How to build a Dyson sphere? Space experts give a plan

In recent decades, the Dyson sphere, a superstructure in science fiction, has been attracting thinkers. Not long ago, Dirk Schulze-Makuch, an astrobiologist at the Center for Astronomy and Astrophysics at the Technical University of Berlin, wrote an article telling people how to build a Dyson sphere.

A theoretical physicist's vision In 1960, British theoretical physicist Freeman Dyson published a one-page paper in Science magazine, describing perhaps the most hopeful scenario ever for the future of human technology.

Dyson envisioned that an advanced civilization could meet its growing energy needs by building a sphere around its own planet and absorbing the energy output of that planet.

Imaginary Dyson Sphere

However, this paper is more theoretical and does not talk about practical engineering applications. Dyson did not provide more details about what this giant structure should look like and how to build it. He simply described the sphere as a "habitable shell" surrounding a planet. But this is enough to attract and inspire many astrophysicists, scientists and science fiction writers.

In some of Dyson's descriptions, the Dyson sphere looks like a huge ring that surrounds a star and almost touches the Earth. In other descriptions, the Dyson sphere is a giant structure that completely wraps around the sun and can capture every bit of energy emitted by the sun. In addition to scientific works, Dyson spheres also appear in novels, movies, and TV shows. For example, in "Star Trek", the Dyson sphere is the home of an advanced civilization.

Dyson was aware of the challenges of building such a behemoth, and he himself was skeptical about the possibility of building a Dyson sphere. However, his Dyson sphere concept inspires ambitious ideas about the future of human civilization and provides a solution to some of humanity's most catastrophic predicaments.

Harnessing the total energy of the sun or other stars can meet our immediate and long-term energy crises, but when we can access the full energy output of a star, it will be far more than just meeting our terrestrial energy needs.

The "Relic" episode of Star Trek: The Next Generation originally aired on October 12, 1992. The starship Enterprise is shown alongside a Dyson sphere.

With so much energy to spare, we could potentially increase our chances of communicating with distant civilizations by sending high-energy laser pulses to exoplanets that might harbor life. These Dyson-powered beams could travel farther into the universe than any currently known means, penetrating denser regions of space, such as dust clouds, that would attenuate the signals we send.

Alternatively, we could use this energy to travel directly to exoplanets—some astrophysicists envision that we could shorten the trip by manipulating the space-time continuum through quantum gravity experiments. Another intriguing idea is to create so-called Kugelblitz black holes out of pure photons, which have been shown to theoretically power future interstellar spacecraft. By warping space-time, we might be able to travel faster than the speed of light, or create wormholes that provide shortcuts across the galaxy.

Even more tantalizing, the nearly unlimited energy provided by a Dyson sphere could solve some of our most critical challenges in extending our lifespans. Proponents of cryogenics realize that using the technology on a large scale and for extended periods of time would require vast amounts of energy, far beyond what is currently available.

In 2018, researchers Alexey Turchin and Maxim Chernyakov proposed that AI might be able to digitally recreate a deceased person in a simulated world using their DNA and other information. Creating a sufficiently rich sample of simulated humans belonging to a nearly immortal race would require a lot of energy and many ethical and philosophical hurdles to clear. But the researchers proposed that Dyson technology could provide the energy needed.

Is it possible to build a Dyson sphere?

Dyson's ambitious vision seems more relevant today than ever. If technology continues on its current growth curve, global energy demand could increase by 50 percent in the next 30 years, according to the U.S. Energy Information Administration.

Wind, solar, and other renewable energy sources will help in the short term, but long-term solutions will require more daring engineering. A Dyson sphere might be a bold solution, but to make it happen we clearly have to overcome many physical and mechanical problems that even a civilization thousands of years more advanced than us might not be able to solve.

As a professor at the Center for Astronomy and Astrophysics at the Technical University of Berlin, I have spent decades exploring the possibility of advanced extraterrestrial civilizations. I have co-authored five books on extraterrestrial life, and my interest in the science has inspired me to continue investigating the possibility that Dyson spheres are advanced extraterrestrial technology. About a decade ago, I became interested in various large-scale projects that could be the work of extraterrestrial civilizations.

A black hole, artistically rendered, distorts space and time, creating a wormhole.

In 2010, I investigated the feasibility of building a Dyson sphere. When I worked with Brooks Harrop, a former physics student of mine at Washington State University in Pullman, we discovered a number of problems with the common concept of a Dyson sphere, not the least of which is the risk of the sphere collapsing. A rigid concentric sphere orbiting a star would experience gravity at every point.

No material known today can resist this force. Engineers might try to solve this problem with a complex system of thrusters that would act as a counterforce to keep the shell in place.

But given the shell’s enormous mass — in most scenarios, the structure has a radius of 93 million miles, the distance between Earth and the sun — such a system would first consume most, if not all, of the energy collected by the shell.

Assuming we can overcome these problems and build this sphere in the distant future: How would it survive meteors, asteroids, radiation, and solar flares? An object with the mass of Halley’s Comet would hit the sphere with the kinetic energy of more than a million Tsar hydrogen bombs, the most powerful nuclear device ever detonated by humans.

Dyson anticipated these risks and conceded that the possibility of a shell or ring around a star was unlikely, but the physicist proposed a solution: a swarm of objects in independent orbits around a star could harvest the energy while avoiding most of the physical and mechanical problems of a solid Dyson sphere.

These satellites can be built and added to the system gradually over time, gradually increasing the energy output of the cluster.

A Dyson swarm of about 10 million satellites could meet humanity's energy needs. That would require many satellites, but modern satellite constellations are setting a precedent for such an engineering feat. SpaceX could launch 240 Starlink communications satellites per month, and by February 2022 it would have more than 2,000 satellites in space.

When completed, the cluster could number tens of thousands—a number far smaller than that of a Dyson swarm, but large enough to capture our imaginations.

A more realistic solution: Dyson swarm

To overcome the difficulties of Dyson's original concept, Harrop and I found a more feasible alternative design: the Dyson Swarm. We named this design the Solar Wind Power Satellite (SWPS). Conventional solar panels collect energy from visible light, but our satellites collect electrons, which make up half of the solar wind (the other half is made up of protons and alpha particles).

The fast solar wind has a speed of about 750 km/s-1, which makes these electrons more energetic than the electrons in the visible light that hit the solar panels. The core of our SWP satellite is a long metal wire pointing to the sun, which is charged to generate a magnetic field, which then guides the incoming electrons into a spherical metal receiver. These electrons generate an electric current, which maintains the magnetic field in the wire and forms a system between the two that can maintain its own stability.

Most of the current will still be used to generate power to beam infrared laser light to a receiving station on Earth. Infrared is the best choice because of the transparent "infrared window" in our atmosphere, which allows wavelengths between about 8 and 13 microns to pass through without being absorbed.

After the laser sends the electrical energy to the receiving station, the remaining electrons will fall back onto the ring sail, where sunlight shining there will excite them, generating enough energy to keep the satellite in orbit around the star.

British-born American theoretical physicist Freeman Dyson (1923-2020) sits in his office at the Institute for Advanced Study in Princeton, New Jersey, on February 24, 2009.

Each SWP satellite weighs about 3.7 metric tons (about three times the weight of a GPS satellite) and provides about 2 megawatts of continuous power output 24 hours a day, enough to power about 1,000 U.S. domestic satellites. A single SWP constellation could meet all of humanity's energy needs.

The satellites can be made from relatively simple, cheap materials; the cost of building each satellite is mainly spent on 950 feet of copper wire. Because the satellites use the solar wind as an energy source, they will absorb minimal heat and operate at nearly 100% efficiency. In contrast, traditional solar cells are expensive to produce because their semiconductors require high-purity silicon, and their efficiency is very low, about 20%.

There are still many technical obstacles facing the Dyson swarm. While SWP satellites require little maintenance, they are not self-cleaning. If the satellites’ sails capture positive ions instead of electrons from the solar wind, the satellites will become less efficient and the performance of the entire system will degrade over time.

We also haven't solved another difficult problem: how to keep satellites in stable positions amid the ever-changing solar wind, and how to arrange the orbits of millions (and perhaps eventually billions) of satellites around their stars.

Although low-power energy delivery laser systems have made great progress in recent years, making the systems work in space remains a challenge. Even small temperature changes of less than one degree Celsius can cause large changes in the wavelength and output efficiency of the laser.

Keeping a constant temperature in space is a tricky business - it's hard to transfer heat from a hotter object to a cooler object without air. There are so many tricky problems that the Dyson Swarm has yet to solve, but perhaps they have already been solved by another civilization.

Are there Dyson spheres in the universe?

In our book Cosmic Zoo: Complex Life on Many Worlds, which I co-authored with William Baines, a senior research fellow at Cardiff University, we argue that once life arises on a planetary body, it will eventually evolve to intelligence—provided the planet remains habitable long enough.

The basis for this argument is that all of the major transitions in the evolution of life on Earth appear to have occurred multiple times, either independently of one another or via different biochemical pathways, suggesting that some of the trillions of other planets in the universe may have gone through the same evolutionary process, and that some of the life forms on those planets may have evolved into intelligence.

Do they have enough advanced technology to build a Dyson sphere? Freeman Dyson hypothesizes that if they built a Dyson sphere, we could detect it.

A traditional Dyson sphere with a solid shell would emit residual energy at mid-infrared wavelengths, detectable by current human instruments. At least one research group has begun looking for this signal.

Jason Wright, professor of astronomy and astrophysics at Penn State, and Matt Povich of the Department of Physics and Astronomy at California Polytechnic State University, have begun searching for strong infrared signatures from Dyson spheres in space using data from NASA's Wide-field Infrared Survey Explorer (WISE).

That search did not find a Dyson sphere, and perhaps the reason our telescopes haven’t seen any megastructures in space is that aliens have come to the same conclusion we infer in our paper: that building a giant, solid Dyson sphere is impractical, even for a civilization more advanced than ours.

While we may never see our sun encased in a megastructure or siphoning energy from millions of satellites orbiting it, science and science fiction inspired by Dyson spheres will continue to inspire our wildest imaginations about life on this planet and beyond.

This may be the most valuable contribution of the Dyson sphere - it sets an ambitious goal for us and paves the way for us to continue to attempt revolutionary discoveries.

References

1. https://www.popularmechanics.com/space/a40230192/dyson-sphere-immortality/

Compiled by: BladeRunne

Reviewer: Liu Yong, Researcher at the National Space Science Center of the Chinese Academy of Sciences, Ambassador of China's Space Science Popularization