Choosing Colony Planets

An alien civilization with a philosophy of life requiring it to spread and disperse life throughout the galaxy, as far as it can, would need to be very circumspect about where to send a seedship. This adventure would require a great amount of effort from the civilization, and perhaps a good fraction of the resources available to it. On Earth, we have not even begun to figure out how this might be done, but we can assure ourselves this is not going to be easy for any civilization. As little would be left to chance as possible.

If we ask ourselves about the possibility of our civilization encountering another one, knowing where they would likely be is a critical question. They start on their origin planet, but then where do they go? We have learned over the last decade or two that there are huge numbers of exo-planets in the galaxy, but of these, which ones might be even initial candidates for an alien civilization's colonies? What are the characteristics of a possible colony planet? If we know that, then we can concentrate our search for alien life, or rather alien civilization, on that class of planet, and spend less on others.

What we cannot assume is that they will only go to other planets which have already originated life. If their philosophy and reason for continuing their existence is to spread life throughout the galaxy, an origin planet would be low on their list – it already has life and there is no need to go there and seed it. That would be superfluous. Instead, they would want to go where there is no life and is not likely to be if the planet is left to itself. Not just any planet would do. There are certainly some detailed criteria for a reasonably nearby planet, within a hundred or two light years, to even be considered as a possibility.

Many planets might only support the alien civilization itself, and not some ecology of plants, animals, microbes or whatever on it.  Their mandate is to spread life, but if the only way that can be done is to establish a colony, then that is the solution to the lack of planets which might be harbors for primitive life.  The alien civilization can set up colonies in many places, but needs to discriminate as to what distinguishes one possibility from another, as far as spreading life goes.  

One dominant aspect of the choice is sustainability. Sustainability means, for some particular alien species or collection of them, the ability to live for a very long period, measured in lifetimes, on the resources and energy located near and accessible to them. It includes the idea that the population should be able to grow up to some minimum value and still live there for that long period. It is about resources existing on the planet, near the surface, but also about being able to extract enough materials to make an energy source that produces much more energy than all the energy needed to collect and process the materials used in the energy generation and distribution process. There must be enough surplus energy for the other half of the problem, providing all the components, such as habitat and food, needed to sustain the new alien population.

The colony starts out with only the equipment that can be carried on the seedship. The development of the colony would consist of several preliminary stages before the uniform growth stage expands the colony up to the desired population. The first stage involves the landing of whatever is necessary to initiate power production with a minimally sized power reactor, create a habitat, and locate and start to mine and process all necessary mineral deposits. A central manufacturing complex would need to be created that can produce, from the ores found, all the specialized items needed for all the operations of the civilization.

Control of this process is not so critical. Can this be done in an automated fashion, or is it necessary to spend time in orbit, gestating the first generation of aliens, before sending them down with the initial lander? Whether the seeding operation is under AI control or under alien control, much the same steps have to be done. The principal difference is that habitats need to be made for the alien landing party, or some additional manufacturing facilities need to be made to enable expansion of the AI capability.

The question of sustainability is not easy to calculate in advance. Yet this is what an alien civilization must do before attempting to spread its population to a new planet or satellite in a distant solar system. They must make an estimate of whether or not a colony could survive on an exoplanet before taking the extreme expense of sending a seedship there The question is not just can the colony survive for a while, but survive and build a large civilization on the planet. The ultimate question involves the possibility that an alien colony, on a colony planet, could create a civilization large enough to send out its own seedship. If the colony planet was a dead-end, without enough resources for the civilization to grow large enough for the project of going out yet further to another colony planet, it should not be chosen.

The calculation depends on what goes along with the seedship. How much energy does it carry to support the transition from nothingness on the planet to a viable colony? Before this is used up, a seedship must arrange for native energy sources on the planet. This might seem to mean a uranium mine, but the uranium metal is actually a small part of what is needed to build an energy-producing fission reactor. Some parts for the first reactor might come from the ship, and this means that sustainability in energy is going to be developed in stages. The energy from the first reactor would need to be deployed toward a variety of tasks.

Total sustainability means that all mandatory mineral resources are present in the planet's crust, easily accessible, and with not too large a cost in transporting them from their mining site to the central location where the colony's initial population will be centered. For an alien civilization attempting to create a very credible and accurate estimate of this, which they would need before a launch, they would have to first collect all possible information about the planet and the solar system it is located in. The only way to do this from their planet is to build huge telescopes, and it also means asymptotic technology as far as planet formation goes, i.e. having geology completely understood, from the time of the gas cloud through all the changes that go on with the crust of the planet. They would need to be able to tell from the spectrum of the star what the gas cloud that created it contained, as for different elements and the relative concentrations of each.

At this point in Earth science, we have not attempted to make any such calculations, and so we don't really know if it is possible, or how accurate it might be. The accuracy is likely a function of the age of the star, as mixing will take place over its history, and the origination elements will also be burned up as they go deeper into the star's core. Light comes from the star's corona, where elements will linger the longest and where transmutation would be slowest.

Data is also available from the spectrum of the planet itself, where it is simply the reflected spectrum of the parent star. This might tell what was in the atmosphere, and what the large areas of the surface have, to a degree. Reflection spectroscopy is necessarily more difficult that emission spectroscopy, but if the telescope is large enough to portray the planet across many pixels, then some information might be gained from each one. Planets rotate, but that should not interfere with the data collection, once the images start coming in. A telescope of large size, perhaps ten kilometers or more in aperature, would be needed.

Information about the nature of the gas cloud that formed the target exo-planet might be gained also by looking at the other planets of the solar system containing it. A gas cloud which undergoes the great transformation from a rotating self-gravitating glob of dust and gas into a proto-star and spinning disk would also have undergone much diffusion, and this implies that at the radius where the target exo-planet condenses there would be some distribution of elements, but at the radii where other planets condense, there would be a different one, and knowing each of them helps the alien scientists to determine the larger picture of the composition and evolution of the cloud.

One kink in this process is that planets don't necessarily stay at the radius where they condense. The effect of the largest planet or the largest few planets might, in some instances, drive a smaller planet to a different orbital radius. The largest planets might also mutually share angular momentum, and drift to different radii as well. Can this be determined from telescopic observations so that the data from all of the planets can be put to use? A good question, and one we on Earth have not begun to fathom.

None of the scientific steps needed seem to be impossible, even from the viewpoint we have now, with our very limited science. An alien civilization a few hundred years further in science than ours should be able to accomplish them, as far as it is possible. Once this mass of data has been collected, perhaps over a century of observation, the estimation of which visible planet would be best to seed can be done.

Affluence in Two Eras of an Alien Civilization

Recall, for reference, that the early history of an alien civilization is divided into eras based on technological change. Some creature on an origin planet evolves intelligence and manipulative skill, and begins to use objects as tools, such as rocks, sticks, fire, and possibly others. This makes the brain grow, and that species is on the road to having a civilization.

On Earth, this early era is called the Stone Age, but that may be because only stone has lasted for the long period of time since this era began. In this blog, eras are divided by what has been labeled grand transformations, as technology completely reworks the civilization and causes most aspects to adapt to it. Provided the planet has animals, the next phase would be hunting in packs or groups, which give rise to the need for communication, and language results, which also makes the brain grow. They would be developing tools for hunting, and for many other tasks as well. Clay or some other formable material might be used here. There is no mandatory ordering of tasks, as one does not depend on the other. Hunting weapons can be developed without having clay pots. This era might be called the Hunting Weapon Era, and much technology gets developed during this period, as the species has been getting smarter and smarter, and more options will be visualized.

After that, assuming climate is reasonably benign and evolution has been doing what it does in the plant kingdom, there would be an Agricultural Grand Transformation. This is where agricultural tools are developed, and the nomadic species, slowly and gradually, settles down so that some of them live in permanent settlements. These tools would be adapted to whatever plants and crops are first conquered by the species, and this might vary by location on the planet. Different areas should have quite different potential crops, as the alien species adapts wild crops to ones which can be reliably grown.

The next era occurs after another transformation happens, the Industrial. Sources of energy are tapped in this era, starting with wind and water if they are available on the planet, and biomass used with fire in a controlled sense. There would likely have been the use of fire for heating of dwellings and for metal working, and the next step is to use it for other purposes. If there are surface quantities of hydrocarbons, they might be used as well. The first engines might be developed to substitute for wind and water power in areas where they are not available and biomass is.

The Industrial Era gives way to the Electronics Era, which runs all the way from the first development of electical communication up through robotics and automation. It depends on the energy sources of the Industrial Era and must therefore come later. Following that the Genetic Grand Transformaion happens, which must also be even later, as it depends on a large amount of computational power being available.

Affluence can be a corrosive influence during these two intermediate eras, the industrial and the electronics, but the bad effects happen in two different ways. It is generated as technology ramps up productivity, and there soon appear many goods, starting with agricultural ones, but soon moving into a panoply of goods satisfying other needs of the members of the civilization. Since any society in a primitive agricultural situation is worried about population growth outrunning agricultural production, with an additional concern possibly arising because of weather or climate changes, the motivation to continue to work in an affluent period would be diminished. If that reduction spreads to the groups which develop technology, the growth rate slows and it might even stop. This represents a potential halt to this civilization's advance to space-faring.

During the electronics era, a second aspect of affluence might set in. Prior to the Genetics Grand Transformation, there might be no ability within the society to improve the genetic mix. This result has been titled idiocracy, and refers to a differential reduction in the per capita intelligence in the civilization. Again, this would permeate all parts of society, including that sector which produces genetic advances. If it stops for this reason, or for a combination of this and the previous reason, technology never reaches the starship level.

How could an advanced alien civilization not notice that this was happening, and do something about it? One possibility is there are no measures in the civilization to measure motivation or average intelligence. This needs to be combined with the gradualness of these changes. The civilization would have no alarm bells going off, only a slight sense that things were deteriorating. And there are so many other things that happen in a society under rapid technological change, that these effects might escape notice completely.

Another possible answer to this is to ask if life in an alien civilization in these two eras will be calm and coordinated or chaotic and divisive? Calmness would come when basic societal questions have been answered, such as what political and economic arrangements should be in place, what goals the civilization should adopt, how should children be educated, and more. At least in the early part of these two eras, what might be called the social aspect of the grand transformation sequence will not have been worked out. There will be a period during economics, politics, education, and psychology become real sciences, with proper definitions, theories, and deductions. But that period may be delayed for various reasons, such as factionalism based on location, background, profession or other divisions. They will also be delayed until what might be called the neurological revolution takes place, and provides the society with a complete explanation of how the brain works. Thus, these two eras may be so disruptive, in the area of social arrangements, that there is no chance that the two ill effects of affluence are even noticed and certainly paid the proper attention.

One way to summarize this is to say that the side effects of affluence, which is the successful application of technology to the problems of the alien civilization such as the provision of food, shelter and other necessities, overwhelm it and cause the rate of progress in technology to gradually slide lower and lower, and the progress itself becomes more and more inconsequential in the innovations it comes up with. This means that the alien civilization will never get to star travel, and never get to visiting Earth.

Colonizing Half-Hot Planets

A half-hot planet is one which is in a close orbit to its star, is tidally locked, and is small enough to not have an atmosphere. Without an atmosphere, the only way heat can come from the side facing the star to the other side is by conduction through the body of the planet, which is bound to be slow. This would allow the side facing away from the star to radiate away a lot of its heat, and be cold. Thus the planet would be half hot and half cold. 

A recent post suggested aliens might migrate to a frozen world, one distant from its star, where the temperature is well below that of the outer edge of the so-called “habitable zone”, which is a poor name for the zone where water can be a liquid. The idea is that with enough technology, the alien colonists do not need solar photons to support their civilization, but can instead mine uranium and low-atomic-number elements useful for fusion. If the planet has enough of those, and the costs of mining it are small compared to the energy it would produce, including all the processing and everything else connected with power generation, the colonists can simply live under the surface in a comfortable environment, while they mined from one place or another all the minerals needed to support a good living standard.

These frozen planets don't have to be planets. A frozen moon would work just as well. As long as the planet doesn't create a terrible environment around itself, from radiation or something else, a moon would do just nicely.

Another thing to consider is that they don't have to be frozen at all. They can be habitable zone planets or moons, but too small to maintain an atmosphere. They cannot be too hot, as the temperature under the surface would be above tolerable temperatures, and this means there would be refrigeration needed for the living conditions, and perhaps also for all the mines. For too hot a planet, this would certainly mean it was unusable. Where exactly would be the average temperature that would make them intolerable is not so easy to determine, but it couldn't be too high.

There is one exception to that: half-hot worlds. In our solar system, we almost have one of these gems: Mercury. Mercury is phase-locked, but not 1:1, but 3:2. Mercury does not keep one face toward the sun at all times, but gradually rotates. If it were phase-locked at 1:1, like the moon is to the Earth, it might be a candidate.

One nice, somewhat speculative, thing is that the dust cloud which forms a solar system might have some differences in the mineral content of different planets, and even some basic trend. It could be that heavier atoms are more populous, relatively, on inner planets. It is not hard to imaging that dust collects like or similar molecules, and some dust grains collect more uranium and thorium than others, and then drift inwards, relative to lighter ones, such as calcium and sodium. When planets get around to condensing, this would mean that there would be more fissionable elements on inner planets, and in fact the most on the innermost planets, including the ones so close that they get phase-locked at 1:1.

In order to make this story complete, the planet would have to be large enough to stay molten after formation, so that the iron-like elements could sink to the center, leaving everything else to condense elsewhere, such as near the surface at a depth suitable for mining. Now the stage is set for an alien starship to land on the cold side, and begin to mine, both for minerals and for living spaces. Lots of other constraints might pop up, such as there being few quakes, strong enough rock to support mining, and so on. There would certainly be multiple more constraints, and it might be interesting to try and think up a list someday, but the main point is that phase-locked, 1:1 only, planets might be excellent places for an alien civilization to spread to.

These planets give off no signature of life, and except for some other alien civilization who was visiting or inhabiting the same solar system, the colonizers would be undetectable. An orbiting ship sent by the original inhabitants of the solar system might see piles of spoil from the mining, or the relic of an old starship, provided it had very good optics.

Now we have an interesting situation at hand. If the idea of living without the use of solar photons works, and mineral wealth alone is enough to make a planet colonizable, there could be lots of alien colonies, perhaps at a density of more than one per ten solar systems. All of them would be undetectable, no matter how hard a second alien civilization in a nearby solar system tried. The only way to find them would be to go to the solar system where they were, and spend a good amount of time scanning the surfaces very carefully, covering every large moon and every small planet not in the too-hot zone but including all the phase-locked ones.

If a colonizer didn't want to be detected, it might be possible to disguise the few local signatures of their presence, so that even this visiting starship would never know they were there. This would involve spreading out the spoils instead of leaving it in an artificial pile, dismantling the starship they arrived in and bringing the pieces underground, and building nothing on the surface outside of a few sensors. There would be wheel tracks from the vehicles used to explore the surface and look for new mining sites, and for transporting the processed minerals back to the home mine, but balloon tires might make this hard to see as well.

The upshot of all this is that the Milky Way might have a huge number of inhabited planets, and we will never know about them unless they choose to inform us. Instead of having only a very few origin planets, which are planets able to originate life and support it while it evolves to having an intelligent creature on it, there might be underground alien colonies almost anywhere there is a suitable planet. These planets and moons probably number in the billions. The age of the galaxy is of the order of 10 or so billion years, so exponential growth might have happened, and aliens are everywhere, just invisible to us.

Vulnerabilities of Population Reduction

There are the obvious ones, which relate to medium scale disasters that could annihilate a single arcology, and if an alien civilization concentrated its population in one, because they were so reduced in population that's all that was needed, it would mean the end of them. There should not be any surprises left in their solar system, meaning they know where all the asteroids are and their orbits, they know where all the subterranean faults are, they understand the risk of tsunamis and don't take that risk, and the same for anything else that happens on their planet, like hurricanes. With no surprises left, and a choice about where to site their single arcology, is there really any vulnerability?

Obviously, if they didn't know these things, it would be premature to reduce population to that level, so for the sake of the argument, figure they do know them and there is no geology left undone. On the psychology side, is there any risk in the slightest degree from one of them becoming psychopathic, and attempting to sabotage an essential system? Again, they are long past asymptotic technology, which includes psychology, so this is not really possible. Furthermore, the genetics grand transformation has given them all good genes and they also understand how to raise youngsters to be stable contributors to the society. They have to go way back to find in their ancient history a time when there was war and dissent, as every alien is rational and logical, and politics is a solid science now, so no reputable alien could raise objections to the way things are done. Technology simply brings calmness to everything it touches. Thus, an alien who had a passing thought about being a saboteur would simply recall that there are no political systems better than the one they have, maybe for tens of thousands of years, and as far as there still exists the abstract concept of justice, they have it.

There would be robots to fill all appropriate roles, and intellos, the biological equivalent of a robot, filling ones where they would be more efficient. Someone eons ago would have figured out how to keep everyone busy and interested, in who knows what, so there would not be any bored malcontents. Technology simply solves problems, one after another, until there are no more. If an alien civilization gets to this state, they can stay in it for as many thousands of years as they want, providing resources are sufficient and their star doesn't get nasty.

It would be hard for them to think of any vulnerabilities they have, or might have in the next millennia, as they have solved those problems already, except for one.

Aliens.

Not the aliens themselves, but aliens of a different sort from a different solar system. Aliens 1 and aliens 2, for convenience. If aliens 2 began traveling in space before they had reached asymptotic technology, or made the deliberate choice to avoid the calming effect it has, they might be going to another solar system with an open mind about annihilating whatever was living there and taking over the planet. This assumes there are two planets with life on them at some reasonably close distance, which could be unlikely or likely – we don't quite know that yet. So aliens 1 might be aware that there are other solar systems nearby them with planets which could have given rise to life, and they were old enough to have evolved a civilization.

One question we haven't resolved yet is could one alien civilization detect another, and how many light years away could this be done. If the answer to the question is that it would be too impractical to do this, or the engineering of the sensors to scan all the solar systems around them cannot be done, meaning there is some limit to what can be detected that we on Earth haven't figured out, and the aliens 1 have figured it out and there is no way around the limit, then they have an indeterminate risk. No telescope, no matter how big, can see finely enough to pinpont the signature of an advanced civilization, and certainly not enough to tell what stage it is in.

This means that the High Council of Alien World 1 can be sitting around thinking of how low a population they want to design for, and they have no way of determining if another alien civilization, aliens 2, is nearby and if they are going to be totally peaceful, or if they mastered space flight before mastering their own psychology, politics, economics, and a few other topics. And they have only their own history to guide them. They got super peaceful and would certainly not try and take over another civilization's world, but their ancient, ancient history says they weren't always this way. And they see a way that star travel could have been invented early on, if there was some motivation to steer technology development that way.

Naturally, they can come up with a master list of every way some alien 2 civilization could try and displace them from their own planet, and from this list, look for ways where having a low population, concentrated in one arcology at the extreme, would make them more vulnerable. Their first conclusion would be that it is very difficult to undertake such a offensive mission, and probably no alien civilization would want to spend that much resources on doing it. Then they might consult the alien 1 who was the most interested in ancient history, and ask him if any faction in ancient alien world 1 had ever chosen to spend some large fraction of their resouces on attacking another faction in a different region. If their history is anything like Earth's, the answer is: most of them did.

Perhaps there is something inevitable in the evolution of thinking beings that forces them through a period of time in which military adventures dominate their history. Or perhaps only a few worlds have such an period. But, if aliens 1 decide that somewhere in the near parts of the galaxy, aliens 2 are building some armada pointing in their direction, then they have a completely new basis for deciding on how much population they want to have. 

Population Reduction in Alien Civilizations

After an alien civilization gets to the point of asymptotic technology, that is, science is over and done with, they have a number of choices to make. One of them is how much population they wish to maintain. The choice is directly related to how long their resources will last, as for a given level of recycling, twice as many aliens use twice as much resources per time period. 

One aspect of this question relates to the process for reducing population. The direct and immediate solution is to simply gestate fewer aliens and allow the population to shrink at whatever level they could choose. It could be as drastic as going from a billion to a million over a few centuries or generations of alien life. The choice of what target to use is related to their view of themselves and their role in the universe. Is it to simply go extinct, or do they plan to go to some other solar system, in one of the many ways possible? If they choose to travel, there is a minimum population necessary to build the ship or ships. If they just are content to go extinct, an unlikely alternative, they could do it quickly with lots of aliens, or slowly, with only a few. Neither is very pleasant, as resource shortages do not make for high living standards.

This question is interesting, but also interesting is the process for getting the population down. There is one question that stands out: what about all the infrastructure? They don't need all the infrastructure that a larger population needs, and they probably don't want to spend the additional energy and resources to maintain it if it is only there for a ghost population.

Consider first fungible architecture. By this time, resource pressure, or at least the knowledge that it will be happening in the future, has mandated that the aliens will live in large arcologies, where recycling is pretty much total. One arcology might be almost identical with another, so there is no reason to keep the second one going if the first one can handle the population post reduction. In an advanced alien civilization, recycling will be part of everyone's life, and everything will be recyclable, even the entire arcology. So over a period of time, the second arcology might be taken apart, and fed into the recycling system of the first one, supposing they are not too far apart so transportation costs are not a significant factor. This adds to the longevity of the resource base.

In order to make an arcology recyclable, it would have to be divisable into parts, so there would not need to be any crowding of a double population into an arcology. Time for this could be stretched out, as by this time the civilization will have figured out it might have a million years on their home planet, so there is no rush to do anything in a short time. If gestation cycles are a hundred years or so, spending a few of them combining arcologies will not affect much over the long term. Aliens in the superfluous arcology could be given the choice of moving to the remaining one, or staying in the part of it which was not yet taken down. By this time, the arcologies would be self sufficient, with their own power plants, industrial sources of nutrition, air filtration, internal transportation, and everything else necessary to have a comfortable life for the alien population. There could well be some residual agriculture, for specialty products or for the amusement of aliens who wanted to be involved with farming for a period of time, and these would simply be reduced according to the population level drop.

What about the non-fungible parts of the infrastructure? Would there be any monuments, historic places, unique but antique buildings? There might have been, but the lifetime of any of these might only be a few thousand years at the highest, and after that, deterioration unless it was periodically rebuilt. Suppose they had preserved something from their earliest eras, before technology was greatly developed, and this was a part of their culture and something they used to maintain their heritage. With a drastic population reduction, as in the example above of a billion to a million, or something proportionate to this, a few heritage sites might be maintained, but not a large number.

It might not be appreciated that heritage could be a very important part of the alien civilization. Heritage is the reason they decide, over and over again in each generation, that they think their civilization is worth preserving and should not be allowed to become extinct. Each generation would have the possibility to reverse the decisions of previous generations, and, for example, stop work on a starship and instead use the capital to change their activities, to, perhaps, have more jet aircraft and spend much more time flying over the landscape and visiting unique sites on their planet, in person. Without heritage sites, the pressure to keep on track with previous generations might grow less, and reach a tipping point.

So, perhaps there is another factor which comes into play when an alien civilization is thinking about its target population for the long, long term. Having sufficient population to build starships may be one, but another might be having enough to maintain a critical number of very important heritage sites.

Almost everything else would have been conquered by technology. There might not need to be a minimum number to maintain the automated operations which provide energy and the standard of living to the population. This particular factor is not clear, but it could very well be that star travel and heritage sites are the only things which feature in the choice of population numbers.

What this means to us is that if these two problems of minimum population result in numbers fairly small, there might only be one arcology on an alien planet. When we have our huge telescopes, able to focus in on planets in different solar systems, looking for one with a thousand dots of light, probably infrared only, this may not be the signature of an alien civilization that we can find. There might be one dot of light, where they all live, and the rest of the planet has been returned to nature. This would be the situation for almost all of the million years of existence of the alien civilization, whereas the huge populations might be only a thousand or less, meaning a tenth of a percent chance of seeing them during this phase. This is one more signature of an alien civilization that needs to be carefully thought through.

BioFactories and Civilization Detection

In an advanced alien civilization which has passed through the genetic grand transformation, when all biological, neurological and psychological research is completed and accurate and consistent theories are available for everything in those fields, and in addition, all the data available about living organisms is known, there would be extensive use of this knowledge. We cannot, from the current state of our ignorance, predict there will be this or that usage, but it seems highly probable that there will be some industrial uses of genetics. Today we have some of this, and as a matter of fact, we have had such factories ever since fermenting was discovered. 

Cheese, risen bread, beer and wine, along with other fermented vegetables, fish, and some other products, are produced by the use of microorganisms here on Earth. These products represent the simplest possible biofactories, but there is no reason whatsoever to think they are the only ones which will be economically efficient once genetics becomes understood. Even if an alien world did not have yeasts which cause bread to rise, the existence of extensive genetic knowledge would allow such a microorganism to be invented, and then the alien civilization would have risen bread, if they wanted it.

These products involve using whole cells, in an agglomeration, to produce chemical changes in other foodstuffs, producing carbon dioxide, alcohol and lactic acid. There is a natural inefficiency in using whole cells for this, as the cell walls slow down the throughput of the chemicals used for input and output by the microbes. If there was a way to have this reaction without cell walls, the biological factories could be more dense, and possibly more efficient and better controlled. Thus, in an advanced alien civilization, we might see biological factories, producing a great many useful materials, without cells. Instead, a vat would serve as a giant cell wall, while the contents were chosen as only those minimally necessary for the biochemical production.

This advance, assuming it is possible, seems to tear down the wall between biology and organic chemistry. Inside the vat there might be no mitochondria, but instead industrially produced ATP was added as fuel for the reaction. Then the proteins that microbes normally use to catalyze and power the transition would consume the ATP fuel and create the right output. Inside a typical cell there are thousands of proteins with different functions, and only those few necessary to synthesize the desired product would be necessary. If the output molecules were smaller than the proteins needed to make them, a filter would be all that was necessary to extract the output. Likewise, input chemicals might be small enough to pass through a filter which blocked the factory proteins.

The pre-genetics method of making medium weight complex organic molecules can be quite tedious using solely the methods of organic chemistry. A tailored genetic process could be more efficient and more productive, based on resource and energy consumption.

As part of the genetics revolution, the biochemistry of nutritional needs will surely be understood. Once that is done, agriculture might be relegated to specialty production, and the majority of food production will take place on these biological factories. There could be no need for sunlight for these factories, although certainly some development of chloroplast-like nodules might happen and vats could be provided with energy in the form of photons, rather than by fuel in the form of ATP.  If this happens, food would be produced by combining nutritional inputs produced separately, and an entirely new food industry would be born. There would be no need for the biofactories to be located outside the arcologies, or wherever the aliens chose to live, but they could be positioned nearby residential areas, to minimize transportation costs and delays.

If agriculture is slated to disappear after the genetics grand transformation, this means that a huge telescope, large enough to image distant exo-planets, would not see huge parts of the dry land of an exo-planet with an advanced alien civilization turned over to monocropping. In fact, there might be very little visible from agricultural uses, as specialty crops could also be produced in biofactories as well. Freshness is not an issue if the fruit or vegetable is grown a kilometer from your residence.

As noted elsewhere, advanced methods of resource usage reduction will be used to prolong the time that the civilization can depend on buried resources. Recycling of resources would be used as well, so there might not be huge quarries that could be visible from space. Energy supplies, whether that would be uranium and thorium or low atomic weight fusion ingredients, would also be preserved by minimizing the losses of energy, such as for heating residential and industrial areas. Insulation would have been perfected. This implies that there would be no giant infrared signature from the arcologies.

In short, three of the main observational items that we on Earth, in later centuries, might have thought to use to detect alien civilizations with a giant space-based telescope would very well not exist. The biggest detectable would have been agriculture, but that disappears with the genetic revolution. Mining sites, such as huge open-air quarries formed by scraping off the top layer of dirt to gain access to shallow buried resources, would not necessarily still be in use. An example of these would be the tar sands region in Canada. Lastly, the habitations themselves would not be emitting light or infrared in massive amounts, such as our Earth cities do today, instead, there would be only minimal energy being spread out and leaking upwards towards space.

Finding something to search for is quite a challenge. Recall that there are only a few millennia between the emergence of the civilization from the primitive hunter-gatherer level up to the asymptotic technology level, and it would be incredibly coincidental if we happened to turn our telescopes on during that interval. If an advanced alien civilization can last a million years, order of magnitude, it is totally likely that we would observe their planet after they had made all the changes needed to last that long, including agriculture replacement, recycling and waste reduction, and resource use minimization. They would essentially be hiding in plain sight.

Planetary Configurations and Stellar Reflection

Tides are interesting things. Tidal force transfers angular momentum from a central body to something orbiting it. If the central body is spinning faster, it adds angular momentum to the orbiting body, moving it gradually outward. Earth's moon is slowly receding from the Earth, as Earth's day is much shorter than the orbital cycle of the moon. If a planet is being driven in toward its star by interactions with other planets further out, there may come a point where the planet is gaining as much angular momentum from the star as it is losing to the outer planets. It is undergoing what might be called a reflection, although this situation has nothing to do with the reflection of light from matter. The sun, at the equator, is rotating about four times faster than Mercury in its orbit, meaning Mercury, from solar tides, is being pushed outward. 

If a planet is at the point of stellar reflection, it is still receiving angular momentum from the sun, and passing it along to the outer planets, who do move outwards. Once they have done this for a while, their effect on the innermost planet will diminish, allowing the tidal force from the star to move this planet outward as well. The innermost planet is temporarily acting as a conduit for stellar angular momentum.

Among the thousands of planets which have been detected by the various astronomical instruments, there are some groups which revolve around the same star, making up exo-solar systems. A few have multiple planets and it might be thought this can show us something about the various patterns that different solar systems can take. While this might be interesting, the important thing is that these distant solar systems might not be stable of long periods, commensurate with the age of the solar system, but might be in the process of slowly rearranging themselves, through the swapping of angular momentum between one another and with the parent star.

The location on at least one planet near the star is advantageous is accelerating the approach to stability, or even to make it possible without the ejection of one or more planets. The interaction of the star with a close planet slowly and continuously transfers angular momentum to the planet, which then transfers it to other planets. But this transfer is associated with a transfer of energy as well, whereas interplanetary interactions largely conserve energy. It is likely not possible for a set of unstable planets to find stable orbits without some energy transfer, and so the stellar interaction mediates that. Science should attempt to figure out just how much assistance planets of different masses at close locations to their star help in this regard, and then they might serve as a semaphore for the posssibility of a stable planetary configuration, which means a planet could stay in a liquid water zone for long enough to evolve land life and maybe even an intelligent alien. Otherwise, there is simply no opportunity.

Earth has been stable in its orbital location for the billions of years of its existence, as otherwise evolution could not have occurred. Evolution from pre-cells to now lasted three to four billion years, and this would have been terminated had the Earth been outside the liquid water zone during the first portion of this period. It can certainly have wandered around inside it, as any planet in a resonant orbit relative to its planetary neighbors would, but the wandering has to be limited in extent.

This alludes to the main point of the search for life via the detection of exo-planets in the habitable zone. They need to have been there for a long, long time, meaning that only long-term stable configurations of planets need to be extensively investigated. A planet which has sat in the liquid water zone, even assuming everything else was optimal, for a hundred million years would not have recognizable life on it. Thus, stability of planetary configurations should be the first thing that is investigated. Luckily enough, that can be investigated without any need for a giant telescope or other astronomical instruments. It simply needs a mountain of computation, or some brilliant theory which obviates the need for patterns to emerge from the data. The brilliant theory could be checked in much less computational time than would be used for an exhaustive search over all possible combinations of planets and their parameters.

The very long time needed for evolution has two effects, a bad and a good one. The bad one is that if we search the sky for exo-planets with a new generation of telescope, one which does not have such strong selectivity effects for close-in planets or ones whose orbital plane lays within a very narrow band, and therefore comes up with thousands of right-sized exo-planets in liquid water zones, we might have to throw ninety percent of them out immediately. These would be the ones where the planet was just passing through the liquid water zone on its way to a more stable orbit further out from the star, or maybe toward the stellar reflection radius. Motion in a not-quite-stable planetary system might take millions of years or even more to occur, and thus finding some planet in the right location might mea absolutely nothing at all.

The good thing is that, in rare instances, planetary radial drift can be just what a planet needs to keep it in the liquid water zone. Hotter stars evolve faster, and an otherwise just perfect planet might find the liquid water zone moving away from it long before it evolved life. But if there was radial drift going on at the same time, the planet, with a large dose of good fortune, might find itself staying within that zone, even as the zone moved from the effect of stellar aging. So, a slightly large class of stellar spectral types can be searched to find planets that might have alien civilizations.

Ice Ages and Alien Civilizations

While it is true that the location of non-habitable planets doesn't matter much in a solar system where a possible planet for an alien civilization exists, there is a significant exception: Climate effects. When a planet co-exists in a solar system with other planets, they exchange angular momentum, which translates into a change in the semi-major axis of rotation. This means that in a stable, resonant planetary system, planets will slowly drift in and away from the star, not very far, but far enough to possibly trigger climate change. And climate change caused by this oscillation in average radius may be almost negligible, or it may be near a threshold where an instability in the climate system on the planet flips from one condition to another.

The obvious one is Ice Ages, but it is not the only one. It is, however, an easy example to discuss. Ice Ages happen because the absorbed solar energy is less because the average rotational radius from the star, averaged over a hundred thousand years or so, is a bit larger than it had been before the Ice Age started, plus there are important feedback effects. Energy absorption depends on the amount of energy emitted and its spectrum, the reflection and absorption in the atmosphere of the planet, and the fraction absorbed by the surface. 

Feedback effects come from the average albedo of the planet, which measures the fraction of energy reflected. When the planet gets a little colder, ice forms, which has a high reflective coefficient for visible light, where much of the energy in a mid-level star exists. A little ice means less absorption, and a colder planet, and more ice – starting the feedback loop. The final state of this loop is the peak of an Ice Age. This final point might be a saturation point, where almost all the available water is frozen, or where the convection of heat away from the warmer equator is insufficient to cool the equatorial regions down to freezing. There might also be a timing question, where the time necessary to freeze the planet is of the same order as the time for orbital change.

Consider a second example. The second feedback effect is much more difficult to detect eons later and has been given no name at all by Earth scientists, and may not be recognized as such. It is when the albedo of a planet is increased not by snow and ice, but by cloud cover. Clouds also reflect solar energy more than rock or other terrain, and once they begin to cool a planet, a “Cloud Age” might occur. Clouds occur at altitudes where there is sufficient moisture, but insufficient heat. High clouds do not lead to rain as low clouds do, but they do reflect well. Unfortunately for science, clouds leave little geological record.

Atmospheres with different compositions may have different types of clouds, and these may also have albedo effects. Atmospheric compositions on exo-planet has not been thoroughly examined, but it seems likely that some constituents might be present in an atmosphere and still have life supported.

Quite naturally, the opposite to an Ice Age might occur when the planet gets shunted in a bit closer to the star, all the ice having been long ago melted and all the high-altitude clouds dissipated. Life starts dying because of thermal effects, and when animal life is migratory but vegetation is not. If vegetation dies off over large areas, one area, a desert forms and less carbon dioxide is recycled back to oxygen. With more carbon dioxide in the atmosphere, heat is trapped near the surface, raising the surface temperature more, killing off more vegetation. Good numbers for this effect might well show it is much less powerful that the other two.

The effects that an Ice Age, and possibly a 'Cloud Age' and a 'Heat Age', to coin a term, would have on an emerging alien civilization are evident. These phenomena would lead to a large reduction in the surface area able to support vegetative life. If a civilization was still dependent on agriculture for its nutrition, or if there was a pre-civilization, perhaps at the pre-city stage, it could be doomed. For the Ice or Cloud Ages, if there was some small area near the equator still not completely blocked off, the numbers of survivors would be limited, and civilization would be stymied. Ice ages on Earth have lasted millions of years, and no civilization could be expected to survive this. Heat Ages would force population to the poles.

But the time scales are not commensurate. Civilizations can be estimated to last of the order of a million years, meaning that they could come into existence during the interregnum of a climate extreme survive, flourish, come to visit Earth if they wish and find it possible, and then disappear before the next extreme starts. These epochs are controlled by the interactions of planets, shuffling angular momentum between one another and slightly shifting their orbital radii. A question which might be answered in short order is: In which type of configuration of planets would there be periods this long between these catastrophic ages, and in which type of configurations, if any, would they be too short to permit a civilization to develop? Knowing how to translate the duration between climate extremes to planetary configurations would immediately tell us which configurations are worth examining in great detail on our hunt for alien life.

These types of calculations can be done now, but there is no clear understanding yet of what to look for. This means that large numbers of scenarios would have to be computed, until a pattern emerged, and the ensemble of possibilities could be winnowed down. Maybe the key variables involve the existence of two gas giants in some particular relationship, orbit-wise, and once this is established, other planetary resonances correspondingly exist and can hold planets. If one of these resonance bands is of the right thermal characteristics, and a potential host of other variables are within some ranges, we might be able to say that some particular planet, out of the millions which will be detected over the next century or two, are 'life-possibles', and deserve a great deal of specialized attention. 

The Formation of Solar Systems

The basic outline of the formation of planetary systems is well-known. A cloud of mostly hydrogen gas is rotating, and subject to its own gravity, it starts to condense. It may not be spherical, but nonetheless, there will be a point of maximum condensation, caused not by gravity at first, but by the pressure generated by the overall gravity pulling everything together. This maximum point will start attracting gas near it and a steadily shrinking ball of gas forms. The center point of the ball will be the densest location, and temperature will mount due to compression happening faster than the ball can cool itself, which happens when the ball becomes dense enough to become opaque. Temperature and density continue to rise, and finally thermonuclear ignition thresholds are passed, and it begins to fuse at the center. Gravity doesn’t stop, and neither does condensation, and larger layers pass the ignition point. At this point, there is a star.

There is a direction of cloud angular momentum, meaning that in general, the cloud is rotating around this axis. Centrifugal force pushes the cloud out, especially near the plane intersecting the new star, while the lack of that force in axial directions leads to a compression there. A disk of gas forms, and it becomes thinner with time. On a tiny scale, condensation into molecules and dust particles happens in the disk, and if the star is large enough, a solar wind begins and blows lighter molecules out further, leading to a partial differentiation of materials in the disk.

The disk is unstable to ring formation, so instead of a smooth disk, with time some dust and gas rings develop, and they continue the condensation process. The particle size increases in the inner part of the disk, and in the outermost part, ices form into particles as well. These particles congeal, and in the middle region, blobs of gas start to form, as the rings are unstable to planetoid formation.

At this point, resonant interactions start to form, and the dominant gravity will be from the densest part of the disk, which is somewhere in the middle. The gas blobs may be in resonance with each other, or anti-resonance. If anti-resonance happens to be the situation in a solar system, the innermost gas blob, now turning into a planet, loses angular moment to the outermost one, and they drive in and out respectively. If a large gas giant planet is driven into near the star, passing by the planets and planetoids between its original formation radius and the star, they will be strongly perturbed and may wind up anywhere in the system. Similar things happen with a large gas giant which is driven outward. The ice giant planets will be scattered and can wind up anywhere. If they go inward far enough, they will lose some of their mass from thermal effects.

The alternate situation, where there is only one large gas giant or two of them fortunately in resonant orbits relative to one another, the solar system is divided into bands, being resonant or anti-resonant. Two gas giants in this situation will exchange angular momentum between each other, but not secularly, only with a to-and-fro situation which keeps both of them near their resonant band’s centers. Smaller planets inside and outside of this which are in antiresonant bands will be scattered out, winding up almost anywhere, while ones in resonant bands will simply engage in moving around within the resonant band. Two of them in the same resonant band will result in one expelling the other, or a violent merger will happen. These types of collisions occur with much less relative velocity than any other interaction in the solar system, as two planets in one resonant band are moving with close to the same orbital speed, not much eccentricity, and a seeming repellant effect. When one of the two planets comes close to the other, it speeds up, changing its orbital parameters, and may pass by the other without doing more than being distorted. This can continue to happen until the two of them get closer and closer in orbital parameters, when a merger finally happens with minimal velocity of impact.

The existence of resonant bands and antiresonant interactions helps to explain why the solar system zoo which we are gradually discovering is so diverse. Rings condense with no resonant interaction, just anywhere, depending on the radial structure of the gas and dust disk, but once they condense, they become subject to another instability leading to planetoid condensation. They might be in resonance with some other planet or anti-resonance, meaning they can travel in radius from the star, ending up in some strange place. This happening with many planets at once can lead to the lack of clear patterns of solar system planet location.

What does this mean about where to best look for aliens? The time scale for planetary rearrangement should be relatively short compared to the time needed for evolution of cells, so if a suitable planet, with the right gravity, atmosphere, and composition, shows up in a thermally favorable location, having other planets in the solar system in strange locations should not affect it. It might be that a solar system which has gone through a period where antiresonant effects took place would have many less planets, so the numbers might be against a planet holding an alien civilization, but if one exists, the other planets should not prevent origination and evolution of life. They will, of course, perturb the orbit over millions of years, but antiresonant effects should be over and the perturbation will be back-and-forth, simply creating a bit more interesting planet to evolve upon.

If there was a veryhot Jupiter and a very cold Saturn in some solar system, and one nice habitable planet in the middle with all the stuff needed to originate life, a civilization arising there might have no interest at all in interplanetary travel, which is the learning stage for interstellar travel, assuming it is possible at all. It is actually quite entertaining to try and think of what life might be like in an alien civilization in the variety of solar systems we are now discovering, bit by bit.

Rain and Life

When we are searching exoplanets for life, one of the premier signals is supposed to be the presence of oxygen. Oxygen typically is chemically combined unless it is renewed, and vegetative life provides this renewal. As all schoolchildren know, photosynthesis involves chlorophyll acting as a catalyst to break carbon dioxide into oxygen, which is released, and carbon which is utilized. But photosynthesis can be done in the oceans by near-surface plants, and while life in oceans would be tremendously interesting, life on land would be even more tremendously interesting. It is very hard to see how intelligent civilizations could evolve underwater, but on land, there is the possibility.

Thus, oxygen might be a great signature for life, vegetative specifically, but not so certain an indicator for alien civilizations. What might be used in addition?

It is certainly worth asking the question. Just consider that a hundred years from now we find ourselves in a galaxy with thousands of planets with life, but all of it wet. Now consider instead of that situation, we are in a galaxy with even hundreds of planets with alien civilizations. Orders of magnitude more interesting.

So, what is beyond oxygen as a signature of life on land? Trivially, there must be dry land, and that would have some reflective signature. Rock doesn't look like water when reflecting sunlight. But just having rock doesn't imply that there is anything living on it. There needs to be some preconditions before life can crawl out of the oceans and take up habitation on dry land. One is rain.

Life needs water. It doesn't need to be immersed in it, but it needs to have it to drink. Water evaporates, and water on land needs to be renewed. That means rain. Water evaporates from the oceans, drifts over the land, condenses into droplets and falls to the ground. There aren't too many other possible mechanisms. One could consider tidal flooding, which might produce wet areas, but if the ocean has dissolved some minerals from the rock, like salt, it might not be drinkable. If there was a lot of volcanic action, possibly someone could come up with a process that, on some suitable planet, might pump water, distill it in the volcanic heat, let it condense elsewhere, and expel it into a river. This complicated a mechanism doesn't seem likely, at least during the later life of the planet. So it is rain that is the mandatory precondition for an alien civilization and for animal life on land as well.

Detecting water vapor in the atmosphere might be the first surrogate for detecting rain. On Earth, water vapor is at a much lower concentration than oxygen, and therefore more difficult to detect; but it is not impossible to foresee that that would be a further step in astronomical capability, once oxygen was detectable. Carbon dioxide might be detectable first, or some other compound or element, such as argon, but eventually water vapor would succumb to astrophysical technology. These gases would likely first be detected for a transiting planet, where the light of the parent star shines through the atmosphere and gets spectrally absorbed. Later they might be detected from reflected light.

Rain would have to be either a local phenomenon, evaporating over most of the ocean area, and then precipitating on some region, or else a seasonal phenomenon, evaporating during one season of the year, and precipitating during another. Wet ground has little difference in albedo than dry ground, however, so even if telescopes grew sufficiently in aperture to see different parts of the exoplanet, seeing wet areas would be quite difficult. But if there was sufficient temperature range on the planet, and there was snow, then a significant albedo change might be detected. This would be even easier in the seasonal case, where evaporation occurred all summer and then all winter, snow happened. A planet with an elliptic orbit might produce this situation.

Another option is clouds. Rain and clouds are not the same thing, but there must be clouds to produce rain. Searching for clouds might be considerably easier that searching for rain. Clouds do change the global albedo, and monitoring for these changes would be an indicator of cloudiness, and by implication, rain.

Another variable which affects the detectability of atmospheric gases is the thickness of the atmosphere. Earth has a very thin atmosphere, about 10 km thick compared to 6000 km radius of the planet. This is to be compared to Venus, with approximately the same radius, but an atmospheric thickness of 250 km. Probably the components of Venus' atmosphere would be much easier to detect on a transiting planet. Clearly one must compare the loss of signal due to the longer transmission path with the larger cross-section of the atmosphere and the lengthened time for absorption. For a reflective signal, the loss of albedo may make the comparison go the opposite way, with thicker atmospheres being more difficult to break down into components.

One interesting question is, if there was an exoplanet with an atmosphere as thick as Venus' atmosphere but of the same composition as Earth's, would rain be possible? One might also make an assumption that the rotation rate was identical to Earth's as well. Similarly the average temperature would be assumed to be the same as Earth's. The vapor pressure of water is the same no matter where it is, so the amount of water in the atmosphere would be the same as Earth's, maybe a half percent on Earth on the average, with more of it at lower altitudes. On the exo-planet it would be a half a hundredth of a percent. Rain forms when the temperature of the atmosphere drops sufficiently that liquid water can form. Would the thermal inertia of a large atmosphere, with 100 times the atmospheric mass of Earth, prevent this temperature drop? Temperature drop comes from heating or cooling of the atmosphere, and a portion of the lower atmosphere gets a certain amount of heating from the solar energy passing through it, which is largely identical and a certain amount from the reflected heat from the planet. On the exoplanet, much more solar energy would be absorbed by the atmosphere, leaving the surface much darker and receiving less energy. Solar energy incident on the atmosphere would be largely identical for different longitudes, meaning much less opportunity for the temperature change that is required for rain. This possibly means that finding an exoplanet with a thick atmosphere would imply no rain, and no land lifeforms, and no alien civilization.

One hypothesis about the reason for the thinness of Earth's atmosphere is that atmospheric mass is almost unaffected by the aging of the planet, and once thin, it stays thin. If the formation of the Earth was mediated by the impact of a protoplanet, which led to the formation of our large moon, and the legacy atmospheric hypothesis is true, looking for a large moon might be the fastest way to find land life and the possibility of a civilization.

Imagining the Goals of an Alien Civilization

It is much easier to imagine some aspects of alien society, such as their energy sources, than other aspects, such as their goals, because we have on Earth made some progress in understanding the possible sources of energy and can make some good guesses as to what might exist in a more advanced society. But with respect to social goals, our technology is very primitive. We hardly understand anything about societies and their goals; even the basis for this technology or scientific knowledge is vague and undeveloped. We have some observations, but nothing equivalent of Newton's law has been figured out yet. Just to appreciate the difficulty involved, think of asking someone in Columbus' time about energy, after explaining the concept to him. He might answer there was wind power, and that's about all. A person who had some education involving ancient Greek science and who had heard of Hero of Alexandria's aeolipile might add steam power, which comes from fire. There would be no way that such a person could estimate what energy usage would look like five hundred years later, or a thousand.

On the other hand, we have some confidence now in understanding electromagnetic energy, kinetic energy, chemical energy, equation of state energy such as compression, and nuclear energy, along with the many ways they exist in nature and how they can be harnessed and converted. A person on Earth today might be able to do a good job in describing the use of energy, and might even be able to imagine how energy might be used in the far future. And if we subscribe to the concept of societal convergence, meaning technology drives society and since technology is the same no matter what planet you live on, all sufficiently advanced societies will have similar features, and therefore what this person imagines for Earth five hunderd years from now would be quite insightful as to what a similarly advanced alien civilization might be doing.

We are in the Columbus era stage of understanding neurology, politics, governance, societal arrangements and whatever else relate to the goals of an alien civilization. We would make grave mis-assumptions to try and use what we think are the goals of Earth's various societies, current and historical, as possible goals of an alien civilization.

Some goals that might pop up from the study of Earth societies' history include empire expansion, maintenance of the existing power structure and factionalization, development of profitable trade connections and routes, collection of items of universal value such as gold, the pursuit of scientific progress and technology, revenge or hatred directed toward some group, usage of a particular economic system, the spread of medical technology to various factions, and so on. These are goals which are appropriate, if at all, for a single planet. Ones which relate to multiple planets might be the expansion of life to dead planets, resettling on other planets as an insurance policy against catastrophes or other events which eliminate life on the home world, and a few others.

Our knowledge of energy and astronomy enable us to realize that some of the one-world goals are ineffectual for a multi-solar system civilization. Each planet of the civilization is almost totally isolated with respect to transportation and communication, not absolutely, but almost totally, by the distances between different solar systems and the huge amounts of energy needed to move anything from one civilization to another. Some minimal communication might be attempted between two solar systems which are not too far from one another, but little can be done with simple information transfer with no transport to implement any agreements, requests, or orders from one planet to another.

An alien civilization which is somehow frozen in its level of technology at something like what Earth has now might also have its goals be chosen from the ones listed above, but technology does not plateau easily. It proceeds forward to the asymptotic conclusion or the society degenerates. So at the very least, we can say that multi-planet civilizations do not have empire-building as their goal, nor the development of trade routes, collection of items to be brought from one solar system to another, and perhaps more.

After an alien civilization moves through its technological development of electronics, robotics, and artificial intelligence, the next area it encounters is genetics. The genetic revolution will overwhelm the electronics revolution, and the concept of factionalization, based on legacy concepts of genetics, local origins, language preferences and so on, will drift away as good genes are made available to all members of future generations beyond some point in time. Technology has shown cost reductions in the electronics phase of development, and when this wave passes genetics, there will be little reason to suspect that good genes would not be universally available.

The same wave of technology would also pass through the quasi-sciences of politics and economics, transforming them into fact-based sciences and enabling an alien society to have wise political structures and economic arrangements. The idea of an alien society having a goal of enforcing some legacy economic system on its members seems a little ridiculous; the optimal system would be known and used everywhere. Why would any region or goup want to use antiquated systems when better ones were instantly available?

For one-planet goals, the one which passes through the filter of advanced society might be the preservation of the civilization via wise use of resources, and the expansion of it to other appropriate planets. The other one is the preservation of life in general on the planet, but more importantly of spreading it to other planets. These are quite dissimilar goals in their effect on the civilization, even though they both originate from the abstraction of the goals of life across all species. There is no reason that both of them could not be accepted and acted upon by any particular alien civilization, except for the cost in resources they both have. If it is true that civilization can establish itself on a much different class of planets that life can evolve upon, it is fair to say that they operate almost independently.

It does not seem possible to extrapolate from goals of Earth societies, current and recent, to goals of a civilization with more advanced technology, by a few centuries of progress. The only way forward is to look for the simplest possible ones, those which derive from the nature of life. Perhaps some others can be found with a different approach, and that is certainly an interesting avenue to follow.

Hunting for Life in the Milky Way

In earlier posts, there was some discussion of what would be the goals of an advanced alien civilization, assuming they had come together to choose one and then to work on it. In a different blog, some more thinking on this matter indicated that the most reasonable and likely goal of the civilization is that of life itself, which is best broken down into five separate goals, survival, reproduction, adaptation, evolution and dispersion. These goals imply many choices that the alien civilization would make, in order to further their alignment with these life goals. The last goal is dispersion, and that means first expansion all over the planet, then the solar system, and then outwards into the galaxy. Just think for a minute what this implies: all or most advanced alien civilizations are going to attempt colonization and seeding, both of which support the dispersion of life.

Neither of these tasks are easy, as has been noted in all the posts in this blog on these topics. Colonization means setting up some replica of the alien civilization on an exoplanet ,while seeding means starting out life with the alien version of DNA on some planet which doesn’t have the prerequisites to become an origin planet on its own, but can support life, being in the habitable zone plus all the other conditions. Current theory here on Earth indicate the cells that did that were cyanobacteria.

Looking for seeded planets would likely be the same as looking for origin planets. Seeding might put photosynthetic organisms into a planetary ocean, and then, after a few hundreds of millions of years, an oxygen atmosphere might exist, which is a tremendous benefit for evolution, allowing life to expand beyond chemotrophs and cyanobacteria cells to a food chain. The oxygen in a seeded planet’s atmosphere would look the same as in an origin planet’s atmosphere.

So, assuming most of the alien civilizations do both seeding of potential life-supporting planets and colonization of others, which are not able to support life, but which provide the resources necessary for the alien civilization to sustain itself for a long time. Which ones should be looked for?

Seeding a planet gets over the hump of life origination, which might be tremendously difficult, rare and improbable, at least according to one theory, mine. Is evolution fairly certain after that, or are there more highly improbable-to-overcome barriers along the way to intelligence? Suppose there aren’t. Suppose evolution is as easy as rolling down a hill. However, it takes a long time. Earth is our only example here, and life took about two and a half billion years after the atmosphere changed to partially oxygen to evolve to intelligence. This means that any alien civilization which evolved in the last two to three billion years has not had enough time yet for their first example of seeding to have led to a new alien civilization, evolved from cyanobacteria to tool-using creatures of one form or another.

This raises the obvious question of when, in the history of the galaxy, was life likely to originate? There are stars around which are ten or so billion years old. Could these have had planets soon after they formed, and perhaps one which met the prerequisites for life to originate? Unfortunately, current astronomical tools do not allow us to figure out much of the history of the galaxy. It likely started out as a gas blob, and condensed irregularly, with stars forming all over it, but more in the denser region in the center. Gas was more dense that now, as by now much has been consumed in star formation, and that implies that stars which formed early would be larger. Large stars live short lives, and end in a supernova explosion. There would not have been the neat division of the galaxy into the disk and the central bulge, so star motion would have been more random and Boltzmann-like. Neither of these two things bode well for planets. Supernovas going off near a planetary system sterilize it, but may also disturb planetary orbits, causing them to be ejected or rarely crash into the star. The passage of a nearby star does the same thing, pulling planets out of their orbit, leading to a planet-planet interaction where the smaller ones get ejected. So, while little definitive is known, it would seem likely that planetary formation in a system which perseveres long enough to originate and evolve life is more likely in the later stages of the galaxy and out in the disk. Finding planets to seed would also be more likely in these conditions.

Putting this together means that seeded planets might be around, but life on them is too young to have evolved into an advanced civilization. There really is a double time here. For life to originate and produce an alien civilization, capable of star travel, might take four billion years since the planet formed into a habitable world, with the right temperatures and everything else needed for life. Then if that civilization seeds another planet, we have another three billion years or so to wait. That is seven total, and seven billion years ago, there might have been so much turmoil in the galaxy that life couldn’t originate and evolve. So, planets which have been seeded might be common, and even many which have had the few hundred million years to produce an oxygen atmosphere. But if we are hunting for alien civilizations, seeded planets are not worth the effort. That leaves origin planets and colonized planets.

The previous post, on frozen worlds, indicates that colonized worlds, if the aliens choose worlds which are the easiest to colonize and which will sustain them for a long time, might look absolutely different from origin worlds. It also indicated, because of the very different time scales involved, that there could be very many of them all over the Milky Way, or at least out in the disk. The idea was simple: if there are sufficient resources on the planet, fusible and fissionable elements, plus all the other minerals necessary to supply the civilization with its raw materials, buried in the ground, they can simply build their civilization under the surface, on a frozen world and maybe some not so frozen. The ratio between colonized worlds and origin worlds might be a thousand to one. There would also be much larger numbers of previously colonized worlds where the alien civilization has used up the minerals and life on the planet was no longer sustainable for them.

How do you detect a mine shaft and a starship landing zone? Maybe there would have to be some surface transportation, if they needed to have mines in multiple locations. It might be possible, with a kilometer sized telescope, to see large oceans on an exoplanet in our vicinity, but even one ten times larger than that could not detect something as small as tens of meters or even a kilometer in size. Looking for a tiny heat source is conceivable, but unlikely as the resolution at deep infrared wavelengths is so much less than in the visible. If the concepts trotted out here and in the last post are viable, it means that alien civilizations are not detectable, and they would have no interest in coming to Earth, either for seeding as we are way past that, or colonizing as there are too many potential difficulties. It wouldn’t align with their goal of dispersing life at all to visit Earth. So the only thing we have any hope of doing is detecting an origin world, but if there is only a few of them,they might be on the other side of the Milky Way or in a different spiral arm. Perhaps a double hope of there being easy ways to originate life and our detecting oxygen in exo-planet atmospheres is the only possible salvation for the quest to find aliens.

Colonizing Frozen Worlds

An alien civilization which has mastered the art and science of traveling between solar systems might have done something else which will surprise us. They might have decided that worlds like their origin world are fine for the origination of life and evolution and technology development, but there are better choices for an established, advanced, expanding civilization. They might like frozen worlds.

Back here on Earth, we are all excited about the developments in the detection of planets around other stars than ours, and are contemplating how we might search for life on them. The great hope is that oxygen in the atmosphere will be the clue. Oxygen is a reactive element, and would combine with exposed rock, removing it from the atmosphere. It is plant life which renews it, by taking in carbon dioxide and releasing oxygen. Before we had plant life on Earth, we had a different atmosphere. Nitrogen is not very reactive, and carbon dioxide even less; they were there. There may have been other constituents, but no matter. Oxygen was not one of them. If life all died out on Earth, the oxygen in the atmosphere would disappear. So atmospheric oxygen has been chosen as the signature of life.

This means that our search for oxygen in the atmosphere of all those exo-planets is directly solely at finding origin planets. To understand what this means, let’s consider an example. Civilization Z originated on planet A101, after a billion years or two of evolution. They used up all the resources, but being a very intelligent civilization, they developed star travel before that happened, so they could travel to other solar systems and use up the resources there, before traveling on. Maybe they had communication between the different colony worlds, and maybe not. Perhaps they always did more than one new world from each colony, after about a million years on each one. Then, to do the very simple math, after one million years there would be two colonies, plus the origin planet which can no longer support a civilization, lacking resources. After two million years there would be four colonies, plus two old colonies which had died out and old A101. After three million years, eight colonies, plus six old colony worlds, now without any civilization, and A101. Just remember, in the calendar of the galaxy, three million years is very, very short. Maybe they would run into some expansion problems at some time, as exponential growth gets large very quickly. For the sake of the example, suppose that at the time we start looking for life in the galaxy there are five thousand colony planets with life, meaning civilization Z, two or three thousand ex-colony planets, and that old origin planet.

So, if some brilliant astronomer wants to find life in the galaxy at this point, there might be five thousand planets with life and a civilization to boot, and one origin planet. Where should he look for life? Origin planets?

To try and figure out what planets might be serving as colonies for civilization Z, ask: "What are they going to need?" Resources, and principal among them, energy. If the planet being considered is not a rogue planet, floating free in interstellar space, there will be a star to orbit around, which is giving off energy in the form of photons. These might be collected. Otherwise, there is uranium and thorium to fission and deuterium and other light nuclei to fuse.

Perhaps there are two stages of resource needs. One relates to the initial time on the planet, after the alien colony ship arrives and lands. Since fission reactors are relatively simple to build, compared with fission ones, at least as far as we know, they might seek planets with lots of uranium, and uranium that is not too old so there is still lots of U-235. Old uranium has only the U-238 left, which is much harder to fission. As uranium ages, the fraction of U-235 goes down. The planet from which civilization Z is expanding might start a hundred thousand years before they need to migrate, and send out some exploration ships. A ten thousand year voyage, and they can start reporting back on what the target planet is made of. So, in this particular scenario of colonization, there is plenty of time to carefully plan their next planetary colonization.

To have uranium, which is thought to be produced in supernova explosions, there would have to have been a few in the previous billion years prior to the formation of the star they are considering. Then there would be uranium, young enough to be useful. Figuring that out might not be too difficult, by looking at the contents of the gas clouds around the solar system in question.

Do they want a larger planet, with an atmosphere, or a smaller planet, maybe Mars-sized, with almost none. This might depend on the details of how planets form crusts and how mineral deposits accumulate in the crust. We’re not too sure of these details now, but if Mars has good mineral deposits, then Mars-like planets might be just what they want. Low gravity means not so much propulsion needed to get out of the gravitational hole. Little atmosphere means no winds to worry about.

Our knowledge of exo-planets is fairly sparse at the current time, but it might be such smaller planets are typically cold. If the star is smaller, but there was a lot of residual angular momentum in the cloud it formed from, there might be many smaller planets, completely frozen, but with excellent mineral resources. Could an advanced alien civilization cope with extreme cold? Can they master insulation? Very likely. Thus, perhaps frozen smaller rocky planets are their preference. If so, even a rogue planet might be just fine. There may be huge numbers of them roaming the galaxy, largely invisible to us.

There is another follow-on conclusion from this possibility. Earth would be of no interest to an alien civilization which was colonizing all the mineral-rich, frozen, small planets in the Milky Way. Earth is too big, with too much atmosphere, too large with too much gravity, and also has the minor inconvenience of already having life on it. Perhaps we should think through the alienology of colonization a bit more to see if this option is a dominant one.