How to Move the Sun: Stellar Engines

Summary

This script explores the concept of stellar engines, megastructures capable of steering stars, as a solution to potential cosmic threats like supernovae. It introduces two theoretical designs: the Shkadov thruster, using solar radiation pressure for slow, steady movement, and the Caplan thruster, a more powerful option using nuclear fusion for rapid relocation. These engines could extend the Sun's life and allow humanity to navigate the galaxy, transforming our solar system into an interstellar ark for future generations.

Takeaways

• 🌌 The universe is dynamic, with stars like our Sun orbiting the galactic center in a chaotic manner, posing potential dangers to Earth.
• 🛣️ Stars in our solar neighborhood move at high speeds, but the vast distances between celestial bodies offer some protection from cosmic threats.
• ⚠️ Future cosmic events, such as supernovae or asteroid showers, could be predicted far in advance but may still pose significant risks to Earth.
• 🚀 To mitigate such threats, a hypothetical megastructure called a 'stellar engine' could be used to move our entire solar system.
• 🔭 A stellar engine could be built using advanced technology, such as a Dyson sphere, to manipulate the movement of stars over galactic timescales.
• 🪄 The Shkadov thruster, a type of stellar engine, uses a giant mirror to reflect solar radiation and create thrust, moving the Sun and the solar system.
• 🌞 The Shkadov thruster must be positioned over the Sun's poles to prevent disrupting the Earth's climate and can only move the Sun vertically and in one direction in the galaxy.
• 🚀 The Caplan thruster, a faster stellar engine concept, uses nuclear fusion and electromagnetic fields to propel the Sun and solar system more quickly.
• 🌟 The Caplan thruster could move the solar system by 50 light years in a million years, providing a means to dodge imminent cosmic threats.
• 🌐 A stellar engine could extend the Sun's life by reducing its mass, as lower mass stars burn slower, thus prolonging the habitability of the solar system.
• 🛰️ Stellar engines represent long-term thinking for civilizations, allowing for interstellar travel and colonization without venturing into the dangers of space.
• 📅 The script concludes with a reflection on the human condition, expressing a mix of disillusion and hope for the future, and a farewell to the year 12,019.

Q & A

What is the Milky Way's galactic center and why do stars orbit it?

The galactic center of the Milky Way is the dense core around which billions of stars, including our Sun, orbit. Stars orbit it due to the gravitational pull exerted by the massive amount of matter concentrated at the center.

Why is the movement of stars in the Milky Way described as chaotic?

The movement of stars is described as chaotic because it is not orderly like a ballet but more akin to a disorganized environment, with stars moving in various directions at high speeds, which can lead to unpredictable interactions.

How far is our Sun from the galactic center and how long does it take to complete an orbit?

Our Sun is approximately 30,000 light years away from the galactic center and it completes an orbit around the center every 230 million years.

What is a stellar engine and why would we need one?

A stellar engine is a hypothetical megastructure designed to steer a star through the galaxy. We might need one to move our solar system out of the way of potential cosmic threats, such as a supernova or a massive object passing by.

Why is it sufficient to move only the Sun and not the entire solar system?

The Sun's gravity holds the solar system together, so moving the Sun would cause the rest of the solar system to follow due to the gravitational pull, making it unnecessary to move each object individually.

What is the Shkadov thruster and how does it work?

The Shkadov thruster is a theoretical stellar engine that functions like a giant mirror. It reflects a portion of the Sun's radiation to create thrust, slowly pushing the Sun in a desired direction, similar to how a rocket uses the momentum of expelled fuel.

What are the challenges in constructing a Shkadov thruster?

The Shkadov thruster must be lightweight, made of materials like aluminum alloys, and shaped correctly to avoid refocusing light back onto the Sun. It also needs to be positioned over the Sun's poles to avoid altering the amount of sunlight reaching Earth.

What is the Caplan thruster and how does it differ from the Shkadov thruster?

The Caplan thruster is another theoretical stellar engine that operates more like a traditional rocket, using nuclear fusion to propel the Sun by shooting out jets of particles. Unlike the Shkadov thruster, it can move the Sun more quickly and in any direction, not just vertically.

How does the Caplan thruster gather and use fuel for propulsion?

The Caplan thruster gathers fuel by using large electromagnetic fields to funnel hydrogen and helium from the solar wind and by heating small regions of the Sun's surface to lift off mass, which is then collected and used in thermonuclear fusion reactors for propulsion.

What are the potential long-term benefits of using a Caplan thruster?

Using a Caplan thruster could extend the Sun's life by reducing its mass, as lower mass stars burn slower. It also allows for the redirection of the solar system's orbit and the possibility of colonizing other stars or even escaping the Milky Way.

What is the significance of the year 12,019 mentioned in the script?

The year 12,019 is a fictional date used in the script to reflect on the past year's events and to express hope for the future. It serves as a narrative device to connect with the audience and to convey a message of perseverance and optimism.

Outlines

00:00

🌌 The Concept of Stellar Engines

The paragraph introduces the dynamic nature of the universe, particularly the Milky Way, where stars, including our Sun, are in constant motion. It highlights the potential dangers of celestial bodies, such as supernovae or passing massive objects, and the idea that we might need to move our solar system to avoid such threats. The concept of a 'stellar engine' is introduced as a megastructure that could potentially move a star, with the Shkadov thruster and the Caplan thruster being two theoretical designs. The Shkadov thruster operates like a giant mirror, using solar radiation to create thrust, while the Caplan thruster functions more like a traditional rocket, using nuclear fusion for propulsion. Both engines are grounded in current physics and are considered feasible by advanced civilizations with the technology to build a Dyson sphere.

05:03

🚀 The Caplan Thruster: A Faster Stellar Engine

This paragraph delves into the workings of the Caplan thruster, a more advanced stellar engine designed to move the Sun more quickly than the Shkadov thruster. It uses electromagnetic fields to gather fuel from the solar wind and the Sun's surface, powered by a Dyson sphere. The thruster operates by expelling jets of radioactive oxygen at extremely high temperatures, creating a powerful propulsion system. To maintain balance and prevent crashing into the Sun, it also shoots a jet of hydrogen back towards the Sun. The paragraph explains that this engine could move the Sun by 50 light years in a million years, allowing us to dodge threats like supernovae. It also suggests that with such technology, we could extend the Sun's life and even explore beyond the Milky Way, turning the solar system into a spaceship for interstellar travel.

Keywords

💡Milky Way

The Milky Way is the galaxy that contains our Solar System, consisting of billions of stars, gas, and dust. It is a spiral galaxy, and the script mentions that stars, including our Sun, orbit its galactic center. The concept of the Milky Way is central to the video's theme of moving the Solar System to avoid potential cosmic threats.

💡Orbit

Orbit refers to the path that an object takes around another object due to gravity. In the script, it is mentioned that stars, like our Sun, orbit the galactic center of the Milky Way, completing an orbit every 230 million years. This concept is essential to understanding the movement of celestial bodies and the challenges of moving the Solar System.

💡Supernova

A supernova is a powerful and bright stellar explosion that occurs at the end of a star's life cycle. The script discusses the potential danger of encountering a supernova, which could be a reason to move the Solar System. This term is vital for understanding the risks that prompt the idea of a stellar engine.

💡Stellar Engine

A stellar engine is a hypothetical megastructure capable of moving a star through space by altering its trajectory. The script introduces the concept of a stellar engine as a solution to potential cosmic threats, such as a supernova or passing massive objects. The Shkadov thruster and the Caplan thruster are examples of stellar engines mentioned in the video.

💡Shkadov Thruster

The Shkadov thruster is a theoretical type of stellar engine that uses a giant mirror to reflect solar radiation and create thrust. The script describes it as a simple yet effective method to slowly move the Sun and, by extension, the Solar System. The Shkadov thruster is an essential part of the video's exploration of moving celestial bodies.

💡Photons

Photons are elementary particles that are the basic units of light. The script explains that photons carry momentum, which is the principle behind the Shkadov thruster's operation. The concept of photons is crucial for understanding how light can be used to generate thrust.

💡Dyson Sphere

A Dyson sphere is a hypothetical megastructure that completely encompasses a star and captures its energy output. The script mentions the Dyson sphere as a prerequisite technology for building a stellar engine, indicating a highly advanced civilization's capability.

💡Caplan Thruster

The Caplan thruster, named after the astrophysicist who designed it for the video, is a theoretical stellar engine that uses nuclear fusion to propel the Sun. It is described as a faster alternative to the Shkadov thruster, capable of moving the Sun more quickly to avoid threats. The Caplan thruster is central to the video's discussion of advanced propulsion methods.

💡Nuclear Fusion

Nuclear fusion is the process by which atomic nuclei combine to form a heavier nucleus, releasing a large amount of energy. The script describes the Caplan thruster using nuclear fusion to generate the energy needed for propulsion. This concept is key to understanding the power source of advanced stellar engines.

💡Solar Wind

Solar wind refers to the stream of charged particles released from the upper atmosphere of the Sun. The script mentions the use of solar wind as a source of fuel for the Caplan thruster, illustrating the concept of harnessing the Sun's own material for propulsion.

💡Interstellar Space

Interstellar space is the space between stars within a galaxy. The script concludes with the idea that stellar engines could allow humanity to travel to other stars without venturing into the dangers of interstellar space, emphasizing the long-term vision of such technology.

Highlights

The Milky Way is in constant motion with billions of stars, including our Sun, orbiting the galactic center.

Stars maintain a chaotic dance rather than an orderly orbit, posing potential dangers to our solar system.

Our solar system's safety is due to the vast distances between celestial objects, despite the constant motion of stars.

Future celestial events, such as supernovae or asteroid impacts, could be predicted thousands or millions of years in advance.

The concept of a stellar engine is introduced as a megastructure to steer a star through the galaxy for the safety of a civilization.

Moving the entire solar system is unnecessary; only the Sun needs to be moved due to gravitational forces.

The Shkadov thruster, a giant mirror, is proposed as a simple stellar engine working on the principle of photon momentum.

The Shkadov thruster must be stationary relative to the Sun and supported by radiation pressure to function correctly.

A parabolic mirror shape is essential for the Shkadov thruster to maximize thrust without refocusing light back onto the Sun.

The Shkadov thruster can only move the Sun vertically in the solar system and in one direction in the Milky Way, limiting travel options.

The Caplan thruster, a faster stellar engine, is designed to move the Sun by shooting out jets of particles at nearly 1 percent the speed of light.

The Caplan thruster requires millions of tons of fuel per second, gathered through large electromagnetic fields from the solar wind.

A Dyson sphere is integral to the Caplan thruster, providing power to refocus sunlight and lift mass off the Sun for fuel.

The Caplan thruster uses radioactive oxygen at nearly a billion degrees as its primary propulsion, extending the Sun's life.

Balancing the thruster is crucial, achieved by accelerating hydrogen and shooting a jet back at the Sun.

The Caplan thruster can move the Sun 50 light years in a million years, providing a means to dodge supernovae.

Stellar engines represent long-term thinking for civilizations, allowing for control over the Sun's galactic orbit over eons.

With a stellar engine, humanity could potentially become an interstellar species, colonizing stars and even escaping the Milky Way.

The video concludes with a reflection on the human era, emphasizing the importance of calendars and the hope for the future.

Transcripts

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.