Is There No Black Hole? New Dark Matter Theory at the Center of the Milky Way

<v Speaker 1>Welcome to Bedtime Astronomy. Explore the wonders of the cosmos
<v Speaker 1>with our soothing Bedtime Astronomie podcast. Each episode offers a
<v Speaker 1>gentle journey through the stars, planets, and beyond, perfect for
<v Speaker 1>unwinding after a long day. Let's travel through the mysteries
<v Speaker 1>of the universe as you drift off into a peaceful
<v Speaker 1>slumber under the night sky.
<v Speaker 2>All right, let's just get straight into it. I want
<v Speaker 2>you to picture something. Picture the Milky Way galaxy, not
<v Speaker 2>just as a band of light in the night sky,
<v Speaker 2>but that classic, you know, top down view, the beautiful
<v Speaker 2>spiral arms, the billions of stars.
<v Speaker 3>The image we all have in our heads exactly.
<v Speaker 2>And now zoom in, go past our little solar system,
<v Speaker 2>past the Orion arm, and head right for that bright,
<v Speaker 2>glowing bulge at the very center, and then keep zooming
<v Speaker 2>right to the absolute bullseye. For decades, we've had this
<v Speaker 2>very comfortable story about what there we have.
<v Speaker 3>The story is Sagittarius A, the supermassive black hole, the anchor.
<v Speaker 2>The cosmic behemoth that holds everything together. It's the standard
<v Speaker 2>model of galactic astronomy. Right, It's been the bedrock.
<v Speaker 3>It absolutely has. We're talking about something with the mass
<v Speaker 3>of four million suns, all crammed into a space that's
<v Speaker 3>all roughly the size of Mercury's orbit around our Sun.
<v Speaker 3>It's the only thing that made.
<v Speaker 2>Sense, right. It's what won the Nobel Prize in physics
<v Speaker 2>back in twenty twenty. The work done by rein Hard
<v Speaker 2>Genzel and Andrea Guez was incredible. They tracked the stars
<v Speaker 2>whipping around that central point.
<v Speaker 3>The violent dance, as it's often called.
<v Speaker 2>A very violent dance, and they proved there was an
<v Speaker 2>unbelievably compact massive object there. The conclusion just seemed inevitable.
<v Speaker 2>It had to be a black hole. Nothing else in
<v Speaker 2>our physics toolkit could possibly fit the math. Until February fifth,
<v Speaker 2>twenty twenty six, just a few days ago, a new
<v Speaker 2>study gets published in the Monthly Notices of the Royal Astronomical.
<v Speaker 3>Society, right, a prestigious journal.
<v Speaker 2>Very and this international team they're looking at the exact
<v Speaker 2>same data, the same Nobel winning observations, the same stars,
<v Speaker 2>the same gravitational effects, and they're essentially raising their hands
<v Speaker 2>and saying, hang on a second, we don't think that's
<v Speaker 2>a black hole.
<v Speaker 3>Which is I mean, that's a bold claim to challenge.
<v Speaker 3>The existence of Sagittarius A as a black hole is
<v Speaker 3>to poke at one of the most fundamental assumptions in
<v Speaker 3>modern astrophysics.
<v Speaker 2>It's a huge deal. But this isn't some fringe idea.
<v Speaker 2>Their argument is really methodical, and it's built on a
<v Speaker 2>potential solution to an even bigger problem, the dark matter problem.
<v Speaker 3>And that's what makes it so compelling. It's not just
<v Speaker 3>saying it's not a. It's proposing its B and B
<v Speaker 3>also explain CD and E.
<v Speaker 2>That's the whole core of this analysis.
<v Speaker 3>Today.
<v Speaker 2>They aren't saying there's nothing there. They're not disputing the
<v Speaker 2>four million solar masses. What they're saying is that it's
<v Speaker 2>not a singularity, it's not a hole in the fabric
<v Speaker 2>of space time.
<v Speaker 3>Instead, it might be a gigantic, incredibly dense clump of
<v Speaker 3>dark matter, a core made of something called fermions.
<v Speaker 2>And if they're right, and that's huge if, but if
<v Speaker 2>they are, this change is basically everything our understanding of gravity,
<v Speaker 2>the way galaxies form and evolve, and you know, it
<v Speaker 2>could finally give us an identity for the invisible stuff
<v Speaker 2>that makes up something like eighty five percent of all
<v Speaker 2>the matter in the universe.
<v Speaker 3>It offers what physicists are always searching for, a unified framework,
<v Speaker 3>a more elegant explanation. Instead of a galaxy being this
<v Speaker 3>collection of disconnected part stars here, black hole there, dark
<v Speaker 3>matter halo somewhere else, this paper proposes that it's all
<v Speaker 3>two sides at the same coin.
<v Speaker 2>A single continuous substance that explains the chaotic, violent center
<v Speaker 2>and the gentle, vast edges of the galaxy. It's a
<v Speaker 2>really beautiful idea.
<v Speaker 3>It is, but it has to stand up to the evidence, right.
<v Speaker 2>So that's what we need to unpack. We need to
<v Speaker 2>start with the reigning champion, the incumbent, the black hole theory.
<v Speaker 2>We need to really understand why it's been so successful
<v Speaker 2>and why it's so hard to challenge.
<v Speaker 3>So then we meet the challenger, this fermionic dark matter core.
<v Speaker 3>What is it and how does it work?
<v Speaker 2>And then we have to weigh the evidence. We'll look
<v Speaker 2>at the stars in the middle, the so called stars
<v Speaker 2>and g sources, and then we'll look at the data
<v Speaker 2>from the very rim of the galaxy, from the Guy
<v Speaker 2>emission and.
<v Speaker 3>The absolutely cannot forget the elephant in the room, or
<v Speaker 3>I guess the shadow in the room.
<v Speaker 2>The picture, the event horizon telescope image.
<v Speaker 3>Yes, we have a photo that supposedly shows the shadow
<v Speaker 3>of a black hole. How do you explain that picture
<v Speaker 3>if there's no black hole to cast a shadow. That's
<v Speaker 3>a very tall order it is.
<v Speaker 2>We will get there, but let's start with the status quo,
<v Speaker 2>the incumbent. Why were we and why are most astronomers
<v Speaker 2>still so convinced that Sagittarius A is a black hole?
<v Speaker 2>It all comes down to those S stars, the S cluster.
<v Speaker 3>Yes, this is a group of surprisingly young, very bright
<v Speaker 3>stars that live the absolute most central part of our galaxy,
<v Speaker 3>the innermost parsec, which is about three light years across.
<v Speaker 2>So this is extreme real estate.
<v Speaker 3>The most extreme, and that the most famous of these
<v Speaker 3>stars is one called S two. We're tracking dozens of
<v Speaker 3>them now, but S two was one of the first
<v Speaker 3>and it's our best studied example. These stars are, for
<v Speaker 3>intents and purposes, are test particles. We can't see the
<v Speaker 3>central object itself because it doesn't emit light. It's dark.
<v Speaker 3>It's dark, But we can watch how these bright stars
<v Speaker 3>move in response to its gravity, and that tells us
<v Speaker 3>everything we need to know.
<v Speaker 2>And their movement is to put it mildly extreme.
<v Speaker 3>It's violent. S two, for instance, is on this long,
<v Speaker 3>stretched out elliptical orbit. It takes about sixteen years to
<v Speaker 3>go around once. But at its closest approach, a point
<v Speaker 3>we call the pery apse, it gets incredibly close to
<v Speaker 3>the central object.
<v Speaker 2>And it speeds up right like a comet whipping around
<v Speaker 2>the Sun.
<v Speaker 3>Exactly like that, but on a scale that's hard to comprehend.
<v Speaker 3>To put it in perspective, the Earth orbits the Sun
<v Speaker 3>at about thirty kilometers per second. That's fast for.
<v Speaker 2>Us, pretty quick.
<v Speaker 3>S two, at its closest approach, has been clocked at
<v Speaker 3>speeds exceeding seven six hundred kilometers per second seven thousand. Yes,
<v Speaker 3>that's about two and a half percent of the speed
<v Speaker 3>of light.
<v Speaker 2>That's just staggering. And to keep a star, an object
<v Speaker 2>that massive, from just flying off into space when it's
<v Speaker 2>moving that fast, the gravitational poll has to be I
<v Speaker 2>can't even imagine.
<v Speaker 3>It has to be immense. And this is the beauty
<v Speaker 3>of orbital mechanics. By precisely measuring the shape and the
<v Speaker 3>period of that orbit, you can use Kepler's laws in
<v Speaker 3>Newton's laws, well actually Einstein since we see general relativistic
<v Speaker 3>effects to calculate the mass of the object it's orbiting.
<v Speaker 2>And that's where the number comes from.
<v Speaker 3>That's where the four million solar masses figure comes from.
<v Speaker 3>The orbits of S two and the other stars demand
<v Speaker 3>that much mass be sitting right there in the middle.
<v Speaker 2>Okay, but mass alone isn't proof of a black hole,
<v Speaker 2>is it. I mean, couldn't it be something else? Like
<v Speaker 2>what if it's a really really dense cluster of old
<v Speaker 2>dead stars like neutron stars or stellar mass black holes.
<v Speaker 3>That's a great question, and it's the first thing astronomers
<v Speaker 3>tried to rule out. So you could, in theory, get
<v Speaker 3>four million solar masses from a cluster of other objects.
<v Speaker 3>The problem is size, the constraint of space.
<v Speaker 2>How close S two gets without crashing into anything exactly.
<v Speaker 3>The perioeps of S two's orbit tells us that all
<v Speaker 3>of that mass has to be contained within a sphere
<v Speaker 3>with a radius of only about one hundred and twenty
<v Speaker 3>times the distance from the Earth to the Sun, so.
<v Speaker 2>One hundred and twenty astronomical units. That sounds big, but
<v Speaker 2>for four million suns.
<v Speaker 3>It's impossibly small. If you tried to pack say four
<v Speaker 3>million neutron stars into that volume of space. They would
<v Speaker 3>be so close together that their orbits would become unstable
<v Speaker 3>in well less than a million years, they'd either fling
<v Speaker 3>each other out, or more likely, they'd merge and rapidly
<v Speaker 3>collapse into a single supermassive black hole.
<v Speaker 2>Anyway, so you'd end up with a black hole.
<v Speaker 3>One a way or another, you would. The same logic
<v Speaker 3>applies to any other conceivable collection of objects. A gas
<v Speaker 3>cloud would be blown away or would have already formed stars.
<v Speaker 3>A cluster of regular stars would be far too big.
<v Speaker 3>You run through the list of known astrophysical.
<v Speaker 2>Objects, it's a process of elimination.
<v Speaker 3>It's a process of elimination, and after you've eliminated every
<v Speaker 3>other possibility within the standard model of physics, the only
<v Speaker 3>thing left that can be that heavy and that small
<v Speaker 3>is a singularity.
<v Speaker 2>A point of infinite density wrapped in an event horizon
<v Speaker 2>from which nothing can escape.
<v Speaker 3>That has been the only working assumption that fits all
<v Speaker 3>the data. It perfectly explains the orbits we.
<v Speaker 2>See until this study comes along the challenger. The paper
<v Speaker 2>is titled Milky Way Center, a supermassive black hole or
<v Speaker 2>a dark matter core. The lead authors are doctor Carlos R.
<v Speaker 2>G Wess and Valentina Crespy part of a big international collaboration,
<v Speaker 2>and they're effectively adding a new suspect to that process
<v Speaker 2>of elimination lineup.
<v Speaker 3>A candidate that wasn't on the books before.
<v Speaker 2>The Fermionic dark matter core. Okay, we need to be
<v Speaker 2>really careful with our terms here because dark matter is
<v Speaker 2>a loaded term for most people. When you say dark matter,
<v Speaker 2>they think of one thing.
<v Speaker 3>Whips weekly interacting massive particles.
<v Speaker 2>Right. This has been the leading theory for what thirty
<v Speaker 2>forty years, These big, heavy, slow moving particles that just
<v Speaker 2>sort of drift around and provide all the extra gravity
<v Speaker 2>we need to hold galaxies together.
<v Speaker 3>That is the cornerstone of the cold dark matter or
<v Speaker 3>CDM paradigm. The idea is that these WIMPs are maybe
<v Speaker 3>one hundred times heavier than a proton, They move slowly,
<v Speaker 3>that's the cold part, and they barely interact with anything
<v Speaker 3>except through gravity.
<v Speaker 2>But the big problem with whimps is we can't find them.
<v Speaker 3>We can't. We have spent decades and billions of dollars
<v Speaker 3>building these incredibly sensitive detectors deep underground, shielded from all
<v Speaker 3>cosmic rays, usually giant vats of liquid xenon or other
<v Speaker 3>materials waiting for a whimp to just bump into one
<v Speaker 3>of our.
<v Speaker 2>Nuclei and nothing, not a single, unambiguous detection, which.
<v Speaker 3>Doesn't mean they're not there. Yeah, but it has certainly
<v Speaker 3>opened the door for people to seriously consider alternative ideas.
<v Speaker 3>And this new paper is built entirely on one of
<v Speaker 3>those alternatives. It's based on fermions.
<v Speaker 2>Okay, so let's define that a fermion is a category
<v Speaker 2>of particle, right like a boson is the other main category.
<v Speaker 2>What's the difference.
<v Speaker 3>The fundamental difference is a quantum mechanical property related to
<v Speaker 3>their spin. But the consequence of that property is what
<v Speaker 3>really matters here. Fermions obey something called the poly exclusion principle.
<v Speaker 2>I remember that from chemistry. It's why electrons and an
<v Speaker 2>atom have to stack up in different energy shells.
<v Speaker 3>That's it, exactly. The poly exclusion principle states that no
<v Speaker 3>two identical fermions can occupy the exact same quantum state
<v Speaker 3>at the exact same time. You can't put them in
<v Speaker 3>the same place with the same energy, in the same spin.
<v Speaker 3>They are, in a sense, antisocial particles. They need their
<v Speaker 3>personal space they absolutely do. Bosons, on the other hand,
<v Speaker 3>love to clump together. You can pile an infinite number
<v Speaker 3>of bosons like photons of light, into the same state.
<v Speaker 3>That's how a laser works.
<v Speaker 2>So fermions are territorial. What happens if you try to
<v Speaker 2>squeeze them into a small space anyway, say with gravity.
<v Speaker 3>They push back. This is the crucial part of the theory.
<v Speaker 3>As you can press a gas of fermions, they start
<v Speaker 3>filling up all the available low energy states. To squeeze
<v Speaker 3>them further, you have to force them into higher and
<v Speaker 3>higher energy states, which requires a tremendous amount of energy.
<v Speaker 3>This resistance, this pushback, is a real physical pressure. It's
<v Speaker 3>called degeneracy pressure.
<v Speaker 2>And this is a known force in the universe. This
<v Speaker 2>isn't theoretical, oh not at all.
<v Speaker 3>It's the force that supports white dwarf stars. A white
<v Speaker 3>dwarf is the remnant of a star like our sun.
<v Speaker 3>Gravity is trying to crush it into nothing, but the
<v Speaker 3>electrons inside, which are fermions, exert enough electron degeneracy pressure
<v Speaker 3>to hold it up and keep it stable for trillions
<v Speaker 3>of years.
<v Speaker 2>Okay, so apply that same idea to dark matter. Our
<v Speaker 2>wheels and his team are not talking about heavy whimps.
<v Speaker 2>They're talking about a very different kind of dark matter particle.
<v Speaker 3>Yes, they're modeling it as a light neutral fermion, sometimes
<v Speaker 3>called a sterile neutrino or a dark keno in the literature.
<v Speaker 3>The specific mass they use is around fifty kilo electron
<v Speaker 3>volts or keV. For comparison, an electron is about five
<v Speaker 3>hundred and eleven k So these are very light particles.
<v Speaker 2>And their theory is that the center of our galaxy
<v Speaker 2>is in a hole. It's a giant, stable ball of
<v Speaker 2>these light dark matter fermions.
<v Speaker 3>Exactly, a huge collection of them, pulled together by their
<v Speaker 3>own gravity over billions of years. As gravity tries to
<v Speaker 3>crush this ball into a single point, into a singularity,
<v Speaker 3>the fermion degeneracy pressure.
<v Speaker 2>Pushes back and it creates a stalemate, a stable equilibrium.
<v Speaker 3>The result is a stable, super dense core. It's not
<v Speaker 3>a singularity. It has no event horizon, it has real
<v Speaker 3>physical size. But and this is the absolute key to
<v Speaker 3>the whole argument, it is so compact, is so massive
<v Speaker 3>that from a distance, its gravitational field is indistinguishable from
<v Speaker 3>that of a black hole of the same mass.
<v Speaker 2>So if you're the star S two and you're making
<v Speaker 2>that high speed turn, you don't know and you don't
<v Speaker 2>care if the object pulling on you is a point
<v Speaker 2>of infinite density or a ball of fermions, the poll
<v Speaker 2>feels exactly the same.
<v Speaker 3>Precisely. The researchers did the math. They calculated the gravitational
<v Speaker 3>potential of this fermionic core, and they found that for
<v Speaker 3>any distance greater than about two or three times the
<v Speaker 3>Schwartz Hill radius, the radius of the black holes of
<v Speaker 3>vent horizon, the gravity is identical to what general relativity
<v Speaker 3>predicts for a black hole.
<v Speaker 2>And the S stars, even S two at its closest,
<v Speaker 2>are always further out than that they are.
<v Speaker 3>They orbit far enough out that they would never notice
<v Speaker 3>the difference.
<v Speaker 2>So the challenger this dark matter core. It survives the
<v Speaker 2>first and most important test. It explains the S star
<v Speaker 2>orbits just as well as the incumbent black hole theory.
<v Speaker 3>It does. It matches the observations perfectly.
<v Speaker 2>But the paper goes much further. It claims this model
<v Speaker 2>does something the standard black hole model can't do. It
<v Speaker 2>solves what they call the core halo problem. This brings
<v Speaker 2>us to this really elegant idea of a unified entity.
<v Speaker 3>This for me, is the most beautiful part of the
<v Speaker 3>entire proposal. To really appreciate why it's such a big deal,
<v Speaker 3>you have to understand just how well messy and disconnected
<v Speaker 3>the current model of the galaxy is.
<v Speaker 2>Right in the standard textbook view, we have all these
<v Speaker 2>separate ingredients that we just kind of stir together. First
<v Speaker 2>you have the baryonic matter that's us, that's stars, gas, planets, dust,
<v Speaker 2>all the normal stuff made of protons.
<v Speaker 3>And neutrons, the stuff we can see.
<v Speaker 2>Then you put a supermassive black hole right in the middle,
<v Speaker 2>which is its own special kind of object formed in
<v Speaker 2>a specific way.
<v Speaker 3>And then surrounding the entire visible galaxy like a giant
<v Speaker 3>invisible sphere, you pour in the dark manner halo, which
<v Speaker 3>is assumed to be made of a completely different substance,
<v Speaker 3>like WIMPs.
<v Speaker 2>It's like building a car where the engine is made
<v Speaker 2>of iron, the chassis made of carbon fiber, and the
<v Speaker 2>tires are made of cheese. They're all there, they interact,
<v Speaker 2>but they're fundamentally different things.
<v Speaker 3>An excellent analogy, and in our cosmological simulations we treat
<v Speaker 3>them as different things. The black hole is one type
<v Speaker 3>of particle in the simulation. The halo is another. They
<v Speaker 3>interact through gravity, but they have distinct origins and properties.
<v Speaker 2>But this new model says no. It says the engine,
<v Speaker 2>the chassis, and the tires are all made of the
<v Speaker 2>same high tech alloy. The entire galaxy, from the hyperdense
<v Speaker 2>core to the most diffuse outer fringe is all made
<v Speaker 2>from the same sea of dark matter fermions.
<v Speaker 3>This is what doctor R. Gwill's highlights in his comments
<v Speaker 3>on the paper. He says, we are proposing that the
<v Speaker 3>supermassive central object and the galaxy's dark matter halo are
<v Speaker 3>two manifestations of the same continuous substance.
<v Speaker 2>A continuous distribution. How does that work? How can one
<v Speaker 2>substance form both a tiny dense core and a giant,
<v Speaker 2>fluffy halo.
<v Speaker 3>It's a natural consequence of how a self gravitating gas
<v Speaker 3>of fermions behaves. The team solve the equations of general
<v Speaker 3>relativistic hydrostatic equilibrium, the Tolmenopenheimer VOLCOF equations for a gas
<v Speaker 3>of these particles. What they found is that it naturally
<v Speaker 3>settles into a two phase structure.
<v Speaker 2>Two phases like water and ice in a way.
<v Speaker 3>In the very center, where the gravitational pressure is at
<v Speaker 3>its absolute maximum, the fermions are forced into that quantum
<v Speaker 3>degenerate state we talked about. They become incredibly dense and compact,
<v Speaker 3>forming the core that mimics the black hole.
<v Speaker 2>Okay, that's phase one, the dense core.
<v Speaker 3>Then as you move outwards from the center, the gravitational
<v Speaker 3>pressure drops at a certain point, it's no longer strong
<v Speaker 3>enough to keep the fermions in that degenerate state. So
<v Speaker 3>there's a transition and they start behaving more like a
<v Speaker 3>classical diffuse gas, and that diffuse gas forms a vast
<v Speaker 3>extended halo.
<v Speaker 2>So the monster in the middle isn't a separate creature
<v Speaker 2>that the galaxy captured. It's just the densest part of
<v Speaker 2>the galaxy itself.
<v Speaker 3>It's the peak of the mountain. It's not a separate
<v Speaker 3>rock placed on top of the mountain. This unifies the
<v Speaker 3>physics in a profound way. You no longer need one
<v Speaker 3>theory to explain how the black hole formed and a
<v Speaker 3>totally separate theory to explain the dark matter halo. They
<v Speaker 3>form together as a single system.
<v Speaker 2>That feels so much more natural as the primordial cloud
<v Speaker 2>of dark matter collapsed in the early universe, this dense
<v Speaker 2>core would just condense out in middle.
<v Speaker 3>It would precipitate out. Yes, And this has another major benefit.
<v Speaker 3>It helps solve a huge puzzle that's come from the
<v Speaker 3>James Web Space Telescope.
<v Speaker 2>Recently, right the impossible early black holes. JWS is seeing
<v Speaker 2>these enormous billion solar mass black holes at extremely high redshifts,
<v Speaker 2>meaning very very early in cosmic history.
<v Speaker 3>So early that there doesn't seem to have been enough
<v Speaker 3>time for a normal stellar mass black hole to grow
<v Speaker 3>that big by eating gas and stars. There's a physical
<v Speaker 3>speed limit to how fast a black hole can feed.
<v Speaker 3>It's called the Eddington limit. If you try to shove
<v Speaker 3>matter in too quickly, the radiation from the meal itself
<v Speaker 3>blows the rest of the food away.
<v Speaker 2>It's a self regulating process, it is, and it makes
<v Speaker 2>it very difficult to explain how these giants got so
<v Speaker 2>big so fast.
<v Speaker 3>But a dark matter core doesn't need to eat. It
<v Speaker 3>forms directly from the gravitational collapse of the halo itself.
<v Speaker 3>It can be born big. This model naturally explains why
<v Speaker 3>we see these gigantic objects so early in the universe's timeline.
<v Speaker 2>That's a very powerful theoretical argument in its favor. But
<v Speaker 2>let's bring it back to the Milky Way, back to
<v Speaker 2>the hard data. We've established that the dense core part
<v Speaker 2>of the model works for the s stars in the center,
<v Speaker 2>but it's a unified model. If you're also changing the halo,
<v Speaker 2>that has to change how the rest of the galaxy spins.
<v Speaker 3>It absolutely does, and this is where the European Space
<v Speaker 3>Agency's Guy emission becomes the crucial second piece of evidence.
<v Speaker 2>KAYA is just a revolutionary instrument. It doesn't take those breathtaking,
<v Speaker 2>colorful pictures like Hubble or Web, but what it does
<v Speaker 2>is arguably more important for understanding our galaxy structure. It's
<v Speaker 2>an astrometry machine.
<v Speaker 3>It's a cosmic surveyor. Its job is to measure the
<v Speaker 3>precise position, distance, and motion of billions of stars in
<v Speaker 3>the Milky Way with unprecedented accuracy.
<v Speaker 2>And from that data we can build the most detailed
<v Speaker 2>map of our galaxy ever created, including its rotation curve.
<v Speaker 3>A rotation curve is a simple but powerful tool. On
<v Speaker 3>the X axis, you plot the distance of a star
<v Speaker 3>from the galactic center. On the I axis, you plot
<v Speaker 3>how fast that star is orbiting.
<v Speaker 2>And if our galaxy was just the stars and gas.
<v Speaker 2>We can see that curve should drop off as you
<v Speaker 2>go further out, just like in our solar system. Mercury
<v Speaker 2>moves super fast, Neptune moves very slowly. That's Kepler's law correct.
<v Speaker 3>The gravitational pull gets weaker with distance, so things should
<v Speaker 3>slow down. But for decades we've known that's not what happens.
<v Speaker 3>In galaxies. We see a flat rotation curve. The stars
<v Speaker 3>on the very edge are moving just as fast as
<v Speaker 3>stars much closer in.
<v Speaker 2>Which is the primary piece of evidence for dark matter
<v Speaker 2>in the first place. There has to be a bunch
<v Speaker 2>of invisible mass out there in a giant halo whose
<v Speaker 2>gravity is keeping those outer stars moving so quickly exactly.
<v Speaker 3>But the latest data from Gaya, at data release three,
<v Speaker 3>it extended that rotation curve further out and with more
<v Speaker 3>precision than ever before, and it saw something new, something
<v Speaker 3>a bit weird. At the very very.
<v Speaker 2>Edge, the curve isn't flat forever, it isn't.
<v Speaker 3>At the outermost observable limits of the Milky Way, the
<v Speaker 3>orbital speeds finally start to drop. We see a Caplerian decline.
<v Speaker 2>So does that mean we're finally reaching the edge of
<v Speaker 2>the dark matter halo. We found the shoreline of the
<v Speaker 2>invisible ocean.
<v Speaker 3>In a sense, yes, we are seeing the gravitational potential
<v Speaker 3>finally beg into weaken. Now here's the problem this poses
<v Speaker 3>for the standard cold dark matter model, the WIMP model
<v Speaker 3>CDM halos are typically modeled with a specific density profile,
<v Speaker 3>most famously the Navarro, Frank White or NFW profile. And
<v Speaker 3>this profile predicts a very large, very fluffy halo that
<v Speaker 3>just sort of trails off gradually into infinity. It has
<v Speaker 3>a power law tail that keeps going for a very
<v Speaker 3>long time.
<v Speaker 2>So a standard WIM halo would predict that the curve
<v Speaker 2>stays flat for much longer. It would struggle to explain
<v Speaker 2>why it drops off so relatively sharply.
<v Speaker 3>It struggles. Yes, you can make it fit, but you
<v Speaker 3>often have to sort of artificially truncate the halo and
<v Speaker 3>the models. You have to say, well, the halo just
<v Speaker 3>stops here. But the fermionic model from our goals is
<v Speaker 3>team it predicts this decline naturally, it's a built in
<v Speaker 3>feature of the model.
<v Speaker 2>Why what is it about these fermion particles that gives
<v Speaker 2>the halo a sharper edge.
<v Speaker 3>It goes back to their quantum nature and the thermodynamics
<v Speaker 3>of the gas. Because the particles aren't cold, they have
<v Speaker 3>some small intrinsic velocity, and because of the phase based
<v Speaker 3>constraints posed by the poly exclusion principle, the resulting halo
<v Speaker 3>structure is naturally more compact. It has a tighter, more
<v Speaker 3>defined boundary than a whim palo.
<v Speaker 2>It's not as fluffy.
<v Speaker 3>It's not as fluffy. And when the researchers took their
<v Speaker 3>unified model the dense core plus the extended halo all
<v Speaker 3>from one equation and compared it to the Gaya rotation
<v Speaker 3>curve data including the normal matter of the disc and bulge,
<v Speaker 3>it was a perfect fit.
<v Speaker 2>It matched the Couplearrian decline at the edge without any
<v Speaker 2>special tweaks.
<v Speaker 3>A beautiful fit right out of the box.
<v Speaker 2>Okay, let's just recap the evidence so far. The fermionic
<v Speaker 2>dark matter core model successfully explains the orbits of the
<v Speaker 2>s stars at the center.
<v Speaker 3>Check.
<v Speaker 2>It provides a unified framework for the core and the halo,
<v Speaker 2>solving a major theoretical headache.
<v Speaker 3>Check.
<v Speaker 2>It naturally explains the existence of supermassive objects in the
<v Speaker 2>very early universe, which JWST has been finding.
<v Speaker 3>Check a big check on that one.
<v Speaker 2>And it perfectly fits the entire galactic rotation curve from
<v Speaker 2>Gaya from the inner parts all the way out to
<v Speaker 2>the Kaplaire decline at the edge.
<v Speaker 3>Check check, and it accomplishes all of this without needing
<v Speaker 3>a singularity, a point where our known laws of physics
<v Speaker 3>literally break down.
<v Speaker 2>That's a pretty compelling case. But let's dig a little
<v Speaker 2>deeper into the central region. There are other strange objects there,
<v Speaker 2>not just the S stars. There are the G sources.
<v Speaker 3>Ah, yes, the G objects G one, especially G two.
<v Speaker 3>These were discovered in the mid two thousands and early
<v Speaker 3>twenty tens, and they've been a puzzle ever since. What
<v Speaker 3>are they, Well, that's a question. Spectroscopically they look like
<v Speaker 3>giant clouds of gas and dust, yeah, But dynamically they
<v Speaker 3>move like stars. They were on these very tight, very
<v Speaker 3>eccentric orbits around the galactic center, just like the.
<v Speaker 2>Stars, and G two became famous because it was on
<v Speaker 2>a collision course, wasn't it, or at least a very
<v Speaker 2>close flyby it was.
<v Speaker 3>Its orbit was predicted to take it right through the
<v Speaker 3>most intense gravitational region around Sagittary USA, and astronomers worldwide
<v Speaker 3>got their telescopes ready for a spectacular show.
<v Speaker 2>What were they expecting to see?
<v Speaker 3>If G two was just a simple gas cloud, they
<v Speaker 3>expected it to be completely torn to shreds by the
<v Speaker 3>black hole's tidal forces, a process called spaghetification, right.
<v Speaker 2>Where the side of the cloud closer to the black
<v Speaker 2>hole gets pulled so much harder than the far side
<v Speaker 2>that it just gets stretched out into a long noodle.
<v Speaker 3>Of gas exactly. And they predicted that this noodle of
<v Speaker 3>gas would then get captured by the black hole, spiral
<v Speaker 3>in and cause a massive flare up as it was consumed.
<v Speaker 3>It was supposed to be our chance to finally see
<v Speaker 3>the dormant monster at the center of our galaxy wake
<v Speaker 3>up and eat.
<v Speaker 2>And then the flyb happened.
<v Speaker 3>And nothing happened. G two sailed right on by. It
<v Speaker 3>got a little stretched, a little distorted, but it remained
<v Speaker 3>a compact object. It swung around the center and just
<v Speaker 3>kept on going along its orbit. The fireworks show was
<v Speaker 3>a total dud.
<v Speaker 2>Which must have been incredibly confusing. How did they explain that.
<v Speaker 3>It was a major puzzle. The leading explanation that emerged
<v Speaker 3>was that G two couldn't be just a gas cloud.
<v Speaker 3>It must have a star hidden inside it, a star
<v Speaker 3>whose gravity was holding the cloud together again against the
<v Speaker 3>black hole's tidal forces.
<v Speaker 2>So it's a star wearing a gas cloud coat.
<v Speaker 3>That became the working hypothesis, But the fumionic core model
<v Speaker 3>offers a completely different and perhaps simpler explanation. A black
<v Speaker 3>hole a singularity is a true point mass. The tidal
<v Speaker 3>forces right next to a point mass are incredibly extreme.
<v Speaker 3>The gravitational gradient, the change in the strength of gravity
<v Speaker 3>over a short distance, is unbelievably steep. That's what rips
<v Speaker 3>things apart su efficiently. Okay, but the dark matter core
<v Speaker 3>isn't a point it's an extended object. It's a ball,
<v Speaker 3>a very dense ball, but a ball. Nonetheless, while the
<v Speaker 3>overall gravity is just as strong, the gredient to that
<v Speaker 3>gravity is much smoother, so.
<v Speaker 2>The tidle forces are gentler. The pull on the near
<v Speaker 2>side of the cloud and the far side of the
<v Speaker 2>cloud is more.
<v Speaker 3>Similar significantly gentler. The researches in this paper argue that
<v Speaker 3>a simple gas cloud with no star inside it could
<v Speaker 3>absolutely survive a close pass by their fermionic core model
<v Speaker 3>without being completely shredded.
<v Speaker 2>So the mystery of the invincible gas cloud G two
<v Speaker 2>is actually it's a piece of evidence against a singularity
<v Speaker 2>and for a distributed extended core.
<v Speaker 3>It is certainly highly consistent with the core hypothesis. It
<v Speaker 3>resolves a long standing observational puzzle in a very neat way.
<v Speaker 2>Okay, the case is getting stronger, but now we have
<v Speaker 2>to face the music. We have to look at the
<v Speaker 2>photograph the event Horizon telescope collaboration. They used a planet
<v Speaker 2>sized array of radio telescopes to take a picture of
<v Speaker 2>Sagittarius A.
<v Speaker 3>The first one of Messa eighty seven's black hole was incredible,
<v Speaker 3>but seeing the one in our own galaxy was a
<v Speaker 3>landmark moment.
<v Speaker 2>It's that iconic image, the blurry, glowing orange doughnut with
<v Speaker 2>the dark patch in the middle, and the EHT team
<v Speaker 2>explicitly called that dark patch the shadow of the black hole.
<v Speaker 2>That sounds like pretty definitive proof.
<v Speaker 3>It is, without a doubt, the strongest piece of evidence
<v Speaker 3>in favor of the black hole model and the biggest
<v Speaker 3>hurdle for any alternative theory to clear.
<v Speaker 2>Let's break down why that shadow exists as I understand it,
<v Speaker 2>because the event horizon is a one way membrane light
<v Speaker 2>can go in, but it can't come out correct.
<v Speaker 3>There's a region around the black hole called the photon sphere,
<v Speaker 3>where photons can orbit, but any photon that crosses a
<v Speaker 3>slightly smaller boundary the event horizon, is captured forever. So
<v Speaker 3>from our perspective, that region appears as a dark silhouette
<v Speaker 3>against the bright glowing plasma in the accretion disk behind
<v Speaker 3>and around it.
<v Speaker 2>So if your fermionic core doesn't have an event horizon,
<v Speaker 2>if it's just a solid or at least a very
<v Speaker 2>dense ball of particles, then light shouldn't be captured. It
<v Speaker 2>should be able to, i don't know, bounce off it
<v Speaker 2>or pass right through it. Since it's dark matter, we
<v Speaker 2>shouldn't see a shadow.
<v Speaker 3>That's what your intuition would tell you. You'd expect to
<v Speaker 3>maybe see a faint glow or perhaps nothing at all,
<v Speaker 3>but not this sharp, dark silhouette.
<v Speaker 2>So how does the new paper explain the picture?
<v Speaker 3>They address this directly, and the answer lies in the
<v Speaker 3>mind bending nature of gravity in general relativity. The dark
<v Speaker 3>matter core, remember, is packing four million solar masses into
<v Speaker 3>a tiny, tiny region. The gravity is so intense that
<v Speaker 3>it causes extreme gravitational lensing.
<v Speaker 2>It bends the path of light that passes near it, it.
<v Speaker 3>Bends it severely. The researchers argue that it bends light
<v Speaker 3>so much that it effectively mimics the appearance of a shadow.
<v Speaker 2>What's the mechanism?
<v Speaker 3>Think about the light coming from the hot plasma behind
<v Speaker 3>the core. As those light rays travel towards us, they
<v Speaker 3>pass by the core and their paths are deflected bend
<v Speaker 3>away from our line of sight. Similarly, light from the
<v Speaker 3>plasma in front of the core is also lensed. The
<v Speaker 3>net effect is that very few photons from the region
<v Speaker 3>directly in front of or behind the core ever reach
<v Speaker 3>our telescopes.
<v Speaker 2>So the darkness we see in the EHT image isn't
<v Speaker 2>a hole where light goes to die. It's a blind
<v Speaker 2>spot created by the core's gravity acting like a warped lens,
<v Speaker 2>shoving the light aside.
<v Speaker 3>That is precisely their argument. The paper site's previous work
<v Speaker 3>and radiate of transfer simulations done by members of the team.
<v Speaker 3>They modeled what a telescope like the EHD would see
<v Speaker 3>if it looked at one of these dense cores surrounded
<v Speaker 3>by hot plasma. The result was a central brightness depression.
<v Speaker 2>A central brightness depression that is a wonderfully scientific way
<v Speaker 2>of saying a dark spot in the middle.
<v Speaker 3>It is, and their key finding is that at the
<v Speaker 3>current resolution of the event horizon telescope, is brightness depression
<v Speaker 3>caused by lensing is visually and statistically indistinguishable from the
<v Speaker 3>shadow cast by a true black hole event horizon.
<v Speaker 2>You're kidding. So the picture we all saw, the one
<v Speaker 2>that was hailed as proof of the black hole, could
<v Speaker 2>be a cosmic optical illusion.
<v Speaker 3>It could be a case of what we might call
<v Speaker 3>gravitational mimicry. The dark matter core mimics the gravitational pull
<v Speaker 3>of the black hole for orbiting stars, and it mimics
<v Speaker 3>the visual appearance of the black hole's shadow.
<v Speaker 2>That is both amazing and incredibly frustrating. So if the
<v Speaker 2>star orbits match and the photo looks the same, how
<v Speaker 2>on earth do you break the tie? Is this just
<v Speaker 2>a philosophical debate? Now we just pick the theory we
<v Speaker 2>find more elegant.
<v Speaker 3>No, absolutely not. Science is not philosophy. We need a definitive,
<v Speaker 3>falsifiable test, need in observation that one model predicts and
<v Speaker 3>the other forbids, and thankfully, the very specific physics of
<v Speaker 3>a black hole's event horizon provides one. The smoking gun
<v Speaker 3>is something called the photon ring.
<v Speaker 2>Okay, is the photon ring different from that big, fuzzy
<v Speaker 2>orange ring we see in the EHT image.
<v Speaker 3>It is very different. That big orange ring is mostly
<v Speaker 3>just the bulk emission from the hot gas in the
<v Speaker 3>accretion disk. The photon ring is a much sharper, much thinner,
<v Speaker 3>and much fainter feature that is predicted to lie right
<v Speaker 3>at the inner edge of that glow.
<v Speaker 2>What is it made of.
<v Speaker 3>It's made of photons that have performed a cosmic tightrob act.
<v Speaker 3>These are light rays that didn't fall into the black
<v Speaker 3>hole and didn't escape immediately, but instead got trapped in
<v Speaker 3>unstable orbits right at the edge of the photon sphere.
<v Speaker 3>They can orbit the black hole one, two, three, or
<v Speaker 3>even more times before finally breaking free and flying towards
<v Speaker 3>their telescopes.
<v Speaker 2>So light that's literally circling the drain.
<v Speaker 3>A perfect description. General relativity makes a very precise prediction.
<v Speaker 3>A true black hole with an event horizon must produce
<v Speaker 3>this feature. It's an infinite stack of ever fainter, ever
<v Speaker 3>sharper subrings. It's a direct signature of the event horizon.
<v Speaker 2>Itself in the dark matter core it has.
<v Speaker 3>No event horizon. It can bend light, it can create
<v Speaker 3>a brightness depression, but it cannot trap photons in these specific,
<v Speaker 3>infinitely looping orbits. It will not produce that sharp, distinct
<v Speaker 3>photon ring structure.
<v Speaker 2>So there it is. That's the test. Find the photon ring.
<v Speaker 3>Find the photon ring.
<v Speaker 2>If it's there, Einstein and the black hole model win
<v Speaker 2>case closed.
<v Speaker 3>If it's missing, then the dark matter hypothesis is not
<v Speaker 3>just a viable alternative. It suddenly becomes the leading explanation
<v Speaker 3>for what's at the center of our galaxy.
<v Speaker 2>So do we have the technology to see this ring?
<v Speaker 2>Is it something we can do today?
<v Speaker 3>Not quite yet. The current EHT image is just too blurry.
<v Speaker 3>It's like looking at a vinyl record and only being
<v Speaker 3>able to see that it's a black circle, but not
<v Speaker 3>being able to see the individual grooves. We need higher resolution.
<v Speaker 2>But that's being worked on.
<v Speaker 1>Oh.
<v Speaker 3>Absolutely. The NEHT, or next generation event horizon Telescope, is
<v Speaker 3>already in development. It will add more telescopes to the
<v Speaker 3>array and use higher observing frequencies, which will dramatically increase
<v Speaker 3>the sharpness of the images. Its primary goal is to
<v Speaker 3>resolve the photon ring of both Sagittarius A and M
<v Speaker 3>eighty seven.
<v Speaker 2>So it's a waiting game, it is.
<v Speaker 3>But there's another way we might be able to break
<v Speaker 3>the tie, and that involves the gravity instrument on the
<v Speaker 3>very large telescope in Chile.
<v Speaker 2>Right gravity is the one that tracks the S stars
<v Speaker 2>so precisely.
<v Speaker 3>With incredible precision, and it's currently undergoing an upgrade to
<v Speaker 3>gravity plus times. This will make it even more sensitive.
<v Speaker 3>It will be able to see fainter stars and crucially
<v Speaker 3>stars that are even closer to the galactic center than
<v Speaker 3>S two. And how would that help, Well, the dark
<v Speaker 3>matter core has a physical size. The model predicts its
<v Speaker 3>radius as about one third of the closest approach of
<v Speaker 3>the S two star. If we could find a star
<v Speaker 3>that orbits inside that predicted radius, that would be definitive proof.
<v Speaker 3>Why because if the object is a black hole, you
<v Speaker 3>can orbit as close as you want, right up until
<v Speaker 3>you hit the event horizon. The gravity outside the event
<v Speaker 3>horizon always acts as if it's coming from a point,
<v Speaker 3>But the object is an extended ball of dark.
<v Speaker 2>Matter, and if you go inside the ball.
<v Speaker 3>The physics completely changes. According to Newton's shell theorem, once
<v Speaker 3>you're inside a spherical mass. You are only pulled by
<v Speaker 3>the mass that is interior to your position. The gravity
<v Speaker 3>from the shell of matter outside of you cancels out.
<v Speaker 2>So the gravitational pull would get weaker. As the star
<v Speaker 2>dives deeper into the core.
<v Speaker 3>Exactly, its orbit would completely stop being a capelarian ellipse.
<v Speaker 3>It would start to precess wildly. It would look more
<v Speaker 3>like a harmonic oscillator, sort of bouncing back and forth
<v Speaker 3>through the center. Finding a star with that kind of
<v Speaker 3>non caplarian orbit would be the ultimate smoking gun. It
<v Speaker 3>would prove the central object is extended and not a point.
<v Speaker 2>This is all leading us to the really big picture,
<v Speaker 2>the so what question. Let's play this out. Let's imagine
<v Speaker 2>for a moment that Argwell's and his team are right.
<v Speaker 2>I say, in five or ten years, any ht looks
<v Speaker 2>for the photon ring and finds nothing or gravity, plus
<v Speaker 2>finds a star swimming around inside the core. What does
<v Speaker 2>that discovery actually due to our understanding of the universe.
<v Speaker 3>The first and most immediate consequence is that it solves
<v Speaker 3>the singularity problem. This is a deep, fundamental headache that
<v Speaker 3>has been at the heart of general relativity since Karl
<v Speaker 3>Schrouzschild first solved Einstein's equations back in nineteen sixteen.
<v Speaker 2>A singularity being a point of infinite density and zero volume.
<v Speaker 3>Yes. And in physics, whatever you get an infinity in
<v Speaker 3>your equations, it's usually a giant flashing red light telling
<v Speaker 3>you that your theory is incomplete, that the math is
<v Speaker 3>broken down and doesn't know how to describe what's really happening.
<v Speaker 2>Nature doesn't really do infinities.
<v Speaker 3>Nature abhors them. If the galactic center is a stable
<v Speaker 3>dark matter core, it means that the ultimate collapse of
<v Speaker 3>matter is halted by a known quantum mechanical principle, the
<v Speaker 3>degeneracy pressure of fermions, before it can reach that in
<v Speaker 3>in a state. It means the laws of physics as
<v Speaker 3>we know them remain valid everywhere in the universe. There
<v Speaker 3>are no holes in reality where the rules don't apply.
<v Speaker 2>That's a huge philosophical shift. It also pretty obviously tells
<v Speaker 2>us what dark matter is, or at least what it's
<v Speaker 2>made of.
<v Speaker 3>He would be the most profound discovery in particle physics
<v Speaker 3>in a century. We would know that dark matter is
<v Speaker 3>composed of these light, sterile neutrino like fermions. We could
<v Speaker 3>stop building bigger and bigger xenon tanks to look for
<v Speaker 3>whimps and pivot our entire experimental strategy towards detecting these
<v Speaker 3>KEYV scale particles.
<v Speaker 2>In other ways, it would connect the unimaginably small scale
<v Speaker 2>of subatomic particles with the unimaginably large scale of galactic
<v Speaker 2>structure in this incredibly direct way.
<v Speaker 3>It's the ultimate dream of physics, a unified theory.
<v Speaker 2>And what about other galaxies. There's an interesting idea touched
<v Speaker 2>on in the research, this concept of an evolutionary track
<v Speaker 2>for these objects.
<v Speaker 3>Yes, the idea of a critical mass. The fermionic core
<v Speaker 3>model predicts that the core is stable only up to
<v Speaker 3>a certain mass limit, just like a white dwarf star
<v Speaker 3>is stable up to about one point four solar masses
<v Speaker 3>the Chandra scar limit.
<v Speaker 2>So as long as the quantum degeneracy pressure is strong
<v Speaker 2>enough to fight gravity, it stays a stable core exactly.
<v Speaker 2>But what if it gets too heavy, if it accretes
<v Speaker 2>too much gas and stars over time, or if our
<v Speaker 2>galaxy merges with another big galaxy.
<v Speaker 3>Then it's possible we could exceed this critical mass for
<v Speaker 3>dark matter. At that point, gravity would finally overwhelm the
<v Speaker 3>quantum pressure and then it would undergo a final catastrophic
<v Speaker 3>collapse into a true singularity, a true supermassive black hole
<v Speaker 3>with an event horizon.
<v Speaker 2>So the universe might be filled with both younger galaxies
<v Speaker 2>or more isolated ones like the Milky Way, might still
<v Speaker 2>have their original dark matter cores, but older, more massive galaxies,
<v Speaker 2>especially ones at the center of huge clusters that have
<v Speaker 2>gone through many mergers.
<v Speaker 3>They might have already collapsed their cores into true black holes.
<v Speaker 3>The monster in a galaxy like Messia eighty seven, which
<v Speaker 3>is over a thousand times more massive than ours six
<v Speaker 3>and a half billion solar manasses, that could very well
<v Speaker 3>be a true collapsed black hole.
<v Speaker 2>So M eighty seven could be a real black hole,
<v Speaker 2>while Sagittarius A is still in this stable prehole state, a.
<v Speaker 3>Failed black hole in a sense, a core that had
<v Speaker 3>enough mass to shape a galaxy but not quite enough
<v Speaker 3>to collapse under its own weight.
<v Speaker 2>That almost makes our galaxy feel shuttler less menacing. We
<v Speaker 2>have a stable heart, not a bottomless strain.
<v Speaker 3>It definitely changes the narrative. It reframes the galactic center
<v Speaker 3>not as a destructive engine of chaos, but as a
<v Speaker 3>gravitational cradle made of the very same substance that holds
<v Speaker 3>our Star and its gentle, sweeping orbit out here in
<v Speaker 3>the suburbs.
<v Speaker 2>Let's go back to that visualization. We started with the
<v Speaker 2>spiral arms, the bulge, the central point. When I picture
<v Speaker 2>it now, the image is different. The central point, the monster.
<v Speaker 2>It's not a separate entity anymore. It's just the sharpest
<v Speaker 2>peak of a vast, invisible mountain range.
<v Speaker 3>That's a perfect analogy. Imagine a huge landscape made entirely
<v Speaker 3>of invisible sand. The peak is incredibly high and steep.
<v Speaker 3>That's the core, but the slopes of that same mountain
<v Speaker 3>extend outwards for hundreds of thousands of light years. That's
<v Speaker 3>the halo. It's all the same sand. We just happen
<v Speaker 3>to live on the gentle lower slopes orbiting that distant peak,
<v Speaker 3>and all.
<v Speaker 2>That sand is passing right through us right now without
<v Speaker 2>us ever feeling it constantly. It's a really humbling perspective.
<v Speaker 2>We spend all our time looking at the stars because
<v Speaker 2>they shine. They're the bright, exciting, look at me part
<v Speaker 2>of the universe. But this theory is a powerful reminder
<v Speaker 2>that the stars are just the sprinkles on the cake,
<v Speaker 2>the actual cake, the structure, the substance. The thing that
<v Speaker 2>is the galaxy is the dark matter, the.
<v Speaker 3>Buryonic matter, the stuff we're made of. It's just a tracer.
<v Speaker 3>We're like foam on the crest of an ocean wave.
<v Speaker 3>The foam shows you where the wave is and how
<v Speaker 3>it's moving. But the foam isn't the wave. The dark
<v Speaker 3>matter is the ocean.
<v Speaker 2>And for half a century we've believed that at the
<v Speaker 2>very center of that ocean was a mysterious whirlpool leading
<v Speaker 2>to nowhere. But maybe it's just the place where the
<v Speaker 2>water is deepest and most still.
<v Speaker 3>It's an incredibly compelling thought. And look, whether this specific
<v Speaker 3>fermionic model turns out to be exactly right and all
<v Speaker 3>its details or not, its real value is that it
<v Speaker 3>forces us to challenge our assumptions. It forces us to
<v Speaker 3>question the black hole plus whimb dogma that has dominated
<v Speaker 3>cosmology for so long.
<v Speaker 2>It forces us to look at the same data, the
<v Speaker 2>star orbits, the Guya curve, the EHT image with fresh
<v Speaker 2>eyes and ask what else could this be telling us.
<v Speaker 3>That's the entire scientific process in a nutshell, it's the
<v Speaker 3>art of resision. The data is the data. S two
<v Speaker 3>is still moving it over seven thousand klongers per second.
<v Speaker 3>The picture is still an orange donut, But the story
<v Speaker 3>we tell ourselves to explain that data, that story is
<v Speaker 3>always up for revision.
<v Speaker 2>I want to leave you with one last thought to
<v Speaker 2>chew on, a final provocative question. If our own galaxy,
<v Speaker 2>the one we know best, might have a dark matter
<v Speaker 2>core instead of a black hole, what about all the others?
<v Speaker 2>In indeed, what about Andromeda? What about the hundreds of
<v Speaker 2>billions of other galaxies we can see the distant quasar's
<v Speaker 2>power or by what we assume are feeding black holes.
<v Speaker 2>Are we looking at a universe filled with these bizarre singularities,
<v Speaker 2>these points where physics dies? Or are we looking at
<v Speaker 2>a universe filled with these dense, silent, stable hearts of
<v Speaker 2>dark matter. If we've potentially misidentified the most important object
<v Speaker 2>in our own backyard, how many others have we gotten wrong?
<v Speaker 3>We might be seeing these shadows all across the cosmos,
<v Speaker 3>and they might all be the result of this extreme
<v Speaker 3>gravitational lensing from dense matter rather than light capture by
<v Speaker 3>event horizons. It opens the fascinating possibility that true singularities
<v Speaker 3>are actually much much rarer than we currently believe.
<v Speaker 2>A universe with fewer holes in it. I have to
<v Speaker 2>say I kind of like the sound of that.
<v Speaker 3>It's certainly a less terminal thought.
<v Speaker 2>We are absolutely going to be keeping a close eye
<v Speaker 2>on the NEHT and the gravity Plus instrument, and you
<v Speaker 2>can be sure that the moment they either find that
<v Speaker 2>photon ring or confirm that it's not there, we will
<v Speaker 2>be back to talk about it.
<v Speaker 3>I'll look forward to it. The hunt for the photon
<v Speaker 3>ring is truly one of the next great quests in Moderness.
<v Speaker 2>Strow me until then, look up at the night sky
<v Speaker 2>and remember what you're seeing is just the pham. The
<v Speaker 2>ocean itself is invisible. Thanks for joining us.
<v Speaker 3>Thank you
<v Speaker 2>L