What is a Dyson Sphere?

Meet the future technology that could harness power and energy from a star in the most unusual way

The Dyson Sphere around a star. A future technology which could harness power and energy from a star by surrounding it with hexagon shaped satellites

The Dyson Sphere around a star. A future technology which could harness power and energy from a star by surrounding it with hexagon shaped satellites. Image credit: J. Wong

First proposed by theoretical physicist Freeman Dyson in 1960, a Dyson sphere is a hypothetical swarm of satellites that would surround a star in order to harness its energy. It is something that is well and truly only in the remit of being possible for a civilisation far more advanced than our own, but nevertheless it is something that has garnered significant interest since it was first theorised.

This particular idea is more commonly known as a Dyson swarm. Some people, however, have discussed the possibility of rather than a swarm of satellites a star could be encased in a solid sphere by a future civilisation, but this is an idea that Dyson himself is keen to stray away from. Indeed, for a planetary system like our own, such a structure would likely require every object in the Solar System other than the Sun to be dismantled and rebuilt into a giant sphere owing to the huge size of the Sun.

Dyson’s initial proposal was suggested as a way that a future civilisation could sate their expected vast energy needs. As the energy requirements of a civilisation increases they may require an ever-growing amount of energy, a crisis perhaps solved only by harnessing the power of stars.

With it this carries further connotations, namely that perhaps there are advanced extraterrestrial races elsewhere in the universe that have built such structures. Dyson postulated that these would radiate a large amount of infrared radiation noticeable even to us here on Earth.

The idea has gained enough ground such that the SETI Institute in California, USA, has been on the lookout for Dyson spheres, while Fermilab near Chicago has carried out their own analysis of observations from outside the Solar System to ascertain the likelihood of the existence of Dyson spheres. Aside from finding four candidates that were “amusing but still ambiguous and questionable,” though, nothing too promising has been found.

While fun to imagine, the logistics of a Dyson sphere are also quite far-fetched. Taking the solid shell idea, this structure would be thin at perhaps just a few tens or hundreds of metres thick with its membrane covered in solar panels, but it would still be many times more massive than Earth. Placed around a star, though, it would have little chance of keeping its structural integrity; if made to rotate so as to keep it in “orbit” around the star, the areas around its artificial equator would be stable but at the poles, where there was no rotation, the structure would succumb to the forces of gravity and collapse.

This is why Dyson himself favours the swarm idea. With this, many thousands of solar energy-gathering satellites would be placed around the star. They could perhaps be tethered together, and they would then beam their energy to a central hub to be utilised by a civilisation. Using separate satellites, all in orbit around the star, the structure would remain intact and huge amounts of energy could be transferred from the star.

While this particular structure might seem impractical, something on a smaller scale could feasibly do a similar job. For example, some theories suggest that a large solar-gathering spacecraft placed between Earth and the Moon would be able to absorb huge amounts of power that could be beamed to our planet. Known as space-based solar power (SBSP), this is something that science fiction writers have favoured and is a much more promising technology than an entire Dyson sphere. However, perhaps many thousands of year in the future when we become interstellar explorers, it may be necessary to find huge resources of energy and, as far as we know, there’s nothing better than an entire star.

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