Speaker 1: Welcome to Bedtime Astronomy. Explore the wonders of the cosmos
Speaker 1: with our soothing Bedtime Astronomie podcast. Each episode offers a
Speaker 1: gentle journey through the stars, planets, and beyond, perfect for
Speaker 1: unwinding after a long day. Let's travel through the mysteries
Speaker 1: of the universe as you drift off into a peaceful
Speaker 1: slumber under the night sky.
Speaker 2: When you close your eyes and picture space exploration, what
Speaker 2: is the very first image that pops into your head?
Speaker 3: Oh, it is definitely something blindingly bright, you know.
Speaker 2: Right, if you are like most of us, it is
Speaker 2: always this extreme illumination. You see those gleaming white space
Speaker 2: suits mm hmm, like the Apollo astronauts bouncing around in
Speaker 2: the harsh, unfiltered glare of the sun.
Speaker 3: Or you picture the gold foil of a lunar lander,
Speaker 3: just you know, catching that intense solar radiation against the
Speaker 3: black sky.
Speaker 2: Exactly. Our entire visual vocabulary for exploring the cosmos is
Speaker 2: defined by extreme almost violent light. I mean light is power.
Speaker 3: Yeah, light is visibility.
Speaker 2: It's how we survive in an environment that is constantly
Speaker 2: trying to kill us.
Speaker 3: It makes complete sense from a biological standpoint and honestly
Speaker 3: from an engineering one too. We rely on the sun
Speaker 3: to charge the batteries on our solar panels. Oh yeah,
Speaker 3: we need bright thruster plumes to visibly confirm trajectory corrections
Speaker 3: in the void. And frankly, we just need the heat
Speaker 3: of that light to keep our instruments from freezing solid.
Speaker 2: Yeah. Our instinct is a human species is basically to
Speaker 2: follow the light. We seek it out and we build
Speaker 2: our entire exploratory architecture around it.
Speaker 3: We do.
Speaker 2: But then you travel to the very bottom of the Moon.
Speaker 2: If you look at the lunar South Pole and you
Speaker 2: hike to the edge of one of these massive ancient
Speaker 2: impact craters, places like Shackleton craters.
Speaker 3: Oh yeah, those are fascinating.
Speaker 2: You look down over the rim and suddenly that light
Speaker 2: is gone completely.
Speaker 3: It really is.
Speaker 2: We are talking about regions of the Moon that have
Speaker 2: literally not seen a single stray photon of direct sunlight
Speaker 2: for billions of years.
Speaker 3: It's incredible to think about.
Speaker 2: It's not just dark in the way a room gets
Speaker 2: dark when you turn off a lamp. It is a permanent, freezing,
Speaker 2: absolute shadow.
Speaker 3: It is the ultimate void. If you were to drop
Speaker 3: down into one of those crators. You are entering an
Speaker 3: environment that is incredibly hostile to the kind of exploratory hardware.
Speaker 2: We usually build because of the cold.
Speaker 3: Yeah, the temperatures plunge to levels that shatter conventional metals.
Speaker 3: There is no solar power to be harvested down there.
Speaker 3: It is, by almost every traditional metric we use in
Speaker 3: aerospace engineering, a totally dead zone.
Speaker 2: And yet here is the wild twist at the heart
Speaker 2: of our conversation today, that horrifying pitch black nothingness. Yeah,
Speaker 2: it turns out to be the absolute perfect environment, arguably
Speaker 2: the most valuable real estate in the entire Solar system
Speaker 2: for humanity's most precise, cutting edge technology.
Speaker 3: It really is a massive paradigm shift.
Speaker 2: We are literally planning to plunge into the darkest, coldest
Speaker 2: abyss imaginable just to build a machine of perfect.
Speaker 3: Light, which is such a profound inversion of how we
Speaker 3: normally operate in space.
Speaker 2: I know.
Speaker 3: And this isn't just some speculative science fiction concept either.
Speaker 3: What we are exploring today is a highly practical, rigorously
Speaker 3: detailed blueprint for the actual future of lunar exploration. Physicists
Speaker 3: have realized that the very things that make these craters
Speaker 3: seem so terrifying and inhospitable, you know, the absolute cold,
Speaker 3: the profound emptiness. Right, those are exactly the conditions required
Speaker 3: to stabilize a piece of quantum technology called an ultrastable laser.
Speaker 3: An ultrastable laser exactly, And by placing this specific instrument
Speaker 3: in this specific dark place, we fundamentally change how we
Speaker 3: navigate through space, how we measure time, and even how
Speaker 3: we listen to the universe itself.
Speaker 2: Okay, I am so ready to get into this. Yeah,
Speaker 2: But if I am sitting here listening to this and
Speaker 2: picturing a perfectly dark, perfectly cold crater, the very first
Speaker 2: thing I think of is a vacuum of space. Sure,
Speaker 2: and we know space is already a vacuum, so I
Speaker 2: had to push back right out of the gate, so
Speaker 2: for it. If the entirety of outer space is already
Speaker 2: this giant empty vacuum, why are physicists so obsessed with
Speaker 2: the extra stillness of these specific lunar craters. What makes
Speaker 2: the vacuum inside a dark hole on the Moon any
Speaker 2: better than the vacuum floating halfway between Earth and Mars.
Speaker 3: Well, we have to define what stillness actually means. When
Speaker 3: we step into the realm of high precision physics, because
Speaker 3: when we casually throw on the word vacuum, we usually
Speaker 3: just mean an environment with no.
Speaker 2: Air, right, like an empty void.
Speaker 3: But the physical world, especially at a microscopic level, is
Speaker 3: incredibly chaotic everywhere, even in the so called vacuum of
Speaker 3: deep space. Space is not perfectly empty, and it is
Speaker 3: certainly not perfectly cold.
Speaker 2: Really.
Speaker 3: No, When a satellite is orbiting the Earth or drifting
Speaker 3: between planets, it is constantly being bombarded.
Speaker 2: Bombarded by what like micro meteorites.
Speaker 3: Sometimes, yeah, but I'm talking about things much smaller and
Speaker 3: much more pervasive. Solar radiation, the solar wind, which is
Speaker 3: basically a stream of charged particles spewed out by the
Speaker 3: sun cosmic rays, and most importantly, fluctuating thermal energy. A
Speaker 3: satellite in space heats up dramatically when it's facing the Sun,
Speaker 3: and then it cools down rapidly when it passes into
Speaker 3: a planetary shadow.
Speaker 2: The temperature swings are wild.
Speaker 3: Exactly, and the materials on that satellite, the aluminum, the titanium,
Speaker 3: the circuitry, they all expand and contract with those temperature swings.
Speaker 3: This creates microvibrations throughout the entire physical structure.
Speaker 2: So even though there's no physical wind blowing against the satellite,
Speaker 2: the fluctuating key to the Sun is basically beating it up.
Speaker 2: On a microscopic level. It's jittering.
Speaker 3: That is a very good way to visualize it. Heat
Speaker 3: is ultimately just atomic motion. It's kinetic energy. If something
Speaker 3: is warm, its constituent atoms are vibrating violently. And if
Speaker 3: you are trying to build an instrument that relies on
Speaker 3: absolute perfect precision measuring things down to the width of
Speaker 3: an atom, even a fraction of a degree of heat
Speaker 3: creates a violent, jittery disruption. Now look at the Moon. Generally,
Speaker 3: the Moon is fantastic for certain types of science because
Speaker 3: it doesn't have the seismic activity of.
Speaker 2: Earth because there are no tectonic plates.
Speaker 3: Exactly, no tectonic plates crashing together. There are no oceans
Speaker 3: pounding against coastlines, no semi trucks driving down the highway
Speaker 3: to create ground noise.
Speaker 2: Yeah, the Earth is super noisy.
Speaker 3: It is. The Moon also lacks an atmosphere, so there
Speaker 3: are no wind or sound waves, which are massive disruptors
Speaker 3: of precision instruments. But the sunlit lunar surface still experiences
Speaker 3: brutal temperature swings.
Speaker 2: Right, It goes from something like two hundred and fifty
Speaker 2: degrees fahrenheit in the direct sunlight down to negative two
Speaker 2: hundred degrees in the lunari yet does a massive thermal
Speaker 2: shock every two.
Speaker 3: Weeks precisely that thermal cycling would completely destroy the alignment
Speaker 3: of an ultra stable laser. But step down into those
Speaker 3: permanently shadowed craters at the South.
Speaker 2: Pole where the sun never shines right.
Speaker 3: Because the sun never crests the rim to hit the
Speaker 3: crater floor, the ambient temperature there rests steadily around fifty
Speaker 3: degrees above absolute zero. That is fifty kelvin.
Speaker 2: Wow, And for context, absolute zero zero kelvin is the
Speaker 2: theoretical limit where all atomic motion essentially stops entirely right.
Speaker 3: Yes, so at fifty kelvin, the random microscopic jitter of
Speaker 3: physical materials is drastically reduced. You are entering a realm
Speaker 3: of thermodynamic stillness that is incredibly difficult and very expensive
Speaker 3: to achieve artificially on Earth.
Speaker 2: I can imagine.
Speaker 3: Furthermore, the vacuum inside these specific craters is actually of
Speaker 3: a higher quality than the general lunar surface.
Speaker 2: Okay, wait, how can a vacuum be of a higher quality.
Speaker 2: It's on the same moon, doesn't the whole Moon share
Speaker 2: the exact same lack of atmosphere.
Speaker 3: It does, but the general lunar surface actually suffers from
Speaker 3: a very faint exosphere.
Speaker 2: Ooh yeah.
Speaker 3: Solar radiation hits the lunar dirt and causes a tiny
Speaker 3: bit of outgassing. It releases trace amounts of helium, ar
Speaker 3: gone and other particles. Plus the solar wind is constantly
Speaker 3: impacting the day side, so it's a.
Speaker 2: Bit dusty and gassy on a microscope level exactly.
Speaker 3: But inside the deep, permanently shadowed craters, the walls physically
Speaker 3: block the solar wind, and because it is so profoundly cold,
Speaker 3: any stray gas molecule that happens to wander into the
Speaker 3: crater instantly freezes solid and sticks to the crater floor.
Speaker 3: Oh wow, it's called a cold trap. So the environment
Speaker 3: inside the crater acts like a natural ultra high vacuum pumpy,
Speaker 3: just continuously scrubbing its own space empty. It effectively eliminates
Speaker 3: any stray acoustic vibrations and drastically reduces the rogue particles
Speaker 3: that could bump into delicate instruments.
Speaker 2: It's almost a paradox. As humans, we usually look for
Speaker 2: warm sennni spots to set up camp because that's what
Speaker 2: keeps our machines running in our bodies from freezing. Right.
Speaker 2: But here the dead zones, the places where absolutely nothing happens,
Speaker 2: where there is no ambient energy, no light, no heat,
Speaker 2: those are the most crucial places to be for this
Speaker 2: specific science. The really are It makes me think about
Speaker 2: how the upcoming Artemis missions are already targeting these exact
Speaker 2: South Pole regions because they contain water ice frozen in
Speaker 2: the shadows. We are heading to the darkest places for
Speaker 2: survival resources, and the physics community is basically saying, hey,
Speaker 2: while you're down there in the dark mining ice, it
Speaker 2: just so happens to be the perfect spot for our
Speaker 2: ultimate precision laser.
Speaker 3: It is the ultimate cosmic coincidence. The conditions required for
Speaker 3: long term human survival, finding ancient ice trapped in these
Speaker 3: cold traps to turn into drinking water and rocket fuel,
Speaker 3: Those are precisely the same conditions required to push the
Speaker 3: boundaries of quantum measurements. The stillness is the currency here
Speaker 3: in physics. If you want to measure a signal with
Speaker 3: unimaginable precision, you have to first silence all the background noise, right,
Speaker 3: and there is literally nowhere quiet or nowhere more still
Speaker 3: than a fifty kelvin shadow that hasn't seen the sun
Speaker 3: since the solar system was young.
Speaker 2: Okay, so we have established this beautifully dead, quiet, freezing environment.
Speaker 2: Let's talk about the actual machine that desperately needs to
Speaker 2: live down there. Yeah, the heart of this entire concept
Speaker 2: is something called an optical silicon cavity. Yes, and I
Speaker 2: want to make sure we really visualize this for everyone listening,
Speaker 2: because the name sounds a bit like, I don't know,
Speaker 2: an abstract math problem. But it is a very tangible
Speaker 2: physical object. It is. It is essentially a block of
Speaker 2: crystalline silicon, and on each end of this block there
Speaker 2: is a mirror. That's the basic anatomy.
Speaker 3: That is the core physical architecture. Just imagine a highly refined,
Speaker 3: beautifully engineered spacer block made of single crystal silicon. It's
Speaker 3: usually quite small, maybe a couple of dozen centimeters.
Speaker 2: Long, so pretty compac very.
Speaker 3: Compact, and bonded to each end of the silicon spacer
Speaker 3: is a highly reflective mirror. But these aren't the kind
Speaker 3: of mirrors you have in your bathroom, I would hope not. Right.
Speaker 3: There are sophisticated, multi layered dielectric coatings designed to reflect
Speaker 3: light with a perfection that borders on the absolute, and.
Speaker 2: The entire purpose of this silicon block is to bounce light.
Speaker 2: You introduce light into the cavity through one of the mirrors,
Speaker 2: and it bounces back and forth endlessly between these two
Speaker 2: perfectly facing mirrored surfaces exactly. But it's not just any light,
Speaker 2: and it doesn't just bounce randomly. The distance between those
Speaker 2: two mirrors dictates exactly which frequencies, basically, which colors of
Speaker 2: light are allowed to exist inside that space.
Speaker 3: That's right.
Speaker 2: If the distance between those mirrors changes by even the
Speaker 2: width of a single atom, the entire system fails. Let's
Speaker 2: talk about why the physical distance is so strictly tied
Speaker 2: to the color of the light.
Speaker 3: Well, it comes down to the fundamental wave nature of
Speaker 3: light and a principle known as resonance. When you shine
Speaker 3: a beam of light into this cavity, the photons bounce
Speaker 3: back and forth between the two mirrors. Because light travels
Speaker 3: as a wave, it has peaks and troughs. Okay, Now
Speaker 3: imagine those waves overlapping as they travel back and forth.
Speaker 3: If the physical distance between the mirrors is an exact,
Speaker 3: perfect multiple of the light's wavelength, the overlapping waves will
Speaker 3: perfectly align.
Speaker 2: So they sort of stack on top of each other exactly.
Speaker 3: Every time a wave bounceounces back, its peak aligns exactly
Speaker 3: with the peak of the next wave coming in. Its
Speaker 3: trough aligns perfectly with the trough. They reinforce each other.
Speaker 3: The amplitude builds up, creating a powerful, highly stable, standing
Speaker 3: wave of light trapped inside the block.
Speaker 2: Now I want to make sure I'm grasping the alternative here.
Speaker 2: What happens if the distance is slightly off. Let's say
Speaker 2: the mirror moves away by a tiny, tiny fraction of
Speaker 2: a millimeter.
Speaker 3: If the distance shifts even slightly, the geometry is broken.
Speaker 3: The wave bounces back, but now it has traveled a
Speaker 3: slightly different distance. When it overlaps with the next incoming wave,
Speaker 3: they are out of sync. A peak of one wave
Speaker 3: will align with the trough of another wave. When a
Speaker 3: peak and a trough meet, they cancel each other out.
Speaker 2: Oh, I see.
Speaker 3: This is called destructive interference. The energy doesn't disappear from
Speaker 3: the universe, of course, but the light wave itself cannot
Speaker 3: sustain its structure inside that specific physical boundary, it scatters
Speaker 3: or is transmitted out and the standing wave collapses.
Speaker 2: Okay, I think I have an analogy for this, but
Speaker 2: correct me if I stray too far. Think about a
Speaker 2: perfectly tuned acoustic instrument. Let's use a guitar. Okay, Sure,
Speaker 2: when you pluck a guitar string, the string is anchored
Speaker 2: at two incredibly fixed points, the nut at the top
Speaker 2: of the neck and the bridge down on the body.
Speaker 2: That physical distance between those two anchor points is completely
Speaker 2: non negotiable. Because of that exact fixed distance, When you
Speaker 2: pluck the string, only one specific pure note let's say
Speaker 2: an A can sustain itself and ring out loudly. All
Speaker 2: the other chaotic vibrations, all the scraping noise of your
Speaker 2: finger hitting the string, quickly die out because those random
Speaker 2: frequencies just don't fit the physical geometry of the string.
Speaker 2: The physical distance ensures the purity of the note that is.
Speaker 3: On the right track, absolutely, but we have to take
Speaker 3: it a step further to truly capture what the optical
Speaker 3: cavity is doing. A guitar string is one dimensional and
Speaker 3: it's vibrating matter. Our cavity is three dimensional, and we
Speaker 3: are dealing with an electromagnetic field photons instead of physical
Speaker 3: strength exactly, But the underlying principle of boundary conditions is identical.
Speaker 3: The distance between the guitar's bridge and the nut is
Speaker 3: the exact equivalent of the distance between our two mirrors.
Speaker 3: The silicon block acts as the neck of the guitar,
Speaker 3: holding the mirrors perfectly rigidly apart.
Speaker 2: Okay, I'm checking.
Speaker 3: The optical cavity acts as the ultimate unforgiving gatekeeper. It
Speaker 3: dictates the physics of the space. It essentially says, only
Speaker 3: light of this exact specific frequency, this exact wavelength is
Speaker 3: allowed to resonate and build power here. Any other frequency
Speaker 3: will destroy itself through interference.
Speaker 2: So if we want to keep our optical guitar perfectly
Speaker 2: in tune, the neck of the guitar, the silicon block
Speaker 2: can never ever bend, warp, expand, or shrink. Never if
Speaker 2: the distance between the mirrors changes by even a fraction
Speaker 2: of an atomic diameter, are perfectly cure color of light shifts,
Speaker 2: the standing wave collapses. It basically goes out of tune.
Speaker 3: And that introduces the terror of thermodynamics that we were
Speaker 3: discussing earlier.
Speaker 2: Oh right, because if he yes.
Speaker 3: In the physical universe, almost everything expands when it gets
Speaker 3: warm and contracts when it gets cold, even a highly
Speaker 3: engineered block of single crystal silicon. If you put this
Speaker 3: silicon cavity on a table in a normal laboratory room
Speaker 3: on Earth, just the microscopic fluctuations in the room's ambient
Speaker 3: air temperature, maybe the air conditioning turns on, or a scientist.
Speaker 2: Walks past, just a person walking past.
Speaker 3: Oh yeah, body heat is more than enough. That would
Speaker 3: cause the silicon block to expand and contract by microscopic amounts.
Speaker 3: The mirrors would constantly be moving closer together and further apart.
Speaker 3: The resonant frequency of the light would drift endlessly. The
Speaker 3: instrument would be completely useless for the kind of extreme
Speaker 3: precision we are chasing.
Speaker 2: Which brings us directly back to our dark, freezing lunar crater.
Speaker 2: We know the Shackleton crator is sitting at a very
Speaker 2: chilly fifty kelvin. That is incredibly cold. It slows down
Speaker 2: a massive amount of that thermal jitter. It does, But
Speaker 2: fifty kelvin is actually not cold enough for the absolute
Speaker 2: perfection we are aiming for here. The physicists need to
Speaker 2: reach a very specific magic number sixteen.
Speaker 3: Kelvin exactly sixteen kelvin.
Speaker 2: Wait, if the ambient environment of the crater floor itself
Speaker 2: is fifty kelvin, how does the machine get colder than
Speaker 2: the dirt it's sitting on. Are we plugging in some giant,
Speaker 2: power hungry cosmic refrigerator down there, because that seems like
Speaker 2: it would defeat the whole purpose of going to a
Speaker 2: dead quiet zone.
Speaker 3: You've hit on one of the most brilliant engineering solutions
Speaker 3: in this entire architecture. It raises a fascinating point about
Speaker 3: how we engineer things for the deep space environment compared
Speaker 3: to how we do it on Earth. Okay, if you
Speaker 3: were sitting in a lab in Colorado or Germany and
Speaker 3: you want to cool a silicon block down to exactly
Speaker 3: sixteen kelvin, you have to build a massive, incredibly complex
Speaker 3: piece of machinery called a cryostat.
Speaker 2: Right. I've seen pictures of those. They look like giant
Speaker 2: metal barrels covered in wires and tubes.
Speaker 3: They are absolute beasts. They require huge amounts of electrical power,
Speaker 3: constant maintenance, and they often rely on circulating liquid helium
Speaker 3: as a coolant. And here is the brutal irony of
Speaker 3: the whole setup. What's that the machinery itself, the pumps,
Speaker 3: the compressors, pushing the liquid helium around creates severe mechanical vibration.
Speaker 3: Of course, so you cool the silicon down to stop
Speaker 3: thermal jitter. But in doing so you introduce mechanical shaking
Speaker 3: from the refrigerator. You then have to build elaborate actively
Speaker 3: controlled isolation tables just to float the cavity and protect
Speaker 3: it from the very machine that is cooling it. It
Speaker 3: is an engineering nightmare of cascading complexities.
Speaker 2: That sounds exhausting it is.
Speaker 3: But on the Moon, inside this permanently shadowed crater, we
Speaker 3: don't need active machinery. We don't need liquid helium pumps.
Speaker 3: We can use the geometry of the universe passively.
Speaker 2: So no power cords, no liquid coolants vibrating the table, just.
Speaker 3: Physics, just physics.
Speaker 2: How exactly do we get it from fifty down to
Speaker 2: sixteen without a.
Speaker 3: Refrigerator by utilizing radiative cooling, specifically through deployable radiation panels.
Speaker 3: The housing of the optical cavity is equipped with thermal
Speaker 3: panels that literally unfold once the rover places the instrument
Speaker 3: on the crater floor. And what these panels do is
Speaker 3: they look up up. Yes, they point away from the
Speaker 3: fifty kelvin lunar dirt, and they look directly out into
Speaker 3: the infinite deep abyss of outer space.
Speaker 2: And space is colder than the greater.
Speaker 3: Vastly colder. Deep space has a background temperature of about
Speaker 3: two point seven kelvin. That is the cosmic microwave background,
Speaker 3: the fading residual radiation left over from the Big Bang itself.
Speaker 2: Wow.
Speaker 3: Now, the laws of thermo dynamics dictate that heat naturally
Speaker 3: flows from warmer objects to colder objects through the Steffon
Speaker 3: Boltzmann law. An object will radiate its thermal energy away
Speaker 3: as infrared light. Because the panels are looking at a
Speaker 3: two point seven kelvin sky, the residual heat inside the
Speaker 3: fifty kelvin silicon block travels up to the panels and
Speaker 3: is radiated away, lost forever into the infinite heat sink
Speaker 3: of the universe.
Speaker 2: That is, honestly mind bending. The machine cools itself simply
Speaker 2: by exposing its heat to the infinite cold of deep space.
Speaker 2: It's like opening a window in winter to cool down
Speaker 2: a hot room. But the window opens into the cosmic void.
Speaker 3: That's a great analogy.
Speaker 2: But wait, if it's looking at a two point seven
Speaker 2: kelvin's guy, why isn't just keep cooling down until it
Speaker 2: hits two point seven kelvin? Why does it stop at sixteen?
Speaker 3: Well, that is where the careful thermal engineering comes in.
Speaker 3: The silicon block isn't just floating in space. It is
Speaker 3: still physically near the fifty kelvin lunar surface. Even with
Speaker 3: heavy thermal shielding around the bottom and sides of the instrument,
Speaker 3: A tiny amount of heat from the lunar dirt will
Speaker 3: slowly conduct or radiate into the device, So.
Speaker 2: It's leaking a tiny bit of heat in from.
Speaker 3: The ground exactly. So the engineers design the surface area
Speaker 3: of the radiation panels very precisely. The panels dump heat
Speaker 3: into space at a specific rate, while the shielding allows
Speaker 3: a microscopic trickle of heat in from the ground. When
Speaker 3: those two rates perfectly balance each other out, the system
Speaker 3: reaches thermal equilibrium.
Speaker 2: I see.
Speaker 3: By designing the panels correctly, they can ensure that this
Speaker 3: equilibrium point lands exactly at sixteen kelvin. It is a natural,
Speaker 3: free vibration free cryogenic freezer.
Speaker 2: Okay, I understand how we get to sixteen calvin now,
Speaker 2: but why sixteen kelvin? Specifically, why go through all the
Speaker 2: trouble of unfolding panels and balancing heat laws. Why not
Speaker 2: just balance it at twenty kelvin or try to push
Speaker 2: it down.
Speaker 3: To ten, Because at exactly sixteen kelvin, crystalline silicon exhibits
Speaker 3: a miraculous, counterintuitive physical property. Its coefficient of thermal expansion
Speaker 3: crosses zero.
Speaker 2: Let's pause and make sure we totally grasp that. You're
Speaker 2: saying it's coefficient of thermal expansion basically the rate at
Speaker 2: which it changes size when the temperature changes becomes zero. Yes,
Speaker 2: but earlier we said everything shrinks when it gets colder
Speaker 2: and expands when it gets warmer. Are you saying silicon
Speaker 2: just stop shrinking at sixteen kelvin? Why would a physical
Speaker 2: material just decide to stop obeying that rule.
Speaker 3: It doesn't stop obeying the rules. It's just a matter
Speaker 3: of two different quantum effects perfectly canceling each other out.
Speaker 2: Oh quantum effects.
Speaker 3: Okay, it gets a bit deep into solid state physics,
Speaker 3: but essentially, the atoms in a silicon crystal are bound
Speaker 3: together in a lattice as you cool it down. The
Speaker 3: primary effect is that the atoms vibrate less, so they
Speaker 3: settle closer together and the material.
Speaker 2: Shrinks right the normal shrinking.
Speaker 3: However, at very low temperatures, you also have to consider
Speaker 3: the specific shape of the energetic bonds between the atoms
Speaker 3: and the behavior of phonons. Phonons are quantized tackets of
Speaker 3: vibrational energy in silicon. Below about one hundred and twenty kelvin,
Speaker 3: certain low energy phonons actually cause the lattice to pull inward.
Speaker 3: As you keep dropping the temperature, the dynamics between the
Speaker 3: standard thermal contraction and these specific phonon interactions shift right
Speaker 3: At exactly sixteen kelvin, the tendency of the material to
Speaker 3: expand due to one effect is perfectly exactly matched by
Speaker 3: its tendency to contract due to the other.
Speaker 2: So it's a thermodynamic tug of war, and at exactly
Speaker 2: sixteen kelvin, it's a dead tie exactly.
Speaker 3: The atomic lattice of the silicon reaches a perfect equilibrium.
Speaker 3: What this means in practice is that right at that
Speaker 3: specific temperature, if the silicon experience is a tiny microscopic
Speaker 3: fluctuation and heat, let's say a micrometeorite hits a rock
Speaker 3: a mile away, and a microscopic pulse of infrared energy
Speaker 3: washes over the crater, warming the silicon by a thousandth
Speaker 3: of a degree. The silicon neither expands nor contracts. It
Speaker 3: becomes thermally immune. It freezes perfectly in place.
Speaker 2: That is the magic trick. So at sixteen kelvin, the
Speaker 2: distance between our two mirrors becomes essentially locked in. Stone
Speaker 2: is physically incapable of changing, even at the temperature wabbles slightly.
Speaker 2: Is the perfect unmoving, indestructible guitar neck.
Speaker 3: Yes. And because we are sitting in a crater with
Speaker 3: no wind to buffet the casing, no seismic shaking from
Speaker 3: the ground, no sunlight to create massive thermal shocks, and
Speaker 3: we are passively cool to the exact temperature where the
Speaker 3: material physically cannot expand or contract, we have finally achieved
Speaker 3: the geometry of absolute stillness. Wow, the space trap between
Speaker 3: those mirrors is now experiencing a perfectly stable physical reality. Right.
Speaker 2: This is a huge milestone in our discussion. We have
Speaker 2: built this incredibly stable box, this sixteen kelvin silicon cavity,
Speaker 2: sitting in the dark maintaining this perfect distance between two mirrors.
Speaker 2: But a box with mirrors doesn't do anything on its own, No,
Speaker 2: it doesn't. It's just an empty cold stage. Now we
Speaker 2: have to actually introduce the light, and this is where
Speaker 2: we get to the concept of the laser lock.
Speaker 3: Precisely, the silicon cavity itself isn't generating any light. It
Speaker 3: is just a filter. We have to bring a laser
Speaker 3: source with us.
Speaker 2: The plan is to take a commercially available laser, something
Speaker 2: high end but fundamentally something you can theoretically build on Earth,
Speaker 2: and place it nearby. Maybe the laser sits right on
Speaker 2: the rim of the crater where it can catch some
Speaker 2: sunlight to power its electronics, or maybe it sits down
Speaker 2: inside the crater next to the cavity, powered by a cable.
Speaker 2: Either way, this commercial laser fires a beam, and a
Speaker 2: small amount of that light is directed down a fiber
Speaker 2: optic cable and inject it into our ultra cold, perfectly
Speaker 2: still optical cavity. And the cavity does something profound to
Speaker 2: the laser. It locks it.
Speaker 3: It does.
Speaker 2: Let's break down what a laser lock actually is.
Speaker 3: To understand the lock, we first have to understand the
Speaker 3: inherent flaw in standard lasers. If you take a standard
Speaker 3: commercial laser, even a very expensive one used in a laboratory,
Speaker 3: and you turn it on to the human eye, it
Speaker 3: seems like a perfectly steady beam.
Speaker 2: Of light, right. It just looks like a solid beam.
Speaker 3: Yeah, But if you measure it with enough precision, you'll
Speaker 3: see that the frequency, the exact specific color of that
Speaker 3: light is constantly wandering.
Speaker 2: Why does it wander? Shouldn't a laser just emit one color.
Speaker 3: In a perfect theoretical world. Yes, But a real laser
Speaker 3: relies on physical components. It has internal diodes that get hot,
Speaker 3: It has a power supply that might have microfluctuations in current.
Speaker 3: The internal cavity of the laser itself vibrates slightly.
Speaker 2: So it's a victim to all those physical imperfections we
Speaker 2: talked about.
Speaker 3: Exactly. All of these physical imperfections cause the frequency of
Speaker 3: the emitted light to drift over time. It wanders around
Speaker 3: the target frequency. In physics, we refer to this as
Speaker 3: a wild or free running laser. It is a relatively
Speaker 3: broad line with meaning the color is smearing out slightly.
Speaker 2: I'm going to try another analogy here. Let's picture that
Speaker 2: commercial layer as a wild, incredibly fast horse. It has
Speaker 2: a ton of energy. It's powerful. But if you put
Speaker 2: it in an open field until it to run straight
Speaker 2: at exactly thirty miles per hour, it's gonna fail. It's
Speaker 2: going to run a little to the left, a little
Speaker 2: to the right, it'll be up to thirty one. It'll
Speaker 2: slid out of twenty nine. It's totally unpredictable. Sure, the
Speaker 2: optical silicon cavity is like a perfectly sized, inescapable, walled
Speaker 2: in circular track. You take that wild horse and you
Speaker 2: force it onto the track, and suddenly, because the track
Speaker 2: never changes size or shape, the horse is forced to
Speaker 2: run at one exact, unwavering speed in a perfect circle.
Speaker 2: It has no choice but to conform to the physical
Speaker 2: constraints of the track.
Speaker 3: I like the imagery, but let's refine it a bit
Speaker 3: to capture the actual mechanism of the lock. Because the
Speaker 3: cavity isn't just a passive physical barrier the light bumps
Speaker 3: into Oh it's not no, it's an active electronic feedback loop.
Speaker 3: It's more like putting a monitor on the horse that
Speaker 3: actively shocks it if it speeds up or slows down.
Speaker 2: Oh wow, Okay.
Speaker 3: Here is how the lock often achieve using a method
Speaker 3: called the Pound driver Hall technique actually functions. The Wild
Speaker 3: laser sends its light into the sixteen Calvin cavity. Remember,
Speaker 3: because of its absolute stillness, the cavity only allows one exact,
Speaker 3: ultra precise frequency to resonate and build up a standing wave.
Speaker 3: The system has a photodetector, a highly sensitive light sensor
Speaker 3: measuring the light that bounces off or escrips the cavity.
Speaker 3: If the Wild laser drifts even a billionth of a
Speaker 3: percentage point away from that exact resonant frequency, the light
Speaker 3: will suddenly stop resonating perfectly inside the silicon block.
Speaker 2: It goes out a tune and the way starts to
Speaker 2: collapse exactly.
Speaker 3: The photo detector instantly sees this drop in resonance. It
Speaker 3: generates an error signal. That error signal is fed into
Speaker 3: a PID controller, which is an electronic processor which calculates
Speaker 3: exactly how far the laser drifted. The control then fires
Speaker 3: a lightning fast electronic signal back up the cable to
Speaker 3: the wild commercial laser. It tells the laser's internal components,
Speaker 3: usually by adjusting the current or physically tweaking a tiny
Speaker 3: piezo crystal on the laser's own internal mirror. You are
Speaker 3: drifting too high. Lower your frequency immediately.
Speaker 2: Oh So, the cavity and the laser are constantly talking.
Speaker 3: To each continuously, billions of times a second. It is
Speaker 3: a relentless aggressive feedback loop. The perfectly still cavity acts
Speaker 3: as the ultimate unforgiving reference point. It disciplines the commercial laser,
Speaker 3: instantly correcting its natural tendency.
Speaker 2: To wander LUs wild.
Speaker 3: Through this constant, high speed electronic correction, the laser is
Speaker 3: forced to emit a single, unwavering color. The frequency of
Speaker 3: the light becomes a permanent, unmoving constant anchored to the
Speaker 3: physical perfection of the sixteen kelvin silicon block.
Speaker 2: That is honestly beautiful. Let's just summarize what we've achieved
Speaker 2: so far. We have taken the absolute chaos and noise
Speaker 2: of the physical world. We stripped it away by hiding
Speaker 2: in a dark fifty kelvin lunar crater where the sun
Speaker 2: never shines and the vacuum is deep. We cooled a
Speaker 2: block of crystalline silicon to exactly sixteen kelvin, so it
Speaker 2: freezes its physical dimensions perfectly, making it totally immune to
Speaker 2: thermal expansion, and then we use that frozen physical distance
Speaker 2: to electronically discipline a wild laser into giving us a perfect,
Speaker 2: unchanging beam of light.
Speaker 3: That's the sequence.
Speaker 2: It is an absolute triumph of physics and engineering. But
Speaker 2: here's the massive pivot.
Speaker 3: Why do we care yes, the so what of the
Speaker 3: entire endeavor?
Speaker 2: Exactly because I'm assuming space agencies aren't going to spend
Speaker 2: billions of dollars in risk landing a rover in a
Speaker 2: pitch black lunar trench just to prove we can make
Speaker 2: a really steady beam of light. Now that we possess
Speaker 2: a laser with an unwavering frequency, how does this purely
Speaker 2: physical achievement transform into the tools we actually need for
Speaker 2: space exploration, specifically timekeeping and navigation. How does a steady
Speaker 2: beam of light become a clock?
Speaker 3: Well, this is where we have to explore the profound
Speaker 3: fundamental between light frequency and time. When we ask what
Speaker 3: is a clock, we are really asking what is the
Speaker 3: most reliable repeating physical event we can count?
Speaker 2: Okay, counting events right?
Speaker 3: If you want to measure the passage of time, you
Speaker 3: need something that ticks. A grandfather clock counts the mechanical
Speaker 3: swings of a pendulum. One swing equals one second. A
Speaker 3: quartz watch like the one you might wear on your wrist,
Speaker 3: counts the physical vibrations of a tiny tuning fork made
Speaker 3: of quartz crystal when electricity runs through. It makes sense,
Speaker 3: but pendulums are affected by variations in gravity and air resistance.
Speaker 3: Quartz crystals expand and contract with the temperature of your wrists.
Speaker 2: They drift just like the wild laser. The ticks aren't
Speaker 2: perfectly uniform.
Speaker 3: Precisely, if your ticks aren't uniform, your clock loses or
Speaker 3: gains time. So to make the ultimate clock, you need
Speaker 3: a pendulum that swings incredibly fast, so you can slice
Speaker 3: time into infinitesimally small pieces. And it must never ever
Speaker 3: change its pace.
Speaker 2: And this is where light comes in.
Speaker 3: This is where light comes in. Light isn't a electromagnetic wave.
Speaker 3: It has peaks and troughs. The frequency of light is
Speaker 3: simply a measurement of how many of those wave peaks
Speaker 3: pass a given point in one single second.
Speaker 2: Okay, I'm tracking with you now.
Speaker 3: A laser that is locked to our sixteen kelvin optical
Speaker 3: cavity is emitting a light wave that oscillates at an
Speaker 3: incredibly high frequency. We are talking on the order of
Speaker 3: hundreds of terahertz, hundreds of trillions of oscillations per second.
Speaker 3: That's a lot of ticks, it is, and because the
Speaker 3: silken cavity is perfectly stable, the frequency of that light
Speaker 3: never changes. Every single oscillation, every single peak of that
Speaker 3: wave is an absolutely perfect, unvarying tick. By building electronics
Speaker 3: that can literally count the peaks of this perfect LightWave
Speaker 3: as they fly past, we are essentially reading the most
Speaker 3: precise ticking clock imaginable. An unchanging optical frequency.
Speaker 2: Is a clock. So instead of counting one swing of
Speaker 2: a brass penilum per second, we're counting roughly four hundred
Speaker 2: trillion swings of a LightWave per second. Exactly because because
Speaker 2: those swings never speed up or slow down thanks to
Speaker 2: the frozen silicon, we know exactly how much time has passed.
Speaker 2: The laser itself acts as a master time signal, and
Speaker 2: this setup would essentially form the backbone of the first
Speaker 2: extraterrestrial optical atomic clock.
Speaker 3: That is the goal. And to understand how big of
Speaker 3: a deal that is, you have to realize that this
Speaker 3: lunar optical clock would rival the most precise, meticulously built
Speaker 3: atomic clocks we currently have sitting in massive climate controlled
Speaker 3: labratories on Earth. We are essentially taking the absolute peak
Speaker 3: of human time keeping capability, compressing it into a small package,
Speaker 3: and permanently installing it on the lunar surface.
Speaker 2: And we desperately need it up there, because if humanity
Speaker 2: is going to have a permanent or even a semi
Speaker 2: permanent presence on the Moon with base camps and rovers,
Speaker 2: time is infrastructure right now. If a spacecraft goes to
Speaker 2: a moon, how does it know what time it is
Speaker 2: and how does it navigate? It has to rely on
Speaker 2: the deep space network, right It relies on time signals
Speaker 2: and navigation data beamed all the way from Earth, which is.
Speaker 3: A massive bottleneck. Space is vast and the speed of
Speaker 3: light is finite. Radio signals take time to travel from
Speaker 3: Earth to the Moon roughly one point three seconds each way.
Speaker 3: By the time a navigation signal reaches a spacecraft entering
Speaker 3: a complex lunar orbit, the data is already slightly old,
Speaker 3: the spacecraft has moved. Furthermore, the deep space network antennas
Speaker 3: on Earth are overbooked. They are trying to talk to
Speaker 3: Mars rovers, Jupiter probes and solar orbiters all at once.
Speaker 3: You cannot run a busy populated lunar outpost if your
Speaker 3: entire navigation and timing system relies on a delayed ping
Speaker 3: from a busy antenna on.
Speaker 2: Earth, which brings us to the whole concept of an
Speaker 2: extraterrestrial GPS. Let's ground this. When you use GPS on
Speaker 2: Earth to drive your car to a coffee shop, your
Speaker 2: phone doesn't just magically know where it is. It is
Speaker 2: communicating with a network of satellites orbiting the Earth, and
Speaker 2: the way GPF actually works is entirely based on time.
Speaker 3: Completely. Every single GPS satellite has an atomic clock on
Speaker 3: board the satellite broadcaster radio signal that basically says, I
Speaker 3: am satellite number four, and exactly when I sent this message,
Speaker 3: my clock read twelve point zero zero zero zero point
Speaker 3: zero zero zero. Your phone receives that signal, your phone
Speaker 3: compares the time the signal was sent to the time
Speaker 3: your phone received it. Because radio waves travel at the
Speaker 3: speed of light, which is a known constant, your phone
Speaker 3: can calculate exactly how far away that satellite is based
Speaker 3: on how long the signal took to arrive.
Speaker 2: The time of flight, Yes.
Speaker 3: Time of flight and if your phone receives those signals
Speaker 3: from four different satellites at the same time, it uses
Speaker 3: geometry trilateration to intersect those distances and pinpoint your exact
Speaker 3: location on the globe down to a few meters. But
Speaker 3: here is the catch. You cannot have accurate navigation without
Speaker 3: absolutely perfect time keeping. Light travels at roughly one foot
Speaker 3: per nanar second. If the clock on a GPS satellite
Speaker 3: drifts by even a single microsecond, just one millionth of
Speaker 3: a second, your phone's calculation will be off by nearly
Speaker 3: one thousand feet. Your map will tell you that you
Speaker 3: are driving into a river.
Speaker 2: That would be a problem. Now take that exact problem
Speaker 2: and put it on the Moon. Imagine you are piloting
Speaker 2: a spacecraft. You are attempting to land near the lunar
Speaker 2: South Pole to access that water ice we talked about earlier.
Speaker 2: You were aiming for a tiny landing zone surrounded by treacherous,
Speaker 2: jagged mountains, and because the sun angle of the pole
Speaker 2: is so low, kind of skimming the horizon, half the
Speaker 2: landscape is completely shrouded in deep, permanent pitch black shadows.
Speaker 2: It is incredibly difficult to see where you are going.
Speaker 2: The illumination contrast is just terrible.
Speaker 3: It is arguably the most hazardous lighting environment in the
Speaker 3: Solar System for a pilot or a landing computer. You
Speaker 3: cannot just eyeball the landing out the window without a
Speaker 3: perfect local navigation system. Landing spacecraft in those regions is
Speaker 3: incredibly dangerous. It's a game of blind luck.
Speaker 2: But if you have this ultra stable laser, this optical
Speaker 2: clock sitting in the Shackleton Crater below, broadcasting a master
Speaker 2: time signal to a small constellation of lunar orbiters, yeah,
Speaker 2: you instantly have a high precision local lunar GPS.
Speaker 3: Precisely The incoming spacecraft can read those time signals, calculate
Speaker 3: its exact distance from the surface and the surrounding mountains
Speaker 3: down to the millimeter, and navigate a precise, safe choreography
Speaker 3: directly into the landing zone, completely independent of Earth. The
Speaker 3: laser hidden in the dark essentially illuminates the invisible navigational
Speaker 3: path for the spacecraft in the sky.
Speaker 2: It's incredible. Whoever establishes a reliable, independent timescale on the
Speaker 2: Moon essentially dictates the infrastructure for all future human exploration
Speaker 2: in the Solar System, where building the roads, the traffic
Speaker 2: lights and the maps of the lunar surface, and they
Speaker 2: are made entirely of perfectly timed light. Every probe, every rover,
Speaker 2: every astronaut will synchronize their operations to the rhythm of
Speaker 2: that sixteen kelvin block of silicon.
Speaker 3: It becomes the heartbeat of the lunar economy. But it
Speaker 3: doesn't stop at logistics and navigation.
Speaker 2: And this is where my mind truly gets blown, because
Speaker 2: as much as I love the idea of lunar GPS
Speaker 2: saving spacecraft from crashing into mountains, the physicists proposing this
Speaker 2: architecture didn't stop there. No, they didn't. They realized that
Speaker 2: once you have a laser that perfectly stable, a clock
Speaker 2: that precise, it doesn't just broadcast time for ships. It listens.
Speaker 2: It becomes a tool to measure the universe itself. The
Speaker 2: plan suggests that if astronauts install a network of these lasers.
Speaker 2: Let's say we put multiple optical cavities in different craters
Speaker 2: across the lunar surface, they could measure the exact physical
Speaker 2: distances between those craters with extreme precision. Right, and this
Speaker 2: precision is so ridiculously high it could act as a
Speaker 2: planetary scale detector. For exotic physics, specifically gravitational waves.
Speaker 3: This is where we cross from complex engineering into fundamental astrophysics.
Speaker 3: A gravitational wave is one of the most violent massive
Speaker 3: events in the cosmos, yet its effect on us is
Speaker 3: incredibly subtle, making it fiendishly difficult to detect. When two
Speaker 3: super massive black holes collide billions of light years away,
Speaker 3: the sheer force of that collision doesn't just create an
Speaker 3: explosion of light or matter. The mass involved is so
Speaker 3: huge and moving so fast that it literally ripples the
Speaker 3: fabric of space time itself.
Speaker 2: We always hear that phrase in sci fi and documentaries,
Speaker 2: the fabric of space time. I want to try and
Speaker 2: visualize this for everyone. Usually, when we think of a wave,
Speaker 2: we think of a wave moving through space, like a
Speaker 2: sound wave moving through the air or water wave moving
Speaker 2: across the surface of a pond. The air and the
Speaker 2: water are the mediums that carry the energy.
Speaker 3: That's the classic visualization.
Speaker 2: But a gravitational wave is not a wave moving through space.
Speaker 2: It is a wave of space.
Speaker 3: That is the crucial mind bending distinction. Space itself is
Speaker 3: the medium. The distance between objects physically changes not because
Speaker 3: the objects are moving, but because the space between them
Speaker 3: is warping.
Speaker 2: Okay, so picture that pond again. If space is the
Speaker 2: water of the pond, and two black holes crash together,
Speaker 2: it's like dropping a massive boulder into the pond. A
Speaker 2: ripple moves outward in all directions at the speed of light.
Speaker 2: When that ripple, that gravitational wave eventually washes over our
Speaker 2: solar system, washes over the Earth, or washes over the Moon.
Speaker 2: What physically happens to the Moon.
Speaker 3: The Moon literally squishes and stretches.
Speaker 2: You mean the solid rock of the moon.
Speaker 3: The solid rock, the dust, the craters, the core. Everything.
Speaker 3: As the wave passes through the three dimensional volume metric
Speaker 3: space that the Moon occupies is temporarily distorted. It stretches
Speaker 3: along one axis and compresses along another, and then oscillates back.
Speaker 2: It's hard to wrap my head around it is.
Speaker 3: If you had two points on the Moon, say two
Speaker 3: craters separated by exactly one hundred kilometers, As the gravitational
Speaker 3: wave washes over them, the physical distance between those two
Speaker 3: craters will increase slightly and then decrease slightly. We are
Speaker 3: talking about a change in distance that is infinitesimally small.
Speaker 3: It might be a shift smaller than the width of
Speaker 3: a single atomic nucleus.
Speaker 2: And normally you would never ever notice that if my
Speaker 2: car suddenly stretched by the width of an atom and
Speaker 2: then went back to normal, I wouldn't feel it. A
Speaker 2: normal telescope couldn't see it, A normal wild laser couldn't
Speaker 2: measure it exactly because, if I understand correctly, if you
Speaker 2: try to use a normal laser as a ruler to
Speaker 2: measure the distance between those craters, the frequency of the
Speaker 2: wild laser drifts so much that the rule you're using
Speaker 2: is vibrating more than the distance is actually changing. You've
Speaker 2: got it.
Speaker 3: The intrinsic noise and thermal drift of a normal laser
Speaker 3: completely drowns out the incredibly faint signal of a gravitational wave.
Speaker 3: You are basically trying to hear a pin drop at
Speaker 3: a rock concert. This is why we build massive billion
Speaker 3: dollar facilities on Earth like LIGO.
Speaker 2: Oh right, the Laser Interferometer Gravitational Wave Observatory.
Speaker 3: Yes, Ligo uses giant four kilometer long vacuum tubes and
Speaker 3: massive suspended mirrors to try and isolate their lasers from
Speaker 3: Earth's noise to measure these waves. But Earth is noisy.
Speaker 3: Trucks drive by the ocean crashes against the shore miles away.
Speaker 3: There are micro earthquakes. It requires herculean engineering to filter
Speaker 3: all that out.
Speaker 2: But the Moon is a dead rock, and our lunar
Speaker 2: laser are perfectly disciplined beam of light tied to that
Speaker 2: sixteen kelvin silicon block in the dark, it is almost
Speaker 2: zero noise. Its frequency is.
Speaker 3: Absolute right, So we set up an interferometry experiment on
Speaker 3: the Moon. You point this ultra stable laser from one
Speaker 3: crater station to another crater station. You measure the distance
Speaker 3: using that perfect light. Because the frequency is so incredibly stable,
Speaker 3: if a gravitational wave passes by and the Moon squishes
Speaker 3: by a fraction of an atom, the laser beam will
Speaker 3: detect it.
Speaker 2: How does it actually detect it mechanically.
Speaker 3: Well, the perfectly stable light will suddenly take a tiny
Speaker 3: fraction of a fraction of a nanosecond longer to reach
Speaker 3: the target crater because the target physically moved away as
Speaker 3: space stretched.
Speaker 2: Oh, because the distance change.
Speaker 3: Exactly, the phase of the light wave shifts. By comparing
Speaker 3: the phase of the scent light with the received light,
Speaker 3: we can measure that subatomic movement.
Speaker 2: We have accidentally built the ultimate physics laboratory, A piece
Speaker 2: of technology, initially designed to give us GPS coordinates for
Speaker 2: an ice mining rover, doubles as a giant planetary scale
Speaker 2: antenna for the most massive cosmic of in the universe.
Speaker 2: We can literally sit in a dark, freezing hole in
Speaker 2: the lunar dirt and feel the microscopic ripples of supermassive
Speaker 2: black holes colliding at the edge of the observable universe.
Speaker 3: It is the beauty of pushing fundamental limits. When you
Speaker 3: push technology to the absolute physical limit of stability, it
Speaker 3: naturally becomes a window into the subtle underlying mechanics of
Speaker 3: the universe. By silencing the noise of thimer dynamics, by
Speaker 3: hiding from the heat of the sun, we allow ourselves
Speaker 3: to hear the quietest, most elusive whispers of gravity.
Speaker 2: That is profound. Yeah, but as much as we are
Speaker 2: sitting here talking about perfect physics, zero expansion coefficients and
Speaker 2: deep space mysteries, someone actually has to build this thing.
Speaker 2: The logistics of turning this from a mathematical theory into
Speaker 2: a real object sitting in a lunar crater are staggering.
Speaker 2: Physicist Junie, who is an absolute legend in the world
Speaker 2: of lasers and precision measurements. Apparently initially view this as
Speaker 2: a crazy.
Speaker 3: Idea, and you can completely understand his initial skepticism. Think
Speaker 3: about the reality of what is being proposed. You were
Speaker 3: taking the most delicate, vibration sensitive instrument known to modern science,
Speaker 3: something that normally sits on massive air floated optical tables
Speaker 3: in climate controlled underground bunkers on Earth, and you want
Speaker 3: to strap it to a rocket. You want to blast
Speaker 3: it into space, surviving the violent acoustic shaking and g
Speaker 3: forces of launch, you fly it to the Moon, and
Speaker 3: then you somehow drop it into a pitch black abyss
Speaker 3: without breaking it. It sounds assurd, It.
Speaker 2: Sounds like a recipe for a very expensive pile of
Speaker 2: shattered silicon.
Speaker 3: But then physicists started consulting with colleagues who actually study
Speaker 3: the lunar surface, looking at the actual empirical data of
Speaker 3: those permanently shadowed regions, and the narrative completely flipped. So
Speaker 3: they realized that the exact ingredients needed for the silicon
Speaker 3: cavity to function, the extreme vibration isolation, the ultra high vacuum,
Speaker 3: the cryogenic temperatures, they were naturally freely available down there.
Speaker 3: The crazy idea wasn't crazy because the environment was hostile
Speaker 3: of the machine. The idea was brilliant because because the
Speaker 3: environment was perfectly naturally tailored for it.
Speaker 2: And the saving grace is the size. Right, the device
Speaker 2: itself isn't massive. The core silicon optical cavity and its
Speaker 2: housing are small enough to easily fit inside a standard
Speaker 2: lunar spacecraft or commercial lunar lander. It doesn't require a massive,
Speaker 2: dedicated heavy lift rocket just for itself. It can piggyback
Speaker 2: as a secondary payload. The complex part is that it
Speaker 2: must be fully assembled, perfectly aligned, and calibrated here on
Speaker 2: Earth before launch.
Speaker 3: Which leads directly to the deployment challenge. On the lunar surface.
Speaker 3: You have this fully assembled microscopic precision instrument, you successfully
Speaker 3: land your spacecraft somewhere on the rim near the south Pole.
Speaker 3: Now you have to actually get it into the shadow.
Speaker 3: This final step is incredibly challenging, primarily because of the
Speaker 3: lighting conditions.
Speaker 2: Right, as we said, the lighting is terrible. It's deep shadow,
Speaker 2: and we can't exactly send an astronaut on a hike
Speaker 2: down into a pitch black crater carrying a priceless physics experiment.
Speaker 2: The terrain is unknown, the regulith is loose, and if
Speaker 2: their spacesuit heating system fails in fifty kelvin, they die exactly.
Speaker 3: Human deployment into the deep crater is out of the
Speaker 3: question for now. The operational plan involves a specialized lunar rover.
Speaker 3: This rover could be remotely controlled from Earth, though you
Speaker 3: have to deal with that one point three second communication lag,
Speaker 3: or mechanically controlled by astronaut sitting safely in a habitat
Speaker 3: on the sunlit rim. The rover carefully picks up the instrument,
Speaker 3: drives it to the edge, and slowly navigates down the
Speaker 3: crater wall into the darkness.
Speaker 2: What are the biggest hazards for the rover on that drive?
Speaker 2: I mean, besides just.
Speaker 3: Falling, aside from driving into an unseen ditch, the two
Speaker 3: biggest enemies are power and dust. Without sunlight, the rover
Speaker 3: can't use solar panels. It either needs a massive battery
Speaker 3: and RTG which is a radioisedtope thermoelectric generator, or it
Speaker 3: needs to unspool a physical power cable from a base
Speaker 3: station on the rim as it drives down. That makes sense,
Speaker 3: and then there's the lunar dust. Lunar regolith is incredibly
Speaker 3: abrasive and it sticks to everything due to startic electricity.
Speaker 3: If a layer of dust gets onto the optical mirrors
Speaker 3: or the thermal radiation panels, the instrument is completely ruined.
Speaker 3: The rover has to place the instrument gently without kicking
Speaker 3: up a cloud of debris.
Speaker 2: So the rover drives down, fights the dust, fights the darkness,
Speaker 2: reaches the target depth where the ambient temperature stabilizes at
Speaker 2: fifty kelvin and gently sets the payload down. Then the
Speaker 2: deployment sequence begins.
Speaker 3: Yes, the protective covers open the thermal radiation panels we
Speaker 3: discussed earlier, unfurl. They point straight up toward the empty
Speaker 3: black sky, and that slow passive bleed of infrared heat begins,
Speaker 3: dropping the core temperature down to that magical sixteen Calvin limit.
Speaker 3: Then the commercial laser, which is sitting safely up on
Speaker 3: the rim in the sunlight, is activated. Its light is
Speaker 3: piped down the fiber opticable into the darkness. It enters
Speaker 3: the cavity, the electronic feedbacklock is achieved, and the extraterrestrial
Speaker 3: clock starts ticking.
Speaker 2: What absolutely blows my mind is the timeline they are
Speaker 2: discussing for this When you hear about something this complex
Speaker 2: involving gravitational waves, relativity, and robotic crater deployment, you naturally
Speaker 2: assume it's a concept paper for the year twenty eighty.
Speaker 2: You'd think so, But the projections estimate that they could
Speaker 2: actually demonstrate a working silicon optical cavity in lower orbit
Speaker 2: within two years, and they could theoretically deploy this on
Speaker 2: the lunar surface within three to five years. Three to
Speaker 2: five years. We are not talking about science fiction for
Speaker 2: our grandchildren. We were talking about technology that could fly
Speaker 2: in the next presidential administration.
Speaker 3: The rapid timeline is entirely possible because of the sheer
Speaker 3: scale and caliber of the human collaboration behind this project.
Speaker 3: You have massive space agencies who are the undisputed masters
Speaker 3: of space flight mechanics and rover logistics. You have national
Speaker 3: metrology institutes who are the world masters at precision measurement,
Speaker 3: quantum mechanics, and timekeeping.
Speaker 2: Yeah, everybody's pitching in.
Speaker 3: It is a highly coordinated, multi agency, international effort pulling
Speaker 3: together the absolute best minds in cryogenics, optical physics, and
Speaker 3: space exploration. They aren't trying to invent new physics from scratch.
Speaker 3: They are taking perfectly understood, proven physics and simply packaging
Speaker 3: it for an alien environment.
Speaker 2: It is an incredibly elegant technological piggyback. We are already
Speaker 2: going back to the moon. We have already designated these
Speaker 2: exact South Pole regions as the primary landing sites, because,
Speaker 2: as we mentioned at the beginning, humanity needs the water
Speaker 2: ice hidden in those shadows to survive long term. We
Speaker 2: are building a highway to the dark.
Speaker 3: We really are.
Speaker 2: And the physicists simply looked at the manifest and said, well,
Speaker 2: since you're heading to the cold, dead dark anyway to
Speaker 2: dig for water, do you mind dropping off our laser.
Speaker 3: It is the ultimate synergy of space exploration. The brute
Speaker 3: force pursuit of basic survival resources creates the logistical bridge
Speaker 3: required to deploy the most delicate advanced physics experiments in
Speaker 3: human history. We use the pickaxe to pave the way
Speaker 3: for the laser.
Speaker 2: We have covered an absolutely massive journey in this conversation today.
Speaker 2: We started by peering over the edge into an empty,
Speaker 2: d freezing pitch black crater, a place that seems completely
Speaker 2: apathetical to life and human endeavor, and step by step
Speaker 2: we unpacked how that exact terrifying nothingness is the key,
Speaker 2: the fifty kelvin ambient cold, the deep self scrubbing vacuum,
Speaker 2: the passive radiation of heat into the cosmos to hit
Speaker 2: that magical sixteen kelvin number where a block of silicon
Speaker 2: freezes its physical dimensions perfectly and refuses to expand or contract.
Speaker 3: We saw how that frozen stillness allows us to lock
Speaker 3: a wild laser, taming its chaotic light into a single, perfect,
Speaker 3: unvarying frequency using electronic feedback, right.
Speaker 2: And how that perfect frequency becomes an extraterrestrial atomic clock
Speaker 2: counting hundreds of trillions of ticks per second, broadcasting a
Speaker 2: master time signal that provides a local lunar GPS to
Speaker 2: safely guide astronauts down into the dark. And finally, how
Speaker 2: that exact same laser network becomes so unimaginably precise that
Speaker 2: it can act as an interferometer, feeling the literal fabric
Speaker 2: of space time, squishing the Moon as gravityational waves wash
Speaker 2: over the Solar System. We traveled from a dark hole
Speaker 2: in the dirt all the way to the grandest mechanics
Speaker 2: of the universe.
Speaker 3: It is a remarkable synthesis of structural engineering and theoretical astrophysics.
Speaker 3: I think the biggest takeaway is how it reminds us
Speaker 3: that environment dictates capability, Yes, exactly. Looking beyond the obvious, bright,
Speaker 3: energetic places on the Moon and instead leveraging the extreme
Speaker 3: stillness of the shadows, we unlock a completely new era
Speaker 3: of precision science. It fundamentally shifts our relationship with the
Speaker 3: lunar surface. The moon is no longer just a destination
Speaker 3: to plant a flag. It is becoming an active, participating
Speaker 3: instrument in our quest to measure and understand reality.
Speaker 2: Which leads me with a thought that I want to
Speaker 2: pass directly to you listening right now. The next time
Speaker 2: you walk outside at night and look up at the
Speaker 2: moon in the sky, I want you to change how
Speaker 2: you see it. We always focus on the bright, glowing face,
Speaker 2: we track the phases of the light catching the sun.
Speaker 2: But look at the shadows, Look at the edges, think
Speaker 2: about those hidden frozen craters at the poles. Can look
Speaker 2: at the most desolate, hostile, lightless regions of our closest
Speaker 2: neighbor and realize they're actually the perfect housing for the
Speaker 2: most precise scientific instruments humanity has ever conceived. It makes
Speaker 2: you wonder what other seemingly dead space is in our
Speaker 2: solar system. The freezing, toxic valleys of Mars, the pitch
Speaker 2: black subsurface oceans of Europa, the shadowed, chaotic rings of
Speaker 2: Saturn are just waiting for us to uncover their hidden,
Speaker 2: unimaginable utility. We just have to be willing to look
Speaker 2: into the dark.