was led by Arpit Arora,
[15:22] Speaker 3: who's a postdoctoral scholar alongside co-authors Nora Schiff and James Davenport.
[15:27] Speaker 2: And what they did was they basically built a universe
[15:30] Speaker 2: inside a computer.
[15:31] Speaker 3: Using highly advanced N-body simulations, yes, they simulated four distinct
[15:36] Speaker 3: Milky Way-sized galaxies. But crucially, they built these virtual galaxies
[15:41] Speaker 3: completely without any dark matter clumps.
[15:43] Speaker 2: No dark matter clumps at all. No subhalos. No invisible
[15:47] Speaker 2: bowling balls. They intentionally removed the very thing everyone was
[15:50] Speaker 2: looking for, creating this massive control group universe.
[15:54] Speaker 3: Because in experimental science, isolating variables is the only real
[15:57] Speaker 3: way to establish true causality.
[15:59] Speaker 1: Right.
[15:59] Speaker 2: You have to know what's causing what.
[16:01] Speaker 3: Exactly. So by removing the dark matters of halos entirely,
[16:04] Speaker 3: they left only the standard visible mass of the host
[16:07] Speaker 3: galaxy and the overarching smooth background gravity to interact with
[16:11] Speaker 3: the objects in the halo.
[16:12] Speaker 2: And then they took these clump-free galaxies and just peppered
[16:16] Speaker 2: them with roughly 15,000 stellar streams. 15,000. 15,000 virtual rivers
[16:23] Speaker 2: of stars. And they just let the simulation run forward
[16:26] Speaker 2: in time for 5 billion simulated years. Which, first of all,
[16:29] Speaker 2: the sheer computational audacity of this is staggering.
[16:32] Speaker 3: That's massive.
[16:33] Speaker 2: I mean, simulating 15,000 interacting stellar streams over 5 billion
[16:36] Speaker 2: years is like trying to calculate the exact trajectory of
[16:41] Speaker 2: every single drop of water in a hurricane for a decade.
[16:44] Speaker 3: That's a really good way to put it. Simulating that
[16:46] Speaker 3: requires immense computational power. Because in n-body simulation, it calculates
[16:51] Speaker 3: the gravitational force exerted by every single particle... On every
[16:55] Speaker 3: other particle at discrete time steps.
[16:56] Speaker 2: Wait, every single particle on every other particle?
[16:59] Speaker 1: Yes.
[16:59] Speaker 3: So when you are dealing with millions of particles representing
[17:02] Speaker 3: the mass of a galaxy and thousands of streams, the
[17:05] Speaker 3: sheer volume of mathematical calculations just scales exponentially. It requires
[17:10] Speaker 3: calculating these continuously shifting gravitational gradients over incredibly vast spans
[17:15] Speaker 3: of time.
[17:15] Speaker 2: But why exactly five billion years? What is the significance
[17:20] Speaker 2: of that massive time span in galactic terms? Like, why
[17:24] Speaker 2: not run it for just a few million?
[17:25] Speaker 3: Well, a few million years is basically a blink of
[17:28] Speaker 3: an eye for a galaxy.
[17:29] Speaker 2: Right.
[17:30] Speaker 3: It takes hundreds of millions of years for a stellar
[17:34] Speaker 3: stream to complete just a single orbit around a galaxy
[17:37] Speaker 3: like the Milky Way. Yeah. So if you want to
[17:39] Speaker 3: see how these streams truly evolve and degrade, you have
[17:42] Speaker 3: to let the clock run for billions of years. to
[17:45] Speaker 3: allow those massive slow-motion orbits to actually play out.
[17:49] Speaker 2: Ah, okay. So it's about letting the physics fully unfold.
[17:52] Speaker 3: Exactly.
[17:52] Speaker 2: So if the underlying assumption of the dark matter hunt
[17:55] Speaker 2: was correct, that these invisible bowling balls are the exclusive
[17:57] Speaker 2: driver of the gaps and kinks, then a simulated universe
[18:01] Speaker 2: completely devoid of those bowling balls should, theoretically, leave the
[18:05] Speaker 2: bowling pins standing perfectly still.
[18:06] Speaker 3: That was the foundational expectation, yes.
[18:08] Speaker 2: The expectation was that the simulation would yield 15,000 perfectly smooth,
[18:13] Speaker 2: uniform filaments of stars. Because if dark matter clumps cause
[18:16] Speaker 2: the irregularities, removing the clumps must remove the irregularities.
[18:20] Speaker 1: Right.
[18:20] Speaker 3: But the universe is never that simple.
[18:23] Speaker 2: No, it is not. Because when ARPIT Aurora and the
[18:26] Speaker 2: team actually analyzed the data after 5 billion simulated years,
[18:31] Speaker 2: the results were just shocking. They fundamentally fractured that entire assumption.
[18:36] Speaker 3: They really did.
[18:37] Speaker 2: Out of 15,000 stellar streams in this control universe, only
[18:41] Speaker 2: 70 remained perfectly smooth and featureless.
[18:44] Speaker 3: Only 70 out of 15,000.
[18:46] Speaker 2: That means 14,930 streams exhibited intense irregularities. And we're not
[18:53] Speaker 2: just talking about minor fuzziness at the edges of the
[18:55] Speaker 2: streams here.
[18:56] Speaker 3: No, the simulation generated severe structural damage across almost the
[19:00] Speaker 3: entire population of these stellar rivers.
[19:02] Speaker 2: I mean, ARPIT Aurora expected some irregularities, right? But the
[19:05] Speaker 2: sheer volume was staggering.
[19:07] Speaker 3: The catalog of aberrations they found was just incredible. The
[19:10] Speaker 3: data revealed wiggles where a stream deviated from its calculated
[19:14] Speaker 3: orbital path in this serpentine pattern.
[19:16] Speaker 2: Like a snake.
[19:17] Speaker 3: Yeah. There were sharp kinks where the stream bent abruptly
[19:20] Speaker 3: as if it had been fractured by a massive point
[19:22] Speaker 3: of mass.
[19:23] Speaker 2: Which is exactly what they thought the dark matter did.
[19:26] Speaker 3: Exactly. There were spurs and branches where ribbons of stellar
[19:30] Speaker 3: material had literally been sheared off the main body of
[19:33] Speaker 3: the stream. There were distinct massive gaps, again, the exact
[19:38] Speaker 3: morphological features of previously attributed directly to those dark matter
[19:42] Speaker 3: bowling balls.
[19:42] Speaker 2: It's crazy.
[19:44] Speaker 3: And there were dense clumps where stars had piled up
[19:47] Speaker 3: into tight nodes along the stream. Some streams were just
[19:50] Speaker 3: totally torn apart, completely shredded into unrecognizable debris fields.
[19:54] Speaker 2: I imagine it's like building a pristine, smoothly paved highway
[19:58] Speaker 2: out in the middle of a barren desert, right? And
[20:01] Speaker 2: you lock it behind a massive fence and you mathematically
[20:04] Speaker 2: confirm that absolutely zero vehicles ever drive on it. You
[20:07] Speaker 2: know for a fact it's empty. But then you come
[20:09] Speaker 2: back five years later and you find the entire highway
[20:11] Speaker 2: completely ripped up by massive potholes, skid marks, collapsed asphalt.
[20:16] Speaker 2: It just defies the core logic of the experiment.
[20:19] Speaker 3: It does. And the psychological and really the paradigmatic impact
[20:22] Speaker 3: of this result on the astronomical community is profound.
[20:25] Speaker 2: I can imagine. People must be reeling.
[20:27] Speaker 3: They are. Because for decades, observational astronomers have been meticulously
[20:31] Speaker 3: cataloging every kink and gap in the Milky Way's stellar streams.
[20:36] Speaker 2: Right. Drawing little maps.
[20:37] Speaker 3: Entire careers have been built on categorizing these features and
[20:41] Speaker 3: publishing papers attributing their specific geometries to dark matter interactions.
[20:47] Speaker 3: And this single simulation demonstrates that the foundational idea that
[20:51] Speaker 3: streams are naturally thin and smooth unless acted upon by
[20:55] Speaker 3: a dark matter clump is just false.
[20:58] Speaker 2: Let me push you on this, though. If 14,930 out
[21:00] Speaker 2: of 15,000 streams were mangled beyond recognition... And there wasn't
[21:05] Speaker 2: a single clump of dark matter present in the entire simulation.
[21:09] Speaker 2: Doesn't this completely destroy our best method for finding dark matter? Like,
[21:12] Speaker 2: is the hunt just doomed?
[21:14] Speaker 3: It definitely complicates it immensely. But to figure out if
[21:17] Speaker 3: the hunt is actually doomed, we have to uncover the
[21:19] Speaker 3: real culprit that mangled these virtual stars in the first place.
[21:22] Speaker 2: Right. If dark matter didn't mangle the virtual stars, what
[21:25] Speaker 2: ripped up the desert highway?
[21:26] Speaker 3: The cause of the wiggles, the kinks, the branches, and
[21:29] Speaker 3: gaps was the internal structure of the host galaxies themselves.
[21:33] Speaker 2: The galaxy itself did it.
[21:34] Speaker 3: Yeah. When we conceptualize the Milky Way, we often simplify
[21:37] Speaker 3: it into this uniform disk of mass that just smoothly
[21:41] Speaker 3: decreases in density as you move outward from the core.
[21:45] Speaker 2: Just a smooth gradient.
[21:46] Speaker 1: Right.
[21:47] Speaker 3: But a real galaxy is highly textured. It is uneven.
[21:50] Speaker 2: And the simulated galaxies were built to accurately mimic that
[21:54] Speaker 2: real mass distribution. Right.
[21:55] Speaker 3: Exactly. The stars, the gas, and the dust are not
[21:59] Speaker 3: spread evenly across the disk at all. You have the
[22:01] Speaker 3: massive central bulge, which is packed tightly with ancient stars.
[22:05] Speaker 3: You have the sweeping spiral arms, which are essentially these
[22:08] Speaker 3: dense traffic jams of stellar material and gas.
[22:11] Speaker 2: Right.
[22:12] Speaker 3: And embedded within those arms, you have giant molecular clouds,
[22:16] Speaker 3: which possess immense localized mass.
[22:18] Speaker 2: So it's lumpy.
[22:19] Speaker 3: It's very lumpy. And this uneven distribution of matter creates
[22:23] Speaker 3: a highly complex gravitational landscape. Gravity isn't simply pulling an
[22:28] Speaker 3: object smoothly toward the geometric center of the galaxy.
[22:30] Speaker 2: It's pulling in different directions.
[22:32] Speaker 3: Right. The gravitational field might be pulling slightly to the
[22:34] Speaker 3: left toward a dense spiral arm or slightly to the
[22:38] Speaker 3: right toward a passing molecular cloud. The density of the
[22:42] Speaker 3: galaxy is constantly fluctuating as you move through it.
[22:45] Speaker 2: I think of it like this. I call it the
[22:46] Speaker 2: gravitational froth.
[22:48] Speaker 3: Oh, I like that.
[22:48] Speaker 2: If you imagine a river of water trying to flow
[22:51] Speaker 2: in a perfectly straight line, right? A smooth, concrete riverbed
[22:55] Speaker 2: will allow for a completely smooth flow. But the gravitational
[22:59] Speaker 2: landscape of the Milky Way is like a riverbed full
[23:02] Speaker 2: of jagged rocks, sudden deep drops, and uneven terrain.
[23:06] Speaker 3: Yes, exactly.
[23:07] Speaker 2: And as the water flows over that uneven terrain, the
[23:09] Speaker 2: varying depths and obstacles create violent rapids, whirlpools, and chaotic
[23:14] Speaker 2: cross currents. The stellar streams are the water, and the
[23:18] Speaker 2: uneven mass of the Milky Way is that jagged riverbed.
[23:21] Speaker 3: That's a perfect analogy. Because as these fragile streams of
[23:24] Speaker 3: stars pass through or even just pass near these denser
[23:27] Speaker 3: regions of the galaxy, the gravitational pull on them is asymmetrical.
[23:31] Speaker 2: It pulls harder on one side than the other.
[23:33] Speaker 3: Exactly. That asymmetrical pull your gravitational froth. It bends and
[23:37] Speaker 3: tears the streams. And the simulation confirmed this by tracking
[23:41] Speaker 3: the orbital paths.
[23:42] Speaker 2: Of the streams. What did they find with the orbits?
[23:44] Speaker 3: They found that the streams that orbited closer to the
[23:47] Speaker 3: galactic core acquired significantly more irregularities than the streams orbiting
[23:52] Speaker 3: further out in the extreme edges of the halo.
[23:54] Speaker 2: Which makes perfect sense, right? Because the central region of
[23:57] Speaker 2: the galaxy is a much denser, clumpier environment. Closer you
[24:01] Speaker 2: get to the center of the galaxy, the more violent
[24:04] Speaker 2: the gravitational froth becomes.
[24:06] Speaker 3: Yes. The central bulge and those inner spiral arms represent
[24:10] Speaker 3: a truly chaotic gravitational environment. The gradient of the gravitational
[24:14] Speaker 3: field there is incredibly steep, and the mass is highly concentrated.
[24:18] Speaker 2: So if a stream goes near there, it's doomed.
[24:20] Speaker 3: Pretty much. If a delicate stellar stream plunges through or
[24:24] Speaker 3: even closely skirts the central bulge, it is subjected to immense,
[24:29] Speaker 3: rapidly changing tidal forces. It's essentially being dragged through a
[24:32] Speaker 3: gravitational blender.
[24:33] Speaker 2: A blender.
[24:34] Speaker 1: Wow.
[24:35] Speaker 2: Yeah.
[24:36] Speaker 3: The streams in the outer halo experience a slightly smoother ride, sure,
[24:40] Speaker 3: but they are still subject to the overarching unevenness of
[24:43] Speaker 3: the galaxy's gravitational field over billions of years.
[24:46] Speaker 2: But, I mean, this presents a massive existential problem for astrophysics,
[24:50] Speaker 2: doesn't it?
[24:51] Speaker 3: Oh, it really does.
[24:52] Speaker 2: Because our own galaxy, standard, uneven, frothy mass, is perfectly
[24:56] Speaker 2: mimicking the theoretical dark matter signal. We spent decades looking
[25:00] Speaker 2: for invisible bowling balls. only to discover that the floor
[25:04] Speaker 2: of the bowling alley is just severely warped and full
[25:06] Speaker 2: of dents, causing the pins to scatter anyway.
[25:09] Speaker 3: It's a frustrating realization. It fundamentally obscures the dark matter
[25:13] Speaker 3: signal we've been looking for.
[25:15] Speaker 2: So where do astronomers even go from here?
[25:17] Speaker 3: Well, it complicates the field immensely. But the University of
[25:21] Speaker 3: Washington team and really the broader astrophysical community, they don't
[25:26] Speaker 3: view this as a dead end.
[25:27] Speaker 2: They see a clear course forward.
[25:29] Speaker 3: Exactly. In the evolution of scientific inquiry, discovering a massive
[25:33] Speaker 3: source of background noise is often the prerequisite for isolating
[25:36] Speaker 3: the true signal.
[25:37] Speaker 2: You have to know the noise to filter it out.
[25:39] Speaker 3: Precisely. The first era of this research assumed every structural
[25:43] Speaker 3: anomaly was caused by dark matter. This new era has
[25:47] Speaker 3: to focus on distinguishing between the background noise of the
[25:49] Speaker 3: galaxy and the true signal of the Cipollos.
[25:52] Speaker 2: So the next immediate step for Arpit Aurora and the
[25:54] Speaker 2: research team is to literally run the simulation again. But
[25:57] Speaker 2: this time... They're going to put the dark matter clumps
[26:01] Speaker 2: back into the virtual universe, right?
[26:02] Speaker 3: That's the plan. They've established the baseline of the mangled
[26:06] Speaker 3: streams caused exclusively by the host galaxy. Now, by reintroducing
[26:11] Speaker 3: the dark matter subholos, they can analyze the data to
[26:14] Speaker 3: see if the dark matter clumps produce distinct, unique irregularities
[26:18] Speaker 3: compared to the galaxy alone.
[26:20] Speaker 2: They're looking for a unique signature. Like, do dark matter
[26:23] Speaker 2: clumps cause sharper, more acute kinks than the gravitational froth?
[26:27] Speaker 2: Do they cause wider, cleaner gaps? Do they affect streams
[26:31] Speaker 2: in the outer halo in a way that the galaxy's
[26:33] Speaker 2: intrinsic froth just can't physically replicate?
[26:36] Speaker 3: Exactly. They are essentially trying to build a taxonomy of
[26:39] Speaker 3: stream features.
[26:40] Speaker 2: A taxonomy? Like medical diagnostics?
[26:42] Speaker 3: Yeah, exactly like that.
[26:43] Speaker 2: Because right now we just know the streams have a cough, right?
[26:46] Speaker 2: But we don't know the cause. The new simulations aim
[26:50] Speaker 2: to provide the diagnostic criteria to look at the curvature
[26:53] Speaker 2: of a specific gap. or, you know, the way stars
[26:56] Speaker 2: pile up at the edge of a kink and definitively
[26:59] Speaker 2: determine whether it was a host galaxy cough or a
[27:03] Speaker 2: dark matter cough.
[27:04] Speaker 3: That is a brilliant way to phrase it. We need
[27:06] Speaker 3: those diagnostic criteria because simulations are, at the end of
[27:09] Speaker 3: the day, purely theoretical frameworks until they're anchored by observational reality.
[27:14] Speaker 2: Right. You need real telescope data to back it up.
[27:16] Speaker 3: Exactly. To build this taxonomy, we need a massive influx
[27:20] Speaker 3: of real-world data. And that is where the Vera C.
[27:22] Speaker 3: Rubin Observatory is going to completely fundamentally changed the landscape
[27:26] Speaker 3: of observational astronomy.
[27:28] Speaker 2: Oh man, the Rubin Observatory. And specifically, its Samani Survey Telescope.
[27:32] Speaker 2: That is arguably one of the most important astronomical instruments
[27:36] Speaker 2: of this entire decade.
[27:37] Speaker 3: It really is. It is designed to conduct the legacy
[27:39] Speaker 3: survey of space and time. It's going to use a 3.2
[27:42] Speaker 3: gigapixel camera to scan the entire visible southern sky every
[27:46] Speaker 3: few nights.
[27:47] Speaker 2: 3.2 gigapixels? That's just absurd.
[27:49] Speaker 3: It's unbelievable.
[27:51] Speaker 2: The optical design and the massive light gathering power of
[27:54] Speaker 2: its 8.4 meter primary mirror make it incredibly sensitive to faint, diffuse,
[28:00] Speaker 2: low surface brightness objects.
[28:01] Speaker 3: Which is exactly what stellar streams are. They are incredibly
[28:05] Speaker 3: faint wisps of stars. I mean, currently, we only know
[28:08] Speaker 3: of a very small fraction of the stellar streams that
[28:11] Speaker 3: likely exist in the Milky Way halo.
[28:12] Speaker 2: We're barely scratching the surface.
[28:14] Speaker 3: But the Rubin Observatory's sensitivity is expected to increase that
[28:18] Speaker 3: catalog exponentially, right?
[28:19] Speaker 2: Oh, massively. We are going to transition from analyzing a
[28:23] Speaker 2: handful of well-known streams to possessing a data set of
[28:26] Speaker 2: potentially hundreds or even thousands of streams, all mapped with
[28:31] Speaker 2: unprecedented precision.
[28:32] Speaker 3: And with that massive observational data set and the highly
[28:35] Speaker 3: detailed new simulations running in parallel, astrophysicists hope to basically
[28:39] Speaker 3: match the theoretical taxonomy to the real-world observations. That's the
[28:43] Speaker 3: ultimate goal. James Davenport, who is one of the co-authors
[28:47] Speaker 3: of the study, he summarizes the situation perfectly. He stated, sadly,
[28:51] Speaker 3: there's no magic wand to reveal the structure of dark matter.
[28:55] Speaker 3: Streams are complex systems, but they're still the most interesting
[28:58] Speaker 3: way to study dark matter close to home.
[29:00] Speaker 2: Close to home. I mean, that phrase is relative in astronomy,
[29:03] Speaker 2: but it's really crucial here, isn't it?
[29:06] Speaker 3: It really is. Because when astrophysicists study dark matter, they're
[29:10] Speaker 3: often relegated to observing the cosmic web.
[29:13] Speaker 2: The massive filaments between galaxies.
[29:15] Speaker 3: Right, these universe-spanning filaments of dark matter that entire galaxy
[29:19] Speaker 3: clusters sit within. Or they analyze the cosmic microwave background
[29:23] Speaker 3: to see the vast primordial imprints of dark matter in
[29:26] Speaker 3: the early universe.
[29:27] Speaker 2: But those observations occur on scales of millions or billions
[29:31] Speaker 2: of light years. The structures are incomprehensibly vast.
[29:34] Speaker 3: Yeah, and the specific localized details are just impossible to
[29:38] Speaker 3: resolve at that scale.
[29:39] Speaker 2: But the stellar stream... are literally right in our cosmic backyard.
[29:42] Speaker 2: They are actively interacting with the dark matter halo that
[29:44] Speaker 2: our own sun is currently orbiting within.
[29:47] Speaker 3: Exactly. So if we can crack the code of the
[29:49] Speaker 3: stellar streams, if we can separate the noise of the
[29:52] Speaker 3: gravitational froth from the signal of the subhalos, we aren't
[29:56] Speaker 3: just learning about dark matter on some abstract, universe-wide scale,
[30:01] Speaker 3: we are mapping the specific localized clumps of dark matter
[30:05] Speaker 3: floating through our own galactic neighborhood.
[30:07] Speaker 2: It is our best and perhaps only chance to generate
[30:11] Speaker 2: a high-resolution map of dark matter on a galactic scale.
[30:14] Speaker 3: It's an incredible opportunity.
[30:16] Speaker 2: But, okay, let me ask you about the nightmare scenario
[30:18] Speaker 2: for this specific avenue of research.
[30:20] Speaker 1: Uh-oh.
[30:21] Speaker 3: Okay.
[30:21] Speaker 2: What happens if they run the new simulation with the
[30:24] Speaker 2: dark matter clumps and they discover that the structural anomalies
[30:27] Speaker 2: are just completely degenerate? Yeah.
[30:29] Speaker 3: That's the fear.
[30:30] Speaker 2: Like what if a dark matter kink is physically and
[30:33] Speaker 2: mathematically indistinguishable from a galaxy kink?
[30:36] Speaker 3: If the signatures are truly degenerate, meaning different physical causes
[30:40] Speaker 3: produce the exact same observable effect on the stellar streams,
[30:44] Speaker 3: then yeah, streams will lose their status as the premier
[30:47] Speaker 3: tool for mapping individual dark matter cellulose.
[30:50] Speaker 2: Because we just wouldn't be able to tell the difference. Right.
[30:52] Speaker 3: It would mean the gravitational froth of the Milky Way
[30:55] Speaker 3: is an impenetrable disguise. We wouldn't be able to peer
[30:58] Speaker 3: through it.
[30:58] Speaker 2: So how long until we know?
[31:00] Speaker 3: Well, we are looking at years of computational refinement, followed
[31:03] Speaker 3: by years of data collection from the Rubin Observatory, before
[31:06] Speaker 3: we have a definitive answer on that.
[31:07] Speaker 2: So we have a long wait. We do. Yeah.
[31:10] Speaker 3: But I will say, even in that absolute worst-case scenario,
[31:14] Speaker 3: the scientific endeavor is not a failure.
[31:17] Speaker 2: How so?
[31:18] Speaker 3: Because by attempting to map the dark matter, and in
[31:21] Speaker 3: doing so, discovering the profound influence of the galaxy's internal structure,
[31:25] Speaker 3: we will have developed an unprecedented, incredibly accurate map of
[31:29] Speaker 3: the Milky Way's own internal gravitational landscape. Oh, I see.
[31:33] Speaker 2: We accidentally mapped the froth perfectly.
[31:35] Speaker 3: Exactly. It's a win-win for astrophysics, even if it's not
[31:38] Speaker 3: the specific win we initially wanted.
[31:40] Speaker 2: That's a great perspective. I mean, we started this exploration
[31:43] Speaker 2: with a sense of observational comfort, right? The astronomical community
[31:47] Speaker 2: thought they had this pristine tool. The assumption was that
[31:50] Speaker 2: stellar streams were smooth, elegant rivers of stars that that
[31:54] Speaker 2: would clearly and simply point us to the invisible dark
[31:57] Speaker 2: matter clumps scattered throughout the universe.
[31:59] Speaker 3: That's a beautiful idea.
[32:01] Speaker 2: But Arpit Arora, Nora Shipp, James Davenport, and the entire
[32:04] Speaker 2: team at the University of Washington have demonstrated that the
[32:07] Speaker 2: Milky Way's own chaotic, frothy gravity is an absolute master
[32:12] Speaker 2: of disguise.
[32:13] Speaker 3: A master of disguise.
[32:13] Speaker 2: Because without a single clump of dark matter present in
[32:17] Speaker 2: their simulated universe... The uneven, jagged mass of the host
[32:21] Speaker 2: galaxy completely mangled 14,930 out of 15,000 streams. It left
[32:27] Speaker 2: them riddled with the exact gaps, kinks, and wiggles that
[32:30] Speaker 2: perfectly mimic the dark forces we've been hunting for.
[32:33] Speaker 3: It really is a humbling reminder of the complexity of
[32:35] Speaker 3: the cosmos. The universe does not provide sterile, isolated laboratories
[32:40] Speaker 3: for us to test our theory. Oh no, it doesn't.
[32:41] Speaker 3: It provides messy, dynamic, deeply entangled systems. The background noise
[32:47] Speaker 3: of the universe is often just as complex and honestly
[32:50] Speaker 3: just as powerful as the exotic signals we're desperately searching for.
[32:53] Speaker 2: And that leaves us with a lingering question, I think.
[32:56] Speaker 2: Because if our own galaxy's standard messy gravity can so
[32:59] Speaker 2: perfectly mimic the exact invisible dark forces we're so desperately
[33:03] Speaker 2: searching for in these stellar streams, what other invisible mysteries
[33:07] Speaker 2: in the cosmos might simply be the normal uneven physics
[33:10] Speaker 2: of the universe playing elaborate tricks on our telescopes?
[33:13] Speaker 3: It really makes you wonder how much we're currently misinterpreting.
[33:16] Speaker 2: It definitely does. Next time you look up at the
[33:18] Speaker 2: night sky, remember that the neat, orderly spiral of the
[33:21] Speaker 2: Milky Way hides a chaotic, turbulent graveyard. And that graveyard
[33:25] Speaker 2: is keeping its secrets very, very well hidden.

Shows are listed from Apple Podcasts' charts and directory, and Podcast Index where it is used. Every show and episode belongs to its publisher and plays from the publisher's own feed; this site hosts none of them.