Dyson spheres are ranked with space elevators and warp drives when it comes to far-fetched ideas and lack of public support, in part because of several variants, with a broad spectrum of feasibility and efficiency, that are floating around, and in part because the most well-known variant is hardest to build, most expensive, and the only one that would be necessary to build in a different solar system entirely.
But what is a Dyson sphere? Dyson spheres are a collection of photovoltaic technology that would encompass a star and collect all, or at least the vast majority of, the light the star emits and turn it into electricity. The idea used in most science fiction novels is that this sphere would be solid, and maybe even habitable. With current technology, this variant, like all the others, is impossible to accomplish. If anyone were to attempt it, it would be accomplished by making a “shell” of sorts with lots of orbiting satellites that would be equipped with solar panels, but not attached to each other in any way. If the “shell” were thick enough, then the satellites could be spaced out enough that there would be no danger of collision. This is not only referred to as a Dyson sphere, but also a Dyson swarm.
Dyson spheres are good for the obvious reason that they would generate large amounts of energy incomparable to any other source. To harvest all of the energy given off by a star would solve all comprehensible energy problems that mankind has, at least in terms of electricity. They would also aid in climate control. If a significant portion of sunlight was blocked, the average temperature of all planets in its orbit would drop. Altering the density of the Dyson swarm, and thus the amount of sunlight that gets through, could change global climates and affect vegetation on said planet. This could solve global warming or, if one does this to a star in a different solar system, reduce the temperatures of nearby planets until they are habitable. When almost infinite energy and possibilities of terraforming are on the table, who wouldn’t want to attempt it?
Realists. Realists wouldn’t want to attempt it. In this day and age, getting a rover to Mars is a big deal and costs incredible amounts of money. To build even one satellite that could get close enough to the sun (closer than mercury) without melting, equip it with solar panels that can withstand that heat, and a battery that wouldn’t be damaged by that would be incredibly expensive. Then, once the battery is full, the question would be how to get that energy to Earth. Beaming energy wirelessly is impossible, unless you ask Nickola Tesla, who said that he could find a way, but died before he could.
That leaves two options. The first is to launch another spacecraft to go collect it and supply the satellite with another battery, which would cost more money than the energy is worth. The second is to have the satellite eject the battery in the direction of earth at a speed that would allow the battery to reach earth in a timely fashion, which would also require more energy than the amount the battery could contain. Either way, even one satellite would use too much energy to make any profit. These problems would be magnified hundreds of times if the satellite were orbiting any other star, because of the sheer distance.
In addition, to build the amount of satellites necessary to build a Dyson swarm around the sun, or most stars, for that matter, would require more raw materials than anyone would ever be able to produce without mining asteroids or other planets, let alone a solid sphere encompassing it.
So, while excellent in theory, Dyson spheres of any form are not likely to be attempted for several centuries, or even millennia, more. This does not, however, discredit Freeman Dyson, the accomplished and published astronomer, who fine tuned and popularized the idea. Dyson spheres remain a very popular topic in many novels, including the “Ringworld” series by Larry Niven. Dyson spheres are also included in some of the “Halo” video game series.
