Basic Information
Dyson Sphere is a term that encompasses several ideas created by scientist Freeman Dyson. A Dyson Sphere is a Stellar Megastructure, or a series of smaller structures that collectively occupy similar space, which incorporate solar collectors. The point of the Dyson Sphere concepts is to allow a civilization to utilize the majority of the power emitted by a star. Therefore, all forms of Dyson Sphere are also Class B Stellar Engines.
As our societies and cities have grown larger and more complex, they have needed more and more energy. Eventually, we will exceed the energy that is available here on earth. A Dyson Sphere is one way to get past that energy crisis hurdle, and thus avert a malthusian catastrophe or a world war over resources.
It is expected that alien species on other planets would face similar problems. As such, those who have managed to avoid destroying themselves may have created something like a Dyson Sphere to solve their energy problems. Creating a Dyson Sphere (of any sort) would elevate the civilization to Type II on the Kardashev Scale.
A Dyson Sphere would absorb light and heat for energy. It's unlikely that an alien race that built a Dyson Sphere would be able to use 100% of the energy they'd so captured, so they'd bleed some of it off as heat. Therefore, if aliens have reached the Type II (or late Type I) level of the Kardashev scale, we may be able to detect them by observing the energy emissions from their stars. Such stars might grow dimmer, and a larger percentage of the energy they did release would be infrared (heat) waves. Following Freeman Dyson's suggestions, SETI searches for infrared anomalies around earthlike stars in the cosmos.
If people from the Earth wanted to build a Dyson Sphere, it would take a huge amount of resources. We would have to mine multiple planets, much of the asteroid belt, etc. The planet Mercury is likely to be involved. It has a huge amount of iron for building materials, and a low gravity that makes it relatively easy to get those harvested resources into space, plus it's much closer to the sun so that saves on travel time. So we might start our Dyson Sphere project by sending robots to Mercury. These robots would not only excavate minerals, but they would assemble more robots. These later generations of robots would in turn assemble the solar sails and solar energy collectors needed for the project, and then fire them into position via giant railgun so that no rocket fuel is needed. Then, with the actual structure in place, we would need to start stripping the ice giants to create the atmosphere and biota for whichever parts of the structure we were planning to inhabit.
Types of Dyson Sphere
- Dyson Bubble - a collection of statites around a star to collect most of it's energy
- Dyson Net - a net connecting the solar collectors of one of the other forms of Dyson Sphere
- Dyson Ring - a single "equator" of a Dyson Swarm, one row of satellites
- Dyson Shell - the most popular concept, yet the least stable one. A solid shell all around a star.
- Dyson Swarm - a collection of orbiting solar power satellites and space habitats
Not quite Dyson Spheres
Similar ideas from other scientists and authors include:
- Dyson-Harrop Satellite - a single statite that beams collected energy from the solar wind to a planet via a laser
- Bubbleworld - an artificial habitat built around a ball of hydrogen gas
- Niven Ring - a single "equator" of a Dyson Shell, per Larry Niven's Ringworld
- A solid shell built around a Gas Giant - would be similar to a Bubbleworld
- Stellar Engine - a category of megastructure designed to turn a star into an engine
Other ideas by Dyson
These are other ideas by Freeman Dyson for space exploration and space habitats:
- Astrochicken - a small self-replicating cybernetic space exploration device
- Dyson Tree - a genetically-engineered plant that turns comets into space habitats
Sources
Game and Story Use
- See Stellar Megastructure for a pretty thorough exploration of the implications of including a Dyson Sphere in your setting.
- Twenty Minutes Into The Future, SETI discovers signs of an alien race far away in the heavens, occupying a Dyson Sphere.
- Meanwhile, a much closer star has yet another civilization much closer to our own in terms of technology level, but not as easy to detect because they aren't engaged in stellar engineering projects that make them recognizable to SETI.
- Some astronomical phenomena - have lead to speculation that someone out there is building a Dyson type object. It also seems that whatever it is, it is not a one-off.
- A Dyson Sphere may be detected from when a distant star begins to dim, kind of like what we've seen at Tabby's Star. The dimming could be caused by more and more statites, satellites, mirrors in space, etc being built around the star, gradually blocking the light originating at that star from reaching us.
- Some sort of grey goo or robot uprising scenario could start on Mercury due to a replication error in a robotic factory. Aside from the usual dangers of such problems, you'd also have the risk that the bots might (intentionally?) block all sunlight from reaching the earth. Fighting back against the threat would mean undoing the work of a stellar megastructure that perhaps had become the main focus of our entire species. If the robots show no sign of trying to extend beyond Mercury and the D-Sphere, it might actually be decided that the best bet is to just quarantine the small uninhabitable planet and let the robots complete their mission of harnessing all the sun's power for us… but that gamble is a Sword of Damocles dangling over everyone. What will the uncontrolled robots do if they finish their primary mission, or evolve beyond it?