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CERN Reveals a Strange New State Inside the Heart of Matter · The Quark Side - Quantum Physics Podcast

• 0:01
  Speaker 1: Welcome to the Quarkside Quantum Physics Podcast, an exploration of
• 0:05
  Speaker 1: the fundamental structure of reality, where quantum laws govern matter, energy,
• 0:11
  Speaker 1: and information. Here, uncertainty is a feature, not a flaw,
• 0:16
  Speaker 1: and understanding begins at the smallest scales.
• 0:27
  Speaker 2: So, I want you to try something real quick. Just
• 0:30
  Speaker 2: hold out your hand and look at it. Or actually,
• 0:33
  Speaker 2: if you're holding your phone or maybe a mug of
• 0:35
  Speaker 2: coffee right now, really feel the weight of it in
• 0:38
  Speaker 2: your palm.
• 0:39
  Speaker 1: Right.
• 0:39
  Speaker 3: Just notice the mass of whatever it is.
• 0:41
  Speaker 2: Exactly. Notice the mass. And if you try to remember
• 0:44
  Speaker 2: your high school science classes, you'd probably tell me that
• 0:46
  Speaker 2: the mass of your hand or that phone, it comes
• 0:49
  Speaker 2: from atoms.
• 0:51
  Speaker 3: Which is what we're all taught, you know.
• 0:53
  Speaker 2: Right. And those atoms are made of protons and neutrons,
• 0:56
  Speaker 2: which are made of even tinier things called quarks. So
• 1:00
  Speaker 2: it's this nice, neat little nesting doll of mass.
• 1:03
  Speaker 3: It's a very comforting picture of reality.
• 1:06
  Speaker 2: But, and here's a massive plot twist, nearly all the
• 1:09
  Speaker 2: mass of the visible universe, so your hand, the device
• 1:13
  Speaker 2: you're holding, the stars in the sky, it doesn't actually
• 1:16
  Speaker 2: come from those quarks.
• 1:17
  Speaker 3: No, it really doesn't.
• 1:18
  Speaker 2: It comes from this invisible, elusive, quote-unquote, glue. It holds
• 1:23
  Speaker 2: them together.
• 1:23
  Speaker 3: Yeah, it completely upends how we usually think about the
• 1:26
  Speaker 3: physical world. I mean, we are talking about gluons here. Right.
• 1:29
  Speaker 3: And for a very long time, our understanding of them
• 1:32
  Speaker 3: has been, well, somewhat blurry. But there's this groundbreaking new
• 1:37
  Speaker 3: measurement from the ALICE experiment at CERN's Large Hadron Collider.
• 1:41
  Speaker 2: Oh, wow.
• 1:42
  Speaker 3: Yeah, it was recently published in Physical Review Letters. And
• 1:45
  Speaker 3: it's finally giving us our clearest view ever of how
• 1:49
  Speaker 3: these mysterious particles actually behave inside atomic nuclei.
• 1:53
  Speaker 2: OK, let's unpack this because I have a bone to
• 1:55
  Speaker 2: pick with the standard science curriculum.
• 1:57
  Speaker 3: I thought you might.
• 1:58
  Speaker 2: I mean, why on earth did we all spend so
• 2:01
  Speaker 2: much time learning about protons and neutrons and electrons, like
• 2:06
  Speaker 2: memorizing the periodic table? But somehow we just completely skipped
• 2:10
  Speaker 2: over the fact that gluons are doing the heavy lifting thing.
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  Speaker 2: for the entire universe's mass?
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  Speaker 3: It's a fair question.
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  Speaker 2: Like that feels like a detail you shouldn't just gloss over.
• 2:18
  Speaker 3: It does feel like a glaring omission. I'll give you that.
• 2:21
  Speaker 3: But you have to remember that science education naturally builds
• 2:25
  Speaker 3: from the visible to the invisible.
• 2:27
  Speaker 2: I guess that makes sense. Right.
• 2:28
  Speaker 3: So protons and electrons, they have electrical charges that we
• 2:31
  Speaker 3: can easily measure and manipulate. I mean, you can build
• 2:34
  Speaker 3: a simple circuit in a classroom to demonstrate an electron.
• 2:37
  Speaker 2: Yeah, with a potato or whatever.
• 2:39
  Speaker 3: Exactly. But gluons, on the other hand, are governed by
• 2:42
  Speaker 3: the strong nuclear force. They don't just exist outside of
• 2:46
  Speaker 3: the particles they bind together.
• 2:47
  Speaker 2: So you can't just put one in a jar?
• 2:49
  Speaker 3: No, you definitely can't isolate a gluon in a high
• 2:52
  Speaker 3: school lab. This foundational knowledge about mass is only just
• 2:56
  Speaker 3: now coming into sharp focus because, honestly, the technology required
• 3:00
  Speaker 3: to actually see gluon behavior at this scale... is monumental.
• 3:05
  Speaker 2: We're talking massive machines.
• 3:07
  Speaker 3: We are. It requires literally some of the most complex
• 3:10
  Speaker 3: machinery humanity has ever built.
• 3:12
  Speaker 2: Okay, so to understand how we are seeing them now,
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  Speaker 2: we need to understand what these gluons are actually doing.
• 3:17
  Speaker 2: And there's this nuclear physicist, Daniel Tapia Takaki.
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  Speaker 3: Yes, from the University of Kansas.
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  Speaker 2: Right, a professor there. And he played a lead role
• 3:25
  Speaker 2: in this CERN research alongside the Czech Technical University. And
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  Speaker 2: his central point is that To understand how matter gets
• 3:33
  Speaker 2: its structure, you have to understand gluons.
• 3:37
  Speaker 3: Because it's their energy that creates mass.
• 3:39
  Speaker 2: Right. Because their energy literally creates the mass.
• 3:43
  Speaker 3: And that comes directly back to Einstein's most famous equation,
• 3:48
  Speaker 3: E equals mc squared.
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  Speaker 2: Energy equals mass times the speed of light squared.
• 3:53
  Speaker 3: Exactly. We often hear that equation and think about atomic bombs, right? Like,
• 3:57
  Speaker 3: Mass turning into this massive amount of energy.
• 3:59
  Speaker 2: Right. Huge explosions.
• 4:00
  Speaker 3: But the equation works in reverse, too. Energy and mass
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  Speaker 3: are fundamentally interchangeable. They are just two sides of the
• 4:07
  Speaker 3: same coin.
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  Speaker 2: Okay.
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  Speaker 3: So the quarks themselves are surprisingly light. If you were
• 4:11
  Speaker 3: to put the three quarks that make up a single
• 4:14
  Speaker 3: proton on a tiny little scale, they would only account
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  Speaker 3: for roughly 1% of the proton's total weight.
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  Speaker 2: Wait, wait.
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  Speaker 1: 1%?
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  Speaker 3: Just 1%.
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  Speaker 2: So if quarks are the bricks of a house... And
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  Speaker 2: gluons are the mortar holding them together. It feels like
• 4:29
  Speaker 2: you're telling me the mortar somehow weighs 100 times more
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  Speaker 2: than the bricks.
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  Speaker 3: It does sound crazy when you put it like that.
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  Speaker 2: I mean, in our everyday world, that makes zero sense.
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  Speaker 3: What's fascinating here is that the mortar analogy is a
• 4:40
  Speaker 3: good starting point, but we have to tweak it. In
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  Speaker 3: the everyday world, mortar is just physical stuff, right? It's
• 4:45
  Speaker 3: cement and sand.
• 4:46
  Speaker 1: Right.
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  Speaker 3: But in the quantum world, the quote-unquote mortar is pure
• 4:51
  Speaker 3: chaotic kinetic energy. Gluons are darting back and forth between
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  Speaker 3: the quarks at literal light speed, and they're carrying the
• 4:58
  Speaker 3: strong nuclear force.
• 5:00
  Speaker 2: So it's not a physical paste, it's movement.
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  Speaker 3: Exactly. The sheer intensity of that binding energy is so
• 5:06
  Speaker 3: immense that, according to E equals mc squared, it physically
• 5:10
  Speaker 3: manifests as weight. The intense energy of the strong force
• 5:15
  Speaker 3: field is literally what gives the proton its heft. And
• 5:18
  Speaker 3: since protons and neutrons make up the bulk of an
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  Speaker 3: atom's weight, energy of these gluons is quite literally what
• 5:24
  Speaker 3: anchors you to the ground.
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  Speaker 2: That is just mind-blowing. But, okay, if they are pure
• 5:29
  Speaker 2: energy darting around at the speed of light, and they
• 5:31
  Speaker 2: are buried super deep inside the nucleus, how do we
• 5:35
  Speaker 2: even look at them?
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  Speaker 3: It's not easy.
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  Speaker 2: Like, you can't just slide an atom under a normal microscope.
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  Speaker 2: So what did CERN actually build to get a clear
• 5:42
  Speaker 2: view of this energy?
• 5:44
  Speaker 3: Well, to see something that small and that deeply embedded...
• 5:47
  Speaker 3: You need a quantum microscope.
• 5:49
  Speaker 2: Okay.
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  Speaker 3: So during what they call Run 2 of the Large
• 5:52
  Speaker 3: Hadron Collider, the scientists didn't use standard protons. They used
• 5:56
  Speaker 3: heavy lead nuclei.
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  Speaker 2: Lead, like the metal.
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  Speaker 3: Right. Lead is a massive element. A lead nucleus has
• 6:02
  Speaker 3: 82 protons, which gives it an incredibly strong positive electrical charge.
• 6:08
  Speaker 3: So they stripped away all the electrons, leaving just the core,
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  Speaker 3: and accelerated these bare heavy lead nuclei to 99.99% the
• 6:14
  Speaker 3: speed of light. So they're flying. They are flying. But,
• 6:19
  Speaker 3: and here's the kicker, rather than smashing them head on,
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  Speaker 3: which is what colliders usually do.
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  Speaker 2: Because it's a collider, yeah. Right.
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  Speaker 3: Instead of doing that, they orchestrated an incredibly precise near-miss.
• 6:28
  Speaker 2: Hold on. I need to stop you there. They spent
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  Speaker 2: billions of dollars building a massive particle collider and then
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  Speaker 2: intentionally missed. They did. That sounds like two speeding cars
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  Speaker 2: flying past each other on a highway without touching. How
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  Speaker 2: does a near-miss help you see inside the nucleus?
• 6:44
  Speaker 3: It's all about what happens to the electromagnetic fields around
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  Speaker 3: those cars when they travel that fast. Because the lead
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  Speaker 3: nuclei have such a huge electrical charge, and because they
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  Speaker 3: are moving at nearly the speed of light, relativity steps in.
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  Speaker 2: Relativity.
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  Speaker 3: These things get weird.
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  Speaker 2: Very weird. Relativity dictates that their electromagnetic fields become intensely compressed.
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  Speaker 2: They literally flatten out into these incredibly strong, sheer walls
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  Speaker 2: of electromagnetic energy.
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  Speaker 3: Okay, I'm picturing like a pancake of energy.
• 7:11
  Speaker 2: Yeah, that's a good way to picture it. And in
• 7:13
  Speaker 2: quantum terms, an electromagnetic field is made of photons.
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  Speaker 3: Particles of light.
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  Speaker 2: Exactly. So as these two flattened nuclei fly past each other,
• 7:23
  Speaker 2: one nucleus essentially acts as this hyper-intense flashlight beaming extremely
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  Speaker 2: high-energy photons at the other nucleus. Okay, let me make
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  Speaker 2: sure I'm getting this. So the speeding cars fly past
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  Speaker 2: each other. They don't crash. But the electromagnetic wind, so
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  Speaker 2: to speak, these photons from car A, it hits the
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  Speaker 2: strong force field of car B.
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  Speaker 3: Yes.
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  Speaker 2: But light hitting an atom doesn't sound that groundbreaking. I mean,
• 7:46
  Speaker 2: we shine light on atoms all the time, don't we?
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  Speaker 3: We do, but definitely not light with this level of energy.
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  Speaker 3: When a photon from the first nucleus strikes the dense
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  Speaker 3: gluon field of the second nucleus, the collision is so
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  Speaker 3: energetic that it creates a very specific reaction.
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  Speaker 2: What kind of reaction?
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  Speaker 3: The energy from that collision spontaneously transforms into a heavy
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  Speaker 3: particle known as a J-slash-si-si.
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  Speaker 2: J-slash-ki-i.
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  Speaker 3: Yeah, it's spelled J-slash-ti, but physicists usually pronounce it J-A-si.
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  Speaker 3: It's a particle made of a specific pair of quarks.
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  Speaker 3: A charm quark and an anti-charm quark, to be exact.
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  Speaker 1: Wait.
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  Speaker 2: You're telling me you can create a brand new physical
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  Speaker 2: object out of literal thin air just by having a
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  Speaker 2: highly charged particle narrowly miss another one?
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  Speaker 3: I am.
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  Speaker 2: The energy from the near miss just materializes into a
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  Speaker 2: new physical particle.
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  Speaker 3: That is exactly what happens. The photon interacts with the
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  Speaker 3: gluon field, and their combined energy is converted into the
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  Speaker 3: mass of the J-A psi particle right there in the
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  Speaker 3: vacuum of the accelerator tube.
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  Speaker 2: That is wild.
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  Speaker 1: Yeah. But, um.
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  Speaker 2: It raises a really obvious question for me. Okay, sure.
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  Speaker 2: Why go through all the trouble of looking at this
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  Speaker 2: completely new J-sci particle? Like, if your goal is to
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  Speaker 2: study gluons, why not just build a detector that looks
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  Speaker 2: directly at the gluons that were already there in the
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  Speaker 2: first place?
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  Speaker 3: Ah, because the universe strictly forbids us from seeing a
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  Speaker 3: gluon on its own. Wait, forbids us? Yeah, it's a
• 9:10
  Speaker 3: principle of quantum chromodynamics. It's called color confinement.
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  Speaker 2: Color confinement, okay.
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  Speaker 3: Gluons carry something called color charge, which is just the
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  Speaker 3: strong force equivalent of an electrical charge. The rules of
• 9:20
  Speaker 3: this specific force dictate that you can never, ever have
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  Speaker 3: a particle with a bare color charge existing on its
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  Speaker 3: own in isolation.
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  Speaker 2: So what happens if you try? Like, if you have
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  Speaker 2: tweezers small enough and you try to pull one gluon
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  Speaker 2: out of the proton?
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  Speaker 3: It's a great thought experiment. Think of the strong force
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  Speaker 3: between quarks, like a really, really thick rubber band.
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  Speaker 2: Okay, a rubber band.
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  Speaker 3: With gravity or electromagnetism, the further you pull two things apart,
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  Speaker 3: the weaker the force gets.
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  Speaker 2: Right. Like magnets getting further away from each other.
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  Speaker 3: Exactly. But with the strong force, the further you pull
• 9:54
  Speaker 3: them apart, the tighter the rubber band stretches. The force
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  Speaker 3: doesn't weaken at all. The tension. just grows and grows.
• 10:01
  Speaker 2: So you just have to pull harder.
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  Speaker 3: Right. But if you keep pulling and you're pouring more
• 10:05
  Speaker 3: and more energy into stretching that rubber band, eventually it snaps.
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  Speaker 2: And when it snaps, you get a.
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  Speaker 3: The massive amount of energy stored in that stretched rubber
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  Speaker 3: band instantly converts into mass.
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  Speaker 2: Oh, E equals MC squared again.
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  Speaker 3: Exactly. It spontaneously creates a brand new pair of quarks
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  Speaker 3: on the broken ends of the rubber band. So you
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  Speaker 3: started with one bound pair, you tried to pull them
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  Speaker 3: apart to look inside, and now you just have two
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  Speaker 3: bound pair. Wow. You can never get the glue on
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  Speaker 3: by itself.
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  Speaker 2: So you literally cannot isolate it without accidentally creating more
• 10:40
  Speaker 2: of the very stuff you're trying to pull apart.
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  Speaker 3: Right. It's frustrating for physicists, but it's how reality works.
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  Speaker 3: So because we can't look at gluons directly, the J-A
• 10:49
  Speaker 3: psi particle becomes the perfect proxy.
• 10:52
  Speaker 2: The proxy?
• 10:52
  Speaker 3: Yeah. When that high-energy photon strikes the nucleus, the probability
• 10:57
  Speaker 3: of a J-A psi being produced depends precisely on the
• 11:00
  Speaker 3: density and the arrangement of the gluons inside that nucleus.
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  Speaker 2: I see.
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  Speaker 3: The J-A psi is basically the footprint left behind by
• 11:07
  Speaker 3: the gluons. By studying how and when the J-A psi
• 11:10
  Speaker 3: is produced... Researchers can reverse engineer exactly what the gluon
• 11:14
  Speaker 3: field looked like at that exact microscopic moment.
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  Speaker 2: Okay, so it's like trying to figure out the exact
• 11:20
  Speaker 2: shape of an invisible ocean floor by measuring the specific
• 11:24
  Speaker 2: kinds of waves that eventually crash onto the beach.
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  Speaker 3: That is a fantastic way to visualize it. And this
• 11:29
  Speaker 3: specific technique actually has a technical name. It's called incoherent
• 11:33
  Speaker 3: JISI photonuclear production.
• 11:36
  Speaker 2: Incoherent. That sounds like me before my morning coffee.
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  Speaker 3: It's a bit of a mouthful, but the key word
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  Speaker 3: there really is incoherent. Older methods of studying nuclei tended
• 11:45
  Speaker 3: to give us an average picture of the whole nucleus.
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  Speaker 2: Like a summary.
• 11:48
  Speaker 3: Right, like taking a long exposure photograph of a really
• 11:51
  Speaker 3: busy street where all the cars and people just become
• 11:53
  Speaker 3: a blurry streak. You see the overall flow, but no details.
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  Speaker 2: Makes sense.
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  Speaker 3: But this incoherent production is sensitive to the local, precise
• 12:02
  Speaker 3: fluctuations in gluon density. It allows researchers to target structure's Much,
• 12:07
  Speaker 3: much smaller than a single proton.
• 12:10
  Speaker 2: Okay, but to target smaller structures, you'd need to be
• 12:14
  Speaker 2: able to zoom in, right?
• 12:15
  Speaker 1: Yes.
• 12:15
  Speaker 2: With a normal microscope, you just swap out the glass
• 12:18
  Speaker 2: lens for a stronger one. Yeah. How do you adjust
• 12:20
  Speaker 2: the focus on a massive particle accelerator where the lens
• 12:24
  Speaker 2: is just two heavy nuclei barely missing each other?
• 12:26
  Speaker 3: You do it by taking advantage of wave-particle duality. The
• 12:30
  Speaker 3: scientists vary something called momentum transfer.
• 12:33
  Speaker 2: Momentum transfer.
• 12:34
  Speaker 3: In quantum mechanics, particles like the photons we are using,
• 12:36
  Speaker 3: they also act as waves. And the higher the energy
• 12:39
  Speaker 3: or the momentum of the photon, the shorter its wavelength becomes.
• 12:43
  Speaker 2: Let me see if I follow this. If I have huge, long,
• 12:46
  Speaker 2: rolling ocean waves and they hit a tiny pebble on
• 12:49
  Speaker 2: the beach, the wave just washes right over it. Right.
• 12:52
  Speaker 2: You couldn't tell the pebble was there just by looking
• 12:54
  Speaker 2: at the wave. But if I have tiny high-frequency ripples
• 12:57
  Speaker 2: in a little puddle, they will bounce off the pebble
• 13:00
  Speaker 2: and reveal its exact shape.
• 13:01
  Speaker 3: Exactly.
• 13:02
  Speaker 2: So higher momentum means shorter wavelengths, which act like tiny
• 13:05
  Speaker 2: ripples that can bounce off smaller details.
• 13:07
  Speaker 3: Precisely. You nailed it. By increasing the momentum transfer, they
• 13:12
  Speaker 3: are actively shortening the wavelength of their photon probe, effectively
• 13:16
  Speaker 3: zooming the microscope in. And they did this across a
• 13:19
  Speaker 3: massive energy range spanning from 20 to 633 billion electron volts.
• 13:25
  Speaker 2: Just to ground that number for a second, because 633
• 13:27
  Speaker 2: billion sounds like a lot, what exactly is an electron
• 13:31
  Speaker 2: volt in everyday terms? Sure.
• 13:33
  Speaker 3: An electron volt is simply the amount of kinetic energy
• 13:36
  Speaker 3: a single electron gains when it passes through a one-volt battery.
• 13:39
  Speaker 2: So not much.
• 13:40
  Speaker 3: No, it's a tiny, tiny amount of energy in our
• 13:42
  Speaker 3: daily lives. For context, a flying mosquito has a kinetic
• 13:46
  Speaker 3: energy of roughly a trillion electron volts.
• 13:48
  Speaker 2: Okay, so a mosquito is a trillion.
• 13:50
  Speaker 3: Right, but a mosquito is made of trillions and trillions
• 13:53
  Speaker 3: of atoms, right? The scientists at CERN were cramming 633
• 13:58
  Speaker 3: billion electron volts into single individual subatomic collisions.
• 14:03
  Speaker 2: Oh, my God.
• 14:03
  Speaker 3: Yeah, it is an unimaginably dense concentration of energy.
• 14:07
  Speaker 2: And this allowed them to zoom in to incredibly small scales.
• 14:11
  Speaker 3: Yeah.
• 14:11
  Speaker 2: I mean, I saw the measurements they achieved. They systematically
• 14:14
  Speaker 2: probed regions from 0.6 femtometers down to 0.3 and finally
• 14:18
  Speaker 2: down to 0.2 femtometers.
• 14:19
  Speaker 3: Which is incredibly small.
• 14:21
  Speaker 2: Yeah, a femtometer is a quadrillionth of a meter. At 0.2 femtometers,
• 14:24
  Speaker 2: we were looking at something roughly one quarter the size
• 14:27
  Speaker 2: of a single proton.
• 14:28
  Speaker 3: Professor Takaki has a really fantastic way of explaining that scale.
• 14:31
  Speaker 3: He noted that if the atomic nucleus was the size
• 14:34
  Speaker 3: of a massive football stadium, reaching a resolution of 0.2
• 14:37
  Speaker 3: femtometers is like sitting in a blimp high above the
• 14:41
  Speaker 3: stadium and being able to clearly spot a detail just
• 14:44
  Speaker 3: a few yards across on the playing field.
• 14:46
  Speaker 2: Wow.
• 14:47
  Speaker 3: It's just an unprecedented level of precision.
• 14:49
  Speaker 2: Okay, so you've built this massive quantum microscope. You zoomed
• 14:53
  Speaker 2: in to a quarter the size of a proton using
• 14:56
  Speaker 2: insane amounts of energy. If the old math and the
• 14:59
  Speaker 2: standard models were right, what should they have seen when
• 15:03
  Speaker 2: they looked at the gluons at that scale?
• 15:06
  Speaker 3: Well, they expected the production of these JSI particles to
• 15:09
  Speaker 3: follow a relatively smooth, predictable pattern. For a long time,
• 15:13
  Speaker 3: the prevailing model in nuclear physics was something called nuclear shadowing.
• 15:18
  Speaker 2: Right, nuclear shadowing. And the traditional way this was explained
• 15:21
  Speaker 2: makes a lot of intuitive sense, I think.
• 15:23
  Speaker 3: It does.
• 15:23
  Speaker 2: The idea was that if you have a ton of
• 15:25
  Speaker 2: gluons packed inside a nucleus, they start to overlap. And
• 15:28
  Speaker 2: just like thick layers of clouds blocking sunlight from reaching
• 15:31
  Speaker 2: the ground, the gluons in the front of the nucleus
• 15:34
  Speaker 2: obscure the gluons in the back.
• 15:36
  Speaker 3: Exactly.
• 15:36
  Speaker 2: So when the photon probe comes in, it can't interact
• 15:39
  Speaker 2: with all of them, which naturally reduces the probability of
• 15:42
  Speaker 2: producing that JSI particle. It's just a passive explanation, just
• 15:45
  Speaker 2: clouds blocking the sun.
• 15:47
  Speaker 3: And that passive explanation successfully described a lot of previous
• 15:50
  Speaker 3: lower resolution measurements. So, naturally, as they zoomed in tighter,
• 15:55
  Speaker 3: they expected the J-A psi production to decrease slightly in
• 15:59
  Speaker 3: a predictable curve, which would be totally consistent with this
• 16:02
  Speaker 3: cloud overlap.
• 16:04
  Speaker 2: But they didn't see that.
• 16:05
  Speaker 3: No, the reality was completely different. When the ALICE experiment
• 16:08
  Speaker 3: zoomed all the way into that 0.2 fantometer mark, the
• 16:12
  Speaker 3: production rate of the J-psi particles suddenly and drastically plummeted.
• 16:16
  Speaker 3: It just It was heavily suppressed, far, far beyond what
• 16:20
  Speaker 3: nuclear shadowing could possibly account for.
• 16:22
  Speaker 2: So it wasn't just a slight dip. It was a
• 16:24
  Speaker 2: massive drop off. And from a data perspective, it wasn't
• 16:27
  Speaker 2: a fluke either, right? Yeah. I read this had a
• 16:29
  Speaker 2: statistical significance of about three standard deviations.
• 16:33
  Speaker 3: Yes. Three standard deviations is the statistical threshold where physicists
• 16:36
  Speaker 3: start taking things very, very seriously.
• 16:38
  Speaker 2: It means it's real.
• 16:39
  Speaker 3: It means there is roughly a 99.7% chance that this
• 16:42
  Speaker 3: drop off is a real physical feature of the universe.
• 16:45
  Speaker 3: and only a 0.3% chance it was just random background
• 16:48
  Speaker 3: noise in the detectors.
• 16:50
  Speaker 2: Okay, so the cloud analogy is dead.
• 16:52
  Speaker 3: The cloud analogy simply could not account for the level
• 16:55
  Speaker 3: of suppression they observed. The data points to an entirely
• 16:59
  Speaker 3: different reality, a phenomenon that was predicted by quantum chromodynamics,
• 17:04
  Speaker 3: but never clearly isolated until right now. It's known as
• 17:07
  Speaker 3: gluon saturation.
• 17:09
  Speaker 2: Here's where it gets really interesting, because... If nuclear shadowing
• 17:13
  Speaker 2: is like passive clouds blocking the sun, this new gluon
• 17:18
  Speaker 2: saturation feels fundamentally different. It is. I'm trying to picture it.
• 17:23
  Speaker 2: Is it more like a chaotic mosh pit at a
• 17:27
  Speaker 2: heavy metal concert? Oh, I like that. Like you have
• 17:29
  Speaker 2: a venue and people keep pouring in and they're running
• 17:31
  Speaker 2: around with crazy. But eventually there's literally no physical space
• 17:35
  Speaker 2: left on the floor for another person to enter. Right.
• 17:37
  Speaker 2: They can't just passively pass by each other anymore. They
• 17:40
  Speaker 2: start violently pushing back against each other. The crowd itself
• 17:44
  Speaker 2: becomes this unified, solid thing that actively resists anyone else joining.
• 17:49
  Speaker 3: The mosh pit is a great visual for the density,
• 17:51
  Speaker 3: but we do have to adjust it slightly for quantum mechanics.
• 17:53
  Speaker 2: Okay, tell me.
• 17:54
  Speaker 3: In a normal mosh pit, the people are still individual
• 17:57
  Speaker 3: people bumping into one another, right?
• 17:59
  Speaker 2: Sure.
• 18:00
  Speaker 3: In gluon saturation, the particles become highly active and interactive.
• 18:05
  Speaker 3: At these extreme densities and tiny spatial scales, the gluons
• 18:09
  Speaker 3: get so impossibly packed together that they begin to physically
• 18:12
  Speaker 3: fuse and recombine.
• 18:13
  Speaker 2: Wait, they merge together?
• 18:15
  Speaker 3: Yes. Gluons can split into two gluons, and two gluons
• 18:19
  Speaker 3: can recombine into one.
• 18:20
  Speaker 2: What? Yeah.
• 18:21
  Speaker 3: As the density increases, the rate at which they recombine
• 18:25
  Speaker 3: starts to perfectly balance the rate at which they split.
• 18:28
  Speaker 3: The sheer density creates a kind of quantum pressure that
• 18:31
  Speaker 3: strictly limits how many gluons can exist in a given region.
• 18:35
  Speaker 2: So they stop being individuals.
• 18:36
  Speaker 3: They stop acting as individual particles bumping into each other
• 18:40
  Speaker 3: and start acting collectively as a single, unified system.
• 18:43
  Speaker 2: So the mosh pit is literally pushing back against the
• 18:46
  Speaker 2: laws of physics, trying to cram more particles into that space.
• 18:49
  Speaker 2: It hits a hard physical limit where the glue just
• 18:51
  Speaker 2: refuses to get any denser.
• 18:53
  Speaker 3: It represents a fundamental limit of matter itself. The strong
• 18:56
  Speaker 3: force is what allows matter to exist, but even the
• 18:59
  Speaker 3: strong force has boundaries.
• 19:00
  Speaker 2: That's wild.
• 19:01
  Speaker 3: When you reach this saturation scale... The gluons self-regulate their
• 19:05
  Speaker 3: own density. This collective behavior is really one of the
• 19:09
  Speaker 3: most challenging and exciting frontiers in modern physics because it
• 19:13
  Speaker 3: shows us how the most basic building blocks of our
• 19:15
  Speaker 3: reality organize themselves under the most extreme conditions possible.
• 19:20
  Speaker 2: It is truly mind-bending when you take a step back
• 19:22
  Speaker 2: and think about what this actually means for our everyday lives.
• 19:25
  Speaker 3: It really is.
• 19:26
  Speaker 2: I mean, next time you tap your desk or pick
• 19:28
  Speaker 2: up a pen or just look up at the stars
• 19:30
  Speaker 2: at night, You weren't just interacting with solid static chunks
• 19:34
  Speaker 2: of matter. Not at all. Underneath it all, at a scale,
• 19:37
  Speaker 2: a fraction of a single proton, there's a densely packed,
• 19:40
  Speaker 2: incredibly energetic, self-regulating field of gluons constantly splitting and fusing.
• 19:46
  Speaker 2: And that invisible chaotic energy is literally what is holding
• 19:50
  Speaker 2: the fabric of your reality together. It's what gives your
• 19:53
  Speaker 2: body its weight.
• 19:54
  Speaker 3: And if we connect this to the bigger picture, this
• 19:57
  Speaker 3: raises an incredibly important question. It's one that isn't completely
• 20:01
  Speaker 3: answered by this experiment alone, but it's the exact reason
• 20:04
  Speaker 3: scientists push these boundaries in the first place. We now
• 20:06
  Speaker 3: know gluons have a maximum density here on Earth. They
• 20:10
  Speaker 3: reach this saturation point where they physically cannot pack any
• 20:14
  Speaker 3: tighter due to their own strong interactions. But what happens
• 20:18
  Speaker 3: in places where the universe actively tries to force them
• 20:21
  Speaker 3: beyond that limit?
• 20:22
  Speaker 2: Oh, wow. Yeah, because the universe is full of environments
• 20:25
  Speaker 2: vastly more extreme than a particle accelerator. Like what happens
• 20:29
  Speaker 2: inside the ultra-dense core of a collapsed star or a
• 20:33
  Speaker 2: black hole where gravity is trying to crush everything into
• 20:37
  Speaker 2: an infinitely dense point?
• 20:39
  Speaker 3: Or what about during the very first microsecond of the
• 20:41
  Speaker 3: Big Bang?
• 20:42
  Speaker 2: Right. When all the matter in the entire universe was
• 20:45
  Speaker 2: compressed into a space smaller than an atom.
• 20:47
  Speaker 3: Precisely. Does the fundamental glue of the universe eventually break
• 20:52
  Speaker 3: under that kind of infinite pressure? Does the rubber band
• 20:55
  Speaker 3: snap in a way we've never seen before?
• 20:57
  Speaker 2: Or does it turn into something else?
• 20:58
  Speaker 3: That's the question. Does it undergo a massive phase transition,
• 21:03
  Speaker 3: transforming into an entirely new state of existence? Like a
• 21:07
  Speaker 3: form of matter we haven't even named yet.
• 21:09
  Speaker 2: Man, that's fascinating.
• 21:10
  Speaker 3: Understanding how gluons behave at their absolute limit here on Earth,
• 21:14
  Speaker 3: inside the Large Hadron Collider, is the crucial first step
• 21:18
  Speaker 3: to unlocking what happens when the cosmos breaks those limits
• 21:21
  Speaker 3: out in the deep universe.
• 21:23
  Speaker 2: That is a staggering thought to leave on. The deeper
• 21:26
  Speaker 2: we look into the tiny invisible spaces between things, down
• 21:29
  Speaker 2: to fractions of a femtometer, the closer we get to
• 21:31
  Speaker 2: understanding the massive, universe-spanning mysteries of how everything began and
• 21:35
  Speaker 2: how it all might end. We want to thank you
• 21:37
  Speaker 2: for joining us on this exploration of the invisible forces
• 21:40
  Speaker 2: that give our world its shape and its weight. Until
• 21:43
  Speaker 2: next time, keep questioning the world around you.