M-Brains trump J-Brains

Robert J. Bradbury (bradbury@aeiveos.com)
Tue, 6 Jul 1999 16:19 PDT

> "den Otter" <neosapient@geocities.com> wrote:
> people to visualize and thus better understand transhuman concepts,
> from nanotech to Jupiter Brains. I'll give it some more thought, though.

J-Brains are an obsolete concept at this point. To start with they were a non-optimal form. Something the size of Jupiter cannot use all of the power available from a star (without melting) and if it were even relatively "solid" as Jupiter is, you would waste most of your energy pumping around the cooling fluid for your computers. [Friction losses mount up when you circulate fluid through something the size of Jupiter.]

Following in the tradition of "you need a cool name to popularize an idea", e.g. "Black Holes", I have christened an optimal computing architecture in the post-singularity age - a "Matrioshka Brain" (M-brain). [Matrioshka's are the carved wooden nesting Russian dolls.] This will be a "legitimate" scientific concept (if there is such a thing) as it will be discussed at the Bioastronomy '99 conference in Hawaii occuring just before the Extro4 conference.

This is (so far as I can tell at this point) an optimal computing (i.e. "intelligence") architecture. A M-brain has several interesting properties

M-brains have the property, that they do most of their communication "inward" (across shorter delay paths) while radiating waste heat "outward" (to supply power for slower layers). There may be an alternate architecture involving nested layers of little J-brains which are themselves structured like M-brains, but this architecture has the problem that the waste heat of a single node heats up all of the surrounding nodes (to both the interior and exterior). There comes a point when the computational advantage you gain (due to decreased communication path delays in J-brain type nodes) is offset in the decline in computational capacity that results from the increased use of materials to "shield" or reflect incoming heat from nearby J-Brains and the power consumed by increased cooling requirements.

Paul Vitanyi, I believe, has shown, that even if you have "hyper-dimensional" (but not faster-than-light) communication paths, you cannot escape the communication-delay problem in computation. So ultimately the optimal architecture will come down to the size of the problem you are trying to solve. While a J-Brain architecture may for a limited set of problems provide the quickest solution, and works great if you only have a few of them in a solar system, an M-Brain architecture (with the greatest computational and communication capacity) seems to be the optimal solution for the largest problems and/or supporting the largest thought machines.

Robert Bradbury