I want to begin with a number that escapes the imagination. Every second, the Sun releases about 3.8 times 10 to the power of 26 joules. Written out, that number would have 27 digits. All of humanity uses a little over 600 exajoules a year, counting electricity, heat and fuel together. The Sun delivers that amount in about 1.6 millionths of a second.

I ran the calculation several times, because the result looks absurd. It holds. Everything our civilization moves, heats and computes in a year amounts to the blink of an eye for our star. More precisely, to a fraction of one, because a blink lasts a hundred thousand times longer.

In the middle of our Milky Way, in an ordinary spiral arm, there is a power plant that makes every human structure vanish by comparison. It has been running for four and a half billion years. It will run for billions more. And we use almost none of it.

What Reaches the Earth

Seen from the Sun, the Earth is a speck of dust. It intercepts about 1.7 times 10 to the power of 17 watts. That is roughly one two-billionth of everything the Sun radiates. The rest flies past us into space.

Of the share that reaches us, we use only a tiny part. Humanity runs on about 20 terawatts. That is around one nine-thousandth of the sunlight striking the Earth. Even if we covered every square meter of the planet with solar cells, we could never go beyond what falls on this small world.

Between what we use today and the total output of the Sun lies a factor of about twenty trillion. A number like that means nothing to anyone. So I translate it into time. Imagine our present consumption as a single second. The whole Sun would then correspond to about 600,000 years. Modern humans have not even existed that long.

That sounds like a task for some distant future. I think that is a mistake. The first step has already been taken.

The First Step Has Been Taken

Anyone who wants to gather solar energy beyond the Earth has to catch it where there is no night, no weather and no atmosphere. That is the basic idea of solar power stations in orbit. For decades it was considered technically possible and economically pointless. That is now changing.

The California Institute of Technology has already transmitted power wirelessly from space with its MAPLE experiment. The American company Aetherflux plans to send power from low Earth orbit to the ground by infrared laser. Overview Energy has agreed a capacity reservation with Meta for up to one gigawatt. An orbital demonstration is planned for 2028, with delivery from 2030. Similar programs are underway in Japan, China and the United Kingdom, and at the European Space Agency.

What stands out is who the customer is. It is not the utilities. It is the operators of large data centers. Their demand for power is growing faster than the grids on Earth can keep up with. The first demand for solar energy from space is coming from computation.

These systems deliver kilowatts, later perhaps gigawatts. Measured against the Sun, that is nothing. But this is the beginning of a development with no natural ceiling, except the Sun itself.

A Planet as Building Material

In 1960, the physicist Freeman Dyson published a short paper whose influence has lasted to this day. His reasoning was simple. Any civilization whose energy demand keeps growing will eventually begin to collect the light of its star on a large scale. Science fiction turned this into a closed sphere around a star. Dyson meant something else. He was thinking of a multitude of separate collectors, each on its own orbit around the star. In other words, a swarm.

Such a swarm needs no miracle material. It needs mass, and a great deal of it. A sphere at the distance of the Earth from the Sun has a surface of about 2.8 times 10 to the power of 23 square meters. The planet Mercury weighs about 3.3 times 10 to the power of 23 kilograms. Spread Mercury evenly over that surface, and you get a little over one kilogram per square meter. That is a thin foil, not a structure.

This is why almost every study treats Mercury as the source of raw material. It lies close to the Sun. It has almost no atmosphere. A large part of it is metal. Its low gravity allows material to be lifted into space with comparatively little energy.

The real lever is a feedback loop. The first collectors supply energy to mine and manufacture further collectors. Each new surface speeds up the next. The Oxford researchers Anders Sandberg and Stuart Armstrong calculated that under favorable assumptions, such a build-out could take decades rather than millennia. Whether those assumptions hold is open. Manufacturing would have to be carried out almost entirely by machines that replicate themselves. We are far from that.

But physics does not stand in the way. The limit is technology, and technology improves.

Why It Will Never Be the Whole Sun

The question of how to use the Sun at 100 percent has a clear answer. It cannot be done.

Every conversion of energy into work leaves waste heat behind. That heat has to be released into something colder, and in the end that is empty space. Even a perfect swarm would deliver only part of the Sun's output as usable work. The rest radiates away as heat. The limit is high, but it lies below the whole.

There is a second reason, and it is simpler. A complete swarm would darken the Earth. Any serious plan has to keep the cone of light toward the Earth clear. Because the Earth receives only one two-billionth of the Sun's output, leaving that gap costs almost nothing. But it shows what this is really about. A swarm decides which light falls where.

Who Holds the Swarm

This is where physics becomes a question of power.

A swarm that collects even one thousandth of the Sun commands roughly ten billion times more energy than the entire Earth uses today. Whoever controls it can direct that energy, sell it or withhold it. They can concentrate light or cast shadow. No economy on Earth could hold its own against such an installation.

We already use the Sun. Every solar panel, every wheat field and every leaf lives on its light. On Earth, nobody takes anything away from anyone else in the process. The light on my roof is not missing from my neighbor's. Whoever wants more sunlight needs more land. That land is spread across countries, climate zones and continents.

In space, this order no longer holds. Almost all the light a swarm gathers would otherwise have flown unused into space. But a swarm can also stand where light was meant to fall on a world. That applies to the Earth, to Mars and to every future settlement. On Earth, no one can take the Sun from someone else. In space, for the first time, it becomes possible.

The first installations will be built by companies, for customers who need power for their data centers. That is not a reproach. This is how technology begins. But the ownership logic that applies to one gigawatt in orbit will quietly become the logic for everything that follows. If we only ask who owns the light of the Sun once the swarm is large enough to answer the question itself, we will have asked too late.

What Our Descendants Will Do With It

I consider it certain that our descendants will use the Sun on a large scale. The reason is plain arithmetic. Since the beginning of industrialization, humanity's energy use has grown on average by a little over two percent a year. If that growth continues, the full output of the Sun is reached in about 1,400 years.

Astronomers call a civilization that reaches this point a Type II civilization. The label sounds like a distant rank. In fact it is only the end of a growth curve we are already traveling along.

So the growth we are used to has a physical limit. It is closer than one might think. Fourteen hundred years back takes us into the early Middle Ages. At the same time, the Sun itself will keep shining for billions of years. The supply is not the problem. The problem is how we handle it.

There is one task for which our descendants will need the swarm, regardless of any demand for power. The Sun is slowly growing brighter, by about ten percent every billion years. In the distant future, this will make the Earth uninhabitable. A swarm that regulates the cone of light toward the Earth could offset that process. It would act as a sunshade that keeps the planet habitable beyond its natural term.

That is the real point of this power plant. Whoever uses the Sun does not only use its energy. They take on responsibility for the light on which all life on Earth depends.

A Sky Without Swarms

Dyson did not write his 1960 paper as a construction manual. He wrote it as a search guide. A swarm around a distant star would have to release its waste heat as infrared radiation. Astronomers could therefore find it.

That is exactly what Project Hephaistos at Uppsala University is attempting. The team searched about five million stars in the catalogs of the Gaia and WISE space telescopes. Seven candidates with conspicuous heat signatures remained. Radio astronomers then showed that obscured galaxies in the background could explain these signals. The James Webb Space Telescope has since resolved two of the candidates in exactly this way. Behind unremarkable stars lay distant, dust-shrouded galaxies.

As far as we can tell today, no one in our neighborhood has visibly enclosed their sun. That allows several readings. Perhaps there is no one. Perhaps civilizations do not grow the way Dyson assumed. Perhaps they fail at the very question I raised above, before they ever reach their star.

I do not read the empty sky as a warning. I read it as an open space. If a civilization in this galaxy learns to use its star without breaking apart over the question of ownership, it could be the first. It could be ours.

When is the right moment for you to decide about the light of the Sun: before the first large collector flies, or only once the swarm is already in place?

| The Planet Futures Organization, the first multiplanetary NGO.

Homepage: https://planet-futures.org