# Tag Info

## Hot answers tagged dyson-spheres

61

A Dyson Sphere is meant to capture radiation and convert it to usable energy. Since an earth-like planet only reflects light back, that point would be moot. In any case, here's some suggestions: Orbital Eggshell Crumbling Civilization Obfuscator Mk I Magrathean homework assignment

44

Let's get this out of the way: classic, rigid Dyson spheres are not stable and neither is a rigid ringworld around a star. A rigid dyson sphere is not stable, since there is no net attraction between a spherical shell and a point mass inside. If the shell is pushed slightly, for example by a meteor hit, the shell will gradually drift off and eventually ...

40

Our sun produces something like $3.8 \times 10^{26}$ Watts. That requires something in the neighborhood of 600 million tonnes of Hydrogen per second. Getting a similar power from fusion would require a similar consumption of Hydrogen. Even for a culture that could build a Dyson sphere, that's a lot of Hydrogen to get if you are not using a star to do it. ...

33

I think the best solution would be a Matrioshka Brain. This is effectively a layered set of Dyson spheres. Once it reaches equilibrium, each shell has a particular temperature differential across it, which can be used to generate work. These shells feed eachother, so the total temperature drop across the entire brain is equal to the temperature of the ...

30

Life on Earth will suffer severely. Instead of the energy coming mostly in visible spectrum, now it will be coming in the far infrared part of spectrum. Skies will be dark - no Sun, no Moon, no planets, except for the stars. Because Earth's atmosphere is much more opaque to far infrared radiation, temperatures will plunge. The vast majority of living ...

30

Mars is the better bet There's a reason why building habitats on Mars makes more sense, and many of them are covered in the Mars Trilogy by Kim Stanley Robinson. The simplest and most plausible reason though is that Mars is already a 'spaceship' in a stable orbit around the sun, so all you have to do is populate it with the people and resources you need. ...

30

Your question is like asking "why build an oil power plant with all the related hassle, when we can chop wood and light a fire?". The answer is: the order of magnitude of the produced energy. A star emits Petawatts of energy, while a fusion power plant can produce Megawatts, several order of magnitude less. And a star saves the hassle of harvesting all the ...

26

Well a Dyson Sphere is named after the person who popularised the idea and also the shape of the object itself. Without paying homage to a person or entity, it makes sense to call it after its function. Around a planet, there's a few functions it could have which allow you to derive a name for it. Defence: A megastructure created with the intent of ...

21

There is no name for the sphere version. The ring version is an Orbital Ring. You could most likely use the term "Planetary Dyson Sphere" or if it is defensive in nature "Planetary Shield". I've also heard the term "shell" used to describe structures similar to what you are asking about. Be aware though that it is a structure with no real value and yet ...

20

This is not a reasonable depiction of a Dyson Sphere. First of all, it must be stated that this kind of Dyson Sphere - a solid "Dyson Shell" - while a popular description, is universally regarded as unrealistic by serious writers, even in the context of a civilization capable of building solar system sized megastructures. Even if the absurd amounts of ...

19

No, you could not. Temperature probably isn't an issue, but a Dyson sphere shouldn't show the proper spectral lines. The-best case scenario This site gives the formula for the temperature of a Dyson Sphere as $$T=\left( \frac{E}{4 \pi r^2 \eta\sigma} \right)^{\frac{1}{4}}$$ where $E$ is the star's energy output, $r$ is the Dyson Sphere's radius, $\eta$ is ...

15

What is missing is parsing the requirement accurately. Type II definition includes "capable of utilizing and channeling the entire radiation output of its star", and then continues to discuss the energy utilization. This does not require actually capturing all solar radiation of their star. For example, we could harness the equivalent energy to all ...

15

In order to keep your dyson sphere hidden, you don't really have to do anything. There's two key things to keep in mind. The whole point of a dyson sphere is to extract as much useful energy as possible to do useful work with. There's a maximal efficiency of any method to extract work from heat energy, and that efficiency is determined by the difference in ...

15

To power nuclear fusion, you need hydrogen. The overwhelmingly largest hydrogen reservoir in any solar system, and conveniently an already working fusion reactor is its star. In other words, there is far more energy to collect from a star than you could ever hope to generate in reactors.

14

Frank Cedano's answer means that the robots building the Dyson sphere can use a tiny proportion of the energy it collects to power a giant space sun lamp to illuminate the Earth (if they want to). If the 11 billion humans on planet Earth also have advanced technology in the year 3030 they can build giant space fusion power generators with a total power ...

13

A Dyson sphere is not stable on itself, for a variety of reasons. On one side, since the sphere encircles completely the star, it does not feel the gravity, so it must be kept on place artificially. This means having rockets or jets of some kind, thus placing extra tensions on the structure. On the other side, the sphere can feel the variations of the ...

12

No. A Dyson sphere would emit something closely matching black-body radiation. A star, while also emitting something close to black-body radiation, has tell-tale spikes in its spectrum. Below is the sun's spectrum compared to what its ideal black-body spectrum would look like: Brown and red dwarfs have their own "fingerprint" signatures, which differ from ...

12

The most logical explanation that springs to mind for me is that a Dyson Sphere or Dyson Swarm is not something you can build overnight. It's a gigastructure far beyond anything humanity would have constructed up to that point. Even with your futuristic technology, I wager it would take years, if not decades, to build. Now, that wouldn't be enough to put ...

11

My intuition is that they will not. A Type II civilization would be able to get fusion energy, information, and raw-materials from multiple solar systems; it is capable of evolutionary intervention, interstellar travel, interstellar communication, stellar engineering, terraforming, star cluster-scale influence and can be expected to be so within 1000 to ...

11

I don't think so, because a dyson sphere would not have the same emission spectrum of a star. Consider two cases: we can have a translucent dyson sphere that lets out some of the light of the star, or we can have a dyson sphere that is opaque and emits light as blackbody radiation due to being heated by the star. The light initially emitted by the star ...

11

So, I'm going to frame challenge this, and say "no alien civilization entirely surrounds their stars with solar collectors." Piecewise assembly Here's the thing about a Dyson Swarm: It's not a single massive project that returns nothing until it's complete. All you need is solar-orbiting structures that (also) collect solar power, and some sort of orbital ...

10

Being careful with your aim You can't not radiate, so if you want to not be observed then you need to make sure you aren't radiating in the direction of your nearest neighbours. To do this you'll need to somehow channel all the energy into a series of directional beams that are aimed in-between the stars closest to you. The amount of power you'll need to ...

9

A Dyson sphere is something that would be built over the course of quite a while. It would probably start as a ring around the Sun that just keeps getting bigger as energy needs go up. It would also be using up most if not all of the extra-solar matter in the solar system in order to create this. There would be plenty of habitat area on the pieces in ...

8

About 31. However, it all depends on the thickness of the shell. This is typically given as mass per cubic meter though, because the material density is difficult to know. We'd probably need more than what we have in our solar system for a one AU Dyson shell. From the wiki article: Anders Sandberg estimates that there is $1.82×10^{26}$ kg of easily ...

8

I think they will figure it out pretty early on, at a fairly low tech level. The reason is the directional light source. At 3 AU the ground will slope up toward the horizon, but it will be so gradual that it will be hard to notice before the haze of distance obscures the view. But at night this stops being as much of an issue. As the light rotates away ...

8

Eternity is a Long Time Imagine if Nero, Ghengis Khan, Joseph Stalin, and Adolph Hitler never died: in fact, they couldn't die. It doesn't actually take a majority of sadists to make a lot of bad things happen, just one in the right place at the right time to lead others. So imagine if every era not only spawned its own monsters, but that none of the rest ...

8

The commonly given reason for building any version of a Dyson Sphere is because the civilization needs an amount of energy comparable to the output of their star. A Dyson sphere captures a significant fraction of that ouput, and does it more or less passively. I would posit that a civilization could not create a Dyson sphere without first having fusion (...

7

You could call it a roof. Or perhaps an armilla? If you were going to get all hard SF about it, a rigid shell around a planet (or indeed around a star) wouldn't be stable, and would indeed fall onto the planet unless it was perfectly centered on the planet's center of mass as @RichardTingle suggests. If it were as low as the ISS, I doubt it could last a ...

7

Just do surface area questions. For any given shell, calculate the area of all of the plates within that shell, and calculate the total surface area of a sphere at that distance from the star. Dividing those will give you the fraction of the time one can expect plates in that shell to shadow shells further out. This should be a more than reasonable ...

7

You might not necessarily like this answer, but... Considering the technological level needed for a society to being able to go through with such a massive project, the location will likely be secondary. You can literally just choose any system you come across that contains one or more planets with (primitive) plant-life1 capable of photosynthesis. The ...

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