What Are Matrioshka Brains?

A Matrioshka Brain is a hypothetical megastructure, based on the Dyson sphere, of immense computational capacity. It is an example of a Class B stellar engine, employing the entire energy output of a star to drive computer systems.

Such a structure would be composed of a collection of one or more (typically more) Dyson spheres built around a star, and nested one inside another. A significant percentage of the shells would be composed of nanoscale computers. These computers would be at least partly powered by the energy exchange between the star and interstellar space.

A shell (or component, should a Dyson swarm be the design model used) would absorb energy radiated onto its inner surface, utilise that energy to power its computer systems, and re-radiate the energy outwards. The nanoscale computers of each shell would be designed to run at different temperatures; shells or components at the core could be nearly as hot as the central star, while the outer layer of the Matrioshka Brain could be almost as cool as interstellar space.



In this episode, Isaac explores the Matrioshka Brain, a nested Layer type of Dyson Sphere designed to turn stars in to giant computers, and conclude our look at Dyson Spheres and other types of Stellar Engines.


The Matryoshka Doll

The ideal mechanism for extracting usable energy as it passes “through” a shell or component, the number of shells (or orbital levels) that could be supported in such a manner, the ideal size of the shells to be constructed, and other details, are all issues of speculation.

This structure has clear structural analogies to Russian Matrioshka dolls, from which the concept derives its name. 1

Creating a Matrioshka Brain with Dyson Spheres

Imagine a computer the size of a solar system. For power, it would use a Dyson sphere—a solar array that completely surrounds the host star to collect almost all of its energy. That energy-collecting sphere would double as an ultra-powerful computer processor.

Once the sphere had collected all the energy it needed, it would pass the excess to another larger Dyson-sphere processor that completely surrounded the first, repeating the process until all of the energy was being used. That’s why this theoretical computer is called a Matrioshka brain: the nested Dyson spheres would resemble matryoshka dolls, or Russian nesting dolls.

Of course, if you surround your star with Dyson spheres, it would be difficult for life on your planet to continue. That’s kind of the point: this Matrioshka brain would be so powerful that a species could upload their entire consciousness into it and live within an alternate universe simulated by the computer.

The species itself could die and its planet could be destroyed, but the civilisation would live on in a digital world identical to the one it left behind. In fact, many people, including Elon Musk, believe we’re living in a simulation like that at this very moment. This provides one answer to the Fermi Paradox—that is, the question of why we haven’t encountered aliens despite the likelihood that they’re out there. It’s possible that any civilisation advanced enough to find us has already decided to abandon reality entirely and upload themselves to a Matrioshka brain.2

How To Build A Matrioshka Brain

Matrioshka Brains may be constructed very slowly over thousands of years using a small fraction of a civilisation’s resources. More likely they will be constructed rapidly using leveraged construction techniques to take advantage of the benefits which can be expected from having significantly expanded computational and information storage capacities. In our solar system we can propose the following construction process:

1 . Convert one or more asteroids into solar power collectors. A 3 mile asteroid receiving 10^10  W of solar power can be converted into solar collectors which can harvest 10^22 W of solar power. Time required: ~several years.

  • 2 . Beam the asteroid derived collector power to Mercury where it is used and convert the bulk of the planet into additional power collectors which harvest the entire solar output of the sun. Time required: < 1 month.
  • 3. Use the entire output of the sun to disassemble the remaining asteroids, comets, moons and minor planets to construct the major portions of the Matrioshka Brain. Time required: ~20 years.
  • 4. Use some fraction of the material from the moons and minor planets to construct thermonuclear reactors that provide the power required to disassemble the gas giant planets
    (Uranus, Neptune, Saturn & Jupiter). Time required: 10-1000 years.

While Drexler 1992 postulates structures of .001 kg/m 2. The energy requirements for the disassembly of the larger planets particularly Saturn and Jupiter are dominated by requirement of getting the material out of the planet’s gravity well.

Even if the entire energy output of the sun were used to disassemble Jupiter, it would still take hundreds of years. Faster disassembly requires supplementing solar power with fusion energy derived from manufactured thermonuclear reactors.

The construction of a small number of solar collectors near the sun could provide high concentrations of beamed power to any point in the solar system. The strongest limit on construction times are likely to be the time required to move power collectors into the proper positions around the sun or the time required to ship materials from outer solar system locations to inner solar system locations, should essential elements be in short supply.

Conversely if non-star centred MBs are desirable, the limit is on moving sufficient mass from various solar systems to gravitationally balanced or minimally disrupted point between the energy sources.

While many authors have focused on the possibility of moving comets, moons or planets for
construction or terraforming purposes, it should be understood that this is not required for MB
construction. First, since the elemental requirements of MB should be known, it would be better to disassemble materials on moons or planets and ship only those molecules or atoms which are absolutely necessary.3

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