Brain Matryoshka is a hypothetical megastructure proposed by Robert Bradbury, based on the Dyson sphere, which has enormous computing power. This is an example of a class B star machine that uses the entire energy potential of a star to power a computer system  . The name of the concept comes from the Russian wooden doll - the dolls  .
The term “dummy brain” was invented by Robert Bradbury as an alternative to the term “brain-Jupiter” - a similar concept, however, which has not a star, but a planetary scale and is optimized for a minimum delay of signal transmission. The design of the nesting brain emphasizes clean capacity and maximizes the energy obtained from the source (star), while the brain-Jupiter is optimized for the speed of calculations  .
Such a structure should consist of at least two (usually more) Dyson spheres, built around a star and nested inside one another. A significant part of the shells will consist of nanocomputers molecular scale. These computers will at least partially receive energy from the exchange between the star and the interstellar medium. The shell will absorb the energy emitted on its inner surface, use it to power computer systems and radiate energy outside. Nanocomputers each shell will be designed to work at different temperatures.
The idea of building such a device does not violate the known laws of physics, although from an engineering point of view, the construction of this structure will require huge expenses, including the fact that the construction of shells will require the use of material from a significant part of the planetary star system.
It is rather difficult to imagine the possible uses of such huge computing resources. One of the ideas proposed by Charles Stross in the novel Accelerando: the nested doll brain can be used to create an exact imitation of reality or to transfer a person's consciousness into virtual reality   . Damien Broderick suggests that the matrioshka brain will be able to simulate entire alternative universes  .
Futurologist and transhumanist Anders Sandberg wrote an essay on the implications of performing calculations of this magnitude on machines like the matryoshka brain, which was published by the Institute for Ethics and New Technologies  .
Robert Bradbury, the author of the concept, used it in the anthology "Year 1,000,000: Science at the Far Edge of Knowledge " (Eng. Year Million: Science at the Far Edge of Knowledge ), which attracted the interest of the Los Angeles Times and Wall Street Journal  [9 ] .
The idea of high-powered computing devices was explored in Nick Bostrom’s essay in The Philosophical Quarterly . Bostrom argues that if people voluntarily evolve to the postman stage, before each evolution step, large-scale computer simulation will be required, requiring machines such as the matryoshka brain. Bostrom goes further, suggesting that people can actually only be participants in large-scale computer modeling  . Raymond Kurzweil mentions this idea several times in The Singularity Is Already Close (2005), following a similar chain of reasoning. He notes that the existence within the computer model can be just as “real” as in the ordinary biosphere — if such a distinction can be made at all  . The concept of the nesting brain is also discussed in an article published in the April 2003 issue of the journal of the British Interplanetary Society  .
Brain-Jupiter is a theoretical computing megastructure about the size of a planet. Unlike the dummy brain, the Jupiter brain is optimized to minimize signal transmission delays and has a compact structure. Providing power and heat dissipation in such a system presents considerable difficulties.
Although a solid dense object with the size and mass of a terrestrial-type planet or gas giant cannot be built from any known material, such a structure can be built as a low density grid with a mass comparable to a large satellite or small planet, but with a much larger volume, or as a dense, but not solid structure with the mass and density of the planet (this requires monitoring the internal temperature gradient to prevent convection).