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: If you take a state of the art supercomputer today
Speaker 2: and you feed it the mathematical equations for two black
Speaker 2: holes colliding, it will take weeks of just NonStop processor
Speaker 2: melting grinding to give you the answer.
Speaker 3: Yeah, and that's if the simulation doesn't crash halfway through,
Speaker 3: which it often used to.
Speaker 2: Right. I mean, we are talking about tracking the absolute
Speaker 2: most extreme violence in the cosmos. It's a collision so
Speaker 2: powerful that it physically bends the geometry of reality itself, which.
Speaker 3: Is incredibly hard to calculate. The numbers get unimaginably huge.
Speaker 2: Exactly. Yeah, but there's this team of physicists of recently
Speaker 2: published some research suggesting that you might be able to
Speaker 2: get the exact same answer using basically the mathematics that
Speaker 2: explains why your morning coffee gets cold.
Speaker 3: It is I mean, it's one of the most counterintuitive
Speaker 3: proposals in modern astrophysics right now.
Speaker 2: It really is. And if you follow astrophysics at all,
Speaker 2: you know about this enduring frustration. Right. But the two
Speaker 2: great paradigms of physics. You've got quantum mechounics and thermodynamaz
Speaker 2: on one side, and then general relativity on the other.
Speaker 3: And they notoriously refuse to speak the same language. It's
Speaker 3: like they're operating in two completely different universes.
Speaker 2: Right, So what we're looking at today is a tangible
Speaker 2: mathematical bridge between them. We are talking about how the
Speaker 2: ultimate agents of cosmic chaos are well secretly governed by
Speaker 2: the mundane physics of your kitchen.
Speaker 3: Yeah, the historical divide you just mentioned, that's really the
Speaker 3: core of the whole problem. General relativity, you know, Einstein's masterpiece.
Speaker 3: It's the ultimate theory of the.
Speaker 2: Macroscopic, the big stuff, planets, galaxies.
Speaker 3: Gravity exactly, and it is entirely deterministic. So if you
Speaker 3: know the precise state of space time right now, Einstein's
Speaker 3: equations should theoretically at least tell you exactly what space
Speaker 3: time will do a second from now.
Speaker 2: A cause is b every single time right.
Speaker 3: But thermodynamics, on the other hand, is a statistical science.
Speaker 3: It does not care about the deterministic path of individual atoms.
Speaker 3: It relies entirely on probability and macro averages.
Speaker 2: Like you don't track every single water molecule in a
Speaker 2: boying pot, You just measure the overall temperature precisely.
Speaker 3: So to suggest that you can bypass the deterministic tracking
Speaker 3: of a black hole merger and instead treat the collision
Speaker 3: like say, a mixing of two hot gases, that is
Speaker 3: a radical departure from how we've calculated these events for decades.
Speaker 2: It's nuts. But before we get into how a black
Speaker 2: hole could possibly behave like a mixing gas, I think
Speaker 2: we really have to establish what exactly is happening during
Speaker 2: one of these mergers, Like let's look at the actual
Speaker 2: physical crest.
Speaker 3: That idea visualizing it is key.
Speaker 2: So we've got two black holes locked in this decaying orbit,
Speaker 2: and because of this sheer mass involved, they're dragging space
Speaker 2: time along with them. They're spiraling inward, approaching a significant
Speaker 2: fraction of the speed of light, and they eventually.
Speaker 3: Touch, and that exact moment of contact is where the
Speaker 3: physics gets incredibly hostile. You have to remember that a
Speaker 3: black hole, it's not a solid object, right, There's no surface,
Speaker 3: no surface you can knock on. The black hole is
Speaker 3: just a region of space where gravity is so intense
Speaker 3: that the escape velocity exceeds the speed of light. The
Speaker 3: boundary of that region is the event horizon.
Speaker 2: So it's just pure math, essentially a mathematical line in
Speaker 2: the sand.
Speaker 3: Exactly, when two black holes merge, you are watching two
Speaker 3: purely mathematical boundaries in space time colliding and reshaping each other.
Speaker 3: The event horizons deform, they reach out toward each other,
Speaker 3: and they snap together into a single, highly distorted, sort
Speaker 3: of peanut shaped horizon.
Speaker 2: I've always loved that visual, a giant cosmic peanut. And
Speaker 2: the energy released when that snapping happens is staggering. I mean,
Speaker 2: a typical merger can release more energy in a fraction
Speaker 2: of a second than all the stars in the observable
Speaker 2: universe combined.
Speaker 3: It's an output of power that literally outshines everything else
Speaker 3: in the universe put together.
Speaker 2: But here's the mechanism I really want to understand. If
Speaker 2: there's no actual physical matter collidinge Like, there's no rock,
Speaker 2: no gas, just event horizons, what exactly is carrying that
Speaker 2: energy away.
Speaker 3: That's the wild part. The energy is carried away by
Speaker 3: the very fabric of reality itself. When those horizons merge,
Speaker 3: the surrounding space time is subjected to catastrophic stress.
Speaker 2: It's again stretched and pulled.
Speaker 3: Right. In general, relativity dictates that accelerating masses produce gravitational waves.
Speaker 3: So just as an accelerat and electrical charge produces electromagnetic waves,
Speaker 3: accelerating masses produce ripples and gravity.
Speaker 2: So in the final moments of that spiral, and especially
Speaker 2: during the actual merger, the black holes are just churning
Speaker 2: space time into waves.
Speaker 3: Yes, they are converting massive portion of their combined mass
Speaker 3: directly into the energy of these gravitational waves. Space time
Speaker 3: itself is stretching and squeezing, undulating outward at the speed
Speaker 3: of light.
Speaker 2: Wow. Okay, I want to use an analogy here to
Speaker 2: help visualize this. If space time is a trampoline, this
Speaker 2: collision isn't just dropping a bowling ball on it. It's like
Speaker 2: two bowling balls smashing into dust, sending these massive ripples
Speaker 2: across the entire surface of the trampoline.
Speaker 3: That's a great way to put it. The trampoline mat
Speaker 3: itself is what's carrying the energy away.
Speaker 2: Okay, so we have this wildly asymmetric, wobbling freshly merged
Speaker 2: black hole. It's highly unstable, and physicist Monica ring Con
Speaker 2: Ramirez describes this exact phase with some really striking imagery.
Speaker 2: She points out that immediately post merger, the remnant black
Speaker 2: hole is ringing like a struck bell.
Speaker 3: Yes, the ring down phase, right.
Speaker 2: It vibrates and it radiates away excess energy through those
Speaker 2: gravitational waves until it finally settles into a calm, stable state.
Speaker 2: But way a bell rings because the metal physically vibrates
Speaker 2: and displaces air molecules. A black hole is, as we said,
Speaker 2: empty space banded by a horizon. What is physically quivering
Speaker 2: if there is no matter there?
Speaker 3: That is the perfect question to exposse just how weird
Speaker 3: general relativity is. When we say it rings, we're talking
Speaker 3: about a phenomenon called quasinormal.
Speaker 2: Modes wisnero modes.
Speaker 3: Okay, yeah, think of space time as a highly taught
Speaker 3: elastic medium like your trampoline met the event horizon is perturbed,
Speaker 3: meaning its geometry is highly irregular, like that peanut ship
Speaker 3: we mentioned.
Speaker 2: Right, it's all lopsided.
Speaker 3: Exactly, and because a black hole naturally wants to be
Speaker 3: perfectly smooth and spherical, or at least a blate if
Speaker 3: it's spinning, the natural laws of gravity forced that irregularity
Speaker 3: to smooth out. The ringing is the actual metric of
Speaker 3: space time oscillating.
Speaker 2: So the horizon is violently shifting from elongated to compressed
Speaker 2: over and.
Speaker 3: Over, yes, shedding the energy of those deformations as gravitational waves.
Speaker 3: It's shedding its asymmetries, and as it sheds them, the
Speaker 3: amplitude of those oscillations decays exponentially. That decay, that fading out,
Speaker 3: is the ringing stopping.
Speaker 2: Okay, so the ringing is literally the new black hole
Speaker 2: ironing out its own wrinkles by throwing gravitational energy out
Speaker 2: into the universe.
Speaker 3: Ironing out its wrinkles is a brilliant way to describe it.
Speaker 2: And when that ringing stops, when the wrinkles are all
Speaker 2: ironed out, we are left with the final remnant. But
Speaker 2: what fascinates me here is the sheer simplicity of that
Speaker 2: final state. Based on the no hair theorem in astrophysics,
Speaker 2: Once a black hole settles down, all of the chaotic
Speaker 2: history of the collision.
Speaker 3: Is just wiped out, completely erased.
Speaker 2: The final object is defined by only two properties, mass
Speaker 2: and spin.
Speaker 3: Well, technically, the no hair theorem allows for three properties.
Speaker 3: It's mass, spin, and electric charge.
Speaker 2: Oh right, charge.
Speaker 3: But know, in a realistic astrophysical setting, black holes have
Speaker 3: negligible charge because they would just quickly attract opposite charges
Speaker 3: from the surrounding plasma and neutralize themselves anyway. So practically speaking,
Speaker 3: it's just two for all practical purposes. Yes, you are
Speaker 3: entirely correct. We only care about two parameters, mass which
Speaker 3: tells us the size of the event horizon, and spin
Speaker 3: or angular momentum, which tells us how fast the black
Speaker 3: hole is rotating.
Speaker 2: So all the intricate details, the varying masses of the
Speaker 2: original black holes, the specific angles they collided at, the
Speaker 2: complex geometry, or the merger, all of that is just gone.
Speaker 3: All that information is swallowed by the horizon or radiated
Speaker 3: away into the universe.
Speaker 2: Mass and spin. That is it. But if the final
Speaker 2: state is just two simple numbers, why on earth do
Speaker 2: we need supercomputers running for weeks to find them? I mean,
Speaker 2: if I smash a two kilogram ball of clay into
Speaker 2: a three kilogram ball of clay. I don't need a
Speaker 2: supercomputer to tell me I have a five kilogram ball.
Speaker 3: Of clay, because black holes do not obey simple Newtonian arithmetic.
Speaker 3: When you smash those two balls of clay together, they
Speaker 3: aren't radiating ten percent of their mass away into the
Speaker 3: geometry of empty space.
Speaker 2: Fair point. The energy loss is massive, right.
Speaker 3: The problem lies in the equations we have to use
Speaker 3: to calculate that loss. Einstein's field equations of general relativity
Speaker 3: are a set of ten highly complex coupled nonlinear partial
Speaker 3: differential equations, the keyword there being nonlinear.
Speaker 2: Let's drill into that nonlinearity because that seems to be
Speaker 2: the fundamental bottleneck here for the computers. Yeah, when we
Speaker 2: say an equation is nonlinear in physics, we usually mean
Speaker 2: the variables feedback into themselves.
Speaker 3: Right, Precisely, in general relativity, mass and energy tell space
Speaker 3: time how to curve, but that curvature dictates how mass
Speaker 3: and energy.
Speaker 2: Moves a chicken and egg situation exactly.
Speaker 3: And because gravitational waves carry energy, the waves themselves exert gravity.
Speaker 3: So you have a situation where the changing shape of
Speaker 3: space generates energy, which changes the shape of space, which
Speaker 3: generates more energy. It is just a catastrophic feedback loop.
Speaker 2: Wow, So how do you even calculate that?
Speaker 3: To solve this mathematically, physicists use something called numerical relativity.
Speaker 3: They break spacetime down into a massive three dimensional grid,
Speaker 3: stepping forward in time in tiny, tiny increments at every
Speaker 3: single intersection on that grid. For every fraction of a microsecond,
Speaker 3: the supercomputer has to recalculate the entire ten component metric tensor.
Speaker 2: That sounds incredibly taxing, and if the grid isn't precise enough,
Speaker 2: the math literally blows up, doesn't it. I know that
Speaker 2: for decades, physicists couldn't even get the simulations to run
Speaker 2: past the first few milliseconds of a merger.
Speaker 3: Oh, it was a nightmare for theoretical physicists. The coordinate
Speaker 3: systems would just fail, The values would shoot up to infinity,
Speaker 3: and the computer.
Speaker 2: Would crash right because it just couldn't handle the infinite
Speaker 2: feedback loop. It wasn't until two thousand and five I
Speaker 2: think that Transpiratory has finally figured out a mathematical trick
Speaker 2: to keep the simulation stable through the actual merger. So
Speaker 2: we're talking about an incredibly brutal, computationally exhausting method.
Speaker 3: It is a tour de force of human computation. You
Speaker 3: are tracking the microscopic evolution of spacetime geometry through sheer
Speaker 3: brute force determinism. You're mapping every single ripple, every distortion
Speaker 3: to see exactly how much mass and spin is radiated away,
Speaker 3: just so you can subtract that from the initial total
Speaker 3: to find out what.
Speaker 2: Is left over, which brings us to the alternate route,
Speaker 2: the shortcut that honestly feels like a cheat code.
Speaker 3: It really does.
Speaker 2: The researchers at Penn State, including bs Sethi, Podcash, Nathan K.
Speaker 2: John To McDaniel, and their colleagues, are proposing that we
Speaker 2: don't need to track the deterministic geometry of space time
Speaker 2: step by step. They argue we can bypass numerical relativity
Speaker 2: entirely by using thermodynamics.
Speaker 3: Which is a huge lead, right.
Speaker 2: But to make that lead, we have to look at
Speaker 2: why black holes and thermodynamics are even allowed in the
Speaker 2: same room together in the first place, because for a
Speaker 2: really long time they absolutely were not.
Speaker 3: Historically, black holes were considered thermodynamic dead ends. I mean
Speaker 3: that classical laws of general relativity state that nothing can
Speaker 3: escape an event horizon, not even light right, And if
Speaker 3: nothing can escape, a black hole cannot emit heat. If
Speaker 3: an object cannot emit heat, its temperature must be absolute zero.
Speaker 2: Okay, that makes sense under classical rule.
Speaker 3: But here's the catch. In classical thermodynamics. If you drop
Speaker 3: a hot cup of coffee, which has a lot of entropy,
Speaker 3: a lot of disordered microscopic states, into a black hole,
Speaker 3: that entropy vanishes from the observable universe.
Speaker 2: Oh I see, and that violates the second law of
Speaker 2: thermodynamics exactly.
Speaker 3: The second law states that the total entropy of the
Speaker 3: universe must always increase.
Speaker 2: Right, Because if you could just throw your entropy into
Speaker 2: a black hole and completely erase it, you're decreasing the
Speaker 2: entropy of the universe. You are cheating the most fundamental
Speaker 2: law of nature. And that paradox that's what led Jacob
Speaker 2: Bekenstein and Stephen Hawking to completely rewrite astrophysics in the
Speaker 2: nineteen seventies, isn't it it is?
Speaker 3: Bekenstein was the first to propose the heresy. Really, he
Speaker 3: suggested that black holes must have entropy, and that the
Speaker 3: entropy must be proportional to the surface area of the
Speaker 3: event horizon, not its volume.
Speaker 2: Not the volume, but the surface area yes.
Speaker 3: So when you throw the coffee cup in, the black
Speaker 3: hole gains mass, its event horizon physically grows, its area increases,
Speaker 3: and therefore its entropy increases, satisfying the second law.
Speaker 2: Boom paradox solved. But Hawking initially hated that idea, didn't
Speaker 2: he because if a black hole has entropy, it must
Speaker 2: have a temperature, and if it has a temperature, it
Speaker 2: must radiate heat. But we just establish nothing can escape
Speaker 2: a black hole. So Hawking actually set out to mathematically
Speaker 2: prove Beckenstein wrong.
Speaker 1: He did.
Speaker 3: Hawking applied quantum field theory to the curved space time
Speaker 3: near the event horizon, fully intending to disprove Beckenstein's theory,
Speaker 3: but instead he.
Speaker 2: Proved him right, which is hilarious and brilliant.
Speaker 3: It's now considered one of the greatest theoretical discoveries of
Speaker 3: the twentieth century. Hawking discovered that black holes are not
Speaker 3: completely black. They glow.
Speaker 2: Let's break down the mechanics of that glow because it
Speaker 2: is crucial for understanding how the Penn State team applies
Speaker 2: thermodynamics to a merger. The glow is Hawking radiation, But
Speaker 2: how does empty space near horizon suddenly radiate particles.
Speaker 3: We have to look at the vacuum of space through
Speaker 3: the lens of quantum mechanics. In quantum field theory, a
Speaker 3: vacuum is not truly empty. It is this boiling sea
Speaker 3: of quantum fluctuation.
Speaker 2: Just psi chaotic massive energy.
Speaker 3: Exactly pairs of virtual particles. A particle and its anti
Speaker 3: particle are constantly popping into existence, borrowing energy from the universe,
Speaker 3: and then instantly annihilating each other to pay the energy back.
Speaker 3: This happens everywhere, all the time, in your living room,
Speaker 3: in deep space, everywhere.
Speaker 2: But when this happens exactly on the razor's edge of
Speaker 2: an event horizon, the script changes dramatically.
Speaker 3: If a pair of virtual particles pops into existence right
Speaker 3: on that boundary, the intense gravitational gradient can pull them
Speaker 3: apart before they even have a chance to annihilate.
Speaker 2: Wow, so the gravity is stronger than their attraction to
Speaker 2: each other.
Speaker 3: Yes, one particle falls past the horizon into the black hole.
Speaker 3: The other particle, just outside the horizon, is violently propelled
Speaker 3: out into the universe. So to an outside observer it
Speaker 3: looks exactly as if the black hole just emitted a particle.
Speaker 3: It radiated heat I've.
Speaker 2: Always struggled with the mass accounting here, though. If the
Speaker 2: black hole absorbs one particle and shoots out the other,
Speaker 2: shouldn't its mass increase or at least just stay the same.
Speaker 2: Why does Hawking radiation cause the black hole to slowly
Speaker 2: evaporate over time?
Speaker 3: It comes down to energy conservation. The virtual particle pair
Speaker 3: was created by borrowing energy from the vacuum. When they
Speaker 3: are separated, the particle that escapes becomes a real particle
Speaker 3: with positive energy.
Speaker 2: Okay, so the universe gains a positive particle.
Speaker 3: Right, So for the Universe's energy ledger to balance, the
Speaker 3: particle that fell into the black hole must have negative
Speaker 3: energy relative to the outside universe. When the black hole
Speaker 3: absorbs that negative energy, its total mass decreases.
Speaker 2: That is such a brilliant mechanism. The universe balances as
Speaker 2: checkbook and the black hole shrinks. And by proving that
Speaker 2: black holes have a temperature and slowly evaporate, Hawking fundamentally
Speaker 2: linked gravity and thermodynamics. He finalized the Beekenstein Hawking formula,
Speaker 2: which mathematically defines the entropy of a black hole.
Speaker 3: And that formula is breathtaking. It incorporates the fundamental consts
Speaker 3: from almost every major branch of physics.
Speaker 2: It's like the ultimate crossover event.
Speaker 3: It really is. It includes Newton's constant for gravity, the
Speaker 3: speed of light for relativity, Plank's constant for quantum mechanics,
Speaker 3: and Boltzmann's constant for thermodynamics. It perfectly weaves them all
Speaker 3: together to state that the entropy of a black hole
Speaker 3: is exactly a quarter of the area of its event horizon.
Speaker 2: But here is the massive problem that the Penn State
Speaker 2: researchers had to confront. Hawking's math, as beautiful as it is,
Speaker 2: was formulated for static, stationary black holes, a black hole
Speaker 2: just sitting out there in the void, slowly glowing. It
Speaker 2: was not designed for the apocalyptic chaos of two black
Speaker 2: holes colliding at half the speed of light. Not at all.
Speaker 2: Taking the thermodynamics of a quiet black hole and trying
Speaker 2: to apply to a violent merger, it seems like trying
Speaker 2: to use a thermometer to measure a bomb going off.
Speaker 3: That's a very accurate comparison. It is a massive leap.
Speaker 3: The Penn State team, led by researchers like Safi Prickash
Speaker 3: and by Shock Prosad, they had to prove that thermodynamic
Speaker 3: rules don't just apply it to quiet black holes, but
Speaker 3: to dynamic, rapidly evolving space times.
Speaker 2: Space times that are literally ripping themselves apart exactly.
Speaker 3: They hypothesize that even in the midst of a violent merger,
Speaker 3: the underlying principles of thermodynamics are still driving the bus. Specifically,
Speaker 3: they proposed the maximum entropy conjecture for black hole mergers.
Speaker 2: Okay, we need to completely define what entropy means in
Speaker 2: the context of a black hole here, because the standard
Speaker 2: analogy everyone learns in high school physics is the messy room. Right. Ye,
Speaker 2: A tidy room has low entropy. A messy room has
Speaker 2: high entropy, just because there are more ways for things
Speaker 2: to be messy than.
Speaker 3: Tidy, the classic example.
Speaker 2: But a black hole isn't a room full of socks
Speaker 2: and books, it's empty space.
Speaker 3: How do you measure the messiness of a completely featureless void.
Speaker 2: Well, the messy room analogy is helpful for basic intuition,
Speaker 2: but to really understand this research, we have to look
Speaker 2: at entropy in terms of statistical mechanics. Entropy is not
Speaker 2: just messiness decisse measure of microstates mapping to a macrostate.
Speaker 3: Microstates and macrostates break that down for me, think of
Speaker 3: a digital photograph on your computer screen. The image you see,
Speaker 3: let's say it's a picture of an apple, that is
Speaker 3: the macrostate, the specific arrangement of millions of individual red, green,
Speaker 3: and blue pixels that make up that image. Those are
Speaker 3: the microstates.
Speaker 2: Okay, so if I change the color of one single
Speaker 2: pixel hidden in the shadow of the apple, the image
Speaker 2: still looks exactly like an apple. To make it's a
Speaker 2: different microstate, but the exact same macrostate exactly.
Speaker 3: Now apply that to a gas in a balloon. The
Speaker 3: overall temperature, pressure, and volume of the gas those make
Speaker 3: up the macrostate. The precise position and velocity of every
Speaker 3: single microscopic gas molecule bouncing around inside the balloon are
Speaker 3: the microstates.
Speaker 2: There's a near infinite number of this, right.
Speaker 3: There are billions of different ways those molecules could be
Speaker 3: bouncing around that would all result in the exact same
Speaker 3: temperature and pressure. Therefore, the gas has high entropy many
Speaker 3: micro states correspond to its single macro state.
Speaker 2: So how does this map onto a black hole? Because
Speaker 2: the no hair theorem says the macrostate of a black
Speaker 2: hole is completely defined by just mass and spin. But
Speaker 2: what are the hidden pixels? What are the micro states
Speaker 2: of a black hole?
Speaker 3: That is one of the deepest mysteries in theoretical physics
Speaker 3: right now. It's heavily researched in string theory and loop
Speaker 3: quantum gravity. We don't have a fully verified quantum theory
Speaker 3: of gravity yet, so we don't know exactly what the
Speaker 3: microscopic building blocks of a black hole actually are.
Speaker 2: So we're flying blind on the micro.
Speaker 3: Level we are, but the Beckenstein Hawking entropy formula guarantees
Speaker 3: that they exist. Even if we can't see the individual
Speaker 3: pixels of the black hole, we know they are there,
Speaker 3: and we know exactly how many there are based purely
Speaker 3: on the surface area of the event horizon.
Speaker 2: Wow. And this allows the Penn state researchers to treat
Speaker 2: the black holes exactly like interacting gases. Physicist Eugenio Bianki
Speaker 2: brought up this specific gas analogy. He said, if you
Speaker 2: take a box of hot oxygen and a box of
Speaker 2: cold nitrogen and you open a valve between them, the
Speaker 2: gases mix. To figure out the final temperature and pressure
Speaker 2: of the mixed gas, you don't need a supercomputer tracking
Speaker 2: the deterministic collision path of every single oxygen and nitrogen molecule.
Speaker 2: That would be impossible. You would just use the laws
Speaker 2: of thermodynamics. Nature will automatically drive the system toward the
Speaker 2: state that has the highest possible number of microstates. Nature
Speaker 2: maximizes the entropy.
Speaker 3: Yes, and nature doesn't maximize entropy out of some cosmic
Speaker 3: desire for chaos. It happens purely through probability. If a
Speaker 3: mixed gas has a trillion times more microstates than a
Speaker 3: separated gas, the system is going to statistically settle into
Speaker 3: the mixed.
Speaker 2: State because it's just overwhelmingly more likely. Right.
Speaker 3: So, the researchers asked if nature always drifts toward the
Speaker 3: highest entropy state simply because it is the most statistically probable.
Speaker 3: Do black hole mergers do the exact same thing.
Speaker 2: And their conjecture says yes. They propose that when these
Speaker 2: two gravitational titans call the final remnant black hole isn't
Speaker 2: determined by the microscopic step by step unspooling of space
Speaker 2: time geometry like the supercomputers calculate, the final mass and
Speaker 2: spin of the remnant is simply whatever mass and spin
Speaker 2: yields the absolute highest possible entropy, taking into account the
Speaker 2: energy that was lost.
Speaker 3: The energy loss is the critical variable here. When the
Speaker 3: gas is mixed in a closed box, energy is perfectly
Speaker 3: conserved within the box. But a black hole merger is
Speaker 3: not a closed box. As we discussed earlier, a massive
Speaker 3: amount of energy and angular momentum is blasted out into
Speaker 3: the universe as gravitational waves during the inspiral and the
Speaker 3: Quasini mo ringing.
Speaker 2: Let's talk about the angular momentum loss because it is
Speaker 2: fascinating how a gravitational wave can carry away spin like
Speaker 2: I can visualize a wave carrying away raw energy, like
Speaker 2: a ripple carrying away the impact energy of a stone
Speaker 2: dropped in a pond. But how does a ripple in
Speaker 2: space time carry away the rotational momentum of the black holes.
Speaker 3: It takes a little visualization. Think about the geometry of
Speaker 3: the waves themselves. Because the black holes are orbiting each other.
Speaker 3: The gravitational waves they emit are not perfectly symmetrical expanding spheres.
Speaker 2: They're not just expanding out like a balloon.
Speaker 3: No, they are emitted in a spiral pattern heavily influenced
Speaker 3: by the orbital mechanics of the binary system. As these
Speaker 3: ripples propagate outward, they physically twist the space time they
Speaker 3: pass through.
Speaker 2: Oh wow, they twist space itself.
Speaker 3: Yes, that twisting motion requires angular momentum. By twisting the
Speaker 3: surrounding universe, the waves are literally sapping rotational energy from
Speaker 3: the merging black holes and carrying it away into the void.
Speaker 2: So the Penza team has to account for all of this.
Speaker 2: They know the starting mass and spin of the two
Speaker 2: original black holes. They know they have to subtract the
Speaker 2: mass and spin that is carried away by the gravitational waves.
Speaker 2: And to find the final state, they need to find
Speaker 2: the configuration that maximizes entropy under those specific conditions. How
Speaker 2: did they actually execute this test? How do you map
Speaker 2: this mathematically?
Speaker 3: They constructed a methodology based on hypothetical states, because you know,
Speaker 3: they couldn't just assume their thermodynamic theory was correct from
Speaker 3: the jump. They needed to compare it against the deterministic
Speaker 3: results generated by those massive numerical relativity.
Speaker 2: Supercomputers gold standard, right, So.
Speaker 3: They took the initial parameters of a known simulated merger.
Speaker 3: Then they mathematically generated a sequence of hypothetical remnant black holes.
Speaker 2: What do you mean by a sequence of hypothetical remnants?
Speaker 3: Imagine a graph the researchers know a certain amount of
Speaker 3: energy and angular momentum is going to be radiated away,
Speaker 3: so they created a mathematical spectrum of possible final black holes,
Speaker 3: each with slightly different combinations of final mass and final
Speaker 3: skin that still obey the basic laws of conservation.
Speaker 2: Like a lineup of possible suspects.
Speaker 3: Exactly, and for every single one of those hypothetical black
Speaker 3: holes on the spectrum, they calculated its thermodynamic entropy using
Speaker 3: the Bickenstein Hawking formula.
Speaker 2: So they're essentially looking for the peak of a curve.
Speaker 2: They map out the entropy for all the possible final states,
Speaker 2: looking for the specific mass and spin combination that represents
Speaker 2: the absolute highest entropy, the ultimate thermodynamic sweet spot for
Speaker 2: that specific collision.
Speaker 3: Precisely, they charted the entropy evolution, accounting for the fluxes
Speaker 3: of energy and angular momentum being radiated to infinity by
Speaker 3: the gravitational waves. They watched the curve rise as the
Speaker 3: system evolved, looking for the apex the maximum entropy state, and.
Speaker 2: The results they found are the core of this entire revelation.
Speaker 2: When they found that peak, the hypothetical black hole with
Speaker 2: the highest possible entropy, they compared its mass and spin
Speaker 2: to the mass and spin calculated by the grueling, weeks
Speaker 2: long supercomputer simulation, and the values matched. The entropy curve
Speaker 2: peaked at virtually the exact same mass and angular momentum
Speaker 2: predicted by numerical relativity.
Speaker 3: The agreement was absolutely staggering. To bypass the microscopic geometric
Speaker 3: tracking entirely, to rely purely on the statistical laws of thermodynamics,
Speaker 3: and to land on the same target. It is a
Speaker 3: profoundalidation of the conjecture.
Speaker 2: Now I have to challenge this here because the literature
Speaker 2: notes that the values matched, but they matched within a
Speaker 2: margin of air of a few percent. You're saying they
Speaker 2: got within a few percent. But in astrophysics, a few
Speaker 2: percent can be a massive discrepancy. I mean, a few
Speaker 2: percent error in an orbital calculation can mean a satellite
Speaker 2: misses Mars entirely and shoots off into deep space.
Speaker 3: That's very true.
Speaker 2: So why should we accept a few percent margin of
Speaker 2: error as a stunning victory here when numerical relativity gives
Speaker 2: us a much more precise number.
Speaker 3: That is a highly valid critique, and it is one
Speaker 3: the physics community wrestles with the thermodynamic calculation is not
Speaker 3: currently a replacement for numerical relativity when we need absolute
Speaker 3: pinpoint precision for observational templates, like for Lego, right like
Speaker 3: when the Lego observatories are trying to match a specific
Speaker 3: gravitational wave signal to a real world source. But you
Speaker 3: have to separate the practical utility from the theoretical revelation. The
Speaker 3: few percent discrepancy likely arises from the approx animations required
Speaker 3: to model the radiation.
Speaker 2: Flexes the exhaust.
Speaker 3: Basically, yes, the exact amount of energy and spin carried
Speaker 3: away by the waves during the most chaotic fractions of
Speaker 3: a millisecond. We don't have perfect analytical models for that
Speaker 3: split second of peak chaos.
Speaker 2: So the error isn't in the thermodynamic principle itself. The
Speaker 2: error is in how accurately we are measuring the exhaust
Speaker 2: of the collision exactly.
Speaker 3: The fact that the maximum entropy principle gets us within
Speaker 3: a few percent of the deterministic calculation is not a
Speaker 3: failure of precision. It is proof of a fundamental underlying mechanism.
Speaker 3: It proves that the universe is actually obeying these statistical laws,
Speaker 3: even in the most extreme gravitational environments.
Speaker 2: I want to try an analogy here to see if
Speaker 2: I'm fully grasping the magnitude of this. Let's say I
Speaker 2: want to figure out the exact shape and layout of
Speaker 2: a shattered glass vase after dropping it off of building.
Speaker 2: The numerical relativity approach is like tracking the exact aerodynamic trajectory, mass,
Speaker 2: and velocity of every single shard of glass as it falls,
Speaker 2: uding how they deflect off each other in mid air,
Speaker 2: and plotting exactly where they land on the pavement.
Speaker 3: Which is impossibly complex, a perfect description of the deterministic approach, right.
Speaker 2: But the thermodynamic approach they just tested is like ignoring
Speaker 2: the shards completely. Instead, you just measure the total kinetic
Speaker 2: energy of the vase before it dropped, measure the total
Speaker 2: heat generated when it hit the ground, and use statistical
Speaker 2: probability to deduce that the shards must have arranged themselves
Speaker 2: in the specific pattern that maximizes the entropy of the impact,
Speaker 2: and you get almost the exact same layout.
Speaker 3: That analogy captures the essence of the breakthrough beautifully. You
Speaker 3: are swapping a microscopic geometric tracking problem for a macroscopic
Speaker 3: thermodynamic state problem by verifying that the final black hole
Speaker 3: remnant corresponds to the state of maximum entropy. The researchers
Speaker 3: have essentially proven that the violent dynamics of space time
Speaker 3: geometry are fundamentally constrained by the same statistical laws that
Speaker 3: govern heat and gases.
Speaker 2: This circles back to the concept of cosmic amnesia, or
Speaker 2: what the void remembers. When those two black holes merge,
Speaker 2: the resulting remnant forgets the intricate geometry of the collision entirely.
Speaker 2: It doesn't retain any memory of the specific pads the
Speaker 2: event horizons took as they twisted together.
Speaker 3: It just lets it all go.
Speaker 2: The universe essentially says, you know, that was too chaotic
Speaker 2: to keep track of. Let's just default to the most
Speaker 2: statistically probable state. The black hole sheds all that complex
Speaker 2: geometric information through the ringing of gravitational waves, driving itself
Speaker 2: toward maximum entropy until only mass and spin remain.
Speaker 3: Which forces physicists to grapple with a monumental question. Bssatya Prakash,
Speaker 3: one of the leading researchers on this project, highlighted that
Speaker 3: this intersection goes far beyond our established models. We have
Speaker 3: always treated thermodynamics as a consequence of particles moving around
Speaker 3: in space time. But if spacetime itself in the form
Speaker 3: of a purely geometric black hole based thermodynamics, it suggests
Speaker 3: something deeper.
Speaker 2: It suggests that the fabric of reality isn't just the
Speaker 2: stage where physics happens. The fabric itself is governed by
Speaker 2: statistical mechanics.
Speaker 3: Could entropy maximization be the fundamental organizing principle of the universe.
Speaker 3: It is a question that flips our understanding of gravity
Speaker 3: on its head. There is a growing movement in theoretical
Speaker 3: physics right now, pioneered by people like Eric Verlynn, suggesting
Speaker 3: that gravity might not be a fundamental force at all.
Speaker 2: Wait, not a fundamental force.
Speaker 3: No, Instead, gravity might be an emergent phenomenon, a byproduct
Speaker 3: of the universe constantly trying to maximize its entropy. This
Speaker 3: research from Penn State provides incredibly compelling mathematical evidence that
Speaker 3: such a connection exists at the most extreme scales.
Speaker 2: That is a staggering paradigm shift if you are a
Speaker 2: physicist who has spent your entire career looking at general
Speaker 2: relativity as the absolute bedrock of gravitational physics. Seeing evidence
Speaker 2: that relativity might just be a macroscopic side effect of
Speaker 2: thermodynamics that must be both terrifying and exhilarating.
Speaker 3: It's the kind of discovery that paves the way toward
Speaker 3: a unified theory of quantum gravity. By showing that the
Speaker 3: deterministic equations of Einstein and the statistical equations of Boltzmann
Speaker 3: arrive at the exact same destination, we are slowly peeling
Speaker 3: back the layers of the illusion. The universe doesn't have
Speaker 3: a separate rulebook for black holes and a separate rule
Speaker 3: book for hot gases. There is one underlying architecture.
Speaker 2: This completely reframes how we look at the cosmos. We
Speaker 2: started this discussion visualizing the most violent, unimaginable event in nature,
Speaker 2: two massive singularities ripping through the fabric of space, unleashing
Speaker 2: more energy than the rest of the visible universe combined.
Speaker 2: It is so easy to look at an event like
Speaker 2: that and think it belongs to a realm of physics
Speaker 2: completely alien to human experience, a realm of hyper complex
Speaker 2: tensor calculus and abstract geometry.
Speaker 3: But the reality uncovered by this research is far more elegant.
Speaker 2: Elegant, and almost poetic. The forces that dictate the violent
Speaker 2: birth of a new black hole. Are the exact same
Speaker 2: forces that dictate why a drop of ink disperses in
Speaker 2: a glass of water. It is all driven by nature's
Speaker 2: inescapable march toward maximum entropy. If the most extreme light
Speaker 2: crushing objects in the cosmos are ultimately bowing to the
Speaker 2: exact same statistical laws that dictate the everyday thermodynamics of
Speaker 2: our lives, the universe is far more unified and far
Speaker 2: more deeply interconnected than we ever dared to imagine. It
Speaker 2: proves that whether you are looking at a messy room,
Speaker 2: a cooling cup of coffee, or the collision of gravitational titans,
Speaker 2: you are watching the exact same invisible hand at work.
Speaker 3: It is a remarkable testament to the universality of physical laws.
Speaker 2: It truly is. It's a reminder that the deepest mysteries
Speaker 2: of the universe might not be solved by building bigger supercomputers,
Speaker 2: but by recognizing the patterns that have been sitting in
Speaker 2: front of us the entire time. Thank you for joining
Speaker 2: us on this journey today. Keep questioning the universe around you,
Speaker 2: and never stop looking for the hidden rules that bind
Speaker 2: it all together.