Speaker 1: Welcome to Bedtime Astronomy. Explore the wonders of the cosmos
Speaker 1: with our soothing Bedtime Astronomie podcast. Each episode offers a
Speaker 1: gentle journey through the stars, planets, and beyond, perfect for
Speaker 1: unwinding after a long day. Let's travel through the mysteries
Speaker 1: of the universe as you drift off into a peaceful
Speaker 1: slumber under the night sky.
Speaker 2: So I want you to imagine something for a second.
Speaker 2: Try to, like, picture looking at a photograph of a galaxy.
Speaker 2: Oka like a massive swirling vortex of billions of stars,
Speaker 2: you know, laced with those glowing veins of purple gas
Speaker 2: and thick dark rivers of cosmic dust.
Speaker 3: Write something like a classic image beamed back from the
Speaker 3: James Webb Space Telescope.
Speaker 2: Exactly, a stunning high definition space image. Now imagine a
Speaker 2: second photograph right next to it, and it looks completely
Speaker 2: identical down to the pixel right, the same complex spiral arms,
Speaker 2: the same chaotic star forming regions, the exact same distribution
Speaker 2: of light and shadow. But there's a fundamental difference between
Speaker 2: these two images.
Speaker 3: And it's a pretty massive difference.
Speaker 2: Yeah, because one is a photograph of our actual universe, right,
Speaker 2: the product of fourteen billion years of messy, chaotic natural evolution, right,
Speaker 2: But the other one is essentially a hallucination. It is
Speaker 2: a product of pure math running on silicon chips in
Speaker 2: a basement somewhere here on Earth. It's incredible to think
Speaker 2: about it really is. So what if we could build
Speaker 2: a universe inside a computer so mathematically perfect, like, so
Speaker 2: unfathomably detailed that if you put those two images side
Speaker 2: by side, even professional PhD holding astronomers couldn't tell you
Speaker 2: which one was real.
Speaker 3: I mean, it sounds completely like science fiction, but it
Speaker 3: is the current, very real frontier of computational astrophysics.
Speaker 2: Today, which is just wild to me.
Speaker 3: It is we are no longer just sketching rough approximations
Speaker 3: of how galaxies might form. We are synthesizing entire cosmoses
Speaker 3: from absolute scratch.
Speaker 2: Wow.
Speaker 3: Yeah, the boundary between observed physical reality and simulated digital
Speaker 3: reality is becoming well incredibled porous.
Speaker 2: Okay, let's unpack this because simulating an entire universe from
Speaker 2: the literal Big Bang all the way to the present
Speaker 2: day sounds like a task that would just melt any
Speaker 2: computer on Earth.
Speaker 3: It definitely pushes the absolute limits of our current hardware.
Speaker 2: I bet. Yet this massive, decade long scientific effort has
Speaker 2: just achieved exactly this. We are looking at a project
Speaker 2: that successfully simulated the evolution of galaxies by tracking the
Speaker 2: absolute smallest like microscopic specs of cosmic.
Speaker 3: Dust, down to the fundamental chemistry.
Speaker 2: Right, and in doing so, they essentially rescued the entire
Speaker 2: standard model of the universe from being thrown in the
Speaker 2: scientific garbage bin.
Speaker 3: They really did. It was a close call for a
Speaker 3: minute there.
Speaker 2: Plus they figured out a way for us to literally
Speaker 2: hear this virtual universe, which we will definitely get into.
Speaker 3: Oh, the sonification stuff is fascinating, but the scope of
Speaker 3: the simulation itself is genuine only difficult to wrap your
Speaker 3: head around, even for the people actively.
Speaker 2: Working on it, I can imagine.
Speaker 3: But this endeavor really highlights a core philosophy of science,
Speaker 3: which is that knowledge is most valuable when it is
Speaker 3: rigorously applied to solve a crisis.
Speaker 2: And there was definitely a crisis.
Speaker 3: Oh absolutely. For decades, astrophysicists have understood the broad theoretical
Speaker 3: strokes of how the.
Speaker 2: Universe expands, that the big picture stuff, right.
Speaker 3: But whenever they tried to actually build a digital model
Speaker 3: of it. The simulated galaxies always looked well, they just looked.
Speaker 2: Wrong, like how wrong.
Speaker 3: They were too clunky, the colors were off, the sizes
Speaker 3: just didn't match reality at all. The breakthrough here from
Speaker 3: this massive international initiative known as the Collibo project is
Speaker 3: that it proves something fundamental, which is, if you want
Speaker 3: to get the massive billion light year macro universe right,
Speaker 3: you have to perfect the microscopic physics first.
Speaker 2: See. And that's the part that gets me because for
Speaker 2: the longest time we weren't just struggling with the microphysics right,
Speaker 2: we were actively blatantly ignoring them.
Speaker 3: Yeah, that's as one way to put it.
Speaker 2: I want to talk about this concept of the heat
Speaker 2: barrier in early simulations because when I first learned about this,
Speaker 2: it sounded completely absurd.
Speaker 3: It is a bit counterintuitive until you understand the math behind.
Speaker 2: It, right. But in all the older legacy simulations of
Speaker 2: the universe, scientists put a hard floor on the temperature
Speaker 2: of their virtual space.
Speaker 3: Didn't They They did a very strict temperature limit.
Speaker 2: They artificially prevented the gas inside their virtual galaxies from
Speaker 2: cooling down below about ten thousand degrees fahrenheit.
Speaker 3: Which just to put that into perspective, for you, is
Speaker 3: significantly hotter than the surface of our sun.
Speaker 2: Wait? Really?
Speaker 3: Oh yeah? So imagine trying to code an entire virtual
Speaker 3: universe where literally nothing, no cloud of gas, no planetary nebula,
Speaker 3: no empty void, is allowed to be cooler than a
Speaker 3: raging stellar surface.
Speaker 2: It sounds like trying to study how a delicate French
Speaker 2: pastry is baked, but your oven only have one setting,
Speaker 2: and that setting is blowtorch.
Speaker 3: That's a great way to describe it, Like, how do.
Speaker 2: You expect to bake a croissant, or in this case,
Speaker 2: forge a star if every ingredient in your digital kitchen
Speaker 2: is instantly vaporized into superheated plasma.
Speaker 3: Well, you don't. You simply don't. And that was the
Speaker 3: glaring flaw of late twentieth and early twenty first century cosmology.
Speaker 2: It seems like such an obvious oversight, it does.
Speaker 3: But to be fair to those early pioneers, it wasn't
Speaker 3: that astronomers didn't want their.
Speaker 2: Universes to be cold, Okay, so why do it?
Speaker 3: It was that modeling cold gas was computationally lethal to
Speaker 3: their machines.
Speaker 2: Lethal How like, is cold gas harder to calculate than
Speaker 2: hot gas. I would assume hot things are more chaotic.
Speaker 3: It's actually the exact opposite. Modeling cold gas is exponentially harder. Really, Yeah,
Speaker 3: when we talk about gas moving through space, we were
Speaker 3: really talking about hydrodynamics. In astrophysics, we treat these massive
Speaker 3: clouds of hydrogen and helium.
Speaker 2: Like a fluid, like water flowing in a river.
Speaker 3: Sort of. Yeah, we have to calculate their pressure, their viscosity,
Speaker 3: how they flow, and crucially, how they react to the
Speaker 3: gravitational pull of dark matter.
Speaker 2: Okay, that makes sense.
Speaker 1: Now.
Speaker 3: When gas is kept artificially hot at ten thousand degrees,
Speaker 3: it has a lot of thermal pressure. It's smooth, it
Speaker 3: expands outward evenly. It predictable exactly. The math to track
Speaker 3: a smooth expanding balloon of hot fluid is relatively straightforward.
Speaker 3: For a supercomputer, it can handle that easily. But what
Speaker 3: happens to a gas when you cool it down?
Speaker 2: It condenses, right, It shrinks and gets thicker, exactly.
Speaker 3: It loses all that outward thermal pressure. So gravity suddenly
Speaker 3: takes over and the gas starts clumping together into microscopic,
Speaker 3: incredibly dense pockets. Oh I see, it becomes chaotic. And
Speaker 3: highly nonlinear. To calculate the hydrodynamics of cold, clumpy gas,
Speaker 3: your computer grid needs a massive, massive increase in resolution.
Speaker 2: Because there's more stuff happening in a smaller area.
Speaker 3: Right, You have to track millions of tiny, independent, highly
Speaker 3: dense collapsing now instead of just one big smooth cloud.
Speaker 2: So the computers just couldn't handle the math exactly.
Speaker 3: If older supercomputers tried to let the gas drop below
Speaker 3: ten thousand degrees, the simulation would essentially choke on the
Speaker 3: math and crash. The algorithm simply couldn't handle the resolution
Speaker 3: required to track all those tiny clumps.
Speaker 2: But the physical reality we actually live in completely relies
Speaker 2: on that cold gas.
Speaker 3: It lies entirely on it.
Speaker 2: Right, Like, if the real universe couldn't cool down, the
Speaker 2: gas would never clump, stars would never form, and you
Speaker 2: and I wouldn't be sitting here talking about it.
Speaker 3: No, we wouldn't. And this is the grand irony of
Speaker 3: early cosmological simulations. Stars only form in molecular clouds that
Speaker 3: are incredibly cold. We are talking just a few degrees
Speaker 3: above absolute zero.
Speaker 2: Wow, that cold.
Speaker 3: Yes, at those freezing temperatures, the gas has virtually zero
Speaker 3: thermal pressure.
Speaker 2: Pushing outward, so gravity just completely takes over.
Speaker 3: Precisely without that outward push, the inward pull of gravity
Speaker 3: finally wins the tug of war. The cold gas collapses
Speaker 3: in on itself, becoming denser and denser until the pressure
Speaker 3: at the core is so extreme that it ignites nuclear fusion.
Speaker 2: And boom, a star is born.
Speaker 3: Exactly, But if your virtual universe is artificially locked at
Speaker 3: ten thousand degrees, the gas is just moving too fast.
Speaker 3: It has too much kinetic.
Speaker 2: Energy, so it just zips right past itself right.
Speaker 3: Gravity can never grab onto it long enough to forge
Speaker 3: a star. What's fascinating here is how this forced scientists
Speaker 3: to reevaluate their entire approach.
Speaker 2: So wait, if the physics in those older simulations physically
Speaker 2: prevented stars from format like mathematically made it impossible, how
Speaker 2: do they get galaxies? Do they just hack the code? H?
Speaker 1: Yeah?
Speaker 3: Essentially, they used a conceptual band aid called subgrid physics.
Speaker 2: Subgrid physics it sounds like a polite way of saying
Speaker 2: we made it.
Speaker 3: Up, well, kind of. Because the computer grid couldn't zoom
Speaker 3: in far enough to simulate actual cooling and collapsing, they
Speaker 3: wrote a statistical workaround an arbitrary rule.
Speaker 2: How did that work?
Speaker 3: The code basically said, Hey, if a pocket of hot
Speaker 3: gas reaches a certain density threshold, just pretend it magically
Speaker 3: cooled down, delete the gas, and spawn a star particle
Speaker 3: in its place.
Speaker 2: Wow. So they were just spawning in stars like items
Speaker 2: in a video game based on a rough guess.
Speaker 3: Exactly, just dropping them in when the math looked close enough.
Speaker 2: That means for years an enormous chunk of our understanding
Speaker 2: of galaxy evolution was built on a giant blind.
Speaker 3: Spot, a huge blind spot.
Speaker 2: We were trying to map the cosmos while completely ignoring
Speaker 2: the actual environment where galaxies build themselves.
Speaker 3: Right, it was an educated guest, But you can only
Speaker 3: rely on statistical band aids for so long before your
Speaker 3: virtual universe diverges so far from reality that it just
Speaker 3: stops being scientifically useful.
Speaker 2: Right, Eventually the cracks are going to show.
Speaker 3: Absolutely Eventually you have to find a way to break
Speaker 3: that heat barrier and let the virtual cosmos freeze.
Speaker 2: And breaking that barrier wasn't just a matter of like
Speaker 2: waiting for Apple or IBM to build a faster microchip, right,
Speaker 2: You actually had to write new physics into the simulation.
Speaker 3: Yes, entirely new physics.
Speaker 2: And this is where the claw reproject completely changes the game.
Speaker 2: To cool the universe down, they had to introduce two
Speaker 2: highly specific ingredients that had never been successfully modeled on
Speaker 2: this scale before, right, right, molecular hydrogen and cosmic dust.
Speaker 3: Yes, and let me stop you there, because it is
Speaker 3: vital to understand why those two things go hand in hand.
Speaker 3: You cannot have cold molecular hydrogen in space without cosmic
Speaker 3: dust rate. Dust is the great enabler of the universe.
Speaker 2: Which is such a wild paradigm shift because normally, if
Speaker 2: you ask an amateur astronomer about dust, they'll just groan.
Speaker 3: Oh, they hate it.
Speaker 2: Right, dust is the annoying haze that blocks the light
Speaker 2: from the beautiful glowing nebulae behind it. It's an obstacle.
Speaker 2: But here dust is essentially the vip of the universe.
Speaker 2: So what does this all mean? Why is it so important?
Speaker 3: Well, because the vacuum of space is an incredibly hostile
Speaker 3: place to build a molecule. The primary ingredient for a
Speaker 3: star is molecular hydrogen, which is just two hydrogen atoms
Speaker 3: bonded together.
Speaker 2: Okay, simple enough.
Speaker 3: In the vast empty expanse of an early galaxy. Trying
Speaker 3: to get two single hydrogen atoms to bump into each
Speaker 3: other and bond is nearly impossible.
Speaker 2: Because space is just too big.
Speaker 3: The space is too vast, the atoms are moving too fast,
Speaker 3: and if they do happen to collide, they usually just
Speaker 3: bounce off each other. Why do they bounce because they
Speaker 3: have nowhere to dump their excess kinetic energy. They hit
Speaker 3: and the energy just pushes them right back apart.
Speaker 2: It's like trying to get two pieces of velcro to
Speaker 2: stick together by firing them out of cannons at each
Speaker 2: other across an empty football stadium.
Speaker 3: That is Yes, that is a brilliant way to visualize it.
Speaker 3: They're just going to ricochet exactly. They need a mediator,
Speaker 3: They need a surface to slow them down. And this
Speaker 3: is exactly where a microscopic grain of cosmic dust comes in. Okay, Now,
Speaker 3: when we say dust in astrophysics, we aren't talking about
Speaker 3: the dust bunnies under your couch.
Speaker 2: Right, It's not skin cells and lint.
Speaker 3: No, No, we are talking about microscopic solid particles of
Speaker 3: silicates or carbon, Essentially tiny grains of sand or soot
Speaker 3: forged in the dying breaths of older stars.
Speaker 2: Okay, so stellar's soot.
Speaker 3: Yes, and these solid grains act as a catalytic docking station.
Speaker 2: So a single hydrogen atom is flying through the stadium
Speaker 2: and instead of hitting another atom, it crashes into this giant,
Speaker 2: well relatively speaking, grain of soot yes.
Speaker 3: It hits the dust grain and actually sticks to its surface.
Speaker 3: The dust grain absorbs the atom's kinetic energy, acting as
Speaker 3: a thermal sink.
Speaker 2: Oh, so it bleeds off the speed exactly.
Speaker 3: Then another hydrogen atom hits that exact same dust grain.
Speaker 3: It wanders around the solid surface until it finds the
Speaker 3: first atom.
Speaker 2: And because they're both slowed down, they bond.
Speaker 3: They form molecular hydrogen and then drift off the dust
Speaker 3: grain together into space.
Speaker 2: So the dust is literally acting like a cosmic anvil
Speaker 2: where the fuel for stars is hammered together.
Speaker 3: It is the factory floor of star formation. But its
Speaker 3: job doesn't end there.
Speaker 2: There's more.
Speaker 3: Oh yeah. Once that molecular hydrogen forms, it is incredibly fragile.
Speaker 3: A galaxy is a violent place, fle with harsh, destructive
Speaker 3: ultraviolet radiation pouring out of young hot stars.
Speaker 2: So it's basically a hostile environment for these new molecules.
Speaker 3: Very hostile if that UV radiation hits our newly formed
Speaker 3: molecular hydrogen, it excites the molecule, heats it up, and
Speaker 3: literally blasts it apart. Oh, it destroys the fuel supply
Speaker 3: for any future stars. It just sterilizes the whole region precisely,
Speaker 3: unless the dust steps in again.
Speaker 2: The VIP returns exactly.
Speaker 3: Cosmic dust is incredibly effective at absorbing ultraviolet light. It
Speaker 3: blankets these cold molecular clouds, acting as a physical shield,
Speaker 3: so it takes the hit right. The UV radiation hits
Speaker 3: the dust on the outside of the cloud, while the
Speaker 3: fragile hydrogen gas safely nestled deep inside remains freezing cold.
Speaker 2: It's like the universe's own SBF ten thousand sunscreen.
Speaker 3: That's a perfect analogy.
Speaker 2: The dust takes the hit so the baby stars can
Speaker 2: incubate in the dark cold center. And the clean Aber
Speaker 2: project was the first time anyone managed to mathematically track
Speaker 2: these microscopic sit grains, like their chemical reactions and their
Speaker 2: shielding effects across an entire simulated.
Speaker 3: Universe on this massive of a scale.
Speaker 2: Yes, that is mind blowing.
Speaker 3: And what's fascinating here is that introducing dust didn't just
Speaker 3: fix the physics. It completely revolutionized the visuals of the
Speaker 3: simulation too. How so, Well, think about it. If the
Speaker 3: dust is absorbing all that intense ultraviolet starlight, that energy
Speaker 3: can't just vanish. The laws of thermodynamics dictate it has
Speaker 3: to go somewhere.
Speaker 2: Right, energy cannot be created or destroyed. So the dust
Speaker 2: heats up and starts glowing in a different wavelength exactly.
Speaker 2: It re emits the energy as intrared light.
Speaker 3: Exactly, and that completely alters how a simulated galaxy appears
Speaker 3: when we look at it. Yeah, for the first time,
Speaker 3: researchers were creating virtual galaxies that didn't just have the
Speaker 3: right mass or gravity.
Speaker 2: They actually looked real.
Speaker 3: They actually look like the galaxies we observed through infrared telescopes.
Speaker 2: I was actually looking at the visual outputs the Collier
Speaker 2: team published. They showed a rendering of a virtual disk
Speaker 2: galaxy structurally very similar to our ow Milky Way, right,
Speaker 2: from two different perspectives.
Speaker 3: Yes, the face on on edge on views right.
Speaker 2: When you look at it face on from the top down,
Speaker 2: it is this brilliant glowing spiral of starlight. But when
Speaker 2: they rotate the simulation and show it to you edge
Speaker 2: on from the side, the starlight is suddenly choked out
Speaker 2: by this dense, dark, suffocating band of dust slicing right
Speaker 2: through the galactic equator.
Speaker 3: It's a dramatic visual shift, it really is.
Speaker 2: It perfectly mimics the real optical telescope images we get
Speaker 2: of edge on galaxies, and that.
Speaker 3: Visual fidelity is what makes this a monumental achievement. We
Speaker 3: are no longer limited to comparing abstract graphs of theoretical mass.
Speaker 2: You know, we're comparing actual pictures exactly.
Speaker 3: We can take a real observed image from a space telescope,
Speaker 3: put it next to a simulated image from collar, run
Speaker 3: both images through the exact same analytical software, and test
Speaker 3: if they match. We can measure the exact obscuration of light.
Speaker 2: But hold on. The sheer computational brute force required to
Speaker 2: do that is I mean, I can't even process it.
Speaker 3: It's staggering.
Speaker 2: You are asking a computer to track microscopic grains of soot,
Speaker 2: calculate the fluid dynamics of freezing gas, apply the gravitational
Speaker 2: pull of billions of dark matter halos, and compute the
Speaker 2: radiation physics of starlight, all across a volume of space
Speaker 2: that spans hundreds of millions of light years.
Speaker 3: It's a lot of math.
Speaker 2: What kind of machine is actually capable of calculating that matrix?
Speaker 3: Well, it requires an architecture that is almost as complex
Speaker 3: as the simulation itself. The physical engine running this was
Speaker 3: the cost Am Supercomputer, which is hosted by the DRAC
Speaker 3: National Facility at Durham University in the UK. Oh but
Speaker 3: hardware alone isn't enough. You can have the absolute fastest
Speaker 3: supercomputer in the world and if your code is inefficient,
Speaker 3: it will still crash when trying to simulate a freezing.
Speaker 2: Galaxy, right because of that resolution bottleneck we talked about
Speaker 2: earlier Exactly.
Speaker 3: The real hero here is the software code they wrote,
Speaker 3: which is called swift.
Speaker 2: Swift Okay, so how does swift handle the math differently
Speaker 2: then the older codes that used to crash when the
Speaker 2: gas got cold.
Speaker 3: Older cosmological codes usually operated on rigid time steps.
Speaker 2: What does that mean?
Speaker 3: It means the computer would calculate the gravity, temperature, and
Speaker 3: velocity of every single particle in the entire universe, move
Speaker 3: the simulation forward by one tick of the cosmic clock,
Speaker 3: and then recalculate everything all over again.
Speaker 2: Oh wow, So which means the computer has to wait
Speaker 2: for the absolute slowest, most complicated calculation to finish before
Speaker 2: the whole universe is allowed to move forward one second exactly.
Speaker 3: It creates massive processing.
Speaker 2: Bottlenecks like a traffic jam.
Speaker 3: Very much like a traffic jam, Swift entirely abandoned that model.
Speaker 3: It uses task based asynchronous parallelism, meaning it breaks the
Speaker 3: universe down into millions of independent tasks. If a cold,
Speaker 3: dense cloud of gas in one corner of the simulation
Speaker 3: is highly chaotic and needs to be calculated in incredibly
Speaker 3: tiny fractions of a second, the processor handles that.
Speaker 2: Locally without making the rest of the universe.
Speaker 3: Wait right, without forcing a quiet, empty void on the
Speaker 3: other side of the virtual universe to slow down and
Speaker 3: wait for it. The code dynamically shifts computational power exactly
Speaker 3: where it is needed the millisecond it is needed.
Speaker 2: So it's essentially a self optimizing universe. It is, And
Speaker 2: even with that hyper efficient code, the scale of the
Speaker 2: simulation they ran is just staggering. I want you, the listener,
Speaker 2: to really internalize these numbers for a second. The largest
Speaker 2: simulation in the Calibra suite required seventy two million CPU
Speaker 2: hours to complete.
Speaker 3: That's seventy two million hours of continuous processing.
Speaker 2: Seventy two million. If you somehow manage to install this
Speaker 2: swift code onto a top of the line twenty twenty
Speaker 2: six gaming laptop and you hit run, your computer would
Speaker 2: have to sit there processing it one hundred percent maximum
Speaker 2: capacity twenty four hours a day for over eight thousand
Speaker 2: years before it finished calculating what calls an A eight did.
Speaker 3: And that seventy two million hours produced a volume of
Speaker 3: space that is unprecedented in its resolution. They build multiple
Speaker 3: simulated universes, but their largest box is a side length
Speaker 3: of four hundred coup moving megaparsex.
Speaker 2: Now wait, co moving megaparsex. A megaparsec is about three
Speaker 2: point twenty six million light years. But what does comoving mean?
Speaker 2: Why not just say a billion light years?
Speaker 3: Well, because the universe is expanding, right. If you measure
Speaker 3: the distance between two galaxies today and then wait a
Speaker 3: billion years, the distance between them will be larger, even
Speaker 3: if the galaxies themselves haven't actually traveled through space.
Speaker 2: The space itself stretched.
Speaker 3: Exactly, space is self stretched. Co moving is a coordinate
Speaker 3: system that expands along with the universe.
Speaker 2: How does that work?
Speaker 3: It's like drawing two dots on a deflated balloon. As
Speaker 3: you blow the balloon up, the dots get further apart,
Speaker 3: but their comoving distance, their relative position on the rubber,
Speaker 3: stays exactly the same.
Speaker 2: Oh, it's a great visual.
Speaker 3: Using co moving MEGAPARSEX allows the simulation to track the
Speaker 3: evolution of matter without the math getting distorted by the
Speaker 3: expansion of space itself.
Speaker 2: That is deeply counterintuitive, right, but it makes perfect sense
Speaker 2: for a simulation tracking fourteen billion years of history. It's
Speaker 2: a SEX. So this massive bos over a billion light
Speaker 2: years across, is just relentlessly churning through these equations. And
Speaker 2: there's a quote about this process from Carlos Frank he's
Speaker 2: the Ogden Professor of Fundamental physics and a core member
Speaker 2: of this team that I found deeply profound.
Speaker 3: Yeah, he summed it up perfectly.
Speaker 2: He pointed out that they didn't paint these galaxies. They
Speaker 2: didn't tell the computer, hey, put a spiral galaxy over here,
Speaker 2: in an elliptical galaxy over there.
Speaker 3: No no hard coating shapes.
Speaker 2: They literally just inputted the raw fundamental equations of gravity, thermodynamics,
Speaker 2: and chemistry, hit play on the Big Bang, and the
Speaker 2: galaxies built themselves.
Speaker 3: It is the ultimate testament to the emergent complexity of physics.
Speaker 2: It really is.
Speaker 3: When you finally provide the equations with sufficient resolution, when
Speaker 3: you respect the dust and the cold gas, reality naturally
Speaker 3: emerges from the math. Wow, the simulated galaxy spontaneously grew
Speaker 3: to have the exact same masses, the exact same colors,
Speaker 3: and the exact same chemical compositions, what astronomers call metallicity
Speaker 3: as the real galaxies we observe.
Speaker 2: Let's actually define metallicity real quick, because astronomers use that
Speaker 2: word very differently than normal people do.
Speaker 3: That's true, they do.
Speaker 2: If I say metal, people think of iron or aluminum, right.
Speaker 3: But to an astrophysicist, the periodic table is incredibly simple.
Speaker 3: There is hydrogen, there is helium, and literally every other
Speaker 3: element in the universe carbon, oxygen, nitrogen, Iron is considered.
Speaker 2: A metal, So oxygen is a metal.
Speaker 3: In astronomy, yes, these heavy metals are forged in the
Speaker 3: nuclear furnaces of early stars and then blasted out into
Speaker 3: space when those stars die in supernovae.
Speaker 4: And then that seeds the next generation exactly that metal
Speaker 4: rich dust then seeds the next generation of stars caliber
Speaker 4: track that exact chemical enrichment process over billions of years.
Speaker 2: Okay, so building this ultimate virtual laboratory is an absolute
Speaker 2: marvel of human engineering. But the critical question is what
Speaker 2: do we do with it?
Speaker 3: Right? Application is key?
Speaker 2: Did spending seventy two million CPU hours actually solve any
Speaker 2: real world problems? Because right around the time the supercomputer
Speaker 2: was redlining, the actual astronomy community was undergoing a massive
Speaker 2: existential crisis, weren't they.
Speaker 3: They were in an absolute panic, and that panic was
Speaker 3: entirely courtesy of the James Web Space Telescope.
Speaker 2: I remember this. When JWST finally launched and sent back
Speaker 2: its first deep field images, it pointed its incredibly sensitive
Speaker 2: infrared sensors at the very edge of the observable universe, right, yes,
Speaker 2: peering into the first few hundred million years, right after
Speaker 2: the Big Bang. Because you know, light takes time to travel,
Speaker 2: so looking far away is literally looking back in time.
Speaker 3: Yes, it's a time machine. And the established standard model
Speaker 3: of cosmology, which is called the Lambda CDM model, incorporating
Speaker 3: dark energy and cold dark matter, had very specific predictions
Speaker 3: for what the universe should look like in that early era.
Speaker 2: What were those predictions?
Speaker 3: The model predicted that really, galaxies should be small, chaotic,
Speaker 3: ragged little clumps of stars slowly building themselves up over
Speaker 3: billions of years, like stepping stones exactly. But when JWST
Speaker 3: looked back at the dawn of time, it didn't find
Speaker 3: ragged little clumps.
Speaker 2: No.
Speaker 3: No, it found massive, incredibly bright, fully formed galaxies.
Speaker 2: They were way too big, way too fast. I remember.
Speaker 2: The headlines were everywhere. JWST breaks the universe, The Big
Speaker 2: Bang theory is wrong.
Speaker 3: It was a very dramatic few months.
Speaker 2: It was as if an archaeologist dug down into a
Speaker 2: Bronze Age settlement and found a fully functional nuclear reactor.
Speaker 2: It violated the established timeline of reality. You could feel
Speaker 2: the tension in the scientific community.
Speaker 3: People were genuinely terrified, right.
Speaker 2: People were terrified that the fundamental blueprint of cosmology, which
Speaker 2: thousands of scientists had dedicated their entire lives to, was
Speaker 2: fundamentally broken.
Speaker 3: The dread was very real. If the standard model was wrong,
Speaker 3: it meant we basically understood nothing about dark matter or
Speaker 3: dark energy.
Speaker 2: We have to start from scratch, essentially.
Speaker 3: Yes, and this is exactly where the Khaliber project proved
Speaker 3: its immense, undeniable.
Speaker 2: Value because they could test it right.
Speaker 3: Doctor of Yenni Chaikin, the lead author of several of
Speaker 3: the major calabor papers, used this brand new virtual universe
Speaker 3: to test the crisis. The team essentially acted as virtual astronomers.
Speaker 3: They aimed a digital version of the James Web Telescope
Speaker 3: into the deep past of their simulated universe to see
Speaker 3: what they would find.
Speaker 2: And here's where it gets really interesting. The standard model
Speaker 2: wasn't broken at all, was it. We just had terrible
Speaker 2: rendering software.
Speaker 3: That is exactly what they proved when doctor Chakin ran
Speaker 3: the virtual observation. The Caliber simulation effortlessly produced those exact
Speaker 3: same massive, hyper bright early galaxies that the real JWST
Speaker 3: was seeing. Wow, they naturally emerged within the strict confines
Speaker 3: of the standard Lambda CDM model.
Speaker 2: Wait, if the standard model allowed for these massive galaxies
Speaker 2: the whole time, why did our previous predictions say they
Speaker 2: shouldn't exist?
Speaker 3: Because the previous predictions were based on legacy simulations that
Speaker 3: couldn't model cold gas and dust.
Speaker 2: Oh the ten thousand degree floor.
Speaker 3: Remember that heat barrier. If your simulated universe artificially prevents
Speaker 3: gas from cooling, you are artificially suppressing the rate at
Speaker 3: which stars can form, So.
Speaker 2: You're stunting their growth in the simulation.
Speaker 3: Precisely, your virtual early universe will look sluggish and dim,
Speaker 3: not because the fundamental laws of cosmology dictate it, but
Speaker 3: because your computer code is stifling the chemistry.
Speaker 2: So the moment Cobbra added the microscopic dust and let
Speaker 2: the gas freeze, the early galaxies suddenly had the fuel
Speaker 2: they needed to ignite massive firestorms of rapid star formation,
Speaker 2: matching the JWST data perfectly.
Speaker 3: Yes, And furthermore, caullibly successfully modeled the intense explosive outflows
Speaker 3: of energy driven by those early stars and super massive
Speaker 3: black holes.
Speaker 2: It all just clicked into place.
Speaker 3: It proved that the universe didn't need entirely new physics,
Speaker 3: It just needed us to model the messy microscopic chemistry correctly.
Speaker 3: If we connect this to the bigger picture, it shows
Speaker 3: the standard cosmological model is perfectly sound.
Speaker 2: I can just imagine the collective exhale across university physics
Speaker 2: departments worldwide.
Speaker 3: Oh, the relief was palpable.
Speaker 2: It's a profound lesson When a new, shiny piece of
Speaker 2: technology like JWST gives you observations that contradict your life's work.
Speaker 2: The immediate reaction shouldn't be to throw out the physics textbook.
Speaker 1: Right.
Speaker 2: Sometimes the overarching theory is perfectly fine, but your ability
Speaker 2: to model its intricate emergent behaviors is just lacking.
Speaker 3: It is a massive victory for the standard model. And
Speaker 3: there's a but here. The universe still has secrets that
Speaker 3: even seventy two million CPU hours couldn't decipher. Because as
Speaker 3: brilliantly as coll A solve the crisis of the massive
Speaker 3: early galaxies, it ran into an absolute brick wall when
Speaker 3: it came to another of Jawst's most bizarre discoveries.
Speaker 2: You're talking about the phenomena that astrophysicists are currently referring
Speaker 2: to as the ghosts in the machine. Yes, the little red.
Speaker 3: Dots and little red dots. It is such an unassuming,
Speaker 3: cute name for what are essentially the most terrifying cosmic
Speaker 3: monsters in the early universe.
Speaker 2: What exactly are they?
Speaker 1: Well?
Speaker 3: Jwst discovered these highly compact, heavily obscured, intensely red sources
Speaker 3: of light buried deep in the first billion years of
Speaker 3: the cosmos. The current consensus is that we're looking at
Speaker 3: the foundational seeds of supermassive black holes.
Speaker 2: Right because we know that almost every large galaxy today,
Speaker 2: including our Milky Way, has a supermassive black hole at
Speaker 2: its dead center. We're orbiting one right now exactly. Some
Speaker 2: of them are billions of times the mass of our Sun.
Speaker 2: But the mystery has always been, Yeah, how did they
Speaker 2: get so monstrously huge so early in the universe's timeline.
Speaker 3: It's a massive timing problem.
Speaker 2: There simply wasn't enough time for a normal sized black
Speaker 2: hole to slowly eat enough gas to get that big.
Speaker 3: And this is where the grand perfect colliber simulation basically
Speaker 3: throws its hands in the air and gives up. Really,
Speaker 3: the simulation cannot mathematically predict or naturally form these early
Speaker 3: supermassive black hole seeds.
Speaker 2: This shocked me. Wait, so after a decade of international collaboration,
Speaker 2: writing millions of lines of the most advanced physics code
Speaker 2: ever conceived, and letting a supercomputer chew on it for
Speaker 2: eight thousand computational years, the scientists still have to manually
Speaker 2: plant black holes in the simulation like they're planting trees
Speaker 2: in a digital garden.
Speaker 3: We do, We literally have to do that. The simulation
Speaker 3: assumes the black hole seeds already exist at a certain
Speaker 3: mass and manually injects them into the centers of the
Speaker 3: virtual early galaxies.
Speaker 2: That feels like a cheat code. Why can we perfectly
Speaker 2: simulate the fluid dynamics of a cold dust cloud condensing
Speaker 2: into a star? Now, we can't simulate the genesis of
Speaker 2: a black hole.
Speaker 3: Because the birth of these specific supermassive seeds requires physics
Speaker 3: that humanity does not fully understand yet.
Speaker 2: We just don't have the equations right.
Speaker 3: Simulating a star is incredibly complex, but we know the
Speaker 3: rules of thermodynamics and nuclear fusion. But the origin of
Speaker 3: these little red dots is a theoretical frontier.
Speaker 2: So what are the theories?
Speaker 3: Well, some cosmologists hypothesize that they form from the direct
Speaker 3: collapse of massive, pristine, metal free gas clouds, meaning.
Speaker 2: The gas cloud gets so heavy it just entirely skips
Speaker 2: the process of becoming a star and immediately crushes itself
Speaker 2: into a black hole singularity.
Speaker 3: Yes, just an instant massive collapse. Other theories suggest they
Speaker 3: are formed from runaway chain reaction collisions inside unbelievably dense
Speaker 3: early star clusters.
Speaker 2: Like a cosmic demolition derby.
Speaker 3: Essentially, yes, but the gravity and density involved in these
Speaker 3: events approach the singularity, the point where our current mathematical
Speaker 3: equations for general relativity literally break down and output infinities.
Speaker 2: The math just stops working exactly.
Speaker 3: To model those events natively without manual human intervention, will
Speaker 3: require grid resolutions that make Colliber look primitive and entirely
Speaker 3: new equations of quantum gravity written into the code.
Speaker 2: It is a phenomenal reality check. The simulation is a
Speaker 2: flawless mirror of nature, right up until the exact millimeter
Speaker 2: where human knowledge itself hits a cliff.
Speaker 3: It is a very stark boundary.
Speaker 2: But the team isn't just packing up their bags, are
Speaker 2: they not?
Speaker 3: At all? While the foundational Colliber runs were completed recently,
Speaker 3: some of the absolute highest resolution simulations are currently running
Speaker 3: right now, eating up more processor hours trying to push
Speaker 3: that boundary further. The work continues, oh absolutely, And the
Speaker 3: data they've already generated is so vast, petabytes upon petabytes
Speaker 3: of information that it will take the global scientific community
Speaker 3: a decade just to fully read and analyze it.
Speaker 2: And while the supercomputers grind away at the next era
Speaker 2: of frontier physics, the scientists have developed a radical, entirely
Speaker 2: new way for humans to experience the petabytes of data
Speaker 2: we already have. This might be my favorite part, which
Speaker 2: brings us to the final and visually, or rather sensorily,
Speaker 2: most fascinating aspect of this endeavor. We aren't just looking
Speaker 2: at the virtual universe anymore. We are hearing it.
Speaker 3: This is a truly innovative approach led by doctor James
Speaker 3: Treyford at the University of Portsmouth.
Speaker 2: Right.
Speaker 3: He was the lead developer of Climber's complex dust model,
Speaker 3: but he also spearheaded the creation of what they call
Speaker 3: sonified videos. They are creating a multisensory cosmos.
Speaker 2: Normally, astrophysics is entirely visual. We look at scatterplots, line graphs,
Speaker 2: and beautiful false color renderings of nebulae. But doctor Treyford
Speaker 2: took this dense, mathematically terrifying digital universe and applied sonification,
Speaker 2: essentially encoding physical astronomical data into sound.
Speaker 3: And let's be clear about what sonification is not. They
Speaker 3: aren't just overlaying a pretty Beethoven symphony onto a video
Speaker 3: of a galaxy spinning.
Speaker 2: It's not just a soundtrack.
Speaker 3: No, they are mapping highly specific physical properties of the
Speaker 3: simulated universe directly to acoustic parameters.
Speaker 2: You give an example, sure.
Speaker 3: For instance, the velocity of stars orbiting the galactic center
Speaker 3: might be mapped to the pitch of the sound. The
Speaker 3: rate at which new stars are forming the star formation
Speaker 3: rate might be mapped to rhythm or volume.
Speaker 2: So instead of trying to read a chaotic line graph,
Speaker 2: you could listen to a galaxy and the pitch would
Speaker 2: literally rise and fall as the galaxy's rotation speeds up
Speaker 2: or slows down precisely.
Speaker 3: Or imagine listening to the sonified data of a galaxy's
Speaker 3: cold gas reserves.
Speaker 2: Okay, what would that sound like?
Speaker 3: You hear a steady, low frequency hum representing the molecular
Speaker 3: hydrogen the fuel right then suddenly the hum is violently
Speaker 3: interrupted by sharp, staccato, high pitched rhythmic bursts.
Speaker 2: What's that?
Speaker 3: That represents the thermal shock waves of supernovae exploding as
Speaker 3: a burst of star formation occurs.
Speaker 2: Wow, it's like atoustic diagnostics if you think about it.
Speaker 2: Human beings do this all the time in everyday life.
Speaker 3: We do.
Speaker 2: Yeah. If you are sitting in traffic and your car's
Speaker 2: engine suddenly starts making a subtle rhythmic ticking noise, your
Speaker 2: brain detects that anomaly instantly, often long before a warning
Speaker 2: light flashes on your dashboard.
Speaker 3: That is exactly the cognitive mechanism doctor Treyford is tapping into.
Speaker 3: This rate is an important question about how we process data.
Speaker 3: Human hearing evolved to be extraordinarily sensitive to patterns, rhythms,
Speaker 3: and subtle changes in frequency.
Speaker 2: Much more so than our eyes.
Speaker 3: Sometimes exactly, our auditory processing can often pick out a
Speaker 3: single anomalous data point in a chaotic environment much faster
Speaker 3: than our visual processing can spot a rogue dot on
Speaker 3: a crowded scatterplot.
Speaker 2: So if a simulated galaxy undergoes a violent merger with
Speaker 2: another galaxy, the visual data on a screen might just
Speaker 2: look like a messy, blindingly bright blob of light hard
Speaker 2: to decipher right, But the Sonifi data would hit your
Speaker 2: ears as a distinct, chaotic acoustic crash followed by a
Speaker 2: settling resonance as the two gravitational fields finally merge and stabilize.
Speaker 3: By making the data multisensory, they are effectively training human intuition.
Speaker 2: That is so cool.
Speaker 3: Science isn't just the cold collection of numbers, It is
Speaker 3: the human comprehension of those numbers. By allowing researchers to
Speaker 3: sit in the lab with headphones on and interactively fly
Speaker 3: through the calabor universe, feeling the rhythm of star formation
Speaker 3: and daring the pitch of dark matter gravity. They are
Speaker 3: building a deeper, almost subconscious instinct for how galaxies evolve.
Speaker 2: It bridges the gap between the incredibly abstract math of
Speaker 2: an expanding universe and the physical sensory experience of the
Speaker 2: human body.
Speaker 3: It makes the math tangible.
Speaker 2: It really does. It is an absolutely wild journey. When
Speaker 2: you zoom out and look at the sheer scope of
Speaker 2: what we've explored today, it.
Speaker 3: Is a testament to how far we have come in
Speaker 3: such a short amount of time.
Speaker 2: We started with crude, legacy simulations that were literally too
Speaker 2: hot to handle, restricted by an artificial ten thousand degree
Speaker 2: floor that completely blinded us to the true nature of
Speaker 2: star formation.
Speaker 3: We couldn't see the forest for the fire, basically.
Speaker 2: Right then, scientists painstakingly cracked the mathematical code of cosmic dust,
Speaker 2: proving that the tiniest, most microscopic spects of soot are
Speaker 2: the ultimate architects and thermal protectors of the largest galaxies
Speaker 2: in existence, the cousin of VIPs. The VIPs, we unleashed
Speaker 2: the unfathomable brute force of the cosm. A eight supercomputer
Speaker 2: or burning through seventy two million asynchronous CPU hours to
Speaker 2: synthesize a one to one scale universe out of pure
Speaker 2: fluid dynamics in gravity, a digital triumphs, and in doing
Speaker 2: so we essentially saved the standard model of the cosmos
Speaker 2: from the terrifying reality bending early observations of the James
Speaker 2: Webs based telescope.
Speaker 3: And yet we are main profoundly humbled by the limitations
Speaker 3: of our own knowledge, staring into the abyss of the
Speaker 3: little red dots, waiting for the next generation of physics
Speaker 3: to explain how the universe's ultimate monsters are born.
Speaker 2: It really is a story of human audacity. And I
Speaker 2: want to leave you with one final mind bending thought
Speaker 2: to ponder as you go about the rest of your day.
Speaker 2: We just spent this entire time dissecting how human beings
Speaker 2: right now, in the twenty twenties, have built computers capable
Speaker 2: of generating a digital universe so physically accurate, so perfectly rendered,
Speaker 2: that even our best professional astronomers cannot distinguish its virtual
Speaker 2: galaxies from reality.
Speaker 3: That is a fact.
Speaker 2: If we could achieve that level of simulation to what
Speaker 2: happens in a century. What happens after a thousand years
Speaker 2: of computational advancement.
Speaker 3: It's almost scary to think about.
Speaker 2: Is it entirely possible that the grand, beautiful, chaotic universe
Speaker 2: you and I are currently observing the stars, the dust,
Speaker 2: the massive early galaxies we see through our telescopes is
Speaker 2: actually just a highly detailed, perfect simulation running on someone
Speaker 2: else's supercomputer.
Speaker 3: The ultimate simulation there is
Speaker 2: Exactly Keep looking up at the stars, everyone, and maybe
Speaker 2: if you listen closely enough, you can hear the hum
Speaker 2: of the processor