Detecting Alien Civilizations

Aliens haven't visited us as far as we can tell. They also haven't sent us messages that we could recognize. So, we have to peer out into space and look for them. Finding a planet which has oxygen in its atmosphere is regarded as a signature of life, as oxygen likes to bind to the exposed surface material and wouldn't exist in the atmosphere if it is not being replenished by life processes. At least that's how Earth works, and other planets may use this design as well. But oxygen or not, this says nothing about detecting aliens themselves. If they have an advanced civilization, they may be beaming messages in space, but we haven't been invited to join the network, and don't have a clue as to how to fill out the application. So we need to look for them, and then perhaps we might send a signal that says we want to chat. At least we would know where to send the signal. Detecting alien civilizations on a planet is difficult because they likely would not create any signatures on the planet which would be visible at lightyears distances, unless we built some very large telescopes. Even then, seeing some city on the planet's surface is unlikely. Perhaps if they traveled in space they might be detected. Consider the background of the signatures we could look for. If there was a planet like Earth, with life and even worse, weather and geological features and water features and more, all these would make the detection of life with low-resolution telescopes difficult. By low resolution, we do not mean little things like Palomar, but instead telescopes which have only ten to a hundred pixels resolution across the diameter of the exo-planet. That means, we would be seeing, at the best, only things which could stand out at those resolutions. What might they be? Suppose there was a very large city somewhere on the planet. This might be a few kilometers across, compared to the size of the planet, which might be several thousand. This is not going to be visible unless there is some spectral assistance. For example, if one pole of the planet was very cold, at the time we observed it, and the city was warm, we might see one pixel bright in the far infrared, surrounded by black (in infrared) pixels. This would be a good option, except infrared is absorbed by any atmosphere we might expect on a Earth-like planet. Maybe they have a thin atmosphere, very warm cities, and very cold polar areas, and then we might see the city. There is a much better chance to see some warm city on a satellite without atmosphere. If they had, on one of their planets, a moon with no atmosphere, but plenty of minerals and other things that were useful for the aliens, and they built some surface habitation there, it would be easier to see. The habitation would certainly be smaller, but the moon might be, for at least part of its orbit, much colder and not only that, more uniform in temperature. Thus, the detetability of a far infrared signal might be easier, even if the habitation was smaller than a city on the origin planet. So, an alien civilization with interplanetary capability might be easier to detect. There does not even need to be the assumption that the origin planet is in the same solar system. No matter how they get to the cold, cold satellite, the detectability calculation is the same. If, for example, their origin planet was on one star of a binary system, and the satellite they were visiting and colonizing was on the other, they would be detectable. And it certainly does not have to be a satellite. Any small world with no or a thin atmosphere would be just as good for detection. It might be that the future of alien space travel from this particular planet was very practical. Since there might not be any planet similar to their home planet within many light years, they might have decided they were going to go to many of the solar systems near them, within say ten light years, and set up colonies wherever they could be self-supporting. This could mean some good fraction of the solar systems around them will have some colony there. Perhaps a good fraction of these colonies would be detectable. How many colonies might there be? Suppose the universe is generous, and it is possible to set up a self-sustaining colony on a wide variety of smaller planets. Because we don't have any good knowledge of this number, none at all actually, because no one seems to have worked on it, let's assume it is 10%. So, if the average density of solar systems around their origin planet is about one in every 10 light year cube, the average alien civilization should have a colonizable solar system within about 9 or 10 light years. If their ship travels at 1% of the speed of light, it should take them about 1000 years of travel, plus some preparation time, to move to their first colony. If the universe is even more generous, and a self-sustaining colony can build their own starship in a thousand years from the foundation, they can start their second round of travel at 2000 years and arrive at the next planet at 3000 years. If they do two at a time, this means by 3000 years they have seven planets. In 2N-1 thousand years, they have 2 to the Nth – 1 planets. This works out to a million planets in about forty thousand years and a billion in less than sixty. These numbers are not realistic, but just are shown here to explain that covering the galaxy with alien colonies doesn't take that long. They could go much, much slower if they chose, and use up fifty million years colonizing the galaxy. Or whatever. If we want to go looking for alien civilizations, so that we can contact them or sell them our planet or just wish them well, it seems there is a fundamental division in how we choose to do it. The deciding question is: Is star travel possible, for an advanced alien civilization with a solar system full of resources and plenty of time to do anything necessary? If the answer is yes, it seems rather foolish to concentrate on looking for their home world. We want to know where could they have a self-sustaining colony, because there could be a billion of those and only one home world. Bad, bad odds. If the answer is no, then we might first ask: why are we doing this? Every civilization is all isolated in their home solar system, and what possible use could it be to find some other set of prisoners? Commiseration? But if someone could come up with a non-nonsensical, seriously rational and utilitarian, answer, for looking for somebody else's home world, we need to do some fundamental research which seems to be virtually ignored. If you want to find the home world of some aliens, you need to figure out what characteristics of the planet and its star are necessary, and what other conditions there are, such as having a satellite, low eccentricity, large gas giants in the same solar system, axial tilt and so on. A simple temperature of water condition is foolishly simple. We need to find the conditions both for life to originate and then, completely separately, for an intelligent civilization to evolve. That's what this blog is all about, but much more could and should be done.

Does the Drake Equation Make Sense? Part 2.

If life originates, and the planet where this happens continues to reside in the liquid water zone, does it evolve to intelligent life? Are there certain conditions which are prerequisites for intelligence to evolve? Would they be common among such planets, or rare?

In this blog, and certainly elsewhere, it is supposed that tool use, starting with fire, then stone and wood, leads to the increasing capacity of the brain of some dominant organism. An equation, similar in form to the Drake equation can be written for this process, involving the evolution of increasingly complex organisms, starting from the first thing to form which constitutes life, a membrane enclosing some proteins that reproduce in some way, and which also produce more membrane. The steps might include the formation of more complex cells, with different features, the ability to exist in different environments and to consume different chemical energy sources. Then the shift to multicellular organisms has to happen, and many steps of evolution might be inserted into the new formula for the progressive development of capabilities of multicellular organisms. Then, back to single celled organisms, a step has to exist to be able to take energy from photons from the star, with the development of some primitive form of chlorophyll. And it goes on and on, as evolution is a horrendously complicated sequence. Regrettably, we do not understand the sequence completely, not even the conditions on the surface of the planet which are required to allow them to happen. The overall probability of producing intelligent species might be 1.0, meaning inevitable, or 0.000001, meaning intelligence is not a particularly useful capability for most creatures on an exo-planet.

The rise to intelligence is perhaps the most difficult of the probabilities in the Drake equation to estimate, as the evidence of most forms of life does not last for billions of years, with only a few exceptions. It should be one of the first orders of those who study it to come up with the new sets of probabilities, so that these can be studied from a normative sense, and then the whole combined into the Drake factor measuring it.

From intelligence to a civilization, mastering technology up to electronics, is another opportunity for sub-probabilities to be estimated. Here it is much easier, as there is history of our development, and it serves as one example, and a base upon which tangents may be followed. This blog includes, in many of the posts, speculation on the steps involved. There seems to be a natural order by which technology progresses, one stage depending on the previous, and there also seems to be a drive, reminiscent of evolution, which pushes creatures to develop successive stages of technology. Figuring out the steps up to the stage of civilization that we currently inhabit is not so difficult, but the postulation of what happens next is extremely controversial. There seems to be a tendency among modern-day humans to forecast dooms that might be imminent, and if one such doom really exists and is universal among intelligent species, reaching broadcast capability might be chancy, and staying there more chancy.

Another of the assumptions inherent in the Drake equation is that broadcasting is the end point of technology, and it would continue for some long period. It hasn't. There is still some, but the term, L, in the Drake formula may be very short as better ways of shipping large quantities of information around the planet have been found and have displaced broadcasting. This seems likely to continue, so L may be, for us, less than a hundred years. With that short a time, being so lucky as to be listening during the particular century out of billions of years of planetary existence is almost impossible to expect.

The Drake equation, if used with the retrospection of all the decades that have passed since it was first written down, may well indicate that the SETI project is hopeless and should never have been attempted. Many people's lives and careers were involved in it, and certainly some, perhaps many, were overwhelmed by the feelings that if they were successful, their fame would be writ large on the pages of scientific history. Some of the participants talked about the success of the project being a grand changer of the direction of human civilization. With such a result, it is not hard to see how the Drake equation was mis-evaluated in many ways so as to provide a justification for the search. Who wants to have their hopes of a glorious legacy be dashed?

The Drake equation, and indeed the SETI project, did have the value of focussing the attention of many individuals, scientist and non-scientists, on the various steps in the formula. It raises the interest level and provides some motivation for doing the hard scientific work necessary for our continued progress. There is little work going on in some very important areas, such as questions of the origination of life, but there might be even less if the burst of energy and excitement that the SETI project ignited had not happened. Understanding evolution is a continuing scientific task, and it might not have been greatly affected by SETI's popularity, but perhaps as the gaps and uncertainties in Drake's formula become more clear, there will be some effect, and some new Darwins will enter the field and erase the dark gaps in the theory.

Mankind has always tried to understand history, and the nature of man and the nature of civilization, but the Drake equation takes all this non-scientific palaver and demands that it be turned into a quantitative measure of how civilization develops. Historians typically do not make much use of the theory of technological determinism, which says that civilization is forced to adapt to technology, which is forced to follow a certain pattern of temporal stages. If history becomes scientific, this might be the result of the Drake and SETI activity with the greatest influence on the future of humanity. Once history becomes more scientific, a better forecast of the potential futures can be given and we would not have to resort to choosing between a dozen different predictions of dooms.

To summarize, the Drake equation inspires work in the following areas: orbital stability for small rocky planets, origin of life from either a unique event or ordinary conditions, the evolution of life through the millions of steps needed to lead to intelligent creatures, and the transformation of history from an art to a science. With the retrospective understanding we now have, the probability of success of the SETI project likely starts with many zeros, and there does not seem to be any redeeming factors in the equation which would raise it even to the order of a few percent or more. Given the amount of effort that was put into it, it was a good start, insofar as it provides motivation for more good science, and also makes non-scientists aware of the possibilities that we are not alone, and with a good amount of further work, we might know just how not alone we are.

Does the Drake Equation Make Sense?

The Drake Equation was developed in the infancy of the SETI project. The Search for Extra-Terrestrial Intelligence was a US-sponsored project starting over sixty years ago, designed to listen for any kind of electromagnetic broadcasts than another intelligent civilization might be emitting. The equation is simplicity itself, just a product of conditional probabilities. Here it is:

N = R_*^.f_p ^.N_e ^.f_l ^.f_i ^.f_c ^.L

and N is the number of detectable alien civilizations in the galaxy,

R_* is the rate at which stars form in the galaxy,

f_p is the fraction of stars which develop planets,

N_e is the number of planets within a planetary systems which have the right conditions for life,

f_l is the fraction of planets with the right conditions for life which develop life,

f_i is the fraction of planets which develop life up to the level of intelligence,

f_c is the fraction of planets with intelligent life that build systems to radiate electromagnetic waves,

L is the length of time such civilizations persist in their radiation.

There are a number of assumptions made which permit the formula for N to be expressed this way. Let us discuss a few of them.

First, the Milky Way galaxy is chosen as the basis for measuring everything. We only know that life can originate on a spiral arm, far away from the bulge and the black holes which inhabit the center. It seems quite reasonable that life needs billions of years to evolve to the stage where a civilization emerges and starts emitting radiation, and in the bulge, distant stellar encounters happen much more frequently than in the spiral arms. A stellar encounter can create a gravitational pull on a planetary system to disturb it, and a planet which had conditions for life prior to the encounter may be moved either inward or outward relative to its star, where the conditions do not hold. Two solutions might be done for this, either change R_* to only count spiral arm stars or modify all the subsequent probabilities to take into account the different conditions between the spiral arms and the central bulge.

Second, the term detectable can be defined a number of ways. Since radiation dies off as the square of the distance travelled, without absorption, and worse with absorption, does detectable mean detectable with some particular equipment? Imagining a ten kilometer aperture radio dish out beyond Neptune's orbit, and compare that with the original SETI equipment. If one wants to be able to detect a civilization's emissions from the other side of the Milky Way, assuming the central bulge does not intervene, something huge would be required on both ends.

Third, the equation seems to be assuming roughly isotropic radiation, spreading equally in every direction, including the one direction that heads toward Earth. Why would any civilization do that? There might be some transitory period when they were broadcasting for their own planetary uses, but if they wanted to communicate from solar system to solar system, they would develop a narrow beam system that would require only a tiny fraction of the power of an isotropic radiator. But then detectable means that Earth is in the beam of such a system. That would be rather fortuitous.

Fourth, the fraction of stars which develop planets might be, as we now know, approximately one, but developing planets does not mean life can evolve on one of them, or certainly not to the threshold of EM emissions. Stars heavier than our star burn out quickly, and if one included them in the count, they could have planets and one could have the right conditions for life, but these conditions would soon change as the star evolved and died. On the other end of the scale, M dwarfs, the most populous kind of star, doesn't have enough energy output to have a planet with the conditions for life, except if it is close in, and there it would be likely phase-locked, with the same face always directed at the star. There are good objections to assuming life could evolve in such a system.

For the mid-range of stars, where our sun resides, there might be planets, and one or two with the conditions for life, but we know little about the migration of planets, even without the evolution of the parent star. Do smaller planets keep their orbits for billions of years in any planetary system, or does it take billions of years for them to gradually migrate inward or outward? If we change the definition to having a planet of the right size in the liquid water zone for billions of years, the number might drop from about 1.0 to 0.00001. Figuring out long-term stability of orbits should be a fairly simple task for the current state of mathematical astrophysics, but it does not seem to have been done in a comprehensive way that enables on to figure out this term in Drake's equation.

Fifth, exactly what does the “conditions for life” entail? If it is made very loose, the corresponding probability would be high, and the subsequent probability would be less to make up for the looseness. If it is made tight, the inverse happens. At the time the Drake equation was written, mankind did not know how life forms, nor what were the conditions needed for it. Now, sixty years later, the same situation exists. We don't know. It is appalling that so little work is done on the origination for life. One particular question is that, are there some conditions in which life forms over a period of time, something large compared to human lifetimes but small compared to solar lifetimes, like a million years? Or is the situation completely opposite, life only forms if some event happens, and the probability of the event might be very, very small.

Just suppose, as hypothesized in this blog, a mild collision with a large planetoid, which becomes a satellite, is necessary for life. The collision would have occurred in the early part of the solar system's existence. Earth-like planets which did not have that collision in their history might be similar in many conditions to ones which did, but, if the hypothesis is correct, only the latter could have life. There are certainly other events in the history of a planet which might affect the origination of life, such as the chemical composition of the crust, volcanic heating, and asteroidal bombardment.

To be generous, life originated three or four billion years ago, and we do not know the conditions of the Earth's surface, so we are limited in imagining how life could originate. The delay in life origination work might be caused by the delay in planet origination work. Neither is in a good state. There is no reason to think that current conditions on the Earth could lead to an origination of life, assuming all consequences of life were removed. One of the conditions discussed in this blog is the existence of organic oceans on the surface, able to nurture membrane formation as well as complex protein formation. Where might they come from? The mild collision hypothesis is a possibility for this.

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.