Latest / The Quark Side - Quantum Physics Podcast / Could Muonium Reveal a Fifth Fundamental Force?

Transcript

Could Muonium Reveal a Fifth Fundamental Force? · 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: I want you to picture something, just for a second. Um,
• 0:30
  Speaker 2: Hold an imaginary apple in your hand.
• 0:32
  Speaker 3: Okay.
• 0:33
  Speaker 2: Now, you know, just let it go. It falls to
• 0:35
  Speaker 2: the ground.
• 0:35
  Speaker 3: Right, as it always does.
• 0:37
  Speaker 2: Exactly. It's like the most mundane, everyday observation in the world.
• 0:42
  Speaker 2: It's something you've expected to happen since you were a
• 0:44
  Speaker 2: toddler dropping food from a high chair.
• 0:46
  Speaker 3: Yeah, it's basically hardwired into our brains from day one.
• 0:50
  Speaker 2: But that simple action, the universality of free fall, it
• 0:54
  Speaker 2: actually forms the bedrock of our entire understanding of the cosmos.
• 0:58
  Speaker 2: I mean, it dates all the way back to Galileo
• 1:00
  Speaker 2: rolling spheres down winter ramps and Isaac Newton watching fruit
• 1:05
  Speaker 2: fall in an orchard.
• 1:06
  Speaker 3: Right. And ultimately, it is the absolute core of Albert
• 1:09
  Speaker 3: Einstein's theory of gravity, the equivalence principle.
• 1:12
  Speaker 2: Which is an incredibly simple rule, right? Everything falls the
• 1:14
  Speaker 2: exact same way.
• 1:15
  Speaker 3: It is comforting in its absolute certainty, honestly. Whether you
• 1:19
  Speaker 3: drop a feather or a solid lead hammer, if you
• 1:22
  Speaker 3: remove air resistance, you know, drop them in a vacuum,
• 1:25
  Speaker 3: they hit the floor at the exact same instant.
• 1:27
  Speaker 1: Right.
• 1:27
  Speaker 2: They fall together.
• 1:28
  Speaker 3: Yeah. And we base pretty much all of modern physics
• 1:32
  Speaker 3: and our entire understanding of how the universe is glued
• 1:35
  Speaker 3: together on this one giant assumption.
• 1:38
  Speaker 2: But this is where it gets incredibly fascinating. What if
• 1:40
  Speaker 2: we're wrong?
• 1:41
  Speaker 3: Well, that's the question.
• 1:42
  Speaker 2: Or I guess more specifically, what if that foundational, seemingly
• 1:46
  Speaker 2: unbreakable rule of the universe is only true for like
• 1:50
  Speaker 2: some of the ingredients in the cosmos? What if we've
• 1:52
  Speaker 2: just been testing the wrong stuff this whole time?
• 1:55
  Speaker 3: It's a profound question, and it takes us way beyond
• 1:58
  Speaker 3: the physics we learned in high school. I mean, when
• 2:00
  Speaker 3: you start poking at the edges of the equivalence principle,
• 2:03
  Speaker 3: you're entering a space where the rules of reality might
• 2:06
  Speaker 3: actually fracture.
• 2:07
  Speaker 2: Wow.
• 2:08
  Speaker 3: Yeah. We assume gravity is a universal constant because we've
• 2:11
  Speaker 3: only ever been able to test it on a tiny
• 2:13
  Speaker 3: mundane fraction of what the universe is actually made of.
• 2:16
  Speaker 2: So today, our mission is to explore a massive groundbreaking
• 2:19
  Speaker 2: experiment currently underway in Switzerland that is putting Einstein-Vries theory
• 2:24
  Speaker 2: to the ultimate test. And they are doing it using exotic,
• 2:29
  Speaker 2: artificially created matter.
• 2:31
  Speaker 3: It is genuinely a journey to the absolute cutting edge
• 2:34
  Speaker 3: of modern experimental physics.
• 2:37
  Speaker 2: We are going to explore how scientists are basically freezing time,
• 2:41
  Speaker 2: building what they call atomic cannons, and potentially hunting for
• 2:46
  Speaker 2: a mysterious fifth fundamental force of nature.
• 2:48
  Speaker 3: Because the reality is we don't actually know if all
• 2:51
  Speaker 3: matter falls at the same rate. Proving it one way
• 2:53
  Speaker 3: or the other requires an absurd level of engineering.
• 2:56
  Speaker 2: So to figure out if we've been testing the wrong stuff,
• 2:59
  Speaker 2: we first kind of have to understand the weird family
• 3:02
  Speaker 2: tree of the universe's building blocks, right? What exactly is
• 3:05
  Speaker 2: the right stuff we should be testing?
• 3:08
  Speaker 3: To understand that, we have to look at the standard
• 3:10
  Speaker 3: model of particle physics. Think of it as the ultimate
• 3:14
  Speaker 3: recipe book for the universe.
• 3:15
  Speaker 2: Okay.
• 3:15
  Speaker 3: According to this model, matter is divided into three distinct generations.
• 3:20
  Speaker 2: And the first generation is basically our entire world.
• 3:22
  Speaker 3: Exactly. The first generation makes up you, me, the chair
• 3:26
  Speaker 3: you're sitting on, the Earth, the sun, all the stars
• 3:28
  Speaker 3: you see. It includes protons, neutrons, and everyday electrons. It
• 3:32
  Speaker 3: is the visible, tangible, stable universe.
• 3:36
  Speaker 2: But then nature decided to make sequels.
• 3:38
  Speaker 3: Yeah, that is essentially what happened. There is a second
• 3:41
  Speaker 3: and even a third generation of matter.
• 3:44
  Speaker 2: Just sitting out there.
• 3:45
  Speaker 3: Right. And you can think of them as exact copies
• 3:48
  Speaker 3: of the first generation, but massively scaled up in weight.
• 3:51
  Speaker 3: These generations contain heavier, highly unstable particles.
• 3:56
  Speaker 2: OK, so for this experiment in Switzerland, what are they using?
• 3:59
  Speaker 3: The star of the show here is a second generation
• 4:01
  Speaker 3: particle called the muon.
• 4:03
  Speaker 2: OK, I've heard the word, but what exactly is a muon?
• 4:06
  Speaker 3: So a muon behaves almost identically to an everyday electron.
• 4:10
  Speaker 3: It has a negative electrical chart, it spins the same way,
• 4:13
  Speaker 3: but it has about 200 times more mass.
• 4:16
  Speaker 2: Wow, so it's just really heavy.
• 4:18
  Speaker 3: Yeah, it is the electron's much heavier, much weirder sibling.
• 4:22
  Speaker 3: And here's the thing that keeps physicists up at night.
• 4:25
  Speaker 3: We still have absolutely no idea why these extra heavier
• 4:28
  Speaker 3: generations exist in the first place.
• 4:30
  Speaker 2: But why do we need a heavier electron?
• 4:31
  Speaker 3: Exactly. Why did nature need three versions of these building blocks?
• 4:36
  Speaker 3: It's a complete mystery.
• 4:37
  Speaker 2: So the question is, if this heavier sibling, the muon,
• 4:41
  Speaker 2: falls into the influence of gravity, does it fall at
• 4:44
  Speaker 2: the exact same rate as the everyday electron we are
• 4:47
  Speaker 2: used to?
• 4:48
  Speaker 3: That is the multi-million dollar question. Does the increasing mass
• 4:52
  Speaker 3: of a second generation particle interact with the fabric of
• 4:55
  Speaker 3: space-time exactly like the lighter first generation particles?
• 4:58
  Speaker 2: I see.
• 4:59
  Speaker 3: Because if we can test the equivalence principle on a muon,
• 5:02
  Speaker 3: we are testing gravity on a fundamentally different type of
• 5:06
  Speaker 3: matter for the very first time in human history.
• 5:08
  Speaker 2: That is incredible. But I imagine testing gravity on a
• 5:11
  Speaker 2: tiny subatomic particle is ridiculously frustrating.
• 5:15
  Speaker 3: Oh, it is an absolute engineering nightmare, primarily because of
• 5:18
  Speaker 3: electrical charge.
• 5:19
  Speaker 2: Right, because you just said the muon has a negative charge,
• 5:22
  Speaker 2: just like an electron.
• 5:23
  Speaker 3: And gravity is unimaginably weak compared to electromagnetism.
• 5:27
  Speaker 2: Like how weak?
• 5:28
  Speaker 3: We're talking about a force that is 10 to the
• 5:30
  Speaker 3: power of 36 times weaker.
• 5:32
  Speaker 2: That is a number I can't even process.
• 5:34
  Speaker 3: It's massive. So if you try to drop a negatively
• 5:37
  Speaker 3: charged particle to see how gravity pulls on it, the
• 5:40
  Speaker 3: tiniest stray electromagnetic field will violently yank that particle around.
• 5:45
  Speaker 2: Oh, so it ruins the trop?
• 5:47
  Speaker 3: Completely. Even the static electricity from a scientist's shirt across
• 5:52
  Speaker 3: the room would overpower the delicate pull of Earth's gravity.
• 5:56
  Speaker 3: It would be like trying to listen to a single
• 5:58
  Speaker 3: whisper while standing on the runway next to a screaming
• 6:01
  Speaker 3: jet engine.
• 6:02
  Speaker 2: You'd never hear the whisper. The jet engine completely drowns
• 6:05
  Speaker 2: it out.
• 6:06
  Speaker 3: Exactly.
• 6:07
  Speaker 2: So to measure gravity on this particle, it has to
• 6:09
  Speaker 2: be electrically neutral.
• 6:10
  Speaker 3: You need a perfectly neutral package. If the total charge
• 6:13
  Speaker 3: is zero, electromagnetism just ignores it, turning off the jet
• 6:17
  Speaker 3: engine and leaving only the whisper of gravity to act
• 6:20
  Speaker 3: on the mass.
• 6:20
  Speaker 2: And this is where the Swiss team comes in with
• 6:23
  Speaker 2: what I can only describe as a Frankenstein atom.
• 6:25
  Speaker 3: Yeah.
• 6:26
  Speaker 2: To get this neutral package, they assemble an exotic artificial
• 6:30
  Speaker 2: atom called muonium.
• 6:31
  Speaker 3: Yes. It's an incredibly elegant solution, actually.
• 6:34
  Speaker 2: That's all?
• 6:35
  Speaker 3: Well... To make muonium, you take a positively charged antimuon
• 6:39
  Speaker 3: and you bind it with a negatively charged everyday electron.
• 6:42
  Speaker 3: The positive and the negative perfectly cancel each other out,
• 6:46
  Speaker 3: giving you a neutral exotic atom that is ready to
• 6:48
  Speaker 3: be dropped.
• 6:49
  Speaker 2: Hold on. My brain just short-circuited a bit.
• 6:51
  Speaker 3: Yeah.
• 6:52
  Speaker 2: You just said we're trying to test a second-generation particle,
• 6:54
  Speaker 2: but now you're saying we're using an antimuon, like antimatter?
• 6:58
  Speaker 3: Yes, an antimuon is antimatter.
• 7:00
  Speaker 2: Doesn't throwing antimatter into a gravity test... Completely ruin the experiment.
• 7:04
  Speaker 2: I mean, does antimatter even fall down?
• 7:07
  Speaker 3: That is actually a very common point of confusion. Antimatter
• 7:10
  Speaker 3: responds to gravity the exact same way regular matter does.
• 7:13
  Speaker 3: It falls down, not up.
• 7:15
  Speaker 2: Wait, really?
• 7:16
  Speaker 3: Yes. Gravity only cares about mass and energy, and an
• 7:19
  Speaker 3: antimuon has the exact same mass as a regular muon.
• 7:23
  Speaker 3: The only difference is that antimatter has the opposite electrical
• 7:26
  Speaker 3: charge of its regular matter counterpart.
• 7:28
  Speaker 2: Oh, I see.
• 7:29
  Speaker 3: So we have to use the tantamuon because its positive
• 7:32
  Speaker 3: charge is the exact required puzzle piece to perfectly balance
• 7:35
  Speaker 3: the negative charge of a normal electron.
• 7:38
  Speaker 2: So it creates that neutral package without altering how gravity
• 7:42
  Speaker 2: will interact with the particle.
• 7:43
  Speaker 3: Exactly. It zeroes out the electrical charge perfectly.
• 7:46
  Speaker 2: Okay, so it's essentially a clever accounting trick to zero
• 7:49
  Speaker 2: it out. We have our perfect test subject. The Frankenstein
• 7:53
  Speaker 2: atom is ready. But there is a massive ticking clock
• 7:57
  Speaker 2: here that makes this entire experiment sound literally impossible.
• 8:01
  Speaker 3: The lifespan of a muon.
• 8:03
  Speaker 2: Right. It lives for just 2.2 microseconds before it decays
• 8:06
  Speaker 2: and vanishes entirely.
• 8:07
  Speaker 3: Yeah, that is 2.2 millionths of a second.
• 8:10
  Speaker 2: That is absurd.
• 8:11
  Speaker 1: It is.
• 8:11
  Speaker 3: That is the entire window you have to create the atom,
• 8:14
  Speaker 3: stabilize it, drop it, and measure how gravity affected it
• 8:17
  Speaker 3: before it literally ceases to exist.
• 8:19
  Speaker 2: I genuinely don't understand how you even track something that
• 8:21
  Speaker 2: disappears that fast. Especially because, from what I gather, when
• 8:26
  Speaker 2: scientists previously tried to make muonium, the atoms were produced
• 8:29
  Speaker 2: in what they call a hot state.
• 8:31
  Speaker 1: Right.
• 8:31
  Speaker 3: And hot in particle physics basically means chaotic and highly energetic.
• 8:35
  Speaker 2: So they were moving fast.
• 8:37
  Speaker 3: Extremely fast. In previous experiments, when scientists successfully created these atoms,
• 8:42
  Speaker 3: the muonium would just fly off in random directions at
• 8:46
  Speaker 3: wildly different, blindingly fast speeds.
• 8:49
  Speaker 2: Like kicking a beehive. Yeah. You can't precisely measure how
• 8:52
  Speaker 2: a single bee is falling if a billion bees are
• 8:55
  Speaker 2: aggressively swarming in every direction for two millionths of a second.
• 8:59
  Speaker 3: You absolutely cannot. You need order. You need to be
• 9:02
  Speaker 3: able to track the trajectory with microscopic precision. And that
• 9:06
  Speaker 3: requires a cold state where the atoms are moving slowly
• 9:09
  Speaker 3: and uniformly.
• 9:10
  Speaker 2: And this is where physics professor Anna Soder, lead author
• 9:13
  Speaker 2: Jesse Zhang, and their teams at ETH Zurich and the
• 9:16
  Speaker 2: Paul Scherer Institute, or PSI, step in.
• 9:18
  Speaker 3: Yeah, the Paul Scher Institute in Switzerland is arguably the
• 9:22
  Speaker 3: only place in the world equipped for this. They house
• 9:24
  Speaker 3: a massive particle accelerator that generates the world's most intense,
• 9:28
  Speaker 3: continuous muon beams.
• 9:30
  Speaker 2: How do they even do that?
• 9:31
  Speaker 3: They achieve it by taking protons and accelerating them to
• 9:34
  Speaker 3: massive speeds before violently smashing them into a carbon target.
• 9:37
  Speaker 3: The resulting debris from that massive collision creates the intense
• 9:41
  Speaker 3: stream of muons needed to even attempt this.
• 9:43
  Speaker 2: But that's still a violent, chaotic stream, right? Their breakthrough
• 9:47
  Speaker 2: was figuring out how to take that chaos and force
• 9:51
  Speaker 2: it into this cold state where the muonium atoms aren't
• 9:54
  Speaker 2: swarming randomly, but are moving parallel to one another at
• 9:57
  Speaker 2: similar speeds.
• 9:58
  Speaker 3: Like a perfectly orderly marching band.
• 10:01
  Speaker 2: Exactly. And the way they achieve this is, I mean,
• 10:03
  Speaker 2: it's one of the most fascinating pieces of experimental physics
• 10:06
  Speaker 2: engineering I've heard of.
• 10:08
  Speaker 3: It really is. To cool these highly energetic particles down
• 10:12
  Speaker 3: and line them up, They fire the antimuons into a
• 10:15
  Speaker 3: thin layer of superfluid helium that has been cooled to
• 10:19
  Speaker 3: near absolute zero.
• 10:21
  Speaker 2: Which is what, minus 273 degrees Celsius?
• 10:23
  Speaker 3: Yes. It is incomprehensibly cold.
• 10:26
  Speaker 2: But they don't just call it a cold liquid. They
• 10:28
  Speaker 2: call superfluid helium a quantum fluid, which honestly sounds like
• 10:31
  Speaker 2: something out of a superhero movie. What does that actually mean?
• 10:34
  Speaker 3: Well, in a normal liquid, like water in a glass,
• 10:36
  Speaker 3: the atoms are bouncing around and interacting individually. But when
• 10:39
  Speaker 3: you cool helium down to just a fraction of a
• 10:42
  Speaker 3: degree above absolute zero, it undergoes this bizarre phase change.
• 10:46
  Speaker 3: The individual helium atoms actually lose their distinct identities. They
• 10:51
  Speaker 3: merge into a single collective quantum state.
• 10:54
  Speaker 2: Like they all give up their individuality and become one
• 10:56
  Speaker 2: giant super atom.
• 10:57
  Speaker 3: Essentially, yes. And because it exists in this strange singular
• 11:01
  Speaker 3: quantum state, The superfluid becomes incredibly rigid in its purity.
• 11:06
  Speaker 2: Right.
• 11:06
  Speaker 3: It tolerates absolutely no impurities or foreign bodies whatsoever.
• 11:10
  Speaker 2: Which turns out to be the secret weapon for the experiment.
• 11:12
  Speaker 3: Exactly.
• 11:13
  Speaker 2: So the accelerator fires an energetic antimion into this absolutely
• 11:17
  Speaker 2: pure quantum fluid. The antimion slows down in the cold.
• 11:21
  Speaker 2: It encounters a free electron, grabs it, and becomes our
• 11:24
  Speaker 2: neutral muonium atom. Right. But the moment it forms, the
• 11:29
  Speaker 2: superfluid helium basically realizes there is an impurity in the pool.
• 11:32
  Speaker 3: Yes, the scientific term is that the newly formed muonium
• 11:35
  Speaker 3: atom has a positive chemical potential relative to the fluid.
• 11:39
  Speaker 2: In layman's terms.
• 11:40
  Speaker 3: In layman's terms, the muonium wants to exist in the
• 11:42
  Speaker 3: lowest possible energy state, but being trapped inside the pure
• 11:46
  Speaker 3: helium forces its energy levels too high, so the quantum
• 11:49
  Speaker 3: fluid rejects it violently.
• 11:51
  Speaker 2: Jesse Zane calls this an atomic cannon. Because the fluid
• 11:54
  Speaker 2: violently rejects the muonium, it converts that chemical potential into
• 11:58
  Speaker 2: kinetic energy, shooting the atom vertically out of the surface
• 12:01
  Speaker 2: of the liquid.
• 12:02
  Speaker 3: It's quite a literal description.
• 12:04
  Speaker 2: It's exactly like trying to hold an inflated beach ball underwater.
• 12:07
  Speaker 2: You push it down, but the water desperately wants to
• 12:10
  Speaker 2: reject that pocket of air, and the second you let go,
• 12:13
  Speaker 2: it shoots straight up to the surface.
• 12:15
  Speaker 3: That is a brilliant analogy. The helium pool literally ejects
• 12:20
  Speaker 3: the muonium atoms upward in a highly controlled, slow-moving beam.
• 12:24
  Speaker 2: But wait, I have a logistical question here that is
• 12:26
  Speaker 2: kind of bothering me. Sure. We just said the helium
• 12:28
  Speaker 2: is cool to absolute zero, or nearly there. Doesn't cooling
• 12:32
  Speaker 2: something to absolute zero mean that all atomic motion stops? Like,
• 12:37
  Speaker 2: it freezes.
• 12:38
  Speaker 3: Usually, yes.
• 12:38
  Speaker 2: So how does the muonium move through a frozen liquid
• 12:41
  Speaker 2: before its 2.2 microseconds run out? Wouldn't it just get
• 12:45
  Speaker 2: stuck in the ice?
• 12:46
  Speaker 3: That brings us back to the bizarre nature of superfluidity.
• 12:49
  Speaker 3: It doesn't act like a solid block of ice at all.
• 12:52
  Speaker 3: A quantum fluid has zero viscosity.
• 12:55
  Speaker 2: Zero viscosity, meaning like zero friction?
• 12:57
  Speaker 3: Absolutely none.
• 12:59
  Speaker 2: Wow.
• 12:59
  Speaker 3: Yeah, so when the muonium atom is moving through this
• 13:02
  Speaker 3: incredibly cold substance, it experiences zero resistance, doesn't drag, it
• 13:06
  Speaker 3: doesn't get stuck. It can move completely unhindered, gliding perfectly
• 13:11
  Speaker 3: through the fluid so it can escape the surface well
• 13:14
  Speaker 3: before its microscopic lifespan expires.
• 13:17
  Speaker 2: That is mind-blowing. We are literally using a frictionless quantum
• 13:21
  Speaker 2: fluid to shoot artificial exotic atoms out of an atomic cannon.
• 13:25
  Speaker 3: It is science fiction turned into reality.
• 13:28
  Speaker 2: Okay, so now that the Swiss team has successfully fired
• 13:31
  Speaker 2: this cold, orderly atomic beam, how do they actually watch
• 13:35
  Speaker 2: the particle fall? I mean, we are still dealing with
• 13:37
  Speaker 2: something that only exists for a fraction of a fraction
• 13:39
  Speaker 2: of a second. You can't just set up a high-speed camera.
• 13:42
  Speaker 3: No, definitely not. The scale is far too small, and
• 13:44
  Speaker 3: the time is much too short for anything resembling traditional photography.
• 13:48
  Speaker 3: This is where Anna Soder and doctoral student Paul Wegman
• 13:51
  Speaker 3: are implementing cryogenic silicon detectors... and a highly specialized tool
• 13:56
  Speaker 3: called an interferometer.
• 13:58
  Speaker 2: Why do the silicon detectors need to be cryogenic?
• 14:00
  Speaker 3: Because they are trying to measure impossibly tiny signals. If
• 14:04
  Speaker 3: the detector is at room temperature, the atoms inside the
• 14:07
  Speaker 3: silicon are vibrating with thermal heat, which creates a lot
• 14:10
  Speaker 3: of electronic noise.
• 14:11
  Speaker 2: So it drowns out the signal.
• 14:13
  Speaker 3: Right. By freezing the detector, you quiet down all that
• 14:16
  Speaker 3: background vibration so you can actually capture the delicate signal
• 14:20
  Speaker 3: of the muonium.
• 14:21
  Speaker 2: Okay, that makes perfect sense. But what about the interferometer?
• 14:24
  Speaker 2: If we aren't watching the atom as a physical object
• 14:27
  Speaker 2: dropping like an apple, what exactly are we measuring?
• 14:30
  Speaker 3: We are actually measuring the wave properties.
• 14:33
  Speaker 2: Of the atoms. Wait, you're measuring a physical particle by
• 14:36
  Speaker 2: looking at its wave? I thought we were dropping a
• 14:38
  Speaker 2: physical thing with mass.
• 14:40
  Speaker 3: Welcome to wave-particle duality.
• 14:41
  Speaker 2: Oh boy.
• 14:42
  Speaker 3: Yeah, at the quantum level, everything including you, me, and
• 14:45
  Speaker 3: this muonium atom exists as both a physical particle and
• 14:49
  Speaker 3: a wave of probability.
• 14:50
  Speaker 2: Okay.
• 14:51
  Speaker 3: The interferometer takes advantage of this. It takes the beam
• 14:55
  Speaker 3: of muonium atoms and physically splits their path into two
• 14:58
  Speaker 3: separate routes, then recombines them at the end. When the
• 15:01
  Speaker 3: paths recombine, the waves interact with each other, creating an
• 15:05
  Speaker 3: interference pattern.
• 15:06
  Speaker 2: Sort of like throwing two pebbles into a perfectly still
• 15:09
  Speaker 2: pond at the exact same time. You get those expanding
• 15:12
  Speaker 2: rings of ripples. And where the ripples crash into each other,
• 15:15
  Speaker 2: they create a distinct, highly predictable pattern of peaks and valleys.
• 15:20
  Speaker 3: That is a perfect visualization. Yes. Now imagine gravity is
• 15:25
  Speaker 3: pulling downward on those atoms as they travel through those
• 15:28
  Speaker 3: two separated paths inside the interferometer.
• 15:31
  Speaker 2: Right.
• 15:32
  Speaker 3: That microscopic gravitational pull will subtly alter their route. When
• 15:36
  Speaker 3: the waves recombine, that tiny change in their path will
• 15:40
  Speaker 3: cause a measurable shift in the interference pattern of those ripples.
• 15:43
  Speaker 2: But to stick with a pond analogy, measuring a gravitational
• 15:46
  Speaker 2: drop over 2.2 microseconds... That sounds like trying to measure
• 15:51
  Speaker 2: if gravity is slightly tilting the pond itself while you're
• 15:54
  Speaker 2: only allowed to look for the duration of a lightning flash.
• 15:56
  Speaker 3: It is incredibly challenging.
• 15:58
  Speaker 2: Is that actually realistic? It feels like trying to measure
• 16:00
  Speaker 2: the growth of a blade of grass during a single blink.
• 16:03
  Speaker 1: Of an eye.
• 16:03
  Speaker 3: It is phenomenally difficult, and your skepticism is totally warranted.
• 16:08
  Speaker 3: But that extreme sensitivity is exactly why traditional dropping fails.
• 16:12
  Speaker 3: We cannot visually see the particle drop.
• 16:14
  Speaker 2: Right, because it's just too fast.
• 16:16
  Speaker 3: Yes. But an interference pattern is extraordinarily sensitive to even
• 16:20
  Speaker 3: the slightest change in the environment. A tiny shift in
• 16:24
  Speaker 3: gravity causes a massive, easily readable shift in the wave pattern.
• 16:28
  Speaker 2: Oh, I see.
• 16:29
  Speaker 3: Measuring quantum wave interference is literally the only way to
• 16:33
  Speaker 3: catch gravity in the act on this microscopic timescale.
• 16:37
  Speaker 2: It is such a clever workaround.
• 16:39
  Speaker 1: Yeah.
• 16:39
  Speaker 2: And the timeline for this is moving surprisingly fast, right?
• 16:42
  Speaker 2: The team plans to test the atomic beam method this year,
• 16:46
  Speaker 2: in 2026.
• 16:47
  Speaker 3: Yes, and if that goes well, the actual gravity experiment
• 16:50
  Speaker 3: will happen in just two to three years.
• 16:52
  Speaker 2: And it's worth noting that this pristine, cold muonium beam
• 16:56
  Speaker 2: isn't just good for the gravity drop. It will also
• 16:58
  Speaker 2: allow for entirely new laser spectroscopy experiments.
• 17:01
  Speaker 3: Yes, that's a huge bonus.
• 17:03
  Speaker 2: Meaning they can probe the atom with lasers to measure
• 17:05
  Speaker 2: its internal structure.
• 17:06
  Speaker 3: Exactly. Because they now have this highly controlled, slow-moving beam...
• 17:11
  Speaker 3: They can hit it with lasers to precisely measure the
• 17:13
  Speaker 3: mass of the muon and other fundamental physical constants with
• 17:17
  Speaker 3: far greater accuracy than we ever have before.
• 17:20
  Speaker 2: So even before we test gravity, we are getting a
• 17:23
  Speaker 2: high-definition upgrade to our understanding of the standard model.
• 17:26
  Speaker 3: It's a win-win for physics.
• 17:28
  Speaker 2: But let's get back to gravity, because this is where
• 17:30
  Speaker 2: the stakes get astronomically high. All of this incredible multi-million
• 17:35
  Speaker 2: dollar engineering, the particle accelerators, the quantum fluids, the interferometers...
• 17:41
  Speaker 2: It all leads to a binary outcome.
• 17:43
  Speaker 3: It really does.
• 17:43
  Speaker 2: Either the muonium falls at the exact same rate as
• 17:46
  Speaker 2: ordinary matter, or it doesn't.
• 17:48
  Speaker 3: And if it doesn't, I mean, if this exotic Frankenstein
• 17:51
  Speaker 3: atom falls even a fraction of a percent slower or
• 17:54
  Speaker 3: faster than an everyday electron, it would be one of
• 17:57
  Speaker 3: the most significant discoveries in the history of physics. No. Currently,
• 18:01
  Speaker 3: physics accepts four fundamental interactions, gravity, electromagnetism, the strong nuclear force,
• 18:08
  Speaker 3: and the weak nuclear force.
• 18:09
  Speaker 2: And those four forces govern literally everything that happens in
• 18:12
  Speaker 2: the visible universe.
• 18:13
  Speaker 1: Yes.
• 18:14
  Speaker 3: But if gravity acts differently on the second generation of particles,
• 18:17
  Speaker 3: it cannot be explained by our current understanding of those
• 18:20
  Speaker 3: four forces.
• 18:21
  Speaker 2: So what would it mean?
• 18:22
  Speaker 3: It would point directly to the existence of a highly
• 18:25
  Speaker 3: theoretical fifth force of nature.
• 18:27
  Speaker 2: A fifth force. That is wild. But despite this absolutely
• 18:33
  Speaker 2: earth-shattering potential... Anna Soder maintains a remarkably grounded view of
• 18:37
  Speaker 2: the whole thing.
• 18:38
  Speaker 3: She does very much so.
• 18:39
  Speaker 2: She says she isn't setting out to break physics. She
• 18:41
  Speaker 2: just wants to be the first to measure if the
• 18:43
  Speaker 2: equivalence principle applies to these heavier generations. She actually said,
• 18:48
  Speaker 2: you know, this alone is quite an inspiring piece of work.
• 18:51
  Speaker 3: And she's entirely correct to frame it that way.
• 18:54
  Speaker 2: But I have to question her restraint there. Isn't proving
• 18:57
  Speaker 2: a fifth force the holy grail of modern physics? Why
• 19:00
  Speaker 2: would the team downplay that and just focus on making
• 19:02
  Speaker 2: a measurement?
• 19:03
  Speaker 3: Because that is the philosophy of rigorous fundamental science. You
• 19:08
  Speaker 3: don't build an experiment wanting a specific answer.
• 19:11
  Speaker 2: Right. Because of bias.
• 19:12
  Speaker 3: Exactly. If you design an experiment desperately trying to find
• 19:16
  Speaker 3: a fifth force, you risk introducing bias into your methodology.
• 19:20
  Speaker 3: You might subconsciously tweak the data or the sensors to
• 19:23
  Speaker 3: find what you want to find. You build the experiment
• 19:25
  Speaker 3: to find the truth.
• 19:27
  Speaker 2: You just want to set up the apparatus and see
• 19:29
  Speaker 2: what nature actually does when you ask it the right question.
• 19:32
  Speaker 3: Breaking physics is just a spectacular byproduct of doing the
• 19:35
  Speaker 3: math correctly. The goal is an accurate measurement. The implementation
• 19:39
  Speaker 3: is what follows.
• 19:40
  Speaker 2: That makes sense. So what does this all mean for
• 19:42
  Speaker 2: you listening to this right now? Why should you care
• 19:46
  Speaker 2: if a microscopic particle in a Swiss lab falls at
• 19:50
  Speaker 2: bit differently?
• 19:51
  Speaker 3: Well, it affects you more than you'd think.
• 19:53
  Speaker 2: Right. Because your entire modern life relies on the assumption
• 19:57
  Speaker 2: that gravity is a fixed universal constant.
• 20:00
  Speaker 3: Take the GPS satellites your phone uses to navigate your car.
• 20:04
  Speaker 1: Okay.
• 20:04
  Speaker 3: They orbit thousands of miles away from Earth's center of mass,
• 20:08
  Speaker 3: which means they experience slightly weaker gravity than we do
• 20:11
  Speaker 3: on the surface. Because of Einstein's theories of relativity, we
• 20:15
  Speaker 3: know that this difference in gravity actually warps space-time, changing
• 20:18
  Speaker 3: how time flows for those satellites.
• 20:20
  Speaker 2: The clocks on the satellites literally tick at a fundamentally
• 20:23
  Speaker 2: different rate than the clocks inside our phones.
• 20:25
  Speaker 3: And the algorithms in your phone and in the satellites
• 20:28
  Speaker 3: have to constantly calculate and correct for that gravitational time dilation.
• 20:33
  Speaker 2: Or your map app would just be completely wrong.
• 20:36
  Speaker 3: Exactly. Now, if gravity isn't universal, if different types of
• 20:41
  Speaker 3: matter respond to the fabric of space time differently, then
• 20:45
  Speaker 3: our fundamental formulas for how the universe operates are incomplete.
• 20:48
  Speaker 2: So our understanding of how the universe is expanding, how
• 20:51
  Speaker 2: black holes form, how galaxies hold together... It all relies
• 20:56
  Speaker 2: on Einstein's equivalence principle being the ultimate law of the land.
• 21:00
  Speaker 3: It is the load-bearing pillar of modern cosmology.
• 21:03
  Speaker 2: It is absolutely staggering to think about. We've gone from
• 21:07
  Speaker 2: Galileo dropping lead spheres down wooden ramps, just watching them
• 21:10
  Speaker 2: hit the dirt, to firing atomic cannons out of absolutely pure,
• 21:14
  Speaker 2: absolute zero quantum fluids.
• 21:16
  Speaker 3: It's quite the leap.
• 21:17
  Speaker 2: We are orchestrating these unimaginably complex choreographed ballets of exotic particles.
• 21:23
  Speaker 2: just to see if something that lives for two millionths
• 21:25
  Speaker 2: of a second falls the way a guy a hundred
• 21:27
  Speaker 2: years ago predicted it would.
• 21:29
  Speaker 3: It's a testament to human curiosity. We simply cannot leave
• 21:32
  Speaker 3: a stone unturned, especially when that stone belongs to an
• 21:35
  Speaker 3: entirely different generation of matter that we still don't fully understand.
• 21:38
  Speaker 2: And before we wrap up, I want to leave you
• 21:40
  Speaker 2: with one final cascading idea to mull over, something we
• 21:44
  Speaker 2: haven't even touched on yet, but that flows naturally from
• 21:46
  Speaker 2: all this.
• 21:47
  Speaker 3: Oh, there are so many cosmological implications if the equivalence
• 21:51
  Speaker 3: principle breaks.
• 21:53
  Speaker 2: Right. Think about the hunt for dark matter.
• 21:55
  Speaker 3: That's a huge one.
• 21:56
  Speaker 2: For decades, astronomers have been looking out at the galaxies,
• 21:59
  Speaker 2: and they see them spinning way too fast. There isn't
• 22:02
  Speaker 2: enough visible stuff, enough first-generation matter, to create the gravity
• 22:07
  Speaker 2: needed to hold those spinning galaxies together.
• 22:10
  Speaker 3: Right, so we assumed there must be this invisible dark
• 22:13
  Speaker 3: matter providing extra gravity. We assume the heavy mass is there,
• 22:17
  Speaker 3: creating a gravitational pull, but we just can't interact with
• 22:20
  Speaker 3: it visually.
• 22:21
  Speaker 2: But? What if we take everything we just talked about
• 22:24
  Speaker 2: and apply it to the cosmos? What if exotic matter
• 22:28
  Speaker 2: simply doesn't play by the same gravitational rules we experience
• 22:31
  Speaker 2: here on Earth?
• 22:32
  Speaker 3: That changes everything.
• 22:33
  Speaker 2: Right. If gravity acts differently on the heavier second generation
• 22:37
  Speaker 2: of matter, what about the heaviest, most invisible things in
• 22:40
  Speaker 2: the universe?
• 22:41
  Speaker 3: If a fifth force exists, or if gravity behaves wildly
• 22:45
  Speaker 3: differently for non-ordinary matter, it could completely rewrite our cosmological models.
• 22:50
  Speaker 2: Exactly. Maybe the dark matter isn't hiding from us. Maybe
• 22:53
  Speaker 2: the mass isn't missing. Maybe we've just been looking at
• 22:56
  Speaker 2: the cosmos with a localized, first-generation set of rules this
• 23:00
  Speaker 2: entire time.
• 23:01
  Speaker 3: If the equivalence principle breaks in that Swiss laboratory, the
• 23:05
  Speaker 3: lens through which we view the entire universe shatters with it.
• 23:08
  Speaker 3: We would have to rebuild our understanding of reality from
• 23:11
  Speaker 3: the quantum scale all the way up to the galactic scale.
• 23:14
  Speaker 2: Yeah. It all comes back to that apple. Next time
• 23:16
  Speaker 2: you drop something, just watch it fall. It seems so simple,
• 23:19
  Speaker 2: so incredibly predictable. but down at the very bottom of
• 23:22
  Speaker 2: reality in the freezing quantum depths of a laboratory. That
• 23:25
  Speaker 2: simple downward motion might just hold the secret to an
• 23:28
  Speaker 2: entirely new universe.