# Would a Dyson sphere be useful as a means of power generation?

I have heard people (quite possibly on this site) say that by the time a civilization is able to make Dyson sphere it will be useless to build one for power and energy needs. So, would a civilization which can easily make a Dyson sphere make one for energy production, or would they have already have moved onto more efficient means?

Edit: by Dyson sphere I also meant Dyson swarm, or any other thing which encapsulates the sun to harvest it's radiation energy. Also, even through the question is similar to the one suggested as a duplicate the answers I am receiving are quite different.

• A star is a natural source of energy that can last for 10 billion years. Trying to beat that by finding some other power source seems meaningless, because the sun is already there. – user71341 Feb 8 at 12:40
• – Willk Feb 8 at 19:04
• Does this answer your question? Would a Type 2 Kardashev Civilization really build a Dyson Sphere around their own sun? It's slightly different but imo still a duplicate. – Zxyrra Feb 8 at 20:36
• Which of the eight distinct questions asked by the OP of the proposed duplicate is this actually a duplicate of? I don't see this particular question addressed in the other suite of queries. That seems to be about motivations and rationales. This query is straight up utility. – elemtilas Feb 9 at 0:02
• @elemtilas Imo it's the semantics of the sub-question, Would a Type 2 Kardashev Civilization really build a Dyson Sphere (around their own sun). Although the OP of that question intended to emphasize the "own sun" part, they still asked the "would ... really build" part, which is what this question asks. I disagree that the other question is too broad - the eight questions are not distinct, but iterations of the same question "is this idea feasible". – Zxyrra Feb 9 at 5:57

Your question seems to be about whether the engineering effort required to build a Dyson sphere (or swarm) might be more usefully spent building something else instead.

Unfortunately, that "something else" is not well defined. If you want to harvest power from natural sources, then your only real choices are stars and stellar remnants. The best way to extract the maximum amount of power from most of those is to wrap them up in some suitable layer of stuff. The specific kind of "stuff" in each case may be different, but the underlying principle is basically the same.

There are more energetic reactions than mere fusion, of course... antimatter is the obvious one. But antimatter doesn't naturally occur in sufficient quantity to compete with stars, so you need to harvest stellar energy to produce your antimatter. Even with the most enthusiastically theoretical physics, you're not going to get more energy out of your antimatter than you put in to creating/harvesting it in the first place.

If you open up the possibility of handwavium fringe physics, then all bets are off, of course. But with a grounding in reality, there isn't really much else you could build instead.

There are also some things that are Dyson-sphere sized, and have Dyson-sphere-sized power requirements. One of those is a Nicoll-Dyson laser: you fit the outside of each element of your Dyson swarm (or the entire outside of your sphere, if you've worked out how to make such a thing) with optical phased arrays, turning the whole shebang into a colossal laser suitable for driving fleets of lightsail starships and providing pretty much the ultimate in plausible-physics-based defense for your star system. There's not really any more plausible or sensible way to power this kind of thing than a Dyson swarm/sphere.

Yes. As far as we know, a Dyson sphere is the way to capture a star's output. Our Sun releases an incomprehensible amount of energy every second whether we capture it or not, so even if you have ultra-cheap smartphone-sized fusion reactors there is no reason to not run your civilization off of solar power.

You only maybe would want alternative sources of energy for operations outside our solar system. Not because you can't beam solar energy that far, but because the difficulty of keeping that beam focused on its target increases with distance.

A Bit More Detail

A Dyson sphere, better described as a Dyson swarm if you go by the descriptions of Freeman Dyson and Olaf Stapledon, serves two basic purposes:

1. Increase the percentage of stellar radiation you can capture
2. Increase your available real estate

The simplest possible Dyson swarm consists entirely of orbiting mirrors that concentrate sunlight onto power collectors. Every new mirror you put in orbit around the star provides more energy for building more mirrors at greater speed, so the construction of this type of swarm is generally expected to proceed exponentially. Humanity has the technology needed to start building this kind of swarm right now, but it isn't economically or politically feasible yet. Kurzgesagt has a video that focuses on this type of Dyson swarm.

Now, a Dyson swarm does not need to be limited to mere mirrors. There is physically no way to concentrate the Sun's entire output onto a single planet without vaporizing it, so to really make use of all of a star's output you need to spread out your infrastructure. A real Dyson swarm would probably contain trillions of orbital habitats and manufactories, supporting sextillions (if not septillions) of people with power and living space to spare. Science and Futurism with Issac Arthur has a video that goes into great detail about this kind of Dyson swarm, as well as its potential variations and additional uses.

• "incomprehensile" for Sol is 3.846×10^26 watts of energy getting blasted out of the surface of the Sun into all directions. To make it more manageable, let's see how much that is per square meter of sun surface, which is approximate 6*10^18 m², for 6.3*10^9 W/m². About 1300 W/m² hit the outer atmosphere of earth and 1000 W/m² reach the ground. That is a difference of about 6*10^6! 6 million times more power! The difference between a single horse (1HP) and 24 Nimitz (each 250k HP) pulling at a square of 1 m². – Trish Feb 15 at 17:41

I think the idea that building a dyson sphere would be more trouble than it's worth comes from the idea of building a dyson sphere that forms a solid shell. Such a construct is scientifically ludicrous, and anyone capable of actually building it would probably not only be beyond the need for stars to provide energy, but beyond the laws of physics in general.

A dyson swarm on the other hand is extremely practical, because it's just a collection of countless individual space stations that are each providing useful energy. You start by building enough stations to cover your current energy needs, which acquire something like 0.0000000001% of the sun's output (which is more than a hundred times our current energy requirements), and you respond to any increase in energy demands by building more stations. Eventually, if human population growth never stops completely (which it might, judging from the UN's research on the matter) our energy needs will grow to the point where we're soaking up an appreciable percentage of the sun's output. There's no reason why we HAVE to build a complete dyson sphere all at once, if we have nothing to spend that energy on.

• sorry for being not clear in the question. When I said Dyson sphere I meant any similar construction. I have edited the question. – meaninglessname Feb 8 at 23:20
• @meaninglessname Sorry, I didn't mean to be that ana! about it. I figured that you meant a dyson swarm, or any structure that would serve the same purpose. I was just responding to the statement that it would be useless by the time it could be built, remembering that thing I heard about how a solid dyson sphere would require more energy to build than it would ever harvest, and putting the two together. – FlyingLemmingSoup Feb 9 at 4:22