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Kurzgesagt (In a Nutshell), How to Move the Sun: Stellar Engines

How to Move the Sun: Stellar Engines

Nothing in the universe is static. In the Milky Way, billions of stars orbit the galactic center.

Some, like our Sun, are pretty consistent, keeping a distance of around

30,000 light years from the galactic center, completing an orbit every 230 million years.

This dance is not an orderly ballet, more like a skating rink filled with drunk toddlers.

This chaos makes the galaxy dangerous.

Our solar neighborhood is constantly changing, with stars moving hundreds of kilometers every second.

Only the vast distances between objects protect us from the dangers out there.

But we might get unlucky in the future. At some point,

we could encounter a star going supernova or a massive object passing by and showering Earth with asteroids.

If something like this were to happen, we would likely know thousands if not millions of years in advance.

But we still couldn't do much about it.

Unless,

we move our whole solar system out of the way.

[Snazzy Kurzgesagt intro music]

To move the solar system,

we need a stellar engine, a megastructure used to steer a star through the galaxy. It's the kind of thing

that might be built by an advanced civilization with Dyson sphere-level technology

that's thinking about their future millions of years ahead of time.

But how do we possibly move the hundreds of thousands of objects in the solar system?

The good news is we can ignore all of that.

We only need to move the Sun; all the other stuff is glued to it by gravity and will follow it wherever it decides to go.

There are lots of ideas about what a stellar engine might look like and how it would work.

We've picked two, grounded in our current understanding of physics, that could be built in theory.

The simplest kind of stellar engine is the Shkadov thruster, a giant mirror.

It works on the same principle as a rocket.

Like rocket fuel, the photons released as solar radiation carry momentum, not a lot but a bit.

For example, if an astronaut turned on a flashlight in space, it would push them backwards very very slowly.

A stellar engine will work a little better than a flashlight because the Sun produces a lot of photons.

The basic idea of the Shkadov thruster is to reflect up to half of the solar radiation

to create thrust, and slowly push the Sun where we want it to go.

In order for the Shkadov thruster to work, it must be kept in the same place, not orbiting the Sun.

Although the Sun's gravity will try to pull it in, it would be supported by radiation pressure which props the mirror up.

This means the mirror would have to be very light, made of micron thin reflecting foil from materials like aluminium alloys.

The mirror's shape is important too,

enveloping the Sun in a giant spherical shell wouldn't work because that would refocus light back to the Sun,

heating it up and creating all sorts of unpleasant problems.

Instead we use a parabola, which sends most of the photons around the Sun and in the same direction, which maximizes thrust.

To prevent accidentally burning or freezing Earth with too much or too little sunlight,

the only safe place to build a Shkadov thruster is over the Sun's poles.

This means we can only move the Sun vertically in the plane of the solar system and one direction in the Milky Way,

which limits our travel options abate.

But that is basically it.

For a civilization capable of building a Dyson Sphere, this is a relatively simple endeavor.

Not complicated, just very hard to build.

At full throttle, the solar system could probably be moved by about a hundred light years over 230 million years.

Over a few billion years, it gives us near complete control over the sun's orbit in the galaxy.

But in the short term, this might not be fast enough to dodge a deadly supernova. That's why we thought we could do better.

So we asked our astrophysicist friend if he could design a faster stellar engine for this video.

He did and wrote a paper about it that's been published in a peer-reviewed journal.

You can find it in our sources document.

We're going to call at our new stellar engine the Caplan thruster.

It works a lot like a traditional rocket: shoot exhaust one way to push yourself the other.

It's a large space station platform powered by a Dyson sphere that gathers matter from the Sun to power nuclear fusion.

It shoots out a very fast jet of particles at nearly 1 percent the speed of light out of the solar system.

A second jet pushes the Sun along like a tugboat.

The Caplan thruster requires a lot of fuel, millions of tons per second.

To gather this fuel, our thruster uses very large

electromagnetic fields to funnel hydrogen and helium from the solar wind into the engine.

The solar wind alone doesn't provide enough fuel though, and that's where the Dyson sphere comes in.

Using its power, sunlight can be refocused to the surface of the Sun.

This heats small regions to extreme temperatures, lifting billions of tons of mass off the Sun.

This mass can be collected and separated into hydrogen and helium.

The helium is burned explosively in thermonuclear fusion reactors.

A jet of

Radioactive oxygen at a temperature of nearly a billion degrees is expelled and becomes our primary source of propulsion from our stellar engine.

To prevent the engine from just crashing into the Sun, it needs to balance itself.

To do this,

We accelerate the collected hydrogen with electromagnetic fields using particle accelerators and shoot a jet back at the Sun.

This balances the thruster and transfers the thrust of our engine back to the Sun.

In as little as a million years, this engine can move the Sun by 50 light years, more than enough to dodge a supernova.

At full throttle, the solar system can be completely redirected in its galactic orbit in 10 million years.

But wait, will we use up the Sun this way?

Fortunately the Sun is so massive that even billions of tons of material will barely scratch the surface.

In fact, this megastructure will actually extend our Sun's life, since lower mass stars

burn slower, keeping the solar system inhabitable for many more billions of years.

With a Caplan thruster, we could turn the entire solar system into our spaceship.

For example, by orbiting backwards in the galaxy and

colonizing hundreds or thousands of stars as we pass by them.

It may even be possible to escape the galaxy entirely and expand beyond the Milky Way.

Stellar engines are the kind of machines built by civilizations thinking not in terms of years or decades but eons.

Since we know that our Sun will die one day, a stellar engine could allow the far future descendants of humans to travel to other stars

without ever having to venture into the terrifying dark abyss of interstellar space.

Until we build a stellar engine, we're adrift and subject to the whims of the Galactic sea.

We may not like where it leads us.

Maybe our descendants will set sail and become an interstellar species for millions of years to come.

This was our last video for the year 12,019 of the human era, and what a year it was.

So much stuff happened everywhere, to so many different people.

Calendars and holidays are just imaginary, but they help us to cut our lives into pieces that our brains can handle.

We're leaving 12,019 behind with a weird mixture of disillusion and hope. The world is screwed up,

But we can fix it. In a few days, this year will be over, and we'll get to try again.

Thank you for watching our videos, and for sticking around for so many years. See you all in 12,020.

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How to Move the Sun: Stellar Engines |||||Sternen-|Maschinen Wie man die Sonne bewegt: Stellare Antriebe Cómo mover el Sol: Motores estelares Comment déplacer le soleil : les moteurs stellaires Come muovere il Sole: i motori stellari 太陽を動かす方法ステラエンジン Hoe de zon bewegen: Sterrenmotoren Jak poruszyć Słońce: Gwiezdne silniki Como mover o Sol: Motores estelares Как сдвинуть Солнце: Звездные двигатели Güneş Nasıl Hareket Eder? Yıldız Motorları Як рухати Сонце: Зоряні двигуни 如何移动太阳恒星发动机

Nothing in the universe is static. In the Milky Way, billions of stars orbit the galactic center. ||||||||||Milliarden|||umkreisen|||

Some, like our Sun, are pretty consistent, keeping a distance of around |||||ziemlich|||||| Certains, comme notre soleil, sont assez constants, se tenant à une distance d'environ

30,000 light years from the galactic center, completing an orbit every 230 million years. ||||||vollendend||||| ||||||完了する|||||

This dance is not an orderly ballet, more like a skating rink filled with drunk toddlers. |||||geordnet|Ballett||||Eislaufen|Eislaufbahn|||betrunkenen|Kleinkinder ||||||バレエ||||||||| Cette danse n'est pas un ballet ordonné, mais plutôt une patinoire remplie de bambins ivres.

This chaos makes the galaxy dangerous.

Our solar neighborhood is constantly changing, with stars moving hundreds of kilometers every second. ||||ständig||||||||| Notre voisinage solaire est en constante évolution, les étoiles se déplaçant de centaines de kilomètres par seconde.

Only the vast distances between objects protect us from the dangers out there.

But we might get unlucky in the future. At some point, ||||unglücklich|||||| Pero podríamos tener mala suerte en el futuro. En algún momento,

we could encounter a star going supernova or a massive object passing by and showering Earth with asteroids. ||||||||||||||regnen||| ||||||||||||||降り注ぐ||| wir könnten auf einen Stern treffen, der eine Supernova verursacht, oder ein massives Objekt, das vorbeizieht und die Erde mit Asteroiden überschüttet. podríamos encontrarnos con una estrella que se convierta en supernova o con un objeto masivo que pase y llene la Tierra de asteroides. nous pourrions rencontrer une étoile qui se transforme en supernova ou un objet massif qui passerait à côté de la Terre et la couvrirait d'astéroïdes.

If something like this were to happen, we would likely know thousands if not millions of years in advance. ||||würde|||||||||||||| Wenn so etwas passieren würde, wüssten wir wahrscheinlich tausende, wenn nicht Millionen von Jahren im Voraus. Si algo así ocurriera, probablemente lo sabríamos con miles o millones de años de antelación. Si une telle chose devait se produire, nous le saurions probablement des milliers, voire des millions d'années à l'avance.

But we still couldn't do much about it. |||||viel|| Aber wir könnten immer noch nicht viel dagegen tun.

Unless,

we move our whole solar system out of the way. movemos todo nuestro sistema solar fuera del camino.

[Snazzy Kurzgesagt intro music] schicke||| おしゃれな|||

To move the solar system,

we need a stellar engine, a megastructure used to steer a star through the galaxy. It's the kind of thing ||||||Megastruktur|||steuern|||||||||| ||||||メガストラクチャー||||||||||||| nous avons besoin d'un moteur stellaire, une mégastructure utilisée pour diriger une étoile dans la galaxie. C'est le genre de chose 我们需要一个恒星发动机,一个用来引导恒星穿越银河系的巨型结构。就是这样的东西

that might be built by an advanced civilization with Dyson sphere-level technology qui pourraient être construites par une civilisation avancée disposant d'une technologie de niveau sphère de Dyson dat zou kunnen zijn gebouwd door een geavanceerde beschaving met Dyson-technologie op bolniveau

that's thinking about their future millions of years ahead of time.

But how do we possibly move the hundreds of thousands of objects in the solar system? Mais comment pouvons-nous déplacer les centaines de milliers d'objets du système solaire ?

The good news is we can ignore all of that. La bonne nouvelle, c'est que nous pouvons ignorer tout cela.

We only need to move the Sun; all the other stuff is glued to it by gravity and will follow it wherever it decides to go. ||||||||||||festgeklebt||||||||||||| ||||||||||||貼り付けられた||||||||||||| Нам нужно только переместить Солнце; все остальное приклеено к нему под действием силы тяжести и будет следовать за ним, куда бы он ни пошел.

There are lots of ideas about what a stellar engine might look like and how it would work.

We've picked two, grounded in our current understanding of physics, that could be built in theory. |||basierend auf|||||||||||| |||基づいた|||||||||||| Nous en avons choisi deux, fondés sur notre compréhension actuelle de la physique, qui pourraient être construits en théorie.

The simplest kind of stellar engine is the Shkadov thruster, a giant mirror. ||||||||Shkadov|Antrieb||| Le moteur stellaire le plus simple est le propulseur Shkadov, un miroir géant. De eenvoudigste soort stellaire motor is de Shkadov-boegschroef, een gigantische spiegel. 最简单的恒星发动机是 Shkadov 推进器,它是一面巨大的镜子。

It works on the same principle as a rocket.

Like rocket fuel, the photons released as solar radiation carry momentum, not a lot but a bit. ||||||||||Impuls|||||| ||||||||||運動量|||||| Comme le carburant d'une fusée, les photons libérés par le rayonnement solaire sont porteurs d'énergie, pas beaucoup mais un peu.

For example, if an astronaut turned on a flashlight in space, it would push them backwards very very slowly. ||||Astronaut||||Taschenlampe|||||||||| ||||||||懐中電灯|||||||||| Par exemple, si un astronaute allumait une lampe de poche dans l'espace, celle-ci le ferait reculer très très lentement. 例如,如果宇航员在太空中打开手电筒,它就会非常缓慢地向后推他们。

A stellar engine will work a little better than a flashlight because the Sun produces a lot of photons. ||||||||||懐中電灯||||||||

The basic idea of the Shkadov thruster is to reflect up to half of the solar radiation L'idée de base du propulseur Shkadov est de réfléchir jusqu'à la moitié du rayonnement solaire.

to create thrust, and slowly push the Sun where we want it to go. ||Schub erzeugen||||||||||| ||推進力|||||||||||

In order for the Shkadov thruster to work, it must be kept in the same place, not orbiting the Sun. |||||||||muss||||||||um den Sonnenorbit|| |||||||||||||||||軌道を回る|| Pour que le propulseur Shkadov fonctionne, il doit rester au même endroit et ne pas être en orbite autour du Soleil.

Although the Sun's gravity will try to pull it in, it would be supported by radiation pressure which props the mirror up. ||||||||||||||||||stützt||| ||||||||||||||||||支える||| Bien que la gravité du Soleil tente de l'attirer vers l'intérieur, il serait soutenu par la pression de radiation qui soutient le miroir vers le haut.

This means the mirror would have to be very light, made of micron thin reflecting foil from materials like aluminium alloys. ||||||||||||Mikron|||Folie||||Aluminiumlegierungen|Legierungen ||||||||||||ミクロン|||||||アルミニウム|合金 Cela signifie que le miroir doit être très léger, composé de feuilles réfléchissantes d'une épaisseur de l'ordre du micron, fabriquées à partir de matériaux tels que les alliages d'aluminium. Dit betekent dat de spiegel heel licht zou moeten zijn, gemaakt van micron dun reflecterend folie van materialen zoals aluminiumlegeringen.

The mirror's shape is important too, |des Spiegels|||| |鏡の||||

enveloping the Sun in a giant spherical shell wouldn't work because that would refocus light back to the Sun, umhüllend|||||||Hülle||||||umlenken||||| 包み込む|||||||||||||再焦点化||||| Envelopper le Soleil dans une gigantesque coquille sphérique ne fonctionnerait pas, car cela refocaliserait la lumière vers le Soleil, het omhullen van de zon in een gigantische bolvormige schaal zou niet werken, want dat zou het licht opnieuw richten op de zon,

heating it up and creating all sorts of unpleasant problems.

Instead we use a parabola, which sends most of the photons around the Sun and in the same direction, which maximizes thrust. ||||Parabel||||||||||||||||maximiert| ||||||||||||||||||||最大化する| 相反,我们使用抛物线,它将大部分光子绕太阳以相同的方向发射,从而最大限度地产生推力。

To prevent accidentally burning or freezing Earth with too much or too little sunlight,

the only safe place to build a Shkadov thruster is over the Sun's poles.

This means we can only move the Sun vertically in the plane of the solar system and one direction in the Milky Way, ||||||||vertikal|||Ebene||||||||||| ||||||||垂直に||||||||||||||

which limits our travel options abate. |||||verringern sich |||||減少する

But that is basically it.

For a civilization capable of building a Dyson Sphere, this is a relatively simple endeavor. ||||||||||||||Unterfangen Pour une civilisation capable de construire une sphère de Dyson, il s'agit d'une entreprise relativement simple. Voor een beschaving die in staat is om een Dyson Sphere te bouwen, is dit een relatief eenvoudige onderneming.

Not complicated, just very hard to build.

At full throttle, the solar system could probably be moved by about a hundred light years over 230 million years. Mit||Vollgas||||||werden|verschoben||||||||| ||全開|||||||||||||||| À plein régime, le système solaire pourrait probablement être déplacé d'une centaine d'années-lumière en 230 millions d'années.

Over a few billion years, it gives us near complete control over the sun's orbit in the galaxy. Sur quelques milliards d'années, il nous permet de contrôler presque totalement l'orbite du soleil dans la galaxie.

But in the short term, this might not be fast enough to dodge a deadly supernova. That's why we thought we could do better. ||||||||||||ausweichen||||||||||| ||||||||||||避ける|||||||||||

So we asked our astrophysicist friend if he could design a faster stellar engine for this video. ||||Astrophysiker||||||||||||

He did and wrote a paper about it that's been published in a peer-reviewed journal. |||||||||||||Fachkollegen||

You can find it in our sources document.

We're going to call at our new stellar engine the Caplan thruster. ||||||||||Caplan-Triebwerk| ||||||||||キャプラン| Nous appellerons notre nouveau moteur stellaire le propulseur Caplan. We gaan onze nieuwe stellaire motor de Caplan-boegschroef noemen.

It works a lot like a traditional rocket: shoot exhaust one way to push yourself the other. |||||||||排気||||||| Le fonctionnement est similaire à celui d'une fusée traditionnelle : il faut tirer des gaz d'échappement d'un côté pour se pousser de l'autre. 它的工作原理与传统火箭非常相似:以一种方式发射废气,从而将自己推向另一种方式。

It's a large space station platform powered by a Dyson sphere that gathers matter from the Sun to power nuclear fusion. ||||||||||||sammelt|||||||| ||||||||||||集める|||||||| Il s'agit d'une grande station spatiale alimentée par une sphère de Dyson qui recueille la matière du soleil pour alimenter la fusion nucléaire.

It shoots out a very fast jet of particles at nearly 1 percent the speed of light out of the solar system. |schießt|||||Strahl|||||||||||||| Il projette un jet de particules très rapide à près de 1 % de la vitesse de la lumière hors du système solaire. それは、太陽系の外に光速のほぼ1パーセントの速度で非常に速い粒子のジェットを放出します。

A second jet pushes the Sun along like a tugboat. |||schiebt||||||Schlepper |||||||||タグボート 2つ目のジェットは、タンカーのように太陽を押します。 第二股喷流像拖船一样推动太阳前行。

The Caplan thruster requires a lot of fuel, millions of tons per second. キャプランスラスタは、多くの燃料を必要とし、毎秒数百万トンです。

To gather this fuel, our thruster uses very large

electromagnetic fields to funnel hydrogen and helium from the solar wind into the engine. |||trichterförmig|||||||||| |||ファネル||||||||||

The solar wind alone doesn't provide enough fuel though, and that's where the Dyson sphere comes in.

Using its power, sunlight can be refocused to the surface of the Sun. ||||||neu fokussiert|||||| ||||||再集中|||||| Met behulp van zijn kracht kan zonlicht opnieuw worden gericht op het oppervlak van de zon.

This heats small regions to extreme temperatures, lifting billions of tons of mass off the Sun. |||||||anhebend||||||||

This mass can be collected and separated into hydrogen and helium.

The helium is burned explosively in thermonuclear fusion reactors. |||verbrannt|||||Reaktoren ||||||||炉

A jet of

Radioactive oxygen at a temperature of nearly a billion degrees is expelled and becomes our primary source of propulsion from our stellar engine. |||||||||||ausgestoßen|||||||Antriebskraft|||| ||||||||||||||||||推進||||

To prevent the engine from just crashing into the Sun, it needs to balance itself. ||||||abstürzen||||||||

To do this,

We accelerate the collected hydrogen with electromagnetic fields using particle accelerators and shoot a jet back at the Sun. ||||||||||Beschleuniger||||||||

This balances the thruster and transfers the thrust of our engine back to the Sun. |gleicht aus||||überträgt||||||||| |バランスを取る||||||||||||| Cela permet d'équilibrer le propulseur et de transférer la poussée de notre moteur vers le Soleil.

In as little as a million years, this engine can move the Sun by 50 light years, more than enough to dodge a supernova. En un million d'années seulement, ce moteur peut déplacer le Soleil de 50 années-lumière, ce qui est largement suffisant pour éviter une supernova.

At full throttle, the solar system can be completely redirected in its galactic orbit in 10 million years. |||||||||umgeleitet||||||| |||||||||再方向転換|||||||

But wait, will we use up the Sun this way?

Fortunately the Sun is so massive that even billions of tons of material will barely scratch the surface. Glücklicherweise||||||||||||||||| Heureusement, le Soleil est si massif que même des milliards de tonnes de matière ne feront qu'effleurer la surface.

In fact, this megastructure will actually extend our Sun's life, since lower mass stars ||||||verlängern|||||||

burn slower, keeping the solar system inhabitable for many more billions of years. ||||||bewohnbar|||||| ||||||居住可能な|||||| brûlent plus lentement, ce qui permet au système solaire de rester habitable pendant encore plusieurs milliards d'années.

With a Caplan thruster, we could turn the entire solar system into our spaceship.

For example, by orbiting backwards in the galaxy and

colonizing hundreds or thousands of stars as we pass by them.

It may even be possible to escape the galaxy entirely and expand beyond the Milky Way. |||||||||vollständig||||||

Stellar engines are the kind of machines built by civilizations thinking not in terms of years or decades but eons. |||||||||||||||||||Äonen |||||||||||||||||||永遠

Since we know that our Sun will die one day, a stellar engine could allow the far future descendants of humans to travel to other stars Puisque nous savons que notre soleil mourra un jour, un moteur stellaire pourrait permettre aux lointains descendants de l'homme de voyager vers d'autres étoiles.

without ever having to venture into the terrifying dark abyss of interstellar space. |||||||furchterregenden||Abgrund||| |||||||||深淵|||

Until we build a stellar engine, we're adrift and subject to the whims of the Galactic sea. |||||||triebslos|||||Launen|||| |||||||漂流している||||||||| Tant que nous n'aurons pas construit un moteur stellaire, nous serons à la dérive et soumis aux caprices de la mer galactique.

We may not like where it leads us.

Maybe our descendants will set sail and become an interstellar species for millions of years to come. |||||in See stechen||||||für||||| Peut-être que nos descendants prendront la mer et deviendront une espèce interstellaire pour des millions d'années.

This was our last video for the year 12,019 of the human era, and what a year it was. |||||||||||Ära|||||| C'était notre dernière vidéo pour l'année 12 019 de l'ère humaine, et quelle année !

So much stuff happened everywhere, to so many different people.

Calendars and holidays are just imaginary, but they help us to cut our lives into pieces that our brains can handle. Les calendriers et les jours fériés sont imaginaires, mais ils nous aident à découper notre vie en morceaux que notre cerveau peut gérer.

We're leaving 12,019 behind with a weird mixture of disillusion and hope. The world is screwed up, ||||||||Desillusionierung|||||ist|verrückt| ||||||||幻滅||||||めちゃくちゃ|上 Nous laissons 12 019 derrière nous avec un étrange mélange de désillusion et d'espoir. Le monde est foutu,

But we can fix it. In a few days, this year will be over, and we'll get to try again.

Thank you for watching our videos, and for sticking around for so many years. See you all in 12,020.