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: Imagine you have spent your entire life living in a
Speaker 2: house like you know every single creaky floorboard in the hallway.
Speaker 3: Right, You've memorized the whole layout exactly.
Speaker 2: You know the precise angle the sunlight hits the kitchen
Speaker 2: window in the morning, and you feel completely, perfectly secure
Speaker 2: in your understanding of this building. You have mapped its dimensions,
Speaker 2: you've calculated its structural integrity. But then you wake up
Speaker 2: one morning and realize something genuinely terrifying.
Speaker 3: Okay, what's that?
Speaker 2: You'll suddenly realize that eighty five percent of the building,
Speaker 2: like the vast majority of the load bearing walls, the
Speaker 2: steel beams, the roof, is completely invisible to you.
Speaker 3: Wow.
Speaker 2: Yeah, you can't see it, you can't touch it. And worse,
Speaker 2: you look down and realize the foundation of this house
Speaker 2: is constantly, unpredictably shifting its shape underneath your feet.
Speaker 3: I mean, that is the deeply unsettling image. It forces
Speaker 3: a complete reevaluation of literally everything you thought you understood
Speaker 3: about your environment. Right, and yet that is precisely the
Speaker 3: reality we're waking up to right now. When we look
Speaker 3: at the universe, it's.
Speaker 2: Wild, and that is exactly the crisis currently facing modern astrophysics.
Speaker 2: So today we are exploring a really groundbreaking mathematical framework
Speaker 2: from the Chinese Academy of Sciences.
Speaker 3: Yeah, specifically the work of Yunchen, Tengpengzu and Zumingzong exactly.
Speaker 2: And they're attempting to solve two of the most stubborn,
Speaker 2: entrenched mysteries in the cosmos.
Speaker 3: The true nature of dark energy and this massive discrepancy
Speaker 3: in how fast the universe is actually expanding.
Speaker 2: Right, So we are going to break down the actual
Speaker 2: mechanics of the cosmos today, looking at the very edge
Speaker 2: of human understanding, because I feel like this stuff can
Speaker 2: get so abstract, right.
Speaker 3: It absolutely can, But we will connect these incredibly complex,
Speaker 3: high level mathematical theories back to the fundamental question of
Speaker 3: how reality actually operates. Because as abstract as the math
Speaker 3: of cosmology can get It is ultimately describing the physical
Speaker 3: space you and I occupy right now.
Speaker 2: The space the listener's sitting in right.
Speaker 3: Now, exactly. We are talking about the mechanics of the universe,
Speaker 3: and while to understand how the rules of the universe
Speaker 3: might be breaking right now, we first have to understand
Speaker 3: what those rules were supposed to be.
Speaker 2: Okay, let's unpack this. Let's start with the bedrock, like
Speaker 2: the standard model of cosmology that scientists have basically relied
Speaker 2: on for decades.
Speaker 3: Right, So, the standard model is known in physics as
Speaker 3: the Lambda CDM.
Speaker 2: Framework glambda CDM. Yeah.
Speaker 3: You can think of it as a structure built on
Speaker 3: three massive pillars. So the first pillar is represented by
Speaker 3: that Greek letter Lambda. Okay, that stands for the cosmological
Speaker 3: constant constant, right, and this is the mathematical value we
Speaker 3: associate with dark energy, which we understand to be the
Speaker 3: mechanism that is actively driving the accelerating expansion of the universe.
Speaker 2: I want to pause on that word constant, because that
Speaker 2: seems to be the lynchpin of this entire discussion. The
Speaker 2: assumption has always been the dark energy just does not change.
Speaker 3: Yeah, that has been the prevailing consensus for a long time.
Speaker 3: The idea is that the density of the dark energy
Speaker 3: remains perfectly fixed, so as the universe expands and creates
Speaker 3: more empty space, more dark energy simply exists to fill
Speaker 3: that new void.
Speaker 2: Keeping the overall density identical to what it was, say,
Speaker 2: a billion years ago exactly.
Speaker 3: And the history of this idea actually goes all the
Speaker 3: way back to Albert Einstein.
Speaker 2: Oh really, yeah.
Speaker 3: When Einstein formulated his theory of general relativity, the equations
Speaker 3: actually suggested the universe should be collapsing.
Speaker 2: In on itself because of gravity, right, yes.
Speaker 3: Due to the gravitational pull of all the matter inside it.
Speaker 3: But to fix this and to keep the universe static,
Speaker 3: which was the philosophical preference of the time, he introduced
Speaker 3: a quote unquote cosmological constant into his equations just.
Speaker 2: To push back against gravity. Basically, yeah, so he essentially
Speaker 2: invented a repulsive force just to balance his mathematical ledger.
Speaker 3: He did. He literally just put it in there to
Speaker 3: make the math work. And when Edwin Hubble later proved
Speaker 3: the universe was actually expanding, it wasn't static at all.
Speaker 3: Einstein famously called the cosmological constant his biggest blunder. Yeah,
Speaker 3: he completely threw it out. But then in the late
Speaker 3: nineteen nineties, a stromer studying distant supernovae discovered that the
Speaker 3: universe wasn't just expanding, it was accelerating exactly. The expansion
Speaker 3: was accelerating. Something was pushing it apart faster and faster.
Speaker 3: So theoretical physicists actually dusted off Einstein's blunder.
Speaker 2: They brought the constant back.
Speaker 3: They reintroduced lambda to the equations, and they called it
Speaker 3: dark energy. And honestly, it worked perfectly to explain the acceleration.
Speaker 2: Okay, so that is pillar one and unchanging constant energy
Speaker 2: pushing everything apart. Yeah, so what is the second pillar
Speaker 2: of this model.
Speaker 3: The second pillar is the CDM, part of the acronym cold.
Speaker 2: Dark matter, Cold dark matter, right.
Speaker 3: And this is the invisible bulk of the cosmos. It
Speaker 3: makes up roughly eighty five percent of all the matter
Speaker 3: in the universe.
Speaker 2: Eighty five percent. That's the invisible house.
Speaker 3: That's the invisible house exactly. And we call it cold
Speaker 3: because it moves slowly compared to the speed of light.
Speaker 2: Why does the speed matter?
Speaker 3: That slow movement is crucial because it allows the dark
Speaker 3: matter to actually clump together under its own gravity. It
Speaker 3: forms this invisible scaffolding, these massive halos that our visible
Speaker 3: galaxies are actually built within.
Speaker 2: But the catch here, and I mean the thing that
Speaker 2: always invites skepticism when you bring this up, is that
Speaker 2: despite making up the vast majority of the matter out there,
Speaker 2: it has never been directly observed.
Speaker 3: We have never caught a particle of dark matter in a.
Speaker 2: Detective which is crazy to think about it.
Speaker 3: It is does an interact with light at all. It
Speaker 3: doesn't absorb it, reflect it, or emit it.
Speaker 2: Which brings up a very natural question, Like, if you're
Speaker 2: listening to this, you might be thinking, if we have
Speaker 2: never directly observed eighty five percent of the matter in
Speaker 2: the universe, how can we be so confident it actually exists?
Speaker 1: Right?
Speaker 2: Like? Are astrophysicists just making up invisible stuff to make
Speaker 2: their broken math work? Again? Isn't just a mathematical house
Speaker 2: of cards?
Speaker 3: I completely understand that skepticism. It's a totally necessary part
Speaker 3: of the scientific process to ask those exact questions. But
Speaker 3: in astrophysics we often have to measure the invisible by
Speaker 3: the shadows it casts. We may not be able to
Speaker 3: put dark matter in a jar in a laboratory desk,
Speaker 3: but we can measure its gravitational pull with extreme precision.
Speaker 2: Okay, so how do we do that?
Speaker 3: Well? The history of this goes back to the astronomer VERA.
Speaker 3: Rubin in the nineteen seventies. She was studying the rotation
Speaker 3: curves of galaxies, specifically the Andromeda galaxy.
Speaker 2: Right, So she was looking at how fast the stars
Speaker 2: were spinning around the galactic center.
Speaker 3: Yes, and based on standard Newtonian physics and the visible
Speaker 3: mass of the galaxy, the stuff we can actually see,
Speaker 3: the stars on the outer edges should have been moving
Speaker 3: much slower than the stars near the dense heavy.
Speaker 2: Core, like how our solar system works exactly.
Speaker 3: Think of our solar system. Mercury zips around the Sun
Speaker 3: very quickly while Neptune plods along very very slowly on
Speaker 3: the outer edge. Makes sense, But Reuben found that the
Speaker 3: stars on the outer edges of Andromeda were moving incredibly fast,
Speaker 3: so fast in fact, that the visible mass of the
Speaker 3: galaxy didn't have anywhere near enough gravitational pull to hold
Speaker 3: them in.
Speaker 2: They should have just flown off.
Speaker 3: They should have been flung out into deep space entirely.
Speaker 3: The only way to explain the physics of what we
Speaker 3: were seeing was the presence of a massive, invisible halo of.
Speaker 2: Matter providing the necessary gravitational glue.
Speaker 3: Exactly, providing the glue. We know the dark matter is
Speaker 3: there because of what it does to the things we
Speaker 3: can see.
Speaker 2: Okay, so it's the mathematical necessity of dark matter to
Speaker 2: exp plain gravity's behavior on a galactic scale.
Speaker 3: That and how light bends around massive objects, a phenomenon
Speaker 3: known as gravitational lensing. The framework is held together by
Speaker 3: the very real, observable effects of gravity.
Speaker 2: Got it. So that leaves the third pillar of the
Speaker 2: LAMB to CDM model. We have dark energy, dark.
Speaker 3: Matter, and the third pillar is ordinary matter. This is
Speaker 3: the baryonic matter, the stuff we know, the stars, the planets,
Speaker 3: the dust, the microphone you are speaking into right now,
Speaker 3: everything we can actually see, touch, and detect through the electromagnetic.
Speaker 2: Spectrum, which is how much of the universe.
Speaker 3: It accounts for a tiny, almost negligible fraction of the
Speaker 3: universe's total composition, roughly five percent five percent.
Speaker 2: So those three pillars a constant dark energy pushing outward,
Speaker 2: invisible dark matter pulling inward, and a tiny sprinkle of
Speaker 2: ordinary matter make up the standard model. Yes, and this
Speaker 2: has been the gold standard because mathematically it predicts the
Speaker 2: observable universe with astonishing accuracy.
Speaker 3: It is incredibly robust. When we look at the distribution
Speaker 3: of galaxies across billions of late years, the model predicts
Speaker 3: that clustering perfectly. It is withstood intense scientific scrutiny for decades.
Speaker 3: It's elegant, it is relatively simple, and it has successfully
Speaker 3: explained almost every major astronomical observation we have thrown at.
Speaker 2: It until right now. Until right now, because we are
Speaker 2: looking at this new analysis of observations from the Dark
Speaker 2: Energy Spectroscopic Instrument or DAAI, and this data is fundamentally
Speaker 2: undermining that first pillar, the cosmological constant. Yes, it is.
Speaker 2: It's suggesting that dark energy might not be a fixed,
Speaker 2: unchanging value at all.
Speaker 3: Right. So DSi is this incredibly powerful instrument mounted on
Speaker 3: a telescope in Arizona. It is designed to map millions
Speaker 3: of galaxies and quasars to trace the expansion history of
Speaker 3: the universe with unprecedented three dimensional precision, like the highest
Speaker 3: resolution map we've got exactly, and the data coming back
Speaker 3: is whispering something revolutionary. It is hinting that the density
Speaker 3: of dark energy might be changing over time. It might
Speaker 3: be evolving.
Speaker 2: Okay, to put this in perspective, this sounds like relying
Speaker 2: on a trusted generation's old family recipe, but suddenly the
Speaker 2: cake keeps exploding in the oven.
Speaker 3: That's a great way to put it.
Speaker 2: Or to use a driving analogy, we thought we're driving
Speaker 2: a car on an endless, perfectly flat highway with the
Speaker 2: cruise control set. The cruise control represents the cosmological constant,
Speaker 2: a steady, unchanging acceleration, but the DSi data is showing
Speaker 2: us that maybe a ghost is actually in the passenger seat,
Speaker 2: pressing its foot down harder and harder on the gas pedal,
Speaker 2: and then maybe letting off slightly. The acceleration is dynamic,
Speaker 2: it is changing.
Speaker 3: That captures the mechanical implication perfectly. If dark energy is
Speaker 3: not a constant, it is a genuine structural tremor. In
Speaker 3: this foundational.
Speaker 2: Framework, the house is shaking.
Speaker 3: The house is shaking violently. It means a core assumption
Speaker 3: we've held since the late nineties and essentially since Einstein
Speaker 3: might be fundamentally flawed. I'm not just tweaking the margins
Speaker 3: of the model here.
Speaker 2: We are questioning the core engine of cosmic expansion itself exactly.
Speaker 2: But the thing is this d side data challenging dark
Speaker 2: energy isn't an isolated problem, is it. It connects directly
Speaker 2: to an even older, more deeply rooted headache in astrophysics
Speaker 2: regarding the speed limit of the universe itself.
Speaker 3: Yes, it walks us right into the Hubble tension.
Speaker 2: Hubble tension. I love talking about this because it's such
Speaker 2: a stubborn mystery. Let's set the stage with Hubble's law. Okay,
Speaker 2: back in the nineteen twenties, Edwin Hubble realizes the universe
Speaker 2: is expanding, and he establishes this beautifully simple linear relationship.
Speaker 2: The farther away a galaxy is from the Milky Way,
Speaker 2: the faster it is flying away from us. If you
Speaker 2: imagine a balloon covered in dots. As you inflate the balloon,
Speaker 2: the rubber stretches. Every dot moves away from every other dot,
Speaker 2: and the docks that are farthest apart have more stretching
Speaker 2: rubber between them, so they appear to move away from
Speaker 2: each other the fastest.
Speaker 3: That's the classic analogy, and it works perfectly. There's a
Speaker 3: rate of that expansion. The speed at which that balloon
Speaker 3: is inflating today is known as the hubble constant. Okay,
Speaker 3: But the problem the tension is that we have two
Speaker 3: completely different, highly precise ways of measuring that exact present
Speaker 3: day expansion rate.
Speaker 2: And they give us two conflicting answers may not match.
Speaker 2: So we have measurement A and measurement B. Let's break
Speaker 2: down the mechanics of measurement A first, which relies on
Speaker 2: looking at the very early universe.
Speaker 3: Right, So, measurement A utilizes the cosmic microwave background or
Speaker 3: the CMB. This is the relic radiation, basically the afterglow
Speaker 3: from just three hundred and eighty thousand years after the
Speaker 3: Big Bang.
Speaker 2: Which in cosmic terms is like right after the universe
Speaker 2: was born.
Speaker 3: Yeah, it's a baby picture. Before that moment, the universe
Speaker 3: was a hot, dense soup of plasma, just protons, electrons,
Speaker 3: and photons all smashing into each other constantly, so.
Speaker 2: Light couldn't travel freely.
Speaker 3: No, it was constantly scattering off the electrons. But as
Speaker 3: the universe expanded, it cooled and eventually cooled enough for
Speaker 3: the electrons to bind to the protons, forming the very
Speaker 3: first neutral hydrogen atoms.
Speaker 2: Okay, and this event has a name.
Speaker 3: Right, Yes, it's called recombination. And suddenly, once that happened,
Speaker 3: the photons were free to travel across the universe completely unimpeded.
Speaker 2: And we can actually still see those exact photons.
Speaker 3: Today, we can. Over billions of years, the expansion of
Speaker 3: the universe has stretched those original high energy photons down
Speaker 3: into the microwave spectrum.
Speaker 2: So when we map this radiation today.
Speaker 3: We see tiny microscopic fluctuations in temperature across the sky.
Speaker 3: These temperature differences correspond to regions of slightly higher or
Speaker 3: lower density in that original primordial plasma.
Speaker 2: Okay, so how does that give us the expansion rate today?
Speaker 3: By looking at these fluctuations and running them through the
Speaker 3: equations of our standard LAMB to CDM model, we can
Speaker 3: predict exactly what the expansion rate of the universe should
Speaker 3: be right now.
Speaker 2: So measurement A is like looking at the biological markers
Speaker 2: in a baby picture f'plying our understanding of human growth
Speaker 2: and calculating a prediction of exactly how tall that person
Speaker 2: will be when they're thirty years old.
Speaker 3: That is precisely the methodology. Now, contrast that with measurement
Speaker 3: B which we call the distance.
Speaker 2: Ladder measurements a distance ladder.
Speaker 3: Instead of looking at the beginning of time and extrapolating
Speaker 3: forward like a prediction, this method looks at the local,
Speaker 3: relatively recent universe and measures the expansion directly.
Speaker 2: But how do we actually do that. You can't just
Speaker 2: stretch a tape measure to another galaxy.
Speaker 3: No, we use what a ghenre is called standard candles.
Speaker 3: A standard candle is an astronomical object whose intrinsic brightness
Speaker 3: is a known absolute value.
Speaker 2: Okay, so we know exactly how bright it truly is. Yes.
Speaker 3: The foundational work for this was actually done by Henrietta
Speaker 3: swan Ligott in the early twentieth century. She was studying
Speaker 3: a specific type of star called a cephed variable. A
Speaker 3: cephed variable, right, These stars physically pulse. They grow brighter
Speaker 3: and dimmer over a regular period of days or weeks,
Speaker 3: and leave it to discovered this direct mathematical relationship between
Speaker 3: the length of a cephade's pulse and its true intrinsic luminosity.
Speaker 2: So if you measure the pulse, you know exactly how
Speaker 2: bright the star actually is at its source exactly. And
Speaker 2: if you know exactly how bright a star actually is,
Speaker 2: and you measure how dim it appears to be from Earth,
Speaker 2: you can calculate precisely how far away it is.
Speaker 3: Because light phage at a perfectly predictable mathematical rate over distance,
Speaker 3: the inverse square law of light.
Speaker 2: Okay, so that works for stars today.
Speaker 3: We use Sepheid variables for nearby galaxies, yes, But for
Speaker 3: much more distant galaxies we use type IA supernovae, exploding stars,
Speaker 3: exploding white dwarf stars. Specifically, they detonate with a very
Speaker 3: consistent known luminosity. They are the ultimate standard candles. So
Speaker 3: by measuring the distance to these objects and simultaneously measuring
Speaker 3: how much their light has been stretched into the red
Speaker 3: end of the spectrum by the expansion of space, which
Speaker 3: we call their red shift, we directly calculate how fast
Speaker 3: the local universe versus expanding right now.
Speaker 2: The measurement B is basically just taking out a tape
Speaker 2: measure and physically measuring the thirty year old adult.
Speaker 3: Today exactly and the tension is this the prediction from
Speaker 3: the early universe. The baby picture gives us a significantly
Speaker 3: slower expansion rate than the direct measurements of the local universe.
Speaker 3: The tape measure.
Speaker 2: How big is the difference.
Speaker 3: We are talking about roughly sixty seven kilometers per second
Speaker 3: per megaparsec from the early universe versus about seventy three
Speaker 3: from the local universe.
Speaker 2: That's a massive gap. It's like having two incredibly expensive,
Speaker 2: hyper accurate spedometers in your car.
Speaker 1: Right.
Speaker 2: One is hooked up to the engine analyzing the fuel
Speaker 2: injection at the start of your road trip to calculate
Speaker 2: your average speed. The other is hooked up to the tires,
Speaker 2: physically measuring the rotation at the end of the trip.
Speaker 2: But they are giving you entirely different average speeds for
Speaker 2: the exact same journey.
Speaker 3: This raises an important question, right yeah, I mean.
Speaker 2: Is it possible one of these spedometers is just fundamentally broken,
Speaker 2: or is the road itself stretching while we drive? Could
Speaker 2: we just be misinterpreting the data.
Speaker 3: Cosmologists have absolutely agonized over that possibility for years. The
Speaker 3: assumption was that there had to be some hidden systematic.
Speaker 2: Error, like someone carried a one in the math, or perhaps.
Speaker 3: We were miscalibrating our standard candles somehow, or our instruments
Speaker 3: reading the CMB had a flaw. But observational technology has
Speaker 3: advanced so dramatically. The instruments are incredibly precise.
Speaker 2: Now, so it's not a mistake the error.
Speaker 3: Bars on both measurements. The margins of error have shrunk
Speaker 3: so significantly that they no longer overlap at all. The
Speaker 3: numbers are too precise to be a mistake. We simply
Speaker 3: can't blame the tools anymore.
Speaker 2: The tools working perfectly they.
Speaker 3: Are, which leaves us with a much more profound alternative.
Speaker 3: The universe itself is behaving in a way our standard
Speaker 3: model simply does not account for.
Speaker 2: The road itself is stretching while we drive, and the
Speaker 2: rules of that stretching are changing exactly.
Speaker 3: The hubble tension is a screaming alarm bell that our
Speaker 3: fundamental understanding of physics, specifically regarding dark energy and cosmic expansion, is.
Speaker 2: Flawed, which brings us back to the core of this
Speaker 2: new research from Young Chen and his team. With a
Speaker 2: standard model shaking and this hubble tension refusing to budge,
Speaker 2: they realized that looking at all the data at once
Speaker 2: was actually creating a tangled mess.
Speaker 3: It was creating a mathematical traffic jam.
Speaker 2: Right. They needed a new way to untangle the history
Speaker 2: of the cosmos.
Speaker 3: So When researchers are confronted with conflicting data sets, the
Speaker 3: instinct is often to just combine everything, hoping the sheer
Speaker 3: volume of data will smooth out the anomalies and reveal
Speaker 3: some average truth.
Speaker 2: Just throw it all on a blunder.
Speaker 3: But Chen, along with Teng Peng Shoe and Swumingzeng, built
Speaker 3: a unified mathematical framework to investigate both the dark energy
Speaker 3: mystery and the Hubble tension simultaneously, and their key innovation
Speaker 3: was methodological.
Speaker 2: They didn't use the blender.
Speaker 3: They decided to stop mashing all the observational data together. Instead,
Speaker 3: they separated out different probes of the universe's expansion based
Speaker 3: entirely on the specific periods of cosmic history they are
Speaker 3: most sensitive to.
Speaker 2: Okay, let's define probes in this context. We're talking about
Speaker 2: the different astronomical phenomena we use to measure distance in time.
Speaker 3: Yes, different probes act as highly specialized windows into distinct eras.
Speaker 3: So in their framework, they strictly isolated the cosmic microwave background.
Speaker 3: They use the CMB solely to probe the high redshift
Speaker 3: early universe.
Speaker 2: They kept the baby picture strictly as a baby picture.
Speaker 3: They did not allow the early universe math to bleed
Speaker 3: into the late universe measurements.
Speaker 2: And for the late universe they use different tools.
Speaker 3: They relied on type Ia supernovae, which we discuss as
Speaker 3: our standard candles, and another incredibly fascinating phenomenon called baryon
Speaker 3: acoustic oscillations or.
Speaker 2: Bao okay, baryon acoustic oscillations. That sounds a concept pulled
Speaker 2: straight from science fiction. What physically is an acoustic ostellation
Speaker 2: in space?
Speaker 3: It goes back to that hot, dense plasma of the
Speaker 3: early universe.
Speaker 2: Talking about before recombination.
Speaker 3: Yes, before recombination, gravity was trying to pull the dark
Speaker 3: matter and the ordinary baryonic matter together into clumps. But
Speaker 3: the intense radiation the photons were exerting this immense.
Speaker 2: Outward pressure so to a tug of war.
Speaker 3: Exactly gravity pulling in, radiation pushing out, and this tug
Speaker 3: of war created actual sound waves, pressure waves rippling outward
Speaker 3: through the plasma, much like dropping a stone into a
Speaker 3: pond and watching the ripples expand.
Speaker 2: Wait, literal sound waves traveling through the early universe.
Speaker 3: Literal sound waves. And when the universe cooled and recombination
Speaker 3: finally happened, the plasma turned into neutral gas. The radiation
Speaker 3: pressure suddenly dropped to zero.
Speaker 2: So what happened to the waves?
Speaker 3: The sound waves effectively stalled. They frozen place. Wow, the
Speaker 3: matter that had been pushed outward by these waves stayed
Speaker 3: exactly where it was, leaving a spherical shell of slightly
Speaker 3: denser matter surrounding the original center of the wave.
Speaker 2: So there are literal rings of denser matter frozen from
Speaker 2: the dawn of time out there.
Speaker 3: Yes, and over billions of years, gravity caused galaxies to
Speaker 3: preferentially form along these slightly denser rings.
Speaker 2: Oh, that's amazing.
Speaker 3: Today, when we match the positions of millions of galaxies,
Speaker 3: we see a faint but mathematically undeniable pattern. There is
Speaker 3: a preferred distance between galaxies corresponding exactly to the size
Speaker 3: of those original frozen sound waves.
Speaker 2: I mean, hoo big there.
Speaker 3: It is roughly four hundred and ninety million light years across.
Speaker 3: Because we know the physics of the early plasma, we
Speaker 3: know exactly how large those sound waves should have been.
Speaker 3: So we use that precise consistent distance as a standard
Speaker 3: ruler to measure the expansion of the universe at different epochs.
Speaker 2: That is an unbelievable piece of deductive reasoning. We literally
Speaker 2: use the frozen echoes of the Big Bang as a
Speaker 2: cosmic tape measure.
Speaker 3: It's one of the most elegant tools in cosmology.
Speaker 2: So Chen and his team have the CMB looking at
Speaker 2: the d past, and they have standard candles and frozen
Speaker 2: sound waves looking at the more recent past. Why is
Speaker 2: physically separating this data in the math so revolutionary Because.
Speaker 3: It breaks what physicists call degeneracies.
Speaker 2: Okay, here's where it gets really interesting, because a degeneracy
Speaker 2: sounds like a flaw, but in math it means something
Speaker 2: very specific.
Speaker 3: It does. Imagine, I give you a simple equation A
Speaker 3: multiplied by B equals twenty four. Without more information, you
Speaker 3: don't know the specific value of A or B.
Speaker 2: It could be six and four, or eight and three,
Speaker 2: or twelve and two exactly.
Speaker 3: That is a degeneracy. Multiple different combinations of parameters yield
Speaker 3: the exact same observable result. In cosmology, when you try
Speaker 3: to fit all the data across all of time into
Speaker 3: a single model, you end up with overlapping data points
Speaker 3: that confuse the equations.
Speaker 2: Everything gets tangled.
Speaker 3: A change in the amount of dark matter in your
Speaker 3: model might be perfectly offset by a change in the
Speaker 3: expansion rate, making it literally impossible to tell which underlying
Speaker 3: physical reality is actually true.
Speaker 2: So by decoupling the probes and letting each probe independently
Speaker 2: make predictions only for its best suited time period, the
Speaker 2: researchers are basically untangling the math. They're saying, let's isolate
Speaker 2: variable A in the early universe and isolate variable B
Speaker 2: in the late universe, so they stop contaminating each other.
Speaker 3: That is precisely the mechanism. If you are trying to
Speaker 3: understand a person's entire life story, you wouldn't use their
Speaker 3: kindergarten report card to predict their four oh one K retirement.
Speaker 2: Plan, right. You have to use different metrics for different
Speaker 2: stages of life.
Speaker 3: The metrics you use to evaluate a five year old
Speaker 3: are totally useless for evaluating a fifty year old. If
Speaker 3: you average the report card with their tax return, you
Speaker 3: would generate a completely nonsensical data set.
Speaker 2: It wouldn't mean anything.
Speaker 3: The physics dominating the early universe are incredibly different from
Speaker 3: the physics dominating the late universe. This multi probe strategy
Speaker 3: allows us to see not just what the universe is doing,
Speaker 3: but identify precisely which theoretical models are preferred by the
Speaker 3: data during specific cosmic epochs.
Speaker 2: So they built this brilliant new history oracle sorting machine,
Speaker 2: and they ran five different dark energy models alongside our
Speaker 2: standard LAMB to CDM model through it. What did this
Speaker 2: new lens actually reveal?
Speaker 3: The analysis yielded four groundbreaking results, and each one paints
Speaker 3: a complex, fascinating picture of our current astrophysical reality.
Speaker 2: Okay, let's debate and explore these one by one. Let's
Speaker 2: start with the first finding. The tension remains.
Speaker 3: Yes. Despite this new highly sophisticated separation of data, the
Speaker 3: Hubble tension, that massive discrepancy between the early universe expansion
Speaker 3: rate and the late universe expansion rate did not disappear.
Speaker 2: It's still there across all five models.
Speaker 3: Across all of them. It is a persistent, undeniable challenge.
Speaker 2: So changing the mathematical lens fixing the degeneracies didn't miraculously
Speaker 2: cure the headache.
Speaker 3: It did not, which leads directly to the second revelation.
Speaker 3: No clear victor emerged among the alternative.
Speaker 2: Models, none of them.
Speaker 3: None of them. No alternative model currently holds a significant
Speaker 3: statistical advantage over the standard lambda CDM model, no matter
Speaker 3: how the data sets are carefully decoupled and combined.
Speaker 2: Wait, so, if the tension remains and no new model
Speaker 2: clearly beats the old model, doesn't that suggest we are
Speaker 2: exactly where we started? Did the study fail?
Speaker 3: It might seem that way on the surface, yes, but
Speaker 3: it actually tells us something profoundly important about the limits
Speaker 3: of our current knowledge. It demonstrates that our current observational data,
Speaker 3: while incredibly precise, just isn't sufficient yet to definitively dethrone
Speaker 3: the standard model.
Speaker 2: The old model is just too stubborn.
Speaker 3: The mathematical architecture of LAMB to CDM is so robust,
Speaker 3: so incredibly good at predicting the broad strokes of the
Speaker 3: universe that myer theoretical tweaks aren't enough to replace it.
Speaker 2: We are missing a massive piece of the puzzle entirely.
Speaker 3: The root of the problem likely lies in a deep
Speaker 3: fundamental flaw in our core understanding of physics that none
Speaker 3: of these five alternative models has properly addressed.
Speaker 2: Yet we're not looking for a minor adjustment.
Speaker 3: No, we are likely looking for a completely new physical mechanism.
Speaker 2: Which perfectly sets up the third revelation. And this is
Speaker 2: the big one. They found compelling evidence that the properties
Speaker 2: of dark energy have evolved since the early universe.
Speaker 3: Yes, this is the paradigm shift, because.
Speaker 2: If dark energy is evolving, the cosmological constant the LAMB
Speaker 2: in LAMB to CDM has to be completely discarded, a
Speaker 2: constant by definition, cannot evolve exactly.
Speaker 3: When running the data through this decoupled framework, the math
Speaker 3: strongly preferred models where dark energy is dynamic, and the
Speaker 3: implications of that are absolutely staggering.
Speaker 2: Tell me why if.
Speaker 3: Dark energy is getting stronger or weaker, or changing its
Speaker 3: fundamental behavior over cosmic time, it completely destroys the mathematical
Speaker 3: foundation of a static vacuum energy.
Speaker 2: So what replaces it?
Speaker 3: Well, in physics, some models propose something called quintessence. It's
Speaker 3: a dynamic, time evolving scalar field that drives the expansion.
Speaker 3: Other models propose something called phantom energy, where the density
Speaker 3: of dark energy actually increases over time.
Speaker 2: And what did the data show?
Speaker 3: The DSi data analyzed through Chen's framework leans heavily toward
Speaker 3: this dynamic reality. The engine driving the universe apart has
Speaker 3: gears and it is actively shifting them.
Speaker 2: That is incredible, which brings us to the fourth, and honestly,
Speaker 2: perhaps the most disruptive revelation from the data, the interacting
Speaker 2: dark sector. Yes, the team identified tentative hints of physical
Speaker 2: interactions between dark matter and dark energy.
Speaker 3: This is where the standard rule book of physics truly
Speaker 3: begins to unravel.
Speaker 2: Okay, wait, so we established earlier that dark matter acts
Speaker 2: like an invisible anchor, right, it's holding galaxies together with gravity, right.
Speaker 2: And we established that dark energy acts like an invisible engine,
Speaker 2: pushing the fabric of the universe apart. Historically, we used
Speaker 2: to think they shared the same universe but completely ignored
Speaker 2: each other.
Speaker 3: They were considered two totally separate, non overlapping domains.
Speaker 2: Me these two invisible ghosts might actually be talking to
Speaker 2: each other.
Speaker 3: What's fascinating here is that the ghost analogy is perfect.
Speaker 3: The suggestion is that these two invisible forces are actually interacting,
Speaker 3: and the phrase interacting in this context implies a transfer
Speaker 3: of energy or momentum.
Speaker 2: How does that even work.
Speaker 3: Well, dark energy could be slowly decaying into dark matter,
Speaker 3: or conversely, dark matter could be decaying into dark energy.
Speaker 3: The anchor in the engine might not be separate systems
Speaker 3: at all.
Speaker 2: It might be part of the exact same machine part.
Speaker 3: Of the exact same complex thermodynamic mechanism. This is so
Speaker 3: controversial and exciting because it suggests a dynamic, breathing universe.
Speaker 2: Rather than just a cold, static set of equations slowly
Speaker 2: winding down in isolation.
Speaker 3: Exactly, it's functioning almost like a biological ecosystem, with forces
Speaker 3: constantly reacting to and feeding off one another. If the
Speaker 3: dark sector is interacting, our current cosmological models are vastly oversimplified.
Speaker 2: We've been trying to model an ecosystem as if it
Speaker 2: were a simple pendulum Exactly.
Speaker 3: The math required to balance an interacting dark sector is
Speaker 3: exponentially more complicated than a simple cosmological constant.
Speaker 2: Wow. Okay, so we have basically shattered the illusion of
Speaker 2: the static universe here. The standard model has deep structural cracks,
Speaker 2: dark energy is likely evolving, and these massive invisible forces
Speaker 2: might actually be transferring a momentum between each other. But
Speaker 2: as the second revelation showed us, we don't have a
Speaker 2: clear victor to replace LAMB to CDM yet. So what
Speaker 2: does this all mean? How do we get there? Are
Speaker 2: we basically sitting in the dark waiting for a bigger,
Speaker 2: more expensive telescope to be built or are we waiting
Speaker 2: for a new Albert Einstein to rewrite the math.
Speaker 3: It's a great question. The conclusions clearly challenge the lambda
Speaker 3: CDM model in its current form, but they also provide
Speaker 3: a clear roadmap for the future of astronomy. Jun Schen
Speaker 3: and his team explicitly lay out two necessary pathways.
Speaker 2: Okay, what's the first one?
Speaker 3: The first pathway involves theoretical reconstruction, developing a completely new
Speaker 3: frameworks specifically for testing dark energy.
Speaker 2: So we need new math.
Speaker 3: We need new math. Cosmologists can no longer rely on
Speaker 3: models that assume a constant vacuum energy as a default baseline.
Speaker 3: The theoretical scaffolding has to be built from the ground
Speaker 3: up to accommodate continuous change over billions of years.
Speaker 2: And what's the second pathway?
Speaker 3: A highly focused, dedicated observational search for these newly hinted
Speaker 3: interactions between dark matter and dark energy.
Speaker 2: So looking for the ghost talking.
Speaker 3: Exactly, we need to actively look for specific mathematical signatures
Speaker 3: in the cosmic microwave background and in the large scale
Speaker 3: clustering of galaxies that would prove unequivocally that energy is
Speaker 3: moving between the two dark components.
Speaker 2: Which is holding us back more right now, the tools
Speaker 2: or the theory, it.
Speaker 3: Is an intricate, continuous dance between the two. You cannot
Speaker 3: have a paradigm shift without both operating in tandem. The
Speaker 3: theoretical leaps, like the decoupled mathematical framework we've discussed today
Speaker 3: are absolutely essential because they tell the observational astronomers where
Speaker 3: to point the telescopes.
Speaker 2: They provide the map.
Speaker 3: Right If theorists didn't mathematically suspect the dark sector was interacting,
Speaker 3: engineers wouldn't design an instrument calibrated to look for the
Speaker 3: specific signature of that interaction.
Speaker 2: The theory tells you what frequency to tune the radio.
Speaker 3: To, yes, and conversely, to actually prove any of this,
Speaker 3: we desperately need a new generation of multiprobe surveys, telescopes
Speaker 3: and instruments that are far more powerful than DCII are
Speaker 3: coming online right now. We are talking about space observatories
Speaker 3: like the EUCLID mission and the upcoming Nancy Grace Roman
Speaker 3: Space Telescope. These instruments are capable of looking much deeper
Speaker 3: into the past, mapping a vastly larger volume of the universe,
Speaker 3: and measuring the distribution of galaxies with a level of
Speaker 3: precision that was unimaginable a decade ago, so they.
Speaker 2: Will give the theorists the raw data they need.
Speaker 3: Exactly. A theory is just a mathematical fantasy until it
Speaker 3: is validated by observation. As Yunchin emphasized, only through combined,
Speaker 3: rigorous efforts across multiple disciplines of astronomy can we hope
Speaker 3: to ultimately explain the mechanism driving cosmic acceleration.
Speaker 2: It operates like a grand relay race. The theorists hypothesize
Speaker 2: a new model and pass the baton to the engineers.
Speaker 2: The engineers build a hyper advanced telescope to test it
Speaker 2: and pass the observational data back to the theorists.
Speaker 3: The theorist realize the model is slightly wrong, adjust the math,
Speaker 3: and the cycle continues round.
Speaker 2: And round, getting incrementally closer to the fundamental truth of
Speaker 2: the universe every single lap.
Speaker 3: That is the scientific method operating on the largest possible scale.
Speaker 3: It is a slow, methodical dismantling of our own ignorance.
Speaker 2: I love that well. It has been an immense intellectual
Speaker 2: journey today. We really started from the comfort of a
Speaker 2: standard model that seemed to have everything figured out.
Speaker 3: A universe neatly divided into ordinary matter, dark matter, and
Speaker 3: a constant dark energy pushing outward.
Speaker 2: Right, and we have realized that the foundational mechanics of
Speaker 2: that universe are shifting. We are looking at a physical
Speaker 2: reality where eighty five percent of our cosmos might be
Speaker 2: governed by shifting, evolving, and interacting invisible forces that we
Speaker 2: are only just beginning to comprehend.
Speaker 3: It is a profoundly humbling realization. It strips away the
Speaker 3: illusion that we have the cosmos fully mathematically constrain.
Speaker 2: But at the same time, if you're listening to this,
Speaker 2: I think it is worth taking a moment to appreciate
Speaker 2: the sheer joy of living in an era where the
Speaker 2: fundamental rules of reality are still being actively written.
Speaker 3: It really is an incredibly exciting frontier.
Speaker 2: It's a massive testament to human curiosity that we are
Speaker 2: sitting here utilizing the frozen sound waves of the Big
Speaker 2: Bang to calculate the changing behavior of invisible energy billions
Speaker 2: of light years away.
Speaker 3: And as we peel back those deepest layers of the universe,
Speaker 3: we are confronted with questions that go far beyond just
Speaker 3: resolving in mathematical tension. Because if this new framework is
Speaker 3: pointing us toward the actual physical reality. It alters our
Speaker 3: perspective on the ultimate timeline of existence.
Speaker 2: The fate of the universe exactly.
Speaker 3: I'll leave you with this thought. If dark energy isn't
Speaker 3: a constant but is actually evolving over cosmic time, and
Speaker 3: if it's actively interacting with dark matter transferring momentum, what
Speaker 3: does that mean for the ultimate fate of our universe?
Speaker 2: The long term prognosis changes completely.
Speaker 3: It does for a long time. The baseline assumption was
Speaker 3: a scenario called the big Freeze, a constant, steady expansion
Speaker 3: driven by the cosmological constant that eventually results in a
Speaker 3: universe that just gets colder, darker, and more isolated forever
Speaker 3: fade out. But if the engine pushing the cosmos apart
Speaker 3: is dynamic, changing its behavior, the possibilities multiply. If dark
Speaker 3: energy is phantom energy growing stronger over time, the universe
Speaker 3: could end in a big rip, literally tearing galaxies, stars,
Speaker 3: and eventually atoms apart. Or conversely, if dark energy is
Speaker 3: transferring its power back into dark matter, could the expansion
Speaker 3: of the universe one day slow down? Could it stop
Speaker 3: or even reverse.
Speaker 2: Thrown into reverse leading to a big crime exact you
Speaker 2: realize the engine is changing gears. You really have to
Speaker 2: wonder where the car is actually driving. We will leave
Speaker 2: you at that massive existential question. I'm all over until
Speaker 2: next time.
Speaker 1: L