Wednesday, February 22, 2017

Formation of Black Hole Swarms

Black hole swarms are collections of black holes, as many as you want up to millions, occupying a small galactic space, like a light year or so. Because black holes are only the size of a planet like Earth, there is virtually no chance two of them will collide. So a swarm, if formed, will simply go on buzzing around for the rest of the age of the universe.

The evidence for massive black holes, thought to occupy the centers of many galaxies, is indirect and matches the evidence that a swarm of black holes would display. So there is no simple way to tell which it is that occupies the dead center of galaxies.

Here’s a little astronomical background. Globular clusters are collections of stars, held together by mutual gravitational attraction. They look like spherical balls of stars, and if you could watch one closely for millennia, you would see the individual stars moving like Brownian motion, going every which way, and having their straight-line orbits disturbed by near stars. The central area of the globular cluster is denser, as most stars are not simply orbiting it a circle around the center, but dive into it, coming out on the other side. The denseness of the center is caused by the relative numbers of stars that happen to be passing through it at any given time, as compared to the number per cubic lightyear which are in the further out regions.

The less kinetic energy a particular star has, the longer it will linger in the center. If there were a lot of stars with not much kinetic energy, the center of the globular cluster would be even denser, as those low KE stars would be spending a lot of time there and increasing the mass density near the center. Then the higher mass in the center would pull in even more stars, again adding to the local density.

Globular clusters exist in which many stars have somehow lost much of their KE and spend their time in the central region of the cluster. The astronomical name for this phenomenon is core collapse. Essentially the core of the cluster has collapsed in upon itself and has grown denser, because somehow kinetic energy was transferred from one subset of stars, the central ones, to the rest, which still go flying out to the edges of the cluster before turning around and coming back in. The process for this KE transfer is gradual and statistical. An ordinary star transfers kinetic energy continually by its gravitational interactions with other stars, and if one gets lucky, it can dump most of its KE on the way in, and then stay in the center. When the center becomes more dense, these interactions become more frequent. Can core collapse happen by this process alone? Once it happens, and say 20% of the stars are restricted to the center, it might stay that way, but the difficulty is in getting it to happen in the first place.

Since the 80’s, astrophysicists have been estimating how long this takes by looking at the number of close interactions a sample star might have, and how likely it was that this could result in a significant reduction in KE, thereby providing another candidate for the central stars in a core-collapse globular cluster. This approach in interesting, but it ignores the fact that stars interact with many other stars at the same time. If there was a clot of a thousand stars, the gravitational force on a sample star could be much greater, and this relaxation time would be shorter. Stars don’t clot like that, but they do have density fluctuations and perhaps even waves of density. Density waves have not been studied much, but they are the likely culprit for the beautiful spirals on galaxies we see. Thus relaxation times might be much shorter than the one-on-one calculation indicates, if there were turbulent agglomerations of stars, density fluctuations and density waves in a globular cluster.

A second feature is the segregation of stars by mass. In a potential field, heavier stars with the same average energy don’t move as far out of the field, simply because they have less velocity for the same energy. On the average, there should be more heavier ones in the center than at the fringes, in a large globular cluster. This means they might be more subject to becoming core-collapse participants than lighter stars. This does not mean that all O stars are found in the center of globular clusters, and M stars are found at the edge, but it does mean that there is a tendency for this to happen, and the relative ratio of O’s to M’s would be different as one goes further out from the center of the cluster.

If an M star interacts with several O stars during its passage through the core of the cluster, it may pick up even more speed than another O might, and then spend even more time out of the core region. And recall that O stars become black holes when they age, meaning that there would be black holes preferentially in the core of a core-collapsed globular cluster. They would not be visible, but would contribute to the severity of the core collapse. Since the lifetime of O and other stars which produce black holes are quite short from a universe time viewpoint, there could be quite a lot of them there.

What works for a globular cluster works even more for an elliptical galaxy or the bulge or bar in a spiral galaxy. There is a mechanism for large stars, destined to become black holes, or more likely, already made black holes, with masses ten to a hundred or more solar masses, to have a core collapse situation in the center of some galaxies, and thereby pretend to be a huge single black hole, confounding observations. The formation of a swarm of black holes is not that unlikely, and the concept is certainly worth considering. Galactic cores are more or less invisible because of the dust and gas there, but perhaps there is some clever way of better finding and discerning black holes that reside there.

Thursday, February 16, 2017

Interstellar Convergence and Intelligent Design

Interstellar convergence is a term, perhaps unique to this blog, that says that evolution drives organisms to optimality, and what is optimal on one planet is close to optimal on another similar origin planet. In other words, planets hundreds of light years apart both with the same mass, stellar class, composition and other details, will have organisms that look similar, and which are similar, down to the cellular level. Interstellar convergence has limits we do not know yet. If it turns out that DNA is the optimal coding chemical for genetics, most planets will have it in their organisms’ genomes. If neural nets are indeed the optimal information processing mechanism that can be grown from genes, then all intelligent aliens will have them. If hands are optimal for tool-using, then all intelligent creatures everywhere will have them. There might be some exceptions, but we are far from being able to figure them out.

Intelligent design is used here in its essence: if genetics is understood, creatures can be designed to fill in whatever niche is desired. It means that aliens, not necessarily super-creatures, but just ordinary, hard-working, well-motivated, intelligent aliens, would be able to design a genome that would lead to a viable, living organism, able to reproduce if that was desired, able to think if that was desired, able to do whatever it was that the designers wanted them to be able to do. They could have docile personalities or be hard-as-hell to manage; this is the designer’s choice.

Here’s another word: self-speciation. This means that an intelligent alien species would have the ability to modify its own genome, and create a different species, if they chose to do so. The different species might be better than the original aliens in some aspect. Evolution is expected to do a good job of moving species to the optimal, but it can’t work after a civilization gets started, so evolution would have created a species that was good for surviving and reproducing in a pre-civilization situation. It would be up to the aliens to modify their own genome, or create a brand-new one, to match what would be optimal for living in the world of giant cities and interplanetary travel.

When alien civilizations start sending their citizens into low planetary orbit and then into interplanetary space, and finally to other planets, satellites or asteroids in their own solar system, they will soon realize that the design that evolution created for life on their home planet was far from optimal for life in other, radially different, environments. They may well embark on some self-speciation to design aliens which were at home in space or on low gravity satellites. If they happened to originate in a solar system which had two planets with similar conditions, but only one which originated life, they might migrate to the other one and modify their genome to better match it. If it had 20% higher gravity, for example, they might want to redo their skeleton to cope with that, and their musculature as well, and perhaps their circulatory system. If there was a planet with less oxygen, the lungs might be modified. If the other planet was an origin planet as well, or life had spread there from meteoritic transmission or some other way from their home planet, and had grown up differently, they might need a different digestive system to be able to consume what grew on the second habitable planet. Once the genetic grand transition had been passed, all of these would be possible. If for some reason, there was not much benefit to be gained, as for example, their naturally evolved bodies tolerated space life with few problems, they could keep their own genome; this seems to be an unlikely possibility.

This self-speciation is not something that one out of all alien civilizations might do. They all figure out the same genetics knowledge, as knowledge doesn’t depend on the planet that finds it; scientific knowledge and technology is universal and the same on all planets.

The stage of interplanetary travel and migration would almost assuredly occur before they attempted any interstellar voyages. The technology developed for going to other planets in their own solar system is an excellent beginning for the technology needed for an interstellar cruise. That technology is quite diverse, involving figuring out how to make something last for a thousand years; how to carry enough energy and propellant to get the trip and the arrival accomplished and still have enough left over for whatever they were going to the new solar system for: as a probe, for colonization, or something quite different. So, it seems likely that they would have a species, similar to their own, that is better adapted for space, and which lives on constructed space stations around some of the planets in their solar system. If there were any satellites worth building a colony on, for mining or anything else, there might well be another variant species living there.

As an aside, an alien civilization at this stage of development is likely past the times of troubles that existed on their home planets. Just because they were a different species, they would not decide they wanted to go to war with the home planet. That is a device of science fiction: taking something of present day Earth and changing the situation to a future one where different planets were inhabited. Neurology and sociology would be well-understood sciences and would have eliminated such a possibility.

Now ask yourself what they would do for colonization, should that be part of their legacy goals for their own set of species. If there was an interesting exo-planet somewhere, and they found it was an origin planet, and already had an intelligent species, would they want to go and colonize it and subjugate the original inhabitants? Not likely. They would understand that the other planet would have evolved creatures optimized for that planet, and if they went and used intelligent design for a creature like their own to live there, they would wind up with something very similar to what was already there. So why bother?

Colonization is likely to take place only on worlds which do not have intelligent species already. It would be superfluous to go there and replace something almost identical. Colonization would go to origin planets with primitive life, not solo planets with intelligent life. This is actually a very small restriction, as life exists for billions of years on an origin planet, before it can evolve intelligent creatures. Much of that time would be suitable for colonization, if it were desired. Intelligent life only lasts for a brief interval, and technological life, probably less than a million years. This would eliminate only a small fraction of planets a space-traveling alien civilization would encounter. In essence, we don’t have to worry about being displaced by aliens. There might be other reasons they would interfere with us, but it is impractical for them to bother colonizing an already inhabited planet.

Monday, February 6, 2017

What Fluid Fuels Might Power Alien Civilizations?

Here on Earth we are in the first part of the industrial grand transformation, and so know a bit about basic chemistry and physics, so we should be able to shed some light on fluid fuels, as they might exist in alien civilizations. If we can list the functions that energy in general must perform in an alien civilization, we might figure out what would be the likely class of fuel used there.

Energy functions in providing temperature control, transportation, communication, power for robotics, preparation of nutrition, surveillance, research, construction, recycling, maintenance and repairs, information transmission and storage, mining and resource extraction, and health. While there may be others, this wide a spectrum probably covers the fuel requirements. Electricity can be used for most of these, and it can be generated at a power plant or locally from a fluid fuel. Power plant generation implies some means of moving the energy from the power plant to the cities where the aliens live, which can mean direct transmission in a network of wiring, or transportation of fluid fuel.

The trade-off between wired electricity and locally generated electricity might be done on the basis of efficiency, or its equivalent, cost in whatever accounting system the alien planet uses. Efficiency depends on how much storage is needed for the energy, as electricity is harder to store than chemical energy. Power plants might work continuously except for maintenance breaks, seasonally if dependent on some seasonal source of power, diurnally if dependent on some solar source, or with another periodicity, such as that related to a large satellite producing tides. There could be a large random contribution or none at all.

Likewise, consumption can have temporal fluctuations in it as well, diurnal, seasonal, or related to other cycles of the civilization. Arrangements can be made to modulate the fluctuations in both production and consumption, but there will likely be some residual mismatch, implying storage of energy is necessary. Storage of hard-to-store-directly electrical energy can be done by transforming it into thermal energy, gravitational energy, mechanical energy or chemical energy, and each transformation, one-way or round trip, has an efficiency cost, which might be of the order of 50%, as opposed to 5%. This does not include the inefficiencies in producing or collecting the energy, which might also be other order of 50%, to use an order of magnitude. The overall result is that most of the energy produced or collected is turned into heat at the production site, as opposed to at the consumption site. This is inevitable in our Earth society or in any alien civilization.

For most of the functional uses of energy in an alien civilization, electrical energy works fine, whether transmitted over long distances or whether generated locally. The utility advantage breaks down in transportation, as energy must be stored and then transported on the vehicle, except for transportation corridors which have electric transmission systems built into them and can couple energy into the mobile vehicles, either kinetic energy or electrical energy.

Inside an arcology, transportation could easily be done electrically, and if the large majority of movement occurred there, there would be no need for fluid fuels for transportation on the inside. On the outside, if there was still some substantial amount of transportation taking place, either gaseous or liquid chemical fuel could be used. Hydrogen is one obvious candidate for a gaseous fuel, but the energy content per volume is low, meaning that tankage needs to be large, and consume considerable volume and weight. The trade-off is between the efficiency of converting hydrogen to some other, more dense fuel, such as an alkane, and carrying around the tank weight. If the whole point is simply to transport energy to an arcology from a distant power source, then the tradeoff is between the production of electricity and then a network of conductors to bring it to the arcology, and the production of hydrogen or a gaseous alkane and then a pipeline or vehicle ensemble to bring it there.

If the energy at the power plant is initially used to create electricity, then it would seem that there is little to be gained from converting to a fluid fuel and then transporting the fuel to the arcology, where it would be converted back to electricity. Our limited knowledge of electrical transmission versus pipelines would indicate there is no way to made the latter more efficient, given the round trip inefficiencies of conversion. Thus, the only use for fluid energy sources would possibly be in transportation outside of the arcologies, in situations where it would not be most efficient to have a wired corridor, such as between two arcologies.

Thus, storage of large quantities of energy, such as at the power plant, and mobile vehicles using significant energy on non-corridor transportation, would be the only two possible uses of fluid chemical energy sources in an alien planet, once they are past the stage where there was abundant fossil fuels. Would the energy storage at a power plant be done with hydrogen or with alkanes? Chemical energy is one of the most dense forms, and so one of these would be the likely choice. The tradeoff of tankage versus chemical form might be based on the duration of the storage, which relates to the amount of material needed to be stored. Diurnal storage might be with hydrogen, as the amount of tankage is not so large, and seasonal storage might be with alkanes, for the opposite reason.

This route of technology would mean that all three of the energy modes, electricity, hydrogen, and alkanes, would be available at a power plant site, and the other use of chemical energy sources, irregular transportation, might avail themselves of either fuel, both originating from the same source. Since alkanes have a significantly lower tankage cost, and have about the same available energy per mass, assuming atmospheric oxygen is used for combustion, then it is likely that an alien civilization would, perhaps unexpectedly, have vehicles analogous to those on Earth. This would be a strange case of interstellar convergence, when the physics, chemistry and other laws of nature push all civilizations in the same direction.

The last use of energy for transportation is for interplanetary travel, or simply to travel into orbit around the alien planet. Here, energy per mass and energy per volume are dominant. To keep tankage costs down on the heaviest stage, solid fuel propellants are used by most Earth launchers with liquid alkanes being the alternative, with liquid hydrogen and oxygen used for higher stages, where energy per mass counts more than energy per volume. This optimum has been well explored, and might be also expected to occur on exo-planets that do not barren areas on their planet where nuclear thrust options might be employed.

Wednesday, February 1, 2017

Alternatives with Arcologies

Somewhere along the pathway from hunting to asymptotic technology, an alien civilization must realize the threat that resource exhaustion poses to their living standards and the status of their civilization. One of the responses to this threat is the adoption of recycling to reduce new resource consumption and substitute re-use and re-cycling.

If recycling is done on a civilization-wide scale, with all citizens participating in the same processes, the efficient organization of the civilization is to have everyone living into cities, structured like arcologies, with the logistics pathways for all goods and waste short and efficient. Efficiency is one of the other tools that the resource exhaustion threat demands.

If the assumption is relaxed that all citizens participate in the large-scale recycle in identical fashion, the concept of universal arcologies becomes superfluous. If the population is large, of the order of ten billion citizens with energy consumption rates perhaps ten times that of industrial civilizations on Earth, then the large majority would have to live in arcologies, but there could be a minority living with disaggregated recycling.

Another factor that might be decisive on the need for arcologies and the fraction of the population living in them is the final trade-off made between robotics and genetics. Robotics need manufacturing centers, but biological solutions to accomplishing some of the civilization’s tasks might need only some facilities for growing the proper organisms, and even these might be biological as well. If some of the population were dispersed, then recycling of all biological goods might be equally dispersed, and only manufactured goods would have to be transported back to some recycling centers, perhaps located in one of the arcologies.

The transportation costs might be ameliorated by some biological conversion of carbon dioxide in the atmosphere to oxygen and separated carbon compounds. This is exactly what photosynthesis does, but if it could be powered alternatively, such as by fusion-generated electricity, it would be more under control of the civilization. Once this was accomplished, some minimal amount of carbon compound liquids or gases could be used as the excellent energy storage medium they are, and a certain amount of transportation could be arranged for to accomplish the recycling of manufactured goods.

Manufactured goods would be designed for efficiency from a whole-life viewpoint, as opposed to what would happen in early industrial times, when the design viewpoint might be manufacturing efficiency or once-through consumption efficiency. If a manufactured item is designed without re-use of parts and recycling of everything else in mind, so that re-use and recycling costs are very high, then the total lifetime costs are very high as well, as the end stages dominate the cost cycle. If instead, manufactured items are designed with a full life-cycle in mind, meaning that a closed loop of resources is attempted, without only energy inputs plus a very small amount of resources to fill in impossible-to-control losses, then there is little energy cost expended in extracting resources and transporting them, as well as processing ores. Instead, the civilization’s energy use is more devoted toward immediate consumption plus recycling costs.

Consider the fraction of the alien population which is dispersed in whatever natural surroundings evolved on their planet. Aside from manufactured goods, everything else in the consumption arena can be recycled in the natural surroundings. Whatever they need for nutrition can be produced either from the surroundings or from wholly biological means, either involving the surroundings or in special micro-facilities, and either using evolved genetics or designed genetics. Most likely the most efficient way of organizing a community living outside the arcologies would be strongly dependent on the locale, the climate, the environment, and other factors that differ all over the planet. Community size could range from an individual, living outside the arcologies for some period of time, up to groups numbering in the order of thousands. Too large an outside community would seem to break the ecology of the area.

There would be costs of moving everything that needed to be moved between the arcologies and the dispersed population. These involve the two-way transport of manufactured goods, plus population transportation and the transport of specialized goods, like seeds or certain biological materials. The transport vehicles would likely be manufactured goods, which would be produced in the arcologies, and recycled there. Energy could be anything simple, such as hydrogen gas for land surface vehicles and carbon compounds for either land or air transport.

Energy production in the dispersed areas might be either locally gathered energy, or transported energy. If energy was not produced in the dispersed areas, this might be the largest single item for transportation. One example might be the frequent transportation of hydrogen gas to the dispersed areas, where it might be transferred from the transport vehicles to community tankage. Just how much energy such a dispersed community might need is probably beyond our estimation ability. If the community was largely utilizing biological means to provide the means of living, then photosynthesis might provide a large part of that energy. Other means of collecting energy from their star’s fusion could happen, but the efficiency that could be achieved is not easily guessed. Given a total control and understanding of genetics, how much of the solar energy falling per meter of planetary surface could be absorbed and turned into accessible energy or carbon-based products?

A few hundred million years of evolution has pushed the efficiency of Earth plants to a range of 0.1 to 2% conversion of solar photo-energy to carbon biomass. A different star would have a different spectrum of light, which affects conversion efficiency. Furthermore there is a second efficiency which relates to the utility of the carbon biomass the plant or other organism produces as far as the uses to which the alien civilization has for it. This efficiency is also low and highly variable, but for bred crop plants might get to a few percent. How much higher could this be pushed with a complete knowledge of genetics plus the ability to design and construct any genetic concept? This number indicates what the collection area might have to be for a community of a given size.

What are the extremes that we might observe with a giant telescope on a planet found to have an alien civilization? One is a planet with nothing but arcologies, perhaps hundreds, all of which would be emitting heat and serve as thermal point sources for the telescope. The other end is a planet with only one arcology, where all manufactured goods were produced, and the remainder of the population dispersed and making use of mostly biological organisms for their life support. Either could be the choice of the governance of the planet, and there does not seem to be any reason why a particular planet could not go one way or another, or more likely, something in the middle. The latter extreme case would have only one thermal source to observe.

Another way to consider alien options is to consider the design of an arcology. Could one be cubic and another be large, low and flat? Something to be considered at another time.