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This article comes from Weixin Official Accounts: SF Chinese (ID: kexuejiaodian), Text: Alastair Gunn, Translation: Mengxue

What is a Dyson sphere? A Dyson sphere is a hypothetical giant structure-unimaginably large-that collects most of the energy emitted by a star.

The basic idea behind a Dyson sphere is to build a spherical structure around a star, surround it, and absorb, transform, and store the energy emitted by the star.

Scientists believe that if advanced civilizations exist in the universe, they may require a lot of energy, and Dyson spheres are the most economical and feasible solution.

Who proposed the Dyson sphere and when? The Dyson sphere is named after physicist Freeman Dyson (1923 - 2020). In 1960, he published a paper on methods for detecting alien civilizations, which mentioned Dyson spheres.

But Dyson admits he was inspired by British author Olaf Stapledon's science fiction novel Star Maker, which was widely acclaimed after its publication in 1937. Stapleton's novel describes each star in the universe as surrounded by "a veil of gauze" that crisscross and "collect the dissipated stellar energy for intelligent use."

Since the concept of a Dyson sphere emerged, many scientists studying extraterrestrial civilizations have considered this possibility.

Does the Dyson sphere really exist? There is no evidence yet that Dyson spheres exist in the universe.

But scientists can say something about whether such a thing is theoretically possible.

First of all, although the level of technology required to build a Dyson sphere is far beyond the current level of human technology, from an engineering point of view, there is no insurmountable obstacle. As long as science and technology developed to a certain extent, humans would definitely be able to build a Dyson sphere if they prepared enough resources. One scientist even estimates that humans will be able to implement it in about 100 years.

However, some scientists believe that this view is too optimistic. In fact, astronomers have set an upper limit on the total number of Dyson spheres that may exist in the universe. This is because the presence of a Dyson sphere blocks the star's light, causing the star's brightness to decrease.

In addition, while the Dyson sphere collects the star's energy, it also radiates some of the energy in the form of infrared rays. By carefully searching for stars that are too dim or too infrared, scientists speculate that up to 10,000 stars within 16,000 light-years of Earth may have Dyson spheres around them (Earth is about 26,000 light-years away from the center of the Milky Way).

Of course, this did not mean that the Dyson sphere actually existed, just that it might exist.

How does a Dyson sphere work? The function of the Dyson sphere is to collect the enormous energy released by the star. We have mastered the basic technology for harnessing the energy of stars-solar cells.

Solar cells work on the "photovoltaic effect," in which photons knock electrons out of atoms, causing positive and negative charges inside the material to separate, creating an electric current. Whatever the variety of Dyson spheres, they probably generate energy by photovoltaic effect.

Some scientists speculate that the energy generated by the Dyson sphere will be transmitted to civilizations near the star through some kind of wireless technology.

What does a science fiction dyson sphere look like? Dyson spheres or similar concepts have appeared in some well-known science fiction works, such as:

Fritz Leiber's The Wanderer (1964)

Larry Niven's Ringworld (1970)

Stephen Baxter's The Time Ships (1995)

Then there was the 1992 sci-fi television series Star Trek: The Next Generation.

Many science fiction writers have described the Dyson sphere as a rigid spherical structure that fits tightly around the entire star, but this was not Dyson's original idea and is unlikely to happen. Other sci-fi works design Dyson spheres into rings and satellite clusters.

How to build a Dyson sphere? There are many possible ways.

One of these is to build a spherical framework around the star (often called a "Dyson shell"). Given the gravitational and radiation pressures of the star, such a structure would probably have to be both elastic and propulsive to change the position of the shell.

However, some scientists believe that such spherical structures may not be stable enough. A Dyson sphere may not be a sphere at all, but it can also take on other forms, such as annular structures, dynamic groups of satellites orbiting stars, and static groups of satellites ("Dyson bubbles") that remain stationary relative to stars.

Scientists have also suggested that raw materials could be obtained from Earth-like planets and that a large number of space robots could be remotely controlled to build such facilities. There are even more grandiose scenarios, such as galaxy-sized "smart dust clouds" that could collect the energy of billions of stars at once.

Could some "strange" cosmic signals come from Dyson spheres? There are many strange and inexplicable signals in the universe, but so far none of them have anything to do with Dyson spheres.

A few years ago, there was a star commonly known as "Tabby Star" whose brightness was reduced for unknown reasons, reminiscent of a Dyson sphere, but further observations revealed that this was actually caused by dust clouds around the star.

Originally published in Science Focus September 2022

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