Jupiter Brains

This document should be considered dated.  The primary problem is the use of the term 'Jupiter Brain'.  A reasonable description of a 'Jupiter Brain' can be found in the appendix of Sandberg, 1999 and is also known as "Zeus".  The computer architecture discussed in this paper is more properly called a Matrioshka Brain (or a Dyson Brain in Sandberg's terms).  An updated version of this paper with more accurate nomenclature may be found here.

Abstract

Predictable improvements in lithographic methods foretell continued increases in computer processing power. Economic growth and engineering evolution continue to increase the size of objects which can be manufactured and power which can be controlled by humans.  Neuroscience is gradually dissecting the components and functions of the structures in the brain.  Advances in computer science and programming methodologies are increasingly able to emulate aspects of human intelligence.  Continued progress in these areas leads to a convergence which results in megascale superintelligent thought machines.  These machines, also referred to as Jupiter Brains, consume the entire power output of stars (~10²⁶ W), consume all of the useful construction material of a solar system (~ 10²⁶ kg), have thought capacities limited by the physics of the universe and are are essentially immortal.

A common mistake encountered in literature discussing the search for extraterrestrial life is the perspective of assuming and applying human characteristics and interests to alien species.  Authors limit themselves by assuming the technologies available to aliens are substantially similar to those we currently possess.  These mistakes bias their conclusions, preventing us from recognizing signs of alien intelligence when we see it.  They also misdirect our efforts in searching for such intelligence.  We should start with the laws on which our particular universe operates and the limits they impose on us.  Projections should be made to determine the rate at which intelligent civilizations, such as ours, approach the limits imposed by these laws.  Using these time horizons, laws and limits, we may be better able to construct an image of what alien intelligence may be like and how we ourselves may evolve.

1. Jupiter Brains
1. Overview
2. Background
1. Computer Trends and Characteristics
2. Solar Power
3. Kardashev Civilization Levels
4. Computer and Human Operations Equivalence
3. Requirements
4. Architectures
5. Construction Methods and Time Scale
6. Limits
1. Power Limits
2. Size Limits
3. Material Limits
4. Longevity Limits
5. Thought Limits
7. Location
8. Evolution
9. Interactions with and between Jupiter Brains
10. Conclusions
11. References

Overview

The two pillars on which the JB arch rests are the extensions of current engineering trends to the largest scale and the smallest scale.  At the largest scale, in their initial stages, JB are limited by the mass and energy provided by individual solar systems.  At the smallest scale, JB are limited by our ability to assemble materials atom by atom.  The terms megascale engineering and nanoscale engineering are generally used to discuss these different perspectives. The union of construction methods at the small and large scale limits to produce the optimal use of locally available energy and matter is the distinguishing feature of Jupiter Brains.

Megascale engineering has its roots in science fiction.  One of the first scientific examinations of megascale engineering was done by mathematician Freeman Dyson (1960) in which he discussed dismantling Jupiter to construct a shell around the sun to harvest all of its energy and provide a biosphere capable of supporting large numbers of people.  Writer Larry Niven addressed some of the problems of gravity in Dyson shells by changing the form of the biosphere from a shell to a rotating Niven Ring.  Other examples of megascale engineering exist in fictional literature but these are the most relevant for the discussion of JB.

Nanoscale engineering was first discussed  by Richard Feynman in 1959.  These ideas were extended by Eric Drexler in his 1981 PNAS paper and Engines of Creation. Much of the engineering basis for nanotechnology is documented in Nanosystems.  Progress in the development of nanotechnology continues and no serious challenges against its ideas have been produced in the last ten years (Merkle, 1998).  Estimates of its full scale development and deployment range from 10 to 30 years in the future.

Megascale and nanoscale engineering currently do not exist.  Megascale engineering results in the progression of trends in the engineering of large scale structures such as pyramids, oil tankers, suspension bridges, tunnels, sky-scrapers and rockets.  Nanoscale engineering results from trend progressions in microelectronic lithographies, micromachining, microvolume and combinatorial chemistry, biotechnology manipulation of genes and proteins, robotics and computer science.

It is paradoxical that many people more easily envision megascale engineering than nanoscale engineering.  The most logical explanation for this is that our senses are able to directly interact with megascale structures, while intermediaries such as atomic force microscopes or enzymes are required to sense and manipulate things at the nanoscale level.  It is important to remember that atomic scale pumps, motors, engines, power generation apparatus and molecular manipulators (enzymes) exist in every individual reading this document.  By mid-1998, the complete genomic DNA sequences (nanoscale programs) for more than 30 different bacteria and yeast (nanoscale assembly and replication machines) were known.  Nanoscale technology exists and is rapidly being domesticated by humans.

As has been pointed out by Dyson [1960, 1968], Kardashev [1985,1988,1997], Berry [1974], and Criswell [1985], the progression of existing population and economic growth, power and mass management trends in our society will enable the construction of Jupiter Brains using existing (non-nanoscale) technologies within at most a few thousand years. Nanoscale assembly per se is not required.  Current trends in silicon wafer production, if continued, would allow the production of sufficient microprocessors, of current primitive designs, to create a JB by 2250.  It would however require most of the silicon in the planet Venus as raw material. A JB built from such processors would have capabilities significantly less than the limits which would be available using nanoscale construction.  Even so, a computing machine built out of even these primitive components would have a thought capacity in excess of a million times the thought capacity of the 5 billion+ people now populating the planet!  A small fraction of this thought capacity devoted to extending engineering methods should in a brief period develop nanoengineering and assembly to its ultimate limits.

Background

Computer Trends and Characteristics

Lithographic methods will continue to improve, transitioning from optical to EUV, to X-ray, to E-beam, to nano-imprint, each at smaller levels of resolution.  This will culminate in nanoassembly with the ability to manipulate individual atoms.   If historic trends were to continue, atomic scale manipulation would be reached by 2050.   In the last 5 years however, the introduction of decreased lithographic scales has been accelerating [SIA, 1997].  The establishment of a company with the goal of producing a nanoassembler (Zyvex) and recent prognostications on nanotechnology development trends [Drexler, 1998], confirming earlier projections provide some reasons for believing that nanoassembly may become possible in the 2010-2015 time frame.

Lithographic technologies enable the construction of very powerful computers based on a two-dimensional technology.  Systems assembly methods using SIMMs and processor cards (Slot-1) effectively convert 2-D chips into 3-D systems.  The addition of optical interconnects (Emcore, Opticomp & others) and high capacity cooling (Beech et. al., 1992; SDL Inc.) allow significant increases in communication bandwidth and processing density.  Nanotechnology enables the construction 3-D computers which allow the computational, communication, power production and delivery and cooling elements to be tightly integrated into a low cost package using a single uniform assembly process.  The development of nanotechnology will be a natural development once the limits of conventional manufacturing and assembly processes are reached.  There is no known process that allows efficiencies and capabilities greater than those offered by nanotechnology.  It is reasonable to assume that nanotechnology and nanoassembly represents a significant plateau in the development of technological civilizations.

Merkle and Drexler have also developed helical logic which requires nanoassembly methods to create computers based on the control of the movement of single electrons.  The limits on computation are dictated by the size of the computational elements and the heat production associated with the computation.  We may assume that the manipulation of single electrons and the use of reversible logic (such as in rod and helical logic) bring us close to the possible limits of computation.  These topics are explored in much greater depth in Merkle & Drexler, 1996, Sandberg, 1999 and Frank & Knight, 1998.

Since the details of rod-logic computers (power consumption, size, computational capacity, etc.) are the best defined for Mega-nanocomputers, they will be used for our discussion.  Beyond rod-logic, helical logic allows an improvement of 10¹¹ in power consumption per operation.  Theoretical limits potentially allow improvements of 10⁹ in cooling capacities (power density) and 10⁴ in operating frequencies.  If integrated implementations near these limits is feasible, throughput increases from 10¹⁰ to 10²⁰ greater than those presented in this paper could be achieved.
 

Solar Power

Kardashev Civilization Levels

Computer and Human Operations Equivalence.

If we assume 6x10¹⁰ neurons * 5x10¹ firings per second * 10³ operations per neuron firing , we end up with a result of 3x10¹⁵ operations per second (300 Trillion operations per second or 300 TeraOps).  This is likely to be at the high end of possible computational capacities since it is assuming that all neurons are being used simultaneously.  This is unlikely to be true since the brain clearly has specialized structures for visual, auditory and odor input; speech output; physical sensation and control; memory storage and recall; language analysis and comprehension; and left-right brain communication.  It is unlikely that all of these structures will be optimally utilized at any point in time.

A high end estimate of 300 TeraOps for human thought capacity does not significantly differ from those found in the literature as outlined in table Y.
 
 

The fact that each of these capacity estimates using different methods, computes values within a range of 10,000 demonstrates how poorly understood the brain is at this time.  The numbers are however in general agreement.  Because of the specialized structures of the brain, it is impossible to focus all of the available capacity on a single problem.  Computers, unlike the brain, can devote all of their capacity to a single problem (assuming the problem fits in available memory).  This would imply that computers do not require the capacity of the brain to achieve equivalence with specialized areas of the brain.  Developing trends in desktop computers are analogous to the multiprocessing occurring in the brain.  It is not uncommon for systems may now execute 10-20 processes simultaneously.  These might include listening to a network, listening to human speech, recording things for permanent storage, displaying things for interpretation, and devoting intensive processing power to search, recognition or analytical processes.  The available computer power is divided among the tasks at hand in the computer, just as in the brain.

Computer capacity has increased significantly in recent years. Current state-of-the-art computers achieve operating levels as follows:

• Deep Blue (Chess computer):
• 200 million (2x10⁸) positions per second = ~3 million MIPS (3x10¹² IPS)
• GRAPE-4 (galactic stellar motion calculations): 1.1 Teraflops (1.1x10¹² FLOPS)
• Intel Teracomputer: 1.8 teraflops (1.8x10¹² FLOPS)
• IBM Teracomputer: 3 teraflops (3x10¹² FLOPS)
• On the drawing board:
• Year 2000: GRAPE-6 (1 petaflop) (10¹⁵ FLOPS)
• Year 2007+: Supercomputer petaflops

Computers have always been better than humans in arithmetic.  They now seem to be approaching our abilities in tasks which require parallel processing.  In recent years, computer systems have demonstrated 'human' abilities such as:

• Besting humans in games such as Blackjack (with random factors) and Checkers & Chess (with non-random principles).  The only game where a human can currently compete against a computer is Go.
• Proving theorems previously unproved by humans.
• "Reading" documents and "understanding" human speech.
• Driving automobiles.

Requirements

1. Designs for the power collectors, computers, communication apparatus and heat radiators required to actually build a JB.
2. A design for self-replicating factories which can build the JB components.   These factories do not have to be constructed using nanotechnology.   They can be constructed with existing manufacturing methods based on the ideas of Von Neumann [1966].  An extensive study of how to construct automated factories for space manufacturing was produced by NASA in 1982.  These factories must either be capable of replicating themselves to cover the surface of a planet and be able to construct apparatus to transport their output to appropriate stellar orbits or they must be self-replicating in a space environment.  Such self-reproducting factories are not strictly necessary for the production of JBs.  They do however serve to decrease the construction time for a JB by many orders of magnitude.

Architectures

Power Collectors

Power collectors or harvesters may have several measures of their effectiveness:
• absolute power harvesting efficiency
• mass or element requirements for a specified harvesting efficiency
• minimal time to construct a relatively efficient harvester
• harvesters with maximal longevity and minimal maintenance requirements

The simplest power collectors would be high efficiency solar cells or collecting mirrors focusing sunlight on solar cells to convert sunlight into electricity.  These devices may typically operate at conversion efficiencies around 30%.  Alternate power collectors might focus infrared radiation in ways that would allow a Stirling cycle to be used to generate electricity.  Even more elaborate methods would attempt to harvest ultraviolet, X-ray, gamma-ray, microwave and radio energy in ways that would allow their conversion to form which may be used to perform work.

Computing Components

Computing components perform the actual work of the Jupiter Brain.  Computing components may have many architectures which are dependent on the nature of the problem being solved.

The computers would typically be NanoCPUs or MegaCPUs with a large amount of nanoscale storage and high efficiency, high bandwidth (optical) communications channels to other similar devices.

Storage Components

Storage components are required to store the data being used as inputs to the computing components and to store the results of the computations.  Storage components may be passive, utilizing elements in specific configurations or locations, electrons in specific spin states or circulating photon packets.

Heat Disposal Components

Any computing element, no matter how efficient, will require heat disposal.  This is a consequence of the second law of thermodynamics.  NanoCPUs may be able to radiate away the heat they generate.  They would require minimum inter-CPU spacings to avoid being baked by neighboring CPUs.   MegaCPUs require active cooling, typically using a circulating cooling fluid between the CPU and heat radiators.  The operating temperature of the CPU is determined by the materials from which it is constructed.  The radiator temperature is determined by the allowed temperatures of the CPU, the cooling fluid and the radiator material.

Radiation Protection Components

For most nanoscale devices, radiation damage is a significant hazard.    The diagnostics and repair of radiation damage would represent a significant drain on time and energy resources unless significant efforts are made to minimize its effects.  Radiation tolerance may be achieved in the following ways:
1. positioning JB in locations where radiation fluxes are minimal;
2. using controlled external power sources (beamed power) instead of uncontrolled internal power sources (stars);
3. active shielding with electric or magnetic fields;
4. passive shielding with bulk mass which is unusable for computer construction or energy production.

Matrioshka Jupiter Brains

MegaCPU JB are limited by their heat dissipation requirements and their heat removal capacity determined by the heat removal "fluid".  The temperature of the radiators will be determined by the boiling point of the fluid or the melting point of frozen solids circulating in the fluid.  It is possible to construct a set of nested  JB similar to Russian Matrioshka dolls.  The architecture of the energy collectors, CPUs and radiators is designed to take advantage of the downhill thermodynamic slope,  Each layer of the "Matrioshka brain" harvests the energy (optical or heat radiation) of the next inner layer, performs what work is possible with that energy and radiates it at an even lower temperature.  The table outlines several possible working fluids and temperature differentials:
 

Table 4. Layers of Matrioshka Jupiter Brains

Circulating Fluid	Radiator Temperature (oK)	Radiator Material
Iron in Aluminum or Silicon	1808	Nickel Oxide
Silicon in Aluminum or Calcium	1683	Nickel Oxide
Calcium in Aluminum	1112	Nickel/Iron Oxide
Aluminum in Sodium or Potassium	934	Nickel/Iron Oxide
Magnesium in Sodium or Potassium	921	Nickel/Iron Oxide
Lithium in Sodium, Potassium or Phosphorus	454	Nickel/Iron Oxide/Graphite
Sulfur in Sodium, Potassium or Phosphorus	385	Nickel/Iron Oxide/Graphite
Sodium in Potassium	371	Nickel/Iron Oxide/Graphite
Ice in Pentane	273	Iron Oxide/Graphite
Ammonia in Methanol	195	Iron Oxide/Graphite
Methanol in Ethanol	179	Iron Oxide/Graphite
Pentane in Ethane	143	Iron Oxide/Graphite
Methyl Silane in Ethane	117	Iron Oxide/Graphite
Argon in Oxygen	84	Iron Oxide/Graphite
Nitrogen in Oxygen	63	Iron Oxide/Graphite
Oxygen in Fluorine	55	Iron Oxide/Graphite

Obviously the Matrioshka Brain architecture is highly dependent on the structural materials from which the energy collectors, computational elements and radiators are constructed.  At higher temperatures the greatest problem is the destruction of the computational elements.  Temperatures of 1808 deg. K will melt most computational component elements.  It is possible to envision rod-logic based nanocomputers constructed from titanium, molybdenum or tungsten components which will operate comfortably at these temperatures.  At lower temperatures, there are few materials which can effectively capture low energy photons implying that direct conversion of photons into electricity will not be possible and thermal energy cycles (e.g. Stirling, Rakine, etc. cycles) must be used.

The elemental availability must also be given consideration.  Iron, Oxygen, Aluminum and Silicon are much more abundant than Nickel, Phosphorus or Fluorine.  Either the more abundant elements must be used in construction of MJB levels or energy must be consumed converting significant amounts of one element into another (iron into tungsten for example).  As the cooler (outer) layers must be larger than the inner layers, these layers will consume a greater mass of materials and should therefore be constructed of the more abundant elements.
 

Power Sources

Construction Methods and Time Scale

1. Convert one or more asteroids into solar power collectors.  A 3 mile asteroid receiving 10¹⁰ W of solar power can be converted into solar collectors which can harvest 10²² 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 JB.  Time required: ~20 years.
4. Use the entire output of the sun, less that utilized by the JB, to disassemble Jupiter and Saturn.  Time required: > 1000 years.

The mass requirements for the solar collectors and CPUs around the Sun are small compared with the mass available.  Only small fractions of the Mercury or the Earth's moon would be required for the construction.  Of some concern is whether specific elements required for CPU construction, such as carbon or sulfur would be available in sufficient quantities.  If this is not the case, then one can turn to the atmosphere of Venus or the asteroids for further material.  The radiator material is of concern since it must have high emmissivity.  One candidate, likely to be available in high abundance is iron oxide.  It has both a high melting temperature and highly abundant among the planets and asteroids.

Construction times are short.  Exponential growth of nanoassemblers would provide sufficient numbers to disassemble and reassemble planets in months.  If non-nano-scale automatons are required the time scale may be years. 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.  There is thousands of times more mass than is required in the moons and planets.  The strongest limit on construction times is likely to be the time required to move the materials into the proper positions around the sun.  Conversely if non-star centered JBs are desirable (see Location), the limit is on moving sufficient mass from various star systems to a balanced or minimally disrupted gravitational point between the energy sources.

While many authors have focused on the possibility of moving moons or planets for construction or terraforming purposes, it should be understood that this is not required for JB construction.  First, since the elemental requirements of JB 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.  Second, moving a large mass to an alternate orbit requires expending a large amount of energy and mass or waiting a long time or both.  Instead the available energy and matter should be used to construct mass-drivers which accelerate material towards positions where optimal energy harvesting and beaming stations may be built.  Once operational, these stations return an increased amount of energy to the moons or planets on which mass harvesting operations are taking place.  This allows an exponential growth in material breakdown, separation, and transport capacity.  Eventually the point is reached where an optimal amount of solar energy is diverted to the transport of  materials optimal for JB construction.

Limits

Power Limits

It can be seen that there is a tradeoff between the amount of power available and the longevity of the power source.  If you want to do a lot of thinking in a short time you can construct a JB around a 10-100 M_sun star.  Unfortunately this massive amount of power increases your cooling requirements significantly and requires such a large diameter for the JB radiators that the amount of construction material available in an individual solar system will likely be insufficient. This then requires importing material from other solar systems or dust clouds creating the requirement that interstellar distance material transit times be incorporated into the construction schedule.  As the lifetime of these large stars is short, presumably you would have to plan the construction and begin the material transfers while the star is still forming.  This requires transferring the materials against the very strong solar wind of a large mass star during its violent and high radiation output formation stage.  Even after the construction of a mega-JB, the large diameter would imply that the transit time for messages between CPUs would be hours or days.  Clearly a mega-JB would only be useful if one wanted to solve well-defined problems which required a great deal of thought in a short period of time.  Since stars more than 1.5 M_sun end their life by becoming supernovae, the JB would have to be disassembled and reassembled elsewhere else unless energy and matter were considered to be so plentiful that the incineration of the megamind is of no concern.  These difficulties all argue against the construction of JB around large mass stars.

However, a non-star centered mega-JB can be constructed and be powered by either externally supplied power or internal thermonuclear reactors.  This avoids the stellar radiation and lifetime problems leaving only the inter-CPU travel time problem.  If this problem is of no concern, then one might find non-star centered mega-JB in regions where there is a high external energy flux (for power harvesting) and relatively long lived stars.  These are the characteristics of globular clusters (GC) which consist of hundreds of thousands to millions of stars in regions of space only a few tens to hundreds of light years in size.  The external light flux in GC is many times greater than that available from a single star.

Astronomers believe that GC are at least 8 billion years old with some estimates as high as 12 billion years.  These ages are based on two observations:

• Large numbers of low luminosity red stars, implying old small mass stars.
• Low metal abundance in the spectra of the stars in the GC, implying old stars formed before significant numbers of supernova had seeded the stellar dust with metals.

Size Limits

Material Limits

There will be ultimate limits on the JB architecture due to insufficient materials.  Possible examples include:

• Insufficient carbon to build the maximum number of diamondoid nanostructures, particularly nanocomputers.
• Insufficient aluminum or magnesium to build solar collecting apparatus capable of harvesting and redirecting the maximum amount of available solar power.
• Insufficient copper, nickel or iron for the construction of highly efficient metal oxide radiator surfaces.
• Insufficient circulating fluid (LNa, LNH₃, LCH₃, LO₂, LN₂, LHe) for the efficient cooling of computers (rod-logic, semiconductor, helical-logic, superconductor) at specified operating temperatures.
• Insufficient rare elements (Sb, In, Cd, Te, Hg, As, B, etc.) used as semiconductor dopants or as layers in solar cells or semiconductor lasers.
• Insufficient silver or gold to build highly effective telescopes for observing or communicating with other civilizations.

For comparison purposes, the following table outlines the elemental composition of three nanostructures designed by Eric Drexler at the Institute for Molecular Manufacturing and a familiar complex of nanomachines.
 
 

This shows clearly the variability that nanomachine compositions may have and illustrate the difficulty we will have in determining what elemental makeup of JB may be.  However, it seems reasonable to say that whatever architectures are chosen, some elements will in excess relative to other elements.  While the carbon, silicon, metals, semiconductor dopant atoms and elements with unusual properties (melting point, hardness, density, ferromagnetism, superconductivity, etc.) are likely to be fully utilized, there may be a significant excess of hydrogen, helium, neon, and perhaps even nitrogen and oxygen.  Possible uses for these materials could include the construction and maintenance of biological zoos [Ball, 1973] or radiation shields and controlled fusion fuel sources.

Obviously substitutions can and will occur.  JB will optimize their structures to make the most efficient use of the readily available elements.  Without knowing the specific material requirements for various JB components it is impossible to predict at this time which elements will be the gold, platinum and silver of a JB culture.   We can presume that very young JB will however use all available matter within a solar system and commence the study of where additional matter should be mined or whether the local star(s) and local JB architecture(s) should be engineered for long term elemental transmutation activities to create element ratios which are better suited for optimal JB architectures.  As element transmutation consumes large amounts of energy and has long time scales it is likely that interstellar mining will initially be a more rapid and less expensive solution to the accumulation of rare and valuable materials.  In the long term, as local resources are exhausted, elemental transmutation will be the only reasonable source of correct material ratios.

As there exists the possibility, pointed out by Kardashev [1997] and presumably by many others, that intelligent life may have existed for 6 billion years or more.  If intelligent life has existed for that long and evolves into JB architectures as postulated here, then interstellar mining activities may have been occurring for billions of years on galactic scales.  This has serious consequences for astrophysical theories about the origin and history of the universe as they depend heavily on observed abundances of metals in stars and interstellar space and assume these ratios have not been adjusted by extraterrestrial intelligences optimizing their personal element ratios.

Even very sloppy single-layer JB architectures come relatively close to the most efficient computing structures possible given the physical laws of this universe.  They will also be able to utilize most of the energy produced by a local star with only a small fraction of the locally available matter.  If computational throughput is the major emphasis of JB (see thought limits), then it may be much more important to construct small-hot JBs and not large-cold JBs (whose radiators would exceed local material requirements). Thus there may be no incentive to go on interstellar mining expeditions and the astrophysicists may be able to sleep nights.

Longevity Limits

Dyson [1979] demonstrated that it is theoretically possible to be immortal in an open universe.  Current results in astrophysics lean towards an open universe structure [REF].  Though Dyson did not indicate exactly what the physical nature of immortal "beings" would be, it is clear that JB which have tremendously greater thought capacity than we do will have a much longer time than our sun has existed in which to consider and solve this problem.

Thought Limits

This is clearly seen when imagining the management of three different planetary probes, one on the moon, one on Mars and one orbiting Saturn.  The moon probe may be managed from earth in real time.  The Mars probe can be given directions between cups of coffee.  The Saturn probe can be given directions only several times a day.  If you expect the more distant probes to do useful work in a reasonable time you have to build into them increased amounts of intelligence and autonomy.

If the thoughts between CPUs in a JB are independent, then the brain can be made very large with little effect.  If however the JB is attempting to solve a problem which requires all of its capacity then it must think slower to maintain synchronization between CPUs as their inter-CPU distance increases.   In theory JBs orbiting in the galactic halo, a KT-III civilization would be able to think collectively, but their "thought" time must be on the order of tens of thousands of years or more.

It should be clear that the two major problems facing JB are how to think more efficiently and how to think smaller.  By thinking more "efficiently", we mean to solve the problem with less heat generation.  If the thought engines generate less heat, they can be placed closer together and can therefore solve a problem more quickly.  It might be useful for very complex problems to devote a significant amount of thought and prototyping to the production of thought engines which are optimal for a specific problem.

McKendree [1997] discusses the possibility of nanotechnology based engineering being able to "surge" the production of various components necessary for the minimal solution times for problems which are well-defined from a computational standpoint.  Using these methods, all of the CPUs in the JB would then be reconstructed for that specific problem, the problem would be "thought about", and after a solution is produced the process would be repeated for other problems.  Current FPGA (field programmable gate array) products from manufacturers such as Xilinx and research in configurable computing (Villasenor & Mangione-Smith, 1997) are the foundations for these JB computational methods.  Alternately, CPU groups or complete JBs may have architectures designed for solving specific types of problems, e.g. galactic stellar motion computations as is now done by the GRAPE computers in Japan.  Some possible architectures could be:

• rapid prototyping for the construction of novel thought machines,
• monitoring architectures to monitor the development of life on all planets of a galaxy,
• massive communication architectures to interpret the signals from JBs from nearby galaxies,
• radiation-hardened JBs for rapid-thought in high energy flux environments such as those near the accretion disks of black holes.

Thinking "smaller" means to develop new architectures which move through the macro-atomic structural level to the sub-atomic structural level.  One can begin to see hints of possible approaches in this arena in single-electron devices, optical computing and quantum computing.   Compute engines built using these methods are "faster", in that more computation is done per time interval, but the limits imposed by heat removal and inter-compute engine communication time still impose limits to thought capacity.  These solutions may provide several orders of magnitude (10²-10⁴) improvement in macro-atomic scale JB but increases beyond this will either be impossible or will involve magic which we cannot comprehend at this time.

Location

• significant mass resources are used for shielding the JB from radiation; or
• a not insignificant fraction of instruction capacity is devoted to redundant hardware and/or the execution of diagnostic programs and energy resources are devoted to the recycling of damaged components.

1. A low radiation flux
2. Large amounts of local, easily harvestable energy
3. A relative abundance of easily utilizable mass
4. A minimum potential for disruption by gravitational or stellar events (e.g. supernova)

If it is possible for JBs to harvest significant amounts of fusionable mass (H, He, etc.) from either stellar lifting or interstellar gas cloud mining, then the construction of migrating JBs is possible.  These JBs may be constructed as solid spheres and may use the harvested elements in large numbers of fusion reactors to generate power.  [Question: Is it possible for a large JB with a solid shell to retain a large mass of H/He as a internal atmosphere as a potential fuel source (or will the H/He collapse into a gas planet)?]   Structures such as this would be found orbiting around the galaxy in the galactic halo.

Evolution of Civilizations

Criswell [1985] defined the concept of "stellar husbandry" which consists of the removal of the atmosphere of a star ("star lifting") and gradually returning the stored materials which are capable of undergoing fusion reactions to allow a significant extension of the lifespan of the star at least 1000 times (to > 10¹⁴ years).  This activity also provides an extensive source of materials for the construction of larger (and cooler) JBs.  If possible, this activity would take tens to hundreds of millions of years.  Since star lifting will eliminate many short term material resource constraints as well as provide a greatly extended lifespan for the JB, it would likely be an important goal.

Combining these perspectives provides a reasonable concept of KT-II evolution.  Initial JB construction utilizes materials from asteroids or planets with the lowest gravity in closest proximity to the star.  Construction is rapid (a few years), may be inefficient in its mass utilization and produces a hot (~500-1500K) JB relatively near the star.  As more material becomes available, larger planets in more distant orbits are dismantled and the JB shell expands or additional layers are constructed which are cooler (~70-300K).  Finally, if star lifting activities are undertaken and large quantities of metals become available, the JB enters its final stages with both a large size (>5 AU radius) and cool temperatures (< 30K).

The ultimate fate of JBs is unclear.  A tradeoff must be made between active thought and information storage.  Material returned to the star (or consumed in thermonuclear reactors) to enable active computation cannot be utilized in information storage.  A means of utilizing all of the potential energy available and gradually converting most of the mass to iron may be developed.  The iron could then be arranged, perhaps utilizing other required elements, in the form of a massive static information store.  The last energy available could be utilized in accelerating these information stores in the direction of untapped energy sources where they could regenerate new JBs.

Interaction with and between Jupiter Brains

If one supposes that the transition period between KT-I civilizations and KT-II civilizations is short (thousands of years) relative to the lifetime of a JB (billions of years), then it makes little sense for JBs to concern themselves with creatures which are much much lower than insects.  Perhaps they may take an interest once a civilization has progressed to the KT-II (JB) level as one now has the equivalent of a "child" which may be rapidly educated.   The mass and energy resources available to JB are so large that they may observe us quite closely for a very long time from a large distance waiting to see if we will make the transition to a JB level .

It seems silly for them to interact with us at the level which we are now at.  More likely, possible future outcomes of pre-KT-I civilizations, like our own, have been computed in some detail (it only takes seconds to compute thousands of thousand-year scenarios for us).  We should not feel too bad however.  A single JB has the same problem relative to a KT-III civilization which we have with them.   KT-III civilizations made up of 10¹¹ or more JBs would think on a radically different time scale than individual JBs.  Since it is likely that the JBs of a KT-III civilization would be separated by light years, the propagation delays between them become are a significant problem.  What does one think about when you yourself can compute an answer to most questions you might transmit before the answer can be received?

Are their galactic JB Oracles which have utilized their design and simulation capacities and mass transmutation or star lifting activities to construct optimal architectures for solving specific types of problems?  The travel time to ask a question and receive an answer from such an Oracle may be 10⁴ - 10⁵ years.  Nanotechnology enables surge construction of optimal problem attack architectures [McKendree, 1997].  So questions must involve problems which cannot be solved with an optimal architecture in the time to receive an answer from an Oracle.  Presumably, individual JB would perform a return-on-investment analysis to determine whether it is more efficient to ask an Oracle or use local resources and reconstruction activities to produce an optimal architecture for thinking about the problem and producing a local solution.  Obviously, utilizing ones resources to attack one problem means that those same resources cannot be used to solve another problem.  The would be significant cost-benefit tradeoffs involved in asking the Oracle(s) or consuming local resources.

A single JB may use a fraction of 1% of its available mass to construct 100 billion telescopes with mirror diameters equal to that of the moon.  These telescopes would fill a planar space corresponding to roughly the orbit of Jupiter.  Using this number of telescopes they should be able to monitor most of the solar systems in the galaxy.  If we assume some reasonable fraction of the galactic dark matter constitutes a KT-III civilization with billions of JB, then we may also assume they can monitor to a significant degree many activities occurring in nearest old galaxies within Kardashev's (1997) "civilization window".  Major activities of JBs may be the monitoring of developing local KT-I civilizations and the nearest remote KT-III civilizations and contributing this information to the galactic gossip.

Given the possible existence of a galactic JB/KT-III civilization for 3-5 billion years, there should be a large directory of problems and answers computed and stored by JBs from preceding times.  There should be a large amount of information about galactic history (stellar births & deaths, civilization histories, lifeform blueprints, etc.).  The galactic knowledge base is potentially huge, but it plagued by the problems of long latency times for information retrieval as well as bandwidth limitations if the volume of information is large. While waiting for the retrieval of answers to questions, JBs may devote their time to devising complex problems which have not been solved and can only be solved in millions of years by a dedicated JB or closely linked JB cluster.  It is difficult to imagine what these problems might be since even one JB seems sufficient to computational capacity to easily solve problems far beyond our current capabilities.

Conclusions

Unfinished

Open Questions

1. What do Jupiter Brains "think" about?
2. What are realistic time estimates for turning Mercury into a Solar Power Array?
3. How rapidly could all of the carbon in the atmosphere of Venus be harvested?
4. How long does it take for a reasonable fraction of solar output (RFSO) to break all chemical bonds in the solar system?
5. How long does it take for a RFSO to transport all non-solar matter in the solar system out of individual planetary gravity wells?
6. What are the energy/mass/time tradeoffs to relocate significant fractions of the mass in the solar system into the inner solar system using a RFSO?
7. Which architectures are really better - IPJB or EPJB?
8. Can the radiation damage problem for nanocomputers be solved by electro/magnetic shielding or must it be solved by mass shielding or relocation to regions remote from radiation sources?
9. If JB do not exist, then one is faced with a serious problem of what makes it so difficult for intelligent life to evolve and achieve the JB level?
10. Even if JB do not exist, is it a reasonable path for humanity to follow?
11. How close can real architectures come to theoretical limits of computational capacity?
12. Are there problems which require so much computer processing power that they can only be answered by suicide JBs such as those who would harvest the energy output of supernova?
13. Is there any way a JB could tolerate the radiation flux associated with harvesting energy from matter falling into a black hole?  Would this be the best use of the matter (its destruction in the pursuit of energy production)?
14. Is there any point to interstellar travel (JB voyaging or JB probe research expeditions) if you can observe all galactic activities with large numbers of telescopes, have high bandwidth communication channels to other JB and can precompute the probable end points of observed developmental paths?
15. If the dark matter is not JB, then what is it?

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