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

在銀河系中，數以萬億計顆的恆星圍繞著銀河中心公轉

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

有些恆星像我們的太陽一樣非常穩定

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

距離銀河系中心約30,000光年

This chaos makes the galaxy dangerous.

每2.3億年完成一次公轉

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

這種舞蹈不像是有序的芭蕾舞

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

更像是一個充滿了醉漢的溜冰場

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

這種混亂使銀河系變得危險

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

我們太陽系的鄰居不斷改變，而恆星每秒移動數百公里

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

只有星體間保持夠多的距離才能保護我們免受危險

But we still couldn't do much about it.

但是在未來我們有可能遇到一些不幸的事

Unless,

在某個時間點

we move our whole solar system out of the way.

我們可能會遭遇到一顆正在爆發的超新星

[Snazzy Kurzgesagt intro music]

或一個巨大的星體經過並用小行星雨砸向地球(紅矮星)

To move the solar system,

如果發生這種情況

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

我們可能會提前幾千年甚至幾百萬年知道

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

但是我們仍然不能做太多事情

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

除非....

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

我們把整個太陽系移走

The good news is we can ignore all of that.

為了要移動太陽，我們需要恆星引擎

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.

一個能夠使恆星轉向並且穿過銀河系的超巨型結構

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

它是一種可能由具有戴森球等級的科技文明

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

為接下來幾百萬年的計劃所建造

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

但要怎麼移動太陽系中數以千百計的物體呢?

It works on the same principle as a rocket.

好消息是，我們可以忽略它們

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

當我們決定要移動時，我們只需要移動太陽

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

所有其他東西都通過重力和太陽黏在一起， 無論走到哪裡，都將跟隨它。

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

關於恆星引擎的外觀及其工作原理，有很多想法。

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

基於目前對物理的理解 我們選擇了兩個可以在理論上可以建造的方式

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

(被動方式)

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

其中一種簡單的恆星引擎就是西卡多夫推進器

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

一個巨大的鏡子

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

它的工作原理與火箭相同

The mirror's shape is important too,

像火箭燃料一樣，由於太陽輻射而釋放的光子攜帶的動量不是很多，而是一點點。

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

例如，如果太空人打開太空中的手電筒

heating it up and creating all sorts of unpleasant problems.

它將以非常非常緩慢地將其向後推動

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

恆星引擎比手電筒要好一些，因為太陽會產生很多光子。

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

西卡多夫推進器的基本原理

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

是反射最多一半的太陽輻射用於產生推力

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

慢慢的推動太陽去我們要去的地方

which limits our travel options abate.

為了保持西卡多夫推進器的運作

But that is basically it.

需要保持在同一位置，而不是圍繞太陽運行

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

儘管太陽的引力會試圖將其拉入，但它會受到太陽的輻射力的支撐。

Not complicated, just very hard to build.

這代表鏡子的材料必須非常輕

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

由鋁合金等材料製成只有紅血球那麼薄的反射鏡

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

鏡子外形也很重要

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.

將太陽包圍在一個巨大的半球形外殼中是行不通的

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

因為那樣會使光重新聚焦到太陽上

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

從而使太陽變熱並產生各種令人不愉快的問題。

You can find it in our sources document.

取而代之的是，我們使用

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

拋物面鏡將大部分光子繞開太陽並向同一方向發送

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

從而使推力最大化

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

為了不讓地球因為陽光太多或太少 導致燒毀或凍結的意外發生

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

唯一建造西卡多夫推進器的安全地點

A second jet pushes the Sun along like a tugboat.

只有在太陽的兩極

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

這意味著我們只能在太陽系的平面內垂直移動太陽

To gather this fuel, our thruster uses very large

在銀河系中只能向一個方向移動

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

這會稍微限制我們的旅行選擇。

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

但是他基本上就是這樣運作

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

對於能夠建立戴森球的文明來說

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

這是相對簡單的工作

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

這並不複雜，只是很難建構

The helium is burned explosively in thermonuclear fusion reactors.

在全力運轉下

A jet of

太陽系將會花費2.3億年的時間來移動100光年的距離

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

在數十億年之後

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

它能夠使我們完全控制太陽環繞銀河的軌道

To do this,

但是在短時間內，這速度並不足以躲避致命的超新星

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

這就是為什麼我們認為我們可以做得更好

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

所以我們請求我們的天體物理學家朋友

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

是否可以為了影片設計一個更快的恆星引擎

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

他做了，並撰寫了一篇有關恆星引擎的論文 並發表在同行評審的期刊上

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

你可以在下面的資料來源找到這篇論文

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

我們命名新恆星引擎為卡普蘭推進器

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

它的工作原理就像傳統的火箭

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

向一端噴射出氣體並把自已推向另一端

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

這是一個由戴森球提供能量 從太陽收集物質用來核融合的大型太空站平台

For example, by orbiting backwards in the galaxy and

它射出非常快速的粒子流，以約接近1%光速的速度來推離太陽系

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

第二條噴流就像拖船一樣推著太陽(藍色光束)

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

卡普蘭推進器需要每秒幾百萬噸的燃料

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

為了收集燃料

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

我們的推進器使用非常大的電磁場

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

將太陽風中的氫與氦導入引擎

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

太陽風並不能提供足夠多的能量

We may not like where it leads us.

這就是為什麼需要戴森球

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

使用戴森球的力量，可以使陽光重新聚焦回太陽的表面

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

這將小範圍加熱到極端溫度

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

使數十億噸的質量脫離太陽

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

這些物質可以被收集並分為氫和氦

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

氦可以在熱核反應堆中燃燒爆炸

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

噴射出接近十億度放射性氧成為我們的主要推力

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

為了預防引擎墜落到太陽裡 它需要平衡自已