Speaker 1: Welcome to the quart Side Quantum Physics Podcast, an exploration
Speaker 1: of the fundamental structure of reality where quantum laws govern matter, energy,
Speaker 1: and information. Here, uncertainty is a feature, not a flaw,
Speaker 1: and understanding begins at the smallest scales.
Speaker 2: Imagine trying to read a microscopic text message, like really microscopic,
Speaker 2: But the only magnifying glass that's actually powerful enough to
Speaker 2: read those tiny letters is well, it's roughly the size
Speaker 2: of the Milky Way galaxy.
Speaker 3: Which is quite the infrastructure problem, right.
Speaker 2: I mean that is the exact, frankly absurd position that
Speaker 2: modern physicists find themselves in today. Okay, let's unpack this
Speaker 2: because our mission today for this deep dive is to
Speaker 2: understand the fundamental building blocks of the universe, and more specifically,
Speaker 2: how scientists are attempting to prove the existence of something
Speaker 2: that they literally physically cannot see.
Speaker 3: Yeah, it really is sort of the ultimate cosmic taunt
Speaker 3: Nature have seemingly hidden the master blueprint of reality behind
Speaker 3: this massive energy barrier that humanity may just never be
Speaker 3: able to cross physically at least.
Speaker 2: But before we get to the invisible strings and the
Speaker 2: galaxy size magnifying glasses, I feel like, we have to
Speaker 2: talk about the crisis, the thing that forced physicists into
Speaker 2: this corner in the first place. Right, The standoff exactly,
Speaker 2: the ultimate standoff in physics, which is basically this massive
Speaker 2: clash between the incredibly massive and the impossibly tiny.
Speaker 3: That is the core of it. Yeah, yeah, because for gosh,
Speaker 3: about a century now, physics has been relying on two
Speaker 3: completely different rule books to describe how the.
Speaker 2: Universe works, and they do not like each other.
Speaker 3: Not at all. So on the grand scale, we use
Speaker 3: Einstein's general theory of relativity.
Speaker 2: The heavy lifter Exactly.
Speaker 3: It's this beautifully elegant framework that explains gravity. It treats
Speaker 3: space and time like a like a smooth, continuous fabric.
Speaker 3: It predicts how planets orbit, how galaxies collide, black hole,
Speaker 3: all the big stuff.
Speaker 2: Right, So it makes perfect sense. It's super predictable, and
Speaker 2: it works flawlessly when you're dealing with anything large, and.
Speaker 3: This is a massive But the moment you zoom in
Speaker 3: to the atomic or you know, sub atomic level, general
Speaker 3: relativity just completely falls apart.
Speaker 2: It just stops working pretty.
Speaker 3: Much because down there the universe is governed by quantum
Speaker 3: mechanics and the quantum realm is well, it is not
Speaker 3: a smooth fabric. It is a jittery, chaotic, highly unpredictable place.
Speaker 3: Particles pop in and out of existence, and things only
Speaker 3: happen in these discrete, choppy, little jumps.
Speaker 2: So we have this smooth, heavy rule book for the
Speaker 2: big stuff and a jittery, completely chaotic rule book for
Speaker 2: the tiny stuff, which you know, if I'm listening to
Speaker 2: this right now, I'm probably thinking, okay, so just use both,
Speaker 2: like use the big book for planets and the small
Speaker 2: book for atoms.
Speaker 3: And honestly, that works perfectly ninety nine percent of the time.
Speaker 3: Can get away with it, right, But the crisis hits
Speaker 3: when you are forced to deal with something that is
Speaker 3: both incredibly massive and incredibly tiny at the exact same time. Oh,
Speaker 3: like what we'll think about the very center of a
Speaker 3: black hole, yeah, or the very first moment of big bang.
Speaker 3: In those extreme, extreme scenarios, you have to combine the
Speaker 3: two rule books. You have to figure out how gravity
Speaker 3: operates at the quantum level, quantum gravity exactly. Finding a
Speaker 3: theory of quantum gravity is the holy grail. But when
Speaker 3: you smash those two math equations together.
Speaker 2: What actually happens, Like mathematically.
Speaker 3: The math literally vomits out infinities.
Speaker 2: Wait, infinities.
Speaker 3: Yeah, So, in a probability equation, a result of one
Speaker 3: means something is one hundred percent guaranteed to happen, and
Speaker 3: infinity means a probability greater than one hundred percent.
Speaker 2: Which makes absolutely zero sense physically none.
Speaker 3: It's the universe's fundamental code. Just flashing of fatal error message.
Speaker 3: The math is telling us, hey, you are missing a
Speaker 3: crucial piece of the.
Speaker 2: Puzzle here, which brings us to the proposed savior, the
Speaker 2: thing that's been floating around the physics world for decades, right,
Speaker 2: string theory.
Speaker 3: String theory is arguably the most famous attempt to fix
Speaker 3: those broken equations, because since the dawn of modern physics,
Speaker 3: we've always treated the smallest building blocks of matter, you know, quarks, electrons,
Speaker 3: as microscopic dots.
Speaker 2: Like zero dimensional points with literally no physical size exactly.
Speaker 3: And string theory proposes this radical shift. It suggests that
Speaker 3: if you were to zoom in, say a billion billion
Speaker 3: times smaller than a single proton, a billion billion unimaginable scales.
Speaker 3: But if you did, those dots are not actually dots
Speaker 3: at all. They're incredibly tiny vibrating one dimensional loops of
Speaker 3: energy strings.
Speaker 2: And just by swapping out the word dots for strings,
Speaker 2: the math suddenly starts behaving.
Speaker 3: It does because a string has physical length, right, So
Speaker 3: it effectively smears out the interaction over space and time.
Speaker 3: And that smearing smooths out those chaotic quantum jitters just
Speaker 3: enough to incorporate gravity without triggering those impossible mathematical infinities.
Speaker 2: Wow, I mean that sounds like a massive victory, Like
Speaker 2: give whoever thought of that a Nobel prize and let's
Speaker 2: go home.
Speaker 3: If only were that simple as always catch a huge one,
Speaker 3: The mathematics of string theory demand a really steep price.
Speaker 3: First of all, the equations only work at the universe
Speaker 3: has at least ten dimensions ten.
Speaker 2: And we only experience four right, three of space, one
Speaker 2: of time.
Speaker 3: Right, The theory argues, the other six are curled up
Speaker 3: so tightly we just can't perceive them. But as you
Speaker 3: can imagine, that alone makes a lot of people highly skeptical.
Speaker 2: Yeah, ten dimensions is a tough pill to swallow. But
Speaker 2: the real problem, the real physical problem, is the proof.
Speaker 1: Right.
Speaker 2: That's where our milky way sized magnifying glass comes in.
Speaker 3: That is the insurmountable hurdle. To physically see something as
Speaker 3: infinitesimally small as a string, you have to probe it
Speaker 3: with an unimaginably high frequency of energy.
Speaker 2: You've got to smash stuff together really really hard.
Speaker 3: Exactly, you accelerate particles and smash them together. Right now,
Speaker 3: we use the Large Hadron Collider in Switzerland, which is
Speaker 3: a ring about seventeen miles in circumference, which is huge,
Speaker 3: it is, But to generate enough power to actually detect
Speaker 3: a string, you would need to build a particle collider
Speaker 3: roughly the size of a galaxy.
Speaker 2: Yeah, checking humanity's current infrastructure budget, I'm pretty sure we
Speaker 2: cannot afford a galaxy size machine anytime soon.
Speaker 3: Not quite.
Speaker 2: So we are completely stuck. Like, if you think about it,
Speaker 2: we have this beautiful theory that flawlessly unites the two
Speaker 2: warring rule books of physics, but it's locked in a
Speaker 2: vault that we can never ever physically open. So how
Speaker 2: do we even proceed? How can we possibly know if
Speaker 2: string theory isn't just an elegant mathematical fantasy you pivot.
Speaker 3: I mean, if you can't break through the front door
Speaker 3: with physical experiments, you have to find a logical backdoor.
Speaker 3: And this is where modern theoretical physicists have recently done
Speaker 3: something just brilliant. They decided to revive a classic, almost
Speaker 3: for gotten mathematical strategy from the nineteen sixties. It's known
Speaker 3: as the bootstrap approach.
Speaker 2: The bootstrap approach like the old phrase pulling yourself up
Speaker 2: by your bootstrap.
Speaker 3: Exactly building something massive out of essentially nothing.
Speaker 2: So how does that work in physics?
Speaker 3: Well, historically this is fascinating. Back in the nineteen sixties,
Speaker 3: prominent physicists, guys like Jeffrey Chew at UC Berkeley and
Speaker 3: Stephen Frauschi at Caltech. They were frustrated.
Speaker 2: Why what was happening.
Speaker 3: Quantum mechanics was just getting incredibly messy. Particle colliders were
Speaker 3: spitting out dozens of new, bizarre particles and nobody can
Speaker 3: make any sense of the underlying rules. So Chew suggested
Speaker 3: they just throw out all their complex models. He wanted
Speaker 3: to us start from absolute scratch.
Speaker 2: Oh, like, wipe the chalkboard completely clean.
Speaker 3: Yes, they adopted the absolute bare minimum universally agreed upon
Speaker 3: rules of basic logic and causality, things you just cannot
Speaker 3: argue with, and they tried to build up the laws
Speaker 3: of physics just from those tiny constraints.
Speaker 2: Did it work well?
Speaker 3: The problem was, in the nineteen sixties, the sheer computing
Speaker 3: power and the mathematical technique needed to actually run those
Speaker 3: massive equations that it didn't exist yet. The bootstrap method
Speaker 3: became way too complex to manage, and it eventually fell
Speaker 3: completely out of fashion.
Speaker 2: Ah. Right, but I'm guessing that today, with supercomputers and
Speaker 2: better math, modern physicists are dusting off this retro technique.
Speaker 3: What's fascinating here is how powerful this method has become.
Speaker 3: In the modern era, physicists like Clifford Chung and Grant
Speaker 3: Remen decided to apply that old bootstrap philosophy to the
Speaker 3: ultimate problem, quantum gravity.
Speaker 2: So instead of assuming string theory is real and trying
Speaker 2: to prove it, they just started with that blank slate exactly.
Speaker 3: They adopted just two basic rules about how energy and
Speaker 3: particles should behave, and they let the mathematics dictate what
Speaker 3: the universe must look like.
Speaker 2: Okay, I have an analogy for this. Tell me if
Speaker 2: I'm on the right track here, go for it. This
Speaker 2: sounds exactly like a Pseudoku puzzle. Oh. I like that, right,
Speaker 2: Because when you sit down with a blank Sudoku grid,
Speaker 2: you don't guess the final picture. You don't just start
Speaker 2: throwing numbers in ran because you think they look nice.
Speaker 2: You only have a few fundamental rules, right numbers one
Speaker 2: through nine. No repeats in a row, no repeats in
Speaker 2: a column, no repeats in a box.
Speaker 3: That is a perfect way to visualize it.
Speaker 2: And the magic of a Sudoku puzzle is that if
Speaker 2: you follow those basic rules strictly mathematically, there is only
Speaker 2: one unique solution that can possibly emerge at the end.
Speaker 2: You don't force the outcome at all. The constraints force
Speaker 2: the outcome.
Speaker 3: That's exactly the same logic they used. These physicists wanted
Speaker 3: to set up the cosmic Sudoku grid. They need to
Speaker 3: find the absolute minimum constraints required for the universe to
Speaker 3: function without tearing itself apart with mathematical infinities.
Speaker 2: Okay, so we need to look at the specific rules
Speaker 2: they plugged into this grid. What is rule number one?
Speaker 3: Rule number one is something they call ultrasoftness. And to
Speaker 3: understand why this rule is necessary, we have to talk
Speaker 3: about a concept called the plank scale.
Speaker 2: Let's translate that. What does the plank scale look like
Speaker 2: in plain English.
Speaker 3: It is the ultimate extreme of physics. It's an energy
Speaker 3: level roughly nineteen orders of magnitude greater than the mass
Speaker 3: of a single.
Speaker 2: Proton, which is hard to picture.
Speaker 3: Right, So to give you an intumitive sense of that scale,
Speaker 3: imagine taking the explosive energy of a full tank of
Speaker 3: jet fuel, okay, and compressing all of that immense power
Speaker 3: down into a space the size of a single subatomic particle.
Speaker 2: Oh wow, that is an incomprehensible level of density and heat.
Speaker 3: It is. And at that extreme scale, general relativity breaks.
Speaker 3: The gravitational pull between particles becomes so intense that if
Speaker 3: they were to actually collide, the resulting mathematical probability equations
Speaker 3: rock it straight to infinity.
Speaker 2: The fatal error recidence.
Speaker 3: Right, the math says, the universe breaks. So to fix
Speaker 3: this on their blank slate, the physicists introduced ultrasoftness. They
Speaker 3: assumed that for reality to exist, nature must have a
Speaker 3: mechanism that softens these interactions at ultimate extremes.
Speaker 2: Wait, I gotta stop you there. How does an interaction
Speaker 2: soften when you have that much energy involved? Like if
Speaker 2: two things are hurtling toward each other with the energy
Speaker 2: of a jet engine. How do they not create a
Speaker 2: catastrophic crash.
Speaker 3: It's weird, I know. Think of it less like physical
Speaker 3: objects colliding and more like sound waves or water waves.
Speaker 3: If two massive ocean waves crash directly into each other,
Speaker 3: you get a violent, localized splash. Right, that's our mathematical infinity.
Speaker 3: But ultrasoftness suggests that at the absolute highest energy extremes,
Speaker 3: particles act more like ripples in a pond. As their
Speaker 3: energy increases, they start to spread.
Speaker 2: Out, spread out.
Speaker 3: Yeah, when they meet, they just glide through one another's frequencies.
Speaker 3: They disperse the energy smoothly instead of creating a localized explosion.
Speaker 2: Oh okay, here's where it gets really interesting. So it's
Speaker 2: like two cars speeding toward each other on a highway.
Speaker 2: Normally you'd expect a catastrophic crash, which is our infinite math,
Speaker 2: but at extremely high speeds, instead of crashing, they decide
Speaker 2: they just don't want to interact. They turn into ghosts
Speaker 2: and pass reely right through one another.
Speaker 3: That's a great way to picture it. By requiring the
Speaker 3: math to follow this rule of ultrasoftness, the interaction probabilities
Speaker 3: drop swiftly as energy rises. The feedback loop of infinite
Speaker 3: energies is prevented and reality holds together.
Speaker 2: And the beauty of this is they didn't assume strings
Speaker 2: were causing this ghost like smearing. They just said, look,
Speaker 2: if the math is going to work, this softening effect
Speaker 2: has to happen regardless of what's causing it.
Speaker 3: Precisely.
Speaker 2: Okay, that's rule one. What about rule two?
Speaker 3: Rule two deals with what physicists call minimal zeros. Now,
Speaker 3: this one gets a little deep into the mechanics of
Speaker 3: something called scattering amplitudes.
Speaker 2: Which means what exactly.
Speaker 3: It's just the technical term for calculating the angles, momentum,
Speaker 3: and spin of particles when they bounce off one another.
Speaker 2: Got it, the mechanics of a sub atomic.
Speaker 3: Car crash exactly. Within these calculations there are very specific
Speaker 3: collision setups, what we call kinematic points. These are exact
Speaker 3: angles and speeds where the math dictates the particles must
Speaker 3: not interact. They must simply bounce away or pass by
Speaker 3: without exchanging any energy.
Speaker 2: Like mathmat called dead zones.
Speaker 3: Yes, they're called zeros.
Speaker 2: But why does the universe need dead zones where nothing happens?
Speaker 3: Because if particles interacted and exchange energy at absolutely every
Speaker 3: possible angle in every possible speed. The sheer volume of
Speaker 3: those interactions would again trigger a runaway feedback loop.
Speaker 2: Ah, the infinities come back right.
Speaker 3: The math requires these zeros to act as safety valves, so.
Speaker 2: Minimal zeros is basically like designing a massive, complex highway system.
Speaker 2: If you have cars interacting at every single intersection, you
Speaker 2: get infinite gridlock. You need red lights. You need points
Speaker 2: where cars are forced not to interact. I love that, yes,
Speaker 2: and the rule of minimal zero says you want the
Speaker 2: absolute fewest number of red lights possible to keep the
Speaker 2: traffic flowing smoothly without a pile up.
Speaker 3: That is a phenomenal analogy. You demand the strict mathematical
Speaker 3: minimum of these non interaction points required for the whole
Speaker 3: system to hold together. You don't want an infinite number
Speaker 3: of red lights because then nothing moves. You want the
Speaker 3: bare minimum.
Speaker 2: Okay, the Sidoku grid is set. We have Rule one ultrasoftness.
Speaker 2: Particles must smear out or turn into ghosts and soften
Speaker 2: their interactions at crazy high energies to avoid an infinite
Speaker 2: crash check and rule two minimal zeros. The universe must
Speaker 2: operate with the absolute fewest number of mathematical red lights
Speaker 2: or dead zones allowed. That's it, two basic rules of
Speaker 2: logic and traffic management.
Speaker 3: Just those two. The researchers deliberately used. No assumptions about
Speaker 3: extra dimensions, no assumptions about microscopic vibrating.
Speaker 2: Loops, just a completely blank slate.
Speaker 3: Right. They took those two unbendable rules and they let
Speaker 3: the mathematical engines run to see what kind of universe
Speaker 3: would naturally emerge. They mapped out every possible mathematical function
Speaker 3: that could satisfy both ultrasoftness and minimal zeros.
Speaker 2: And out of all the infinite possibilities of how the
Speaker 2: universe could be structured, how many valid mathematical solutions did
Speaker 2: they actually find?
Speaker 3: They found exactly one, just one.
Speaker 2: The Sudoku puzzle solved itself.
Speaker 3: Only one unique mathematical function satisfied both of those logical constraints.
Speaker 3: And this is really the climax of the whole endeavor,
Speaker 3: because that singular mathematical function was not some random string
Speaker 3: of new numbers. It was the exact defining formula of
Speaker 3: string theory.
Speaker 2: No way.
Speaker 3: Yes, as Clifford Chung put it, they started with basic
Speaker 3: logic and the strings just fell out.
Speaker 2: That gives me literal chills. The strings just fell out.
Speaker 2: You don't even go looking for string theory. Pure logic
Speaker 2: traps the truth in a corner, and string theory is
Speaker 2: the only thing left standing in the room.
Speaker 3: It's incredible and it wasn't just a vague approximation either.
Speaker 3: The solution that emerged from the bootstrap math perfectly matched
Speaker 3: something known as the string spectrum.
Speaker 2: The string spectrum.
Speaker 3: Yeah. To appreciate this, we have to look back again
Speaker 3: to the late nineteen sixties to an Italian physicist named
Speaker 3: gabrielle Vinzziano.
Speaker 2: Right, I know this one. He was looking at the
Speaker 2: messy data coming out of particle colliders at CERN.
Speaker 3: He was Article colliders back then were spitting out a
Speaker 3: confusing spray of subatomic debris, just particles of all different maps,
Speaker 3: masses and spins. It looked like chaotic junk. But Vineziano
Speaker 3: managed to write down a mathematical formula that described all
Speaker 3: these varying masses.
Speaker 2: And what did it look like.
Speaker 3: His formula revealed a beautiful infinite tower or a ladder
Speaker 3: of massive spinning particles where the mass and spin increased
Speaker 3: in very discrete, orderly steps.
Speaker 2: Like climbing the rungs of a ladder. But what was
Speaker 2: actually causing those steps?
Speaker 3: Well, a the time, Benenciano didn't know. But a few
Speaker 3: years later other physicists looked at his formula and realized
Speaker 3: that this mysterious tower of particles corresponded perfectly to the
Speaker 3: harmonic series of a vibrating string.
Speaker 2: Oh, I see, So it's literally like plucking a guitar
Speaker 2: string or a violin string. You don't just get static noise,
Speaker 2: You get a fundamental bass note, and then you get
Speaker 2: a distinct mathematical series of overtones or harmonics. Exactly are
Speaker 2: you saying? Those different microscopic harmonics are the different subatomic particles.
Speaker 3: That is the core beauty of the theory. A single
Speaker 3: fundamental entity of vibrating microscopic string can create the entire
Speaker 3: zoo of subatomic particles just by changing its tune. An
Speaker 3: open ended string vibrating in its fundamental mode produces the
Speaker 3: mass and spin of a photon, the particle of light.
Speaker 2: Wait, so if a different vibration gives you a different particle,
Speaker 2: what vibration gives you gravity? Ah?
Speaker 3: If the string is a closed loop, like a tiny
Speaker 3: rubber band, and it vibrates in a specific mode, the
Speaker 3: math perfectly describes the graviton. The graviton, yeah, the theoretical
Speaker 3: particle that carries the force of gravity. It is built
Speaker 3: in from the start. That was the huge breakthrough in
Speaker 3: the nineteen seventies. String theory naturally contained gravity operating smoothly
Speaker 3: at the quantum level without throwing infinite errors.
Speaker 2: So, bringing it back to this new research, by just
Speaker 2: applying rule one and rule two to a blank slate,
Speaker 2: this infinite tower of musical particles just naturally emerged from
Speaker 2: the equations.
Speaker 3: Every single bit of it, the precise interaction strengths, the harmonics,
Speaker 3: the behavior of gravity, all of it emerged automatically as
Speaker 3: the only logical way to satisfy ultrasoftness and minimal zeros.
Speaker 2: Okay, I have to ask the crucial skeptical question here.
Speaker 2: Let me push back for a second. Do if the
Speaker 2: math leads to exactly one solution, and that solution perfectly
Speaker 2: mirrors string theory, does this mean string theory is officially
Speaker 2: a fact? Like have we bypassed the galaxy sized collider
Speaker 2: and proven it using just math?
Speaker 3: It is vital to make a distinction here. No, this
Speaker 3: does not mean string theory is officially proven as a
Speaker 3: physical experimental fact we still have not directly observed to
Speaker 3: string science fundamentally relies on physical.
Speaker 2: Observation, So we can't throw a parade just yet.
Speaker 3: Not a parade, no, but maybe a quiet, deeply profound
Speaker 3: celebration in the theoretical physics department, because what this provides
Speaker 3: is incredibly robust theoretical proof. Before this, you could argue
Speaker 3: that string theory was just one of many possible arbitrary
Speaker 3: ways to fix the math. But this research shows that
Speaker 3: if you accept two highly logical, almost unavoidable constricts about
Speaker 3: how high energy particles behave, the math doesn't yield an
Speaker 3: in definite number of garbage solutions. It yields one deeply
Speaker 3: elegant framework.
Speaker 2: So what does this all mean when we step back
Speaker 2: from the massive equations, plank scales and the quantum jitter.
Speaker 2: What does this tell us about the fundamental nature of reality?
Speaker 3: Well, if we connect this to the bigger picture, it
Speaker 3: implies a universe that is far less ratrary than we thought.
Speaker 3: As prominent physicists have pointed out, this boostrap approach narrows
Speaker 3: the playing field of reality.
Speaker 2: Narrowing it down just one option.
Speaker 3: Right, It shows us that the universe isn't a random
Speaker 3: collection of laws bolted together. It strongly implies that the
Speaker 3: fundamental nature of existence is tightly constrained by pure logic.
Speaker 2: So, to everyone listening to this right now, the universe
Speaker 2: might not be random at all. The puzzle of reality
Speaker 2: might only have one valid configuration. The pieces literally cannot
Speaker 2: fit together any other way without breaking the universe. You
Speaker 2: don't necessarily need to see everything to prove it exists.
Speaker 2: Sometimes pure logic traps the truth in a corner.
Speaker 3: Precisely, which leaves us with a truly fascinating and maybe
Speaker 3: slightly unnerving puzzle to ponder on our own.
Speaker 2: Oh, what's that?
Speaker 3: If this cosmic sudoku puzzle proves that string theory is
Speaker 3: the only possible answer based on these two basic assumptions,
Speaker 3: what happens if string theory is eventually proven wrong?
Speaker 2: Wait, if it's proven wrong, Yeah.
Speaker 3: Let's say we find a way to definitively disprove it.
Speaker 3: If we want to find another model of the universe,
Speaker 3: which of these supposedly unbreakable fundamental assumptions about reality are
Speaker 3: we going to have to throw away?
Speaker 2: Are we throwing away the red lights or are the
Speaker 2: ghost cars?
Speaker 3: Exactly If it's not string theory, then either particles don't
Speaker 3: soften a high energies or the universe requires infinite red lights,
Speaker 3: and either of those options breaks our understanding of logic completely.
Speaker 2: Wow, So we're backed into a corner. Either the invisible
Speaker 2: strings are real, or the very foundation of logic itself
Speaker 2: has a flaw we haven't found yet. That is a
Speaker 2: staggering thought to leave on.