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Matrioshka Brain: How advanced civilizations could reshape reality

Future or extraterrestrial civilizations could create megastructures the size of a solar system.

  • Advanced civilizations are likely to create megastructures to harness the energy of the stars.
  • These megastructures could be nested, creating "Matrioshka Brains" – the Universe's most powerful supercomputers.
  • Matrioshka Brains could be used to simulate reality and remake the Universe.

Why create a Matrioshka Brain

To some people, like Elon Musk, the troubling thought is that we don't really know whether we live in a "real" or impressively-rendered digital world. What makes the prospect of us living in a simulation more than a tired billionaire's flight of fancy is the possible existence of Matrioshka brains, theoretical megastructures that could harness the power of stars.

To understand how they would work, we need to look very far into the future.

With the advent of scientific thinking, humans discovered a seemingly reliable method for probing the world around us. We learned much about what the world is made of and how to bend some parts of it to our will. But what we learned and developed technologically is likely negligent compared to what's about to come, especially if we project our current rate of progress. One prediction is that the needs of an advanced society for more energy will at some point lead to the creation of megastructures called Dyson Spheres. These would encircle stars like our Sun to harness their energy.

Dyson Spheres

Freeman Dyson, the physicist who came up with the idea of Dyson Spheres saw their possible existence as something to keep in mind when searching for alien life. His 1960 paper "Search for Artificial Stellar Sources of Infra-Red Radiation" advocates looking for unusual emission signatures of hypothetical structures like Dyson Spheres to spot other spacefaring civilizations.

But as inventor Robert Bradbury wrote, Dyson saw his spheres as quite specifically as a place to live. For example, a "layer of habitats for human beings orbiting the Sun between the orbits of Mars and Jupiter." What Bradbury came up with is an extension of that idea - what if a Dyson sphere was turned into a computer, the most powerful machine in the Universe?

"If extraterrestrial intelligent beings exist and have reached a high level of technical development, one by-product of their energy metabolism is likely to be the large-scale conversion of starlight into far-infrared radiation," wrote Freeman Dyson. "It is proposed that a search for sources of infrared radiation should accompany the recently initiated search for interstellar radio communications.

Artist's concept of a Dyson sphere. Credit: Adam Burn.

Bradbury's year million proposal

What Bradbury envisioned in the anthology "Year Million: Science at the Far Edge of Knowledge" is that far in the future, we'd have the technology to create a set of nested shells around a star – each shell essentially being a Dyson Sphere. Because this megastructure would resemble a Russian nested Matryoshka doll, where smaller dolls fit inside larger ones, he called the concept a "Matrioshka Brain". This solar-system-sized machine would be the most powerful computer in the Universe, harvesting all the useful energy from a star, while rendering it "essentially invisible at visible wavelengths".

To work as a giant computer, or the "highest capacity thought machine" as Bradbury wrote, a Matrioshka Brain (MB) would draw power from the star and spread it through the shells. One shell (or sphere) would collect all the energy it could draw from the star and then would pass on the excess to another larger processing shell that would surround it. This would repeat until all the energy was exhausted.

The shells would be made of computronium - a hypothetical material which nears the theoretical limit of computational power. The inner shells would run at a temperature close to the star's while the outer shells would be at the temperature of interstellar space.

If they were built in our solar system, the Matrioshka Brain shells would have orbits ranging from inside Mercury's to outside Neptune's, claimed Bradbury.


How and when we could get a Matrioshka Brain

Needless to stay, the scope of the engineering and resources required for such a project would be tremendous and far beyond what humans can currently muster. One technology mentioned by Bradbury that is actually being created now and can lead to the construction of such immense structures are self-replicating factories. The company Made in Space has been making headway in its implementation and design of 3D printing tech in space, with the ultimate goals of putting factories that build themselves into orbit.

How would you, a superpower civilization that ranks high on the Kardashev scale, use such a computer, which could conceivably have all the power of the Sun at its disposal? Among science fiction aficionados, uses of this hypothetical super-tool, a class B stellar engine, could range from uploading human minds into virtual reality to changing the structure of the universe, as imagined author Charles Stross. The computers could also be used to simulate reality, potentially creating a whole alternate universe. This, of course, leads to the question - how real is our current universe?

What if the whole world around you was just a very good simulation? One that engages all your senses, feeding you information about supposed smells, sights and sounds. But, ultimately, it's a computer program that's running and none of the things you think you are encountering are actually there. And what's the difference if the simulation is so amazingly realistic?

The mere prospect of Matrioshka Brains makes these questions have real potency. For what it's worth, Bradbury predicted that if current trends (circa 2000) were projected, humans would be able to build such a machine brain by 2250. He thought it would require most of the silicon from the planet planet Venus as raw material. Even so, the first MB would have the "thought capacity in excess of a million times the thought capacity of the 6 billion+ people," wrote Bradbury.

For more on Matrioshka Brains, check out Bradbury's paper on how to build one.

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The multifaceted cerebellum is large — it's just tightly folded.

Image source: Sereno, et al
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  • The so-called 'little brain' is nearly 80% the size of the cerebral cortex when it's unfolded.
  • This part of the brain is associated with a lot of things, and a new virtual map is suitably chaotic and complex.

Just under our brain's cortex and close to our brain stem sits the cerebellum, also known as the "little brain." It's an organ many animals have, and we're still learning what it does in humans. It's long been thought to be involved in sensory input and motor control, but recent studies suggests it also plays a role in a lot of other things, including emotion, thought, and pain. After all, about half of the brain's neurons reside there. But it's so small. Except it's not, according to a new study from San Diego State University (SDSU) published in PNAS (Proceedings of the National Academy of Sciences).

A neural crêpe

A new imaging study led by psychology professor and cognitive neuroscientist Martin Sereno of the SDSU MRI Imaging Center reveals that the cerebellum is actually an intricately folded organ that has a surface area equal in size to 78 percent of the cerebral cortex. Sereno, a pioneer in MRI brain imaging, collaborated with other experts from the U.K., Canada, and the Netherlands.

So what does it look like? Unfolded, the cerebellum is reminiscent of a crêpe, according to Sereno, about four inches wide and three feet long.

The team didn't physically unfold a cerebellum in their research. Instead, they worked with brain scans from a 9.4 Tesla MRI machine, and virtually unfolded and mapped the organ. Custom software was developed for the project, based on the open-source FreeSurfer app developed by Sereno and others. Their model allowed the scientists to unpack the virtual cerebellum down to each individual fold, or "folia."

Study's cross-sections of a folded cerebellum

Image source: Sereno, et al.

A complicated map

Sereno tells SDSU NewsCenter that "Until now we only had crude models of what it looked like. We now have a complete map or surface representation of the cerebellum, much like cities, counties, and states."

That map is a bit surprising, too, in that regions associated with different functions are scattered across the organ in peculiar ways, unlike the cortex where it's all pretty orderly. "You get a little chunk of the lip, next to a chunk of the shoulder or face, like jumbled puzzle pieces," says Sereno. This may have to do with the fact that when the cerebellum is folded, its elements line up differently than they do when the organ is unfolded.

It seems the folded structure of the cerebellum is a configuration that facilitates access to information coming from places all over the body. Sereno says, "Now that we have the first high resolution base map of the human cerebellum, there are many possibilities for researchers to start filling in what is certain to be a complex quilt of inputs, from many different parts of the cerebral cortex in more detail than ever before."

This makes sense if the cerebellum is involved in highly complex, advanced cognitive functions, such as handling language or performing abstract reasoning as scientists suspect. "When you think of the cognition required to write a scientific paper or explain a concept," says Sereno, "you have to pull in information from many different sources. And that's just how the cerebellum is set up."

Bigger and bigger

The study also suggests that the large size of their virtual human cerebellum is likely to be related to the sheer number of tasks with which the organ is involved in the complex human brain. The macaque cerebellum that the team analyzed, for example, amounts to just 30 percent the size of the animal's cortex.

"The fact that [the cerebellum] has such a large surface area speaks to the evolution of distinctively human behaviors and cognition," says Sereno. "It has expanded so much that the folding patterns are very complex."

As the study says, "Rather than coordinating sensory signals to execute expert physical movements, parts of the cerebellum may have been extended in humans to help coordinate fictive 'conceptual movements,' such as rapidly mentally rearranging a movement plan — or, in the fullness of time, perhaps even a mathematical equation."

Sereno concludes, "The 'little brain' is quite the jack of all trades. Mapping the cerebellum will be an interesting new frontier for the next decade."

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