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In 2016, the world's most powerful billionaire set out to build a spacecraft that could reach another star within our lifetime.

They handed over 100 million dollars to Silicon Valley's best engineers to make it real, and today it's stuck by a physics problem no code can solve.

The secret to interstellar travel isn't building a better computer.

It's a microscopic piece of glass sitting in Texas with no engine,

no moving parts, no AI that can steer itself more precisely than any drone ever built.

And it might be the only thing that actually gets us to another star.

Chapter 1.

The 100 Million Dollar Ghost Ship Alpha Centauri, the target of breakthrough starshot, is 4.37 light years from the Earth.

That's 25 trillion miles away.

But how far is that really?

One of the fastest objects humanity has ever launched is the New Horizons probe.

It was moving at roughly 36,000 miles per hour when it launched from Earth.

Still, if you put New Horizons on a track and aimed it at Alpha Centauri, it would arrive in approximately 78,000 years.

Which is to say not in your lifetime, or your children's lifetimes, or during the lifetimes of any civilization that would even recognize the people who built it.

78,000 years ago, the great wave of modern humans hadn't swept across the globe yet.

We hadn't even invented agriculture, writing, the wheel, government, money, or organized religion.

All of that entire timeline fits inside the travel time of our fastest spacecraft to the nearest star.

And if you're wondering, the Apollo moon ships, the fastest piloted spacecraft humanity has ever flown, would do far worse.

They would take a staggering 114,000 years to reach the Alpha Centauri system.

That makes New Horizons' 78,000 years feel almost optimistic.

When Yuri Milner, a Russian billionaire physicist, stood on a stage in New York in 2016, this was the time and distance problem he set out to solve.

Forget chemical rockets, stop trying to carry fuel across trillions of miles, because fuel has mass, and mass requires more fuel to move it,

which adds more mass, which requires more fuel, it's a spiral.

And that's exactly why rockets are mostly just fuel tanks to begin with.

Instead, leave the fuel on the ground and a massive array of lasers,

then build a spacecraft so small and light it weighs just 0.03 ounces or one gram.

At its center is a chip the size of a postage stamp carrying a camera, a processor, a battery, and a transmitter,

and attach it all to a sail 13 feet wide but only a few hundred atoms thick.

All of that means that the pressure of light itself can push the craft through space.

Breakthrough Starshot called it the Star Chip, and it seemed simple in theory fire lasers at its sail

and then watch it accelerate to over 37,200 miles per second in a matter of minutes.

At 20% of the speed of light, it would only take 20 years to arrive at Alpha Centauri, and that's quite an improvement on the whole 78,000.

The timeline has been condensed into a single generation, not all of the generations.

And just to improve the odds that at least some survived the journey, they would send not one star chip but a fleet of a thousand of them.

Even Milner's team knew that redundancy is cheaper than regret.

A twenty-year journey is a number humans can hold in their head.

Never mind the fact that when Star Chip finally arrives at Alpha Centauri, the distances will be

so staggering it would take four years alone to beam the images back to Earth via its own onboard lasers.

Four years is a drop in the bucket.

We could at least conceivably be alive to see that data come back.

And so the crowd at the 2016 event applauded, because this idea was genuinely worth applauding.

What the Enterprise did not spend a lot of time talking about was the all-important laser array.

That alone would need to generate 100 gigawatts of power to function.

That's roughly the combined electrical output of approximately 100 nuclear power plants, all firing simultaneously.

The entire United Kingdom, every light, every factory, every phone charger, and every coffee machine in every office in London,

generally runs on less than 40 gigawatts on a normal day.

So Starshot's lasers would need two and a half times the entire power grid of Britain aimed at a stamp in space.

It's not like this was any secret.

The engineers knew the project's logistical parameters, and they set it anyway.

There was a plan, apparently, to solve this energy problem later.

They didn't.

They also didn't solve the other problem, the one that would have killed the tiny spacecraft before it left the solar system, regardless of how much power was available.

The problem that the 100 million dollar budget could not touch.

Chapter 2.

The Slippery Beam The massive laser beam, the one propelling the tiny spacecraft that takes an insane amount of energy to operate, is also the beam that absolutely destroys it.

This will happen immediately by design, as a direct consequence of the laws of physics the moment the sail drifts even slightly off-center.

Which it inevitably will.

The universe is not a laboratory with controlled conditions.

The laser has to travel through hundreds of miles of churning, turbulent atmosphere before it even reaches the spacecraft.

Imagine balancing a marble on top of another marble.

It is theoretically possible.

The geometry allows it, but the instant that the top marble moves even a fraction of a millimeter to the side, gravity won't be there to gently nudge it back.

It accelerates away.

The more it moves, the faster it goes.

The instability feeds itself.

Now imagine the top marble is a spacecraft, made of material thinner than a soap bubble.

The bottom marble is a laser beam carrying the energy output of a hundred nuclear power plants, and falling off means instant vaporization.

That is beam-riding instability.

Researchers who study this problem found something almost poetically discouraging.

A flat sail is never stable on a laser beam.

Even if you spin it or modify the shape any way you want, a flat sail is never stable.

Full stop.

At gentle speeds, this is an annoying engineering problem.

You might even be able to correct for it by installing sensors that detect wobble, onboard computers to process the error,

or maybe some thrusters to just nudge the spacecraft back to center.

That whole loop might take a few hundred milliseconds, which is workable.

But this is all theoretically taking place at 20% the speed of light.

At those speeds, a few hundred milliseconds is an eternity.

By the time the sensors detected the wobble, processed it, and sent the signal to the thruster, and then waited for it to fire,

the spacecraft will have traveled almost 11,200 miles.

That correction window, or just the gap between the wobble beginning and the spacecraft ceasing to exist, is measured in microseconds.

One millionth of a second.

The fastest thrusters on the earth can't act upon a correction loop that fast.

The spacecraft would vaporize before the mechanical valves even had time to open.

And that is before we get to the space dust.

The path from Earth to Alpha Centauri contains an estimated 100 sextillion particles including dust, hydrogen, and helium atoms.

At 20% the speed of light, each one hits the spacecraft like a bullet.

Researchers at the Korea Astronomy and Space Science Institute ran the numbers

and they They found that a steel spacecraft would accumulate craters 0.15 inches wide

and 0.04 inches deep across its surface long before it reached its destination.

A sufficiently large dust particle would destroy the craft entirely.

Breakthrough Starshot was conceived as a Silicon Valley project, and Silicon Valley's answer to this is simply write better code, faster code, smarter code.

If the correction loop is too slow, why not just optimize the correction loop?

Well, if the processor can't keep up, design a faster processor.

This approach works on essentially every problem that software has ever been asked to solve, and that's why it is the default response of an entire

generation of engineers who have watched software eat the world and concluded that software can eat anything.

But it can't eat the scale of this journey.

Because traveling to another star system isn't a software problem dressed up as a hardware problem.

at light speed is not a bug you could easily troubleshoot.

100

The signal that tells the thruster to fire still has to pass through physical hardware.

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But the spacecraft is moving at incredible speeds, so even a tiny delay means it's already covered in an enormous amount of distance by the time anything responds.

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And that is not a software problem you can optimize, because physics moves faster than code.

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You have to respect the original Breakthrough Starshot team.

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Before the project got off the ground, they publicly posted an engineering challenges list for the project, and made it admirably transparent.

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The list acknowledged this problem directly.

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Beam instabilities are everything, as are those differential forces on the sail and the differential heating.

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It reads like a coroner's report before the patient was even born.

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They sat with this problem for nine years.

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Nine years of small grants, academic conferences, hopeful papers, and the dawning awareness

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that the correction problem could not be solved with with the tools and budget the project had brought to solve it.

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You cannot out-compute a wobble that kills the spacecraft faster than computation is physically possible.

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What you would need is a spacecraft that corrects the wobble before it knows the wobble happened.

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A spacecraft that doesn't detect instability and respond to it.

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A spacecraft that simply can't become unstable, by virtue of what it's made of regardless of what the beam does to it.

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Now that sounds like science fiction.

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It also sounds like exactly what a team of doctoral students in Texas spent the last several years building.

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Chapter 3.

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The Dart and the Texans The doctoral students in Dr. Shofeng Lun's lab at Texas A&M University were not,

119

by any conventional measure, the people you would expect to solve this.

120

A $100 million Silicon Valley initiative had already failed, and they were backed by some of the most famous scientists alive.

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They didn't have the benefit of any celebrity spokespeople or press events in New York.

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Instead, they were working with a fabrication facility on a campus in College Station, Texas, a city best known for football and being roughly two hours from anywhere else.

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What they built is called a MetaJet.

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The current prototypes are tens of microns across.

125

For reference, a single strand of human hair is roughly 50 to 120 microns wide.

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Which means you could line up a small fleet of MetaJets across something you previously considered too small to see.

127

The whole device weighs less than a paperclip.

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It has no thrusters, no moving parts, no onboard computer, and no steering system of any kind.

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And the best part?

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A laser still propels it, but the structure of the material itself keeps it on course, the same way a groove keeps a needle in a record.

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Or in other words, the beam does one job and the material does another.

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Here's why that second part matters so much.

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Even if breakthrough Starshot solved the beam riding problem, managed to build a sail that stays perfectly centered on the laser

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and the craft survived the thermal load while accelerating to 20% the speed of light, there is still a massive problem waiting on the other side of that journey.

135

You don't know where you're going.

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Space is not empty.

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There are rogue particles, gravitational tugs from objects hundreds of billions of kilometers away, and absolutely no landmarks.

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A spacecraft crossing 4.37 light years is subject to every one of those influences for every second of a twenty-year journey.

139

Each nudge is tiny, but they add up.

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The Starshot engineers defined a successful arrival as getting within one astronomical unit of Alpha Centauri.

141

That doesn't sound like much until you realize what one astronomical unit actually means.

142

It allows for a missed distance of up to 93.2 million miles.

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That's roughly the distance from the Earth to the Sun.

144

And that was them being generous.

145

The bullseye was already the size of Earth's entire orbit, and an unsteered light sail couldn't reliably hit it.

146

Their own researchers admitted

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that the tiny vibrations in the laser array alone were many orders of magnitude away from the accuracy the mission required.

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Even with help, the probe would probably still miss the target the size of a planet's entire orbital path.

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Imagine throwing a dart from New York City and trying to hit a bullseye in London, but you can't see the target, and the target is moving,

150

and once the dart leaves your hand And you won't be able to adjust it for 20 years.

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That's the navigation problem.

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As we know, any conventional fix to the steering problem adds mass.

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Add mass on a spacecraft whose entire propulsion system is light pressure, and that can lead to an inevitable collapse.

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The steering system that saves the mission is also the steering system that makes the mission impossible.

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That is, the specific, elegant, maddening trap that breakthrough Starshot never escaped.

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The MetaJet escapes it by refusing to play.

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There's no steering system to add mass because the steering isn't a system, it's a property, built into the material before the ship even leaves the ground.

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Which means understanding how it works requires getting very small very fast.

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Chapter 4.

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The Groove in the Record The MetaJet is built from a class of material called MetaSurface, an ultra-thin sheet of silicon covered in arrays of nanoscale pillars.

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The pillars are far smaller than the width of a human hair.

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They're also so small

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that the patterning across a mere surface the size of your fingernail contains enough structural variation to encode an entire multi-volume encyclopedia.

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The height, the diameter, and the spacing of those metasurface pillars are precisely designed to control exactly what happens to light when it strikes the surface.

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Change one pillar by a few nanometers and you change the trajectory of your ship.

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The entire navigation of an interstellar spacecraft is encoded in measurements you could not resolve with a standard lab microscope.

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Here's what those pillars do.

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When you hold a garden hose and water shoots straight forward, the hose kicks straight back in your hands.

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That's basic physics.

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Newton's third law, the water goes one way, your hand gets pushed the other.

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Now put a bent nozzle at the end of it.

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Suddenly, the water exits at an angle and the hose kicks sideways instead of backwards.

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It's the same water pressure, enacting a completely different direction of force.

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The nozzle doesn't add any energy, it simply changes where the water went, and the reaction follows automatically.

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The Meta-Surface pillars are the nozzle, and the laser is the water pressure.

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When light strikes a conventional reflective surface like a mirror, it bounces straight back and pushes the sail straight forward.

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The Meta-Jet's pillars are designed to bend the outgoing light at a precise angle, so If the light exits sideways, the sail is pushed sideways.

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Nobody or nothing is required on board to program the nozzle.

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The shape is the program.

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That's the beauty of this system.

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The further it drifts, the harder it gets pushed back into position.

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It literally can't stay off course.

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As for the heat, which we were told would vaporize any conventional reflective materials under full laser load,

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the metasurface survives as a consequence of its ability to reflect light, not absorb it.

185

The photons do all the work, changing the direction and transferring momentum, rather than dumping all their energy into the material as heat.

186

For context, the previous best answer to this problem was graphene, one of the strongest materials humans have ever produced.

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Then, to survive the dust particles during the journey,

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researchers proposed folding the sail into a needle-like profile to minimize the cross-sectional area hitting the particles.

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The MetaJet silicon metasurface is a different answer entirely.

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just stronger, smarter.

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In laboratory testing, Lens' team demonstrated full three-dimensional movement using a single fixed laser beam.

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They got the MetaJet prototype to go forward, sideways, and lift from all one light source with no fuel, no steering input, or any contact of any kind.

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It was the first time any optical propulsion system had ever achieved this, and to the team's knowledge, nobody else has done it.

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The beam does one job, the material does the other.

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And the material never gets tired, runs out of propellant, or never has to wait for a computer to tell it what to do.

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Chapter 5.

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4.37 Light Years, Give or Take Lant's team is not alone.

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Researchers at Caltech have been working on a similar stability problem for laser drive light sales, and other groups have been working on the same problem from other angles.

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The fact multiple serious research teams have independently converged on material-based

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solutions to the steering problem posed by Breakthrough Starshot is no coincidence.

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The field has realized

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that the Silicon Valley instinct to throw software at it was always the wrong tool for this particular job.

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The MetaJet prototypes are currently tens of microns across.

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A real interstellar sail needs to be feet wide, and nobody at Texas A&M or anywhere else is pretending that that gap is small.

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But here's what makes it bridgeable in a way no previous approach was.

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The physics scale with laser power, not device size.

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The same principles that move a micron-scale prototype in a laboratory tank will move a meter-scale sail under gigawatt-class beams.

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The mechanism doesn't change, only the engineering does, and engineering unlike physics, negotiates.

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The next milestone is microgravity testing, demonstrating that the metajet behaves in space conditions the way it behaves in the lab.

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Landsteam is currently applying for funding to make that happen.

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Certainly a quieter, smaller, less photogenic task than a press conference at One World Trade Center with Stephen Hawking in attendance.

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It will also, if it works, mean considerably more.

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In the end, Breakthrough Starshot threw millions of dollars and nine years at the stars and quietly ran out of road.

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A group of doctoral students in College Station spent roughly the same period asking a different question entirely.

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Instead of building a better computer for the ship, what if the ship didn't need one at all?

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The device that may eventually carry humanity's first message to another star has no engine, No steering computer or moving parts, it weighs less than an eyelash,

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and it steers using light the same way a bowling ball uses a hill.

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Alpha Centauri is still 4.37 light years away.

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That number hasn't changed.

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What did change in a fabrication lab two hours away from

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anywhere is whether we as a species have any business believing we might actually get there.

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And we just might.

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Because every attempt to go further into space keeps running into the same truth, you have to solve the problems closest to home first, find out why NASA wants to go back to the moon,

224

or watch this instead.

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本课的词汇与口语要点

这节 B2 级别的口语课以视频“20% Speed of Light!! NEW Light Engine is INSANE!”为素材。视频中反复出现的词有：spacecraft, laser, beam, sail。这段视频共有 224 个句子、3234 个单词可供跟读。讲话部分时长为 18:33。说话人语速自然，每分钟约 174 个词，接近日常对话。只有 76% 的单词属于英语最常用的 3,000 词，词汇难度较高。

视频中的重点词汇

视频中最难的 15 个单词，附发音和释义：

单词	发音	释义
spacecraft 名词	/ˈspeɪsˌkɹæft/	航天器
laser 名词	/ˈleɪzɚ/	激光, 雷射
sail 名词	/seɪl/	帆, 風帆 /风帆
beam 名词	/ˈbiːm/	梁, 橫梁
steer 动词	/stɪɹ/	掌舵, 驾驶
breakthrough 名词	/ˈbɹeɪk.θɹuː/	突破
silicon 名词	/ˈsɪləˌkɑn/	硅, 矽
pillar 名词	/ˈpɪlɚ/	柱子, 支柱
researcher 名词	/ˈɹiˌsɝ.t͡ʃɚ/	研究員 /研究员, 研究者
correction 名词	/kəˈɹɛkʃən/	修正, 校正
marble 名词	/ˈmɑɹ.bəl/	大理石
prototype 名词	/ˈpɹəʊtətaɪp/	原型, 雏形
particle 名词	/ˈpɑɹtək(ə)l/	粒子
interstellar 形容词		星際 /星际
micron 名词	/ˈmaɪkɹɒn/	微米

视频中出现的短语动词

单词	释义
come back 动词	回來 /回来, 返回
find out 动词	找出, 查明
hand over 动词	交出, 移交

视频中的语法

说话人最常用的结构，并附上视频中的原话：

结构	视频中的用法
被动语态 be + 过去分词 — 强调发生了什么，而不是谁做的	has been condensed · is measured · was conceived
现在完成时 have/has + 过去分词 — 过去发生但与现在仍有关联的事	has ever launched · has ever flown · has been condensed
定语从句 who / which + 从句 — 补充说明人或事物	people who built · milliseconds, which is

需要注意的发音

说话人用了 27 次缩略和弱读形式，例如 can't, didn't, doesn't。请按听到的简短形式来说。

“th” 音: breakthrough /ˈbɹeɪk.θɹuː/, thruster /ˈθɹʌ.stɚ/, thermal /ˈθɜːməl/
“sh” 和 “zh” 音: correction /kəˈɹɛkʃən/, fabrication /fæbɹɪˈkeɪʃən/, propulsion /pɹəˈpʌlʃən/, differential [dɪfəˈɹənʃəɫ], navigation /nævɪˈɡeɪʃən/
长单词——注意重音位置: instability /ɪnstəˈbɪlɪti/, astronomical /ˌæs.tɹəˈnɑm.ɪ.kəl/, fabrication /fæbɹɪˈkeɪʃən/, millisecond /ˈmɪlɪˌsɛkənd/, differential [dɪfəˈɹənʃəɫ]

中文母语者容易读错的音：

/v/ — 不要读成 /w/，上齿轻触下唇: reflective /ɹɪˈflɛktɪv/, groove /ɡɹuv/, behave /bɪˈheɪv/, navigation /nævɪˈɡeɪʃən/, invent /ɪnˈvɛnt/
词尾辅音 — 要读清楚，后面不要加元音: spacecraft /ˈspeɪsˌkɹæft/, sideways /ˈsaɪdweɪz/, prototype /ˈpɹəʊtətaɪp/, nudge /nʌd͡ʒ/, dart /dɑɹt/
/r/ 和 /l/ 的区别: marble /ˈmɑɹ.bəl/, particle /ˈpɑɹtək(ə)l/, doctoral /ˈdɒktəɹəl/, astronomical /ˌæs.tɹəˈnɑm.ɪ.kəl/, propulsion /pɹəˈpʌlʃən/

如何用这段视频练习

先完整听一遍视频，不要开口，记下不认识的单词。
先用 0.75 倍速逐句跟读，熟练之后再回到正常速度。
录下自己的声音并与原声对比，特别注意 spacecraft, laser, sail 这类单词。

什么是跟读法？

跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。

影子跟读法: 阅读完整分步指南 →

跟读练习: 20% Speed of Light!! NEW Light Engine is INSANE! - 通过视频学习英语口语

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